CBCT assessment of mandibular molar furcation following root canal retreatment using engine-driven instruments.

This study employed e-Vol DXS cone beam computed tomography (CBCT) software to assess dentin remnants in the furcation area of mesial canals in mandibular molars during root canal retreatment (RCR). Four groups (Reciproc®, ProTaper Next®, Race Evo®, Protaper Gold®) were subjected to RCR, and CBCT images were captured before (T1) and after (T2) treatment. Measurements of remaining dentin thickness at 1 mm and 3 mm below the furcation were scrutinized. Results revealed no significant differences in mean thicknesses of mesiobuccal (MB) and mesiolingual (ML) canals at 1 mm and 3 mm from the furcation pre-treatment (T1). Post-treatment (T2) showed analogous findings, with no significant differences in mean thicknesses. However, disparities were found between MB and ML canals at both distances, both before and after retreatment. In essence, the evaluated instruments exhibited safety in RCR, implying that they are appropriate for use in critical areas of mandibular molars without inducing excessive wear. This study underscores the reliability of these instruments in navigating danger zones during RCR, and contributes valuable insights for dental practitioners who handle complex root canal scenarios in mandibular molars.

Molar enamel-dentine junction shape of Pliobates cataloniae and other Iberian pliopithecoids.

The phylogenetic relationships of the small-bodied catarrhine Pliobates cataloniae (∼11.6 Ma, NE Iberian Peninsula) have been controversial since its original description. However, the recent report of additional dentognathic remains has supported its crouzeliid pliopithecoid status. Based on the available hypodigm, the molar enamel-dentine junction (EDJ) shape of P. cataloniae is compared with that of other pliopithecoids from the same basin as well as both extinct and extant hominoids to further evaluate its pliopithecoid affinities. We also quantitatively compare the EDJ shape among these taxa by means of landmark-based three-dimensional geometric morphometrics using principal component analysis (PCA), canonical variate analysis, and between-group PCA. Permutation tests are performed to test whether Pliobates variation exceeds that of extant hominoid genera. Results indicate that Pliobates is similar in molar EDJ shape to other pliopithecoids, particularly crouzeliids. The variation displayed by Pliobates upper molars is less marked at the EDJ level than at the outer enamel surface, probably owing to differential enamel wear and intraspecific differences in enamel thickness. Multivariate analyses of EDJ shape show that all pliopithecoids (including Pliobates) cluster together in the PCAs, canonical variate analyses, and between-group PCAs and occupy a different portion of the morphospaces from extinct and extant hominoids. Posterior and typicality probabilities strongly support the classification of Pliobates as a pliopithecoid, wheras permutation tests fail to reject the single-genus hypothesis for the P. cataloniae hypodigm. We conclude that P. cataloniae is a crouzeliid pliopithecoid, as recently supported by cladistic analyses of craniodental characters, and that previous cladistic results that supported a stem hominoid status are attributable to postcranial convergences with crown hominoids. Our results further highlight the potential of three-dimensional geometric morphometrics analyses of the EDJ shape for better informing fossil primate alpha-taxonomy by means of quantitatively testing hypotheses about tooth shape variation.

Fluctuating arch symmetry: a comparison of two methods of assessment - applicability and efficiency.

INTRODUCTION: Symmetry is balance, some correspondence in the size, form, and arrangements of parts on opposite sides of a plane, line, or point. The opposite of this concept is asymmetry, or imbalance. OBJECTIVE: This retrospective study compared two methods for assessing arch symmetry with linear measurements based on triangles, to determine their applicability and efficiency. METHODS: Two groups were enrolled: children (n=20) and adults (n=20), and the arch symmetry was assessed from linear measurements. Method 1: the incisor-canine (INC), canine-molar (CM), and incisor-molar (INM) distances (paired t-test and Pearson correlation). Method 2: a mathematical equation between the cusps measurements of the canines and the distobuccal of the first molars leading to result 1 (t-test for one sample and bootstrapping analysis). Dental casts were digitized and analyzed using a software program. The Bland-Altman test compared the methods (α=0.05). RESULTS: The Bland-Altman test revealed concordance between the methods; however, separately the results were different: In method 1, the mandibular arch did not demonstrate correlation (children, INC r=0.33; CM r=0.45; INM r=0.51; adults, CM r=0.46; INM r=0.35), however, the maxilla revealed a strong correlation in children and a strong/moderate correlation in adults. In method 2, both arches were symmetrical (p>0.05). CONCLUSION: Method 1 may be appropriate during orthodontic treatment, and method 2 may be indicated for final treatment. These methods are useful; however, only method 1 identified the side of asymmetry. The methods can contribute to future studies in syndromic and non-syndromic patients, before and after orthognathic surgeries and orthodontic treatment, comparing results.

