Hypodontia: Prevalence and pattern amongstthe living Druze population – A Near Easterngenetic isolate
Firas Alsoleihat ∗, Ameen KhraisatDepartment of Conservative Dentistry and Fixed Prosthodontics, Faculty of Dentistry, University of Jordan,Amman 11942, Jordan
a r t i c l e i n f o
Article history:Received 20 September 2013Accepted 5 March 2014
a b s t r a c t
The Druze population is a small-sized Near Eastern genetic iso-late with high rates of consanguineous marriages. The presentstudy aimed at investigating prevalence, pattern and distributionof hypodontia in the permanent dentition, excluding wisdom teeth,amongst this population. Panoramic radiographs, dental casts, andanamnestic records of 85 un-admixed Druze schoolchildren (45males, 40 females; age range = 14–18 years, mean age = 16 years,SD = 0.5 years) were examined for evidence of hypodontia. Thosewith any type of facial clefts or craniofacial syndromes wereexcluded. Hypodontia prevalence was 11.8% (11.1% for males, 12.5%for females) with no statistically significant difference betweensexes. The average number of missing teeth per child was 1.4 (1.2for males, 1.6 for females). The majority (90%) of affected indi-viduals exhibited minor hypodontia (one or two teeth missing).The most commonly missing teeth were upper lateral incisors andcanines, followed by lower and upper second premolars. Asym-metrical hypodontia was more prevalent. Maxillary, left side, andanterior segment predominance were observed. The distinct fea-tures of hypodontia among the Druze population are the relativelyhigh prevalence of minor hypodontia, and the upper lateral incisorsand canines being the most commonly missing teeth.
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Introduction
Familial (non-syndromic) hypodontia, defined as congenital absence of varying numbers ofdeciduous and/or permanent teeth as an isolated trait, is one of the most common developmen-tal abnormalities in humans, and the most common dental anomaly across diverse ethnic groups(Bergstrom, 1977; Brook, 1974; Buenviaje and Rapp, 1984; Castaldi et al., 1966; Helm, 1968; Ingervallet al., 1972; Johannsdottir et al., 1997; Locht, 1980; Mckibben and Brearley, 1971; Salem, 1989;Thilander and Myrberg, 1973). The frequency and pattern of hypodontia are well documented inthe literature. The previously reported global scale for the prevalence rate of hypodontia, exclud-ing third molars, ranges from as low as 2.2% in a Saudi Arabian sample (Salem, 1989) to as highas 15.68% in a Hungarian sample (Gabris et al., 2001) except for the extraordinarily high frequency(36.5%) observed among the Dariusleut Hutterite Berthren of Western Canada, which is a European-derived genetic isolate (Mahaney et al., 1990), and for the extremely low frequency of 0.3% observedin a Jewish sample (Rosenzweig and Garbarski, 1965). However, it is noteworthy that another studyof an Israeli Jewish male sample reported a higher frequency of hypodontia (5.3%) (Goren et al.,2005). This wide range could possibly be attributed to variation in many factors including methodsof sampling and investigation, as well as the distribution of age, sex, and ancestral origin of individ-uals (Aasheim and Øgaard, 1993; Bäckman and Wahlin, 2001; Davis, 1987; Eidelman et al., 1973;Silverman and Ackerman, 1979; Rosenzweig and Garbarski, 1965; Wisth et al., 1974). It appears thatthe prevalence of hypodontia observed in samples that belong to the Sub-Saharan African ances-tral category is generally relatively low with a narrow range from 2.75% to 6.30% (Diagne et al.,2001; Ducka-Karska, 1983; Garner and Yu, 1978; Harris and Clark, 2008; Kayembe and Ntumba,1987; Ng’ang’a and Ng’ang’a, 2001; Onyeaso and Oneyeaso, 2006). Amongst Sino-American (Sinodont)samples, such as: Chinese, Japanese and Korean, the reported frequencies are relatively high with anarrow range from 8.5% to 11.3% (Chung et al., 2008; Davis, 1987; Endo et al., 2004, 2006; Fujitaet al., 2009; Goya et al., 2008; Kim, 2011; Lai and Seow, 1989; Niswander and Sujaku, 1963; Sharma,1983; Tsai and King, 1998; Wu and Feng, 2005; Yanagida and Mori, 1990; Zhu et al., 2007). West-ern Eurasian samples showed the widest range of hypodontia prevalence from 2.2% to 15.7%, evenwhen excluding the extremely low or high outlying frequencies mentioned earlier (Mahaney et al.,1990; Rosenzweig and Garbarski, 1965). Although limited number of studies observed the prevalenceof hypodontia in Sunda-Pacific (Austronesian or Sundadont) samples, it appears that the prevalencerange is also wide, extending from 2.8% to 8.6% (Dechkunakorn et al., 1990; Intaraprasong et al., 1983;Nik-Hussein, 1989; Stecker et al., 2007). Unfortunately, no accessible data were available regardingthe prevalence of hypodontia amongst the Sahul-Pacific (Australo-Melanesian or Proto-Sundadont)category.
With the exception of a few studies (Grahnen, 1956; Maklin et al., 1979; Lai and Seow, 1989;Salem, 1989; Ng’ang’a and Ng’ang’a, 2001), most of the previous reports demonstrated that hypodon-tia is more prevalent in females than males (about 3:2 female-to-male ratio). Most of the previousinvestigations conducted on Western Eurasian, Sub-Saharan African and Sunda-Pacific samples haveshown that the most common congenitally absent teeth are either lower second premolars (LP2s) orupper lateral incisors (UI2s), however, the lower lateral incisor (LI2) or LP2 agenesis was found to bethe most frequent type of dental agenesis amongst East Asian (Sinodont) populations (Chung et al.,2008; Davis, 1987; Endo et al., 2004, 2006; Fujita et al., 2009; Goya et al., 2008; Kim, 2011; Lai andSeow, 1989; Niswander and Sujaku, 1963; Sharma, 1983; Tsai and King, 1998; Wu and Feng, 2005;Yanagida and Mori, 1990; Zhu et al., 2007).
The living Druze population is a small Near Eastern minority of about one million individualsresiding primarily in Syria (40–50%) and Lebanon (30–40%), and to a lesser extent in Israel (6–7%) andJordan (1–2%), in addition to about 100,000 individuals in the Druze Diaspora (Nissim, 2003; Shlushet al., 2008). The Druze population is famous for its endogamy (Falah, 2000; Jobling, 2004; Nissim,2003) which is also corroborated by some genetic studies such as Shlush et al. (2008). This socialpractice of endogamy and consanguineous marriage, in addition to the fact that the Druze doctrinesfirmly close their religion to new converts, prohibited admixture with other populations, and thus ledto genetic isolation of the Druze minority from the larger population majorities of the countries wherethey co-reside (Jobling, 2004; Shlush et al., 2008).
