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Original Article MESIODISTAL CROWN DIMENSIONS OF THE PERMANENT DENTITION IN DIFFERENT MALOCCLUSIONS IN SAUDI POPULATION: AN AID IN SEX DETERMINATION 1 IBAD ULLAH KUNDI ABSTRACT The objective of this study was to compare the mesio-distal tooth sizes in Saudi boys and girls among different malocclusions and to determine whether there is any gender dimorphism present. The dental casts of 120 subjects (60 boys, 60 girls) between 12 and 16 years of age, with Class I, Class II div 1, Class II div 2 and Class III malocclusions were used. Each group consisted of 30 subjects. An electronic digital caliper was used to measure the mesio-distal tooth sizes of the upper and lower permanent teeth (first molar to first molar). Almost all the teeth mesio distal widths has statistically significant difference between the malocclusion groups except maxillary right and left first molars and mandibular right lateral incisor. Male female comparisons indicate the presence of sexual dimorphism except in the maxillary and mandibular central and lateral incisors. The mesio-distal sizes of upper right and left second premolars, upper left canine and first molar were significantly larger in the boys than in the girls. In the lower arch the mesio-distal widths of right and left canines and right first molar were significantly larger in the boys than in the girls. Statistically highly significant sexual dimorphism shown by mandibular canines could be used as adjuncts for the determination of gender in individuals, as well as in groups, such as in mass disasters and archaeological sites. Key Words: Mesiodistal tooth width, Malocclusion groups, Orthodontic patients, Sexual dimorphism. INTRODUCTION Mesiodistal tooth size measurement is an important step in the diagnostic process, especially in management of complex cases.1 The most common forms of malocclusion which are crowding and spacing are due to the discrepancies of the size of the teeth and the size of the bony bases.2,3 Failure to compensate for these discrepancies during treatment generally results in unsatisfactory alignment and occlusion of the teeth at the end of orthodontic treatment. Crowded dental arches are associated with the large teeth relative to the size of the jaws and small teeth are associated with the spaced dental arches, both conditions can be localised to a few teeth or affect all teeth.2 Teeth size variations can be caused by multiple factors such as heredity3, race4, gender5, environment6 and secular changes.7 The genetic basis for this variation is best explained by a polygenic model of inheritance by Lundstrom.8 He compared 97 pairs of Correspondence: Dr Ibadullah Kundi, BDS, FCPS, M Orth RCS Ed, Assistant Professor Orthodontic, Aljouf College of Dentistry, Aljouf University, Sakaka Aljouf Saudi Arabia Phone: 00923339172381, 00966542048412 E-mail: [email protected] Received for Publication: July 6, 2015 Approved: July 16, 2015 like-sex monozygotic and dizygotic twins and found a stronger correlation in mesiodistal tooth size between monozygotic twins. He concluded that tooth size with in a given population is determined to a large extent by genetic factors. Keene9 reported racial differences in tooth sizes among the American Negroes and their Caucasian counter parts in caries-free naval recruits. Before we can know if a tooth is under or oversize it is necessary to have data on tooth sizes for the relevant ethnic, gender and malocclusion group.3,10,11 These data are important for orthodontic clinical diagnosis and treatment planning and may be useful in forensic dentistry12 and as records marking technological advances, environmental variations and dietary improvements affecting tooth size.10 In order to improve the quality of dental care available, there is a great need for data on the mesiodistal crown dimensions of the individual permanent teeth of Saudi population. The main purpose of the study was to assess whether the diagnostic criteria derived from the mesiodistal crown dimensions of permanent dentition of other populations can be used interchangeably in Saudi population. The objectives of the present study were to compare the mesio-distal tooth sizes among different malocclusion groups and to see the gender dimorphism of tooth sizes in different malocclusion groups. Pakistan Oral & Dental Journal Vol 35, No. 3 (September 2015) 429 Mesiodistal crown dimensions METHODOLOGY In this cross sectional study, mesio-distal tooth sizes were measured on the dental casts of 120 Saudi adults (60 boys, 60 girls) . The adults who were between 13 and 22 years of age had Class I (N = 30), Class II