Micro-Morphological Features of the Er:YAG-Lased Interface in Primary Teeth: 12 Months Randomized Split-Mouth Trial.

Despite considerable improvements in oral health, dental caries remains a public health issue. The most frequently used technique to remove caries is through rotating drills. New minimally invasive strategies were introduced into dental practice, such as the use of lasers to perform highly controlled tissue ablation while limiting pain and discomfort, as well as overcoming drill phobia. The objective was to assess and compare treatment with Er:YAG laser versus a conventional rotary treatment during cavity preparation in children with regard to bond interface quality. In a randomized trial using a split-mouth design, 40 (9-12 year-old) children with 80 carious primary molars were included. The cavity in one quadrant was treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. Twenty restored teeth were extracted after one year. The SEM histological evaluation of bond interface results demonstrated no statistically significant differences between restorations placed following bur preparation and those placed following the Er:YAG laser preparation, and both treatments demonstrated promising results. Over a one-year period, no statistically significant differences in the bond interface quality were observed following class I cavity preparation in primary teeth with either Er:YAG laser or a conventional rotary bur.

Restoration Integrity in Primary Teeth Prepared Using Erbium/Yttrium-Aluminum-Garnet Laser: A Randomized Split-Mouth Clinical Study.

The most frequently used and universally accepted technique for removing caries is mechanical ablation of decayed tissues by rotating drills. New minimally invasive strategies, such as the use of lasers to perform highly controlled tissue ablation, have been introduced in dental practice. The aim of this study was to assess and compare treatment with a 2940 nm erbium/yttrium-aluminum-garnet (Er:YAG) laser versus a conventional rotary treatment during cavity preparation in children with regard to restoration integrity. In a randomized, controlled, blinded trial using a split-mouth design, 40 (9-12-year-old) children with 80 carious primary molars were included. The cavity in one quadrant was randomized to be treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. At the one-year follow-up, clinical examinations were conducted to assess the integrity of the restorations according to the Ryge criteria. The data were analyzed using SPSS version 22 (IBM Inc., Chicago, IL, USA). The average age of the participants was 9.4 ± 1.29 years. Males accounted for 51.4% of the participants. The Ryge criteria showed clinical success of restorations, and there was no discernible difference between the conventional and laser intervention techniques. Over one year, no statistically significant differences in the clinical integrity based on the Ryge criteria were found following class I cavity preparation in primary teeth with either procedure.

Evaluation of Resin Infiltration, Fluoride and the Biomimetic Mineralization of CPP-ACP in Protecting Enamel after Orthodontic Inter-Proximal Enamel Reduction.

BACKGROUND: This study investigated the effect of using different agents for protecting enamel proximal surfaces against acidic attack after interproximal reduction (IPR) using the trans micro radiography technique. METHODS: Seventy-five sound-proximal surfaces were obtained from extracted premolars for orthodontic reasons. All teeth were measured miso-distally and mounted before being stripped. The proximal surfaces of all teeth were hand stripped with single-sided diamond strips (OrthoTechnology, West Columbia, SC, USA) followed by polishing via Sof-Lex polishing strips (3M, Maplewood, MN, USA). Three-hundred micrometers of enamel thickness was reduced from each proximal surface. The teeth were randomly divided into 5 groups: group 1 (control un-demineralized) received no treatment, group 2 (control demineralized) had their surfaces demineralized after the IPR procedure, group 3 (fluoride) specimens were treated with fluoride gel (NUPRO, DENTSPLY, Charlotte, NC, USA) after the IPR, group 4 (Icon) resin infiltration material (Icon Proximal Mini Kit, DMG, Bielefeld, Germany) was applied after IPR, group 5 (MI varnish) specimens were treated with Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) containing varnish (MI Varnish, G.C, USA, St. Alsip, IL, USA) after the IPR. The specimens in (groups 2-5) were stored in a 4.5 pH demineralization solution for 4 days. The trans-micro-radiography (TMR) technique was conducted to evaluate the mineral loss (∆Z) and lesion depth of all specimens after the acid challenge. The obtained results were analyzed statistically using a one-way ANOVA at a significance level of α = 0.05. RESULTS: The MI varnish recorded significant ∆Z and lesion depth values compared to the other groups p > 0.05. There was no significant difference in ∆Z and lesion depth between the control demineralized, Icon, and fluoride groups p < 0.05. CONCLUSION: The MI varnish increased the enamel resistance to acidic attack, and thus can be considered an agent capable of protecting the proximal enamel surface after IPR.

