Lased Dentin Research Articles

In vitro evaluation of laser vs. handpiece for tooth preparation

Background:The erbium-doped yttrium aluminium garnet (Er:YAG) laser has been revealed to effectively ablate dental hard tissues, and its utilisation to caries eradication and cavity preparation is envisaged. Nevertheless, only a limited research has been performed on the Er:YAG laser's capacity to treat caries.Aim and Objectives:The efficiency of caries elimination with an Er:YAG laser in vitro was equated to that of traditional mechanical therapy in this study.Methodology:The investigation made use of teeth that had suffered from root caries. The Er:YAG laser was used to treat half of each tooth, while the other half was either removed with a conventional bur or left untouched as a control. Each therapy was evaluated in terms of how long it took to remove cavities, histological examinations of decalcified serial sections, scanning electron microscopy (SEM) analyses and the density of the dentin.Result:A longer treatment time was required for the Er:YAG laser to completely eradicate carious dentin because of its precise irradiation strategy. However, the Er:YAG laser was effective in removing diseased and softening carious dentin with little heat injury to neighbouring intact dentin, much as the bur treatment. It was also shown that the Er:YAG laser treatment had a lower amount of vibration than other methods. The SEM study of the lased dentin surface revealed characteristic micro-irregularities.Conclusion:The Er:YAG laser system appears to be a potential novel technical option for caries therapy, based on our findings.

Influence of Adhesive Systems on Bond Strength of Resin Composite to Er,cr :ysgg Lased Dentin under Simulated Pulpal Pressure

Influence of Adhesive Systems on Bond Strength of Resin Composite to Er,cr :ysgg Lased Dentin under Simulated Pulpal Pressure

Shear Bond Strength of a Multi-Mode Adhesive to Bur-Cut and Er,Cr:YSGG Lased Dentin in Different Output Powers

Statement of the Problem: Universal or multi-mode adhesives are new adhesive systems that can be used in both etch-and-rinse (ER) and self-etch (SE) modes. Lesser technical sensitivity and dual use of these adhesives have made them popular among dentists. Studies are being conducted to analyze the advantages and disadvantages these adhesives in different conditions. Purpose: The aim of this study was to compare shear bond strength (SBS) of a multi-mode adhesive in different etching modes to Er,Cr:YSGG laser ablated and bur-cut dentin. Materials and Method: Buccal and lingual surfaces of 30 sound human molars, randomly divided to three groups, were prepared by bur and Er,Cr:YSGG (4 Watt and 5 Watt, 20 Hz, 96% water, 60% air, and 600-µm spot size) to reach a flat surface in superficial dentin. Each group was randomly divided into 2 subgroups (ER and SE), and then Scotchbond Universal adhesive was applied. Composite cylinders were attached to the surfaces and cured. Specimens were stored in 37 °C water for 24 hours and thermocycled (500 cycles) and were tested for SBS and failure modes were determined by stereomicroscope. Data was analyzed using SPSS19 and one- way ANOVA and Tukey’s post hoc tests and p< 0.05 was considered as significance level. Results: Bur-cut dentin with ER method had the highest mean SBS value (33.80 MPa). SBS in bur-cut and 4Watt laser in ER mode were significantly higher than SE mode (p= 0.002 and p= 0.000 respectively). Highest mean SBS value in lased dentin was achieve in 4 Watt ER mode. Conclusion:SBS of Scotchbond universal adhesive to dentine is highest in bur-cut and ER mode and in 4-Watt lased-dentin is higher than 5-Watt lased-dentin. Moreover, in 4-Watt lased-dentin, SBS of ER mode is more than SE mode.

Evaluation of sub-surface penetration and bonding durability of self-etching primer systems to Er:YAG laser treated cervical dentin.

