BaburAshraf Quraishi1 , Syed Sheeraz Hussain2 , Arif-ur- Rehman Alvi3
How to CITE:
Quraishi BA,Hussain SS,AlviAR. Comparison of arch width dimensions among Class-I and Class-II division 1malocclusion groups. J PakDentAssoc. 2012;21(03): 145 – 152
The aimof this study is to
1) compare the arch width dimensions in adultswith Class I occlusion to those with Class II Division 1 malocclusion.
2) Compare and calculate difference between maxillary and mandibular archwidth in both groups.
3)Correlate archwidth dimensions for sexual dimorphismwithin the group & between groups.
This was a cross- sectional study conducted atAlvi Dental Hospital & Fatima Jinnah Dental College. A total of 100 Class I subjects (43 males and 57 females) and 85 Class II division 1 (43 males and 42 females) patients, from 13- 24 years of age were included. The inclusion criteria was,(i) having all permanent teeth erupted from 1st molar to 1st molar,(ii) no history of previous orthodontic treatment. Patients with syndromes or grossly carious teeth and posterior cross- biteswere excluded. Intermolar, iniercanine, interalveolar width and arch lengthweremeasured in both arches. Students t- test was used to compare groups.
Meanmaxillary intermolar, intercanine&interalveolarwidth for Class I groupwas 51.6mm, 34.2mm and 59.5mmand forClass II division 1 itwas 49.2mm, 32.5mmand 57.2mm, respectively.Males of both the groupsexhibited larger arch width dimensions than the females indicating significant gender dimorphism. Mean intermolarwidth differencewas 1.2mmforClass I and -1.0 forClass II group
Maxillary dental arch is narrower in Pakistani adults with Class II Division 1 malocclusion, as intermolar, intercanine and interalveolar dimensionswere significantly smaller thanClass I sample (p=.000).Males of both the groups had larger archwidth dimensions than the females.Archwidth difference was negative for Class II group indicating posterior crossbite tendency.
archwidth,Class I,Class II division 1, archwidth difference, sexual dimorphism.
The stability of treatment results is very important for both the patient and the clinician. One of the most debated subjects in orthodontics has been the stability of dental arch dimensions after treatment. The causes of dental relapse remain unknown and it appears to be multi-factorial along with continued growth . Growth of arch width occurs till early teens and this is the period during which most patients seek orthodontic treatment. Therefore, understanding of these changeswill help in the formulation of treatment and retention plans. Modern orthodontics offers variety of treatment options for correction of transverse discrepancies of the dental arches A general perception is that maxillary arch width is narrow inClass II patients. Frohlic studied dental casts of untreated individualswithClass IIDiv 1 andClass IIDiv 2 malocclusions, from deciduous to permanent dentition. He found that arch width data of his study did not differ from the Class I data published by Moorrees . Staley observed the arch width dimensions of a Class II sample and compared to a sample of normal occlusion. He also found that the maxillary dental arch is constricted in a Class II sample. Buschang , compared arch widths of adult females and found the longest and narrowest maxillary arches in Class IIDivision 1 sample. Bishara et al evaluated a longitudinal sample and concluded thatafter eruption of the second permanent molar, one should expect little or no change in arch dimensions. Staley , Tollaro , Sayin and Lux subtracted the mandibular intermolar width from the maxillary intermolar width to obtain the transverse discrepancy. This difference turned out to be a simple parameter for assessing the extent and severity of transverse discrepancy. The aim of this study was to evaluate arch width difference in an adult malocclusion group comprising of Class II division 1 patient from a corresponding sample of adults having normal occlusion.
