Objectives: To investigate clinically the differences in proximal contact strengths of Class II posterior composite resin restorations (PCR's) placed with three different techniques.

Methods: 86 Patients (61 female, 25 male) from two dental practices volunteered after informed consent. Patients were randomly assigned to one of three groups: Group 1) Pre-wedging + Tofflemire (Produits Dentaire SA) + 1001c matrix (Hawe Neos), including pressure by hand-instrument during polymerization, Group 2) Pre-wedging + Palodent sectional matrix + Bi-Tine separation ring (Dentsply), Group 3) Pre-wedging + Contact Matrix System sectional matrix + separation ring (Danville Materials). Proximal contact strength (PCS) was measured in Newton using a modified Tooth Pressure Meter as described by Dšrfer et al. (2000) directly before (PCSB) and after (PCSA) restoration placement. Data were statistically analyzed using ANOVA at p=0.05 using Bonferroni correction for multiple testing.

Results: Differences in PCS (PCSA-PCSB) were observerd between the three techniques. The Tofflemire system produced statistically significant larger PCS reduction compared to the Palodent system (p<0.01).

	PCSA-PCSB (N)	95% CI	Contact Matrix	Tofflemire
Palodent	0.54	[-1.062; 2.14]	p= 0.36	p< 0.01
Contact Matrix	-0.73	[-2.294; 0.84]		p= 0.21
Tofflemire	-2.17	[-3.364; -0.98]

Conclusion: Class II posterior composite resin restorations inserted using a sectional matrix system combined with separation rings demonstrated the strongest proximal contacts compared to the circumferential matrix system. This study was supported by Danville Materials, San Ramon, CA and Dentsply Caulk, Milford, DE.