Effect of different power parameters of Er,Cr:YSGG laser on human dentine

Laser debonding of ultrathin occlusal veneers fabricated from different CAD/CAM ceramic materials

BACKGROUND

Erbium lasers safely offer the possibility of reuse for debonded restorations. Since these lasers have a high affinity for water molecules, they are absorbed by resin cement causing explosive ablation of the cement and thus, the restoration debonds. The efficiency of this process depends on many factors, including the ceramic type, its chemical composition and thickness. Therefore, this study was designed to test the time taken to debond ultrathin occlusal veneers made of three types of milled ceramic materials and evaluate the integrity of these restorations after debonding.

METHODS

Three ceramic types were evaluated in this study: lithium disilicate (IPS Emax CAD), highly condensed lithium disilicate (GC initial®LiSi), and translucent zirconia (Katana zirconia STML). Each group consisted of 8 occlusal veneers of 0.5 mm thickness. The samples were cemented to the occlusal surfaces of the upper molar teeth. An Er; Cr: YSGG laser was applied to the occlusal veneers using the scanning method, and time until debonding was calculated. The debonded samples were then inspected under a stereomicroscope for possible damage. Numerical data are presented as the mean with 95% confidence interval (CI), standard deviation (SD), minimum (min.) and maximum (max.) values. Normality and variance homogeneity assumptions were confirmed using Shapiro-Wilk's and Levene's tests, respectively. Data were normally distributed and were analyzed using one-way ANOVA followed by Tukey's post hoc test. The significance level was set at p < 0.05 for all tests. Statistical analysis was performed with R statistical analysis software version 4.3.2 for Windows (R Core Team (2023). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/).

RESULTS

There was no significant difference in debonding time between the different materials (p = 0.995). The longest debonding time was found for Katana STML (87.52 ± 20.45) (seconds), followed by Emax (86.94 ± 20.63) (seconds), while the lowest value was found for LiSi initial (86.14 ± 25.16) (seconds). In terms of damage to the debonded veneers, The Emax and zirconia samples showed no damage. However, 40% of the LiSi samples fractured during debonding, and 20% exhibited cracks. Only 40% of the LiSi samples were sound after debonding.

CONCLUSION

Er; Cr: YSGG laser can be used efficiently to remove ceramic occlusal veneers. However, its effect on LiSi restorations needs further research.

Occluding Efficiency of Different Desensitizing Agents and Er,Cr:YSGG Laser on Dentin Tubules

PURPOSE

This study aimed to evaluate the effects of two desensitizers and the Er,Cr:YSGG laser on human dentin tubules, applied alone or in combination.

METHODS

Ninety-six dentin specimens were obtained from extracted third molars and divided into six groups: Group 1: no-treatment (Control); Group 2: nano-hydroxyapatite desensitizer (NhapD); Group 3: NhapD+Er,Cr:YSGG laser (L); Group 4: Er,Cr:YSGG laser (L); Group 5: glutaraldehyde desensitizer (GD); and Group 6: GD+L, respectively. All specimens were evaluated using scanning electron microscopy. The diameter and the number of open dentin tubules, the tubules' occluding ratio, and the mineral coverage area were measured via the Image J software at 2000× magnification. Atomic force microscopy was used to determine the blocking mechanism of desensitizing treatments and the surface morphology of dentin specimens. One-way ANOVA and Tukey tests were used for statistical analysis.

RESULTS

The number of open tubules and the mean diameter of tubules for all treatment groups showed statistically significant differences from the control group The NhapD+L group had a significantly lower number of open tubules than the L and GD groups. The NhapD+L and L groups significantly had higher occluding ratios than the other groups.

CONCLUSIONS

The present study showed that the Er,Cr:YSGG laser alone was effective in terms of tubule occlusion and also contributed to increasing the occluding ratio of nano-hydroxyapatite. It may be recommended to use the Er,Cr:YSGG laser with nano-hydroxyapatite desensitizers to achieve effective tubule occlusion.

Shear bond strengths of bur or Er:YAG laser prepared dentine to composite resin with or without low-level laser conditioning: an in vitro study

This study aims to compare the different modes of cavity preparation while evaluating the effect of low-level laser therapy (LLLT) on dentine before bonding in terms of shear bond strength between composite resin and dentine. Fifty human molar teeth were mounted on acrylic blocks and dentine specimen were prepared after which they were randomized into four equal groups. Cavity preparation mode differed in respective groups. After etching, bonding; composite resin was placed and polymerized on the prepared dentine surfaces. The specimens were kept in an environment simulating oral cavity and then shear tested in a universal testing machine. The failure surfaces of the specimen teeth were subjected to SEM micrographic evaluation. The cavity prepared with diamond abrasive points had a higher shearing load at failure that was statistically significantly different from the ones prepared with laser. That with diamond abrasive points followed by LLLT of the cavity surface with Nd:YAG laser had a higher bond strength than the ones prepared with just Er:YAG laser and there was no statistically significant difference between these and the ones prepared with diamond abrasive points alone. SEM analysis of the failure mode in bur-cut dentine showed the presence of a hybrid layer at the interface. Surface conditioning of the same with Nd:YAG laser before etching suggested a recrystallisation of dentine due to the heat produced. Cavity preparation with Er:YAG laser leads to reduced shear bond strength to adhesive restorative materials when compared with that using burs and high-speed handpiece.

The influence of pulse duration and exposure time of Er,Cr:YSGG laser on lithium disilicate laminate debonding, an in vitro study

Problem statement

Grinding restorations, such as veneers, with rotary instruments, is the conventional removal approach. It may be accompanied by micro-fractures that affect the adjacent healthy dental structures. Differentiation of the veneer from the dental structure, as well as the resin cement, is not a highly selective procedure when rotary instruments are used. Moreover, the rotary instruments may lead to scratches and overheating of the enamel. Patient discomfort is another disadvantage, due to the noise of the drill.

Purpose

The purpose of this in vitro study was to examine the effectiveness of a 2790 nm Er,Cr:YSGG laser to debond lithium disilicate laminate, utilizing two distinct pulse durations and various exposure times. The shear bond strength, intrapulpal temperature, and adhesive remaining index were evaluated.

Methods and materials

This study included three groups of 75 extracted permanent mandibular incisors: G1, G2 (laser-treated groups were classified according to the pulse duration) and C (control group). Twenty five samples were regarded for each group. Both test groups were irradiated with a 3 W output power of Er,Cr:YSGG laser, for a variety of time intervals (20 s, 30 s, 40 s, 50 s, and 60 s). Five samples were tested for each time interval. During irradiation, the temperature in the pulp chamber was monitored using a K-type thermocouple connected to a digital multilogger thermometer that was introduced into the prepared sample pulp chamber. Subsequently, the shear bond strength was measured for G1 and G2, in addition to the control group (no irradiation). The adhesive remaining index was examined microscopically. The area was measured and analysed, and then, transformed into scores for comparisons. Finally, One untreated sample and two other samples of the highest power value from laser-treated groups were examined for their surface morphology by scanning electron microscope (SEM).

