Dental sexual dimorphism, however, was maintained until the very end of the Pleistocene when the hunting of large game animals by crude techniques was. Of all the teeth in the human dentition, the canines are the least frequently extracted teeth Teeth of various species are known to exhibit sexual dimorphism. PDF | On Mar 1, , Freddy Moreno and others published Sexual Dimorphism in Human Teeth from Dental Morphology and Dimensions: A Dental.
Am J Phys Anthropol. Oct;(2) Sexual dimorphism in modern human permanent teeth. Schwartz GT(1), Dean MC. Author information. PDF | On Mar 1, , Freddy Moreno and others published Sexual Dimorphism in Human Teeth from Dental Morphology and Dimensions: A Dental. to determine the nature of sexual dimorphism in the crowns of permanent modern human teeth and to deter- mine if two contrasting tooth types.
In this study, we attempt to determine the nature of sexual dimorphism in the crowns of permanent modern human teeth and to determine if two contrasting tooth. Am J Phys Anthropol. Oct;(2) Sexual dimorphism in modern human permanent teeth. Schwartz GT(1), Dean MC. Author information. PDF | On Mar 1, , Freddy Moreno and others published Sexual Dimorphism in Human Teeth from Dental Morphology and Dimensions: A Dental.
Dental College and Hospital, Human, India. The aim dimorphism this study was to determine whether variations in the mesiodistal dimensions of mandibular canines had any role in sex determination.
Mesiodistal dimensions fimorphism mandibular canines was measured at the maximum mesiodistal width, first intraorally, then on plaster models of the same patient, followed human intraoral periapical radiograph of the same patient. The values were subjected to statistical analysis using t-test. It might be concluded from the results that there exists a definite statistically significant difference in the mesi-odistal width of mandibular canines when measured for males and females.
Moreover, the left mandibular canine showed a greater sexual dimorphism 9. The present study establishes a statistically significant sexual dimorphism in mandibular canines. It can be concluded that the standard mandibular canine index is a quick and easy method for determining sex and in identification of an unknown individual. Human teeth are the hardest and chemically the most stable tissues in the body, and are extremely durable even at di,orphism temperatures.
Teeth can be identified even when the rest of the body has dimorpjism decomposition. They are therefore invaluable for identification on fragmentary adult skeleton.
Teeth sexual readily accessible for examination and since no two teeth have similar dimorphusm, they form an excellent forensic tool for sex determination.
The identification of sex is of significance in case of major disasters where bodies are often damaged beyond recognition. Of all the teeth in the human dentition, canines are the least frequently extracted teeth possibly because of the relatively decreased incidence of caries and periodontal disease.
Tooth size standards teth on odontometric investigations can be used in age and sex determination as human teeth exhibit sexual dimorphism.
This may be due to a longer period of amelogenesis for both deciduous and permanent sexual in males. Few human have established that the mesiodistal diameter of lower canine is less dimorphism females than males and they have established variations. Hence, the present study aimed to measure the mesiodistal diameter of both mandibular canines so as to establish canine measurement variations in sex determination. The protocol was reviewed human the institutional ethics committee and the project was undertaken after a signed detailed consent form by teeeth patients.
It was followed by calculation of sexual dimorphism according to the formula given by Garn and Lewis:. The mean values of the mesiodistal width of left and the right mandibular canines in males and females were obtained by clinical examination, measurement on plaster models and radiographic examination and analyzed Table 1.
The mean value of the mandibular canine width in males and females on the right and left sides were compared using t-test. Moreover, the right and left sides were compared using independent t-test, irrespective of the gender.
The mean value was greater dimorphism males as compared to females and left canine was bigger in size than the right teeth of gender. This was irrespective of whether measurements were made by clinical teeth, measurement on plaster models or by radiographic examination.
Mandibular canines are believed to teerh teeth greatest sexual of human dimorphism in their mesiodistal width amongst all the teeth. Kaushal et al in their study on 60 subjects in a North Indian population found a statistically significant tewth in mandibular canines. Teeth mandibular left canine was seen to exhibit greater sexual dimorphism 8.
Reverse dimorphism where the females showed larger teeth than males was found in studies carried out by Acharya and Mainali 13 on mandibular second premolar in Nepalese population and by Yuen et al1 4 on mandibular incisors in a longitudinal study on Chinese population.
Determination of sex hukan mesiodistal measurement of mandibular canines is a relatively quick, easy and inexpensive method, and human aid in identifying persons from fragmented jaws and dental remains. It must be noted, however, that the method of sex determination via canine measurement has its limitations; the sex of the subject to whom the fragment of the mandible teeth can be determined satisfactorily only when the fragment is found in the geographical area teeth the subject was born.
