Effect of occlusal hypofunction on centre of resistance in maxillary central incisor using the finite element method

OBJECTIVES

To determine differences in the location of centre of resistance (Cres) between functional and hypofunctional teeth and to evaluate the relationship between the pulp cavity volume and locations of the Cres, using the finite element (FE) method.

DESIGN

Retrospective cohort study.

PARTICIPANTS

FE models of right maxillary central incisor, derived from cone-beam computed tomography (CBCT) images of 46 participants, were divided into normal function (n = 23) and hypofunction (n = 23) groups using anterior overbite and cephalometric measurements.

METHODS

Measurements of the tooth and pulp cavity volume were made from the CBCT. Cres levels were presented as percentages of the root length from the root's apex. All data were analysed and compared using the independent t-test (P < 0.05). The relationship between the location of Cres and volume ratios were evaluated statistically.

RESULTS

The means of the pulp cavity/tooth volume and root canal/ root volume ratio of the maxillary central incisor in the anterior open bite group were significantly greater than those in the normal group. The average location of Cres in the anterior open bite group was 0.6 mm (3.7%) apically from the normal group, measured from root apex. The difference was statistically significant (P < 0.01). There was a significant correlation between root canal/root volume ratio and locations of Cres (r = -0.780, P < 0.001).

CONCLUSIONS

The Cres in the hypofunctional group was located more apical than the functional group. As the pulp cavity volume increased, the level of Cres shifted apically.

Evaluation of Radicular Dentin Thickness in Maxillary and Mandibular Central Incisor, Canine, and Premolar Teeth

Background This study aimed to compare the radicular dentin thickness in single-rooted maxillary and mandibular anterior and premolar teeth by measuring on four different surfaces (buccal, lingual, mesial, and distal) at three different levels (apical, middle, and coronal). Methods A total of 150 single-rooted human anterior and premolar teeth were included in the present study. The teeth were sectioned at the cemento-enamel junction (CEJ; coronal), 4 mm away from the apex (apical), and the midpoint between these two distances (middle). First, the teeth were divided buccolingually into two parts, and the dentin thickness in the mesial/distal region was measured. Subsequently, both parts were divided again to measure the dentin thickness in the buccal/lingual region. All measurements were recorded, and statistical analysis was performed. Results Apical radicular dentin thickness was significantly less than CEJ (p < 0.001). The maxillary central incisor, maxillary, and mandibular canine exhibited the maximum radicular dentin thickness, whereas the mandibular premolars showed the minimum. Radicular dentin thicknesses on the lingual and buccal surfaces were significantly higher than those on other surfaces (p < 0.001). Conclusion The lowest radicular dentin thickness values were observed in the premolars, especially on mesial and distal surfaces. Considering these areas as danger zones and paying attention during dental procedures are essential to avoid possible complications.

Comparative Analysis of Three Nickel-Titanium Rotary Files in Severely Curved L-Shaped Root Canals: Preparation Time, Aberrations, and Fracture Rates

Background

This simulated study of 30 severely curved L-shaped root canals aimed to compare preparation time, aberrations, width measurements, and fractured files of three nickel-titanium (Ni-Ti) files, namely, ProTaper, ProTaper Next (PTN), and WaveOne (WO).

Methods

Thirty simulated L-curved root canals of resin blocks were randomly divided into three groups. The canals were prepared to a tip size of 25 using ProTaper, PTN, and WO rotary file systems. Pre- and post-operative views for each sample were captured by a professional camera at a standardized distance and position. Blue India ink was injected into the pre-operative canals, and red India ink was injected into the post-operative canals to give a clear superimposition image. Five points were assessed through the halfway of the canal to the orifice (area between the beginning of curvature and apical end point). Preparation time, aberrations, width measurements, and fractured files were recorded and analyzed.

Results

Mean preparation time was longest in ProTaper (4.89±0.68 minutes). PTN and WO were the fastest in preparing the canals (about 3 minutes). A statistically significant difference was found between WO and ProTaper & PTN and ProTaper (p=0.000), while the difference was non-significant (p > 0.05) between WO and PTN. Nine aberrations consisting of three zips, one ledge and one outer widening were related to ProTaper, while WO recorded a ledge and fractured file, but for PTN system, it verified an outer widening and ledge. Only one WO file fractured, with no deformation observed in the other instruments. No significance was recorded among the width measurements in the different levels.

Conclusion

ProTaper next achieved faster cutting than the ProTaper and WO file systems. PTN maintained the best apical termination position and produced the least canal aberration, followed by WO and ProTaper.