Results

The debonding protocols were safe relative to the intrapulpal protocol. The temperature rise after an exposure time of 50 s and 60 s was significantly different from an exposure time of 20 s, 30 s, and 40 s, in both groups (p < 0.05). Both G1 and G2 significantly outperformed the control group in shear bond strength. There was no significant difference between G1 and G2 at any of the tested exposure times (p > 0.05). Nevertheless, the 60 s exposure time showed the lowest shear bond strength.

Conclusion

Regarding intralpulpal temperature, both modes can be safely used to remove laminate veneers. In sum, an exposure time of 50 s and a pulse duration of 60 μs demonstrated superior results for SBS, adhesive remaining index, and temperature values.

Clinical implication

Lithium disilicate laminate veneers may be removed quickly, safely, and comfortably. Laser-assisted debonding of porcelain laminate veneer is recommended and does not cause any damage to the veneer or enamel surface.

Removal of lithium disilicate veneers with Er,Cr:YSGGL laser: now? Or after ageing?

This study was purposed to assess the impact of ageing and resin cements polymerized with different modes on the removal time of lithium disilicate (LiSi) ceramics using Er,Cr:YSGG laser. Ninety LiSi slabs (6 × 6 × 1 mm) were cemented to freshly extracted bovine teeth using cements polymerized with different modes (light-curing (LC), dual-curing (DC), self-curing (SC)). The specimens were divided into subgroups according to ageing conditions (no thermal cycling, 5000 or 30,000 thermal cycling). After that, Er,Cr:YSGG laser was applied until LiSi slabs were debonded; the removal time was recorded. Vickers microhardness test, SEM and EDS analyses were performed for specimens with the longest exposure time to laser application in the groups. One uncemented sample was also used as a control. Data were analyzed with two-way ANOVA and Tukey post hoc test. Ageing and cement polymerization mode significantly affected the removal time of LiSi specimens. The removal time for the self-curing resin cement group (22.67 ± 12.68 s) was significantly longer than for cements polymerized with other methods (LC = 10.833 ± 7.28 s, DC = 12.0 ± 7.96 s). Removal time was significantly reduced after ageing in all polymerization modes; however, there were no significant differences between 5000 (11.83 ± 7.52 s) and 30,000 (11.83 ± 7.26 s) thermal cycling groups. Self-curing resin cements had prolonged the laser-aided removal time for LiSi ceramics. It can be concluded that Er,Cr:YSGG laser-aided removal of LiSi veneers after clinical use can be done more faster than its immediate removal.

Effect of Nd:YAG and Er:YAG laser tooth conditioning on the microleakage of self-adhesive resin cement

Statement of problem

Recently, the application of lasers in restorative dentistry has been considered for cavity preparation and surface conditioning of enamel and dentin. However, the beneficial effects of cavity surface conditioning by laser irradiation on microleakage are still controversial.

Purpose

This study aimed to compare the microleakage of self-etch adhesive resin cement with Nd:YAG and Er:YAG laser tooth surface conditioning to evaluate the capabilities of these lasers as a reliable replacement for etching cavities.

Materials and methods

Fifty-four class V cavities were prepared on the buccal and lingual surfaces of 27 sound human premolar teeth. The samples were randomly divided into three groups (n = 18): group 1: no conditioning; group 2: conditioned with Er:YAG laser (2940 nm, 10 Hz, 1.2 W); group 3: conditioned with Nd:YAG laser (1064 nm, 1.5 W, 10 Hz). All the cavities were filled with self-adhesive resin cement. After curing and polishing, the samples were immersed in 2% methylene blue solution for 24 h, and after being embedded in acrylic resin, they were sectioned longitudinally and examined under a stereomicroscope. The data were submitted to Kruskal–Wallis and Dunn tests (α = 0.05).

Results

The lowest microleakage mean rank was observed in the Er:YAG group (19.19), and the highest mean rank was noted in the Nd:YAG group (33.08), with significant differences between the three groups (P-value = .01). Pairwise comparisons demonstrated significant differences between the Er:YAG and Nd:YAG groups (P-value = .004) as well as Er:YAG and no conditioned groups (P-value =.022).

Conclusion

The irradiation of the Er:YAG laser (2940 nm, 10 Hz, 1.2 W) on cavity surface resulted in less marginal microleakage of self-etch adhesive resin cement restorations compared to Nd:YAG (1064 nm, 1.5 W, 10 Hz) and no conditioning groups.

Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet Laser for Root Conditioning and Reduction of Postoperative Morbidity in the Treatment of Gingival Recession Defects: A Randomized Controlled Clinical Trial

Objective: This clinical trial evaluates the effect of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) root surface biomodification and laser harvesting of de-epithelialized gingival graft (DGG) on root coverage clinical outcomes and postoperative morbidity, and compares this to the conventional blade-harvested DGG method without Er,Cr:YSGG root surface biomodification in treatment of Miller's class I, II gingival recessions (GR). Background: The application of laser technology to enhance tooth root coverage clinical outcomes as well as the impact of laser on postoperative morbidity after harvesting autogenous soft tissue grafts requires further research. Methods: This study is a randomized, single-blinded controlled trial, including 24 volunteers with isolated GR defects. They were allocated into three treatment groups to receive one of the following three interventions: blade-harvested DGG (control group: B-DGG); Er,Cr:YSGG-harvested DGG and root surface biomodified [test 1 group: L-laser-harvested DGG (L-DGG)/laser root biomodification (LRB)]; and B-DGG and Er,Cr:YSGG root surface biomodification (test 2 group: B-DGG/LRB). Clinical and radiographic parameters were recorded at baseline (1 week before surgery) and 3, 6, and 9 months postoperatively. Results: Root coverage did not show a statistically significant difference between control and test groups. Statistically significant differences were found for Visual Analog Scale on the day of surgery and day 3 and 4 postoperatively, as well as pain medication on the day of surgery favoring the L-DGG group. Conclusions: The use of Er,Cr:YSGG laser in root surface biomodification improved root coverage outcomes at 9 months. Even these changes were not statistically significant from the control group; the L-DGG technique was associated with decreased postoperative morbidity in the palatal donor site.

