OBJECTIVETo reconstruct the centric relation of upper and lower edentulous dental models with two methods, to compare the reconstruction accuracy of the vertical and horizontal distance, and to provide some references to computer aided design and computer aided manufacture for complete denture.

METHODSDental models and rims made from five edentulous patients in clinical were obtained.Each model was stocked with 10 identical size positioning cylinders (20 cylinders on each pair models) on 5 side-surfaces of basement. Twelve center point pairs were paired between upper and lower models from 20 cylinder bottoms. The vertical and horizontal distances of 12 center point pairs were regarded as the evaluation items. Firstly, upper and lower models and rims were scanned separately. Then, models and rims (fixed in centric relation respectively with positioning articulator and rubber banding) were scanned.In software, all the data were registered to reconstruct centric relation based on common region. Digital models were measured with software tools, and real models were measured with a contact measurement arm. The differences of the homologous items between two methods were analyzed with paired-t test.

RESULTSThe vertical distance errors for dental articulator positioning method was (0.356 ± 0.200) mm and that of the rubber band method was (0.382 ± 0.299) mm, and paired-t test between the two methods showed no significant differences (P > 0.05). The horizontal errors were (0.010 ± 0.411) mm and (0.104 ± 0.476) mm, and paired-t test showed significant differences (P < 0.05).

CONCLUSIONSComparing with rubber band method, dental articulator positioning can significantly increases three-dimensional reconstruction accuracy of edentulous jaw gypsum models' horizontal relation.