Intensity of quartz-tungsten-halogen light-curing units used in private practice in Toronto

Hands-on training based on quantifying radiant exposure improves how dental students cure composites: Skill retention at 2-year follow-up

INTRODUCTION

The durability and longevity of composite restoration are much dependent on the accurate delivery of the energy required to polymerise the material. This study aimed to investigate the extent to which undergraduate dental students acquire and retain light-curing skills following hands-on training.

MATERIALS AND METHODS

Hands-on training comprises faculty tutoring for critical aspects of the light-curing procedure, such as distance and angulation of the light-curing tip. Assessments of the students' ability to deliver a specified radiant exposure to class III and I simulated RBCs using a dental simulator (MARC-PS^® ) at three different time points after the training. Data were analysed using repeated measure ANOVA.

RESULTS

Immediately after the training, students' performance on curing was improved (p < .05). Overall, the radiant exposure increased after training, but the students lost some of the benefits with time. For curing in the anterior section (anterior sensor-class III), the mean radiant exposure values increased by approximately 20% after the training. After 2 years, the values were 15% greater than baseline values. For curing in the posterior section (posterior sensor-class I), the mean radiant exposure values increased by approximately 150% after the training. A significant decrease (p < .05) was observed; however, the radiant exposure values were still 82% greater than the baseline after 2 years.

CONCLUSION

A hands-on training dedicated to light-curing procedures facilitated acquisition and retention up to a 2-year follow-up of skill on how light cure composite inside the mouth. The training was more relevant for curing in posterior areas, where orientation can significantly impact light-curing. A hands-on training where the radiant exposure can be measure gave objective measurement metrics to guide the curing performance. This approach is an effective means of teaching practical skills to dental students.

The Ability of Dental Practitioners to Light-Cure Simulated Restorations

CLINICAL RELEVANCE

Using a patient simulator, dental professionals were tested to determine their ability to light-polymerize simulated restorations in their dental practice. After receiving specific instructions and training using the simulator, their ability to deliver sufficient light to polymerize restorations was significantly and substantially improved.

SUMMARY

Objectives: To determine the ability of dental professionals to deliver a radiant exposure of at least six J/cm2 in 10 seconds to simulated restorations.Methods and Materials: The study initially examined 113 light-emitting-diode (LED) light polymerization units (LPUs) used in dental offices to determine if they could deliver at least 6 J/cm2 radiant exposure (RE) in 10s. This assessment was completed by using a laboratory-grade light measuring device (checkMARC, BlueLight Analytics, Halifax, NS, Canada). The participating dental professionals whose LPUs could deliver 6 J/cm2 then used their own LPU to light-cure simulated anterior and posterior restorations in the MARC Patient Simulator (BlueLight Analytics). They then received specific instructions and were retested using the same LPUs. Data were statistically analyzed with a series of one-way analysis of variance (ANOVA), two-way ANOVA, paired-samples t-tests, Fisher post hoc multiple comparison tests, and McNemar tests with a preset alpha of 0.05 (SPSS Inc).Results: Ten (8.8%) LPUs could not deliver the required RE to the checkMARC in 10s and were eliminated from the study. For the anterior restoration, most dental practitioners (87.3%) could deliver at least 6 J/cm2 before instructions. After receiving additional light-curing instructions, only two (1.9%) participants were unable to deliver 6 J/cm2 to the anterior location. At the posterior location, only 55.3% (57) participants could deliver at least 6 J/cm2 before the instructions. After receiving these instructions, an additional 32 participants delivered at least 6 J/cm2. Overall, after receiving instructions on how to use the LPU correctly, the participants improved the amount of RE they delivered to anterior and posterior restorations by 22.5% and 30%, respectively.Conclusion: This study revealed that at the baseline, 44.7% of participating dental professionals failed to deliver 6 J/cm2 in 10s to the posterior simulated restoration when using their own LPU.

Assessment of the radiant emittance of damaged/contaminated dental light-curing tips by spectrophotometric methods

Objectives

This study investigated the effects of physically damaged and resin-contaminated tips on radiant emittance, comparing them with new undamaged, non-contaminated tips using 3 pieces of spectrophotometric laboratory equipment.

Materials and Methods

Nine tips with damage and/or resin contaminants from actual clinical situations were compared with a new tip without damage or contamination (control group). The radiant emittance was recorded using 3 spectrophotometric methods: a laboratory-grade thermopile, a laboratory-grade integrating sphere, and a portable light collector (checkMARC).

