Evaluation and Comparison of Marginal Fit and Internal Fit of Cast Titanium and Machine Milled Titanium Retainers in 3 Unit Fixed Partial Denture – An In-Vitro Study

Abstract

Aim - To evaluate and compare the marginal fit and internal fit of titanium retainers fabricated by casting method and CAD/CAM method in 3 unit FPDs.

Materials and Method - Tooth preparation is done in 44 and 46 with 45 as a pontic in a typodont model. Impressions of the prepared teeth were taken using medium viscosity and soft putty material using one stage impression technique and 30 sets of Type IV gypsum stone dies were prepared. The casts were divided into 2 groups and 15 cast titanium and machine milled titanium fixed partial dentures were fabricated.  The replica technique is used to replicate the intaglio surface of the retainers. The Samples are sectioned and observed in a FESEM and axial, occlusal and marginal gaps were recorded.

Results - The following results were obtained: 1. The Cast Titanium Samples had a better marginal accuracy/fit than the CAD/CAM titanium samples in both the premolar and molar regions. 2. The CAD/CAM Titanium samples had a better axial (mesial and distal) fit than the Cast titanium samples in the molar samples. 3. There was no significant difference in the axial fit (mesial and distal) between the CAD/CAM and Cast titanium samples in the premolar samples. 4. The occlusal fit of the Cast titanium samples was better than the CAD/CAM samples and the occlusal discrepancies were always higher than the axial and the marginal discrepancies.

Conclusion - There is significant difference in the marginal and internal fit between the Cast and CAD/CAM group of molar retainers. There is no significant difference in the fit when comparing the axial fit of the premolar group of both Cast and CAD/CAM titanium premolar retainers, but significant difference can be noted in the marginal fit and the occlusal fit of the Cast and CAD/CAM titanium pre molar retainers.