| Summary: | 碩士 === 中山醫學大學 === 牙醫學系碩士班 === 99 === Depending on the degree of severity, the facial characteristics of Angle’s Class III malocclusion with mandibular prognathism may show a straight to concave profile. People would seek for treatment of mandibular prognathism owing to factors such as facial esthetics, poor chewing function, interpersonal relationship and psychological impacts. For adult Class III malocclusion with severe mandibular prognathism, treatment frequently requires a combination of orthodontic and orthognathic surgical procedures. The aims of this study were to investigate the profile changes in lower face and the correlations between soft and hard tissue changes in Angle’s Class III malocclusion cases after mandibular setback surgery with intraoral vertical ramus osteotomy (IVRO) approach.
The sample of this study included 21 Taiwanese patients (11 males, 10 females) with skeletal Class III malocclusion (ANB : - 4°; Wits: -14.1 mm). All the 21 patients have completed a combined fixed orthodontic treatment and orthognatic surgical treatment with IVRO mandibular setback and six weeks of maxillo-mandibular fixation at Chung Shan Medical University Hospital during 2009 and 2010. The pretreatment (T0), pre-surgical (T1) and post-treatment (T2) lateral cephalographs were collected. All the soft and hard tissue changes were measured and analyzed by paired t test. In this study the mean patient’s age was 22 ±3.9 years, and mean treatment time was 25.9 months.
The results of this study showed that:
(1)The mean ANB angle increased 5.37° (pretreatment ANB - 4.04°; post-treatment ANB 1.33 °).
(2)The mean Nasolabial angle increased 11.20°. (pretreatment Nasolabial angle 91.49°; posttreatment Nasolabial angle 102.69 °).
(3)The mean Wits A/B distance decreased 8.43 mm. (pretreatment Wits A/B -14.14 mm; post-treatment Wits A/B 5.71 mm) .
(4)The patients underwent mandibular surgery had an average of 10.93 mm setback at the osseous pogonion (Pog). Five parts of the soft tissue were analyzed and revealing that: (a). the mean setback at most retrusive point of upper lip (sls) was 0.60 mm , the setback ration of Pog / sls was 1:0.05 ; (b). the mean setback at most protrusive point of upper lip (ula) was 1.45 mm , the setback ration of Pog / ula was 1:0.13; (c) . the mean setback at most protrusive point of lower lip (ils) was 8.69 mm , the setback ration of Pog / ils was 1:0.79 ; (d). the mean setback at most retrusive point of lower lip (ila) was 7.29 mm , the setback ration of Pog / ila was 1:0.66 . And the last analysis showed that mean soft tissue pogonion (pog) was setback 9.30 mm, the setback ratio of hard to soft tissue pogonion Pog/pog was1:0.85.
This study showed that mandibular setback surgery was effective for improvement of adult Class III prognathic profile by significant changes seen in ANB angle , Nasolabial angle and the distances of Wits A/B. The soft tissue changes of the lower face differed at different parts (pog, sls, ula, ils, and ila as in this study), and the soft to hard tissue ratio also different in subjects with mandibular prognathism. We hope more cases can be collected to obtain more detail data that would be helpful in surgical prediction for prospective Taiwanese Class III orthognathic surgery patients
|
|---|