Results

A significant difference between the laboratory-grade thermopile and the laboratory-grade integrating sphere was found when the radiant emittance values of the control or damaged/contaminated tips were investigated (p < 0.05), but both methods were comparable to checkMARC (p > 0.05). Regardless of the method used to quantify the light output, the mean radiant emittance values of the damaged/contaminated tips were significantly lower than those of the control (p < 0.05). The beam profile of the damaged/contaminated tips was less homogeneous than that of the control.

Conclusions

Damaged/contaminated tips can reduce the radiant emittance output and the homogeneity of the beam, which may affect the energy delivered to composite restorations. The checkMARC spectrophotometer device can be used in dental offices, as it provided values close to those produced by a laboratory-grade integrated sphere spectrophotometer. Dentists should assess the radiant emittance of their light-curing units to ensure optimal curing in photoactivated, resin-based materials.

Types of polymerisation units and their intensity output in private dental clinics of twin cities in eastern province, KSA; a pilot study

Objectives

Light-cured resin-based composites (RBCs) are the preferred option to restore teeth. Dental light-curing units (LCUs) should deliver adequate light energy to ensure good mechanical properties, dimensional stability, and biocompatibility of the RBC. The aim of this study was to determine the types of LCUs and their intensity output in private dental clinics.

Methods

A form was developed to record information related to the type of curing lights and their intensity output. A total of 400 curing devices were evaluated using a digital radiometer in 58 private dental clinics. For each device, three separate 10-s readings were taken and the average was calculated. For quartz tungsten halogen (QTH) units, a light intensity below 300 mW/cm² was considered unsatisfactory, whereas for light-emitting diode (LED) units, a reading below 600 mW/cm² was considered unsatisfactory.

Results

Out of 400 curing lights, 354 were LEDs and 46 were QTH units. A total of 13% of the lights were considered unsatisfactory. Of the LED units, 12.4% had a light intensity of less than 600 mW/cm², whereas QTH had 17.3% units with an intensity of less than 300 mW/cm².

Conclusion

The frequency of LCUs showed a trend towards LED units in private dental clinics, whereas the mean intensity value from the LED was higher than that from QTH units. Overall, the radiometer is a good tool to assess the intensity output of LCUs.

Efficiency of light curing units in a government dental school

The light intensity of a light-curing unit is a crucial factor that affects the clinical longevity of resin composites. This study aimed to investigate the efficiency of light-curing units in use at a local governmental dental school for curing conventional and bulk-fill resin materials. A total of 166 light-curing units at three locations were examined, and the brand, type, clinic location, diameter of curing tip, tip cleanliness (using a visual score), and the output (in mW/cm² using a digital radiometer) were recorded. Only 23.5% of the units examined had clean tips, with the graduate student clinical area containing the highest percentage of clean tips. Further, tips with poor cleanliness score values were associated with significantly lower output intensities. A small percentage (9.4%) of units was capable of producing intensities higher than 1,200 mW/cm² and lower than 600 mW/cm² (7.6%). The majority of the low intensity units were located in the undergraduate student area, which also contained the highest number of units with intensities between 900 and 1,200 mW/cm². The output of all the units in service was satisfactory for curing conventional resin composites, and most units were capable of curing bulk-fill resin materials.

Intensity output and effectiveness of light curing units in dental offices

BACKGROUND

The aims of the study were measuring the light intensity of light curing units used in Qazvin's dental offices, determining the relationship between the clinical age of these units and their light intensity, and identifying the reasons for repairing them.

MATERIAL AND METHODS

In this cross-sectional study, the output intensity of 95 light curing devices was evaluated using a radiometer. The average output intensity was divided up into four categories (less than 200, 200-299, 300-500, and more than 500 mW/cm2). In addition, a questionnaire was designed to obtain information mainly about the type, clinical age, and frequency of maintenance of the units and the reasons for fixing them. Data were analyzed using Kolmogorov-Smirnov, chi-squared, and t-tests (p< 0.05) on SPSS 24.

