Impact of mandibular overdentures on maxillary resorption and its association with masticatory function: A prospective longitudinal study with 3 years of follow-up.

Objective: This longitudinal clinical study monitored annually the maxillary and mandibular bone remodeling and masticatory function in complete denture (CD) wearers rehabilitated with implant-retained mandibular overdentures (MO) over three years and combined radiographic and masticatory function data to assess the correlation between bone remodeling and masticatory function.

Design: Thirty-nine MO wearers were monitored annually to assess changes in: i) residual ridge in the anterior and posterior maxillary region; ii) posterior height and posterior area index (PAI) in the mandible; and iii) masticatory function. Bone remodeling was measured through linear and angular measurements using panoramic radiographs. Masticatory function was evaluated by swallowing threshold test, to determine the median particle size (X50) and homogenization index (B). A mixed-effects multilevel regression model estimated differences between radiological and masticatory parameters over time, with associations verified using Pearson's correlation test.

Results: Significant changes in mandibular bone variables (PAI and L1/R1, L2/R2, L3/R3; p ≤ 0.01) occurred when transitioning from CD to MO, showing a reduction in PAI values and slight reduction in mandibular linear measurements. Improvements in masticatory parameters were also observed, highlighting the benefits of transitioning to MO. Over three years of MO usage, significant changes in all radiographic bone parameters were found, with increased PAI and maxillary bone values in the first year. The correlations between masticatory function and radiological parameters indicated that mandibular morphology can significantly influence masticatory function especially in patients wearing CDs. Following the transition to MO, only one consistent significant correlation was observed between X50 and R3/L3 at the 1-year and 3-year intervals.

Conclusion: Continuous changes in bone parameters were observed in MO wearers, with stabilization of maxillary ridge resorption and ongoing mandibular remodeling, alongside slight changes in masticatory function, suggesting transitory correlations between linear changes in the posterior region of mandible and masticatory function over time.