Cone beam computed tomography analysis of the root and canal morphology of the maxillary second molars in a Syrian subpopulation.

AIM: To investigate the root number and morphology of the maxillary second molars in the Syrian population besides bilateral symmetry, and the effect of gender. METHODS: 250 Cone Beam Computed Tomography (CBCT) images (140 females, 110 males) were examined by two endodontists. The detailed analysis included the number of roots, the number of canals and their configurations, bilateral symmetry, and relation to gender. The evaluation was made according to Vertucci classification by analyzing the CBCT images at all levels (Axial, Coronal, Sagittal, Oblique, and 3D). The Chi-square statistical analysis was performed to compare the canals' morphologies and bilateral symmetry in both genders via SPSS. RESULT: The most common shape of the upper second molars is three roots (90.4%). There were significant differences between males and females regarding the symmetry of the number of roots (P < 0.05). The root canal configuration was mainly Vertucci type I classification in the Distobuccally (93.4%) and palatal root (99.6%). The most common type in the mesial root was type I (29.5%), showing all varieties of Vertucci classifications (except VII, and VIII) percentage of MB2 of 70.5%. The ratio of symmetry was (59.6%) with no significant statistical difference between the genders (P = 0.708). CONCLUSION: Most maxillary second molars in the examined Syrian population were types (II) (associated with MB2 cases with three roots and four canals). In terms of symmetry, the number of roots surpassed the canal configuration. Males had a greater symmetrical tendency in the number of roots than females.

Position and frequency of lateral canals in carnassial teeth of dogs.

Carnassial teeth, as one of the most important teeth in dogs, are commonly affected by different types of injuries and pathological disorders, which require endodontic treatment. Lateral canals, which leave the main root canal, and apical deltas are present in the root canal system of dogs. These canals represent small branches that leave the main root canal at a sharp angle and terminate in a region of the periodontal ligament on the external root surface. In this study, 200 teeth were included, of which 100 were superior fourth premolars and 100 were inferior first molars. Lateral canals were present in a total of 30 roots of superior fourth premolar teeth, whereas in inferior first molars, these canals were found in 3% of roots. In superior fourth premolars, lateral canals were mostly present in the apical third, 86%, while 14% were present in the middle third of the root. In inferior first molars, lateral canals were found in 3% of the roots, 2% in the apical third and 1% in the middle third of the roots. The knowledge of the complex root canal morphology is essential for any endodontic treatment. Due to the presence and frequency of lateral canals, it is imperative to perform more thorough cleaning and instrumentation while performing endodontic treatment on superior fourth premolars compared to inferior first molars.

Testing the patterning cascade model of cusp development in Macaca fascicularis mandibular molars.

OBJECTIVE: Molar crown configuration plays an important role in systematics, and functional and comparative morphology. In particular, the number of cusps on primate molars is often used to identify fossil species and infer their phylogenetic relationships. However, this variability deserves renewed consideration as a number of studies now highlight important developmental mechanisms that may be responsible for the presence of molar cusps in some mammalian taxa. Experimental studies of rodent molars suggest that cusps form under a morphodynamic, patterning cascade model of development (PCM) that involve the iterative formation of enamel knots. This model posits that the size, shape and location of the first-forming cusps determines the presence and positioning of later-forming cusps. DESIGN: Here we test whether variation in accessory cusp presence in 13 Macaca fascicularis mandibular second molars (M2s) is consistent with predictions of the PCM. Using micro-CT, we imaged these M2s and employed geometric morphometrics to examine whether shape variation in the enamel-dentine junction (EDJ) correlates with accessory cusp presence. RESULTS: We find that accessory cusp patterning in macaque M2s is broadly consistent with the PCM. Molars with accessory cusps were larger in size and possessed shorter relative cusp heights compared to molars without accessory cusps. Peripheral cusp formation was also associated with more centrally positioned primary cusps, as predicted by the PCM. CONCLUSIONS: While these results demonstrate that a patterning cascade model is broadly appropriate for interpreting cusp variation in Macaca fascicularis molars, it does not explain all manifestations of accessory cusp expression in this sample.

