Effect of manual and electrical brushing on the enamel of sound primary teeth and teeth with induced white spot lesions.

PURPOSE: To evaluate the effect of different electrical brushing systems on the surface roughness and wear profile of the enamel of sound primary teeth and teeth with induced white spot lesions. METHODS: 45 specimens were obtained from sound primary incisors, and the buccal surface was divided into four parts: sound enamel; enamel with white spot lesions; sound enamel with brushing; and enamel with white spot lesions and brushing. Specimens were randomly divided into three groups (n =15), according to the different brushing systems: Group 1 - Electric rotating toothbrush (Kid's Power Toothbrush - Oral B); Group 2 - Sonic electric toothbrush (Baby Sonic Toothbrush); and Group 3 - Manual toothbrush (Curaprox infantil) (control). The specimens were analyzed for surface roughness and wear profile. Data were analyzed by appropriate statistical tests, with a significance level of 5%. RESULTS: Regarding the surface roughness, no significant difference was observed between the groups. However, with respect to the wear profile, Group 1 caused significantly higher wear in the sound tooth enamel and in the presence of white spot lesions, in comparison to the other brushing systems (2 and 3) (P< 0.05), which did not cause wear. Manual and electric brushing (rotational and sonic) did not increase surface roughness in primary tooth enamel. However, the electric rotational brushing caused significant wear of the sound and demineralized enamel surface of primary teeth. CLINICAL SIGNIFICANCE: None of the toothbrushing systems tested caused significant alterations on sound dental enamel. However, rotational toothbrushing on enamel of primary teeth with white spot lesion increased wear.

Influence of Er,Cr:YSGG laser on dentin acid resistance after erosive challenge.

PURPOSE: To evaluate the influence of the Er,Cr:YSGG laser with or without the 5% fluoride varnish on the acid resistance of dentin after erosive challenge. METHODS: 36 incisors were selected and sectioned, obtaining 72 specimens of 4 mm × 4 mm and randomly divided into eight groups (n = 9). In G1: application of Er,Cr:YSGG (0.1W; 5Hz, air 55%); G2: laser (0.25W; 5Hz, air 55%); G3: fluoride varnish + laser (0.1W; 5Hz, air 55%); G4: fluoride varnish + laser (0.25W, 5Hz, air 55%); G5: fluoride varnish + laser (0.1W; 5Hz, without air); G6: fluoride varnish + laser (0.25W, 5Hz, without air); G7: fluoride varnish and G8: no treatment. When used, the laser was irradiated without water cooling, scanning mode during 10 seconds. The surface roughness data were subjected to ANOVA. For wear profile, we used Kruskal-Wallis test and Dunn post-hoc, all with α= 0.05. RESULTS: The results showed no statistically significant difference when comparing the groups as regards to the surface roughness (P> 0.05). Regarding the percentage of lost volume, the G5 and G6 groups presented the best results (G5 = 7.8% and G6 = 8.5%), with the lowest loss of dentin volume compared to other groups (P< 0.05). The G8 group (no treatment) had the highest lost volume (G8 = 39.1% followed by the G7 group (fluoride varnish), which had 25.9%. CLINICAL SIGNIFICANCE: The use of Er,Cr:YSGG laser and fluoride varnish can be an effective method to increase the acid resistance of dentin after erosive challenges, and limit problems related to hypersensitivity.

Surface roughness and bacterial adhesion on root dentin treated with diode laser and conventional desensitizing agents.

The treatments for dentin hypersensitivity (DH) may change the surface roughness of the root dentin, which can lead to biofilm accumulation, increasing the risk of root caries. The aim was to compare the surface roughness of root dentin after different treatments of DH and the biofilm formation on those surfaces. After initial surface roughness (Sa) assessment, 50 bovine root fragments received the following treatments (n = 10): G 1-no treatment; G2-5% sodium fluoride varnish; G3-professional application of a desensitizing dentifrice; G4-toothbrushing with a desensitizing dentifrice; and G5-diode laser application (908 nm; 1.5 W, 20 s). The Sa was reevaluated after treatments. Afterward, all samples were incubated in a suspension of Streptococcus mutans at 37 °C for 24 h. The colony-forming units (CFU) were counted using a stereoscope, and the results were expressed in CFU/mL. The one-way ANOVA and the Tukey's tests compared the roughness data and the results obtained on the bacterial adhesion test (α = 5%). G2 (2.3 ± 1.67%) showed similar Sa variation than G1 (0.25 ± 0.41%) and G5 (5.69 ± 0.99%), but different from group G3 (9.05 ± 2.39%). Group 4 showed the highest Sa variation (30.02 ± 3.83%; p < 0.05). Bacterial adhesion was higher in G4 (2208 ± 211.9), suggesting that bacterial growth is greater on rougher surfaces. The diode laser and the conventional treatments for DH may change the surface roughness of the root dentin, but only brushing with desensitizing dentifrice induced a higher bacteria accumulation on root dentin surface.

