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Scientific Reports Jun 2022Tooth development is governed largely by epithelial-mesenchymal interactions and is mediated by numerous signaling pathways. This type of morphogenetic processes has...
Tooth development is governed largely by epithelial-mesenchymal interactions and is mediated by numerous signaling pathways. This type of morphogenetic processes has been explained by reaction-diffusion systems, especially in the framework of a Turing model. Here we focus on morphological and developmental differences between upper and lower molars in mice by modeling 2D pattern formation in a Turing system. Stripe vs. spot patterns are the primary types of variation in a Turing model. We show that the complexity of the cusp cross-sections can distinguish between stripe vs. spot patterns, and mice have stripe-like upper and spot-like lower molar morphologies. Additionally, our computational modeling that incorporates empirical data on tooth germ growth traces the order of cusp formation and relative position of the cusps in upper and lower molars in mice. We further propose a hypothetical framework of developmental mechanism that could help us understand the evolution of the highly variable nature of mammalian molars associated with the acquisition of the hypocone and the increase of lophedness.
Topics: Animals; Mammals; Mice; Molar; Morphogenesis; Odontogenesis; Signal Transduction; Tooth Germ
PubMed: 35701484
DOI: 10.1038/s41598-022-13539-w -
Folia Morphologica 2022The aim of the study was to analyse the morphology of the apical foramen in permanent maxillary and mandibular human teeth.
BACKGROUND
The aim of the study was to analyse the morphology of the apical foramen in permanent maxillary and mandibular human teeth.
MATERIALS AND METHODS
The anatomic parameters include shapes (rounded, oval, uneven, flat and semilunar) and location (centre, buccal/labial, lingual/palatal, mesial, and distal) of the apical foramina was evaluated. The shapes and locations of apical foramen were analysed based on tooth type (central incisor, lateral incisor, canine, premolars, and molars) arch type (maxillary and mandibular), and position (anterior and posterior). All the teeth were investigated for the apical foramina shape and location using a stereomicroscope at a magnification of 10×. Descriptive statistics performed using SPSS (Version 21.0, IBM, NY, USA) at p value less than 0.05.
RESULTS
The common shape of apical foramina was round (65%) and location was centre (32%). The frequency of deviation of apical was 68% in overall teeth. Apical foramina in maxillary anterior teeth showed more deviation while posterior teeth in mandibular teeth. The most common shape of apical foramina was round (65.1%) followed by (31%) and flat and semilunar shapes are very rare in studied subjects.
CONCLUSIONS
The most frequent direction of deviation is the distal surface, followed by the mesial surface. The variation is more common in mandibular posterior teeth, while maxillary posteriors showed the least difference. The commonest shape of the apical foramen is of a round shape, followed by the oval. The oval shape of the apical foramen is most frequent with central incisors.
Topics: Bicuspid; Humans; Mandible; Maxilla; Molar; Tooth Apex
PubMed: 33330969
DOI: 10.5603/FM.a2020.0143 -
Head & Face Medicine Mar 2023This retrospective cohort study aimed to compare treatment results between bilateral extraction of upper second molars (M2) and first premolars (P1) in terms of... (Comparative Study)
Comparative Study
BACKGROUND
This retrospective cohort study aimed to compare treatment results between bilateral extraction of upper second molars (M2) and first premolars (P1) in terms of treatment timing, cephalometry, upper third molar alignment and relapse in the long-term.
METHODS
Fifty-three consecutively treated Caucasian patients with a brachyfacial pattern, skeletal class I and dental class II requiring extraction in the maxilla due to crowding were retrospectively divided into group I (M2 extracted; N = 31) and II (P1 extracted; N = 22). Fixed appliances were inserted after extraction and after distalisation of the first molars in group I. Post-treatment lateral cephalograms were digitally analysed and compared between groups. Six to seven years later relapse and success of upper third molar alignment were clinically evaluated as well as orthodontic treatment duration, pre-treatment age and gender recorded.
RESULTS
After debonding patients with second molar extraction showed significantly smaller values for the Wits-appraisal, but higher values for index and facial axis. Extracting first premolars caused significantly more retroinclination/-position of anterior teeth and an increased profile concavity, more relapse and less successful alignment of upper third molars. Orthodontic treatment duration, pre-treatment age and gender were not significantly different between groups.
CONCLUSIONS
Bilateral extraction of upper first premolars or second molars may solve dental crowding in skeletal class I dental class II patients with a brachyfacial growth pattern. Upper second molar extraction seems to affect maxillary third molar alignment, long-term stability and dental and soft-tissue cephalometric parameters positively, but no intervention proved to be clearly superior.
