Accuracy of using novel bite registration caps to record the intercuspal position by intraoral scanning for fixed implant prostheses with different edentulous span lengths.
OBJECTIVES In distal extension cases involving multiple missing teeth planned to be restored with implant-supported fixed prostheses, the accuracy of digital recording the maximum intercuspation position (MIP) using intraoral scanners (IOS) remains insufficient. This in vitro study aimed to evaluate the effect of a novel developed bite registration cap on the accuracy of digital MIP recording by IOS in distal extension cases with different edentulous span lengths. METHODS A series of prefabricated bite registration caps was designed to be retained on the top of the healing abutments. Three pairs of reference stone casts containing implant analogs and representing different edentulous conditions (2,3 and 4 missing teeth), were mounted on a mechanical articulator. Two groups were created based on the landmarks used for bite registration: bite registration caps (test group) and healing abutments (control group). Each group was further divided into 3 subgroups based on edentulous span length (2, 3, or 4 missing teeth). In each subgroup, the casts were digitized with an IOS, and the scan datasets were duplicated 10 times and articulated by buccal bite registrations (n=10). Maxillary occlusal surface deviations and linear distance deviations between interarch markers were calculated to evaluate the accuracy of MIP recording. Two-way ANOVA with Tukey post hoc tests was used to analyze maxillary occlusal surface deviations (α=.05). The linear distance deviations were compared by Mann-Whitney U test and Kruskal-Wallis test (α=.05). RESULTS Both the registration method and edentulous span length significantly affected the trueness of MIP recording, with a significant interaction between these 2 factors (P<.001). For cases with 2, 3, and 4 missing teeth, the maxillary occlusal surface deviations in the test and control groups were 55.5 ± 6.7 μm vs 71.4 ± 10.4 μm, 56.6 ± 3.0 μm vs 78.0 ± 8.0 μm, and 56.1 ± 3.5 μm vs 171.5 ± 10.3 μm, respectively. Across all edentulous conditions, maxillary occlusal surface deviations in the test group were significantly lower than those in the control group (P<.001). In the control group, the maxillary occlusal surface deviations were significantly greater in distal extension conditions with 4 missing teeth than in those with 2 or 3 missing teeth (P<.001). From the second premolar to the second molar, the absolute values of the linear distance deviations were significantly higher in the control group than in the test group (P<.01). CONCLUSION Compared with the control group, the use of bite registration caps significantly reduced the maxillary occlusal surface deviations and linear distance deviations, thereby improving the trueness of digital MIP recording in distal extension cases restored with implant-supported fixed prostheses. Notably, the trueness was clinically unacceptable in distal extension cases with four missing teeth without the use of bite registration caps. These findings suggest that under in vitro conditions, the bite registration caps can enhance the trueness of IOS-based MIP recording in distal extension cases restoring with implant-supported fixed prostheses. CLINICAL SIGNIFICANCE The application of the novel bite registration caps improved the trueness of digital MIP recording by IOS in distal extension cases restoring with implant-supported fixed prostheses.