Comparative Finite Element Analysis of Endocrowns and Traditional Restorations for Endodontically Treated Mandibular First Molars

BACKGROUND This study evaluated 2 endocrown designs and traditional restoration with a conventional crown using post and core to find the best restoration design for endodontically treated mandibular first molars. MATERIAL AND METHODS Three 3D finite element models were constructed: (1) post and core restoration, (2) endocrown butt joint margin design, and (3) endocrown with shoulder finish line. The intact tooth geometry was extracted with computed tomography, then modified to the selected restoration designs. Bone and mucosa geometry was simplified and represented as 3 cylinders. Two loading cases were examined on E-max crowns as 400N and 200N vertically and 45º oblique, respectively, that were located at buccal cusp tips and central fossa by nodal force distributed on circular areas with 0.5-mm diameter in each location. RESULTS Traditional restoration kept crown deformation and stresses at lower levels than did endocrowns. Results of the butt joint margin design were comparable to that of shoulder finish line design. Cement had the lowest stress values under shoulder finish line design, while the remaining tooth indicated the superiority of butt joint margin design, with less stresses by 20% and 24%, compared with traditional and shoulder finish line restorations, respectively. CONCLUSIONS The 3 tested restoration designs worked well. Although the differences were small, according to stress analysis results, conventional restoration by post and core achieved the best performance, followed by butt joint margin, which ensures lowest level of stresses on dentine. Finally, the shoulder finish line endocrown can replace the other designs but with higher stress levels.

Effect of natural antioxidants on bond strength recovery of resin-modified glass ionomers to the NaOCl-affected pulp chamber dentin

OBJECTIVE

This study evaluated the effect of two natural antioxidants on the compromised bond strength of a resin-modified glass ionomer (RMGI) to the sodium hypochlorite (NaOCl)-affected pulp chamber dentin.

METHODS

Forty-two sound third molars were split into halves. The exposed pulp chamber dentin was ground to provide the flat dentin surfaces and divided into seven groups (n = 12), according to the solutions used for immersion: (1) Control, distilled water; (2) NaOCl, 5.25% NaOCl for 20 min; (3) NaOCl/Ethylenediaminetetraacetic acid (EDTA); 5.25% NaOCl for 20 min + 17% EDTA for 1 min; (4) NaOCl/TA, 5.25% NaOCl + 10% tanic acid (TA) for 5 min; (5) NaOCl/EDTA/TA, 5.25% NaOCl + 17% EDTA + 10% TA for 5 min; (6) NaOCl/PA, 5.25% NaOCl+ 10% proanthocyanidin for 5 min; and (7) NaOCl/EDTA/PA, 5.25% NaOCl+ 17% EDTA + 10% PA for 5 min. The RMGI was bonded on the treated dentin using a Tygon tube. After 24 h of storage, microshear bond strength (µSBS) was tested. Data in MPa were submitted to one-way analysis of variance and Tamhane test.

RESULTS

NaOCl significantly decreased the µSBS; NaOCl/EDTA and NaOCl/TA significantly increased the µSBS, higher than the control group (p < .05); and in the NaOCl/EDTA/TA group, the increased bond strength was at the level of the control group (p > .05). NaOCl/PA and NaOCl/EDTA/PA and NaOCl groups had comparable µSBS.

CONCLUSION

TA could be suggested to provide effective bonding of RMGI and immediate sealing of the pulp chamber dentin after NaOCl irrigation.

Hematological and Biochemical Responses of Newly Formulated Primary Root Canal Obturating Material: An In Vivo Study

Background and objective Any drug or medicinal agent, when implanted into the body, gets biotransformed by various organ systems and the toxic byproducts of this process alter the normal physiological process. In this experimental study, we aimed to quantify the safety of newly formulated primary root canal obturating material by investigating the hematological and biochemical parameters related to liver function. Methodology Forty-eight Wistar rats (weighing 250-350 grams) were classified into three groups (n=16) through random allocation. Preoperative blood samples were collected by puncturing the orbital venous plexus, the values of which were used as control. Zinc oxide eugenol (ZOE), calcium hydroxide iodoform paste (Metapex), and newly formulated triple antibiotic obturating paste (TAOP) were implanted (100 µg) into dorsal connective tissues. Blood samples on the seventh, 15th, and 30th postoperative days were evaluated respectively by analyzing hematological, hepatic, and, renal function tests for acute and chronic inflammatory responses. Results  The intra-group and inter-group comparisons among all the test materials after seven days exhibited high significance in terms of hemoglobin (Hb), mean corpuscular volume (MCV), neutrophils, and serum glutamic-oxaloacetic transaminase (SGOT) (p<0.001), while others showed mixed responses (p<0.05 to p>0.05). After 15 days, the comparisons showed high significance with respect to packed cell volume (PCV), mean cell volume (MCV), and serum creatinine (p<0.001), while others showed significant to nonsignificant differences (p<0.05 to p>0.05). At the end of 30 days, all the parameters showed mixed responses (p<0.001 to p>0.05). Conclusion The newly formulated obturating material TAOP showed lower adverse hematological, hepatic, and renal effects in experimental animals compared to other test materials, with most parameters reverting to normal after 30 days.