Topics: Humans; Bicuspid; Malocclusion; Molar; Retrospective Studies; Treatment Outcome
PubMed: 36882841
DOI: 10.1186/s13005-023-00353-6 -
Journal of Endodontics Sep 2021This study aimed to use micro-computed tomographic imaging to analyze the quality of the endodontic preparation of mesial canals in mandibular molars provided by 3...
INTRODUCTION
This study aimed to use micro-computed tomographic imaging to analyze the quality of the endodontic preparation of mesial canals in mandibular molars provided by 3 instrumentation protocols.
METHODS
Forty-five extracted mandibular molars with 2 independent mesial canals were selected, and the initial micro-computed tomographic imaging was performed. The initial volume values of the canals were submitted to statistical analysis for paired division. The groups were determined according to the final enlargement of the canal and the working length adopted (ie, G25.06/+1 mm, G35.05/foramen, and G50.01/-1 mm). At the end of each instrumentation sequence, the root canals were scanned and analyzed with regard to the increase in the total and apical volume, centralization, and preparation transportation and the percentage of the total and apical uninstrumented walls.
RESULTS
For the intragroup comparison, the Wilcoxon test was used, and for the intergroup analysis, the Kruskal-Wallis and Dunn tests were used (P < .05). In the analysis of the canal total volume, a statistical difference was found between G25.06/+1 mm and the remaining groups (P < .05). In the apical third, a statistical difference was observed between G25.06/+1 mm and G50.01/-1 mm (P < .05). No statistical difference was found between the groups in terms of centralization and transportation of the preparation or in terms of the percentage of the total or apical uninstrumented walls.
CONCLUSIONS
The preparation of the mesial canals of mandibular molars up to larger tip files but with a lower taper at 1 mm before the foramen resulted in a larger volume of apical preparation, kept the preparation centralized, and provided safe apical dentin wear without excessive cervical wear.
Topics: Dental Pulp Cavity; Molar; Root Canal Preparation; X-Ray Microtomography
PubMed: 34139263
DOI: 10.1016/j.joen.2021.06.008 -
American Journal of Orthodontics and... Aug 2021Uprighting mesially tipped molars is often a necessary step before implant placement. However, the orthodontic treatment can be lengthy and discourage patients from...
INTRODUCTION
Uprighting mesially tipped molars is often a necessary step before implant placement. However, the orthodontic treatment can be lengthy and discourage patients from choosing implant prostheses. Periodontally accelerated osteogenic orthodontics is reported to facilitate molar movements. This study aimed to evaluate the biomechanical effects of various corticotomy and osteotomy approaches on the uprighting of a mesially tipped mandibular second molar in a 3-dimensional finite element analysis model.
METHODS
The initial tooth displacement and periodontal ligament (PDL) strain in 9 finite element analysis models with various corticotomy and osteotomy simulations were compared under 3 intended tooth movement scenarios: distal crown tipping, mesial root movement with restraints, and mesial root movement without restraints.
RESULTS
Corticotomy or osteotomy approaches altered the tooth displacement and the PDL strain in all 3 intended molar uprighting scenarios. The 2 most extensive surgical approaches, the combined mesial and distal osteotomy with horizontal corticotomy and the circumferential corticotomy at root apex level, resulted in increased tooth movement but had a distinct impact on PDL strain.
CONCLUSIONS
It was revealed that different combinations of corticotomy and osteotomy had a biomechanical impact on orthodontic molar uprighting movements.
Topics: Finite Element Analysis; Humans; Molar; Osteotomy; Tooth Movement Techniques; Tooth Root
PubMed: 34099344
DOI: 10.1016/j.ajodo.2020.06.034 -
Journal of Orthodontics Dec 2022To find the effect of extraction of the lower first permanent molar in children (aged 8-11 years) on the position and angle of the developing third molar.
OBJECTIVE
To find the effect of extraction of the lower first permanent molar in children (aged 8-11 years) on the position and angle of the developing third molar.
DESIGN
Retrospective radiographic analysis.
PARTICIPANTS
Two cohorts of participants were identified: an extraction group, who had extraction of one or more first permanent molars aged 8-11 years; and a non-extraction group, who retained all mandibular teeth. Both cohorts previously had panoramic radiographs taken at mean ages of 9.7 years (T1), before extraction, and 12.12 years (T2). In total, there were 61 third molars with an associated extracted first permanent molar and 60 third molars with an associated retained first permanent molar.
