The effect of different enamel surface treatments on the microleakage of fissure sealants

Microleakage Assessment of Different Preparation Techniques and Pit and Fissure Sealants in Permanent Molars

BACKGROUND

This study aimed to evaluate the predisposition of microleakage in permanent molar teeth following different preparation techniques for pits and fissure sealants.

METHODS

In this cross-sectional analytical study, a dye penetration method was employed to evaluate microleakage in dental restorations. A total of 104 extracted molars were randomly assigned into two groups and further subdivided into two subgroups based on a class of sealant (filled/unfilled resin) containing 26 teeth each. Teeth in one group were prepared by a conventional method using pumice and acid etching with 37% phosphoric acid, and teeth in the other group were prepared with a 1/4-round carbide bur in a low-speed handpiece and then acid etched. In each group, 26 teeth were sealed with a filled sealant, and 26 teeth with an unfilled sealant. The chi-square test was used for the comparison of microleakage between the groups.

RESULTS

Unfilled sealants prepared with bur preparation showed the lowest degree of microleakage. The greater number of teeth (17) showed no microleakage in the group of teeth prepared using the bur preparation technique. Furthermore, in dye penetration analysis, the subgroup of teeth that were filled with unfilled sealants showed a greater number of teeth (57.6%), with zero penetration, and the dye penetration scores were statistically significant among the groups with different preparation techniques (p=0.002).

CONCLUSION

Teeth whose pits and fissures were prepared through 1/4 carbide bur and filled with unfilled pits and fissure sealants show less microleakage than those prepared with the conventional method and filled with filled sealants. Therefore, the choice of surface preparation technique for pit and fissure sealants can influence the effectiveness of the sealant in preventing microleakage.

Application of Laser Treatment in Adhesive Bonding of Liners to Polymethyl Methacrylate Denture Resins: A Systematic Review and Meta-Analysis

Objective: This systematic review and meta-analysis aimed to assess the influence of laser treatment on adhesive bonding of liners to polymethyl methacrylate (PMMA) denture base resins. Methods: The focused question was: "Does the application of laser treatment (Intervention) influence the adhesive bonding strength (Outcome) of liners to PMMA denture base resins (Population) as compared with untreated or unconditioned surfaces (Control)?" In vitro and clinical reports as well as reports on influence of laser treatments on bonding strength of liners to PMMA denture resins in comparison with untreated surfaces were included. Reports without any control group[s], without any application of laser[s] for PMMA denture bases that did not utilize PMMA denture bases, and not evaluate bond strength of PMMA denture base resins were excluded. An electronic search was conducted on PubMed, Scopus, and Web of Science. Meta-analyses were performed for calculating the standard mean difference (SMD) with a 95% confidence interval (95% CI). Results: Nine of the 12 included studies found that laser irradiation treatment produced significant surface texture alterations of the PMMA denture base and improved the adhesion between the PMMA denture base and soft lining. According to the meta-analysis, tensile bond strength showed an SMD of -2.49% (95% CI: -3.89 to -1.08; p = 0.0005), suggesting a statistically significant difference between the control and test groups (i.e., favoring laser-treated samples than untreated samples). Regarding shear bond strength scores, the outcomes showed an SMD of -2.24% (95% CI: -3.79 to -0.69; p = 0.005), suggesting a statistically significant difference between the control and test groups (i.e., favoring laser-treated samples than untreated samples). Conclusions: Despite the high heterogeneity among the included studies, it can be concluded that laser treatment might improve the bonding strengths of liners to PMMA denture base resins as compared with untreated surfaces. To validate the aforementioned conclusions, further verification is required through the implementation of well-designed randomized controlled trials with large sample sizes.

Evaluation of the marginal integrity of various pit and fissure sealants

PURPOSE

To evaluate the marginal integrity of various pit and fissure sealants subjected to different application methods.

