Effect of a Diode Laser (445 nm) on Polymerization Efficiency of a Preheated Resin Composite Used for Luting of Indirect Composite Restorations.

PURPOSE: The aim of this study was to evaluate the polymerization efficiency of a preheated resin composite used as a luting agent for indirect restorations light-cured by a blue diode laser (445 nm). METHODS: Bronze molds were used to prepare cylindrical specimens of a laboratory composite (Ceramage) with dimensions 2, 3, and 4 mm in height and 8 mm in diameter. The molds had additional height of 120 µm for the placement of the preheated resin composite. A nanohybrid resin composite (Enamel Plus HRi) was preheated at 55°C to use as a luting agent. Photopolymerization was followed for 20 seconds using three light sources: a diode laser emitting at 445 nm (SiroLaser Blue) and two light-emitting diode (LED) units (Bluephase Style and Valo). Degree of conversion (DC) of the preheated resin composite was evaluated using Fourier transform infrared spectroscopy. RESULTS: The results indicated that the main effects of the analysis were significant for both material thickness (p<0.001) and polymerization method (p<0.001). The preheated resin composite was not polymerized under 4-mm-thick specimens, independent of the light-curing unit. For 2-mm material thickness, there was no difference among the three light-curing units (p=0.383), while 3-mm Bluephase Style presented very low DC. CONCLUSIONS: Diode laser (445 nm) achieved better polymerization efficiency at the same fluence compared to the LED unit at 3-mm depth, implying a better mechanical behavior and potential improved adhesion of the luting material to dentin.

Elution of Monomers From CAD-CAM Materials and Conventional Resin Composite in Distilled Water and Artificial Saliva.

PURPOSE: The purpose of this study was to evaluate the leaching pattern of different types of polymer computer-aided design and computer-aided manufacturing (CAD-CAM) materials with a conventional resin composite. METHODS AND MATERIALS: Specimens of three representatives by type of polymer CAD-CAM blocks and one conventional resin composite were suspended using a silk thread in distilled water and artificial saliva. After one day, seven days, 14 days, 30 days, and 60 days, the analysis of the eluates for the detection of bisphenol A (BPA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA) and bisphenol A-glycidyl dimethacrylate (Bis-GMA) was quantified by utilizing high-performance liquid chromatography (HPLC). RESULTS: TEGDMA was the main eluted monomer for the polymer CAD-CAM materials for both solutions. However, there was a decreasing pattern throughout the tested period. On the contrary, there was a constant release of monomers from the conventional resin composite. Bisphenol-A was released only by the conventional resin composite and in both solutions chosen. CONCLUSIONS: Different types of polymer CAD-CAM materials release minimal or no monomers compared to the conventional resin composite material. The methods of fabrication of polymer CAD-CAM materials produces better properties than the conventional resin composite with a dramatic decrease of monomer elution.

Evaluation of Monomer Elution and Surface Roughness of a Polymer-Infiltrated Ceramic Network CAD-CAM Material After Er,Cr:YSGG Laser-assisted Tooth Bleaching.

PURPOSE: The aim of this in vitro study was to examine the effect of Er,Cr:YSGG laser-assisted tooth bleaching treatment on the elution of monomers and surface roughness of a hybrid computer-aided design-computer-aided manufacturing (CAD-CAM) material, and to compare it with a resin composite for direct restorations. METHODS AND MATERIALS: Forty specimens of a hybrid CAD-CAM material (Enamic) and forty of a conventional resin composite (Tetric) were fabricated and randomly divided into four groups (n=10). Half of the specimens of each material were stored in distilled water and the other half in artificial saliva for 7 days. At the end of this period, the storage medium was analyzed by high-performance liquid chromatography (HPLC), and the surface roughness parameters of the specimens were evaluated by optical imaging noncontact interferometric profilometry. Afterwards, half of the specimens of each tested material received a conventional in-office tooth bleaching treatment and the other half an Er,Cr:YSGG laser-assisted bleaching treatment, and then they were again incubated in distilled water and artificial saliva for an additional 7-day time period. At the end of this period, the effect of the bleaching treatments on elution of monomers and surface roughness of the tested materials was evaluated. RESULTS: Bisphenol A (BPA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), and bisphenol A-glycidyl dimethacrylate (BisGMA) were eluted from the conventional resin composite into both the solutions tested. Only TEGDMA was eluted from the hybrid CAD-CAM material. However, no statistically significant differences were found among the surface roughness parameters of both materials. Both the conventional and Er,Cr:YSGG laser-assisted tooth bleaching treatments affected the monomer elution from the composite resin. However, there were no statistically significant differences (p<0.05) between the treatments. CONCLUSIONS: According to the results of this study, tooth bleaching with Er,Cr:YSGG laser or conventional technique is safe, even if the bleaching agent comes in contact with hybrid CAD-CAM restorations.