Comparison between Shear Bond Strength of Er:YAG and Er,Cr:YSGG Lasers-Assisted Dentinal Adhesion of Self-Adhering Resin Composite: An Ex Vivo Study

(1) Background: Bonding composite to tooth structure is still evolving with a substitute for phosphoric acid being the main challenge. Lately, a self-adhering composite (SAC) was developed, promising to simplify bonding to tooth structure. Unfortunately, retention especially to dentin, was not as good as the gold standard three steps bonding system. During the last 2 decades, lasers were used to enhance shear bond strength of composite to tooth structure. However, the literature provided limited information regarding laser efficiency in the immediate, as well as the long term, adhesion success of SACs to dentin. The purpose of our study was to define the optimal irradiation conditions to improve the adhesion of self-adhering flowable resin composite to dentin exposed to Er:YAG and Er,Cr:YSGG laser irradiation. (2) Methods: Seventy-two freshly extracted human third molars, prepared to have flat dentinal surfaces, were randomly divided into three groups (n = 24) including a control group (Group 1) in which dentin was left without laser irradiation. The other two groups (Group 2 and 3) received standardized irradiation at a speed of 1 mm/second with Er:YAG (60 mJ; SSP mode = 50 μs; 10 Hz; fluency of 9.4 J/cm²; beam diameter: 0.9 mm; air 6 mL/min; and water 4 mL/min), and Er,Cr:YSGG: 1.5 W; fluency of 17.8 J/cm²; turbo handpiece with MX5 short insert; 20 Hz under air/water spray (65% air, 55% water). Self-adhering flowable resin was applied to dentin in all groups. Half of the specimens were stored in water for 24 h while the other half underwent 3000 thermal cycles. Later, all specimens received a shear bond strength test. Fracture observation was done first under a stereomicroscope then by using a scanning electron microscope. (3) Results: The mean values of shear bond strength for both laser-treated dentin groups (Er:YAG laser: 13.10 ± 1.291, and Er,Cr:YSGG: 14.04 ± 5.233) were higher than in the control group 1 (8.355 ± 2.297) before thermocycling. After thermocycling, shear bond strength decreased in all groups as follows: 10.03 ± 1.503, 10.53 ± 2.631, and 02.75 ± 1.583 for Er:YAG, Er,Cr:YSGG, and nonirradiated dentin, respectively. Shear bond strength values showed a significant difference between the control group (Group 1) and both lasers groups (Group 2 and 3). Statistical analysis of stereomicroscope observation revealed no significant difference between laser irradiation and failure mode (p < 0.136). SEM observation of the dentin surface in both laser-irradiated groups showed opened tubules, absence of smear layer as well as an increase of resin infiltration into dentinal tubules. (4) Conclusion: Er:YAG and Er,Cr:YSGG lasers enhance self-adhering flowable resin shear bond strength values and improve its longevity by eliminating the smear layer, opening dentinal tubules and increasing resin infiltration into the microstructure.

Debonding Time and Dental Pulp Temperature With the Er, Cr: YSGG Laser for Debonding Feldespathic and Lithium Disilicate Veneers

Introduction: The removal of ceramic veneers is a time-consuming procedure in a dental office. Little research has been done in alternative removal techniques for ceramic veneers. The objective of this study was to evaluate the removal of feldspathic and lithium disilicate reinforced glass ceramic veneers by Er, Cr: YSGG and to measure debonding time and pulpal temperature increase during veneer removal. Methods: Fifty-seven bovine incisor teeth were prepared and divided into 3 groups. Ceramic specimens with a thickness of 0.7mm, a width of 4mm and a length of 8 mm were fabricated from feldspathic ceramic, lithium disilicate reinforced glass ceramic HT (high translucency) and lithium disilicate reinforced glass ceramic MO (medium opacity) (19 for each group). Specimens were cemented on the labial surface of incisors using resin cement. The Er, Cr: YSGG laser was applied to each specimen at 2.5 W and 25 Hz. Debonding time was measured for each specimen, and the intrapulpal temperature was detected in 3 specimens for each group. Data were analyzed via one-way analysis of variance (ANOVA) at significance level of 0.05 (α = 0.05). Results: Mean debonding time was 103.68 (26.76), 106.58 (47.22) and 103.84 (32.90) seconds for feldspathic, lithium disilicate MO, and lithium disilicate HT respectively. There was no significant statistical difference among the groups (P value = 0.96). The intrapulpal temperature increase was less than 1°C in all groups. Conclusion: Er, Cr: YSGG can successfully be used to efficiently debond feldspathic and lithium disilicate reinforced glass ceramic veneers. There was no significant difference for debonding time among these ceramic materials. During ceramic laminate veneer removal by laser irradiation, no irritating temperature rise was detected.

The Effect of Diode and Er,Cr:YSGG Lasers on the Bond Strength of Fiber Posts

Background: Laser irradiation modifies the topography and composition of dentin surface aiming to increase the retention of bonded posts. Objective: To assess the effect of dentin irradiation with Er,Cr:YSGG or diode lasers on the bond strength of fiber posts using self-adhesive resin cement. Materials and methods: Sixty bovine root canals were root-canal treated, post spaces were prepared, and subsequently fiber posts were cemented. The samples were distributed according to the surface treatment: distilled water (control), Er,Cr:YSGG (1.5 W, 20 sec), or diode (1.5 W, 20 sec) lasers. Bond strengths were assessed by pull-out (n = 10) or push-out testing (n = 10). Pearson's correlation was calculated. Failure mode after testing and the depth of tags in the dentinal tubules were analyzed by confocal laser microscopy. Data were submitted to analysis of variance and Tukey's test. A p < 0.05 was considered significant. Results: In the push-out test, Er,Cr:YSGG laser had significantly different higher values (5.43 ± 0.10 MPa) compared to the control (4.79 ± 0.05 MPa). Diode laser values were not significantly different from the other groups (5.12 ± 0.27 MPa). In the pull-out test, there were no significant differences between Er,Cr:YSGG (6.86 ± 2.16 MPa) and diode (8.43 ± 1.77 MPa) lasers, and both had significant differences compared to the control (4.18 ± 1.29 MPa). No correlation was found. Adhesive failures were predominant in all groups, and no significant differences in tag penetration among the groups were found. Conclusions: The Er,Cr:YSGG laser increases the bond strength of resin cement and fiber post to dentin in both tests, compared to control group without laser treatment. Diode laser only enhanced bonding for pull-out test.

