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.

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.

Does pulp cavity affect the center of resistance in three-dimensional tooth model? A finite element method study.

OBJECTIVES: To compare the center of resistance (Cres) of the maxillary central incisor in models with and without the pulp cavity and to evaluate the association of pulp cavity/tooth volume ratio and difference in Cres position between the two models. MATERIALS AND METHODS: CBCT images of the right maxillary central incisor were collected from 18 subjects. Pulp cavity/tooth volume ratio was measured, and finite element models of teeth and periodontal structures were generated. Cres location was presented as a percentage of root length measured from the root apex. Differences in Cres positions between models were compared using the paired t-test, while the correlation between pulp cavity/tooth volume ratio and a difference in Cres was evaluated by Pearson's correlation coefficient. RESULTS: For the pulp cavity model, the average location of the Cres measured from the apex of the root was 58.8% ± 3.0%, which resulted in a difference of 4.1% ± 1.1% (0.5 mm) apically, when compared with the model without pulp cavity. Differences in Cres between the models were statistically significant (P < 0.01), while the correlation between pulp cavity/tooth volume ratio and a difference in Cres between models was significantly positive (r = 0.709, P = 0.001). CONCLUSIONS: In the pulp cavity model, the Cres was located in a more apical position. The difference in Cres between models increased as the pulp cavity/tooth volume ratio increased. CLINICAL RELEVANCE: The line of force must be applied more apically in the pulp cavity model to achieve the desired orthodontic tooth movement.

Fracture resistance and biomechanical behavior of different access cavities of maxillary central incisors restored with different composite resins.

OBJECTIVES: The aim of this study was to compare the effect of three different access cavities on the tissue removal, deflection, fracture resistance, and stress distribution of extracted maxillary central incisors. MATERIALS AND METHODS: Forty human maxillary central incisors were randomly assigned in four experimental group (n = 10) including conservative access cavity "CAC," traditional access cavity "TAC," invasive access cavity "IAC," and without access cavity (control group). Cone-beam computed tomography "CBCT" scans were used to evaluate the tissue removal during the different access cavities. All specimens were restored with composite resin (Admira Fusion, Voco, Cuxhaven, Germany) and embedded in acrylic resin blocks after simulating the periodontal ligament using red wax, then the specimens were submitted to the deflection test applying a load of 250 N and to the load-to-fracture test after artificial aging in a mechanical cycling machine (150 N, 5 × 106 cycles, 10 Hz). Lastly, stress distribution was assessed by three-dimensional finite element analysis (3D-FEA), simulating the specimens restoration by two types of composite resins of low and high elastic modulus (8 and 18 GPa respectively) after the access cavities. The data were submitted to Shapiro-Wilk and KS normality tests. Then, they were analyzed by one-way ANOVA and Tukey tests with a significance level (α ≤ 0.05). RESULTS: CBCT scans showed a significant difference of worn tissues in CAC and TAC when compared to the IAC (P < 0.0001). In deflection test, CAC showed lower deformation values than the TAC and IAC. Load-to-fracture test presented no significant difference among the three experimental groups (P = 0.6901). 3D-FEA showed that the more conservative the access cavity, the higher the stress magnitude. CONCLUSIONS: CAC promote less worn tissue; however, this does not improve the stress distribution or fracture resistance of endodontically treated maxillary incisors. CLINICAL RELEVANCE: Clinicians should reconsider the pros and cons of the conservative access cavity.

Three-dimensional volumetric evaluation of dental pulp cavity/tooth ratio in anterior open bite malocclusion using cone beam computed tomography.

