Marginal fit of interim fixed dental prosthesis fabricated with 3D printing and CAD/CAM technology using two finish line designs before and after thermal cycling : (an in-vitro study) /

Abstract

Restorative fabrication techniques (3D printing and milling) is one of the factors which affect the marginal fit of the provisional restorations. 3D printing CAM fabrication technique has gained great popularity in recent years. However, the technique that will be effective for producing tooth supported provisional dental prosthesis with predictable marginal accuracy has minimal scientific evidence. So, the aim of the present study was to compare the influence of CAM techniques, 3D printed and milled interim fixed dental prosthesis on the vertical margin gap using two different finish line designs, before and after thermal cycling. Therefore, in the present study 28 fixed dental prosthesis were designed on CAD software using STL files of scanned models. Restorations were divided into two groups according to fabrication technique: group A (14 3D printed restorations) and group B (14 Milled restorations). Each group was subdivided in half according to finish line design (knife-edge and shoulder). All restorations were cemented with a long-term temporary cement under 3 Kg of load according to manufacturer’s instructions. The stereomicroscope was used to assess the marginal fit of the provisional dental prosthesis on the 3D printed models before thermocycling. Five measurement points were taken from each surface (buccal, lingual, mesial, and distal), with a total of 30 measurements for each FDPs. The samples underwent thermocycling for 5,000 cycles under temperatures of 5 and 55 °C, with dwelling times of 60 seconds and transfer times of 15 seconds. Finally, the marginal fit was measured again after thermocycling and with the aid of an image analysis software, the vertical marginal gap was assessed at these points.