Evaluation of the information provided in the instruction manuals of dental light-curing units.

OBJECTIVE: This study evaluated the completeness and accuracy of information in LCU instruction manuals from 40 manufacturers. MATERIALS AND METHODS: Instruction manuals from 40 LCUs (20 from leading manufacturers and 20 budget units) were reviewed. Twenty-eight parameters across five categories were assessed using a binary scale (0=incorrect/missing, 1=correct). The categories and their respective evaluation scores were: LCU characteristics (43%), instructions for use (7%), safety precautions (14%), maintenance recommendations (29%), and regulatory certification (7%). These scores were combined to produce a final score. RESULTS: Scores from leading manufacturers ranged between 46-86%, while the budget category ranged from 18-68%. All manuals provided information about the wavelength/spectrum of the LCU. Only Valo X and Valo Cordless reported power values and used the term "irradiance" instead of "intensity." Details such as LED type and active tip emission area were often missing. Instructions on how to use the LCU to photo-cure resins were frequently limited. Although most manuals addressed safety precautions, several lacked details on heat issues and general health precautions. All manuals included maintenance instructions, though information on replacement parts was often missing. Among the LCUs, 85% stated they were CE certified, 32% held both FDA and CE certification, and 63% claimed compliance with ISO and/or IEC standards. CONCLUSIONS: There were notable differences in the completeness and accuracy of the instruction manuals. Manuals from major manufacturers generally provided more comprehensive information than their budget counterparts. CLINICAL SIGNIFICANCE: Instruction manuals should contain accurate information to help clinicians deliver the highest standard of care. The lack of important information about the LCUs in the manuals is concerning.

Gloss Retention on Enamel and Resin Composite Surfaces After Brushing Teeth with Commercial and Modified Dentifrices.

OBJECTIVES: We examined the surface gloss and roughness of a dental composite and human enamel after brushing with a new bioactive glass (BCF201) additive designed to treat dentine hypersensitivity. METHODS: We prepared 2 cohorts of samples: a resin-based composite (RBC) and human enamel. Each cohort received 20 000 brushing cycles with Colgate Optic White Enamel (Colgate Optic), Sensodyne Whitening Repair and Protect (Sensodyne), Colgate Enamel Health Sensitivity Relief (Colgate-EN) with and without BCF201 added or Germiphene Gel 7 HT (Gel 7) with and without BCF201 added. The average gloss and roughness of the enamel and RBC surfaces were measured before brushing and after 20 000 back-and-forth brushing cycles. A linear regression function was applied to the gloss results, and the data were analyzed using ANOVA and a Tukey post-hoc test (α = 0.05). RESULTS: After 20 000 brushing cycles, the control (Gel 7) had no significant effect on the gloss or roughness of the RBC. However, the choice of dentifrice had a significant effect on both gloss and roughness (p < 0.001). With respect to RBC, after brushing, surface roughness was ranked from smoothest to roughest: Gel 7 = Gel 7 plus BCF201 > Colgate-EN plus BCF201 = Colgate Optic = Colgate-EN > Sensodyne. With respect to enamel, the smoothest to the roughest surfaces after brushing were: Gel 7 plus BCF201 = Sensodyne = Colgate-EN plus BCF201 > Gel 7 = Colgate Optic = Colgate-EN. CONCLUSION: The bioactive glass additive had no adverse effect on the surface roughness or gloss of human enamel or RBC. SIGNIFICANCE: The addition of BCF201 appears to have a polishing effect on RBC and enamel and reduced the abrasive effects of Colgate-EN on RBC and enamel.

Effect of repeated heating and cooling cycles on the degree of conversion and microhardness of four resin composites.

