Evaluation of Experimental Composite Resin with Trimethylbenzoyl Diphenylphosphine Oxide (TPO) as a Novel Water-Soluble Photoinitiator − An In vitro Study

Background: Composite resin restorations are widely used in dentistry as direct filling restorative materials because of their good physical and mechanical properties, ease of handling, preservation of remaining tooth structure and aesthetics. Aim: The aim of this study is to synthesize composite resin by combining water soluble 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO) photoinitiator (Type I) with camphorquinone (CQ) photoinitiator (Type II) and to investigate its physical properties such as colour stability, surface roughness, polymerisation shrinkage and monomer release, comparing with the 3M™ Filtek™ Z 350 XT Universal Restorative A3 Body shade composite resin containing CQ photoinitiator. Materials & Methods: Cylindrical disc-shaped flat resin specimens were fabricated using metal moulds. Forty samples each from the experimental and 3M™ Filtek™ Z 350 XT Universal Restorative A3 Body shade composite resin group were taken. Group I: Experimental composite ( n = 40). Group II: 3M™ Filtek™ Z 350 XT Universal Restorative A3 Body shade (control group) ( n = 40). Results: When compared to CQ, type I photoinitiator, i.e., Diphenyl (2,4,6 trimethylbenzoyl) phosphine oxide (TPO), showed favourable characteristics such as increased colour stability, decreased surface roughness and decreased monomer release. Conclusion: Combining water-soluble photoinitiator (type I) such as TPO with CQ (type II) provides a synergistic effect by increasing its physical properties, such as colour stability and surface roughness; and decreasing monomer release.