Protocols for cleaning the incisor access cavity contaminated with epoxy resin sealer

This study compared different methods for cleaning the sealer-contaminated access cavity of upper incisors. After standard endodontic access, the canals of 50 extracted maxillary incisors were chemomechanically prepared and obturated with gutta-percha and epoxy resin sealer. Teeth were randomly assigned to one of five different pulp chamber cleaning protocols (n = 10): air/water spray, ethanol-saturated cotton pellet (CP), ethanol-saturated microbrush reaching the root filling (MB), MB + air polishing (PROPHYflex; KaVo), or MB + etching with 37% phosphoric acid. Each tooth was split and the sealer-covered area of the pulp chamber was determined on images taken before and after cleaning using image analysis software. The sealer-covered area was compared across groups using one-way ANOVA. Greatest mean sealer-covered area reduction was observed for MB + etching (98.0%), MB + air polishing (95.2%), and MB alone (92.8%), yielding a significantly higher sealer-covered area reduction than after air/water spray (8.3%) and ethanol-saturated cotton pellet (53.4%). The upper incisor access cavity is best cleaned with an ethanol-saturated microbrush reaching up to the root filling, followed by air/water spraying and etching. The use of cotton pellets should be discouraged.

Cleaning efficacy of various root canal irrigants in primary teeth: a scanning electron microscopic study

Root canal irrigation plays an important role in debridement and disinfection of the root canal system. The present study aimed to evaluate the efficacy of 17% ethylenediaminetetraacetic acid (EDTA), 2% iodine-potassium iodide (IKI), and 1% and 3% concentrations of sodium hypochlorite (NaOCl) for root canal irrigation in the anterior primary teeth. A total of 60 anterior primary teeth were selected and assigned to 1 of 4 irrigation groups (n = 15): 1, 17% EDTA; 2, 3% NaOCl; 3, 2% IKI; and 4, 1% NaOCl. The root canals in all groups were subsequently irrigated with normal saline following a 30-minute incubation period. The prepared specimens were cut longitudinally and imaged using scanning electron microscopy to evaluate the cleaning efficacy in the coronal, middle, and apical thirds. Data were analyzed using descriptive statistics as well as nonparametric Kruskal-Wallis and Mann-Whitney U tests. Group 2 (3% NaOCl) showed the greatest efficacy for cleaning the entire root canal (P < 0.01). Analysis of the different parts of the root canal revealed that group 2 also demonstrated the greatest efficacy in achieving a clean apical portion (P < 0.01). According to the results of the present study, 3% NaOCl offered a better performance in irrigating the root canals of primary teeth.

Clinical implications of a diagnosis of taurodontism: A literature review

Taurodontism is a morphological anomaly involving multirooted teeth that is characterized by a vertical shift of the pulp chamber and shortening of the roots. The literature was analyzed to determine the impact of a diagnosis of taurodontism on dental treatment. A total of 85 full-text publications from the years 2005-2021 were analyzed and 20 publications were included in this research. The endodontic treatment of a taurodont tooth is challenging due to the apical displacement of the pulpal chamber floor and the incorrect configuration of the root canal system, or the presence of additional canals. In terms of prosthetics, the use of taurodont teeth as abutments is not recommended as they lack stability due to shorter roots. The extraction of taurodont teeth can be complicated due to an apical shift of the root furcation. In periodontology, taurodont teeth can have a better prognosis as there is less chance of furcation involvement. From an orthodontic point of view, it is important to note that taurodont teeth are not sufficiently embedded in the alveolus and have a greater tendency for root resorption. With regard to genetic diseases, it has been reported that this anomaly can exist as an isolated feature. However, the majority of authors agree that taurodontism is associated with conditions such as Down syndrome, Klinefelter syndrome, cleft lip and palate, hypodontia, amelogenesis imperfecta, and others. From a clinical standpoint, it is very important to diagnose taurodontism before treatment. A diagnosis of taurodontism can be important in the early diagnosis of malformations that commonly occur with this condition.

