Radiographic assessment and management of two deeply and horizontally impacted maxillary central incisors: A clinical case report

This case report describes the treatment of a 9-year-old boy with impacted maxillary central incisors due to 2 supernumerary teeth. A sequential approach comprising of surgical removal of the supernumerary teeth and 2 stages of surgical exposure and orthodontic traction of the impacted teeth resulted in correct repositioning of incisors. Close monitoring and multidisciplinary cooperation during various stages of treatment led to a successful esthetic outcome, with optimal periodontal health and functional occlusion.

Clinical analysis of the tooth-implant papilla for two narrow-diameter titanium-zirconium implants in the anterior area: prospective controlled clinical study

BACKGROUND

Rehabilitation of the anterior area when the mesio-distal space is reduced is a challenge for the clinician, due to the patient's anatomical limitations and aesthetic requirements. Narrow Diameter Implants (NDI) are an option of treatment when the standard diameter implant is not possible, but the evidence is scarce. This prospective clinical study aims to analyze the formation of the tooth-implant papilla between the implant and the adjacent natural tooth in the maxillary lateral incisors and mandibular incisors.

METHODS

A total of 40 patients treated with NDI, of titanium-zirconium (Ti-Zr) alloy i.e., 2.9 mm Test Group (TG) and 3.3 mm Control Group (CG), were included. The mesiodistal distance between the adjacent natural teeth was used for implant selection, maintaining 1.5 mm between the fixation and the adjacent tooth. Clinical assessment was performed by a clinical examiner at 6 and 12 months after the final prosthesis. The primary variable was the Jemt Papillary Index. Also, implant survival rate (SR), complications, Implant Stability Quotient (ISQ), and patient-reported outcomes measures (PROMs) such as aesthetics, chewing, phonation, comfort, and self-esteem were analyzed.

RESULTS

A significant amount of papilla filling was observed concerning the baseline, with a trend towards more formation of the papilla in the TG, with a JPI score of 3. No significant differences were observed between the two groups regarding implant SR, clinical parameters, and complications. In terms of PROMs, a higher satisfaction in the TG was observed, with significant intergroup differences for aesthetics, comfort, self-esteem, and primary stability ISQ (TG: 59.05 (SD: 5.4) vs. CG: 51.55 (SD: 5.7)).

CONCLUSIONS

The 2.9 mm diameter Ti-Zr implants achieved a formation of papilla similar to 3.3 mm implants in the anterior region at 12 months of follow-up after the final prosthetic restoration. The use of Ti-Zr implants with a diameter of 2.9 mm to rehabilitate single teeth in areas of the anterior region, where the mesiodistal distance is limited, showed favorable clinical results and a high degree of satisfaction during 1 year of observation similar to 3.3 mm dental implants.

TRIAL REGISTRATION

This study was retrospectively registered in ClinicalTrials.gov with the number NCT05642520, dated 18/11/2022.

Developmental characteristics of the permanent upper lateral incisor in unilateral cleft lip and palate

OBJECTIVES

This study aims to provide insights into the developmental characteristics of the upper lateral incisor in individuals with unilateral clefts.

MATERIALS AND METHODS

Panoramic radiographs of a consistent group of Caucasian children taken over time (ages 6, 9, and 12) were extensively reviewed. The study assessed the distribution pattern, eruption path, tooth development, and crown size of the upper lateral incisor within the cleft region.

RESULTS

The most commonly observed distribution pattern was the lateral incisor located distal to the cleft, accounting for 49.2% of cases. Furthermore, a significant delay in tooth development of the upper lateral incisor on the cleft side was noted at ages 6 and 9 (p > 0.001). Compared with the non-cleft side, these incisors often erupted along the alveolar cleft and exhibited microdontia (88.3%, p < 0.041).

CONCLUSION

Lateral incisors on the cleft side display unique distribution patterns, microdontia, and delayed tooth development. Careful monitoring of the cuspid eruption is essential, as it can influence the eruption of the lateral incisor.

CLINICAL RELEVANCE

A comprehensive understanding of the development of the upper lateral incisor relative to the cleft is vital for determining its prognosis over time. The position of the upper lateral incisor can also influence the timing and prognosis of secondary alveolar bone grafting. Preserving the upper lateral incisor favors arch length, perimeter, and symmetry in individuals with unilateral clefts.

Incisor torque expression characteristics in two passive self-ligating brackets placed at different heights. A finite element investigation

Objective

This study investigated torque expression in maxillary incisors using two passive self-ligating bracket types (Damon Q and Pitts 21) placed at different heights using the Finite element method.

Materials and methods

Two passive self-ligating brackets, Damon Q (Ormco, USA) and Pitts 21 (OC Orthodontics, USA) were 3D modeled using micro-computed tomography. Damon Q (0.022ˮ x 0.028″ slot size) and Pitts 21 (0.021ˮ x 0.021″ slot size) brackets were placed on a maxillary central incisor at predetermined vertical heights. Arch wires of size 0.019ˮ x 0.025″ stainless steel (Damon Q) and 0.020ˮ x 0.020" Titanium Molybdenum (Pitts 21) were placed in the bracket slots.

Results

Pitts 21 brackets showed higher torquing moments at all bonding heights as compared to Damon Q brackets. The minimum torquing moment was 9.03Nmm at 5 mm for Damon Q and the maximum torquing moment was 14.92Nmm for Pitts 21 at a bracket bonding height of 8 mm. Total deformation for Pitts 21 at a height of 5 mm from the incisal edge was 0.61 × 10-6mm as compared to that of Damon Q which was 0.41 × 10-6mm. Lowest Von Mises stress values were at 27.07 MPa in Damon Q brackets at a bracket height of 5 mm from the incisal edge. Highest Von Mises stress values were 36.80 MPa for Pitts 21 brackets at a bracket height of 8 mm from the incisal edge.

Conclusion

Pitts 21 brackets exhibited superior torquing characteristics compared to Damon Q. Total deformation in Pitts 21 was higher than Damon Q at all tested bracket bonding heights.

Dynamic patterns of histone lactylation during early tooth development in mice

Histone lactylation on its lysine (K) residues has been reported to have indispensable roles in lung fibrosis, embryogenesis, neural development, inflammation, and tumors. However, little is known about the lactylation activity towards histone lysine residue during tooth development. We investigated the dynamic patterns of lactate-derived histone lysine lactylation (Kla) using a pan-Kla antibody during murine tooth development, including lower first molar and lower incisor. The results showed that pan-Kla exhibited temporo-spatial patterns in both dental epithelium and mesenchyme cells during development. Notably, pan-Kla was identified in primary enamel knot (PEK), stratum intermedium (SI), stellate reticulum (SR), dental follicle cells, odontoblasts, ameloblasts, proliferating cells in dental mesenchyme, as well as osteoblasts around the tooth germ. More importantly, pan-Kla was also identified to be co-localized with neurofilament during tooth development, suggesting histone lysine lactylation may be involved in neural invasion during tooth development. These findings suggest that histone lysine lactylation may play important roles in regulating tooth development.

Retrospective evaluation of traction time for impacted dilacerated maxillary central incisors in mixed dentition

PURPOSES

This study aimed to contribute to understanding the factors affecting the time of traction treatment of impacted dilacerated maxillary central incisors.

METHODS

This retrospective study included children aged 8 - 11 years with a history of trauma, who applied to the pediatric dentistry clinics of Marmara University, School of Dentistry, between December 2013 and December 2019, and were treated for unilateral impacted dilacerated maxillary upper central incisors. Children's age, sex, digital panoramic radiographs, cone-beam computed tomography, and intraoral photographs were retrieved from electronic dental health records. The effects of children's age, sex, the direction of impacted teeth, distance of the teeth to the top of the alveolar crest, and root dilaceration level on traction time were analyzed by Mann-Whitney U test and Spearman's rank correlation coefficient test.

RESULTS

The inverse position of the incisors significantly increased the traction time (P = 0.012). However, the traction time did not differ according to the sex of the children (P = 0.707) or the level of root dilaceration (P = 0.429). No correlation was observed between the traction time and the age of children (P = 0.644) or the distance of the incisors from the top of the alveolar crest (P = 0.397).

CONCLUSIONS

In cases of the forced eruption of for the impacted dilacerated maxillary central incisors, the direction of the teeth should be evaluated when deciding on the treatment plan, as it may affect the treatment time.

Measurement of the apical anatomy of immature maxillary central incisors using cone-beam computed tomography

OBJECTIVE

To investigate the CBCT findings of the apical anatomy of immature maxillary central incisors.

METHODS

CBCT images of 100 immature maxillary central incisors in Nolla 8 and 100 immature maxillary central incisors in Nolla 9 were collected. The mesiodistal and carniocaudal diameters of the apical foramen of immature maxillary central incisors were measured by software included with CBCT, as well as the mesiodistal, carniocaudal and facioligual diameters of the apical shadow. The apical shadow and apical foramen diameters were compared between Nolla 8 and Nolla 9. Data were analyzed using the MedCalc software package.

