Buccal Cusp Tips Research Articles

Diagnosing Maxillary Occlusal Cant with average 3D Skeletofacial Model Template.

Diagnosing maxillary occlusal cant involves varied methods, yet classification remains incomplete. This includes determining if the cant results from equal faults on both sides or if one side exhibits overdevelopment while the other underdevelops. This study introduces an innovative average 3D skull template for classifying maxillary occlusal cant instances. Sixty adult patients were divided into two groups: 30 with a mesoprosopic facial type and 30 with a leptoprosopic facial type. Using seven pairs of anatomical landmarks (N, Or (L, R), Lo (L, R), Zy (L, R)), the average skull models were aligned and superimposed onto the patients' skull models. Image resizing facilitated optimal registration area fitting. Vertical distances from the U6 mesial buccal cusp tip to the FH plane were measured to analyze occlusal cant, classified into three classes: overdevelopment (Class A), underdevelopment (Class B) and equal fault on both sides (Class C). In the mesoprosopic group, Class B t was most common (40%), followed by Class A (27%) and Class C (33%). In the leptoprosopic facial type group, Class B remained prevalent (50%), followed by Class A (43%) and Class C (7%). Statistical analysis revealed a significant association between facial types and the three classes. Contrary to expectations, equal fault patterns were not predominant; instead, underdevelopment of the maxilla constituted the majority of occlusal cant cases. Utilizing average 3D skeletofacial models as templates emerges as an effective tool and alternative for diagnosing the instance of maxillary occlusal cant. Therapeutic, II.

A Cross-Sectional Cone-Beam Computed Tomography Study of Root Canal Morphology and Configuration of Mandibular Premolars in Saudi and Sudanese Subpopulations

Abstract Objective To evaluate and compare the root canal morphology of mandibular premolars in Saudi and Sudanese subpopulations and between males and females within each group using cone-beam computed tomography (CBCT). Materials and Methods A cross-sectional study was done between May 2022 and July 2023. Six hundred premolars from Saudi and Sudanese subpopulations were evaluated using CBCT for their number of roots, type of root canal configuration based on Vertucci's classification, and average canal length measured from the buccal cusp tip to the root end. Statistical Analysis Statistical comparisons were made between males and females within each subpopulation and the two subpopulations using the chi-square test for root number and type of root canal configuration and an independent sample t-test for the canal length. Results Most mandibular premolars in both subpopulations had a single root, with type I root canal configuration. However, Sudanese showed various canal configurations (I, II, III, IV, and V) compared with Saudis, which was statistically significant in the first canal of the first mandibular premolar (p < 0.05). Also, there were statistically significant differences in canal length between Saudi males and females (p < 0.05) and between Saudis and Sudanese (p < 0.05) in the first and second premolars. Conclusion Although most mandibular premolars in Saudi and Sudanese subpopulations exhibited a single root and type I canal configuration, variations exist between and within the groups, highlighting ethnic and gender differences and emphasizing the need for dentists' attention.

GEOMETRIC ANALYSIS OF THE MANDIBULAR FIRST PREMOLAR AND CORRELATION WITH ITS FUNCTIONS USING FINITE ELEMENT METHOD

Introduction: The geometric analysis is of important value for exploring the functional adaptation of the human teeth. The mandibular first premolar is one of the permanent teeth that has unique geometric features to properly perform its functions. Purpose: To assess the geometric features of the mandibular first premolar functional and the stress analysis of the static occlusal forces using finite element method. Materials & Methods: Ten human extracted mandibular first premolars were photographed from different aspects to analyze the geometric morphology of the premolars. Dimensional measurements were done by Image J software. Cone beam computerized tomographies were taken to the teeth to construct three-dimensional models for finite element analysis of 150 newtons axial load on buccal cusp tip and distal marginal ridge of each tooth. Results: The descriptive and numerical geometric analysis of the images revealed increased lingual inclination and prominence of the buccal cusps in comparison to the lingual cuspsallowing the proper esthetic and masticatory functions. The finite element analysis revealed that there is harmonious stress distribution with relatively high stress concentration in the dentin of the cervical regions of the crowns and roots. The tooth morphology affects the stress distribution. Conclusion: The mandibular first premolar geometric characteristics are critical toits functional performance. The lingual inclination and the cuspal interrelations are of great importance in the geometric pattern of the mandibular first premolars. The stress distribution is homogeneous in the tooth and supporting tissues with a relative increase in the cervical region.