This study aimed to investigate self-etching bonding systems penetrating in sub-surface dentin layer after Er:YAG laser irradiation and micro-shear bonding durability over a period of 1 year. Dentin slices obtained from extracted human third molars were prepared. Two self-etching adhesive systems were evaluated: Clearfil SE Bond and Clearfil Tri-S Bond. Specimens were tested for micro-shear bond strength with one of the following treatments: Er:YAG laser irradiation and 600-grit silicon paper polishing at 24 h, 7 days, 6 months and 1 year. The adhesive interfaces between bonding agents and lased cervical dentin were studied. No hybrid layer could be observed for lased dentin. The slim resin tags could be seen penetrating through the lased subsurface layer. Bond strength to lased dentin after 6 months and 1 year were significantly decreased (p<0.05).

Structural and Morphological Changes in Human Dentin after Ablative and Subablative Er:YAG Laser Irradiation.

This study investigated the influence of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls. Forty sound human premolars were selected and randomly assigned into four groups. Class V cavities were prepared either with an Er:YAG laser (groups 1 and 2; 15 Hz, 250 mJ for enamel, 10 Hz, 200 mJ for dentin) or with a high speed handpiece (groups 3 and 4). The specimens in groups 1 and 3 served as the control, whereas those in groups 2 and 4 were exposed to subablative laser irradiation following cavity preparation (10 Hz, 50 mJ). After bisecting the specimens, one half was subjected to microhardness assessment and the other half was evaluated by SEM-EDS analysis. Microhardness was significantly greater in the specimens prepared by both ablative and subablative laser irradiation (group 2) than that of the bur-prepared cavities (groups 3 and 4) (P < 0.05). The quantity of calcium ion was significantly greater in cavities prepared by the Er:YAG laser (groups 1 and 2) compared to that of the bur cavities (groups 3 and 4) (P < 0.05). Subablative irradiation improved microhardness and weight percentage of calcium ion in both laser and bur cavities, but the difference was not significant compared to that of the relevant control group (P > 0.05). Cavity preparation with an Er:YAG laser could be considered as an alternative to the conventional method of drilling, as it enhances the mechanical and compositional properties of lased dentin, especially when combined by subablative irradiation.

Bonding strategies of resin cement to Er,Cr:YSGG lased dentin: micro-CT evaluation and microshear bond strength testing.

Pretreatment of the tooth surface is essential for establishing effective micromechanical retention between it and the restoration. The purpose of this study was to evaluate the bond strength between the resin and the Er,Cr:YSGG laser irradiated dentin and to examine morphologic characterization of the dentin-resin interface. In addition, the study evaluated the quantity of opened and closed dentinal tubules. Thirty extracted human molars were sectioned into samples of 1 mm thickness. The samples were randomly assigned to two groups containing 15 specimens each. Surface treatments were not applied to the samples in the control group and the samples in the experimental group were irradiated with an Er,Cr:YSGG laser. Two resin cement samples were polymerized on the surface of each sliced dentin. The microshear bond strength (μSBS) between dentin and cement (n = 30 for each group) was measured with a universal testing machine. The topography and morphology of the resin-dentin interface were evaluated by micro-CT (n = 20 for each group). The areas of closed tubular space, closed porosity, area of open tubular space, open porosity, total area of tubular space and fractal dimension were investigated by micro-CT. The data for each parameter were analyzed by Shapiro-Wilk and Student's t test (p&lt;0.05). µSBS values for control group were higher than experimental group. Dentin surfaces in the control group revealed less closed and more opened dentin tubules compared to the experimental group. Total area of tubular space was found to have decreased due to the laser ablation. There was no significant difference between the fractal dimensions of the control and experimental groups. The lased dentin surface was not favorable for the bonding mechanism due to alterations in the dentinal structure.

