Highly efficient optical fiber sensor for instantaneous measurement of elevated temperature in dental hard tissues irradiated with an Nd:YaG laser.

In this in vitro experiment, the effect of 1.064 µm pulsed laser on both enamel- and dentin-dental tissues has been investigated. A total of fifty-five dental hard tissue samples were exposed to Nd:YAG laser that possesses a pulse width of 9 ns and 850 mJ of total energy. An optical fiber sensor was put behind the samples to measure the temperature instantaneously. A novel, to the best of our knowledge, fiber sensor has been proposed and used to measure the heat generated in dental hard tissues instantaneously after the application of laser irradiation on the tissue surface. This optical sensor exhibits a fast response time of about 1 ms and high sensitivity with about 1.975 nm/°C. The findings of this study in decreasing the probability of pulpal necrosis structure while handling the tooth, whether for ablation, welding, or tooth resurfacing purposes, may establish standards for dentists and laser manufacturers (healthcare professionals) that should be followed.

Influence of Diode Laser for the Treatment of Dentin Hypersensitivity on Microleakage of Cervical Restorations.

Noncarious cervical lesions (NCCLs) are a common clinical finding often linked with dentin hypersensitivity (DH). Aim. The aim of the study was to evaluate the influence of diode laser for the treatment of DH on microleakage of subsequent NCCL restorations. Materials and Methods. Forty-eight extracted human premolars were collected. All teeth received standardized cervical preparation on both the buccal and palatal surfaces and were randomly divided into three groups (n = 16) according to the restorative material used: nanohybrid composite resin (CR), resin-modified glass ionomer (RMGI), and conventional glass ionomer (GIC). The prepared cavities on the palatal surfaces were treated by diode laser using SIROlaser Blue (Sirona Dental Systems, Bensheim, Germany) prior to restoration, while preparations on the buccal surfaces were directly restored. After thermocycling, the teeth were immersed in methylene blue dye for microleakage evaluation under 40x magnification at both occlusal and cervical margins. The Kruskal-Wallis test followed by the Bonferroni tests was conducted to determine inter- and intragroup differences (P < 0.05). Results. All restorative materials tested showed some degree of microleakage with no statistically significantly different scores with or without the use of laser desensitization prior to restorative treatment. Group CR showed the least microleakage, followed by group RMGI, while group GIC showed the highest. Cervical margins showed greater microleakage than the occlusal margins where the difference was statistically significant in the RMGI group without laser pretreatment (P = 0.006) and in both groups CR (P = 0.02) and RMGI (P = 0.006) with the laser pretreatment. Conclusion. Application of diode laser for the treatment of DH prior to the restoration of teeth with NCCL did not affect the microleakage of all the restorative materials tested. All the materials showed some degree of microleakage, which was higher in gingival margins compared to occlusal margins. The resin composite shows the least microleakage among all the tested materials.

Dentinal tubule penetration of endodontic sealers after nonthermal plasma treatment: A confocal laser scanning microscopy study.

One of the factors affecting the success of endodontic treatment is to fill the root canal system hermetically. The aim of this in vitro study was to evaluate the effect of nonthermal plasma (NP) on dentinal tubule penetration of root canal sealers using confocal laser scanning microscopy. Forty mandibular premolar teeth were selected and the root canals were prepared with large-Waveone-Gold rotary-files. Specimens were divided into four experimental groups according to sealer and NP treatment (n = 10). G1: AH-Plus (AH) G2: nonthermal plasma application + AH-Plus(AH-P) G3: Endosequence-BC(BC) G4: nonthermal plasma application + Endosequence-BC(BC-P). Cold lateral-condensation technique was used for the obturation of root canals. The roots were sectioned horizontally and the sections were examined under confocal laser scanning microscopy. The maximum tubule penetration and percentage of penetration values were obtained from the microscopy images and were statistically analyzed with repeated measurements-ANOVA and the Tukey (HSD) test (p < 0.05). The percentages of dentinal tubule penetration of the groups were not statistically different. The maximum tubule penetration of the AH-P was statistically lower than that of the BC-P (p < 0.05). Plasma application had no affect on the percentage of dentinal tubule penetration. Under the conditions of this in vitro Endosequence-BC sealer showed higher maximum tubule penetration values than AH-Plus after NP treatment. Percentage of dentinal tubule penetration values of experimental groups was similar.