Micro-Computed Tomography Evaluation of Minimally Invasive Shaping Systems in Mandibular First Molars

The aim of this study was to compare the shaping ability of a modified ProTaper Next technique (PTNm) with that of TruNatomy (TN) in lower molars mesial curved canals using micro-computed tomography (Micro-CT). Sixty mesial canals of first mandibular molars were randomly assigned between two groups (n = 30). After canal scouting with K-File #10, glide path and shaping were carried out with TN or PTNm systems. The PTNm sequence consists of ProGlider, followed by ProTaper Next X1 and apical finishing with NiTiFlex #25 up to working length (WL) to ensure adequate apical cleaning. Samples were scanned using micro-CT and pre- and post-shaping volumes were matched to analyse geometric parameters: the volume of removed dentin; the difference of canal surface; centroid shift, minimum and maximum root canal diameters; cross-sectional areas; the ratio of diameter ratios (RDR) and the ratio of cross-sectional areas (RA). Measurements were assessed 2 mm from the apex and in relation to the middle and coronal root canal thirds. Data were analysed using ANOVA (p < 0.05). No statistically significant differences were found between the groups for any parameter at each level of analysis, except for RA at the coronal level (p = 0.037). The PTNm system showed the tendency to enlarge more in the coronal portion with a lower centroid shift at apical level compared with TN sequence (p > 0.05). Both PTNm and TN sequences demonstrated similar maintenance of original anatomy during the shaping of lower molar mesial curved canals.

Dental students' observations about teaching of endodontic access cavities in a French dental school

INTRODUCTION

Teaching in French universities has undergone deep changes for several years. Dental studies are no exception to the rule. Endodontics is one of the most difficult fields requiring good knowledge of anatomy before performing clinical procedures. The access cavity is the key step of endodontic therapy. The aim of this study was to collect and understand what students feel and expect from theoretical and practical training on endodontic access cavity.

MATERIALS AND METHODS

A questionnaire survey on the teaching and learning of endodontic access cavities in a French dental school was sent by e-mail to the 4th-year students (n = 66). The questionnaire consisted of 13 questions of different formats. Qualitative variables were analysed using a word cloud according to the words of the participants. Students were also asked how to improve teaching with new educational tools.

RESULTS

60 students answered the questionnaire (response rate of 90.9%). When students were asked which stage of endodontic treatment they feared the most, performing access cavity came in 3rd place. Upper molar (71%) and lower molar (58%) appeared to have the most difficult endodontic access cavities. Within the word cloud gathered after students' answers analysis, the words "fear," "perforation," "cavity" and "axis" were highlighted. Amongst the 3 new educational tools proposed to students, most were in favour of realistic models of teeth with their ideal endodontic access cavity (79%).

DISCUSSION

This study highlighted the feelings of students during their hands-on training on endodontic access cavities. Although they seemed satisfied with practical classes on endodontic access cavities, this step seemed to be stressful for students especially because of the great internal anatomical variabilities of teeth. To help them better understand the root canal anatomy and improve their training, students asked for new educational resources, especially macro-models of teeth with their optimal access cavities.

CONCLUSION

This study showed that students are seeking for innovative resources in addition to traditional resources that would make it easier for them to visualise the root canal system and help them feel more comfortable and facilitate learning when performing endodontic access cavities.

Quantitative Analysis of Biofilm Removal Following Instrumentation with TRUShape and Vortex Blue File Systems: Microbiological Study

Mesial roots and isthmuses of mandibular molars are difficult areas to obtain adequate disinfection of root canal walls, and consequently microorganisms can survive treatment. The present study compared, through real-time polymerase chain reaction (qPCR), the effectiveness of TRUShape (TS) (Dentsply Tulsa Dental Specialties, Tulsa, OK) and Vortex Blue (VB) (Dentsply Tulsa Dental Specialties, Tulsa, OK) in removing Enterococcus faecalis (E. faecalis) from the mesial canals and isthmuses of mandibular molars. Fifty extracted human lower molars were inoculated with E. faecalis OG1RF for 14 days, and then an initial bacterial sample was collected with paper points from mesiobuccal and mesiolingual canals and isthmuses. The specimens were randomly divided into four groups (n = 10 teeth; 20 canals each), according to instrumentation system: TS 25/0.06, TS 30/0.06, VB 25/0.06 and VB 30/0.06. The remaining 10 teeth were divided between positive control, inoculated teeth without instrumentation or irrigation, and negative controls, teeth without inoculation. After instrumentation, the final sample was taken using paper points and DNA was isolated. Primers specific for E. faecalis were used for qPCR. The bacterial reduction between pre- and post-instrumentation was calculated. One-way analysis of variance (ANOVA) with Bonferroni's multiple-comparisons tests were for statistical analysis with significance of (p < 0.05). All file systems were able to reduce the load of E. faecalis from the prepared root canals, however, TS size 30 removed significantly more bacteria than size 25. Interestingly, regardless of the size, TS files removed significantly more E. faecalis biofilm (p < 0.05) than did VB files (63.7% vs 50.8% for size 25, and 69.5% vs 56% for size 30). In conclusion, when combined with irrigation, TS file system is more effective than VB in reducing E. faecalis biofilms from mesiobuccal and mesiolingual canals and the isthmuses of mandibular molars.

