-
BMC Ecology and Evolution Jul 2021Placodontia is a Triassic sauropterygian reptile group characterized by flat and enlarged crushing teeth adapted to a durophagous diet. The enigmatic placodont Henodus...
BACKGROUND
Placodontia is a Triassic sauropterygian reptile group characterized by flat and enlarged crushing teeth adapted to a durophagous diet. The enigmatic placodont Henodus chelyops has numerous autapomorphic character states, including extreme tooth count reduction to only a single pair of palatine and dentary crushing teeth. This renders the species unusual among placodonts and challenges identification of its phylogenetic position.
RESULTS
The skulls of two Henodus chelyops specimens were visualized with synchrotron tomography to investigate the complete anatomy of their functional and replacement crushing dentition in 3D. All teeth of both specimens were segmented, measured, and statistically compared to reveal that H. chelyops teeth are much smaller than the posterior palatine teeth of other cyamodontoid placodonts with the exception of Parahenodus atancensis from the Iberian Peninsula. The replacement teeth of this species are quite similar in size and morphology to the functional teeth.
CONCLUSION
As other placodonts, Henodus chelyops exhibits vertical tooth replacement. This suggests that vertical tooth replacement arose relatively early in placodont phylogeny. Analysis of dental morphology in H. chelyops revealed a concave shape of the occlusal surface and the notable absence of a central cusp. This dental morphology could have reduced dental wear and protected against failure. Hence, the concave teeth of H. chelyops appear to be adapted to process small invertebrate items, such as branchiopod crustaceans. Small gastropods were encountered in the matrix close to both studied skulls.
Topics: Animals; Dentition; Jaw; Odontogenesis; Phylogeny; Tooth
PubMed: 34225664
DOI: 10.1186/s12862-021-01835-4 -
BioEssays : News and Reviews in... Dec 2018Efforts from diverse disciplines, including evolutionary studies and biomechanical experiments, have yielded new insights into the genetic, signaling, and mechanical... (Review)
Review
Efforts from diverse disciplines, including evolutionary studies and biomechanical experiments, have yielded new insights into the genetic, signaling, and mechanical control of tooth formation and functions. Evidence from fossils and non-model organisms has revealed that a common set of genes underlie tooth-forming potential of epithelia, and changes in signaling environments subsequently result in specialized dentitions, maintenance of dental stem cells, and other phenotypic adaptations. In addition to chemical signaling, tissue forces generated through epithelial contraction, differential growth, and skeletal constraints act in parallel to shape the tooth throughout development. Here recent advances in understanding dental development from these studies are reviewed and important gaps that can be filled through continued application of evolutionary and biomechanical approaches are discussed.
Topics: Animals; Biological Evolution; Biomechanical Phenomena; Cell Differentiation; Cell Proliferation; Dentition; Fishes; Fossils; Gene Expression Regulation, Developmental; Stem Cells; Tooth
PubMed: 30387177
DOI: 10.1002/bies.201800140 -
International Journal of Paediatric... Sep 2020Primary and permanent teeth composition may influence dissolution and degradation rates.
BACKGROUND
Primary and permanent teeth composition may influence dissolution and degradation rates.
AIM
To compare the dissolution and degradation of primary and permanent teeth.
DESIGN
Enamel and dentin powders were obtained from primary molars and premolars and incubated within different pH buffers. Calcium and inorganic phosphate release was quantified in the buffers by atomic absorption and light spectrophotometry. A colorimetric assay was used to assess the MMP activity of primary dentin (PrD) and permanent dentin (PeD). Collagen degradation was assessed by dry mass loss, change in elastic modulus (E), and ICTP and CTX release. Data were submitted to ANOVA and Tukey's tests (α = 0.05).
RESULTS
Similar dissolution was found between PrD and PeD after 256 hours. At pH 4.5, enamel released more minerals than dentin whereas at pH 5.5 the inverse result was observed. MMP activity was similar for both substrates. PrD showed higher dry mass loss after 1 week. In general, greater reduction in E was recorded for PrD. Higher quantities of ICTP and CTX were released from PrD after 1 week.
