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Ko D(J, Kelly T, Thompson L, Uppal JK, Rostampour N, Webb MA, Zhu N, Belev G, Mondal P, Cooper DML, Boughner JC. Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space. J Dev Biol 2021; 9:jdb9010008. [PMID: 33809066 PMCID: PMC8006249 DOI: 10.3390/jdb9010008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/18/2021] [Accepted: 03/01/2021] [Indexed: 11/30/2022] Open
Abstract
For humans and other mammals to eat effectively, teeth must develop properly inside the jaw. Deciphering craniodental integration is central to explaining the timely formation of permanent molars, including third molars which are often impacted in humans, and to clarifying how teeth and jaws fit, function and evolve together. A factor long-posited to influence molar onset time is the jaw space available for each molar organ to form within. Here, we tested whether each successive molar initiates only after a minimum threshold of space is created via jaw growth. We used synchrotron-based micro-CT scanning to assess developing molars in situ within jaws of C57BL/6J mice aged E10 to P32, encompassing molar onset to emergence. We compared total jaw, retromolar and molar lengths, and molar onset times, between upper and lower jaws. Initiation time and developmental duration were comparable between molar upper and lower counterparts despite shorter, slower-growing retromolar space in the upper jaw, and despite size differences between upper and lower molars. Timing of molar formation appears unmoved by jaw length including space. Conditions within the dental lamina likely influence molar onset much more than surrounding jaw tissues. We theorize that molar initiation is contingent on sufficient surface area for the physical reorganization of dental epithelium and its invagination of underlying mesenchyme.
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Affiliation(s)
- Daisy (Jihyung) Ko
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Tess Kelly
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Lacey Thompson
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Jasmene K. Uppal
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Nasim Rostampour
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Mark Adam Webb
- Canadian Light Source, University of Saskatchewan, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada; (M.A.W.); (N.Z.); (G.B.)
| | - Ning Zhu
- Canadian Light Source, University of Saskatchewan, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada; (M.A.W.); (N.Z.); (G.B.)
| | - George Belev
- Canadian Light Source, University of Saskatchewan, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada; (M.A.W.); (N.Z.); (G.B.)
| | - Prosanta Mondal
- Clinical Research Support Unit, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada;
| | - David M. L. Cooper
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
| | - Julia C. Boughner
- Department of Anatomy, Physiology & Pharmacology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada; (D.K.); (T.K.); (L.T.); (J.K.U.); (N.R.); (D.M.L.C.)
- Correspondence:
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Pitirri MK, Begun D. Ontogenetic insights into the significance of mandibular corpus shape variation in hominoids: Developmental covariation between M 2 crypt formation and corpus shape. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 171:76-88. [PMID: 31710703 DOI: 10.1002/ajpa.23969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 10/18/2019] [Accepted: 10/27/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVES Here, we quantify and compare the cross-sectional shape of the mandibular corpus between M1 and M2 during growth in Pan paniscus, Pan troglodytes, and Pongo pygmaeus. The goal is to assess the hypothesis that the shape of the corpus is influenced by the development of permanent molars in their crypts, by examining ontogenetic changes in corpus shape and investigating covariation between corpus shape and M2 and M3 molar crypt forms. MATERIALS AND METHODS Ontogenetic changes in mandibular corpus shape were assessed using landmarks and semilandmarks, and measurements of length, width, and height were used to quantify molar crypts (M2 and M3 ). Ontogenetic changes in corpus growth from the eruption of M1 to the eruption of M3 were evaluated for each species through generalized Procrustes analysis and principal components analysis in shape-space and form-space. The relationship between corpus shape and molar crypt form was investigated at three different developmental stages using two-block partial least squares (2B-PLS) analysis. RESULTS The results show clear differences in growth patterns among all three species and provide evidence that species-level differences in mandibular corpus growth occur prior to the emergence of M1 . The results of the 2B-PLS analysis reveal that significant covariance between corpus shape and molar crypt form is limited to the developmental stage marked by the emergence of M1 , with covariance between corpus shape and M2 crypt width. Corpora that are relatively narrower in the inferior portion of the cross section covary with relatively narrower M2 crypts. CONCLUSIONS These results have important implications for understanding the taxonomic and phylogenetic significance of mandibular corpus shape variation in the hominoid fossil record.