Effect of radiotherapy on the chemical composition of root dentin.

BACKGROUND: The radiotherapy can directly affect the bond strength of the adhesive materials, interfering in the prognosis of restorative treatments, which may be caused by chemical changes in dentin structure. METHODS: Twenty inferior homologues premolars were distributed in 2 groups (in vitro study) (n = 10): nonirradiated and irradiated. The specimens were submitted to the analysis of phosphate (ν1 PO43- ;ν2 PO43- ;ν4 PO43- ), carbonate (ν3 CO32- ), amide I, CH2 , amide III, and amide I/III ratio by confocal Raman spectroscopy. Data were submitted to statistical analysis (T test, P < .05). RESULTS: In intracanal dentin, the irradiated group had lower ν4 PO43- values (1.23 ± 0.06) compared to nonirradiated group (1.40 ± 0.18) (P < .05), with no difference for ν1 PO43- and ν2 PO43 peaks (P > .05). The irradiated (1.56 ± 0.06) had lower carbonate, amide III (1.05 ± 0.19), and amide I/III ratio values (0.19 ± 0.06) compared to nonirradiated group (1.42 ± 0.10, 1.28 ± 0.24, and 0.31 ± 0.10, respectively) (P < .05). For medium dentin irradiated group (1.30 ± 0.12) had lower phosphate values compared to nonirradiated group (1.48 ± 0.22) (P < .05). In cementum, there was no statistical difference between the groups. CONCLUSION: The radiotherapy was able to cause changes in ν4 PO43- , carbonate, and amide III peaks of root dentin.

Physical properties of root cementum: Part 27. Effect of low-level laser therapy on the repair of orthodontically induced inflammatory root resorption: A double-blind, split-mouth, randomized controlled clinical trial.

INTRODUCTION: The purpose of this 2-arm-parallel split-mouth trial was to investigate the effect of low-level laser therapy (LLLT) on the repair of orthodontically induced inflammatory root resorption (OIIRR). METHODS: Twenty patients were included in this study, with 1 side randomly assigned to receive LLLT, and the other side served as a sham. Eligibility criteria included need for bilateral maxillary first premolar extractions as part of fixed appliance treatment. OIIRR was generated by applying 150 g of buccal tipping force on the maxillary first premolars for 4 weeks. After the active force was removed, the teeth were retained for 6 weeks. LLLT commenced with weekly laser applications using a continuous beam 660-nm, 75-mW aluminum-gallium-indium-phosphorus laser with 1/e2 spot size of 0.260 cm2, power density of 0.245 W/cm2, and fluence of 3.6 J/cm2. Contact application was used at 8 points buccally and palatally above the mucosa over each tooth root for 15 seconds with a total treatment time of 2 minutes. After 6 weeks, the maxillary first premolars were extracted and scanned with microcomputed tomography for primary outcome OIIRR calculations. Subgroup analysis included assessment per root surface, per vertical third, and sites of heaviest compressive forces (buccal-cervical and palato-apical). Randomization was generated using www.randomization.com, and allocation was concealed in sequentially numbered, opaque, sealed envelopes. Blinding was used for treatment and outcome assessments. Two-tailed paired t tests were used to determine whether there were any statistically significant differences in total crater volumes of the laser vs the sham treated teeth. RESULTS: Total crater volumes were 0.746 mm3 for the laser treated teeth and 0.779 mm3 for the sham. There was a mean difference of 0.033 ± 0.39 mm3 (95% CI, -0.21 to 0.148 mm3) greater resorption crater volume in the sham group compared with the laser group; this was not statistically significant (P = 0.705). No harm was observed. CONCLUSIONS: No significant difference was found between LLLT and sham control groups in OIIRR repair.

Influence of Nd:YAG laser on the penetration of a bioceramic root canal sealer into dentinal tubules: A confocal analysis.