METHODS
A digital radiographic analysis was carried out on the panoramic radiographs to measure the movement of the third molar, vertically and horizontally, and its angle. The magnification of the T1 and T2 radiographs was calibrated. Reliability of the radiographic analysis was confirmed via intra- and inter-rater reliability tests. The extraction and non-extraction groups were compared via independent sample tests.
RESULTS
The third molar moved significantly more mesial in the extraction group ( < 0.001) and the angle uprighted significantly more than the non-extraction group ( < 0.001). Vertically, the third molar moved inferiorly in both cohorts with no significant difference.
CONCLUSION
In the developing dentition, extraction of the lower first permanent molar encouraged mesial movement and uprighting of the developing third molar. This may improve the likelihood of future eruption of the third molar.
Topics: Humans; Child; Molar, Third; Retrospective Studies; Reproducibility of Results; Mandible; Radiography, Dental, Digital; Radiography, Panoramic; Molar; Tooth Eruption; Tooth Extraction
PubMed: 35475356
DOI: 10.1177/14653125221093086 -
BMC Oral Health Feb 2020Better understanding of the danger zone anatomy in mesial roots (MRs) of mandibular first molars (MFMs) may serve to decrease the risk of mishaps. This study aimed to...
BACKGROUND
Better understanding of the danger zone anatomy in mesial roots (MRs) of mandibular first molars (MFMs) may serve to decrease the risk of mishaps. This study aimed to measure the minimal distal dentine thicknesses of danger zone in MRs of MFMs in a native Chinese population using cone-beam computed tomography (CBCT).
METHODS
CBCT images of 1792 MFMs from 898 Chinese patients were analyzed. The minimal distal dentine thicknesses of the mesiobuccal (MB) and mesiolingual (ML) canals below the furcation 1, 2, 3, 4, 5 mm were measured. The association between the minimal distal dentine thicknesses and the root lengths, patient's age and gender, side were assessed.
RESULTS
The minimal distal dentine thicknesses of MB and ML canals are located 3 ∼ 4 mm below the furcation for both men and women. There are no differences between MB and ML canals, while the minimal distal dentine thicknesses of MB and ML canals were higher in men than women (P < 0.05), except at 1 and 3 mm of ML canals (P > 0.05). The minimal distal dentine thicknesses of MB and ML canals increased with age in both men and women at each location (P < 0.05). The minimum distal dentine thickness at every location were significantly different between long teeth and short teeth both in men and women (P < 0.05), with short teeth having the smallest mean values. There are no significant differences between two sides (P > 0.05).
CONCLUSIONS
The minimal distal dentine thicknesses of MRs in MSMs have close correlation with root length, patient's age and gender.
Topics: Adolescent; Adult; China; Cone-Beam Computed Tomography; Dental Pulp Cavity; Dentin; Female; Humans; Male; Mandible; Middle Aged; Molar; Tooth Root
PubMed: 32028960
DOI: 10.1186/s12903-020-1026-8 -
Journal of Endodontics Sep 2022This prospective study was designed to determine the prognosis of second molars with external root resorption (ERR-M2s) caused by embedded third molars (EM3s) following...
INTRODUCTION
This prospective study was designed to determine the prognosis of second molars with external root resorption (ERR-M2s) caused by embedded third molars (EM3s) following EM3 removal and explore related predictors.
METHODS
This study consecutively enrolled 58 participants who had asymptomatic second molars with apical external root resorption caused by EM3s. EM3s were extracted, and follow-up examinations were conducted at 1 week, 4 weeks, and 6 months. The primary outcome was prognosis of ERR-M2s after third molar extraction without any further intervention, as assessed via clinical and radiographic examinations. Potential predictors (sex, age, number of roots, EM3s position, type and degree of external root resorption) of prognosis were analyzed via univariable and multivariable analyses.
RESULTS
A total of 63 ERR-M2s from 58 patients (16 males and 42 females; 19-57 years of age) were evaluated. At the last follow-up, 56 teeth (89%) remained asymptomatic and normal response to heat and cold tests. According to univariable analyses, ERR-M2s were more likely to remain normal response to heat and cold tests in younger patients. In the multivariable analysis, older age (odds ratio, 1.118; 95% confidence interval, 1.026-1.219; P < .05) and the type of all roots affected (odds ratio, 0.073; 95% confidence interval, 0.007-0.754; P < .05) were significantly associated with poor prognosis.
CONCLUSIONS
Asymptomatic ERR-M2s have a high probability of remaining normal pulp without further intervention after EM3 extraction, especially in younger patients. No intervention except follow-up and observation is necessary.
