Ex Vivo Assessment of Natural Teeth Wear against Zirconia and Novel Glass-Fiber-Reinforced Composite Crowns in Primary Teeth by a Three-Dimensional Assessment Method

Abstract

Objectives. The main purpose of the study was to assess the material wear, antagonistic natural primary teeth wear, and microhardness of zirconia (ZR), a recently launched novel glass-fiber-reinforced composite crown (GFRC). The research question was, are these aesthetic crowns resulting in antagonistic natural primary tooth wear and the crown material itself? Methods. Forty-five primary canines were divided into three groups (15 per group) and mounted against Zr (Group A), GFRC (Group B), and natural teeth as control (Group C) in the wear test machine. All samples were assessed for surface wear with pre- and post-3-dimensional scanning. In addition, microhardness was assessed for all three groups. Results. The mean microhardness value for the Zr disc was 1157 ± 7 HV; for the GFRC disc, it was 29.35 ± 2 HV; while with natural teeth, it was 105 ± 4 HV. There was a statistically significant difference in teeth wear in the prescan and postscan in the natural tooth ( $p<0.05$ ) group, highly significant difference ( $p<0.001$ ) in the ZR group, and no significant difference in the GFRC group. Conclusion. There is more significant wear loss of glass-fiber-reinforced composite discs as compared to zirconia. In addition, the wear of the antagonistic tooth with zirconia and natural teeth is more remarkable than with GFRC. There is a vast difference of microhardness between natural teeth and zirconia (almost 10 times higher) which suggests further scope of study. Clinical Relevance. Pediatric dentistry deals with the transition of dentition from primary to permanent through mixed dentition. Selection of restorative material needs to be done cautiously when we are dealing with primary teeth and young permanent teeth as antagonistic teeth. Wear of the crown material itself and opposing natural teeth are essential factors that should be considered in selecting crowns in clinical practice. The present study results can be extrapolated to clinical practice, and the practitioner can consider various factors in selecting full-coverage crowns for primary teeth. The vast difference in aesthetic crowns and natural teeth microhardness indicates a further need for research. Additionally, there is no literature published for the recently launched GFRCs.