Effect of build orientation in gloss, roughness and color of 3D-printed resins for provisional indirect restorations.

OBJECTIVES: The purpose of this study was to evaluate the effect of build orientation of 3D-printed provisional resins (3DRs) on gloss (Gs), surface roughness (Sa), maximum profile valley depth (Rv), and color difference (∆E00). METHODS: PMMA CAD/CAM blocks (Vita Temp/Vita) were sectioned and served as a Control. Four 3DRs (Cosmos-SLA/Yller, Cosmos-DLP/Yller, PriZma-Bioprov/Makertech, Nanolab/Wilcos) were obtained as discs (15-mm diameter, 2.5-mm thickness) in three orientations (0°, 45°, and 90°) using different 3D printers (Form 2/Formlabs, P30/Straumann, Hunter/Flashforge, W3D/Wilcos, respectively). Samples were then cleaned with isopropyl alcohol prior to post-curing in specific post-curing units. Half of the samples' surface was covered with an adhesive tape and submitted to 10,000 toothbrushing (TB) cycles. The Gs and Sa at the brushed and not brushed surfaces were evaluated with a glossmeter (Novo-curve) and a laser confocal microscope (OLS5000) (n = 10), which also obtained the Rv and 3D representative images of the interface between not brushed and brushed surfaces. Electron microscopy images of the surface of some samples was also performed (n = 3). On another set of samples (n = 5), the coordinates of luminosity and color were obtained with a spectrophotometer (Easyshade V) at baseline and after 16.7 h and 200 h of UVB aging, to calculate the ∆E00 using CIEDE:2000 formula. Additionally, 3DRs photoinitiators were identified using a minispectrometer (USB2000 +) (n = 5). Data of Gs and Sa were submitted to three-way-, Rv to two-way-, and ∆E00 to mixed-ANOVA tests, followed by Tukey's test (α = 0.05). For all variables, results from experimental groups were compared to control using Dunnett's test (α = 0.05). Student's t-test was used to compare the control at different TB cycles (Gs, Sa) or aging periods (∆E00) (α = 0.05). RESULTS: Build orientation of 3DRs did not influence any of the variables studied. The 10,000 TB cycles resulted in a decrease in Gs and increase in Sa for all resins tested. The control showed higher Gs after 10,000 TB cycles than Cosmos-SLA and Nanolab resins. Compared to all 3DRs, Control presented lower ∆E00 after 200 h of UVB aging. All 3DRs presented higher ∆E00 than the clinically acceptable after 200 h of UVB aging. Lucirin® TPO was identified in all 3DRs, although PriZma might also present other photoinitiators and Nanolab might present Irgacure 369. SIGNIFICANCE: Alterations in build orientation are very useful and frequently performed in the day-today of 3D-printing, thus its effect in the optical properties and in the topography of 3D-printed restorations is very relevant. For the evaluated 3D-printed provisional resins, build orientation did not influence any of the variables studied (Gs, Sa, Rv, and ∆E00), even after toothbrushing cycles and UVB aging.

Effect of different root caries treatments on the sealing ability of conventional glass ionomer cement restorations.