Occlusal Loading Effect on Stress Distribution of Endodontically Treated Teeth: Finite Element Analysis Study.

Evaluate the influence of occlusal loading on the stress distribution of endodontically treated teeth after root canal preparation with different file's sizes and tapers by means of finite element analysis. Seven three-dimensional models of a single-rooted, single-canal lower second premolar were established, one healthy control and six endodontically treated and restored models. The shape of root canal preparations followed file configurations 30/.05, 30/.09, 35/.04, 35/.06, 40/.04, and 40/.06. Von- Mises equivalent stresses were calculated by applying 30 N, 90 N and 270 N loads to the buccal cusp tip, each one at 90º, 45º and 20º angles from the occlusal plane simulating occlusion, dental interference and laterality, respectively. 45º loading was more prone to formation of higher stress values. The simulation of occlusion and laterality resulted in maximum stress areas located at the inner side of the root curvature, while under occlusal interference they were on the lingual surface over the tooth's long axis. The angulation of occlusal loading and magnitude were determinants for stress distribution on dental structure. Both variations of size and taper were not determinants for the increase in the maximum stress areas.

Curve of Spee modification in different vertical skeletal patterns after clear aligner therapy: a 3D set-up retrospective study

ObjectiveThe purpose of the present study was to evaluate: (1) changes in the curve of Spee (COS) after clear aligner therapy and (2) whether such changes correlated with the patient’s skeletal patterns.Materials and methodsThree-dimensional mandibular models of 106 patients (47 males and 59 females; mean age 22.3 SD ± 3.4 years) treated with clear aligners were retrospectively analysed. The perpendicular distance between the occlusal reference plane and the buccal cusp tip of each lateral tooth was measured. Five angular cephalometric measurements (PP-MP, PP-OP, OP-MP, AFH, and PFH) were performed and correlated with the T1–T0 difference in linear distances. The patients were divided into three groups according to facial divergence. Variance analysis with Tukey post hoc correction was performed to evaluate the differences among groups.ResultsThe one-way ANOVA test showed a statistically significant difference for all analysed variables, except for the change in the distance of the second molar from the occlusal reference plane. Tukey’s HSD test showed the following differences: In normodivergents, the T1–T0 difference in the distance of the first molar from the occlusal plane was 1 mm greater than that observed in the hyperdivergent group (p < 0.05); in the normodivergent group, the T1–T0 difference in the distance of the second premolar from the occlusal plane was 1.23 mm greater than that observed in the hyperdivergent group (p < 0.05), while in the hypodivergent group, it was 1.08 mm greater than in the hyperdivergent group (p < 0.05); finally, in normodivergents, the T1–T0 difference in the distance of the first premolar from the occlusal plane was 0.97 mm greater than that observed in the hyperdivergent group (p < 0.05).ConclusionTreatment with aligners did not lead to a clinically significant change in COS depth. However, when dividing the sample into groups based on craniofacial divergence, COS depth change differed significantly between the three groups.

Role of Mucobuccal Sulci in Determination of Occlusal Vertical Dimension in Dentate Subjects.

