Pergamon Archs oral Biol. Vol. 41, No. 7, pp. 641 645, 1996

Copyright © 1996 Elsevier Science Ltd. All rights reserved Printed in Great Britain

PII: S0003-9969(96)00066-0 0003-9969/96 $15.00 + 0.130

MESIODISTAL CROWN DIAMETERS OF PERMANENT TEETH IN JORDANIANS

F. N. HATTAB, ~'* S. AL-KHATEEW and I. SULTAN 2

aDepartments of Restorative and Pediatric Dentistry, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan and 2Department of Orthodontics, Faculty of Dentistry, Jordan

University of Science and Technology, Irbid, Jordan

(Accepted 17 June 1996)

Summary--Mesiodistal crown diameters were measured from dental casts of the permanent teeth of 198 Jordanians (86 males and 112 females), aged 13.4-19.1 years. The differences in the crown diam- eters between the right- and left-hand sides of the dental arch were not significant, suggesting that either right- or left-side measurements could be taken to represent the tooth size of the study population. Males had significantly larger teeth than females, ranging from p < 0.05 for the incisors to p < 0.001 for the first molars. In both sexes, the maxillary lateral incisors showed the greatest variability [coeffi- cient of variation (CV) 8.8%] and the first molar the least (CV 5.8%) in mesiodistal diameter. Canines displayed greater sexual dimorphism in crown size than any other tooth class. The cumulative tooth widths of males exceeded those of females by a sum of 3.1 mm in the maxilla and 3.6 mm in the mand- ible. These differences were statistically significant (p < 0.01). Comparisons of the mesiodistal crown di- ameters between population groups showed that Jordanians have tooth sizes close to those of Iraqis, but significantly larger than those of Yemenite-Jews, Caucasians and Chinese. Copyright © 1996 Else- vier Science Ltd.

Key words: permanent dentition, tooth size, Jordanians.

Mesiodistal crown diameter, also called tooth size, tooth crown size, or tooth width, provides signifi- cant information on human evolution and biological problems as well as in forensic and clinical odontol- ogy. Evolutionary anthropologists use mesiodistal diameter to trace the reduction of tooth size that appears to be a concomitant of selective forces, technological and dietary changes during human evolution (Bermudez de Castro and Nicolas, 1995). Tooth size furnishes human biologists with an insight into the genetic relation between populations and environmental adaptation (Margetts and Brown, 1978; Kieser, 1990). Of clinical interest is the interrelation between tooth size and arch align- ment in which large teeth are associated with dental crowding (Lundstrom, 1969; Doris et al., 1981; Radnzic, 1988). Moreover, a relation has been noted between tooth size and third molar eruption and impaction (Forsberg, 1988).

Tooth size exhibits a continuous range of vari- ation among individuals and between populations. Accumulated evidence indicates that tooth size reflects a complex interaction between a variety of genetic and environmental factors (Townsend and Brown, 1978; Garn et al., 1979; Alvesalo et al., 1991). Sexual dimorphism in the extent and pattern of tooth-size variation characterizes modern

*To whom all correspondence should be addressed.

humans. Several studies have demonstrated that mesiodistal crown diameters of males are consider- ably larger than those of females, the largest differ- ences being found in the canines (Seipel, 1946; Moorees et al., 1957; Barrett et al., 1963). Sexual dimorphism in tooth size is more pronounced in the permanent than in the deciduous dentition (Garne t al., 1967; Black, 1978). The explanations proposed for tooth-size dimorphism between males and females include: sex variation in odontogenic timing and enamel thickness; males having larger bodies than females; effects of sex chromosomes in promot- ing tooth growth; and other hormonal influences (reviewed by Kieser, 1990). Because odontometric data on the Jordanian population are not available and there is a paucity of such data on Arabs in gen- eral, we have now sought to determine the mesiodis- tal crown diameters of the permanent teeth in Jordanians and to compare our findings with those for similar and different ethnic groups.

The sample comprised 198 individuals (86 males and 112 females) who were born of Jordanian parents and grew up in Jordan. All were apparently healthy and presented to the dental clinic at Jordan University of Science and Technology for orthodon- tic and other treatment needs. The mean age (+SD) of the males was 15.7 (+2.6) years and females 15.1 (+__2.2) years. Teeth were selected for measurement only if they were morphologically normal, not

641

642 F .N. Hattab et al.

noticeably affected by attrition and caries or had been restored, and were fully erupted to the occlusal plane. Individuals with a history of orthodontic treatment were excluded.