In this study we compared the microleakage of conventional glass ionomer cement (GIC) restorations following the use of different methods of root caries removal. In vitro root caries were induced in 75 human root dentin samples that were divided in five groups of 15 each according to the method used for caries removal: in group 1 spherical carbide burs at low speed were used, in group 2 a hand-held excavator was used, and in groups 3 to 5 an Er,Cr:YSGG laser was used at 2.25 W, 40.18 J/cm(2) (group 3), 2.50 W, 44.64 J/cm(2) (group 4) and 2.75 W, 49.11 J/cm(2) (group 5). The air/water cooling during irradiation was set to 55%/65% respectively. All cavities were filled with GIC. Five samples from each group were evaluated by scanning electron microscopy (SEM) and the other ten samples were thermocycled and submitted to a microleakage test. The data obtained were compared by ANOVA followed by Fisher's test (p≤0.05). Group 4 showed the lowest microleakage index (56.65 6.30; p<0.05). There were no significant differences among the other groups. On SEM images samples of groups 1 and 2 showed a more regular interface than the irradiated samples. Demineralized dentin below the restoration was observed, that was probably affected dentin. Group 4 showed the lowest microleakage values compared to the other experimental groups, so under the conditions of the present study the method that provided the lowest microleakage was the Er,Cr:YSGG laser with a power output of 2.5 W yielding an energy density of 44.64 J/cm(2).

Physical and mechanical properties of a dental resin adhesive containing hydrophobic chitin nanocrystals.

OBJECTIVES: In this paper we propose embedding natural fillers, such as pristine and functionalized chitin nanocrystals, into resin adhesives to produce photopolymerizable dental filled adhesives with enhanced biocompatibility, hydrophobicity, mechanical resistance, and anti-bacterial properties. METHODS: Chitin nanocrystals (ChNC) were functionalized with decanoyl chloride and methacrylic anhydride to produce ChNC-C10 and ChNC-MA, respectively. These hydrophobically functionalized chitin nanocrystals were incorporated into a resin adhesive at concentrations of 0.5-3.0 wt% to assess the materials' physical and mechanical properties through Fourier-transform infrared (FTIR) spectroscopy, solid-state NMR spectroscopy, X-ray diffraction (XRD), elemental analysis, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), flexural strength, microhardness, and water sorption tests. RESULTS: The analytical techniques confirmed the successful preparation of chitin nanocrystals from commercial chitin powder derived from shrimp shells and the efficient hydrophobization of their surface. Electron microscope images indicated that the increased hydrophobicity of ChNC-C10 promotes the formation of layered structures throughout the resin adhesive, while ChNC-MA tends to form aggregates in the matrix. Adhesives filled with ChNC-C10 enhanced their flexural strength, microhardness, and thermal stability and decreased their water sorption and degree of conversion. Adhesives filled with ChNC-MA resulted in improvements in microhardness, in water sorption and degree of conversion, although they did not exhibit augmentation of their flexural strength and thermal stability. SIGNIFICANCE: In light of the improved physical and mechanical properties with respect to the control, resin adhesives filled with anti-bacterial chitin nanocrystals are promising new materials for dental applications, especially those filled with low/moderate amounts of ChNC-C10.

Effects of prolonged use of over-the-counter bleaching agents on enamel: An in vitro study.

This study evaluated the effects of four over-the-counter (OTC) bleaching products on the properties of enamel. Extracted human molars were randomly assigned into four groups (n = 5): PD: Poladay (SDI), WG: White Teeth Global (White Teeth Global), CW: Crest3DWhite (Procter & Gamble), and HS: HiSmile (HiSmile). The hydrogen peroxide (H2 O2 ) content in each product was analyzed via titration. Twenty teeth were sectioned into quarters, embedded in epoxy resin, and polished. Each quarter-tooth surface was treated with one of the four beaching times: T0: control/no-bleaching, T14: 14 days, T28: 28 days, and T56: 56 days. Materials were applied to enamel surfaces as recommended. Enamel surfaces were examined for ultramicrohardness (UMH), elastic modulus (EM), superficial roughness (Sa), and scanning electron microscopy (SEM). Ten additional teeth were used to evaluate color and degree of demineralization (DD) (n = 5). Data were statistically tested by two-way ANOVA and Tukey's tests (α = 5%). Enamel surfaces treated with PD and WG presented UMH values significantly lower than the controls (p < .05). Elastic modulus (E) was significantly reduced at T14 and T28 for PD, and at T14 for HS (p < .05). A significant increase in Sa was observed for CW at T14 (p < .05). Color changes were observed in the PD and WG groups. Additionally, DD analysis showed significant demineralization at T56 for CW. Overall, more evident morphological alterations were observed for bleaching products with higher concentrations of H2 O2 (p < .05), PD, and WG. Over-the-counter bleaching products containing H2 O2 can significantly alter enamel properties, especially when application time is extended.

Laser irradiation prevents root caries: Microhardness and scanning electron microscopy analysis.