OBJECTIVES: To assess and compare pulp cavity/tooth volume ratio of maxillary permanent teeth between patients exhibiting anterior open bite malocclusion and those exhibiting anterior normal overbite using cone beam computed tomography (CBCT). MATERIALS AND METHODS: 3D dental images from 44 patients aged between 15 and 29 years were analyzed. The DICOM files of all dental images were imported into an image processing software for calculating pulp cavity volume and tooth volume. Differences of pulp cavity volume, tooth volume, and pulp cavity/tooth volume ratio of each tooth type from both types of occlusions were analyzed using the independent t test. The intra-class correlation coefficient was used to evaluate intra-examiner reliability. RESULTS: The means of pulp cavity/tooth volume ratio in anterior open bite group were significantly greater than those in anterior normal overbite group (central incisor p = 0.001; lateral incisor p = 0.00025 and canine p = 0.004). The means of root canal/root volume ratio in anterior open bite group were significantly greater than anterior normal overbite group (central incisor p = 0.00001; lateral incisor p = 0.00007; and canine p = 0.001), whereas there were no significant differences of the means of pulp chamber/crown volume was observed. CONCLUSION: Anterior open bite malocclusion might lead to an increase of the pulp cavity volume and decrease of the tooth volume due to occlusal hypofunction. CLINICAL RELEVANCE: Orthodontic force should be carefully determined in anterior open bite patient due to the greater root canal volume and lesser root volume.

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.

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.

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.

Detection of Streptococcus mutans in symptomatic and asymptomatic infected root canals.

OBJECTIVES: To investigate the presence of Streptococcus mutans in root canals of symptomatic necrotic teeth (SNT) and their associated acute apical abscesses (AAA) and in the root canals of asymptomatic necrotic teeth (ANT). It also aimed to investigate the presence of the cnm and cbm genes in specimens that harbored S. mutans. MATERIALS AND METHODS: DNA was extracted from samples collected from 10 patients presenting pulpal necrosis associated with radiographic evidence of apical periodontitis (ANT) and from 10 patients in need of endodontic therapy due to the presence of pulpal necrosis (SNT) and AAA. The control group consisted of 10 patients with teeth with normal vital pulp and requiring endodontic treatment for prosthetic reasons. The presence of S. mutans was detected by quantitative real-time-PCR (qPCR) using species-specific primers. Samples harboring S. mutans were further evaluated for the presence of CBP genes by qPCR as well. RESULTS: All studied sites showed a high prevalence of S. mutans, except the control group. Specifically, 60% of ANT and 70% of AAA/SNT paired samples were positive for S. mutans. The cnm gene was detected positive for S. mutans only in ANT samples (66.6%). The cbm gene was not detected in any of the investigated sites. CONCLUSIONS: S. mutans was found in high prevalence in both asymptomatic and symptomatic endodontic infections, including in abscesses, but it was not detected in the root canals of teeth with normal vital pulp. Interestingly, cnm+ S. mutans was only detected in asymptomatic/chronic primary endodontic infections associated with apical lesion. Therefore, it appears that cnm, and possibly other CBPs, may play an underestimated role in chronic endodontic infections. CLINICAL RELEVANCE: A high prevalence of Streptococcus mutans cnm+ gene was detected only in asymptomatic primary endodontic infections associated with apical lesion. Therefore, it appears that this collagen-binding protein gene plays an underestimated role in asymptomatic/chronic endodontic infections.

Pulp volume changes after piezocision-assisted tooth movement: a randomized clinical trial.

BACKGROUND: Orthodontic treatment may result in undesirable side effects, such as root resorption and a decrease in the size of the pulp tissue which could be associated with the duration of the orthodontic treatment. Piezocision-assisted tooth movement was introduced as a minimally invasive surgical procedure to shorten orthodontic treatment time. This prospective randomized clinical trial was aimed to compare the pulp volume changes of maxillary anterior teeth after en-masse retraction with or without piezocision-assisted orthodontics. METHODS: Patients who required orthodontic treatment with bilateral maxillary first premolar extractions and en-masse retraction were recruited. Patients were randomly divided into extraction with piezocision, or only extraction, serving as controls. Pulp volume and root length changes of the maxillary six anterior teeth were measured and compared between the two groups using a 3-Dimensional analytical software. Paired and independent sample t-tests were used to compare within and between groups. Bivariate correlation was done between the mean change in pulp volume and its corresponding root length. The significance level was set at α = 0.05. RESULTS: A total of 23 patients were included, 12 in the piezocision, and 11 in the control group. At the end of the en-masse retraction phase, (mean = 122.74 ± 3.06 days) pulp volume was significantly decreased in all six anterior teeth in both groups (P < 0.01). The decrease in pulp volume was not statistically different between both groups, (P > 0.05). There was a statistically significant but moderate correlation only between the pulp volume change of the right canine and its root length, r = 0.44, P = 0.034. CONCLUSIONS: The effect of piezocision-assisted orthodontic tooth movement on the pulp volume was comparable to the conventional orthodontic treatment. The degree of change in pulp volume does not appear to be related to the amount of root resorption. Trial registration NCT03180151. Registered December 25, 2016, retrospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT03180151 .

