Critical appraisal. Quartz-tungsten-halogen and light-emitting diode curing lights.
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Body Temperature↗
Biomedical subjects
Howard W Roberts
Publications and source records attributed to Howard W Roberts.
Accuracy of LED and halogen radiometers using different light sources.
PURPOSE: To determine the accuracy of commercially available, handheld light-emitting diode (LED) and halogen-based radiometers using LED and quartz-tungsten-halogen (QTH) curing lights with light guides of various diameters. METHODS: The irradiance of an LED curing light (L.E. Demetron 1, SDS/Kerr, Orange, CA, USA) and a QTH curing light (Optilux 501, SDS/Kerr) were measured using multiple units of an LED (Demetron L.E.D. Radiometer, SDS/Kerr) and a halogen radiometer (Demetron 100, SDS/Kerr) and compared with each other and to a laboratory-grade power meter (control). Measurements were made using five light guides with distal light guide diameters of 4, 7, 8, 10, and 12.5 mm. For each light guide, five readings were made with each of three radiometers of each radiometer type. Data were analyzed with two-way analysis of variance/Tukey; alpha = 0.05. RESULTS: In general, both handheld radiometer types exhibited significantly different irradiance readings compared with the control meter. Additionally, readings between radiometer types were found to differ slightly, but were correlated. In general, the LED radiometer provided slightly lower irradiance readings than the halogen radiometer, irrespective of light source. With both types of handheld radiometers, the use of the larger-diameter light guides tended to overestimate the irradiance values as seen in the control, while smaller-diameter light guides tended to underestimate. CLINICAL SIGNIFICANCE: The evaluated LED or halogen handheld radiometers may be used interchangeably to determine the irradiance of both LED and QTH visible-light-curing units. Measured differences between the two radiometer types were small and probably not clinically significant. However, the diameter of light guides may affect the accuracy of the radiometers, with larger-diameter light guides overestimating and smaller-diameter guides underestimating the irradiance value measured by the control instrument.
Analysis of Variance↗
Evaluation of field dental equipment in a deployment environment.
Dental officers and technicians must have reliable, durable, well-performing field dental equipment to enable them to provide dental care to deployed troops in operational environments. Unfortunately, no organized program exists to test such equipment before its purchase and use in the field. This article presents the results of a project conducted by the Naval Institute for Dental and Biomedical Research and the Air Force Dental Evaluation and Consultation Service to evaluate commercially available field dental equipment through laboratory testing and clinical-user evaluations in theater. The purpose of this 2-year project was to identify the best-performing and most cost-effective field dental equipment for possible future procurement. Initial laboratory testing was performed at the Naval Institute for Dental and Biomedical Research, and the equipment was then shipped to Kuwait for in-theater environmental and clinical-user testing. A seven-member scientific team of military dental officers and technicians was deployed for 1 month to perform in-theater testing under regional environmental conditions and to coordinate clinical-user evaluations. The testing provided beneficial results by identifying equipment that performed properly and equipment that exhibited shortcomings serious enough to render it inadequate for operational use. It is recommended that the project serve as a model for future testing and evaluation of medical/dental equipment by all of the military services.
Dental Equipment↗
Oral surgical handpiece use time parameters.
PURPOSE: To evaluate the clinical usage time parameters of handpieces used in oral surgical procedures. METHOD AND MATERIALS: One hundred randomly selected clinical oral surgery exodontia procedures were timed to record lengths of continuous segments of both handpiece use and non-usage. Providers with experience ranging from general dentists to board certified oral surgeons were timed during surgical exodontia treatment involving 1 to 4 teeth of various complexities. Usage times were compared with manufacturers' recommendations that on times should not exceed 20 seconds in any 50-second interval (20/50 rule). RESULTS: Handpiece run time increased with the number of teeth and surgical case complexity (both P < .001) but was unrelated to operator experience (P = .763), in a 3-predictor model (R2 = 0.20; P < .001). Ninety-four of the 100 cases experienced at least 1 second in violation of the 20/50 rule and 42% of all run seconds were in violation. CONCLUSION: Clinicians should be aware of recommended handpiece duty use cycles. Manufacturers' recommendations about handpiece use time cycles do not reflect actual clinical usage. Under the conditions of this study, actual surgical handpiece use time was not correlated with user experience. Less experienced providers did require longer to complete treatment, but increased treatment times were due to time spent that did not require surgical handpiece use.
