Nazir Ahmed*, Mubassar Fida**
Assistant Professor, Department of Orthodontics, Sardar Begum Dental College & Hospital, Gandhara University Peshawar.
Program Director,Orthodontics, The Aga Khan University Hospital, Karachi.
Correspondence: “Dr.Nazir Ahmed” email@example.com
How to CITE:
J Pak Dent Assoc 2010;19(2):94-98
The aim of this study was to compare the dimensions of dental arches among the three malocclusion groups and see the gender dimorphism in these dimensions.
This was a cross sectional study conducted at dental clinics, the Aga Khan University Hospital, Karachi. A total of 110 patients belonging to different malocclusion groups were evaluated. Our inclusion criteria were 1) Presence of all permanent teeth from first permanent molar to first permanent molar 2) No previous orthodontic treatment and 3) Age range of 13-30 years. All patients suffering from some developmental anomalies and/or syndromes were excluded.
The mean maxillary intermolar, inter 1st premolar, inter 2nd premolar and intercanine widths and arch depth were 49.96mm, 40.13mm, 44.84mm, 34.02mm and 39.41mm respectively for the entire sample. The mean mandibular intercanine, inter 1st premolar, inter 2nd premolar and intermolar widths and arch depths were 26.90mm, 33.40mm, 38.72mm, 43.49mm and 33.72mm respectively for the whole group. Significant differences were found in maxillary inter-premolars and inter-molar widths among the three groups. A comparison between the two genders showed significant differences in mandibular intercanine and intermolar widths among the three groups.
Significant differences were found in maxillary intermolar and interpremolar widths among the three malocclusion groups. Class III group had the largest maxillary intermolar and interpremolar widths followed by Class I group. Male subjects had significantly larger maxillary and mandibular intermolar widths and mandibular intercanine widths than females.
Arch dimensions, Malocclusion groups, Gender dimorphism.
The dimensions of dental arches including arch lengths, widths and depths have considerable implications in orthodontic diagnosis and treatment planning, affecting the space available, dental esthetics, and stability of the dentition1. Information regarding arch dimensions in human populations is important to clinicians in orthodontics, prosthodontics, and oral surgery. It is also of interest to anthropologists and other students of human oral biology2. A survey of arch size could help the clinician in choosing correct size and shape stock impression trays for prosthodontic treatment. In addition the sizes of artificial teeth and the overall form of the artificial dental arch at the wax trial stage are amenable to modification by the dental surgeon in orthodontic treatment3. When upper and lower jaws have complementary dimensions of both arches and tooth structure, a potentially harmonious occlusion may exist4. The growth changes of arch widths in normal occlusion subjects and a comparison of arch widths in normal occlusion and individual malocclusion samples have been studied extensively5-8. Changes in arch dimensions and their possible correlation with age, sex, orthodontic treatment and extractions of permanent teeth have also been investigated9-12. Also many investigators have studied an association of crowding and mesiodistal crown dimensions with dental arch dimensions13,14. However only few studies have compared the arch dimensions among the three malocclusion groups. The aim of this study was to compare the dimensions of dental arches among the three malocclusion groups and to see any gender dimorphism.
A total of 110 patients who belonged to different malocclusion groups (Angle’s Class I=40, Class II=40 and Class III=30) were included in this study. The data were collected from pre-treatment orthodontic casts and files of orthodontic patients at the dental clinics of Aga Khan University Hospital Karachi. The inclusion criteria for subjects were as follows:
1) All permanent teeth from first permanent molar to first permanent molar. (2) No previous orthodontic treatment.
(3) Age range 13-30 years.
Patients with developmental anomalies and/or syndromes were excluded. The arch dimensions which include arch depth, and arch widths between canines, first and second premolars and first molars in both arches were measured for each patient with a vernier caliper (Munchner model, Munich, Germany). These arch dimensions are defined as follows:
- Inter-canine width was measured as horizontal distance between the cusps tips of upper and l o w e r permanent canines.
- The first and second premolars widths were measured as horizontal distances between the buccal cusps tips of corresponding teeth in upper and lower arches.
