Sintering dental porcelain with CO2 laser: porosity and mechanical characterization

Authors

  • Ricardo Sgura Universidade de São Paulo
  • Mariana Cavalcante Reis Universidade de São Paulo
  • Marcello Rubens Barsi Andreeta Universidade de São Paulo
  • Antônio Carlos Hernandes Universidade de São Paulo
  • Igor Studart Medeiros Universidade de São Paulo

DOI:

https://doi.org/10.14295/bds.2013.v16i1.856

Abstract

Aim: This work evaluated dental porcelain sintering by CO2 laser irradiation. Methods: Two commercial veneering porcelains were used: VM7 and VM9 (VITA Zahnfabrik).  Porcelain disks (0.35 mm dia. x 2.0 mm) were sintered by a continuous CO2 laser (Coherent, USA – 35 W e ?= 10.6 ?m) in two irradiances (20 and 23 W/cm2) and exposure times: 5 and 10 min. A control group was sintered in a conventional oven following manufacturer’s instructions. After sintering, one of the disks surfaces was mirror polished. Superficial pores (%) were assessed by images obtained in an optical microscope (100x) submitted to the software Image J analysis. Apparent density was measured by Archimedean’s method. Microhardness and fracture toughness (Indentation Fracture - IF) were determined with a Vickers indenter (Shimadzu). Results: Porosity ranged between 4.0 and 5.9% for irradiated specimens; control group had 6.0 and 4.7% of porosity for porcelain VM7 and VM9 respectively. Density of porcelain VM7 irradiated for 10 min. with irradiance of 23 W/cm2 was significantly higher than control group. Microhardness and fracture toughness of irradiated specimens were similar to control. The measurements of some irradiated groups were not possible to achieve because the tests revealed irregular marks after indentation. Conclusions: Porcelain sintering with CO2 laser in some fluences produced a material with superficial porosity similar to that obtained in conventional oven. Microhardness and fracture toughness could not be measured for all irradiated groups suggesting some subsuperficial defect caused by entrapped gases or cracks originated by temperature gradient along the specimen.

Author Biographies

Ricardo Sgura, Universidade de São Paulo

PhD student

Departamento de Biomateriais e Biologia Oral

Faculdade de Odontologia

Mariana Cavalcante Reis, Universidade de São Paulo

Graduate student

Faculdade de Odontologia

Marcello Rubens Barsi Andreeta, Universidade de São Paulo

PhD

Grupo de Crescimento de Cristais e Materiais Cerâmicos

Instituto de Física de São Carlos

Antônio Carlos Hernandes, Universidade de São Paulo

PhD

Grupo de Crescimento de Cristais e Materiais Cerâmicos

Instituto de Física de São Carlos

Igor Studart Medeiros, Universidade de São Paulo

PhD

Departamento de Biomateriais e Biologia Oral

Faculdade de Odontologia

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Published

2013-03-28

Issue

Section

Clinical or Laboratorial Research Manuscript