Topics: Cone-Beam Computed Tomography; Female; Humans; Male; Molar; Molar, Third; Prognosis; Prospective Studies; Retrospective Studies; Root Resorption; Tooth Resorption; Tooth, Impacted
PubMed: 35792201
DOI: 10.1016/j.joen.2022.06.008 -
American Journal of Orthodontics and... Sep 2021The center of resistance (C) is regarded as the fundamental reference point for predictable tooth movement. Accurate estimation can greatly enhance the efficiency of...
INTRODUCTION
The center of resistance (C) is regarded as the fundamental reference point for predictable tooth movement. Accurate estimation can greatly enhance the efficiency of orthodontic tooth movement. Only a handful of studies have evaluated the C of a maxillary first molar; however, most had a low sample size (in single digits), used idealized models, or involved 2-dimensional analysis. The objectives of this study were to: (1) determine the 3-dimensional (3D) location of the C of maxillary first molars, (2) evaluate its variability in a large sample, and (3) investigate the effects of applying orthodontic load from 2 directions on the location of the C.
METHODS
Cone-beam computed tomography scans of 50 maxillary molars from 25 patients (mean age, 20.8 ± 8.7 years) were used. The cone-beam computed tomography volume images were manipulated to extract 3D biological structures via segmentation. The segmented structures were cleaned and converted into virtual mesh models made of tetrahedral triangles having a maximum edge length of 1 mm. The block, which included the molars and periodontal ligament, consisted of a mean of 7753 ± 2748 nodes and 38,355 ± 14,910 tetrahedral elements. Specialized software was used to preprocess the models to create an assembly and assign material properties, interaction conditions, boundary conditions, and load applications. Specific loads were applied, and custom-designed algorithms were used to analyze the stress and strain to locate the C. The C was measured in relation to the geometric center of the buccal surface of the molar and the trifurcation of the molar roots.
RESULTS
The average location of the C for the maxillary first molar was 4.94 ± 1.39 mm lingual, 2.54 ± 2.7 mm distal, and 7.86 ± 1.66 mm gingival relative to the geometric center of the buccal surface of the molar and 0.136 ± 1.51 mm lingual (P <0.01), 1.48 ± 2.26 mm distal (P <0.01), and 0.188 ± 1.75 mm gingival (P >0.01) relative to the trifurcation of the molar roots. In the anteroposterior (y-axis) and the vertical (z-axis) planes, the C showed significant association with root divergence (P <0.01).
CONCLUSIONS
The C of the maxillary first molar was located apical and distal to the trifurcation area. It showed significant variation in its location. The 3D location of and also varied with the force direction. In some samples, this deviation was large. For accurate and predictable movement, tooth-specific C need to be calculated.
Topics: Adolescent; Adult; Child; Cone-Beam Computed Tomography; Finite Element Analysis; Humans; Maxilla; Molar; Tooth Movement Techniques; Tooth Root; Young Adult
PubMed: 34272138
DOI: 10.1016/j.ajodo.2020.04.033 -
International Journal of Environmental... May 2020The purpose of the presented Artificial Intelligence (AI)-tool was to automatically segment the mandibular molars on panoramic radiographs and extract the molar...
The purpose of the presented Artificial Intelligence (AI)-tool was to automatically segment the mandibular molars on panoramic radiographs and extract the molar orientations in order to predict the third molars' eruption potential. In total, 838 panoramic radiographs were used for training ( = 588) and validation ( = 250) of the network. A fully convolutional neural network with ResNet-101 backbone jointly predicted the molar segmentation maps and an estimate of the orientation lines, which was then iteratively refined by regression on the mesial and distal sides of the segmentation contours. Accuracy was quantified as the fraction of correct angulations (with predefined error intervals) compared to human reference measurements. Performance differences between the network and reference measurements were visually assessed using Bland-Altman plots. The quantitative analysis for automatic molar segmentation resulted in mean IoUs approximating 90%. Mean Hausdorff distances were lowest for first and second molars. The network angulation measurements reached accuracies of 79.7% [-2.5°; 2.5°] and 98.1% [-5°; 5°], combined with a clinically significant reduction in user-time of >53%. In conclusion, this study validated a new and unique AI-driven tool for fast, accurate, and consistent automated measurement of molar angulations on panoramic radiographs. Complementing the dental practitioner with accurate AI-tools will facilitate and optimize dental care and synergistically lead to ever-increasing diagnostic accuracies.
Topics: Artificial Intelligence; Dentists; Humans; Molar; Professional Role; Radiography, Panoramic
PubMed: 32466156
DOI: 10.3390/ijerph17103716