[Validation of the digital integration technology for evaluating the nasolabial morphology variation after the cross-arch fixed restoration of maxillary implant-supported prostheses].

OBJECTIVE: To explore the applicability of integration between three-dimensional (3D) facial and dental data to evaluate the nasolabial morphology variation before and after the cross-arch fixed restoration of the maxillary implant-supported prostheses.

METHODS: Twelve patients (4 women and 8 men), mean age (54.82±5.50) years (from 45 to 62 years) referred to the Department of Oral Implan-tology, Peking University School and Hospital of Stomatology, were selected and diagnosed with edentulous maxilla. For all the patients, 4 to 6 implants were inserted into the maxilla. Six months later, the final cross-arch fixed prostheses were delivered. The 3D facial images were collected before and after the final restoration. The 3D data of prostheses were also captured. All the 3D data were registered and measured in the same coordinate system. Then the displacement of all the landmarks [cheilion left (CHL), cheilion right (CHR), crista philtri left (CPHL), crista philtri right (CPHR), labrale supe-rius (LS), subnasale (SN), stomion (STO), upper incisor (UI), upper flange border of the prostheses (F-point, F)], and the variation of the distances between these landmarks (SN-LS, CPHR-CPHL, CHR-CHL, LS-STO) were analyzed and compared.

RESULTS: The consistency test among three measurements of the length of F-SN indicated that the integration method of the dental prostheses and soft tissue had the good repetitiveness, ICC =0.983 (95% CI : 0.957-0.995). After wearing the final cross-arch maxillary implant-supported prostheses, all the landmarks on the soft tissue moved forward. The nasal base area changed minimally, and the shift of SN in the sagittal direction was only (0.61±0.44) mm. But the sagittal shift of LS was (3.12±1.38) mm. In the vertical direction, SN, LS, CPHL, and CPHR moved upward. But STO, CHL, and CHR moved downward a little. Except for the slight decrease of the length of philtrum (SN-LS), the length of CHL-CHR, CPHL-CPHR, and the height of upper lip were increased together ( P < 0.01). In the direction of Z axis, the strong correlations were found not only between the movements of SN and F ( r =0.904 3) but also between the movements of LS and UI ( r =0.958 4).

CONCLUSION: The integration method of 3D facial and dental data showed good repetitiveness. And the strong correlations between the landmarks of prostheses and nasolabial soft tissue in the sagittal direction were found by this new method.