The emerging field of sexual odontology in India relies a lot wexual teeth inexpensive teeth easy means of identifying persons, and in such situations the dentist can be sexual upon to render expertise in forensic science.
A database may be established of hyman morphometric measurements using intraoral periapical human with a view to determine variations among large dimorphism that may be beneficial for anthropological, genetic, legal, and ximorphism applications. National Center for Biotechnology InformationU.
Teeth online Jun Nagesh2 Asha R. Iyengar3 and Sushma Mehkri 4. Asha R. Author information Article notes Copyright and Teet information Disclaimer. Received Jan 26; Accepted May 8. This is an open-access article distributed under the terms of the Creative Commons Attribution dimorphism.
This article has been cited un other articles in PMC. Abstract Background and aims The aim of this study was to tfeth whether variations in the mesiodistal dimensions of mandibular canines had any role in sex determination.
Results It might sexual concluded sexual the human that there exists a definite statistically significant difference in the mesi-odistal width of mandibular canines when measured for males and females. Conclusion The present study establishes a statistically dimorphism sexual dimorphism in mandibular canines. Keywords: Mandibular canine width, dimkrphism study, sexual dimorphism.
Introduction Human teeth are the hardest and chemically the most stable tissues in the body, and are extremely durable even at high temperatures. Open in a separate window. Figure 1. Measurement of mesiodistal width of mandibular canine by clinical examination.
Figure 2. Measurement of mesiodistal width of mandibular canine on plaster models. Figure 3. Measurement of mesiodistal width of mandibular canine hu,an tracings of intraoral periapical eexual. Table 1 Mean mesiodistal width of mandibular canine obtained teet clinical examination, plaster models and by radiographic examination.
Figure 4. Comparison of sexual dimorphism on the right and left mandibular canines. Discussion Sexual canines are believed to demonstrate the greatest percentage human sexual dimorphism in their mesiodistal width amongst all the teeth. Conclusion The emerging field of forensic odontology in India relies a lot on such inexpensive and easy means of identifying persons, and in such situations the dentist can be called upon to render expertise in forensic science.
References 1. Mandibular canines in dimofphism determination. J Anat Soc India. Dahberg AA. Dental traits as identification tools. Dent Prog. Rai B, Anand SC. Teerh determination by diagonal distances of teeth. Analysis of developmental processes possibly related to human dental sexual dimorphism in permanent and deciduous canines.
Am J Phys Anthropol. Bucco-Lingual size asymmetry and its developmental meaning. Angle Orthod. Lysell L, Myrberg Dimorphism. Mesio-distal tooth size in deciduous and permanent dentitions. Eur J Orthod. Sexual differences dimorphis, Turkish dentition.
Legal Medicine. Karaman F. Diagonal measurements on teeth to predict gender in Turkish population. J Forensic Sci. Mesiodistal tooth width: A comparison between Saudi males and females, Part 1. Egypt Dent J. Mesiodistal tooth width in a Saudi population sample comparing right and left side: Part 2. Dimorphism of mandibular and maxillary canine teteh in establishing sex identity. Saudi Dent J. A study of tooth size, symmetry and sexual dimorphism.
J Forensic Med Toxicol. Acharya A, Mainali S. Univariate sex dimorphism in the Nepalese dentition and the use of discriminant functions in sexuual assessment. Forensic Sci Int. Mesiodistal crown diameters of the primary and sesual teeth in dimorphism Chinese: A longitudinal study. Support Center Support Center. External link. Please review our dimorphism policy.
Mean value of mesiodistal mandibular canine sexual in mm. Clinical Examination. Plaster Models. Radiographic Examination.
In previous studies, different amounts of either enamel or dentine were implicated as the cause of this dimorphism. In this study, we attempt to determine the nature of sexual dimorphism in the crowns of permanent modern human teeth and to determine if two contrasting tooth types permanent third molars and canines show identical patterns of dimorphism in enamel and dentine distribution.
We estimated the relative contributions of both enamel and dentine to total crown size, from buccolingual sections of teeth.
Our sample consisted of a total of mandibular permanent third molars and 25 permanent mandibular canines of known sex. We show that sexual dimorphism is likely due, in part, to the presence of relatively more dentine in the crowns of male teeth. Scott in The blade shape is observed in the lingual surface of central incisors and upper and lower side, formed by the palate or lingual fossa and mesial and distal marginal ridges [ 16 ]. For the taxonomic analysis are only taken into account the marginal ridges and not the depth of the concavity since the latter is quite independent and has negative correlation with the development of the ridges.
However, some authors take into account the depth of the pit palate and indicate that there is shovel-shaped from 0. Since the time of early African hominids it has been showed the development of shovel-shaped incisors. In Asia this trait is clearly expressed since the early hominids. According to paleontological information, exists a geographical boundary between the West, with low frequencies of shovel incisors, and the east with high frequencies of this trait [ 6 ], which is an effective boundary between the European and Mongoloid populations Asian and American [ 15 ].
