Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually

Statement of problem. Interim restorations represent an essential treatment step; however, the optimal resin material for long-term interim restorations requires investigation. Purpose. The purpose of this in vitro study was to compare the color stability, water sorption, wear resistance, surface hardness, fracture resistance, and microleakage of computer-aided design/computer-aided manufacturing-(CAD/CAM) fabricated interim restorations with those of manually fabricated interim restorations. Material and methods. Epoxy replicas were made from a prepared maxillary first premolar. On the replicas, interim crowns were fabricated and divided into the following groups: CAD/CAM poly(methyl methacrylate) (PMMA) blocks (CC), autopolymerizing temporary resin (AP), automix temporary resin (AM), and thermoplastic resin (TP). After cementation, all specimens were subjected to thermocycling and dynamic fatigue. The CIE Laboratory color coordinates were then recorded before and after immersion in coffee, tea, carbonated cola, and red wine. Water sorption was evaluated by using an immersion technique. Wear resistance was measured in a surface abrasion device. Vickers microhardness was measured on polished specimens. Fracture resistance was evaluated by axial loading with a universal testing machine. Marginal dye penetration was evaluated by sectioning the interim restorations after immersion in methylene blue (alpha=.05). Results. Colorimetric analysis revealed a large degree of color alteration (SE) in the manually fabricated interim restorations: AP = Delta E of 6.7 +/- 2); AM = Delta E of 7.1 +/- 1.5), and TP = Delta E of =5.4 +/- 3.1. The CC group demonstrated color stability (Delta E=2.1 +/- 0.2). CAD/CAM interim restorations demonstrated significantly lower water sorption, higher wear resistance, higher surface hardness, and significantly higher fracture resistance (1 289 +/- 56N) compared with manually fabricated interim restorations (AP=996 +/- 45, AM=899 +/- 37, and TP=1179 +/- 41). The stereomicroscopic examination of sectioned specimens demonstrated the absence of dye penetration in all tested specimens. Conclusions. CAD/CAM interim crowns presented stable physical and mechanical properties and may be used for long-term interim restorations.