Comparative Evaluation of the Effect of Radiation on the Marginal Adaptation of Different Composite Restorative...

Radiotherapy is an essential component of the management of head and neck cancers; however, it adversely affects both dental hard tissues and restorative materials, potentially compromising the marginal integrity of restorations. As marginal adaptation is a key determinant of restoration longevity, evaluating the performance of different resin-based restorative materials under irradiated conditions is of clinical importance. The aim of this study was to comparatively evaluate the effect of therapeutic radiation on the marginal gap of different composite restorative materials using an in vitro model.

A total of 36 freshly extracted human premolars were randomly assigned to four groups (n = 9 each) according to the restorative material used: nanofilled composite resin, giomer, ormocer, and bulk-fill flowable composite (SureFil SDR Flow Plus, Dentsply Sirona, Charlotte, NC). Standard class V cavities were prepared and restored according to the manufacturers' recommendations. The marginal gap at the tooth and filling material junction was assessed using scanning electron microscopy before and after exposure to a cumulative radiation dose of 70 Gy, delivered according to the conventional head and neck radiotherapy protocol. Statistical analysis was performed using one-way analysis of variance (ANOVA), Tukey's honestly significant difference post-hoc test, paired t-test, and Shapiro-Wilk test. Statistical significance was set at p < 0.05.

Before radiation exposure, a statistically significant difference in the marginal gap was observed between the four restorative materials (p < 0.001). Ormocer exhibited the lowest mean marginal gap (4.27 ± 0.32 µm), whereas giomer demonstrated the highest (6.30 ± 0.42 µm). After radiation exposure, the significant intergroup differences persisted (p < 0.001). Ormocer continued to show the lowest marginal gap (4.86 ± 0.30 µm), while SureFil SDR Flow Plus exhibited the highest (7.08 ± 0.30 µm). Intragroup analysis revealed a significant increase in the marginal gap following radiation exposure for all restorative materials (p < 0.05), with the greatest effect observed in the SureFil SDR Flow Plus group (Cohen's d = 2.38).

Therapeutic radiation significantly increased the marginal gap of all evaluated restorative materials. Among the materials tested, ormocer demonstrated the best marginal adaptation and the greatest resistance to radiation-induced deterioration, suggesting its potential clinical advantage in restoring teeth in patients undergoing head and neck radiotherapy.