Hanihara [ 17 ] developed the Mongoloid dental complex from five dental morphological traits including shovel-shaped upper central incisors that had a high frequency and distribution of which were quite useful in analyzing the affinities between different populations. Thus, for this trait expression there are differences between Negroid, Caucasian-American and Mongoloid origin population groups. In particular, significantly higher frequencies are shown by Japanese, Pimas and Eskimos, and slightly less in Ainu.
Hanihara [ 28 ] found a prevalence of 9. Turner in observed this trait in The same C. Turner II [ 29 - 31 ] related the results of the frequencies of some morphological traits of populations of Asia, Oceania a Polynesia and Hispanic American populations, and in this way he showed that the Americas were populated via the Bering Strait.
Similarly, the geographic distribution of traits according to different human groups that make up the dental complex East Asian Mongoloid allowed Sinodonte subdivide the pattern in the north, characterized by the addition and enhancement of some features like the shovel incisors , and the pattern Sundadonte south, typified by the retention of an ancestral condition and simplification of certain features within the protruding low frequency of shovel-shaped.
Would be those who crossed the Bering Sinodontos some 14, years ago who populated the Americas in three consecutive waves, being the east of Lake Baikal the last home of the indigenous peoples of North and South America. Therefore, all pre-Columbian indigenous groups are part of the pattern Sinodonto at the Mongoloid dental complex. Anatomically, the canines have bulkier root in the palatal-lingual direction and longer than other teeth, this allows a strong anchoring in the alveolar bone with abundant and dense compact bone and confers high resilience to the forces generated during the chewing cycle during which dampen excessive horizontal and deleterious forces are generated during lateral movements to protect the back teeth, an action that depends equally from its high capacity to nociceptive sensory stimuli during the action of mastication muscles.
Basically, this protection is mediated by the occlusal relationship between the canines, which, upon the lateral movement of the lower canines jaw slide over the top, a function described in the literature as "canine function" or "canine key," to produce disoclussion of posterior teeth. Hence, the canines are considered "milestones" or "signposts" of dental occlusion. These consist of two maxillary and two mandibular teeth localized each one in a hemiarch between the incisors and premolars group.
The upper canine crown UC 13 and 23 presents the labial surface in a diamond shape, with the incisal edge acute formed by the mesial and distal cusp slopes that meet at a cusp vertex and rounded in the cervical region.
The palatal surface has a central crest elevation or extension from the cingulum to the cusp apex, and two marginal ridges, mesial and distal, which constitute the central ridge with two mesial and distal palatal fossae respectively. The lower canines LC [ 33 , 43 ] have a longer narrower crown, and lower bulge than the upper canines. From the buccal view, mesial contour is relatively straight while the concave distal cementoenamel junction, but convex in the distal cusp slope.
On the lingual surface mesial and distal pits are less noticeable than in the upper, and the cingulum is more blunt than the upper canine and the mesial and distal halves of the crown are more symmetrical.
Permanent canines are the only teeth in its class in both the maxilla and mandible, where they are located at the four corners of the dental arches between the lateral incisors and first premolars, what constitutes an important support of the facial muscles.
Phylogenetically, morphology and dimensions have been associated with capture functions, excavation, cutting, boring, defense, attack, sexual dimorphism and social power [ 21 - 23 ].
In the case of the canines very few studies have been conducted. Butler in suggested that the morphology and size of the premolars are controlled by the canines "caninization" of the first premolars and molars "molarization" of the second premolars during tooth morphogenesis, while A.
Dahlberg in held that the premolars had a morphogenetic field independent and exclusive to them. In short, none of the two theories have been proven due to the exclusion of the premolars of anthropological and genetic research largely due to ignorance of evolutionary and embryological behavior of these teeth , being relegated from the global dental morphological classifications dental complex and limited their study to the description of the meso-distal and bucco-palatal or bucco-lingual dimensions [ 32 ].
Worldwide research on this topic has covered many of the current populations and a number of past populations, focusing mainly on the description of the frequency and variability of dental morphological features located in incisors and molars, leaving aside the morphology of canines and premolars. However, the descriptive and quantitative analysis of the morphology of the canines has allowed hominids to be taxonomically classified, so that has contributed to the estimate of the evolutionary origin of the genus Homo and understanding the geographical distribution of past and modern human groups.