Clinical Competence↗
Effect of light dispersion of LED curing lights on resin composite polymerization.
PURPOSE: This study evaluated the effect of light dispersion of halogen and LED curing lights on resin composite polymerization. MATERIALS AND METHODS: One halogen (Optilux 501, SDS/Kerr, Orange, CA, USA) and five light-emitting diode (LED) curing lights (SmartLite iQ, Dentsply Caulk, Milford, DE, USA; LEDemetron 1, SDS/Kerr; FLASHlite 1001, Discus Dental, Culver City, CA, USA; UltraLume LED 5, Ultradent Products, South Jordan, UT, USA; Allegro, Den-Mat, Santa Maria, CA, USA) were used in this study. Specimens (8 mm diameter by 2 mm thick) were made in polytetrafluoroethylene molds using hybrid (Z100, 3M ESPE, St. Paul, MN, USA) and microfill (A110, 3M ESPE) composite resins. The top surface was polymerized for 5 seconds with the curing light guide tip positioned at a distance of 1 and 5 mm. Degree of conversion (DC) of the composite specimens was analyzed on the bottom surface using micro-Fourier Transform Infrared (FTIR) spectroscopy (Perkin-Elmer FTIR Spectrometer, Wellesley, PA, USA) 10 minutes after light activation. DC at the bottom of the 2 mm specimen was expressed as a percentage of the mean maximum DC. Five specimens were created per curing light and composite type (n=5). Percent mean DC ratios and SDs were calculated for each light under each testing condition. Data were analyzed by analysis of variance (ANOVA)/Tukey's test (alpha = .05). A beam analyzer (LBA-700, Spiricon, Logan, UT, USA) was used to record the emitted light from the curing lights at 0 and 5 mm distances (n=5). A Top Hat factor was used to compare the quality of the emitted beam profile (LBA/PC, Spiricon). The divergence angle from vertical was also determined in the x- and y-axes (LBA/PC). Mean values and SDs were calculated for each light under each testing condition (0 and 5 mm, x- and y-axes) and analyzed by a two-way ANOVA/Tukey's test (alpha = .05). RESULTS: For DC ratios, significant differences were found based on curing light and curing distance (p < .05). At 1 mm, Optilux 501 and FLASHlite 1001 produced significantly higher DC ratios with the hybrid resin composite. No differences were found among lights with the microfill at 1 mm. At 5 mm, SmartLite iQ, FLASHlite 1001, LEDemetron 1, and UltraLume LED 5 produced significantly higher DC ratios with the hybrid resin composite, whereas LEDemetron 1 and SmartLite iQ produced significantly higher DC ratios with the microfill resin composite. The UltraLume LED 5, Allegro, and Optilux 501 had significant reductions in mean DC ratios at curing distances of 1 and 5 mm with both resin composite types. For dispersion of light, significant differences were found in Top Hat factor and divergence angle (p < .001). SmartLite iQ had overall the highest Top Hat factor and lowest divergence angle of tested lights. A linear regression analysis relating pooled DC with pooled Top Hat factors and divergence angles found a very good correlation (r2 = .86) between dispersion of light over distance and the ability to polymerize resin composite. CLINICAL SIGNIFICANCE: The latest generation of LED curing lights provides DC ratios similar to or better than the halogen curing light at a curing distance of 5 mm. Dispersion of light plays a significant role in the DC of resin composite. To maximize curing effectiveness, light guides should be maintained in close proximity to the surface of the light-activated restorative material.
Analysis of Variance↗
Disinfectants' effect on mercury release from amalgam.
