Effect of different light-curing devices and aging procedures on composite knoop microhardness

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Composite resins are widely used in restorative dentistry.
• The effectiveness of light-curing devices and aging significantly impacts material properties.
• Micro-hardness is a critical indicator of composite resin's mechanical integrity.

Purpose of the Study:

• To evaluate the impact of different light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS, Plasma Arc/PAC) on composite resin micro-hardness.
• To assess the effects of various aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, and combinations) on micro-hardness.
• To determine the interaction between light-curing methods and aging on the top and bottom surfaces of composite resin cylinders.

Main Methods:

• Knoop micro-hardness testing was performed on 2-mm composite resin cylinders.
• Tests were conducted on both top (T) and bottom (B) surfaces before and after aging.
• Aging protocols included Mechanical Cycling (MC), Thermal Cycling (TC), Storage (S), and combined procedures (MC+TC, MC+TC+S).

Main Results:

• Plasma Arc (PAC) exhibited reduced polymerization effectiveness compared to Halogen (HAL) on both surfaces before aging.
• After Thermal Cycling (TC), PAC and Argon Laser (LAS) showed lower effectiveness than HAL and LED on the top surface.
• Mechanical Cycling + Thermal Cycling + Storage (MC+TC+S) and Storage (S) significantly affected micro-hardness values across all light-curing devices.

Conclusions:

• Plasma Arc (PAC) light-curing may result in composite resins of reduced quality.
• Storage aging procedures were identified as the most detrimental to the polymer hardness.
• The choice of light-curing device and aging conditions are critical factors influencing the long-term performance of dental composites.