METHODS

A total of 253 non-carious human third molars extracted and randomly divided into two groups according to the preparation method employed: invasive or non-invasive. Eight fissure sealant materials were tested: nano-filled flowable composite (Filtek Ultimate Flow), nanohybrid flowable composite (GrandioSo Flow), micro-hybrid flowable composite (Majesty Flow), resin-based unfilled fissure sealant (ClinPro Sealant), resin-based filled fissure sealant (Fissurit FX), resin-based highly filled fissure sealant (GrandioSeal), giomer-based fissure sealant (BeautiSealant), and glass ionomer-based fissure sealant (Fuji Triage). Samples were subjected to two-year cyclic thermo-mechanical and brushing simulations. Two observers quantitatively evaluated the restoration margins and classified them as either "permanent restoration edge", or if a gap larger than 250 μm was evident, "gapping at the restoration edge". The extent of the gap was recorded as a percentage relative to the total length of the restoration edge.

RESULTS

The baseline marginal adaptation had no significant effect on the marginal adaptation (P > 0.05). However, the preparation method and type of fissure sealant material had a significant impact on the marginal adaptation (P < 0.05).

CONCLUSION

On the basis of quantitative analysis, the highest marginal integrity was observed for flowable composites, whereas the lowest was observed for glass ionomer-based fissure sealant.

Comparative Evaluation of Penetrative and Adaptive Properties of Unfilled and Filled Resin-Based Sealants When Placed using Conventional acid Etching, Lasing, and Fissurotomy Bur Technique of Enamel Preparation: An in vitro Scanning Electron Microscope Study

Background

There is a confusion regarding selection of unfilled or filled sealant and method of enamel preparation before sealant application. This study was carried out to compare three techniques of enamel preparation using both unfilled and filled type of sealants.

Objective

The objective of the study is to assess the penetrative and adaptive ability of filled and unfilled sealants in three techniques of enamel fissure preparations.

Materials and Methods

Total 36 extracted teeth were divided into 3 groups, each containing 12 samples. The samples of Group A were prepared by conventional acid etching with 37% phosphoric acid, and the Group B was subjected to Er: YAG lasing, while in Group C, fissurotomy followed by acid etching was done. The sealant placement was carried out using split tooth design in all the samples. Assessment of penetration and adaptation was done under scanning electron microscope using the scoring criteria adopted by Kane B et al. and Dukic W et al.

Results

Group A and Group C showed better adaptation than Group B. Statistically, no significant difference was observed in the penetration property among three techniques. Similarly, the unfilled and filled sealant showed statistically nonsignificant results for the penetration and adaptation comparison.

Conclusion

Irrespective of the sealant material selected, the conventional method of acid etching alone or in conjunction with fissurotomy bur for better retentiveness seems to be an acceptable choice of treatment modality. The study will help the clinicians to choose the sealant material and technique of enamel preparation.

The effect of the Er: YAG laser on the clinical success of hydrophilic fissure sealant: a randomized clinical trial

Purpose:

The aim of this study was to assess the effect of the Er:YAG laser on the clinical success of a hydrophilic fissure sealant over 12 months.

Subject and methods:

This study was conducted on 132 permanent first molars from 44 (19 girls and 25 boys) patients aged 7-11 years. The teeth were divided into three groups. The first group (Group A-control) of teeth were etched with phosphoric acid, the second group of teeth (Group L) were etched with an Er:YAG laser, and the third group of teeth (Group A+L) were etched with both the Er:YAG laser and phosphoric acid. Clinical evaluations were performed at baseline and at 3-, 6-, 9- and 12-month follow-up visits. The data were analyzed with Pearson chi-square tests, Cochran Q tests and Kaplan-Meier analysis.

Results:

At the end of the 12 months, total retention rates were 72.7%, 59.1%, and 65.9% in the acid group, the laser group and the laser and acid group, respectively. Although there was no statistically significant difference between group retention rates (p>0.05), the lowest retention rate was found in the laser group at the end of the 12-month follow-up period. No new caries were observed in any group during the study period.