Comprehensive Analysis of Mandibular First Molar Root and Canal Morphology in Saudi Patients Using Cone Beam Computed Tomography (CBCT).

BACKGROUND The goal of conventional endodontic therapy is to clean the root canal system thoroughly, restore tooth function, and prevent re-infection. Success depends on understanding root canal morphology, resolving apical periodontitis, and using proper techniques. Studies highlight variations in root canal anatomy, with cone-beam computed tomography (CBCT) being crucial for accurate diagnosis despite its high cost and limited availability. MATERIAL AND METHODS This retrospective study reviewed CBCT images of 1820 (907 male, 913 female) patients aged 18 to 78 years. Analysis included 2081 mandibular first molars for variations in root and canal morphology and right- and left-side symmetry. Inter-orifice distance was measured, along with distance from the cementoenamel junction (CEJ) to the level of canal bifurcation. RESULTS In this study, 96.01% of teeth had 2 roots and 3.89% had 3 roots. The percentages of canal configuration were 77.70% for 3 canals, 21.58% for 4 canals, 0.67% for 2 canals, and 0.05% for 1 canal. The inter-orifice distance was 2.07 mm for 2 canals in 1 root and 2.86 mm for 2 canals in separate distal roots. Distance from the CEJ to canal bifurcation varied significantly between 2 canals within 1 distal root (3.35 mm), 2 canals in separate distal roots (1.60 mm), as well as between distal (3.35 mm) and mesial roots (1.10 mm). CONCLUSIONS In mandibular first molars, only 3.89% have additional distolingual roots. Sex and ethnicity showed no influence on number of roots and canals. Distal canals showed a deeper bifurcation and greater inter-orifice distance than did mesial canals.

[Transverse characteristics of normodivergent patients in different sagittal skeletal patterns].

PURPOSE: This study aimed to measure and analyze the transverse indicators of normodivergent patients with different sagittal skeletal malocclusions, to explore the transverse characteristics of different sagittal skeletal malocclusions. METHODS: Lateral cephalograms and CBCT of 90 normodivergent patients with skeletal Class Ⅰ, Ⅱ and Ⅲ in their permanent dentition were collected. Dolphin software was applied to measure the widths of the basal bone, alveolar bone, dental arch and buccolingual inclination angle of the corresponding teeth in the maxillary and mandibular canine, premolar and molar areas. SPSS 22.0 software package was applied for statistical analysis of the data. RESULTS: The widths of the mandibular basal bone in canine, premolar and molar areas of skeletal Class Ⅲ were (27.15±2.74), (39.30±2.82) and (59.97±2.93) mm, respectively. The widths of the mandibular alveolar bone of skeletal Class Ⅲ were (25.38±1.78), (34.51±2.28) and (47.72±2.73) mm, respectively. The dental arch widths of the maxillary premolar and mandibular canine areas of skeletal Class Ⅲ were (48.70±2.35) and (30.69±2.31)mm, respectively. The above data of skeletal Class Ⅲ were significantly larger than those of skeletal Class Ⅰ and Ⅱ(P＜0.01). The dental arch widths of the maxillary canine, maxillary molar and mandibular molar areas of skeletal Class Ⅲ were (38.88±1.90), (59.51±3.40) and (56.01±2.86)mm, respectively, which were significantly larger than those of skeletal Class Ⅱ(P＜0.05). The maxillomandibular width difference of basal bone in the canine, premolar and molar areas of skeletal Class Ⅲ were (4.69±2.84), (2.31±2.39) and (3.27±2.05) mm, respectively, which were significantly less than that of skeletal Class Ⅰ and Ⅱ(P＜0.01). Compared with skeletal Class Ⅰ, the maxillary canines and first molars of skeletal Class Ⅱ had larger lingual inclination level, while the maxillary first premolars and first molars of skeletal Class Ⅲ had larger buccal inclination level, the mandibular canines and the mandibular first premolars of skeletal Class Ⅲ had larger lingual inclination level(P＜0.01). CONCLUSIONS: For normodivergent patients, the width of the mandibular base bone, alveolar bone, and maxillary and mandibular dental arch in skeletal Class Ⅲ is the widest, which is more likely to have width discrepancy in basal bone. In skeletal Class Ⅲ, the maxillary teeth are buccally inclined, and the mandibular teeth are ingually inclined. In skeletal Class Ⅱ, the maxillary teeth are lingually inclined, and the mandibular teeth are compensatory upright.