RESULTS

A total of 95 light curing units were examined, with 61 (64.2%) of them being of the LED type and 34 (35.8%) of the QTH type. While average light intensity in LED units was significantly higher than in QTH devices, the two device types were not significantly different regarding desirable light intensity (i.e., ≥ 300 mw/cm2). A negative correlation was observed between clinical age and light intensity. In addition, bulb replacement in QTH devices was over three times as much as in LED units. Also, repairing QTHs was more than twice as much frequent as fixing LEDs. The most common reason for repair was the breakage of the tip of the device.

CONCLUSIONS

The light intensity of LED units is significantly higher than that of QTH devices, and the frequency of repairing in QTHs was significantly more than in LEDs. Furthermore, light intensity decreases with aging, and dentists should regularly monitor the conditions of light units. Key words:Light curing unit, radiometer, light intensity, dental equipment, dental offices.

Guidelines for the selection, use, and maintenance of LED light-curing units - Part 1

Light curing is a critical step in the restorative process when using light-activated resin-based composites, but it is frequently not given the attention it deserves. The selection of a reliable light curing unit (LCU) that meets the practitioner's needs is an important equipment purchase. Using an inappropriate LCU may seriously compromise the quality of care without the practitioner realising their mistake until years later. The importance of the subject is reflected by the rapidly increasing use of light-cured composites and the decline in the use of amalgam. Many changes have occurred in the equipment and materials available for making light-cured restorations in the last twenty years. This article is part of a two-part series that will describe those changes and recommend guidelines for the selection, use, and maintenance of light emitting diode light-curing units (LED LCUs). This paper (Part 1) discusses terminology, clinical studies, the development of LCUs in dentistry, the aims of light-curing, and the need to deliver an adequate amount of energy. The interaction between light source and material is briefly described to demonstrate the complex nature of the resin photopolymerisation process.

Influence of physical assessment of different light-curing units on irradiance and composite microhardness top/bottom ratio

The aim of this study was to evaluate the influence of the physical assessment of different light-curing units from 55 dental offices on the irradiance and composite microhardness top/bottom ratio, and the influence of the radiometers for LED or QTH light sources on irradiance measurement. The irradiance of each light-curing unit was evaluated with two radiometers, either for LED or QTH light. A questionnaire regarding the type of source (LED or QTH), time of use, date of last maintenance and light-curing performance assessment applied. The physical assessments were evaluated regarding damage or debris on the light tip. For each light-curing unit, three composite specimens were made (diameter = 7 mm; thickness = 2 mm) with polymerizing time of 20 s, in order to perform the microhardness (Knoop) test. Data were analyzed by Kruskal-Wallis and Dunn test (α = 0.01). There was wide variation in irradiance (0-1000 mW/cm(2)). Approximately 50 % of the light-curing units presented radiation lower than 300 mW/cm(2); 10 % of light-curing units, especially those with LED source, presented values higher than 800 mW/cm(2), and 43 % of light-curing units worked with adequate irradiance between 301 and 800 mW/cm(2). In almost 60 % of cases, no maintenance of light-curing units was performed in a period of 3 to 10 years. The age of the light-curing units and the use of inadequate tips interfered negatively in irradiance. The data emphasize the importance of periodic maintenance of light-polymerizing, light-curing units.

Contemporary issues in light curing

This review article will help clinicians understand the important role of the light curing unit (LCU) in their offices. The importance of irradiance uniformity, spectral emission, monitoring the LCU, infection control methods, recommended light exposure times, and learning the correct light curing technique are reviewed. Additionally, the consequences of delivering too little or too much light energy, the concern over leachates from undercured resins, and the ocular hazards are discussed. Practical recommendations are provided to help clinicians improve their use of the LCU so that their patients can receive safe and potentially longer lasting resin restorations.

A survey of power density of light-curing units used in private dental offices in Changchun City, China

This study investigated power density and relevant information related to light-curing units used in private dental offices in Changchun City, China. The power density of 196 light-curing units used in private dental offices in Changchun City was measured using a simple random sampling method. Relevant information included the brand, type, years of operation, frequency of use, model numbers and types of light guide, resin buildup on the light guides, damage caused by the light guides, required maintenance of the curing lights, and ratio of the unit and chair number. There were 132 quartz tungsten halogen (QTH) units and 64 light-emitting diode units. The power density range was defined as 0-1,730 mW/cm(2). The mean power density was 453.1 mW/cm(2). The mean years of operation of the light-curing units were 3.96. The majority of dentists never tested the power density of the light-curing units and a considerable number of light guide surfaces showed resin buildup and damage. In Changchun City, the majority of light-curing units were QTH. Some units needed to be replaced due to aging. The majority of dentists were not aware that the light-curing units require periodic testing and maintenance. The data herein indicate the importance of periodic testing of the power density of light-curing units and timely replacement of the components and then guarantee the quality of medical services and their benefits to patients.