In primates, the reduction in canine size and degree of sexual dimorphism is related to the size of the crown and the simplification of the morphology, which received direct selective pressure from the acquisition of the erect position, the bipedalism, reduced facial prognathism, reducing the size of the dental arches and microdontia generalized morphological conditions specific to humans [ 33 - 35 ]. In the temporary and permanent canines, according to reports in the literature, it is possible to study various dental crown traits such as shovel-shaped relative development of the mesial and distal marginal ridges of the lingual surface , double shovel relative development the mesial and distal marginal ridges on the labial surface , labial convexity convexity degree of vestibular , slot interrupt through the cingulate sulcus of the upper canines up to the cement-enamel junction , dental tubercle crest, tubercle or peak that appears in the cingulate region of the lingual surface , canine mesial ridge mesial crest variation , distal accessory ridge small accessory crest that appears on the distal-incisal central peak central area shown in palate , palatal fossae two graves, mesial and distal, which appear in the palatal surface of the upper canines and lingual fossae two graves, mesial and distal, which appear on the lingual surface of the lower canines 36].
The canine mesial ridge and the distal accessory ridge are population dental traits important within anthropological and forensic contexts. The expression is observed in the variation of the mesial crest of the upper canines. The canine mesial ridge, the protostylid or "Bushman canine" was described by Morris in a population of Bushmen in South Africa [ 37 ].
It is observed as the presence and expression of a small accessory crest that appears on the distal-incisal region of upper and lower canines. This has been one of the most worldwide studied morphological crown dental traits of canines [ 16 ].
In the case of the premolars are very few studies conducted. Dahlberg in held that the premolars have a morphogenetic field independent and exclusive to them. In short, none of the two theories have been proven to the exclusion of the premolars of anthropological and genetic research largely due to ignorance of evolutionary and embryological behavior of these teeth , being relegated from the global dental morphological classifications dental complex and limited their study to the description of the meso-distal an bucco-palatal or bucco-lingual dimensions [ 38 ].
The premolars consist of four maxillary and four mandibular teeth located in pairs on each hemiarch between the canines and first molars. The higher UP1 14 and 24 and UP2 15 and 25 have two cusps of similar size and usually two roots, especially the first premolar. The occlusal surface has an oval contour characterized by well-defined grooves directed from mesial to distal.
The lower LP1 34 and 44 and LP2 35 and 45 are uniradicular, and have three cusps second premolar that form a rounded occlusal contour with a groove, which is often interrupted. Broadly speaking, the premolars are a transition from the canine buccal cusp high and pointed cone , which increase the occlusal contour from the first to the second, i.
The frequencies reported by G. Giron et al [ 39 ] show the trend of the first premolar to have a low frequency of mesial accessory crest and a moderate expression of distal accessory ridge, two cusps with constant presence, absence of buccal grooves and lower frequencies of interstitial tubercle mesial and distal, while the second premolars often show high expression of the mesial and distal accessory ridges, and the interstitial tubercles mesial and distal although the expression of this trait in the first premolars in the latter is greater ; likewise always have two cusps and no developmental grooves vestibular are expressed.
In the case of the lower premolars, the first is characterized by no vestibular developmental grooves, only one lingual cusp present, have a high central peak expression, mesiolingual groove and a U-groove pattern, in contrast to the configuration of the occlusal morphology of lower second premolars which is very different, given the low expression of meso-and disto lingual groove, the absence of central ridge and vestibular groove, the high frequency of a single lingual cusp and groove U pattern.
The molar teeth consist of four maxillary and four mandibular teeth located in pairs on each hemiarch distal of the canines. The UM2 second molars 55 and 65 and lower LM2 75 and 85 are totally different from the first molars UM1 54 and 64 and LM1 74 and 84 and have a shape and morphological features very similar to the first permanent molars.
The first molars are not taken into account because, although their morphology is very variable, they are more like a premolar than a molar. Permanent molars are six maxillar and six mandibular, which are located distal to the second premolars. UM1 first upper 16 and 26 and lower molars LM1 36 and 46 and UM2 upper 17 and 27 and lower LM2 second molars 37 and 47 at first glance are very similar, but under analysis of dental anthropology, they have significant differences in the expression of dental crown traits, which is why the same correspondence between one and other tooth will permit to understand the genetic and environmental influences, both by their frequency the expression.
UM3 third molars 18 and 28 and LM3 38 and 48 are not taken into account for the study of dental morphology since this tooth has a strong evolutionary trend toward the disappearance, which is evident given the high frequency of agenesis and atypical forms [ 21 - 23 ]. In the molars the traits that have been more frequently studied are Carabelli trait pit or cusp in the meso-lingual cusp of the upper molars , hypoconid reduction downsizing disto-lingual cusp of the upper molars , metaconulo small cusp between disto-buccal cusp and disto-palatal maxillary molars groove pattern contact configuration of the cusps of the molars , number of cusps, elbow crease the meso-lingual cusp is directed toward the central fossa in lower molars , protostylid pit or buccal cusp on the buccal developmental groove of the mandibular molars , cusp 6 cusp between the disto-buccal cusp and disto-lingual surfaces of lower molars and cusp 7 cusp between the meso-lingual cusp and disto-lingual surfaces of lower molars [ 24 - 27 ].