Context: A promising option for the prevention of dental caries is the use of laser irradiation. Aims: Evaluate the effects of Er:YAG, Nd:YAG, and CO2 laser irradiation, associated or not to 2% sodium fluoride (2% NaF), on root caries prevention. Material and Methods: One hundred and four human root dentin samples were divided in eight groups (n = 13). A 9-mm2-area on each dentin sample was delimited and treated as follows: G1: no treatment (control); G2: 2% NaF; G3: Er:YAG; G4: 2% NaF + Er:YAG; G5: Nd:YAG; G6: 2% NaF + Nd:YAG; G7: CO2; G8: 2% NaF + CO2. When used, the 2% NaF was applied before irradiation for 4 min. The samples were subjected to a 2-week cariogenic challenge, consisted of daily immersion in de-remineralizing solutions for 6 h and 18 h, respectively. Knoop hardness (KHN) were evaluated (10 g and 20 s) at different depths from the dentin surface. The samples (n = 3) were prepared for scanning electron microscopy (SEM). Microhardness data were analysed by one-way analysis of variance (ANOVA) and Fisher's test (α = 5%). Results: The Er:YAG laser group (KHN = 41.30) promoted an increase in acid resistance of the dentin (P < 0.05) when compared to all groups. There was no synergism between laser irradiation and 2% NaF application. Morphological changes were observed after irradiation with all lasers; carbonization and cracks were also observed, except when Er:YAG were used. Conclusions: Er:YAG laser irradiation can safely increase the acid resistance of the dentin surface of the root, since it promoted a significant increase in surface hardness. The application of 2% NaF did not result in a synergistic effect.

Characterization of polymethylmethacrylate microspheres loaded with silver and doxycycline for dental materials applications.

OBJECTIVES: The manufacturing of polymethylmethacrylate(PMMA) microspheres loaded with doxycycline(DOX) and/or silver sulfate(Ag2SO4) to be incorporated into glass ionomer cement(GIC). METHODS: PMMA microspheres were manufactured with Ag2SO4(1-5%) and/or DOX(5-15%). Particle size, encapsulation efficiency and drug release were measured by light microscope, ICP, and HPLC. Microspheres were added to a dental GIC(20%w/w). Drug release and DTS were investigated. Minimum inhibitory concentration and antibacterial effects of PMMA microspheres into GIC materials were tested. RESULTS: The median diameter of 50 µm was obtained for microspheres. DOX was encapsulated at an efficiency of 8.3% using a theoretical loading of 15%DOX + 5%Ag2SO4. The Ag2SO4 encapsulation efficiency was 0.63% using a theoretical loading of 5%AgSO4. All groups showed burst release within the first day and continued released up to 15 days, with 60-83% of DOX and approximately 30% of silver. For GIC, approximately 15% of DOX and 0.18% of silver were released in a 7-day period. Microbiological results showed an antimicrobial effect against S. mutans when the lead formulation of microspheres was added. The DTS was reduced by the inclusion of microspheres. SIGNIFICANCE: PMMA microspheres containing DOX and Ag2SO4 offer a sustained antimicrobial activity for dental applications and promising potential for the biomedical field.

Phosphoric acid containing proanthocyanidin enhances bond stability of resin/dentin interface.

Proanthocyanidin (PA) is a promising dentin biomodifier due to its ability to stabilize collagen fibrils against degradation by matrix metalloproteinases (MMPs); however, the most effective protocol to incorporate PA into bonding procedures is still unclear. This study evaluated the effect of dentin biomodification with a PA acid etchant on MMP activity, adhesive interface morphology and resin-dentin microtensile bond strength. Sound extracted human molars were flattened to expose dentin and acid-etched for 15 s according to the groups: EXP - experimental phosphoric acid; EXP+PA - experimental phosphoric acid 10% PA; TE - total-etching system; SE - self-etching system. Samples were restored with composite resin and stored in distilled water (37ºC). MMP activity and interface morphology were analyzed after 24 h by in situ zymography (n=6) and scanning electron microscopy (n=3), respectively. The resin-dentin microtensile bond strength (µTBS) was evaluated after 24 h and 6 months storage (n=6). Significantly higher MMP activity was detected in etched dentin compared with untreated dentin (p<0.05), but no difference among acid groups was found. Resin tags and microtags, indicative of proper adhesive system penetration in dentinal tubules and microtubules, were observed along the hybrid layer in all groups. There was no difference in µTBS between 24 h and 6 months for EXP+PA; moreover, it showed higher long-term µTBS compared with TE and EXP (p<0.05). The results suggest that 15 s of biomodification was not sufficient to significantly reduce MMP activity; nonetheless, EXP+PA was still able to improve resin-dentin bond stability compared with total- and self-etching commercial systems.