Structural Integrity Evaluation of Large MOD Restorations Fabricated With a Bulk-Fill and a CAD/CAM Resin Composite Material.

AIMS: To evaluate the effect of two composite restorative techniques (direct bulk fill vs indirect CAD/CAM) on the fracture resistance and mode of fracture of extended mesio-occlusal-distal (MOD) cavity preparations. METHODS: Fifty-one sound human mandibular third molars were divided into three groups (n=17). Extended bucco-lingual MOD cavities were prepared. Teeth in group 1 were restored with a bulk-fill resin composite (Filtek Bulk-Fill Posterior Restorative), teeth in group 2 were restored with composite computer-aided design/computer-aided manufacturing (CAD/CAM) inlays (Lava Ultimate), and teeth in group 3 served as control and remained intact. All specimens were submitted to thermocycling, and a fracture resistance test was performed using a Universal testing machine (0.5 mm/min). Mode of fracture was classified into five types. One-way analysis of variance and the Duncan test were used to analyze the fracture load data at a significance level of α = 0.05. A chi-square test was used for the analysis of fracture mode between the restorative groups. RESULTS: Statistical analysis showed significant differences in fracture resistance among the experimental groups. The teeth restored with the bulk-fill composite exhibited lower fracture resistance (1285.3±655.0 N) when compared to the teeth restored with the composite CAD/CAM inlays (1869.8±529.4 N) (p<0.05). Mode of fracture showed the same distribution between the restorative groups. CONCLUSIONS: Although both types of restorations failed at loads larger than those found in the oral cavity, the CAD/CAM composite inlays increased the fracture resistance of teeth with large MOD cavities when compared to direct bulk-fill composite restorations. The majority of fracture types were intraorally repairable for both restorative techniques.

Clinical evaluation of a surface pre-reacted glass (S-PRG) filler-containing dental sealant placed with a self-etching primer/adhesive.

AIMS: To clinically evaluate the retention rates and caries-prevention effect of a resin-based, non-etch and rinse, self-etch primed pit and fissure sealant containing Sealant Pre-reacted Glass Ionomer Cement (S-PRG) fillers, in comparison to a conventional resin-based sealant over an 18-month period. METHODS: There were 81 children, aged 6-12 years old, who were randomly assigned to one of two sealant-groups, either the self-etch primed sealant (Beautisealant, Shofu) or the conventional etch and rinse sealant (Seal it, Spident). A total of 218 sealants of both groups were placed on first permanent molars with either sound surfaces (The International Caries Detection and Assessment System [ICDAS], code 0) or incipient enamel caries lesions (ICDAS code 1) according to the manufacturers' instructions. Each sealant restoration was independently evaluated in terms of retention and caries status at 6, 12 and 18 months. The data were statistically analysed with the Chi-squared test and z-test and the level of significance was preset at α = 0.05. RESULTS: The differences between the complete retention rates of the two sealant groups were statistically significant in all periods of evaluation (p < 0.01). Survival rates of each sealant-group were comparable on sound (ICDAS 0) and enamel caries lesions (ICDAS1). Caries prevention effect of the two sealant groups was similar at the end of the evaluation period. CONCLUSIONS: The clinical performance of the S-PRG filler-containing dental sealant placed with a self-etching primer was poor regarding its retention. Its significantly higher loss did not lead to more carious occlusal surfaces at the 18-month recall.