Ethnical Anatomical Differences in Mandibular First Permanent Molars between Indian and Saudi Arabian Subpopulations: A Retrospective Cross-sectional Study.

AIM AND OBJECTIVE: The variation in the anatomy of the root canal system has anthropological and demographic significances. The aim of this study was to compare the number of roots, root canals, and internal canal morphology of permanent mandibular first molars between Indian and Saudi Arabian populations. MATERIALS AND METHODS: A total of 523 (255 teeth of Indian sample and 268 teeth of Saudi Arabian sample) mandibular first molar (M1) were included for comparative analysis using cone-beam computed tomography images based on the inclusion criteria. The external and internal morphologies were assessed and compared by trained endodontist and the data was recorded. RESULTS: M1 with three roots were found in 3.9% of the Indian population and 6% of the Saudi population. Overall, high prevalence was observed in two roots (95.0%), three canals (70.4%), Vertucci type IV of the mesial root (56.0%), and Vertucci type I of the distal root (76.7%). Comparison between Indian and Saudi Arabian molars revealed significant differences in relation to the number of canals (p <0.001), Vertucci types of the mesial root (p = 0.008), and Vertucci types of the distal root (p <0.001). Differences between genders for the whole sample revealed significant differences in relation to Vertucci types of the distal root (p = 0.025) with a relatively high male prevalence of type I (54.4%) and type IV (57.1%). CONCLUSION: The predominant parameters of M1 were two roots, three canals, Vertucci type II and IV mesial root configuration, and type I distal root configuration irrespective of both populations. The root canal morphology of Indian and Saudi Arabian populations shares a common trait of Asian origin. CLINICAL SIGNIFICANCE: The likelihood of predicting the complex system of the root canal with marked preference to ethnic identity would be a clinical benefit for the dentist performing root canal treatment. How to cite this article: Mashyakhy M, Vinothkumar TS, Arthisri AS et al. Ethnical Anatomical Differences in Mandibular First Permanent Molars between Indian and Saudi Arabian Subpopulations: A Retrospective Cross-sectional Study. J Contemp Dent Pract 2021;22(5):484-490.

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.

C-shaped canals in mandibular molars of a Brazilian subpopulation: prevalence and root canal configuration using cone-beam computed tomography.

OBJECTIVES: To assess C-shaped root canal configuration by identifying its prevalence and each configuration type proportion, according to tooth (mandibular first or second molar) and demographic characteristics in a Brazilian population, using cone-beam computed tomography (CBCT). Moreover, it was verified if there is a relationship between root canal configuration observed in two-dimensional reconstructions of CBCT and presence of C-shape. METHODS: Mandibular jaw CBCT scans (184 males and 220 females, aged 15 to 80 years), which presented 1464 mandibular molars (710 first molars and 754 second molars), were assessed. Teeth were evaluated for the presence and type of C-shaped root canals by observing the roots at five levels in CBCT axial reconstructions. Root canal configuration was assessed in panoramic reconstructions. Data were statistically analyzed at a significance level of 5%. RESULTS: Of the 1464 mandibular molars, 125 (8.5%) were classified as C-shaped. This variation was more prevalent in females (n = 107, 85.6%) and in second molars (n = 108, 86.4%). C1 (uninterrupted C-shaped canal) was the most prevalent type of C-shaped configuration (41.76%), while C5 (no canal lumen) was the least prevalent type (0.96%). Single root with single canal in panoramic reconstructions was the most predominant configuration for C-shaped teeth (n = 54, 43.2%). Fused roots presented 17.2 higher odds of being associated with C-shaped root canals than non-fused roots. CONCLUSIONS: C-shaped root canals were more prevalent in mandibular second molars and in females. Additionally, clinicians should bear in mind the greater possibility of C-shaped configuration in mandibular molars with fused roots. CLINICAL RELEVANCE: Mandibular molars with C-shaped canals present a clinical challenge. A higher C-shaped proportion was noted in radiographic fused root types, which had 17.2 higher odds of presenting such anatomy when compared to radiographic non-fused roots. Root radiographic features may help in diagnosis of complex C-shaped morphologies.

