Bonding Behavior of Conventional PMMA towards Industrial CAD/CAM PMMA and Artificial Resin Teeth for Complete Denture Manufacturing in a Digital Workflow.

Dominik Klaiber,Fabian Huettig,Juergen Geis-Gerstorfer,Sebastian Spintzyk,Alexey Unkovskiy,Andrea Klink

doi:10.3390/ma14143822

Abstract

When applying a digital workflow, custom artificial resin teeth have to be integrated into a milled complete denture base, using polymethylmethacrylate (PMMA) applied with a powder–liquid technique. Debonding of denture teeth from dentures is reported to be a frequent complication. No evidence is provided as to which method of surface treatment may enhance the bonding strength. The bonding strength between artificial teeth and PMMA (Group A, n = 60), as well as between the PMMA and industrial PMMA (Group B, n = 60), was investigated following no treatment, monomer application, sandblasting, oxygen plasma, and nitrogen plasma treatment. Surface-roughness values and SEM images were obtained for each group. Shear bond strength (SBS) and fracture mode were analyzed after thermocycling. Within Group A, statistically significant higher SBS was found for all surface treatments, except for nitrogen plasma. In Group B, only nitrogen plasma showed a statistically lower SBS compared to the reference group which was equivalent to all surface treatments. Conclusions: Within the limitations of the present study, the monomer application can be proposed as the most effective surface-treatment method to bond custom artificial teeth into a milled PMMA denture base, whereas nitrogen plasma impairs the bonding strength.

Highlights

Despite of great strides in prophylaxis and a higher number of remaining teeth in the elderly by 2030 in Germany, the amount of patients in need of complete dentures due to edentulism will keep prevalent in industrialized countries, e.g., with about 1 to 2 million people in Germany during the upcoming decade [1,2]
Denture bases are made from polymethylmethacrylate (PMMA) based on a powder-liquid system, whereas denture teeth are mostly made from micro-filled reinforced polyacrylic or a micro-/nano-filled composite material
The specimens in Group A exhibited a stepwise lines profile for all groups except the sandblasting, whereas, in the Group B, the uniformly rough surface can be observed for all specimens

Summary

Introduction

Despite of great strides in prophylaxis and a higher number of remaining teeth in the elderly by 2030 in Germany, the amount of patients in need of complete dentures due to edentulism will keep prevalent in industrialized countries, e.g., with about 1 to 2 million people in Germany during the upcoming decade [1,2]. A conventional workflow to fabricate a complete denture implies manual and timeconsuming waxing of the base with prefabricated artificial resin teeth, and its transfer into polymerized acrylate. The milling of a denture base using prefabricated acrylic resin blanks was reported to have some clinical advantages over the conventional workflow [8]. Besides aspects in the lab workflow, some industrial polymerized PMMA blanks offer a lower monomer release over time [9,10], but all offer an initially low monomer release. This leads to the same problem of inferior bonding capacity as known from industrial custom resin teeth ( made from PMMA) [11]

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Conclusion