An &amp;lt;i&amp;gt;in Vitro&amp;lt;/i&amp;gt; Comparison of Bonding Effectiveness of Different Adhesive Strategies on Erbium:Yttrium-Alluminum-Garnet Laser Irradiated Dentin

Background: To date there is not a material considered ideal for the lased dentin. Objective: To compare the bond strength to human lased dentin of self-etch and etch-and-rinse adhesive systems, a self-adhesive resin composite and a glass-ionomer cement. Methods: Forty human molars were sectioned to obtain a 2 mm-thick slab of mid-coronal dentin. The occlusal surface of each slab was polished by SiC paper (P600) for 10 s. Then an half part of dentin slabs was randomly selected for receiving treatment with 2.94 μm Er:YAG laser (DEKA, Smart 2940D Plus) with 10 Hz at 100 mJ, pulse duration of 230 μs with contact tip. Dentin slabs were randomly divided into four groups (n = 10). Six conical frustum-shaped build-ups were constructed on the occlusal surface of each dentin slab using bonding agents (OptiBond Solo Plus Group 1; OptiBond All-in-one Group 2) combined with a resin composite (Premise Flow), self-adhesive resin composites (Vertise Flow Group 3) and a glass-ionomer cement (Ketac-Fil Group 4). Specimens were subjected to μSBS test. Data were analyzed by a mixed model and Tukey’s test. Results: Measured bond strengths were (mean ± standard deviation): 20.8 ± 5.5 MPa (laser treatment) and 15.6 ± 4.5 MPa (SiC paper) for Group 1, 18.9 ± 5.3 MPa (laser treatment) and 14.0 ± 4.3 MPa (SiC paper) for Group 2, 7.9 ± 2.8 MPa (laser treatment) and 4.3 ± 2.2 MPa (SiC paper) for Group 3, 4.7 ± 1.9 MPa (laser treatment) and 2.6 ± 1.2 MPa (SiC paper) for Group 4. The inferential analysis showed that the dentin laser treatment significantly affected the bond strength within each individual group. On dentin treated with laser the bond strengths recorded for build-ups constructed with etch and rinse and self-etch adhesive systems were significantly higher than those recorded for build-ups constructed with self-adhesive resin composite and glass-ionomer cement (p < 0.0001). Similarly, on dentin treated with SiC paper the bond strengths recorded for build-ups constructed with etch and rinse and self-etch adhesive systems were significantly higher than those recorded for build-ups constructed with self-adhesive resin composite and glass-ionomer cement (p < 0.0001). Conclusion: Er:YAG laser treatment has increased the shear bond strength of all the adhesive materials used.

Comparative Evaluation of the Etching Pattern of Er,Cr:YSGG & Acid Etching on Extracted Human Teeth-An ESEM Analysis.

Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose. The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens. Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification. Chi Square and Student "t" statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05<p>0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the 't' value of student 't' test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78μm and GrD3 of 1.09μm. The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent.

Tensile Bond Strength of Resin Composite to Er,Cr:YSGG Lased Dentin Bonded With Different Adhesive Systems

Aims: Tensile bond is important for assessing the success of adhesive restorative materials. The aim of this study is to evaluate the tensile bond strength of resin composite restoration to Er,Cr:YSGG lased dentin bonded with three types of adhesive systems. MATERIALS AND METHODS: Occlusal enamel of eighteen molars samples was removed to expose the underlining dentine. Er,Cr:YSGG laser irradiation was performed to central dentin. Samples were assigned randomly to three groups (N = 6): Group Ι: dentin was treated total etch adhesive (Adper single bond, 3M ESPE); Group II: treated with all in one self—etch adhesive (Adper easy one, 3M ESPE); Group III: treated with two step self—etch adhesive (Clearfil SE bond, Kurary). A translucent plastic tube was fixed and filled incrementally with hybrid resin then small metal screw with ring head was embedded in last increment. Samples were stored in distilled water at 37°C for 24 hours. Tensile bond strength was measuredd using universal testing machine (Digital Force Gauge IMADA CO., LTD, Japan), the failure mode was evaluated. Then statistical analysis was done include descriptive, one way analysis of variance test, and Post Hoc tests. RESULTS: A significant differences in tensile bond strength were observed among groups (p < 0.05). Total etch adhesive bonded demonstrate significantly higher tensile bond strength value than one step self–etch and two step self–etch adhesives (p < 0.05). No significant differences were observed between one step self–etch and two step self–etch adhesives (P>0.05). CONCLUSION: The tensile bond strength of resin composite to Er,Cr:YSGG lased dentin was influenced by adhesive type. Total etch adhesive bonded had higher tensile bond strength than one step and two steps self–etch adhesives.

