Marginal and Internal Gap of Handmade, Milled and 3D Printed Additive Manufactured Patterns for Pressed Lithium Disilicate Onlay Restorations

Statement of the problem: On a pressed lithium disilicate restoration, the budding up of a wax pattern of the future restoration is a necessary step on the fabrication process. Conventionally a wax pattern can be produced by handmade or milled procedures; however; the development of additive manufacturing technologies allows a neoi fabrication method. Purpose: the present study measured the marginal and internal gap of handmade, milled and additive MarlffiaCtored patterns loran onlay reM)raiorl. Material and methods: A preparation of an onlay restoration was made on an extracted mandibular tooth. A definitive cast Was fabricated from a conventional silicone impression of the prepared tooth. Three groups were established: handmade (f/MI, trilled 040 and additive manufactured (AM); 4 specimens per group were obtained. I he marginal and internal gap of each pattern was measured on the extracted molar through a computed tomography test. Sixty measurements were done to measure the marginal gap and another 60 measurements were calculated to analyze the internal gap on each pattern on the prepared tooth. A total of 1.440 measurements were completed. WW1 -Whitney and hirkey statistical tests were used for pair comparison. Results: The mean of the marginal and internal gap was of 67.56 ! 6.08 pm and 50.62. 3.26 pm for the KM group, 85.28 !, 2.17 OM and 96t 1.07 pm for the Mi group and 86.49,! 1.74 pm and 91.86.! 2.88 pin for the AM group. respectively. The KM group presented significantly lower ruarginaf (p,-0.029) and internal (0,-0.029) gap compared to the MI_ and AM groups, There was no statistical significant difference (p=0.466) on the marginal gap between the Mt and the AM groups, but the AM group. showed significantly (p-0.020) smaller internal gap than the Mt group. Conclusions: Ali the groups presented less than 100 pin marginal and internal gap, which is considered clinically acceptable. Clinical implications: [he three fabrication processes are viable options for manufacturing patterns for lithium disilicale onlay restorations. but the best marginal and internal fit was still obtained by the conventional handmade procedures.