In vitro effectiveness of different dental bleaching protocols using violet LED.

PURPOSE: There has been growing demand for dental bleaching worldwide, however, despite being effective, hydrogen peroxide (HP) can negatively affect the dental structure. Thus, new techniques, such as violet LED light have emerged and need to be studied. The aim of this study was to analyze and compare the effectiveness of violet LED light alone or combined with 35% HP gel. METHODS: Six different tooth bleaching techniques (n = 10) were performed in intrinsically pigmented bovine teeth: G1 - 35% HP (1x/week for 4 weeks, 45 min of gel application); G2 - 35% HP (1x/week for 4 weeks, 15 min of gel application); G3 - violet LED (1x/week for 4 weeks); G4 - violet LED (2x/week for 2 weeks); G5 - violet LED (4x/week for 1 week); G6 - Violet LED + 35% HP (hybrid technique, 1x/week for 4 weeks, 15 min of gel application). Specimens were submitted to color evaluation at predetermined times using Konica Minolta® spectrophotometer, and the surface morphology (n = 3) was qualitatively analyzed by Scanning Electron Microscope (SEM). Data of the color change test were analyzed considering a 5% level of significance. RESULTS: There was significant difference in color (p <0.05) for all groups after bleaching protocols. SEM analysis revealed that the greatest change in surface occurred in Group G1, with demineralization of the dental enamel. When considering the same time interval, there were no statistical differences for axis L*, but differences were shown for axis a* (G2, G3, G4 ≥ G1, G5 ≥ G6) and b* (G1, G2, G3, G4, G5 > G6). Regarding the comparison of ΔE00 between groups, results showed statistical difference between groups, with G1 ≥ G2, G5, G6 ≥ G3, G4. CONCLUSION: Bleaching protocols with less time (15 min) or no exposure to 35% HP (violet LED, 4x/week) could promote bleaching results as those obtained by the conventional technique using 35% HP for 45 min, with no enamel surface changes, showing to be a promising alternative to tooth bleaching.

Antimicrobial activity of Desplac® oral gel in the subgingival multispecies biofilm formation.

Natural products are well-known due to their antimicrobial properties. This study aimed to evaluate the antimicrobial effect of Desplac® product (composed of Aloe Vera, Propolis Extract, Green Tea, Cranberry, and Calendula) on the subgingival biofilm. Two different protocols were used to treat the 33-species biofilms: (A) 2×/day (12/12 h) for 1 min with Desplac® or Noplak Toothpaste (Chlorhexidine + Cetylpyridinium Chloride) or Oral B ProGengiva (stannous Fluoride) or a placebo gel; (B) a 12-h use of the Desplac® product or 0.12% chlorhexidine gel or a placebo gel. After 7 days of biofilm formation, the metabolic activity (MA) and biofilm profile were determined by 2,3,5-triphenyltetrazolium chloride and Checker-board DNA-DNA hybridization, respectively. Statistical analysis used the Kruskal-Wallis test followed by Dunn's post-hoc. In protocol A, all treatments presented reduced MA compared to the placebo (p ≤ 0.05). The Desplac®-treated biofilm showed a similar microbial profile to other antimicrobials, although with higher bacterial total counts. In protocol B, MA of Desplac®-treated biofilms was lower than the placebo's MA but higher than chlorhexidine-treated biofilms (p ≤ 0.05). Pathogen levels in Desplac®-treated biofilms were lower than in placebo-treated biofilms and elevated compared to the chlorhexidine-treated biofilms (p ≤ 0.05). Desplac® inhibited the biofilm development and disrupted the mature subgingival biofilm, highlighting its effect on Tannerella forsythia counts.

Twelve-Month Follow-Up of Different Dentinal Hypersensitivity Treatments by Photobiomodulation Therapy, Nd:YAG and Nd:YAP Lasers.