Effects of an Er,Cr:YSGG Laser on Bone Regeneration in Critical-Sized Calvarial Defects of Rats Exposed to Inhalation of Cigarette Smoke

Objective: To evaluate the effect of the Er,Cr:YSGG laser on healing of critical-sized calvarial defects (CSDs) in rats submitted to inhalation of cigarette smoke. Background: Smoking has been implicated with the delay in the bone healing after osteotomy procedures, then the use of the Er,Cr:YSGG laser for osteotomy in smokers could be an alternative to the conventional drills. Methods: One hundred animals were randomly allocated into four groups: trephine-the CSDs were made with a trephine drill in healthy rats; Er,Cr:YSGG-the CSDs were made with the Er,Cr:YSGG laser in healthy rats; Trephine-S-the CSDs were made with a trephine drill in rats exposed to cigarette smoke; and Er,Cr:YSGG-S-the CSDs were made with the Er,Cr:YSGG laser in rats exposed to cigarette smoke. The inhalation of cigarette smoke started 7 days before the surgical procedure until euthanasia (immediately, 7, 15, 30, or 60 days after the surgical procedure). A histometric analysis and a histological description were performed to evaluate (1) the residual linear lengths and bone formation in the CSDs; (2) the quality of bone healing. Results: The use of Er,Cr:YSGG laser induces more bone formation compared with the trephine in smokers; however, the closure of the CSD was only superior in the Er,Cr:YSGG-S group compared to the Trephine-S group at the 60-day period. Conclusions: The use of the Er,Cr:YSGG laser stimulated the bone repair process after osteotomy procedures in animals submitted to exposure of inhalation of cigarette smoke.

Laser Aided Ceramic Restoration Removal: A Comprehensive Review

Introduction: All-ceramic restorations are being widely used due to its various advantages. However, they have restricted durability and may have to be removed. The conventional procedure for removal is grinding the restoration with rotary instruments which are considered time-consuming and inconvenient. A newer advantageous method is the application of lasers for debonding ceramics from the tooth surface. The objective of this study is to provide a comprehensive literature review on laser-aided ceramic restorations debonding. Methods: We searched PubMed and Google Scholar databases. Seven articles from 2011 to 2018 were identified. Studies were assessed for the efficacy of laser application and the amount of pulpal temperature rise. Results: Studies selected were categorized according to variables including shear bond strength, debonding time and intrapulpal temperature. Oztoprak and Iseri investigated that erbium-doped yttrium, aluminum, and garnet (Er:YAG) laser application reduced shear bond strength of ceramic laminate veneers. The time of debonding took an average of 190 seconds in Rechmann's study and 106 seconds in Morford's study. One of the main issues while using the laser is thermal irritation of the pulp. A 5.5°C temperature increase may cause pulpal damage according to Zach and Cohen. Philips et al and Rechmann et al reported no intrapulpal harm due to temperature increase. Additionally, Phillips et al demonstrated that the laser setting affects both the debonding time and the temperature alterations and that a laser adjustment of 2.5 W/25 Hz would be the best safest group. Conclusion: Removal of ceramic crowns and veneers from tooth surfaces can be successfully done by Er:YAG laser application in a less time-consuming procedure and without any harm to the underlying dentin. However, a temperature rise in the pulp may occur which could be overcome by adequate air water cooling.

Fracture resistance of root-filled teeth after cavity preparation with conventional burs, Er: YAG and Er,Cr: YSGG lasers

Purpose

The aim of the present study is to compare the fracture resistance of teeth after access cavity preparation with conventional rotary burs, Erbium-doped yttrium aluminum garnet laser (Er:YAG) and Erbium, cromium: yttrium scandium gallium garnet laser (Er,Cr:YSGG) lasers.

Materials and methods

Fifty five intact mandibular molars were divided into 3 negative groups (groups 1, 2, 3; n=5 for each), 3 study groups (groups 4, 5, 6; n=10 for each) and 1 positive control group (intact teeth; n=10). Access cavities of groups 1, 2 and 3 were prepared with conventional burs, Er:YAG laser and Er,Cr:YSGG laser respectively. After root canal obturation, their coronal portions were left non-restored. Access cavities of groups 4, 5 and 6 were prepared by using the same equipment but their coronal portions were restored with composite resinafter root canal obturation. Following thermocycling, fracture strength was evaluated with a Universal Testing Machine. Mean force at which each sample is fractured was recorded in Newton unit and statistically analyzed.

Results

Fracture resistance of group 7 (intact teeth) was significantly higher than all other groups (p<0.001). Differences among the fracture resistance values of groups 4, 5 and 6 were not significantly different but they were significantly higher than those of groups 1, 2 and 3 (p<0.001). No significant difference was found between Groups 1, 2 and 3.

Conclusion

Preparing access cavities with either laser or bur has no effect on the fracture resistance of teeth with root canal treatment.

Effect of Er:YAG laser energy densities on thermally affected dentin layer: Morphological study

BACKGROUND AND AIMS

Physical and chemical composition of dentin is subject to modification when irradiated with Er:YAG laser. Temperature rise causes water evaporation and micro-mechanical ablation of dentin. The misuse of laser parameters could affect negatively dentin collagen fibers leading to failure in bonded composite restorations. The aim of this in vitro study was to evaluate the effect of Er:YAG laser radiation at different levels of energy on the morphology of thermally affected dentin layer.

MATERIALS AND METHODS

Forty-eight freshly extracted human third molars were randomly divided into six groups (n = 8). In all groups, except for the control groups, dentin was subject to irradiation with H02 handpiece Er:YAG laser in non-contact mode (SSP mode = 50 µs; 10 Hz; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min) with the following levels of energy (40, 60, 80, 100, and 120 mJ) respectively. Teeth were sliced longitudinally. Photo-ablated cavities were observed. The cavity depth and dentin fiber collagen deterioration were measured.

RESULTS

Laser irradiation increased the depth of dentinal crater from 46.57 µm to 178.2 µm, when energy level increased from 40 mJ to 120 mJ. A superficial black layer, representing dentinal affected collagen fibers, was present in all groups except for control group. When comparing the thickness of the black layer, there was no significant difference between groups. It increased at 40 mJ to 28.17 µm then decreased to 15.19 µm at 60 mJ and then increased again for 80 mJ to 19.93 µm, 100 mJ to 22.87 µm and 120 mJ to 28.53 µm. Only one group (60 mJ) showed low values and significant difference as compared to the other irradiated groups, when multiple comparisons tests (ANOVA) were made using Newman-Keuls test.

CONCLUSION

Dentin organic matrix presented the minimum alteration when Er:YAG laser is used specifically at an appropriate level of energy (60 mJ).