Aim: To find out the distance between the mucobuccal sulci of maxillary and mandibular arches and the cusp tips of posterior teeth and evaluate the occlusal vertical dimension in dentate subjects. Study Design:Cross sectional observational study. Place and duration: Prosthodontic department of Lahore Medical and Dental College, Lahore, from 2nd September 2022 till 2nd December 2022. Methodology: A total of 45 dentate subjects including 20 males and 25 females were selected. Alginate impressions (irreversible hydrocolloid) of both arches were taken in stock trays. Impressions were poured in hard plaster and stone casts were fabricated. Digital vernier caliper with accuracy of 0.01mm was used for recording the distance from the depth of mucobuccal sulci of both arches to the cusp tips of all posterior teeth of the respective arches. The distance from maxillary mucobuccal sulcus to the mandibular mucobuccal sulcus in maximum intercuspation was also calculated. Result: The distances measured from the maxillary mucobuccal sulcus to the buccal cusp tips of maxillary first premolar, second premolar and first molar were found to be 16.86mm; 15.94mm, and 15.45mmrespectively. The distances measured from the mandibular mucobuccal sulcus to the buccal cusp tips of mandibular first premolar, second premolar and first molar were 17.02mm, 15.14mm and 14.26mmrespectively. The mean distance recorded from the depth of maxillary and mandibular sulci in maximum intercuspation positions showed shortest distance at first molar areai.e.; 26.88mmas compared to the distance found in first premolar 35.22mm and second premolar 35.63mmareas. Conclusion: The mean distances recordedbetween maxillary and mandibular sulci in intercuspation position were 35.22mm, 35.63mm and 26.88mm respectively. These values may be helpful in determination of occlusal vertical dimension by selecting appropriate teeth and shaping occlusal rims while fabricating complete dentures Keywords: Dentate, Dental arch, Mucobuccal sulcus, Maxilla, Mandible, Occlusal vertical dimension, Posterior teeth.

Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.

Correlation of Arch Width and Vertical Facial Morphology in Untreated Adults at a Tertiary Care Centre: A Cross-sectional Study

Introduction: The vertical dimension of a face is crucial in determining facial aesthetics and harmony. It is important for the orthodontist to understand the relationship between dental arch width and facial morphology for correct diagnosis and proper treatment plan. Aim: To determine the relationship between the vertical face pattern, dental arch width and also, to compare arch widths among both untreated female and male adults. Materials and Methods: This quantitative cross-sectional study was conducted in the Department of Orthodontics and Dentofacial Orthopaedics, at Sharad Pawar Dental College, Sawangi, Wardha, Maharashtra, India. The duration of the study was 1 month, from June 2019 to July 2019. Dental casts and lateral cephalograms were collected from 50 untreated adults (25 males and 25 females), aged between 18 to 30 years, who had minimal spacing, crowding and no crossbite. On every patient’s cephalogram, the angle between the plane of the mandible to the cranial base anterior Sella Nasion (SN) angle was calculated. Intercanine, intermolar, and interpremolar widths were measured on dental casts. Females and males arch width were compared. The significance of the differences was assessed using Student’s t-test, one-way Analysis of Variance (ANOVA) test and regression analysis. Results: The mean age of male study participants in the study was 24.44±5.04 years, whereas, mean age of females was 24.88±3.08 years. There were 25 males and 25 females of 18-30 years with mean age of 24 and 25 years, respectively. Arch widths of males were found to be significantly greater than, those of females (p&lt;0.05) and it was observed that, interarch width decreased significantly as the Sella Nasion-Mandibular Plane (SN-MP) angle increased. Regression analyses of male subjects revealed a significant positive relationship between the SN-MP angle. Whereas, the SN-MP angle and width of maxillary first premolar’s buccal cusp tip and the width of the second premolar (most buccal and buccal cusp tip), was found to have a strong correlation in female subjects. Conclusion: It was found that, the width of the dental arch is related to vertical face morphology and gender. During orthodontic therapy, it is recommended to use individualised archwires based on each individual’s pretreatment arch shape and width.