Variations in the alveolar bone morphology in maxillary molar area: a retrospective CBCT study.

BACKGROUND: This study quantitatively analyzed the anatomic structure of the alveolar bone in the maxillary molar region at three potential locations for Temporary Anchorage Device (TAD) placement. Additionally, the study compared the variability in this region across different age groups, sagittal skeletal patterns, vertical facial types, and sexes. METHODS: In this retrospective cone-beam computed tomography study, the buccal alveolar bone was analyzed in the posterior molar area of 200 patients, the measurement items include buccal alveolar bone height, alveolar bone thickness, interradicular distance, and maxillary retromolar space. RESULTS: Buccal alveolar height was greatest in the U56 region. The interradicular space was largest in the U56 region and increased from the alveolar crest to the sinus floor. Buccal alveolar bone thickness was highest in the U67 region and generally increased from the alveolar crest to the sinus floor. The maxillary retromolar space gradually increased from the alveolar crest to the root apex. CONCLUSIONS: TADs are safest when placed in the buccal area between the maxillary second premolar and the first molar, particularly at the 9 mm plane. The U67 region is the optimal safe zone for TAD placement for maxillary dentition distalization. TADs placement in adolescents can be challenging. Maxillary third molar extraction can be considered for maxillary dentition distalization.

Marginal Gingival Thickness Assessment in Three- To Six-Year-Old Preschool Children.

Purpose: Although gingival thickness has been extensively studied in permanent dentition, the literature regarding marginal gingival thickness in primary dentition is insufficient. The purpose of this study was to assess the variations in marginal gingival thickness in preschool-age children. Methods: A cross-sectional study of 4,109 primary teeth was conducted. Using a reamer, the transgingival probing method was employed to assess marginal gingival thickness in healthy preschoolers. Inter-examiner and intra-examiner reproducibility were assessed via the intraclass correlation coefficient. Results: Descriptive statistics revealed that primary maxillary left second molars had the highest mean marginal gingival thickness (1.06 mm), whereas primary mandibular right central incisors had the lowest mean marginal gingival thickness (0.74 mm). Gender-based independent sample t-tests revealed significant differences in the values of primary maxillary right canines (females had greater values than males; P=0.03) and primary mandibular right first molars (males had greater values than females; P=0.01). An inter-arch comparison revealed significant differences between the primary second molars (maxillary more than mandibular; P=0.001). Conclusions: This study reports the first documented marginal gingival thicknesses of primary dentition. It reveals substantial variations in the values of primary maxillary right canines and primary mandibular right first molars and between primary maxillary and mandibular second molars.

Evaluation of the pit and fissure system in primary and permanent molars with micro-computed tomography and 3D printing.

This study aimed to characterize the anatomical and physiological features of pits and fissures in primary and permanent molars by microtomographic (micro-CT) examination and three-dimensional (3D) printing. The occlusal surfaces of 84 primary molars and 60 permanent third molars were examined. The samples were scanned with micro-CT and the occlusal surface separated. The areas of the crown, its occlusal part, and fissures and pits were calculated. Digital impression of the occlusal surface was created and 3D printed. The frequency of different fissure types was determined by direct observation. Data were subjected to statistical analysis using Mann-Whitney U Test and chi-square test (p < 0.05). There was statistically significant difference between the ratio of occlusal surface and the crown area for the molars in primary and permanent dentitions (24.78% and 28.85% respectively, p < 0.05). In terms of the percentage ratio of the fissure area to the occlusal surface (24.24% and 22.30%) and the fissure area to the crown (6.02% and 6.52%), no significant difference was observed (p > 0.05). V-shaped fissures were predominant in both primary and permanent teeth, with a higher occurrence in primary dentition (59.48%, p < 0.05). Permanent molars exhibited a higher prevalence of I-type and U-type fissure configurations compared to primary molars (p < 0.05), with I-type fissures being the least common in primary molars. In both dentitions there was no statistically significant difference in the prevalence of IK-configuration (p > 0.05). The fissure depth was significantly greater in permanent molars than primary molars (p < 0.05). In conclusion, this study revealed remarkable diversity in fissure morphology among primary and permanent molars.

