Optimizing Resin Sealant Microhardness: The Impact of Curing Distance, Time, and Light-Curing Mode

Abstract

Background: Effective polymerization of resin-based pit and fissure sealants is essential for their clinical success and longevity. One of the most widely used indirect indicators of polymerization efficiency is microhardness, which reflects the material’s mechanical integrity and degree of monomer conversion. Objectives: The current research evaluated the effect of varying irradiance intensities, exposure times, and curing distances using a multi-emission peak Light Emitting Diode (LED) curing device on the microhardness of a resin-based sealant.

Materials and methods: A total of ninety disc-formed samples were constructed utilizing an opaque mold using light-curingopaque-filled sealant (UltraSeal XT plus).The specimens were split into 18 groups (n = 5) based on curing distances (2 mm, 4 mm, and 6 mm), three curing modes [Standard (1000 mW/cm²), High-Power Plus (1400 mW/cm²), and Xtra-Power (3200 mW/cm²)], and two curing durations per mode. Knoop microhardness testing was performedon every sample's top and bottom surfaces.

Results: All main effects (curing setting, distance, and curing period) were statistically significant for both top and bottom surfaces. The extended curing times and reduced distances generally produced higher microhardness values. Notably, while higher irradiance levels improved bottom surface microhardness in some configurations, inconsistent performance was observed at higher intensities over shorter durations. The Standard mode with extended curing time consistently produced superior top surface microhardness.

Conclusions: The microhardness of resin-based sealants was significantly affectedby curing distance, curingperiod, and the light-curing mode.  The extended exposure times and reduced distance improve surface and bottom microhardness.