Survival rate of disk and screw-type implants used for the retention of extraoral prostheses

Abstract

Statement of problem: Implant-supported and implant-retained extraoral prostheses are reliable treatment options for patients with craniofacial defects. They provide stable retention and therefore enhance the patient's appearance and quality of life. Despite studies on survival rates of extraoral implants, little attention has been paid to the design of the implants used to support and retain extraoral prostheses.

Purpose: The purpose of this longitudinal clinical study was to assess the long-term survival rate (1 to 12 years, mean 6 years) of 2 different designs of implants (disk: single, double, and triple and screw-type) used for extraoral epithesis anchorage.

Material and methods: Twenty-six participants with orbital and nasal defects, 10 of whom had had radiation treatment, were included in the study. Disk implants and extraoral (EO) screw implants were used and placed in the periorbital (15 participants) and perinasal regions (11 participants). Data were analyzed by using the Chi-square test and the Fisher Exact test for qualitative variables and the Mann-Whitney U test for comparison of quantitative variables. Implant survival rates were calculated by Kaplan-Meier analysis.

Results: The overall 12-year survival rate of all implants was 90.3% (mean=79 months), with 92.9% for nasal (mean=84 months) and 88.2% for orbital (mean=75 months) implants. Related to the implant design, survival rates were as follows: for single-disk implants, 90.2%; for double disks, 94.6%; for triple disks, 88.3%; and for screw implants, 83.3%. In nonradiated participants, the implant survival rate was 97.6%, and for radiated participants, 76.1%.

Conclusions: Survival rates for implant-retained craniofacial prostheses are limited. The nasal site seems to be a more predictable implant site than the orbital site, with a higher overall survival rate. Also, implants inserted in radiated tissues have lower survival rates for both anatomic sites, with statistically significantly lower results in the orbital region. The most reliable type of implant among the disk implants used was the double disk in the orbital site and the single disk in the nasal site, which may indicate the advantages of some designs in specific areas.