Finite element analysis of rotary nickel-titanium endodontic instruments: A critical review of the methodology

Finite element analysis has been a valuable research tool for rotary nickel-titanium endodontic files over the last two decades. This review aims to summarise and critique the methodology as used in currently available endodontic literature for finite element analysis of rotary nickel-titanium instruments. An electronic literature research in PubMed and Scopus databases was performed using the appropriate search terms, and the titles and abstracts were screened for relevance. The review revealed an inconsistent approach to the finite element method, particularly with regards to the boundary conditions in which the instruments are tested. Moreover, there is a lack of experimental data to validate in silico findings. A standardised protocol to finite element analysis of rotary endodontic instruments could be considered for future studies.

Relationship between maxillary posterior molar roots and the maxillary sinus floor: Cone-beam computed tomography analysis of a western Chinese population

OBJECTIVE

This study aimed to assess the positional relationships between the maxillary sinus and the first and second molars in a western Chinese population by using cone-beam computed tomography.

METHODS

This study included 212 patients (652 maxillary molars and 1956 roots). Patient demographics (sex and age) and cone-beam computed tomography data regarding the relationship between molar roots and the maxillary sinus were obtained. This relationship was stratified into four types for statistical analysis.

RESULTS

Sex and side did not significantly influence the distance between maxillary molar roots and the maxillary sinus. However, the distance between maxillary molar roots and the maxillary sinus increased with age. The mesiobuccal root of the second molar was nearest to the maxillary sinus. The most common relationship type involved absence of root contact with the sinus border and presence of a maxillary sinus cross-section above the root apex.

CONCLUSIONS

Compared with other teeth, the maxillary posterior teeth have a complex anatomical structure and are closely related to the sinus. These findings may serve as reference information for root canal treatment, tooth extraction, dental implant, and other dental clinical procedures among patients in western China.

Phenotypic and Genotypic Characterization of Streptococcus mutans Strains Isolated from Endodontic Infections

Streptococcus mutans plays an important role in caries etiology and eventually in systemic infections. However, it is often found in infected root canals, but the pathophysiological characteristics of strains residing in this site are largely unknown. Here, we characterized strains of S. mutans isolated from root canals of primary (PI) and secondary/persistent (SI) endodontic infections in relation to serotype and genotype; presence of genes coding for collagen binding proteins (CBPs); collagen binding activity and biofilm formation capacity; ability to withstand environmental stresses; systemic virulence in Galleria mellonella; and invasion of human coronary artery endothelial cells and human dental pupal fibroblasts. Samples from 10 patients with PI and 10 patients with SI were collected, and a total of 14 S. mutans isolates, belonging to 3 genotypes, were obtained. Of these, 13 were serotype c, and 1 was serotype k. When compared with the reference strains, the clinical isolates were hypersensitive to hydrogen peroxide. Remarkably, all 14 strains harbored and expressed the CBP-encoding gene cbm, showing increased binding to collagen, enhanced systemic virulence in G. mellonella, and ability to invade human coronary artery endothelial cells and human dental pupal fibroblasts when compared with CBP-negative strains. Whole genome sequence analysis of PI and SI isolates revealed that these strains are phylogenetically related but genetically distinct from each other. Our findings highlight the importance of CBPs in facilitating colonization and persistence of S. mutans in collagenous substrates such as root canals and their potential role in the pathogenesis of endodontic infections.

Microbial ecology and predicted metabolic pathways in various oral environments from patients with acute endodontic infections

AIM

To assess in a cross-sectional clinical study the effect of antibiotics on the diversity, structure and metabolic pathways of bacterial communities in various oral environments in patients with acute primary infections.

METHODOLOGY

Samples of saliva (SA), supragingival biofilm (SB) and from the pulp cavity (PC) were collected from teeth with acute primary infections and then grouped according to previous use of antibiotics (NoAtb = no antibiotics [n = 6]; Atb = antibiotics [n = 6]). DNA sequencing was conducted using MiSeq (Illumina, San Diego, CA, USA). The V1-V3 hyper-variable region of the 16S rRNA gene was amplified. A custom Mothur pipeline was used for 16S rRNA processing. Subsequent analyses of the sequence dataset were performed in R (using vegan, phyloseq and ggplot2 packages) or QIIME.

