European Journal of Prosthodontics and Restorative Dentistry (2018) 26, 31–38 ejprd.org - Published by Dennis Barber Journals. Copyright ©2018 by Dennis Barber Ltd. All rights reserved. •••••••••••••••••••••••••••••••• EJPRD Marginal and Internal Gap of Handmade, Milled and 3D Printed Additive Manufactured Patterns for Pressed Lithium Disilicate Onlay Restorations ABSTRACT Statement of the problem: On a pressed lithium disilicate restoration, the building 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; how- ever, the development of additive manufacturing technologies allows a new fabrication method. Purpose: The present study measured the marginal and internal gap of handmade, milled and additive manufactured patterns for an onlay restoration. Material and methods: A preparation of an onlay restoration was made on an extracted mandibular tooth. A de- finitive cast was fabricated from a conventional silicone impression of the prepared tooth. Three groups were established: handmade (HM), milled (ML) and additive manufactured (AM); 4 specimens per group were obtained. The marginal and internal gap of each pat- tern 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. Mann-Whitney and Turkey statistical tests were used for pairwise comparison. Results: The mean of the marginal and internal gap was of 67.56 ± 6.08 μm and 80.62 ± 3.26 μm for the HM group, 85.28 ± 2.17 μm and 96 ± 1.97 μm for the ML group and 86.49 ± 1.74 μm and 91.86 ± 2.88 μm for the AM group, respectively. The HM group presented significantly lower marginal (p=0.029) and internal (p=0.029) gap compared to the ML and AM groups. There was no statistical significant difference (p=0.486) on the marginal gap between the ML and the AM groups, but the AM group, showed significantly (p=0.029) smaller internal gap than the ML group. Conclusions: All the groups presented less than 100 μm marginal and internal gap, which is considered clini- cally acceptable. Clinical implications: The three fabrication processes are viable options for manufacturing patterns for lithium disilicate onlay restorations, but the best marginal and internal fit was still obtained by the conventional handmade procedures. INTRODUCTION Since 1882, when Herbst introduced the frst ceramic inlays, and thanks to improvements in all-ceramic materials characteristics, adhesion tech- niques and fabrication technologies, this kind of conservative restoration is an acceptable alternative for large cavities. 1-12 In 2006, a pressed lithium di- silicate glass-ceramic LDGC (IPS Emax.Press, Ivoclar Vivadent) was introduced. Keywords 3D Printing Stereolithography Additive Manufacturing Technologies Lithium Disilicate Pressed Onlay Restorations Multijet Technology Authors Dr. Marta Revilla-León * ‡ (DDS, HSD) Dr. Marina Olea-Vielba ‡ (DDS, MS) Dr. Ana Esteso-Saiz ‡ (DDS, MS) Iñaki Martínez-Klemm ‡ (RDT) Mutlu Özcan § (DDS, DMD, PhD) Address for Correspondence Prof. Marta Revilla León * Email: revilla@revillaresearchcenter.com * Assistant Faculty and Assistant Program Director of Aegd Program, General Dentistry Department, College of Dentistry, Texas A&M University ‡ Revilla Research Center § University of Zürich Received: 07.06.2017 Accepted: 27.11.2017 doi: 10.1922/EJPRD_01733RevillaLeon08