CONCLUSIONS
Primary and permanent teeth presented similar demineralization rates. Collagen degradation, however, was faster and more substantial for PrD.
Topics: Dentin; Dentition, Permanent; Matrix Metalloproteinases; Molar; Solubility
PubMed: 32077547
DOI: 10.1111/ipd.12632 -
The Journal of Clinical Pediatric... Jan 2021This study examines how accurate pediatric dentists are at estimating dental arch lengths by comparing their model estimations (guesstimating the arch length without...
OBJECTIVES
This study examines how accurate pediatric dentists are at estimating dental arch lengths by comparing their model estimations (guesstimating the arch length without measuring) to the Tanaka and Johnston mixed dentition arch length analysis.
STUDY DESIGN
This study consisted of two parts, a survey of practitioners and a model estimating and measuring component. The survey was designed and given to 44 pediatric dentists to determine how many were practicing orthodontics and using arch length analyses routinely. Then 18 pediatric dentists and 13 pediatric dental residents examined 20 sets of mixed dentition models and estimated how much space was available. These estimations were compared to the calculated gold standard, the Tanaka and Johnston arch length analysis of the same models.
RESULTS AND CONCLUSIONS
More than half of the dentists surveyed that practice comprehensive orthodontics use arch length estimates. Pediatric dentists and pediatric dental residents are just as good as each other at estimating arch length. Pediatric dentists and pediatric dental residents underestimated arch length by -3.6 and -3.1 mm, respectively. More research needs to be done to determine if model estimation is a clinically acceptable way to judge arch length.
Topics: Bicuspid; Child; Dental Arch; Dentition, Mixed; Humans; Odontometry; Orthodontics
PubMed: 33690829
DOI: 10.17796/1053-4625-45.1.10 -
Scientific Reports Mar 2019Morphological integration and modularity are important for understanding phenotypic evolution because they constrain variation subjected to selection and enable...
Morphological integration and modularity are important for understanding phenotypic evolution because they constrain variation subjected to selection and enable independent evolution of functional and developmental units. We report dental integration and modularity in representative otariid (Eumetopias jubatus, Callorhinus ursinus) and phocid (Phoca largha, Histriophoca fasciata) species of Pinnipedia. This is the first study of integration and modularity in a secondarily simplified dentition with simple occlusion. Integration was stronger in both otariid species than in either phocid species and related positively to dental occlusion and negatively to both modularity and tooth-size variability across all the species. The canines and third upper incisor were most strongly integrated, comprising a module that likely serves as occlusal guides for the postcanines. There was no or weak modularity among tooth classes. The reported integration is stronger than or similar to that in mammals with complex dentition and refined occlusion. We hypothesise that this strong integration is driven by dental occlusion, and that it is enabled by reduction of modularity that constrains overall integration in complex dentitions. We propose that modularity was reduced in pinnipeds during the transition to aquatic life in association with the origin of pierce-feeding and loss of mastication caused by underwater feeding.
Topics: Animals; Caniformia; Dental Occlusion; Dentition; Female; Male; Phylogeny; Tooth
PubMed: 30862801
DOI: 10.1038/s41598-019-40956-1 -
The Bulletin of Tokyo Dental College Jan 2023In this study, original leeway space was determined using plaster models prepared from the same individuals over successive years and compared with that reported in an...