RESULTS

Twelve patients aged from 22 to 56 years were recruited. Participants in the Atb group had taken the beta-lactamics amoxicillin (5/6) or cephalexin (1/6) for 2-3 days. A total of 332 bacterial taxa (OTUs) were identified, belonging to 120 genera, 60 families and nine phyla. Firmicutes (41%) and Bacteroidetes (38%) were the most abundant phyla in all samples. Taxa clustered significantly by oral site (PCoA analysis; P < 0.05, ANOSIM). Use of antibiotics had little effect on this clustering. However, SA, SB and PC had different degrees of richness, diversity and evenness. The greatest diversity was observed in SB samples and the least diversity was observed in PC samples. Metabolic prediction identified 163 pathways and previous use of antibiotics had a major effect on the estimated functional clustering in SA and PC samples.

CONCLUSION

The ecological niche had a strong influence on the bacterial content of samples from various oral sites. Previous exposure to antibiotics may exert an effect on the phylogenetic composition of SA. Metabolic pathways appear to be modulated by antimicrobial agents in SA and PC samples. The dynamics of host/microbial interactions in the apical region and the functional ecology of the infected pulp cavity should be revisited.

Comparative Effect of Two Red Lights on Streptococcus mutans Biofilms and Assessment of Temperature Variances in Human Teeth During In Vitro Photodynamic Antimicrobial Chemotherapy

Objective: The goals of this investigation were to compare the effect of photodynamic antimicrobial chemotherapy (PACT) with two different red lights on in vitro Streptococcus mutans biofilms, as well as to assess the temperature variances caused by PACT on human teeth. Methods: S. mutans biofilms (n = 3) were grown on hydroxyapatite disks, and the antimicrobial effect of PACT was evaluated using toluidine blue O (100 μg/mL) associated with Laserbeam^® (LB 56.6 J/cm²) and LumaCare™ (LC -56.6, 158.5, 317.0, and 475.6 J/cm²). Pulpal temperature variances were analyzed using a digital thermocouple placed into the pulp chamber and positioned at the cement-enamel junction level of five teeth samples during irradiation times of 300, 600, and 900 sec for LB, and 22, 60, 120, and 180 sec for LC. The mean average temperature variance was calculated for each group. All data were analyzed through analysis of variance. Results: LB (900 sec) and LC (22 sec) induced similar reductions in the viability of microorganisms. LB did not cause statistically significant increase of temperature, regardless of experimental time, and LC caused temperature increase within the safe spectrum up to 60 sec. Conclusions: PACT seems to be a minimal invasive approach for reducing the viability of cariogenic bacteria. Thus, when applied in vitro for times equal or inferior to 900 and 60 sec for LB and LC, respectively, these light sources might be considered harmless to tooth structures.

Root canal configuration and its relation with endodontic technical errors in premolar teeth: a CBCT analysis

AIM

To evaluate the association between endodontic technical errors and the root canal configuration (RCC) of human premolars, as well as their relationship with periapical lesions through cone-beam computed tomography (CBCT) images.

METHODOLOGY

The sample consisted of CBCT scans belonging to 136 patients, totalling 152 root filled premolars (185 roots). CBCT images were evaluated by two oral radiologists. RCC was recorded according to Vertucci's classification, and the endodontic treatment quality was judged on the presence and type of technical endodontic errors (underfilling, overfilling, nonhomogeneous filling, nonfilled canal, fractured instruments, root deviation and absence of coronal restoration). In addition, the presence of periapical lesions associated with each RCC was recorded. Data were expressed by frequencies and percentages, and intraobserver agreement was calculated using the Kappa test.

RESULTS

The most common RCC was type I (71%), followed by type IV (15%), type II (8%), type V (3%), type VI (1%) and type III (1%). Types VII and VIII were not observed in the sample. Underfilling was the most frequent endodontic technical error for most RCCs, except for types IV, V and 'other', whose most frequent error was a nonfilled canal. The presence of technical errors was greater with an increase in the proportion of the periapical lesions. The intraobserver agreement was excellent.

CONCLUSIONS

There was an increase in the prevalence of endodontic technical errors and in the presence of periapical lesions as the anatomical complexity of the root canals increased. Underfilled and nonfilled canal were the most frequent endodontic technical errors.

Ex Vivo Detection of Apical Delta in Premolars: A Comparative Study Using Periapical Radiography, Cone-beam Computed Tomography, and Micro-computed Tomography

INTRODUCTION

Imaging methods are essential for the correct identification of root canal anatomy, which is a key factor for successful endodontic therapy. This study aimed to evaluate the performance of periapical radiography (PR) and cone-beam computed tomographic (CBCT) imaging in identifying the apical delta (AD) using micro-computed tomographic imaging as the gold standard.