Composite filling removal with erbium:yttrium-aluminum-garnet laser: morphological analyses.

Considering the increase in esthetic restorative materials and need for improvement in unsatisfactory restoration substitution with minimal inadvertent removal of healthy tissues, this study assessed the efficacy of erbium:yttrium-aluminum-garnet (Er:YAG) laser for composite resin removal and the influence of pulse repetition rate on the morphological analyses of the cavity by scanning electron microscope. Composite resin fillings were placed in cavities (1.0 mm deep) prepared in bovine teeth, and the 75 specimens were randomly assigned to five groups according to the technique used for composite filling removal (high-speed diamond bur, group I, as a control, and Er:YAG laser, 250 mJ output energy and 80 J/cm(2) energy density, using different pulse repetition rates: group II, 2 Hz; group III, 4 Hz; group IV, 6 Hz; group V, 10 Hz). After the removal, the specimens were split in the middle, and we analyzed the surrounding and deep walls to check for the presence of restorative material. The estimation was qualitative. The surfaces were examined with a scanning electron microscope. The results revealed that the experimental groups presented bigger amounts of remaining restorative material. The scanning electron microscopy (SEM) analyses showed irregularities of the resultant cavities of the experimental groups that increased proportionally with increase in repetition rate.

Peracetic acid as a single endodontic irrigant: effects on microhardness, roughness and erosion of root canal dentin.

The aim was to assess the effects of 1% peracetic acid (PAA) as a single endodontic irrigant on microhardness, roughness, and erosion of root canal dentin, compared with 2.5% sodium hypochlorite (NaOCl) and with 2.5% NaOCl combined with 17% EDTA. Forty human, single-rooted tooth hemisections were submitted to Knoop microhardness test, before and after the following irrigation protocols: PAA = 1% PAA; NaOCl = 2.5% NaOCl; NaOCl-EDTA-NaOCl = 2.5% NaOCl +17% EDTA +2.5% NaOCl; and SS = saline. Another 40 roots were instrumented, irrigated with the same protocols, and sectioned longitudinally. The roughness analysis was performed on the mesial section using a confocal laser scanning microscope, whereas erosion was analyzed on each third of the distal section, using a scanning electron microscope. The data were analyzed using ANOVA and Tukey post-tests, and Kruskal-Wallis and Dunn post-tests (α = .05). The PAA and NaOCl-EDTA-NaOCl groups showed no significant differences (p > .05); both promoted reduction in microhardness and increase in roughness, compared with the NaOCl and SS groups (p < .05). NaOCl-EDTA-NaOCl promoted higher erosion in the cervical and middle thirds than the other groups (p < .05); there was no difference among PAA, NaOCl, and SS (p > .05). There was also no difference among the groups regarding the apical third (p > .05). PAA used as a single endodontic irrigant caused reduction in root canal dentin microhardness and increase in roughness in a similar way to NaOCl-EDTA-NaOCl; however, PAA caused less erosion than NaOCl-EDTA-NaOCl.

Radiotherapy Activates Matrix Metalloproteinases in the Dentinoenamel Junction of Primary Teeth.

Purpose: Radiation-related caries is characterized by enamel delamination near the dentinoenamel junction (DEJ). We investigated the activity and expression of the matrix metalloproteinases (MMPs) -2 and -9 in order to understand disease pathogenesis in teeth submitted or not to radiotherapy (RT).
Methods: In situ zymography and immunofluorescence assays were performed to evaluate the activity and expression of MMPs -2 and -9, respectively. Twelve primary second molars were randomly assigned into two experimental subgroups: irradiated and nonirradiated. Dental fragments were exposed to radiation at a dose fraction of two Gy for five consecutive days until reaching the total dose of 60 Gy. The percentage of fluorescence in the DEJ was evaluated in three distinct regions of the tooth (cervical, cusp, and pit). The regions were photographed under fluorescence microscopy at 1.25× and 5× magnification.
Results: The intensity of fluorescence per mm 2 in the DEJ was higher in the cervical region of irradiated primary teeth (P <0.05) versus nonirradiated ones. In these areas, immunofluorescence revealed expression of MMPs -2 and -9.
Conclusion: Radiotherapy can increase the activity of MMPs -2 and -9 in the cervical region of the DEJ of primary teeth.