In this retrospective study, data for three different laser-assisted approaches for the management of dentinal hypersensitivity (DH) was collected (n = 920 teeth). In total, 387 teeth were treated with photobiomodulation (PBM) therapy with 660 nm red light laser (PBM group), 327 were treated with the Nd:YAG laser (1064 nm) and 206 were treated with the Nd:YAP laser (1340 nm). To assess the effectiveness of each treatment, a visual analogue scale (VAS) was used, where zero represented no pain at all and ten represented the greatest pain. VAS was used before (T0), immediately after (T1), one week after (T2), four weeks after (T3), six months after (T4) and one year after treatment (T5). Means and standard deviations of VAS at different follow-up times were calculated. Values were compared within and between groups. Statistical significance was considered to be achieved when p-value was less than 0.05. Confidence level was proposed to be 99% with a P value lower than 0.001. Within groups, a statistically significant reduction was obtained when the mean value of VAS at T0 was compared with T5. At T5, the PBM group had the highest reduction of VAS (with mean value of 0), while the Nd:YAG and Nd:YAP groups had scores of 1.065 ± 0.674 and 4.665 ± 0.674, respectively. Conclusion: this retrospective study showed that PBM therapy and irradiation with Nd:YAG and Nd:YAP lasers are effective in managing DH pain. However, PBM therapy was the only procedure that showed complete pain relief at six and twelve months after treatment.

Immediate Evaluation of the Effect of Infrared LED Photobiomodulation on Childhood Sleep Bruxism: A Randomized Clinical Trial.

The gold standard for the management of sleep bruxism (SB) is the use of a rigid occlusal splint; however, there are limitations for its use in children and alternatives to the management of SB are needed. Photobiomodulation therapy has been used with positive results in temporomandibular disorders. This study aimed to evaluate the effects of photobiomodulation therapy with infrared LED in children with SB. Thirty children were divided into three groups: Group 1: control/absence of bruxism (n = 10); Group 2: SB treated with infrared LED (n = 10); Group 3: SB treated with occlusal splint (n = 10). Electromyographic evaluation of masseter, anterior temporalis, and upper trapezius, and salivary dopamine levels were assessed before and after treatments. Data were statistically analyzed using two-way mixed model ANOVA. An increase in the temporalis and right masseter EMG activity at rest was observed in Group 3, with large effect size (p < 0.05). Left masseter and temporalis EMG activity did not differ over time in the LED group, similar to the control group. Moreover, the EMG activity of masticatory muscles during chewing and upper trapezius muscle did not differ over time in all groups. The results also pointed to a difference in the levels of dopamine between children with and without SB, with Group 3 showing higher levels in the pre-treatment time compared to controls (p < 0.025). In conclusion, an increase in the masticatory muscles activity at rest was observed in children undergoing splint therapy. Moreover, a difference in the levels of salivary dopamine was found between children with and without SB.

Photobiomodulation for the Treatment of Primary Headache: Systematic Review of Randomized Clinical Trials.

The purpose of this study was to evaluate the efficacy and safety of photobiomodulation as an adjuvant treatment for primary headache. A systematic review of randomized clinical trials was performed. For such, electronic searches were performed in the MEDLINE, Embase, Cochrane Library, LILACS, PEDro, PsycInfo, Clinicaltrials.gov., and WHO/ICTRP databases, with no restrictions imposed regarding language or year of publication. We included studies that assessed any photobiomodulation therapy as an adjuvant treatment for primary headache compared to sham treatment, no treatment, or another intervention. The methodological assessment was conducted using the Cochrane Risk of Bias tool. The certainty of the evidence was classified using the GRADE approach. Four randomized clinical trials were included. Most of the included studies had an overall high risk of bias. Compared to sham treatment, photobiomodulation had a clinically important effect on pain in individuals with primary headache. Despite the benefits reported for other outcomes, the estimates were imprecise, and the certainty of the evidence was graded as low. These findings are considered insufficient to support the use of photobiomodulation in the treatment of primary headache. Randomized clinical trials, with higher methodological quality, are needed to enhance the reliability of the estimated effects.

Evaluation of the Combination of CO2 Laser and Bifunctional Bonding Agents for Composite Resin Repairs After 1 Year of Aging.

Objective: to evaluate the bond strength of repairs to composite resin restorations treated with CO2 laser and bifunctional monomers after 1 year of aging. Background: Adequate bond strength between a composite restoration and resin repair agent can be achieved through mechanical and/or chemical treatment. However, the longevity of such repairs is unknown. Methods: Resin blocks (volume: 125 mm3) were created. Failure surfaces were either not treated or were treated before the repair with a universal adhesive, a silane bonding agent and/or CO2 laser. The blocks were distributed into six groups (n = 6 per group): resin+resin group (RRG), universal adhesive+resin group (ARG), silane+universal adhesive group (SAG), laser+silane+universal adhesive group (LSAG), laser+universal adhesive group (LAG), and laser+silane group (LSG). After treatment, repairs were made with another resin composite. "Sticks" (1.0 mm2 in area and 1.0 cm in length) were cut from the specimens in each group and immersed in distilled water at 37°C. Microtensile bond strength was evaluated after 1 year of aging. Bond strength values were compared using the Kruskal-Wallis test and Dunn's test. Results: Bond strength was significantly higher in the LSAG compared with the RRG, adhesive system, LSG, whereas statistically similar results were found for the SAG, LSAG, and LAG. Bond strength was lowest in the RRG. The LSAG and LAG presented predominantly cohesive fractures. Conclusions: The bond strength of composite resin repairs was satisfactory over time. Treatment with CO2 laser contributed to the maintenance of bond strength during the 1-year storage period and bifunctional monomers present in the universal adhesive on the irradiated repair surface were of fundamental importance to the maintenance of bond strength values, as demonstrated by microtensile bond test and fracture pattern analysis.

