| Objective:The aim was to study the influence on buccal corridors in adult patients with Angle’s class III malocclusion by extraction and non-extraction treatment to research the relevant factors that have effects on buccal corridor and to help drawing up the orthodontic treatment plan and assessing the results clinically by analyzing the pretreatment and posttreatment frontal smiling photographs and cephalometrics of Angle’s class Ⅲ malocclusion adult patients who had received orthodontic treatment either with or without premolar extractions.Methods:1 The subjects’ inclusion criteria and grouping: In this selected retrospective study, forty-five adult patients with Angle’s Class III malocclusion who attended and had finished their orthodontic treatment in the Department of Orthodontics, Hospital of Stomatology, Hebei Medical University from January 2012 to September 2014 were selected and divided into two groups: the non-extraction group(25 patients, 18 females and 7 males,the average age was 21.7±2.6y) and extraction group(20 patients, 17 females and 3 males,the average age was 20.3±2.4y). The extraction patients had 4 premolars extracted(1 in each quadrant), with no discrimination toward which premolars were extracted. The selection criteria were as follows: patients from 17 to 25 years’ old(with 17 and 25 included), without potential development; with permanent and complete occlusion(the third molar was not included); mesial or superior mesial molar relationship, reduced or reversed overjet;-5o<ANB<1°; The exclusion criteria: patients with previous orthodontic treatment or maxillofacial operation experience;maxillofacial trauma;cleft lip and palate. All subjects had been treated with maxillary and mandibular straight-wire technique and finished with normal overjet and overbite. All the teeth were well aligned with normal molar relationships after treatment. Frontal smile photographs and cephalometrics were taken in the same department before and after treatment with clear landmarks of both hard and soft tissues. The study was approved by the patients and informed consents were signed. The average treatment time in the non-extraction group were 18.8±5.4 months and 26.5±4.2 months in the extraction group.2 Methods of taking frontal smile photographs before and after treatment:the patients had their eyes looking forward with the Frankfort horizontal(FH) plane and the interpupillary line parallel to the floor and were asked to give a relaxed, natural smile. The pronunciation of English Letter “E” was of avail if natural smile could not be obtained. All the photographs were taken by the trained radiologist in the same location with the same digital camera(EOS 40 D, Canon, Japan) and the same ambient lighting.3 Pretreatment and posttreatment cephalometrics were taken by the radiologists all of whom were trained uniformly with the same panoramic jaw tomography unit(CRANEX®D, Finland). The patients were asked to stand and look forward with the Frankfort horizontal(FH) plane parallel to the floor and with centric occlusion, breathing evenly, loose lip and no swallowing or speaking.4 Measurement of the photographs and cephalograms: The photographs were uploaded and inputted into the Smile Measure software to mark the gauge points. We obtained the buccal corridor area ratio with the soft ware. All lateral cephalograms obtained were inputted into a cephalometric program(Winceph 8.06), and then the image analysis window was opened. In order to get the clear images, the gray-scale of the images was adjusted, then the landmarks were signed, and the measurements were obtained with the software. Signed the landmarks and then ran the software. The magnification was corrected during the measurement process.5 Statistical analyses: The statistical analysis was performed with SPSS 13.0. The arithmetic mean and standard deviation were calculated for each variable. Paired t-test and independent t-test was separately performed to evaluate the treatment effects within and between groups. The relationship between the variables and the buccal corridor area ratio was analyzed with Pearson’s correlation analysis. Statistical significance was established at P<0.05.Results: 1 Changes of buccal corridor:In the non-extraction group, buccal corridor area ratio decreased significantly from(3.65±0.73)% to(3.42±0.83)% after treatment(P<0.01);In the extraction group, the changes of buccal corridor area ratio was not statistically significant(P>0.05);There was no statistically significant difference in change of the buccal corridor area ratio between the two groups. 