In-vivo-wear in composite and ceramic full mouth rehabilitations over 3 years

The aim of this study was to quantify and to compare the wear rates of premolar (PM) and molar (M) restorations of lithium disilicate ceramic (LS2) and an experimental CAD/CAM polymer (COMP) in cases of complex rehabilitations with changes in vertical dimension of occlusion (VDO). Twelve patients with severe tooth wear underwent prosthetic rehabilitation, restoring the VDO with antagonistic occlusal coverage restorations either out of LS2 (n=6 patients, n=16 posterior restorations/patient; N=96 restorations/year) or COMP (n=6 patients; n=16 posterior restorations/patient; N=96 restorations/year). Data was obtained by digitalization of plaster casts with a laboratory scanner at annual recalls (350 +/- 86 days; 755 +/- 92 days; 1102 +/- 97 days). Each annual recall dataset of premolar and molar restorations (N=192) was overlaid individually with the corresponding baseline dataset using an iterative best-fit method. Mean vertical loss of the occlusal contact areas (OCAs) was calculated for each restoration and recall time. For LS2 restorations, the mean wear rate per month over 1 year was 7.5 +/- 3.4 mu m (PM), 7.8 +/- 2.0 mu m (M), over 2 years 3.8 +/- 1.6 mu m (PM), 4.4 +/- 1.5 mu m (M), over 3 years 2.8 +/- 1.3 mu m (PM), 3.4 +/- 1.7 mu m (M). For COMP restorations, the mean wear rate per month over 1 year was 15.5 +/- 8.9 mu m (PM), 28.5 +/- 20.2 mu m (M), over 2 years 9.2 +/- 5.9 mu m (PM), 16.7 +/- 14.9 mu m (M), over 3 years 8.6 +/- 5.3 mu m (PM), 9.5 +/- 8.0 mu m (M). Three COMP restorations fractured after two years and therefore were not considered in the 3-year results. The wear rates in the LS2 group showed significant differences between premolars and molars restorations (p=0.041; p=0.023; p=0.045). The wear rates in COMP group differed significantly between premolars and molars only in the first two years (p<0.0001; p=0.007). COMP restorations show much higher wear rates compared to LS2. The presented results suggest that with increasing time in situ, the monthly wear rates for both materials decreased over time. On the basis of this limited dataset, both LS2 and COMP restorations show reasonable clinical wear rates after 3 years follow-up. Wear of COMP restorations was higher, however prosthodontic treatment was less invasive. LS2 showed less wear, yet tooth preparation was necessary. Clinicians should balance well between necessary preparation invasiveness and long-term occlusal stability in patients with worn dentitions.