Evaluation of the Antimicrobial Effect of Photodynamic Therapy and Er:YAG Laser Irradiation on Root Canals Infected with Enterococcus faecalis.

Objective: To carry out a histological and morphometric analysis of the antimicrobial effect of Er:YAG laser irradiation combined with photodynamic therapy (PDT) on root canals infected with Enterococcus faecalis. Background: PDT and Er:YAG laser irradiation may be alternatives for effective endodontic disinfection but there are no data on the combination of these therapies. Materials and methods: Forty single-rooted bovine teeth had their roots contaminated with E. faecalis for 72 h. The teeth were randomly divided into four groups (n = 10): group 1, irrigation with 2.5% sodium hypochlorite (NaOCl); group 2, Er:YAG laser (λ2940 nm, 15 Hz, 100 mJ); group 3, PDT with 0.07% methylene blue as photosensitizer and laser irradiation (λ660 nm, power 40 mW, 5 min); and group 4, Er:YAG laser + PDT. After treatment, the teeth were examined by confocal laser scanning microscopy to verify bacterial viability, and morphometric analysis of the images was performed. Results: The PDT and Er:YAG + PDT treatments promoted the greatest reduction in bacteria among the proposed therapies, whereas 2.5% NaOCl was the least effective in bacterial elimination. A statistically significant difference (p < 0.05) was observed among the groups studied, except between the group combining Er:YAG and PDT and the group treated with PDT alone. Conclusions: PDT combined or not with Er:YAG laser was found to be more effective in root canal disinfection when compared with the other groups.

In vitro analysis of human tooth pulp chamber temperature after low-intensity laser therapy at different power outputs.

In vitro studies have provided conflicting evidence of temperature changes in the tooth pulp chamber after low-level laser irradiation of the tooth surface. The present study was an in vitro evaluation of temperature increases in the human tooth pulp chamber after diode laser irradiation (GaAlAs, λ = 808 nm) using different power densities. Twelve human teeth (three incisors, three canines, three premolars and three molars) were sectioned in the cervical third of the root and enlarged for the introduction of a thermocouple into the pulp chamber. The teeth were irradiated with 417 mW, 207 mW and 78 mW power outputs for 30 s on the vestibular surface approximately 2 mm from the cervical line of the crown. The highest average increase in temperature (5.6°C) was observed in incisors irradiated with 417 mW. None of the teeth (incisors, canines, premolars or molars) irradiated with 207 mW showed temperature increases higher than 5.5°C that could potentially be harmful to pulp tissue. Teeth irradiated with 78 mW showed lower temperature increases. The study showed that diode laser irradiation with a wavelength of 808 nm at 417 mW power output increased the pulp chamber temperature of certain groups of teeth, especially incisors and premolars, to critical threshold values for the dental pulp (5.5°C). Thus, this study serves as a warning to clinicians that "more" is not necessarily "better".

Influence of the parameters of the Er:YAG laser on the apical sealing of apicectomized teeth.