Minimum residual root dentin thickness of mandibular premolars restored with a post: A finite element analysis study

Statement of problemThin root dentin after post space preparation will increase the risk of root fracture. However, the minimum residual root dentin thickness to be preserved after post space preparation is unclear. PurposeThe purpose of this finite element analysis (FEA) study was to measure the residual root dentin thicknesses and analyze the stress distributions of post-restored mandibular premolars. Material and methodsThe cone beam computed tomography (CBCT) data of 90 first and second mandibular premolars from Chinese participants (44 men, 46 women; aged between 20 and 79 years) were analyzed. Cross-sections 5 to 9 mm from the radiologic apex were used to measure the buccolingual and mesiodistal root diameters. The probability that the residual thickness of the buccolingual and mesiodistal root walls would be no less than 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mm after post space preparation with a #2 Peeso reamer was calculated. Six 3-dimensional finite element models of cast post-restored mandibular premolars with 0.5, 0.6, 0.7, 0.8, 0.9, and 1 mm mesial and distal root dentin thicknesses were established. A static force of 100 N was applied to the buccal cusp tip at 45, 60, 75, and 90 degrees to the long axis of the tooth, and the maximum tensile stress and von Mises stress were analyzed. The Bonferroni post hoc test (αcorrected=.003) was used for multiple comparisons. ResultsThe buccolingual root diameter of mandibular premolars was wider than the mesiodistal root diameter. The probabilities that the mesiodistal residual root dentin thickness of mandibular first and second premolars at 5 mm from the apex would be no less than 1 mm after post space preparation with a #2 Peeso reamer were only 10% and 28%, respectively. The maximum tensile stress was at a minimum when the mesial and distal residual root dentin thickness was 0.6 mm in the external cervical dentin adjacent to the crestal bone and 1 mm in the apical dentin corresponding to the apex of the post. The maximum tensile stress of the mandibular premolar model with 0.6-mm mesial and distal residual root dentin thicknesses was lower than that with 0.9 mm and 1.0 mm thicknesses (Pcorrected<.001). ConclusionsShort posts or smaller instruments for post space preparation are recommended to obtain a 1-mm residual root dentin thickness in the mesiodistal direction of mandibular premolars. If a 1-mm thickness cannot be preserved, a minimum residual root dentin thickness of 0.6 to 0.9 mm in the mesiodistal direction should be retained.

Does Resin Cement Type and Cement Preheating Influence the Marginal and Internal Fit of Lithium Disilicate Single Crowns?

This paper assesses the effect of cement type and cement preheating on the marginal and internal fit of lithium disilicate single crown. Methods: 40 maxillary premolars were selected, restored with lithium disilicate single crowns. Teeth were randomly assigned into four groups (n = 10) based on cement type (Panavia SA or LinkForce) and preheating temperature (25 °C or 54 °C). After fabrication of the restoration, cements were incubated at 25 °C or 54 °C for 24 h, and each crown was cemented to its corresponding tooth. After 24 h, all specimens were thermally aged to (10,000 thermal cycles between 5 °C and 55 °C), then load cycled for 240,000 cycles. Each specimen was then sectioned in bucco-palatal direction and inspected under a stereomicroscope at x45 magnification for marginal and internal fit evaluation. The data were statistically analyzed (significance at p ≤ 0.05 level). Results: At the mid-buccal finish line, mid-buccal wall, palatal cusp, mid-palatal wall, mid-palatal finish line, and palatal margin measuring points, there was a significant difference (p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 25 °C and the group cemented with LinkForce at 25 °C, while there was no significant difference (p > 0.05) at the other points. At all measuring points, except at the palatal cusp tip (p = 0.948) and palatal margin (p = 0.103), there was a statistically significant difference (p ≤ 0.05) between the lithium disilicate group cemented with Panavia SA at 54 °C and the group cemented with LinkForce at 54 °C. Regardless of cement preheating, statistically significant differences were found in the buccal cusp tip, central groove, palatal cusp tip, and mid-palatal wall (p ≤ 0.05) in the lithium disilicate group cemented with Panavia SA at 25 °C and 54 °C, as well as the mid-palatal chamfer finish line and palatal margin in the LinkForce group cemented with Panavia SA at 25 °C and 54 °C. At the other measurement points, however, there was no significant difference (p > 0.05). Conclusions: The type of resin cement affects the internal and marginal fit of lithium disilicate crowns. At most measuring points, the cement preheating does not improve the internal and marginal fit of all lithium disilicate crowns.

