Comparison of surface properties of universal shade and conventional resin-based composites after degradation and repolishing.

PURPOSE: To investigate the discoloration, line roughness and gloss of conventional and universal shade resin-based composites. METHODS: Clearfil AP-X (AP-X) and Estelite Sigma Quick (EQ) samples were prepared. Discoloration, roughness, and gloss were measured on mirror-polished, alkaline-degraded, and repolished surfaces. The superficial layer degraded by alkaline immersion (degraded layer) was ground off from the sample surface. After removing the degraded layer, the surface was polished with aluminum oxide powder (1.0 µm and 0.3 µm), to create a repolished specimen. Scanning electron microscopy observations were made of the specimens. RESULTS: The results were compared with those for Omnichroma (OC) from a previous study. All the materials showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials. CLINICAL SIGNIFICANCE: The materials tested showed different responses to degradation and repolishing, but repolishing of AP-X, for surface roughness and gloss, was more effective at restoring pre-degradation properties. Repolishing effectively removed discoloration in all materials.

Effect of low power Er:YAG laser irradiation of CAD-CAM resin-based composites on resin bonding.

PURPOSE: To investigate the effect of painless low-power Er:YAG laser irradiation of conventional and polymer-infiltrated ceramic network (PICN) type CAD-CAM resin-based composites (RBCs) on resin bonding. METHODS: An Er:YAG laser system, phosphoric acid etchant, universal adhesive, RBC, and two types of CAD-CAM RBC block were used. Microtensile bond strength, fracture mode, scanning electron microscopy (SEM) observations of bonding interfaces and CAD-CAM surfaces, and surface roughness of ground and pretreated surfaces were investigated. As pretreatment methods, low-power Er:YAG laser irradiation and air-abrasion with alumina particles were used. RESULTS: The effect of low-power Er:YAG laser irradiation of CAD-CAM RBCs on bonding to repair resin varied depending on the type of CAD-CAM RBCs. CLINICAL SIGNIFICANCE: The low-power Er:YAG laser irradiation of the conventional CAD-CAM RBCs was shown to be effective as a surface pretreatment for resin bonding, while the laser irradiation of PICN-type CAD-CAM RBCs was not effective.

Investigation on the Biaxial Flexural Strength of Universal Shade Resin-Based Composites.

The biaxial flexural strength of universal shade and conventional dental resin-based composites before and after alkaline degradation was investigated. Disk samples were prepared from these resin-based composites, and some of the specimens were immersed in 0.1 M NaOH solution to create deteriorated samples. The biaxial flexural strength of the samples before and after the alkaline degradation test was measured and statistically tested. The fracture surfaces after the biaxial flexural test were observed using a scanning electron microscope. The results showed that the biaxial flexural strength of the paste-type universal shade resin-based composite before alkaline degradation was significantly (19%) higher than that of the conventional type, but no difference was observed between the materials after alkaline degradation. On the other hand, the biaxial flexural strength of the flowable universal shade resin-based composites was significantly (around 35%) lower than that of the conventional composite, with or without degradation. Although, for paste-type materials, the biaxial flexural strength of universal shade resin-based composites was higher than that of conventional resin-based composites before alkaline degradation, after degradation the two materials showed similar values. For flowable materials, the biaxial flexural strength of universal shade resin-based composites was lower than that of conventional resin-based composites regardless of the presence or absence of degradation processes. These results suggest that some caution should be used when deciding whether to use flowable universal shade resin-based composite to fill a cavity.

Evaluation of the Repolished Surface Properties of a Resin Composite Employing Structural Coloration Technology.

Resin composites employing structural coloration have recently been developed. These resins match to various tooth shades despite being a single paste. To accomplish this, the filler and base resin are tightly bonded, which is thought to provide excellent discoloration resistance. Here, we investigated the surface properties of one of these resins, including the discoloration of the repolished surface. We developed an innovative in vitro method to adjust the repolished surface, in which structural degradation is removed according to scanning electron microscopy (SEM) observation rather than by the naked eye. The resin samples (20 mm (length) × 10 mm (width) × 4 mm (depth)) were manufactured using this resin material. After accelerated aging of the resin by alkaline degradation, the resin was repolished and the discoloration (ΔE*ab), surface roughness (the arithmetic mean roughness (Ra)), and glossiness (the 60° specular) were measured. SEM observation showed that the appearance of the bond between the organic composite filler and base resin on the repolished surface was different from that on the mirror-polished surface. This revealed that according to our in vitro method it was difficult to make the repolished surface structurally identical to the mirror-polished surface. Among the properties of the repolished surface, the degree of discoloration did not change despite the rougher and less glossy surface. It can be concluded that the factors that induce discoloration in this resin composite are independent of the surface roughness and glossiness.

Clinical effectiveness of direct resin composite restorations bonded using one-step or two-step self-etch adhesive systems: A three-year multicenter study.

The purpose of this multicenter clinical study was to compare the mid-term clinical effectiveness of direct resin composite restorations using one-step or two-step self-etch adhesives (1-SEAs or 2-SEAs). In total, 352 restorations of class I-V cavities and non-carious cervical lesions in vital teeth (1-SEAs; 52 cases, 2-SEAs; 300 cases) were placed at nine university hospitals and evaluated according to the modified USPHS criteria at baseline, and after 1, 2, and 3 years. The recall rates were 86.6% (1 year), 80.1% (2 years), and 62.2% (3 years). Two restorations failed due to fracture during the follow-up, and there was no significant difference in survival rates between 1-SEAs (97.6%) and 2-SEAs (99.4%). However, 2-SEAs exhibited significantly lower occurrences of discoloration, marginal discoloration, fracture, and plaque retention. Moreover, the subjects reported a significantly lower postoperative hypersensitivity and higher overall satisfaction at all evaluation periods if 2-SEAs were used.

