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Journal of Anatomy Jan 2022Molar morphology is shaped by phylogenetic history and adaptive processes related to food processing. Topographic parameters of the occlusal surface, such as sharpness...
Molar morphology is shaped by phylogenetic history and adaptive processes related to food processing. Topographic parameters of the occlusal surface, such as sharpness and relief, can be especially informative regarding diet preferences of a species. The occlusal surface can however be deeply modified by wear throughout an animal's life, potentially obliterating other signals. Age being difficult to assess in wild populations, especially small rodents, experimental studies of wear through age in laboratory populations may constitute a powerful way to assess its impact on molar geometry and topography, and to validate descriptors of molar morphology that could mitigate this issue. Molar morphology was therefore quantified using 3D geometric morphometrics and topographic estimates in four groups of house mice: wild-trapped mice, lab-bred offspring of these wild mice, typical laboratory mice, and their hybrids. Three descriptors of the molar morphology were considered: the surface of the whole molar row, the surface of the first upper molar, and a truncated template of the first upper molar mimicking advanced wear. Increasing wear with age was demonstrated in the different groups, with a more pronounced effect in the wild-trapped population. The geometry of the molar row is not only modified by wear, but also by the relative position of the late developing molars on the jaw due to loading during mastication. As a consequence, the alignment of the molars is modified in wild mice, showing a qualitative difference between wild animals and their lab-bred offspring. Results obtained from the lab should thus be transferred with caution to the interpretation of differences in wild populations. Topographic estimates computed for the first upper molar seems to provide more stable parameters than those based on the whole molar row, because issues related to non-planar occlusal surface along the molar row are discarded. The truncated template was proven efficient in discarding the wear effect to focus on genetic differences, allowing an efficient characterization of the hybridization signature between wild and lab mice. Dominance of the wild phenotype for the first molar shape supports that the lab strain evolved in a context of relaxation of the selective pressures related to nutrition.
Topics: Animals; Diet; Laboratories; Mastication; Mice; Molar; Phylogeny
PubMed: 34333769
DOI: 10.1111/joa.13529 -
International Journal of Oral Science Feb 2024Mammalian teeth, developing inseparable from epithelial-mesenchymal interaction, come in many shapes and the key factors governing tooth morphology deserve to be...
Mammalian teeth, developing inseparable from epithelial-mesenchymal interaction, come in many shapes and the key factors governing tooth morphology deserve to be answered. By merging single-cell RNA sequencing analysis with lineage tracing models, we have unearthed a captivating correlation between the contrasting morphology of mouse molars and the specific presence of PRX1 cells within M1. These PRX1 cells assume a profound responsibility in shaping tooth morphology through a remarkable divergence in dental mesenchymal cell proliferation. Deeper into the mechanisms, we have discovered that Wnt5a, bestowed by mesenchymal PRX1 cells, stimulates mesenchymal cell proliferation while orchestrating molar morphogenesis through WNT signaling pathway. The loss of Wnt5a exhibits a defect phenotype similar to that of siPrx1. Exogenous addition of WNT5A can successfully reverse the inhibited cell proliferation and consequent deviant appearance exhibited in Prx1-deficient tooth germs. These findings bestow compelling evidence of PRX1-positive mesenchymal cells to be potential target in regulating tooth morphology.
Topics: Animals; Mice; Mesenchymal Stem Cells; Molar; Morphogenesis; Tooth Germ
PubMed: 38369512
DOI: 10.1038/s41368-024-00277-0 -
Proceedings of the National Academy of... Jan 2021Identifying developmental explanations for the evolution of complex structures like mammalian molars is fundamental to studying phenotypic variation. Previous study...
Identifying developmental explanations for the evolution of complex structures like mammalian molars is fundamental to studying phenotypic variation. Previous study showed that a "morphogenetic gradient" of molar proportions was explained by a balance between inhibiting/activating activity from earlier developing molars, termed the inhibitory cascade model (ICM). Although this model provides an explanation for variation in molar proportions, what remains poorly understood is if molar shape, or specifically complexity (i.e., the number of cusps, crests), can be explained by the same developmental model. Here, we show that molar complexity conforms to the ICM, following a linear, morphogenetic gradient along the molar row. Moreover, differing levels of inhibiting/activating activity produce contrasting patterns of molar complexity depending on diet. This study corroborates a model for the evolution of molar complexity that is developmentally simple, where only small-scale developmental changes need to occur to produce change across the entire molar row, with this process being mediated by an animal's ecology. The ICM therefore provides a developmental framework for explaining variation in molar complexity and a means for testing developmental hypotheses in the broader context of mammalian evolution.