METHODS

PR and CBCT images of 110 human premolars (120 root canals) were obtained using the VistaScan digital intraoral system (Durr Dental, Beitigheim-Bissinger, Germany) and the 3D Accuitomo CBCT unit (J Morita, Kyoto, Japan), respectively. Two oral radiologists assessed the PR and CBCT images for the presence of ADs using a 5-point scale. Additionally, in the CBCT images, the number of apical foramina was also evaluated. The gold standard was established by means of micro-computed tomographic imaging. The diagnostic values related to PR and CBCT imaging were compared using the McNemar test. The detection of the number of foramina was compared using the paired t test (α ≤ 0.05).

RESULTS

ADs were present in 40 root canals (33.3%). Both PR and CBCT images differed significantly from the gold standard (P < .05) in the detection of ADs. CBCT imaging showed higher values than PR for all diagnostic tests (P < .05). Despite the moderate accuracy of PR (0.62) and CBCT imaging (0.73), these methods presented very low sensitivity values (0.07 and 0.35 for PR and CBCT, respectively). CBCT imaging had a tendency of underestimating the number of foramina (P < .05).

CONCLUSIONS

CBCT imaging showed better performance than PR in the detection of ADs; both imaging modalities underestimate its presence when compared with the gold standard. In general, the number of apical foramina cannot be reliably assessed using CBCT imaging.

Oxidative stress in patients with endodontic pathologies

BACKGROUND

Apical periodontitis (AP) is an inflammatory disease affecting periradicular tissues. It is a widespread condition but its etiopathogenetic mechanisms have not been completely elucidated and the current treatment options are not always successful.

PURPOSE

To compare oxidative stress (OxS) levels in the saliva and the endodontium (root canal [RC] contents) in patients with different endodontic pathologies and in endodontically healthy subjects.

PATIENTS AND METHODS

The study group of this comparison study included 22 subjects with primary chronic apical periodontitis (pCAP), 26 with posttreatment or secondary chronic apical periodontitis (sCAP), eight with acute periapical abscess, 13 with irreversible pulpitis, and 17 healthy controls. Resting saliva samples were collected before clinical treatment. Pulp samples (remnants of the pulp, tooth tissue, and/or previous root filling material) were collected under strict aseptic conditions using the Hedström file. The samples were frozen to -80°C until analysis. OxS markers (myeloperoxidase [MPO], oxidative stress index [OSI], 8-isoprostanes [8-EPI]) were detected in the saliva and the endodontium.

RESULTS

The highest MPO and 8-EPI levels were seen in pCAP and pulpitis, while the highest levels of OSI were seen in pCAP and abscess patients, as well as the saliva of sCAP patients. Controls showed the lowest OxS levels in both RC contents and saliva. Significant positive correlations between OxS markers, periapical index, and pain were revealed. Patients with pain had significantly higher OxS levels in both the endodontium (MPO median 27.9 vs 72.6 ng/mg protein, p=0.004; OSI 6.0 vs 10.4, p<0.001; 8-EPI 50.0 vs 75.0 pg/mL, p<0.001) and saliva (MPO 34.2 vs 117.5 ng/mg protein, p<0.001; 8-EPI 50.0 vs 112.8 pg/mL, p<0.001) compared to pain-free subjects.

CONCLUSION

OxS is an important pathomechanism in endodontic pathologies that is evident at both the local (RC contents) and systemic (saliva) level. OxS is significantly associated with dental pain and bone destruction.

Diagnostic Accuracy of Periapical Radiography and Cone-beam Computed Tomography in Identifying Root Canal Configuration of Human Premolars

INTRODUCTION

The aim of this study was to assess the diagnostic accuracy of periapical radiography (PR) and cone-beam computed tomographic (CBCT) imaging in the detection of the root canal configuration (RCC) of human premolars.

METHODS

PR and CBCT imaging of 114 extracted human premolars were evaluated by 2 oral radiologists. RCC was recorded according to Vertucci's classification. Micro-computed tomographic imaging served as the gold standard to determine RCC. Accuracy, sensitivity, specificity, and predictive values were calculated. The Friedman test compared both PR and CBCT imaging with the gold standard.

RESULTS

CBCT imaging showed higher values for all diagnostic tests compared with PR. Accuracy was 0.55 and 0.89 for PR and CBCT imaging, respectively. There was no difference between CBCT imaging and the gold standard, whereas PR differed from both CBCT and micro-computed tomographic imaging (P < .0001). CBCT imaging was more accurate than PR for evaluating different types of RCC individually. Canal configuration types III, VII, and "other" were poorly identified on CBCT imaging with a detection accuracy of 50%, 0%, and 43%, respectively. With PR, all canal configurations except type I were poorly visible.

CONCLUSIONS

PR presented low performance in the detection of RCC in premolars, whereas CBCT imaging showed no difference compared with the gold standard. Canals with complex configurations were less identifiable using both imaging methods, especially PR.