1ボトル1ステップシステムのEr:YAGレーザー照射歯質に対する接着

Various studies have revealed that the Er:YAG laser is effective in endodontic, periodontal and surgical treatments, and it is used in actual clinical practice. In particular, the Er:YAG laser shows excellent clinical effects when cutting hard tooth tissue, and there have been many studies on adhesive restoration involving teeth irradiated with Er:YAG laser. In this study, focusing on the one-bottle one-step bonding system, we performed tensile bond and marginal leakage tests to evaluate its adhesive properties to enamel and dentin irradiated with Er:YAG laser.Experiment 1Flat bovine enamel or dentin surfaces were prepared using a model trimmer and water-resistant polishing paper (#600), and were irradiated with Er:YAG laser (100mJ, 10pps). Non-irradiated specimens were used as a control. After bonding procedures were performed on these adherent surfaces of 3mm in diameter, the specimens were stored in 37°C distilled water for 24 hours, and were divided into two experimental groups: the 24-hour storage group and the thermal stress group. In the thermal stress group, the specimens were subjected to 2,000 or 5,000 thermocycling in water from 5°C to 55°C with a dwell time of 30s at each temperature. Thereafter, a tensile bond test was performed in each group (n = 10).Experiment 2Saucer cavities (3mm in length, 2mm in width, and 1.5mm in depth) in extracted human molars were prepared setting the anatomical cervical line as the center, using a high-speed cutting diamond point. The marginal line was placed in the enamel on the coronal side and in the dentin on the gingival side. After cavity preparation, the internal cavity walls were uniformly irradiated with Er:YAG laser (100mJ, 10pps). Non-irradiated specimens were used as a control (n = 10). After bonding and filling procedures, these specimens were stored in 37°C distilled water for 24 hours, and thermo-stressed after finishing and polishing. Then, the dye-penetration test was performed according to the following procedures. The root apex was sealed using glass-ionomer cement, and the tooth surface was fully coated with nail varnish except for the area approximately 1mm off the cavity margin. After immersion in 0.5% basic fuchsin at 37°C for 24 hours, each specimen was cut longitudinally at the center of the cavity using a low-speed diamond saw. The degree of dye penetration into the coronal (enamel) or cervical (dentin) wall was evaluated by optical microscopy.From these experiments, the following conclusions were obtained:1. In the tensile bond test, the lased dentin exhibited lower bond strength than the non-irradiated dentin, while enamel showed almost the same bond strength regardless of the laser irradiation.2. In the dye penetration test, marginal microleakage was observed in the dentin cavity wall, whereas good marginal integrity was demonstrated at the enamel margin.

Surface characteristics changes and resin- or GIC-bond to lased dentin and preventive lasercure for dental hard tissue

Surface characteristics changes and resin- or GIC-bond to lased dentin and preventive lasercure for dental hard tissue

Analysis of the interfacial micromorphology and bond strength of adhesive systems to Er:YAG laser-irradiated dentin