Anatomical relationship between maxillary posterior teeth and the maxillary sinus in an Indonesian population: a CT scan study.

BACKGROUND: The anatomical proximity between the root apex of the maxillary posterior teeth and the maxillary sinus can lead to complications, including odontogenic maxillary sinusitis. While several studies have investigated similar variables in different populations, there is limited research on the Indonesian population. This study aimed to describe the anatomical position of the maxillary posterior teeth in relation to the floor of the maxillary sinus using CT scans. METHODS: A total of 122 patients (432 maxillary premolars and 1,282 maxillary molars) underwent CT scans to evaluate 1,711 roots. The vertical relationship between the root apex of the maxillary posterior teeth and the maxillary sinus was classified into three types: IS (inside sinus), CO (sinus contact), and OS (outside sinus). RESULTS: The IS type was predominantly found in the palatal roots of the first molars, accounting for 20% of the total roots in this type. The CO type was most frequently observed in the mesiobuccal roots of the second molars, representing 18% of the total roots in this type. The OS type was most commonly found in the first premolar, comprising 20% of the total roots in this type. CONCLUSIONS: The palatal roots of the first molars exhibited the highest frequency of proximity to the maxillary sinus. CT scans can effectively assess the relationship between the root apex of the posterior teeth and the maxillary sinus. CLINICAL RELEVANCE: Clinicians should consider this information comprehensively when planning treatments for maxillary molars.

Credibility of Pont's index in Egyptian population.

BACKGROUND: Many indices have been suggested to help orthodontists in predicting the ideal dental arch width. One of these was Pont's index which was established by Pont. He suggested equations to predict the ideal maxillary dental arch width (interpremolar and intermolar) from the combined mesiodistal width of the maxillary incisors. This study aimed to test the applicability of Pont's index as an orthodontic diagnostic tool in Egyptian population and to compare the results with those obtained from studies of different ethnic subjects. METHODS: This study was performed using dental casts of 184 Egyptian individuals (82 males and 102 females; age range, 19-24 years). The casts were divided into 46 casts with normal occlusion, 46 casts with class I, 46 casts with class II and 46 casts with class III malocclusion, according to Angle's classification. Alginate impressions were taken for all patients and poured immediately using dental plaster. The real models were transformed into digital models using three-dimensional laser scanner to allow digital model analysis. Predicted arch widths were calculated using Pont's equations. The predicted values were compared to the measured values. RESULTS: Intra class correlation coefficient (ICC) (absolute agreement) between measured and predicted arch widths was determined. Poor absolute agreement was found between measured arch width values and the corresponding values calculated according to Pont's index. CONCLUSION: According to the results of this study, Pont's index is not a reliable method for predicting the ideal dental arch widths in Egyptian populations.

Morphological study of distal furcation in mandibular first molars based on cone beam computed tomography images in Beijing population.

OBJECTIVES: This retrospective study explored the incidence of independent distal-lingual root (DLR) in mandibular first molars and the morphologic features of distal furcations through cone beam computed tomography (CBCT) in Beijing population. METHODS: A total of 401 CBCT images of both mandibular first molars existed were included. The sex of the patients, the incidence of DLR, the distal root trunk length (DRT), the locations of distal furcation entrance (DFE), and the separation angle of distal furcation (ADF) were recorded. RESULTS: The incidence rates of DLR were 33.2% on the subject level and 26.8% on the tooth level. The incidence of DLR was not different between genders but was higher on the right sides. The DRT values were 4.15 mm±1.02 mm. The ADF was 65.56°±11.56°. The DFE was located lingually, and 97.2% DFE was located more apically than buccal/lingual furcations. CONCLUSIONS: A high incidence of DLR was found in the Beijing population. The DRT was longer than buccal and lingual sites. The DFE was located lingually with a wide separation. Understanding the morphological features of distal furcation can help clinicians to make proper treatment plans.

Radiographic evaluation of enamel thickness of permanent teeth: relevance and applicability.

