Evaluation of Hardness and Fracture Toughness of Feldspathic Porcelain by Various Surface Finishing Techniques

Abstract

Introduction: Dental porcelain is fired at a high temperature inside the furnace and subsequently glazed for intraoral use as a restoration. There is no clarity on the correlation between physical properties of porcelain and its surface finishing techniques. Aim: To evaluate surface hardness and fracture toughness of feldspathic porcelain with different porcelain surface finishing methods. Materials and Methods: This in-vitro descriptive study was conducted between November 2018 to August 2019 at Department of Prosthodontics, Ragas Dental College and Hospital, Tamil Nadu, India, with 40 samples of Nickel Chrome (NiCr) alloy specimens, with addition of porcelain. The sample were divided into four groups S1: Unpolished, S2: Polished, S3: Autoglazed, S4: Add-on glaze according to the finishing procedures used with each group containing 10 samples. All samples were tested for surface hardness and Fracture toughness and were subjected to One-way Analysis of Variance (ANOVA), Bonferroni posthoc tests and Statistical Package of the Social Sciences (SPSS) California, USA. Results: Mean value of fracture toughness (in MPa1/2) for 0.2 kg load was 0.729672 for S1, 1.187567 for S2, 0.89482 for S3, 1.324399 for S4. Mean value of surface hardness (in kg/mm2) for 1 kg load was 360.048 for S1, 519.166 for S2, 508.817 for S3, 527.916 for S4. Maximum deviation of 24.752 and error of 7.8273 was found in S4, least deviation of 10.7760 and error of 3.4077 was found in S1 group. Conclusion: The glazed porcelain had the highest micro hardness and fracture toughness followed by polished porcelain and autoglazed porcelain.

Keywords

• dental casting technique
• dental polishing
• dental porcelain
• hardness test
• porcelain metal alloys