Conclusion:

Etching with the Er:YAG laser, phosphoric acid or a combination of both methods provided similar results for the clinical success of hydrophilic based fissure sealant.

Ameloplasty is counterproductive in reducing microleakage around Resin Modified Glass Ionomer and Resin based fissure sealants

Objective:

To compare the microleakage around resin modified glass ionomer cement (RMGIC) based sealants and flowable resin based sealants placed with or without ameloplasty in extracted human teeth.

Methods:

This in-vitro experimental study was conducted at the Operative Dentistry Department, Dow University of Health Sciences, Karachi, Pakistan from June 2017 to December 2018. Sixty extracted human molars and premolars were assigned to four groups (n=15) each, according to the type of fissure sealant (flowable resin based sealant or resin modified glass ionomer based sealant) used and either placed with or without ameloplasty. Specimens were thermocycled and then immersed in 1% methylene blue for 24 hours. Specimens were then sectioned and examined using stereo-microscope (50X) for microleakage that was scored on an ordinal scale. Mann-Whitney U test and Ordinal regression were applied. Level of significance kept at 0.05.

Results:

There was a statistically significant difference (p-value <0.001) between the two sealant types for the microleakage scores. Sealants placed with ameloplasty demonstrated significantly higher microleakage values (p-value <0.001).

Conclusion:

Microleakage was found to be more pronounced in RMGIC based sealants compared to the resin based sealants. Ameloplasty resulted in higher leakage around the sealants irrespective of the chemistry of material.

Pit and fissure sealants penetration capacity and their correlation with fissure morphology

Background and aims

Pit and fissure sealant placement corresponds to an effective approach of the prevention of caries on occlusal surfaces. Fissure morphology and dental material characteristics are the key factors for sealant effectiveness. The aim of this in vitro study was to compare the penetration ability of two commercially available pit and fissure sealants.

Methods

Twenty sound human premolars extracted for orthodontic purpose have been sealed according to manufacturer’s instructions as follows: Group I (n=10), light-cured unfilled resin-based sealant, Admira Seal® (Voco GmbH); Group II (n=10), resin modified glass ionomer sealant without varnish, GC Fuji Triage® (GC Corporation). The teeth have been sectioned buccal-lingually in the middle of the occlusal surface, and the sections were examined at 40× with an inverted microscope.

Results

Penetration of the sealants was found to be greater in U-type fissure pattern (91.69%) followed by V-type (75.42%), IK-type (71.24%) and then in I-type (63.98%). The depth of penetration of GC Fuji Triage® (82.85%) demonstrated to be superior to Admira Seal® (76.28%).

Conclusion

U fissure design was more common than other fissure patterns and showed significantly higher penetration for the two type of sealants evaluated. Resin modified glass ionomer sealant used in the present study perform comparably with the filled resin sealant.

Influence of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in Er, Cr:YSGG laser-prepared cavities

Objective:

To evaluate the effect of gamma radiation on microshear bond strength and nanoleakage of nanofilled restoratives in laser-prepared cavities.

Materials and Methods:

Twenty-eight flat buccal dentin surfaces were prepared for microshear bond strength test. Er, Cr:YSGG laser was used to prepare another 28 Class V cavities on the buccal surfaces of the molars. All teeth were divided into four groups; 1^st group: Application of Filtek Z350 nanocomposite material, 2^nd group: As the 1^st group and then exposure to gamma radiation, 3^rd group: Application of Ketac N100 nanoglass ionomer, and the 4^th group: As the 3^rd group and then gamma irradiated. The bond strength test was performed after storage in artificial saliva for 24 h. For the nanoleakage test, teeth were submerged in a solution of ammoniacal silver nitrate, sectioned, and then examined under a scanning electron microscope. The collected data were statistically analyzed.

Results:

Nanocomposite showed higher bond strength values than nanoglass ionomer. Despite the fact that gamma radiation did not decrease nanocomposite bond strength, it decreased nanoglass ionomer bond strength. Nanoglass ionomer-restored cavities showed higher silver ion penetration than nanocomposite in both control and gamma-irradiated groups.