Miniscrew insertion sites of infrazygomatic crest and mandibular buccal shelf in different vertical craniofacial patterns: A cone-beam computed tomography study.

ObjectiveTo identify optimal areas for the insertion of extra-alveolar miniscrews into the infrazygomatic crest (IZC) and mandibular buccal shelf (MBS), using cone beam computed tomography (CBCT) imaging in patients with different craniofacial patterns.MethodsCBCT reconstructions of untreated individuals were used to evaluate the IZC and MBS areas. The participants were divided into three groups, based on the craniofacial pattern, namely, brachyfacial (n = 15; mean age, 23.3 years), mesofacial (n = 15; mean age, 19.24 years), and dolichofacial (n = 15; mean age, 17.79 years). In the IZC, the evaluated areas were at 11, 13, and 15 mm above the buccal cusp tips of the right and left first molars. In the MBS, the evaluated areas were at the projections of the first molars’ distal roots and second molars’ mesial and distal roots, at a 4- and 8-mm distance from the cementoenamel junction. Intergroup comparisons were performed with analysis of variance and the Tukey test.ResultsThere was no statistically significant difference in the IZC bone thickness among the groups. For MBS bone availability, some comparisons revealed no difference; meanwhile, other comparisons revealed increased MBS bone thickness in the brachyfacial (first molars distal roots) and dolichofacial (second molars mesial and distal roots) patterns.ConclusionsThere was no significant difference in the IZC bone thickness among the groups. The facial skeletal pattern may affect the availability of ideal bone thickness for the insertion of extra-alveolar miniscrews in the MBS region; however, this variability is unlikely to be clinically meaningful.

Evaluation of Growth and Development of Adolescents' Dental Arch Asymmetry with Normal Occlusion Using Three-Dimensional Digital Models.

Objective The purpose of this study was to observe the dental arch asymmetry in 12-year-olds with normal occlusion during the early permanent dentition stage. Methods Ninety-two 12-year-old students (46 males and 46 females) who had normal occlusion during early permanent dentition were selected from a junior high school in Tangshan, China. Once per year for three consecutive years, a dental cast was obtained from each subject, and the cast was scanned with a 3D digital scanner (R700 3D). The median palatal plane (MPP) and transverse palatal plane (TPP) were used as the reference plane for the transverse and anteroposterior measurements, respectively. Results Most of the dental arch asymmetry indicators decreased with age, but these differences were not statistically significant. The values of the midincisal edge of the upper central incisors (U1), midincisal edge of the upper lateral incisors (U2), upper canine cusp tip (U3), upper first premolar buccal cusp tip (U4), upper second premolar buccal cusp tip (U5), upper first molar mesiobuccal cusp tip (U6MB), and upper first molar distobuccal cusp tip (U6DB) to the TPP were 0.019 mm, 0.279 mm, 0.017 mm, 0.016 mm, 0.016 mm, 0.027 mm, and 0.200 mm, respectively; these values were larger in males than in females (P < 0.05). The values of 2–5, 6MB, and 6DB-TPP were 0.154 mm, 0.102 mm, 0.119 mm, 0.259 mm, 0.206 mm, and 0.123 mm, respectively, larger in the mandibular than in the maxillary dental arch (P < 0.05). The values of the midincisal edge of the lower central incisors (L1), midincisal edge of the lower lateral incisors (L2), lower canine cusp tip (L3), lower first premolar buccal cusp tip (L4), lower second premolar buccal cusp tip (L5), lower first molar mesiobuccal cusp tip (L6MB), and lower first molar distobuccal cusp tip (L6DB) to the MPP were 0.399 mm, 0.197 mm, 0.258 mm, 0.248 mm, 0.214 mm, 0.575 mm, and 0.531 mm, respectively, larger than L1-5, L6MB, and L6DB-TPP (P < 0.05). Conclusion The asymmetry of the dental arch in 12-to-15-year-olds with normal occlusion did not change significantly with age. The anteroposterior asymmetry of the maxillary dental arch is larger in males than in females. With the exception of the central incisor, the anteroposterior asymmetry of the mandibular dental arch is larger than that of the maxillary dental arch. The transverse asymmetry of the mandibular dental arch is larger than the anteroposterior asymmetry.