OBJECTIVE: The aim of this in vitro study, is to evaluate the penetration of a bioceramic root canal sealer into dentinal tubules at 3 mm and 5 mm from the apex after Nd:YAG laser irradiation. METHODS: Forty freshly extracted human mandibular premolars were prepared using Reciproc® and irrigated with 17% ethylenediaminetetraacetic acid (EDTA). Teeth were divided into 4 groups: group 1, obturated with control sealer (AH Plus®); group 2, obturated with bioceramic sealer (Endosequence BC Sealer®); group 3, Nd:YAG laser + control sealer (AH Plus®); and group 4, Nd:YAG laser + bioceramic sealer (Endosequence BC Sealer®). The samples were transversely sectioned 3 mm and 5 mm from the apex and examined using confocal laser scanning microscopy. Two parameters were measured: 1) sealer penetration into dentinal tubules of the root canal and 2) sealer penetration into the perimeter of the root canal walls. RESULTS: Penetration analysis showed that bioceramic sealer had a higher penetration at depths of 3 and 5 mm than that of the control sealer, regardless of laser use (p <0.05). Perimeter analysis showed that there was no difference between both sealers at a depth of 3 mm (p <0.05), regardless of laser use. At a depth of 5 mm, bioceramic sealer and laser showed a greater perimeter of penetration (p <0.05) than the control sealer. CONCLUSION: The use of Nd:YAG laser did not compromise the penetration of bioceramic sealer into dentinal tubules of root canals at 3 mm and 5 mm from the apex.

Glass Ionomer Cements can be used for Bonding Orthodontic Brackets After Cancer Radiation Treatment?

Patients undergoing radiotherapy treatment present more susceptibility to dental caries and the use of an orthodontic device increases this risk factor due to biofilm accumulation around the brackets. The objective of this study was to evaluate the shear bond strength to irradiated permanent teeth of orthodontic brackets bonded with conventional glass ionomer cement and resin-modified glass ionomer cement due to the fluoride release capacity of these materials. Ninety prepared human premolars were divided into 6 groups (n=15), according to the bonding material and use or not of radiation: CR: Transbond XT composite resin; RMGIC: Fuji Ortho LC conventional glass ionomer cement; GIC: Ketac Cem Easymix resin-modified glass ionomer cement. The groups were irradiated (I) or non-irradiated (NI) prior to bracket bonding. The specimens were subjected to a fractioned radiation dose of 2 Gy over 5 consecutive days for 6 weeks. After the radiotherapy, the brackets were bonded on the specimens with Transbond XT, Fuji Ortho LC and Ketac Cem Easymix. After 24 h, the specimens were subjected to shear bond strength test. The image of enamel surface (classified by Adhesive Remnant Index - ARI) was also evaluated and its frequency was checked among groups/subgroups. The shear bond strength variable was evaluated with ANOVA and Tukey's post-hoc test. GIC group showed the lowest adhesion values among the groups (p<0.05). There was no statistically significant difference among non-irradiated and irradiated groups (p>0.05). As for the ARI, the CR-I group showed the highest material retention on enamel surface among the irradiated groups. RMGIC group showed the highest values for shear bond strength and presented ARI acceptable for clinical practices.

Effect of 2.94 µm Er: YAG laser on the chemical composition of hard tissues.

The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 µm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/ c m 2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analyzed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.

Glass ionomer cements can be used for bonding orthodontic brackets after cancer radiation treatment?

Abstract Patients undergoing radiotherapy treatment present more susceptibility to dental caries and the use of an orthodontic device increases this risk factor due to biofilm accumulation around the brackets. The objective of this study was to evaluate the shear bond strength to irradiated permanent teeth of orthodontic brackets bonded with conventional glass ionomer cement and resin-modified glass ionomer cement due to the fluoride release capacity of these materials. Ninety prepared human premolars were divided into 6 groups (n=15), according to the bonding material and use or not of radiation: CR: Transbond XT composite resin; RMGIC: Fuji Ortho LC conventional glass ionomer cement; GIC: Ketac Cem Easymix resin-modified glass ionomer cement. The groups were irradiated (I) or non-irradiated (NI) prior to bracket bonding. The specimens were subjected to a fractioned radiation dose of 2 Gy over 5 consecutive days for 6 weeks. After the radiotherapy, the brackets were bonded on the specimens with Transbond XT, Fuji Ortho LC and Ketac Cem Easymix. After 24 h, the specimens were subjected to shear bond strength test. The image of enamel surface (classified by Adhesive Remnant Index - ARI) was also evaluated and its frequency was checked among groups/subgroups. The shear bond strength variable was evaluated with ANOVA and Tukey's post-hoc test. GIC group showed the lowest adhesion values among the groups (p<0.05). There was no statistically significant difference among non-irradiated and irradiated groups (p>0.05). As for the ARI, the CR-I group showed the highest material retention on enamel surface among the irradiated groups. RMGIC group showed the highest values for shear bond strength and presented ARI acceptable for clinical practices.

