ผลของคอมพอเมอร์แบบติดแน่นในการป้องกันการดันขึ้นและทิปปิ้งของฟันกรามจากการใช้ยูทิลิตี้ อาร์ช

Abstract

Introduction Deepbite with deep curve of Spee can be treated orthodontically by utility arch but the extrusion and distal crown tipping of lower first molar is common side effect. Patients that increased lower facial height and/or convex profile should be done by intrusion of lower incisors without extrusion of molar in order to prevent the aggravation of convex facial profile. In order to maintain molar position and angulation during intrusion of lower incisors, the intrusive force and clockwise moment must be created at lower first molars by using fixed compomer raise was applied to the mesial part of occlusal surface of lower first molars. The authors had developed a technique by which were expected to simultaneously and effectively create force to intrude lower incisors and maintain molar position. Objectives To investigate the effect of fixed compomer raise bite on molar extrusion and distal crown tipping during the use of utility arch. Moreover, to obtain possible information from patients on the orthodontic treatment with fixed appliance combined with fixed compomer raised bite. Materials and methods 24 patients with deep curve of Spee were included in this study. Patients were randomly divided into two groups. The control group comprised 12 patients (age 18.5 ± 4.6 years) treated with utility arch with asymmetrical V-bend. The experimental group consisted of 12 patients (age 18 ± 2.0 years) treated with utility arch with asymmetrical V-bend with fixed compomer raise bite. The utility arch was activated at buccal segment at 1/3 of the interbracket span which created force level of 40 g measured at the midline in both groups. In experimental group, the lower first molars also were added fixed compomer raise bite. Lateral cephalograms and lower impression were taken to evaluate skeletal, dental and intermolar width changes at before intrusion of lower incisors (TO) and after intrusion of lower incisors (T1). Statistics were used to evaluate within group changes between TO and T1 and between group changes. All patients in both groups were answered the questionnaire about patient discomfort its and pain after this procedure was applied. Results In the control group, lower incisors were intruded 1.8 ± 0.5 mm. Overbite was decreased 2.3 ± 0.6 mm. Lower first molars were extruded 0.5 ± 0.3 mm while lower first molars were distal crown tipped 3.1 ± 2.1°. Extrusion of lower second molars 0.3 ± 0.2 mm and backward rotation of the mandible (MP- SN) 0.6 ± 0.7° were presented with significant difference when compared between pre-intrusion and post-intrusion data. The occlusal plane, facial contour angle and intermolar width in lower arch were maintained. From a questionnaire found that 2 of 12 patients complained discomfort in mild level after the utility arch was activated to intrude lower incisors and disappeared 3 days later. Overbite in experimental group was decreased 2.1 ± 0.4 mm. Lower incisors were intruded 1.7 ± 0.7 mm. Lower first molars were intruded 0.3 ± 0.3 mm and distal crown tipped 3.1 ± 2.7°. Extrusion of lower second molars 0.3 + 0.3 mm and mandibular plane (MP- SN) was increased 0.4 ± 0.4 °. The difference in all of these parameter between pre-intrusion and post-intrusion were statistically significant. But the occlusal plane, facial contour angle and intermolar width in lower arch compared between pre-intrusion and post-intrusion were not significantly changes. From the questionnaire found that all patients described discomfort after the attachment of fixed compomer raise bite for 5 days. However, 8 patients suffered from short-term pains in lower first molars, the pains subsided within 4 days. Comparing between two groups, no statically significant alteration was observed in any variables. Whereas vertical change of the lower first molars and occlusal plane change were statically significant. Conclusion: No difference amount of lower incisors intrusion and extrusion of lower second molar and angulation of lower first molar changes were compare between two groups. However, in experimental group, statically significant of intrude lower first molars which subsequently create less steep of occlusal plane. After fixed compomer will be removed. Lower molars may extrude into the interocclusal space. It might be implied that fixed compomer raise bite applied on the mesial part of occlusal surface of lower first molars cannot maintain lower first molar position and angulation during intrude lower incisor with utility arch.