OBJECTIVE: This study evaluated the effect of repeatedly heating and cooling four resin-based composites (RBCs) for up to six cycles. MATERIALS AND METHODS: Four commercial RBCs were heated to 68°C and cooled to room temperature for up to six cycles before photocuring at 30°C. Specimens spent a total of 0, 30, 60, 90, 120, 150 min, or 7 days at 68°C. The degree of conversion (DC) was measured at the bottom of the specimens immediately after photocuring. The Vickers microhardness was measured at the top and bottom of the RBC surfaces 24 h after photocuring. The data were analyzed using one-way analysis of variance, Dunnett's or Bonferroni post-hoc tests, and Spearman correlation analysis (α = 0.05). RESULTS: For two brands of RBC, the DC decreased at various time points; however, these decreases were small, and there was no correlation (negative or positive) between the number of heating cycles and the DC for any of the RBCs. Repeated heated and cooling resulted in small changes in the hardness (compared to the control) in both directions (Dunnett; p < 0.05). Two of the RBCs showed a significant, positive correlation between the number of heating cycles and their hardness at the bottom surface. CONCLUSION: Repeated heating, cooling, and then reheating the RBCs for up to 1 week had little overall effect on their DC and microhardness values. The 2 mm thick specimens of all four RBCs achieved a bottom: top hardness ratio exceeding 0.8 after a 20 s exposure to light from a commercial LED curing light CLINICAL SIGNIFICANCE: Six repeated dry heating and cooling cycles of up to 1 week in duration had little effect on the DC and the microhardness of four commercial resin-based composites.

Effect of Resin Cement Mixing and Insertion Method into the Root Canal on Cement Porosity and Fiberglass Post Bond Strength.

PURPOSE: To evaluate the method of resin cement mixing and insertion into the root canal on resin cement porosity and fiberglass-post push-out bond strength (PBS). MATERIALS AND METHODS: One hundred twenty human single-rooted teeth were sectioned to a length of 15 mm, en-do-dontically filled, and received a fiberglass post cemented with 3 self-adhesive resin cements (RelyX U200, seT, Panavia SA) using 4 mixing methods/insertion techniques (handmix/endodontic file, handmix/Centrix syringe, automix/conventional tip, automix/endo tip). The samples were scanned using micro-CT. Two slices from the cervical, middle, and apical thirds were submitted to push-out bond strength (PBS) testing, and failure modes were classified. The PBS, volume of resin cement, and porosity data were analyzed using ANOVA and Tukey's test. RESULTS: The porosity was lowest in the cervical third and highest in the apical third, irrespective of the resin cement. The porosity was lower in the the automix/endo tip group compared to the handmix/endodontic file group. The use of Centrix or endo tip reduced the porosity and increased the PBS in the apical third compared with the use of endodontic files. The root canal depth reduced the PBS for U200 and seT when handmix/endodontic files were used. U200 and seT using the automix method increased the PBS, thus eliminating the effect of root region, irrespective of the insertion technique. In general, U200 showed higher PBS and Panavia lower PBS. Adhesive failure between root dentin and resin cement was predominant. CONCLUSIONS: Automixing the cement and using an endo tip produces fewer voids and increased the bond strengths.

Visible Light Curing Devices - Irradiance and Use in 302 German Dental Offices.

PURPOSE: To determine the irradiance delivered by visible-light curing (VLC) units and obtain information about the exposure times and the maintenance protocols used by dentists. MATERIALS AND METHODS: The irradiance (mW/cm2) delivered by 526 VLCs from 302 dental offices from the Rhine-Main area, Germany, was measured using an integrating sphere (IS) and a MARC patient simulator (M-PS); additional information was gathered using a survey. RESULTS: Irradiance was measured from 117 standard quartz-tungsten-halogen (QTH), 5 high-power QTH, 2 LED 1st-generation, 333 LED 2nd-generation, 61 LED 3rd-generation, and 8 plasma-arc curing (PAC) units. Depending on the measurement method, 8% (IS) or 11% (M-PS) of the VLCs delivered < 400 mW/cm2. Depending on the VLC, the shortest exposure times required to deliver a radiant exposure of 16 J/cm2 ranged from 7 to 294 s. The number of exposure cycles used by dentists when light curing a restoration ranged from 1 to 14. The shortest total exposure time used by dentists on a restoration was 5 s, the maximum was 200 s, and the median was 20 s. Of the 526 VLCs, 41% had intact, undamaged light tips. Only half of the dental offices checked the irradiance from their VLCs regularly, 97% disinfected the VLC, and 86% used eye protection. CONCLUSION: Approximately 10% of the VLCs delivered < 400 mW/cm2 and 14% of the dental offices used no form of eye protection. To achieve sufficient light curing of RBC restorations, more awareness about the VLCs used in the dental office is required.