Comparative evaluation of microleakage of a carbomer/fluoroapatite-enhanced glass-ionomer cement on primary teeth restorations.

AIM: Carbomer cement represents a novel glass-ionomer which gradually mineralises into fluoroapatite. Purpose of this study was to evaluate microleakage around restorations in deciduous teeth made with composite resin, conventional glass-ionomer cement, resin-modified glass-ionomer cement and carbomer/fluoroapatite-enhanced glass-ionomer cement. MATERIALS AND METHODS: A group of 40 primary upper canines, primary upper and lower molars was divided into 4 groups (n=10). Class I cavities were prepared by diamond cylindrical bur at high speed and were restored with a composite resin (Group 1), with a glass- ionomer cement (Group 2), with a resin-modified glass-ionomer cement (Group 3) and with a carbomer/fluoroapatite-enhanced glass- ionomer cement (Group 4). Hard tissue's bonding involved, in the case of composite resin a total etch bonding procedure, and in glass ionomers the use of their respective primers. Restorations were finished and polished. A 24-hour water storage was followed by thermocycling (1500 cycles, 5°C - 36°C - 55°C - 36°C with a dwell time of 15 seconds) and dye penetration test with immersion in 5% methylene blue for 24 hours. In order to assess the degree of microleakage longitudinal cuts were produced by means of a microtome at 0.5 mm and at 1 mm from the restoration margin, and photographs were taken with a stereomicroscope at 100X. Microleakage was classified according to the number of surfaces and the depth at which dye penetration was observed. Data were analysed with ANOVA and post-hoc analysis was performed with Bonferonni test (p<0.05). RESULTS: Statistical analysis exhibited no significant statistical difference between Group 2 and Group 3 (p>0.05). Statistical difference was exhibited between Group 3 and Group 4 (p<0.01), with Group 4 exhibiting lower microleakage values. Group 1 exhibited the lowest mean microleakage values and statistical difference in comparison with all groups (p<0.001). Group 4 exhibited the lowest microleakage values among the cements. CONCLUSION: Superior marginal integrity is achieved in restored primary teeth when composite resin is used. If the clinical case suggests the use of a glass-ionomer cement, carbomer/fluoroapatite-enhanced glass-ionomer cement is prefered in terms of microleakage.

Fluoride release and recharging ability of new dental sealants.

AIM: This in vitro investigation was to evaluate the fluoride release and recharge abilities of three recently introduced dental fissure sealants (FS). METHODS: Three dental FS were assessed: Teethmate F-1 (Kuraray), Fissurit F (Voco), BeautiSealant (Shofu), and a conventional glass ionomer cement FX-II (Shofu) as a control. Eight cylindrical specimens (7 × 2 mm) of each material were made and immersed individually in 5 ml de-ionized water in plastic containers. Fluoride release of the tested materials was evaluated during the experimental period (28 days) utilising a fluoride ion-selective electrode. At the end of the test period, the specimens were soaked for 5 min in a fluoride solution (0.05 % NaF) and fluoride release was evaluated for the next 5 days. The data were statistically analysed using one-way ANOVA and Bonferroni post hoc test and the level of significance was preset at α = 0.05. RESULTS: The total fluoride release over the 28-day period for each material was: FX-II (408.6 ± 45.66 µg/cm(2)) > Teethmate F-1 (89.45 ± 12.32 µg/cm(2)) > Fissurit F (68.62 ± 8.72 µg/cm(2)) > BeautiSealant (33.32 ± 4.91 µg/cm(2)), (p < 0.05). After the re-fluoridation of the specimens with 0.05 % NaF solution the cumulative fluoride re-release during the 5-day period for each material was: FX-II (99.53 ± 13.21 µg/cm(2)) > Teethmate F-1 (9.76 ± 1.62 µg/cm(2)) > BeautiSealant (5.69 ± 0.89 µg/cm(2)) > Fissurit F (4.76 ± 0.72 µg/cm(2)), (p < 0.05). CONCLUSIONS: The three tested sealants exhibited different capabilities to release and uptake fluoride ions after re-fluoridation but significantly lower than the glass ionomer tested.