Evaluation of light-curing units in rural and urban areas

OBJECTIVES

To evaluate the distribution of light-curing units (LCU) used in an urban area (Riyadh) and a rural area (Kharj) of Saudi Arabia, and to compare their irradiance values.

METHODS

The study involved three dental centers in urban areas and two in rural areas, all of which were parts of a single healthcare institution providing dental services. The light outputs (power mW) from 140 LCUs were measured by laboratory-grade spectrometry, and the irradiance (mW/cm(2)) was calculated from the tip area of each LCU. The minimum acceptable irradiance outputs for the quartz-tungsten-halogen (QTH) and light-emitting diode (LED) units were set at 300 and 600 mW/cm(2), respectively. The ages of these units and the protocol used to light-cure the resins were also determined.

RESULTS

The total number of LCUs was 140, 112 (78%) in urban areas, and 28 (22%) in rural areas. In rural areas, only 7 of the 22 (32%) QTH units delivered irradiances greater than 300 mW/cm(2) and were therefore considered clinically acceptable, whereas 4 of the 6 (66.7%) LED units delivered values greater than 600 mW/cm(2). In urban centers, 43 of 61 (70.5%) LED units and 25 of 61 (49%) QTH units were considered clinically acceptable. Irradiance values for both QTH (P < 0.01) and LED (P < 0.05) units were significantly better in urban than in rural areas.

CONCLUSIONS

Urban areas had a greater distribution of LCUs than rural areas. Overall, irradiance values were significantly higher in urban areas.

General dental practitioners' knowledge of polymerisation of resin-based composite restorations and light curing unit technology

OBJECTIVE

Clinical successful use of resin-based composite restorations (RBCs) depends on knowledge of material and light curing unit (LCU) related factors. The purpose of this study was to evaluate general dental practitioners' knowledge of polymerisation of RBCs and LCU technology.

METHODS

Members of the Active Research Group of the Faculty of General Dental Practice (UK) in England, Scotland and Wales engaged in primary dental care were sent a letter introducing the study and asking for their cooperation, followed by an email containing a link to the online survey questionnaire, hosted on Surveymonkey.com. The questionnaire enquired about current LCUs, and asked a series of questions on material science.

RESULTS

Sixty-six percent of the 274 members contacted responded. Fifty-seven percent used LED units, 25% quartz tungsten halogen (QTH), and 1% plasma arc (missing: 17%). Thirty percent reported having access to a radiometer. Appropriate responses regarding the degree of conversion of composite and adhesive materials were given by 32% and 23% respectively, and 22% agreed that LED and QTH LCUs had comparable efficiency in polymerising composites. Thirty-three percent were aware that RBCs eluted substances that may have adverse local or systemic consequences. Fifty-eight percent stated that if polymerisation of RBC is slowed down, polymerisation stress will be lower, and 43% said that polymerisation shrinkage will be reduced if the degree of conversion is reduced. Knowledge (measured by appropriate responses to these questions) was not related to years since qualification (r=-0.05, n=168, p=0.53).

CONCLUSION

The study suggests that dentists' knowledge of curing RBC restorations and LCUs is poor. This indicates that there is a need for training and guidance in this aspect of primary dental care.

Evaluation of Light Intensity Output of QTH and LED Curing Devices in Various Governmental Health Institutions

Evaluating the intensity of a light curing unit regularly prior to the application of tooth-colored restorative materials is essential to assure the quality of restorative procedures.