Topics: Animals; Biological Evolution; Diet; Humans; Mammals; Models, Theoretical; Molar; Morphogenesis
PubMed: 33443174
DOI: 10.1073/pnas.2008850118 -
BMC Oral Health Oct 2023The aim of this study was to determine whether there is any association between molar incisor hypomineralization and developmental dental anomalies.
BACKGROUND
The aim of this study was to determine whether there is any association between molar incisor hypomineralization and developmental dental anomalies.
METHODS
Two pediatric dentists evaluated panoramic radiographs of 429 children aged 8-14 years with molar incisor hypomineralization (study group) and 437 children without molar incisor hypomineralization (control group) in terms of developmental dental anomalies. Twelve different developmental dental anomalies were categorized into four types: size (microdontia, macrodontia); position (ectopic eruption of maxillary permanent first molars, infraocclusion of primary molars); shape (fusion, gemination, dilaceration, taurodontism, peg-shaped maxillary lateral incisors); and number (hypodontia, oligodontia, hyperdontia) anomalies.
RESULTS
No significant difference was observed in the frequencies of developmental dental anomalies between the study and control groups in total, females, and males (p > 0.05). A statistically significant difference was found between the distribution of developmental size, position, shape, and number anomalies between the study and control groups (p = 0.024). The most common anomaly in both groups was hypodontia (6.3% and 5.9%, respectively). There was a significant difference between the study and control groups in terms of subtypes of shape anomaly in all children and females (p = 0.045 and p = 0.05, respectively).
CONCLUSIONS
While a significant difference was observed between the distributions of types of developmental dental anomalies between individuals with and without molar incisor hypomineralization, there was no difference in terms of the frequency of developmental dental anomalies.
Topics: Male; Child; Female; Humans; Anodontia; Case-Control Studies; Molar Hypomineralization; Tooth Abnormalities; Tooth, Supernumerary; Molar; Prevalence; Dental Enamel Hypoplasia
PubMed: 37865729
DOI: 10.1186/s12903-023-03540-8 -
ELife Feb 2020Do developmental systems preferentially produce certain types of variation that orient phenotypic evolution along preferred directions? At different scales, from the...
Do developmental systems preferentially produce certain types of variation that orient phenotypic evolution along preferred directions? At different scales, from the intra-population to the interspecific, the murine first upper molar shows repeated anterior elongation. Using a novel quantitative approach to compare the development of two mouse strains with short or long molars, we identified temporal, spatial and functional differences in tooth signaling center activity, that arise from differential tuning of the activation-inhibition mechanisms underlying tooth patterning. By tracing their fate, we could explain why only the upper first molar reacts via elongation of its anterior part. Despite a lack of genetic variation, individuals of the elongated strain varied in tooth length and the temporal dynamics of their signaling centers, highlighting the intrinsic instability of the upper molar developmental system. Collectively, these results reveal the variational properties of murine molar development that drive morphological evolution along a line of least resistance.
Topics: Animals; Biological Evolution; Biological Variation, Population; Embryo, Mammalian; Female; Male; Mice; Molar; Phenotype; Pregnancy; Signal Transduction; Tooth Eruption
PubMed: 32048989
DOI: 10.7554/eLife.50103 -
Journal of Dentistry Apr 2022The biomechanical response of an autotransplanted tooth and surrounding bone to occlusal loads is not well-known. The aim of the present study was to investigate the...
OBJECTIVE
The biomechanical response of an autotransplanted tooth and surrounding bone to occlusal loads is not well-known. The aim of the present study was to investigate the effect of root form and occlusal morphology on stress distribution in autotransplanted teeth and surrounding bone by using finite element analysis (FEA).