Effect of mold type, diameter, and uncured composite removal method on depth of cure.

OBJECTIVE: This study compared the effects of mold material and diameter on the thickness of cured composite remnants and depth of cure (DOC) of resin-based composites (RBC). MATERIAL AND METHODS: One Polywave® curing light was used to photo-cure two shades of the same "bulk-fill" RBC in 4, 6, or 10-mm internal diameter metal or white Delrin® molds. For 60 specimens, the uncured RBC was manually scraped away as described in the ISO 4049 depth of cure test. The remaining 60 specimens were immersed in tetrahydrofuran for 48 hours in the dark. Maximum lengths of remaining hard RBC and their DOC values were compared using analysis of variance (ANOVA) and Tukey-Kramer post hoc multiple comparison tests (α = 0.05). RESULTS: Specimen thickness and DOC were always greater using the white Delrin® molds compared to metal molds (p < 0.001). Increase in mold diameter significantly increased specimen thickness and DOC when made in the metal molds and in the 6-mm diameter Delrin® molds (p < 0.01). Increasing the diameter of the Delrin® molds to 10-mm did not increase specimen thickness or DOC. Sectioning and staining of specimens revealed an internal, peripheral transition zone of porous RBC in the solvent-dissolved specimens only. CONCLUSION: Mold material and internal diameter significantly influenced cured composite remnant thickness as well as depth of cure. The existence of an outer region of RBC that is hard, yet susceptible to solvent dissolution, requires further investigation. CLINICAL RELEVANCE: The depth of cure results obtained from a 4-mm diameter metal mold may not represent the true potential for evaluating composite depth of cure. A universally acceptable mold material and diameter size need to be established if this type of testing is to be useful for evaluating the relative performance of a given type of LCU and RBC.

The dental curing light: A potential health risk.

Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition, many dental personnel use magnification loupes. This study measured the effect of magnification loupes on the "blue light hazard" when the light from a dental curing light was reflected off a human tooth. Loupes with 3.5x magnification (Design for Vision, Carl Zeiss, and Quality Aspirator) and 2.5x magnification (Design for Vision and Quality Aspirator) were placed at the entrance of an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A model with human teeth was placed 40 cm away and in line with this sphere. The light guide tip of a broad-spectrum Sapphire Plus (Den-Mat) curing light was positioned at a 45° angle from the facial surface of the central incisor. The spectral radiant power reflected from the teeth was recorded five times with the loupes over the entrance into the sphere. The maximum permissible cumulative exposure times in an 8-hr day were calculated using guidelines set by the ACGIH. It was concluded that at a 40 cm distance, the maximum permissible cumulative daily exposure time to light reflected from the tooth was approximately 11 min without loupes. The weighted blue irradiance values were significantly different for each brand of loupe (Fisher's PLSD p < 0.05) and were up to eight times greater at the pupil than when loupes were not used. However, since the linear dimensions of the resulting images would be 2.5 to 3.5x larger on the retina, the image area was increased by the square of the magnification and the effective blue light hazard was reduced compared to without the loupes. Thus, although using magnification loupes increased the irradiance received at the pupil, the maximum cumulative daily exposure time to reflected light was increased up to 28 min. Further studies are required to determine the ocular hazards of a focused stare when using magnification loupes and the effects of other curing lights used in the dental office.

Effect of exposure time on the polymerization of resin cement through ceramic.

PURPOSE: This study measured the effects of using three different exposure times to cure one resin cement through two types of ceramic. MATERIALS AND METHODS: One light-curing resin cement (Variolink II, Ivoclar Vivadent) was exposed for 20 s, 40 s, or 60 s with a BluePhase G2 light (Ivoclar Vivadent) on the high power setting through 1.0 mm of either ZirPress (ZR) or Empress Esthetic (EST) ceramic (Ivoclar Vivadent). The degree of conversion (DC) of the resin was measured 100 s after light exposure. The Knoop microhardness (KHN) was measured 5 min after light exposure and again after 24 h. The DC and KHN results were analyzed with ANOVA followed by Scheffe's post-hoc multiple comparison tests at α = 0.05. RESULTS: Increasing exposure time had a significant effect on the KHN and DC values for the resins exposed through both ceramics. As exposure times increased, the influence of the ceramic was reduced; however, the microhardness values were greater for the cement exposed through EST ceramic. When the exposure time was increased from 20 s to 40 s, microhardness values for the resin increased by 39.6% through the EST ceramic. When exposed for 60 s, there were no differences between the 100-s DC values or 5-min KHN values using either ceramic (p > 0.05). There was an excellent correlation between the DC at 100 s and the microhardness values measured at 5 min. CONCLUSION: Resin polymerization was greater through EST than ZR ceramic. At least 40 s to 60 s from the Blue- Phase G2 on high power mode is required to cure this resin cement through 1.0 mm of ceramic.