- The inter-molar widths were measured as horizontal distances between the mesiobuccal cusp tips of upper and lower first permanent molars.
- The arch depth was measured as a perpendicular distance in the midsagittal plane from the most labial midpoint between the central incisors to a line connecting the distal surfaces of first permanent molars.
The means, standard deviations and ranges of arch dimensions of the each malocclusion group were measured individually and then compared with each other to see any difference among them. One-way ANOVA was used to compare the arch dimensions among the three malocclusion groups. Independent sample t-test was used when two of the three malocclusion groups were compared in varying combinations. To see gender dimorphism in the entire sample and in individual malocclusion group, independent sample t-test was used.
Method error was determined by randomly selecting 15 pairs of dental casts and recording the same measurement by the same operator two weeks after the first measurements. A paired sample t-test was applied to the measurements. No significant difference was found between the first and second measurements
The mean age for the entire sample was 17.4 years. Regarding gender distribution in different malocclusion groups, Class I group comprised of 19 males and 21 females, Class II group had 18 males and 22 females while Class III group had 16 males and 14 females. Significant differences were found in maxillary interpremolar and intermolar widths among the three malocclusion groups as shown in Table I
A comparison between individual malocclusion groups showed that Class I subjects had significantly larger maxillary interpremolar (First and Second premolar) widths than Class II subjects, while the intermolar width differences between these two groups narrowly escaped statistical significance (p=0.058) as shown in Table II
Class III malocclusions showed significantly larger maxillary interpremolars and intermolar widths when compared with Class II group (Table III). A comparison between Class I and Class III groups showed significant differences in maxillary intermolar widths and arch depths, with Class III subjects having larger intermolar widths than Class I subjects. However the mean maxillary arch depth was found to be larger in Class I than in Class III group as shown in Table IV
A comparison between males and females in the entire group showed significant differences in mandibular intercanine and intermolar widths among the three groups, with male subjects having larger arch widths than females as shown in Table V.
A comparison between the two genders in individual malocclusion groups showed no significant difference in arch dimensions between males and females in Class I group (Table VI). In Class II group, however, significant differences were found between the two genders in maxillary and mandibular intermolar widths (Table VI), with males having larger values than females in both arches. In Class III group, the difference between male
And female subjects was significant in mandibular intercanine and intermolar widths (Table VI) with males having larger widths than females.
This study compared the maxillary and mandibular arch dimensions among the three malocclusion groups. Investigators15,16 who studied transverse dental arch changes reported that molar and canine arch widths were mostly stabilized after 13 years of age with very little or no changes thereafter. Therefore the minimum age of the subjects included in this study was chosen on the basis of these previous studies and we assumed that the arch widths of the subjects studied were fully developed.
A significant difference was found in maxillary intermolar and interpremolar widths among the three groups. Class II subjects had the smallest mean intermolar and interpremolar widths followed by Class I subjects, while the largest values of maxillary arch widths were noted for Class III subjects. This can be interpreted that Class II malocclusion subject had the narrowest maxilla as compared to other malocclusion groups. Similar results were reported by Al-Khateeb and Abu-Alhaija17, Staley et al18, Lux et al19 and Sayin and Turkkahraman5. However some studies have reported results in contrast to our study like study by Frohlich20 who found no difference in inter-molar widths among the malocclusion groups he studied.
A comparison between individual groups showed no significant difference in maxillary intermolar widths between Class I and Class II subjects. Similar results were found by Bishara et al21 who compared normal occlusion with Class II group and found no difference in intermolar widths between the two groups. Walkow and Peck7 also found the same results, when they compared transverse arch dimensions between normal occlusion and Class II Division 2 subjects. However Sayin and Turkkahraman5 and Staley et al18 have reported a significant difference in intermolar widths between Class I and Class II malocclusions.
However most of the above studies showing significant differences in intermolar widths between these two malocclusion groups have compared only Class II Division 1 subjects with normal occlusion groups. In our study the two subdivisions of Class II malocclusion were combined into a single group which can be a reason for no significant difference in intermolar widths between the two groups.
