Survival of root canal-treated teeth adjacent to an implant: A retrospective case-control study.

OBJECTIVES: To evaluate the survival of root canal treated (RCT) teeth adjacent to an implant compared with that of RCT teeth of the same patient non-adjacent to an implant. MATERIALS AND METHODS: RCT tooth of each patient adjacent to an implant were included in the test group. The control group consisted of another RCT tooth of the same patient; the control RCT tooth was not adjacent to an implant and selected to be of the same type of the RCT tooth in the test group. 72 teeth of 36 patients with at least 4-year follow-up were included. In addition to survival, other clinical and demographic parameters investigated were age, sex, tooth type and position, presence of a crown, presence of retreatment, presence of a post-core, presence of adjacent edentulous area, presence of implant-supported fixed prosthetic restoration on the antagonist tooth and periapical health status. Pearson Chi-Square and Fisher Exact tests were used to compare the test and the control groups with categorical variables (α=0.05). Survival curves were obtained by the Kaplan-Meier method, and the Log-rank test was performed to compare the survival probabilities (α=0.05). RESULTS: No significant difference in survival rates was observed between the test and the control groups (p = 0.72). Similarly, no significant relationship was found between the investigated clinical variables and the survival rates of RCT teeth (p>0.05). Survival times differed depending on the presence of an adjacent edentulous area (p<0.001) and the periapical health status (p = 0.026). CONCLUSIONS: RCT teeth with unhealed periapical tissues had a shorter cumulative survival time. Similarly, those adjacent to an edentulous area had shorter cumulative and complication-free survival times. CLINICAL SIGNIFICANCE: This is the first study to determine the survival outcome of a RCT tooth adjacent to an implant compared to a non-adjacent one in the same patient. Being adjacent to an implant did not have a detrimental effect on the survival time and rate of RCT teeth.

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 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; however, 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 definitive 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 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. 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 a considered clinically acceptable. CLINICAL IMPLICATIONS: The three fabrication processes are viable option for manufacturing patterns for lithium disilicate onlay restorations, but the best marginal and internal fit was still obtained by the conventional handmade procedures.

3D Metal Printing - Additive Manufacturing Technologies for Frameworks of Implant-Borne Fixed Dental Prosthesis.

An edentulous patient was rehabilitated with maxillary metal-ceramic and mandibular metal-resin implant-supported fixed dental prosthesis (FDP). Metal frameworks of the FDPs were fabricated using 3D additive manufacturing technologies utilizing selective laser melting (SLM) and electron beam melting (EBM) processes. Both SLM and EBM technologies were employed in combination with computer numerical control (CNC) post-machining at the implant interface. This report highlights the technical and clinical protocol for fabrication of FDPs using SLM and EBM additive technologies.