2 Changes of cephalometric measurements 2.1 Changes of measurements before and after treatment in the non-extraction groupSagittal changes: SNA increased from 80.45±3.41° to 81.61±3.81(P<0.01), ANB increased from-2.01±0.46° to-0.62±0.48°(P<0.01), NA-P(°) increased from-4.86±1.15° to-2.28±1.19°(P<0.01), Wits(mm) increased from-8.1±3.02 mm to-5.82±2.99mm(P<0.01);Vertical change:MP-FH increased significantly from 24.94±4.94° to 25.96±5.62°(P<0.01);Dental changes: U1-SN(°) and U1-NA(°) increased from 107.62±5.47° to 112.00±4.88°(P<0.01),and from 27.17±4.71° to 30.39±6.12°(P<0.05) separately, U1-L1(°) decreased from 131.35±7.04° to 126.19±8.68°(P<0.05).Soft tissue changes: the nasolabial angle and G-TN-Pog R decreased from 94.56±9.54° to 91.33±7.58° and from 152.53±4.86° to 151.13±4.42° respectively; TUL-Eline and ANB(R) increased from-2.17±0.43 mm to-1.69±0.44 mm and from 3.88±1.95° to 4.84±1.90° respectively. All of the changes were statistically significant(P<0.05).There were no significant differences in the other variables(P>0.05). 2.2 Changes of measurements before and after treatment in the extraction gro-upSagittal changes:SNA decreased from 78.97±4.30° to 78.43±4.17°, SNB decreased from 79.74±4.47° to 78.50±4.43°, ANB increased from-0.78±0.24° to-0.07±0.24°, Wits(mm) increased from-5.70±2.39 mm to-4.03±1.53 mm, NA-PA(°) increased from-0.44±0.67° to 1.14±0.69°, NP-FH(°) decreased from 87.11±2.90° to 86.28±2.67°. All of the changes were statistically significant(P<0.05);Vertical changes: MP-FH and ANS-Me/N-Me increased from 28.09±3.73° to 28.97±4.59° and from 0.55±0.02 to 0.56±0.02° respectively,both were statistically significant(P<0.05).Dental changes: U1-NA(°) decreased from 28.79±3.99 to 23.99±2.65°, U1-NA(mm) decreased from 8.91±2.51 mm to 5.93±1.48 mm, U1-SN(°) decreased from 108.10±5.76° to 104.01±5.06°, L1-NB(°) decreased from 26.53±4.45° to 21.67±3.61°,L1-NB(mm) decreased from 5.91±2.41 mm to 3.43±1.62 mm, L1-MP(°)decreased from 91.12±5.79° to 86.37±4.70°, U1-L1(°) increased from 125.12±7.12° to 133.62±5.37°. All of the differences were statistically significant(P<0.01).Soft tissue changes:the nasolabial angle increased from 94.57±9.27° to 98.68±7.98°, TUL-Eline and TLL-Eline decreased significantly from-0.49±0.45 mm to-1.76±0.39 mm and from 2.26±0.46 mm to-0.03±0.33 mm respectively. G-TN-Pog R decreased from 151.34±5.74° to 149.63±5.58°. All of the changes were statistically significant(P<0.01).There were no significant differences in the other variables(P>0.05). 2.3 Changes between extraction and non-extraction groupSNA increased by 1.16±0.24° in the non-extraction group and decreased by 0.54±0.18° in the extraction group; SNB decreased by 0.27±0.17° and 1.24±0.25° in the non-extraction and extraction group respectively; ANB increased by 1.39±0.17° and 0.71±0.26° in the non-extraction and extraction group respectively; ANS-Me/N-Me increased by 0.0007±0.0013° and 0.0076±0.0019°; U1-NA(°) increased by 3.22±1.17° in the non-extraction group and decreased by 4.80±0.88° in the extraction group;U1-NA(mm) increased by 0.81±0.52 mm in the non-extraction group and decreased by 2.97±0.50 mm in the extraction group; U1-SN(°) increased by 4.38±1.19° in the non-extraction group and decreased by 4.10±1.01° in the extraction group;L1-NB(°) increased by 0.50±1.14° in the non-extraction group and decreased by 4.86±0.77° in the extraction group; L1-NB(mm) increased by 0.50±0.36 mm in the non-extraction group and decreased by 2.47±0.46 mm in the extraction group; L1-MP(°) increased by 0.74±1.15° in the non-extraction group and decreased by 4.75±0.86° in the extraction group; U1-L1(°) decreased by 5.15±1.85° in the non-extraction group and increased by 8.51±1.21° in the extraction group; nasolabial angle decreased by 3.23±1.17° in the non-extraction group and increased by 3.06±1.33° in the extraction group; TUL-Eline increased by 0.48±0.15 mm in the non-extraction group and decreased by 1.28±0.24 mm in the extraction group; TLL-Eline decreased by 0.01±0.21 mm and 1.89±0.31 mm in the non-extraction group and extraction group respectively. All of the changes were of statistical significance(P<0.05). 3 The correlation analysis between buccal corridor area ratio and other variablesSignificant negative correlations were found with the MP-FH(r=-0.299, P<0.05), L1-NB(°)(r=-0.430, P<0.01), L1-NB(mm)(r=-0.345, P<0.05), L1-MP(°)(r=-0.430,P<0.01), TLL-Eline(r=-0.320,P<0.05)and the buccal corridor area ratio. U1-L1(°)(r=0.311, P<0.05) and nasolabial angle(r=0.482, P<0.01) were significantly positively correlated with buccal corridor area ratio.Conclusion:Extraction treatment has no effect on the buccal corridors of patients with Angle’s class III malocclusion; non-extraction treatment leads to smaller buccal corridors of patients with Angle’s class III malocclusion; buccal corridors of patients with Angle’s class III malocclusion change with the vertical facial skeletal types,lower central incisors’ inclination and the amount of the retraction of the upper and lower lip. |
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