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.

Prevotella strains and lactamic resistance gene distribution in different oral environments of children with pulp necrosis.

AIM: To determine the presence of Prevotella species, the cfxA/cfxA2, blaZ and blaTEM genes associated with resistance to lactamic agents in different oral niches of children with pulp necrosis. METHODOLOGY: Children with pulp necrosis in primary teeth had samples of saliva, supragingival, pulp chamber and root canal biofilms collected and tested for Prevotella species (P. intermedia, P. nigrescens, P. tannerae) and for beta-lactam resistance genes (cfxA/cfxA2, blaZ and blaTEM). The presence of bacterial DNA was examined through PCR, with a specific primer directed to the 16S rRNA gene. Specific primers were used to detect the Prevotella species and beta-lactam resistance genes. The chi-square test was used to analyse associations between the presence of bacteria and clinical variables. The Cochran's Q test was used to assess whether the proportion of gene detection is the same between different sites. RESULTS: Thirty-two teeth were sampled from 27 patients with a mean age of 5.5 years (±1.76). The total detection rate of Prevotella strains was 29.1%, 25%, 21.8% and 32.29% in saliva, supragingival, pulp chamber and root canal samples, respectively. P. nigrescens was the most commonly detected species in all oral niches. The previous use of antibiotics was associated with detection of P. nigrescens in saliva (P = 0.03). Pain was associated with the presence of P. nigrescens (P = 0.04) and P. tannerae (P = 0.01) in pulp chamber biofilm. blaTEM was detected in the four oral niches, being more frequent (23.8%) in supragingival biofilm (Cochran's Q test, P = 0.04). The presence of P. intermedia in SB and PC was associated with the detection of blaTEM in saliva (P = 0.04). The cfxA/cfxA2 and blaZ genes were not detected in any of the four oral niches. CONCLUSIONS: The oral cavity of children with pulp necrosis had a variable distribution of Prevotella strains in different niches. Saliva, supragingival biofilm, pulp chamber and root canals of primary teeth with necrotic pulps can harbour resistance genes to beta-lactams agents.

Impact of contracted endodontic cavities on fracture resistance of endodontically treated teeth: a systematic review of in vitro studies.

OBJECTIVE: This systematic review was performed to answer the following question: do contracted endodontic cavities (CECs) increase resistance to fracture in extracted human teeth compared to traditional endodontic cavities (TECs)? METHODS: A literature search without restrictions was carried out in PubMed, Science Direct, Scopus, Web of Science, and Open Grey databases. Articles were selected by two independent reviewers. In addition, a reference and hand search was also fulfilled. All included in vitro studies evaluated the influence of CECs on strength to fracture in extracted human teeth and compared to TECs. The quality of the selected studies was evaluated and they were classified as having a low, moderate or high risk of bias. RESULTS: A total of 810 articles were obtained in the electronic search. After the application of the eligibility criteria, reference and hand search, and duplicate removal, six studies were included in this systematic review. All included studies evaluated the influence of CECs on strength to fracture in extracted human teeth and compared to TECs. Characteristics investigated in the selected articles included the sample size and tooth type, access cavity design, filling and restoration procedures, load at fracture test characteristics, and results. The studies demonstrated large variability among the fracture resistance values and standard deviations and low power. Three of the reviewed studies presented low risk of bias and the other three showed medium risk of bias. CONCLUSION: Overall, this systematic review of in vitro studies showed that there is no evidence that supports the use of CECs over TECs for the increase of fracture resistance in human teeth. CLINICAL RELEVANCE: Recently, CECs have gained attention in endodontics due to maximum tooth structure preservation including the pericervical dentin, which could improve the strength to fracture of endodontically treated teeth. However, the influence of access cavity design on fracture resistance remains limited and controversial.

