M. Rosentritt*, M. Behr, C. Kolbeck, R. Lang, G. Handel. .
The fracture of composite facings may result in replacement of a fixed partial denture (FPD) unless a reliable intraoral repair method can be provided. The aim of this in vitro study was to test the fracture strength of an intraoral repair method of a adhesively luted fiber-reinforced composite crown (Connect/BelleGlas, Girrbach). Shear bond strength (SBS) of a composite (Tetric Ceram, Ivoclar) to the fiber-reinforced composite material were determined on 5 samples of each series after 24h and thermal cycling (TC: 6000 thermal cycles [5°C/55°C]) using different mechanical surface treatments (T1-T5). The system providing the most reliable bond strength values (CoJet, Espe) was used as a pre-treatment for the facing repair of 8 premolar crowns. Fracture strengths (Zwick testing maschine;v=1mm/min) of original FPD was determined after thermocycling and mechanical loading (TCML) (O), after first repair and TCML (R1) and second repair and TCML (R2). TCML was performed to simulate a wearing period of 5 years and a wearing period of 2 years after each repair. (6000 thermal cycles [5°C/55°C], 1.2x 106 mastication cycles [50N]= five year wearing period). Median and percentiles (25%/75%) were calculated. Statistical analysis was performed using Mann-Whitney-U- and Kruskal-Wallis-Test (p=0.05). Treatment (T1-T5) SBS [MPa] (after: 24h/TC) Design FPD fracture strength [N] no treatment 15/13 (after TCML simulating median (25%/75%) Diamond 12/18 x years) air abrading (EMS) 20/11 O: original (TCML: 5 years) 1380 (900/2180) air abrading (Hager) 11/25 R1: 1. repair (TCML 2 years) 1660 (1330/1850) air abrading (CoJet) 21/17 R2: 2. repair (TCML 2 years) 2090 (1620/2630) The repair of the FPD with air abrading/silanisation pre-treatment and a light curing composite provides very good fracture strength. Therefore a necessary replacement of the restoration because of intraoral fracture perhaps can be avoided.