Failures in the sealing of the tooth apex have been considered to be responsible for most of the failures of apical surgeries. The Er:YAG laser has been proposed as an alternative for the use of rotator instruments in surgical endodontics due to its precision, lack of vibration, less post-operative discomfort, bacterial reduction, and less stress for patients and professionals. Following approval by the ethics committee, 12 extracted human canines without previous endodontic treatment with anatomically normal roots and free from apical lesions were washed in running tap water and disinfected. The teeth were sectioned axially at the crown-root junction and submitted to routine endodontic treatment. The apical limit was set at 1 mm before the apical foramen. The root canals were routinely filled with Gutta-Percha points and Sealer 26 and were randomly distributed into two groups (n = 6). In group I, apicectomy was performed with the Er:YAG laser (KAVO KEY Laser II®, Germany, λ = 2.940 nm, pulsed mode, 2051 tip, with air spray cooling, 250 mJ/15 Hz). Apical cut was performed of perpendicular mode 3 mm from the apical foramen. In group II, the same procedures and the same sequence as above was used, varying only the parameters of the Er:YAG laser (400 mJ/6 Hz). Sealing of the cervical end the apex was carried out with acrylic resin; the roots were covered by a layer of epoxy glue and two layers of nail polish. The specimens were divided into groups and fixed, by the cervical third, on wax. Impermeabilization of the residual root apical third was performed following the same procedures used in the cervical third but the residual apex was left free from the impermeabilization. After that, the roots were immersed in a 2% methylene blue solution and placed in a bacteriological oven for 48 h and then washed in running tap water for 2 h. The samples were sagittally split into two parts. The segments were visually observed and the one showing the greatest level of dye leakage was selected and kept in an individual container and coded accordingly. Apical staining was measured using a stereoscopic magnifying glass, a compass, and a caliper. The measurement was performed by three endodontists, previously calibrated, and unaware of the sample coding. The results showed that group I showed the greatest level of dye leakage. There was a significantly difference between the groups (p = 0.001). It is concluded that the apicectomies carried out with 400 mJ/6 Hz showed the smallest infiltration value.

Evaluation of the Whitening Effectiveness of Violet Illumination Alone or Combined with Hydrogen Peroxide Gel.

Objective: To evaluate the effectiveness of the whitening and washing steps of a treatment using violet illumination (VI) alone or combined with hydrogen peroxide gel. In addition, we evaluated the color change after cleaning the tooth with and without mineral oil. Methods: First, 16 bovine teeth were extracted and stored in 5% thymol solution. Next, the teeth were collected and cleaned. Then, the teeth were stained with instant coffee solution for 24 h. The teeth were divided in four groups: control, VI without 35% hydrogen peroxide gel (VI), VI with 35% hydrogen peroxide gel (VI + gel), and VI without 35% hydrogen peroxide gel and cleaned with mineral oil before washing (VI + oil). Results: The whitening treatment VI + gel was able to completely restore the teeth whiteness and make the teeth 31.2% less yellow than prior coffee staining. The VI + oil treatment led to about 3.7 times the whiteness and yellowness changes observed in the VI treatment and restored 51% of the whiteness lost by staining. Conclusions: The VI + gel treatment can be recommended against coffee stains and should be further investigated for other types of tooth stains. In addition, cleaning the tooth surface with mineral oil could be an alternative to increase the performance of whitening treatments.

Longitudinal, Randomized, and Parallel Clinical Trial Comparing a Violet Light-Emitting Diodes System and In-Office Dental Bleaching: 6-Month Follow-Up.

Objective: This in vivo study compared two bleaching techniques with regard to the degree of tooth sensitivity (TS), color change, and treatment stability for a 6-month follow-up period. Materials and methods: Sixty volunteers were selected according to inclusion and exclusion criteria and submitted to in-office bleaching. For group 1, we performed one bleaching session with a 35% hydrogen peroxide gel and a second bleaching session after 7 days; for group 2, we performed two bleaching sessions with two applications per session, each session with a 7-day interval, using a light-emitting diodes (LEDs) device emitting violet light (405-410 nm) without employing peroxide-containing bleaching gel. TS was recorded immediately before and immediately after each bleaching session using the Variance Analogic Scale. The color of upper central incisors and upper canines at baseline was recorded immediately after each bleaching session, after 15, 30, and 180 days, with a value-oriented shade guide used by two well-trained observers. Results: The two whitening protocols results were similar regarding the immediate effectiveness and 6-month stability of tooth whitening. Dental bleaching with violet LED did not promote postoperative pain sensitivity at any of the evaluated times. However, dental bleaching performed with 35% hydrogen peroxide promoted higher postoperative pain sensitivity. Conclusions: The violet light alone provided dental bleaching and had the clinical advantage of promoting less immediate postoperative sensitivity; however, an unwanted repigmentation occurred after dental bleaching with light alone.

Effect of Er:YAG Laser and Association of Protocols on the Demineralized Enamel Microhardness.