As no ethical committee board existedwhen the study was initiated so no ethical approval could be obtained.The subjects used in this study were patients with Class II division 1 malocclusion visiting Alvi Dental Hospital & Fatima Jinnah Dental College&Hospital, for orthodontic treatment. Class I normal occlusion sample was collected from students of three secondary schools and two dental colleges, willing to participate by signing the consent form. A total of 185 subjects were selected on basis of Angle’s molar classification and no attempt was made to select the subjects on basis of skeletal jaw relationship. Orthodontic records included clinical examination, maxillary and mandibular casts trimmed in centric occlusion. The criteria for inclusion were Pakistani adults with no history of previous orthodontic treatment. None of the subjects had missing or extracted teeth, tooth anomalies, grossly carious or restored teeth or craniofacial syndromes. Fully erupted permanent incisors, canines, premolars and first molars in both maxillary and mandibular arches were present. A strict selection criterionwas applied for both the groups as given below.
Class I Group:
100 adults (43 males & 57 females) with Class I occlusionwere selected. The criteria for inclusionwere:
Class Imolar relationship.
1-Well- aligned dental arches; if spacing or crowdingwas present itwas less than2mm.
2-No anterior or posterior cross bite.
Class IIDivision 1Group:
85 adults (43 males & 42 females), with Class II Division 1 Malocclusion were selected. The criteria for inclusion were:
1- Bilateral Class II molar relationship (full step molar relationship only).
2- Proclinedmaxillary incisors.
3-Less than3mmof crowding or spacing in either arch.
4-No anterior or posterior cross bite.
Arch width dimensions are fully developed by 13 years in girls and by 15 years in boys as indicated by previous growth studies . Based on these findings, the age for the samplewas selected, assuming that nomore growthwas expected. Themean age ofClass I samplewas 20 years and 18 years forClass IIDivision 1 sample (Table No 1). To minimize examiner bias all 185 casts were measured in a random order, irrespective of the type of occlusion. The measurements on the dental casts were performed using sharpened digital Vernier Calipers (SontaxCo., Japan) to the nearest 0.01mm.
Six transverse and two sagittal measurements as stated in earlier studies were performed on the maxillary andmandibular casts. Themeasurements are as follows (Fig 1, 2): Maxillary & Mandibular intercanine width: The maximum linear distance between the cusp tips of canines. Maxillary intermolar width: The maximum linear distance between the mesiobuccal cusp tips of molars or the center of the cusp tipwear facets in cases of attrition. Mandibular intermolar width: The maximum distance between themost gingival extensions of the buccal groove on themolars. Maxillary & Mandibular interalveolar width: The maximum distance at the mucogingival junction above the level of buccal groove of firstmolars. Maxillary & Mandibular arch length: Distance between line connecting the distal surface of first molars and the labial surface of central incisors.
Statistical analysis of the data was performed using SPSSv 16.0 package. Descriptive analysis for data included mean, standard deviation, minimum and maximum ranges of the maxillary and mandibular cast measurements. Independent t- test was used to determine difference between Class II division 1 and the reference sample (p<.05). The independent t- test was also performed to calculate gender dimorphism among both groups (p <.05). Measurement error was evaluated by randomly selecting 30 casts among each group for remeasurement after two weeks interval from the initial measurements. All the measurements were repeated and data entered in SPSS v 16.0. Paired t-test was used to compare the result of the first and second readings. The correlation coefficient between the first and the second readingwas high (Table 2)
When Class I group was compared t Class II Division 1 group the difference was statistically significant (p= .000) indicating a constricted arch in the Class II group (Table 3).Mandibular intermolarwidthwas similar in both groups (Table 4). However,males of Class I and Class II Division 1 had statistically significant larger maxillary and mandibular intermolar dimensions when compared to females of respective groups (p=.000&p=.001) (Table 5).
Class I subjects had larger maxillary intercanine width than Class II Division 1 and the difference was highly significant (p=.000) (Table 3). There was no difference when males were compared between groups, but females of Class II Division 1 had smaller maxillary intercanine width than the females of Class I (Table 6). Mandibular intercanine width for both the groups was found to be similar (Table 4).Males of Class II Division 1 group had larger intercanine width than the females (p=.001) (Table 6).