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The Druze population is generally thought to be Arabs who separated from Islam in the 11th century(Firro, 1992). Recent genetic clustering analyses have shown close ancestral relationships betweenthe Druze people and Turkish Cypriots and identified similarities of the Druze people to the generalSyrian and Lebanese populations, as well as to a number of Jewish groups such as Ashkenazi (GermanJews), Sephardi (Spanish Jews), Iraqi, and Moroccan Jews (Behar et al., 2010). Moreover, a dentalmorphological study, based on 19 non-metric dental traits, has shown a relatively closer affinity forthe living Druze people in Israel to all the Jewish groups included in the study (Eastern European Jews,Kurdish Jews, Moroccan Jews and Mount Zion Skeletal Jews), excluding the Habbanites, as well as toBedouin Arabs and Circassians than to the Habbanite Jews, contemporary Nubians and Samaritans(Sofaer et al., 1986). In addition, a recent dental morphologic analysis has shown that the living Druzepopulation is very closely related biologically to living Jordanians, who belong to the Near EasternArabs (Alsoleihat and Khraisat, 2013). Therefore, it appears that the Druze population is most likelyancestrally closest to the Near Eastern Arabs and Jews.
The Druze population is almost completely an endogamous group whose individuals do not gener-ally intermarry with their Arab neighbors (Firro, 1992). It has been hypothesized and demonstrated,in a number of previous studies, that high rates of consanguineous marriages are associated withincreased frequencies of dental anomalies and agenesis (Eswar et al., 2003; Maatouk et al., 2008;Mahaney et al., 1990; Nelsen et al., 2001; Vona et al., 1993).
The present study aims at investigating the prevalence of dental agenesis, excluding third molars,among the living Druze population and comparing the findings of the study with the results availablein the literature and obtained from diverse ethnic groups. This would shed light on the influence of highrates of endogamy and consanguineous marriages on the prevalence of dental agenesis. In addition,this would also help assessing the degree of orthodontic needs for this population.
Materials and methods
A representative sample was obtained in 2011 by selecting 85 un-admixed Druze school children(45 males and 40 females), from the main two schools in Al-Azraq (Al-Azraq ash-Shamali school formales, Al-Azraq ash-Shamali school for females), which is a city located in the east of Jordan. It isnoteworthy to mention that the majority (about 60%) of Druze in Jordan (also known as Bani Ma’roof)live in this one town called Al-Azraq and the vast majority (more than 95%) of the schoolchildrenof this town go to either of these two schools, as confirmed by the director of these two schools.Only less than 5% of the Druze schoolchildren in Al-Azraq go to Al-Azraq al-Janubi school for malesand Al-Azraq al-Janubi school for females; these were not included in the present study. It is alsonoteworthy to mention that present study involved most of the Druze school children in Al-Azraq inthe age range of 14–18 years, since the Druze who live in Al-Azraq are a small population (i.e. about8000 individuals) according to various sources. Therefore, the authors believe that the sample of thestudy is largely representative of the majority of the living Druze population in Jordan. Ethical approvalfor conducting this type of study was obtained from the authorized body, the Ethical Committee ofthe Faculty of Dentistry/University of Jordan, prior to commencement of the study. Informed consentswere obtained from the parents of all children who chose to participate in the study before the childrenwere subjected to dental examination, radiographic imaging, or impression taking. The average ageof the selected individuals was 16 years (SD = 0.5), being between the ages of 14 and 18 years. In thisage range, the children were old enough to have a reliable confirmation of congenital absence of anyof the permanent teeth; due to the fact that it has been previously demonstrated that no tooth hasbeen found to initiate crown mineralization beyond the age of 12 years across diverse ethnic groups(Aasheim and Øgaard, 1993; Harris and McKee, 1990; Rantanen, 1967). Moreover, the children, inthis age range, are young enough to have minimum tooth loss, and dental records which are reliableenough to document extractions and avulsions. They were selected according to the following criteria:all individuals were apparently healthy with no history of serious childhood illnesses, and with nodevelopmental anomalies such as ectodermal dysplasia, facial clefts and craniofacial syndromes, andhave no history of previous orthodontic treatment, and no history of tooth extraction or accidentrelated tooth loss.
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Unadmixture status of individuals in this study was determined by self-report because there is noobjective criterion to distinguish admixed individuals; however, this was further confirmed by thedirectors of the schools who are local Druzes of Al-Azraq. Also they helped to rule out any possibleadoption of Druze self-identification by schoolchildren with different (e.g. Chechen or Palestinian)ethnic background.
Panoramic radiographs, dental casts, and anamnestic records were the only sources of informationused in this study to diagnose hypodontia. Several previous studies have demonstrated the reliabilityof panoramic radiographs for the diagnosis of hypodontia (Aasheim and Øgaard, 1993; Bäckman andWahlin, 2001; Nik-Hussein, 1989; Nordgarden et al., 2002; Wisth et al., 1974). A tooth was diagnosed tobe congenitally absent when no evidence of crown calcification could be identified at the tooth site onthe panoramic radiograph and no evidence of previous extraction of the tooth could be found. Dentalcasts, clinical dental examination, as well as medical and dental records were used as supplements toexclude those with teeth missing due to extraction or avulsion, and to ensure accurate diagnosis ofhypodontia.
The panoramic radiographs and dental casts of the individuals of the present study werereexamined by another observer three months after the first observation, and 100% reproducibilitywas achieved in the diagnosis of hypodontia.
The prevalence of hypodontia was calculated by tooth type and sex. Statistical differences betweenfrequencies or means of groups were tested by independent samples t-test between percentages ormeans, respectively (Statistics Calculator, 1997–2010 StatPac, Inc.). Statistical significance was setat the 0.05 probability level. The prevalence of hypodontia in a particular group was calculated bydividing the number of individuals with hypodontia by the total number of individuals in that group.The average number of congenitally missing teeth per hypodontic individual for a particular groupwas calculated by dividing the total number of missing teeth by the total number of individuals withhypodontia in that group. The relative frequency of agenesis for a particular tooth type amongst thehypodontic individuals of the present sample was calculated by dividing the number of missing teethcorresponding to the tooth type considered by the total number of missing teeth. The prevalenceof symmetrical hypodontia was calculated as the number of symmetrical cases of dental agenesisdivided by the total cases of agenesis whether symmetrical or asymmetrical. The dental casts and thepanoramic radiographs of the individuals of the present study are currently housed at the museum ofthe Faculty of Dentistry of the University of Jordan.
Results
A total of 10 (5males and 5females) schoolchildren out of 95 (45males and 40 females) were foundto exhibit hypodontia in the permanent dentition. Therefore, the prevalence of hypodontia among thissample is 11.8% (11.1% among males and 12.5% among females). However, this difference betweenmales and females is not statistically significant (p = 0.842).
The total number of congenitally missing permanent teeth, among this sample was 14 (6 amongmales and 8 among females), with an average of 1.4 per hypodontic child (1.2 for males and 1.6 forfemales). This difference is also statistically insignificant (p = 0.395).
The number of missing teeth per child in the present sample ranged from 1 to 2 for males and from 1to 3 for females. The percentage of children having 1 missing tooth among those with hypodontia was70% (80% (4 out of 5 individuals) for males, 60% (3 out of 5 individuals) for females; p = 0.5097); thosewith 2 missing teeth constituted 20% (20% (1 out of 5 individuals) for males, 20% (1 out of 5 individuals)for females), and those with three missing teeth represented 10% (0% (0 out of 5 individuals) for males,20% (1 out of 5 individuals) for females; p = 0.3226) Out of those exhibiting hypodontia, the prevalenceof oligodontia, defined as having five or more missing teeth, was 0% in both males and females. Themale-female difference was statistically insignificant in the percentages of children in each groupclassified by the number of missing teeth.
