Peri-Implant Marginal Bone Loss in Mandibular Full-Arch Rehabilitations: 1-Year Follow-Up

Objectives: This study aimed to clinically access the influence of the number of supporting implants, its connection design and the rehabilitation type on peri-implant marginal bone loss of mandibular full-arch rehabilitations during the first year of loading.
Methods: Completely edentulous participants were enrolled for comparative clinical trial. Maxillary arches were rehabilitated with conventional heat-polymerized dentures and mandibular arches were treated by insertion of 2, 3 or 4 implants, with external or conical implant-abutment connections, supporting overdentures or screw-retained prosthesis. Bone level measurements were recorded through standardized digital X-ray images made after 3 and 12 months of loading. Bone loss around implants for each tested variable was analyzed and compared via one-way ANOVA and Chi-square test. A type one error of <0.05 was accepted as statistical significance.
Results: A total of 106 implants were inserted in 38 consecutive patients (age range: 42-75years) rehabilitated with bar-clip overdentures retained by 2 implants (n=19) or screw-retained prosthesis (n=19) over 3 or 4 implants. After 1-year follow-up 6 immediately loaded implants were lost (5.7%). Mean bone loss around implant ranged from -2.46 to 1.78mm. Implant connection design did not statistically influence bone loss around implants (p=0.743). However, despite bone level remained statistically stable for screw-retained prosthesis (p=0.460), overdentures led to significantly increased bone loss after 1-year evaluation (p=0.002). One-way ANOVA showed that the number of implants beneath the screw-retained prosthesis did not influence the mean bone loss around implants after 1-year follow-up (p=0.919).
Conclusions: Rehabilitations with overdentures supported by 2 implants were associated with increased marginal bone loss around studied implants. Despite screw-retained prosthesis over 3 and 4 implants were more favorable for peri-implant marginal bone maintenance, increasing the number of implants (from 3 to 4) did not allow better results on marginal bone loss. Within treated patients, implant-abutment connection design was not associated with increased marginal bone loss.