The difference was statistically significant for maxillary interalveolar width (p=.002) (Table 3). No difference was observed between the mandibular interalveolar widths for both groups (Table 4). Males of both Class I and Class II Div 1 had larger mandibular interalveolar dimensions when compared to females of respective groups (Table 7).
Due to proclined maxillary incisors in Class II Division 1 sample, larger arch length was observed as compared to Class I group (p=.000)(Table 3) and same trend was followed for males and females (Table 8). Mandibular arch length of Class II Div 1 group was slightly larger than Class I group and the difference was statistically significant (p=.01)(Table 4).Males of Class II Division 1 group had larger arch length than females and the difference was statistically significant (p=.02) (Table8).
The arch width difference was calculated by subtracting the mandibular dimension from its corresponding maxillary dimension (Table 9). The mean intermolar difference for Class I group was calculated to be 1.2mm 1.4. TheClass II group had amean difference of -1.0 mm 2.2. The difference between the two groups was highly significant (p=.000). The intercanine widths difference was statistically significant (p=.000). The interalveolar differencewas also statistically significant (P=.001).
Growth of human facial skeleton and associated dental arches is an ongoing process and rapid changes occur during late mixed dentition stage. Once permanent dentition is established the changes are insignificant .The inter molar width is the most commonly measured dimension for arch width studies. The findings of our study indicate that the maxilla is smaller in Class II Division 1 sample and the difference was statistically significant and it is in agreement with findings of Staley , Ahmed and other studies . Mandibular intermolar dimensions were similar for both groups and our results were similar to that of Staley , Buschang , Sayin and Lux Staley suggested that when a Class I cast is handheld in a Class II molar relationship the buccal overjet increases. Therefore in a Class II Division 1 subject,posterior teeth compensate for the anteroposterior jaw discrepancy by palatal movement of maxillary molars to achieve good interdigitation with mandibular molars. The current study also supports the tooth compensation hypothesis that due to narrowmaxilla and anteroposterior jaw discrepancy the posterior crossbite tendency in Class II Division 1 subjects is masked. Bishara reported that posterior crossbite tendency detected from early mixed dentition onwards continues into adolescence and is not self-corrective. Therefore posterior crossbite should be dealt as early as possible.
Most studies have evaluated growth of arches by choosing landmarks only on the teeth. It should be kept in mind that the buccolingual position of teeth changeswhen there is a transverse or anteroposterior jaw discrepancy. Therefore interalveolar dimension is also a good measurement to evaluate length of the bony bases and it helps us understandwhether themolars are tipped towards the buccal or the palatal side. Interalveolar width dimension was significantly larger for Class I sample when compared to Class II Division 1 sample. The literature review shows that interalveolar dimensions were only evaluated by Staley and Sayin . Our findings are in agreementwith Staley indicating narrowmaxillary bony base and it is in contrast to Sayin who indicated that the transverse discrepancy in Class II Division 1 originates from palatally tipped posterior teeth and not narrow bony base. No difference was noted among the groups for mandibular interalveolar dimension, which supports the observation of Staley and Sayin .Although Class II Division 1 sample without any posterior crossbite of even a single tooth was selected but the results indicate a posterior crossbite tendency, which is clinically not visible.
Frohlich compared intercaninewidths of both arches and found no difference between Class II and Class I group. Staley reported that Class I group had larger maxillary intercanine width, but no differences were found for mandibular intercanine width. Bishara compared intercanine widths of Class II Division 1 with Class I group fromdeciduous to permanent dentition stage and found no differences in maxillary and mandibular intercanine widths. Sayin concluded that maxillary intercanine width was larger in Class II Division 1 group as compared to normal occlusion group. Our findings indicate that in normal occlusion group maxillary intercaninewidthwas significantly largerwhen compared to Class II Division 1 subjects, again indicating that Class II sample had a narrower arch.Our finding are in contrast to the findings of Bishara , Sayin and Frohlich but supports the findings of Staley . When the mandibular intercanine width was compared, both the groups had similar dimensions.