BACKGROUND: Mercury environmental discharge is under increased scrutiny by the U.S. Environmental Protection Agency (EPA). Dental amalgam should be processed properly to prevent an additional environmental burden. Some processing agencies require that submitted amalgam be noninfectious. Investigations have demonstrated that oxidizing disinfectants mobilize mercury from amalgam into solution and add mercury to the environmental burden if it is disposed of improperly. The authors conducted a study to evaluate the effect of representative disinfectants on amalgam mercury release. METHODS: The authors sized a high-copper spherical amalgam alloy to match that typically found in dental unit suction traps. They exposed 20 grams of the alloy to several disinfectant solutions and evaluated the filtered supernatant solution for mercury content. RESULTS: Chlorine disinfectant materials discharged the most mercury ions, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. The quaternary ammonium compound did not discharge mercury ions above the detection limit (0.2 parts per billion) into solution. CONCLUSIONS: A quaternary ammonium compound did not mobilize mercury ions into solution when used as a disinfectant agent for amalgam. Chlorine disinfectants mobilized mercury ions the most, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. CLINICAL IMPLICATIONS: Dentists are obligated to be good environmental stewards and should follow practices that reduce environmental mercury release. Dental personnel should be aware that oxidizing disinfectants mobilize mercury ions into solution, which will be added to the environment if they are processed improperly. If required by processing, dental personnel should consider the different oxidizing effects of commonly used disinfectants.
Anti-Infective Agents, Local↗
The effect of a translucent post on resin composite depth of cure.
OBJECTIVE: To evaluate the effect of a light-transmitting post on the depth of cure of a resin composite. METHODS: Acetate resin molds were filled with resin composite in which a light-transmitting post was inserted into the center and photopolymerized to the manufacturer's recommendations. Identical molds without a light-transmitting post were photopolymerized in a similar matter and served as a control. Molds were sectioned on a water-cooled, diamond saw at prescribed distances and the depth of cure was determined using a Knoop Hardness bottom-to-top ratio criterion. Data within each group were analyzed using 2-way (depth-by-distance) repeated measure ANOVA. Between-group contrasts (post versus no post) were accessed by a 3-way (2 within-subjects and 1 between-subjects) ANOVA with critical p = 0.05. RESULTS: The presence of the post did increase (p < 0.001) Knoop Hardness values in simulated apical regions as compared to a control. However, there was no difference in the depth of cure between the groups (3-way analysis p = 0.2) and also when evaluated using an 80% bottom-to-top Knoop Hardness ratio. SIGNIFICANCE: The results suggest that these posts may have a limited utility when judged against a Knoop Hardness ratio criterion.
Analysis of Variance↗
Statistical estimation of resin composite polymerization sufficiency using microhardness.
With respect to determining sub-surface resin polymerization sufficiency, this study compared a traditional method of applying linear regression to bottom- to top-surface Knoop hardness ratios to an alternative method based on nonlinear regression. Inverse linear regression on ratios was used to estimate the exposure duration required for 80% bottom-surface hardness with respect to the top, in six light-by-material groups. Alternatively, a one-phase, two-parameter, exponential association of the form Y=Y(max)(1-e(-kt)) (where Y(max) is maximum hardness, k is a rate constant, and t is exposure duration), was used to model hardness. Inverse nonlinear regression estimated, for each condition, the exposure duration required for the bottom surface to achieve 80% of corresponding condition (light and material) top-surface Y(max). Mathematically, analysis of ratios was demonstrated to yield potentially less precise and biased estimates. Nonlinear regression yielded better statistical fit and provided easily accessible tests for differences in k across light-system groups. Another recently proposed nonlinear model for polymerization, Y=Y(max)kt(n)/(1+kt(n)), was also considered. While this new model has substantially greater phenomenological and mechanistic justification, we found that the model-fitting process was more sensitive to initial parameter values and sometimes yielded untenable results when applied to our data. However, we believe that these problems would not occur if sample points are well distributed across a wide range of exposure durations, and that the model, Y=Y(max)kt(n)/(1+kt(n)), should be considered for such data sets.
Analysis of Variance↗
Polymerization efficiency of LED curing lights.