RESULTS

For immature maxillary central incisors, the mesiodistal and facioligual diameters of the apical foramen were 2.75±0.68 mm and 3.28±0.74 mm in Nolla 8 and 1.50±0.51 mm and 1.92±0.79 mm in Nolla 9. The mesiodistal, facioligual and carniocaudal diameters of the apical shadow were 3.84±0.73 mm, 4.49±0.68 mm and 3.41±1.27 mm in Nolla 8 and 2.76±0.60 mm, 3.41±0.80 mm and 2.06±0.65 mm in Nolla 9, respectively.

CONCLUSIONS

The immature maxillary central incisors in Nolla 8 have a larger apical shadow and apical foramen than those in Nolla 9. The apical region of the maxillary central incisors in Nolla 8 was more likely to have a broad, blurred lamina dura. With the development of the apical foramen, the lamina dura in the apical region tended to be clear and sharp.

CLINICAL SIGNIFICANCE

To our knowledge, this is the first study to radiologically analyse the in vivo anatomy of the apical foramen and apical shadow of immature maxillary central incisors. The results of this study provide a more detailed understanding of the apical anatomy of the immature maxillary central incisor for the diagnosis and treatment of apical lesions.

Measurement of the Dentin Wall Thickness of the Maxillary Central Incisor in Relation to the Stage of Root Development: A Pilot Study

Objective

The aim of this study was to determine the average dentin wall thickness (DWT) of the maxillary central incisor (MCI) required for performing finite element analysis (FEA) models of root development.

Material and methods

A total of 137 intraoral periapical radiographs of MCI in children aged 7 to 11 years were examined and then classified into 5 groups according to root development stages, which included 1/2 of root development (S1), 3/4 of root development (S2), more than 3/4 of root development (S3), complete development with wide-open apex (S4) and complete development with closed apex (S5). DWT was measured at three reference (horizontal) lines: at a distance of 1 mm from the apex (M), 4 mm from the apex (L) and at the cervical line (K). The distal dentin wall thickness (M1, L1, and K1), the pulp thickness (M2, L2, and K2), the mesial dentin wall thickness (M3, L3, and K3), and the apex thickness (N) were measured using the diagnostic software Soredex Scanora 5.1.2.4. Statistical analysis compared the values of the parameters K, L, and M between developmental stages (multivariate ANOVA) and the linear correlations between the parameters (Pearson's correlation analysis). All analyses were performed at significance level α = 0.05.

Results

There were statistically significant differences between the developmental stages for parameters L and M, while no significant differences were found for parameter K. Most of the correlations between the parameters were statistically significant, with the values of the Pearson correlation coefficient R > 0.6 considered practically significant. All parameters on the same reference line for distal and mesial dentin wall thickness and for pulp thickness correlated well with each other (R = 0.46 - 0.68), but there was no statistically significant correlation with total root thickness on the same reference line (parameters K, L, or M), except for parameter K3 (R = 0.42).

Conclusion

Despite the limitations of this study, the mean values of the selected parameters for the 5 groups of developmental stages of the maxillary central incisor could be used to model dentin wall thickness using finite element analysis.

Lower incisor inclination and thickness of the alveolar process and mandibular symphysis in the development of gingival recession: A retrospective cohort study

Introduction

Retrospective studies have found conflicting results regarding the relationship between lower incisor inclination and the development of gingival recession (GR) after orthodontic treatment.

Objective

This study aimed to investigate the relationship between lower incisor inclination and alveolar process (AP) and mandibular symphysis (MS) thickness in the development of GR.

Materials and Methods

Frontal intraoral photography and cephalometric radiography were conducted before (T0) and after (T1) orthodontic treatment of 62 subjects. The presence of GR was considered when the cementoenamel junction was visible in the lower incisor on the frontal intraoral photograph. The circumstances for improvement, stability, and worsening of the gingival situation were based on the reduction, maintenance, and increase in the number of lower incisors with GR before and after treatment. To measure the incisor-mandibular plane angle (IMPA) and the thickness of the AP and the MS were used the cephalometric radiographs.

Results

Men had a significantly thicker MS than women at T0 and T1 (p < 0.0004). There was a significant reduction of approximately 10% in AP between T0 and T1 (p < 0.0001). Among subjects without GR at T0, 70.4% presented a stable gingival situation at T1. For subjects with 1 lower incisor with GR at T0, 50% showed improvement in the gingival situation at T1, 21.4% remained stable, and 28.6% experienced worsening. Sixteen lateral incisors presented a worsening gingival situation, representing an increase of 129% compared to the central incisors.

Conclusion

No relationship was found between lower incisor inclination and the thickness of the AP and MS in the development of GR.

Evaluation of alveolar bone morphology of incisors with different sagittal skeletal facial types by cone beam computed tomography: A retrospective study

Background

Safe orthodontic tooth movement should be performed within the alveolar bone. The purpose of this study was to evaluate the morphology of the alveolar bone of incisors.

Materials and methods

This retrospective study included pretreatment cone beam computed tomography of 120 patients with malocclusion. Patients were divided into 4 groups (Class I, Class II division 1, Class II division 2 and Class III) according to the subspinale-nasion-supramental (ANB) angle and occlusal relationship. The sagittal root positions, anterior and posterior root-cortical bone angles (AR-CA and PR-CA), root-crown ratios (RCR) and alveolar bone thickness were evaluated.

Results

The sagittal root positions were mainly positioned against the labial cortical plate in the maxillary incisors of the Class II division 2 group and engaged by both the labial and palatal cortical plates in the mandibular incisors of the Class III group. The AR-CA was lower than that in the other groups (P < 0.01) in the maxillary incisors of the Class II division 2 group, and the AR-CA and PR-CA were lower than those in the other groups (P < 0.01) in the mandibular incisors of the Class III group. The alveolar thickness showed no significant difference between the Class II division 1 group and the Class I group (P > 0.05), the middle and lower anterior alveolar thickness (LAAT and MAAT) were lower than those in other groups (P < 0.01) in the maxillary incisors of the Class II division 2 group, and the alveolar thickness at the measurement sites of the middle and lower line were lower than those in other groups (P < 0.01) in the mandibular incisors of the Class III group. The RCR had a moderate positive correlation with the LAAT.

Conclusion

Based on several limitations, this study found that maxillary incisor roots were at risk of penetrating the alveolar bone of Class II division 2 patients, and mandibular incisors may have a relatively small range of safe movement on both the labial and lingual sides of Class III patients during orthodontic treatment.

A micro-computed tomographic analysis of the root canal systems in the permanent mandibular incisors in a Chinese population

BACKGROUND

Comprehensive understanding of the root canal system complexity is critical important for successful root canal therapy. A double root canal system may be present in permanent mandibular incisors with a variable incidence in different ethnic populations. Ignorance or improper management of this canal variation can lead to treatment failure. This in vitro study aimed to identify the anatomic features of root canal systems in the mandibular incisors in a Chinese population by using micro-CT.

METHODS

A total of 106 permanent mandibular incisors (53 central incisors and 53 lateral incisors) were collected from a native Chinese population. The teeth were scanned by a micro-CT scanner and then reconstructed three-dimensionally. The canal configurations were detected by Vertucci's classification, and the number and location of the accessory canals were also identified. The long (D) and short diameters (d) of the main and accessory canals were measured and D/d ratio was calculated at different root levels (cemento-enamel junction [CEJ] level, mid-root level and 1, 2, 3 and 4 mm from the apex). The root canal curvatures in the double-canaled mandibular incisors were measured at the proximal view by using modified Schneider's method. Chi-square test or Fisher's exact test was used for comparison of occurrence rates. Comparison of means from multiple groups was performed by using one-way ANOVA and LSD post-hoc test.

RESULTS

In regard to the occurrence of double root canals, gender difference was neither detected in the mandibular central (16.0% [male] vs 14.3% [female]; p = 0.862), nor in the mandibular lateral incisors (26.9% [male] vs 33.3% [female]; p = 0.611). Age group difference was also not detected in the mandibular central (p = 0.717) and lateral incisors (p = 0.521). The incidence of double root canals was 15.1% (8/53) in the central incisors, and 30.2% (16/53) in the lateral incisors, but the difference did not reach statistical significance (p = 0.063). The most frequent non-single canal type was the type III (1-2-1) (18.9% [20/106]), and the other types identified included 1 case of type II (2-1) and 3 cases of type V (1-2). The incidence of accessory canals was 17.9% (19/106), with a mean level of 1.92 ± 1.19 mm from the apex. The frequency of long-oval (2 ≤ D/d < 4) and flattened canals (D/d ≥ 4), as well as the mean value of D, d and D/d ratio increased from the apical 1 mm to the apical 4 mm level (the D/d ratio increased from 1.9 to 2.9 for the single canals, from 1.4 to 3.3 for the buccal canals and from 1.2 to 2.3 for the lingual canals), and the D/d ratio reached the peak at the mid-root level. Double curvatures were detected in 33.3% (8/24) of the buccal canals and 37.5% (9/24) of the lingual canals, and the difference has no statistical significance (p = 0.063). The degrees of the primary curvatures were 21.5 ± 7.1 degrees for the buccal and 30.1 ± 9.2 degrees for the lingual canals, and the degrees of secondary curvatures were 27.0 ± 11.4 degrees for the buccal and 30.5 ± 12.5 degrees for the lingual canals in the double curvatures. The degrees of the single curvatures were 14.2 ± 6.3 degrees for the buccal and 15.6 ± 6.0 degrees for the lingual canals. Significant difference was detected among above 6 groups of canal curvatures (p = 0.000), and severe curvatures (≥ 20 degrees) were more frequently detected in the double curved canals.

