title: Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins.
abstract: BACKGROUND
  Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin.
  
  
  METHODS
  Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM).
  
  
  RESULTS
  In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001).
  
  
  CONCLUSIONS
  Triad VLC resin can be polymerized by argon ion laser with 1 W/mm(2) power and exposure time of 8 min to satisfy ADA specification. Impact strength, surface hardness of laser cure was better than light cure and heat cure resin. Flexural strength of light cure was better than laser cure and heat cure resin. The SEM study showed similar density on surface, the fractured surface of heat cure resin was dense and compact.
authors.affiliation: Professor, Department of Prosthodontics, AJ Institute of Dental Science, Mangalore, Karnataka, India.
authors.forename: S Srinivasa
authors.initials: SS
authors.lastname: Murthy
authors.affiliation: Reader, Department of Pedodontics, Dayanand College of Dental Science, Bengaluru, Karnataka, India.
authors.forename: Gargi S
authors.initials: GS
authors.lastname: Murthy
keywords: Argon ion laser; denture base resin; flexural strength; hardness; impact strength; laser; light polymerization; scanning electron microscope study; visible light cure resin