Nanohybrid vs. fine hybrid composite in extended Class II cavities after six years

In a controlled prospective split-mouth study, clinical behavior of two different resin composites in extended Class II cavities was observed over six years.

Thirty patients received 68 direct resin composite restorations (Solobond M + Grandio: n=36; Syntac + Tetric Ceram: n=32) by one dentist in a private practice. All restorations were replacement fillings, 35% of cavities revealed no enamel at the bottom of the proximal box, in 48% of cavities remaining proximal enamel width was <0.5mm. Restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, four, and six years.

Success rate was 100% after six years of clinical service, while the drop out of patients was 0%. Neither materials nor localization of the restoration (upper vs. lower jaw) had a significant influence on clinical outcome in any criterion after six years (p>0.05; Mann-Whitney U-test). Molar restorations performed worse regarding marginal integrity (4 years), filling integrity (6, 12, 24, 48 months), and tooth integrity (4 and 6 years). Irrespective of the resin composite used, significant changes over time were found for all criteria recorded (Friedman test; p<0.05). Marginal quality revealed a major portion of overhangs having been clearly reduced after the one year recall (baseline: 44%; 6 months: 65%; 1 year: 47%; 2 years: 6%; 4 years: 4%; and 6 years: 3%). Beyond the 1 year recall, negative step formations significantly increased due to wear (p<0.05), having been more pronounced in molars (87% bravo after 4 years) than in premolars (51% bravo after 4 years). Tooth integrity significantly deteriorated due to enamel cracks, which increased over time (p<0.05). Enamel chippings and cracks were significantly more frequent in molars (26% bravo after 4 years to 35% after six years) than in premolars (9% bravo after 4 years, 11% after six years). Restoration integrity over time mainly suffered surface roughness and wear (28% after one year, 75% after two years, 84% after four years, 91% after six years).

Both materials performed satisfactorily over the 6-year observation period. Due to the extension of the restorations, wear was clearly visible after six years of clinical service with 91% bravo ratings.