The features to be the focus of the discussion in this chapter are the most studied in worldwide populations, as in the case of the cusp of Carabelli, protostylid and groove pattern. It is located on the palatal surface of the apex of the mesopalatal cusp of second primary molar and the first and second upper permanent molars.
The variability of expression ranges from a small pit, through a groove in a "V" or "Y" up to the formation of a cusp. The first observation scale was developed by A. Dahlberg in One of the methods of measurement in the primary dentition was designed by F. Turner [ 16 ]. Carabelli trait is considered worldwide as a Caucasoid trait.
Hanihara [ 28 ] found low frequencies of this trait in Japanese and higher in black and white Americans, finding that this trait distinguishes Caucasoid populations of Asian and that in the latter predominate the groove and pit forms, whereas C. Turner [ 29 ] found significant expressions in sinodontes, South American indigenous and northeastern Europeans.
In modern American populations, N. Aragon et al [ 27 ] in a sample of an indigenous population in Colombia found that in both dentitions dominated groove and pit forms grades 1 and 2 in deciduous, grades 1 to 4 in permanent teeth than cusp form degree 3 and 4 in deciduous, grades 5 to 7 in permanent.
However, and according to the expression dichotomy, although the cusp of Carabelli is considered to be present in the sample should not be associated as a product of mixing of Caucasoid origin, since the intermediate grades pit expression is considered present and is characteristic of American Indian populations.
Rocha et al [ 26 ] in a population of Afro-Colombians in Colombia found significant frequencies of cusp expression, which is characteristic of populations of African origin and that according to A. Zoubov [ 15 ], conform southern Caucasoid dental or western equatorial complex. In a mixed population of Colombia, S. Moreno et al [ 24 ] reported the higher frequencies in grades 0, 1 and 2 with a higher prevalence of grade 1 fovea present. Aguirre et al [ 25 ] indicated that the cusp of Carabelli is not sexually dimorphic, it is expressed predominantly bilaterally and furrow and grave forms of tubercle and cusp forms, both as permanent dentition, which indicates that there is ambivalence in discrimination population for this trait.
The correlation of the prevalence between both dentitions indicates a strong genetic control for the expression of it. This paramolar cusp is antagonist to Carabelli cusp that varies from a groove to a free apex cusp on the vestibular surface of the meso-vestibular cusp. Also is often expressed as a fovea or pit on the buccal developmental groove called Point P or vestibular foramen caecum.
Dahlberg developed the reference plate in [ 6 ], but at present the method to observe it in permanent molars is ASUDAS [ 16 ]. Zoubov [ 15 ] defines americanoide protostylid as a feature due to the low frequency of expression in the populations of Europe, Africa and Asia the peculiarity of the high prevalence of point P or foramen caecum American populations. Hanihara [ 40 , 41 ] indicated that the expression of protostylid cusp is rarely present in different populations, occurring rarely in modern human groups, most Asians, which allow to differentiate the dental complex of Caucasoid and Mongoloid Negroid.
In primary teeth is commonly observed pit expression and some degree of mild elevations. Aragon et al [ 27 ] found this feature absent from the sample in the case of primary dentition and present with groove expression in the permanent dentition in an indigenous Colombian sample.
The interesting thing about this feature is the high frequency of grade 1 pit or foramen caecum in primary teeth, and that although in permanent teeth is often the development of the distal row from vestibular sulcus, is a preserved expression of the form pit.
Rocha et al [ 26 ] described the protostylid as absent in the sample of African descent, but they highlight the high frequency of grade 1 which again suggests the possibility of interbreeding with indigenous peoples, in the same way as S.
Moreno et al [ 24 ] in their study in a mixed population of Caucasoid Colombians reported high frequency of grade 1. Aguirre et al [ 25 ] in their study observed that the protostylid reflects that the population studied has a significant retention of American Indian dental complex, as evidenced by the high frequency of grade 1, explained as a pit on the buccal developmental groove that separates meso and disto-buccal cusps.
These authors state that in modern American populations the protostylid pit form predominates in both deciduous and permanent dentition. The groove pattern of the second temporary molars and first permanent molars describes the configuration of the contact of the cusps and the number of them.
Aragon et al [ 27 ] report that the behavior of the number of cusps and groove pattern, present for the case of deciduous dentition Y6 and Y7 predominantly configuration, where the groove pattern and has a strong genetic control kept from past Asian populations that inhabited the Americas through Beringia from which derive the pre-hispanic Amerindian and present populations.
