Atomic analysis and knoop hardness measurement of the cavity floor prepared by Er,Cr:YSGG laser irradiation in vitro

Effect of surface treatments and bonding type on elemental composition and bond strength of dentin

The objective of this study was to explore the effect of different surface treatments and bonding types on elemental composition and bond strength of dentin. Under water cooling, 1.5 mm of tooth structure containing just dentin was cut from 39 extracted human molars. Dentin surfaces were untreated (control) or treated by erbium: yttrium aluminum garnet or femtosecond laser (n = 13, each). One sample from each group underwent scanning electron microscopy. Then, dentin surfaces were bonded by Clearfil SE Bond or Clearfil SE Protect (n = 6, each). Energy dispersive X-ray spectroscopy was performed both after surface treatment and bonding application. The dual-polymerized resin cement was applied to dentin surfaces with a special teflon mold (diameter:3 mm × height:3 mm). After polymerization of the resin cement, shear force was applied at the resin cement-dentin interface. Elemental composition value (weight%) of dentin after surface treatment was analyzed by one-way analysis of variance (ANOVA), and the difference value in pre and post-bonding elemental composition by two-way ANOVA. Paired t-tests were executed to compare the weight% values of each element before and after each bonding application. Bond strength was analyzed by two-way ANOVA. The post-hoc test was Tukey's honest significant difference test. Both laser treatments increased the mineral content of dentin, compared to the controls (P<0.05). Application of bonding agents decreased the mineral content of dentin compared to the surface treated dentin. Bond strength was unaffected by either surface treatment or bonding type (P>0.05). For resin cementation, either surface treatment is suitable. After laser treatment, Clearfil SE Bond is recommended over Clearfil SE Protect.

Comparative evaluation of effect of chlorhexidine application on dentin bond strength with two different adhesives after ER, CR: YSGG phototherapy: an in vitro study

This study aimed to assess the efficacy of phototherapy with an Er, Cr:YSGG laser on the bond strength of dentin using two different adhesive systems after chlorhexidine (CHX) application. Twenty-four non-carious human molar teeth were separated into three main groups: negative control Group A (Group A), CHX and phototherapy with an Er, Cr:YSGG laser (Group PC), and CHX with conventional diamond bur (no phototherapy) (Group C). These groups were divided into two subgroups based on adhesives: Clearfil Universal Quick Bond and Clearfil SE Bond. To evaluate the microtensile bond strength, the occlusal enamel surfaces of the teeth were removed with a low-speed, water-cooled diamond bur to expose hard dentin tissue. The teeth within Group PC were treated with Er, Cr:YSGG phototherapy. The surfaces were then disinfected with 0.2% chlorhexidine gluconate. Subgroups were applied according to the manufacturer's instructions using the adhesive systems mentioned above. Following adhesive application, the teeth were restored with composite resin. A microtensile bond strength test was performed on the test sticks obtained from the teeth using a universal test device. Data were analyzed using variance analysis (ANOVA) at a significance level of p < 0.05. Among all groups, the highest bond strength was achieved with Clearfil SE Bond with CHX + phototherapy (45.6 ± 4.2), while the lowest was achieved with Clearfil Universal Quick Bond without phototherapy (control group) (27.0 ± 6.7) (p < 0.05). Phototherapy with Er, Cr: YSGG following chlorhexidine application enhanced the bond strength of both the bond systems (p < 0.05).

Clinical effects of laser-based cavity preparation on class V resin-composite fillings

The aim of the present clinically controlled two-year study was to investigate the influence of laser-based cavity preparation on the long-term performance of Class V resin-composite fillings. Class V non-carious lesions (n = 75) were randomly assigned to two test and one control group. Cavities in both test groups were prepared using an Er,Cr:YSGG laser (Waterlase MD, Biolase, Irvine, California, USA). The device was operated at 3 W (150 mJ, 30 J/cm²), 50% water, 60% air, 30 Hz in H mode. Subsequently, laser-prepared tooth surfaces in test group I (n = 21) were additionally conditioned by acid etching (etch-and-rinse). Laser-prepared cavities of test group II (n = 21) received no additional acid conditioning. After application of an adhesive, all cavities were restored using the resin-composite Venus®. For cavities in the control group (n = 33) conventional diamond burs were used for preparation which was followed by an etch-and-rinse step, too. The fillings were evaluated immediately (baseline) and after 6, 12 and 24 months of wear according to the C-criteria of the USPHS-compatible CPM-index. The results showed that after 24 month of wear, laser-preparation was associated with fillings of high clinical acceptability. Compared to conventional bur-based treatment, laser-based cavity preparation resulted in fillings with high marginal integrity and superior marginal ledge configurations (p = 0.003). Furthermore, laser-preparation combined with additional acid-conditioning (test group I) resulted in fillings with the best marginal integrity and the lowest number in marginal discoloration, especially at the enamel-composite margins (p = 0.044). In addition, total loss of fillings was also less frequently observed in both laser groups as compared to the control. The results clearly demonstrate that laser-based cavity preparation will benefit the clinical long-time performance of Class V resin-composite fillings. Furthermore, additional acid-conditioning after laser preparation is of advantage.

Effects of Er, Cr: YSGG Laser on Shear Bond Strength of the Orthodontic Brackets for 5 and 10 Seconds: An In Vitro Study

Objectives. The study designed to compare the effect of erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser at different power outputs and short periods of time (5 and 10 s) and acid etching on the shear bond strength (SBS) and failure mode of metallic orthodontic brackets. Material and methods. A total of sixty-nine human premolars extracted for orthodontic purposes were used. 60 teeth were randomly assigned to one of the five treatment groups. (n = 12): group 1: 37% phosphoric acid etching and groups 2–5: the enamel surface irradiated by the Er, Cr: YSGG laser operated at different power outputs (1 W, 1.5 W, 2 W, and 2.5 W), each laser group was divided into two subgroups (n = 6) according to exposure time (5 s and 10 s). Nine teeth were not subjected to SBS testing but were prepared for scanning electron microscopy (SEM). The nonparametric Kruskal–Wallis test was used to evaluate the data; the SBS and adhesive remanent index (ADI) were evaluated. Results. The mean SBS for all laser groups and the acid-etched group were comparable, with no significant differences except for the 1 W group for 5 and 10 s and the 1.5 W group for 5 s. For the ARI scores, no statistically significant difference was found among the groups ( $P=0.059$ ), and the majority of the samples had ARI type 2 or 3. Conclusion. The laser irradiation at 2 and 2.5 W for 5 s was similar to that produced by acid etching, whereas the laser irradiation at 2 and 2.5 W at 10 s was higher compared with that obtained with acid etching and adequate to etch the enamel.