Intra-pulpal temperature rise of different tooth types during dental bleaching supported by an Er,Cr:YSGG laser. A pilot study.

The purpose of this pilot in vitro study was to evaluate the temperature increase in the pulp chamber of the teeth, during Er,Cr:YSGG bleaching, as well as to show which teeth are the most susceptible in terms of pulp temperature increase during laser-activated bleaching treatment. Although Er:YAG studies have been published on this subject, it is the first time Er,Cr:YSGG wavelength is tested. Fifteen teeth were tested--3 each of the following--(maxillary central incisors, lateral incisors, canines, premolars and mandibular incisors). The bleaching procedure comprised an Er,Cr:YSGG laser (2780 nm, Waterlase MD, Biolase, USA) and a yellow-coloured bleaching agent with a concentration of 38 % H2O2 (Power whitening, WHITEsmile GmbH, Germany). The tip used was a 6-mm long Z-type glass tip (MZ8) of a 800 µm diameter. Average output power was set to 1.25 W, pulse duration 700 µs (S-mode), whilst the pulse repetition rate was 10 Hz. The results showed that the most susceptible teeth in terms of pulp temperature increase were the lateral maxillary incisors and the mandibular incisors. The mean temperature increase on these teeth was 1.06 and 1.00 °C, respectively, on 60 s Er,Cr:YSGG-supported bleaching.

Viscoelastic properties, creep behavior and degree of conversion of bulk fill composite resins.

OBJECTIVES: The aim of this study was to investigate the viscoelastic properties and creep behavior of bulk fill composites under different conditions and evaluate their degree of conversion. METHODS: Seven bulk fill composites were examined: everX Posterior (EV), SDR (SD), SonicFill (SF), Tetric EvoCeram Bulk Fill (TE), Venus Bulk Fill (VE), x-tra base (XB) and x-tra fil (XF). Each material was tested at 21°C, 37°C and 50°C under dry and wet conditions by applying a constant torque for static and creep testing and dynamic torsional loading for dynamic testing. Degree of conversion (%DC) was measured on the top and bottom surfaces of composites with ATR-FTIR spectroscopy. Statistical analysis was performed with two-way ANOVA, Bonferroni's post hoc test and Pearson's correlation coefficient. RESULTS: Shear modulus G ranged from 2.17GPa (VE) to 8.03GPa (XF) and flexural modulus E from 6.16GPa (VE) to 23GPa (XF) when the materials were tested dry at 21°C. The increase of temperature and the presence of water lead to a decline of these properties. Flowable materials used as base composites in restorations showed significantly lower values (p<0.05) than non-base composites, while being more prone to creep deformation. %DC ranged from 47.25% (XF) to 66.67% (SD) at the top material surface and 36.06% (XF) to 63.20% (SD) at the bottom. SIGNIFICANCE: Bulk fill composites exhibited significant differences between them with base flowable materials showing in most cases inferior mechanical properties and higher degree of conversion than restorative bulk fill materials.

Comparison of elastomeric impression materials' thixotropic behavior.

The improved flow characteristics of new elastomeric impression materials are significant factors in the selection ofsuitableproductsfor clinical applications. The aim of this study was to assess the thixotropic behavior and compare the flow characteristics of seven different elastomeric impression materials using a shark fin test. One polyvinylsiloxane showed the highest shark fin height values, while the newly formed vinylsiloxanether material exhibited no significant differences when compared with two polyvinylsiloxanes. One of the five polyvinylosiloxanes presented significantly lower shark fin values than all other materials. It was concluded that flow characteristics for most of the tested materials are acceptable.

Mechanical viscoelastic behavior of dental adhesives.