Comparison of frequency of post-obturation pain of single versus multiple visit root canal treatment of necrotic teeth with infected root canals. A Randomized Controlled Trial.

OBJECTIVE: To determine the pain of single versus multiple visit endodontic treatment after obturation in teeth with necrotic pulps and infected canals. METHODS: The randomized controlled study was conducted from January to June 2016 at Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan. Dental patients aged 18-60 years of either gender were selected who were subjected to computer-generated randomisation. Both maxillary and mandibular single rooted teeth till second premolar were included. Single visit endodontic treatment to Group-I subjects was carried out by gaining access to canals, cleaning, shaping and obturation at same visit whereas in Group-II patients, who underwent multiple visits, cleaning and shaping was followed by placement of intra-canal medicament, while obturation was done 5 days later. Patients were recalled within 48 hours after obturation to record the pain score using visual analogue scale.. RESULTS: Of the 60 patients, 30(50%) were in each of the two groups. There was no significant difference in post-operative pain in the two groups (p=0.8). The frequency of post-operative pain was not significant either (p>0.05). The post-operative mean pain score was 2.23±1.736 in Group-I and 2.38±1.94 in Group-II (p=0.8).. CONCLUSIONS: Treatment carried out in single visit or multiple visits showed no difference in pain frequency.

In Vivo and In Vitro Effectiveness of Rotary Nickel-Titanium vs Manual Stainless Steel Instruments for Root Canal Therapy: Systematic Review and Meta-analysis.

INTRODUCTION: This systematic review evaluated the effectiveness of nickel-titanium (NiTi) rotary files compared to stainless-steel (SST) hand files. METHODS: An electronic search was performed on Medline, EMBASE, CENTRAL and Scopus databases up to February 2016. An additional hand searching was performed in 13 journals. The studies were classified according to study type and the outcome variables. Two reviewers independently applied eligibility criteria, extracted data, and three reviewers independently assessed the quality of the evidence of each included study according to The Cochrane Collaboration's procedures. A meta-analysis was performed whenever it was possible. RESULTS: The electronic and hand search strategies yielded 1155 references of studies after removal of duplicates. Four clinical studies (two prospective and two retrospective studies) and 18 in vitro studies (on extracted teeth) were included for the qualitative synthesis after full-text evaluation of the eligible studies. The overall level of methodological quality of the studies included can be considered inadequate. Only one clinical study was judged at low risk of bias, whereas most non-clinical studies had a low risk of bias. Three meta-analyses, based on a very limited number of studies, could be performed. Each meta-analysis contained two studies. Of these, one meta-analysis was based on clinical studies. CONCLUSIONS: The results of this systematic review suggested that NiTi rotary instruments were associated with lower canal transportation and apical extrusion when compared to SST hand files, whereas both groups had similar outcomes in terms of success of therapy, amount of residual bacteria, and cleansing ability after treatment. However, due to the limited evidence available, these results should be interpreted with caution. Consequently, more randomized control trials using standardized protocols are needed in order to provide more solid recommendations.

Age estimation of a sample of Pakistani population using Coronal Pulp Cavity Index in molars and premolars on Orthopantomogram.

The aim of the present study was to assess the validity of tooth-coronal index (TCI) in the age estimation. This retrospective charts review was conducted at the Aga Khan University Hospital, Karachi from January 2016 to March 2016, and comprised 315 teeth of 80 individuals. The teeth were analysed on Orthopantomogram. TCI was calculated for unrestored mandibular premolars and molars. Pearson\\\'s correlation was applied to assess correlation between chronological age and TCI. Besides, 30(37.5%) subjects were male and 50(62.5%) female, and 140(44.4%) teeth were of male subjects and 175(55.6%) were of females. The mean correlation coefficient between chronological age and TCI was -0.27. The highest negative correlation was observed for tooth No.47 in males (r=-0.72) whereas among females the highest negative correlation was noted for tooth No.36 (r=-0.61).There was very weak correlation between age and TCI of a tooth. Therefore, TCI index could not be predictably used for age estimation in the studied population.

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.