Effect of different power settings of Er,Cr:YSGG laser before or after tribosilicatization on the microshear bond strength between zirconia and two types of cements.

The aim of this study was to evaluate the effect of different output powers of Er,Cr:YSGG laser and the association with tribochemical silica coating on the bond strength between zirconia ceramic and two resin cements. One hundred ninety-two zirconia ceramic bars (IPS e-max ZirCAD Ivoclar Vivadent-) were sectioned (6 × 6 × 4 mm), sintered, and randomly divided into 12 groups for each cement system according to the surface treatment (n = 8): C-without treatment (control); R-tribochemical coating + resin cement (control); 2L-laser (2.0 W) + resin cement; 2LR-laser (2.0 W) + tribochemical coating + resin cement; R2L-tribochemical coating + laser (2.0 W) + resin cement; 2.5L-laser (2.5 W) + resin cement; 2.5LR-laser (2.5 W) + tribochemical coating + resin cement; R2.5L-tribochemical coating + laser (2.5 W) + resin cement; 3L-laser (3.0 W) + resin cement; 3LR-laser (3.0 W) + tribochemical coating + resin cement, R3L-tribochemical coating + laser (3.0 W) + resin cement; and RPHO-tribochemical + resin cement + photoactivation (control). After the surface treatment, the respective primers were applied, and resin cements, Multilink N, Ivoclar Vivadent (M), and Panavia F 2.0, Kuraray Medical Inc. (P), were inserted into Tygon molds which were bonded to the zirconia bars. Each specimen received two cements bars. After 24 h of storage in a relative humidity (100%) at 37 °C, they were evaluated by the microshear test speed of 1 mm/min. The microshear values were analyzed by one-way ANOVA and Tukey's test (α = 0.05). ANOVA showed statistically significant differences among the evaluated groups. The highest bond strength was observed in RPHO, which statistically differed from all groups. The lowest bond strength was observed in M2.5L (Multilink N) and in P3LR (Panavia F 2.0). It can be concluded that the lowest power output tested was suitable and showed bond strength values similar to tribochemical silica deposition. The light curing is important to adhesion and the tribosilicatizated surface achieves similar microshear values to untreated surface in absence of light.

Microwave radiation is effective at disinfecting dental stone surfaces without changing their physical properties.

The aims of this study were to evaluate the effectiveness of different microwave radiation regimens for disinfection of type IV dental stone surfaces and to assess the influence of these regimens on surface roughness and dimensional change following disinfection. Three hundred cylindrical (20 × 2-mm) test specimens were made in type IV stone and divided into subgroups of 20 according to the microorganisms tested (Staphylococcus aureus, Escherichia coli, or Candida albicans) and the 900-W microwave radiation protocol (cycles of 3, 5, or 7 minutes; a positive control; or a negative control). To test physical changes, 80 test specimens were made with the same dimensions except that they had 2 parallel and symmetrical indentations measuring 8 × 4 mm. These specimens were divided into 4 subgroups of 20 each (a subgroup for each radiation time and a negative control). The mean dimensional change and roughness data were analyzed by mixed models for repeated measures and Tukey-Kramer tests. Disinfection was analyzed with descriptive statistics. For E coli and C albicans, all radiation times proved effective at sterilizing the test specimens. For S aureus, sterilization was achieved with 5 and 7 minutes of exposure; however, colonies were observed in 10 Petri dishes (50%) exposed to 3 minutes of microwave radiation. No statistically significant difference in dimensional change or surface roughness was observed for any radiation regimen (P > 0.05).

The effect of cigarette smoking on early osseointegration of dental implants: a prospective controlled study.

