Variability in cusp size of human maxillary molars, with particular reference to the hypocone

Takahashi, Masami; Kondo, Shintaro; Townsend, Grant; Kanazawa, Eisaku

doi:10.1016/j.archoralbio.2007.06.005

Cited by 41 publications

(50 citation statements)

References 20 publications

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“…In addition, both men and women had greater measurements with respect to the total cusp area, area of occlusal table, and occlusal table ratio in the first molars than in the second molars. These results correspond with the results of previous studies, which showed that the faster the cusp develops, the greater the cusp becomes, i.e., late-developing teeth more frequently have reduced overall size than early-developing teeth because the former have more spatial restrictions [3,5,8,10,[18][19][20][21][22].…”

Section: Discussionsupporting

confidence: 81%

“…There may be two explanations for no significant sex difference in the size of the hypoconulid of the mandibular second molars. First, the latest-calcifying hypoconulid has the greatest variability and the hypoconulid appears less frequently in mandibular second molars because of greater spatial restrictions than mandibular first molars [8,10]. Secondly, it might be assumed that the periods of completion of mandibular first and second molar cusp formation (mandibular first molar: 2.5~3 years of age, mandibular second molar: 7~8 years of age) are much before adolescence, during which there is production and secretion of sex hormones.…”

Section: Discussionmentioning

confidence: 99%

“…In a study in the natives of Australia, it was reported that cusps of the maxillary first molar which form early show less variations than cusps of the maxillary second molar which form later [8]. In addition, sex differences existed in the maxillary second molars than in the maxillary first molars.…”

Section: Introductionmentioning

confidence: 99%

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Variations in the Cusps of Mandibular Molars in Koreans

Yoo

Kim

2014

Korean J Phys Anthropol

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: This study aimed to investigate the cusp size and morphological characteristics of permanent mandibular molars in Koreans with reference to the hypoconulid, and to analyze the differences and correlations between both sexes as well as between first and second mandibular molars. We obtained data from dental casts of 110 adults (78 males and 32 females). Mesiodistal and buccolingual diameters of first and second mandibular molars, the area of five cusps (protoconid, metaconid, hypoconid, entoconid, and hypoconulid), as well as the total cusp area and occlusal table area were measured. Paired t-test was performed to analyze the morphological differences between first and second mandibular molars and the sex differences between both sexes using SPSS program. Crown diameters and cusp areas of mandibular first molars were larger than those of mandibular second molars in both sexes. The hypoconulid was the most variable in size and morphological pattern among the five cusps, and the first molars showed a higher incidence of hypoconulid than the second molars. Except for the entoconid area of the first molar (p= =0.06) and the hypoconulid area of the second molar (p= =0.24), all other mean values were larger in males than in females, demonstrating a significant sexual dimorphism. These data suggest that the teeth which develop late in ontogeny tend to be smaller in size and more variable in morphological characteristics.

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Section: Discussionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

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Variations in the Cusps of Mandibular Molars in Koreans

Yoo

Kim

2014

Korean J Phys Anthropol

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“…The tooth analysed in this study is the upper first molar (M 1 ) as it is the least variable of the three maxillary molars (Morris, 1986;Bailey, 2004) and most published studies have used this tooth, and hence provide comparable data (Morris, 1986;Ozaki et al, 1987;Bailey, 2004;Harris and Dinh, 2006;Takahashi et al, 2007;Bailey et al, 2008;Pressley, 2008;Quam et al, 2009). Occlusal wear had to be kept to a minimum in order for the four cusps to be easily and correctly identified.…”

Section: Methodsmentioning

confidence: 99%

Dental microevolution in Portuguese Neolithic and modern samples using an alternative morphometric analysis

Fernandes

Silva

O’Donnabhain

et al. 2013

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Most studies of dental microevolution have used the standard methodologies employed in dental anthropology: buccolingual/mesiodistal lengths and the frequencies of non-metric dental traits. In this work we use the occlusal polygon method which is based on a polygon created by linking the four molar cusp apices using digital analysis. This method has been used to identify different evolutionary trends in Neandertal and modern humans; our objective was to assess the existence of changes in the occlusal polygon area, and thus the general morphology of first upper molars, between two Portuguese samples from the Late Neolithic (4130 ± 90 BP) and the early 20th century. This method allows us to evaluate both tooth size and relative cusp position in the occlusal plane. Contrary to the accentuated tooth size reduction commonly found from the past 10000 years using buccolingual/ mesiodistal measurements, no statistically significant change of the total occlusal area of the crown was observed between these samples. Nevertheless, we report an increase of 7.45% in the size of the occlusal polygon and hence 9.38% in its relative area, from 27.30% of the total crown area to 30.30% over this time span. This result implies that microevolutionary changes among Portuguese populations led to changes in the positions of the cusps relative to one another in the first upper molar, whereas the location of their apices have moved away from the centre of the crown to a more peripheral position. This apparent increasing trend contrasts with the one reported in studies of both Neandertals and modern humans.

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“…Within the molar series, variations in number, form and size of teeth have been reported in many mammalian species 3−9) . Although some explanations and hypotheses relating to these variations have been proposed 10−15) , the patterns of molar morphology vary in different species of mammals, including humans 3,5,16) , so additional investigations of mammalian dentitions that have not yet been described are still needed.…”

Section: Introductionmentioning

confidence: 99%

An odontometric study on the maxillary molars in Australian marsupials. -I. The koala (Phascolarctos cinereus)

Ueno

Iimura

Yoshida

et al. 2010

Okajimas Folia Anat. Jpn.

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Summary: Crown dimensions of the maxillary molars were measured in the koala (Phascolarctos cinereus). There were no significant differences in crown diameters between the first and second molars, however the fourth molars were reduced in all crown diameters. The third molar was smaller than the first or second molars in buccolingual crown diameters but there were no significant differences in mesiodistal crown diameters. It is proposed that the similar shapes of the first and second molars are associated with similar types of masticatory activity involving these teeth, The shape of the third molar, which is reduced in size buccolingually, may be linked to the koala's occlusal function which is characterized by a condylar action that leads to differences in movement between opposing anterior and posterior molar teeth during the occlusal stroke. The fourth molar, the smallest of the molar teeth in crown diameter, erupts significantly later than the other molars, and its reduction may be explained by the terminal and distal reduction theories. It is proposed that the pattern of molar morphology in the koala is associated with both masticatory activity linked to its characteristic occlusal function, as well as reflecting the sequence of tooth emergence.

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Variability in cusp size of human maxillary molars, with particular reference to the hypocone

Cited by 41 publications

References 20 publications

Variations in the Cusps of Mandibular Molars in Koreans

Variations in the Cusps of Mandibular Molars in Koreans

Dental microevolution in Portuguese Neolithic and modern samples using an alternative morphometric analysis

An odontometric study on the maxillary molars in Australian marsupials. -I. The koala (Phascolarctos cinereus)

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