How far is the root apex of a unilateral impacted canine from the root apices’ arch form?

Prevalence and characteristics of impacted teeth in Korean orthodontic patients at ten university dental hospitals

Objective

This study aimed to investigate the prevalence and characteristics of impacted teeth (ITs) in orthodontic patients at university dental hospitals in Korea.

Methods

This study included 14,774 patients who visited the Department of Orthodontics at 10 university dental hospitals in Korea between 2020 and 2022 and underwent orthodontic diagnosis. The prevalence and characteristics of ITs were investigated using orthodontic diagnostic records, radiographs, and diagnostic casts.

Results

The prevalence of ITs, excluding third molar impaction, in Korean orthodontic patients was 13.6% (n = 2,014). The prevalence of ITs in pediatric orthodontic patients was 24.5% (n = 1,614). Of these patients, 68.2% had one IT, 27.5% had two ITs, 24.3% had bilateral IT, and 75.7% had unilateral IT. The most frequent IT was the maxillary canine (50.1%), followed by the mandibular second molar (11.7%), and maxillary second premolar (9.6%). An abnormal eruption path (46.5%) was the most frequent etiology. Orthodontic traction after surgical exposure (70.6%) was the most frequent treatment option. Among the patients with ITs, 29.8% had other dental anomalies, such as tooth agenesis (8.7%), microdontia (8.0%), and supernumerary teeth (5.1%). Furthermore, 50.8% had complications such as cystic lesions (18.3%), transposition (17.7%), and root resorption (14.8%). Among the patients with maxillary canine impaction, 62.2% had labial maxillary canine impaction and 21.1% had palatal maxillary canine impaction.

Conclusions

The prevalence of ITs in Korean orthodontic patients at university dental hospitals was high, particularly in pediatric orthodontic patients.

Maxillary basal arch forms in operated adult patients with cleft lip and palate using root apices: A pilot study

OBJECTIVES

The purpose was to identify the maxillary basal arch forms utilizing the root apices and compare the maxillary basal arch form of groups with cleft lip and palate (CLP) and normal group.

MATERIALS AND METHODS

This study included 30 patients (21.8 ± 3.5 years old) with unilateral CLP (ULCP group) and 30 patients (20.9 ± 2.2 years old) with bilateral CLP (BCLP group). The normal group consisted of 30 non-cleft patients (21.2 ± 2.3 years old) with normal occlusion. Three-dimensional (3D) Cartesian coordinates of the root apices of each tooth were determined using cone-beam computed tomography. The 3D coordinates were projected onto the palatal plane to create the 2D coordinates. Thereafter, the basal arch forms were constructed by the Procrustes superimposition. Finally, For the basal arch form comparisons among groups, the inter-root widths were measured.

RESULTS

Both CLP groups had a narrower inter-root width than the normal group. The BCLP group had significantly narrower premolar and molar widths than the UCLP group (P < .05). Especially, the inter-first molar width of the UCLP and BCLP groups was 3.7 ± 0.7 (P < .001) and 6.6 ± 0.8 (P < .001) mm smaller than that of the normal group, respectively.

CONCLUSIONS

We used the root apices to identify the basal arch forms. The basal arch form of patients with CLP was narrower than that of the normal group. The basal arch form of patients with BCLP was narrower than that of patients with UCLP. Our findings may help clinicians better comprehend basal arch forms in patients with CLP and transverse discrepancies.

Comparison of root apex's position between unilateral and bilateral palatally impacted canines: A pilot study

INTRODUCTION

The purpose was to determine whether the location of the root apices of unilateral palatally impacted canines differs from that of bilateral palatally impacted canines using cone-beam computed tomography.

METHODS

The subjects were divided into 3 groups: a bilateral palatally impacted canine group (BPG; n = 28), a unilateral palatally impacted canine group (UPG; n = 28), and a control group (CG; n = 28) that included contralateral normally erupted canines in the UPG. After selecting the root apex in the onDemand3D program, 3-dimensional coordinates were extracted. These 3-dimensional coordinates were converted using the MATLAB program to 2-dimensional coordinates via projection on the palatal plane. Procrustes analysis was used to superimpose these 2-dimensional coordinates. The x- and y-coordinates of the root apices were used to measure the distance between the origin and root apex.