OBJECTIVE: This study evaluated the effect of cigarette smoking on the percentage of early bone-to-implant contact (BIC%), the bone density in the threaded area (BA%) as well as the bone density outside the threaded area (BD%) around micro-implants with sandblasted acid-etched surface retrieved from human jaws. MATERIAL AND METHODS: Twenty-two subjects (mean age 55.4 ± 4.5 years) were divided in two groups: smokers (n = 11 subjects) and never-smokers (n = 11 subjects). Each subject received one micro-implant during conventional mandible or maxilla implant surgery. After 8 weeks, the micro-implants and the surrounding tissue were removed and prepared for histomorphometric analysis. RESULTS: Two micro-implants placed in smokers showed no osseointegration. Early stages of maturation of the newly formed bone were present, mainly in the never-smokers. Marginal bone loss, gap, and fibrous tissue were present around some implants retrieved from smokers. Histometric evaluation indicated that the mean BIC% ranged between 25.9 ± 9.1 and 39.8 ± 14.2 for smokers and non-smokers, respectively (P = 0.02). Smokers presented 28.6 ± 10.1 of BA% while never-smokers showed 46.4 ± 18.8 (P = 0.04). The mean of BD% ranged between 19.1 ± 7.6 and 28.5 ± 18.8 for smokers and never-smokers, respectively (P = 0.21). CONCLUSION: Cigarette smoking has a detrimental effect on early bone tissue response around sandblasted acid-etched implant surface topographies.

Surface alterations of zirconia and titanium substrates after Er,Cr:YSGG irradiation.

This study investigated changes in the roughness parameters (Sa in µm(2) and Ra in µm) of yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) and large-grit sandblasted acid-etched (SLA) titanium (TI) materials after decontamination by erbium chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation. Twenty disks were analyzed in this study: 10 disks of Y-TZP (5 mm in diameter and 3 mm in height), standardized with CAD-CAM procedures, and 10 disks of SLA TI (5 mm in diameter and 4 mm in thickness). Disks were randomized into four groups (n = 5), according to whether laser irradiation was performed: Y-TZP_G1 and TI_G1 were not treated by laser (control groups), whereas Y-TZP_G2 and TI_G2 were irradiated with Er,Cr:YSGG laser (1.5 W/20 Hz, air-water cooling proportion of 80%/25%). The surface topography of the disks was analyzed by confocal light microscopy. The mean Sa and Ra values were calculated from five profiles from each group. The results were statistically analyzed by t-test at the 95% confidence level (α = 0.05). For Y-TZP, the Sa results (in mean ± SD) for Y-TZP_G1 and Y-TZP_G2 were 2.60 ± 1.1 and 0.80 ± 0.17 µm(2), respectively, and the Ra results were 2.01 ± 0.71 and 0.18 ± 0.15 µm, respectively (both p < .05). For SLA TI, the Sa results for TI_G1 and TI_G2 were 1.99 ± 0.5 and 3.37 ± 0.75 µm(2), respectively, and the Ra results were 1.78 ± 0.53 and 3.84 ± 0.63 µm, respectively (both p < .05). Er,Cr:YSGG laser irradiation alters the surface roughness of zirconia and SLA TI.

Bond Strength of a Flowable Bulk-fill Resin Composite in Class II MOD Cavities.

PURPOSE: To evaluate the microtensile bond strength (µTBS) of a bulk-fill low-stress resin-based composite to dentin from gingival walls of Class II MOD cavities. MATERIALS AND METHODS: Class II MOD cavities were prepared in 44 human molars with the distal and mesial proximal boxes 4 and 6 mm deep, respectively. Eight experimental groups (n = 11) were obtained by a factorial design including 1. "composite" in two levels: a bulk-fill low-stress composite (SureFil SDR Flow, Dentsply Caulk) and a conventional composite (Filtek Z350 XT, 3M ESPE); 2. "filling technique" in two levels: bulk-fill (Bf) and incremental (In); and 3. "depth" in two levels: 4 mm and 6 mm in order to create different polymerization conditions. Twenty-four hours after placement of restorations, teeth were sectioned into beams with a cross-sectional bonded area of approximately 1 mm2. Bonded beams obtained from the gingival walls of the proximal boxes were tested in tension at a crosshead speed of 1 mm/min. Data were submitted to a 3-way ANOVA followed by a post-hoc Tukey's test (p < 0.05). RESULTS: ANOVA failed to identify significant differences for the triple and double interaction between factors. However, significant differences were observed for the factors "composite" and "filling technique" (p < 0.05). SDR presented significantly higher µTBS values for bulk and incremental filling techniques (p < 0.05), and the incremental filling technique presented significantly higher µTBS values for both composites (p < 0.05). CONCLUSION: It can be concluded that the bulk-fill flowable composite SDR may improve the bond strength to the gingival walls of Class II MOD cavities.