Comparison of apical centring ability between incisal-shifted access and traditional lingual access for maxillary anterior teeth

The aim of this study was to compare the apical centring ability of incisal-shifted access (ISA) with that of traditional lingual access (TLA). Fifteen three-dimensional printed resin models were prepared from the computed tomography data for a human maxillary central incisor and divided into ISA (n = 7), TLA (n = 7) and control (n = 1) groups. After access preparation, these models were shaped to the working length using K-files up to #40, followed by step-back procedures. An apical portion of the model was removed at 0.5 mm coronal to the working length. Microscopic images of each cutting surface were taken to measure the preparation area and the distance of transportation. TLA created a larger preparation area than ISA (P < 0.05). The distance of transportation (mean ± standard deviation) was 0.4 ± 0.1 mm for ISA and 0.7 ± 0.1 mm for TLA (P < 0.05). Access cavity preparation has a significant effect on apical centring ability. ISA is beneficial to maintaining apical configuration.

Clinical effectiveness of basic root canal treatment after 24 months: a randomized controlled trial

INTRODUCTION

The purpose of this study was to investigate the effectiveness of basic root canal treatment (BRT) with tactile working length determination in terms of radiographic and clinical outcome parameters compared with endodontic treatment with standard radiographic working length control.

METHODS

This was a clinical, multicenter, controlled, open-label trial to evaluate BRT effectiveness after 24 months. The primary end point was the apical extension score of the radiographic quality parameter of root canal fillings. The secondary radiographic end point was the periapical index, and the secondary clinical end point was tooth tender to percussion. The safety end point was tooth loss as a consequence of endodontic failure. Statistical analyses of binary and categoric data were calculated using cross tables and the chi-square test.

RESULTS

BRT with tactile working length determination compared with standard radiographic working length control did not significantly differ in terms of radiographic and clinical outcomes after 24 months. The apical extension of the root canal fillings and the periapical anatomic structures showed no significant differences according to radiographic analyses (P = .5). Corresponding results were found in clinical aspects of tooth tender to percussion (P = .6) and tooth loss (P = .7).

CONCLUSIONS

Tactile working length determination in BRT resulted in comparable treatment outcomes compared with standard endodontic treatment with radiographic working length control and turned out to be an accurate method in BRT.

Visibility of dental pulp spaces in dental ultrasound

The purpose of this study was to assess the feasibility of dental ultrasound with conventional sonographic equipment. The teeth of three adult volunteers who had cone beam CT examinations performed previously with clinical indications and one extracted tooth were examined using linear and compact (hockey stick) sonographic probes. The sonographic images were compared with cone beam CT images reconstructed accordingly. Dental pulp spaces were demonstrated in all teeth not covered with prosthetic crowns. The dentin and pulp were best visualized at the level of the neck of the teeth. The dentin was hypoechoic, and the superficial layer comprising the cementum and the pulp spaces were hyperechoic. Dental ultrasound is feasible with general purpose sonographic machines. The buccal surfaces of all teeth are accessible with a compact (hockey stick) probe. Visualization and differentiation of dental pulp spaces, dentin and the superficial layer comprising cementum is possible in the portions of teeth not covered by the alveolar bone or prosthetic crowns. The dental pulp spaces are best seen at the level of the tooth neck. Pulp and endodontic fillings can be distinguished on ultrasound.

Location and dimensions of access cavity in permanent incisors, canines, and premolars

Background:

Ideal access cavity assures unobstructed straight-line access to the apical third of the root canal and preserves tooth structure.

Aim:

The aim of the study was to determine the location and dimensions of access cavity with straight-line access in incisors, canines, and premolars and to evaluate the largest diameter of their root canals in the mesiodistal and vestibulooral direction.

Materials and Methods:

Twenty extracted teeth of each group were randomly selected and digitally radiographed from the mesiodistal and vestibulooral direction. Position of the straight-line access midline in relation to anatomical landmarks (incisal edges, fissures, and cusps) was recorded. The largest diameters in mesiodistal and vestibulooral direction were measured. Relative frequencies of access position and mean and standard deviation of both diameters were calculated.

Results:

For the anterior teeth, the predominant location of straight-line access was from incisal edge, except for maxillary central incisors, where location was equally distributed between incisal edge and oral surface. In mandibular premolars, the straight-line access was positioned vestibular from central fissure. In mesiodistal direction, the largest diameter was found for maxillary central incisors and canines (1.54 mm), while the smallest diameter was found for mandibular incisors (0.64 mm). In vestibulooral direction, the largest diameter was found for maxillary first premolar (5.28 mm), while the smallest diameter was found for maxillary lateral incisor (1.39 mm).

Conclusions:

Knowledge of location and size of access cavity facilitates achieving balance between straight-line access to the apical third of the root canal and preservation of tooth structure.