The distribution of missing teeth by sex is shown in Tables 1 and 2. The results vary with respectto the most commonly missing teeth between males and females. Among males with hypodontia,the most frequently missing teeth were the upper lateral incisors (UI2s; 4 cases), followed by uppercanines (UCs; 1 case) and second premolars (UP2s; 1 case) which showed equal rates of agenesis. None
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Table 1Raw data of the distribution of missing teeth by sex and side amongst the Druze sample.
Sex/side Tooth type (n)
UI2 UC LP2 UP2
Male/right side 1 1 0 1Male/left side 3 0 0 0Female/right side 0 1 1 1Female/left side 1 2 2 0
n – number of missing teeth, UI2 – upper lateral incisor, UC – upper canine, LP2 – lower second premolar, UP2 – upper secondpremolar.
Table 2Distribution of hypodontia frequencies by sex amongst the Druze sample.
Percent Percent p-Value PercentMales Females Sexes pooled
Frequency by tooth site 20.0% (1/5) 14.3% (1/7) 0.79 16.7% (2/12)
UI2 – upper lateral incisor, UC – upper canine, LP2 – lower second premolar, UP2 – upper second premolar.
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of lower second premolars (LP2s) were found to be congenitally missing among the male group of thepresent study. On the other hand, the order of absence frequency among females with hypodontia wasas follows: UCs (3 cases) and LP2s (3 cases) followed by UI2s (1 case) and UP2s (1 case). When bothsexes were combined, the order of agenesis rates among children with hypodontia was as follows:UI2s (5 cases) UCs (4 cases), LP2s (3 cases), and UP2s (2 cases). There are apparent differences in thepattern of hypodontia between males and females especially regarding the agenesis frequencies ofUI2s, UCs and LP2s; however statistical significance was only found in UI2 agenesis.
The prevalence of symmetrical hypodontia was 16.7% (2 out of 12 cases) among the Druze childrenexhibiting any degree of hypodontia (20.0% (1 out of 5 cases) among males and 14.3% (1 out of 7 cases)among females; p = 0.7993), with the most common symmetrical hypodontia among this sample (sexespooled) being LP2 agenesis (50% of the time; 1 out of 2 cases of LP2 agenesis), followed by UI2 agenesis(25% of the time; 1 out of 4 cases of UI2 agenesis). However, the difference between these two typesof symmetrical agenesis was statistically insignificant (p = 0.5734). The congenital absence of UCs andUP2s was found asymmetrical in all hypodontic cases among this sample.
The ratios of missing teeth in the upper and lower jaws, on the right and left sides, and in the anteriorand posterior segments were calculated and compared. All missing teeth among male children withhypodontia were maxillary teeth, equally distributed on the right and left sides, and with the majority(83.3%; 5 out of 6 cases) being in the anterior segment. Among females 62.5% (5 out of 8 cases) ofmissing teeth with hypodontia were maxillary, 62.5% (5 out of 8 cases) being on the left side (60% (3out of 5 cases) with respect to maxillary teeth and 66.7% (2 out of 3 cases) with respect to mandibularones); and equally distributed in the anterior and posterior segments (80% (4 out of 5 cases) in theanterior segment with respect to maxillary teeth and 0% (0 out of 3 cases) with respect to mandibularones). When sexes were pooled, 78.6% (11 out of 14 cases) of missing teeth were maxillary, 57.1%(8 out of 14 cases) being on the left side (54.5% (6 out of 11 cases) with respect to maxillary teethand 66.7% (2 out of 3 cases) with respect to mandibular ones); 64.3% (9 out of 14 cases) being in theanterior segment (81.8% (9 out of 11 cases) with respect to maxillary teeth and 0% (0 out of 3 cases)with respect to mandibular ones).
Discussion
The prevalence of hypodontia, among the Druze sample was 11.1% for males, 12.5% for females, and11.8% for both sexes pooled. These rates are at the high end of the wide range previously reported forWestern Eurasia, which extends from 2.2% to 15.68%. However, the closest reported frequencies amongWestern Eurasia to the rates of hypodontia in the present study are those reported by Hunstadbraten(1973) who studied a sample of Norwegians, Behr et al. (2011) and Hickel and Hickel (1989) whostudied German samples, O’Dowling and McNamara who studied an Irish sample (1990), Ajami et al.(2010) and Vahid-Dastjerdi et al. (2010) who studied Persian samples, and Maatouk et al. (2008) whostudied a Tunisian genetic isolate. Interestingly, the hypodontia prevalence in the Druze sample isvery close to the reported frequencies of hypodontia in a number of studies previously conducted onEastern Asian (Sinodont) samples (Chung et al., 2008; Goya et al., 2008; Kim, 2011). This is difficult toreconcile since the Druze population do not share a recent common ancestry with Sinodont popula-tions. Surprisingly, on the other hand, hypodontia prevalence among the Druze sample is distinctlyhigher than the reported frequencies of hypodontia in a number of Near Eastern Arabian samples(Abu Alhaija et al., 2005; Albashaireh and Khader, 2006; al-Emran, 1990; Salem, 1989; Salama andAbdel-Megid, 1994), which is inconsistent with their close biological ancestry. This distinctly higherprevalence of hypodontia among the Druze population is possibly related to isolation and the highrates of consanguineous marriages. It is known that the social organization of the Druze encouragesinter-marriages between close relatives and discourages marriage with anyone outside the Druzepopulation. This is consistent with the results of some previous studies conducted on genetic isolatesthat are characterized by high rates of endogamy (Eswar et al., 2003; Maatouk et al., 2008; Mahaneyet al., 1990; Nelsen et al., 2001), which observed ostensibly higher rates of hypodontia among thesegroups. Alternatively, this dissimilarity might be attributed to the close family relations of the studiedindividuals in Al-Azraq as they are all descendants of a small number of families which settled downin Jordan in early 20th century.
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This study also revealed that the prevalence rate of hypodontia is slightly higher in females thanin males among the Druze sample, but this difference is statistically insignificant. This statisticallyinsignificant female predominance in the frequency of hypodontia is consistent with the findingsof the majority of previous studies, with the exception of the following studies (Grahnen, 1956; Laiand Seow, 1989; Maklin et al., 1979; Ng’ang’a and Ng’ang’a, 2001; Salem, 1989). In this regard, only afew previous studies demonstrated statistically significant male-female differences (Bergstrom, 1977;Brook, 1974; Nordgarden et al., 2002; Ringqvist and Thilander, 1969; Rosenzweig and Garbarski, 1965;Topkara and Sari, 2011). These findings might suggest a more tendency for the X chromosome towardpermitting dental numerical reduction versus a balancing effect of the Y chromosome in conservingthe same number of teeth.