The effect of baking soda when applied to bleached enamel prior to restorative treatment.

This in vitro study evaluated the effect of 10% baking soda solution and sodium bicarbonate powder (applied with jets) when applied to bleached enamel prior to restorative treatment. The surfaces of 40 bovine incisors were flattened and divided into 5 groups (n = 8): Group B (bleached and restored, negative control), Group W (bleached, stored in distilled water for 7 days, and restored), Group BSJ (bleached, abraded with baking soda jet for 1 min, and restored), Group BSS (bleached, application of 10% baking soda solution for 5 min, and restored), and Group R (restored, without bleaching, positive control). The samples were bleached in 1 session with 3 applications of 35% HP-based gel and activated with a LED appliance for 9 min each. Resin composite cylinders (2 mm height and 0.8 mm diameter) were made on the enamel surface after the acid etching and a conventional 1-step single vial adhesive application was performed. After storage in distilled water (37 ± 1°C, 24 hr), the microshear bond test was performed (1 mm/min). ANOVA and Tukey tests were applied to compare the results. The mean results of these tests showed that Groups W, BBS, and R were not statistically different. These groups also indicated a higher bond strength when compared with Groups B and BSJ. The application of 10% baking soda solution for 5 min may be an alternative pre-restorative treatment for bleached enamel, but further studies are needed to consider whether or not this treatment may be effectively used in clinical practice.

Antibacterial Activity of a Bioactive Tooth-Coating Material Containing Surface Pre-Reacted Glass in a Complex Multispecies Subgingival Biofilm.

Bioactive materials were developed with the ability to release fluoride and provide some antimicrobial potential, to be widely used in dentistry today. However, few scientific studies have evaluated the antimicrobial activity of bioactive surface pre-reacted glass (S-PRG) coatings (PRG Barrier Coat, Shofu, Kyoto, Japan) on periodontopathogenic biofilms. This study evaluated the antibacterial activity of S-PRG fillers on the microbial profile of multispecies subgingival biofilms. A Calgary Biofilm Device (CBD) was used to grow a 33-species biofilm related to periodontitis for 7 days. The S-PRG coating was applied on CBD pins from the test group and photo-activated (PRG Barrier Coat, Shofu), while the control group received no coating. Seven days after treatment, the total bacterial counts, metabolic activity, and microbial profile of the biofilms were observed using a colorimetric assay and DNA-DNA hybridization. Statistical analyses were applied; namely, the Mann-Whitney, Kruskal-Wallis, and Dunn's post hoc tests. The bacterial activity of the test group was reduced by 25.7% compared with that of the control group. A statistically significant reduction was observed for the counts of 15 species: A. naeslundii, A. odontolyticus, V. parvula, C. ochracea, C. sputigena, E. corrodens, C. gracilis, F. nucleatum polymorphum, F. nucleatum vincentii, F. periodonticum, P. intermedia, P. gingivalis, G. morbillorum, S. anginosus, and S. noxia (p ≤ 0.05). The bioactive coating containing S-PRG modified the composition of the subgingival biofilm in vitro, thereby decreasing colonization by pathogens.

Microtensile bond strength of resin composite to dentin treated with Er:YAG laser of bleached teeth.

