Initial third molar development is delayed in jaws with short distal space: An early impaction sign?

Marchiori, Denver; Packota, Garnet V.; Boughner, Julia C.

doi:10.1016/j.archoralbio.2019.06.010

Cited by 15 publications

(11 citation statements)

References 34 publications

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“…Rather, these findings emphasize the distinction that jaw length and space are vital for proper molar eruption and emergence into occlusion, but do not seem essential for timely molar initiation and morphogenesis. Applying our findings to human wisdom teeth: earlier M3 development increases the likelihood of proper M3 eruption [48], but the size of total jaw length and retromolar space may not explain earlier or later M3 development. To explain the etiology of other misfits between human dentitions and jawbones, such as dental crowding and malocclusion, our findings imply that it is more informative to study variables acting during late stages of tooth development (i.e., eruption) that help properly integrate teeth within the jawbone and the dental arcade.…”

Section: Implications For Human Dental Development and Dental Healthmentioning

confidence: 75%

Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

Kelly

Thompson

et al. 2021

JDB

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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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Section: Implications For Human Dental Development and Dental Healthmentioning

confidence: 75%

Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

Kelly

Thompson

et al. 2021

JDB

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“…Knowing the spatiotemporal association between jaw and molar formations and the late completion of the posterior part of the palate in its growth sequence, one could speculate that jaws growing an overall larger size might be developmentally and mechanistically associated with a greater growth of lateforming posterior molars in comparison to anterior ones. Speculation about an association between molar proportions and jaw size is not new (e.g., Ford, 1980;Monson et al, 2019b), and links between jaw dimensions and third molar development are for instance welldocumented in humans (Kömerik et al, 2014;Marchiori et al, 2019). However, more research is needed in that direction as the validity of an association between jaw growth and molar proportions and the potential mechanisms behind it remains extremely obscure.…”

Section: Potential Correlates and Mechanisms Behind The Allometric Pa...mentioning

confidence: 99%

Segmental Series and Size: Clade-Wide Investigation of Molar Proportions Reveals a Major Evolutionary Allometry in the Dentition of Placental Mammals

Billet¹,

Bardin²

2021

Systematic Biology

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Iterative segments such as teeth or limbs are a widespread characteristic of living organisms. While their proportions may be governed by similar developmental rules in vertebrates, there is no emerging pattern as regards their relation to size. Placental mammals span eight orders of magnitude in body size and show a wide spectrum of dietary habits associated with size and reflected in their dentitions, especially molars. Although variation in size constitutes an important determinant for variation in biological traits, few major allometric trends have been documented on placental molars so far. Molar proportions have been intensively explored in placentals in relation to developmental models, but often at a small phylogenetic scale. Here, we analyzed the diversity of upper molar proportions in relation to absolute size in a large sample of placental species (n = 286) encompassing most of the group’s dental diversity. Our phylogenetically informed analyses revealed a twofold pattern of evolutionary integration among upper molars: while molars covary in size with each other, their proportions covary with the absolute size of the entire molar field. With increasing absolute size, posterior molars increase in size relative to anterior ones, meaning that large-sized species have relatively large rear molars while the opposite is true for small-sized species. The directionality of proportional increase in the molar row exhibits a previously unsuspected allometric patterning among placentals, showing how large-scale variations in size may have influenced variation in dental morphology. This finding provides new evidence that processes regulating the size of individual molars are integrated with overall patterns of growth and calls for further testing of allometric variation in the dentition and in other segmental series of the vertebrate body.

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“…While a deficiency of retromolar space is a known risk factor for end-molar impaction, Marchiori et al [23] investigated delayed third molar development as a factor leading to impacted wisdom teeth. They found that a lack of jaw space distal to the second molars was related to less well-developed third molars, and a severe deficiency of space was associated with an absence of third molar tooth germ development in early childhood.…”

Section: Discussionmentioning

confidence: 99%

Midfacial development and the wisdom of teeth: A case series

Singh¹,

Lee

2021

Preprint

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Initial third molar development is delayed in jaws with short distal space: An early impaction sign?

Cited by 15 publications

References 34 publications

Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

Segmental Series and Size: Clade-Wide Investigation of Molar Proportions Reveals a Major Evolutionary Allometry in the Dentition of Placental Mammals

Midfacial development and the wisdom of teeth: A case series

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