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

Effect of damage or contamination to the tips of 200 light-curing units

OBJECTIVE

The light-curing unit (LCU) has become a vital piece of dental equipment that must be correctly maintained. This study investigated the impact of contamination and physical damage to the light tip on the power and radiant emittance values from old and new LCUs.

MATERIALS AND METHODS

Two investigators assessed 200 LCUs in dental clinics. The extent of contamination and physical damage to the light-curing unit (LCU) tips was recorded using a scale ranging from 0 to 8, where 0 indicates the absence of damage or contamination, and 8 represents severe damage or contamination. Then, the radiant emittance and power values of the LCU tip were measured using a digital radiometer (Bluephase meter II; Ivoclar, Schaan, Liechtenstein). LCUs that were more than five years old were classified as old. Spearman correlation coefficient was used to determine the relationship between the condition of the LCU and radiant emittance/power (p = 0.05).

RESULTS

There were no significant differences in the percent reduction of the power and radiant emittance from the values reported by the manufacturers, as well as the presence of contamination or physical damage scores between old and relatively new light-curing tips (p > 0.05). The mean ± standard deviation percentage reductions in power and radiant emittance from the manufacturer's stated values were 19.2 ± 17.63% and 3.9 ± 16.49%, respectively. Contamination and physical damage had significant positive correlations with the reduction in the power (r = 0.22070, p = 0.0017 and r = 0.27422, p < 0.0001, respectively) and the reduction in the radiant emittance (r = 0.28626, p < 0.0001 and r = 0.36650, p < 0.0001). Increased contamination and physical damage scores corresponded to greater percent reductions in the power and radiant emittance (p < 0.05).

CONCLUSIONS

Contamination and physical damage to the LCU can negatively impact the light output from LCUs.

CLINICAL RELEVANCE

To ensure optimal performance, dentists should regularly monitor the output of their LCUs and examine the devices for any signs of physical damage or contamination.

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.

Evaluation of Radiant Power of the Light Curing Units Used in Clinics at Governmental and Privates Dental Faculties

Background

 To evaluate the radiant power of the light cure units (LCUs) in relation to their type, radiant exitance, number of years in clinical use, and condition of LCUs tips in governmental and public clinics in Dental Faculties in Sana'a City.

Materials and Methods

LCUs were collected from different colleges at Sanaa City, Yemen, then LCU data as type, clinical age (<1 year, between 1-5 and ˃ 5-years), tip condition was visually inspected for damage and adhering debris, and the radiant exitance values of the tested LCUs. Radiant exitance values were subcategorized into three groups: <400, 400-850, and >850 mW/cm², labeled as inadequate, marginal, and adequate radiant exitances, respectively. A Woodpecker radiometer was used with a mode lasting of 20 seconds was used with each LCU. Descriptive statistics of the different parameters were evaluated with SPSS version 25. One-way ANOVA and Mann-Whitney tests were performed to determine the mean difference between the groups with a significance value of ˂ 0.05 was considered.

Results

Two hundred twenty-three LCUs were surveyed, and the majority were Light-emitting diode (LED). Forty-nine (21.9%), 117 (52.4%), 57 (25.6%) recorded lesser than, 400-850, and more than 850 mW/cm², respectively. Radiant exitances of < year-old units were found to be higher than those of units used for ˃ 5 years with significant differences (p=0.001). The ANOVA test showed significant differences between the radiant exitance with clinical age and LCU tip conditions and a strong correlation p ˃ 0.050.

Conclusion

LED curing lights were the most used in the tested Dental Faculties. More than half of the used LCU offered sufficient radiant exitance. Clinical age, the presence or absence of composite buildups, and damage to curing tips showed significantly affect radiant exitance values.

Improper Light Curing of Bulkfill Composite Drives Surface Changes and Increases S. mutans Biofilm Growth as a Pathway for Higher Risk of Recurrent Caries around Restorations

How dentists cure a resin-based material has deleterious effects on the material's properties and its interaction with surrounding dental tissues. Biofilm accumulation has been implicated in the pathogenesis of carious lesions around dental restorations, with its composition manifesting expressed dysbiosis in patients suffering from dental caries. To evaluate the influence of varying radiant exposure on the degree of conversion (DC%), Streptococcus mutans biofilm growth, and surface roughness of bulk-fill composites under different light-curing conditions. Two light-curing units (LCU) at 600 and 1000 mW/cm² were used to simulate curing conditions with different angulations (∢20° and ∢35°) or 2 mm-distance displacements of the LCU tip. The radiant exposure (RE) was assessed, and the composites were analyzed for DC%. Biofilm formation was induced over the bulk-fill composites and analyzed via colony-forming units counting and scanning electron microscopy (SEM). The surface roughness was analyzed via a profilometer and SEM after biofilm formation. Curing conditions with different angulation or displacement decreased RE compared to the "optimal condition". The moderately (∢35°) angulated LCU tip and low (600 mW/cm²) radiant emittance significantly reduced the DC% (p < 0.05). The difference in DC% between the top and bottom of the composites ranged from 8 to 11% for 600 mW/cm² and 10 to 20% for 1000 mW/cm². Greater S. mutans biofilm and surface changes were found in composites with non-optimal RE delivery (e.g., tip displacement and angulation) (p < 0.05). Inadequate polymerization of bulk-fill composites was associated with more biofilm accumulation and surface topography changes. Overall, non-optimally performed curing procedures reduced the amount of delivered RE, which led to low DC%, more biofilm formation, and higher surface roughness. The improper light-curing of bulk-fill composites compromises their physicochemical and biological properties, which could lead to inferior clinical performance and reduced restorative treatments' longevity.

Utilizing Light Cure Units: A Concise Narrative Review

The use of photo-curable resin composite restorations is an essential treatment modality in modern dental practice. The success and longevity of these restorations depend on achieving predictable and effective polymerization. Understanding the dynamics of the polymerization and the effect of light cure units (LCUs) on this process is paramount. The goal of this concise narrative review is to provide a simplified presentation of basic principles of composite chemistry, polymerization reactions, and photo-curing with relevant terminologies. Clinical guidelines for choosing and maintaining LCUs, as well as safety precautions and factors under the control of the clinician are listed. Finally, clinical recommendations of LCUs’ usage and monitoring are included to aid practitioners in achieving predictable polymerization during the placement of direct resin composite restorations.