CONCLUSIONS

Double-canaled mandibular incisors were not uncommon in the Chinese population, and type 1-2-1 was the most frequent non-single canal type. Gender and age did not significantly impact the occurrence of a second canal in mandibular incisors. Long-oval and flattened canals were very common at different root levels and their incidence increased from apex to the mid-root level. Severe curvatures were frequently detected in the double canal systems, especially in those canals with double curvatures.

Root morphology of lateral incisors adjacent to impacted maxillary canines: A cone-beam computed tomography retrospective cross-sectional study

INTRODUCTION

To compare the root morphology of the maxillary lateral incisors (MLIs) adjacent to an impacted (IMC) versus non-impacted maxillary canine (non-IMC).

MATERIALS AND METHODS

This cross-sectional study included cone beam computed tomography (CBCT) images derived from 154 subjects (with unilateral/bilateral impacted maxillary canines or without canine impaction). Each MLI was considered as a unit of analysis. Thus, the study group included 122 MLIs adjacent to impacted maxillary canine (IMCG) and the control group included 122 MLIs adjacent to a non-impacted maxillary canine (CG). Groups were matched by age, sex and evaluation side. Root length, root dilaceration angle and root convergence angle were evaluated in both the coronal and sagittal planes. Comparisons between groups were made with Student's t-test and the chi-square test with Bonferroni correction (P<0.008, P<0.01, respectively).

RESULTS

The root measurements of the MLIs showed some significant differences between the groups. The coronal root length was 0.52mm shorter but not highly significant (P=0.032), the coronal root dilaceration angle was 7.51° smaller (P<0.001), and the coronal root convergence angle was 1.28° greater (P<0.001) in the IMCG compared to the CG. The orientation of root dilaceration in the MLIs showed significant differences between the groups: it was mostly distopalatal in the GC (87.5%), to a lesser extent in the IMCG (58.9%) and also mesiopalatal in the IMCG (22.3%), (P=0.001).

CONCLUSIONS

The root morphology of MLIs adjacent to an IMC showed a tendency of shorter length, smaller root dilaceration and greater root convergence in the coronal section than MLIs adjacent to a non-IMC.

Clinical effects of different prescriptions on the inclination of maxillary and mandibular incisors by using passive self-ligating brackets

Objective

Controlling the incisal inclination is fundamental in orthodontics. However, the relationship between the inclination prescription and its clinical outcome is not obvious, and the incisal inclination changes generated by different bracket prescriptions were investigated.

Methods

Twenty-eight non-extraction dental Class II patients (15 females, 13 males; mean age = 12.9) were retrospectively analyzed. Patients were treated using passive self-ligating fixed appliances with three inclination prescriptions for maxillary incisors (high, standard, low), and two for mandibular incisors (standard, low). Clinical outcomes were compared among different prescriptions, and regression analysis was used to explain the effects of bracket prescriptions and to understand the prescription selection criteria (α = 0.05).

Results

For maxillary central incisors, low and high prescriptions were related to linguoversion (p = 0.046) and labioversion (p = 0.005), respectively, while standard prescription maintained the initial dental inclination. Maxillary lateral incisors did not show significant changes. For mandibular incisors, low prescription led to linguoversion (p = 0.005 for central incisors, p = 0.010 for lateral incisors), while standard prescription led to labioversion (p = 0.045 for central incisors, p = 0.005 for lateral incisors). The factors affecting inclination changes were the imposed change and selected prescription, while prescription selection was influenced by the initial dental inclination and initial intercanine distance.

Conclusions

The direction of correction of incisal inclination can be controlled by choosing a certain prescription, but the final inclination may show limited consistency with it. The amount of imposed inclination change was the most relevant predictor of the clinical outcome.

Comparing the Boxgrove and Atapuerca (Sima de los Huesos) human fossils: Do they represent distinct paleodemes?

The early Middle Pleistocene human material from Boxgrove (West Sussex, UK) consists of a partial left tibia and two lower incisors from a separate adult individual. These remains derive from deposits assigned to the MIS 13 interglacial at about 480 ka and have been referred to as Homo cf. heidelbergensis. The much larger skeletal sample from the Sima de los Huesos (Atapuerca, Spain) is dated to the succeeding MIS 12, at about 430 ka. This fossil material has previously been assigned to Homo heidelbergensis but is now placed within the Neanderthal clade. Because of the scarcity of human remains from the Middle Pleistocene and their morphological variability, this study assessed whether the Boxgrove specimens fit within the morphological variability of the homogeneous Sima de los Huesos population. Based on morphometric analyses performed against 22 lower incisors from Sima de los Huesos and published material, the data from the Boxgrove incisors place them comfortably within the range of Sima de los Huesos. Both assemblages present robust incisors distinct from the overall small recent Homo sapiens incisors, and Boxgrove also aligns closely with Homo neanderthalensis and some other European Middle Pleistocene hominins. Following morphological and cross-sectional analyses of the Boxgrove tibia compared to seven adult Sima de los Huesos specimens and a set of comparative tibiae, Boxgrove is shown to be similar to Sima de los Huesos and Neanderthals in having thick cortices and bone walls, but in contrast resembles modern humans in having a straight anterior tibial crest and a suggestion of a lateral concavity. Based on the patterns observed, there is no justification for assigning the Boxgrove and Sima de los Huesos incisors to distinct paleodemes, but the tibial data show greater contrasts and suggest that all three of these samples are unlikely to represent the same paleodeme.

Solitary Median Maxillary Central Incisor Syndrome: A Case Report

Aim

This report intends to present a case of solitary median maxillary central incisor syndrome (SMMCI) and its multidisciplinary team approach for diagnosis of other associated anomalies, with special emphasis on their management.

Background

Solitary median maxillary central incisor syndrome is a unique developmental condition characterized by only maxillary central incisor and a series of developmental defects, appearing as a syndrome. The appearance of a single incisor may take place due to the union of two incisor teeth or the absence of tooth germs. The mechanism of the fusion is still uncertain.

Case description

A 9-year-old female child reported with a chief complaint of pain in the right lower back tooth for the past 10 days. The presence of a single maxillary central incisor was an incidental finding. Then a detailed history and multidisciplinary evaluations revealed the diagnosis of SMMCI syndrome.

Conclusion

The effort in diagnosing and managing this syndrome had a strong impact on the child's life of which the parent was highly motivated and got a better understanding of associated problems of overall development.

Clinical significance

In SMMCI syndrome, the patient requires a multidisciplinary health team in order to improve their quality of life. It is of greater importance to diagnose the syndrome and treatment of these median line deformities.

How to cite this article

Balasubramanian S, Haridoss S, Swaminathan K. Solitary Median Maxillary Central Incisor Syndrome: A Case Report. Int J Clin Pediatr Dent 2022;15(4):458-461.

An update of the aetiological factors involved in molar incisor hypomineralisation (MIH): a systematic review and meta-analysis

PURPOSE

To systematically review the aetiological factors associated with molar incisor hypomineralisation (MIH). To this day, the aetiology remains unknown. Determining risk factors would allow risk assessment and enhance early diagnosis of MIH in young patients. The aim was to assess, evaluate and summarise the relationship between MIH and reported aetiological hypotheses.

METHODS

Electronic database searches of MEDLINE, EMBASE, EBSCO, LILACS and Cochrane Library were conducted. Authors conformed to PRISMA guidelines. Studies were screened, data extracted, assessment of risk of bias and calibration was completed by two independent reviewers. Meta-analyses with heterogeneity calculations were performed.

RESULTS

Of the potential 8949 studies, 64 studies were included in the qualitative analysis whilst 45 were included in the quantitative analysis. Prenatal factors: results are inconclusive as only unspecified maternal illnesses appear to be linked to MIH. Perinatal factors: prematurity (OR 1.45; 95% CI 1.24-1.70; p = 0.0002) and caesarean delivery (OR 1.45; 95% CI 1.09, 1.93; p < 0.00001) are associated with an increased risk of developing MIH. Birth complications are also highlighted. These three factors can lead to hypoxia, and children with perinatal hypoxia are more likely to develop MIH (OR 2.76; 95% CI 2.09-3.64; p < 0.0001). Postnatal factors: measles, urinary tract infection, otitis media, gastric disorders, bronchitis, kidney diseases, pneumonia and asthma are associated with MIH. Fever and antibiotic use, which may be considered as consequences of childhood illnesses, are also associated with MIH. Genetic factors: an increasing number of studies highlight the genetic and epigenetic influences in the development of MIH.

CONCLUSION

Several systemic and genetic and/or epigenetic factors acting synergistically or additively are associated with MIH, revealing a multifactorial aetiology model. Peri- and postnatal aetiological factors are more likely to increase the odds of causing MIH than prenatal factors.