The Effect of Er:YAG Laser on a Shear Bond Strength Value of Orthodontic Brackets to Enamel-A Preliminary Study

We sought to evaluate the effects of Er:YAG laser (LightTouch, LightInstruments, Israel) conditioning on enamel roughness and shear bond strength of orthodontic brackets on enamel. Eighteen human molars (n = 9) and premolars (n = 9), were divided into 3 groups depending on the enamel conditioning method; Er:YAG laser (G1, n = 6), conventional etching with 37% orthophosphoric acid (G2, n = 6), Er:YAG laser combined with conventional etching (G3, n = 6). Er:YAG laser parameters were as follows: energy: 100 mJ, frequency: 10 Hz, exposure time: 10 s, applicator diameter: 600 μm, fluence: 35.37 J/cm², distance: 1 mm away from a tooth, cooling: 80%. An MTS 858 MiniBionix^® machine was used to determine the shear bond strength (MTS System, Eden Prairie, MN, USA). The enamel structure was assessed using X-ray microtomography (SkyScan 1172, Bruker, Kontich, Belgium). The highest values of shear bond strength were obtained in the G3 group (9.23 ± 2.38 MPa) and the lowest values in the G2 group (6.44 ± 2.11 MPa) (p < 0.05). A significant change in the enamel surface was noted after applying laser, reaching up to 9% of enamel thickness, which was not observed in the etched samples. Moreover, the Er:YAG laser-irradiated enamel surface was characterized by the greatest roughness. The combined use of an Er:YAG laser with a conventional etching improves the adhesion of composite materials to the tooth.

Shear bond strength of acid and laser conditioned enamel and dentine to composite resin restorations: An in vitro study

Objective

To compare the shear bond strength of enamel or dentin conditioned with either Er,Cr:YSGG (erbium, chromium: yttrium–scandium–gallium–garnet) laser or phosphoric acid to composite resin restoration.

Material and methods

Forty posterior human extracted teeth were used. After mesiodistal sectioning of the teeth crowns, the samples were randomly divided into two groups—in the first group (E), bonding was performed on the enamel after roughening and in the second group (D), the enamel was removed and bonding was performed on the dentin. These groups were further randomly divided into two subgroups according to the type of etching (n = 20 each). In the acid‐etched groups (EA and DA), the surfaces were etched with 37% phosphoric acid. In the laser‐conditioned groups (EL and DL), the surfaces were conditioned with Er,Cr:YSGG laser. Total‐etch adhesive system was used to bond all the 80 specimens resin composite. The composite was vertically light‐cured, and the specimens were subjected to a shear bond strength test. Modes of bond failure were determined with a stereomicroscope.

Results

The highest shear bond strength was observed for the DA group (16.25 ± 1.10 MPa, p < 0.0001), whereas the lowest was observed for the DL group (8.56 ± 0.67 MPa). The adhesive failure mode was the most frequently observed in all groups.

Conclusions

The shear bond strength of composite resin bonded to enamel and dentin etched with phosphoric acid was higher than when conditioned with Er,Cr:YSGG laser. Thus, laser conditioning is not recommended.

Composite removal by means of erbium, chromium:yttrium-scandium-gallium-garnet laser compared with rotary instruments

BACKGROUND

Complete removal of existing composite restorations without unnecessary removal of tooth structure is challenging. The authors compared the amount of tooth structure removed and composite remaining in Class III preparations when using an erbium laser or a rotary instrument.

METHODS

Mesiolingual and distolingual preparations were prepared in 14 extracted anterior teeth, restored with shade-matched composite, finished, and polished. One restoration was removed with an erbium, chromium:yttrium-scandium-gallium-garnet laser and the other with a rotary instrument (handpiece and carbide burs). Gypsum models made from vinyl polysiloxane impressions of the preparation and removal stages were scanned. The 2 scans were precisely aligned to calculate the amount of tooth structure removed and residual composite, which were statistically compared (t test) between the bur and laser groups.

RESULTS

Rotary instruments removed significantly more tooth structure than the laser in terms of mean depth (P = .0017) but not maximum depth (P = .0762). Although mean depth of tooth loss was smaller in the laser group, the area of tooth loss was significantly larger (P = .0004) because the rotary instrumentation left significantly more composite than the laser in terms of volume (P = .0104), mean depth (P = .0375), maximum depth (P = .0318), and area (P = .0056).

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The erbium, chromium:yttrium-scandium-gallium-garnet laser was more selective in removing existing composite restorations than a rotary instrument because it removed less tooth structure and left behind less composite. Unintentional loss of tooth structure and unnoticeable residual composite are inevitable when removing existing composites. Erbium lasers are alternative means of composite removal that may be more selective than a rotary instrument.

Effects of Erbium:Yttrium-Aluminum-Garnet Laser Irradiation on Bovine Dentin Contaminated by Cariogenic Bacteria

Objective: This study was performed to determine the bactericidal effects of erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation and the morphological and chemical composition changes in bovine dentin. Methods: Dentin slabs were prepared from bovine incisors, and then cultured with Streptococcus mutans to produce bacteria-infected dentin samples. The samples were randomly divided into five groups with Er:YAG laser irradiation energy densities of 0, 6.37, 12.73, 19.11, and 25.47 J/cm². After irradiation, samples were stained and observed by confocal laser scanning microscopy. The bactericidal abilities were measured using live/dead staining. The morphology and chemical components were investigated by scanning electron microscopy and energy-dispersive spectrometry. Results: After irradiation, the elimination of bacteria and the smear layer were significantly better in the high energy density groups (19.11, 25.47 J/cm²) than in the low energy density groups (6.37, 12.73 J/cm²; p < 0.001). On morphological examination, the group with minimum energy density (6.37 J/cm²) showed superficial melting. In the high energy density groups (12.73, 19.11, and 25.47 J/cm²), laser-irradiated dentin showed a clean surface with open orifices. Significant increases were observed in the weight percentages of calcium (from 19.75 ± 0.69 to 34.47 ± 2.91, p < 0.001) and phosphate (from 8.58 ± 0.43 to 15.10 ± 1.81, p < 0.001), whereas significant decreases were observed for oxygen (from 49.84 ± 0.69 to 36.39 ± 2.86, p < 0.001) and carbon (from 26.06 ± 3.58 to 12.80 ± 2.26, p < 0.01) with increasing energy density. Conclusions: This study confirmed that Er:YAG laser irradiation has bactericidal and dentin conditioning effects.