OBJECTIVES: The purpose of the study was to evaluate the mechanical properties of dental adhesive materials at different testing temperatures after dry and wet storage. METHODS: Specimens (d=1 mm, l=18 mm) from six materials were tested: Silorane Adhesive System (SL), Heliobond (HE), One-Step Plus (OS), Optibond Solo Plus (OP), cmf Adhesive System (CF) and Protobond (PR). Static and creep testing was performed by applying a constant torque below the proportional limit of the materials, while dynamic testing consisted of dynamic torsional loading. Experiments were performed after 24h of dry and wet storage under temperatures from 21°C to 50°C and various viscoelastic parameters were calculated. RESULTS: Shear modulus ranged from 0.19 to 1.99 GPa, while flexural modulus from 0.67 to 5.69 GPa. Most of the materials were affected by the presence of water and increase of temperature. OP showed the highest recovery after creep, while SL exhibited the highest permanent deformation. SIGNIFICANCE: Contact with water after polymerization and increase of temperature resulted in a decline of the mechanical properties, especially for the HEMA-containing adhesives.

Dynamic and static mechanical analysis of resin luting cements.

Various types of indirect restorations are available for dental treatment and resin cements are commonly used as a luting medium. The aim of this study was to evaluate the mechanical properties of contemporary resin luting agents under different testing conditions and temperatures. The materials tested were Choice 2 (CH), Clearfil Esthetic Cement (EC), Resicem (RC) and RelyX Unicem (RX). Each material was examined after 24 h of storage at 21 °C dry and wet at 21, 37 and 50 °C under dynamic and static testing and parameters such as shear and flexural modulus, loss tangent, dynamic viscosity and Poisson's ratio were calculated. The resin cements were also subjected to creep testing under different constant loads for 3 h and a recovery time of 50 h. The material with the highest modulus was CH, while RX had the lowest. All resin cements were affected by the presence of water with RX being the least affected and by the increase of temperature, with RC being the least susceptible. None of the materials exhibited full recovery after creep testing and permanent deformation ranged from 0.43% to 5.53%. The resin cements tested in this study showed no major transitions under the different testing conditions. Their behavior was satisfactory for restorations that do not require increased mechanical properties. However, in the case of stress-bearing restorations the conditions in the oral cavity may affect the performance of these materials.

Inhibition of demineralization in vitro around fluoride releasing materials.

Replacement of restorations because of secondary caries is a continuing problem in restorative dentistry. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in buccal and lingual surfaces of 30 extracted premolars and restored with one of three polyacid modified resin composites (F-2000, Hytac and Compoglass F), a resin modified glass-ionomer cement (Fuji II LC) a conventional glass ionomer (Ketac-Fil), and a resin composite (Z-100). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that restoration of caries with polyacid modified resin composites and resin modified glass ionomer cements may be of great importance in the prevention of secondary caries around the restorations in roots. Clinical Relevance Light cured fluoride-releasing restorations may inhibit caries-like lesions. Inhibition of demineralization in vitro around fluoride releasing materials.

The effect of home-use fluoride gels on glass-ionomer, compomer and composite resin restorations.

The purpose of this study was to investigate the resistance to dissolution by two home-use fluoride gels on the surface integrity of glass-ionomer, resin modified glass-ionomer, compomer and composite resin restorations. Class V cavities prepared in extracted teeth were restored with a glass-ionomer (Fuji II), a resin modified glass-ionomer (Vitremenr), two compomers (Dyract and F-2000) and a composite resin (Z-100). Groups of five specimens of each material were treated for 24 h with one of the following: (i). distilled water, (ii). neutral fluoride gel and (iii). acidulated phosphate fluoride (APF) gel. Surface degradation of the restorations was studied using standard electron microscopy (SEM), rated according to specific criteria and statistically analysed by the Wilcoxon test (rank sums). Acidulated phosphate fluoride was found to have a significant effect on all examined materials, while minimal effects resulted from the neutral fluoride gel compared with the control group. The effect of home-use fluoride gels on glass-ionomer, compomer and composite resin restorations.

