Effect of layer thickness on the flexural strength of multiple-unit laser-sintered metal frameworks.

Necati Kaleli, Yurdanur Uçar, Orhun Ekren, Çağrı Ural

Journal: The Journal of prosthetic dentistry 2022;127(4):651-658

PMID: 33640087

Full Text on Elsevier Science View on PubMed

Abstract

STATEMENT OF PROBLEM

Laser sintering devices have been increasingly used to fabricate the metal frameworks of metal-ceramic restorations. In the fabrication process, the sintering layer thickness is an important parameter; however, information on how it may affect the flexural strength of metal frameworks remains limited.

PURPOSE

The purpose of this in vitro study was to evaluate the flexural strength of 3-unit and 4-unit cobalt-chromium (Co-Cr) metal frameworks laser sintered with 20-μm, 30-μm, and 40-μm layer thicknesses.

MATERIAL AND METHODS

Three-unit and 4-unit master metal die models with premolar and molar abutments were prepared through direct metal laser sintering (DMLS). A total of 40 metal frameworks (n=10 for each metal die model) were fabricated by the lost-wax technique (group C, served as the control group) and through DMLS with 20-μm, 30-μm, and 40-μm layer thickness (experimental groups LS20, LS30, and LS40, respectively). Each metal framework was cemented to a master die with a polyvinyl siloxane impression material and then subjected to a 3-point bend test at a crosshead speed of 1 mm/min. The yield force of each metal framework was used to calculate the flexural strength. Data were statistically analyzed by using 1-way ANOVA followed by a Tukey honestly significant difference (HSD) test and an independent-samples t test (α=.05) The microstructure of the fracture surface was evaluated by scanning electron microscopy.

RESULTS

Group C reported the lowest mean flexural strength (P<.05), whereas group LS20 reported the highest mean flexural strength, although no significant difference (P>.05) in flexural strength was observed among the DMLS groups. The 3-unit metal frameworks exhibited a statistically significant higher mean flexural strength than the 4-unit metal frameworks (P<.05).

CONCLUSIONS

The sintering layer thickness did not significantly affect the flexural strength of the laser-sintered metal frameworks. However, the DMLS groups reported a higher mean flexural strength than the cast group.

Address: Assistant Professor, Department of Dentistry Services, Vocational School of Health Services, Ondokuz Mayıs University, Samsun, Turkey. Electronic address: [email protected].; Professor, Department of Prosthodontics, Faculty of Dentistry, Çukurova University, Adana, Turkey.; Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Çukurova University, Adana, Turkey.; Professor, Department of Prosthodontics, Faculty of Dentistry, Ondokuz University, Samsun, Turkey.

DOI: 10.1016/j.prosdent.2020.10.006