Influence of chewing load on wear rate of polymethyl methacrylate double cross-linked...

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Purpose of the Study: Compare occlusal wear of PMMA DCL denture teeth under two different loads in vitro. Materials & Methods: Sixteen mandibular second premolars (SR Orthoplane DCL) with a flat occlusal surface (specimens) were worn by sixteen maxillary second premolar-antagonists (Ortholingual DCL). These teeth were subjected in a chewing simulator (CS-4, SD Mechatronik) up to 240,000 loading cylces at 19.6N (LL ≈ full denture) and 68.6N (HL ≈ implant-overdenture) and TC (2,222 x 5 °C-55 °C). Replicas of mandibular teeth were obtained at 0, 10,000; 20,000; 40,000; up to 240,000 cycles with polyvinyl-siloxane impressions and dental stone. Antagonist-replicas were made at baseline and at 240,000 cycles. The volumetric wear was determined with Geomagic after scanning replicas with a laser scanner. Linear regressions and ANOVA were used for statistical analysis. Results: The wear rate of the HL-specimens was significantly higher than that of the LL-group (p<0.0001). The LL-wear rate became linear after 60,000 cycles and was calculated to be 0.182 x 10 -6 mm3/stroke. The HL-wear rate was linear from 20,000 to 140,000 cycles and was 1.056 x 10 -6 mm3/stroke, then up to 240,000 cycles 0.656 x 10 -6 mm3/stroke. At 240,000 cycles the HL-group showed significantly higher antagonist-wear (p< 0.0001). The antagonists in both groups demonstrated higher wear than their opposing specimens (p<0.08). Conclusions: HL generated significantly higher wear of both the specimens and the antagonists. The antagonists showed higher wear than the specimens. As a clinical consequence one may expect more wear of denture teeth in implant supported overdentures than in full dentures. Keywords: wear, denture, PMMA, cross linked, in vitro.

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