Conclusion:

Gamma radiation has no effect on bond strength and nanoleakage of nanocomposite so that it can be placed before radiotherapy. On the other hand, the bond strength of nanoglass ionomer was adversely affected by gamma radiation.

Microleakage and penetration depth of different fissure sealant materials after cyclic thermo-mechanic and brushing simulation

The aim of the study was to evaluate microleakage and the penetration-depths of different fissure-sealant materials applied with/without enameloplasty after cyclic aging. One-hundred-sixty mandibular molars were divided into non-invasive and enameloplasty preparation groups and eight material subgroups, including: flowable composites (microhyrid, nanohybrid, and nanofilled), three resin-based (unfilled, filled, and highly-filled), a giomer-based, and a glass-ionomer-based fissure sealant. Specimens were subjected to two-year cyclic chewing and brushing simulation. After 5% basic-fuchsin dye penetration, specimens were sectioned and scored under stereomicroscope. Kruskal-Wallis statistical data showed that preparation type significantly affected the penetration of all tested materials (p<0.05), but not significantly affected microleakage (p>0.05). Flowable composites showed the best and the glass-ionomer-based sealant showed the worst penetration and microleakage. Slight preparation of fissures is not important in microleakage. However, enameloplasty significantly enhanced the depth of penetration of the sealants. Flowable composites offer promising results at the fissure sealing.

An in vitro investigation of pre-treatment effects before fissure sealing

BACKGROUND

Fissure sealants prevent occlusal caries in permanent molars. Enamel preparation methods are used before fissure sealing.

AIMS

To investigate effects of bioglass air-abrasion pre-treatment with and without an adhesive, on fissure enamel of permanent teeth, with respect to etchability, microleakage and microtensile bond strength.

DESIGN

Half of the occlusal surfaces of 50 extracted premolars underwent bioglass air-abrasion. Dye was applied to the entire occlusal surface. Photographs were taken to score etched surface by dye uptake. Adhesive was applied to 25 of the bioglass-treated areas and all teeth were fissure sealed, sectioned, and evaluated using confocal microscopy. Buccal and lingual surfaces of a further eight premolars were acid-etched and randomly received: air-abrasion, adhesive, both, or none before sealant application for microtensile bond strength measurement in half of the samples immediately and half following 6 months of water immersion.

RESULTS

Linear mixed models and multinomial logistic regression were used (P = 0.05). Bioglass air-abrasion significantly improved enamel etchability and reduced microleakage. The addition of an adhesive made no difference to either microleakage or microtensile bond strength. The combination of bioglass abrasion and adhesive led to more cohesive, rather than adhesive, failure.

CONCLUSIONS

Bioglass air-abrasion improved enamel etchability and reduced microleakage irrespective of the adhesive use but neither pre-treatment affected the microtensile bond strength.

The effect of ultrafast fiber laser application on the bond strength of resin cement to titanium

The purpose of this study was to investigate the effect of ultrafast fiber laser treatment on the bond strength between titanium and resin cement. A total of 60 pure titanium discs (15 mm × 2 mm) were divided into six test groups (n = 10) according to the surface treatment used: group (1) control, machining; group (2) grinding with a diamond bur; group (3) ultrafast fiber laser application; group (4) resorbable blast media (RBM) application; group (5) electro-erosion with copper; and group (6) sandblasting. After surface treatments, resin cements were applied to the treated titanium surfaces. Shear bond strength testing of the samples was performed with a universal testing machine after storing in distilled water at 37 °C for 24 h. One-way ANOVA and Tukey's HSD post hoc test were used to analyse the data (P < 0.05). The highest bond strength values were observed in the laser application group, while the lowest values were observed in the grinding group. Sandblasting and laser application resulted in significantly higher bond strengths than control treatment (P < 0.05). Ultrafast fiber laser treatment and sandblasting may improve the bond strength between resin cement and titanium.