Evaluation of Bioactive Glass and Low Viscosity Resin as Orthodontic Enamel Sealer: An In Vitro Study.

The study aimed to evaluate the effect of applying fluoride bioactive glass (FBAG) and Alpha-Glaze® (resin sealer) on the shear bond strength of orthodontic brackets to enamel bonded by Transbond XT, brushing−abrasion durability, and their protective effect against simulated cariogenic acidic attack. Materials include 135 extracted premolars that were divided into three groups­FBAG, Alpha-Glaze, and control. The shear bond strength test was measured using an Instron Universal Testing Machine. The brushing abrasion challenge took place with a tooth-brushing simulator. Transmitted light microscopy examinations were performed after the specimens were demineralized for 4 days. The results show that the shear bond strength values of the three groups did not report any statistically significant differences: FBAG (28.1 ± 5.5 Mpa), Alpha-Glaze (32.5 ± 7.4 Mpa), and control (30.7 ± 6.5 Mpa) p < 0.05. The Adhesive Remenant Index (ARI) study showed chipping of enamel in 6.6% of Alpha-Glaze and control specimens and 40% of specimens had their enamel surface covered with resin. Furthermore, 30% of the FBAG and 100% of the Alpha-Glaze sealer specimens resisted the abrasion test. In conclusion, FBAG can serve as an orthodontic-sealer capable of protecting the enamel surface surrounding orthodontic brackets. However, the Alpha-Glaze sealer did not offer the capability of protecting the enamel.

A Novel Evaluation Method for Detecting Defects of the Bonded Orthodontic Bracket-Tooth Interface.

BACKGROUND: Orthodontic patients are at high risk to develop caries. This study is introducing a clinical method detecting interfacial defects between ceramic brackets and enamel utilizing optical coherent tomography in addition to using the nanoleakage expression in vitro test. METHODS: Transbond XT primer and moisture insensitive primer (MIP) were bonded to 75 human premolar enamel surfaces and divided into (XTD), (MIPD), and (MIPW) groups. The (XTD) and (MIPD) groups had ceramic brackets bonded to dry enamel surfaces using TransBond and moisture insensitive primers, respectively, while the (MIPW) samples were bonded to moist enamel using moisture insensitive primer. All specimens were examined under crosspolarization optical coherence tomography. Debonding forces of the brackets to 45 teeth (15 teeth/group). 30 bonded specimens (15 specimens/group) were cross-sectioned to detect the nanoleakage expression using scanning electron microscope equipped with energy-dispersive spectroscopy (SEM/EDS). The degree of conversion of the specimens in the experimental groups was tested using attenuated total reflectance Fourier transform infrared spectroscopy (FTIR/ATR). RESULTS: Optical coherence tomography detected the interfacial defects between the ceramic brackets and tooth structure. One way ANOVA showed that (XTD) and (MIPD) groups recorded significantly higher bond strength values and less nanoleakage expression when compared to MIPW (p > 0.05). CONCLUSIONS: Optical coherence tomography can be utilized to detect interfacial adhesive-tooth defects. Dry enamel surfaces improve the quality of the enamel/primer interface (200 words).

The Efficiency of Fluoride Bioactive Glasses in Protecting Enamel Surrounding Orthodontic Bracket.

OBJECTIVES: The aim of this study was to evaluate the protective effect of using four different fluoride bioactive enamel sealers against an acidic erosion challenge. MATERIALS AND METHODS: A sample of 50 freshly extracted sound upper premolars had their buccal surface bonded to 50 orthodontic brackets using Transbond PLUS color change adhesive; the first four groups had four compositions of fluoride bioactive glasses based on 37 mol% SiO2, 43.9-53.9 mol% CaO, 6.1 mol% P2O5 and CaF2, and 0-10 mol% of Na2O applied to their surfaces and the fifth group served as control (which was not treated by any bioactive sealer). All specimens were challenged by 1% citric acid for 18 minutes which was stirred by a magnetic stirrer. The enamel surfaces next to the orthodontic brackets were examined by SEM. The Wilcoxon signed-rank test was used to compare the area covered by the fluoride bioactive pastes before/after erosion (p < 0.05). Samples from the layer formed on top of the examined teeth were tested before/after erosion to be examined by the attenuated total reflectance Fourier-transform infrared spectroscopy (FTIR/ATR). RESULTS: The FTIR/ATR test showed that fluoride bioactive pastes' applications resulted in the formation of a hydroxyapatite-rich layer; the SEM analysis showed that the aforementioned layer significantly resisted erosion challenge when compared to the control group (p < 0.05). CONCLUSIONS: Fluoride bioactive pastes can efficiently protect the enamel surfaces next to orthodontic brackets from acidic erosion challenges.

