| Objectives: The objectives of this experiment was to study the widths of bone and dental arch in class II, division 1 malocclusion, to make sure which position was really narrow in the arch of class II, division 1 malocclusion, to reveal the correlation between vertical facial skeletal types and the widths of class II, division 1 malocclusion, to provide the evidence for treatment design in clinical.Methods: 120 patients with class II, division 1 malocclusion and 20 average-angel patients with class I were selected from dental hospital of Hebei Medical College. Patients with class II, division 1 were divided into two groups according to the cause of malocclusion. One group was called"Maxilla overgrown", the other group was called"Mandible dysplasia". There were 60 patients in each group. The"Maxilla overgrown"group was the first test group; the"Mandible dysplasia"group was the second test group; average-angel patients with class I was the controlled group. In each of these two test groups, there were three groups according to the different vertical facial skeletal types, they were high-angel group, average-angel group and low-angel group, 20 patients in each group. The dental casts and posteroanterior cephalograms were measured. On the dental casts,18 parameters were measured: dental arch widths in canine Wu3,Wl3, in the first premolar Wu4,Wl4 and in the first molar Wu6,Wl6; alveolar arch widths in canine 3╂3alveolar,3╂3alveolar, in the first premolar 4╂4alveolar,4╂4alveolar and in the first molar 6╂6alveolar,6╂6alveolar; basal bone widths in canine 3╂3bone,3╂3bone, in the first premolar 4╂4bone,4╂4bone and in the first molar 6╂6bone,6╂6bone. On the posteroanterior cephalograms 8 parameters were measured: Zyg-Zyg, Cdl-Cdl, Go-Go, Ln-Ln, Mx-Mx, Um-Um, Lm-Lm, Mas-Mas.The datus were dealt with by SAS V8—analysis of variance, rank sum test, correlation analysis.Results1 The results of the comparison of the widths among the first test group with average-angel, the second test group with average-angel and the controlled group:1.1 The results of posteroanterior cephalograms :There was significant difference among the three groups in Um-Um (P<0.05). There were no significant differences among the three groups in other indexes(P>0.05). The comparison of two groups found: There was no significant difference between the first test group and the second test group, but both of them were smaller than the controlled group in Um-Um, which had statistical difference.1.2 The results of dental casts There were significant differences among the three groups in 6╂6alveolar,6╂6bone and Wu6 (P<0.05). There were no significant differences among the three groups in other indexes(P>0.05). The comparison of two groups found: There was no significant difference between the first test group and the second test group, but both of them were smaller than the controlled group in 6╂6alveolar and 6╂6bone; the second test group was smaller than the controlled group in Wu6, which had statistical difference.2 The results of the comparison of the widths among the first test group with high-angel,the second test group with high -angel and the controlled group2.1 The results of posteroanterior cephalogramsThere were significant differences among the three groups in Mas-Mas,Um-Um,Mx-Mx (P<0.05). There were no significant differences among the three groups in other indexes (P>0.05). The comparison of two groups found: The second test group was smaller than the controlled group in Mas-Mas;there was no significant difference between the first test group and the second test group, but both of them were smaller than the controlled group in Um-Um,Mx-Mx, which had statistical difference.2.2 The results of dental castsThere were significant differences among the three groups in 6╂6alveolar,6╂6bone,Wu6 (P<0.05). There were no significant differences among the three groups in other indexes(P>0.05). The comparison of two groups found: There was no significant difference between the first test group the second test group, but both of them were smaller than the controlled group in6╂6alveolar,6╂6bone,Wu6, which had statistical difference.3 The results of the comparison of the widths among the first test group with low-angel,the second test group with low-angel and the controlled groupThere were no significant differences among the three groups in all indexes (P>0.05).4 The results of the comparison of the widths among different vertical facial skeletal types in the first test group4.1 The results of posteroanterior cephalogramsThere was significant difference among the high-angel,average-angel and low-angel groups in Um-Um (P<0.05). There were no significant differences among the three groups in other indexes(P>0.05). The comparison of two groups found: The width of patients with low-angel was bigger than the width of patients with high-angel, which had statistical