Characterisation and microleakage of a new hydrophilic fissure sealant - UltraSeal XT® hydro™

Objectives

The aim of this study was to characterise the new hydrophilic fissure sealant, UltraSeal XT^® hydro™ (Ultradent Products, USA), and to investigate its in vitro resistance to microleakage after placement on conventionally acid etched and sequentially lased and acid etched molars.

Material and Methods

The sealant was characterised by Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Vickers indentation test. Occlusal surfaces of extracted human molars were either conventionally acid etched (n=10), or sequentially acid etched and laser irradiated (n=10). UltraSeal XT^® hydro™ was applied to both groups of teeth which were then subjected to 2,500 thermocycles between 5 and 55°C prior to microleakage assessment by fuchsin dye penetration.

Results

UltraSeal XT^® hydro™ is an acrylate-based sealant that achieved a degree of conversion of 50.6±2.2% and a Vickers microhardness of 24.2±1.5 under standard light curing (1,000 mWcm^-2 for 20 s). Fluoride ion release is negligible within a 14-day period. SEM and EDX analyses indicated that the sealant comprises irregular submicron and nano-sized silicon-, barium-, and aluminium-bearing filler phases embedded in a ductile matrix. Laser preconditioning was found to significantly reduce microleakage (Mann-Whitney U test, p<0.001). The lased teeth presented enhanced surface roughness on a 50 to 100 μm scale that caused the segregation and concentration of the filler particles at the enamel-sealant interface.

Conclusion

Laser preconditioning significantly decreased microleakage and increased enamel surface roughness, which caused zoning of the filler particles at the enamel-sealant interface.

The impact of Er:YAG laser enamel conditioning on the microleakage of a new hydrophilic sealant--UltraSeal XT hydro

UltraSeal XT® hydro™ is a new hydrophilic, light-cured, methacrylate-based pit and fissure sealant which has been developed by Ultradent Products, USA. The sealant is highly filled with a 53 wt.% mixture of inorganic particles which confer both thixotropy and radiopacity. The principal purpose of this study was to investigate the microleakage of UltraSeal XT® hydro™ as a function of different enamel etching techniques. The occlusal surfaces of sound, extracted human molars were either acid etched, Er:YAG laser irradiated or successively laser irradiated and acid etched. UltraSeal XT® hydro™ was applied to each group of teeth (n = 10) which were subjected to a thermocycling process consisting of 2500 cycles between 5 and 50 °C with a dwell time of 30 s. Microleakage assessments were then carried out using 0.5 % fuchsin dye and optical microscopy. The microleakage score data were analysed using the Kruskal-Wallis, Mann–Whitney U test with Bonferroni adjustment. No significant differences in microleakage were noted between the individually acid etched and laser-irradiated groups (p > 0.05); however, teeth treated with a combination of laser irradiation and acid etching demonstrated significantly lower microleakage scores (p < 0.001). Electron microscopy with energy-dispersive X-ray analysis revealed that the mineral filler component of UltraSeal XT® hydro™ essentially comprises micrometre-sized particles of inorganic silicon-, aluminium- and barium-bearing phases. Laser etching increases the roughness of the enamel surface which causes a concentrated zoning of the filler particles at the enamel-sealant interface.

Effect of Er,Cr:YSGG Laser at Different Output Powers on the Micromorphology and the Bond Property of Non-Carious Sclerotic Dentin to Resin Composites

BACKGROUND

The objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites.