Silica-Based Bioactive Glasses and Their Applications in Hard Tissue Regeneration: A Review.

Regenerative medicine is a field that aims to influence and improvise the processes of tissue repair and restoration and to assist the body to heal and recover. In the field of hard tissue regeneration, bio-inert materials are being predominantly used, and there is a necessity to use bioactive materials that can help in better tissue-implant interactions and facilitate the healing and regeneration process. One such bioactive material that is being focused upon and studied extensively in the past few decades is bioactive glass (BG). The original bioactive glass (45S5) is composed of silicon dioxide, sodium dioxide, calcium oxide, and phosphorus pentoxide and is mainly referred to by its commercial name Bioglass. BG is mainly used for bone tissue regeneration due to its osteoconductivity and osteostimulation properties. The bioactivity of BG, however, is highly dependent on the compositional ratio of certain glass-forming system content. The manipulation of content ratio and the element compositional flexibility of BG-forming network developed other types of bioactive glasses with controllable chemical durability and chemical affinity with bone and bioactivity. This review article mainly discusses the basic information about silica-based bioactive glasses, including their composition, processing, and properties, as well as their medical applications such as in bone regeneration, as bone grafts, and as dental implant coatings.

Fluoride bioactive glass paste improves bond durability and remineralizes tooth structure prior to adhesive restoration.

OBJECTIVE: The current study aimed at examining a fluoride containing bioactive glass (BiominF®) paste as a temporary filling material capable of remineralizing the demineralized enamel or dentin, and its ability to decrease a simulated dentinal fluids pressure on the resin/dentin interface, without affecting the shear bond strength of a universal bonding agent to enamel and dentin. METHODS: 60 premolars were utilized for the acid resistance, trans-microradiography (TMR) and shear bond strength (SBS) experiments. Enamel and dentin discs were demineralized for 4 days to create a subsurface demineralized zone followed by applying BiominF® paste, 1.23% acidulated phosphate fluoride, or a temporary filling material for 24 h. 30 extracted human non-carious third molars were utilized for the pulpal pressure experiment in which direct communication to the pulp chamber was created by cutting at a level approximately 1 mm below the cemento-enamel junction while the coronal enamel was ground to expose mid coronal dentin. The dentin surface was exposed to a simulated pulpal pressure. The dentin surfaces had BiominF® paste, an oxalate desensitizing agent, or temporary filling material followed by application of a universal adhesive system. RESULTS: One way ANOVA showed that BiominF® paste remineralized effectively the demineralized enamel or dentin, did not affect the bond strength of the enamel and dentin surfaces to the tested adhesive system p < 0.05, and improved the acid resistance of the demineralized enamel and dentin against a secondary erosive challenge. Moreover, BiominF® paste decreased the nanoleakage expression in the dentin/adhesive interface exposed to a simulated pulpal pressure. SIGNIFICANCE: BiominF® paste may serve as a temporary filling material that may improve the longevity of adhesive restorations and help to conserve tooth structures by preserving the demineralized enamel and dentin form cutting during cavity preparation.

Orthodontic Bracket Bonding Using Self-adhesive Cement to Facilitate Bracket Debonding.

PURPOSE: To evaluate shear bond strength (SBS), adhesive remnant index (ARI), and orthodontic bracket base after debonding of orthodontic brackets bonded using two different adhesives. MATERIALS AND METHODS: Ninety sound human premolars were divided into three groups of n = 30. 1. Transbond, where brackets were bonded with Transbond XT (3M Unitek); 2. Multilink, where brackets were bonded with Multilink Speed (Ivoclar Vivadent); 3. Multilink+etch, where brackets were bonded using Multilink Speed after etching enamel. ARI scores were obtained using a stereomicroscope. SEM was used to evaluate the treated enamel surfaces and the base of the brackets. One-way ANOVA was performed to statistically analyze SBS. The Kruskal-Wallis test was conducted to investigate ARI scores, followed by multiple comparison tests (p < 0.05). RESULTS: SBS was significantly lower in the Multilink group compared to the other groups (p < 0.05). SEM evaluation revealed minimum penetration of resin tags within the enamel and that most of the resin was attached to the base of the brackets in the Multilink group compared to the other two groups (p < 0.05). CONCLUSION: Application of Multilink Speed on nonetched enamel provides acceptable SBS of orthodontic brackets bonded to enamel with minimum penetration of resin tags into enamel and less residual resin on tooth surfaces.