Biomechanical behavior of maxillary premolars with conservative and traditional endodontic cavities.

OBJECTIVE: The objective was to evaluate the effects of the configuration of endodontic cavities with parallel or divergent walls, versus traditional endodontic cavities, on stress distribution, fracture resistance, and fracture mode of maxillary premolars by using both fracture-strength and finite element tests. METHOD AND MATERIALS: Thirty-two maxillary first premolars were divided into four groups (n = 8), according to the type of endodontic cavities: without endodontic cavities (control); conservative; conservative with diverging walls; and traditional. After performing root canal treatment and restoration, fracture resistance was evaluated by oblique compressive load. The stress distribution was evaluated by nonlinear finite element analysis by means of micro-computed tomography, operated at 50 kV and 800 mA. The fracture resistance data were analyzed by statistical software. RESULTS: Higher stress concentration was observed on the coronal portion of the palatal cusp and the palatal root dentin. Stress concentration on the palatal root dentin was similar for all groups. The stress level on the palatal cusp and at the proximal crests was slightly increased in the traditional endodontic cavities group compared with conservative endodontic cavities. Stress distribution in restored teeth was similar to that of intact teeth. No significant differences were observed in the fracture resistance among different endodontic cavities' design (P = .32). All groups had values similar to those of the control group (P > .05). CONCLUSIONS: Regardless of the cavity design, conservative endodontic cavities that preserve marginal ridge integrity did not affect the resistance to fracture, failure mode, or stress distribution in maxillary premolars restored with composite resin. Endodontically treated teeth displayed biomechanical behavior similar to sound teeth.

Influence of pulse repetition rate on temperature rise and working time during composite filling removal with the Er:YAG laser.

OBJECTIVE: The purpose of this study was to assess the efficacy of Er:YAG laser energy for composite resin removal and the influence of pulse repetition rate on the thermal alterations occurring during laser ablation. MATERIALS AND METHODS: Composite resin filling was placed in cavities (1.0 mm deep) prepared in bovine teeth and the specimens were randomly assigned to five groups according to the technique used for composite filling removal. In group I (controls), the restorations were removed using a high-speed diamond bur. In the other groups, the composite fillings were removed using an Er:YAG laser with different pulse repetition rates: group 2-2 Hz; group 3-4 Hz; group 4-6 Hz; and group 5-10 Hz. The time required for complete removal of the restorative material and the temperature changes were recorded. RESULTS: Temperature rise during composite resin removal with the Er:YAG laser occurred in the substrate underneath the restoration and was directly proportional to the increase in pulse repetition rate. None of the groups had a temperature increase during composite filling removal of more than 5.6 degrees C, which is considered the critical point above which irreversible thermal damage to the pulp may result. Regarding the time for composite filling removal, all the laser-ablated groups (except for group 5 [10 Hz]) required more time than the control group for complete elimination of the material from the cavity walls. CONCLUSION: Under the tested conditions, Er:YAG laser irradiation was efficient for composite resin ablation and did not cause a temperature increase above the limit considered safe for the pulp. Among the tested pulse repetition rates, 6 Hz produced minimal temperature change compared to the control group (high-speed bur), and allowed composite filling removal within a time period that is acceptable for clinical conditions.

Assessment of thermal alteration during class V cavity preparation using the Er:YAG laser.

OBJECTIVE: The aim of this study was to evaluate in vitro the pulp thermal alterations during class V cavity preparations using the Er:YAG laser and high-speed water flow. MATERIALS AND METHODS: Forty human teeth were selected and prepared for the thermocouple adaptation in the pulp chamber. The specimens were assigned to four groups: (1) laser 300 mJ/3 Hz, (2) laser 300 mJ/4 Hz, (3) high-speed 9 mL/min water flow, and (4) high-speed 100 mL/min water flow. The temperature was measured before the beginning and at the end of the preparation, as well as during the procedures. The groups were analyzed by scanning electron microscopy. RESULT: Data analysis disclosed temperature reduction at high-speed drilling with the high-speed total water flow group, and these values were statistically different from the other groups. The results of the 9-mL/min water flow group were similar to those of the 300-mJ/3-Hz group and different from the 300-mJ/4-Hz laser group. CONCLUSION: The laser promoted a greater increase in temperature only when compared with high-speed handpiece and water flow rate of 100 mL/min.