A retrospective institutional study of human age determination by evaluating the pulp length and width ratio of the maxillary lateral incisor on panoramic radiographs in Indonesian subjects

Purpose

The pulp length to width (PL/W) ratio of the maxillary lateral incisor can be used as an age determination method. This study aimed to investigate the correlation between the PL/W ratio of the maxillary lateral incisor on panoramic radiographs and human chronological age in Indonesian subjects.

Materials and Methods

This study analyzed with 134 maxillary lateral incisors on 113 panoramic radiographs from patients who visited the Oral and Maxillofacial Radiology Unit of Dental Hospital Universitas Padjadjaran, Bandung, Jawa Barat, Indonesia, from 2013 to 2018 (age range: between 11 to 60 years). The pulp length was measured from the pulp chamber roof to the apical foramen, and the pulp width was measured on the cervical area of the cementoenamel junction in millimeters using Fiji ImageJ open-source software. Simple linear regression (in SPSS) was used to analyze the results. The reliability of the observers was evaluated.

Results

The PL/W ratio of the maxillary lateral incisor was significantly correlated with chronological age (P<0.01). No statistically significant difference was found in the PL/W ratio between the left and right maxillary lateral incisors (P=0.333). There was a very strong correlation (r=0.939) between the PL/W ratio of the maxillary lateral incisor and human chronological age, with the following formula: age= -3.057+1.875×PL/W ratio (R²=0.882, standard error of estimate: 4.659).

Conclusion

The PL/W ratio of the maxillary lateral incisor on panoramic radiograph can be used for age determination in Indonesian subjects.

Maintaining a Hopeless Traumatized Maxillary Central Incisor as a Transient Treatment Option: A Case Report with a 3-Years Follow-Up

An open apices tooth is among the rare types of traumatic dental injuries is horizontal root fracture. Many factors may affect the treatment and prognosis of root fractures, like the time between trauma and treatment, degree of dislocation and mobility, stage of tooth development, fracture site, and patient's age. This case presents a horizontal root fracture of a maxillary central incisor in an 8-year-old boy. The tooth was considered for extraction due to excessive mobility and deep probing depth, but the patient's parents refused to extract the tooth. After one year, during the follow-up examination, we noticed an unprecedented healing process had been initiated. Due to the weak crown-to-root ratio, the traumatized tooth was splinted to the surrounding teeth to reduce the wrecking forces and promote healing. In a three-year follow-up, the cone-beam computed tomography examination showed that the coronal and apical fragments continued to develop separately. Also, it was observed that the mobility and probing depth were reduced significantly.

A Maxillary Lateral Incisor with Type V Canal Morphology: A Case Report

A detailed root canal morphology description is of utmost importance for the success of endodontic treatment. Therefore, clinicians require a thorough knowledge of the root canal anatomy and its variations and anomalies in all the tooth types. This study reports a permanent upper lateral incisor exhibiting an uncommon root canal system morphology: a single-rooted tooth with one main root canal bifurcating into two distinct root canals in the apical third, with two apical foramina (type V root canal morphology).

Assessment of the relationship between the maxillary sinus and the canine root tip using cone beam computed tomography

BACKGROUND

The purpose of the present study is to investigate the relationship between the maxillary sinus and the canine root apices in cone beam computed tomographic images (CBCT) and to assess the amount of extension of the maxillary sinus to the anterior region of the jaw in different sexes and age groups.

METHODS

CBCT of 300 individuals (154 males and 146 females) over 20 years (with a mean age of 35.12 ± 8.40 years) were evaluated. The subjects were categorized into three age groups (20-30, 30-40, and 40-50 years). When the maxillary sinus extended to the canine area, the vertical distance between them was measured, and their relationship was classified into three types: I (more than 2 mm distance), II (less than 2 mm distance or in-contact), and III (interlock).

RESULTS

413 out of 600 maxillary sinuses (68.8%) were extended into the canine area or beyond. Among them, 15 maxillary sinuses pneumatized into the incisor area (2.5%). The prevalence of the maxillary sinuses extended to the anterior region of the jaw was not significantly different between genders. However, it was significantly less frequent in the older age group and more frequent on the left side. In addition, the mean amount of anterior extension of the maxillary sinus (mm) was significantly lower in the older age group. Type I was the most frequent vertical relationship between the maxillary sinuses and canine apices with no significant difference in gender, side, and age groups.

CONCLUSIONS

In most cases, the maxillary sinus extended to the canine area and sometimes reached the incisor region. This necessitates paying more attention to the maxillary anterior sextant during surgical procedures.

Constitutive activation of β-catenin in odontoblasts induces aberrant pulp calcification in mouse incisors

During dentin formation, odontoblast polarization ensures that odontoblasts directionally secrete dentin matrix protein, leading to tubular dentin formation; however, little is known about the major features and regulatory mechanisms of odontoblast polarization. In a study of epithelial cell polarization, β-catenin was shown to serve as a structural component of cadherin-based adherens junctions to initiate cell polarity. However, the role of β-catenin in odontoblast polarization has not been well investigated. In this study, we explored whether β-catenin participated in odontoblast polarization to regulate the secretion of mineralization proteins. We established Col1-CreErt2; β-catenin exon3fl/fl (CA-β-catenin) mice, which constitutively activate β-catenin in odontoblasts. CA-β-catenin mice exhibited disorganization and depolarization of incisor odontoblasts. Moreover, the incisor dentin was hypomineralized, and ectopic calcification was found in mouse incisor pulp. In addition, by constitutive activation of β-catenin, the expression levels of the core polarity molecule Cdc42 and its downstream polarity protein complex Par3-Par6-aPKC were decreased in the incisors of CA-β-catenin mice. These findings suggest that β-catenin plays an essential role in dentin formation by regulating odontoblast polarization.

Anomalous incisor morphology indicates tissue-specific roles for Tfap2a and Tfap2b in tooth development

Mice possess two types of teeth that differ in their cusp patterns; incisors have one cusp and molars have multiple cusps. The patterning of these two types of teeth relies on fine-tuning of the reciprocal molecular signaling between dental epithelial and mesenchymal tissues during embryonic development. The AP-2 transcription factors, particularly Tfap2a and Tfap2b, are essential components of such epithelial-mesenchymal signaling interactions that coordinate craniofacial development in mice and other vertebrates, but little is known about their roles in the regulation of tooth development and shape. Here we demonstrate that incisors and molars differ in their temporal and spatial expression of Tfap2a and Tfap2b. At the bud stage, Tfap2a is expressed in both the epithelium and mesenchyme of the incisors and molars, but Tfap2b expression is restricted to the molar mesenchyme, only later appearing in the incisor epithelium. Tissue-specific deletions show that loss of the epithelial domain of Tfap2a and Tfap2b affects the number and spatial arrangement of the incisors, notably resulting in duplicated lower incisors. In contrast, deletion of these two genes in the mesenchymal domain has little effect on tooth development. Collectively these results implicate epithelial expression of Tfap2a and Tfap2b in regulating the extent of the dental lamina associated with patterning the incisors and suggest that these genes contribute to morphological differences between anterior (incisor) and posterior (molar) teeth within the mammalian dentition.

Craniofacial Growth in Adolescence and its Influence on the Mandibular Incisor Crowding

Background

To analyze craniofacial growth during adolescence from the ages of 12 to 21 years and its relation to late mandibular incisor crowding.

Material and Methods

The study included 61 orthodontically untreated subjects (49% males). Lateral cephalograms were used to assess the jaw growth and inclination of the incisors. Little's Irregularity Index and the anterior mandibular dental arch depth of mandibular dentition were measured.

Results

A reduction of the skeletal class angle (ANB) was observed in both genders, although it was significant only in males (η2=0.188; p=0.015). The growth of the mandible was more prominent compared to that of the maxilla, and it was more prominent in males than in females. The skeletal vertical dimension, however, demonstrated a significant reduction in both genders (η2=0.527-0.593, p<0.001). The mandibular incisors tended to retrocline in both genders, while the maxillary ones tended to procline in males, and slightly retrocline in females. A decrease in the mandibular dental arch depth occurred in both genders (η2=0.259; p<0.05). An increase in the irregularity of incisors for 1.8±1.7 mm on average (95% CI 1.3-2.2; η2=0.520; p<0.001) was observed in both genders. A logistic regression revealed that less sagittal growth of maxilla (increase of SNA angle ≤2°) and reduction of convexity in skeletal sagittal interjaw relationship (reduction of ANB ≥1°) were significant predictors of the occurrence of crowding (Δ Little Irregularity Index ≥1mm) yielding odds ratios of 4.9 and 4.8.

Conclusions

The differential growth of the maxilla and mandible is related to the occurrence of late crowding, mostly in smaller amounts in maxillary sagittal growth compared to the mandible.

Equine Standing Surgical Extraction Techniques

Dental repulsion techniques reported in the past decades have a high incidence of complications. Although the practice of surgical extractions in horses is limited because of the training, instrumentation, and experience required to perform these techniques, veterinarians should be aware these procedures are available, general anesthesia is not required, and when performed by skilled veterinary dentists they have low complication rates. Surgical techniques are often used after failure of other extraction techniques to remove retained tooth root and fragments or to debride chronically contaminated orofacial lesions. However, surgical extractions should be considered during initial treatment planning of all complicated cases.