The number of congenitally absent teeth per child in both sexes combined among the Druze samplewas 1.4. This figure is slightly lower than the previously reported range of 1.5–4.8, and is closest tothat reported by Davis (1987) who studied a sample of Chinese school children. This relatively highprevalence of hypodontia and small number of missing teeth per individual among the living Druzemight be characteristic for this population. However, further comparative data are required from othergroups that belong to the Middle Eastern Arab regional group to confirm this postulation. This studyalso demonstrated that the number of missing teeth per individual among the Druze sample is slightlygreater in females than males, but the difference is again not statistically significant. It is noteworthythat many previous studies have shown inconsistent findings as to which sex is predominant in thisregard (Aasheim and Øgaard, 1993; Bäckman and Wahlin, 2001; Bergstrom, 1977; Byrd, 1943; Castaldiet al., 1966; Grahnen, 1956; Haavikko, 1971; Horowitz, 1966; Hunstadbraten, 1973; Magnusson, 1977;Muller et al., 1970; Ng’ang’a and Ng’ang’a, 2001; Nik-Hussein, 1989; Ringqvist and Thilander, 1969;Rolling, 1980; Rose, 1966; Rosenzweig and Garbarski, 1965; Thompson and Popovich, 1974; Volk,1963; Wisth et al., 1974; Zimmerman, 1967).
The frequency of 90% in children with one or two missing teeth among the children exhibiting anydegree of hypodontia in the present study is within, but occupying the high end of the previouslyreported worldwide range of 75% in the Norwegian population (Hunstadbraten, 1973) to 97.4% in theChinese population (Davis, 1987), except for the very low prevalence rate of 49.0% reported by Laiand Seow (1989). In contrast, the prevalence of oligodontia in the present study was found to be 0.0%occupying the lowest end of the previously reported world range of 0.0% in the Eurocanadian (Castaldiet al., 1966) and Chinese populations (Davis, 1987) to 11.3% in a Swedish sample (Grahnen, 1956).
The finding of the present study, that the upper lateral incisor has the highest rate of agenesis inchildren with minor (one or two teeth missing) or moderate hypodontia (three or four teeth miss-ing), followed by the upper canines, the upper second premolars and the lower second premolarsin a decreasing order, is partly in agreement with those of a number of studies conducted on LatinAmerican samples (Gomes et al., 2010; Medina, 2012; Silva Meza, 2003) and on Sunda-Pacific samples(Intaraprasong et al., 1983; Nik-Hussein, 1989), and with those observed by Shafi et al. (2008) in anEnglish sample; Szepesi et al. (2006) and Gabris et al. (2001, 2006) in Hungarian samples; Struzak-Wysokinska et al. (1990) in a Polish sample; Topkara and Sari (2011), Celikoglu et al. (2010) andSisman et al. (2007) in Turkish samples; Vahid-Dastjerdi et al. (2010) in a Persian sample; Rosenzweigand Garbarski (1965) in a Near Eastern Jewish sample; Werther and Rothenberg (1939), Byrd (1943),Zimmerman (1967) and Muller et al. (1970) in Euroamerican samples; and Ruprecht et al. (1986) ina Saudi Arabian sample. These studies showed that the upper lateral incisors are the most frequentlymissing teeth, followed, in most of these studies, by the lower second premolars; or, in some of them,by the upper second premolars (Intaraprasong et al., 1983; Vahid-Dastjerdi et al., 2010), except for onestudy where the UI2 was followed by the LI2 (Nik-Hussein, 1989). On the other hand, the findings ofthe present study, regarding the order of frequency of congenitally missing teeth, completely disagreewith those observed in Sinodont samples, which showed that the lower second premolars (Endo et al.,2006; Goya et al., 2008; Kim, 2011; Zhu et al., 2007) or the lower lateral incisors (Chung et al., 2008;Davis, 1987; Niswander and Sujaku, 1963) are the most commonly missing teeth in those samples,and also disagree with those observed in Sub-Saharan African samples (Diagne et al., 2001; Ng’ang’aand Ng’ang’a, 2001) and the majority of Western Eurasian samples (Aasheim and Øgaard, 1993; Ajamiet al., 2010; Bäckman and Wahlin, 2001; Behr et al., 2011; Bergstrom, 1977; Brown, 1957; Buenviajeand Rapp, 1984; Byrd, 1943; Castaldi et al., 1966; Dolder, 1937; Gimnes, 1964; Glenn, 1961, 1964;
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Gonzalez-Allo et al., 2012; Goren et al., 2005; Grahnen, 1956; Gulzow and Peters, 1977; Haavikko,1971; Horowitz, 1966; Hunstadbraten, 1973; Ingervall et al., 1972; Johannsdottir et al., 1997; Lai andSeow, 1989; Lynham, 1990; Maatouk et al., 2008; Magnusson, 1977; Maklin et al., 1979; ManriqueMora et al., 1991; Mckibben and Brearley, 1971; Nordgarden et al., 2002; Ringqvist and Thilander,1969; Rolling, 1980; Rose, 1966; Sabes and Bartholdi, 1962; Silverman and Ackerman, 1979; Thilanderand Myrberg, 1973; Thompson and Popovich, 1974; Volk, 1963; Wisth et al., 1974) including Near East-ern Arab samples (Abu Alhaija et al., 2005; Albashaireh and Khader, 2006; al-Emran, 1990; Salamaand Abdel-Megid, 1994; Salem, 1989). These studies showed that the lower second premolars are themost common type of dental agenesis among these population groups, followed by either the uppersecond premolars or the upper lateral incisors. The partial or complete dissimilarity of the findings ofthe present study regarding the distribution of hypodontia among the Druze population to the findingsof the above-mentioned studies conducted on Sinodont, Sundadont and Sub-Saharan African popula-tions is consistent with the different ethnic origin of the Druze population from these three groups.While the dissimilarity to the findings in the above-mentioned Western Eurasian samples especiallyNear Eastern Arabs and Jews is more difficult to reconcile since they belong to the same ancestralcategory (i.e. they share a recent common ancestor). A possible explanation for this might be thatthe Druze population has undergone a major genetic drift from the Western-Eurasian category lead-ing to distinct dental characteristics from other groups belonging to Western-Eurasia, with which itshares a recent common ancestor over a relatively short time span. Similar dental microdifferentiationamong groups having recent common ancestral relationships has been well documented in the NearEastern Jews (Sofaer et al., 1986), the Southwest American Indians (Scott and Dahlberg, 1982; Scottet al., 1983), the Yanomama Indians of Venezuela (Brewer-Carias et al., 1976), and Melanesians (Harris,1977). Such genetic drifts leading to local differentiation in dental characteristics among biologicallyrelated groups over a relatively short period are generally viewed as a consequence of colonizationevents, population structure such as high rates of endogamy, and small population size (Scott andTurner, 1988).
It is also noteworthy that the finding of the present study that the upper canines were the mostcommonly missing teeth in females (3 out of 8 cases) and the second most commonly missing teeth(following upper lateral incisors) in males (1 out of 6 cases) and in both sexes combined (4 out of14 cases), which is dissimilar to all previous investigations across diverse ethnic groups. These previ-ous studies showed extreme rarity of upper canine agenesis. It appears that the relatively high rateof upper canine agenesis amongst hypodontic individuals is characteristic for the Druze population.This finding is difficult to reconcile and inconsistent with the general consideration, according to But-ler’s evolutionary morphogenic field model (Butler, 1963) and Osborn’s clone model (Osborn, 1978),which state that the upper canines are one of the most stable teeth (similar to lower canines and themesial members of various dental classes, such as: central incisors, first premolars, and first molars)and least affected by morphometric reduction or agenesis. However, this finding is consistent withthe Svinhufvud’s et al. (1988) anatomical model which suggests that teeth adjacent to the junctionbetween the premaxilla and maxilla proper (upper lateral incisors and canines) could exhibit somedegree of instability. However, this model failed to account for the considerable stability of uppercanines across diverse ethnic groups. Therefore, the relatively high rate of upper canine agenesisamongst the Druze population seems to be more likely due to a mutation or mutations in a gene or anumber of genes that act specifically on the odontogenesis of upper canines rather than genes witha more general action on the development of the whole dentition. Such mutations are more likely toaccumulate in isolated genetic pools due to high rates of endogamy and small population size-whichis the situation for the Druze population.