In this study, original leeway space was determined using plaster models prepared from the same individuals over successive years and compared with that reported in an earlier study. The plaster models used for measurement were prepared from a normal dentition group comprising 64 patients and a crowded dentition group comprising 29. The mesiodistal crown width of the deciduous canines, deciduous first molars, and deciduous second molars, as well as that of the canines, first premolars, and second premolars was measured. Leeway space was then calculated and the results compared with that previously reported. The average maxillary and mandibular leeway spaces calculated in the same individuals were 1.46 and 2.66 mm, respectively, whereas those calculated from data collected from different individuals were 0.89 and 2.83 mm, respectively. No direct statistical comparison of leeway space between this and the earlier report was possible. The present results did indicate, however, that it was larger in the maxilla than previously reported. A larger leeway space is advantageous for the normal arrangement of the permanent teeth. While the mesiodistal crown width of some of the lateral segment teeth in the present study was significantly larger in boys than in girls, no significant difference was observed in leeway space between sexes. The mesiodistal width was larger in multiple permanent teeth such as canines in the crowded dentition group, and this difference was significant in boys. On the other hand, no difference was observed in mesiodistal width in the deciduous teeth between the two groups. These results showed a tendency toward larger teeth and less leeway space in the permanent dentition in the crowded dentition group, which may have been a factor in why such crowding occurred.
Topics: Humans; Odontometry; Molar; Tooth Crown; Bicuspid; Malocclusion
PubMed: 36384757
DOI: 10.2209/tdcpublication.2021-0046 -
Australian Dental Journal Jun 2014Tooth development has attracted the attention of researchers since the 19th century. It became obvious even then that morphogenesis could not fully be appreciated from... (Review)
Review
Tooth development has attracted the attention of researchers since the 19th century. It became obvious even then that morphogenesis could not fully be appreciated from two-dimensional histological sections. Therefore, methods of three-dimensional (3D) reconstructions were employed to visualize the surface morphology of developing structures and to help appreciate the complexity of early tooth morphogenesis. The present review surveys the data provided by computer-aided 3D analyses to update classical knowledge of early odontogenesis in the laboratory mouse and in humans. 3D reconstructions have demonstrated that odontogenesis in the early stages is a complex process which also includes the development of rudimentary odontogenic structures with different fates. Their developmental, evolutionary, and pathological aspects are discussed. The combination of in situ hybridization and 3D reconstruction have demonstrated the temporo-spatial dynamics of the signalling centres that reflect transient existence of rudimentary tooth primordia at loci where teeth were present in ancestors. The rudiments can rescue their suppressed development and revitalize, and then their subsequent autonomous development can give rise to oral pathologies. This shows that tooth-forming potential in mammals can be greater than that observed from their functional dentitions. From this perspective, the mouse rudimentary tooth primordia represent a natural model to test possibilities of tooth regeneration.
Topics: Animals; Biological Evolution; Dentition; Diastema; Humans; Image Processing, Computer-Assisted; Imaging, Three-Dimensional; In Situ Hybridization; Mice; Odontogenesis; Regeneration; Tooth; Tooth, Supernumerary
PubMed: 24495023
DOI: 10.1111/adj.12130 -
BioMed Research International 2022This study aimed to conduct a compendious review of root canal morphology of "permanent mandibular teeth in different regions of Saudi Arabia" to obtain a large sample... (Review)
Review
This study aimed to conduct a compendious review of root canal morphology of "permanent mandibular teeth in different regions of Saudi Arabia" to obtain a large sample representing the total population. A detailed search through the databases Web of Science, Scopus, and PubMed was conducted following the PRISMA guidelines. The data were analyzed based on the following inclusion criteria: original full-length original articles that reported the variables of interest "(number of roots, number of canals, Vertucci's classification system and C-shaped canals or mid-mesial canals)" of the mandibular teeth and conducted on Saudi subjects. The retrieved data were presented as frequencies and percentages. The results revealed that 56.6% of mandibular central incisors had one canal and Vertucci type I (56.6%), while 57.4% of the mandibular lateral incisors had one canal, with Vertucci types I and III most frequent. In mandibular canines, 91.8% had one canal and 8.2% had two canals. Most of the mandibular first premolars had one root (86.6%), while almost all mandibular second premolars (91.5%) had one canal, and 96.9% had Vertucci type I configuration. Among the mandibular first molars, three and four canals were prevalent in 58.7% and 40.6%, respectively. The majority of mesial roots had Vertucci type IV (60.6%), and most of distal roots had Vertucci type I (72.2%). Most of the mandibular second molars had three canals (87.3%) and showed Vertucci type IV (39.4%) canals for mesial roots and Vertucci type I (95.6%) for distal roots. The C-shaped canals were seen in 8% of first premolars and 9.8% of second molars. The middle mesial canal was found in 4.2% and 0.4% of first and second molars, respectively. This review could represent "the population of Saudi Arabia as the included samples were combined from different regions of the country." Some variations were noticed within the same group of teeth from different regions. However, the overall results of combined samples were comparable to the other international studies.