Development of a computer-assisted learning software package on dental traumatology.

The development of computer-assisted learning software packages is a relatively new field of computer application. The progress made in personal computer technology toward more user-friendly operating systems has stimulated the academic community to develop computer-assisted learning for pre- and postgraduate students. The ability of computers to combine audio and visual data in an interactive form provides a powerful educational tool. The purpose of this study was to develop and evaluate a computer-assisted learning package on dental traumatology. This program contains background information on the diagnosis, classification, and management of dental injuries in both the permanent and the deciduous dentitions. It is structured into chapters according to the nature of the injury and whether injury has occurred in the primary or permanent dentition. At the end of each chapter there is a self-assessment questionnaire as well as references to relevant literature. Extensive use of pictures and video provides a comprehensive overview of the subject.

Effect of a resin-modified glass ionomer liner on volumetric polymerization shrinkage of various composites.

OBJECTIVE: The aim of this study was to evaluate the volumetric polymerization shrinkage of a selection of composite resins alone, and in contact with a resin-modified glass ionomer (RMGI) liner. METHODS: Volumetric polymerization shrinkage was measured for five different composite resins by means of the Watts and Cash deflecting disk method. Shrinkage measurements were determined for 300 s for each composite alone, and when placed over pre-cured RMGI liner. Each sample was placed within a brass ring fixed to a glass microscope slide. A linear vertical displacement transducer (LVDT) was brought into contact with a flexible glass coverslip placed over the composite sample. On curing, the contraction of the setting composite sample caused distortion of the coverslip, the resulting deflection being recorded via the LVDT by means of data-logging software. All RMGI samples were prepared at 85% relative humidity (RH) and 35 degrees C. In all cases the composite was light-cured at ambient RH and 35 degrees C. RESULTS: Analysis of the data demonstrated statistically significantly less shrinkage for each composite when cured in contact with the set RMGI liner than when cured alone, at p < 0.001. SIGNIFICANCE: Use of an RMGI liner was found to significantly reduce volumetric polymerization contraction for all the light-curing composite resin restorative materials tested.

Degree of microleakage of some pit and fissure sealants: an in vitro study.

The purpose of this study was to evaluate and compare the degree of microleakage exhibited by five resin sealants (Concise, Helioseal, Durafil. Fissurit, Sci-Pharm) and a glass-ionomer sealant (Fuji Glass lonomer Type III). The fissure systems of the occlusal surfaces of freshly extracted teeth were opened using a pear-shaped bur; the preparations were confined to enamel. For each material, 14 teeth were prepared. From each group, seven teeth were thermocycled through 5 degrees, 37 degrees, 60 degrees and 37 degrees for 2000 cycles, and the other seven teeth were not thermocycled. All teeth were immersed in 0.5% solution of basic fuchsin dye for 48 hours. Each tooth was sectioned longitudinally in the buccolingual direction and three 1 mm-thick sections (distal, central and proximal) were obtained from each tooth. Each section was cleaned, examined, and photographed in a stereomicroscope. All the materials presented microleakage in both the thermocycled and non-thermocycled specimens; the degree of microleakage was greater in the thermocycled specimens. The results support the practice of opening up questionably carious fissures and removing caries (if present) before sealing.

Standards of orthodontic treatment in cases treated by undergraduate students at Bristol Dental Hospital from 1982 to 1992.

Recent changes in the teaching of orthodontics to undergraduates and postgraduates at Bristol Dental School led us to examine treatment results achieved by undergraduates over a 10-year period. In a sample of 225 orthodontic cases (mean pre-treatment age 12.5 years) which presented for the final BDS examination there was good evidence that students were achieving acceptable treatment results before 1988. The mean percentage reduction of PAR scores for the period 1982-1987 was 64%. In contrast, in the more recent period 1988-1992, the mean percentage reduction of the PAR scores achieved by the students was 47%. This statistically significant reduction appeared to correlate with changes in teaching staffing levels since other factors such as age, type of malocclusion, appliance type or initial PAR scores were not significantly different in any of the years examined.