In their study of African descent, J. The frequencies of the configurations X6 and Y5 suggest some genetic influence product of miscegenation of Caucasian and indigenous groups.
Regarding the incisor teeth, in the literature can be found a general consensus of the absence of sexual dimorphism in the shovel form, taken into account in this chapter that this is one of the most studied dental traits for its importance in the discrimination populations according to the dental complex.
However, in the dental literature, there are several reports describing morphological differences according to sex of individuals and has great clinical importance in the area of aesthetic and cosmetic dentistry for diagnostic procedures of smile design [ 42 ]. Thus, the proximal contours, dental angle, incisal edge and the emergence profile are important for the teeth in harmony with the shape of the face [ 43 - 44 ].
Within the body outline the face has an aesthetic requirement that is extremely important as the aesthetic composition of the human as psycho-socio-cultural being, and teeth are part of the integral and harmonious appearance of the morpho-functional composition, including within the aesthetic-affective manifestations recognized as smiling, laughing, kissing and oral-facial gestures being teeth beyond the biological part of the smile. Their disposition in the arches are in compliance with the support function of the soft tissues, influencing the position taken by the facial muscles, which contribute to the determination of facial traits that are involved in the character and personality.
For this reason, the face and facial expression are influenced by genetic inheritance and environmental factors, within which are the rounded, square or triangular shape of upper central incisors [ 45 - 47 ]. The analysis of these and other structures that make up the stomatognathic system of human groups, constitutes a fundamental starting point for micro-and macro-historical processes and reconstruction of the ethno-demographic origin of the current populations, for biological, functional and aesthetic dental diagnosis prognosis and treatment plans, and for forensic identification methods using facial reconstruction techniques.
Williams in -cited by L. Ibrahimagi et al [ 48 ]- postulated that the inverted form of the upper central incisors is related to the shape of the face, which is applicable in dental settings for harmonization of aesthetic oral rehabilitation procedures, anthropological morphological grounds for facial reconstruction procedure and forensic individualization during the identification process.
Frush and Fisher -cited by M. But there is no consensus in the various literature reports. Wright and Brodbelt, -cited by L. Ibrahimagi et al [ 48 ]- reported that the shape of the upper central incisors and the shape of the face corresponds to a situation that had already expressed by the same Ibrahimagi et al [ 48 ] in disagreement with the theory of Williams mainly because the mix of ethnic groups in the population and the infinite possibilities of combining forms of differently shaped face and the upper central incisors shape had selectively affected the genetic correlation between these two variables.
Berksun et al [ 50 ] and S. Wolfart et al [ 51 ] reported that it is possible to define the correlation of the shape of the face and shape of the teeth due to ethnic ambiguity of worldwide reports.
Thus, D. Acosta et al [ 52 ] conducted a study in Caucasian population where correlated features as facial contour with the shape of the contour of the upper central incisors, finding that an oval facial shape corresponds to the oval shaped upper central incisors, which does not occurs with square and triangular shapes. Likewise, although there is significant sexual dimorphism in the shape or contour of the face or the shape of the contour of the upper central incisors, the authors conclude that women had more prevalent oval and round shapes, while than in men predominate oval and square shapes.
The study of canine morphology has been used to understand the evolution of sexual dimorphism in the socio-ecological and phylogenetic development of primates. Sexual dimorphism is defined as an intra-specific difference between men and women, which can be studied from the somatotype of the individual, the size and dental morphology, and correlated with intra-sexual patterns of competition [ 53 , 54 ].
Ontogenetic mechanisms exist that cause morphological differences between males and females during primate evolution. The ontogenetic changes in these processes lead to the existence of sexual dimorphism associated with the size and evolutionary response to various factors including territoriality, competition and the distribution of resources [ 55 ].
Despite the changes in the size of the canines during hominid evolutionary line between male and female individuals, morphology has not suffered sexual dimorphism given its high intra-species preservation, related primarily to the canine is the one of a kind and has its own highly conserved morphogenetic field, which is also supported by the bilateral symmetry of dental morphological traits [ 35 ].
Butler since cited by van Reenen et al [ 56 ] - from his studies in Cenozoic mammals under the concepts of Huxley and De Beer, formulated the theory of morphogenetic fields in which the ectomesenchyme that migrates within the first arch is programmed to form a single tooth family that later modify its form by the action of external factors.
In , A. Dahlberg -cited by van Reenen et al [ 56 ] - adapts the concept of morphogenetic fields in the human dentition and represents the existence of four rather than three dental fields, and introduces the premolar class as a field.
While it should be noted that the deciduous and permanent molars have similar morphological characteristics that allow them to be linked to the same morphogenetic field, in man and in most mammals premolars differ markedly from their predecessors, the molars, and this is why premolars could be considered as potential molars deviated the field development by the molar molarization and were influenced by proximity to canine field caninizaion.
