Reactive changes in dental tissues in response to curing light exposure: An experimental study

BACKGROUND: The use of curing lamps has considerably improved the quality of dental treatment. Curing light exposure protocols are primarily based on the effectiveness (completeness) of cure. The risk of heat impact on the dental pulp and surrounding tissues is a downside of curing light radiation. There is a need for experimental confirmation of differentiated selection of curing light exposure protocols (intensity and time of exposure) in terms of minimum impact on tissues.

AIM: To assess the effect of curing light on dental tissues.

MATERIALS AND METHODS: An experimental simulation of the use of curing light in dental practice during dental restoration was performed. The experiment was performed in 50 rats randomized into four groups: Group 1 (control, n=5) and Groups 2–4 (treatment, n=15 each). The control group was not exposed to curing light. In the treatment groups, mandibular incisors of the experimental animals were exposed to curing light in three modes. The animals were sacrificed by decapitation after 7 days in Group 1 and after 1, 3, and 7 days in Groups 2–4. A total of 100 teeth were extracted for pathomorphological examination. A total of 320 histological sections (enamel, dentin, and pulp slides) were prepared, stained, and examined. The descriptive method was used to assess the findings.

RESULTS: Changes in the pulp showed pathomorphological signs of acute inflammation, most prominent on Day 3, which was considered a defense response of the pulp to irritation. The microvasculature showed the most significant changes, with increased, inhomogeneous blood filling, plasmorrhagia of capillary walls, and stasis in capillary lumen. There were no morphological changes in hard dental tissues.

The initial response of the dental pulp to curing light exposure in experimental animals was uniform and unaffected by the technical specifications of curing lamps. On Day 7, there was no morphological response in the pulp when exposed to diode light at 1,000 and 1,400 mW/cm². At this point, the microscopic appearance of the pulp exposed to diode curing light at 3,200 mW/cm² was generally comparable to that at baseline, with residual perivascular cellular infiltration of the stroma and capillary congestion.

CONCLUSION: The experimental findings indicate a risk of negative photochemical reactions in the pulp following curing light exposure during treatment of patients with hard dental tissue pathologies. The data on the effect of curing light on the dental pulp can be used in real-world dental practice when selecting a composite curing algorithm during dental restoration to reduce the risk of unexpected reactions to curing light.