Resumo Pacientes submetidos a tratamento radioterápico apresentam maior suscetibilidade à cárie dentária e o uso de aparelho aumenta esse fator de risco devido ao acúmulo de biofilme dental ao redor dos bráquetes. Assim, o objetivo deste estudo foi avaliar a resistência ao cisalhamento de bráquetes ortodônticos colados com cimento de ionômero de vidro convencional (CIV) e o modificado por resina (CIVMR), devido à capacidade de liberação de flúor desse material em dentes permanentes irradiados. Noventa pré-molares humanos foram divididos em 6 grupos (n=15), de acordo com o materila de colagem e com o uso ou não de radiação: RC: Transbond XT; CIVMR: Fuji Ortho LC; RMGIC: Ketac Cem Easymix. Os grupos for irradiados (I) ou não-irradiados (NI) previamente à colagem dos bráquetes. Os espécimes foram submetidos a doses fracionadas de radiação de 2 Gy/dia, durante 5 dias consecutivos, por 6 semanas. Depois da termociclagem e radioterapia, os bráquetes foram colados sobre os espécimes com Transbond XT, Fuji Ortho LC e Ketac Cem Easymix. Depois de 24 h, os espécimes foram sumetidos ao teste de resistência ao cisalhamento. A imagem da superfície do esmalte (classificado pelo Índice de Remanescente Adesivo-IRA) também foi avaliada. O IRA foi distribuido em tabelas de contingência e analisado quanto à frequência entre grupos/subgrupos. O teste de resistência ao cisalhamento foi avaliado por ANOVA e pós-teste de Tukey. CIVMR apresentou os menores valores de adesão entre os grupos (p<0,05). Entre os grupos irradiados e não-irradiados não houve diferença estatística significante (p>0,05). Quanto ao IRA, RC-I apresentou maior retenção de compósito na superfície do esmalte do que os demais subgrupos. CIVMR pode ser utilizado para colagem de bráquetes metálico e apresentou IRA aceitável para práticas clínicas.

The effect of low-level laser therapy on orthodontically induced root resorption: a pilot double blind randomized controlled trial.

Background: The effect of low-level laser therapy (LLLT) on accelerating orthodontic tooth movement has been extensively studied; however, there is limited knowledge on the use of LLLT on orthodontic root resorption. Objective: To investigate the effect of LLLT on orthodontically induced inflammatory root resorption (OIIRR) and to compare the difference between pulsed and continuous LLLT on OIIRR. Trial design: Double-blind, single-centre 3-arm parallel split-mouth randomized controlled trial. Participants: Twenty adolescent patients who required bilateral maxillary first premolar (MFP) orthodontic extractions were recruited from the Sydney Dental Hospital between October 2014 and December 2014. Intervention: All MFPs were tipped buccally for 28 days to induce OIIRR. The experimental premolars (n = 20) received LLLT and the control premolars (n = 20) received placebo-laser on days 0, 1, 2, 3, 7, 14, and 21. Ten experimental premolars received LLLT via continuous delivery and 10 received pulsed delivery. Laser parameter: AlGaAs diode laser of 808 nm wavelength, 0.18 W power, 1.6 J per point, and duration of 9s for continuous mode and 4.5 s for pulsed mode. Outcome: The difference in root resorption crater volume between LLLT and placebo-laser and continuous or pulsed laser delivery after 28 days. Randomization: Randomization was computer-generated, with allocation concealment by opaque sequentially numbered sealed envelopes. Blinding: The participants and operator were blinded. Results: Eighty-eight patients were screened and 20 patients were randomized. Forty premolars were analysed. LLLT resulted in 23 per cent less root resorption compared to the placebo (P = 0.026). Pulsed laser delivery resulted in 5 per cent less root resorption than continuous; however, this was not statistically significant (P = 0.823). No harm was observed. Conclusion: Teeth treated with LLLT had less total root resorption than placebo-laser. Furthermore, there was minimal difference between pulsed or continuous delivery of LLLT. Trial Registration: Clinical Trials Registry (ACTRN12616000829415). Protocol: The protocol was not published before trial commencement.

