Neuroplasticity in the Adaptation to Prosthodontic Treatment

Aims: To investigate cerebral cortical changes by using functional magnetic resonance imaging (fMRI) after denture renewal and to test how these relate to prosthodontic treatment adaptability as measured by chewing efficiency and maximum bite force. Methods: Ten complete denture wearers (five women and five men, mean age ± standard deviation: 70.3 ± 9.1 years) participated in the study. Each had their complete dentures renewed and underwent an fMRI examination with three functional tasks (lip pursing; jaw tapping; jaw clenching) as well as a color-mixing test for chewing efficiency and unilateral maximum bite force measurements. Recordings were performed with the old dentures (T0) and with the new dentures on insertion (T1) and at 1 week (T2) and 3 months postinsertion (T3). At T1, denture stability and retention (S/T) were assessed by two independent operators. Wilcoxon signed rank tests and Spearman's rho correlation were carried out for data analysis. Results: The right and the left precentral gyrus (PRCG) and postcentral gyrus (POCG) were identified with significant activation across all three functional tasks. A statistically significant increase in the level of activity between T0 and T2 (POCG: P = .022; PRCG: P = .017) was found during jaw clenching tasks. Both regions of interest (PRCG, POCG) appeared to correlate with S/T of the new dentures while the subject performed a lip-pursing task (PRCG: r = 0.689, P = .027; POCG: r = 0.665, P = .036). The chewing efficiency and maximum bite force increased significantly during the adaptation to replacement dentures (chewing efficiency: T1-T2 P = .032, T2-T3 P = .012; maximum bite force right side: T2-T3 P = .047). Conclusion: Changes in brain activity occurred in the adaptation to replacement dentures and appeared to regain preinsertion activity levels during motor tasks involving the dental occlusion after 3 months postinsertion. Keywords: bite force, chewing efficiency, complete denture, fMRI, neuroplasticity