Objective: The aim of this study was to analyze the microhardness of demineralized enamel following different treatments (fluoride varnish, Er:YAG laser, and Er:YAG laser associated with fluoride varnish). Methods: Forty-eight enamel blocks (4 × 4 × 7 mm) were divided into six groups (n = 8): (S) Sound; (DE) Demineralized; (DED) DE + Duraphat® 5% (fluoride varnish); (DEL20) DE + Er:YAG laser (20 mJ pulse mode; 0.20 W; 10 Hz; 60 sec; 1.18 J/cm2; 11.83 W/cm2); (DEL50) DE + Er:YAG laser (50 mJ pulse mode; 0.50 W; 10 Hz; 60 sec; 2.95 J/cm2; 29.58 W/cm2); (DEL20D) DE + Er:YAG laser (20 mJ) + Duraphat 5%. The irradiation was performed at 1 mm distance from the surface using a tip (AS7066X, L-14 mm, D-1.3 mm in diameter) in water/air spray refrigeration (level 6). The enamel blocks were submitted to pH cycling (4 h into DES solution +20 h into RE solution for 8 days and the solutions were changed every day). Knoop microhardness was measured (50 g/15 sec, six readings per sample) and data were analyzed by Kruskal-Wallis test at 5% significance. Results: After treatments, DF group showed higher microhardness values than all the groups. Also, DEL20D group showed similar results with H group according to the microhardness analysis (p < 0.05). Conclusions: It could be concluded that Duraphat 5% treatment showed better results when compared with all tested groups, however, the association of Er:YAG Laser 20 with Duraphat 5% also showed promising results.

In Vitro Evaluation of the Effectiveness of Dental Bleaching with Carbamide Peroxide and Violet Light.

Objective: The aim of the current study was to use the CIELab system to evaluate the performance of the whitening treatment involving violet light-emitting diode (LED) combined with a home 10% and 22% carbamide peroxide dental bleaching technique on dental enamel. Methods: Fifty blocks of bovine dental enamel were divided into five groups: control group (control), receiving only LED irradiation; Whitening 10%, receiving 10% carbamide peroxide treatment; Whitening 10%+VL, receiving 10% carbamide peroxide treatment combined with LED irradiation; Whitening 22%, receiving 22% carbamide peroxide treatment; and Whitening 22%+VL, receiving 22% carbamide peroxide treatment combined with violet LED irradiation. Color tests were performed before the protocols, after 1 week and after 2 weeks of treatment by using a spectrophotometer and the CIELab parameters: L*, (a*) and (b*). The Whitening 10%, Whitening 10%+VL, Whitening 22% and Whitening 22%+VL groups were submitted to 10% and 22% carbamide peroxide 8 h per day for 14 days, whereas the Control was only stored in artificial saliva. For irradiation in the Control, Whitening 10%+VL, and Whitening 22%+VL groups, we used violet LED at a wavelength of 405-410 nm activated for 60 permanent seconds and 30 sec of pause once per week. As all data exhibited normal distribution, the comparisons were performed by using two-way repeated-measures analysis of variance. A post hoc t-test was employed, followed by the Ryan-Holm stepdown Bonferroni procedure. Results: After 1 week, the Whitening 22%+VL group differed significantly from all other groups in relation to hue, while no difference was found between the remaining groups (p < 0.05). Analyzing lightness, the Whitening 22%+VL and Whiteness10%+VL groups differed from the other groups (p > 0.05). In the 2nd week, the Whitening 22%+VL groups differed significantly from all other groups (p < 0.05) in hue, chroma, and lightness. The comparative analysis of bleaching times within the same group revealed significant differences in the Whitening 22%+VL group between baseline and week 1, baseline and week 2, as well as weeks 1 and 2 in terms of hue (p > 0.05). In the Whitening 22%+VL group, significant differences (p < 0.05) were found between baseline and week 2 as well as between weeks 1 and 2 in chroma (p > 0.05). In the Whitening 22%+VL group, statistically significant differences (p < 0.05) were found between baseline and week 1, baseline and week 2, as well as between weeks 1 and 2 in lightness. In the Whitening 10%+VL group, statistically significant differences (p < 0.05) were found between baseline and week 1, between baseline and week 2, as well as between weeks 1 and 2 in lightness. Conclusions: Tooth whitening treatment involving 10% and 22% carbamide peroxide combined with violet light promoted changes in the three axes of color (ΔH, ΔC, and ΔL) of the specimens evaluated. The use of the gel bleach alone was more efficient when the higher concentration was used. When violet light was combined with the gel, the lower concentration was more efficient.

A Randomized Comparative Clinical Study to Evaluate the Longevity of Esthetic Results of Gingival Melanin Depigmentation Treatment Using Different Laser Wavelengths (Diode, CO2, and Er:YAG).