Intra-pulpal and subsurface temperature rise during tooth irradiation with 808 nm diode laser: an in vitro study.

AIM: This in vitro study evaluated the pulpal and subsurface temperatures during proximal tooth surface irradiation with different settings of an 808 nm diode laser. MATERIALS AND METHODS: The elevation of pulpal and subsurface temperature during irradiation was measured using thermocouples positioned in the centre of the pulp chamber (n=30) and in the centre of a prepared 1.5 mm deep coronal cavity (n=30). Each sample was irradiated 3 times within one-week interval using different exposure settings. A temperature increase of 3.5°C was regarded as critical value for pulpal heath. Results were analysed with one-way ANOVA and Duncan post hoc tests. Micromorphological investigation by digital microscopy was carried out for the irradiated and non-irradiated tooth surface. RESULTS Measurable temperature increase within the pulp chamber (delta PT) and the subsurface (delta ST) were observed with all laser settings tested. The highest recorded delta PT and delta ST were 3.1°C and 8.5°C, respectively. Delivery mode, beam diameter, and exposure time influenced the temperature rise. No alterations on the enamel surface were observed when inspected by the digital microscope after undergoing irradiation with the tested parameters. Cconclusion: From the thermal point of view, under the conditions of the present study the application of an 808 nm diode laser on the outer surface of the tooth at 1W in the continuous mode and at 5W in the pulsed mode for two cycles of 30 s each proved to be safe.

Analysis of Human Tooth Pulp Chamber Temperature After 670 nm Laser Irradiation: In Vitro Study.

OBJECTIVE: One of the limiting factors of employing laser radiation on dental therapies is the potential of causing thermal injuries to pulp tissues. The purpose of this study was to evaluate intra-chamber temperature increase on extracted human teeth exposed to 670 nm wavelength InGaAlP laser diode radiation. MATERIALS AND METHODS: In vitro intra-chamber temperature measurements of 12 standardized human teeth (incisors, canines, premolars, and molars; n = 3) were taken both before and after laser radiation. A type-K thermocouple fast-response thermocouple wire with a 0.5 mm diameter probe was inserted into the tooth pulp chamber (ICEL-Manaus-brand). The laser device Lasotronic-brand InGaAlP laser diode was used to irradiate tooth enamel, perpendicularly to the external surface for 30 sec, with power of levels of 340, 272, 204, 136, and 68 mW. The measurements were taken at three time points: 0, 30 sec, and 3 min after the laser irradiation. Measurements were repeated 24 h after removal and reinsertion of the probe in the pulp chamber. The temperature gradient (ΔT in °C) was calculated (ΔT = final temperature-initial temperature) for each group. Data of ΔT were statistically analyzed by two-way analysis of variance (ANOVA) at the 95% confidence level and compared by Tukey post hoc test (α = 0.05). RESULTS: ANOVA showed statistically significant differences to the interaction of factors (p < 0.05). The highest ΔT values obtained were observed to incisors with 340 mW, 272 mW; 204 mW of power (respectively 4.7°C, 4.2°C, and 3.1°C); and canines presented the lowest ΔT (0.8°C-0.3°C) with no influence of power output. CONCLUSIONS: Since the thermal increase was observed in this study, especially in incisors, attention should be paid to avoid pulpal damage.

Transmission of Curing Light through Moist, Air-Dried, and EDTA Treated Dentine and Enamel.