RESULTS

The distance between the root apex of the canine and the origin was 17.43 ± 1.78 mm in BPG, 17.96 ± 1.87 mm in UPG, and 13.96 ± 0.95 mm in CG. There was no statistically significant difference between UPG and BPG. However, there was a statistically significant difference between the CG and impacted groups (UPG and BPG). The same results were found for the x- and y-coordinates.

CONCLUSIONS

The location of the root apices of unilateral palatally impacted canines is similar to that of bilateral palatally impacted. The location of root apices of palatally impacted canines differs from that of normally erupted canines.

Maxillary dimensions and arch shape with palatally displaced canines

BACKGROUND/OBJECTIVES

The aim of this study was to explore the effect of palatally displaced canines on maxillary dimensions and arch shape.

METHODS

Occlusal and skeletal landmarks were plotted on cone beam computed tomography (CBCT) images of 156 orthodontic patients: 78 with palatally displaced canines (PDC) (27 left, 28 right, and 23 bilateral) and 78 controls using Mimics™ (Materialise, Belgium). Arch forms were created, and arch width, depth, and skeletal dimensions were measured. T-test (P < 0.05) was used to compare the groups. Geometric Morphometrics (GM) analysis was used to compare the groups and to explore the pattern of covariation between two sets of landmarks.

RESULTS

The unilateral PDC group showed an increased first premolar, second premolar, molar widths, and an increased molar depth. No significant difference was found in arch form. The skeletal measurements were generally larger in the PDC group, but the transverse measurements were the most significant. Discriminant Function Analysis (DFA) with cross-validation allowed an accurate classification of 85.9% of the control group and 66.7% of the PDC group. The Mahalanobis distance displayed significant differences among three combinations of groups. Strong covariance was found between the second premolar and all other landmarks.

LIMITATIONS

The small sample sizes of the stratified groups precluded recognition of statistical significance.

CONCLUSIONS

Patients with unilateral PDC displayed significantly wider first, second premolar, and first molar widths, and increased first molar depths. There were no significant differences in arch form; however, GM showed significant differences between the groups and a prominent covariance function for the 2nd premolars.

The position and morphology characteristics of multiple impacted anterior teeth in the unilateral maxillary area: A retrospective study based on cone-beam computed tomography

INTRODUCTION

This study investigated the position and morphologic characteristics of multiple impacted anterior teeth in the unilateral maxillary area.

METHODS

Cone-beam computed tomography images of 21 patients (11 males and 10 females; median age 9.42 years [9.08-11.29]) with multiple teeth impacted were collected and imported into Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). The vertical height, crown orientation, twist direction, and root curvature of each impacted tooth were described. The crown length, root length, and root canal width of impacted and homonym teeth were measured.

RESULTS

The positions of the impacted lateral incisors are lower than that of the other 2 anterior teeth. Most crowns of impacted central incisors are positioned distally, labial surfaces in mesial torsion, with most roots, bent toward the distal and labial. Crowns of impacted lateral incisors are positioned mesiolabially, with labial surfaces mostly in distal torsion, and most roots bent toward the mesial and labial. Crowns of impacted canines are mostly positioned mesiolabially, with labial surfaces in mesial torsion. The crowns and roots of the impacted central and lateral incisors were shorter than those of the homonym (P <0.05); however, the difference in crown length is clinically negligible, and there was no difference in root canal widths. There was no difference in the comparison of parameters for the canine group.

CONCLUSIONS

There are certain rules in the vertical height, crown orientation, twist direction, and root curvature of multiple impacted anterior teeth in the unilateral maxillary area. Root development of impacted central and lateral incisors was restricted.