METHODS

Two hundred bovine incisors characterized by non-carious sclerotic dentin were selected, and the seventy-two teeth of which for surface morphological analysis were divided into nine groups according to various treatments (A: the control group, B: only treated with the adhesive Adper Easy One, C: diamond bur polishing followed by Adper Easy One, D-I: Er,Cr:YSGG laser irradiating at 1W, 2W, 3W, 4W, 5W, 6W output power, respectively, followed by Adper Easy One). The surface roughness values were measured by the non-contact three-dimensional morphology scanner, then the surface micromorphologies of surfaces in all groups were assessed by scanning electron microscopy (SEM); meanwhile, Image Pro-Plus 6.0 software was used to measure the relative percentage of open tubules on SEM images. The rest, one hundred twenty-eight teeth for bond strength test, were divided into eight groups according to the different treatments (A: only treated with the adhesive Adper Easy One, B: diamond bur polishing followed by the above adhesive, C-H: Er,Cr:YSGG laser irradiating at 1 W, 2 W, 3 W, 4 W, 5 W, 6 W output power, respectively, followed by the above adhesive), and each group was subsequently divided into two subgroups according to whether aging is performed (immediately tested and after thermocycling). Micro-shear bond strength test was used to evaluate the bond strength.

RESULTS

The 4W laser group showed the highest roughness value (30.84±1.93μm), which was statistically higher than the control group and the diamond bur groups (p<0.05). The mean percentages ((27.8±1.8)%, (28.0±2.2)%, (30.0±1.9)%) of open tubules area in the 4W, 5W, 6W group were higher than other groups (p<0.05). The 4W laser group showed the highest micro-shear bond strength not only in immediately tested (17.60±2.55 PMa) but after thermocycling (14.35±2.08MPa).

CONCLUSION

The Er,Cr:YSGG laser at 4W power can effectively improve the bonding property between non-carious sclerotic dentin and resin composites by increasing the roughness and mean percentage area of open tubules.

Influence of cavity preparation with Er,Cr:YSGG laser and restorative materials on in situ secondary caries development

OBJECTIVE

The aim of this study was to evaluate the influence of cavity preparation and restorative materials containing fluorides in the prevention of secondary caries lesion development in situ.

METHODS

A total of 120 blocks obtained from human teeth were divided into two groups and standardized cavities were prepared using diamond burs (DB) or Er,Cr:YSGG-laser [20 Hz, 4.0W, 55% water, 65% air (LA)]. They were divided into three subgroups according to the restorative material (n=20): glass-ionomer cement (GI), resin modified glass-ionomer (RM) or composite resin (CR). Blocks were fixed in palatal intra-oral appliances worn in situ by 20 human volunteers, who dropped 20% sucrose solution eight times daily. After 21 days, blocks were removed and restorations were cross-sectioned to evaluate microhardness [Knoop hardness number (KHN)] underneath enamel surface from 30 to 200 μm. Factors "cavity preparation," "restorative materials," and "depth" were evaluated by three way ANOVA, followed by Tukey test (p<0.05).

RESULTS

The results showed lower microhardness in cavities prepared with DB than in cavities prepared with LA. At 30 μm, there were no statistical significant differences with regard to "cavity preparation" or "restorative materials" factors. In depth evaluation, the enamel microhardness progressively increased as a function of depth for the GI groups. In the groups prepared with LA at 60 μm/90 μm, there were no significant differences between GI and RM materials, whose microhardnesses were significantly higher than that of CR.

CONCLUSIONS

Cavity preparation using Er,Cr:YSGG laser increases caries resistance of enamel walls, and reduce caries lesion depth development regardless of fluoride presence in the restorative material. CR showed higher caries lesion development than GI, and RM showed intermediate results.

Enamel pretreatment with Er:YAG laser: effects on the microleakage of fissure sealant in fluorosed teeth

Objectives

The purpose of this in vitro study was to evaluate the microleakage and penetration of fissure sealant in permanent molar teeth with fluorosis after pretreatment of the occlusal surface.

Materials and Methods

A total of 120 third molars with mild dental fluorosis were randomly divided into 6 groups (n = 20). The tooth surfaces were sealed with an unfilled resin fissure sealant (FS) material. The experimental groups included: 1) phosphoric acid etching (AE) + FS (control); 2) AE + One-Step Plus (OS, Bisco) + FS; 3) bur + AE + FS; 4) bur + AE + OS + FS; 5) Er:YAG laser + AE + FS; and 6) Er:YAG laser + AE + OS + FS. After thermocycling, the teeth were immersed in 0.5% fuchsin and sectioned. Proportions of mircoleakage (PM) and unfilled area (PUA) were measured by digital microscope.