Comparison of the different retention appliances produced using CAD/CAM and conventional methods and different surface roughening methods

The purposes of this study are to conduct an in vitro comparison of the shear bond strength, breakage mode, and wire deformation of three different types of retainers and to compare the subsequent enamel surface changes. Two hundred seventy intact lower incisor teeth were embedded in acrylic blocks in pairs. Dead wire and CAD/CAM-fabricated and fiber-reinforced wires were applied to the teeth roughened with acid and Er:YAG or Er,Cr:YSGG laser. The surface roughness was observed by scanning electron and atomic force microscopy. The samples were analyzed for shear bonds. The dead wire and acid group were found to have the highest bonding strength and the strengths for all groups in which acid was used as an agent were found to be higher than others. Deformation of retainers was most noted in the dead wire-acid group. Among all the groups, the CAD/CAM-fabricated wire group showed the least deformation, with no deformation observed. In this study, it was determined that there is a significant correlation between ARI scores and agents. Consequently, acid etching was found to create more enamel surface roughness than laser groups. It was also seen that the combined use of the acid method and dead soft wire had the highest bond strength, even though it was not statistically significant. It was concluded that CAD/CAM-fabricated wire provides the opportunity for reuse in clinical applications due to its lack of deformation, being more conservative for the patient, and being more advantageous for the clinician in terms of session time, considering the residual adhesive amount left on the enamel surface.

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.

A comparative evaluation of retention of pit and fissure sealants placed with conventional acid etching and Er,Cr:YSGG laser etching: A randomised controlled trial

Aim: The aim of this study was to compare the retention rates of sealant placed either with conventional acid etching or Er,Cr:YSGG laser pretreatment of enamel surface. Materials and methods: This is a prospective, single blind randomised controlled clinical trial enrolling 200 permanent first molars in 50 patients, aged 6-12 years for sealant placement. Study followed split mouth design where each side of the arch was randomly allocated to the two treatment group. Group A(Acid etch group): 37 % phosphoric acid (Scotchbond, 3M ESPE, Seefeld, Germany) was applied for 15 seconds, rinsed with water for 20 seconds and then air-dried using air spray. Group L(Laser etch group): Fissures were prepared with an Er,Cr:YSGG laser system (Waterlase, BIOLASE Technology, San Clemente, CA, USA) emitting photons at a wavelength of 2.78 µm. Laser irradiation at 1.5 W (60% air and 40% water), in a noncontact mode, with a repetition rate of 20 Hz for 10seconds was used. Pit and fissure sealant (3M ESPE, Clinpro) was applied and cured for 20 seconds. One blinded, calibrated examiner, who was unaware of which preparation method has been used and who was not involved in the treatment procedures, evaluated the sealant at baseline and at 3, 6, 9 and 12 month follow-up visits. Results: It was observed that overall retention rate in group A was slightly higher as compared to group L at all time periods, however, the difference was statistically non-significant (p-value>0.05).

CONCLUSION

Er,Cr:YSGG laser etching is comparable to acid etching in terms of retention and patient acceptability.

Microindentation hardness and calcium/phosphorus ratio of dentin following excavation of dental caries lesions with different techniques

BACKGROUND

The aim of this in vitro study was to evaluate the microindentation hardness and chemical composition of residual dentin left at the cavity bottom following removal of carious dentin using the Carisolv chemomechanical and Er:YAG laser caries excavation methods in comparison with the conventional tungsten-carbide bur excavation.

METHODS

Sixty-nine extracted permanent teeth with occlusal dentin caries were assigned into three groups according to caries removal technique. Carious dentin excavation was guided by tactile method and a caries-staining dye. In stereomicroscope images (100×) of the samples, the presence or absence of residual caries was defined. The Knoop hardness value of the cavity floor was determined and atomic analysis of treated cavities was performed by energy dispersive X-ray spectroscopy.

RESULTS

The Knoop hardness value of residual dentin left at the cavity bottom was lower (One-way ANOVA, Dunnett-C, p < 0.05) and the percentage of samples with remaining carious dentin was higher after Carisolv excavation than those obtained after conventional and laser excavations (Kruskal-Wallis, Mann-Whitney U, p < 0.05). No significant differences were found between the quantities of calcium content (Ca wt%), phosphorus content (P wt%) and calcium/phosphorus ratio of the cavities treated by three techniques (Kruskal-Wallis, Mann-Whitney U, p > 0.05).

CONCLUSION

The results indicated that Er:YAG laser was more comparable to conventional bur excavation than chemomechanical method in the efficacy of caries removal with regard to microindentation hardness of remaining dentin and both Carisolv gel and Er:YAG laser did not alter chemical composition of residual dentin in the treated cavities.

Different pulse modes of Er:YAG laser irradiation: effects on bond strength achieved with self-etching primers

OBJECTIVE

The aim of this study was to compare the effects of different pulse modes of Er:YAG laser on shear bond strength (SBS) of orthodontic brackets bonded with self-etching primers (SEP) and phosphoric acid etching.

MATERIALS AND METHODS

A total of 120 human mandibular third molars were randomly assigned to 3 groups of 40 specimens depending on the bonding procedure to be used. The groups were divided into two subgroups according to the pulse mode of the erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation as medium-short pulse (MSP) mode and quantum-square pulse (QSP) mode at 120 mJ, 10 Hz, 1.2 W. In each subgroup, the mesio- or distobuccal tooth surfaces were randomly assigned as experimental or control sides. After surface preparation with different modes of Er:YAG laser on experimental side, whole buccal tooth surfaces were treated with phosphoric acid etching or two different SEPs. Then metallic brackets were bonded with Transbond XT (3 M Unitek, Monrovia, CA, USA) or Kurasper F (Kuraray, Okayama, Japan). SBS values and the amount of adhesive remaining on the tooth after debonding were assessed. One-way analysis of variance (ANOVA) was used to evaluate the changes in mean SBS between groups resulting from laser etching, followed by post hoc test of Tukey.

RESULTS

There were statistically significant differences between the experimental and control sides of all groups (p < 0.05).

CONCLUSION

Laser etching with QSP and MSP modes increases the SBS of metallic brackets and Er:YAG laser irradiation with QSP mode increases the SBS of SEPs.

Microleakage of Self-Etch Adhesive System in Class V Cavities Prepared by Using Er:YAG Laser with Different Pulse Modes

OBJECTIVE

In vitro studies evaluated cementum surface morphology and microleakage of three different energy density parameters of Erbium: Yttrium Aluminum Garnet (Er:YAG) laser compared with diamond bur preparation on class V cavities with self-etch adhesive system and composite resin restoration.

