Avaliação clínica do efeito da distribuição dos implantes na retenção e estabilidade de overdentures mandibulares retida por 4 mini-implantes

Abstract

Retention and stability are essential determinants for the clinical performance and satisfaction of users of implant-retained mandibular overdentures. Despite advances in the use of mini-implants, gaps remain regarding the influence of the geometric distribution of these implants on long-term clinical and biomechanical outcomes. Thus, the aim of this study was to evaluate the influence of mini-implant distribution on the retention and stability of mandibular overdentures retained by four mini-implants after four years of follow-up. This is an observational study, derived from a previous randomized clinical trial. Thirty-one edentulous patients rehabilitated with mandibular overdentures retained by four mini-implants were evaluated and classified into groups with favorable and unfavorable polygonal distribution based on three-dimensional tomographic analysis. The variables analyzed included geometric and biomechanical parameters, frequency and time of replacement of retentive matrices, clinical stability of the prosthesis, retention force, bite force until displacement, and patients' subjective perception of retention and stability of the overdenture. Data were analyzed using descriptive and inferential statistics, with normality tests, parametric or non-parametric bivariate comparisons, correlation analysis, internal consistency assessment, and cluster analysis (k-means), adopting a significance level of 5% (α = 0.05). Unfavorable polygonal distributions were associated with a higher incidence of replacements of retentive matrices and a shorter time of use of the last installed matrix (p < 0.05). In addition, patients in this group reported a greater perception of instability and displacement of the overdenture. No significant differences were observed between the groups regarding clinical stability tests, retention force, and bite force until displacement. It is concluded that patients' subjective perception of retention and stability, and the need for matrix replacement in mandibular overdentures retained by four mini-implants, are more strongly associated with the geometric distribution of the implants than with the isolated magnitude of the retentive force, highlighting the importance of adequate biomechanical planning for long-term clinical success