Development of a maxillomandibular arch form based on the center of resistance of teeth using cone-beam computed tomography

INTRODUCTION

Controlling transverse discrepancies is necessary to ensure stable and functional occlusion. Altered molar inclinations can camouflage the transverse relationship. The purpose of this research was to evaluate the maxillomandibular relationship of the center of resistance (CR) of the arch form created by the CR of teeth and compare these CR arch forms by their skeletal patterns.

METHODS

Sixty patients with minor crowding and normal posterior overjet were divided into 3 groups according to ANB angle: skeletal Class I group had ANB angle between 0° and 4° (n = 20), skeletal Class II group had ANB angle >4° (n = 20), and skeletal Class III group had ANB angle <0° (n = 20). The 3-dimensional coordinates of the CR were estimated using cone-beam computed tomography images and projected on the CR occlusal plane to obtain the 2-dimensional coordinates. The CR arch forms were constructed and evaluated using Matlab (MathWorks, Natick, Mass).

RESULTS

On comparing maxillomandibular CR arch form widths, the maxilla was significantly larger than the mandible of the canine and first premolar. The mandible was larger in the first molar of the skeletal Class III group. The maxillomandibular CR arch form width ratios were between 0.97 and 1.35. On comparing maxillomandibular CR arch form areas, the maxilla was significantly larger than the mandible in the anterior segment, and the mandible was larger in the posterior segment. The ratios were between 0.86 and 2.25. In between-group comparison, the skeletal Class III group showed significantly greater arch forms in the mandible.

CONCLUSIONS

CR arch forms had significant maxillomandibular differences throughout the arch. The maxillomandibular ratios could be a reference for site-specific transverse discrepancy analysis.

Three-dimensional changes in root angulation of buccal versus palatal maxillary impacted canines after orthodontic traction: A retrospective before and after study

INTRODUCTION

The aim of this study was to three-dimensionally compare the root angulation changes after orthodontic traction of buccally versus palatally maxillary impacted canines (MICs).

MATERIAL AND METHODS

This retrospective study included patients from a private dental office of both sexes, older than 12 years, with at least one unilateral or bilateral buccal or palatal MIC, no loss of permanent teeth, with complete apical closure at the beginning of traction, and with CBCTs taken at pretreatment (T₀) and after orthodontic traction (T₁). The sample was divided in two groups according to their impaction site: buccal versus palatal. In all the scans, the MIC was segmented and the root angulation changes after traction were evaluated. The assessment included the sigma angle (projected on the XZ plane or coronal tomographic view), the delta angle (projected on the XY plane or axial view) and the epsilon angle (projected on the YZ plane, or sagittal view). Intragroup comparisons were performed with Wilcoxon signed-rank tests. Intergroup comparisons were performed with t-tests or Mann-Whitney U tests. Finally, the influence of MIC characteristics on the measured angles were evaluated with multiple linear regression analyses (α=0.05).

RESULTS

Thirty-three patients (16 men, mean age: 20.38; 17 women, mean age 18.37) with forty-five orthodontically treated MIC (19 buccal versus 26 palatal) were finally included. The palatal MICs showed greater mediolateral uprighting than the buccal MICs, root displacement towards the midsagittal plane, as demonstrated by the sigma angle (palatal group: 37.58±15.08°; buccal group: 29.17±31.15°; P=0.164) and delta (palatal group: -76.90±26.55°; buccal group: -30.56±41.67°; P<0.001)angle changes. The buccal MICs showed greater anteroposterior uprighting, anterior root displacement, as demonstrated by the epsilon angle (palatal group: -4.63±12.37°; buccal group: -25.96±17.79°; P<0.001).

CONCLUSIONS

Mediolateral and anteroposterior root angulation show significant differences after traction between buccal and palatal MICs. Palatal MICs showed greater medial root displacement while buccal MICs showed greater anterior root displacement. This condition should be considered for better planning of traction and orthodontic finishing.

Root dilaceration in maxillary impacted canines and adjacent teeth: A retrospective analysis of the difference between buccal and palatal impaction

INTRODUCTION

This research aimed to analyze the prevalence of root dilaceration in buccally impacted canines (BICs) and palatally impacted canines (PICs) with their adjacent teeth based on a retrospective cone-beam computed tomography (CBCT) investigation.