METHODS
Seven FEA models representing different autotransplanted tooth situations were generated: (a) first molar, (b) third molar, (c) root canal-treated third molar, (d) root canal-treated, ankylosed, third molar, (e) crowned third molar, (f) crowned and root canal-treated third molar, (g) root canal-treated, ankylosed, and crowned third molar. Load (200 N) was applied on the occlusal surface, parallel to the long axis of the tooth. Maximum von Mises stress values on dentin and surrounding bone were calculated for each situation.
RESULTS
Differences in stress distribution were observed among models. In ankylosed model, stress was primarily observed at the coronal region of the tooth. The stress was observed more at the coronal region of the tooth in crowned models compared with the non-crowned models. The stress distribution was homogeneous with root canal-treated and crowned autotransplanted tooth.
CONCLUSIONS
The occlusal morphology and root form of the autotransplanted tooth affected the stress in surrounding bone at the transfer site and the biomechanical response of the tooth. The stress was more homogeneous in crowned tooth and primarily observed at the coronal region, which may decrease the risk for root resorption.
CLINICAL SIGNIFICANCE
Root configuration, occlusal form and root canal treatment induce significant changes on the stress distribution on teeth and bone, including characteristic stress concentration and increased stress values. Clinicians can consider crowning autotransplanted teeth for improved stress distribution within the tooth structure.
Topics: Finite Element Analysis; Humans; Molar; Molar, Third; Stress, Mechanical; Tooth, Nonvital
PubMed: 35247471
DOI: 10.1016/j.jdent.2022.104082 -
BMC Oral Health Nov 2023To observe the three-dimensional positional relationship between impacted mandibular third molars (IMTMs) and mandibular canal close contacts using cone beam computed...
OBJECTIVE
To observe the three-dimensional positional relationship between impacted mandibular third molars (IMTMs) and mandibular canal close contacts using cone beam computed tomography (CBCT).
METHODS
A total of 101 patients with IMTMs were selected who met the diagnostic criteria for 142 teeth (no bone wall imaging area between IMTMs and the mandibular canal, a high-density bone cortical imaging area only, or a ≦1 mm bone imaging area). The parameters of the rotating CBCT anode were set as follows: 110 kV, 40-50 mA; the focal point and exposure field were set as 0.3 mmh and a high-resolution zoom, respectively; the exposure time and image layer thickness were set as 5.4 s and 0.25 mm. Three-dimensional reconstruction was performed, and the position of the mandibular canal through the IMTM area was observed continuously from the coronal, horizontal and sagittal planes.
RESULTS
We found that the mandibular canal was interrupted below the third molar (TM) in 85 cases, accounting for 59.86% of all cases. The mandibular canal was located below the buccal and lingual curvatures in 33 and 19 cases, respectively, accounting for 23.23% and 19%. In addition, a small number of mandibular canals were also located on the buccal side of the mandibular molars (2.82%). We also found one case of direct insertion of the mandibular third molar (MTM) into the mandibular canal. In addition, the mandibular canal passed through the IMTM region with 125 close contacts at the roots (88.03%); 14 mandibular canals were in contact with all teeth and 3 were in contact with the crown.
CONCLUSION
The use of CBCT can provide a dynamic and comprehensive understanding of the three-dimensional positional relationship of the mandibular alveolar nerve canal passing through the IMTM area, providing a high clinical reference value when extracting IMTMs and reducing the risk of injury to the inferior alveolar nerve.
Topics: Humans; Molar, Third; Mandibular Canal; Molar; Mandible; Tooth, Impacted; Cone-Beam Computed Tomography; Mandibular Nerve
PubMed: 37924035
DOI: 10.1186/s12903-023-03548-0 -
Stomatologija 2020Evaluate the influence of different wound closure methods in terms of pain, swelling, trismus, infection and healing time after third molar extraction. (Review)
Review
OBJECTIVE
Evaluate the influence of different wound closure methods in terms of pain, swelling, trismus, infection and healing time after third molar extraction.
MATERIAL AND METHODS
A literature analysis was performed according to PRISMA guidelines in search of clinical trials published between 2015 and 2020. Databases were searched using different combinations of the following keywords: mandibular impacted OR retained wisdom teeth OR third molar removal OR extraction AND surgical removal AND discomfort OR pain OR trismus OR swelling AND drain OR drainage. The literature search resulted in a total of 364 publications. Finally, 12 study articles were used in the present review, following a selection based on the preestablished eligibility criteria.