Intra- and inter-brand accuracy of four dental radiometers

This study measured the accuracy and precision of four commercial dental radiometers. The intra-brand accuracy was also determined. The light outputs from 14 different curing lights were measured three times using four brands of dental radiometers and the results were compared to two laboratory-grade power meters that were used as the "gold standard". To ensure proper representation, three examples of each brand of dental radiometer were used. Data collected was analyzed using ANOVA, with 95% confidence intervals, comparing the laboratory-grade meters to the dental radiometers. Bioequivalence was established where the confidence interval for the irradiance values was within ±20% of the "gold standard" reading. Forest plots were used to highlight bioequivalence values. The two laboratory-grade meters differed by less than 0.6%. Overall, all three examples of the Bluephase and SDI radiometers as well as two examples of the LEDRadiometer and one CureRite meter were bioequivalent to the gold standard. However, the type of curing light measured had a significant effect on the accuracy of the radiometer. There was significant variability of the irradiance readings between radiometer brands, and between irradiance values recorded by the three samples of each brand studied. This made it impossible to definitively rank the radiometer brands for accuracy. Within the ±20% bioequivalence limits of this study, there was a clinically significant difference in the irradiance readings between radiometer brands and the choice of curing light affected the results. There was also significant variation in irradiance readings reported by different examples of the same brand of radiometer. Whether in clinical practice or in research, dental radiometers should not be used when either the irradiance or energy delivered needs to be accurately known.

The effect of tooth bleaching on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of tooth bleaching on substance P (SP) expression in healthy human dental pulp. Forty pulp samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Thirty of these premolars were assigned into three different tooth-bleaching protocols: group 1 (n = 10): Opalescence Xtra Boost (Ultradent Products, South Jordan, UT) (38% H(2)O(2)) for 15 minutes; group 2 (n = 10): Lase Peroxide (DMC, Brazil) (35% H(2)O(2)) activated with infrared laser diode (Biolux; BioArt, Brazil) for 3 minutes, and group 3 (n = 10): Zoom! Whitening System (Discuss Dental, Culver City, CA) (25% H(2)O(2)) light activated for 20 minutes. The remaining 10 healthy premolars serve as a control group. Teeth were anesthetized immediately after bleaching and were extracted 10 minutes later. All pulp samples were processed and SP was measured by radioimmunoassay. Greater SP expression was found in the Zoom! Whitening System, followed by the Lase Peroxide group, Opalescence Xtra Boost, and the lower SP values were for the control group. Analysis of variance showed statistically significant differences between groups (p = 0.0001). Tukey HSD post hoc tests showed significant differences in the light (p < 0.01) and laser (p < 0.05) activated bleaching systems when compared with control values. It can be concluded that light- and laser-activated tooth-bleaching systems increase SP expression in human dental pulp significantly higher than normal values.

Investigation of polymerisation shrinkage strain, associated cuspal movement and microleakage of MOD cavities restored incrementally with resin-based composite using an LED light curing unit

OBJECTIVES

To investigate the polymerisation shrinkage strain, associated cuspal movement, degree of conversion (DC) and cervical gingival microleakage of mesio-occlusal-distal (MOD) cavities restored with four resin-based composite (RBC) filling materials placed incrementally using a light emitting diode (LED) light curing unit (LCU).

METHODS

Standardised extensive MOD cavity preparations on extracted teeth were performed on 40 sound upper premolar teeth. Restoration of the teeth involved the placement of RBCs in eight increments with the appropriate bonding system before irradiation using an LED LCU. Buccal and palatal cusp deflections at each stage of polymerisation were recorded using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in a 0.2% basic fuchsin dye for 24 h, sagittally sectioned and examined for cervical microleakage. The DC was determined using a Fourier transform infra-red (FT-IR) spectrometer.

RESULTS

No significantly difference (P=0.677) in cuspal movement was recorded for Z100 (13.1+/-3.2 microm) compared with Filtek Z250 (8.4+/-3.5 microm), P60 (7.3+/-3.8 microm) and Admira (6.7+/-2.7 microm). The LED LCU deflections were compared with a halogen LCU used in a conventional (Fleming GJP, Hall D, Shorthall ACC, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with posterior filling materials of varying reported volumetric shrinkage values. Journal of Dentistry, 2005;33:139-146) and soft-start mode (Fleming GJP, Cara RR, Palin WM, Burke FJT. Cuspal movement and microleakage in premolar teeth restored with posterior filling materials cured using 'soft-start' polymerization. Dental Materials, 2006, , in press) and a significant reduction in cuspal movement was identified for curing type and material type (P<0.001 and P=0.002, respectively). No significant differences were noted between the four RBC materials investigated when the DC or microleakage scores were examined for the LED LCU.

SIGNIFICANCE

It would appear that irradiation of RBCs using the LED LCU offered a significant reduction in associated cuspal movement in large MOD cavities. However, the microleakage scores following polymerisation were significantly increased with dye penetration into the pulp chamber from the axial wall evident in teeth restored with the LED LCU.