45S5 Bioglass paste is capable of protecting the enamel surrounding orthodontic brackets against erosive challenge.

OBJECTIVES: This study aimed at evaluating the effect of using a 45S5 bioglass paste and a topical fluoride as protective agents against acidic erosion (resembling acidic beverage softdrinks intake) for enamel surrounding orthodontic brackets. MATERIALS AND METHODS: Sample of 21 freshly extracted sound incisor and premolar teeth was randomly divided into three equal groups: a bioglass group (Bioglass) (NovaMin, 5-mm average particle, NovaMin Technology), a Fluoride group (Fluoride) (Gelato APF Gel, Keystone Industries), and a control group (Control). Orthodontic brackets were bonded to the utilized teeth usingMIP (Moisture Insensitive Primer) and Transbond PLUS color change adhesive. All specimens were challenged by 1% citric acid for 18 min. The top enamel surfaces next to the orthodontic brackets were examined by SEM-EDS. Wilcoxon Signed-Rank test was used to compare the area covered by the 45S5 bioglass paste before/after erosion P < 0.05. RESULTS: 45S5 bioglass paste application resulted in the formation of an interaction layer that significantly resisted erosion challenge P < 0.05. The fluoride and control specimens showed signs of erosion of the enamel next to the orthodontic brackets (P < 0.05). CONCLUSION: 45S5 bioglass paste can efficiently protect the enamel surfaces next to orthodontic brackets for acidic erosion challenges.

Fourier-transform infrared spectroscopy/attenuated total reflectance analysis for the degree of conversion and shear bond strength of Transbond XT adhesive system.

OBJECTIVE: The objectives of this study were to evaluate the degree of conversion (DC) for Transbond XT curing light of intensity 1,600 mW/cm2 by using variable curing durations and to determine the effect of the tested curing durations adopted in the current experiment on shear bond strength of Transbond XT resin cement. MATERIALS AND METHODS: A total of 85 orthodontic ceramic brackets (Victory series; 3M Unitek) were utilized in the current experiment. The bonding system used in the current study was Transbond XT Primer followed by Transbond PLUS Color Change Adhesive (3M Unitek) that cured for 3, 6, and 9 seconds. The method was done by polymerization of the adhesive under a ceramic bracket for 40 ceramic brackets. The other 45 brackets were divided into three groups (n=15) according to the curing time duration (3, 6, and 9 seconds). The bonded specimens in each group were debonded using a shear load applied at the bracket bases by the blades of an Instron universal testing machine (ElectroPlus E1000; Instron) and directed in an occlusogingival direction with a crosshead speed of 0.5 mm/min utilizing 50 kg load cell. RESULTS: One-way ANOVA revealed that 6 and 9 seconds curing by the Ortholux light cure scored significantly higher values when compared to the 3 seconds curing. CONCLUSION: Curing the Transbond XT for 6 and 9 seconds recorded a significant improvement of bond strength and DC.

A Novel Fluoride Containing Bioactive Glass Paste is Capable of Re-Mineralizing Early Caries Lesions.

White-spot-lesions (WSL) are a common complication associated with orthodontic treatment. In the current study, the remineralization efficacy of a BiominF® paste was compared to the efficacy of a fluoride gel. METHODS: Orthodontic brackets were bonded to 60 human premolars buccal surfaces, which were covered with varnish, except a small treatment area (3 mm²). All specimens were challenged by a demineralization solution for 4 days. Specimens were assigned into 4 groups: BiominF® paste, Fluoride (4-min application), fluoride (twenty four hours application), and the control (n = 15). After cross-sectioning, enamel slabs having a thickness of approximately 100⁻120 µm were obtained. A TMR (Transverse Micro Radiography) technique was used to observe the sub-surface enamel lesions' depth and mineral density, and their response to the remineralization protocols. One way ANOVA was used to analyze the results (α = 0.05). The top and the cross-sectional surfaces were observed using SEM/EDS. RESULTS: Specimens treated with BiominF® paste showed significant decrease in delta z values, however lesion depth showed no significant difference when compared to the other three groups (p < 0.05). SEM/EDS observation showed the formation of crystal like structures on top of enamel demineralized surfaces, when treated with BiominF® paste. In conclusion BiominF® paste can be considered an effective remineralizing agent for white spot Lesions.

Long-term durability of orthodontic mini-implants.