Background: Gingival melanin hyperpigmentation is due to excessive deposition of melanin granules. The duration of pigmentation reappearance after treatment using different laser wavelengths remains controversial. Objective: The study aims to assess the longevity of gingival depigmentation (GD) and the consistency in esthetic results as three laser wavelengths (Er:YAG laser, CO2 laser, and diode laser, 980 nm) were used in two different groups (smokers and nonsmokers). This is attained by comparing the periods of time in each group before pigmentation reappearance. Methods: Seventy-two subjects were divided into daily smokers (S) and nonsmokers. Subjects underwent a randomized GD with: Erbium laser (Er), CO2 laser (CO2), and Diode laser (Diode). The subjects were divided into six groups: S and nonsmokers were treated with three different wavelengths. Irradiation was performed until there was no visible pigmentation. For qualitative measurement, Hedin Melanin Index (HMI) was used, before treatment, after 2 weeks, and until 60 months. Pigmentation reappearance of degree 1 or above of the HMI was noted. Descriptive statistics were also calculated. Results: HMI showed a 0 in all groups after 14 days of treatment. The time before pigmentation rebound was: Diode > CO2 > S-Diode > S-CO2 > Er > S-Er. The first signs of relapse shown among all groups were seen in the group S-Er group. The longest time before rebound was observed with the Diode group for the nonsmoker. Conclusions: Diode laser provides the longest-term stability in treatment. Smoking negatively affects the longevity of GD. Er laser gives the shortest time before the reappearance of gingival pigmentation.

Effect of Surface Treatment with CO2 Laser on Bond Strength in Composite Resin Restorations.

Objective: Evaluate the bond strength of repairs made on composite resin following the treatment of the surface of the flaw with different bonding agents and/or CO2 laser. Background: The influence of CO2 laser and its interaction with other bonding agents on the surface of the flaw is not yet known. In this study, CO2 laser was chosen to treat the surface of the flaw due to its capacity to promote irregularities on the surface that enhance mechanical micro-retention. Methods: A block was created with Vitra APS nanohybrid composite resin (color: A3; FGM, Joinville, Brazil) measuring 5 mm in width, length, and depth (volume: 125 mm3). The surface of the flaw was treated before the repair with an adhesive, silane bonding agent, and/or CO2 laser. Six specimens were created in composite resin for each group (total: n = 36): G1: resin+resin; G2: adhesive+resin; G3: laser+adhesive; G4: laser+silane+adhesive; G5: silane+adhesive; G6: laser+silane. After the repair, the surfaces of the fracture of all specimens, which were submitted to the microtraction test, were analyzed under an optical microscope. Bond strength values obtained according to the type of surface treatment were tabulated and submitted to the Kruskal-Wallis test. Dunn's test was used to compare means. Results: G3 and G4 had significantly higher bond strength values compared to all other groups tested. Adhesive fractures predominated in all groups. However, G3 and G4 had a higher percentage of cohesive fractures compared to the other groups. Conclusions: The application of CO2 laser as a surface treatment led to greater bond strength of composite resin repairs in comparison with the groups that only received treatment with a burr and silanization. The groups submitted to CO2 laser also had a significantly lower number of adhesive failures when submitted to the microtraction test.

Microleakage of "Bulk-Fill" Composite Resin for Class II Restorations Pretreated With CO2 Laser in Deciduous Molars: An In Vitro Study.

Introduction: Microleakage has been reported to cause dentin hypersensitivity because of the passage of bacteria and their products through the restoration-tooth interface and is one of the main reasons for replacement of restorations. CO2 laser can be used for treatment of dentin hypersensitivity. Thus, this study aimed to evaluate in vitro the microleakage in composite restorations following surface pretreatment with acid etching and CO2 laser. Methods: Twelve human caries-free primary molars were selected. Class II cavities were prepared on occlusal mesial and occlusal distal surfaces. Specimens were randomly divided into four groups (n=6): Group 1 (G1) - 37% phosphoric acid gel etching + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 2 (G2) - 37% phosphoric acid gel etching + SDR Bulk-Fill Flow (Dentsply); Group 3 (G3) - CO2 laser irradiation + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 4 (G4) - CO2 laser irradiation + SDR Bulk-Fill Flow (Dentsply). Surfaces were restored with bonding agent (Natural Bond DE, DFL). Specimens were cut longitudinally and immersed in 0.5% methylene blue solution for 4 hours. Microleakage scores were assessed under a magnifying glass at x3,5 and qualitatively analyzed by scanning electron microscope (SEM). Data were analyzed using nonparametric Wilcoxon test (P < 0.05). Results: Scores prevailed between 0 and 2, however, no statistically significant difference was found among the groups (P = 0.05). Conclusion: It could be concluded that all composite resins bulk fill did not show significant difference among them regarding microleakage using either CO2 laser or 37% phosphoric acid etching.