Behavior of human periodontal ligament cells on dentin surfaces ablated with an ultra-short pulsed laser

This study aimed to evaluate the effects of an ultrashort pulsed laser (USPL) (1064 nm, 20 ps, 100 kHz) with different laser fluences (F, 4, 6, 8 J/cm²) and pulse overlaps (PO, 0, 50%) on human periodontal ligament cells (hPDLs) behavior. Dentin samples were ablated with USPL with different combinations of fluences and pulse overlaps; some samples were ablated with an Er:YAG laser (2940 nm, 150 µs, 100 mJ/pulse, 5 J/cm²) and some samples were ground with a carbide bur. Then hPDLs were grown on the samples after different treatments. Dentin morphology and cell adhesion were observed with SEM and gene expressions were measured by RT-PCR. The results showed dentin surfaces ablated with USPL when F = 4 J/cm², PO = 0, and F = 6 J/cm², PO = 0 were partially intact with obvious ridges and valleys and cells on these surfaces grew mostly along the valleys. USPL ablated surfaces in other groups were entirely ablated and cell cluster formation was observed. The RT-PCR results showed an upregulation of osteocalcin of cells grown on the dentin after some laser treatment. It can be concluded that USPL could improve the attachment and differentiation of hPDLs and thus potentially promote periodontal tissue regeneration.

Comparing fibroblast attachment in root surface scaling with Er, Cr:YSGG laser versus ultrasonic scaler: A SEM study

BACKGROUND AND OBJECTIVES

The regeneration of periodontal support is the main concern in periodontal therapy. The aim of this in vitro study was to investigate the fibroblasts attachment on root surfaces after scaling with Er, Cr:YSGG laser and ultrasonic instruments using scanning electron microscopy (SEM).

METHODS

72 root plates of ∼6 × 4 × 1 mm³ in dimension were prepared from 27 single-rooted human mature teeth and were then divided into four groups. One group irradiated with a G6 tip of Er, Cr:YSGG laser (2.78 µm, 0.75 W, pulse duration of 140 µs, repetition rate of 20 Hz) for 5 to 7 s, and the other groups were scaled with ultrasonic alone or laser-ultrasonic. The control group was subjected to neither laser nor ultrasonic scaling. Subsequently, Viability and proliferation rates were done using MTT assay on days 3 and 5. Finally the cell attachment was observed using SEM.

RESULTS

The data derived from MTT and cell-attachment analysis indicated that laser-ultrasonic scaling tended to increase cell-viability by the lapse of time (within 3-5 days), with significantly better cell-attachment compared with other groups on days 3 and 5 (p < .05). The comparison of the difference in fibroblast cell attachment rate on both the third and the fifth day with independent T-Test indicated a significant rise on the fifth day compared to the third day of study (p < .05).

CONCLUSION

Indeed, both Er, Cr:YSGG laser and ultrasonic scaling may promote fibroblast attachment on dentinal root surfaces more than laser or ultrasonic scaling alone.

In vitro microleakage of class v composite restorations prepared by Er,Cr:YSGG laser and carbide bur

Background: The aim of this in vitro study was to compare the degree of microleakage on enamel and dentin margins of class V cavities prepared with either a high-speed drill or an Er,Cr:YSGG laser (2780 nm) and to associate their use with a beveling method for the margin. Method and Materials: Sixty bovine incisors were randomly distributed into three groups. Group 1 (G1) cavities were laser prepared and bur beveled, group 2 (G2) cavities were bur prepared and beveled, while cavities of group 3 (G3) were laser prepared and beveled. Cavities were restored with selective enamel etching, using the same bonding agent and nano-hybrid resin composite for all groups. After thermocycling, microleakage was assessed using a methylene blue dye penetration method. Results: Statistical analysis (Mann-Whitney, Kruskal-Wallis and post-hoc Dunn’s multiple comparison tests) demonstrated significantly higher microleakage for dentin compared to enamel margins in G1. Enamel margin microleakage was found to be significantly higher at G3 compared to G1 (p=0.032) and G2 (p=0.001), while no significant differences were found between G1 and G2 (p=0.850). Regarding dentin margins, G2 group performed significantly better than G1 and G3 (p<<0.001), while there was no significant difference among G1 and G3 scores (p=1.000). Conclusions: The conventional cavity preparation method seems to perform better in terms of microleakage than the Er,Cr;YSGG laser. Laser-prepared cavities could perform better in terms of microleakage if an additional step of enamel bur-beveling is performed prior to restoration.

The Effect of Energy Densities on the Shear Bond Strength of Self-Adhering Flowable Composite to Er:YAG Pretreated Dentin

Objective. To investigate the shear bond strength of self-adhering flowable resin composite, to dentin, after exposing it to Er:YAG laser radiation, at different energy densities. Materials and Methods. Sixty freshly extracted human third molars were randomly divided into five groups (n = 12). In the control group, dentin was left unirradiated, whereas, in the other four groups, dentin was irradiated with Er:YAG laser in noncontact mode (MSP mode = 100 µs; 10 Hz; beam diameter: 1.3 mm; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min), and respectively, with the following level of energy (50 mJ, 60 mJ, 80 mJ, and 100 mJ). Then, self-adhering flowable resin composite was bonded to all prepared dentin surfaces. Shear bond strength (SBS) was applied and fractured surfaces were examined using scanning electron microscopy. Results. SBS values showed significant differences in 60 mJ (P < 0.05) compared to other groups. Morphological evaluation revealed tags or plugs in dentinal tubules, especially when 60 mJ and 80 mJ were used. All four groups tended to leave more residues on the dentin surface, than the control group. Conclusion. Er:YAG dentin irradiation may enhance SBS of the self-adhering flowable resin composite when it is used at the appropriate low level of energy density.

Assessment of Microleakage of a Composite Resin Restoration in Primary Teeth Following Class III Cavity Preparation Using Er, Cr: YSGG laser: An In Vitro Study

Introduction: Marginal seal integrity is important for a successful adhesive dental restoration. Alterations caused by laser irradiation in the enamel and dentin surface can affect the marginal integrity of adhesive restorations. The aim of this study was to evaluate the microleakage of a composite resin restoration in primary teeth following laser irradiation of enamel and dentin. Methods: Forty freshly extracted sound human primary maxillary and mandibular anterior teeth were used in this study. The teeth were randomly divided into two groups (I and II), with 20 teeth in each. In group I, proximal cavities (Class III) were prepared using an airotor hand -piece and diamond bur. The cavities were etched for 15 seconds with 35% phosphoric acid gel, rinsed with water for 15 seconds, air dried and a bonding agent was applied onto the cavity surfaces and light cured for 20 seconds. The cavities were restored with composite resin and light cured for 40 seconds. In group II, proximal (Class III) cavities were prepared using Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) (Er,Cr:YSGG) (Biolaseiplus, wave length 2.78 μm). The cavity was then rinsed, air dried and without etching, a bonding agent was applied and light cured for 20 seconds. The cavities were restored in the same manner as that of group I. The treated teeth were mounted on acrylic resin blocks and were subjected to a thermocycling regimen. Following, the teeth were immersed in 2% methylene blue for 24 hours. The teeth were sectioned longitudinally in a bucco-lingual direction using a diamond disc at slow speed. The sections of all the groups were examined under a stereomicroscope for micro-leakage. Results: The mean scores for microleakage in group I was 1.95 ± 1.31 and in group II it was 1.4 ± 1.27. There was no significant difference between the two groups (P = 0.882). Conclusion: No significant difference in microleakage was noticed between the composite resin bonded to lased enamel and dentin and the teeth preparedwith conventional method.

