17 November 2023

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Evaluation of wear resistance opposing zirconia: 3D printed vs. prefabricated denture teeth Introduction

Lorenzo Breschi

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Zirconia (ZrO2) is currently one of the most used and promising restorative materials in dentistry due to its excellent mechanical properties, good biocompatibility and satisfying aesthetic properties. However, due to its high strength and hardness, a variable degree of wear of restorative materials can be observed when present in the antagonist arch to zirconia restorations during occlusion. 

The wear of dental materials is a complex process and, ideally, it should match that of natural enamel. In this respect, prefabricated acrylic resin denture teeth demonstrated a more biomimetic wear pattern compared to ceramic denture teeth, even though they still need to be improved. Some attempts have been made to enhance their wear properties by incorporating various cross-linking agents and organic and inorganic fillers. Additionally, the recent introduction of three-dimensional (3D) printed resin has opened up new possibilities.

In this regard, Pham et al. have conducted an in vitro study to evaluate the wear resistance of a recently developed 3D printed denture teeth resin compared to three commercially available prefabricated denture teeth when opposed to zirconia.

Materials and methods

The study involved the evaluation of 88 maxillary first molar denture teeth, divided into four groups: C (n=24; Classic; Dentsply Sirona, York, PA), DCL (n=20; SR Postaris DCL; Ivoclar Vivadent, Schaan, Liechtenstein), IPN (n=20; Portrait IPN; Dentsply Sirona, York, PA) and F (n=24; Denture Teeth A2 Resin 1 L; Formlabs, Somerville, MA). Groups C, DCL and IPN were commercially available prefabricated denture teeth, while group F consisted of 3D printed denture tooth specimens fabricated from a methacrylate-based photopolymerizing resin using stereolithography (SLA).

All denture teeth specimens were subjected to a three-body wear simulation with a PMMA abrasive slurry. The in vitro wear test was conducted with a four station Leinfelder-style apparatus with monolithic zirconia antagonist bullet-shaped styli. A load force of 36–40 N at 1.7 Hz was applied for 200,000 cycles. The maximum depth of wear was measured using a lab grade scanner, accurate to 7 μm, and analyzed with a software program. Data underwent statistical analysis (p<0.001).

Results

The one-way ANOVA revealed that different denture tooth materials significantly influenced the depth of wear (p<0.001). Notably, the mean vertical depth of wear for the 3D printed denture teeth (0.016 ± 0.010 mm) was statistically less than the prefabricated denture teeth (p<0.001) Furthermore, the highly cross-linked denture teeth, DCL (0.036 ± 0.011 mm) and IPN (0.035 ± 0.014 mm), exhibited a significantly higher wear resistance compared with the conventional acrylic denture teeth (0.058 ± 0.014 mm) (p<0.001), while no significant difference in depth of wear was observed between DCL and IPN (p>0.001).

Conclusion

Within the limitations of this in vitro study, the authors concluded that denture tooth material significantly influences the depth of wear when opposed to zirconia. Specifically, the 3D printed denture teeth displayed superior wear resistance in comparison to the commercially available prefabricated denture teeth.

For more information: Pham DM, Gonzalez MD, Ontiveros JC, Kasper FK, Frey GN, Belles DM. Wear Resistance of 3D Printed and Prefabricated Denture Teeth Opposing Zirconia. J Prosthodont. 2021 Dec;30(9):804-810.