A comparison of maxillary intermolar width between Class I and Class III and between Class II and Class III group showed a significant difference between these groups. Class III subjects had the largest maxillary intermolar widths followed by Class I subjects. Same result was reported by Braun et al3 who found that Class III maxillary dental arch widths are greater than the arch widths of Class I subjects. However Uysal et al22 found a statistically significant difference in maxillary intermolar widths between Class III malocclusion and normal occlusion groups, with the smaller maxillary intermolar width in Class III subjects than normal occlusion group. These larger molar widths in Class III subjects can be attributed to dental compensation in maxillary arch for wider mandibular arch which is commonly found in Class III subjects. But still further studies are needed to compare the dental arch dimensions of Class III malocclusion with other groups as very little studies were found in literature on this group.
A comparison of mandibular arch dimensions among the three malocclusion groups did not show any significant difference among these groups. Comparisons between individual groups i.e. between Class I and Class II, Class I and Class III and Class II and Class III, were also done but no significant differences were found. Similar results were found by Frohlich20, Bishara et al21, Tollaro et al23 and Sayin and Turkkahraman5. However some other studies have shown results in contrast to our studies.
Al-Khateeb and Abu-Alhaija17 reported wider mandibular arches in Class III individuals than Class II subjects especially in the posterior part of dental arches. Similarly studies by Lux et al19 and Buschang et al6 also reported wider mandibular arches in Class I subjects when compared with Class II group. Uysal et al8 found that subjects with Class II Division 2 malocclusion had significantly larger mandibular intermolar and intercanine widths as compared to normal occlusion group. Usyal et al22 in an another study compared arch dimensions of Class III subjects with normal occlusion group and concluded that Class III subjects had wider mandibular arches than normal occlusion group. These differences in the results can be due to small sample size in our study and sample selection criteria, as in our study, subjects were allocated into various malocclusion groups purely on Angle’s dental classification rather than skeletal classification.
To see any gender dimorphism, a comparison was done between males and females in the entire sample. No significant difference was found in the maxillary arch dimensions between the two genders. However in the mandible, a statistically significant difference was found in the intermolar and intercanine widths among the three groups, with male subjects having larger intercanine and intermolar widths than females. The difference was found to be highly significant (p<0.001) in molar region. This is in agreement with other studies by Tavas24, Younes2 and Diwan and Elahi25 but in disagreement with the findings of Al-Khateeb and Abu-Alhaija17 and Sarhan and Diwan26. When considered in individual malocclusion groups, Class I group showed no gender dimorphism in maxillary and mandibular arch dimensions.
In Class II group significant difference was found between males and females in maxillary and mandibular intermolar widths; in both cases males having larger widths than females. In Class III group, a statistically significant difference was found between the two genders in mandibular intercanine and intermolar widths; in both cases males having larger arch widths than females.
Huth et al27 found a significant gender dimorphism in all maxillary arch transverse dimensions in normal occlusion and Class II (Division 1 and 2) subjects while in the mandible gender differences were found for inter-molar widths only. Males were found to have larger measurement than females in all groups. Thus a part of their study is in agreement with our study
The findings of the present study indicated that:
Significant differences were found in maxillary intermolar and interpremolar widths among the three malocclusion groups. Class III group had the largest maxillary intermolar and interpremolar widths followed by Class I group while Class II group had minimum transverse maxillary arch widths. The differences in maxillary intercanine widths and arch depth among the three malocclusion groups were not statistically significant. No significant differences were found in mandibular arch dimensions among three malocclusion groups. Males had significantly larger mandibular intercanine and intermolar widths than females in the entire sample. Maxillary intermolar widths were significantly larger in male subjects than females in Class II group
The authors would like to thank University Research Council (URC) of the Aga Khan University Karachi, for approving the grant for this research project and Dr Farhan Raza Khan, Senior Instructor in Operative Dentistry, the Aga Khan University Hospital Karachi, for his statistical help
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