Three-Dimensional Finite Element Analysis of Stress Distribution in a Tooth Restored with Full Coverage Machined Polymer Crown

The effect of a restored machined hybrid dental ceramic crown–tooth complex is not well understood. This study was conducted to determine the effect of the stress state of the machined hybrid dental ceramic crown using three-dimensional finite element analysis. Human premolars were prepared to receive full coverage crowns and restored with machined hybrid dental ceramic crowns using the resin cement. Then, the teeth were digitized using micro-computed tomography and the teeth were scanned with an optical intraoral scanner using an intraoral scanner. Three-dimensional digital models were generated using an interactive image processing software for the restored tooth complex. The generated models were imported into a finite element analysis software with all degrees of freedom concentrated on the outer surface of the root of the crown–tooth complex. To simulate average occlusal load subjected on a premolar a total load of 300 N was applied, 150 N at a buccal incline of the palatal cusp, and palatal incline of the buccal cusp. The von Mises stresses were calculated for the crown–tooth complex under simulated load application was determined. Three-dimensional finite element analysis showed that the stress distribution was more in the dentine and least in the cement. For the cement layer, the stresses were more concentrated on the buccal cusp tip. In dentine, stress was more on the cusp tips and coronal 1/3 of the root surface. The conventional crown preparation is a suitable option for machined polymer crowns with less stress distribution within the crown–tooth complex and can be a good aesthetic replacement in the posterior region. Enamic crowns are a good viable option in the posterior region.

Finite Element Analysis of effect of cusp inclination and occlusal contacts in PFM and PEEK implant-supported crowns on resultant stresses

BackgroundEffect of prosthesis design on occlusal overload and long-term implant stability cannot be overstated. In Porcelain Fused to Metal (PFM) crowns, low cusp inclination and occlusal contacts limited to central fossa ensure axially directed forces on an implant but often pose esthetic and functional challenges. It is theorized that resilient Polyetheretherketone (PEEK) crowns have shock absorption capacity for favorable stress distribution. This study compared two implant crown materials and evaluated the effect of cusp inclination and occlusal contact distribution on resultant stresses. MethodsThirty 3D finite element models of implant-supported PFM and PEEK crowns, generated using Solidedge 3D CAD solid modeling software (v19, Siemens PLM Software Inc.,US), were used to study the effect of 3 cups inclinations (0°, 15°, 30°) under five load conditions, with 300N force distributed over one, two, or three contact areas and exported to ANSYS (v18.1, ANSYS Inc. Pennsylvania, US) for stress analysis. ResultsMaximum stress in both PFM and PEEK models was at the neck of the implant under Load 3(300N distributed over three contact areas: central fossa, buccal cusp tip, marginal ridge). Minimum stress in all models was under Load 1(300N applied at one contact area in central fossa). Maximum stresses were recorded for 30° cusp inclination in PFM models. ConclusionIn both PFM and PEEK crown models, contact areas placed away from the implant axis generated greater implant and peri-implant stresses and had more effect on resultant stresses than that of increase in cusp inclination. The effect of cusp inclination on the resultant stresses was dependent on the crown material.

A population-based observational morphologic measurements of anatomic landmarks in maxillary and mandibular molar

Aim: The aim of this study is to study the morphological measurements of external and internal anatomic landmarks in human maxillary and mandibular molars and their correlation with critical pulp chamber morphology.Materials and Methods: A total of 200 mandibular and maxillary molar teeth of patients were evaluated. Teeth whose pulp chamber were not violated by caries, restoration, fracture crown, and those having closed apex were included in the study. Teeth were subjected to radiovisiography of bitewing projection and imaging tool was utilized for measuring-A: Distance from the pulp chamber floor to the furcation, B: Distance from the pulp chamber ceiling to the furcation, C: Distance from the buccal cusp tip to the furcation, D: Distance from the buccal cusp to the floor of the pulp chamber, E: Distance from the buccal cusp to the ceiling of pulp chamber, and F: Pulp chamber height. Differences in the measurements were examined using the Student's t-test and Pearson correlations. All results were considered statistically significant if P < 0.05.Results: There were significant differences found among the various measurements between young and old population groups (P < 0.05). The highest percentage variance was found for the height of the pulp chamber (P < 0.001).Conclusions: The knowledge of pulp chamber morphology should be integrated with preoperative radiograph and intraoperative tactile perception during endodontic access preparation.

