Whitening efficacy and tooth sensitivity in a combined in-office and at-home whitening protocol: A randomized controlled clinical trial.

OBJECTIVE: This controlled randomized clinical trial determined the whitening efficacy and the intensity and absolute risk of tooth sensitivity in dual whitening when prefilled at-home whitening trays were used between in-office whitening intervals. MATERIALS AND METHODS: An in-office whitening agent containing 35% hydrogen peroxide was used. A prefilled tray with a whitening agent containing 6% hydrogen peroxide was used for at-home whitening. Sixty-six subjects were randomly assigned to three groups. Group I: at-home whitening was performed 10 times between the in-office whitening treatments. Group II: at-home whitening was performed five times between the in-office whitening treatments. Group III: only in-office whitening was performed. The tooth color changes were evaluated using a spectrophotometer. A visual analog scale was used to express the pain intensity. RESULTS: All the groups showed increased ΔE*ab, ΔE00 , and ΔWID with increased whitening sessions. Group I at the 3rd whitening session showed significantly higher ΔE*ab, ΔE00 , and ΔWID than group III. Tooth sensitivity showed higher values up to 24 h after whitening. CONCLUSIONS: Although dual whitening with the prefilled tray and in-office whitening had higher whitening ability than in-office whitening alone, the intensity and absolute risk of tooth sensitivity was similar. CLINICAL RELEVANCE: The dual whitening might produce faster and stronger whitening effects than in-office whitening alone.

Influence of bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer.

This study investigated the effect of the bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer. The bonding durability of a universal adhesive was compared with those of two conventional two-step adhesives by shear bond strength testing after thermal cycling. The primer was applied (with or without phosphoric acid pre-etching), and the specimens were divided into three groups based on the bonding agent application method used as follows: (i) strong air-flow application, (ii) gentle air-flow application, and (iii) gentle air-flow + second bonding application. The shear bond strength was determined after thermal cycling. All the factors (bonding agent application method, adhesive system, and storage condition) significantly influenced the dentin shear bond strength both with and without phosphoric acid pre-etching. The specimens exposed to gentle air-flow showed a higher shear bond strength than did those exposed to strong air-flow and gentle air-flow + second bonding. The bond durability of the tested adhesive systems was influenced by the bonding agent application method, and this trend was material dependent. The G2-Bond Universal exhibited the same or greater dentin bond durability to the other two-step adhesive systems.

Evaluation of structural coloration of experimental flowable resin composites.

OBJECTIVE: To examine the effect of filler contentTo examine the effect of filler content on structural coloration of experimental flowable resin composites. OVERVIEW: Experimental composites containing spherical fillers and different filler contents (30, 40, 50, 60 and 70 wt%), a structural colored resin composite (Omnichroma), and a nanohybrid flowable resin composite (Gracefil LoFlo) were used. The optical characteristics of the specimens were measured on standard black and white backgrounds using a spectrophotometer under CIE D65 illuminant and the L*a*b* values were determined. The color matching abilities to artificial teeth were evaluated using the ΔE*ab and ΔE00 color difference formulas. One-way analysis of variance and Tukey's post hoc test were used. The spectral reflectance of experimental composites showed different trends in different backgrounds, plate thickness, and filler contents. In particular, higher spectral reflectance was observed on the white background at wavelengths ranging from 450 to 700 nm in both 1.5 and 3.0 mm plates when compared to the black background. The percent reflectivity tended to decrease with a decrease of the filler contents. The color matching abilities of the experimental composites improved with the increase in the filler contents. CONCLUSIONS: Structural coloration of the flowable resin composites were affected by the filler contents. CLINICAL SIGNIFICANCE: Clinical Significance: Higher filler contents might be needed to achieve the optimal color properties of structural colored flowable resin composites, thereby improving the restoration esthetics.

Handling properties and surface characteristics of universal resin composites.

OBJECTIVE: This study investigated the handling and surface characteristics of universal resin composites and determined the interrelations among the composites' handling, mechanical, and physical properties. METHODS: Five recently introduced universal resin composites were tested. Twelve specimens per material were used to measure the stiffness and stickiness (handling properties) of the resin composite pastes. Additionally, surface properties (Knoop hardness number [KHN], surface roughness [Sa], surface gloss [SG], water contact angle [CA], and surface free energy [SFE]) of cured resin composites were determined in 12 specimens per material immediately after preparation (baseline) and after subjection to thermal cycles (TCs). RESULTS: Handling and surface properties of the resin composites were material dependent. All the resin composites showed significantly lower KHN in the post-TC subgroups than that in the baseline subgroups. However, the influence of TC on the other surface properties was dependent on the material used. Some resin composites did not indicate any significant differences in Sa, SG, or CA between the baseline and post-TC groups. SIGNIFICANCE: Although the resin composites in the baseline groups presented with different handling and surface properties, the surface properties of most of the composites were significantly affected by TC. Extremely strong positive or negative correlations were observed between stiffness and stickiness, KHN and Sa, KHN and SG, Sa and SG, and CA and SFE. Most correlations between the handling and surface properties were weak. Therefore, the selection of resin composites in clinical situations should be based on comprehensive consideration of their properties.

Influence of Different Application Methods on the Bonding Effectiveness of Universal Adhesives to Dentin in the Early Phase.

PURPOSE: To investigate the changes in the dentin bond strengths of universal adhesives during the early phase and evaluate the effect of a double-layer adhesive application on the performance of the dentin bond. MATERIALS AND METHODS: Three universal adhesives and a two-step self-etch adhesive were employed to ascertain the shear bond strengths (SBS) of specimens to bovine dentin with the use of the etch-and-rinse or self-etch mode. The specimens were further divided into two groups based on adhesive application in a single or a double layer. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h prior to SBS measurement and the adhesives' Knoop hardness number (KHN). RESULTS: All the adhesives showed increased SBS with prolonged storage periods regardless of the adhesive layer (single or double) or etching mode. Most universal adhesives in the double adhesive layer groups showed significantly higher SBS than single adhesive layer groups for the same storage period. All the adhesives also showed increased KHN with increased storage period. CONCLUSION: The SBS and KHN values of the adhesives increased with increasing storage duration over a 24-h period. Double adhesive layer application mediated increased dentin bond strength in the early phase.

Influence of one-step professional mechanical tooth cleaning pastes on surface roughness and morphological features of tooth substrates and restoratives.

PURPOSE: This study investigated the influence of professional mechanical tooth cleaning (PMTC) pastes on the surface texture of different subject materials. METHODS: Two one-step PMTC pastes, Clinpro Cleaning Paste for PMTC (CP) and PRG Pro-Care Gel (PG), and multiple-step PMTC pastes, Merssage Regular (MR), Merssagge Fine (MF), and Merssage Plus (MP), were used. For comparison, PMTC was performed using distilled water without paste (DW). The subjected materials used were bovine enamel (ENA) and dentin (DEN), a resin composite (FSU), and lithium disilicate (IEC). The prepared specimens were polished using a #2000-grit silicon carbide paper. PMTC was performed using a brush at 1,000 rpm for 15 s. RESULTS: The surface roughness (Ra) values of the specimens before and after PMTC were measured by laser scanning microscopy. The Knoop hardness number (KHN) of the subjected material was obtained. The types of PMTC pastes and subject materials had a significant influence on the Ra values and KHN. For the majority of subject materials, the descending order of Ra values after PMTC was MR > MF > CP > PG > MP > DW. The descending order of KHN of the materials was IEC > ENA > FSU > DEN. CONCLUSION: Although one-step PMTC pastes appeared to be effective, it is important to consider the subject material during PMTC.