MATERIAL AND METHODS

Standard class V cavities were prepared at cervical area below the cementoenamel junction (CEJ) in 80 extracted premolars, by using a diamond bur on the buccal surface. All teeth were randomly allocated into four groups: Group 1, diamond bur; Group 2, Er:YAG 50 mJ/15 Hz, 3.77 J/cm(2); Group 3, Er:YAG 75 mJ/15 Hz, 5.65 J/cm(2); and Group 4, Er:YAG 100 mJ/15 Hz, 7.53 J/cm(2). Five cavities from each group were evaluated by scanning electron microscopy (SEM). The 15 remaining cavities from each group were restored with self-etch adhesive and nano-hybrid composite. After thermocycling, all sample teeth were immersed in 0.2% methylene blue dye and sectioned buccolingually. Statistics were analyzed using the one way ANOVA and Mann-Whitney U tests with Bonferroni correction.

RESULTS

The morphology showed micro-irregularities in the cementum surface of the laser group with the absence of a smear layer. The microstructure characteristics were increased surface roughness followed by increasing laser energy transmission. The Er:YAG laser groups were statistically significant, with less microleakage than the diamond bur group (p<0.05). There was statistically significant difference between the occlusal and gingival microleakage in all the groups (p<0.05). When the laser groups were compared, the lowest microleakage was achieved with energy density at 3.77 J/cm(2) on the occlusal and gingival cementum margin, which showed less microleakage than at energy densities of 5.65 and 7.53 J/cm(2) with Er:YAG laser.

CONCLUSIONS

These observations indicate that the micro-irregularities of the cementum surface could facilitate the formation of a hybridization zone with a self-etch adhesive system. Therefore, the microleakage of Er:YAG laser irradiation was significantly decreased compared with diamond bur cavities.

Micromorphology analysis and bond strength of two adhesives to Er,Cr:YSGG laser-prepared vs. bur-prepared fluorosed enamel

Preservation of enamel during composite veneer restorations of fluorosed teeth could be achieved by conservative preparation with Erbium lasers. This study evaluated the effect of fluorosed enamel preparation with Er,Cr:YSGG vs. conventional diamond bur on the micromorphology and bond strength of a self-etch and an etch-and-rinse adhesives. Er,Cr:YSGG laser or diamond bur preparation was performed on the flattened midbuccal surfaces of 70 extracted human premolars with moderate fluorosis (according to Thylstrup and Fejerskov index, TFI = 4-6). Adper Single Bond (SB) with acid etching for 20 or 40 s and Clearfil SE Bond (SEB) alone or with additional etching was applied in four laser groups. The same adhesive procedures were used in three bur groups except for 40 s of etching along with SB. After restoration, microshear bond strength was measured (MPa). Data were analyzed using ANOVA and Tamhane tests (α = 0.05). Six additional specimens were differently prepared and conditioned for scanning electron microscopy evaluation. The highest and lowest bond strengths were obtained for bur-prepared/SB (39.5) and laser-prepared/SEB (16.9), respectively, with a significant difference (P = 0.001). The different adhesive procedures used associated to two adhesives exhibited insignificantly lower bonding in laser-prepared groups compared to bur-prepared ones (P > 0.05), with the exception of additional etching/SEB, which bonded significantly higher to bur-prepared (36.4) than to laser-prepared enamel (18.7, P = 0.04). Morphological analyses revealed a delicate etch pattern with exposed enamel prisms on laser-prepared fluorosed enamel after acid etching and less microretentive pattern after self-etching primer. The etch-and-rinse adhesive was preferred in the laser-prepared fluorosed enamel in terms of bonding performance.

Microleakage in Class V cavities with self-etching adhesive system and conventional rotatory or laser Er,Cr:YSGG

OBJECTIVE

To analyse microleakage in Class V cavity preparation with Er;Cr:YSGG at different parameters using a self-etching adhesive system.

BACKGROUND

Several studies reported microleakage around composite restorations when cavity preparation is done or treated by Er;Cr:YSGG laser. We want to compare different energy densities in order to obtain the best parameters, when using a self-etching adhesive system.

METHODS

A class V preparations was performed in 120 samples of human teeth were divided in 3 groups: (1) Preparation using the burr. (2) Er;Cr:YSGG laser preparation with high energy 4W, 30 Hz, 50% Water 50% Air and (3) Er;Cr:YSGG laser preparation lower energy 1.5 W, 30 Hz, 30% Water 30% Air. All the samples were restored with self-etching adhesive system and hybrid composite. Thermocycling (5000 cycles) and immersed in 0.5% fuchsin. The restorations were sectioned and evaluated the microleakage with a stereomicroscope.

RESULTS

Lower energy laser used for preparation showed significant differences in enamel and dentin. To group 3, the microleakage in the enamel was less, whilst the group 1, treated with the turbine, showed less microleakage at dentin level. Group 2 showed the highest microleakage at dentin/cement level.

CONCLUSION

Burr preparation gives the lowest microleakage at cement/dentin level, whilst Er;Cr:YSGG laser at lower power has the low energy obtains lowest microleakage at enamel. On the contrary high-energy settings produce inferior results in terms of microleakage.

Morphological analysis of the resin-dentin interface in cavities prepared with Er,Cr:YSGG laser or bur in primary teeth

OBJECTIVE

The purpose of this study was to analyze the resin-dentin interface in cavities prepared with laser or bur in primary teeth.

BACKGROUND DATA

Erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser was expected to be an alternative cavity preparation method, enhancing surface alterations and producing morphological changes.

METHODS

Twenty extracted primary molar teeth were divided to four groups according to one of four cavity preparation and pretreatment regimens: Er,Cr:YSGG laser (G1), Er,Cr:YSGG laser+acid-etching (G2), bur (G3), and bur+acid-etching (G4). After applying composite resin to the cavities, the teeth were sectioned. The resin-dentin interface was analyzed under scanning electron microscopy (SEM) and ion analysis was performed with SEM-energy-dispersive X-ray spectroscopy (EDX) after immersion in ammoniacal silver nitrate solution.

RESULTS

In G1 and 2, the surfaces were wavy, and in G3 and 4, the surfaces were smooth. Microcracks were seen in some of the lased cavities. In G1 and 2, dentin tubules were exposed and there was lack of a smear layer. In G3, there were gaps and a smear layer in the resin-dentin interface, but no gaps or smear layer were observed in G4. In G2, the resin tags were increased, and some resin tags were broken in cavities, which were prepared with laser (G1 and 2).

CONCLUSIONS

According to the results of this study, acid-etching was recommended after laser preparations, to have a better adhesion.