This study evaluated the effects of different parameters of dentin irradiation with erbium -doped yttrium aluminum garnet (Er:YAG) laser on bond strength to dentin and analyzed the ultramorphological characteristics of resin-laser-irradiated dentin interfaces using a transmission electron microscope (TEM). Dentin surfaces were abraded with SiC paper (600 grit) or Er:YAG laser-irradiated (120/4, 140/6, 180/4, or 200/6mJ/Hz). Three adhesive systems were tested: Single Bond Plus (3M ESPE), Clearfil Protect Bond (Kuraray Med.), and Clearfil Tri-S Bond (Kuraray Med.). Treatments were performed over flat dentin surfaces of human third molars. Specimens were stored in distilled water for 1week or 6months and prepared for a microtensile bond strength test and interfacial ultrastructure for analysis. Microtensile bond strength data (n = 5) were analyzed with three-way analysis of variance. Irradiation with Er:YAG laser did not reduce the bond strength values for self-etching adhesives even after 6months of water storage. The hybrid layer formation was observed only when the adhesives were applied to non-irradiated dentin (control group). Nanoleakage occurred in all resin-dentin interfaces using Single Bond Plus for both periods. Nanoleakage pattern and bond strength of self-etching adhesives to dentin were less affected by Er:YAG laser irradiation and by the 6-month storage in water than was those of the etch-and-rinse adhesive. TEM analysis revealed no hybridization when dentin was laser-irradiated. Minimally invasive caries removal has been proposed. Nevertheless, bonding mechanisms to lased dentin are not entirely described. Knowing the interaction between the treated dentin and bonding agents and its behavior over time is of utmost importance for new technologies. Regarding that, two-bottle self-etching adhesive system provided a more consistent evidence of its better behavior when bonding to lased substrate.

Nd:YAG Laser Irradiation of Etched/Unetched Dentin Through an Uncured Two-step Etch-and-Rinse Adhesive and its Effect on Microtensile Bond Strength

To evaluate whether Nd:YAG laser irradiation of etched and unetched dentin through an uncured adhesive affected the microtensile bond strength (µTBS). Flat dentin surfaces were created in 19 extracted human third molars. Adper Single Bond (SB) adhesive was applied over etched (groups 1 to 3) or unetched dentin (groups 4 to 6). The dentin was then irradiated with a Nd:YAG laser through the uncured adhesive, using 0.75 or 1 W power settings, except for the control groups (groups 1 and 4). The adhesive was light cured and composite crowns were built up. After 24 h, the teeth were sectioned into beams, with cross-sectional areas of 0.49 mm2, and were stressed under tension. Data were statistically analyzed using two-way ANOVA and Tukey's test (α = 5%). Dentin surfaces of fractured specimens and the interfaces of untested beams were observed under scanning electron microscopy (SEM). Acid etching, laser irradiation, and their interaction significantly affected bonding (p < 0.05). Laser irradiation did not improve bonding of etched dentin to resin (p > 0.05). However, higher µTBS means were found on unetched lased dentin (groups 5 and 6), but only in comparison to group 4, where neither lasing nor etching was performed. Groups 4 to 6 showed the lowest µTBS means among all groups tested (p < 0.05). Laser irradiation did not change the characteristics of the hybrid layers created, while solidification globules were observed on lased dentin surfaces under SEM. Laser irradiation of dentin through the uncured adhesive did not significantly improve the µTBS in comparison to the suggested manufacturer's technique.

Occluding Effect of Nd:YAG Laser and Different Dentin Desensitizing Agents on Human Dentinal Tubules In Vitro: A Scanning Electron Microscopy Investigation

This in vitro study aimed to microscopically evaluate and compare the occluding effect of the Nd:YAG laser and different dentin desensitizing agents on human dentinal tubules. The Nd:YAG laser (SunLase™ 800) and four commercially available and professionally applied dentin desensitizers (Gluma® desensitizer, Tenure Quick®, Quell™ desensitizer, and VivaSens®) were investigated in this study. Sixty-four extracted intact human molars were used. Each dentin surface was divided by shallow indentation into two halves, one of which was used for treatment and the other of which served as a control. The dentin surfaces were etched to remove any smear plugs and to mimic the open dentinal tubules of sensitive dentin using 0.5 M ethylenediaminetetraacetic acid (pH 7.4) for two minutes (applied with a microbrush) and then rinsed with an air-water syringe for 30 seconds. The laser samples (n=16) were randomly divided into four groups of four samples each. These groups were the step-up technique group, the 14-day group, the one-minute group, and the two-minute group. Forty-eight samples were treated with the four tested desensitizing agents and were randomly divided into four groups (n=12/group). Each group was further subdivided into three subgroups (n=4). Samples of the first subgroup were treated for 14 days, while those of the second subgroup were treated once. Samples of the last subgroup were fractured longitudinally after a single treatment. All of the samples were then examined under a scanning electron microscope. The Nd:YAG laser-irradiated dentin showed reduction or complete obliteration of the dentinal tubule lumen; thus, the treatment modified the original dentinal structure. The lased dentin surface in the two-minute group showed bubble-like changes in the area of the dentinal tubules' orifices. Statistically, the two-minute group was found to have a significantly higher percentage of partially or fully occluded tubules than did the one-minute group. All of the studied desensitizing agents produced occlusion of the dentinal tubules; however, the appearance of the precipitates, the level of coverage, and the degree of dentinal occlusion varied among the tested products. Throughout the specified period of this study, occlusion and/or narrowing of the open dentinal tubules have been successfully achieved with both treatment approaches.

