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Computer-aided design of occlusal contacts and clearance in posterior implant-supported single crowns: A randomized
Liang Shao1, XiaoLe Zhao1, Sui Li2
1Graduate student, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Center of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology & Research Center of Engineering and Technology for Computerized Dentistry Ministry of Health & NMPA Key Laboratory for Dental Materials, Beijing, PR China.
Statement Of Problem:
The conventional waxing method of designing occlusion relies on the skill of the dental laboratory technician and the use of articulating paper, resulting in limited accuracy. However, the clinical effects of computer-aided design (CAD) occlusal contacts and clearance in implant-supported crowns remain insufficiently investigated.
Purpose:
The purpose of this randomized clinical trial was to compare the effects of CAD occlusal contacts and clearance with those of the waxing method in posterior implant-supported single crowns.
Material And Methods:
Sixty patients with a single missing posterior tooth scheduled for an implant-supported crown were enrolled and randomized into 2 groups. After making impressions and pouring definitive casts, crowns with an 80-μm occlusal clearance for light contacts were designed. The control group used the waxing method with articulating paper to design the occlusion, while the test group adopted a digital antagonist tool after cast scanning. The designed occlusal clearance was calculated by using digital casts of the designed crowns. Occlusal clearance of finished crowns on the definitive casts was evaluated with a silicone interocclusal record. During delivery, the crowns were scanned, and the occlusion was evaluated. Occlusal adjustment indicators were calculated. The independent-samples t test, Mann-Whitney U test, and Pearson chi-squared test were used to analyze the statistical differences (α=.05).
Results:
Compared with the control group, the test group showed significantly lower mean ±standard deviation maximum occlusal adjustment distance (361.0 ±126.1 µm versus 451.5 ±179.3 µm, P=.037), but the root mean square (RMS) in the 2 groups was not significantly different (P=.121). The test group demonstrated significantly higher median (interquartile range) minimum designed occlusal clearance (72.4 [6.0] μm versus 26.1 [54.2] μm, P<.001) and lower median (interquartile range) RMS of occlusal clearance of finished crowns (116.2 [117.1] μm versus 227.3 [126.4] μm, P=.005) than the control group, both of which were closer to the design value (80 µm). Patient satisfaction before adjustment was significantly higher in the test group than in the control group (P=.005). Adjustment time and volume, lateral interference, and occlusal contact scores in the 2 groups were not significantly different (P>.05).
Conclusions:
Compared with the waxing method, CAD occlusion for implant-supported single crowns reduced occlusal adjustment distance, controlled occlusal clearance closer to the design value, and improved initial patient satisfaction.
