Francis K. Mante

This study investigated the effect of Polymethyl vinyl ether-co-maleic anhydride (PVM/MA) copolymer incorporation and aging with thermocycling on the shear bond strength (SBS) of an etch-and-rinse adhesive (Adper Single Bond Plus-ASB) and two different self-etch adhesive systems (Clearfil SE Bond-CSE and Fluorobond II-FLB) to dentin. Adhesive systems were applied to 240 dentin sections randomly selected from the occlusal surfaces of 60 extracted molar teeth. The test groups were as follows (n=20): (G1) Pure Clearfil SE (CSE) Bond; (G2) CSE with copolymer (50 mg/ml PVM/MA); (G3) Pure FL II Bond (FLB); (G4) FLB with copolymer (50 mg/ml PVM/MA); (G5) Pure Adper Single Bond (ASB); and (G6) ASB with copolymer (50 mg/ml PVM/MA). A resin composite (Clearfil Majesty Posterior) was applied to the dentin surfaces and light-cured. Half of the specimens from each group were tested immediately after preparation (IM) and the other half was tested after exposure to 20,000 thermal cycles (TC; 5-55 °C). SBS values were measured at a crosshead speed of 0.5 mm/min. Data were analyzed with ANOVA and Tukey's HSD. The PVM/MA copolymer incorporation improved the performance of CSE in the IM group and ASB in the TC group, however, it showed no influence in the other adhesive groups. The self-etch adhesive CSE with the PVM/MA copolymer showed the highest bond strength to dentin surfaces in the IM group (22.0±1.7 MPa). However, copolymer corporation did not increase bonding performance of Fluor containing bonding agent FLB. Thermocycling of test specimens significantly decreased bond strengths in all test groups except for ASB resin adhesive with PVM/MA copolymer. Incorporating PVM/MA into ethanol-based, hydrophilic all-in-one bonding agents may offer a valuable strategy to improve the long-term stability of adhesive systems.

Radiation therapy for head and neck cancers often leads to radiation-induced caries and microstructural dentin alterations. This laboratory study evaluated the impact of radiation on dentin microhardness and the effectiveness of various topical fluoride treatments in mitigating these effects. One hundred dentin specimens from extracted human teeth were irradiated with a cumulative dose of 60 Gy, simulating therapeutic conditions. Post-irradiation, specimens received weekly applications of silver diamine fluoride (SDF), SDF with potassium iodide, or sodium fluoride varnishes with and without additional compounds. Dentin microhardness was measured using the Knoop hardness test at three key phases: baseline, immediately after reaching a cumulative irradiation dose of 60 Gy, and weekly for five weeks following repeated fluoride applications. At baseline, the average Knoop Hardness Number (KHN) was 57.6 ± 3.9. After irradiation, the average KHN decreased significantly to 41.2 ± 8.1, reflecting an approximate 30% reduction in dentin hardness across all groups (p < 0.0001). Five weeks of weekly fluoride treatments led to partial recovery of microhardness, with average KHN values ranging from 42.4 to 54.3, but none of the groups returned to baseline hardness levels. Notably, no significant differences were found among the fluoride treatments in their ability to enhance microhardness. These findings underscore the detrimental effects of radiation therapy on dentin integrity and emphasize the need for targeted dental management strategies. While fluoride applications provide some protective benefit, their limitations highlight the necessity of comprehensive approaches to prevent radiation-related dental deterioration in head and neck cancer patients.

Head and neck cancers are a significant global health burden, with radiation therapy being a frequently utilized treatment. The aim of this systematic review was to provide a critical appraisal of laboratory studies that assessed the effect of irradiation on the adhesive performance of resin-based biomaterials. The analysis included 23 laboratory studies obtained from five databases, with most studies using human enamel, dentin, or both, and bonding procedures involving the fabrication of direct restorations, standardized specimens, bonding of orthodontic brackets, and luting of endodontic fiber posts. The protocols used for irradiation varied, with most studies exposing specimens made from extracted teeth to irradiation using cabinet irradiators to simulate treatment of head and neck cancer. The findings indicate that irradiation reduces the bond strength of dental adhesives and resin-based composites on flat, ground enamel and dentin specimens, with different adhesives and timing of irradiation having a significant impact on adhesive performance. Irradiation also increased microleakage in most studies. The effect of irradiation on marginal adaptation of direct resin-based composite restorations was inconclusive. This systematic review indicates that irradiation has detrimental effects on the adhesive performance of resin-based biomaterials and highlights the need for further clinical and laboratory studies evaluating the performance of adhesive materials and approaches to improve it.

Polymethyl methacrylate (PMMA), an acrylic resin used in orthodontic appliances and removable dentures for its biocompatibility and esthetics, may harbor bacteria on its surface. The present study investigated a new PMMA formula with Gantrez: an antibacterial copolymer of methyl vinyl ether and maleic acid (PVM/MA). Samples were tested for mechanical properties (surface hardness, flexural strength, water sorption, and water solubility) and effects against Streptococcus mutans. Six groups (0%-control, 5%, 10%, 15%, 20%, and 25% Gantrez) of n = 12 were fabricated for physical property tests and analyzed with one-way ANOVA and Prism 6. From these results, three groups (0%, 5%, and 10% Gantrez) were selected for antibacterial tests, and data were analyzed with one-way ANOVA and Tukey’s multiple comparison test. Adding 5% and 10% Gantrez into PMMA significantly decreased S. mutans adhesion. There was no significant difference between the control vs. 5%, 10%, 15%, and 20% Gantrez (p > 0.05) for surface hardness, the control vs. 5% Gantrez (p > 0.05) for flexural strength, and the control vs. 5 and 10% Gantrez for water sorption and water solubility. Overall, incorporating 5% Gantrez into PMMA may be a promising solution to reduce bacterial adhesion without changing the acrylic resin’s physical properties.

Objective. To determine the effects of preirradiation fluoride treatments on the Knoop hardness of dentin. Materials and Methods. Human posterior teeth mounted into acrylic resin molds were polished with silicon carbide (SiC) abrasives and 3‐micron diamond paste. The Knoop hardness of dentin was measured with a Leco hardness instrument. The teeth were divided into groups of ten teeth per group as follows: no treatment (control), treatment with silver diamine fluoride (SDF), MI varnish (MI), and cavity shield (CS). The teeth were exposed to 2 Gy of daily radiation for six weeks using an X‐Rad 320ix biological irradiator. Hardness was measured weekly, before, during, and after irradiation. The teeth were stored in artificial saliva at 37^oC between radiation treatments. Results. In preirradiation dentin, a Knoop hardness value of 58.8 (14.1) KHN was obtained. Treatment with SDF significantly increased KHN before irradiation. Immediately after radiation treatment, hardness was significantly reduced in all experimental groups. Postirradiation fluoride treatments increased the hardness of dentin to varying degrees. Conclusions. Preirradiation fluoride treatment does not provide protection from decreases in the hardness of dentin. Treatment of teeth with fluoride formulations after radiation progressively restores the hardness of dentin to different degrees.