The current study aimed at examining surface and chemical composition changes of retrieved mini-implants after different periods of service as aids of anchorage for orthodontic patients. This study examined 72 retrieved orthodontic self-tapping and self-drilling mini-implants, 1.7 mm in diameter and 8 mm in length (OrthoEasy system, Forestadent, Pforzheim, Germany) from 36 adult orthodontic patients (18 men and 18 women, mean age = 23 years). The retrieved mini-implants were divided into 3 groups according to service period: 3-6 months (3M-6M) group, 6-12 months (6M-12M) group, and 12-24 months (12M-24M) group, with 24 mini-implants in each group. The control group (As Received) comprised of 24 unused mini-implants of the same type (AR group). All mini-implant heads and threaded bodies were examined for chemical characterization and topographical features by SEM-EDS. The average weight percentages for the following elements Ti, Al, and O2 were obtained and compared among the 4 groups. There was significant decrease in titanium content and deterioration for the surface properties for all parts of the mini-implants after being used inside patients' oral cavities for more than 6 months p < 0.05. The period of mini-implant service inside patients' oral cavities should not exceed 6 months.

The durability of a hydroxyapatite paste used in decreasing the permeability of hypersensitive dentin.

Objectives: Various agents are currently available for treatment of hypersensitive dentine, however, their resistance to erosion intraorally by various erosive drinks is still questionable. The aim of this study is to test the efficacy of a hydroxyapatite paste to decrease dentine permeability and resist an erosion challenge. Methods: Hydroxyapatite powder was mixed with 25% phosphoric acid to form a paste which was applied on dentine having patent dentinal tubules orifices (treated with EDTA, 2 min) and the resulting layer formed on top of dentine was irradiated by Nd:YAG laser. The treated dentin surfaces were exposed to erosion challenge (6% citric acid, 1 min). Dentine permeability was measured before/after the application of the hydroxyapatite paste before/after the erosion challenge before/after the application of Nd:YAG laser using a split chamber device. The top and the fractured dentine surfaces were examined with scanning electron microscope (SEM). Moreover, the chemical nature of the compounds formed on top of dentine surface was examined using the SEM equipped with energy- dispersive X-ray spectroscope (EDS) and FTIR/ATR (Attenuated Total Reflectance Fourier Transform Infrared) techniques. The Mann-Whitney test (p < 0.05) was used to compare the effects of using the hydroxyapatite paste on dentine permeability and calcium/phosphate ratio of the treated dentine surfaces. Results: The application of the hydroxyapatite paste to dentine significantly decreased dentine permeability (p < 0.05). Hydroxyapatite paste was able to occlude patent dentinal tubule orifices with a layer of calcium-phosphate compounds and the application of Nd:YAG laser on the aforementioned layer improved its erosion resistance. Conclusion: Hydroxyapatite paste applied with the technique adopted in the current study has a high potential to be a useful aid in the treatment of dentine hypersensitivity. However, cost and knowledge for using Nd:YAG laser are important factors should be taken into consideration before using the aforementioned technique.

The effect of a bioglass paste on enamel exposed to erosive challenge.

OBJECTIVES: The current study is evaluating the effect of using a 45S5 bioglass paste and topical fluoride application on the cross sectional micro-hardness and the chemical surface changes of eroded enamel. METHODS: Enamel discs were obtained from the buccal surface of one hundred extracted human non-carious third molars. The enamel surfaces were ground flat and each disc was coated with two layers of acid resistant nail varnish except for an exposed treatment window (3mm×2mm) on the buccal surface of the tooth. All specimens were challenged for 60 min by orange juice (Tropicana, Chicago, USA) pH 3.85+0.5. The specimens were divided into four groups: the 45S5 bioglass paste group, fluoride gel group (5 min application), fluoride gel group (24h application) while the rest of specimens served as control. The cross-sectional micro-hardness of 20 specimens from each group was measured. Five specimens from each group had their top eroded enamel surfaces examined by SEM-EDS. One-way ANOVA was used to compare the cross-sectional micro-hardness of the three groups p<0.05. RESULTS: 45S5 bioglass paste application significantly improved the sub-surface eroded enamel when compared to fluoride and control specimens (p<0.05). CONCLUSION: 45S5 bioglass paste can efficiently improve the micro-hardness of the sub-surface eroded enamel surface. CLINICAL SIGNIFICANCE: The use of the 45S5 Bioglass paste can be used efficiently as a potent remineralizing agent for the sub-surface enamel lesions resulting from erosive challenges.

Cytotoxicity of 45S5 bioglass paste used for dentine hypersensitivity treatment.