The present study revealed that symmetrical hypodontia is much less prevalent (16.7%; 2 out of12 cases) than asymmetrical dental agenesis among the Druze sample. This is in disagreement withmany previous reports which reported that symmetrical hypodontia is more prevalent (Bäckman andWahlin, 2001; Bergstrom, 1977; Byrd, 1943; Castaldi et al., 1966; Endo et al., 2006; Glenn, 1964; Goyaet al., 2008; Grahnen, 1956; Horowitz, 1966; Hunstadbraten, 1973; Lai and Seow, 1989; Maatouk et al.,2008; Magnusson, 1977; Maklin et al., 1979; Muller et al., 1970; Ng’ang’a and Ng’ang’a, 2001; SilvaMeza, 2003; Silverman and Ackerman, 1979; Volk, 1963; Zimmerman, 1967). However, few previ-ous studies (Davis, 1987; Glenn, 1961; Grahnen, 1956; Haavikko, 1971) have shown the opposite,
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thus similar to the finding of the present study. The finding of the present study, that the most com-mon symmetrical hypodontia among the Druze sample is LP2 agenesis, followed by UI2 agenesis, isin agreement with most previous studies which demonstrated that the most common symmetricalhypodontia is LP2 agenesis, followed by either UI2 or UP2 agenesis (Castaldi et al., 1966; Endo et al.,2006; Gimnes, 1964; Grahnen, 1956; Mckibben and Brearley, 1971; Silverman and Ackerman, 1979;Szepesi et al., 2006; Volk, 1963).
The present study demonstrated that more teeth were missing from the maxilla than from themandible among the Druze children exhibiting any degree of hypodontia which ranged in the affectedindividuals of the present study from one to three missing teeth per individual (i.e. minor to mod-erate hypodontia). Many previous studies have shown inconsistent findings regarding which dentalarch is predominant in terms of how many teeth per arch are missing (Aasheim and Øgaard, 1993;Albashaireh and Khader, 2006; Bäckman and Wahlin, 2001; Bergstrom, 1977; Brown, 1957; Byrd,1943; Davis, 1987; Dolder, 1937; Endo et al., 2006; Glenn, 1961, 1964; Grahnen, 1956; Haavikko, 1971;Horowitz, 1966; Hunstadbraten, 1973; Legovic et al., 1990; Magnusson, 1977; Maklin et al., 1979;Muller et al., 1970; Ng’ang’a and Ng’ang’a, 2001; Nordgarden et al., 2002; Ringqvist and Thilander,1969; Rolling, 1980; Rose, 1966; Rosenzweig and Garbarski, 1965; Ruprecht et al., 1986; Sabesand Bartholdi, 1962; Salama and Abdel-Megid, 1994; Silva Meza, 2003; Silverman and Ackerman,1979; Thompson and Popovich, 1974; Topkara and Sari, 2011; Werther and Rothenberg, 1939;Wisth et al., 1974; Zhu et al., 2007; Zimmerman, 1967). However, some previous investigationsobserved maxillary predominance in this regard, which is consistent with the finding of the presentstudy (al-Emran, 1990; Sisman et al., 2007; Struzak-Wysokinska et al., 1990; Vahid-Dastjerdi et al.,2010).
The present study demonstrated that, in the present sample, the left side is predominant, especiallyin the mandible, in terms of the number of missing teeth per side. This finding disagrees with manyprevious investigations which showed that there is similar distribution of missing teeth between theright and left sides (Aasheim and Øgaard, 1993; Albashaireh and Khader, 2006; Bäckman and Wahlin,2001; Bergstrom, 1977; Brown, 1957; Byrd, 1943; Dolder, 1937; Endo et al., 2006; Grahnen, 1956;Magnusson, 1977; Maklin et al., 1979; Muller et al., 1970; Ringqvist and Thilander, 1969; Rolling,1980; Rose, 1966; Rosenzweig and Garbarski, 1965; Silva Meza, 2003; Sisman et al., 2007; Thilanderand Myrberg, 1973; Thompson and Popovich, 1974; Wisth et al., 1974; Zhu et al., 2007; Zimmerman,1967).
The present study found that in the Druze children with one or two teeth absent, the majority ofmissing teeth are in the anterior segment when only maxillary teeth or when all teeth are consid-ered, while when only mandibular teeth are considered, the congenital absence occurs exclusively inthe posterior segment. When all children with any degree of hypodontia are considered and whenthe whole dentition is included in the comparison, the overall anterior predominance considerablydecreases. This finding agrees with the findings of some previous reports which pointed out that ante-rior tooth agenesis is predominant in individuals with one or two teeth absent, but the reverse is trueof individuals with three or more missing teeth (Aasheim and Øgaard, 1993; Endo et al., 2004, 2006;Muller et al., 1970; Øgaard and Krogstad, 1995).
The findings of the present study provide useful information to dental practitioners on where tofocus in dental examination when hypodontia is alleged in patients from the Druze population. Inaddition, the findings suggest great orthodontic need for this population due to the relatively highprevalence of hypodontia (11.8%) and the observation that dental agenesis occurs predominantly(64.3% (9 out of 14 cases)) in the upper anterior segment.
Conclusions
The distinct features of hypodontia among the Druze population, in comparison with other popu-lations, are the relatively high prevalence rate of minor (one or two teeth missing) hypodontia, theextreme rarity of oligodontia (five or more teeth missing), and the upper lateral incisor and uppercanine agenesis being the most common type of congenital dental absence among males and females,respectively.
210 F. Alsoleihat, A. Khraisat / HOMO - Journal of Comparative Human Biology 65 (2014) 201–213
Acknowledgments
This research was conducted at the Faculty of Dentistry of the University of Jordan, and supportedby a grant from the Deanship of Academic Research of the University of Jordan (109/2009-2010). Wewould like to thank Dr. Mahmoud Alnsour, Dr. Khadijah Al-zoubi and Dr. Reham Al-Najjar for helpingus taking the impressions for the dental arches, to thank Mr. Ziad Nazik for pouring the impressionsand preparing the dental casts, to thank Mr. Ramzi Bani Marof for arranging the school visits, and tothank the directors of schools involved.
References
Aasheim, B., Øgaard, B., 1993. Hypodontia in 9-year-old Norwegians related to need of orthodontic treatment. Scand. J. Dent.Res. 101, 256–260.
Abu Alhaija, E.S., Al-Khateeb, S.N., Al-Nimri, K.S., 2005. Prevalence of malocclusion in 13–15 year-old North Jordanian schoolchildren. Community Dent. Health 22, 266–271.