Ultrastructural analysis of root canal dentine irradiated with 980-nm diode laser energy at different parameters.

OBJECTIVE: The purpose of this in vitro study was to investigate using the scanning electron microscope (SEM) the ultrastructural morphological changes of the radicular dentine surface after irradiation with 980-nm diode laser energy at different parameters and angles of incidence. BACKGROUND DATA: There have been limited reports on the effects of diode laser irradiation at 980 nm on radicular dentin morphology. MATERIALS AND METHODS: Seventy-two maxillary canines were sectioned and roots were biomechanically prepared using K3 rotary instruments. The teeth were irrigated with 2 mL of distilled water between files and final irrigation was performed with 10 mL of distilled water. The teeth were then randomly divided into five groups (n = 8 each) according to their diode laser parameters: Group 1: no irradiation (control); group 2: 1.5 W/continuous wave (CW) emission (the manufacturer's parameters); group 3: 1.5 W/100 Hz; group 4: 3 W/CW; and group 5: 3 W/100 Hz. Laser energy was applied with helicoid movements (parallel to the canal walls) for 20 sec. Eight additional teeth for each group were endodontically prepared and split longitudinally and irradiation was applied perpendicularly to the root surface. RESULTS: Statistical analysis showed no difference between the root canal thirds irradiated with the 980-nm diode laser, and similar results between the parameters 1.5 W/CW and 3 W/100 Hz (p > 0.05). CONCLUSION: When considering different output powers and delivery modes our results showed that changes varied from smear layer removal to dentine fusion.

Histological and Thermometric Examination of Soft Tissue De-Epithelialization Using Digitally Controlled Er:YAG Laser Handpiece: An Ex Vivo Study.

OBJECTIVE: The purpose of this study was histological and thermometric examination of soft tissue de-epithelialization using digitally controlled laser handpiece (DCLH) - X-Runner. BACKGROUND DATA: Commonly used techniques for de-epithelialization include scalpel, abrasion with diamond bur, or a combination of the two. Despite being simple, inexpensive and effective, these techniques are invasive and may produce unwanted side effects. It is important to look for alternative techniques using novel tools, which are minimally invasive and effective. MATERIALS AND METHODS: 114 porcine samples sized 6 × 6 mm were collected from the attached gingiva (AG) of the alveolar process of the mandible using 15C scalpel blade. The samples were irradiated by means of Er:YAG laser (LightWalker, Fotona, Slovenia), using X-Runner and HO2 handpieces at different parameters; 80, 100, and 140 mJ/20 Hz in time of 6 or 16 sec, respectively. The temperature was measured with a K-type thermocouple. For the histopathological analysis of efficiency of epithelium removal and thermal injury, 3 random samples were de-epithelialized with an HO2 handpiece, and 9 random samples with an X-Runner handpiece with different parameters. For the samples irradiated with DCLH, we have used three different settings, which resulted in removing 1 to 3 layers of the soft tissue. The efficiency of epithelium removal and the rise of temperature were analyzed. RESULTS: DCLH has induced significantly lower temperature increase compared with HO2 at each energy to frequency ratio. The histological examination revealed total epithelium removal when HO2 handpiece was used at 100 and 140 mJ/20 Hz and when DCLH was used for two- and threefold lasing at 80, 100, and 140 mJ/20 Hz. CONCLUSIONS: Er:YAG laser with DCLH handpiece may be an efficient tool in epithelium removal without excessive thermal damage.

Infrared Laser Improves Collagen Organization in Muscle and Tendon Tissue During the Process of Compensatory Overload.

