Clinical evaluation of composite restorations in Er:YAG laser-prepared cavities re-wetting with chlorhexidine.

OBJECTIVES: The objective of this study was to evaluate longitudinally the composite restorations, performed in cavities prepared by Er:YAG or conventional bur, and dentin re-wetting with water or chlorhexidine. MATERIALS AND METHODS: Twenty individuals with four active caries with cavitation reaching the dentin located on the occlusal surface of molars counterparts are selected. The teeth of each individual were randomly assigned into four groups: (I) Er:YAG laser (260 mJ/4 Hz) re-wetting with chlorhexidine, (II) Er:YAG laser (260 mJ/4 Hz) re-wetting with deionized water, (III) conventional method re-wetting with chlorhexidine, and (IV) conventional method re-wetting with deionized water. The teeth were isolated, prepared cavities, phosphoric acid etching, and re-wetting according to previously assigned method. Restoration was performed employing the Single Bond 2 and Z350XT resin. Clinical follow-up was held after the polishing of the restoration (baseline) and 6 and 12 months of the making of the restoration using the modified USPHS criteria. The restorations were qualitatively analyzed by means of photographs. In the evaluation period, replicas of the restorations were analyzed by SEM. Data were analyzed by statistics using chi-square test (p < 0.05). RESULTS: After 12 months of clinical evaluation, groups prepared with laser and re-wetting with chlorhexidine and water showed the lowest marginal staining value. There was no statistical difference between the groups for other factors. SEM analysis revealed that a non-expressive amount of restorations showed gaps and irregularities of tooth-restoration interface after 6 and 12 months compared to the baseline. CONCLUSION: The restorations performed in laser-prepared cavities, regardless of the re-wetting, presented the best clinical performance over the evaluated period. CLINICAL RELEVANCE: Laser-prepared teeth, regardless of re-wetting, showed greater resistance to marginal discoloration.

Mechanical properties and modeling of drug release from chlorhexidine-containing etch-and-rinse adhesives.

OBJECTIVES: To evaluate the effects of chlorhexidine (CHX) addition in different concentrations into simplified etch-and-rinse adhesives on the ultimate tensile strength (UTS), water sorption (WS), solubility (SO) and the rate of CHX release over time. METHODS: We added CHX diacetate to Ambar [AM] (FGM) and XP Bond [XP] (Dentsply) in concentrations of 0, 0.01, 0.05, 0.1 and 0.2 wt%. For UTS (n=10 for each group), adhesive specimens were constructed in an hourglass shape metallic matrix with cross-sectional area of 0.8 mm(2). Half of specimens were tested after 24 h and the other half after 28 days of water storage in tension of 0.5 mm/min. For WS and SO (n=10 for each group), adhesive discs (5.8 mm×1.0 mm) were prepared into a mold. After desiccation, we weighed and stored the cured adhesive specimens in distilled water for evaluation of the WS, SO and the cumulative release of CHX over a 28-day period. For CHX release (n=10 for each group), spectrophotometric measurements of storage solution were performed to examine the release kinetics of CHX. We subjected data from each test to ANOVA and Tukey' test (α=0.05). RESULTS: XP Bond adhesive showed significantly more WS and SO and lower UTS than Ambar. In general, the addition of CHX did not alter WS, SO and UTS of the adhesives. XP showed a higher CHX release than AM (p<0.05) in all concentrations and the final amount of CHX release was directly proportional to the initial CHX concentration added to the adhesives. After 28 days of water storage, approximately 20% of CHX was released from XP and 8.0-12.0% from AM. CONCLUSIONS: Addition of CHX to commercial adhesive is a feasible method to provide a controlled release of CHX over time without jeopardizing WS, SO and UTS of the adhesives. SIGNIFICANCE: Manufacturers should consider adding CHX to commercial adhesives to provide a controlled release of CHX over time.

Effects of chlorhexidine-containing adhesives on the durability of resin-dentine interfaces.

