The objective and quantitative analysis of malocclusion: Part 2. Influence of malocclusion compenents to treatment difficulty / 대한치과교정학회지

As one of the variations in growth and development of the craniofacial complex, malocclusion shows lack of concordance in the recognition and severity of malocclusion for dentists as well as the acceptance and need of orthodontic treatment for the patient. The purposes of this study were 1) to examine the relationships between objective malocclusion severity and subjective treatment difficulty, 2) to evaluate the effect of malocclusion components to the subjective perceived difficulty of treatment, 3) to establish the weighted values of malocclusion components to reflect the treatment difficulty. 100 pairs of dental casts with the general characteristics of malocclusion, were selected from the orthodontic departments of Kyunghee University and Samsung Medical Center. The severity of malocclusion was evaluated by the author with the PAR index. The perceived treatment difficulty and the estimated treatment duration on these dental models were evaluated by 8 experienced orthodontists. The relationships between the objective malocclusion severity and the subjective treatment difficulty were statistically evaluated, and the weighted values of malocclusion components to reflect treatment difficulty were statistically formulated. There were significant relationships between objective malocclusion severity and subjective treatment difficulty. The malocclusion components which significantly affected the treatment difficulty and their weighted values in parentheses were as follows; upper anterior alignment (1), overbite (2), buccal occlusion (3), midline (4), and overjet (5). This study provides the fundamental principle to evaluate the objective malocclusion severity which is reflected by the subjective treatment difficulty of Korean orthodontists.

The objective and quantitative analysis of malocclusion: Part 1. Objective malocclusion severity and subjective treatment difficulty / 대한치과교정학회지

The evaluation of malocclusion has to be done quantitatively and qualitatively. This will be lead toward an analysis of malocclusion severity as well as treatment difficulty. The method of proper evaluation of malocclusion severity and treatment difficulty is necessary to assess treatment effect and efficiency for the orthodontists and to establish fundamentals for planning and executing the health-related policies in private and public institutions. The purposes of this study as the first part of the objective and quantitative analysis of malocclusion were 1) to measure treatment difficulty based on the opinions of several orthodontists, and 2) to investigate the relationships between objective malocclusion severity and subjective treatment difficulty. 100 pairs of dental casts that had various types and severity of malocclusion were selected from the orthodontic departments of Kyunghee University and Samsung Medical Center. The objective malocclusion severity was measured with the PAR (Peer Assessment Rating) index and the subjective treatment difficulty was evaluated by 8 experienced orthodontists. The relationships between objective malocclusion severity and subjective treatment difficulty were statistically evaluated. There were significant relationships between objective malocclusion severity and subjective treatment difficulty, especially in the measurements of the upper anterior alignment, the buccal occlusion, the overjet, the overbite and the midline discrepancy in the malocclusion components. The results of this study can provide the background knowledge to develop a new occlusal index, which contains both the malocclusion severity and treatment difficulty for Korean orthodontists.

An electromyographic investigation of masticatory muscles in normal occlusion and Class III malocclusion / 대한치과교정학회지

The purpose of the present study was to investigate the differences of EMG activity of the masticatory muscles between normal occlusion and Class III malocclusion during various jaw functions. 46 subjects of 18.4-25.7 years were employed in this study: 26 subjects were normal occlusions, and 20 subjects were Class III malocclusions. The EMG data from the anterior and posterior temporal, anterior and posterior masseter muscles in both sides as mandibular elevators and supra-hyoid muscle group (close to the anterior belly of digastric muscle in right side) as mandibular depressor were recorded with the Medelec MS 25 electromyographic machine. The EMG recordings were analyzed during mandibular rest position, maximal biting, mastication with chewing gum, and swallowing of peanuts. All data were recorded and statistically processed. 1. The maximal mean amplitude of the anterior temporal muscle was stronger significantly in Class III malocclusion than in normal occlusion, and then the posterior temporal was weaker during mandibular rest position. 2. The maximal mean amplitudes in the anterior and posterior temporal muscles and the anterior masseter muscle of Class III malocclusion was weaker significantly than that of normal occlusion during maximal biting. 3. During mastication of the chewing gum, the maximal mean amplitudes of Class III malocclusion was weaker significantly than normal occlusion in the anterior and posterior temporal muscles of the working side, and the duration of Class III malocclusion was longer in the anterior temporal muscles of both sides, and the posterior temporal and the anterior masseter muscle of the balancing side. There were significant increasings of the latency in balancing anterior temporal, working posterior temporal muscles and supra-hyoid muscle group of Class III malocclusion. The silent period durations was 16.36 ms in Class III malocclusion while 10.76 ms in normal occlusion, which was statistically different (P<0.05). 4. At swallowing of peanuts, the maximal mean amplitude of Class malocclusion was weaker significantly in the posterior temporal muscle than that of normal occlusion. There was no significant difference of duration between normal occlusion and Class III malocclusion. 5. The muscle activities of Class III malocclusion had a tendency of decrease less than normal occlusion. And then the muscle activities of the anterior temporal and anterior masseter muscles in Class III malocclusion showed the tendency of the increase more than other muscles of Class III malocclusion.