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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 μm (PM), 7.8 ± 2.0 μm (M), over 2 years 3.8 ± 1.6 µm (PM), 4.4 ± 1.5 µm (M), over 3 years 2.8 ± 1.3 µm (PM), 3.4 ± 1.7 µm (M). For COMP restorations, the mean wear rate per month over 1 year was 15.5 ± 8.9 μm (PM), 28.5 ± 20.2 μm (M), over 2 years 9.2 ± 5.9 µm (PM), 16.7 ± 14.9 µm (M), over 3 years 8.6 ± 5.3 µm (PM), 9.5 ± 8.0 µm (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.
Objective: This paper presents a novel digital workflow that expedites and facilitates the manufacturing of high-end full-ceramic restorations based on “Print and Press”-Technology combined with 3D-printed colored 3D-models.
Clinical considerations: Despite ongoing innovations and developments in the digital workflow, the precision, and the final esthetic outcome is still limited compared with conventional press ceramics. The proposed method combines the advantages of digital scan- and design technologies with the proven conventional press-technology to accomplish high-end full-ceramic restorations. The restoration is digitally designed, the data set is 3D-printed in resin that can be burned out, subsequently conventionally embedded and pressed. Final esthetic finishing of the partial restorations is done on a 3D-printed physical colored 3D-model.
Conclusion: The report describes synergetic effects of digital and analog procedures. 3D-printed colored 3D-models can positively support the manufacturing of full ceramic restorations regarding their optical integration. Therefore, the use of 3D-printed colored 3D-models signifies a new innovative technique with many promising application areas.
Clinical significance: The combination of excellent clinical long-term data for pressed ceramic restorations and proven digital processes, like intraoral scanning, design, and additive manufacturing, in the dental field promise an individual workflow for predictability and excellent esthetics.
Popular media now often present 3D printing as a widely employed technology for the production of dental prostheses. This article aims to show, based on factual information, to what extent 3D printing can be used in dental laboratories and dental practices at present. It attempts to present a rational evaluation of todays´ applications of 3D printing technology in the context of dental restorations. In addition, the article discusses future perspectives and examines the ongoing viability of traditional dental laboratory services and manufacturing processes. It also shows which expertise is needed for the digital additive manufacturing of dental restorations.