The light-curing unit: An essential piece of dental equipment

BACKGROUND Light-curing is a crucial step during the application of composite resin restorations. Composite's success depends on delivering enough light energy to the resin to achieve adequate polymerization. However, dentists are not recognizing the importance of proper light-curing technique. OBJECTIVES To measure light energy delivered to simulated restorations by preclinical dental students and dentists in internship year. To evaluate the effect of experience and training on the clinician's ability to light-cure composite restorations. METHODS A group of 50 preclinical dental students and a group of 50 internship dentists light-cured for 10 seconds, a simulated class III and class I restorations positioned in a patient simulator (MARC-Patient Simulator [BlueLight Analytics Inc., Canada]) that measured the irradiance and energy delivered by the curing light. Then participants received individualized training on optimizing their light-curing technique. They were retested after the training. Statistical analysis was done with two-way ANOVA and Tukey's test. RESULTS Participants delivered an average of 60% more energy after the instructions, which is a significant improvement (P < 0.05). The number of participants that failed to deliver the minimum amount of energy (6 J/cm²) decreased significantly from 37.5% to 2.5%. There was a significant difference in the amount of energy delivered by the Preclinical and Internship groups (P < 0.05). CONCLUSION Initially, many participants were not using the curing light properly. Light-curing technique improved with training and using a patient simulator. Experience can enhance the operator's ability to light-cure composite restorations. However, a training session can improve light-curing performance more than years of experience.

Training and experience effect on light-curing efficiency by dental practitioners.

Composite materials are the most common materials in use in modern dentistry. Over the years, the methods of photopolymerization of composite materials have been improved with the use of various devices, such as quartz tungsten halogen lamps (QTHs), light-emitting diode units (LEDs), plasma-arc lamps and argon-ion lasers. This study aimed to compare the mechanical properties of a composite material, depending on the time and mode of photopolymerization. One hundred and forty rectangular specimens (25 × 2 × 2 mm) and forty-two disc-shaped samples (5 mm diameter and 2 mm thickness) were prepared from shade A2 Boston composite resin. Samples were cured using the following seven photopolymerization protocols: four fast-cure modes (full power for 3, 5, 10, and 20 s), two pulse-cure modes (5 and 10 shots of 1 s exposures at full power), and one step-cure mode (soft start with a progressive cycle lasting 9 s). Specimens were subjected to a flexural strength test, Vickers microhardness test, and FTIR spectroscopy test. A 2-factor ANOVA and post-hoc tests were carried out to assess the differences in the flexural strength parameter between the tested groups of samples before and after aging. A mixed-model ANOVA was carried out to assess the differences in the Vickers microhardness parameter between the tested groups of samples before and after aging. The lowest values of flexural strength (p < 0.001) and Vickers microhardness (p < 0.001) were obtained for the 3 s mode for the pre- and post-aging groups. The FTIR mapping tests showed a much more homogeneous chemical structure of the composite after 20 s of continuous irradiation, compared to the sample irradiated for 5 s in the continuous mode. The mode and cure time affects the mechanical properties of the composite resin. Appropriate selection of the cure mode and time ensures better mechanical properties of composite resin. This suggests that the survival of dental restorations within the oral cavity could be extended by using longer photopolymerization durations.

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How the Duration and Mode of Photopolymerization Affect the Mechanical Properties of a Dental Composite Resin

Depth of cure of 10 resin-based composites light-activated using a laser diode, multi-peak, and single-peak light-emitting diode curing lights.

The selection of an accurate tooth shade has always been a challenging task for dental practitioners in restoring the natural appearance of teeth. Various factors can influence shade selection, such as different lighting conditions, clearness and opaqueness of teeth, eye fatigue, aging and color vision problems. It is imperative to have a sound knowledge about the concept of shades and its selection protocol for obtaining good esthetics outcomes. To attain the best esthetics, four elementary contributing factors are essential: exact position, shape, surface texture and shade. The current analysis focuses on several features of shade, sensitivity of shades, optical properties of the teeth, visual and innovative instrumental techniques for shade selection, protocols for shade selection and factors affecting dental shade selection.

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An Overview of Shade Selection in Clinical Dentistry


 
 Light-curing is a crucial step during the application of composite resin restorations. The clinical success of composite depends on the Light-Curing Units (LCU) to deliver adequate light energy to polymerize the resin. However, light-curing usually does not receive the proper awareness it deserves.
 
 
 
 This study aims to evaluate the effect of contamination and debris of the LCU’s tip on its light output. Determine the effect of damage to the LCU’s tip such as chipping, dents and scratches. Additionally, it evaluates the effect of plastic barrier sleeves.
 
 
 
 Sixty LED LCUs were tested using MARC™ Resin Calibrator (BlueLight Analytic Inc., Halifax, Canada) to measure their irradiance and energy before and after cleaning their tips. They were also tested with and without a clear plastic barrier. Additionally, four damaged LCUs received new tips and were tested again. Kruskal-Wallis H and One-Way ANOVA tests were used for statistical analysis.
 
 
 
 Cleaning the LCUs’ tips showed significant improvement, an average increase of 8.2%. However, some units increased by up to 47% in irradiance and energy values. Replacing the damaged tip with a new one significantly improved the output of the LCUs, increasing light energy by up to 73%. The barrier used in this study caused 7% reduction in the energy delivered by the LCUs. The statistical analysis showed that cleaning the LCUs and replacing their damaged tips resulted in a significant increase in energy (p<0.05).
 
 
 
 Unclean or damaged LCUs’ tips can drastically reduce the light output of the LCUs, reducing the quality of the composite restorations. Clinicians are strongly recommended to regularly monitor, clean and maintain their curing lights.


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Effect of Contamination, Damage and Barriers on the Light Output of Light-Curing Units

Out of the 180 participants, 57.9% were females, and 42.2% were males. Eighty-three percent were 35 years old or less, 12.2% were between 36 and 50 years, and 4.4% were 50 years or older. Most participants were UAE graduates (84.4%). Majority of the participants would delay surgical intervention of the approximal carious lesion until it reaches the dentine-enamel junction (41%), and 27% would wait further until it reaches into the outer dentine, while only 21% would intervene when the lesion is limited to enamel. The majority of the participants preferred simple box preparation (72.8%), and most of them chose composite as the restorative material (85%).

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Restorative Treatment Decisions on Approximal Caries Among Practicing Dentists in the College of Dentistry Clinics, Ajman University, United Arab Emirates

Shade selection is a crucial step in achieving aesthetically-pleasing restorations, and it is affected by the dentist’s ability to match the shade of the patient’s teeth. Color Deficiency Disease (CVD) has been thought to be a potential factor affecting color perception. The study aims to find the prevalence of CVD between dentists and dental students and to evaluate its effect on shade matching ability.

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Ahmad Abdo

Papers

Training and experience effect on light-curing efficiency by dental practitioners.

Effect of Contamination, Damage and Barriers on the Light Output of Light-Curing Units

Restorative Treatment Decisions on Approximal Caries Among Practicing Dentists in the College of Dentistry Clinics, Ajman University, United Arab Emirates

Prevalence of Color Vision Deficiency among Dental Practitioners and its Effect on Shade Matching Ability