Hygroscopic Expansion Influence on Cuspal Deflection of Tooth Composite Restoration

Introduction: Polymerization shrinkage can result in gap formation between the composite material and tooth structure with subsequent plaque accumulation, which affect the esthetic quality of a restoration and initiate periodontal diseases.

Aim: The aim of this study was to evaluate the effect of hygroscopic expansion on the cusp deflection of tooth composite restoration.

Study Design: Invitro study using human premolars.

Place and Duration of Study: Preventive and operative dental sciences in Alfarabi Dental Sciences, Riydah, KSA between July and September 2017.

Materials and Methods: Eighty (80) human premolars extracted for orthodontic reasons. In each of the extracted premolar mesio- occluso distal cavity (MOD) was prepared and divided into two main groups (40 each) according to the restorative material, each main group randomly divided into two groups according to bonding used (20 each), subdivided into four equal subgroups (5 teeth per each) according to immersion in normal saline, Specimens were stored in saline for four-time interval (immediate, 2, 4 &12) weeks. Cuspal deflection was detected by digital caliper.

Results: There was a significant difference between the last two groups which filled with composite resin while the control teeth showed no significant difference. The cavities which restored with silorane (P90) resin-based composites and bonded with its consensual adhesive recorded the least Cuspal deformations.

Conclusions: Cuspal deformation was decreased by hygroscopic expansion in teeth restored with a hydrophobic resin composite, while a hydrophilic composite restoration shows over-compensated the polymerization shrinkage causing tooth expansion.