Thermography and conversion of fast-cure composite photocured with quad-wave and laser curing lights compared to a conventional curing light.

OBJECTIVES: This study investigated effects of the different emittance-mode protocols from three light curing units (LCUs): (i) a Laser (Monet); (ii) a quad-wave (PinkWave); (iii) a conventional LED (Elipar S10) on the temperature rise (ΔT) and degree of conversion (DC) when photo-curing fast or conventional bulk-fill resin-based composites (RBC). The aim was to correlate ΔT and DC, and the radiant exposure delivered to RBC specimens. METHODS: A 3D-printed resin mold of 4 mm depth was filled with two bulk-fill RBCs: Tetric PowerFill® (fast photo-polymerised composite) (TPF) or Tetric EvoCeram® Bulk-Fill (EVO). Three LCUs were used: (i) Monet laser for 1 s and 3 s (MONET-1 s, MONET-3 s); (ii) PinkWave quad-wave used for 3 s in Boost mode (PW-3 s) and for 20 s in standard mode (PW-20 s); (iii) Elipar S10 for 5 s (S10-5 s) and for 20 s in standard mode (S10-20 s). 2-dimensional temperature maps were obtained before, during and for 60 s after the LCU had turned off using a thermal imaging camera. Thermal changes were analysed at five depths: (0, 1, 2, 3, and 4 mm from the top surface of the RBC). The maximum temperature rise (Tmax) and the mean temperature rise (ΔT) were determined. Cylindrical-shaped specimens were prepared from each material using a stainless-steel split mold (4 × 4 mm) and light-cured with the same protocols. The DC was measured for 120 s and at 1 h after LCU had turned off using Fourier Transform Infrared Spectroscopy (FTIR). Data were analysed using Three-way ANOVA, One-way ANOVA, independent t-tests, and Tukey post-hoc tests (p < 0.05). RESULTS: Radiant exposures delivered by the various irradiation protocols were between 4.5-30.3 J/cm2. Short exposure times from MONET-1 s and PW-3 s delivered the lowest radiant exposures (4.5 and 5.2 J/cm2, respectively) and produced the lowest ΔT and DC. The longer exposure times in the standard modes of PW-20 s, S10-20 s, and MONET-3 s produced the highest Tmax, ΔT, and DC for both composites. The ΔT range among composites at different depths varied significantly (31.7-49.9 °C). DC of TPF ranged between 30-65% and in EVO between 15.3-56%. TPF had higher Tmax, ΔT for all depths and DC compared to EVO, across the LCU protocols (p < 0.05), except for PW-20 s and MONET-3 s. The coronal part of the restorations (1-2 mm) had the highest ΔT. There was a positive correlation between ΔT and DC at 4-mm depth after 120 s SIGNIFICANCE: Longer, or standard, exposure times of the LCUs delivered greater radiant exposures and had higher DC and ΔT compared to shorter or high-irradiance protocols. The fast photo-polymerised RBC had comparatively superior thermal and conversion outcomes when it received a high irradiance for a short time (1-5 s) compared to the conventional Bulk-Fill RBC.

Effects of single-peak vs polywave light-emitting diode curing lights on the polymerization of resin cement.