Objective. This study measured light transmission through enamel and dentin and the effect of exposed dentinal tubules to light propagation. Methods. Light attenuation through enamel and dentin layers of various thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) was measured using specimens that were (1) moist and (2) air-dried (n = 5). Measurements were repeated after the specimens were treated with EDTA. Specimens were transilluminated with a light curing unit (maximum power output 1869 mW/cm(2)), and the mean irradiance power of transmitting light was measured. The transmission of light through teeth was studied using 10 extracted intact human incisors and premolars. Results. Transmitted light irradiance through 1 mm thick moist discs was 500 mW/cm(2) for enamel and 398 mW/cm(2) for dentin (p < 0.05). The increase of the specimen thickness decreased light transmission in all groups (p < 0.005), and moist specimens attenuated light less than air-dried specimens in all thicknesses (p < 0.05). EDTA treatment increased light transmission from 398 mW/cm(2) to 439 mW/cm(2) (1 mm dentin specimen thickness) (p < 0.05). Light transmission through intact premolar was 6.2 mW/cm(2) (average thickness 8.2 mm) and through incisor was 37.6 mW/cm(2) (average thickness 5.6 mm). Conclusion. Light transmission through enamel is greater than that through dentin, probably reflecting differences in refractive indices and extinction coefficients. Light transmission through enamel, dentin, and extracted teeth seemed to follow Beer-Lambert's law.

Effect of gamma irradiation on the wear behavior of human tooth dentin.

OBJECTIVES: The objective of this study was to evaluate the effect of gamma irradiation on the wear behavior of human tooth dentin in terms of possible alterations in crystallinity, grain size, and composition. MATERIALS AND METHODS: Human premolars (n = 19) were collected to obtain the perpendicular or parallel to the direction of the dentin tubule specimens. Each specimen was subjected to 60 Gy of gamma irradiation, in daily increments of 2 Gy. The nanoscratch tests were conducted. The scratch traces were observed via scanning electron microscope (SEM) and surface profilometer. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the alteration of crystallography and chemical composition of dentin after irradiation. The change of surface microhardness (SMH) was also evaluated. RESULTS: The nanoscratch results showed that the friction coefficient of dentin after irradiation became higher, and the depths and widths of scratch were greater than that of dentin before irradiation. Additionally, irradiation decreased the crystallinity of dentin and induced the formation of bigger crystals. The carbonate/mineral ratio was increased. Furthermore, a significant reduction in microhardness after irradiation was observed. The main damage mechanisms consisted of the formation of delamination and crack in both the specimens cut perpendicular and parallel to tubule dentin after irradiation. CONCLUSION: Irradiation affected directly the wear behavior of tooth dentin, accompanied by the alterations in crystallography, chemical composition, and surface microhardness of dentin. CLINICAL RELEVANCE: This would help extend understanding the influence of irradiation on dentin and provide suggestions for selecting more suitable materials for irradiated tooth.

The local anaesthetic effect of a dental laser prior to cavity preparation: a pilot volunteer study.

OBJECTIVES: It has been suggested that laser preconditioning can produce dental anaesthesia. This study aimed to assess the response of the dental pulp to laser preconditioning. METHODS: The effects of laser preconditioning, sham laser (negative control), and composite curing light (positive control) on the response of the dental pulp to electric pulp testing was investigated in this double-blind crossover trial with six volunteers. The Er,Cr:YSGG laser or curing light was shone on a premolar tooth in a sweeping motion for 30 seconds (in the sham treatment, the laser was not activated) in blindfolded volunteers subjected to a consistent aural stimulus. Treatment method at each visit was randomized and performed by a researcher not involved in pulp testing. Teeth were pulp tested twice initially by another member of the research team to get baseline readings, immediately following the treatment, and thereafter every two minutes for 10 minutes. Results were analyzed using analysis of variance and an independent-sample t-test. RESULTS: There were no significant differences in pulpal response between treatments (p>0.05). CONCLUSION: Laser preconditioning did not affect pulpal response as measured by an electronic pulp tester. Laser preconditioning did not result in any pain or noticeable symptoms for both teeth and soft tissues.

Connective tissue graft associated or not with low laser therapy to treat gingival recession: randomized clinical trial.

BACKGROUND: To evaluate the treatment of gingival recession with a connective tissue graft (CTG) alone or in combination with low-level laser therapy (CTG + L). METHODS: Forty patients presenting 40 Miller Class I and II gingival recessions were included. The defects were randomly assigned to receive either CTG (n = 20) or CTG + L (n = 20). A diode laser (660 nm) was applied to the test sites immediately after surgery and every other day for 7 days (eight applications). RESULTS: The mean percentage of root coverage was 91.9% for the test group and 89.48% for the control group after 6 months (p > 0.05). The test group presented more complete root coverage (n = 13, 65%) than the control group (n = 7, 35%) (p = 0.04). Dentine sensitivity decreased significantly after 6 months in both groups (p < 0.001). The two groups showed improvement in aesthetics at the end of treatment. CONCLUSIONS: Low-level laser therapy may increase the percentage of complete root coverage when associated with CTG.

