Update on Enamel Bonding Strategies

Optimal strategies for the application of an adhesive differ between enamel and dentin because of the differences in their composition. The development of adhesive systems has mainly focused on the bonding of dentin, rather than on the enamel, by etching with phosphoric acid (PA). Dental adhesive technologies continue to rapidly advance, and various adhesive systems have been developed since the study of Buonocore in 1955. He introduced the enamel acid-etch technique. Then, the etch-and-rinse (ER) system was developed, and subsequently, the self-etch (SE) system. Universal adhesives are a new generation of one-bottle SE adhesives that can be applied with either ER mode or SE mode, or a combined system involving selective enamel etching mode. Since the combination of PA etching and the SE system differs from conventional ER systems, the enamel bonding strategy should be carefully considered. This concise review of the literature on reliable enamel bonding strategies should prove helpful to clinicians to choose an appropriate adhesive system to achieve optimal clinical outcomes

Bonding to caries-affected dentin

SummaryDentin adhesive systems have dramatically developed during the past decades. In a prepared cavity for an adhesive composite restoration, large areas of the cavity floor are composed of caries-affected dentin after removal of caries-infected dentin, not normal dentin. Caries-affected dentin is different in morphological, chemical and physical characteristics from normal dentin. Therefore, caries-affected dentin has still problems as bonding substrate compared with normal dentin. That is, caries-affected dentin produces lower bond strength and poor quality of the hybrid layer than normal dentin. In addition, when exposed the adhesive interface of caries-affected dentin in oral environment, the poor quality of the hybrid layer would compromise the longevity of the composite restoration due to hydrolysis of the resin and collagen fibrils. The improvement of bonding potential to caries-affected dentin could lead to reinforcement of tooth-composite restoration complex, protecting secondary caries and tooth fracture

Evaluation of dental caries, tooth crack, and age-related changes in tooth structure using optical coherence tomography

Optical coherence tomography (OCT) is an imaging technique that can visualize the internal biological structure without X-ray exposure. Swept-source OCT (SS-OCT) is one of the latest version of OCT, wherein the light source is a tunable laser that sweeps near-infrared wavelength light to achieve real-time imaging. The imaging depth of OCT is highly influenced by the translucency of the medium. The medium that does not transmit light and the deeper structure beyond the range of light penetration depth are not relevant for OCT imaging. In OCT, sound enamel is almost transparent at the OCT wavelength range, and enamel and dentin can be distinguished from each other as the dentin-enamel junction (DEJ) appears as a dark border. Demineralized enamel and dentin are imaged as bright zones because of the formation of numerous micro-porosities where the backscatter of OCT signal is increased. In cavitated caries at interproximal or occlusal hidden zone, the upper margin of the cavity reflects the signal showing a distinct bright border in the SS-OCT image. SS-OCT is capable of determining crack penetration depth even when the cracks extended beyond the DEJ. SS-OCT has a high degree of sensitivity and specificity for the detection of dental caries and tooth cracks. SS-OCT is also capable of detecting non-carious cervical lesions and occlusal tooth wear in cross-sectional views to estimate the amount of tooth structure loss

Diagnosis of Occlusal Tooth Wear Using 3D Imaging of Optical Coherence Tomography Ex Vivo

The aim of this study was to assess the utility of 3D imaging of optical coherence tomography (OCT) for the diagnosis of occlusal tooth wear ex vivo. Sixty-three extracted human molars with or without visible tooth wear were collected to take digital intraoral radiography and 3D OCT images. The degree of tooth wear was evaluated by 12 examiners and scored using 4-rank scale: 1-slight enamel wear; 2-distinct enamel wear; 3-tooth wear with slight dentin exposure; 4-tooth wear with distinct involvement of dentin. The degree of tooth wear was validated by the histological view of confocal laser scanning microscopy (CLSM). The sensitivity, specificity, and area under the curve (AUC) of receiver operating characteristic analysis were calculated. Diagnostic accuracy was compared with the agreement with CLSM observation using weighted kappa. The results were statistically analyzed at a significance level of alpha = 0.05. Three-dimensional OCT showed significantly higher sensitivity (p 0.05). Three-dimensional OCT could visualize and estimate the degree of tooth wear and detect the dentin exposure at the tooth wear surface accurately and reproducibly. Consequently, a new guideline for tooth wear assessment can be proposed using OCT