Comparative Analysis of Continuous versus Reciprocating Instruments in Retreatment of Flat-oval Root Canals

Introduction

Flat-oval root canals of incisors can be problematic in retreatments. This study assessed the efficacy of continuous and reciprocating rotation instruments in retreatment of flat-oval root canals in lower incisors via micro-computed tomography (micro-CT). File systems studied were ProTaper universal retreatment rotary system associated with ProTaper Next (PTUR+PTN), D-RaCe associated with iRaCe (DR+iR), Reciproc (REC), and WaveOne (WO).

Materials and Methods

Thirty-two mandibular incisors with flat root canal were divided into 4 groups (n=8). The groups were initially prepared with PTN, iRaCe, REC, and WO, then instrumented, filled, and subjected to micro-CT analyses. All the canals were then retreated with the PTUR+PTN, DR+iR, REC, and WO, and then subjected to new micro-CT analysis which allowed quantification of residual filling material volume and change in the diameter of the root canal apical third. Endodontic retreatment time was also quantified. Data were analyzed with One-Way ANOVA and post hoc t tests.

Results

None of the systems completely removed the filling material. The groups differed in terms of remnant filling material volume (PTUR+PTN=2.9±1.1 mm³; DR+iR=3.6±3.1 mm³; REC=4.9±1.9 mm³; WO=3.1±1.9 mm³) and retreatment time (PTUR+PTN=1:36±0:12 sec; DR+iR=0:57±0:13 sec; REC=2:10±0:44 sec; WO=2:03±0:31 sec), but had similar values in terms of change in apical root canal diameter (P>0.05).

Conclusions

Based on this in vitro study, the type of endodontic instrument did not affect the diameter of the root canal apical third. However, PTUR with ProTaper Next had the lowest residual filling material volume and second lowest retreatment time, in flat-oval root canals in mandibular incisors.

Unraveling Impacted Maxillary Incisors: The Why, When, and How

Failure of eruption of maxillary incisors requires careful diagnosis and treatment planning. The cause of impaction may vary from physical obstruction in the path of eruption, tooth material arch length discrepancy to malformation of the tooth. General principles of management of the condition include removal of physical obstruction, creation of space, and surgical exposure with or without traction. The treatment of an unerupted tooth depends upon its age, position, etiology, and amount of space in the dental arch. This case series elaborates on three different cases of incisor impaction with different etiologies and varying ranges of complexity. Three-dimensional radiography was utilized in all cases to accurately visualize the impacted tooth and its relation to adjacent structures. All the cases required different approaches and were completed in varying time durations. Meticulous treatment planning resulted in well-aligned satisfactory functional and esthetic results.

How to cite this article: Jain S, Raza M, Sharma P, et al. Unraveling Impacted Maxillary Incisors: The Why, When, and How. Int J Clin Pediatr Dent 2021;14(1):149–157.

Tomographic evaluation of buccal bone in different skeletal patterns and incisors inclination

OBJECTIVE

The aim of this study was to correlate the absence of BB with skeletal patterns and incisor inclination using cone-beam computed tomography (CBCT).

METHODS

The sample comprised CBCT images of 45 patients undergoing orthodontic treatment. BB was classified in each third of the anterior teeth as critical, slender, regular, and thick. The skeletal pattern was determined by the ANB (A point, nasion, B point) angle and the incisor inclination using the 1.NA and 1.NB measurements and the interincisal angle (1:1).

RESULTS

In both analyses, the skeletal pattern of class II revealed better BB in the cervical and middle thirds than classes I and III. A higher proportion of critical BB was found in the middle thirds, and the apical third presented the best regular and thick BB conditions, mainly class I. Less BB was observed in middle and apical thirds in the upper incisors and in cervical thirds in lower incisors, mostly when they were more upright.

CONCLUSIONS

Knowledge of alveolar bone height and thickness can alter the treatment plan in orthodontics. During orthodontic treatment, more attention should be paid to the lower incisors and vertical teeth because of poor BB conditions, especially in class III skeletal patterns.

Clinical Approach to External Cervical Resorption in the Anterior Teeth: A Case Report Study

External cervical resorption (ECR) is a pathology that is difficult to diagnose early, and because it is often confused with root decay, it can be treated inadequately and even result in tooth loss. Currently, treatment does not have a defined protocol, being widely varied in the literature. This article proposes that cases of ECR should be treated individually, following different criteria, based on aspects related to the patient and the tooth involved. Furthermore, this work illustrates, through a case report, how a patient can present unique characteristics that require treatment to be case-dependent and should be discussed among a multidisciplinary team.

[Esthetic proportions of maxillary anterior teeth of 120 Chinese adults]

OBJECTIVE

To analyze the esthetic proportions of maxillary anterior teeth in term of the apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown in 120 Chinese adults.

METHODS

Maxillary gypsum casts were obtained from the dental laboratories of stomatological hospitals in North China, Southeast China, and Southwest China, according to the inclusion criteria and exclusion criteria. Standardized digital photographs of each cast were recorded. The apparent widths and actual widths and heights of the central incisors, lateral incisors and canines were determined by ImageJ software for the calculation of apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown. The ideal apparent widths proportion (Golden proportion and Preston proportion) and width/height ratio (0.80) were tested. The gender, arch side, and regional differences were investigated.

RESULTS

The apparent widths proportion of the lateral/central incisor was 0.724±0.047, of the canine/lateral incisor was 0.814±0.092. The width/height ratio of the central incisor was 0.848±0.072, of the lateral incisor was 0.834±0.094, of the canine was 0.883±0.098. The esthetic proportions were different from the predicted ideal ratio (P < 0.001). The apparent widths proportion of lateral/central incisor was significantly larger in the right side than that in the left side (0.730± 0.044 vs. 0.718±0.050), and was significantly smaller in North China than that in Southwest China (0.711±0.051 vs. 0.731±0.044). The width/height ratio of the central incisor was significantly larger in the female than that in the male (0.855±0.074 vs. 0.835±0.068), and in the right side than that in the left side (0.855±0.073 vs. 0.842±0.072). The width/height ratio of the lateral incisor was significantly larger in the female than that in the male (0.843±0.097 vs. 0.817±0.084).

CONCLUSION

The apparent widths proportion of adjacent teeth and the width/height ratio of the clinical crown in Chinese adults are different from the foreigner's. The esthetic proportion parameters have significant population specificity, and the measurements cannot be generalized as well as it should be applied with caution.

Smad4-dependent transforming growth factor-β family signaling regulates the differentiation of dental epithelial cells in adult mouse incisors

Teeth consist of two major tissues, enamel and dentin, which are formed during development by epithelial and mesenchymal cells, respectively. Rodent incisors are useful experimental models for studying the molecular mechanisms of tooth formation because they are simultaneously growing in not only embryos but also adults. Members of the transforming growth factor-β (TGF-β) family regulate epithelial-mesenchymal interactions through an essential coactivator, Smad4. In the present study, we established Smad4 conditional knockout (cKO) mice and examined phenotypes in adult incisors. Smad4 cKO mice died with severe anemia within one month. Phosphorylated Smad1/5/9 and Smad2/3 were detected in epithelial cells in both control and Smad4 cKO mice. Disorganized and hypoplastic epithelial cells, such as ameloblasts, were observed in Smad4 cKO mice. Moreover, alkaline phosphatase expression and iron accumulation were reduced in dental epithelial cells in Smad4 cKO mice. These findings suggest that TGF-β family signaling through Smad4 is required for the differentiation and functions of dental epithelial cells in adult mouse incisors.

Correlation analysis of gingival recession after orthodontic treatment in the anterior region: an evaluation of soft and hard tissues

Purpose

The aim of this study was to investigate and identify the main causes of periodontal tissue change associated with labial gingival recession by examining the anterior region of patients who underwent orthodontic treatment.

Methods

In total, 45 patients who had undergone orthodontic treatment from January 2010 to December 2015 were included. Before and after the orthodontic treatment, sectioned images from 3-dimensional digital model scanning and cone-beam computed tomography images in the same region were superimposed to measure periodontal parameters. The initial labial gingival thickness (IGT) and the initial labial alveolar bone thickness (IBT) were measured at 4 mm below the cementoenamel junction (CEJ), and the change of the labial gingival margin was defined as the change of the distance from the CEJ to the gingival margin. Additionally, the jaw, tooth position, tooth inclination, tooth rotation, and history of orthognathic surgery were investigated to determine the various factors that could have affected anterior periodontal tissue changes.

Results

The mean IGT and IBT were 0.77±0.29 mm and 0.77±0.32 mm, respectively. The mean gingival recession was 0.14±0.57 mm. Tooth inclination had a significant association with gingival recession, and as tooth inclination increased labially, gingival recession increased by approximately 0.2 mm per 1°.

Conclusions

In conclusion, the IGT, IBT, tooth position, tooth rotation, and history of orthognathic surgery did not affect labial gingival recession. However, tooth inclination showed a significant association with labial gingival recession of the anterior teeth after orthodontic treatment.