Prevention of dentine caries using silver diamine fluoride application followed by Er:YAG laser irradiation: an in vitro study

To evaluate the preventive effect of Er:YAG laser (EYL) irradiation followed by silver diamine fluoride (SDF) application on dentine with cariogenic biofilm challenge. Twenty-four dentine slices were prepared from extracted sound human third molars. Each slice was cut into four parts for SDF application, followed by EYL irradiation (group SL), SDF application (group S), EYL irradiation (group L) and water (group W). The specimens were subjected to cariogenic biofilm challenge for 12 h, followed by immersion in a buffered remineralising solution containing calcium chloride and sodium hypophosphate for 12 h at 37 °C. Surface morphological changes in the specimens were examined using scanning electronic microscopy. Elemental analysis was performed using energy-dispersive X-ray spectrometry. Micro-mechanical properties were investigated by nano-indentation. The specimen surfaces of groups SL and L showed laser melting contours with narrowed dentinal orifices. Group S showed a partial tubular occlusion. A porous surface was observed in group W, indicating demineralisation. The mean (SD) fluoride weight percentages were 3.93 (0.91), 3.10 (0.61), 0.17 (0.09) and 0.32 (0.07) in groups SL, S, L and W, respectively, (p < 0.001; SL, S > L, W). The mean (SD) micro-hardness values in GPa were 1.84 (0.22), 0.49 (0.13), 0.41 (0.11) and 0.30 (0.06) in groups SL, S, L and W, respectively, (p < 0.001; SL > S > L, W). The mean (SD) elastic moduli in GPa were 75.1 (7.2), 20.0 (1.3), 24.3 (5.2) and 20.2 (2.8) in groups SL, S, L and W, respectively, (p < 0.001; SL > S, L, W). SDF application followed by EYL irradiation on a dentine surface increased its resistance to cariogenic biofilm challenge.

Comparison of Acid Versus Laser Etching on the Clinical Performance of a Fissure Sealant: 24-Month Results

Objective

To compare the clinical performance of a pit and fissure sealant placed with the use of different enamel preparation methods, i.e. acid or Er,Cr:YSGG laser etching, over 24 months.

Methods

Sixteen subjects (15 female, 1 male) with no restorations or sealant present on their fissures and no detectable caries participated. Using a table of random numbers, a total of 112 sealants (56 with acid-etching, 56 with laser etching) were placed on the permanent premolar and molar teeth. All restorative procedures except for application of the laser were performed by the same dentist. After completion of the fissure preparation either with acid or laser, the adhesive was applied; then a pit and fissure sealant, Clinpro Sealant, was placed and polymerized. Clinical evaluations were done at baseline and at 6-, 12-, 18-, and 24-month follow-up visits by two calibrated examiners, who were unaware of which etching method had been used. The retention of sealants and caries were evaluated with the aid of a dental explorer and an intra-oral mirror. Each sealant was evaluated using the following criteria: 1=completely retained; 2= partial loss; 3= total loss. The Pearson chi-square test was used to evaluate differences in the retention rates among the sealants used with different etching methods.

Results

All patients attended the 24-month follow-up visit and all sealants were evaluated (total recall rate 100%). At the end of 24 months, 83.9% of the sealants from laser group and 85.7% of those from acid-etch group were recorded as “completely retained”. There were no statistically significant differences in retention rates among the preparation methods after all evaluation periods (p&gt;0.05). No statistically significant differences were found between the retention rates of premolar and molars at each evaluation period. No secondary caries was detected in association with any sealants. Conclusion: The clinical performance of fissure sealants placed after acid or Er,Cr:YSGG laser etching was similar.

Nanoleakage in primary teeth prepared by laser irradiation or bur

The aim of this in vitro study was to analyze hybrid layer and nanoleakage of composite resin restorations in cavities prepared by either Er,Cr:YSGG laser or bur, followed by acid etching in primary teeth. Ten extracted primary molar teeth were randomly allocated into two groups consisting of ten cavities according to surface treatment regimen: Er,Cr:YSGG laser + acid etching(group 1) and bur + acid etching(group 2). Restorations of all samples were completed. Then, teeth were sectioned and immersed to ammoniacal silver nitrate solution. After polishing, hybrid layer thicknesses were examined under scanning electron microscopy (SEM) and ion analysis was carried out with SEM/energy dispersive X-ray spectroscopy preparation in terms of nanoleakage. Hybrid layer thickness and the amount of silver ions were assessed for the acid-etched groups. The collected data were analyzed with independent sample t test and Spearman's rank correlation. In groups 1 and 2, the mean hybrid layer thicknesses were 4.25 ± 1.41 and 5.24 ± 1.07 μm and the silver ion percentages were 10.97 ± 13.81 and 22.79 ± 21.62 %, respectively. Although no significant correlation was observed between the increase of hybrid layer thickness and the amount of silver ions, more silver ions were observed in group 2 (p < 0.05). According to the results of this study, acid-etched cavities prepared with laser promoted better results when compared to the acid-etched cavities prepared with bur.

The effect of Nd:YAG and Er,Cr:YSGG lasers on the microhardness of human dentin

The current investigation determined the microhardness of dentin tissue irradiated with erbium, chromium-doped yttrium scandium gallium garnet (Er,Cr:YSGG) and neodymium-doped yttrium-aluminum garnet (Nd:YAG) lasers. Thirty non-carious human molars were used in this study. Dentin disks were prepared by horizontal sectioning of one third of the occlusal surface. Halves of dentin specimens were irradiated with 3.5- and 4.5-W Er,Cr:YSGG lasers and with a 2-W Nd:YAG laser. The remaining halves served as controls. The microhardness measurements were recorded with a Vickers surface microhardness tester. The results were statistically evaluated by paired t test and one-way ANOVA (p = 0.05). Laser irradiation has significantly reduced the microhardness of dentin within each group compared to its control. Moreover, statistically significant differences were observed among the different groups (p < 0.05). The 3.5-W Er,Cr:YSGG laser produced the greatest reduction in microhardness of dentin followed by 4.5 W and Nd:YAG laser. The differences between all the groups were statistically significant. It was concluded that both laser devices used in this study have resulted in significant thermal damage and subsequent reduction in dentin microhardness values.

Effect of Tooth Surface Preparation on the Bonding of Self-Etching Primer Adhesives

The effectiveness of some self-etching primer adhesive systems is not significantly affected by the mode of rotary instrumentation used in dentin preparation.

Evaluation of different enamel conditioning techniques for orthodontic bonding

OBJECTIVE

The aim of this study was to compare the effects of different enamel conditioning techniques for bracket bonding.

METHODS

Ninety-one human premolars were randomly divided in six groups of 15 specimens each. The enamel surfaces of the teeth were etched with 35% orthophosphoric acid in Group 1, with a self-etching primer in Group 2, sandblasted in Group 3, sandblasted and etched with 35% orthophosphoric acid in Group 4, conditioned by Er:YAG laser in Group 5 and conditioned by Er:YAG laser and etched with 35% phosphoric acid gel respectively in Group 6. After enamel conditioning procedures, brackets were bonded and shear bonding test was performed. After debonding, adhesive remnant index scores were calculated for all groups. One tooth from each group were inspected by scanning electron microscope for evaluating the enamel surface characteristics.