The objective of this study was to evaluate the influence of Er:YAG laser (λ = 2.94 µm) on microtensile bond strength (µTBS) and superficial morphology of bovine dentin bleached with 16% carbamide peroxide. Forty bovine teeth blocks (7 × 3 × 3 mm(3)) were randomly assigned to four groups: G1- bleaching and Er:YAG irradiation with energy density of 25.56 J/cm(2) (focused mode); G2 - bleaching; G3 - no-bleaching and Er:YAG irradiation (25.56 J/cm(2)); G4 - control, non-treated. G1 and G2 were bleached with 16% carbamide peroxide for 6 h during 21 days. Afterwards, all blocks were abraded with 320 to 600-grit abrasive papers to obtain flat standardized dentin surfaces. G1 and G3 were Er:YAG irradiated. Blocks were immediately restored with 4-mm-high composite resin (Adper Single Bond 2, Z-250-3 M/ESPE). After 24 h, the restored blocks (n = 9) were serially sectioned and trimmed to an hour-glass shape of approximately 1 mm(2) at the bonded interface area, and tested in tension in a universal testing machine (1 mm/ min). Failure mode was determined at a magnification of 100× using a stereomicroscope. One block of each group was selected for scanning electron microscope (SEM) analysis. µTBS data was analyzed by two-way ANOVA and Tukey test (α = 0.05). Mean bond strengths (SD) in MPa were: G1- 32.7 (5.9)(A); G2- 31.1 (6.3)(A); G3- 25.2 (8.3)(B); G4- 36.7 (9.9).(A) Groups with different uppercase letters were significantly different from each other (p < .05). Enamel bleaching procedure did not affect µTBS values for dentin adhesion. Er:YAG laser irradiation with 25.56 J/cm(2) prior to adhesive procedure of bleached teeth did not affect µTBS at dentin and promoted a dentin surface with no smear layer and opened dentin tubules observed under SEM. On the other hand, Er:YAG laser irradiation prior to adhesive procedure of non-bleached surface impaired µTBS compared to the control group.

Surface roughness evaluation and shade changes of a nanofilled resin composite after bleaching and immersion in staining solutions.

PURPOSE: To investigate the effect of bleaching and staining solutions on roughness and shade changes in a nanofilled resin composite [Filtek Supreme (FS)]. METHODS: FS specimens (n = 135) were light cured and separated into groups (n = 45) that were bleached with 10% carbamide peroxide (CP) agent or 16% or 35% hydrogen peroxide (HP). In the first two groups the bleaching gel was used for 4 hours a day, during 14 days, and for the third group in three sessions of 45 minutes. Each group was subdivided (n = 15) and immersed in coffee, red wine or distilled water for 3 hours a day during 40 days. The roughness values (Ra) and shade (parameter CLELab) were evaluated at baseline, after bleaching and after staining. The data was analyzed by ANOVA and Tukey test or Kruskal Wallis. RESULTS: The effects on specimens varied depending on the bleaching product and staining solution. FS after bleaching and after staining presented higher roughness. In the evaluation of shade changes after bleaching, it was observed that resin color changed and that 35% hydrogen peroxide bleached the resin more than the others. After staining in three solutions, all specimens changed color and wine showed the higher staining capacity.

Argon ion laser and halogen lamp activation of a dark and light resin composite: microhardness after long-term storage.

UNLABELLED: The objective of this study was to evaluate in vitro light activation of the nano-filled resin composite Vita shade A1 and A3 with a halogen lamp (QTH) and argon ion laser by Knoop microhardness profile. MATERIALS AND METHODS: Specimens of nanofilled composite resin (Z350-3 M-ESPE) Vita shade A1 and A3 were prepared with a single increment inserted in 2.0-mm-thick and 3-mm diameter disc-shaped Teflon mold. The light activation was performed with QTH for 20 s (with an intensity of approximately 1,000 mW/cm(2) and 700 mW/cm(2)) and argon ion laser for 10 s (with a power of 150 mW and 200 mW). Knoop microhardness test was performed after 24 h and 6 months. The specimens were divided into the 16 experimental groups (n = 10), according to the factors under study: photoactivation form, resin shade, and storage time. Knoop microhardness data was analyzed by a factorial ANOVA and Tukey s tests at the 0.05 level of significance. RESULTS: Argon ion laser was not able to photo-activate the darker shade of the nanofilled resin composite evaluated but when used with 200 mW it can be as effective as QTH to photo-activate the lighter shade with only 50% of the time exposure. After 6 months storage, an increase in the means of Knoop microhardness values were observed. CONCLUSIONS: Light-activation significantly influenced the Knoop microhardness values for the darker nanofilled resin composite.

Clinical Evaluation of In-Office Dental Bleaching Using a Violet Light-Emitted Diode.