RESULTS
The significant difference between various wound closure ways and postoperative pain, swelling and trismus has been found in 8 of 12 analyzed articles. Three of five established beneficial effect of drain application. In other articles, examining different wound closure methodologies, significant benefits were found by using buccally based triangular, buccal mucosal-advancement, and modified envelope flap. Suture-less anterior releasing incision and secondary wound closure also could be favorable after removing impacted third molars.
CONCLUSION
There was no significant effect of a rubber drain on swelling, pain, trismus, or wound infections after removal of the asymptomatic impacted third molar(s). Secondary wound closure was found to ensure lower pain, swelling and trismus ratio with comparison to primary wound closure.
Topics: Humans; Mandible; Molar, Third; Pain, Postoperative; Tooth Extraction; Tooth, Impacted; Trismus
PubMed: 33847282
DOI: No ID Found -
Forensic Science International May 2023Reliability, or repeatability, of permanent tooth staging techniques is usually expressed as Cohen's Kappa. This single value obscures information about the quantity and...
Reliability, or repeatability, of permanent tooth staging techniques is usually expressed as Cohen's Kappa. This single value obscures information about the quantity and allocation of disagreements. In this study we assess and compare intra-observer reliability of permanent tooth staging techniques described by Nolla, Moorrees et al. and Demirjian et al. The sample was panoramic radiographs of healthy dental patients made up of 100 males and 100 females aged 6-15 years. All permanent teeth on the left side (excluding third molars) were scored twice. Weighted Kappa and percentage agreement were calculated. Results show Kappa values for all teeth combined as 0.918, 0.922 and 0.938 for Demirjian (number of teeth N = 2682), Nolla (N = 2698) and Moorrees (N = 2674) respectively. A comparison of Kappa values between upper and lower teeth showed marginally higher values for upper incisors and lower molar for all three scoring methods. Small differences in Kappa values were noted between tooth types with the upper first molar having smaller values than other teeth. Percentage agreement ranged from 81 % (Moorrees), 86 % (Nolla) to 87 % (Demirjian). Tooth stage differences between first and second assessments were not more than one stage. Our findings show that Demirjian scoring is marginally more reliable than Nolla or Moorrees. We suggest that (1) data for reliability are tabulated in full to show the quantity and allocation of disagreement between first and second readings, and (2) that the reliability sample is sufficiently large with a wide age range to include multiple different tooth stages.
Topics: Male; Female; Humans; Reproducibility of Results; Age Determination by Teeth; Dentition, Permanent; Tooth; Molar, Third; Molar; Radiography, Panoramic
PubMed: 37011430
DOI: 10.1016/j.forsciint.2023.111654 -
The Angle Orthodontist May 2020To assess the effects of piezocision on the rate of mandibular second molar protraction.
OBJECTIVES
To assess the effects of piezocision on the rate of mandibular second molar protraction.
MATERIALS AND METHODS
Thirty-one subjects (average age: 22.26 ± 5.63 years) who presented with at least one extracted mandibular first molar were selected to participate in the study. The subjects were subdivided into one of two groups, 22 molars each: group 1, where piezocision was performed immediately before molar protraction and group 2, where molar protraction was performed with no piezocision. Piezocision was performed by making two vertical incisions mesial and distal to the extraction space, and bone cuts were done with a length up to the mucogingival line at a depth of 3 mm. The rate of second molar protraction, duration of space closure, and level of interleukin-1-β (IL-1β) in gingival crevicular fluid (GCF) during the first month of space closure were recorded.
RESULTS
During the first 2 months after surgery, the rates of second molar protraction were 1.26 ± 0.12 mm/month and 0.68 ± 0.19 mm/month in the piezocision and no piezocision groups, respectively (P < .001). Duration of lower first molar space closure was 9.61 ± 0.98 months in the piezocision group and 10.87 ± 1.52 months in the no piezocision group (P < .01). The level of IL-1β in GCF was higher in the piezocision group compared to the no piezocision group, up to 1 week after surgery (P = .02).
CONCLUSIONS
Although piezocision doubled the rate of second molar protraction during the first 2 months after surgery, overall second molar protraction was increased by only 1 month.
Topics: Adolescent; Adult; Humans; Mandible; Molar; Young Adult
PubMed: 33378435
DOI: 10.2319/080419-511.1