METHODS

Pretreatment CBCT images of 145 subjects with unilateral maxillary canine impaction and 145 age- and sex-matched subjects without impaction were used. Prevalence of dilaceration (subclassified to root curvature and apical hook based on severity) in canines and adjacent teeth was determined in CBCT records. The root length of maxillary impacted canines was measured for further morphologic evaluations.

RESULTS

Impacted canines had a significantly higher prevalence of root dilaceration than the control group and compared with the erupted contralateral canines in the experimental group (P < 0.001 for both). A significantly higher prevalence of root dilaceration was found in adjacent lateral incisors of the PICs subgroup than that of the control group (P < 0.001). Adjacent premolars had a higher prevalence of dilacerated roots in the PICs subgroup (P < 0.001) than the control group, but not for the BICs subgroup. Significantly higher prevalence of curvature (P < 0.001 for both) and hook (P = 0.008 and P < 0.001, respectively) were found in BICs and PICs roots compared with the control group. Both types of impacted canines had significantly shorter roots than the control group (P < 0.001 for both).

CONCLUSIONS

BICs and PICs have a higher tendency to present root dilaceration and shorter roots. Unlike BICs, adjacent teeth to PICs were more frequently observed to have root dilaceration.

Comparison of maxillary basal arch forms using the root apex in adult women with different skeletal patterns: A pilot study

INTRODUCTION

This study aimed to establish maxillary basal arch forms using the root apices and to determine the differences in the basal arch forms in adult women with different sagittal skeletal patterns.

METHODS

This retrospective study included 91 adult women, with either a Class I (n = 24), Class II Division 1 (n = 22), Class II Division 2 (n = 23), or Class III (n = 22) malocclusion, who underwent cone-beam computed tomography. Three-dimensional coordinates of the root apices were determined using the multiplanar reformation mode of OnDemand3D software (Cybermed Inc, Seoul, South Korea). Two-dimensional coordinates were converted from acquired 3-dimensional coordinates via projection on the palatal plane, and the Procrustes superimposition method was used to build the basal arch form. Finally, interroot width measurements were performed for basal arch form comparisons.

RESULTS

There were significant differences among the 4 groups (P <0.05) with respect to the intercanine width. The intercanine width of Class II Division 1 group was significantly narrower than that of the other groups. The Class II Division 1 and Class II Division 2 groups tended to have tapered arch forms and squared arch forms, respectively.

CONCLUSIONS

We established maxillary basal arch forms using the root apices. The Class II Division 1 group had a significantly narrower intercanine distance. The use of the root apex to depict the basal arch form seems reasonable.

Influence of restoration thickness on the stress distribution of ultrathin ceramic onlay rehabilitating canine guidance: a 3D-finite element analysis

BACKGROUND

The rehabilitation of canine guidance can be performed with adhesive indirect materials, but can the restoration thickness be reduced without mechanical disadvantages? Thus the goal of this study was to analyze the stress of upper canines which received different thicknesses of ceramic fragments for the rehabilitation of the canine guidance using finite element analysis.

METHODS

A superior canine was modeled using a computer aided design software. The dental tissues were individually shaped containing enamel, dentin and periodontal ligament. The following three different ceramic fragment thicknesses were then implemented: 0.3, 0.7 and 1.5 mm. Lithium disilicate was chosen as the ceramic material. The solid geometries were exported to the analysis software. The materials were considered isotropic, homogeneous and linear. The set was submitted to efforts in the incisal third in the palatine face to analyze maximal principal stress, mimicking mandibular lateral movement. The applied load was 100N, and the fixation region was on the medullary bone.

RESULTS

For restoration, the thinner the ceramic, the higher the stress concentration was; while for the adhesive surface of teeth, the thicker the ceramic, the higher the stress concentration.

CONCLUSIONS

The smaller the ceramic thickness was, the lower stress concentration showed at the adhesive interface, while the stress concentration was higher on the restoration intaglio surface.