Objective: To clinically evaluate the effect of the violet light-emitted diode (LED) light (405-410 nm) associated to in-office dental bleaching with 35% carbamide peroxide, on tooth color change and sensitivity. Participant's satisfaction after treatment was also evaluated. Materials and methods: A total of 50 participants were selected and randomized into a treatment group (n = 25): G1-two bleaching sessions of 30 min each, with 7-day interval (D0 and D7); G2-two bleaching sessions (same protocol as G1) associated with violet LED light, 30 min each session. The color evaluation was performed before and after 7 days of the second session (D0 and D14); the medium third of buccal surface of canine and central incisor teeth were evaluated under VITA Shade Guide and spectrophotometry (subjective and objective). Tooth sensitivity was evaluated immediately after the treatment and after 48 h of each bleaching session (D0, D2, D7, and D9), and a self-perception questionnaire was applied on D14. Results: Data were subjected to nonparametric Mann-Whitney test and both canine and central incisor teeth presented color change. Group G2 showed significantly more change than G1. Fisher's exact test showed no statistically significant dental sensitivity differences between groups. Both groups reported a high level of satisfaction but chi-square test showed statistically higher satisfied patients with dental bleaching in G2 than G1. Conclusions: The violet LED light (405-410 nm) could improve dental bleaching effectiveness, without sensitivity increase.

Mechanical Properties of the Mandible in Postmenopausal Women Under Aledronate Treatment.

AIMS: This study evaluated the mechanical properties of mandibular bone tissue retrieved from postmenopausal women under alendronate treatment. METHODS: Twenty postmenopausal women were divided into two groups: healthy postmenopausal subjects (control group) and osteoporotic subjects treated with alendronate (alendronate group). Mandibular bone samples were retrieved with a trephine bur at the time of dental implant placement and fixed in 4% formalin. Samples were processed for hard tissue histology, and the bone surface was analyzed for nanohardness measurement. Nanohardness and elastic modulus were evaluated by using a Berkovich tip with elastic modulus of 1.016x106 MPa, Poisson coefficient of 0.3, and a load of 100 mN. Each cycle was configured with a load time of 18 seconds (speed of 1 mN/second), the discharge time of 18 seconds, and a rest time of 5 seconds during indentation at a depth of 10 µm. RESULTS: The control group presented the highest values for nanohardness and elastic modulus (p less than 0.05) in relation to the osteoporotic subjects. CONCLUSIONS: Within the limitations of the study, it can be concluded that treatment with alendronate negatively influenced the mechanical properties of mandibular bone in postmenopausal women by reducing bone nanohardness and elastic modulus.

In vitro evaluation of enamel surface roughness and morphology after orthodontic debonding: Traditional cleanup systems versus polymer bur.

INTRODUCTION: The primary aim of this randomized in vitro study was to compare the effectiveness of carbide, fibreglass and polymer burs on resinous remnant removal after bracket debonding, by the evaluation of enamel surface roughness and morphology. The secondary objective was to compare the time dispended on the procedures. METHODS: The buccal surfaces of 28 bovine incisors were analysed by a profilometer to initial roughness measurement (Ra-T1). Brackets were bonded with a light-cured resin and debonded with a debonding plier. The samples were randomly divided into four groups, according to the bur used (n=7): A-Tungsten carbide; B-Fibreglass; C-Polymer; D-Polymer with 75% ethanol pre-treatment. The second roughness measurements were made after resin removal (Ra-T2). Time for removal procedures was also recorded. The third measurements were made after polishing (Ra-T3). Scanning Electronic Microscopy was performed in two samples of each group: after resin removal and after polishing. Results of roughness and time measurements were statically analysed by analysis of variance with post-hoc Bonferroni. RESULTS: After polishing, tungsten carbide (P=0.1555) and fibreglass burs provided final surface roughness statistically similar to the baseline condition (P=1.0000). Yet, polymer burs, associated (P<0.0001) or not to alcohol (P<0.0001), provided surface roughness significantly higher when compared to baseline values. Polymer burs were more time-consuming on resinous remnant removal than tungsten carbide and fibreglass burs (P<0.05). CONCLUSION: Polymer burs were less effective and more time-consuming to remove the remaining resin than tungsten carbide and fibreglass burs. The polishing step created smoother surfaces regardless of the burs used for resin removal.

Severe phenytoin-induced gingival enlargement associated with periodontitis.

