Masticatory Function in Overdentures: a Randomized Clinical Trial With 4-Year Follow-Up Comparing Regular and Extra-Short Implant Retention

Objectives: The long-term masticatory function of patients wearing overdentures (IOD) is not fully understood, requiring further exploration. In this clinical survey, we assessed the masticatory function of patients who wore overdentures for up to 4 years, making a comparison between IOD retained by conventional implants and those retained by a combination of conventional and extra-short implants.
Methods: This randomized clinical trial consisted of 20 complete edentulous (6 men, 14 women) (mean age 69.1 ± 9.6, ranging from 51 to 84 years of age). After receiving new complete dentures (CD), they were randomly assigned to two groups: control (two intraforaminal conventional mandibular implants (4.1 x 8-12 mm) (Tissue Level, Straumann, Switzerland) and experimental (four implants - two intraforaminal conventional implants and two extra-short posterior mandibular implants (4.1 x 4 mm) (Tissue Level, Straumann, Switzerland) (n=10 each). After 4 months, the implants were splinted with a bar, and a new IOD was made with the clip captured intraorally. The upper CD was used during the entire study. Masticatory performance (X₅₀) and swallowing threshold (X₅₀ and number of cycles) were measured by the sieving method. Measurements were taken after adapting to the new CD and at 6, 12, and 48 months of overdenture use. Data were analyzed using repeated measures ANOVA, followed by Sidak’s multiple comparison test (α=0.05).
Results: Four patients were lost (1 deceased, 2 relocated from the city, 1 transitioned to an implant-supported fixed prosthesis) (2 patients per group). Overall, masticatory performance significantly improved after replacing the CD into IOD (P=0.031), regardless of the group (P=0.67). Another improvement was observed after 6 months (P=0.027) for both groups, with no changes in the subsequent follow-up periods (P>0.05). Regarding the swallowing threshold, significant improvements were observed in both X₅₀ (P=0.0001) and number of cycles (P=0.0001) after IOD installation, with no differences between groups (P>0.05).
Conclusions: The masticatory function shows significant improvements following the replacement of a CD by an IOD, especially after 6 months of prosthesis use. The number of implants retaining the IOD appears to have minimal influence on masticatory function.