Alveolar bone thickness and fenestration of incisors in untreated Korean patients with skeletal class III malocclusion: A retrospective 3-dimensional cone-beam computed tomography study

Purpose

The purpose of this study was to evaluate vertical bone loss and alveolar bone thickness in the maxillary and mandibular incisors of patients with skeletal class III malocclusion. This study also aimed to evaluate the periodontal condition of class III malocclusion patients who had not undergone orthodontic treatment.

Materials and Methods

The sample included cone-beam computed tomography scans of 24 Korean subjects (3 male and 21 female). Alveolar bone thickness (ABT), alveolar bone area (ABA), alveolar bone loss (ABL), and fenestration of the maxillary and mandibular incisors were measured using 3-dimensional imaging software.

Results

All incisors displayed an ABT of less than 1.0 mm from the labial surface to root level 7 (70% of the root length). A statistically significant difference was observed between the mandibular labial and lingual ABAs and between the maxillary labial and mandibular labial ABAs. The lingual ABA of the mandibular lateral incisors was larger than that of the mandibular central incisors. ABL was severe on the labial surface. A statistically significant difference was observed between the maxillary and mandibular labial ABL values(21.8% and 34.4%, respectively). Mandibular lingual ABL (27.6%) was significantly more severe than maxillary lingual ABL (18.3%) (P<0.05). Eighty-two fenestrations were found on the labial surfaces of the incisors, while only 2 fenestrations were observed on the lingual surfaces. Fenestrations were most commonly observed at root level 6.

Conclusion

Careful evaluation is needed before orthodontic treatment to avoid iatrogenic damage of periodontal support when treating patients with class III malocclusion.

A questionnaire study on perception and clinical management of molar incisor hypomineralisation (MIH) by Irish dentists

AIM

Molar incisor hypomineralisation (MIH) is a significant global health problem frequently encountered by dentists. The aim of this questionnaire-based study was to gain a better understanding of how dentists in the Republic of Ireland perceive and manage MIH. In addition, to compare these findings with results of existing international studies.

METHODS

Following ethical approval, an online survey was created consisting of 16 questions based on previous surveys regarding perception and treatment of MIH. Photographs and information regarding three specific cases were also included. The questionnaire was distributed by email and the data were analysed using SPSS statistical software.

RESULTS

The total number of respondents was 230, of which 204 were general dentists. The majority of dentists (58%) reported that they observe MIH on a weekly basis. Those dentists exclusively in private practice and respondents aged 36 and older were less likely to note frequent MIH (p = 0.042). The vast majority of respondents felt either confident or very confident in diagnosing MIH (91%). Overall, 71% reported to feel comfortable managing MIH; however, those in private practice only (p = 0.023) and those aged 36 and older (p = 0.011) were less likely to report being comfortable managing MIH. The most commonly cited barrier to care was the child's behaviour, followed by difficulty in achieving local anaesthesia. Composite resin was the most commonly selected material used to restore teeth affected by MIH (84%). In the scenario on cavity design, the results showed a similar number of dentists selected the most conservative and the most aggressive preparation indicating a disparity among choices.

CONCLUSIONS

MIH is frequently encountered by Irish general dentists. The overall wide disparity of responses is in line with other studies, and further highlights the need for the development of strong treatment guidelines and continuing dental education to assist dentists in treatment planning for MIH.

[Cone-beam CT analysis on the treatment efficacy in the vertically impacted maxillary central incisors]

Objective: To analyze the treatment efficacy in the vertically impacted maxillary central incisors using cone-beam CT (CBCT) and explore the treatment timing and the influence of orthodontic traction on the root development and alveolar bone height in the mixed dentition. Methods: Twenty-two patients with vertically impacted maxillary central incisor who were admitted to the Department of Orthodontics, Stomatological Hospital affiliated to Nanjing Medical University from December 2012 to December 2017 were selected [12 males and 10 females, (9.2±0.9) years]. Based on the dental age, patients were classified as early treatment group (teeth ranging from a third to two thirds of root formation, n=12) and late treatment group (teeth with nearly or fully complete root formation, n=10). The contralateral maxillary central incisor was used as the control. Three-dimensional reconstruction of CBCT before treatment, after treatment and one year after treatment was carried out to measure root length, tooth surface area, tooth volume, labial and lingual apical alveolar bone thickness, the loss of labial alveolar bone height and intraosseous root ratio. The clinical crown length was measured in the mouth. The difference values of the measurement variables between the impacted teeth and the control teeth were calculated and analyzed(measurement values of impacted teeth were subtracted from control values). Results: The values of root length difference beween the impacted teeth and the control teeth in the early and late treatment group were (1.58±1.56) mm and (2.57±1.00) mm, respectively after the treatment and the values were significantly less than those corresponding values before treatment [(3.47±1.40) and (3.36±0.79) mm] (P<0.05). After the treatment, the values of the surface area and volume difference between the impacted teeth and the control teeth in the early treatment group [(0±34) mm(2) and (-10±44) mm(3)] were significantly less than those corresponding values before treatment [(38±31) mm(2) and (55±70) mm(3)] (P<0.05). The value differences of any measurement variables between the early and late treatment group were not significantly different after the treatment (P>0.05). The root length and intraosseous root ratio of the impacted teeth after the treatment in the early and late treatment group were significantly less than those of the control teeth after the treatment (P<0.05). The clinical crown length, the loss of labial alveolar bone height of the impacted teeth after the treatment were significantly larger than those of the control teeth after the treatment (P<0.05). Conclusions: Orthodontic traction promoted the root growth and development of the vertically impacted maxillary central incisors. However, the root length and alveolar bone height still cannot reach the normal level after treatment. Treatment timing had no effect on root development and alveolar bone height of vertically impacted maxillary central incisors in mixed dentition.

Predisposing factors for external apical root resorption associated with orthodontic treatment

Objective

This study aimed to identify possible risk factors for external apical root resorption (EARR) in the maxillary incisors after orthodontic treatment.

Methods

The root length of 2,173 maxillary incisors was measured on periapical radiographs of 564 patients who received orthodontic treatment. The Kappa test was performed to evaluate intraexaminer and interexaminer reproducibility. Multiple binary logistic regression was used to determine the association between EARR and various factors. Odds ratios and 95% confidence intervals were reported.

Results

The risk of developing EARR was 70% higher in orthodontic treatment with maxillary premolar extraction (p = 0.004), 58% higher in patients with increased overjet (p = 0.012), 41% lower in two-phase orthodontic treatment (p = 0.037), and 33% lower in patients with deep bite (p = 0.039). The lateral incisors were 54% more likely to develop EARR (p < 0.001), dilacerated roots were 2.26 times more likely to develop EARR (p < 0.001), and for each additional millimeter of root length, the risk of EARR increased by 29% (p < 0.001).

Conclusions

The potential risk factors for EARR after orthodontic treatment included treatment with maxillary premolar extraction, increased overjet at the beginning of treatment, and dilacerated roots.

Regulation of IGF-I by IGFBP3 and IGFBP5 during odontoblast differentiation in mice

OBJECTIVES

Although intracellular signaling pathways of insulin-like growth factor I (IGF-I) related to the proliferation of dental pulp cells have been investigated, the switching mechanism from cell proliferation to differentiation during odontogenesis remains elusive. This study aimed to elucidate the role of IGF binding protein (IGFBP) 3 and 5 in regulation of IGF-I during odontoblast differentiation in mouse incisors.

METHODS

The detailed expression patterns of IGF-I, IGF-I receptor (IGF-IR), IGFBP3, and IGFBP5 together with that of an odontoblast differentiation marker, nestin, were examined by immunohistochemistry and/or in situ hybridization using paraffinized sections of TetOP-H2B-GFP mouse incisors at postnatal 4 weeks.

RESULTS

Undifferentiated dental papilla cells and preodontoblasts (preOB) showed intense IGF-I- and IGF-IRα-positive reactions, and the expression was observed in differentiated odontoblasts, such as immature odontoblasts (iOB) and mature odontoblasts (mOB). IGFBP3/Igfbp3 was transiently expressed in preOB and early iOB, and the intensity of expression gradually reduced with the progression of odontoblast differentiation. In contrast, immunohistochemical analysis for IGFBP5 identified a positive reaction in the undifferentiated dental papilla cells and differentiated odontoblasts, and the expression of Igfbp5 was reduced in the differentiated odontoblasts.

CONCLUSION

The present study demonstrated the expression patterns of IGF-I, IGF-IR, IGFBP3, and IGFBP5 during odontoblast differentiation in mouse incisors. These results suggested that IGFBP3 regulates the transition from the proliferative to differentiation stage by inhibiting the action of IGF-I on the proliferation of dental papilla cells, and that IGFBP5 plays an important role in the maintenance of the differentiated odontoblasts during tooth development.