Phosphoric acid containing proanthocyanidin enhances bond stability of resin/dentin interface

Abstract Proanthocyanidin (PA) is a promising dentin biomodifier due to its ability to stabilize collagen fibrils against degradation by matrix metalloproteinases (MMPs); however, the most effective protocol to incorporate PA into bonding procedures is still unclear. This study evaluated the effect of dentin biomodification with a PA acid etchant on MMP activity, adhesive interface morphology and resin-dentin microtensile bond strength. Sound extracted human molars were flattened to expose dentin and acid-etched for 15 s according to the groups: EXP - experimental phosphoric acid; EXP+PA - experimental phosphoric acid 10% PA; TE - total-etching system; SE - self-etching system. Samples were restored with composite resin and stored in distilled water (37ºC). MMP activity and interface morphology were analyzed after 24 h by in situ zymography (n=6) and scanning electron microscopy (n=3), respectively. The resin-dentin microtensile bond strength (μTBS) was evaluated after 24 h and 6 months storage (n=6). Significantly higher MMP activity was detected in etched dentin compared with untreated dentin (p<0.05), but no difference among acid groups was found. Resin tags and microtags, indicative of proper adhesive system penetration in dentinal tubules and microtubules, were observed along the hybrid layer in all groups. There was no difference in μTBS between 24 h and 6 months for EXP+PA; moreover, it showed higher long-term μTBS compared with TE and EXP (p<0.05). The results suggest that 15 s of biomodification was not sufficient to significantly reduce MMP activity; nonetheless, EXP+PA was still able to improve resin-dentin bond stability compared with total- and self-etching commercial systems.

Resumo A proantocianidina (PA) é um biomodificador dentinário promissor devido a sua capacidade de estabilizar as fibrilas colágenas contra a degradação por metaloproteinases da matriz (MMPs); no entanto, o protocolo mais eficaz para a incorporação de PA em procedimentos adesivos ainda não está claro. Este estudo avaliou o efeito da biomodificação da dentina com um condicionador ácido contendo PA na atividade de MMPs, morfologia da interface adesiva e resistência à microtração resina-dentina. Molares humanos extraídos foram lixados para exposição da dentina e condicionados com ácido por 15 s de acordo com os grupos: EXP - ácido fosfórico experimental; EXP+PA - ácido fosfórico experimental com 10% PA; TE - sistema total-etch; SE - sistema self-etch. As amostras foram restauradas com resina composta e armazenadas em água destilada (37ºC). A atividade de MMP e morfologia da interface foram analisadas após 24 h por zimografia in situ (n=6) e microscopia eletrônica de varredura (n=3), respectivamente. A resistência à microtração resina-dentina (μTBS) foi avaliada após 24 horas e 6 meses de armazenamento (n=6). Atividade de MMP detectada na dentina condicionada foi significativamente maior em comparação com a dentina não tratada (p <0,05), mas não houve diferenças entre os diferentes ácidos. Tags e microtags de resina, indicativos de uma penetração adequada do sistema adesivo nos túbulos e microtúbulos dentinários, foram observadas ao longo da camada híbrida em todos os grupos. Não houve diferença entre os valores de μTBS de 24 h e 6 meses para EXP+PA; além disso, EXP+PA apresentou maiores valores de μTBS após 6 meses em comparação com TE e EXP (p <0,05). Os resultados sugerem que a biomodificação por 15 s não foi suficiente para reduzir significativamente a atividade de MMP; apesar disso, EXP + PA foi capaz de melhorar a estabilidade da interface resina-dentina em comparação com sistemas total- e self-etch comerciais.

In Vitro Evaluation of Dentin Hydraulic Conductance After 980 nm Diode Laser Irradiation.