Topics: Dental Pulp Cavity; Dentition; Humans; Mandible; Molar; Saudi Arabia; Tooth Root
PubMed: 35958809
DOI: 10.1155/2022/2400314 -
Brazilian Oral Research 2016The aim of the present study was to search for scientific evidence concerning the association between breastfeeding and bottle feeding and risk of malocclusion in mixed... (Review)
Review
The aim of the present study was to search for scientific evidence concerning the association between breastfeeding and bottle feeding and risk of malocclusion in mixed and permanent dentitions. An electronic search was performed in eight databases up to February 2015. Additionally, a gray literature search and hand searches of the reference lists of the selected studies were also carried out. There were no restrictions on language or on year of publication. The methodology of the included articles was evaluated using the Newcastle Ottawa scale. Out of the 817 identified citations, six studies fulfilled the eligibility criteria and were included in the systematic review. One study showed that children with mixed and permanent dentitions breastfed for more than 6 months presented greater mean protrusion of mandibular incisors and inclination of maxillary incisors compared with those breastfed for less than 6 months or those who were bottle-fed (p < 0.05). One study revealed that breastfeeding and bruxism were associated with Class II [OR = 3.14 (1.28 - 7.66)] and Class III [OR = 2.78 (1.21 - 6.36)] malocclusion in children with permanent dentition, while another study showed that an increase in breastfeeding duration was associated with a lower risk of malocclusion in children with both mixed and permanent dentitions (p < 0.001). Three studies did not report any significant association. Risk of bias was high in most selected articles. These findings do not support an association between breastfeeding and bottle feeding and the occurrence of malocclusion in mixed and permanent dentitions.
Topics: Adolescent; Bottle Feeding; Breast Feeding; Child; Child, Preschool; Dentition, Mixed; Dentition, Permanent; Female; Humans; Male; Malocclusion; Risk Assessment; Risk Factors
PubMed: 27050935
DOI: 10.1590/1807-3107BOR-2016.vol30.0022 -
The International Journal of... Feb 1995Neural crest cells migrate along specific pathways to reach the mandibular and maxillary arches where they condense under specific areas of the ectoderm which will give... (Review)
Review
Neural crest cells migrate along specific pathways to reach the mandibular and maxillary arches where they condense under specific areas of the ectoderm which will give rise to the primary and permanent dentition. In the mouse, the trigeminal ganglion becomes evident on E9 and the superior cervical sympathetic ganglion E13. Several studies have suggested that nerves in the vicinity of the developing teeth could influence the surrounding tissues and initiate tooth development, whereas other investigators have suggested that tooth development will proceed without an intact innervation. Innervation of the dental papilla has been reported as early as the cap stage in human teeth using an antibody to PGP 9.5. A large variety of putative neurotransmitters have been localized in the nerves of the dental pulp. Many of the putative neurotransmitters function in vasoregulation while others have unknown functions. A hypothesis is presented describing a possible signal transduction pathway between odontoblasts and nerve terminals.
Topics: Animals; Dental Papilla; Dental Pulp; Humans; Nerve Fibers; Neurotransmitter Agents; Odontoblasts; Odontogenesis; Signal Transduction; Tooth
PubMed: 7626406
DOI: No ID Found