RESULTS

The laser and acid etched group showed the highest mean shear bond strength (SBS) value (13.61 ± 1.14 MPa) while sandblasted group yielded the lowest value (3.12 ± 0.61 MPa).

CONCLUSIONS

Although the SBS values were higher, the teeth in laser conditioned groups were highly damaged. Therefore, acid etching and self-etching techniques were found to be safer for orthodontic bracket bonding. Sandblasting method was found to generate inadequate bonding strength.

The impact of Er,Cr:YSGG laser on the shear strength of the bond between dentin and ceramic is dependent on the adhesive material

The bond joint between dentin and ceramic is a critical determinant in prosthodontic dentistry. The laser is an alternative to the diamond bur for preparing tooth cavities. However, the impact of lasers on the bond between the laser-irradiated dentin and the ceramic remains a matter of controversy. We determined the shear strength of bonds between ceramic blocks and human dentin discs prepared with either an Er,Cr:YSGG laser or a diamond bur. A total of 180 dentin discs were randomly assigned to four groups. Three groups of discs were prepared with the Er,Cr:YSGG laser irradiation (2 W, 30 Hz, 50% H(2)O, 70% air) and the fourth group was prepared with a diamond bur. In one of the laser groups the discs surfaces were also treated with phosphoric acid and in another with phosphoric acid and mechanical smoothing using a dental excavator. The ceramic blocks were bonded to the dentin discs with Syntac adhesive (together with Variolink II curing system), ExciTE adhesive (together with Variolink II curing system) or RelyX self-adhesive cement. The shear strength of the bond between ceramic and dentin was significantly higher following dentin surface treatment with the laser alone than following treatment with the diamond bur and Variolink II/Syntac (p = 0.021) but not significantly higher than following treatment with the diamond bur and Variolink II/ExciTE (p = 0.138) or RelyX (p = 0.150). A significant difference was not observed when the laser-treated dentin was conditioned with phosphoric acid and mechanical smoothing. These findings demonstrate that the bond between dentin and ceramic may be stronger after laser irradiation; however, the selection of the adhesive material is an additional factor that affects the bond strength.

Effect of acid and laser etching on shear bond strength of conventional and resin-modified glass-ionomer cements to composite resin

Success in sandwich technique procedures can be achieved through an acceptable bond between the materials. The aim of this study was to compare the effect of 35% phosphoric acid and Er,Cr:YSGG laser on shear bond strength of conventional glass-ionomer cement (GIC) and resin-modified glass-ionomer cement (RMGIC) to composite resin in sandwich technique. Sixty-six specimens were prepared from each type of glass-ionomer cements and divided into three treatment groups as follows: without pretreatment, acid etching by 35% phosphoric acid for 15 s, and 1-W Er,Cr:YSGG laser treatment for 15 s with a 600-μm-diameter tip aligned perpendicular to the target area at a distance of 1 mm from the surface. Energy density of laser irradiation was 17.7 J/cm(2). Two specimens in each group were prepared for evaluation under a scanning electron microscope (SEM) after surface treatment and the remainder underwent bonding procedure with a bonding agent and composite resin. Then the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Two-factor analysis of variance and post-hoc Tukey test showed that the cement type, surface treatment method, and the interaction of these two factors significantly affect the shear bond strength between glass-ionomer cements and composite resin (p < 0.05). Surface treatment with phosphoric acid or Er,Cr:YSGG laser increased the shear bond strength of GIC to composite resin; however, in RMGIC only laser etching resulted in significantly higher bond strength. These findings were supported by SEM results. The fracture mode was evaluated under a stereomicroscope at ×20.

The effect of different preparation and etching procedures on the microleakage of direct composite veneer restorations

OBJECTIVES

The aim of this in vitro study was to compare the microleakage of direct composite veneer restorations prepared by a conventional dental bur or Er,Cr:YSGG (erbium, chromium doped yttrium scandium gallium garnet) laser and etched with different procedures.

METHODS

Fifty maxillary incisor teeth prepared for direct veneers with gingival margins in dentin and incisal margins in enamel were randomly divided into five groups (n = 10): group 1 (control), prepared with diamond bur and etched with phosphoric acid; group 2, prepared with diamond bur and etched with Er,Cr:YSGG laser (Waterlase MD/Biolase); group 3, prepared with laser and not etched; group 4, prepared with laser and etched with phosphoric acid; and group 5, prepared and etched with laser. After the application of the etch and rinse adhesive system (Prime & Bond NT/Dentsply), teeth were restored with the nano ceramic restorative material (Ceram X Duo/Dentsply), subjected to thermocycling and immersed in 0.5% basic fuchsin dye for 24 h. The teeth were sectioned longitudinally and dye penetration was evaluated by a binocular stereomicroscope equipped with a measuring device. Data were analyzed by Kruskal-Wallis and Wilcoxon signed ranks tests. The level of significance was set at p = 0.05.

RESULTS

Significant differences were observed in enamel of the five groups (p < 0.05). Minimal microleakage was observed in groups 1 and 3. The highest microleakage was evaluated in group 5 (p < 0.05). No significant differences were found among the five groups in dentin (p > 0.05). No differences were recorded between the microleakage values in enamel and dentin within each group and this was valid for all groups (p > 0.05).

CONCLUSIONS

The results confirmed that enamel and dentin surfaces prepared with Er,Cr:YSGG laser for direct composite veneer restorations may provide comparable sealing.

In vivo dentin remineralization by calcium-phosphate cement

Minimally invasive caries-removal procedures remove only caries-infected dentin and preserve caries-affected dentin that becomes remineralized. Dental cements containing calcium phosphate promote remineralization. This study evaluated the in vivo remineralization capacity of resin-based calcium-phosphate cement (Ca-P) used for indirect pulp-capping. Carious and sound teeth indicated for extraction were randomly restored with the Ca-P base or without base (control), followed by adhesive restoration. Study teeth were extracted after three months, followed by elemental analysis of the cavity floor. Mineral content of affected or sound dentin at the cavity floor was quantified by electron probe micro-analysis to 100-mum depth. After three months, caries-affected dentin underneath the Ca-P base showed significantly increased calcium and phosphorus content to a depth of 30 mum. Mineral content of treated caries-affected dentin was in the range of healthy dentin, revealing the capacity of Ca-P base to promote remineralization of caries-affected dentin.

The effect of Er,Cr:YSGG laser and air abrasion on shear bond strength of a fissure sealant to enamel

PURPOSE

The authors conducted an in vitro study to evaluate the shear bond strength of a fissure sealant to enamel pretreated with erbium,chromium:yttrium, scandium,gallium,garnet (Er,Cr:YSGG) laser or air abrasion followed by acid etching.