PURPOSE: This study examined the effect of selecting a single-peak blue vs a polywave blue/violet emission LED curing light on the degree of conversion (DC) and Knoop microhardness (KHN) of resin cements when light cured through a ceramic disk. MATERIALS AND METHODS: Two shades (A1 and A4) of resin cement (Variolink II) were placed in a 0.5-mm-thick ring. The top surfaces were covered with a Mylar strip and further covered with a disk of 1-mm-thick Empress Esthetic ceramic, shade A2. The specimens were light cured by means of an Elipar-S10 (3M ESPE, single-peak blue LED) or BluePhase-G2 (Ivoclar Vivadent, polywave blue/violet LED) curing light, both for 20 s, directly on the surface of an attenuated total reflectance FT-IR plate at 30°C. The DC of the resin was calculated after 100 s. The specimens were removed, and the Knoop microhardness was tested immediately and again after 24-h storage in the dark at 37°C and 100% humidity. Five specimens were made in each group. The DC and Knoop microhardness results were analyzed with ANOVA and Fisher's PLSD at α = 0.05. RESULTS: The choice of curing light had no significant effect on the DC and only a small effect on the immediate and 24-h KHN values. Shade A4 of the resin cement was harder and had a higher DC than shade A1. CONCLUSION: When light cured for 20 s, Variolink II resin cement can be light cured with either the single-peak or the polywave curing light. Shade A4 of the cement was slightly harder than A1.

Skill Retention of Light-Curing Technique Using Only Verbal Instructions versus Using an Instructional Video: A 2-Year Follow-Up Study of Dental Students.

Purpose: To evaluate the retention of light-curing skills among dental students after two years of clinical experience and determine if there are any differences in the skills retention between students who received verbal instructions or those who had received an instructional video. The students' satisfaction with past learning, self-confidence, and general knowledge about light-curing were also evaluated. Methods: This study is a 2-year evaluation of previous work. Students had previously been divided into two groups: those who received only verbal instructions, and those who received only an instructional video about the correct light curing technique to use clinically. Each student had light-cured simulated restorations (anterior and posterior) for 10 sec using the Managing Accurate Resin Curing-Patient Simulator (MARC-PS) (BlueLight Analytics, Halifax, Nova Scotia, Canada) and a multiple-emission peak light-emitting-diode (Bluephase N, Ivoclar Vivadent, Schaan, Liechtenstein) curing light. Students then received instructions according to their assigned group and light-cured the simulated cavities again. Two years later, students from both groups light-cured the same simulated cavities. Then, they completed a modified version of the National League of Nursing (NLN) satisfaction and self-confidence questionnaire and answered light-curing knowledge questions. Statistical analysis: The mean radiant exposure values delivered before receiving specific instructions on light curing, immediately after, and two years after instruction for both teaching methods (Friedman test followed by Wilcoxon signed-rank post hoc test), and the difference between both teaching methods was assessed (two-sample Wilcoxon rank-sum test). The satisfaction and self-confidence scores were compared between teaching method groups (Wilcoxon rank-sum test) (p<0.05). Results: The mean and median irradiance values ranged between 194-1777 and 1223-1302 mW/cm2 before instructions, 320-1689 and 1254-1394 mW/cm2 immediately after instructions, and 95-1945 and 1260-1331 mW/cm2 two years later regardless of the simulated restoration or the teaching method. The mean and median radiant exposure values ranged between 2-23 and 12.5-13.6.4 J/cm2 before instructions, 3-28 and 12.8-14.3 mW/cm2 immediately after instructions, and 0.7-20 and 12.8-13.6 mW/cm2 two years later regardless of the simulated tooth being light cured and the teaching method. Students retained their light-curing skills after two years of clinical experience, with no significant differences between both groups. The instructional video group delivered significantly higher radiant exposure values (p=0.021) when light-curing the anterior tooth than the posterior. Students were satisfied with their past learning and confident in their light-curing skills (p=0.020). There were statistical differences in how well the two groups remembered what they had been taught about light-curing. Only 5.7% of students answered all knowledge questions correctly. Conclusion: Students retained their light-curing skills after two years of clinical experience, with no significant difference between verbal instructions or instructional video teaching methods. However, their knowledge about light curing remained very poor. Nevertheless, the students were satisfied with how they had been taught and had confidence in both teaching methods.

Effect of Tooth Brushing Cycles and Dentifrice Fluoride Concentration on a Glazed CAD/CAM Ceramic.

