Modern human molar enamel thickness and enamel–dentine junction shape

Smith, Tanya M.; Olejniczak, Anthony J.; Reid, Donald J.; Ferrell, Rebecca J.; Hublin, Jean‐Jacques

doi:10.1016/j.archoralbio.2006.04.012

Cited by 138 publications

(139 citation statements)

References 47 publications

Supporting

Mentioning

124

Contrasting

Unclassified

Order By: Relevance

“…Previous studies have demonstrated significant differences in hominoid enamel thickness among tooth positions and between maxillary and mandibular rows, 28,38,40 thus tooth positions were assessed separately. The Mann-Whitney U test was performed with IBM SPSS Statistics software (v.18), where sample sizes were four or greater to compare enamel thickness indices and their components between mainland Asian and Indonesian fossil orangutans.…”

Section: Methodsmentioning

confidence: 99%

“…A better understanding of enamel thickness may also help to sort fossil orangutans from hominins in mixed Asian Pleistocene primate faunas, which are particularly difficult to distinguish from external morphology alone. 5,24,36,37 Finally, these results are considered in light of recent studies of enamel thickness within fossil and extant Homo sapiens, 35,[38][39][40] which are known to show a similar pattern of dental reduction over the same period. Given the significance of enamel thickness in assessments of hominoid systematics 28,29,32,35,41 and dental functional morphology, 33,34,42,43 characterization of enamel thickness within a geographically and temporally diverse hominoid genus will also permit more refined comparisons of limited samples of other fossil apes and humans.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

Smith

Bacon²,

Demeter

et al. 2011

Hum Origins Res

View full text Add to dashboard Cite

Orangutans (Pongo) are the only great ape genus with a substantial Pleistocene and Holocene fossil record, demonstrating a much larger geographic range than extant populations. In addition to having an extensive fossil record, Pongo shows several convergent morphological similarities with Homo, including a trend of dental reduction during the past million years. While studies have documented variation in dental tissue proportions among species of Homo, little is known about variation in enamel thickness within fossil orangutans. Here we assess dental tissue proportions, including conventional enamel thickness indices, in a large sample of fossil orangutan postcanine teeth from mainland Asia and Indonesia. We find few differences between regions, except for significantly lower average enamel thickness (AET) values in Indonesian mandibular first molars. Differences between fossil and extant orangutans are more marked, with fossil Pongo showing higher AET in most postcanine teeth. These differences are significant for maxillary and mandibular first molars. Fossil orangutans show higher AET than extant Pongo due to greater enamel cap areas, which exceed increases in enamel-dentine junction length (due to geometric scaling of areas and lengths for the AET index calculation). We also find greater dentine areas in fossil orangutans, but relative enamel thickness indices do not differ between fossil and extant taxa. When changes in dental tissue proportions between fossil and extant orangutans are compared with fossil and recent Homo sapiens, Pongo appears to show isometric reduction in enamel and dentine, while crown reduction in H. sapiens appears to be due to preferential loss of dentine. Disparate selective pressures or developmental constraints may underlie these patterns. Finally, the finding of moderately thick molar enamel in fossil orangutans may represent an additional convergent dental similarity with Homo erectus, complicating attempts to distinguish these taxa in mixed Asian faunas.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

Smith

Bacon²,

Demeter

et al. 2011

Hum Origins Res

View full text Add to dashboard Cite

show abstract

“…Comparing just M1s, thus removing any possible variation in enamel thickness due to differences in molar type Berner, 1993, 1994;Smith et al, 2005Smith et al, , 2006, Sivapithecus and P. nyanzae have thicker enamel than Pan or Gorilla, yet all of these species have broadly similar M1 cusp formation times (Beynon et al, 1998;Smith et al, 2005). Enamel thickness is governed by the rate and duration of enamel secretion, and the number of active cells producing enamel (Grine and Martin, 1988).…”

Section: Enamel Thicknessmentioning

confidence: 99%

Molar crown formation in the Late Miocene Asian hominoids, Sivapithecus parvada and Sivapithecus indicus

