The effect of in-office bleaching materials with different pH on the surface topography of bovine enamel.

This study evaluated the alterations of surface topography of the bovine enamel caused by different pH of in-office bleaching agents. 23% H2O2 with pH 5.5, 7.0 and 8.5 were applied on the bovine tooth specimens (n=10) and photo-irradiated for 10 min. The bleaching procedure was repeated three times and specimens were subjected to linear surface roughness (Ra) and Vickers microhardness test (VHN) at baseline and after three consecutive applications. The morphological alterations were observed before and after third bleaching application. Data were analyzed by two-way ANOVA followed by Tukey's HSD. The pH of the bleaching agent significantly affects the Ra and VHN (p<0.05). Low pH yielded a significant increase in Ra and decrease in VHN. All the groups showed morphological alterations and profound effect was found in pH 5.5 group. It was concluded that the pH of the bleaching agent can affect Ra, VHN and surface morphology.

Clinical efficacy of nanohydroxyapatite-containing toothpaste at relieving dentin hypersensitivity: an 8 weeks randomized control trial.

OBJECTIVE: The objective of this study was to investigate and compare the effectiveness of several toothpastes containing nanohydroxyapatite (nano-HAP) to relieve dentin hypersensitivity (DHS) with that of a commercial desensitizing dentifrice containing calcium sodium phosphosilicate (CSPS). MATERIALS AND METHODS: In this double-blind, randomized, parallel-group clinical trial, patients diagnosed with DHS and qualified to participate were randomized into four groups: toothpaste containing 10% nano-HAP (10%nano-HAP), 15% nano-HAP (15%nano-HAP), 10% nano-HAP supplemented with potassium nitrate (KNO3) (10%nano-HAPKN), or CSPS. Subjects' baseline and post-treatment sensitivities were assessed using visual analog scale (VAS) after the application of ice-cold and air stimuli. Subjects used their assigned toothpaste for routine toothbrushing twice daily. Post-treatment sensitivity was assessed every 2 or 8 weeks. Mean change in VAS (mm) from baseline at each time point were compared using random-intercept, mixed-model analysis and Duncan test (P < 0.05). RESULTS: With either air or cold stimulus, VAS indicated a significant (P < 0.001) reduction from baseline DHS at each time point with all test toothpastes. Among the nano-HAP toothpastes, 15%nano-HAP and 10%nano-HAPKN were consistent in DHS reduction with both stimuli. With either stimuli, the CSPS did not significantly differ from 15%nano-HAP and 10%nano-HAPKN at any time point. CONCLUSIONS: Toothpaste containing nano-HAP (10 or 15%) alone or supplemented with KNO3 was as effective as CSPS for relief of DHS symptoms when used at least twice daily.

Prevention of white spot lesions around orthodontic brackets using organoselenium-containing antimicrobial enamel surface sealant.

OBJECTIVES: To investigate the antimicrobial potential of organo-selenium compound when applied as enamel surface sealant or primer (DenteShield™ [DS]) around orthodontic brackets to prevent enamel demineralization. METHODS: Human teeth were randomly assigned to seven treatment groups (15/group): control (No primer or sealant), Leopard light primer (LLP), DS Primer (DS-P), DS Enamel Surface Sealant (DS-S), Pro Seal, Opal Seal and combined DS-P/DS-S (DS-PS). Following etching, the tooth surface was coated with their respective material (except control group) and a bracket was bonded on each treated surface. All samples were subject to cariogenic challenge in a continuous flow microbial caries model at 37 °C in an incubator for 28 days. Demineralization was evaluated with Transerse microradiography to determine mineral loss (Δz) and lesion depth (LD). Data was statistically analyzed using Bonferroni protected Mann-Whitney tests (α = 0.05). RESULTS: Demineralization was obsessrved only in Control and LLP groups. Control group had significantly (p < 0.001) greater mean LD (109.47 ± 34.22 µm) and mean Δz (2251.07 ± 514.26 vol%µm) when compared with the LLP with mean LD (44.98 ± 11.69 µm) and Δz (700.67 ± 310.66 vol%µm). All other groups did not develop any lesions. CONCLUSIONS: Selenium-based primer and sealant used alone or in combination were effective in protecting enamel from demineralization around brackets. The combination of primer and enamel surface sealant has no added benefit. SIGNIFICANCE: DS-S and DS-P containing antimicrobial organo-selenium compound can prevent whitespot lesions development when applied on tooth surface during orthodontic treatment. Light primer applied alone on tooth surface may not provide adequate protection for the enamel around orthodontic appliances.

Effect of pH of bleaching agent on tooth bleaching action in vitro.

This study investigated the effect of pH of bleaching agent, photo-irradiation time or application times on bleaching action using hematoporphyrin-stained papers (HSPs) and artificially stained bovine-teeth (BT). 23% H2O2 with pH 5.5, 6.0, 7.0, 8.0 and 9.0 were applied on the specimens. HSP was photo-irradiated for 1, 3 and 5 min. BT were photo-irradiated for 10 min and the bleaching was repeated ten times (n=10). CIE L*a*b* of the specimens were measured before and after the procedure. Data were analyzed by repeated-measures ANOVA followed by multiple comparisons with Bonferroni correction. For the HSP, longer irradiation time and higher pH yielded significantly higher color difference (ΔE). As for BT, increasing application times and higher pH resulted in higher ΔE. It was concluded that the pH of the bleaching agent significantly improved the bleaching effect with increased photo-irradiation time for HSP and with an increase of repeated application times for BT.

In Vitro Study on the Effect of a New Bioactive Desensitizer on Dentin Tubule Sealing and Bonding.