OBJECTIVE: This descriptive observational study aimed to determine clinically relevant and applicable data of enamel thickness (ETH), considering the mesio-distal differences of anterior and posterior permanent teeth and their relationships. MATERIAL AND METHODS: The sample consisted of right-sided standardized radiographs of 34 individuals (21 females and 13 males), aged between 13 and 24 (average 16) years, with all permanent teeth intact and without crowding. Four periapical and four interproximal radiographs were obtained and digitized. ETH measurements (mesial to distal contact points at the dentin-enamel junction) were performed after correction for radiographic image magnification. The Students' t-test was applied to the differences between paired means, with the Pearson correlation to evaluate the correlation between them. RESULTS: The mesial and distal ETH increased from the anterior to the posterior teeth. Incisor ETH ranged between 0.60 and 0.84 mm. Canines, premolars, and molars were more than 1.0 mm thick, and molar enamel reached values between 1.26 and 1.44 mm. CONCLUSION: Distal ETH was significantly greater than the mesial ETH, and progressively thicker from the anterior to posterior teeth. Interproximal reduction (IPR) of the lower central and upper lateral incisors should be avoided, reduced, or performed on their distal surfaces. There is a positive and significant correlation between ETH and the mesial and distal surfaces of the teeth. Periapical radiographs and evaluation of the remaining ETH are necessary in cases of retreatment. The location and number of tooth size discrepancies should be considered in treatment planning and appropriately compensated with IPR.

Morphological and morphometric study of the hominin dental casts from Grotta-Riparo di Uluzzo C (Apulia, southern Italy).

OBJECTIVES: Grotta-Riparo di Uluzzo C (Apulia, southern Italy) is a pivotal site for investigating the evolution of the Middle Paleolithic and the earliest phases of the Upper Paleolithic in southern Italy, as the extensive stratigraphic record of this site includes a thick Mousterian sequence followed by the Uluzzian. Here, we investigate the taxonomic affinity of seven unpublished deciduous human teeth retrieved from the site of Uluzzo C in 1960. MATERIALS AND METHODS: The teeth are represented by seven plaster dental casts, which are housed at the Museo Civico di Paleontologia e Paletnologia in Maglie (Lecce, Apulia). The location of the original specimens remains unknown, rendering these casts the only human remains evidence yielded by Uluzzo C to date. Based on occlusal-view photographs and digital models of the casts, we examined the external morphology and morphometry of the teeth, comparing them to Homo sapiens and H. neanderthalensis samples. Through geometric morphometric methods and statistical analyses, we analyzed the crown outline of the deciduous molars. RESULTS: The teeth show morphological and morphometric features that are variably found in H. neanderthalensis, H. sapiens, or both. Specifically, crown outline analysis shows that all molars fall within H. neanderthalensis variability, except for Uluzzo 853 (lower right deciduous first molar), which falls within H. sapiens variability. DISCUSSION: This study provides the first taxonomic assessment of the hominin teeth from Uluzzo C. The results contribute additional insights into the Paleolithic peopling of southern Italy during a crucial period marked by the persistence of post-Tyrrhenian Neanderthal techno-complexes and the arrival of H. sapiens.

Dental topography of prosimian premolars predicts diet: A comparison in premolar and molar dietary classification accuracies.

OBJECTIVES: This study tests whether (1) premolar topography of extant "prosimians" (strepsirrhines and tarsiers) successfully predicts diet and (2) whether the combination of molar and premolar topography yields higher classification accuracy than using either tooth position in isolation. MATERIALS AND METHODS: Dental topographic metrics (ariaDNE, relief index, and orientation patch count rotated) were calculated for 118 individual matched-pairs of mandibular fourth premolars (P4) and second molars (M2). The sample represents 7 families and 22 genera. Tooth variables were analyzed in isolation (P4 only; M2 only), together (P4 and M2), and combined (PC1 scores of bivariate principal component analyses of P4 and M2 for each metric). Discriminant function analyses were conducted with and without a measure of size (two-dimensional surface area). RESULTS: When using topography only, "prosimian" P4 shape predicts diet with a success rate that is slightly higher than that of M2 shape. When absolute size is included, premolars and molars perform comparably well. Including both premolar and molar topography (separately or combined) improves classification accuracy for every analysis beyond considering either in isolation. Classification accuracy is highest when premolar and molar topography and size are included. DISCUSSION: Our findings indicate that molar teeth incompletely summarize the functional requirements of oral food breakdown for a given diet, and that the mechanism selecting for premolar form is more varied than what is expressed by molar teeth. Finally, our findings suggest that fossil P4s (in isolation or with the M2) can be used for meaningful dietary reconstruction of extinct primates.