PURPOSE: To evaluate the effect of tooth brushing and dentifrice fluoride (F-) concentration on changes in color and translucency (ΔE00 and ΔT00, respectively), surface gloss (GS), surface roughness (Sa), and microstructure of a glazed CAD/CAM ceramic. MATERIALS AND METHODS: Ceramic blocks (e.max/CAD) were sectioned into rectangular plates (14 x 12 x 1 mm), and one surface of each sample was glazed. Samples were divided into three groups according to the F- concentration in the dentifrice (0, 1,100, and 5,000 µg/g) and were then subjected to 60,000 tooth brushing cycles. Luminosity and color were measured using a spectrophotometer at baseline and after every 20,000 cycles to obtain their ΔE00 and ΔT00 values. Another set of samples was prepared to measure the GS with a gloss meter and the Sa with a confocal laser microscope. The GS and Sa results were subjected to analysis of variance, Tukey test, and Dunnett test (α = .05). RESULTS: After 60,000 tooth brushing cycles, all of the variables were clinically acceptable, and there were no significant differences in the ΔE00, ΔT00, GS, or Sa among the fluoridated dentifrices. The GS values decreased significantly as the number of tooth brushing cycles increased. CONCLUSION: The ΔE00, ΔT00, GS, and Sa values were all clinically acceptable after the glazed e.max/CAD ceramic had been subjected to 60,000 tooth brushing cycles with dentifrices containing up to 5,000 µg/g of F-.

The potential 'blue light hazard' from LED headlamps.

Many dental personnel use light-emitting diode (LED) headlamps for hours every day. The potential retinal 'blue light hazard' from these white light headlamps is unknown. METHODS: The spectral radiant powers received from direct and indirect viewing of an electronic tablet, an LED curing light, a halogen headlamp, and 6 brands of LED headlamps were measured using integrating spheres attached to fiberoptic spectroradiometers. The spectral radiant powers were measured both directly and indirectly at a 35 cm distance, and the maximum daily exposure times (tMAX) were calculated from the blue weighted irradiance values. RESULTS: The headlamps emitted very different radiant powers, emission spectra, and color temperatures (K). The total powers emitted at zero distance ranged from 47 mW from the halogen headlamp to 378 mW from the most powerful LED headlamp. The color temperatures from the headlamps ranged from 3098 K to 7253 K. The tMAX exposure times in an 8 h day when the headlamps were viewed directly at a distance of 35 cm were: 810 s from the halogen headlamp, 53 to 220 s from the LED headlamps, and 62 s from the LED curing light. Light from the LED headlamps that was reflected back from a white reference tile 35 cm away did not exceed the maximum permissible exposure time for healthy adults. Using a blue dental dam increased the amount of reflected blue light, but tMAX was still greater than 24 h. CONCLUSIONS: White light LED headlamps emit very different spectra, and they all increase the retinal 'blue light hazard' compared to a halogen source. When the headlamps were viewed directly at a distance of 35 cm, the 'blue light hazard' from some headlamps was greater than from the LED curing light (tMAX = 62 s). Depending on the headlamp brand, tMAX could be reached after only 53s. The light from the LED headlamps that was reflected back from a white surface that was 35 cm away did not exceed the maximum permissible ocular exposure limits for healthy adults. CLINICAL RELEVANCE: Reflected white light from dental headlamps does not pose a blue light hazard for healthy adults. Direct viewing may be hazardous, but the hazard can be prevented by using the appropriate blue-light blocking glasses.

Power output from 12 brands of contemporary LED light-curing units measured using 2 brands of radiometers.