Bioactive mineral-based dentin desensitizers that can quickly and effectively seal dentinal tubules and promote dentin mineralization are desired. This in vitro study evaluated a novel nanohydroxyapatite-based desensitizer, Predicta (PBD, Parkell), and its effect on bond strength of dental adhesives. Human dentin discs (2-mm thick) were subjected to 0.5 M EDTA to remove the smear layer and expose tubules, treated with PBD, and processed for surface and cross-sectional SEM examination before and after immersion in simulated body fluid (SBF) for four weeks (ISO 23317-2014). The effects of two dental desensitizers on the microshear bond strength of a universal adhesive and a two-step self-etch system were compared. SEM showed coverage and penetration of nanoparticles in wide tubules on the PBD-treated dentin at the baseline. After four weeks in SBF, untreated dentin showed amorphous mineral deposits while PBD-treated dentin disclosed a highly mineralized structure integrated with dentin. Desensitizers significantly reduced microshear bond strength test (MSBS) of adhesives by 15-20% on average, depending on the bonding protocol. In conclusion, PBD demonstrated effective immediate tubules sealing capability and promoted mineral crystal growth over dentin and into the tubules during SBF-storage. For bonding to desensitizer-treated dentin, a two-step self-etching adhesive or universal bond with phosphoric acid pretreatment are recommended.

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 (α = 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.

Effect of light irradiation condition on gap formation under polymeric dental restoration; OCT study.

OBJECTIVE: To investigate the effect of two light-curing systems; quartz tungsten-halogen (QTH) and light-emitting diode (LED), and irradiation time on interfacial gap formation of dental composite resin restorations bonded with an adhesive resin using optical coherence tomography (OCT). MATERIALS AND METHODS: Forty cavities were prepared in extracted human molar teeth and divided into four groups (n=10) based on the type of light curing system QTH (LITEX 680A) and LED (Demi Plus) and curing duration (10 s or 40 s). A single-step self-etching dental adhesive (Tetric® N-Bond; Ivoclar Vivadent AG, Schaan, FL, Liechtenstein) was applied and polymerized with QTH for 10 s (QTH-10), or for 40 s (QTH-40). Similarly, the adhesive in LED-10 and LED-40 groups was polymerized with an LED for 10 s or 40 s, respectively. Then, all specimens were restored with Filtek™ Z350 XT flowable composite (3M ESPE AG, St. Paul, MN, USA) and immersed in ammoniacal silver-nitrate contrasting solution. Cross-sectional images were recorded at every 250µm using cross-polarization OCT system (CP-OCT; IVS-300, Santec, Komaki, Aichi, Japan). Image analysis to quantify the percentage of gap at resin-dentin interface was performed using a custom plugin for ImageJ software. RESULTS: Data analysis using one-way ANOVA showed a significant difference in mean gap percentage between the four test groups (p<0.0001). Mean gap percentage values were 75.8%, 53.2%, 9.9% and 5.6%. The highest for LED-10 followed by LED-40 (p <0.05). QTH-40 revealed a slightly better adaptation compared with QTH-10, but the difference between them was not significant (p <0.05). CONCLUSION: CP-OCT with a contrast agent is a useful non-invasive imaging tool for dental composite resin materials. QTH showed better results than LED under the experimental conditions. When using an LED light-curing unit, prolonged irradiation improved interfacial adaptation of dental composite bonded with a self-etching adhesive.

Effects of fiber reinforcement on adaptation and bond strength of a bulk-fill composite in deep preparations.

OBJECTIVE: This study investigated the effect of plasma-treated leno weaved ultra-high-molecular-weight polyethylene fiber placement on gap formation and microtensile bond strength (MTBS) of a bulk-fill composite in deep cavity. METHODS: Resin composite molds (3 mm width, 4 mm depth) were treated with Clearfil SE Bond 2 and restored with 3 techniques : (1) Surefil SDR flow (SDR) placed in bulk (BLK), (2) SDR placed in two unequal increments (INC) and (3) SDR placed after an increment of SDR placed with wetted polyethylene fiber (Ribbond Ultra) at the cavity floor (FRC). As a control, the cavities were bulk-filled with SDR and no bonding agent (n = 12). All the specimens were subjected to real-time and 3D imaging by SS-OCT (1330 nm) to calculate the total volume of gap formed (mm3) at the cavity floor and between the composite increments. For MTBS, the occlusal cavities of the similar dimensions (3 × 3 × 4 mm3) were prepared on extracted molars with similar composite placement techniques (BLK, INC and FRC). After 24 h 37 °C water storage, the specimens were sectioned using a diamond saw to create 0.7 × 0.7 mm2 beams for MTBS, and subjected to bond testing at a crosshead speed of 1 mm/min. Data for both tests was analyzed by one-way ANOVA and multiple-comparisons with Bonferroni correction (α = 0.05). RESULTS: The gap volumes were different among the groups (p < 0.05). The largest cavity floor gaps (mm3) were observed in the control group (2.00 ± 0.08); followed by BLK (0.74 ± 0.20) and INC (0.02 ± 0.01). In FRC, the cavity floor was gap-free in all specimens but some separation was observed between the two increments. MTBS values (MPa) were 13.8 ± 7.6, 31.7 ± 12.5 and 28.3 ± 8.5 for BLK, INC and FRC groups. There was no significant difference between FRC and INC and both were different from BLK (p < 0.05). SIGNIFICANCE: Gap formation of the bulk-fill composite at cavity floor was significantly reduced with the placement of a fiber-reinforced increment at the base of the deep preparation. The fiber-reinforced increment acts as a shrinkage stress breaker and protects the bonded interface at deep dentin.