PURPOSE: The purpose of this study was to compare the curing efficiency of three commercially available light-emitting diode (LED)-based curing lights with that of a quartz tungsten halogen (QTH) curing light by means of hardness testing. In addition, the power density (intensity) and spectral emission of each LED light was compared with the QTH curing light in both the 380- to 520-nm and the 450- to 500-nm spectral ranges. MATERIALS AND METHODS: A polytetrafluoroethylene mold 2 mm high and 8 mm in diameter was used to prepare five depth-of-cure test specimens for each combination of exposure duration, composite type (Silux Plus [microfill], Z-100 [hybrid]), and curing light (ZAP Dual Curing Light, LumaCure, VersaLux, Optilux 401). After 24 hours, Knoop hardness measurements were made for each side of the specimen, means were calculated, and a bottom/top Knoop hardness (B/T KH) percentage was determined. A value of at least 80% was used to indicate satisfactory polymerization. A linear regression of B/T KH percentage versus exposure duration was performed, and the resulting equation was used to predict the exposure duration required to produce a B/T KH percentage of 80% for the test conditions. The power densities (power/unit area) of the LED curing lights and the QTH curing light (Optilux 401) were measured 1 mm from the target using a laboratory-grade, laser power meter in both the full visible light spectrum range (380-780 nm) and the spectral range (between 450 and 500 nm), using a combination of long- and short-wave edge filters. RESULTS: The emission spectra of the LED lights more closely mirrored the absorption spectrum of the commonly used photoinitiator camphorquinone. Specifically, 95% of the emission spectrum of the VersaLux, 87% of the LumaCure, 84% of the ZAP LED, and 78% of the ZAP combination LED and QTH fell between 450 and 500 nm. In contrast, only 56% of the emission spectrum of the Optilux 401 halogen lamp fell within this range. However, the power density between 450 and 500 nm was at least four times greater for the halogen lamp than for the purely LED lights. As a result, the LED-based curing lights required from 39 to 61 seconds to cure a 2-mm thick hybrid resin composite and between 83 and 131 seconds to adequately cure a microfill resin composite. By comparison, the QTH light required only 21 and 42 seconds to cure the hybrid and microfill resin composites, respectively. CLINICAL SIGNIFICANCE: The first-generation LED-based curing lights in this study required considerably longer exposure durations than the QTH curing light to adequately polymerize a hybrid and a microfill resin composite.
Composite Resins↗
The effect of electrical dental equipment on a vagus nerve stimulator's function.
BACKGROUND: Dental patients who have epilepsy with pharmacologically refractory seizures may be treated with an implanted pulse generator that electrically stimulates the left vagus nerve. The pulse generator functions like a cardiac pacemaker. Some electrical dental devices have been shown to cause electromagnetic interference with the function of cardiac pacemakers. The potential effect of similar dental equipment on vagus nerve stimulators is unknown. METHODS: Common electrical dental devices were operated at maximum power settings in close proximity to a representative vagus nerve stimulator. The author assessed any interference of the dental devices with the nerve stimulator function by observing oscilloscope tracings. RESULTS: Under the conditions of this evaluation, none of the dental devices tested altered the function of the vagus nerve stimulator. CONCLUSIONS: Some commonly used electrical dental devices may be used in close proximity to patients who have implanted vagus nerve stimulators without adverse effects on the nerve stimulator function. CLINICAL IMPLICATIONS: Dentists and dental hygienists may encounter patients with implanted vagus nerve stimulators, and they need to be cognizant of developments in the treatment of epilepsy. Under the conditions of this study, use of common dental electrical devices did not alter the function of a vagus nerve stimulator. The findings of this study, however, should not be generalized to all types of electrical dental or medical devices, as a recent report indicates that treatment with diathermy devices is contraindicated for patients with implanted nerve stimulators.
Dental Amalgam↗
Effect of latex glove contamination on bond strength.