OBJECTIVES: 45S5 bioglass mixed with 50% phosphoric acid has been suggested to treat dentine hypersensitivity and incipient enamel caries. This study is going to evaluate the biocompatibility of using the aforementioned technique with the rat pulpal cells. METHODS: The relative cytotoxicity of 45S5 bioglass on rat dental pulp cells was compared to the cytotoxicity of a temporary filling material (Caviton; GC, Japan), Type 1 glass ionomer cement (Fuji I; GC, Tokyo, Japan) and commercial desensitising agent (SuperSeal; Phoenix Dental, Fenton, MI, USA) using a transwell insert model. Cell viability was measured by means of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The number of viable cell counts were compared using one way ANOVA (p<0.05). The morphological alterations of the pulp cells were observed directly by phase contrast microscope. RESULTS: The results of this study indicated that cell viability recorded by the 45S5 bioglass paste group did not differ significantly from those of the Caviton, glass ionomer or superseal, moreover pulpal cells microscopic analysis revealed that 45S5 bioglass elicited minimal toxic effect. CONCLUSIONS: 45S5 bioglass paste can serve as a biocompatible material that can potentially be used safely on dentine.

Effect of Er:YAG laser on dentin bonding durability under simulated pulpal pressure.

PURPOSE: To evaluate the effects of Er:YAG laser ablation on the microtensile bond strength and the nanoleakage of Er:YAG-lased dentin bonded to a self-etching adhesive system with and without pulpal pressure. MATERIALS AND METHODS: Twenty flat dentin surfaces were obtained from extracted molars. Ten specimens were irradiated by Er:YAG laser, other specimens (control group) were ground using #600 SiC paper. Direct communication to the pulp chamber was created by cutting at a level approximately 1 mm below the cementoenamel junction and parallel to the occlusal surface. The experimental groups were exposed to a simulated pulpal pressure of 15 cm H2O. Each specimen was restored using an adhesive and a photocured composite. The specimens were then sectioned vertically to obtain dentin/adhesive slabs. Ninety-six slabs were prepared for microtensile bond testing. Sixty-four slabs were immersed in ammoniacal silver nitrate tracer solution for 18 h, then rinsed thoroughly, and immersed in photodeveloping solution for 6 h prior to their examination by FE-SEM. RESULTS: The method of dentin preparation and the pulpal pressure storage condition significantly affected the microTBS, while the storage duration did not (p < 0.05). The nanoleakage patterns observed in the dentin/bond interface differed depending on whether the dentin was conventionally prepared or ablated by Er:YAG laser. CONCLUSION: Er:YAG laser ablation to dentin adversely affected the microTBS and the sealing ability of SE Bond bonded to dentin under simulated pulpal condition.

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.

Effect of Er:YAG laser treatment on the microstructure of the dentin/adhesive interface after acid-base challenge.

PURPOSE: The aim of this study was to evaluate the effect of Er:YAG laser ablation on the microstructure of the dentin/adhesive interface after acid-base challenge in vitro. MATERIALS AND METHODS: Thirty-two extracted third molars were used. One pair of disk-shaped specimens was obtained from the midcoronal dentin of each tooth. One surface in each pair was subjected to Er:YAG laser irradiation, while the other was ground using 600-grit SiC abrasive paper. The specimens were assigned to 4 groups with 8 pairs in each group. A self-etching primer (Clearfil SE-Bond), a bonding adhesive (Clearfil SE-Bond), and a photocuring composite (Clearfil AP-X) were applied accordingto manufacturer's instructionsto create dentin-resin "sandwiches" of each pair, except in group IV, where no primer was applied. The specimens were stored in demineralizing solution for 20 min in groups I and IV, 60 min in group II, and 120 min in group III. After immersion in 5% NaOCl, all the specimens were polished and argon-ion etched. Finally, the interfaces between the dentin and bonding agent were observed under a scanning electron microscope. RESULTS: All specimens in groups I to III showed an acid-base resistant zone, except those of group IV, which debonded completely. A statistically significant difference was found in the thickness of the acid-base resistant zone between group I vs groups II and III for both abraded and Er:YAG-irradiated surfaces. There was no statistically significant difference in the thickness of the acid-base resistant zone between groups II and III for both conventionally prepared and Er:YAG-irradiated surfaces. CONCLUSION: The existence of an acid-base resistant zone followingthe application of the SE Bond system on both abraded and Er:YAG-lased human dentin, regardless of the acid-base challenge duration, was confirmed.