OBJECTIVES: This study evaluated the effect of addition of diacetate CHX in different concentrations into two simplified etch-and-rinse (ER) adhesive systems (XP Bond [XP] and Ambar {AM}) on the ultimate tensile strength (UTS), degree of conversion (DC), 60-day cumulative water sorption (WS), solubility (SO) and CHX release (CR) as well as the immediate (IM) and 1-year (1Y) resin-dentine bond strength (µTBS) and nanoleakage (NL). METHODS: Ten experimental adhesive systems were formulated according to the addition of CHX diacetate (0 [control], 0.01, 0.05, 0.1 and 0.2%) in the two ER. For UTS and DC, specimens were constructed and tested after 24h. For WS, SO and CR, after specimens build-up, they were stored in water and the properties measured after 60 days. The occlusal enamel of fifty molars was removed and the adhesives were applied in dentine surface after 37% phosphoric acid etching. After composite resin build-ups, specimens were longitudinally sectioned to obtain resin-dentine bonded sticks (0.8mm(2)). Specimens were tested in tension at 0.5mm/min in the IM or 1Y. For NL, 2 bonded sticks from each tooth were prepared and analyzed under SEM. The data were submitted to appropriate statistical analysis (α=0.05). RESULTS: The addition of CHX did not influence UTS, DC, WS and SO (p<0.05). Higher CR was observed in adhesives with higher concentration of CHX (p<0.05). After 1Y, significant reductions of µTBS and increases of NL were observed in the control groups (p<0.05). Reductions of µTBS and increase of NL over time were not observed (AM) for CHX-containing adhesives or it was less pronounced than the control (XP) regardless of the CHX concentration. CONCLUSIONS: The addition of CHX diacetate in concentrations until 0.2% in the simplified ER adhesive systems may be an alternative to increase the long-term stability of resin-dentine interfaces, without jeopardizing the adhesives' mechanical properties evaluated.

Reflections about adhesive systems / Reflexiones acerca de los sistemas adhesivos

The adhesive systems are responsible for an efficient union between teeth and resin, resulting in a longevity restoration. They are organic molecules di or multifunctional that contain reactive groups that interact with dentin and with the resin monomer of composite resin. The adhesive systems are characterized by wet adhesion, which is a result of presence of hidrophylics radicals in their compositions, to promote a better bond and the best properties of the adhesion. Adhesive systems may use two different strategies to interact with the dental structure: total-etching and self-etching technique. The total-etching systems require a conditioning, a rinsing and a priming step in order to allow involvement of collagen fibers by the resin monomers and the formation of the so-called ‘hybrid layer’. The total-etching promotes the cleaning of dentin, also promotes superficial demineralization and delivers collagen fibrils to participate of an interface union mechanism teeth/ adhesive system/restorative material. Self-etching adhesive systems are characterized by demineralization and infiltration of resin monomers simultaneously. This technique is attractive because reduced sensitivity associated with retaining the smear layer and smear plugs, thereby, minimize the possibility of inadvertent contamination of the bonding surface with dentinal surface through dentinal fluid transudate.

Los sistemas adhesivos son responsables de una unión eficaz entre los dientes y la resina, dando como resultado una restauración durable. Son moléculas orgánicas bi o multifuncionales que contienen grupos reactivos que interactúan con la dentina y con el monómero de resina de composite. Los sistemas adhesivos se caracterizan por la adhesión húmeda, que es el resultado de la presencia de radicales hidrofílicos en sus composiciones, para promover una mejor adherencia y las mejores propiedades de la adhesión. Los sistemas adhesivos pueden utilizar dos estrategias diferentes para interactuar con la estructura dental: Técnica de grabado total y auto-grabado. Los sistemas de grabado total requiere un acondicionamiento, un lavado y un paso de priming con el fin de permitir la participación de las fibras de colágeno por los monómeros de resina y la formación de la llamada capa híbrida. El grabado total promueve la limpieza de la dentina, también promueve la desmineralización superficial y condiciona a las fibrillas de colágeno para participar de un mecanismo de interfaz de unión diente/sistema adhesivo /material de restauración. Los sistemas adhesivos autograbantes se caracterizan por la desmineralización y la infiltración de los monómeros de resina de forma simultánea. Esta técnica es atractiva debido a la sensibilidad reducida asociada a conservar la capa de barro dentinario y tapones de barro dentinario, reduciendo al mínimo la posibilidad de contaminación accidental de la superficie de unión con la superficie de la dentina a través del líquido dentinario trasudado.