Ajami, B.A., Shabzendedar, M., Mehrjerdian, M., 2010. Prevalence of hypodontia in nine- to fourteen-year-old children whoattended the Mashhad School of Dentistry. Indian J. Dent. Res. 21, 549–551.
Albashaireh, Z.S., Khader, Y.S., 2006. The prevalence and pattern of hypodontia of the permanent teeth and crown size and shapedeformity affecting upper lateral incisors in a sample of Jordanian dental patients. Community Dent. Health 23, 239–243.
al-Emran, S., 1990. Prevalence of hypodontia and developmental malformation of permanent teeth in Saudi Arabian schoolchil-dren. Br. J. Orthod. 17, 115–118.
Alsoleihat, F., Khraisat, A., 2013. The phenetic distances of the living Druze from other human populations suggest a majorgenetic drift from the Western Eurasian ancestral category. Homo – J. Comp. Hum. Biol. 64, 377–390.
Bäckman, B., Wahlin, Y.B., 2001. Variations in number and morphology of permanent teeth in 7-year-old Swedish children. Int.J. Paediatr. Dent. 11, 11–17.
Behar, D.M., Yunusbayev, B., Metspalu, M., Metspalu, E., Rosset, S., Parik, J., Rootsi, S., Chaubey, G., Kutuev, I., Yudkovsky, G.,Khusnutdinova, E.K., Balanovsky, O., Semino, O., Pereira, L., Comas, D., Gurwitz, D., Bonne-Tamir, B., Parfitt, T., Hammer,M.F., Skorecki, K., Villems, R., 2010. The genome-wide structure of the Jewish people. Nature 466, 238–242.
Behr, M., Proff, P., Leitzmann, M., Pretzel, M., Handel, G., Schmalz, G., Driemel, O., Reichert, T.E., Koller, M., 2011. Survey ofcongenitally missing teeth in orthodontic patients in Eastern Bavaria. Eur. J. Orthod. 33, 32–36.
Bergstrom, K., 1977. An orthopantomographic study of hypodontia, supernumeraries and other anomalies in school childrenbetween the ages of 8–9 years. An epidemiologic study. Swed. Dent. J. 1, 145–157.
Brewer-Carias, C.A., Le Blanc, S., Neel, J.V., 1976. Genetic structure of a tribal population, the Yanomama Indians. XII. Dentalmicrodifferentiation. Am. J. Phys. Anthropol. 44, 5–14.
Brook, A.H., 1974. Dental anomalies of number, form and size: their prevalence in British schoolchildren. J. Int. Assoc. Dent.Child. 5, 37–53.
Brown, R.V., 1957. The pattern and frequency of congenital absence of teeth. Iowa Dent. J. 43, 60–61.Buenviaje, T.M., Rapp, R., 1984. Dental anomalies in children: a clinical and radiographic survey. J. Dent. Child. 51, 42–46.Butler, P.M., 1963. Tooth morphology and primate evolution. In: Brothwell, D.R. (Ed.), Dental Anthropology. Pergamon Press,
New York.Byrd, E.D., 1943. Incidence of supernumerary and congenitally missing teeth. J. Dent. Child. 10, 84–86.Castaldi, C.R., Bodnarchuk, A., Zacherl, W.A., 1966. Incidence of congenital anomalies in permanent teeth of a group of Canadian
children aged 6–9. J. Can. Dent. Assoc. 32, 154–159.Celikoglu, M., Kazanci, F., Miloglu, O., Oztek, O., Kamak, H., Ceylan, I., 2010. Frequency and characteristics of tooth agenesis
among an orthodontic patient population. Med. Oral Patol. Oral Cir. Bucal 15, e797–e801.Chung, C.J., Han, J.H., Kim, K.H., 2008. The pattern and prevalence of hypodontia in Koreans. Oral Dis. 14, 620–625.Davis, P.J., 1987. Hypodontia and hyperodontia of permanent teeth in Hong Kong schoolchildren. Community Dent. Oral
Epidemiol. 15, 218–220.Dechkunakorn, S., Chaiwat, J., Sawaengkit, P., 1990. Congenital absence and loss of teeth in an orthodontic patient group. J. Dent.
Assoc. Thailand 40, 165–176 (in Thai).Diagne, F., Diop-Ba, K., Yam, A.A., Diop, F., 2001. Prevalence of dental agenesis: a radiologic and clinical study in Dakar. Orthod.
Fr. 72, 313–315 (In French).Dolder, E., 1937. Deficient dentition. Statistical survey. Dent. Rec. 57, 142–143.Ducka-Karska, K., 1983. Various dental anomalies in the black population of Lubumbashi (Zaire). Odontostomatol. Trop. 6,
127–130 (in French).Eidelman, E., Chosack, A., Rosenzweig, K.A., 1973. Hypodontia: prevalence amongst Jewish populations of different origin. Am.
J. Phys. Anthropol. 39, 129–133.Endo, T., Ozoe, R., Kubota, M., Akiyama, M., Shimooka, S., 2006. A survey of hypodontia in Japanese orthodontic patients. Am. J.
Orthod. Dentofacial Orthop. 129, 29–35.Endo, T., Yoshino, S., Ozoe, R., Kojima, K., Shimooka, S., 2004. Association of advanced hypodontia and craniofacial morphology
in Japanese orthodontic patients. Odontology 92, 48–53.Firro, K.M., 1992. A History of the Druzes. Brill, Leiden.Eswar, N., Begum, S.R., Sivanandhy, G., Eswar, P., 2003. Association of parental consanguinity prevalent among those patients
having dental anomalies. A retrospective study of 42 cases. Indian J. Dent. Res. 14, 33–38.Falah, S., 2000. The Druze in the Middle East. Israel Defense office, Jerusalem, pp. 112–113.Fujita, Y., Hidaka, A., Nishida, I., Morikawa, K., Hashiguchi, D., Maki, K., 2009. Developmental anomalies of permanent lateral
incisors in young patients. J. Clin. Pediatr. Dent. 33, 211–215.
F. Alsoleihat, A. Khraisat / HOMO - Journal of Comparative Human Biology 65 (2014) 201–213 211
Gabris, K., Tarjan, I., Csiki, P., Konrad, F., Szadeczky, B., Rozsa, N., 2001. Prevalence of congenital hypodontia in the permanentdentition and its treatment. Fogorv. Sz. 94, 137–140 (in Hungarian).
Gabris, K., Fabian, G., Kaan, M., Rozsa, N., Tarjan, I., 2006. Prevalence of hypodontia and hyperdontia in paedodontic andorthodontic patients in Budapest. Community Dent. Health 23, 80–82.
Garner, L.D., Yu, P.L., 1978. Is partial anodontia a syndrome of Black Americans? Angle Orthod. 48, 85–88.Gimnes, H., 1964. Congenital absence of teeth in Oslo school children. Dent. Abstr. 9, 237.Glenn, F.B., 1961. Incidence of congenitally missing permanent teeth in a private pedodontic practice. J. Dent. Child. 28,
317–320.Glenn, F.B., 1964. A consecutive six-year study of the prevalence of congenitally missing teeth in a private pedodontic practice
of two geographically separated areas. J. Dent. Child. 31, 264–270.Gomes, R.R., da Fonseca, J.A., Paula, L.M., Faber, J., Acevedo, A.C., 2010. Prevalence of hypodontia in orthodontic patients in
Brasilia, Brazil. Eur. J. Orthod. 32, 302–306.Gonzalez-Allo, A., Campoy, M.D., Moreira, J., Ustrell, J., Pinho, T., 2012. Tooth agenesis in a Portuguese population. Int. Orthod.