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

INTRODUCTION

Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose.

AIM

The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens.

MATERIALS AND METHODS

Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification.

RESULTS

Chi Square and Student "t" statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05<p>0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the 't' value of student 't' test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78μm and GrD3 of 1.09μm.

CONCLUSION

The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent.

In vitro investigation on Ho:YAG laser-assisted bone ablation underwater

Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism.

Influence of Different Proportions of External Irrigation During the Er,Cr:YSGG Laser Irradiation on Wear and Roughness of Root Surface

INTRODUCTION

The aim of this study was to evaluate the influence of different levels of external irrigation during irradiation with an erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the roughness and wear of dental tissue during scaling procedures.

METHODS

Twenty-Five uniradicular bovine teeth had the proximal surfaces planed and divided into 3 regions: upper, middle and lower. The upper region was treated with hand instruments, the middle region was not treated and served as a control, and the lower region was treated by the Er,Cr:YSGG laser. The teeth were randomly divided into five groups according to the different proportions of external irrigation used during the laser irradiation: G1: 10%; G2: 20%; G3: 30%; G4: 40% and G5: 50%. The samples were analyzed for roughness and wear on the root surface irradiated with the laser.

RESULTS

There were no differences in the surface roughness and wear parameters between the groups irradiated with the laser, but the laser irradiation produced a rougher surface of the dentin than treatment with hand scaling.

CONCLUSION

Changes in the external irrigation level did not influence the wear and roughness of root surfaces treated with an Er,Cr:YSGG laser.

Surface Treatment by Different Parameters of Erbium:Yttrium-Aluminum-Garnet (Er:YAG) Laser: Scanning Electron Microscope (SEM) Evaluation

INTRODUCTION

This study aimed to assess the Scanning Electron Microscope (SEM) analysis of tooth surface irradiated by erbium:yttrium-aluminum-garnet (Er:YAG) laser with various parameters.

METHODS

Number of 25 extracted human third molars free of caries were used in this study. The teeth were put into 5 groups for laser irradiation as follows: group 1 (power: 0.5 W, Energy: 50 mJ); group 2 (power: 1 W, Energy: 100 mJ); group 3 (power: 1.5 W, Energy: 150 mJ); group 4 (power: 2 W, Energy: 200 mJ); group 5 (power: 2.5 W, Energy: 250 mJ). All samples were prepared by repetition rate of 10 Hz and duration of 230 μs, using a non-contact handpiece at a distance of 4 mm. Then, the samples were prepared for SEM examination.

RESULTS

SEM evaluation of every 25 samples, treated by Er:YAG, showed that all groups had exposed dentinal tubules without any melted area or cracks.

CONCLUSION

In this study we used SEM to investigate ablated dentine with different parameters of Er:YAG laser energy. Our findings support these conclusions. All powers of laser below 3 W are proper for ablation, and make no cracks.

Effects of Er,Cr:YSGG laser parameters on dentin bond strength and interface morphology

Previous studies have shown the effects of Er,Cr:YSGG laser irradiation on the dentin bond strength; but there are few reports that show the significance of the irradiation with different laser parameters on dentin bond strength and interface morphology. This in-vitro study attempted to evaluate the microtensile bond strength (μTBS) and interface morphology of resin-dentin interfaces, either followed by treatment with Er,Cr:YSGG laser irradiation with different parameters or not. The flattened dentin samples of 35 bovine teeth were embedded into acrylic blocks and randomly divided into seven groups according to surface treatments using Er,Cr:YSGG lasers with different parameters: 3 W/20 Hz, 3 W/35 Hz, 3 W/50 Hz, 1.5 W/20 Hz, 1.5 W/35 Hz, 1.5 W/50 Hz, or no laser treatment (n = 5). Composite buildups were done over bonded surfaces and stored in water (24 hours at 37°C). Specimens were sectioned into sticks that were subjected to μTBS testing and observed under FE-SEM. Control groups (27.70 ± 7.0) showed statistically higher values than laser-irradiated groups. There were no significant differences among laser groups. Despite that, increasing the pulse frequency yielded slightly higher bond strength. Depending on laser settings, Er,Cr:YSGG laser irradiation caused interfacial gaps and resin tags with wings morphology. With the parameters used in this study, Er,Cr:YSGG laser irradiation promoted morphological changes within resin-dentin interfaces and negatively influenced the bond strength of adhesive systems.

A microscopic analysis of the effects of root surface scaling with different power parameters of Er,Cr:YSGG laser

The aim of this study was to evaluate the effects of different power parameters of an Erbium, Cromium: Yttrium, Scandium, Gallium, Garnet laser (Er,Cr:YSGG laser) on the morphology, attachment of blood components (ABC), roughness, and wear on irradiated root surfaces. Sixty-five incisive bovine teeth were used in this study, 35 of which were used for the analysis of root surface morphology and ABC. The remaining 30 teeth were used for roughness and root wear analysis. The samples were randomly allocated into seven groups: G1: Er,Cr:YSGG laser, 0.5 W; G2: Er,Cr:YSGG laser, 1.0 W; G3: Er,Cr:YSGG laser, 1.5 W; G4: Er,Cr:YSGG laser, 2.0 W; G5: Er,Cr:YSGG laser, 2.5 W; G6: Er,Cr:YSGG laser, 3.0 W; G7: scaling and root planning (SRP) with manual curettes. The root surfaces irradiated by Er,Cr:YSGG at 1.0 W and scaling with manual curettes presented the highest degrees of ABC. The samples irradiated by the Er,Cr:YSGG laser were rougher than the samples treated by the manual curette, and increasing the laser power parameters caused more root wear and greater roughness on the root surface. The Er,Cr:YSGG laser is safe to use for periodontal treatment, but it is not appropriate to use irradiation greater than 1.0 W for this purpose.

