Visible-light curing units: correlation between depth of cure and distance between exit window and resin surface

Area of Science:

• Restorative Dentistry
• Dental Materials Science
• Photopolymerization

Background:

• Proximal dental cavities vary in depth, particularly in posterior teeth.
• Effective polymerization of light-cured dental resins is crucial for restoration longevity.
• The distance between the curing light and the resin surface can influence polymerization depth.

Purpose of the Study:

• To measure the depth of proximal cavities in various posterior teeth.
• To investigate the relationship between irradiation distance and the depth of cure for dental resins.
• To assess the microhardness of polymerized resin at different depths and distances from the light source.

Main Methods:

• Bitewing radiographs were used to measure proximal cavity depths.
• Scrape tests and microhardness measurements evaluated resin cure depth and quality.
• Experiments utilized four different curing units and two restorative resins at varying irradiation distances.

Main Results:

• Proximal cavity depths commonly ranged from 4-7 mm, with 15% exceeding 8 mm in upper molars.
• Depth of cure decreased moderately and linearly with increased irradiation distance.
• A 12 mm irradiation distance reduced the depth of well-cured resin by approximately 1 mm compared to close contact.

Conclusions:

• Cavity depth in posterior teeth can be significant, potentially challenging complete resin polymerization.
• Irradiation distance is a critical factor affecting the depth of cure in dental resins.
• Maintaining close proximity between the curing light and resin surface is recommended for optimal polymerization.