Measuring maxillary and mandibular transverse dimensions separately is one side of the coin, unless they are correlated. Staley suggested to calculate the difference between maxillary and mandibular arch width dimensions to evaluate the extent of crossbite present, which might have been masked by anteroposterior jaw discrepancy or dental compensation. He reported that intermolar and interalveolarwidth differenceswere larger in Class I group when compared to Class II Division 1.
Tollaro divided the Class II Division 1 group into one with posterior transverse discrepancy and one without posterior transverse discrepancy and compared them with normal occlusion group. They found that the Class II Division 1 group with posterior transverse discrepancy had narrow maxillary arch width when compared to other groups. Lux and co-workers reported that molar differences were due to smaller transverse maxillary skeletal base and a narrow maxillary intermolar dimension, and this trend is observed throughout the observation period. The result of the present study indicates that intermolar width difference was greater in Class I group as evident by positive mean values. In contrast most of Class II Division 1 group exhibited negative value, emphasizing posterior crossbite tendency. With respect to width differences, Staley found that among males the Class I group differed from Class II
Division 1 group by 4.5mm in males and by 3.6mm for females. Lux using different landmarks to study intermolar difference than those used in this study, found that molar difference were 2.5 mm for boys and 1.5 mm for girls of Class II Division 1 group. Our findings are in agreementwith Sayin , Staley andTollaroindicates that intermolar width difference was greater in Class I group as evident by ositive mean values. In contrast most of Class II Division 1 group exhibited negative value, emphasizing posterior crossbite tendency. With respect to width differences, Staley found that among males the Class I group differed from Class II Division 1 group by 4.5mm in males and by 3.6mm for females. Lux using different landmarks to study intermolar difference than those used in this study, found that molar difference were 2.5 mm for boys and 1.5 mm for girls of Class II Division 1 group. Our findings are in agreementwith Sayin , Staley andTollaro. This trendwas also observedwhen Class I intercanine width difference was compared to Class II Division 1 intercanine width difference. Class II Division 1 had smaller canine difference indicating narrow maxillary arch in the anterior region too. Class IIDivision 1 also had a smaller interalveolar difference than Class I group and the findings are in agreementwithStaley and Sayin Sexual dimorphism existed in most of the variables that were analyzed. Staley , Buschang Moyers and Lux , previously reported similar findings. Both maxillary and mandibular dimensions were larger in males as compared to females. Class I and Class II Division 1 males had larger intermolar, intercanine and interalveolar width than females of corresponding group. Mean overjetwas large due to selection criteria forClass II group.
When our findings were compared with the previous study by Ahmed in our population, there was partial agreement in results because of two reasons. Firstly different landmarks were selected and secondly they combined the Class II div 1and Class II div 2 together because of which no difference in Class I and Class II groupwas found in their study.The present study confirms that a direct relationship exists between anteroposterior and transverse dimensions of the jaws as seen in Class II Division 1 cases compared to normal occlusion group. Lux et al emphasized that due to individual variations, the findings present tendencies and not growth laws. The clinician should realize the relationship between sagittal and transverse dimensions and pay close attention to this relationship in diagnosis and treatment planning.The arch width difference is a simple, easy and effective way of diagnosing crossbites even if they are not present visually and should be performed by the clinicians on a regular basis.
Intermolar, intercanine and interalveolar dimensions were greater in Class I sample when compared to Class II division 1 sample. Mandibular arch width dimensions were similar for both groups. Class I and Class II Division 1 males had larger maxillary and mandibular intermolar, intercanine and interalveolar width dimensions when compared to females of corresponding groups. When archwidth differenceswere calculated,Class II Division 1 had smaller values as compared to Class I group, indicating a narrow maxillary arch without any visible crossbite.
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