Bonding of adhesives to Er:YAG laser-treated dentin

The shear bond strength of adhesives applied to dentin was investigated after irradiation with an erbium-doped yttrium aluminum garnet (Er:YAG) laser. Superficial and deep dentin specimens from human molars were treated either with carbide bur or an Er:YAG laser. Two etch and rinse adhesives (Single Bond and XP Bond) and two self-etch adhesives (Prompt L-Pop and Xeno III) were employed to bond the composite. Shear bond strength (SBS) was determined after storage in water for 24 h using a universal testing machine with a crosshead speed of 0.5 mm/min. Failure patterns and modes were analyzed and evaluated using a stereomicroscope. In addition, samples were processed for Scanning Electron Microscopy SEM evaluation. A linear mixed model was used, and pairwise comparisons were made using the Bonferroni test. Results showed significant differences between the levels of dentin treatment (p=.01) in carbide bur-cut dentin and lased dentin, as well as significant interaction effects due to the depth of dentin and the bonding system used. The etch and rinse adhesives bonded less effectively with lased dentin than with carbide bur-cut dentin, while self-etch adhesives bonded equally well with lased and bur-cut superficial dentin but much less effectively with lased deep dentin than with bur-cut deep dentin. SEM revealed a predominantly adhesive failure mode in laser-ablated fractured specimens, while a mixed failure mode was apparent in the bur-cut fractured specimens. Cavities prepared by laser seem less receptive to adhesive procedures than conventional bur-cut cavities.

Effects of ultramorphological changes on adhesion to lased dentin—Scanning electron microscopy and transmission electron microscopy analysis

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (μTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to μTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest μTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin.

Acid resistance of dentin after erbium:yttrium-aluminum-garnet laser irradiation

The purpose of this study was to evaluate the acid resistance of erbium:yttrium-aluminum-garnet (Er:YAG) lased sub-surface dentin using a scanning electron microscope (SEM). Dentin disks were exposed to a single pulse of Er:YAG laser irradiation at 80 mJ/pulse under water spray, with the contact sapphire tip vertical to the dentin surfaces (n = 15). Five specimens from the laser-ablated dentin surfaces were observed. Ten specimens were crosscut, exposing the center of the lased point. For five of the specimens, the sub-surface of the lased dentin, with or without 10% phosphoric acid treatment, was evaluated. We used the remaining five specimens to analyze the degree of acid treatment on crosscut surface by observing the re-crosscut surfaces at the lased point. The irradiated dentin surfaces were irregular, scaly or flaky. Three sub-layers were observed in the sub-surface: a superficial, less decalcified layer; an intermediate most decalcified layer; and a deep, normal shade layer. Er:YAG laser irradiation affected the acid resistance of sub-surface dentin.