difference.4.2 The results of dental castsThere were significant differences among the high-angel,average-angel and low-angel groups in 6╂6bone,Wu6 (P<0.05). There were no significant differences among the three groups in other indexes (P>0.05). The comparison of two groups found: The width of patients with low-angel was bigger than the width of patients with high-angel in 6╂6bone; There was no significant difference between low-angel group and average-angel group, but both of them were bigger than high-angel group in Wu6, which had statistical difference.5 The results of the comparison of the widths among different vertical facial skeletal types in the second test group5.1 The results of posteroanterior cephalogramsThere were significant differences among the high-angel,average-angel and low-angel groups in Mas-Mas,Um-Um (P<0.05). There were no significant differences among the three groups in other indexes (P>0.05). The comparison of two groups found: The width of patients with low-angel was bigger than the width of patients with high-angel and average-angel in Mas-Mas, which had statistical difference, but there was no significant difference between high-angel group and average-angel group. There was no significant difference between low-angel group and average-angel group in Um-Um,but both of them were bigger than high-angel group, which had statistical difference.5.2 The results of dental castsThere was significant difference among the high-angel,average-angel and low-angel groups in 6╂6alveolar,6╂6bone,Wu6 (P<0.05). There were no significant differences among the three groups in other indexes (P>0.05). The comparison of two groups found: The width of patients with average-angel were bigger than the width of patients with high-angel and average-angel in 6╂6alveolar,6╂6bone, which had statistical difference. There was no significant difference between low-angel group and average-angel group in Wu6, but both of them were bigger than high-angel group, which had statistical difference.6 The correlation between vertical facial skeletal types and the widths in the first test group6.1 The results of posteroanterior cephalogramsThe correlation analysis indicated that there was negative correlation between Um-Um and SN-Mp, the correlation coefficient was -0.425. There were no significant correlations between other indexes and SN-Mp(p>0.05).6.2 The results of dental castsThe correlation analysis indicated that there was negative correlation between 6╂6bone,Wu6 and SN-Mp, the correlation coefficients were -0.390,-0.598. There were no significant correlations between other indexes and SN-Mp(p>0.05).7 The correlation between vertical facial skeletal types and the widths in the second test group7.1 The results of posteroanterior cephalogramsThe correlation analysis indicated that there was negative correlation between Mas-Mas,Um-Um and SN-Mp, the correlation coefficients were -0.393,-0.542. There were no significant correlations between other indexes and SN-Mp(p>0.05).7.2 The results of dental castsThe correlation analysis indicated that there was negative correlation between 6╂6alveolar,6╂6bone,Wu6 and SN-Mp, the correlation coefficients were -0.416,-0.383,-0.476. There were no significant correlations between other indexes and SN-Mp(p>0.05).Conclusions1 The posterior widths of maxilla and dental arch in angle's II1"Maxilla overgrown"malocclusion patients with average-angel and high-angel were narrower than the widths of angle's I malocclusion patients with average-angel. So, rapid maxillary expansion might be conducted. However, it was not narrow in angle's II1 malocclusion patients with low-angel. So, it was not necessary to expand maxilla of angle's II1"Maxilla overgrown"malocclusion patients with low-angel.2 The middle widths of face in angle's II1"Mandible dysplasia"malocclusion patients with high-angel, the posterior widths of maxilla and dental arch in angle's II1"Mandible dysplasia"malocclusion patients with average-angel and high-angel were narrower than the widths of angle's I malocclusion patients with average-angel. So, rapid maxillary expansion might be conducted. However, it was not narrow in angle's II1 malocclusion patients with low-angel. So, it was not necessary to expand maxilla of angle's II1"Mandible dysplasia"malocclusion patients with low-angel.3 There was negative correlation between vertical facial skeletal types and posterior widths of maxilla and dental arch in angle's II1"Maxilla overgrown"malocclusion. The widths came bigger gradually along with SN-MP from big to small.4 There was negative correlation between vertical facial skeletal types and the middle widths of face,posterior widths of maxilla and dental arch in angle's II1"Mandible dysplasia"malocclusion. The widths came bigger gradually along with SN-MP from big to small. |
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