For every individual, alginate impressions were taken in suitable perforated trays for the upper and lower dental arches, and cast immediately in dental stone. Mesiodistal crown diameter was registered for each maxillary and mandibular permanent tooth from the first molar on one side to the correspond- ing tooth on the other side. The mesiodistal diam- eter of a tooth was obtained by measuring the greatest distance between the approximal surfaces of the crown using a sliding caliper held parallel to the occlusal and vestibular surfaces. I f a tooth was rotated or malposed in relation to the curvature of the dental arch, the measurement was taken between the points on the approximal surfaces of the crown where it was considered that contact with adjacent teeth would normally occur. An electronic digital sliding caliper was used for all measurements. Measurements were made by two observers (F.N.H. and S.A.).

The experimental and interobserver errors were 0.09 and 0.16 ram, respectively, suggesting that measurement error was of little importance com- pared with biological variation in crown widths. The mean mesiodistal diameters, the SD and the SEM for the teeth of males and females are shown in Tables 1 and 2, respectively. Statistical analysis

(paired t-test) revealed no significant differences between the width of teeth on left- and fight-hand sides of the dental arch. In males, the coefficient of correlation between the left- and right-hand sides varied between 0.75 and 0.83. The corresponding figures for females were 0.73 and 0.84. The differ- ences between the mean width of any individual teeth on the right- and left-hand sides were very small and ranged from 0.00 to 0.18 mm, with the greatest differences representing only one-ninth of the SD of the mean for the total tooth-size measure- ments. In males, the mean tooth width for the right- hand side was 7.81 mm and for the left 7.79 mm. The corresponding figures for females were 7.54 and 7.53 mm. These findings indicate that right- or left- side measurements, for both sexes, could be taken to represent mesiodiatal crown diameters in this population.

In both males and females, the SD and coefficient of variation (CV = 100 x SD/x) o f tooth-size measurements showed that variability differed between individual teeth, with the maxillary lateral incisors showing the greatest variability (8.8%), the lower lateral incisors the next greatest (7.3%), and the first molars the :least (5.8%). There were only slight variability differences by sex, averaging 6.5% for males and 6.7% for females. The mean width of the upper canines was greater than that of the lower canines, with and average of 0.99 mm in males and 0.95 mm in females. In both sexes, the upper first

Table 1. Mesiodistal crown diameters (in ram) of the upper and lower teeth in males

Tooth and Absolute side n* x SD SEM Range xt

Maxilla I~R (11) 86 8.99 0.61 0.066 7.06-10.30 8.94 L (21) 84 8.89 0.67 0.073 6.77-10.62 I2R (12) 85 6.99 0.66 0.072 5.69-8.86 6.93 L (22) 80 6.86 0.59 0.066 5.41-7.87 C R (13) 79 8.10 0.59 0.066 6.86-9.57 8.01 L (23) 81 7.92 0.62 0.069 6.48-9.45 P~R (14) 80 7.19 0.49 0.055 5.95-8.31 7.20 L (24) 78 7.20 0.47 0.053 6.13-8.42 P2R (15) 77 6.99 0.43 0.049 5.59-8.02 7.00 L (25) 76 6.94 0.46 0.053 5.53-7.77 M~R (16) 83 10.57 0.53 0.058 9.30-11.76 10.56 L (26) 79 10.54 0.53 0.060 9.17-11.59

Mandible IiR (41) 82 5.67 0.33 0.036 4.83-6.57 5.63 L (31) 81 5.60 0.30 0.033 4.85-6.33 IER (42) 80 6.23 0.43 0.048 4.73-7.12 6.26 L (32) 79 6.29 0.46 0.052 5.04-7.05 C R (43) 81 6.94 0.44 0.049 5.85-7.86 7.02 L (33) 80 7.10 0.56 0.063 5.09-8.23 PIR (44) 75 7.39 0.45 0.052 5.89-8.13 7.37 L (34) 79 7.34 0.52 0.059 5.90-8.18 PzR (45) 78 7.40 0.41 0.046 6.30-8.68 7.46 L (35) 75 7.51 0.39 0.044 6.78-8.41 MIR (46) 80 11.29 0.62 0.069 9.24-12.24 11.32 L (36) 82 11.34 0.62 0.068 9.22-12.0

Values in parentheses denote the FDI tooth notation system. *Number of individuals. tAbsolute mean values (right- and left-hand measurements combined).