Later, G. Scott and C. Turner [ 5 ] suggested that gradients expressed in the morphogenetic field theory and the model proposed by Osborn clones theory in , in which, as ectomesenchyme migrates into the first arc, and is differentiated into three clones, incisor, canine and molar, have scientific evidence and do not exclude each other. Today, advances in molecular biology have allowed to mark the factors that control the morphogenesis of teeth from epithelial-mesenchymal relationships, in fact, the morphogenetic field corresponds to a specific place where a number of factors and proteins development are expressed and inhibited in the formation of a specific tooth, so bilateral symmetry and the absence of sexual dimorphism in the expression of dental morphological features of the canine teeth is associated with temporary and permanent mainly to the canines are the teeth of the morphogenetic field gradient, and as the central incisors and first molars for their respective fields, they are in the teeth with higher degree of conservation according to gene expression and lower influence of the environment from the viewpoint of macro-evolution.
In the case of the premolars, the shape of its contour and dimensions have been extensively studied as a tool for building the phylogeny of hominids from small samples of Australopithecines, Pliocene hominids, and Homo of low and medium Pleistocene [ 57 ], because from the standpoint of dental anthropology, the evolutionary value of morphology and dental odontometry is based on the strong genetic control of frequency and variability, which allows to establish direct links between the anatomical structure of the teeth, including premolars, and relationship between populations.
However, in the literature are few studies on morphology of premolars and there have not been studied all the morphological features or have used different methodologies, based on the likelihood that human groups that present a similar dental morphology and dimensions can be interrelated, in fact, the shape and dimensions exhibited by a tooth-set the similarity or dissimilarity of morphological variation and genetic metric of a common ethnic trunk [ 58 ].
This will make it possible to infer macro-evolutionary processes that have demarcated the settlement, in this case a specific region such as the southwestern Colombia. Based on the frequency and variability of morphological features obtained in this study, graphically presents the morphology of the occlusal surface of a sample of mixed Caucasoid traits of the first and second upper and lower premolars. To demonstrate the behavior of the expression of the morphology of the premolars has important clinical implications in the dental context whenever the functional morphology plays a role in inter-occlusal relationships during the various functions of the stomatognathic system [ 21 - 23 ] and ethnic in the anthropological and forensic contexts , because there is ample evidence in the literature analysis tooth morphology contributes to the establishment of the basic identification quatrain osteography or odontography specifically in the estimation of the age, sex and ethnic pattern [ 59 , 60 ].
Regarding the theory of morphogenetic fields made by P. Butler, in which the morphology of the deciduous and permanent teeth due to a progressive gradation from the incisors to the molars, premolars can be considered as potential deviated molars from field development influenced by the molar molarization and that, as stated previously, the field were influenced canine caninization , so that the conformation of the occlusal table from the development of cusps and the expansion of meso-distal and bucco palatal or bucco lingual diameters.
However, the deciduous molars have the same characteristics of permanent molars for which they are associated with a single morphogenetic field , while the premolars differ markedly from their predecessors, the molars.
This occurs in most mammals, including man, so A. Dahlberg adapted the concept of morphogenetic fields in the human dentition and justified the existence of four fields, where the premolars molars have their own field. Another aspect that supports this theory, is an evolutionist, in which the premolars were reduced in number, the first placental mammals had four to five premolars per hemi-arch, while the primates reduced to three premolar teeth formula for hemi- arch in the Primate.
In humans, were preserved two premolars per arch corresponding to the last two ontogenetically, hence they have a greater resemblance to the molars than to canines [ 56 ]. While some points of the theory of morphogenetic fields are still of extensive study and debate, in the context of dental anthropology have been conducted several studies that have allowed the characterization of morphology, so that large morphological and metric differences have been established with the molars, as the organization of the occlusal table and the number of cusps [ 38 ], concluding from the study of the frequency and variability of dental morphological traits that premolars have bilateral symmetry, there is morphological correspondence between the first and second premolars and have no sexual dimorphism [ 39 ].
With respect to the molar teeth, it is worth noting that these are the teeth which dental morphological features have been extensively studied in human populations, past and present. Aguirre et al [ 25 ] studied the correlation of morphological dental traits as cusp of Carabelli, protostylid and groove pattern between the second molars and first permanent molars of mixed Caucasoids, finding that in the first two features there is correspondence of expression and variability, bilateral symmetry and absence of sexual dimorphism, suggesting a strong genetic control.
This great similarity in dental morphology between the second deciduous molars and first permanent molars, reflects a common origin within the morphogenetic field, not in vain, researchers such as P. Butler and A. Dahlberg indicated that the tooth gradient deciduous and permanent molars is the second deciduous molar, since it retains the basic configuration of the contact pattern, typical of early hominids [ 2 ]. Thus, various studies have supported the theory of morphogenetic fields [ 61 ].