Ultrashort pulsed laser conditioning of human enamel: in vitro study of the influence of geometrical processing parameters on shear bond strength of orthodontic brackets.

The surfaces of 63 extracted premolar teeth were processed with intense ultrashort laser pulses (λ = 795 nm; pulse duration, 120 fs; repetition rate, 1 kHz) to produce cross patterns with different pitches (s) in the micrometer range in order to evaluate the influence of such microstructures on the shear bond strengths of orthodontic brackets to enamel. The samples were classified in nine groups corresponding to the control group (raw samples) and eight different laser-processed groups (cross patterns with s increasing from 15 to 180 µm). Brackets were luted with Transbond(TM) XT adhesive resin to all the samples; after 72 h, they all were submitted to strength test in a universal testing machine. Additionally, a third of the samples underwent morphological analysis of the debonded surface by means of scanning electron microscope microscopy and an analysis of the failure mode based on the adhesive remnant index. The results showed that enamel microstructuring with ultrashort laser pulses remarkably increase the bond strength of brackets. Dense cross patterns (s < 90 µm) produce the highest increase of bond strengths as compared to control group whereas light ones (s > 90 µm) give rise to smaller improvements of the bond strength. A strong correlation of this behavior with the predominant failure mode in both scenarios was found. So far, the best compromise between suitable adhesive efficiency, processing time minimization, and enamel surface preservation suggests the performance of cross patterns with pitches in the order of 90 µm.

Pulpal thermal changes following Er-YAG laser debonding of ceramic brackets.

Lasers are effective in debonding ceramic brackets. Unfortunately, while reducing the adhesive bond strength, lasers are also reported to increase pulpal temperature. The aim of this study was to evaluate the shear bond strengths and temperature increase levels after debonding ceramic brackets using an Er-YAG laser with or without water-cooling. Sixty polycrystalline upper premolar ceramic brackets were placed on the labial surface of sixty human premolar teeth which were randomly divided into three groups of twenty. A laser pulse at 5 W for 9 seconds was delivered to each bracket in both study groups either with water-cooling (water group) or without water-cooling (waterless group) using an Er-YAG laser. Debonding was performed 45 seconds after laser exposure and shear bond strengths were measured. Data comparison revealed a statistically significant difference between the groups. Mean temperature increases of 2.41°C and 4.59°C were recorded for the water and waterless laser groups, respectively. The shear bond strength value for the control group was 22.76 MPa and 10.46 and 6.36 MPa for the water and waterless laser groups, respectively. The application of Er-YAG laser with water-cooling was an efficient and safe method of debonding ceramic brackets.

Effect of carbon dioxide laser irradiation on enamel surface microhardness around orthodontic brackets.

INTRODUCTION: In this study, we aimed to determine the effect of carbon dioxide laser irradiation on enamel surface microhardness. METHODS: In this single-blind interventional clinical trial, 16 patients needing at least 2 premolars extracted for orthodontic purposes participated. In each subject, 1 premolar was treated with the carbon dioxide laser (beam diameter, 0.2 mm; power, 0.7 W); the other was exposed to a visible guiding light as the control. A t-loop was ligated to the bonded brackets to increase caries risk. After at least 2 months, the teeth were extracted, and the surface microhardness was measured. Scanning electron microscope evaluation was performed on 1 sample from each group. Normal distribution of the data was assessed by the Kolmogorov-Smirnov and Shapiro-Wilks tests. Mean microhardness values of the 2 groups were compared using paired t tests. RESULTS: The data had normal distributions. Means and standard deviations of the microhardness in the laser-treated and control groups were 301.81 ± 94.29 and 183.9 ± 72.08 Vickers hardness numbers, respectively; this was different significantly (P <0.001). Scanning electron microscopy showed the enamel surface melting in the laser-treated specimens. CONCLUSIONS: Carbon dioxide laser treatment results in higher enamel surface microhardness around orthodontic brackets. Patients at high risk of caries might benefit from this intervention. Exact control of the laser irradiation parameters is recommended.