Tooth-crown diameter in Jordanians 643

Table 2. Mesiodistal crown diameters (in mm) of the upper and lower teeth in females

Tooth and Absolute side n* x SD SEM Range xt

Maxilla IIR (11) 112 8.66 0.52 0 .049 7.18-9.90 8.63 L (21) 109 8.61 0.53 0.051 6.15-10.19 I2R (12) 104 6.72 0.60 0 .059 5.30-8.52 6.70 L (22) 104 6.67 0.56 0 .055 5.43-7.94 C R (13) 101 7.68 0.50 0 .050 6.05-9.02 7.62 L (23) 102 7.57 0.52 0.051 6.17-8.74 P1R (14) 103 7.02 0.47 0 .046 5.88-8.63 7.03 L (24) 105 7.04 0.44 0 .043 5.77-8.51 P2R (15) 100 6.84 0.54 0 .054 5.58-8.83 6.82 L (25) 101 6.79 0.45 0 .045 5.80-8.35 M1R (16) 107 10.25 0.57 0.055 7.81-12.12 10.23 L (26) 109 10.21 0.58 0.056 7.70-12.05

Mandible I~R (41) 110 5.54 0.39 0 .037 4.48-6.89 5.54 L (31) 106 5.55 0.45 0 .044 4.74-8.82 I2R (42) 107 6.09 0.52 0 .050 5.00-9.97 6.07 L (32) 105 6.05 0.40 0 .039 5.21-7.12 C R (43) 106 6.61 0.45 0 .044 5.43-8.86 6.67 L (33) 107 6.70 0.44 0 .043 5.84-7.97 P1R (44) 98 7.03 0.39 0 .039 6.02-8.10 7.03 L (34") 104 7.03 0.42 0.041 5.64-8.76 P2R (45) 101 7.16 0.48 0 .048 6.06-8.75 7.20 L (35) 99 7.23 0.56 0 .056 6.22-9.98 MIR (46) 97 10.84 0.66 0.067 9.19-12.59 10.87 L (36) 101 10.90 0.69 0.069 / 9.44-12.93

Values in parentheses denote the FDI tooth notation system.

premolars were wider than the upper second premo- lars, averaging 0.20 mm wider, or 2.9%. In contrast, the lower second premolars were wider than the first premolars (0.13 mm, or 1.8%). In the mand- ible, the lateral incisors were wider than the central incisors, by an average of 0.63 mm (10.0%) in males and 0.53 rnm (8.7%) in females.

In considering the extent and pattern of sexual dimorphism, males had larger teeth than females. Statistical analysis (independent t-test) showed that all teeth in males, with the exception of the lower central incisors, have significantly greater mesiodis- tal dimensions than in females, from p < 0.05 for the incisors to p < 0.001 for the first molars. In ab- solute terms, the largest sexual dimorphism in mesiodistal tooth size was exhibited by the mandib- ular first molar (0.45 mm), with the maxillary and mandibular canines next in order of difference (0.39 and 0.35 mm, respectively). Calculation of percen- tage sexual dimorphism revealed that the mandibu- lar central incisors exhibited the least (1.6%), whilst the upper and lower canines displayed the most (5.2%), more than any other tooth class. The over- all percentage dimorphism was 3.6% on average (Table 3).

The cumulative mesiodistal crown width was cal- culated as the sum of the widths of individual teeth in each arch up to and including the first permanent molars. In males, the cumulative widths of the maxillary and mandibular teeth were 97.2 and 90.1 mm, respectively. The corresponding widths in females were 94.1 and 86.7 mm. These differences in

cumulative width between males and females (3.1 mm in the maxilla and 3.4 mm in the mandible) were statistically significant (p < 0.01).

We found insignificant differences between the right- and left-hand mesiodistal crown diameters in both sexes. Furthermore, the most variable tooth in terms of crown size was the maxillary lateral incisor, while the first molar was the most stable. These results are in agreement with those reported in other population groups (Moorrees et al., 1957; Barrett et al., 1963; G a r n e t al., 1967; Lee and Goose, 1972), but contradicting those of Lundstrum (1948), who found a definite difference between left and right tooth measurements. Harzer (1987) pro- vides evidence that the left-right differences between homologous teeth are smaller than the differences between the teeth of monozygotic twins, suggesting that the side differences can be attributed to en- vironmental influences. According to G a r n e t al. (1979), intra-individual variations in crown size and similarities between isomeres and antimeres might well be derived from specific intrauterine events during odontogenesis and less from genetic effects.

Our results on sexual dimorphism show that the mesiodistal crown diameters of these males are sig- nificantly greater than those of these females. Canines were the most sexually dimorphic teeth in the arch, with a percentage difference of 5.2% (Table 3). Similar findings, but of varying magni- tudes, have been reported for other ethnic groups. Among different population groups, the percentage dimorphism in canine size indicates that males

644 F.N. Hattab et al.

Table 3. The mean mesiodistal diameters (left + right/2, in mm) of maxillary and mandibular permanent dentition in Jordanians with other populations

Tooth Jordanians Iraqis Yemenites Caucasians (Jewish)