Three-dimensional mandibular dental changes with aging

This study aimed to evaluate the 3-dimensional (3D) mandibular dental changes over 42years using the registration of digital models. The sample comprised digital dental models of 8 untreated subjects (4 males and 4 females) with normal occlusion measured longitudinally at ages 17years (T1) and 60years (T2). Using 13 landmarks placed on the mucogingival junction, we registered the T2 model on the T1 model. Three-dimensional changes in the position of the landmarks on the buccal cusp tip of the posterior teeth and incisal edge of the central incisors were measured by 2 examiners. Registration and measurements were performed using SlicerCMF (version 3.1; http://www.slicer.org) software. Intra- and interrater agreements were evaluated using intraclass correlation coefficients and the Bland-Altman method. One-sample t tests were used for evaluating interphase 3D dental changes (P<0.05). Adequate intra- and interrater reproducibility was found. From T1 to T2, the mandibular teeth showed significant 3D positional changes. A significant dental eruption relative to the mucogingival junction was observed for the anterior and posterior teeth. Anteroposterior movements of mandibular teeth were not significant except for the right molar that drifted mesially. Transverse movements included slight lingual tipping at canines and premolars regions. Dental changes in untreated normal occlusion were very slight from early to mature adulthood. The eruption of the mandibular teeth was the most consistent finding. A tendency for mesial movement of molars and lingual movement of first premolars and canines was observed in the mandible during the aging process.

Monitoring of simulated occlusal tooth wear by objective outcome measures

ObjectivesThis in vitro study explored quantitative outcome measures as clinical indicators of simulated occlusal tooth wear progression. MethodsTen sound, extracted human premolars were selected and submitted to occlusal tooth wear simulation in 0.5-mm steps (0/0.5/1.0/1.5 mm). At each step, enamel thickness on the buccal cusp tips was evaluated using cross-polarization optical coherence tomography (CP-OCT) and micro-computed tomography (μ-CT). The occlusal surface of each premolar was also scanned at each step using a 3D digital intraoral scanner, followed by morphological characterization using standard topography attributes (Slope, Relief, RFI, OPCr). Repeated measures ANOVA assessed differences in simulated wear levels for the μ-CT and CP-OCT data as well as the topography values. Correlations were also calculated between the μ-CT/CP-OCT and topography data. ResultsSignificant differences were observed for enamel thickness at each simulation wear stage, for both CP-OCT (p < 0.001) and μ-CT (p < 0.001), with good agreement between methods (intraclass correlation: 0.89). For topography analysis, as wear increased, the average Slope, RFI, and Relief values decreased, and average OPCr values increased, with more significant differences shown for Slope. Slope showed significant (p < 0.05) positive correlations with CP-OCT. OPCr showed significant negative correlations with μ-CT, and CP-OCT (p < 0.05). RFI and Relief were not correlated with either μ-CT or CP-OCT (p > 0.05). ConclusionsOur findings suggest the potential of PS-OCT for measuring enamel thickness changes in the cusp tips of the occlusal surface. Similarly, conventional intraoral scanners can serve effectively for monitoring overall tooth wear when combined with dental topographic analyses of resultant point clouds. Clinical significanceCP-OCT measures of enamel thickness and dental 3D topographic attributes showed potential as objective outcomes for the clinical monitoring of occlusal tooth wear. Their combination provided a comprehensive understanding of the tooth wear development process.