BACKGROUND: Given the increasing use of photo-activated resins in dentistry, dentists and researchers need a user-friendly dental radiometer to measure the power output from dental light-curing units (LCUs). OBJECTIVE: Our goal was to measure the accuracy of two brands of dental radiometers in reporting the power (mW) from twelve brands of contemporary LCUs compared to a 'gold standard' (GS) reference value obtained from an integrating sphere attached to a fiberoptic spectroradiometer. METHODS: The power output was measured from two units of 12 brands of LCUs, five times on the ''GS" system, five times on two Bluephase Meter II dental radiometers, and five times on two Mini Gig hand-held spectroradiometers. The emission spectrum was also recorded using the 'GS' integrating sphere. The power values reported by each meter were subjected to t-tests to compare the two examples of each LCU, and 3-way ANOVA followed by Bonferroni's post-hoc tests. Regression analyses were also performed to determine the relationship between the data from the hand-held radiometers and the 'GS' integrating sphere. RESULTS: There was a large difference in the power values (mW) and the emission spectra from the 12 brands of LCUs on their standard-settings (p<0.001). Except for one LCU (Dental Spark @ 15.1%), the differences between the two LCUs of the same brand were less than 5.3% when measured using the 'GS' integrating sphere. Regression analyses showed a highly significant agreement between the power values reported from the two brands of radiometers and the 'GS' integrating sphere (R2 > 98%). CONCLUSION: We concluded that the power values reported from both brands of dental radiometers we tested were accurate, provided that the light source did not emit wavelengths of light that were beyond the radiometer's detection limit.

A Blinded Comparative Study of Four Commercially Available LEDs and a Laser Light Curing Device.

OBJECTIVE: This study determined the effectiveness of five light-curing units (LCUs; four light-emitting diode [LED] and one laser) used on different settings to photo-activate four conventional resin-based composites (RBCs). MATERIALS AND METHODS: A total of 108 RBC specimens were photo-activated in a white Delrin mold representing a mesial-occlusal-distal (MOD) class II restoration in a molar tooth. The proximal boxes were 5 mm deep, and the mesial-distal length was 12 mm. Immediately after photo-curing, the RBC specimens were immersed in a solvent to remove the uncured materials, after which they were photographed and deidentified. A Research Electronic Data Capture survey was created using these images and sent to respondents who blindly assessed the ability of the various LCUs to photo-cure the MOD restorations. RESULTS: There were significant differences in how the five curing lights had cured RBCs. One-way analysis of variance (ANOVA), pairwise t-test, Welch's one-way ANOVA, and Kruskal-Wallis rank test in the blinded survey data showed significant differences between the LED curing lights used for two 10-second cures and the laser curing light used for 1 second, and LED lights at lower settings. CONCLUSION: There was a significant difference in how the curing lights could photo-cure the RBCs used in this study. The laser curing light used for 1 second produced the worst results in all four RBCs. CLINICAL SIGNIFICANCE: When used for 1 second, the laser curing device does not photo-cure conventional RBC materials as well as the LED curing lights used for 10 seconds.

Effect of thickness on the degree of conversion of two bulk-fill and one conventional posterior resin-based composites at high irradiance and high temporal resolution.

OBJECTIVES: This study: 1) measures the effect of sample thickness and high irradiance on the depth-dependent time delay before photopolymerization reaction onset; 2) determines if exposure reciprocity exists; 3) measures the conversion rate at four irradiance levels; 4) determines the time, t0, at which the maximum DC rate is reached for two bulk-fill and one conventional posterior resin-based composites (RBCs). METHODS: Tetric PowerFill IVA shade (Ivoclar Vivadent) and Aura bulk-fill ultra universal restorative (SDI), and one conventional posterior resin-based composite (RBC), Heliomolar A3 (Ivoclar Vivadent), that were either 0.2 mm, 2 mm, or 4 mm thick were photocured using a modified Bluephase G4 (Ivoclar Vivadent) light-curing unit (LCU) that delivered a single emission band (wavelength centered at 449 nm). The same radiant exposure of 24 J/cm2 was delivered at irradiances ranging from 0.5 to 3 W/cm2 by adjusting the exposure time. PowerFill was also photocured for 3 s or 6 s using a Bluephase PowerCure LCU (Ivoclar Vivadent) on the 3 s mode setting. The degree of conversion (DC) was measured in real-time at a high temporal resolution at 30 °C using Attenuated Total Reflection (ATR) FTIR spectroscopy with a sampling rate of 13 DC data points per second. The DC data were analyzed using a phenomenological autocatalytic model. The RBC viscosity was measured at 21 °C and 30 °C. Light transmission through the RBC samples at 22 °C was monitored with time to calculate the extinction coefficients of the RBCs. RESULTS: The time delay before photopolymerization started increased as the RBC thickness increased and the irradiance decreased. An autocatalytic model described the DC data. The time t0 was less than 77 ms for the 0.2 mm thick samples of PowerFill irradiated using the highest irradiance of 3 W/cm2. Among the three RBCs for each sample thickness and irradiance level, the PowerFill had the smallest time t0. There was a time delay of 0.59 s and 1.25 s before the DC started to increase at the bottom of 4 mm thick samples for the PowerFill and Aura, respectively, when an irradiance of 1 W/cm2 was delivered. The time delay increased to 3.65 s for the Aura when an irradiance of 0.5 W/cm2 was delivered. The extinction coefficients near 449 nm were 0.78 mm-1, 0.76 mm-1, and 1.55 mm-1 during the first 2 s after the start of photocuring of PowerFill, Aura, and Heliomolar, respectively. Only PowerFill followed exposure reciprocity. At T = 30 °C, the viscosity was 3400, 17000, and 5200 Paˑs for PowerFill, Aura, and Heliomolar, respectively. SIGNIFICANCE: The time delay between when photopolymerization starts at the top and bottom of 2- or 4-mm thick RBC restorations may affect the structural integrity of the bond between the tooth and the bottom of the restoration. Only PowerFill followed exposure reciprocity between irradiance levels of 0.5 to 3 W/cm2. Exposure reciprocity did not occur for Aura or Heliomolar, neither of which are optimized for short light exposure or high irradiance conditions.