Differences in the shape and direction-course of the nasopalatine canal among dentate, partially edentulous and completely edentulous subjects

We aimed to analyze the nasopalatine canal shape and anatomical variations of the buccal bone wall and compare the effect of the presence or absence of the central maxillary incisors on the nasopalatine canal. The shape of the nasopalatine canal and the dimensions of the buccal bone wall were measured in 150 patients who underwent a cone-beam computed tomography study. We found that the most prevalent shape of the nasopalatine canal was funnel (31%) and the most common direction-course was slanted-straight (33%). The buccal bone wall in relation to the nasopalatine canal was thickest at the anterior nasal spine level and narrowest at the level of the most anterior-inferior point of the buccal cortex of the maxilla. A statistically significant difference was detected between morphology and direction-course of the nasopalatine canal and dental status. In sum, the study of the nasopalatine canal showed multiple variations. Precise knowledge of these variations may help to decrease the incidence of complications during implantology treatment and during facial and dental surgery.

[Analysis of the discrepancy of crown-root morphology of central incisors among different skeletal malocclusion using cone-beam CT]

Objective: To investigate the discrepancy of crown-root morphology of upper and lower central incisors in adult patients with different skeletal malocclusions using cone-beam CT (CBCT). Methods: Patients visiting the Department of Orthodontics, College of Stomatology, Xi'an Jiaotong University from January 2015 to December 2017 were selected, including 108 cases (52 males, 56 females, aged from 18 to 30 years, mean age 25.8 years). According to CBCT data and cephalometric analysis, 66 patients with average angle were selected as the sagittal skeletal group, including 24 Class Ⅰ patients, 20 Class Ⅱ and 22 Class Ⅲ patients. In the other selected 66 skeletal Class Ⅰ patients including 21 low angle patients, 24 average angle patients (from the sagittal skeletal Class Ⅰ subgroup) and 21 high angle patients. Invivo 5 software was used to locate the CBCT image three dimensionally and then obtain the middle labio-lingual section of right central incisor. Auto CAD 2007 software was applied to measure the angle formed by the long axis of root and the extension line of the long axis of crown (Collum angle), and the angle between the long axis of crown and the lip tangent line passing through the center of the labial surface of crown (labial surface angle). One-way ANOVA and Scheff were used to analyze the discrepancies among classifications and Pearson correlation analysis was used to determine the correlation between the Collum angles and labial surface angles. Results: Significant differences were found in Collum angles and labial surface angles among different sagittal skeletal patterns (P<0.05). The Collum angle of maxillary central incisors in Class Ⅱ patients was 5.18°±4.97° and the average labial surface angle was 17.78°±3.74°, which were both significantly higher than that of maxillary central incisors in Class Ⅰ and Ⅲ subgroups (P<0.05). Similarly, the above two angles of mandibular central incisors in Class Ⅲ were 5.59°±5.64° and 15.32°±3.05°, which were significantly higher than that of mandibular central incisors in Class Ⅰ and Ⅱ subgroups (P<0.05). There was no significant difference among different vertical skeletal patterns (P>0.05). Notably, the Collum angles of maxillary or mandibular central incisors presented significantly positive correlation with labial surface angles (maxillary: r=0.723, P<0.001; mandibular: r=0.752, P<0.001). Conclusions: The long axis of the crown of the maxillary central incisor in skeletal Class Ⅱ patients and the mandibular central incisor in skeletal Class Ⅲ patients are obviously deviated toward the lingual side relative to the long axis of the root, and correspondingly there is a greater labial surface angle of the crown, which indicates that equivalent positioning deviation during bracket bonding can cause greater torque expression error.

The Role of Epithelial Stat3 in Amelogenesis during Mouse Incisor Renewal

The aim of this study was to evaluate the role of epithelial signal transducer and activator of transcription 3 (STAT3) in mouse incisor amelogenesis. Since Stat3 is expressed in the epithelial component of developing and adult mouse teeth, we generated and analyzed Krt14Cre/+;Stat3fl/fl mutant mice in which Stat3 was inactivated in epithelia including ameloblast progenitors and ameloblasts, the cells responsible for enamel formation. Histological analysis showed little enamel matrix in mutant incisors compared to controls. Delayed incisor enamel mineralization was demonstrated using micro-computed X-ray tomography analysis and was supported by an increase in the pre-expression distance of enamel-enriched proteins such as amelogenin, ameloblastin, and kallikrein-4. Lastly, scanning electron microscopy analysis showed little enamel mineralization in mutant incisors underneath the mesial root of the 1st molar; however, the micro-architecture of enamel mineralization was similar in the erupted portion of control and mutant incisors. Taken together, our findings demonstrate for the first time that the absence of epithelial Stat3 in mice leads to delayed incisor amelogenesis.

First Permanent Molars and Permanent Incisors Teeth by Tooth Prevalence of Molar-Incisor-Hypomineralisation in a Group of Spanish Schoolchildren

Background

Molar-incisor-hypomineralisation (MIH) is a disturbance in dental development that commonly involves first permanent molars but permanent incisors may also be compromised. The prevalence of MIH in the literature varies between 2.5% and 40% of the world child population. Little information is gained on the prevalence of MIH among children in Spain.

Aim

The aim of this study was to investigate the prevalence of MIH among school children from Barcelona, Spain.

Material and methods

A cross-sectional study which included 705 children, aged 6 -14 years and 11 months was carried out. Full mouth examinations were performed using the European Academy of Paediatric Dentistry (EAPD) criteria for the diagnosis of MIH.

Results

A total of 56 cases of MIH were found, 22 (39.3%) boys and 34 (60.7%) girls. The prevalence was 7.94% (6.39% for boys and 9.41% for girls). MIH lesions were seen more often in girls than boys (χ² = 4.9, p= 0.023) the male/female ratio being 1:1.54. Upper teeth were more prevalent than lower teeth in both genders with an upper/lower ratio of 1.86/1 for boys and 1.68/1 for girls.

Conclusion

Considered either by gender or by teeth, upper teeth and girls were ahead in our sample.

Modulation of incisor eruption in rats by sympathetic efferents

INTRODUCTION

Intact neural supply is necessary for tooth eruption. Sympathetic denervation accelerates or decelerates the eruption rate depending on the tooth condition (intact or injured). The aim of this study is to reexamine the role of the sympathetic innervation, through the observation of the effects of pre or post ganglionic chemical sympathectomy on the eruption of intact rat incisors.

MATERIALS AND METHODS

Different groups of rats were subjected to either ganglionic or peripheral chemical sympathectomy and the observed effects on incisor eruption were compared to those made on intact/sham groups or on rats subjected to inferior alveolar nerve (IAN) lesion.

RESULTS

The total amount of eruption in control/naïve rats, measured over a total period of 144 h, was 3 ± 0.15 mm and decreased to 2.57 ± 0.06 mm (n = 8; p < 0.01) or 2.8 ± 0.10 mm (n = 8; p < 0.05) following treatment with guanethidine and hexamethonium, respectively. This amount decreased to 1.8 ± 0.14 mm (p < 0.001 vs. control, n = 7; or p < 0.01 vs. sham, n = 5) in rats subjected to IAN lesion.

CONCLUSION

Sympathectomy delayed tooth eruption. Blocking the sympathetic effectors with guanethidine exerted more potent effects than ganglionic block with hexamethonium. Intact sympathetic supply is required for tooth growth under normal conditions.

Plasticity within the niche ensures the maintenance of a Sox2+ stem cell population in the mouse incisor

In mice, the incisors grow throughout the animal's life, and this continuous renewal is driven by dental epithelial and mesenchymal stem cells. Sox2 is a principal marker of the epithelial stem cells that reside in the mouse incisor stem cell niche, called the labial cervical loop, but relatively little is known about the role of the Sox2⁺ stem cell population. In this study, we show that conditional deletion of Sox2 in the embryonic incisor epithelium leads to growth defects and impairment of ameloblast lineage commitment. Deletion of Sox2 specifically in Sox2⁺ cells during incisor renewal revealed cellular plasticity that leads to the relatively rapid restoration of a Sox2-expressing cell population. Furthermore, we show that Lgr5-expressing cells are a subpopulation of dental Sox2⁺ cells that also arise from Sox2⁺ cells during tooth formation. Finally, we show that the embryonic and adult Sox2⁺ populations are regulated by distinct signalling pathways, which is reflected in their distinct transcriptomic signatures. Together, our findings demonstrate that a Sox2⁺ stem cell population can be regenerated from Sox2^- cells, reinforcing its importance for incisor homeostasis.

Mice dental pulp and periodontal ligament endothelial cells exhibit different proangiogenic properties

Dental pulp is a highly vascularized tissue with a high regenerative capacity. This is attributed to its unique blood supply and the presence of progenitor or postnatal dental pulp stem cells. Here we aimed to isolate and compare the angiogenic properties of endothelial cells (EC) prepared from mouse dental pulp and periodontal ligament (PDL). EC were isolated from 4-week-old wild type immorto mice. Mice were sacrificed and after mandible isolation, the molar and incisor teeth and the PDL from molar teeth were dissected. EC were prepared by collagenase digestion of tissues and affinity purification using magnetic beads coated with platelet/endothelial cell adhesion molecule-1 (PECAM-1/CD31) antibody. EC prepared from incisor and molar pulps and PDL were examined for expression of appropriate markers by fluorescence-activated cell sorting (FACS) analysis. The proliferation, migration, and capillary morphogenesis of EC were evaluated. Ex vivo sprouting angiogenesis from various tissues was also compared. Data were analyzed at the level of significance of P<0.05. Pulp EC prepared from incisors proliferated and migrated significantly faster than molar and PDL EC (P<0.05). In addition, molar and PDL EC formed a more extensive capillary network when plated on Matrigel. This is consistent with the lower proliferative and migratory characteristics of these cells compared with incisor EC (P<0.05). However, PDL tissue showed significantly more sprouting area than molar and incisor pulp tissues (P<0.05). Thus, pulp EC from molar and incisor and PDL EC present different proangiogenic properties. Collectively our results suggest that EC from different tooth tissue have unique characteristics related to their target tissue and function.

