Occlusal Relationship of Crowns fabricated by Two Impression Techniques

Objectives: When we fabricate crowns, we have to pay attention to reconstruct occlusal relationships as well as inter-proximal relationships and marginal fitness. Usually, the height of crowns fabricated by the indirect methods are approximately 100 to 200 µm higher than the ideal height because of the distortion of the periodontal ligaments in function. Therefore, dentists have to do occlusal adjustment prior to cementing. However, sometimes designated occlusal relationships were lost in the process of these occlusal adjustments, unfortunately. The purpose of this study was to evaluate the occlusal relationships of crown fabricated with two kinds of impression techniques. Methods: Eight subjects whose premolars or molars need to be treated with crowns were enrolled in this study. After preparation for crown, two kinds of impression methods (normal indirect impression method (NIM), bite impression method (BIM)) were performed and two types of full cast crowns were fabricated. After occlusal adjustment of crown, occlusal relationships during moderate clenching were recorded with occlusal contact checking materials and evaluate the number and area of occlusal contacts region under 10µm. Results: The number of occlusal contacts of the crown fabricated by NIM and BIM were 4.4±2.4 and 6.9±3.1, respectively. The Wilcoxon signed-rank test showed a significant difference between two groups (p<0.05). On the other hands, the area of occlusal contacts of the crown fabricated by NIM and BIM were 1.612±1.374 mm² and 1.859±1.850 mm², respectively. There was no significant difference between two groups (p<0.05). Conclusion: Within the limitation of this study, there is a possibility that the crowns fabricated by BIM may have more occlusal contacts than the crowns fabricated by NIM and the occlusal form around the occlusal contacts may be different.