Influence of cavity depth and restoration of non-carious cervical root lesions on strain distribution from various loading sites

BackgroundWe aimed to investigate the load-induced strain variation in teeth with unrestored and resin-based composite restored non-carious cervical lesions (NCCLs).MethodsTwelve extracted premolars were provided for measuring buccal-side root NCCLs. Strain gauges were fixed at four measuring sites of each tooth, two at the buccal surface and two at the lingual surface. NCCLs were prepared with occlusal margins at the cemento-enamel junction. A static 9-kg load was applied at seven occlusal loading points: buccal cusp tip (BC), inner inclination of the BC, lingual cusp tip (LC), inner inclination of the LC, center of the mesial marginal ridge or distal marginal ridge, and center of the central groove. The strain was detected at each site in teeth with NCCL depths of 0 (control), 0.5, 1.0, and 1.5 mm. Each NCCL was restored using an adhesive composite resin, and the strains were re-measured.ResultsThe strains at the NCCL occlusal and gingival margins decreased with increasing defect depths, and the effect was significant when the depth of the defect was 1.5 mm. Loading on the buccal and lingual cusps induced prominent strain variation. The strains at all depth distribution recovered to nearly intact conditions when the NCCLs were restored.ConclusionsNCCLs at 1.5 mm depth are detrimental, but they can be restored using resin composites.Clinical significanceThe existence of NCCLs should not be ignored. The depth of the NCCL may affect the progression of the lesion. Resin composite restoration is an appropriate method for preventing persistent NCCL deterioration.

Superimposition of maxillary digital models using the palatal rugae: Does ageing affect the reliability?

The aim of this study was to evaluate the reliability of 3-dimensional maxillary dental changes using two methods of digital model superimposition. The Department of Orthodontics of Bauru Dental School, University of São Paulo and University of Michigan Craniofacial Growth Center. Fifteen subjects with normal occlusion. The sample was composed of digital study models of 15 normal occlusion subjects taken at 13 (T1), 18 (T2) and 60years of age (T3). Using the software SlicerCMF 3.1, superimposition (registration) was conducted using 9 landmarks placed on the incisive papilla, second and third palatal rugae and 10mm distal to the third palatal rugae. Two registration methods were compared: landmarks (LA) and regions of interest (ROI). Three-dimensional changes of landmarks on the buccal cusp tip of posterior teeth bilaterally and the incisal edge of the right central incisor were measured by three examiners. Intraclass correlation coefficients and Bland-Altman method evaluated intra- and inter-examiner agreements. Good or excellent intra-examiner agreement was found for T1-T2 and T2-T3 measurements using both registration methods. Inter-examiner agreements were good to excellent for T1-T2 measurements and poor to fair for most T2-T3 measurements. Mean T1-T2 differences were less than 0.5mm for most measurements. Maxillary digital dental models of patients with normal occlusion superimposed on palatal rugae showed an adequate reliability for a 5-year interval comparison using landmarks or regions of interest. Lower than acceptable reproducibility using both superimposition methods was found for a 40-year interval comparison.

Ideal Electrode Placement Site of Electric Pulp Tester: A Clinical Study

Introduction: Endodontic diagnosis is the essential aid in deciding the treatment plan though it has limitations and shortcomings. Electric pulp testers are widely used for endodontic diagnosis. Such testing requires the tip of electrode to be in optimal position on the surface of the tooth. Aim: The aim of the study is to determine the ideal electrode placement site of electric pulp tester for the mandibular premolars. Material and Methods: Electric pulp tester was used to assess the response of the tooth. A sample size of 60mandibular premolar teeth were included in the study. The electrode tip of electric pulp tester was placed on different sites on the buccal aspect of the tooth. The response of the tooth was evaluated. Results: The lowest response for mandibular premolar was observed to be on the tip of the buccal cusp. The threshold level was said to increase from the buccal cusp tip to middle third and cervical third. It was also concluded that there was no significant difference found between male and female and also with respect to age in response to level of perception of threshold. Conclusion: It is necessary to place the electrode tip of the electric pulp tester at the appropriate site for the accurate diagnosis.