10, 198–210.Goren, S., Tsoizner, R., Dinbar, A., Levin, L., Brezniak, N., 2005. Prevalence of congenitally missing teeth in Israeli recruits. Refuat.
Hapeh. Vehashinayim 22, 49–53 (in Hebrew).Goya, H.A., Tanaka, S., Maeda, T., Akimoto, Y., 2008. An orthopantomographic study of hypodontia in permanent teeth of Japanese
pediatric patients. J. Oral Sci. 50, 143–150.Grahnen, H., 1956. Hypodontia in the permanent dentition. Odontol. Revy. 7 (Suppl. 3), 1–100.Gulzow, H.J., Peters, R., 1977. Epidemiology of hypodontia in the permanent dentition. Dtsch. Zahnarztl. Z. 32, 545–549 (in
German).Haavikko, K., 1971. Hypodontia of permanent teeth. An orthopantomographic study. Suom. Hammaslaak Toim. 67,
219–225.Harris, E.F., 1977. Anthropologic and Genetic Aspects of the Dental Morphology of Solomon Islanders, Melanesia. Department
of Anthropology, Arizona State University, Tempe.Harris, E.F., Clark, L.L., 2008. Hypodontia, an epidemiologic study of American black and white people. Am. J. Orthod. Dentofacial
Orthop. 134, 761–767.Harris, E.F., McKee, J.H., 1990. Tooth mineralization standards for blacks and whites from the middle southern United States. J.
Forensic Sci. 35, 859–872.Helm, S., 1968. Malocclusion in Danish children with adolescent dentition: an epidemiologic study. Am. J. Orthod. 54, 352–366.Hickel, R., Hickel, R., 1989. The incidence and causes of missing front teeth in children and youths. Fortschr. Kieferorthop. 50,
309–315 (in German).Horowitz, J.M., 1966. Aplasia and malocclusion: a survey and appraisal. Am. J. Orthod. 52, 440–453.Hunstadbraten, K., 1973. Hypodontia in the permanent dentition. J. Dent. Child. 40, 115–117.Ingervall, B., Seeman, L., Thilander, B., 1972. Frequency of malocclusion and need of orthodontic treatment in 10-year old
children in Gothenburg. Swed. Dent. J. 65, 7–21.Intaraprasong, A., Puanaiyaka, R., Wattanasandaporn, D., 1983. The number of dental anomalies found in a group of Thai children.
J. Dent. Assoc. Thailand 33, 123–133.Jobling, M.A., 2004. Human Evolutionary Genetics. Garland Science, New York, pp. 392.Johannsdottir, B., Wisth, P.J., Magnusson, T.E., 1997. Prevalence of malocclusion in 6-year-old Icelandic children. A study using
plaster models and orthopantomograms. Acta Odontol. Scand. 55, 398–402.Kayembe, B., Ntumba, M.K., 1987. Local retention of various deciduous teeth in adolescent and adult subjects in Zaire. Odon-
tostomatol. Trop. 10, 97–100 (in French).Kim, Y.H., 2011. Investigation of hypodontia as clinically related dental anomaly: prevalence and characteristics. ISRN Dent.,
http://dx.doi.org/10.5402/2011/246135.Lai, P.Y., Seow, W.K., 1989. A controlled study of the association of various dental anomalies with hypodontia of permanent
teeth. Pediatr. Dent. 11, 291–296.Legovic, M., Ceranic, I., Cehich, A., 1990. Anomalies in the number of permanent teeth in orthodontic patients in 2 localities in
Croatia. Schweiz. Monatsschr. Zahnmed. 100, 286–290 (in Italian).Locht, S., 1980. Panoramic radiographic examination of 704 Danish children aged 9–10 years. Community Dent. Oral Epidemiol.
8, 375–380.Lynham, A., 1990. Panoramic radiographic survey of hypodontia in Australian Defence Force recruits. Aust. Dent. J. 35, 19–22.Maatouk, F., Baaziz, A., Ghnima, S., Masmoudi, F., Ghedira, H., 2008. Survey on hypodontia in Sayada, Tunisia. Quintessence Int.
39, e115–e120.Magnusson, T.E., 1977. Prevalance of hypodontia and malformations of permanent teeth in Iceland. Community Dent. Oral
Epidemiol. 5, 173–178.Mahaney, M.C., Fujiwara, T.M., Morgan, K., 1990. Dental agenesis in the Dariusleut Hutterite Brethren: comparisons to selected
Caucasoid population surveys. Am. J. Phys. Anthropol. 82, 165–177.Maklin, M., Dummett Jr., C.O., Weinberg, R.W., 1979. A study of oligodontia in a sample of New Orleans children. J. Dent. Child.
46, 478–482.Manrique Mora, M.C., Ostos Garrido, M.J., Gonzalez Rodriguez, E., 1991. Prevalence of dental agenesis in an Andalucian popu-
lation. Rev. Eur. Odonto-estomatol. 3, 49–56.Mckibben, D.R., Brearley, L.J., 1971. Radiographic determination of the prevalence of selected dental anomalies in children. J.
Dent. Child. 38, 390–398.Medina, A.C., 2012. Radiographic study of prevalence and distribution of hypodontia in a pediatric orthodontic population in
Venezuela. Pediatr. Dent. 34, 113–116.Muller, T.P., Hill, I.N., Petersen, A.C., Blayney, J.R., 1970. A survey of congenitally missing permanent teeth. J. Am. Dent. Assoc.
81, 101–107.Nelsen, K., Tayles, N., Domett, K., 2001. Missing lateral incisors in Iron Age South-East Asians as possible indicators of dental
212 F. Alsoleihat, A. Khraisat / HOMO - Journal of Comparative Human Biology 65 (2014) 201–213
Ng’ang’a, R.N., Ng’ang’a, P.M., 2001. Hypodontia of permanent teeth in a Kenyan population. East Afr. Med. J. 78, 200–203.Nik-Hussein, N.N., 1989. Hypodontia in the permanent dentition: a study of its prevalence in Malaysian children. Aust. Orthod.
J. 11, 93–95.Nissim, D., 2003. The Druze in the Middle East: Their Faith, Leadership, Identity and Status. Sussex Academic Press, Brighton
and Oregon.Niswander, J.D., Sujaku, C., 1963. Congenital anomalies of teeth in Japanese children. J. Phys. Anthropol. 21, 569–574.Nordgarden, H., Jensen, J.L., Storhaug, K., 2002. Reported prevalence of congenitally missing teeth in two Norwegian counties.
Community Dent. Health 19, 258–261.O’Dowling, I.B., McNamara, T.G., 1990. Congenital absence of permanent teeth among Irish school-children. J. Ir. Dent. Assoc.
36, 136–138.Øgaard, B., Krogstad, O., 1995. Craniofacial structure and soft tissue profile in patients with severe hypodontia. Am. J. Orthod.