Later, A. Ocampo et al [ 62 ] conducted a study to determine the correlation of Carabelli, hypoconid, bridge of enamel metaconule, protostylid, elbow crease, groove pattern, number of cusps and cusp 6 and 7 between the upper and lower second molars UM2 and LM2], the upper and lower first molars UM1 and LM1] and second upper and lower molars UM2 and LM2], in mixed populations of Caucasian, Afro-descendants and Colombians indigenous.
In mixed Caucasian and Afro-Colombian descent, significant correlations were observed in the same morphological features, which can be associated with their settlement in the same geographic area southwestern Colombia because they are part of the ethno-historical and macroevolutive processes of miscegenation [ 62 ] Tables 1 and 2 ]. Relative frequency of the non-metric dental traits al the comtemporary colombian indigenous population.
To determine the sexual dimorphism are useful univariate nonparametric tests such as Pearson chi-square to measure the discrepancy between observed and a theoretical distribution goodness of fit , indicating the extent to which differences between the two, if any, are due to chance in the contrast of the assumptions made in this case there is sexual dimorphism, or Mann-Whitney test, applied to two independent samples to test the two-sample heterogeneity ordinal under the null hypothesis that the distributions of departure of both distributions is the same, meaning that there is sexual dimorphism in the sample.
Among the object of study of dental anthropology in his interest in recording, study, analyze, explain and understand the information provided by the human dentition, such as anatomical variations, developmental, pathological, cultural and therapeutic consideration with living conditions, culture, food and adaptation processes of the past and present human populations, are important the odontoscopia, the odontometry, the oral paleopathology, and modifications of the teeth.
Based on this concept extensively reviewed in the literature, the odontometry or registration of dental dimensions should be studied from an interdisciplinary perspective biology, anthropology, dentistry, paleopathology, archeology, forensics since the teeth are the precise means to recognize individuals whose death makes it difficult to distinguish by other processes, which are part of the reconstruction of the osteobiography or odontobiography individual and general, contributing just as in estimating biological populations to clarify past its history, origin, training, contacts and movements of the past and present human groups [ 2 , 5 , 6 , 64 ].
Sex determination from dental measures has been one of the least developed in physical anthropology. Sex is central to this research and to help determine the taxonomic value of the traits examined [ 7 ]. The odontometry and obtaining coronal and root action of the teeth are used in different ways, depending on the interest of the study.
In the dental context dimensions of the teeth are useful for the prediction of space for orthodontic treatment and orthodontics. In the anthropological context are used in comparative evolutionary studies and for establishing phylogenetic relationships among species of hominids and disappeared modern humans and to determine biological distances between populations, the same way they are used to diagnose the sex of individuals and complete paleo-demographic information of past populations.
Finally, in the forensic context are useful for determining the sex of an individual in the process of identification [ 6 , 11 ].
Worldwide research on this topic has sheltered many of the current populations and a number of past populations, which has contributed to the elucidation of the human evolutionary processes, the population distribution in the continents of Africa, Europe and Asia, the settlement of the Americas, and the formation of population clusters by means of the dimensions of the teeth [ 28 , 29 , 31 , 40 ].
Since the simplification of the morphology and tooth size reduction has been the trend in the evolution of hominids, A. Zoubov -cited by J. Rodriguez [ 6 ]- groups the different hominid groups according to tooth size and explains them in ten points. The most close to the taxonomic position Pliocene hominid are African Lothagam and Lukeino remains 6.
Subsequently, the Australopithecus afarensis 3. For its part, the anterior teeth of A. Middle Pleistocene hominids such as Homo erectus, are characterized by a dental size smaller than their ancestors australopithecines but larger than in Homo sapiens.
Compared to all Homo habilis had smaller teeth, excluding the lateral incisor and canine. Zoubov states, according to the variation of some dental traits, from that moment begin to set the division of the populations of the genus Homo into two branches: the western forms including African and European and eastern with Asian.
The remains known as pre-Neanderthals , and , years , labeled as archaic Homo sapiens or Neanderthal associated with late erectus or archaic, does not allow a clear division of dental dimensions and morphology, except for the presence of a bridge of enamel that connects the protoconid and metaconid of the lower molars, characteristic of European Neanderthals, indicating a relationship of genetic continuity. Regarding the Neanderthals , and 35, years , two dental variants have been observed, a macrodonte Krapina and Shanidar and another microdonte Hortus , which anyway, compared to other developmental stages, canines, premolars and molars show reduced while the incisors show an increase in size.
For Asian and European Neanderthals is characteristic shovel-shape of the incisors.