Male Female Male Female Male Female Male Female

Maxi l la I1 8.94 8.63 (3.6) 8.99 8.81 8.49 8.44 8.78 8.40 12 6.93 6.70 (3.4) 6.91 6.87 6.44 6.37 6.64 6.47 C 8.01 7.62 (5.1) 8.04 7.81 7.43 7.43 7.95 7.53 P~ 7.20 7.03 (2.4) 7.18 7.07 6.82 6.71 7.01 6.85 P2 7.00 6.82 (2.6) 6.92 6.90 6.52 6.52 6.82 6.62 Ml 10.56 10.23 (3.1) 10.65 10.58 10.32 10.32 10.81 10.52 Mandible Ii 5.63 5.54 (1.6) 5.60 5.66 5.31 5.25 5.42 5.25 12 6.26 6.07 (3.1) 6.20 6.20 5.69 5.66 5.95 5.78 C 7.02 6.67 (5.2) 7.01 6.80 6.49 6.32 6.96 6.47 P1 7.37 7.03 (4.8) 7.15 7.06 6.73 6.71 7.07 6.87 P2 7.46 7.20 (3.6) 7.37 7.26 7.06 6.97 7.29 7.02 MI 11.32 10.87 (4.7) 11.27 11.06 10.74 10.68 11.18 10.74

exceed females by from 3 to 9% (Kieser, 1990). Garne t al. (1967) proposed a hypothesis of a canine field of sexual dimorphism, suggested that the greater the canine dimorphism the greater the sexual dimorphism of adjacent teeth. No such relation could be obtained from our data or those reported by others (Bailit et al., 1968; Kieser e t al. , 1985). Comparison of sexual dimorphism between Jordanians and other populations (Table 3) revealed that the overall percentage sexual dimorphism of the present sample was considerably higher than that of Iraqis and Yemenite-Jews (3.6 versus 1.2 and 0.8%, respectively), but lower than that of Caucasians (3.9%). These findings confirm those of Haeussler e t al. (1989), who found noticeable inter- population differences in sexual dimorphism. There was concordance in the sexual dimorphism ranking of first molars among Jordanians, Iraqis and Caucasians, with the maxillary molar ranked ninth to tenth and the mandibular molar ranked fourth in the three populations.

Table 3 presents the absolute mean of the mesio- distal crown diameters of Jordanians as compared with those of Iraqis (Ghose and Baghdady, 1979), Yemenite-Jews (Koyoumdjisky-Kaye et al. , 1976) and Caucasians (Moorrees e t al. , 1957). The mean mesiodistal diameter for the Jordanian males was 7.80 mm, for the Iraqis 7.78 mm, for Yemenites 7.34 mm and for Caucasians 7.66 mm. The pattern and magnitude of crown diameters in Jordanian males were generally similar to those in Iraqi males. The only significant difference obtained was between the lower first premolars (t = 2.82, p < 0.001), with the Jordanian teeth having a larger crown size than those of the Iraqis, Another interesting contrast was that the first molar was the most dimensionally stable tooth in Jordanians, whereas in Iraqis it was the least stable (Ghose and Baghdady, 1979). The mean mesiodistal diameters for Jordanian males were significantly larger than for Yemenite males

(p < 0.001). With the exception of canines, the Jordanian males had significantly larger teeth than those of Caucasians, ranging from p < 0.05 to p < 0.001. Interestingly, the maxillary first molar in Jordanian males was the only tooth that had a smaller crown size than in the other populations (Table 3). In contrast to the males, Jordanian females had an average crown size of 7.53 mm, which was consistently smaller than for Iraqi females (7.68 mm), but larger than for Yemenites (7.28 mm) and for Caucasians (7.38). With the exception of the premolars, the mean mesiodistal crown diameters of Jordanian females were signifi- cantly smaller than those of Iraqi females at levels ranging from p < 0.05 to p < 0.001. As was the case for males, the mesiodistal diameters for Jordanian females were significantly larger than for Yemenite (p < 0.001) and Caucasian females (p < 0.05 to p < 0.001), with the exception of the maxillary canine, in which the difference did not reach statistical significance, and the maxillary first molar, which had a smaller crown size in females. Reviewing the literature of different population groups revealed that the teeth of Jordanians were 1.6% larger than those of a Chinese population (Lee and Goose, 1972). On the other hand, the tooth size of Jordanians was 4.9% (0.40 mm) and 5.0% (0.41 mm) less than that of Australian abori- gines (Barrett et al. , 1963) and African Negroes (Kieser et al. , 1990), respectively. The last two eth- nic groups are thought to have the largest teeth in various contemporary populations.

The findings of the present study suggest that some definite dimorphism in mesiodistal crown size exists between similar racial groups living in differ- ent geographic areas, as indicated by the compari- son between Jordanians and Iraqis. This raises the question of the effects of environmental factors on tooth size. Our findings may also provide useful in- formation for comparative studies of tooth size.

Tooth-crown diameter in Jordanians 645

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