[Classification of the anatomical structures of maxillary central incisor root by cone-beam CT]

Objective: To examine the root position of the maxillary central incisors and to provide clinical reference before the immediate implant placement. Methods: Cone-beam CT (CBCT) data of the maxillary central incisors of 934 patients (934 incisors) was selected and the root position classsified. The sagittal root position in the alveolar bone was classified as buccal, middle, or palatal. The buccally positoined type was further classified into three subtypes of Ⅰ,Ⅱ, and Ⅲ. Results: Most of the maxillary incisor root (95.4% [891/934]) was positioned buccally. Among the buccal-type incisors, the subtypes Ⅰ, Ⅱ and Ⅲ accounted for 47.5% (423/891), 44.2% (394/891), and 8.3% (74/891). In the 4 mm apical to the cemento-enamel junction and the middle of the root, the thickest buccal bone wall was 0.86 and 0.95 mm, the thickest palatal bone wall was 1.65 and 2.37 mm. In the apical location, the thickest buccal bone wall was 1.89 mm, the thickest palatal bone wall was 7.83 mm. Conclusions: Most of the maxillary central incisors studied are positioned buccally, and half of these patients have adequate buccal bone and are suitable for immediate implant placement.

The Effect of Er:YAG Laser on Entroccocus faecalis Bacterium in the Pulpectomy of Anterior Primary Teeth

Introduction: Successful root canal therapy depends on the complete elimination of microorganisms such as Entroccocus faecalis, which is impossible to achieve with the traditional methods. Lasers are recently introduced as a new method to solve the problem. The present study is planned and performed to examining the antibacterial effect of Er: YAG laser. Methods: Sixty extracted anterior primary teeth were prepared and sterilized. E. faecalis bacterium was cultured in canals. Samples were randomly divided into two groups. The first group was disinfected by NaOCl 5/25% and Er: YAG laser and the second group just by NaOCl 5/25%. Samples of canal contents were cultured and colony counts were calculated. The results were analyzed statistically by SPSS software and Mann Whitney test. Results: There was no significant difference between colony counts in both groups (P=0.142). But the number of colonies in the first group was lower than in the second group. Conclusion: Although, Er: YAG laser cannot completely eliminate E. faecalis bacterium, its simultaneous use with NaOCl decreases E. faecalis.

Presence of dental signs of congenital syphilis in pre-modern specimens

OBJECTIVE

Tooth morphology can vary due to genetic factors, infectious diseases and other environmental stresses. Congenital syphilis is known to interrupt tooth formation i.e. odontogenesis and amelogenesis, producing specific dental characteristics. Variation of those characteristics can occur, resulting in dental signs "not typical" of the disease, however, they are described in the 19th century literature. Past treatments of congenital syphilis with mercury also interrupted dental processes resulting in significantly different dental signs. The aim of this study is to examine the dentition of the oldest (pre 15th century) cases attributed to congenital syphilis to determine whether their dental processes have been affected by either congenital syphilis itself, its treatments (mercury) or a combination of both (syphilitic-mercurial).

DESIGN

Comparisons of dental signs of congenital syphilis and its mercuric treatments as described by Hutchinson, Moon and Fournier in the 1800s and in standardised methods as established by modern studies, are made with the dentition of specimens found in archaeological sites in Mexico, Italy, Turkey and Austria dating back to the Terminal Formative Period, Classical Antiquity, Byzantine times and Middle Ages.

RESULTS

The dentitions of a child from Oaxaca, Mexico, St. Pölten, Austria, and two juveniles from Classical Antiquity site Metaponto, Italy, show signs attributed to syphilis only. One adolescent from Byzantine site Nicaea, Turkey, shows dental signs characterised as syphilitic-mercurial.

CONCLUSIONS

Dental abnormalities observed in Mediterranean individuals match a range of signs attributable to congenital syphilis and its treatments, more so than the New World case. Therefore, it is likely that these individuals suffered from congenital syphilis.

Analysis of the root position of the maxillary incisors in the alveolar bone using cone-beam computed tomography

Purpose

The purpose of this study was to measure the buccal bone thickness and angulation of the maxillary incisors and to analyze the correlation between these parameters and the root position in the alveolar bone using cone-beam computed tomography (CBCT).

Materials and Methods

CBCT images of 398 maxillary central and lateral incisors from 199 patients were retrospectively reviewed. The root position in the alveolar bone was classified as buccal, middle, or palatal, and the buccal type was further classified into subtypes I, II, and III. In addition, the buccolingual inclination of the tooth and buccal bone thickness were evaluated.

Results

A majority of the maxillary incisors were positioned more buccally within the alveolar bone, and only 2 lateral incisors (0.5%) were positioned more palatally. The angulation of buccal subtype III was the greatest and that of the middle type was the lowest. Most of the maxillary incisors exhibited a thin facial bone wall, and the lateral incisors had a significantly thinner buccal bone than the central incisors. The buccal bone of buccal subtypes II and III was significantly thinner than that of buccal subtype I.

Conclusion

A majority of the maxillary incisor roots were positioned close to the buccal cortical plate and had a thin buccal bone wall. Significant relationships were observed between the root position in the alveolar bone, the angulation of the tooth in the alveolar bone, and buccal bone thickness. CBCT analyses of the buccal bone and sagittal root position are recommended for the selection of the appropriate treatment approach.

Dental mesenchymal stem cells

Mammalian teeth harbour mesenchymal stem cells (MSCs), which contribute to tooth growth and repair. These dental MSCs possess many in vitro features of bone marrow-derived MSCs, including clonogenicity, expression of certain markers, and following stimulation, differentiation into cells that have the characteristics of osteoblasts, chondrocytes and adipocytes. Teeth and their support tissues provide not only an easily accessible source of MSCs but also a tractable model system to study their function and properties in vivo In addition, the accessibility of teeth together with their clinical relevance provides a valuable opportunity to test stem cell-based treatments for dental disorders. This Review outlines some recent discoveries in dental MSC function and behaviour and discusses how these and other advances are paving the way for the development of new biologically based dental therapies.

Influence of Light Conditions and Light Sources on Clinical Measurement of Natural Teeth Color using VITA Easyshade Advance 4,0® Spectrophotometer. Pilot Study

OBJECTIVES

The purpose of this study was to evaluate and compare lightness (L), chroma (C) and hue (h), green-red (a) and blue-yellow (b) character of the color of maxillary right central incisors in different light conditions and light sources.

MATERIALS AND METHODS

Two examiners who were well trained in digital color evaluation participated in the research. Intraclass correlation coefficients (ICCs) were used to analyze intra- and interobserver reliability. The LCh and L*a*b* values were determined at 08.15 and at 10.00 in the morning under three different light conditions. Tooth color was assessed in 10 subjects using intraoral spectrophotometer VITA Easyshade Advance 4.0^® set at the central region of the vestibular surface of the measured tooth.

RESULTS

Intra- and interobserver ICC values were high for both examiners and ranged from 0.57 to 0.99. Statistically significant differences in LCh and L*a*b* values measured in different time of the day and certain light condition were not found (p>0.05). Statistically significant differences in LCh and L*a*b* values measured under three different light conditions were not found, too (p>0.05).

CONCLUSIONS

VITA Easyshade Advance 4.0^® is reliable enough for daily clinical work in order to assess tooth color during the fabrication of esthtic appliances because it is not dependent on light conditions and light sources.

Effect of dark discolouration and enamel/dentine fracture on the oral health-related quality of life of pre-schoolers

AIM

To determine the effect of different types of dental trauma on oral health-related quality of life (OHRQoL) among pre-school children.

METHODS

Four hundred fifty-nine Brazilian pre-schoolers aged 3-5 years were submitted to an oral examination in the school environment for the evaluation of dental trauma using the criteria proposed by Andreasen et al. (2007). Parents answered a questionnaire on the OHRQoL of the children using the Early Childhood Oral Health Impact Scale (ECOHIS) and another one on socio-demographic characteristics of the children and their families. The questionnaires were sent to the parents to be answered at home. Descriptive statistics, Mann-Whitney test and Poisson regression were used for statistical analysis.

RESULTS

Children with dark discolouration and enamel-dentine fracture without pulp exposure had higher mean ECOHIS scores than those without these alterations. The multivariate regression analysis demonstrated that pre-school children with dark discolouration (PR 1.79; 95% CI 1.24-2.58) and enamel-dentine fracture without pulp exposure (PR 1.89; 95% CI 1.22-2.92) had a higher impact on quality of life than those without these alterations.

CONCLUSION

Dark discolouration and enamel-dentine fracture without pulp exposure were associated with a negative impact on the life of pre-schoolers.