The potential of phenytoin to induce gingival hyperplasia has been well-established. High levels of dental plaque and calculus have been reported as a critical co-factor for the development and severity of phenytoin-induced gingival hyperplasia. This article documents a severe gingival enlargement associated with periodontitis (in a patient under combined anti-epileptic therapy) and provides a rational model for its clinical management. Initially, full-mouth scaling and root planing, oral hygiene instructions, and phenytoin withdrawal were performed; however, clinical results demonstrated partial resolution of maxillary gingival hyperplasia. Subsequently, surgical therapy was indicated for the maxillary teeth. Complete reduction of gingival enlargement and improvement of clinical periodontal parameters were observed after the surgical therapy. This case report clearly describes the challenges that oral and medical health practitioners face when developing appropriate prevention and treatment programs for epileptic patients, particularly those with periodontal disease.

The effect of in-office in combination with intracoronal bleaching on enamel and dentin bond strength and dentin morphology.

AIM: The aim of this study was to evaluate in vitro effects of the combination of in-office and intracoronal bleaching on enamel and dentin bond strength and on dentin morphology. METHODS AND MATERIALS: Bleaching treatment was performed on 128 bovine teeth for three weeks. Intracoronal bleaching was performed in groups G1 to G3, and in the other groups a combination of in-office and intracoronal bleaching was performed. The following agents and materials were used (n=16): G1- sodium perborate and water (SP); G2- 37% carbamide peroxide (CP); G3- 35% hydrogen peroxide (HP); G4- HP + cotton pellet soaked in water (CPW); G5- HP + SP; G6- HP + CP; G7- HP + HP; and G8- CPW (control). Seven days after bleaching treatment the teeth were sectioned into two halves. One half of each tooth was ground to obtain a flat dentin surface. Dentin and enamel fragments were treated with a dentin/enamel resin adhesive. Resin composite was inserted in two increments and polymerized for 20 seconds. Following the restorative procedures, specimens were sectioned into beams with a rectangular cross-sectional area of approximately 1 mm2. Microtensile testing was performed in a universal testing machine. Bond strengths (in MPa) were calculated and the data were submitted to an analysis of variance (ANOVA) and the Tukey test (a=0.05). For the scanning electron microscopy (SEM) observation, the exposed pulp chambers (n=5) were fixed, dehydrated, dried in a Critical Point dryer, and gold-sputter coated for analysis at standardized magnifications (500X, 1000X, and 2000X). RESULTS: None of the bleaching techniques reduced the enamel bond strength, the best results observed were with the intracoronal treatments with SP and HP. In dentin all bleaching techniques reduced the bond strength with the exception of the in-office HP application technique. The SEM results demonstrated similar dentin surfaces for the G1, G3, G6, and G7 groups with more open dentin tubules found than in the other groups. CONCLUSION: None of the bleaching techniques tested reduced the bond strength of enamel, but they all reduced the bond strength of dentin with the exception of the group only treated with in-office bleaching using 35% HP. The worst bond strength results to dentin were observed in groups that received intracoronal bleaching with SP.

Argon laser: a light source alternative for photopolymerization and in-office tooth bleaching.

The argon laser is an alternative light source that can be used for the photopolymerization of resin-based dental materials and for tooth bleaching. The argon laser emits specific laser lines with wavelengths that correspond to the absorption peak of camphoroquinone, the initiator of polymerization for the adequate photocuring of resin composite. The collimated beam of the argon laser does not decrease with distance and an optical fiber has access to all cavity areas. In addition, the temperatures produced by an argon laser when curing resin-based materials and performing in-office tooth bleaching are significantly lower than those of conventional photocuring units. Argon is one of the three dental laser wavelengths that have been cleared by the FDA for tooth whitening. This article reviews the literature to examine the role that argon lasers can play in dental treatment.

Efficiency of polymerization of bulk-fill composite resins: a systematic review.