BACKGROUND: Dentin hypersensitivity treatments are based on the physical obliteration of the dentinal tubules to reduce hydraulic conductance. The aim of the present study is to evaluate the hydraulic conductance of bovine root dentin after irradiation with a 980-nm diode laser, with or without associated fluoride varnish. METHODS: Sixty bovine root dentin specimens were divided into six groups (n = 10 in each group): G1, G3, and G5 (0.5 W, 0.7 W, and 1 W diode laser, respectively); G2, G4, and G6 (fluoride varnish application + 0.5 W, 0.7 W, and 1 W diode laser, respectively). The dentin hydraulic conductance was evaluated at four time periods with a fluxmeter: 1) with smear layer, 2) after 37% phosphoric acid etching, 3) after the treatments, and 4) after 6% citric acid challenge. After the dentinal fluid flow measurements, specimens were also evaluated for mineral composition using energy dispersive X-ray spectroscopy (EDS). RESULTS: Analysis demonstrated a better result with increased irradiation power (P < 0.001), especially if the diode laser irradiation was associated with the application of fluoride varnish (P < 0.001), ensuring a greater reduction in permeability. Considering the groups treated only with laser irradiation, the 1 W group was superior when compared with the 0.5 W and 0.7 W irradiated groups immediately after treatment (P < 0.001). After citric acid testing, all groups showed similar results, except when comparing the 1 W groups with the 0.5 W groups (P = 0.04). EDS results of the irradiated groups showed an increase in the proportion of calcium and phosphorus ions, which demonstrates a superficial composition modification after laser treatments. CONCLUSION: Laser irradiation of exposed dentin promoted significant reduction in the dentin hydraulic conductance, mainly with higher energy densities and association with fluoride varnish.

Shear bond strength to enamel of primary teeth irradiated with varying Er:YAG laser energies and SEM examination of the surface morphology: an in vitro study.

OBJECTIVE: This study aimed to assess in vitro the influence of Er:YAG laser energy on the shear bond strength of a total-etch adhesive system to lased enamel of primary teeth, and to observe by SEM the morphological appearance of laser-ablated enamel surfaces. MATERIALS AND METHODS: For the SBS test, primary canines were assigned to four groups (n = 12): a control (G1) and three groups irradiated with different Er:YAG laser energies- 60 mJ/2 Hz (G2), 80 mJ/2 Hz (G3), and 100 mJ/2 Hz (G4). In all groups, enamel surfaces were acidetched, Single Bond was applied, and resin cylinders were fabricated from Z250 resin. Bond strength was tested in shear (0.5 mm/min). For morphological analysis, 21 specimens were irradiated using the same energies, with or without acid-etching, and observed by SEM. RESULTS: SBS means, in MPa, were: G1-14.28 (+/-3.24); G2-18.48 (+/-4.58); G3-17.82 (+/-4.38); G4-16.59 (+/-5.40). Overall, Er:YAG laser ablation of primary teeth enamel, prior to the adhesive protocol, influenced the shear bond strength. Bond strengths recorded after irradiation with energies of 60 and 80 mJ were statistically similar among them (p > 0.05), and both were superior to those yielded by the acid-etched control group (p < 0.05). No significant difference (p < 0.05) was found between bond strengths recorded for control specimens and those irradiated with 100 mJ. SEM analysis revealed that the increase of laser energy resulted in increasingly uneven and microroughened surfaces, regardless of acid-etching association. CONCLUSIONS: The favorable results of the present study suggest that Er:YAG laser irradiation may be a viable approach for the preparation and treatment of primary teeth enamel prior to the placement of adhesive restorative systems.

Influence of the use of Er:YAG laser for cavity preparation and surface treatment in microleakage of resin-modified glass ionomer restorations.

This study quantitatively assessed the amount of microleakage on Class V cavities prepared by Er:YAG laser and high-speed handpiece, varying the surface treatment and restoring with a resin-modified glass ionomer cement. Fifty cavities were prepared using either an Er:YAG laser device or a carbide bur at high speed. The surface treatment was performed as follows: Er:YAG laser irradiation (G1); 40% polyacrylic acid (G2); laser + acid (G3); finishing with low speed + laser + acid (G4); conventional bur preparation + acid (G5-control). The samples were restored with Fuji II LC, thermocycled, isolated and immersed in a 50% AgNO3 solution. The restorations were serially sectioned and the extent of dye penetration was measured in milimeters using specific computer software. Data were analyzed by two-way ANOVA and Tukey test. The lowest degree of microleakage was observed for G5, which was statistically similar (p>0.05) to G4 but different (p<0.05) from all the other experiental groups. Lesser microleakage was observed at the occlusal margins than at the cervical margins (p<0.05). It may be concluded that the use of Er:YAG laser for cavity preparation and surface treatment negatively affected the marginal sealing of resin-modified glass ionomer restorations.