Marginal and Internal Adaptation of Zirconia Crowns on 3D Printed Model in comparsion to conventional stone Model
Abstract: ABSTRACT Aim & Hypothesis: The aim of this study was to compare the marginal and internal adaptation of final restoration fabricated on 3D-printed models with conventional stone models. The hypothesis was that final restorations fabricated on conventional stone models would have better marginal and internal adaptation than those fabricated on 3D-printed models. Material & Methods: Tooth ... read more#3 in a typodont was prepared for an all-ceramic crown. An impression of the preparation was taken using polyether impression material. An extra-hard dental epoxy resin material was then used to fabricate the master model. After that ten polyether impressions were taken and poured using a dental stone type IV. A Trios Intraoral scanner was used to obtain ten digital impressions. All of the impression files were used to build digital 3D-printed models, which were then printed with a BEGO (Vareso) 3D printer. Ten models were obtained from each group. A lab scanner was used to scan both groups and the designed zirconium crowns. The crowns were milled out using a lab milling machine. The accuracy of the marginal and internal adaptations were measured under a light microscope at 16X magnification using the cement replica technique. The specimen was cut mesio-distally at the center of the marginal ridges, and bucco-palatally on the tip of the mesiopalatal cusp of the abutment tooth. Eight measurements (mesial marginal adaptation, distal marginal adaptation, buccal marginal adaptation, palatal marginal adaptation, mesial marginal ridge, distal marginal ridge, central fossa, and mesiopalatal cusp tip) were conducted on each abutment tooth. The eight measurements were then documented, and an average value for marginal adaptation and for internal adaptation was calculated for each tooth. Results: For both marginal and internal adaptation of zirconium crowns, there was no significant difference between the two groups. The conventional gypsum model group had a lower mean value of marginal and internal discrepancy (45.5 4.4 μm) (68.0 6.8 μm) compared to the 3D-printed model group (46.4 5.2 μm) (73.7 7.1 μm) respectively. The independent-samples t-test did not reveal any significant difference between the conventional and 3D-printed models (p=0.679 for marginal discrepancy and p=0.086 for internal discrepancy). Conclusion: Within the limitations of this study, we can conclude that 3D-printed models are comparable to conventional stone models in terms of the marginal and internal fits of the single-unit final restorations fabricated onto them.
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Posthodontics.
Advisor: Ala Ali.
Committee: Uukio Kudara, Matthew Finkelman, and Vasilliki Tsakalelli.
Keyword: Dentistry.read less