Results

Overall, there were significant differences among all groups in the PM (p = 0.00). Group 3 showed the greatest PM, and was significantly different from groups 2 to 6 (p < 0.05). Group 6 showed the lowest PM. Pretreatment with Er:YAG with or without adhesive led to less PM than bur pretreatment. There were no significant differences among groups in PUA.

Conclusions

Conventional acid etching provided a similar degree of occlusal seal in teeth with fluorosis compared to those pretreated with a bur or Er:YAG laser. Pretreatment of pits and fissures with Er:YAG in teeth with fluorosis may be an alternative method before fissure sealant application.

The effect of an erbium, chromium: yttrium-scandium-gallium-garnet laser on the microleakage and bond strength of silorane and micro-hybrid composite restorations

Objective:

The aim of this in vitro study was to compare the microleakage and bond strength of Class V silorane-based and universal micro-hybrid composite restorations prepared either with diamond bur or with an erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr:YSGG) laser.

Materials and Methods:

A total of 160 molar teeth were used for microleakage assessment and shear bond strength (SBS) test. The specimens were prepared using either diamond bur or 3 W-, 4 W- and 5 W-20 Hz Er, Cr:YSGG laser irradiation. All specimens were subjected to thermocycling (500 times at 5 ± 2°C to 55 ± 2°C, dwell time 15 s and transfer time 10 s). Microleakage was assessed using a 0.5% basic-fuchsin solution. The bond strengths were determined using a microtensile tester at a crosshead speed of 0.5 mm/min. The Kruskal Wallis test was used for the analysis of microleakage and a one-way analysis of variance test was used to analyze the SBS (P < 0.05).

Results:

No statistically significant differences were found (P > 0.05) between Er, Cr:YSGG laser and bur preparation methods regarding microleakage and bond strength values.

Conclusion:

Irradiation with Er, Cr:YSGG laser was confirmed to be as effective as conventional methods for preparing cavities before adhesive restorations.

Self-etch bonding agent beneath sealant: Bond strength for laser-irradiated enamel

OBJECTIVES

This study evaluated the in vitro shear bond strength (SBS) of a resin-based pit-and-fissure sealant (Fluroshield [F], Dentsply/Caulk) associated with either an etch-and-rinse (Adper Single Bond 2 [SB], 3M/ESPE) or a two-step self-etch adhesive system (Adper SE Plus [SE], 3M/ESPE) on Er: YAG laser-irradiated enamel.

MATERIALS AND METHODS

Seventeen sound third molar crowns were embedded in acrylic resin, and the mesial-distal enamel surfaces were flattened. The enamel sites were irradiated with a 2.94-μm wavelength Er: YAG laser (120 mJ, 4 Hz, noncontact mode/17 mm, 20 s). The specimens were randomly assigned to three groups according to the bonding technique: I - 37% phosphoric acid etching + SB + F; II - SE + F and III - F applied to acid-etched enamel, without an intermediate layer of bonding agent. In all of the groups, a 3-mm diameter enamel-bonding site was demarcated and the sealant cylinders were bonded. After 24 hours in distilled water, the shear bond strength was tested at a crosshead speed of 0.5 mm/minute. The data were analyzed by one-way ANOVA and Tukey's test. The debonded specimens were examined with a stereomicroscope to assess the failure modes.

RESULTS

The mean SBS values in MPa were I = 6.39 (±1.44); II = 9.50 (±2.79); and III = 5.26 (±1.82). No statistically significant differences were observed between groups I and III; SE/F presented a significantly higher SBS than that of the other groups (P = 0.001). With regard to the failure mode, groups I (65%) and II (75%) presented adhesive failures, while group III showed 50% adhesive failure. Cohesive failure did not occur.