Comparison of the operative time and presence of voids of incremental and bulk-filling techniques on Class II composite restorations.

OBJECTIVES: To compare the operative time and presence of air voids on Class II restorations fabricated by dental practitioners with 1 to 5 years of experience using incremental and bulk-filling techniques. METHOD AND MATERIALS: Four techniques were evaluated: incremental, bulk-filling, bulk-filling with heated composite, and snowplow technique. Standardized mandibular first molars with a MOD (mesial, occlusal, and distal) cavity were used. Voluntary operators made two restorations using each technique and the time required for each restoration was recorded. The restorations were scanned by micro-computed tomography to calculate the volume of the restoration occupied by air voids. The "operative time" and "volume of air voids" were analyzed individually by two-way ANOVA and Tukey HSD post hoc (α = .05) for the factors operator and insertion technique. A correlation between "operative time" and "volume of air voids" was evaluated using Pearson coefficient (α = .05). RESULTS: The incremental technique required significantly longer time, yet no differences were observed between the bulk-filling techniques. There were no significant differences between techniques regarding the volume of air voids. A significant, but weak, and inverse linear correlation (P = .0059; r = -.29; r2 = 8.41%) was found between the operative time and volume of air voids. CONCLUSION: There were no significant differences in the volume of air voids among the evaluated techniques, although bulk-filling techniques required a shorter operative time. Hence, implementing bulk-filling techniques by dental schools and restorative dental practitioners with different levels of expertise may reduce chair time and produce a volume of air voids similar to the incremental technique.

Effect of distance on irradiance and beam homogeneity from 4 light-emitting diode curing units.

PURPOSE: To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights. METHODS: Four light-emitting diode curing lights were evaluated: Fusion, Bluephase 16i, Demi and FlashLite Magna. The irradiance at the centre of the light beam (ICB) was measured at 1.0 to 9.0 mm from the emitting tip using a 3.9-mm diameter probe connected to a spectrometer. The uniformity of the beam from each curing light was characterized by means of the "top hat factor" at 2.0, 4.0, 6.0 and 8.0 mm from the emitting tip. The useful beam diameter, within which irradiance values were greater than 400 mW/cm2, was calculated. The ICB, top hat factor and useful beam diameter were compared by analysis of variance and Fisher's protected least significant difference test at α = 0.01. RESULTS: At all distances, the ICB was lowest for the FlashLite Magna and highest for the Fusion. Only the Fusion maintained an ICB above 1000 mW/cm2 at the 8.0 mm distance. For distances between 2.0 and 8.0 mm, the top hat factors were similar for the Fusion and the Demi, lower for the Bluephase 16i and lowest for the FlashLite Magna. CONCLUSIONS: Beam homogeneity, top hat factors and ICB varied significantly among the curing lights. These results indicate that deep restorations may not be adequately cured if the curing time is based on data obtained when the curing light is positioned close to the radiometer or resin. In addition, a single irradiance value cannot be used to describe the light output from a curing light.