Mahoney

Smith

Schwartz

et al. 2007

Journal of Human Evolution

View full text Add to dashboard Cite

During the past decade, studies of enamel development have provided a broad temporal and geographic perspective on evolutionary developmental biology in Miocene hominoids. Here we report some of the first data for molar crown development in one hominoid genus, Sivapithecus. The data are compared to a range of extant and extinct hominoids.Crown formation times (CFTs), daily rates of enamel secretion (DSR), Retzius line number and periodicity, and relative enamel thickness (RET) were calculated in a mandibular first molar of Sivapithecus parvada and a maxillary first molar of Sivapithecus indicus from the Siwalik sequence of Pakistan. A CFT of 2.40 years for the protoconid of S. parvada and 2.25 years for the protocone of S. indicus lie within the range of first molar (M1) formation times for the majority of Miocene hominoids (1.96e2.40 years, excluding Proconsul heseloni), and are similar to an M 1 from Gorilla (2.31 years) and M 1 s from Pan (2.22e2.39 years). This is unlike the longer CFTs in modern humans, which appear to be linked with their extended growth period. In contrast to extant great apes and humans, daily rates of enamel secretion are rapid in the Sivapithecus M1s during the early stages of growth, which seems to be a common pattern for most Miocene apes. The rapid accumulation of cuspal enamel in the Sivapithecus molars produced thicker enamel than either Pan or Gorilla in a comparable period of time. Future studies on larger samples of living and fossil hominoids are needed to clarify trends in crown development, which may be better understood in the context of life history strategies coupled with good data on body mass and brain size.

show abstract

“…It has been studied in both extant and extinct primate species to understand taxonomic and phylogenetic relationships (e.g. Schwartz, 2000a;Kono, 2004;Smith et al, 2005Smith et al, , 2006Smith et al, , 2008Smith et al, , 2009aOlejniczak et al, 2008a, b;Suwa et al, 2009) and tooth function (e.g. Macho andBerner, 1993, 1994;Macho, 1994;Schwartz, 2000b).…”

Section: Introductionmentioning

confidence: 99%

“…Macho andBerner, 1993, 1994;Macho, 1994;Schwartz, 2000a, b;Grine, 2002Grine, , 2005Smith et al, 2005Smith et al, , 2006Smith et al, , 2008, which often limits sample sizes. Two-dimensional X-ray projection radiography has been used to quantify enamel thickness non-destructively in fossil specimens (e.g.…”

Section: Introductionmentioning

confidence: 99%

Enamel thickness in Asian human canines and premolars

Feeney

Zermeno

Reid

et al. 2010

View full text Add to dashboard Cite

Dental enamel thickness continues to feature prominently in anthropological studies of ape and human evolution, as well as studies of preventative oral care and treatment. Traditional studies of enamel thickness require physical sectioning of teeth for linear and scaled measurements. Recent applications of microtomographic imaging allow scientists to employ larger and more diverse samples, including global samples of recent humans as well as fossil hominin teeth. Unfortunately, little is known about the degree of enamel thickness variation among human populations, particularly across the dentition. This study employed microtomography to virtually image, section, and quantify the average enamel thickness of a sample of clinically extracted Indonesian canine and premolar teeth. This virtual sample was compared to physically sectioned African and European teeth. The results demonstrate that average enamel thickness is similar among human dentitions; no significant differences were detected within tooth positions, which is surprising given developmental differences between European and African canines and premolars. When populations were combined, differences were found in average enamel thickness between maxillary and mandibular premolars, and between canines and premolars within both dental arcades. This finding is potentially due to differences in premolar morphology and a trend of increasing enamel thickness distally throughout the dentition. The finding of limited population variation within tooth positions and significant variation between tooth positions is consistent with previous two-dimensional and three-dimensional studies of human molar enamel thickness. Average enamel thickness in canines and premolars does not differ between the sexes in our sample, although male teeth tend to have larger enamel and dentine cross-sectional areas, enamel-dentine junction lengths, and bi-cervical diameters. Males have significantly greater dentine area and enamel-dentine junction length than females for maxillary canines and premolars. The results of this study suggest that enamel thickness values in mixed-populations of humans are appropriate for comparisons with fossil hominins.

show abstract

Modern human molar enamel thickness and enamel–dentine junction shape

Cited by 138 publications

References 47 publications

Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

Molar crown formation in the Late Miocene Asian hominoids, Sivapithecus parvada and Sivapithecus indicus

Enamel thickness in Asian human canines and premolars

Contact Info

Product

Resources

About