CONCLUSION

The application of the two-step self-etch bonding agent (Adper SE Plus) beneath the resin pit-and-fissure sealant placement resulted in a significantly higher bond strength for the Er:YAG laser-irradiated enamel.

Peel strength of denture liner to PMMA and polyamide: laser versus air-abrasion

PURPOSE

This study investigated the effect of laser parameters and air-abrasion on the peel strength of silicon-based soft denture liner to different denture resins.

MATERIALS AND METHODS

Specimens (N=180) were prepared out of three different denture base resins (Rodex, cross-linked denture base acrylic resin; Paladent, heat-cured acrylic resin; Deflex, Polyamide resin) (75 mm × 25 mm × 3 mm). A silicon-based soft denture liner (Molloplast B) was applied to the denture resins after the following conditioning methods: a) Air-abrasion (50 µm), b) Er,Cr:YSGG laser (Waterlase MD Turbo, Biolase Technology) at 2 W-20 Hz, c) Er,Cr:YSGG laser at 2 W-30 Hz, d) Er,Cr:YSGG laser at 3 W-20 Hz, e) Er,Cr:YSGG laser at 3 W-30 Hz. Non-conditioned group acted as the control group. Peel test was performed in a universal testing machine. Failure modes were evaluated visually. Data were analyzed using two-way ANOVA and Tukey's test (α=.05).

RESULTS

Denture liner tested showed increased peel strength after laser treatment with different parameters (3.9±0.4 - 5.58±0.6 MPa) compared to the control (3.64±0.5 - 4.58±0.5 MPa) and air-abraded groups (3.1±0.6 - 4.46±0.3 MPa), but the results were not statistically significant except for Paladent, with the pretreatment of Er,Cr:YSGG laser at 3 W-20 Hz. Polyamide resin after air-abrasion showed significantly lower peel strength than those of other groups (3.1±0.6 MPa).

CONCLUSION

Heat-cured acrylic resin, PMMA, may benefit from Er,Cr:YSGG laser treatment at 3 W-20 Hz irradiation. Air-abrasion of polyamide resins should be avoided not to impair their peel bond strengths to silicon-based soft denture liners.

Evaluation of different types of enamel conditioning before application of a fissure sealant

The aim of the study was to compare fissure sealant quality after mechanical conditioning of erbium-doped yttrium aluminium garnet (Er:YAG) laser or air abrasion prior to chemical conditioning of phosphoric acid etching or of a self-etch adhesive. Twenty-five permanent molars were initially divided into three groups: control group (n = 5), phosphoric acid etching; test group 1 (n = 10), air abrasion; and test group 2, (n = 10) Er:YAG laser. After mechanical conditioning, the test group teeth were sectioned buccolingually and the occlusal surface of one half tooth (equal to one sample) was acid etched, while a self-etch adhesive was applied on the other half. The fissure system of each sample was sealed, thermo-cycled and immersed in 5% methylene dye for 24 h. Each sample was sectioned buccolingually, and one slice was analysed microscopically. Using specialized software microleakage, unfilled margin, sealant failure and unfilled area proportions were calculated. A nonparametric ANOVA model was applied to compare the Er:YAG treatment with that of air abrasion and the self-etch adhesive with phosphoric acid (α = 0.05). Test groups were compared to the control group using Wilcoxon rank sum tests (α = 0.05). The control group displayed significantly lower microleakage but higher unfilled area proportions than the Er:YAG laser + self-etch adhesive group and displayed significantly higher unfilled margin and unfilled area proportions than the air-abrasion + self-etch adhesive group. There was no statistically significant difference in the quality of sealants applied in fissures treated with either Er:YAG laser or air abrasion prior to phosphoric acid etching, nor in the quality of sealants applied in fissures treated with either self-etch adhesive or phosphoric acid following Er:YAG or air-abrasion treatment.