Effect of Er,Cr:YSGG laser application in the treatment of experimental periodontitis

The purpose of this study was to evaluate the influence of an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser in the absence or presence of manual scaling and root planning (SRP) for the treatment of induced periodontitis in rats. Ligatures were placed in the subgingival region of the maxillary first molar. After a 7-day period, the ligatures were removed, and 40 rats were randomly divided into four groups (G), as follows: (GI) no treatment, (GII) scaling and root planning (SRP) with curettes, (GIII) Er,Cr:YSGG laser irradiation and (GIV) SRP with curettes followed by Er,Cr:YSGG laser irradiation. Seven and 30 days after the treatment, the animals were sacrificed and histologic, histometric and immunohistochemistry analyses were performed. All groups showed similar histopathological characteristics during the evaluation period. The histometric analysis was confirmed using Bonferroni and paired t tests. At 7 and 30 days, groups II, III and IV exhibited greater bone formation in the furcation area when compared to group I (p < 0.0001; p < 0.05). During the 7-day period, the groups irradiated with the laser (III and IV) showed a statistically larger new bone area than the group treated with SRP (II) (p < 0.01). Immunohistochemistry analysis revealed that the control group exhibited a higher expression of tartrate-resistant acid phosphatase (TRAP) and the receptor activator of nuclear factor κΒ ligand (RANKL) when compared to groups II, III and IV (p < 0.05). All treatments were able to reduce the inflammatory processes, consequently enabling the repair of periodontal tissues. The results achieved with the application of the Er,Cr:YSGG laser suggest that this laser can stimulate greater bone formation, especially over a shorter period of time.

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.

Influence of different pulse durations of Er:YAG laser based on variable square pulse technology on microtensile bond strength of a self-etch adhesive to dentin

OBJECTIVE

The aim of the study was to evaluate the microtensile bond strength of a composite resin to dentin modified with three different pulse durations of the Er:YAG laser based on variable square pulse technology and with one self-etch adhesive.

MATERIALS AND METHODS

The entire occlusal enamel was removed to obtain flat dentin surface for 48 human molar teeth. The teeth were randomly divided into four experimental groups (n=12 per group), according to the pretreatment of dentin: (1) control group; (2) super short pulse (SSP) (50 μsec); (3) medium short pulse (MSP) (100 μsec); and (4) short pulse (SP) (300 μsec) with Er:YAG laser. The energy of the laser used was 80 mJ with average power of 0.8 W. The microtensile bond strength was tested with a universal testing machine. Two specimens from each experimental group were subjected to scanning electron microscopic (SEM) examination, to observe the irradiated surface.

RESULTS

Dentin surface treated with SSP showed significantly lower microtensile bond strength values (24±9.8 MPa) in comparison with the control group and SP group (35.3±12.8 and 32.9±10.7 MPa, respectively), (p<0.05). The MSP and SP groups did not show any statistically significant difference in microtensile bond strength in comparsion with the control group (p>0.05).

CONCLUSIONS

The use of SP and MSP of the Er:YAG laser with one step self-etch adhesive does not impair or improve the microtensile bond strength in dentin, whereas SSP may not be suitable for dentin surface treatment prior to bonding procedures.

Effect of Er,Cr:YSGG laser on human dentin fluid flow

The aim of the current investigation was to assess the rate and magnitude of dentin fluid flow of dentinal surfaces irradiated with Er,Cr:YSGG laser. Twenty extracted third molars were sectioned, mounted, and irradiated with Er,Cr:YSGG laser at 3.5 and 4.5 W power settings. Specimens were connected to an automated fluid flow measurement apparatus (Flodec). The rate, magnitude, and direction of dentin fluid flow were recorded at baseline and after irradiation. Nonparametric Wilcoxon signed ranks repeated measure t test revealed a statistically significant reduction in fluid flow for all the power settings. The 4.5-W power output reduced the flow significantly more than the 3.5 W. The samples showed a baseline outward flow followed by inward flow due to irradiation then followed by decreased outward flow. It was concluded that Er,Cr:YSGG laser irradiation at 3.5 and 4.5 W significantly reduced dentinal fluid flow rate. The reduction was directly proportional to power output.

Effect of Er,Cr:YSGG and Er:YAG laser irradiation on the adhesion of blood components on the root surface and on root morphology

The aim of this study was to conduct an in vitro evaluation, by scanning electron microscopy (SEM), of the adhesion of blood components on root surfaces irradiated with Er,Cr:YSGG (2.78 µm) or Er:YAG (2.94 µm) laser, and of the irradiation effects on root surface morphology. Sixty samples of human teeth were previously scaled with manual instruments and divided into three groups of 20 samples each: G1 (control group) - no treatment; G2 - Er,Cr:YSGG laser irradiation; G3 - Er:YAG laser irradiation. After performing these treatments, blood tissue was applied to 10 samples of each group, whereas 10 samples received no blood tissue application. After performing the laboratory treatments, the samples were observed under SEM, and the resulting photomicrographs were classified according to a blood component adhesion scoring system and root morphology. The results were analyzed statistically (Kruskall-Wallis and Mann Whitney tests, α= 5%). The root surfaces irradiated with Er:YAG and Er,Cr:YSGG lasers presented greater roughness than those in the control group. Regarding blood component adhesion, the results showed a lower degree of adhesion in G2 than in G1 and G3 (G1 × G2: p = 0.002; G3 × G2: p = 0.017). The Er:YAG and Er,Cr:YSGG laser treatments caused more extensive root surface changes. The Er:YAG laser treatment promoted a greater degree of blood component adhesion to root surfaces, compared to the Er,Cr:YSGG treatment.

Er,Cr:YSGG laser influence on microleakage of class V composite resin restorations

One of the most challenging issues following restoration is microleakage. The aim of this study was to investigate the effects of Er,Cr:YSGG laser with and without acid etching on microleakage of class V composite restorations. A total of 68 human intact premolars were selected, disinfected, and randomly allocated to four experimental groups (n = 16) as well as positive and negative controls (n = 2 each). Dimensionally, similar class V cavities were prepared on buccal surface of each tooth under the following conditions: group 1, bur cavity preparation and chemical etching (BE); group 2, bur cavity preparation and Er,Cr:YSGG laser conditioning (BLc); group 3, Er,Cr:YSGG laser cavity preparation and chemical etching (LE); and group 4, Er,Cr:YSGG laser cavity preparation and Er,Cr:YSGG laser conditioning (LLc). All samples were restored with composite. The teeth were sealed and immersed in 1 % methylene blue for 48 h before being sectioned. The microleakage evaluation was done under a stereomicroscope (×20). The leakage scores were recorded and Kruskal-Wallis and Mann-Whitney tests were used for statistical evaluations. The highest microleakage score was seen in gingival margins of group 4 (LLc) and the lowest in occlusal margins of group 3 (LE). The overall difference in leakage scores among the groups was statistically significant (p < 0.001) with gingival margins showing a significantly higher score than its occlusal counterparts (p < 0.001). It was noted that less microleakage could be achieved when cavities were prepared by laser compared to bur. In addition, less microleakage was seen in acid-etched cavities than laser-conditioned counterparts.