Analysis of the interfacial micromorphology of adhesive systems in cavities prepared with Er,Cr:YSGG, Er:YAG laser and bur

The purpose of this in vitro study was to evaluate the interaction pattern of adhesive systems on laser and bur cavities. Cavities were prepared according to the following groups (n=9): (G1) conventional diamond bur (No. 1013); (G2) Er:YAG laser (250 mJ, 4 Hz, 80.6 J/cm2); (G3) Er,Cr:YSGG laser (3.5 W, 20 Hz, 61.7 J/cm2). After cavity preparation, specimens were divided into three subgroups differing the adhesive systems used (n=3): (GA) AdheSE; (GB) Clearfil standard error (SE) Bond; (GC) Single Bond. After insertion of a micro-hybrid composite resin, the specimens were sectioned across the bonded surface dividing the teeth into two halves, which were prepared for SEM analysis. Cavities prepared with laser appeared to be more irregular than the bur cavities. Different patterns of gap formation and resin tags could be observed, showing the differences, advantages, and disadvantages of both types of cavities. Under the settings of the present study, resin tags were more pronounced in lased dentin than bur prepared dentin independently of the bonding systems used. On the other hand gap formation between dentin and resin in laser prepared cavities was observed suggesting collagen alteration.

Analysis of Er:YAG Lased Dentin Using Attenuated Total Reflectance Fourier Transform Infrared and X-ray Diffraction Techniques

The purpose of this study was to investigate the chemical characteristics of dentin after Er:YAG laser irradiation using various output energies with or without water irrigation. Analysis was carried out by means of attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) and X-ray diffraction (XRD). Furthermore, the relative infrared peak intensities of dentin specimens were compared statistically. Results showed that Er:YAG laser with an output energy of 100 mJ/pulse with water irrigation did not cause any detectable change in dentin. However, a higher energy output or the absence of water irrigation affected the organic portion of dentin. With XRD, no obvious phase changes were observed between the XRD pattern of the control (non-irradiated) dentin powder and those after Er:YAG irradiation - regardless of Er:YAG laser output energy or dehydration condition. It was suggested that the intrinsic water content of dentin - together with extrinsic water irrigation - were important factors to achieving the desired outcome of dentin ablation by Er:YAG laser.

酸化チタン液浴下におけるＮｄ：ＹＡＧレーザーの根管内照射が根管壁象牙質に及ぼす影響について

A fine flexible glass fiber made of quartz has been developed to transmit laser beams more effectively to a specific area. This may increase the potential usefulness of the Nd: YAG laser for root canal treatment. Recent investigations revealed that colloidal TiO2 irradiated by lasers generated laser photolysis and electron paramagnetic resonance (EPR). The aim of this study was to evaluate root canal preparation using Nd: YAG laser with TiO2 solution.Twenty-seven roots removed at 11mm from the apex were used. Root canal patency was confirmed using a No.10 K-file. Then, each sample was fixed to a movable stage, and the fiber tip was inserted near to the apex. The root canal walls were irradiated for 10 sec by Nd: YAG laser. The fiber tip was moved from the apical portion of the root canal towards the canal orifice at a speed of 1mm/sec. The root canal was filled with 5% TiO2 solution during lasing. As to laser irradiating parameters, the output energy was 120mJ, pulse frequency was 15, 30 and 60pps, and the repetition of lasing was 2, 4 and 8 times. Before lasing, the fiber was processed by Nd: YAG laser irradiation through itself in TiO2 solution for 30 sec. This procedure changed the laser irradiating pattern from straight to spherical. The lased samples were evaluated by contact microradiography, digital microscopy and scanning electron microscopy. The mean rates of increase of longitudinal cross sectional root canal space were 100.13±5.51% (15pps, 2 times), 94.42±14.37% (15pps, 4 times), 97.91±8.02% (15pps, 8 times), 100.16±20.88% (30pps, 2 times), 120.52±16.40% (30pps, 4 times), 103.55±10.66% (30pps, 8 times), 102.41±8.46% (60pps, 2 times), 101.01±24.54% (60pps, 4 times), and 96.13%±1625% (60pps, 8 times), respectively. No carbonization of the lased dentin surfaces was observed by digital microscopy and scanning electron microscopy when pulse repetition rate was less than 20pps. In conclusion, the lasing parameters of pulse energy 120mJ and repetition rate 30pps may be appropriate for Nd: YAG laser irradiation of root canals filled with TiO2 solution.