METHODS

The authors sectioned extracted sound premolars mesiodistally and used the buccal and lingual surfaces for experimental analysis. They divided specimens randomly into three groups of 15 each according to the enamel surface pretreatment methods: group A, 37 percent phosphoric acid; group B, air abrasion followed by acid etching with 37 percent phosphoric acid; group C, irradiation with Er,Cr:YSGG laser followed by acid etching with 37 percent phosphoric acid. After applying a bonding system, the authors bonded cylinders of sealant to the enamel surfaces by using transparent gelatin tubes (0.7 millimeter in diameter and 1 mm in height) and then polymerized them. They stored all specimens in distilled water at 37 degrees C for 24 hours. They tested shear bond strength by using a universal testing machine with a crosshead speed of 0.5 mm per second. The authors analyzed the data by means of one-way analysis of variance and Tukey-Kramer post hoc tests (alpha = .05).

RESULTS

The bond strength of group B specimens was statistically higher than those of group A and group C specimens (P < .05). The authors found no statistically significant differences in shear bond strength between surfaces treated with Er,Cr:YSGG laser and those treated with acid etching alone (P > .05).

CONCLUSION

Pretreatment of enamel surfaces with air abrasion increased the bond strength of fissure sealant, but pretreatment with Er,Cr:YSGG laser did not increase the effectiveness of conventional acid etching of enamel in sealant bonds.

Influence of etching time on bond strength in dentin irradiated with erbium lasers

The purpose of this in vitro study was to evaluate the effect of etching time on the tensile bond strength (TBS) of a conventional adhesive bonded to dentin previously irradiated with erbium:yttrium-aluminum-garnet (Er:YAG) and erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers. Buccal and lingual surfaces of 45 third molars were flattened until the dentin was exposed and randomly assigned to three groups (n = 30) according to the dentin treatment: control (not irradiated), irradiated with Er:YAG (1 W; 250 mJ; 4 Hz; 80.6 J/cm(2)) laser or Er,Cr:YSGG (4 W; 200 mJ; 20 Hz; 71.4 J/cm(2)) laser, and into three subgroups (n = 10) according to acid etching time (15 s, 30 s or 60 s) for each experimental group. After acid etching, the adhesive was applied, followed by the construction of an inverted cone of composite resin. The samples were immersed in distilled water (37 degrees C for 24 h) and subjected to TBS test [50 kilogram-force (kgf), 0.5 mm/min]. Data were analyzed by analysis of variance (ANOVA) and Tukey statistical tests (P < or = 0.05). Control group samples presented significant higher TBS values than those of all lased groups. Both irradiated groups exhibited similar TBS values. Samples subjected to the different etching times in each experimental group presented similar TBS. Based on the conditions of this in vitro study we concluded that Er:YAG and Er,Cr:YSGG laser irradiation of the dentin weakens the bond strength of the adhesive. Moreover, increased etching time is not able to modify the bonding strength of the adhesive to irradiated dentin.

Shear bond strength of composite bonded to Er,Cr:YSGG laser-prepared dentin

OBJECTIVE

The purpose of this in vitro study was to evaluate dentin bond strength to resin composite following high-speed rotary or Er,Cr:YSGG laser preparation using two different adhesive systems.

MATERIALS AND METHODS

One hundred and forty dentin specimens were prepared from human molars. Seventy specimens were prepared with a high-speed diamond bur and 70 of the specimens were prepared with an Er,Cr:YSGG laser. Each group was subdivided into 7 groups of 10 teeth and etched with either 37% H3PO4, laser etched at two different power levels (1.25 W and 3 W), or not etched. Nano-hybrid composite resin cylinders 4 x 2 mm in size (Tetric EvoCeram, Vivadent) were bonded to the dentin surfaces with the application of an etch-and-rinse adhesive (Exite/Vivadent), or a self-etching adhesive (AdheSe/Vivadent). After storage in distilled water and thermocycling, a shear bond strength test was performed on all specimens and the data were statistically analyzed.

RESULTS

ANOVA detected significant differences between the tested groups (p < 0.001). Duncan's multiple comparison test showed that Excite-applied specimens that were prepared with laser and laser etched (1.25 W or 3 W) had higher mean bond strengths. Both AdheSe- and Excite-applied specimens prepared with the diamond bur and laser etched (1.25 W) showed the lowest mean bond strength values (p < 0.05).

CONCLUSION

The results suggest that dentin surfaces prepared with the Er,Cr:YSGG laser and etched with the laser (at either 1.25 or 3 W) may provide comparable or increased composite resin bond strengths, depending on the adhesive used.

Effects of Er:YAG laser irradiation and manipulation treatments on dentin components, part 2: energy-dispersive X-ray fluorescence spectrometry study

The effects of laser etching, decontamination, and storage treatments on dentin components were studied by energy-dispersive X-ray fluorescence spectrometry (EDXRF). Thirty bovine incisors were prepared to expose the dentin surface and then divided into two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in aqueous thymol solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ). Samples were analyzed by micro-EDXRF, yielding three spectra for each area (before and after treatment). Surface mappings covering an area of 80x60 points with steps of 20 mum were also performed on selected specimens. The amount of Ca and P in group A specimens decreased significantly (P<0.05) after the acid etching and the CaP ratio increased (P<0.001). Er:YAG laser-etching using lower laser energies did not produce significant changes in dentin components. The mapping data support the hypothesis that acid etching on dentin produced a more chemically homogeneous surface and thus a more favorable surface for the diffusion of adhesive monomers.

Effect of different laser devices on the composition and microhardness of dentin

This study determined the compositional changes and microhardness of the cavity floor prepared by Er,Cr:YSGG and Er:YAG lasers and compared the results with the conventional method of bur preparation. Fifteen non-carious human molars were used in this study. On the buccal and lingual surfaces of each tooth, two cavities (mesio-distal 3 mm, inciso-gingival 3 mm, depth 2 mm) were prepared with two different laser devices (Er,Cr:YSGG laser; Waterlase MD and Er:YAG laser; KaVo Key Laser 3) and a high-speed turbine. The teeth were embedded into polyester resin and cross-sectioned. The microhardness measurements from the floor of each half cavity were recorded with the Vickers surface hardness tester. The remaining halves of the cavities were subjected to SEM-EDS atomic analysis. The results were statistically evaluated by one-way ANOVA and Kruskal Wallis tests (p = 0.05). No significant differences were observed among the microhardness values, quantities of Ca (Ca weight %), P (P weight %) and Ca/P ratio of the lased and conventionally prepared cavities (p > 0.05). The cavity preparation techniques and differences in laser devices did not significantly alter the composition and microhardness of dentin tissue. Both laser devices used in this study were observed to lead to minimal thermal damage in the dentin tissue and minimal thermally-induced changes in dentinal compositions.