Diagnosis of Occlusal Caries with Dynamic Slicing of 3D Optical Coherence Tomography Images

Detecting the extent of occlusal caries is a clinically important but challenging task required for treatment decision making. The aim of this study was to assess the diagnostic power of 3D swept-source optical coherence tomography (OCT) for evaluation of occlusal caries in comparison with X-ray radiography. Extracted human molars not exhibiting American Dental Association (ADA) criteria advanced caries were mounted in a silicone block and digital dental radiographs were captured from the buccal side. Subsequently, occlusal surfaces were scanned with a prototype Yoshida Dental OCT. Thirteen examiners evaluated the presence and extent of caries on radiographs and dynamically sliced 3D OCT video images, using a 4 level scale-0: intact; 1: enamel demineralization without cavitation; 2: enamel caries with cavitation; 3: dentin caries with or without cavitation. Sensitivity, specificity and area under operating characteristic curves (Az) were statistically analyzed (alpha = 0.05). Reliability analysis showed an excellent agreement among the 13 examiners for both methods. The OCT presented a significantly higher sensitivity and Az value for the detection of caries compared to radiographs (p < 0.05). Radiography showed especially low sensitivity for dentin caries (0-2 versus 3). Dynamic slicing of 3D OCT volumes is a powerful adjunct tool to visual inspection to diagnose the dentin occlusal caries in vitro

Replacing mandibular central incisors with a direct resin-bonded fixed dental prosthesis by using a bilayering composite resin injection technique with a digital workflow : A dental technique

A straightforward technique is presented for an interim or short-term definitive esthetic replacement of missing anterior teeth requiring no tooth preparation. Composite resins are injected into transparent silicone indices fabricated from 3D-printed casts of a digital waxing. The dentin core is formed of a durable short fiber-reinforced injectable composite resin and veneered with an enamel-shade composite resin for enhanced esthetics. Besides being noninvasive, this technique is more straightforward than traditional options, reducing chair time while providing an accurate outcome

The effect of reduced glutathione on the toxicity of silver diamine fluoride in rat pulpal cells

Introduction: Due to its ability to arrest untreated dental caries, silver diamine fluoride (SDF) has been advocated for indirect pulp capping procedures. However, the high concentrations of silver and fluoride in SDF raise concerns about its biocompatibility to pulpal tissues.&nbsp;Objectives: This study aimed to investigate the effect of SDF on the viability, alkaline phosphatase (ALP) activity, and morphology of pulpal-like cells (RPC-C2A) and to evaluate the influence of reduced glutathione (GSH) on SDF-induced cytotoxicity and deposit formation on dentin.&nbsp;Methodology: The cytotoxicity of diluted 38% SDF solutions (10-4 and 10-5), with or without the addition of 5 mM or 50 mM GSH, was evaluated at 6 and 24 hours. Cell viability was detected using WST-8 and the effect on ALP activity was performed using an ALP assay kit. Cell morphology was observed using a phase-contrast microscope. Scanning electron microscopy analysis was conducted to evaluate the effect of GSH incorporation or conditioning on SDF-induced deposit formation on dentin discs. Cytotoxicity data were analyzed by two-way analysis of variance (ANOVA) and Tukey post hoc tests (p&lt;0.05).&nbsp;Results: There were significant differences between the groups. The results demonstrated that all tested SDF dilutions caused a remarkable cytotoxic effect, while the addition of GSH prevented SDF-induced damage at 6-hour exposure time in the higher dilution of SDF. Dentin treated with plain SDF or GSH-incorporated SDF solution showed deposit formation with occluded dentinal tubules, unlike the other groups.&nbsp;Conclusion: SDF severely disturbed the viability, mineralization-ability, and morphology of pulpal-like cells, while controlled concentrations of GSH had a short-term protective effect against SDF-induced damage. GSH showed an inhibitory effect on SDF-induced dentinal deposit formation. Further research is warranted to evaluate the effect of GSH on caries-arresting, anti-hypersensitivity, and antibacterial functions of SDF