Evidence-based consensus for treating incipient enamel caries in adults by non-invasive methods: recommendations by GRADE guideline.

Remineralization treatment, which offers the advantage of being non-invasive, is increasingly being used as a minimal intervention treatment in managing incipient enamel caries. The aim of this review was to develop EBM guideline for optimized strategies for non-invasive treatment of incipient enamel caries. Japanese Society of Conservative Dentistry (JSCD) guideline committee formulated a Guideline for treating incipient enamel caries using the GRADE system, which is the global, mainstream standard for guideline development. The committee selected the most frequent clinical questions (CQs) in treating incipient enamel caries and identified clinically important outcomes in evaluating the efficacy of treatments. Using extensive electronic and manual searches, relevant randomized controlled trials and controlled clinical trials were identified. Based on evidence profiles produced by the committee, the panel discussed the effects, benefits and disadvantages of the selected treatments, as well as their cost effectiveness and feasibility, in order to achieve a consensus in treating incipient enamel caries non-invasively. A recommendation was made for each clinical question after voting by the panel members. Based on the evidence profile and panel discussions for each CQ, the experts strongly recommended application of topical fluoride to inhibit cavitation of incipient enamel caries, and to diminish white spot lesions.

Immobilization of simulated reducing agent at the surface of SiO2 fillers in dental composite resins.

To reduce the leachability of reducing agents from composite resins, immobilization of a simulated reducing agent at the surface of SiO2 fillers was examined. SiO2 plates were immersed in 2% 3-aminopropyltriethoxy silane/ethanol solution, and then immersed in dimethyl sulfoxide with 0.25 wt% 4-dimethyl amino benzoic acid (DMABA), 2.0 wt% 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, and 0.5 wt% N-hydroxysuccinimide. Wide-scan spectrum of X-ray photoelectron spectroscopy did not detect carbon contamination. However, narrow scan detected an O=C-N peak at 399.8 eV, suggesting that DMABA could be immobilized on silane-coupled SiO2 plates. Further, surface plasmon resonance analysis indicated the adsorption of MMA at the surface of reducing agent-immobilized plate.

Direct adhesive pulp capping: pulpal healing and ultra-morphology of the resin-pulp interface.

PURPOSE: To test the hypothesis that healing of adhesively capped pulps may depend on the type of adhesive system used and its specific application approach. MATERIALS AND METHODS: Buccal Class V cavities were prepared in 24 intact monkey teeth. After exposing the pulps, infiltration anesthesia (Xylocaine containing 1:80,000 epinephrine) was administered around the root apex. Two adhesives that make use of a different hybridization approach, Clearfil Liner Bond II (CLB-II) and Super-Bond D Liner II (SB-II) were directly applied to the exposed cavities. The pulpal response was histopathologically investigated using light microscopy at 3 and 90 days. In addition, the resin-pulp interface was characterized by transmission electron microscopy in an attempt to elucidate the underlying mechanisms of healing. RESULTS: In the CLB-II capped pulps, little inflammation was detected at 3 days with the bonding resin intimately attached to the exposed pulpal tissue. At 90 days, a complete dentin bridge was formed in close adaptation to the resin cap. The ultra-structure of a thin intermediary layer at the bridge front resembled a so-called "reversal line". This layer typically appears during remodeling of bone to couple the newly formed to the old osseous tissue. In the SB-II capped pulps, an acute inflammation was in progress immediately beneath the bonding resin at 3 days. This tissue was resorbing the resin that had infiltrated relatively deeply into the pulp. Whereas healing of CLB-II capped pulps appeared to have been initiated promptly, healing of SB-II capped pulps was probably retarded. The formed soft-tissue hybrid layer had first to be resorbed before the formation of a dentin bridge could have been initiated. Hence, the dentin bridge was not completely finished at 90 days and no evidence of a "reversal line"-like layer could be detected. These results suggested that although both the adhesives tested appeared effective as pulp capping materials, the process and duration of healing substantially differed.

Ways of enhancing pulp preservation by stepwise excavation--a systematic review.

OBJECTIVES: The best possible methods and materials in stepwise excavation for deep caries in permanent teeth were investigated. The review considers the questions from many aspects including clinical success, effects of reducing cariogenic bacteria, possibility of hardening softened dentin, and likelihood of generating tertiary dentin. DATA: This systematic review includes the use of data from randomized controlled trials, controlled clinical trials as well as from case series in which pulp exposure resulted following the treatment and removal of deep caries. Only studies of caries in permanent teeth were considered. Those involving treatment of primary teeth were excluded. SOURCES: An electronic search was conducted in the databases of MEDLINE and Igaku Chuo Zasshi (Japanese) from 1970 to 2008. The electronic search was supplemented by a manual search of the references lists of all the relevant studies. STUDY SELECTION: The electronic and manual searches of journals retrieved a total of 266 English and 130 Japanese papers. According to the inclusion and exclusion criteria, 10 English and 3 Japanese studies were finally identified. CONCLUSION: Our research suggests that stepwise excavation is effective for pulp preservation in extremely deep caries that do not show clinical symptoms of irreversible pulpitis. Calcium hydroxide, as well as antimicrobials and polycarboxylate cement combined with tannin-fluoride preparation, is effective in reducing bacteria and promoting remineralization of the carious dentin that remained after stepwise excavation. Further clinical trials with a high level of study design should be conducted to identify the best methods of removing carious dentin using stepwise excavation.