This systematic review assessed the literature to evaluate the efficiency of polymerization of bulk-fill composite resins at 4 mm restoration depth. PubMed, Cochrane, Scopus and Web of Science databases were searched with no restrictions on year, publication status, or article's language. Selection criteria included studies that evaluated bulk-fill composite resin when inserted in a minimum thickness of 4 mm, followed by curing according to the manufacturers' instructions; presented sound statistical data; and comparison with a control group and/or a reference measurement of quality of polymerization. The evidence level was evaluated by qualitative scoring system and classified as high-, moderate- and low- evidence level. A total of 534 articles were retrieved in the initial search. After the review process, only 10 full-text articles met the inclusion criteria. Most articles included (80%) were classified as high evidence level. Among several techniques, microhardness was the most frequently method performed by the studies included in this systematic review. Irrespective to the "in vitro" method performed, bulk fill RBCs were partially likely to fulfill the important requirement regarding properly curing in 4 mm of cavity depth measured by depth of cure and / or degree of conversion. In general, low viscosities BFCs performed better regarding polymerization efficiency compared to the high viscosities BFCs.

Comparing depth-dependent curing radiant exposure and time of curing of regular and flow bulk-fill composites.

The effect of restoration depth on the curing time of a conventional and two bulk-fill composite resins by measuring microhardness and the respective radiosity of the bottom surface of the specimen was investigated. 1-, 3- and 5-mm thick washers were filled with Surefil SDR Flow-U (SDR), Tetric EvoCeram Bulk Fill-IVA (TEC) or Esthet-X HD-B1 (EHD), and cured with Bluephase® G2 for 40s. Additional 1-mm washers were filled with SDR, TEC or EHD, placed above the light sensor of MARC®, stacked with pre-cured 1-, 3- or 5-mm washer of respective material, and cured for 2.5~60s to mimic 2-, 4- and 6-mm thick composite curing. The sensor measured the radiosity (EB) at the bottom of specimen stacks. Vickers hardness (VH) was measured immediately at 5 locations with triplicate specimens. Nonlinear regression of VH vs EB by VH=α[1-exp(-EB/ß)] with all thickness shows that the values of α, maximum hardness, are 21.6±1.0 kg/mm2 for SDR, 38.3±0.6 kg/mm2 for TEC and 45.3±2.6 kg/mm2 for EHD, and the values of ß, rate parameter, are 0.40±0.06 J/cm2 for SDR, 0.77±0.04 J/cm2 for TEC and 0.58±0.09 J/cm2 for EHD. The radiosity of the bottom surface was calculated when the bottom surface of each material attained 80% of α of each material. The curing times for each material are in agreement with manufacturer recommendation for thickness. It is possible to estimate time needed to cure composite resin of known depth adequately by the radiosity and microhardness of the bottom surface.

Er,Cr:YSGG Laser Energy Delivery: Pulse and Power Effects on Enamel Surface and Erosive Resistance.

BACKGROUND: High power lasers have been suggested as a useful tool for dental caries and erosion prevention due to the increase of enamel acid resistance. OBJECTIVE: to evaluate the effect of Er,Cr:YSGG (erbium,chromium:yttrium, scandium, gallium, garnet) laser irradiation pulse frequency and power on enamel surface and acid erosion resistance. METHODS: By combining pulse frequency (5-75 Hz) and power settings (0.10-1.00 W), 20 irradiated groups and one nonirradiated control group were tested. A total of 63 bovine enamel blocks (n = 3/group) were prepared for surface hardness and roughness evaluation, performed in three phases: baseline, after irradiation, and after erosive challenge. Enamel blocks were irradiated with Er,Cr:YSGG laser with MZ8 tip (iPlus; Waterlase, Biolase, CA) for 30 sec according to experimental group and submitted. Erosive challenge consisted of four cycles alternating immersion in 0.01 M HCl (5 mL/mm2; 2 min; at 37°C) and immersion in artificial saliva for 3 h. Analysis of variance (three-way ANOVA), Tukey's test, and Pearson correlation were performed for the statistical analysis (p < 0.05). RESULTS: After irradiation, groups irradiated with pulse frequency of 10 and 15 Hz showed a decrease in surface hardness. After erosive challenge, 5 and 75 W groups showed increase in surface hardness; 0.25, 0.5, 0.75, and 1 W groups showed minor alterations in surface roughness. CONCLUSIONS: the irradiation of Er,Cr:YSGG laser with different parameters of power and pulse frequency settings may alter enamel surface and erosive resistance differently. Pulse frequency of 30 Hz and power of 0.50 W was considered the best parameter to prevent enamel acid erosion.