Temporary restorative resins using non-phthalate ester plasticizers

A study on the characteristics of resin composites for provisional restorations

In this study, we evaluated the characteristics of five commercial resin composites used for provisional restorations. The inorganic filler contents of the resins were measured, and three-point bending, wear, surface hardness, water absorption, and staining tests were performed. The specimens underwent additional three-point bending tests after water storage and undergoing thermal stresses at 5°C and 55°C (10,000 cycles). Data were analyzed using one- or two-way analysis of variance and Bonferroni post-hoc tests. Pearson's correlation coefficient was used for pairwise comparisons. Each resin composite presented with different mechanical properties, based on variations in the inorganic filler content. The flexural strength of each resin composite was significantly decreased after water storage. There has a positive correlation between flexural strength and dynamic hardness but a negative correlation between flexural strength and maximum wear depth. The types and contents of the inorganic fillers, the composition of the monomer in the resin matrix, and the addition of plasticizers can affect the properties of the material.

Effects of citrate ester plasticizers and bis (2-ethylhexyl) phthalate in the OECD 28-day repeated-dose toxicity test (OECD TG 407)

Citrate esters are considered functional alternatives to phthalate plasticizers, but their toxicity remains poorly understood. The toxicity of citrate esters, including triethyl 2-acetylcitrate (ATEC) and trihexyl O-acetylcitrate (ATHC), were examined together with that of bis (2-ethylhexyl) phthalate (DEHP) using the Organization for Economic Co-operation and Development Test Guideline 407 (OECD TG407). Following 28-day oral administration, no significant differences in body weight or the weight of the brain, pituitary, heart, epididymis, seminal vesicles, or coagulating gland were found between the vehicle control and DEHP, ATEC or ATHC groups. In the 400 mg/kg day DEHP group, liver, adrenal, thymus, spleen, kidney, testis, and prostate weights were significantly increased. In the 400 mg/kg day ATHC group, kidney, adrenal, thymus, testis and prostate weights were significantly increased. In the 400 mg/kg day ATEC group, kidney, adrenal and testis weights were significantly increased. Hepatocyte size was significantly increased in the 400 mg/kg day DEHP group, suggestive of hepatotoxicity, but was not increased in the ATEC or ATHC groups. There were no significant differences in white blood cell, red blood cell or platelet counts, hemoglobin concentrations, hematocrit, mean corpuscular volume, fasting glucose, insulin, or testosterone concentrations between the vehicle control and DEHP, ATEC and ATHC groups. In the ATHC 400 mg/kg day group, T3 was decreased while T4 was increased, suggestive of disruption of thyroid function. The results of the OECD TG407 subacute repeated dosing toxicity test indicate ATEC is less toxic compared to ATHC or DEHP and could be recommended as an alternative to phthalate plasticizers.

Effects of resin-based temporary filling materials against dentin demineralization

This study investigated the in vitro anti-demineralization effects of resin-based temporary filling materials containing surface prereacted glass-ionomer (S-PRG) filler on dentin. Bovine root dentin specimens with a 3×3 mm experimental surface were divided into four treatment groups: DuraSeal (DU) as a control, S-PRG filler-free temporary material (S0), material containing 10% (S10) and 20% (S20) S-PRG filler. Each material was applied to 3×2 mm of the experimental surface, and the specimens were immersed in 8% methylcellulose gel demineralization system for one week at 37˚C. Mineral profiles and integrated mineral loss (IML) of lesions induced on the surface (3×1 mm) adjacent to the materials were computed by transversal microradiography. S10 and S20 yielded thick surface layers and shallow lesion bodies, with significantly lower IML than DU and S0 (p<0.05, Tukey's test). These findings indicate that temporary filling resin-based materials containing over 10% of S-PRG filler content have anti-demineralization effects on adjacent dentin.