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.

The effect of erbium family laser on tensile bond strength of composite to dentin in comparison with conventional method

The purpose of this study was to evaluate the effect of Er:YAG and Er,Cr:YSGG laser on tensile bond strength of composite resin to dentine in comparison with bur-prepared cavities. Fifteen extracted caries-free human third molars were selected. The teeth were cut at a level below the occlusal pit and fissure plan and randomly divided into three groups. Five cavities were prepared by diamond bur, five cavities prepared by Er:YAG laser, and the other group prepared by Er,Cr:YSGG laser. Then, all the cavities were restored by composite resin. The teeth were sectioned longitudinally with Isomet and the specimens prepared in dumbbelled shape (n = 36). The samples were attached to special jigs, and the tensile bond strength of the three groups was measured by universal testing machine at a speed of 0.5 mm/min. The results of the three groups were analyzed with one-way ANOVA and Tamhane test. The means and standard deviations of tensile bond strength of bur-cut, Er:YAG laser-ablated, and Er,Cr:YSGG laser-ablated dentine were 5.04 ± 0.93, 13.37 ± 3.87, and 4.85 ± 0.93 MPa, respectively. There is little difference in tensile bond strength of composite resin in Er,Cr:YSGG lased-prepared cavities in comparison with bur-prepared cavities, but the Er:YAG laser group showed higher bond strength than the other groups.

Ablative potential of four different pulses of Er:YAG lasers and low-speed hand piece

OBJECTIVE

The aim of the study was to evaluate the ablation rate of caries in dentin with fluorescence-feedback controlled Er:YAG, Variable Square Pulse technology (VSPt) based Er:YAG working in different pulse durations, and steel bur.

MATERIALS AND METHODS

Sixty human molar teeth with caries in dentin, extracted for periodontal reasons, were selected for this study. All selected teeth were randomly divided into five groups, each containing twelve specimens: (1) group FFC, fluorescence feedback-controlled Er:YAG laser; (2) group SSP (super short pulse: 50 μs); (3) group MSP (medium short pulse; 100 μs); (4) group SP (short pulse; 300 μs); and (5) group SB, steel bur in a slow-speed hand piece. A profilometer was used to determine the volume of the ablated caries in dentin. The clinical and real ablation rates of caries in dentin were calculated. Two specimens from each experimental group were selected randomly and subjected to SEM examination.

RESULTS

The volumes of the ablated caries in dentin in the SSP and SB groups were statistically significantly different in comparison with other experimental groups (p<0.05). The clinical and real ablation rate of caries in dentin was the highest for the SSP group (0.15±0.05 and 0.17±0.05 mm(3)/sec, respectively) and statistically significantly different in comparison with the MSP and SB groups (p<0.05). The SB and FFC groups revealed a dentin surface with a smear layer and closed dentinal tubules on SEM micrographs. In the SSP, MSP, and SP groups, an irregular surface without a smear layer was found.

CONCLUSIONS

Taking into consideration the experimental conditions of the present study, SSP was the most efficient in ablation of caries in dentin, providing a smear layer-free surface with open dentinal tubules.

Influence of the angle of irradiation of the Er,Cr:YSGG laser on the morphology, attachment of blood components, roughness, and root wear: in vitro study

BACKGROUND AND OBJECTIVES

To evaluate the influence of the working tip angulation of the Er,Cr:YSGG laser on the morphology, attachment of blood components, roughness, and wear on irradiated root surfaces compared to scaling and root planing (SRP).

STUDY DESIGN/MATERIALS AND METHODS

The present study used 45 teeth, of which 25 were used for the analysis of the morphology and the attachment of blood components and 20 were used for the analysis of the roughness and of the root wear. The teeth were randomly divided into five groups according to the treatment applied: (G1) Laser Er,Cr:YSGG-30°; (G2) Laser Er,Cr:YSGG-45°; (G3) Laser Er,Cr:YSGG-60°; (G4) Laser Er,Cr:YSGG-90°; and (G5) SRP.

RESULTS

The root surfaces irradiated with the Er,Cr:YSGG laser working angulation tip of 45° and 60°, and the samples scaled with manual instruments presented greater attachment of blood components than the group where the Er,Cr:YSGG laser irradiated at working tip angulation of 30° and 90° (P<0.05). The samples irradiated with the Er,Cr:YSGG laser were rougher than the samples scaled with manual instruments (P<0.05). The group that was irradiated with the Er,Cr:YSGG laser at an angle of 30° presented the least wear in comparison to all the other treatments (P<0.01).

CONCLUSIONS

The irradiated root surfaces proved to be rougher than those scaled with manual instruments; however, irradiation at working tip angulations of 45° and 60° produced results of attachment of blood components and root wear comparable with those obtained with manual instrumentation.

Effect of instrumentation using curettes, piezoelectric ultrasonic scaler and Er,Cr:YSGG laser on the morphology and adhesion of blood components on root surfaces: a SEM study

This study used scanning electron microscopy (SEM) to evaluate the morphology and adhesion of blood components on root surfaces instrumented by curettes, piezoelectric ultrasonic scaler and Er,Cr:YSGG laser. One hundred samples from 25 teeth were divided into 5 groups: 1) Curettes; 2) Piezoelectric ultrasonic scaler; 3) Curettes plus piezoelectric ultrasonic scaler; 4) Er,Cr:YSGG laser; 5) Curettes plus Er,Cr:YSGG laser. Ten samples from each group were used for analysis of root morphology and the other 10 were used for analysis of adhesion of blood components on root surface. The results were analyzed statistically by the Kruskall-Wallis and Mann-Whitney tests with a significance level of 5%. The group treated with curettes showed smoother surfaces when compared to the groups were instrumented with piezoelectric ultrasonic scaler and the Er,Cr:YSGG laser. The surfaces instrumented with piezoelectric ultrasonic scaler and Er,Cr:YSGG laser, alone or in combination with hand scaling and root planing, did not differ significantly (p>0.05) among themselves. No statistically significant differences (p>0.05) among groups were found as to the adhesion of blood components on root surface. Ultrasonic instrumentation and Er,Cr:YSGG irradiation produced rougher root surfaces than the use of curettes, but there were no differences among treatments with respect to the adhesion of blood components.