Dentoalveolar bone height in Class I adults with different vertical patterns: A cross-sectional study.

BACKGROUND: Facial divergence during growth and development affects both the anterior and posterior alveolar bone dimensions in the maxilla and mandible, and the dentoalveolar compensation mechanism in severe vertical skeletal discrepancies remains unclear. AIMS: To evaluate the: (1) difference in dentoalveolar heights among subjects with different vertical facial patterns; (2) association between the dentoalveolar bone height and other cephalometric variables; (3) effect of sex on dentoalveolar height measurements. MATERIAL AND METHODS: Non-growing subjects with skeletal Class I (0°

Assessment of the Shaping Ability of R-Motion 30 .04 and 25 .06 in Mesial Canals of Mandibular Molars Based on Automated Computational Measurement.

INTRODUCTION: The aim of this study was to evaluate changes in geometry following root canal preparation using R-Motion instruments with different apical sizes and tapers. METHODS: Fifty-four mesial canals of mandibular molars with single curvature of angles ranging between 20° and 30° were stratified into 3 groups according to their internal anatomy (R-Motion 25/.06, 30/.04, Reciproc Blue) (n = 18 per group). Micro-computed tomography was used to standardize the samples before instrumentation and, after instrumentation, to assess canal transportation, changes in canal volume and centering ability. Canals were irrigated with 17% EDTA and sodium hypochlorite, and the final rinse included subsonic agitation of these solutions. Measurements were analyzed automatically using the Dragonfly software (Come, Montreal, Canada) and were confirmed by a technician and an endodontist, based on a previously validated methodology. The results were analyzed using the Kruskal-Wallis's and Mann-Whitney's tests. The level of statistical significance was set at 5%. RESULTS: Significant differences were found in the coronal third for canal transportation, with Reciproc Blue R25 having greater values compared with both R-Motion instruments (P < .05) and greater changes in volume when compared with R-Motion 30/.04 (P < .05). CONCLUSIONS: R-Motion of apical size and taper 25/.06 and 30/.04 were associated with similar changes in geometry following root canal preparation in curved mesial canals of mandibular molars, whereas Reciproc Blue was associated with greater canal transportation in the coronal root third.

Worldwide Prevalence of Single-rooted with a Single Root Canal and Four-rooted Configurations in Maxillary Molars: A Multi-center Cross-sectional Study with Meta-analysis.

INTRODUCTION: To evaluate the prevalence of single root with a single root canal and four-root configurations in the maxillary first and second molars, and analyze how geographic region, ethnicity, sex, and age impact these outcomes. METHODS: Researchers from 44 nations examined 26,400 maxillary molars using cone-beam computed tomography scans to gather data on the proportions of single roots with single canals and four-root configurations. All observers underwent prior calibration regarding the step-by-step assessment protocol and anatomical concepts to ensure consistent evaluations across all assessed locations. Tests were conducted to evaluate the intraobserver and interobserver reliability. Demographic data including ethnicity, gender, and age were collected for each participant. The potential impact of imaging voxel size and field-of-view on bias was also assessed. The primary results were depicted as odds ratios and untransformed proportion forest plots with 95% confidence intervals. Additionally, a meta-analysis was performed to compare various subgroups and identify sources of variation among them. Statistical significance was set at 5%. RESULTS: The prevalence of single-rooted with a single canal and four-rooted configurations in the maxillary first molar was 0.16% and 0.28%, respectively, while in the maxillary second molar, it was 2.56% and 0.83%. Males tended to exhibit lower percentages of single roots with a single canal (P < .05) and higher percentages of four-rooted configurations (P > .05) in the second molar, whereas the African subgroup displayed lower proportions for both configurations. Additionally, in both teeth, single roots with a single canal were more prevalent among older patients. Voxel size and field-of-view did not significantly influence the results (P > .05). CONCLUSIONS: The proportions of single-rooted with a single canal and four-rooted configurations were low, and demographic factors such as geographic region, ethnicity, sex, and age may have influenced the outcomes for the maxillary second molar.