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Affiliation(s)
- M K Pitirri
- Department of Anthropology, Pennsylvania State University, University Park, Pennsylvania.,Department of Anthropology, University of Toronto, Toronto, Ontario
| | - David Begun
- Department of Anthropology, University of Toronto, Toronto, Ontario
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Boughner JC, Der J, Kuykendall KL. A multivariate approach to assess variation in tooth mineralization using free-lived and captive-raised chimpanzees (P. troglodytes). AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 158:452-62. [DOI: 10.1002/ajpa.22800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 06/05/2015] [Accepted: 06/09/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Julia C. Boughner
- Department of Anatomy and Cell Biology; University of Saskatchewan; Saskatoon SK Canada
| | - Jasmine Der
- Department of Anatomy and Cell Biology; University of Saskatchewan; Saskatoon SK Canada
| | - Kevin L. Kuykendall
- Department of Archaeology; University of Sheffield; Sheffield United Kingdom
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Morita W, Yano W, Nagaoka T, Abe M, Ohshima H, Nakatsukasa M. Patterns of morphological variation in enamel-dentin junction and outer enamel surface of human molars. J Anat 2014; 224:669-80. [PMID: 24689536 PMCID: PMC4025894 DOI: 10.1111/joa.12180] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2014] [Indexed: 11/29/2022] Open
Abstract
Tooth crown patterning is governed by the growth and folding of the inner enamel epithelium (IEE) and the following enamel deposition forms outer enamel surface (OES). We hypothesized that overall dental crown shape and covariation structure are determined by processes that configurate shape at the enamel-dentine junction (EDJ), the developmental vestige of IEE. This this hypothesis was tested by comparing patterns of morphological variation between EDJ and OES in human permanent maxillary first molar (UM1) and deciduous second molar (um2). Using geometric morphometric methods, we described morphological variation and covariation between EDJ and OES, and evaluated the strength of two components of phenotypic variability, canalization and morphological integration, in addition to the relevant evolutionary flexibility, i.e. the ability to respond to selective pressure. The strength of covariation between EDJ and OES was greater in um2 than in UM1, and the way that multiple traits covary between EDJ and OES was different between these teeth. The variability analyses showed that EDJ had less shape variation and a higher level of morphological integration than OES, which indicated that canalization and morphological integration acted as developmental constraints. These tendencies were greater in UM1 than in um2. On the other hand, EDJ and OES had a comparable level of evolvability in these teeth. Amelogenesis could play a significant role in tooth shape and covariation structure, and its influence was not constant among teeth, which may be responsible for the differences in the rate and/or period of enamel formation.
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Affiliation(s)
- Wataru Morita
- Laboratory of Physical Anthropology, Department of Zoology, Graduate School of Science, Kyoto UniversityKyoto, Japan
| | - Wataru Yano
- Department of Oral Anatomy, Division of Oral Structure, Function and Development, Asahi University School of DentistryMizuho, Gifu, Japan
| | - Tomohito Nagaoka
- Department of Anatomy, St. Marianna University School of MedicineKawasaki, Kanagawa, Japan
| | - Mikiko Abe
- Department of Anatomy and Cell Biology, Graduate School of Medicine, Osaka City UniversityOsaka, Japan
| | - Hayato Ohshima
- Division of Anatomy and Cell Biology of the Hard Tissue, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental SciencesNiigata, Japan
| | - Masato Nakatsukasa
- Laboratory of Physical Anthropology, Department of Zoology, Graduate School of Science, Kyoto UniversityKyoto, Japan
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