| Objectives: The retrospective study was designed to observe correlative factors which has influenced on buccal corridor in Class ⅡDivision 1 malocclusion and to study the changes of buccal corridor by comparing the pretreatment and posttreatment frontal smiling photographs and lateral cephalograms. In order to provide a more comprehensive theoretical basis and help for making clinical orthodontic treatment plan.Methods: Sample selection: There were 18 extraction and 17 non-extraction orthodontic patients with Class Ⅱ Division 1 malocclusion who have finished their orthopedic treatment from the Department of Orthodontics, Hospital of Stomatology, Hebei Medical University from 2011 to 2013 selected. Inclusion criteria: All the patients’ average ages at the time of records were 18-25 y. The molars showed class Ⅱocclusion, 5° < ANB < 9°, the maxillary incisors inclined to lip and the anterior tooth had excessive overjet(OJ>3mm); All had permanent dentitions with no congenitally missing teeth, with the possible exception of the third molars, no supernumerary teeth, no embedded teeth; no previous orthodontic treatment history; no operation history;no trauma history or no systemic diseases. The data on pretreatment and posttreatment frontal smiling photographs, and cephalometrics were complete, clear and recognizable. All the subjects volunteered for the investigation and signed the informed consent. Sample grouping: The final sample consisted of the records of 35 patients. These subjects included 18 patients who had 4 premolars extracted(7 boys, 11 girls, with a mean pretreatment age of 21.7±0.7years)and 17 patients who had no premolars extracted(7 boys, 10 girls, with a mean pretreatment age of23.8±1.2years). All subjects had been treated with straight wire appliance(SWA). The mean treatment times were 22.0±1.03 months for the extraction group and 18.7±1.1 months for the non-extraction group. The treatment objectives were to have Class Ⅰcanine and molar relationships and normal overjet and overbite with well-aligned and interdigitated teeth at the end of the treatment. Cephalometrics: All cephalometrics of the patients were taken before and after treatment by one same technician with CRANEX®D panoramic X-ray. The subjects were asked to relax the muscle around mouth, to calm breathing and not to swallow in natural head position and centric occlusion. Posed frontal smile photographs: Each subject’s pretreatment and posttreatment posed frontal smile photographs were taken in the same location with the same ambient lighting and a digital camera(EOS 40 D, Canon, Tokyo, apan). The subjects had their heads in natural head position and the frankfort plane parallel to the ground plane. They were asked to give a relaxed,natural smile and make smile practice that the pronunciation of English Letter E was carried out if natural smile could not be achieved. The photographs were then uploaded into the computer as JPEG files. All cephalograms were digitized with Winceph 8.06 software by 1 examiner and corrected the mangnification during the measurement process. All posed smiling photographs were made and calculated as ratios used by Smile Measure software. Each measurement was measured 3 times then collected the average values. Statistical analysis: SPSS13.0 software was used for the statistical analysis. Statistical significance was established at α=0.05. Descriptive statistics were calculated for all raw demographic and photographic measurements.Results: 1 The results of buccal corridor area ratio(BCAR) before and after treatment The ratio of the extraction group was 4.43±0.61% before treatment and after treatment the ratio incresed to 4.82±0.55%; there was a significant different between pretreatment and posttreatment(P<0.01). The ratio of the non-extraction group before treatment was 4.48±0.53%, and that reduced to 4.27±0.53% after treatment, but there were no significant differences(P>0.05). The BCAR changes of before and after treatment were 0.33±0.07%,-0.31±0.06% in extraction group and in the non-extraction group respectively. There were significant differences(P<0.01). 2 The results of measurement of soft and hard tissues before and after treatment The U1-NA, U1-NA distance, U1-SN, L1-NB distance, G-TN-Pog R, TUL-ELine, TLL-ELine in the extraction group decreased after treatment; the U1-L1, ANS-Go/N-Me,(SA-TUL)-FH,(SB-TLL)-FH,(SA-TUL)-(SB-TLL) and the length of the upper lip increased after treatment; so there was significant difference in all measurements(P<0.01). There were no significant differences between other pretreatment and posttreatment measurements(P>0.05). The L1-NB, L1-NB distance, L1-MP, TLL-ELine in the non-extraction group had a statistically significant increases after treatment(P<0.01); and the U1-L1, Wits were statistically significant decreased after treatment(P<0.01). There were no significant differences in other measurements before and after treatment.(P>0.05). For the between treatment group outcomes, the changes of U1-NA in extraction group and non-extraction group before and after the treatment were-13.76±1.49° and-1.84±1.65°; the U1-NA distance were-4.05±0.49 mm, 0.81±0.39mm; the U1-SN were-14.41±1.66°,-1.18±0.56°; the L1-NB were-2.50±1.74°, 7.43±2.13°; the L1-NB distance were-1.80±0.45 mm, 2.09±0.625mm; the L1-MP were-1.96±1.71°, 7.54±2.19°; the U1-L1 were 15.59±2.23°,-5.15±2.23°; the TUL-Eline were-2.20±0.32 mm,-0.07±0.35mm; TLL-Eline were-2.57±0.317 mm,-1.26±0.29mm; the length of the upper lip were 0.75±0.19 mm, 0.03±0.11mm; the(SB-TLL)-FH were 5.00±1.46°, -2.04±1.67°; the nasolabial angle were 2.39±1.76°,-2.74±1.66°; the(SA-TUL)-(SB-TLL) were 10.45±3.12°,-0.93±1.77°; the G-TN-Pog R were-1.77±0.39°, 0.11±0.39°; and ANS-Me/N-Me were 0.0056±0.0017,-0.0006±0.0014 respectively. There were significant differences in these measurements between the extraction and non-extraction groups(P<0.05). 3 The result of correlation analysis between buccal corridor area ratio(BCAR) and other variables There were significantly positive correlations between BCAR and the skeletal vertical pattern, S-G0/N-Me, U1-L1,(SB-TLL)-FH(P<0.05). Among the denture pattern measurements, there were statistically significant negative correlations in U1-NA, U1 to NA plane, U1-SN, L1-NB, L1-NB distance, L1-MP, TUL-ELine, TLL-ELine.(P<0.01).Conclusions: 1 There was significant difference in BCAR between the extraction and non-extraction groups. 2 To control the amount of BCA for achieving a better esthetic smile, it is necessary to observe the vertical pattern of the face and the incline of the the upper incisors and lower incisors. |
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