div 1 (N = 30), Class II div 2 (N = 30) and Class III (N = 30) malocclusions. Pretreatment orthodontic casts were used to obtain the data for this study. Subjects were included if all permanent teeth, except the third molars, were present and there was no history of previous orthodontic treatment. Subjects were excluded if a dental cast had an impression and/or casting artefact affecting the crowns of the teeth, Clinically evident interproximal dental caries, an alteration in the number or shape of the teeth that might affect the diameter of the dental arch, any oral habit that might influence the dental arch, experience of orthodontic treatment prior to the start of examination. Impressions were taken in Alginate impression material (Lygin Chromatic, Dentamerica) and were poured in orthodontic plaster within half an hour to avoid any shrinkage of impressions. Measuring technique: Measurements were made directly on the unsoaped plaster dental casts. All the measurements were done by the author under natural light. An electronic digital vernier caliper (Figure I) specially designed for dental use, (Mitu toyo; Kawasaki, Kanakawa, Japan) with sharpened points was used to measure the mesiodistal tooth width. The procedure for measuring the mesiodistal tooth width was performed as described by Hunter and Priest.13 The caliper beaks were inserted from the facial aspect of the teeth and held perpendicular to the long axis of the tooth. The beaks were then closed until gentle contact with the predetermined contact points of the tooth was made. The measurements included the mesiodistal width of all the twelve maxillary and mandibular teeth from the right first permanent molar to the left first permanent molar. STATISTICAL ANALYSIS Statistical analysis was performed using computer software Statistical Package for Social Sciences (SPSS) version 18. An analysis of variance (ANOVA) was used to determine whether statistically significant differences existed between malocclusion groups and the post hoc Scheffe test was used to determine which groups were different from each other. Student’s t-test was used to investigate gender differences in the samples. The significance level was set at p < 0.05 for all statistical tests. cant difference between the malocclusion groups except mandibular right and left first molars and mandibular right lateral incisor. The upper lateral incisors in the Class II div 1 group were significantly smaller than the upper lateral incisors in the Class I malocclusion group. Both upper and lower canines were significantly larger in the Class I group than the corresponding canines in the Class II div 1 group. Maxillary second premolars were significantly larger in Class 1 group than Class II div 1 group which were again significantly smaller than Class III group. (Table 1) In the mandibular arch canines were significantly larger in Class 1 malocclusion than Class II div 1 malocclusion. Second premolars were significantly larger in Class II div 1 malocclusion than Class I malocclusion. First permanent molars were significantly larger in Class I than Class II div 1 malocclusion and in Class III malocclusion first molars were significantly larger than Class II div 1 malocclusion. (Table 1) To investigate the sexual dimorphism, the malocclusion groups were combined. The data from 60 boys were compared with the data from 60 girls (Table 2). The mesio-distal sizes of upper right and left second premolars, upper left canine and first molar were significantly larger in the boys than in the girls. In the lower arch the mesio-distal widths of right and left canines and right first molar were significantly larger in the boys than in the girls. DISCUSSION One of the basic fundamentals with which the orthodontist has to deal in constructing the denture is tooth size, specifically the mesiodistal width of the teeth.14 It is essential for the clinician to know the size of individual tooth and groups of teeth, to make an adequate diagnosis and treatment plan.15 The Orthodontic examination may be incomplete without a careful analysis of the patterns of mesiodistal crown size relationships. A discrepancy in tooth size may affect the relationship between the upper and lower arches and the excellence of the treatment outcome. We compared the tooth sizes in Saudi population at Aljouf with Class I, Class II Div 1, Class II Div 2 and Class III malocclusions and in the boys and girls. The early permanent dentition provides the best time for tooth size measurements because there is RESULTS The results are given in Tables 1 and 2. Almost all the teeth mesio distal widths has statistically signifiPakistan Oral & Dental Journal Vol 35, No. 3 (September 2015) Fig 1: Electronic digital vernier caliper (Mitu-toyo; Kawasaki, Kanakawa, Japan) 430 Mesiodistal crown dimensions TABLE 1: COMPARISONS OF THE MESIO-DISTAL TOOTH WIDTHS (MM) IN THE MALOCCLUSION GROUPS Arch Tooth Upper 1 R L 2 R L 3 R L 4 R L 5 R L 6 R L 1 R L 2 R L 3 R L 4 R L 5 R L 6 R L Lower Class I Mean ± SD 9.53 ±0.77 a 9.51±0.73 a 7.81± 0.84 a 7.78 ± 0.85 a 8.58 ±0.72 a 8.58 ± 0.73 a 7.87 ± 0.70 a 7.85 ± 0.72 a 7.98 ± 0.64 a 7.98 ± 0.61 a 7.42 ± 0 .73 7.37 ± 0.60 6.06 ± 0.76 a 6.00 ± 0.55 6.85 ± 0.65 6.85 ± 0.65 7.72 ± 0.62 a 7.73 ± 0.64 a 7.98 ± 0.64 a 7.98 ± 0.60 a 7.42 ± 0.73 7.37 ± 0.60 a 11.73 ± 0.67 a 11.73 ± 0.67 a Class II div 1 Mean ± SD 9.03±0.67 9.00±0.64 a 7.00±0.64a 7.09±0.62 a1 7.98±0.44 a 7.92±0.53 a 7.32±0.56 a 7.30±0.61 a1 6.79±0.63 a 6.79±0.64 a 10.33±0.69 10.33±0.69 5.65±0.51 5.65±0.51 6.37±0.52 6.53±0.64 7.21±0.40 a 7.21±0.41 a 7.30±0.59 a1 7.27±0.67 a1 7.27±0.62 7.27±0.63 a1 10.98±0.76 a1 10.98±0.76 a1 Class II div 2 Mean ± SD 9.22±0.58 9.22±0.58 7.30±0.89 7.18±0.81 a1 8.35±0.71 8.35±0.73 7.47±0.66 7.37±0.68 7.02±0.62 7.05±0.65 10.53±0.77 10.55±0.74 5.62±0.43 a 5.62±0.43 6.42±0.51 6.47±0.54 7.42±0.64 7.45±0.65 7.65±0.60 7.62±0.61 7.67±0.58 7.62±0.61 11.43±0.68 11.43±0.68 Class III Mean ± SD 8.83±1.45 a 9.17 ±0.63 7.31±0.81 7.48±0.63 8.28±0.69 8.38±0.56 7.45±0.61 7.39±0.60 a2 7.23±0.64 a2 7.26±0.61 a2 10.42±0.98 10.59±0.69 5.96±0.95 5.72±0.48 6.60±0.56 6.55±0.51 7.54±0.64 7.50±0.65 7.51±0.52 7.58±0.47 a1 7.76±0.62 7.78±0.60 a2 11.51±0.66 a2 11.62±0.55 a2 P 0.03* 0.02* 0.00* 0.00* 0.01* 0.00* 0.00* 0.01* 0.00* 0.00* 0.09 0.07 0.01* 0.03* 0.06 0.00* 0.01* 0.01* 0.00* 0.00* 0.00* 0.00* 0.00* 0.00* The letters indicate groups significantly different from each other (Scheffe test) a1: Significantly different from group 1 a2: Significantly different from group 2 * : Significant values P > 0.05 TABLE 2: GENDER COMPARISON OF THE MESIO-DISTAL TOOTH WIDTHS (mm) Upper Lower Tooth 11 12 13 14 15 16 41 42 43 44 45 46 Male 9.150 7.360 8.393 7.550 7.232 10.633 5.726 6.650 7.667 7.675 7.775 11.567 Female 9.158 7.319 8.110 7.498 6.992 10.427 5.770 6.467 7.278 7.545 7.555 11.317 P 0.962 0.975 0.035* 0.671 0.058* 0.173 0.770 0.089 0.000* 0.176 0.066 0.058* Tooth 21 22 23 24 25 26 31 32 33 34 35 36 Male 9.300 7.418 8.437 7.475 7.247 10.707 5.842 6.658 7.667 7.692 7.775 11.525 Female 9.150 7.347 8.182 7.478 6.992 10.443 5.842 6.542 7.285 7.533 7.580 11.308 P 0.222 0.616 0.040* 0.979 0.033* 0.050* 0.638 0.294 0.001* 0.263 0.101 0.109 * : Indicates Significant difference P > 0.05 Pakistan Oral & Dental Journal Vol 35, No. 3 (September 2015) 431 Mesiodistal crown dimensions generally less attrition and fewer teeth have been extracted.16 It is also more convenient and accurate to measure the mesiodistal widths of teeth on study casts than intra-orally.17 Dunn and Dobzhansky15 have indicated that although all human beings belong to a single species, humans inhabiting different parts of the world and different malocclusions are exposed to different environments and are not alike. Ajayi et al found some variations in tooth sizes between gender and among different racial and ethnic groups.18 In the mandibular arch, the mean mesiodistal crown dimension of the central incisor was smaller than the lateral incisor as reported in other studies.15,19 However, these results do not agree with the findings of Moss whose approach could have been influenced by a small sample size and the fact that they used extracted teeth which were less in number than the complete set of teeth available from each individual.15 The boys in our study had larger teeth than girls. This gender difference is supported by previously published studies on the sizes of teeth in different populations.3,15,20-23 This is in contrast with the previous findings on Bangladeshi population where there was no significant difference between males and females.24 Various theories have been given in the literature for this sexual dimorphism According to Moss, it is because of the greater thickness of enamel in males due to the long period of amelogenesis as compared to females. However, in females the completion of calcification of the crown occurs earlier in both deciduous and permanent dentition as quoted by de Vito.25 Sex chromosomes are also known to cause different effects on tooth size. The 'Y' chromosome influences the timing and rate of body development, thus producing slower male maturation, and acts additively and to a greater extent than the 'X' chromosome.25 According to Pratibha et al25, ‘Y’ chromosome has a direct effect on tooth size, which may be related to a more non-specific effect