Effect of dentin desensitizers on resin cement bond strengths

Introduction: The crown preparation promotes the exposure of dentin tubules. Thus, to avoid post-operative sensitivity, the first approach involves the use of dentin adhesives, and the second one the use of dentin desensitizers. Objective: This study evaluated the effect of dentin desensitizers on microtensile bond strengths (µTBSs) of a resin cement to dentin. Material and methods: Twenty bovine teeth were prepared until obtaining flat dentin surfaces. A standardized smear layer was created (#600-grit SiC paper). The samples were randomly divided into the following four groups (n = 5): no treatment (Control), treatment with Gluma Desensitizer (Heraeus Kulzer), Super Seal (Phoenix Dental) and Teethmate Desensitizer (Kuraray Noritake Dental). The dentin surfaces were then treated with ED Primer II (Kuraray Noritake Dental). Twenty composite blocks, 4 mm thick (Estenia C&B, Kuraray Noritake Dental) were used. The composite surfaces were abraded with aluminum oxide (50 µm), and then silanized. The composite block was bonded to the dentin surface with a resin cement (Panavia F 2.0, Kuraray Noritake Dental) according to he manufacturer’s instructions. After 24-hour storage (37ºC, 100% RH), the bonded samples were cut into beam–shaped microtensile specimens and loaded in tension until failure. Data were analyzed with one-way ANOVA and the Dunnett’s test (α = 0.05). An SEM was used to examine the failure modes. Results: The µTBSs (MPa ± SD) were: 24.4 ± 3.2 (Control), 14.0 ± 5.6 (Gluma Desensitizer), 8.6 ± 4.7 (Super Seal), and 34.7 ± 4.6 (Teethmate Desensitizer), in which there were significant differences among the four groups (p < 0.05). The Teethmate Desensitizer group showed the highest µTBS, while the Super Seal group showed the lowest mean of µTBS to dentin. Conclusion: The efficacy of the desensitizers is material-dependent; Gluma Desensitizer and Super Seal decreased the µTBSs, however, Teethmate Desensitizer improved it

Effects of mechanical abrasion challenge on sound and demineralized dentin surfaces treated with SDF

This study evaluated the effect of mechanical abrasion on the surface integrity, color change (Delta E) and antibacterial properties of demineralized and sound dentin surfaces treated with silver-diammine-fluoride (SDF). The dentin specimens were divided into two groups: sound and demineralized dentin, then divided into three sub-groups, control (no-treatment), SDF, and SDF+potassium-iodide (KI). Each sub-group was further divided into two groups, one exposed to mechanical brushing and the other without brushing. Specimens were analyzed for the Delta E, surface roughness/surface loss and antibacterial properties (CFU, optical density and fluorescent microscope). Repeated Measures ANOVA was used for statistical analysis of color change while one-way ANOVA was used for CFU analysis. SDF and SDI+KI groups showed significant reduction in Delta E with brushing in the sound dentin group unlike the demineralized group. The surface roughness values were higher for both SDF and SDF+KI groups but roughness values significantly decreased after brushing. Both SDF and SDF+KI groups revealed significantly less surface loss than control. The SDF group showed high anti-bacterial effect after brushing, unlike SDF+KI group. So, we concluded that mechanical brushing improved the esthetic outcome. While, SDF and SDF+KI could protect the dentin surface integrity. SDF-treated dentin possesses an antibacterial property even after mechanical brushing

Effect of Surface Pre-Reacted Glass Ionomer Containing Dental Sealant on the Inhibition of Enamel Demineralization.

The effect of a surface pre-reacted glass ionomer (S-PRG)-containing sealant on the demineralization inhibition and remineralization of intact enamel adjacent to the sealant material was investigated. BeautiSealant (BTS, S-PRG sealant, Shofu), Teeth Mate F-12.0 (TMF, fluoride-releasing sealant, Kuraray Noritake Dental), and an experimental silica-filler sealant were investigated. After pH cycling for 10 days, the enamel surface adjacent to the sealant material was observed using confocal laser microscopy and scanning electron microscopy. The polymerized sealant disks were immersed in a demineralized solution (pH: 4.3) to measure pH change. The enamel specimens with polymerized sealant disks were additionally immersed in demineralized solution, followed by energy-dispersive X-ray spectroscopy. The demineralized area of BTS was significantly smaller than that of TMF and SS (p &lt; 0.05). The surfaces adjacent to the sealant of TMF and SS were demineralized, while the surface of BTS was comparatively intact. An increase in pH values were observed in the BTS and TMF groups. Enamel surfaces presented an inhibition of demineralization for BTS and TMF, but not for SS. Fluoride uptake from the polymerized sealant was greater for BTS than for TMF. The S-PRG-containing sealant showed a buffering ability, demineralization inhibition, promotion of remineralization, and it can be advised for clinical applications