This investigation was designed to determine the effectiveness of the posterior occlusal schemes on masticatory activity during mastication in complete denture. Twelve edentulous subjects were selected for this study. All subjects had no past history and no functional abnormality on masticatory system and TMjoint And, they had residual ridge of favorable morphology, firm mucosa and Class I skeletal jaw relationship,
Twelve experimental denture with interchangeable occlusions(0-degree teeth, 30-degree teeth, Levin teeth and S-A teeth) were constructed for this study.
The masticatory performance was analyzed by means of standard sieve(10, 16, 20, 30sieve), and the electrical activity from selected muscles(Temporalis and Masseter muscle) was recorded simultaneously with electromyography (Bio-Pak system) as the subject masticated test foods (rice, peanut and gum) with four different occlusal schemes. Mandibular movement was, also, measured with Sirognathography(Bio-Pak system). These recordings were performed in immediately , after 1 week and after 2 weeks of insertion of complete denture.
The results were as follows;
1. The average masticatory performance of 0-degree artificial teeth was higher than any other artificial teeth.
2. Masticatory performance in denture wearer was affected preferentially by food and artificial occlusal schemes
3. During chewing, there was a statistical difference of EMG activity between masseter and temporal muscle(p<0.01).
Especially, EMG activity of working masticatory muscle was highly affected by food rather than by artificial occlusal schemes.
4. In denture wearer, the velocity of opening was not affected by food, whereas, the velocity of closing was faster in soft food chewing than in hard food chewing, and the amount of vertical displacement was grater in chewing of soft and large bolus than in chewing of hard and small bolus. However, the amount of lateral displacement showed conversely(p<0.05).
5. It was considered that masticatory performance in denture wearer is not affected by the condition of residual ridge, the history of denture wear, the preference,the adaptation to artificial teeth and the total mesiodistal length of artificial posterior teeth.
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