BACKGROUND: The photobiomodulation using the low-level laser therapy (LLLT) exerts a positive modulating effect on the synthesis of collagen in skeletal muscles and tendons. However, few studies have addressed this effect during the compensatory overload. OBJECTIVE: Evaluate the effect of infrared laser on the deposition and organization of collagen fibers in muscle and tendon tissue during compensatory overload of the plantar muscle in rats. MATERIALS AND METHODS: Wistar rats were submitted to bilateral ablation of the synergist muscles of the hind paws and divided in groups: Control, Hypertrophy, and Hypertrophy (H)+LLLT (780 nm, 40 mW, 9.6 J/cm2 and 10 s/point, 8 points, total energy 3.2 J, daily), evaluated at 7 and 14 days. Muscle cuts were stained with Picrosirius-Red and hematoxylin-eosin and tendon cuts were submitted to birefringence for determination of collagen distribution and organization. RESULTS: After 7 days an increase was observed in the area between beam muscles in H+LLLT (25.45% ± 2.56) in comparison to H (20.3% ± 3.31), in mature fibers and fibrilis in H+LLLT (29346.88 µm2 ± 2182.56; 47602.8 µm2 ± 2201.86 respectively) in comparison to H (26656.5 µm2 ± 1880.46; 45630.34 µm2 ± 2805.82 respectively) and in the collagen area in H+LLLT (2.25% ± 0.19) in comparison to H (2.0% ± 0.15). However, after 14 days a reduction was observed in the area between beam muscles in H+LLLT (13.88% ± 2.54) in comparison to H (19.1% ± 2.61), in fibrils and mature fibers in H+LLLT (17174.1 µm2 ± 2563.82; 32634.04 µm2 ± 1689.38 respectively) in comparison to H (55249.86 µm2 ± 1992.65; 44318.36 µm2 ± 1759.57) and in the collagen area in H+LLLT (1.76% ± 0.16) in comparison to H (2.09 ± 0.27). A greater organization of collagen fibers in the tendon was observed after 7 and 14 days in H+LLLT groups. CONCLUSIONS: Infrared laser irradiation induces an improvement in collagen organization in tendons and a reduction in the total area of collagen in muscles during compensatory atrophy following the ablation of synergist muscles.

Er:YAG Laser for Metal and Ceramic Bracket Debonding: An In Vitro Study on Intrapulpal Temperature, SEM, and EDS Analysis.

OBJECTIVE: To evaluate the effects of bracket removal using an erbium laser on the pulp temperature and enamel surface. BACKGROUND: Removal of orthodontic brackets with conventional debonding pliers may result in enamel cracks. To avoid damage to the enamel surface and effectively remove metal or ceramic brackets, different types of lasers, such as Nd:YAG, CO2, TM:YAP, diode laser, or Er:YAG, have been introduced for debonding. MATERIALS AND METHODS: A total of 55 brackets (n = 55; 20 metal and 35 ceramic ones) were bonded to 55 caries-free premolars extracted for orthodontic indications. Brackets were irradiated with Er:YAG laser (Morita, Irvine, CA) with a wavelength of 2940 nm at a power of 3.4 W, energy 170 mJ, frequency 20 Hz, pulse duration 300 µs, tip diameter 0.8 mm, air/fluid cooling 3 mL/s, and time of irradiation: 6 sec. Debonding was made by scanning (n = 15; 6 sec irradiation at distance of 2 mm from the bracket with an "S" shape movement) and circular (n = 15; 6 sec irradiation at distance of 1 mm from the bracket) motion technique in ceramic brackets or the circular motion technique in metal brackets (n = 15). The number of 10 nonirradiated teeth with ceramic (n = 5) or metal brackets (n = 5) was used as a control in SEM test and EDS analysis. The damage in tooth enamel surface and the calcium percentage were analyzed by means of scanning electron microscope (JEOL 6610LV, JEOL, Japan) and energy dispersive X-ray spectroscopy (EDS, Oxford, United Kingdom). Temperature changes in the pulp were measured by K-type thermocouple. Evaluation of the Adhesive Remnant Index (ARI) on the enamel surface of each tooth was examined after bracket debonding. RESULTS: The scanning method has caused significantly lower temperature increase (mean: 0.83°C) compared with circular motion technique around the ceramic brackets (mean: 1.78°C; p = 0.0001) or the metal brackets (mean: 1.29°C; p = 0.015). ARI score showed no differences between the study groups (p = 0.57). SEM analysis revealed no cracks on enamel surface after laser-assisted debonding in comparison with the control samples where cracks were found. EDS showed a higher mean percentage of the calcium (30.7-85.8%) for all test groups compared with control samples (mean: 7%; p = 0.0002). The amount of the calcium elements was higher for metal brackets in comparison with ceramic ones (p = 0.0002). CONCLUSIONS: Er:YAG laser-assisted debonding causes a minor increase in the pulp temperature and reduced the risk of enamel damage compared with conventional bracket removal.