of hetrerochromatism or cellular activity. Kalia26 quoted that according to Townscend, the difference in size has been attributed to differently balanced hormonal production between the sexes consequent to the differentiation of either male or female gonads during the sixth or seventh week of embryogenesis rather than any direct effect of sex chromosome themselves. According to Lewis et al. there is a low significant correction between sexual dimorphism of teeth and body size and it has been supported by Frayer and Wolpoff.25 Our results showed that sexual dimorphism was observed for maxillary and mandibular canines and maxillary second premolars included in the study be- tween males and females. Highly statistically significant dimorphism was exhibited by only two permanent maxillary anterior teeth, i.e right and left maxillary canines. In this study, result of maxillary canine dimorphism was in accordance with Khangura et al27 who also reported similar findings in their study. Otuyemi and Noar28 showed dimorphism in maxillary canines bilaterally. According to Garn et al22, teeth have behaved in many ways through the course of evolution, ranging from reduction of the entire dentition to reduction of one group of teeth in relation to another. It has been postulated that in the evolution of primates, canines are functionally not masticatory but are related to threat of aggression. A transfer of this aggressive function occurred from the teeth to the fingers in man. Until this transfer was complete, survival was dependent on canines especially in the males. Thus in present day humans the sexual dimorphism in canines is not mere coincidence but based on functional activity.29 Another reason for this dimorphism could be a biologic variation, which is a characteristic of life and is attributed to family, genetics and environmental factors.29 Variation in food resources exploited by different populations has also been explained as one such environmental cause.25 Our results showed statistically highly significant sexual dimorphism for mandibular canine as compared to maxillary canine (Table 2). This corroborates with the findings of Kaushal et al30 and Garn et al22 who also reported statistically significant sexual dimorphism for mandibular canine. However, Minzuno reported that maxillary canine showed a higher degree of sexual dimorphism compared to the mandibular canine in a Japanese population.27 Khangura et al27 quoted various factors for this dimorphism. They suggested variation in food resources exploited by different populations as one such environmental cause. Other authors have suggested that there could be a complex interaction between a variety of genetic and environmental factors that are responsible for dimorphism. A study conducted by Hashim and Murshi on Saudi males and females in the age group of 13-20 years, to determine the teeth in human dentition with the highest likelihood of dimorphism, had found that only the canines in both the jaws exhibited a significant sexual difference, while the other teeth did not.31 CONCLUSION Almost all the teeth mesio distal widths has statistically significant difference between the malocclusion groups. A higher variability was found in the maxillary lateral incisor as compared to other teeth. This tooth should be examined carefully to exclude any major size and shape discrepancy. Pakistan Oral & Dental Journal Vol 35, No. 3 (September 2015) 432 Mesiodistal crown dimensions Our values for mesiodistal crown dimensions for the present population could be used for treatment planning regarding space management, operative dentistry and management of malocclusion for the local population. These conclusions could greatly influence clinical decision making, and further studies should be undertaken in this field. Male female comparisons indicate the presence of sexual dimorphism. Girls have smaller permanent teeth than boys. No significant differences were present between male and female in the mesiodistal crown dimensions of mandibular and maxillary incisors. The results of the present study revealed that mandibular canines showed statistically highly significant sexual dimorphism and could be used as adjuncts for the determination of gender in individuals, as well as in groups, such as in mass disasters and archaeological sites. REFERENCES 1 Santoro M, Ayoub ME, Pardi VA, Cangialosi TJ. Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition of Dominican Americans. Angle Orthod 2000; 0: 303-7. 2 Bermúdez de Castro JM, Nicolas ME. Posterior dental size reduction in hominids: the Atapuerca evidence. 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