PURPOSE: This study examined the effect of powdered and powder-free latex glove contamination on bond strength. MATERIALS AND METHODS: Sixty caries-free human third molars were mounted in acrylic, sectioned with a diamond saw to expose a flat occlusal dentin surface, and finished with 400- and 600-grit silicon carbide paper. Teeth were assigned to one of 5 groups: 1) no latex glove contamination (control); 2) powdered latex glove contamination before etching; 3) powder-free latex glove contamination before etching; 4) powdered latex glove contamination after dentin bonding agent application but prior to resin composite placement; 5) powder-free latex glove contamination after dentin bonding agent application but prior to resin composite placement. Excite dentin bonding agent was used per manufacturer's instructions. Z-250 resin composite was applied in 2- x 2-mm increments using a split Teflon mold, each light cured for 20 s. Bonded samples were thermocycled 500 cycles between 5 degrees C and 55 degrees C water baths. Specimens were stored in 37 degrees C distilled water. One-week shear bond strength values were determined using a Tinius Olsen testing machine at a crosshead speed of 0.5 mm/min. Results were analyzed with one-way ANOVA (alpha = 0.05). RESULTS: No significant difference (p = 0.47) in bond strength was found between the experimental groups and the control. Groups 1, 2, 3, and 5 exhibited predominantly mixed failures while the majority of samples in Group 4 showed adhesive failures. CONCLUSION: Under the conditions of this study, contamination of dentin by powdered or powder-free latex gloves did not significantly affect bond strength. Future research should be directed toward evaluating the effects of dentin contamination on bond strength of other bonding agents and include ultrastuctural examination in determining what role, if any, powder plays as a contaminant.
Composite Resins↗
The effect of resin composite pins on the retention of class IV restorations.
Standardized Class IV cavity preparations were made in 48 human incisors. They were then divided into three groups of 16 teeth each. Group 1 was prepared with no internal retentive features. Groups 2 and 3 included an internal pin channel prepared with a #330 and a #329 bur, respectively. All specimens were restored with a micro-hybrid resin-based composite restorative material and a fifth generation dentin bonding system. Specimens were loaded to failure in an Instron Universal Testing Machine perpendicular to the long axis of the teeth. There was no evidence to suggest a difference in force required to dislodge the restoration among the three groups tested (p=0.185). Resin composite pins do not increase the retention of Class IV resin composite restorations.
Acid Etching, Dental↗
Thermal emission and curing efficiency of LED and halogen curing lights.
The purpose of this study was to compare the thermal emission and curing efficiency of LED (LEDemetron 1, SDS/Kerr) and QTH (VIP, BISCO) curing lights at maximum output and similar power, power density and energy density using the same light guide. Also, another LED curing light (Allegro, Den-Mat) and the QTH light at reduced power density were tested for comparison. Increase in temperature from the tips of the light guides was measured at 0 and 5 mm in air (23 degrees C) using a temperature probe (Fluke Corp). Pulpal temperature increase was measured using a digital thermometer (Omega Co) and a K-type thermocouple placed on the central pulpal roof of human molars with a Class I occlusal preparation. Measurements were made over 90 seconds with an initial light activation of 40 seconds. To test curing efficiency, resin composites (Z100, A110, 3M/ESPE) were placed in a 2-mm deep and 8-mm wide plastic mold and cured with the LED and QTH curing lights at 1- and 5-mm curing distances. Knoop Hardness Numbers (KHN) were determiped on the top and bottom surfaces (Leco). Bottom hardness values were expressed as a percentage of maximum top hardness. No significant differences were found in maximum thermal emission or KHN ratios between the LED (LEDemetron 1) and the QTH (VIP) at maximum output and similar energy densities (ANOVA/Tukey's; alpha=0.05).
Body Temperature↗
Effect of handpiece maintenance method on bond strength.
This study evaluated the effect of dental handpiece lubricant on the shear bond strength of three bonding agents to dentin. A lubrication-free handpiece (one that does not require the user to lubricate it) and a handpiece requiring routine lubrication were used in the study. In addition, two different handpiece lubrication methods (automated versus manual application) were also investigated. One hundred and eighty extracted human teeth were ground to expose flat dentin surfaces that were then finished with wet silicon carbide paper. The teeth were randomly divided into 18 groups (n=10). The dentin surface of each specimen was exposed for 30 seconds to water spray from either a lubrication-free handpiece or a lubricated handpiece. Prior to exposure, various lubrication regimens were used on the handpieces that required lubrication. The dentin surfaces were then treated with total-etch, two-step; a self-etch, two-step or a self-etch, one-step bonding agent. Resin composite cylinders were bonded to dentin, the specimens were then thermocycled and tested to failure in shear at seven days. Mean bond strength data were analyzed using Dunnett's multiple comparison test at an 0.05 level of significance. Results indicated that within each of the bonding agents, there were no significant differences in bond strength between the control group and the treatment groups regardless of the type of handpiece or use of routine lubrication.
Acid Etching, Dental↗