CAD/CAM Fiber Posts Fabricated With Different Scanning Techniques: Laboratory Study

Objectives: The study was aimed at assessing push-out strength and cement layer thickness of luted fiber posts fabricated with CAD/CAM technology following three different scanning techniques: 1) direct scanning of the post space; 2) scanning of a polyether impression of the post space; 3) scanning of a plaster model of the post space.
Methods: In 18 endodontically treated single-rooted premolars an oval-shaped post space was prepared. Roots were randomly assigned to 3 equally sized groups. In Group 1 (Direct Scanning, DS) the post space preparation was sprayed with a scan powder (Powder Scan Spray, Vita) and scanned with inEos 4.2 scanner (Sirona); in Group 2 (Impression Scanning, IS) an impression of the post space was taken with a polyether impression material (Permadyne Garant 2:1, 3M ESPE) and scanned with the same scanner as in Group 1; in Group 3 (Model Scanning, MS) a polyether impression (Permadyne Garant 2:1, 3M ESPE) of the post space was recorded and poured with scannable plaster (Gesso Laser 4, Chemident), thus obtaining a plaster model that was then scanned with the same scanner used in the other groups. Posts were computer-designed using the InLab 3.88 software (Sirona), and milled from experimental fiber-reinforced composite blocks (RTD), using inLab MC-XL CAD/CAM milling unit (Sirona). Posts were luted with the Gradia Core resin cement (GC). Twenty-four hours after luting, the posted roots were transversally sectioned to obtain specimens for push-out testing and microscopic observations of the thickness of the cement layer.
Results: Post push-out strength was measured in MegaPascals, while cement layer thickness was recorded in micrometers. The measured values were statistically analyzed.
Conclusions: Posts fabricated following DS demonstrated the strongest retention and the difference was statistically significant (p<0.001). In MS group the cement layer was significantly thicker (p<0.001). No statistically significant differences among root levels emerged for either assessed variable.