[Individual and precise occlusal design for posterior full-crown restorations based on physiological tooth...

Objective: To apply an individual and precise occlusal design method based on physiological tooth displacement for the digital design of posterior full crowns, and to explore its clinical effectiveness. Methods: This was a prospective randomized controlled study. From February 2024 to January 2025, patients who visited the Department of Prosthodontics, Peking University School and Hospital of Stomatology, with tooth defects in the second premolars or first molars and planned for full-crown restoration were enrolled. After tooth preparation, intraoral scanning was performed to obtain data of the maxillary and mandibular posterior dentitions and occlusal buccal surfaces on the side of the prepared tooth. Patients were randomly assigned using a random number method to undergo restoration design. Control: full crowns were designed according to a conventional protocol, using an automatically registered occlusal relationship based on the buccal surfaces. The occlusal clearance values were set based on previous studies and the clinical experience of the dental technician. Experimental: an individual occlusal design technique based on physiological tooth displacement was employed. Intraoral scan data underwent single-tooth segmentation and registration to derive virtual occlusal relationships in occlusion, followed by calculation of occlusal clearances of adjacent teeth. The occlusal clearance for the full crown was set as the mean value of the adjacent teeth's occlusal clearances. After fabrication of zirconia full crowns for both groups, they were delivered for clinical try-in. Occlusal evaluations were performed before and after occlusal adjustment. Primary outcomes included qualitative evaluation of occlusal fitness (qualitatively classified into three categories: acceptable occlusion, high occlusion and low occlusion) and occlusal adjustment height, while secondary outcomes comprised occlusal adjustment volume, articulating paper markings, occlusal clearance values, and occlusal adjustment time. Results: A total of 38 patients [12 males, 26 females; age: (39.5±13.2) years] were included in this study. Thirty-eight posterior full crowns were fabricated, with 19 allocated to the test group and 19 to the control group. The occlusal status before occlusal adjustment was as follows: in the test group, 4 crowns had acceptable occlusion, 15 had high occlusion, and none had low occlusion; in the control group, 1 crown had acceptable occlusion, 14 had high occlusion, and 4 had low occlusion. The number of cases with acceptable occlusion was significantly higher in the experimental group than in the control group (U=122.00, P=0.022). The occlusal adjustment height of the experimental group [(39.1±17.0) μm] was significantly lower than that of the control group [(79.5±50.2) μm] (t=-2.85, P=0.009). No significant differences were observed in adjustment time, volume, or articulating paper evaluation (all P>0.05). Conclusions: Using a virtual occlusal registration method for single-tooth segmentation based on the physiological tooth mobility and quantitatively referencing the occlusal contacts of adjacent teeth, this study significantly improved the occlusal suitability of full crowns and reduced the occlusal adjustment required.