Effect of dynamic fatigue loading on the adaptation and retention of maxillary single dentures reinforced with digitally constructed zirconia and cobalt-chromium frameworks.

Abstract

Background: The impact of dynamic fatigue loading on denture adaptation and retention is clinically important. Zirconia and cobalt-chromium (Co-Cr) frameworks enhance denture strength, but their performance under cyclic loading remains unclear.

Objectives: The aim of the study was to evaluate the adaptation and retention of maxillary single dentures reinforced with digitally constructed Co-Cr or zirconia frameworks after a simulated 1 year of function.

Material and methods: Three types of maxillary single dentures were constructed on maxillary master casts. Group A included maxillary dentures without reinforcement (control group), whereas groups B and C encompassed maxillary dentures reinforced with digitally designed and milled Co-Cr and zirconia frameworks, respectively (n = 13/group). Acrylic resin was conventionally processed on stone casts. Initial adaptation was evaluated for each denture using Geomagic software, which allowed for accurate matching and superimposition of the scanned master cast with the standard tessellation language (STL) file of the scanned fitting denture surface obtained with the use of a desktop scanner. Initial retention was evaluated using a universal testing machine. Dynamic fatigue loading of 50 N at a speed of 60 mm/s was applied in the chewing simulator, after which final adaptation and retention values were recorded. Paired t-tests were conducted to compare results within each group, and one-way analysis of variance (ANOVA) was performed to compare the 3 groups. When ANOVA revealed significant differences, Tukey's honestly significant difference (HSD) test was used for post hoc pairwise comparisons. The significance level was set at p ≤ 0.05.

Results: Group C showed the most favorable adaptation after dynamic fatigue loading (0.31 ±0.04 mm), while group B exhibited the least favorable adaptation (0.61 ±0.08 mm). Regarding retention, group C demonstrated the highest values (20.04 ±0.96 N), while group B exhibited the lowest values (9.32 ±0.78 N). Significant differences were observed among the 3 groups for both adaptation and retention.

Conclusions: Maxillary single dentures reinforced with zirconia frameworks may represent a successful alternative to Co-Cr frameworks for prosthetic rehabilitation using digital technology.