Dentofacial Orthop. 108, 472–477.Onyeaso, C.O., Oneyeaso, A.O., 2006. Occlusal/dental anomalies found in a random sample of Nigerian schoolchildren. Oral
Health Prev. Dent. 4, 181–186.Osborn, J.W., 1978. Development, Function and Evolution of Teeth. Academic Press, London.Rantanen, A.V., (Ph.D. dissertation) 1967. The age of eruption of the third molar teeth. Acta Odontol. Scand. 25, 1–86.Ringqvist, M., Thilander, B., 1969. The frequency of hypodontia in an orthodontic material. Sven. Tandlak. Tidskr. 62, 535–541.Rolling, S., 1980. Hypodontia of permanent teeth in Danish schoolchildren. Scand. J. Dent. Res. 88, 365–369.Rose, J.S., 1966. A survey of congenitally missing teeeth, excluding third molars, in 6000 orthodontic patients. Dent. Pract. 17,
107–114.Rosenzweig, K.A., Garbarski, D., 1965. Numerical aberrations in the permanent teeth of grade school children in Jerusalem. Am.
J. Phys. Anthropol. 23, 277–283.Ruprecht, A., Batniji, S., el-Neweihi, E., 1986. Incidence of oligodontia (hypodontia). J. Oral Med. 41, 43–46.Sabes, W.R., Bartholdi, W.L., 1962. Congenital partial anodontia of permanent dentition: a study of 157 cases. J. Dent. Child. 29,
211–213.Salama, F.S., Abdel-Megid, F.Y., 1994. Hypodontia of primary and permanent teeth in a sample of Saudi children. Egypt Dent. J.
40, 625–632.Salem, G., 1989. Prevalence of selected dental anomalies in Saudi children from Gizan region. Community Dent. Oral Epidemiol.
17, 162–163.Scott, G.R., Dahlberg, A.A., 1982. Microdifferentiation in tooth morphology among Indians of the American southwest. In: Kurten,
B. (Ed.), Teeth: Form, Function, and Evolution. Columbia University Press, New York, pp. 259–291.Scott, G.R., Turner II, C.G., 1988. Dental anthropology. Ann. Rev. Anthropol. 17, 99–126.Scott, G.R., Potter, R.H.Y., Noss, J.F., Dahlberg, A.A., Dahlberg, T., 1983. The dental morphology of Pima Indians. Am. J. Phys.
Anthropol. 61, 13–31.Shafi, I., Phillips, J.M., Dawson, M.P., Broad, R.D., Hosey, M.T., 2008. A study of patients attending a multidisciplinary hypodontia
clinic over a five-year period. Br. Dent. J. 205, 649–652.Sharma, J.C., 1983. Dental morphology and odontometry of the Tibetan immigrants. Am. J. Phys. Anthropol. 61, 495–505.Shlush, L.I., Behar, D.M., Yudkovsky, G., Templeton, A., Hadid, Y., Basis, F., Hammer, M., Itzkovitz, S., Skorecki, K., 2008. The Druze:
a population genetic refugium of the Near East. PLoS ONE 3 (5), e2105, http://dx.doi.org/10.1371/journal.pone.0002105.Silva Meza, S., 2003. Radiographic assessment of congenitally missing teeth in orthodontic patients. Int. J. Paediatr. Dent. 13,
112–116.Silverman, N.E., Ackerman, J.L., 1979. Oligodontia: a study of its prevalence and variation in 4032 children. J. Dent. Child. 46,
470–477.Sisman, Y., Uysal, T., Gelgor, I.E., 2007. Hypodontia. Does the prevalence and distribution pattern differ in orthodontic patients?
Eur. J. Dent. 1, 167–173.Sofaer, J.A., Smith, P., Kaye, E., 1986. Affinities between contemporary and skeletal Jewish and non-Jewish groups based on tooth
morphology. Am. J. Phys. Anthropol. 70, 265–275.Stecker, S.S., Beiraghi, S., Hodges, J.S., Peterson, V.S., Myers, S.L., 2007. Prevalence of dental anomalies in a Southeast Asian
population in the Minneapolis/Saint Paul metropolitan area. Northwest Dent. 86, 25–28.Struzak-Wysokinska, M., Kaminska, K., Wysokinska-Miszczuk, J., 1990. Congenital absence of permanent teeth. Czas. Stomatol.
43, 199–201 (Polish).Svinhufvud, E., Myllarniemi, S., Norio, R., 1988. Dominant inheritance of tooth malpositions and their association to hypodontia.
Clin. Genet. 34, 373–381.Szepesi, M., Nemes, J., Kovalecz, G., Alberth, M., 2006. Prevalence of hypodontia in 4–18-year-old children in Department of
Paediatric Dentistry, Faculty of Dentistry, University of Debrecen from 1999 to 2003. Fogorv. Sz. 99, 115–119 (in Hungarian).Thilander, B., Myrberg, N., 1973. The prevalence of malocclusion in Swedish schoolchildren. Scand. J. Dent. Res. 81,
12–21.Thompson, G.W., Popovich, F., 1974. Probability of congenitally missing teeth: results in 1191 children in the Burlington Growth
Centre in Toronto. Community Dent. Oral Epidemiol. 2, 26–32.Topkara, A., Sari, Z., 2011. Prevalence and distribution of hypodontia in a Turkish orthodontic patient population: results from
a large academic cohort. Eur. J. Paediatr. Dent. 12, 123–127.Tsai, S.J., King, N.M., 1998. A catalogue of anomalies and traits of the permanent dentition of southern Chinese. J. Clin. Pediatr.
Dent. 22, 185–194.Vahid-Dastjerdi, E., Borzabadi-Farahani, A., Mahdian, M., Amini, N., 2010. Non-syndromic hypodontia in an Iranian orthodontic
population. J. Oral Sci. 52, 455–461.Volk, A., 1963. Absence of tooth germs in children. Dent. Abstr. 8, 768.Vona, G., Piras, V., Succa, V., Distinto, C., 1993. Dental agenesis in Sardinians. Anthropol. Anz. 51, 333–340.Werther, R., Rothenberg, F., 1939. Anodontia. A review of its etiology with presentation of a case. Am. J. Orthod. 25, 61–81.Wisth, P.J., Thunold, K., Boe, O.E., 1974. Frequency of hypodontia in relation to tooth size and dental arch width. Acta Odontol.
F. Alsoleihat, A. Khraisat / HOMO - Journal of Comparative Human Biology 65 (2014) 201–213 213
Wu, H., Feng, H.L., 2005. A survey of number and morphology anomalies in permanent teeth of 6 453 youths between 17 to 21years old. Zhonghua Kou Qiang Yi Xue Za Zhi 40, 489–490 (in Chinese).
Yanagida, I., Mori, S., 1990. Statistical studies on numerical anomalies of teeth in children using orthopantomograms – congenitalhypodontia. Osaka Daigaku Shigaku Zasshi 35, 580–593 (in Japanese).
Zhu, J.X., Zheng, S.G., Ge, L.H., 2007. Clinical analysis of simple hypodontia. Zhonghua Kou Qiang Yi Xue Za Zhi 42, 716–717(in Chinese).
