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Polymerization depths of contemporary light-curing units using microhardness.
F A Rueggeberg1, J W Ergle, D J Mettenburg
1Dental Materials Section, Department of Oral Rehabilitation, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USA. frueggeb@mail.mcg.edu
Journal of Esthetic Dentistry
|January 28, 2004
Summary
New light-curing technologies offer faster composite curing times, but depth of cure remains limited. High-intensity units and lasers can reduce exposure, yet composite increments should not exceed 2 mm for optimal hardness.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Dental composites require adequate light curing for optimal physical properties and longevity.
- Various light-curing units (LCUs) and protocols exist, influencing the depth of cure.
- Understanding the efficacy of different LCUs is crucial for predictable clinical outcomes.
Purpose of the Study:
- To investigate the depth of cure of dental composites using diverse light-curing units and exposure protocols.
- To compare the Knoop hardness of cured composite at various depths.
- To establish the effectiveness of conventional and novel curing methods.
Main Methods:
- Composite samples (Herculite XRV, A2) were cured using conventional quartz tungsten halogen (QTH), soft-start, high-intensity QTH, plasma arc (PAC), and argon laser units.
- Cured samples were sectioned, and Knoop hardness was measured incrementally from the surface.
- Hardness values were statistically compared to a standard 40-second conventional QTH exposure.
Main Results:
- Conventional QTH lights showed similar hardness profiles, with no significant difference at 2 mm.
- Soft-start techniques yielded hardness comparable to conventional methods at 2 mm.
- High-intensity QTH and argon laser achieved equivalent hardness at 2 mm with reduced exposure times (10s and 5s, respectively).
- Plasma arc curing required at least 10 seconds for comparable hardness.
- Depth of cure generally did not exceed 2 mm across most tested scenarios.
Conclusions:
- Conventional QTH units with varying tip diameters exhibit similar curing characteristics.
- Soft-start techniques are effective when used per manufacturer guidelines.
- High-intensity QTH and argon laser units can shorten curing times effectively.
- Plasma arc curing requires a minimum 10-second exposure for adequate results.
- Regardless of LCU, composite increments should be limited to 2 mm for uniform hardness.