Effect of erbium:yttrium-aluminum-garnet laser energies on superficial and deep dentin microhardness

This study evaluated the microhardness of superficial and deep dentin irradiated with different erbium:yttrium-aluminum-garnet (Er:YAG) laser energies. Seventy-two molars were bisected and randomly assigned to two groups (superficial dentin or deep dentin) and into six subgroups (160 mJ, 200 mJ, 260 mJ, 300 mJ, 360 mJ, and control). After irradiation, the cavities were longitudinally bisected. Microhardness was measured at six points (20 microm, 40 microm, 60 microm, 80 microm, 100 microm, and 200 microm) under the cavity floor. Data were submitted to analysis of variance (ANOVA) and Fisher's tests (alpha = 0.05). Superficial dentin presented higher microhardness than deep dentin; energy of 160 mJ resulted in the highest microhardness and 360 mJ the lowest one. Values at all points were different, exhibiting increasing microhardness throughout; superficial dentin microhardness was the highest at 20 microm with 160 mJ energy; for deep dentin, microhardness after irradiation at 160 mJ and 200 mJ was similar to that of the control. The lowest energy increased superficial dentin microhardness at the closest extent under the cavity; deep dentin microhardness was not altered by energies of 160 mJ and 200 mJ.

Laser etching of enamel for orthodontic bonding

INTRODUCTION

The purposes of this study were to assess the shear bond strength, the surface characteristics, and the adhesive remnant index scores of teeth prepared for bonding with erbium, chromium doped: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser etching, and to compare laser etching with phosphoric-acid etching and a self-etching primer.

METHODS

Sixty-four premolars, extracted for orthodontic purposes, were randomly divided into 4 groups, and a different method was used to prepare the tooth enamel in each group for bonding: irradiation for 15 seconds with a 0.75-W Er,Cr:YSGG laser; irradiation for 15 seconds with a 1.5-W Er,Cr:YSGG laser; etching with 37% phosphoric acid; application of a self-etching primer. After surface preparation, standard edgewise stainless steel premolar brackets were bonded; 1 tooth in each group was not bonded and was examined under a scanning electron microscopic. The brackets were debonded 24 hours later; shear bond strengths were measured, and adhesive remnant index scores were recorded.

RESULTS

Irradiation with the 0.75-W laser produced lower shear bond strengths than the other methods. No statistically significant differences were found between 1.5-W laser irradiation, phosphoric-acid etching, and self-etching primer. Adhesive remnant scores were compared with the chi-square test, and statistically significant differences were found between all groups; when the 0.75-W laser irradiation group was excluded, no statistically significant differences were observed.

CONCLUSIONS

Irradiation with a 1.50-W laser produced sufficient etching for orthodontic bonding, but irradiation with the 0.75-W laser did not.

Influence of dentin cavity surface finishing on micro-tensile bond strength of adhesives

The current trend toward minimal-invasive dentistry has introduced innovative techniques for cavity preparation. Chemical vapor deposition (CVD) and laser-irradiation technology have been employed as an alternative to the common use of regular burs in high-speed turbines.

OBJECTIVES

The purpose of this study was to assess the influence of alternative techniques for cavity preparation on the bonding effectiveness of different adhesives to dentin, and to evaluate the morphological characteristics of dentin prepared with those techniques.

METHODS

One etch&rinse adhesive (OptiBond FL, Kerr) and three self-etch systems (Adper Prompt L-Pop, 3M ESPE; Clearfil SE Bond, Kuraray; Clearfil S3 Bond, Kuraray) were applied on dentin prepared with a regular bur in a turbine, with a CVD bur in a turbine, with a CVD tip in ultrasound and with an Er,Cr:YSGG laser. The micro-tensile bond strength (microTBS) was determined after storage in water for 24h at 37 degrees C, and morphological evaluation was performed by means of field-emission-gun scanning electron microscopy (Feg-SEM).

RESULTS

Feg-SEM evaluation revealed different morphological features on the dentin surface after the usage of both the conventional and alternative techniques for cavity preparation, more specifically regarding smear-layer thickness and surface roughness. CVD bur-cut, CVD ultra-sonoabraded and laser-irradiated dentin resulted in lower microTBSs than conventionally bur-cut dentin, irrespective of the adhesive employed.

SIGNIFICANCE

The techniques, such as CVD diamond-bur cutting, CVD diamond ultra-sonoabrasion and laser-irradiation, used for cavity preparation may affect the bonding effectiveness of adhesives to dentin, irrespective of their acidity or approach.

Influence of Er,Cr:YSGG Laser Treatment on Microtensile Bond Strength of Adhesives to Enamel

Er,Cr:YSGG laser irradiation produced morphological alterations on enamel, which may adversely influence the bond strength of certain adhesives, depending on their approach and composition.

Shear bond strength of composite bonded to erbium:yttrium-aluminum-garnet laser-prepared dentin

The purpose of this study was to evaluate the dentin bond strength to resin composite following erbium:yttrium-aluminum-garnet (Er:YAG) laser preparation using different adhesive systems. Seventy dentin specimens prepared from human molar teeth were randomly assigned to seven groups of ten. The first five groups were prepared with an Er:YAG laser 2940 nm at the manufacturer's recommended settings and (1) acid etched, and etch-and-rinse adhesive Excite was applied; (2) Excite was applied; (3) two-step self-etching adhesive AdheSE was applied; (4) laser etched (120 mJ/10 Hz), and Excite was applied; (5) laser etched, and AdheSE was applied. The last two groups were added as controls (prepared with a diamond bur): (6) acid etched, and Excite was applied; (7) AdheSE was applied. Nanohybrid composite cylinders 4 mm x 2 mm were bonded to the dentin surfaces. After the specimens had been stored in distilled water and had undergone thermocycling, the shear bond strength was tested and the data were analyzed statistically. The Duncan multiple comparison test showed that specimens prepared with a diamond bur and with acid and Excite applied showed the highest mean bond strength (13.01 +/- 2.09 MPa), followed by those prepared with Er:YAG and with AdheSE applied (11.5 +/- 3.59 MPa) and those prepared with a diamond bur and with AdheSE applied (10.75 +/- 1.95 MPa), but there were no significant differences among them (P > 0.05). Er:YAG-prepared specimens, with acid, Excite (3.28 +/- 0.95 MPa) and specimens that were laser etched and with AdheSE applied (3.37 +/- 0.63 MPa) showed the lowest mean values for bond strength (P < 0.05). The results suggested that dentin surfaces prepared with Er:YAG laser may provide comparable composite resin bond strengths depending on the adhesives used.