The effect of infection-control barriers on the light intensity of light-cure units and depth of cure of composite

Effect of infection control barriers on the light output from a multi-peak light curing unit

OBJECTIVES

Curing lights cannot be sterilized and should be covered with an infection control barrier. This study evaluated the effect of barriers when applied correctly and incorrectly on the radiant power (mW), irradiance (mW/cm2), emission spectrum (mW/nm), and beam profile from a multi-peak light-curing unit (LCU).

METHODS

Five plastic barriers (VALO Grand, Ultradent; TIDIShield, TIDI Products; Disposa-Shield, Dentsply Sirona; Cure Sleeve, Kerr; Stretch and Seal, Betty Crocker) and one latex-based barrier (Curelastic, Steri-Shield) were tested. The radiant power (mW) and emission spectrum (mW/nm) from one multi-peak LCU (VALO Grand, Ultradent) was measured using an integrating sphere. LCU tip internal diameter (mm) was measured, then the tip area and irradiance (mW/cm2) were calculated. The beam profiles were measured using a laser beam profiler.

RESULTS

When applied correctly, the plastic barriers reduced the radiant power output by 5-8%, and the latex-based barrier by 16%. When the plastic seam or barrier opaque face was positioned over the LCU tip, the power output was reduced by 8-11%. When the plastic barriers were wrinkled, the power output was significantly reduced by 14-26%. The wrinkled latex-based barrier reduced by 28%, and further reduced the violet light. The beam profiles illustrated the importance of correctly barrier use without wrinkles over the tip.

CONCLUSIONS

Plastic barriers applied correctly reduced the light output (mW) by 5-8%. The barriers applied incorrectly significantly reduced the light output by 14-26%. The latex-based barrier wrinkled also reduced the amount of violet light.

CLINICAL RELEVANCE

Infection control curing light barriers should be used to prevent cross-infection between patients. However, they must be applied correctly to reduce their negative effects on the light output.

Infection Control Barrier and Curing Time as Factors Affecting the Irradiance of Light-Cure Units

Objective

The objective of the study is to investigate the effect of infection control barrier (ICB) and curing time on irradiance of light cure units (LCUs).

Methods

Irradiance (mW/cm²) of the LCUs at a government dental school were recorded with and without ICB at 0 (T₀), 10 (T₁₀), and 20 (T₂₀) seconds using a digital radiometer. Data were analyzed using IBM^® SPSS^® Statistics Version 17 for Windows software for the analysis of variance and Bonferroni methods at 0.05 significance level.

Results

Using ICB resulted in a statistically significant effect on the irradiance mean (P < 0.01). A significant difference existed between the four different brands of LCUs at different time intervals, irrespective of the use of ICB. At T₀ and T₁₀, the mean output of Acteon mini-light-emitting diode (LED) was significantly higher than that of either the Kerr Demi Ultra or the Kavo Polylux II. At T₂₀, E-Morlit's mean irradiance was significantly higher than that of Kerr Demi Ultra, which in turn was significantly higher than that of the Kavo PolyLux II. The mean irradiance of the LEDs was significantly higher than that of the halogens irrespective of barrier placement and at all-time points.

Conclusion

The ICB used in this study resulted in a statistically significant reduction in the irradiance output. No significant difference in the irradiance was found at different curing time intervals for the tested units regardless of ICB usage.

Effect of Curing Light Barriers and Light Types on Radiant Exposure and Composite Conversion

PURPOSE

Previous research investigated the effects of curing tip barriers on light output and composite properties, but no study has measured the effect of a wide variety of barriers and curing light types on delivered radiant exposure and the resulting composite cure 2 mm below the radiated surface.

MATERIALS AND METHODS

Six barrier materials and six curing light types were tested. Spectroradiometry was used to measure irradiance with and without barriers for each light type, and radiant exposure values were determined for a commercial camphorquinone-based dental composite material. Composite monomer conversion was measured at 10 minutes following exposure for each light type/barrier condition (N = 5) using infrared spectroscopy. Results were subjected to one-way analyses of variance for radiant exposure and conversion among barrier types within a given curing light: preset alpha 0.05.

RESULTS

All barriers significantly reduced radiant exposure compared with the uncovered tip, but the use of the two polywave LEDs covered with a latex-based barrier demonstrated significantly lower conversion values.

CONCLUSIONS

Although light-curing barriers reduce radiant exposure to a restorative material over a recommended exposure, this reduction is not sufficient to cause significant reduction in composite cure, except when using a latex-based barrier and a polywave LED curing light.

CLINICAL SIGNIFICANCE

Clinicians need to be aware of the possible interaction between curing light barriers and curing light type in order to optimally photocure restorative materials.

The effect of disposable infection control sleeves on the total energy delivered by dental LCUs

AIM

This study compared the effect of seven different disposable cross-infection control sleeves on the total energy delivered (J/cm2) by four different dental light-curing units (LCUs).

METHODS

Four LCUs and seven disposable sleeves (six proprietary brands and a general-purpose cellophane wrap) were used. Anterior and posterior tooth position was included as a third factor. Total energy delivered was measured for each LCU without a sleeve (control) and with each sleeve and for each tooth position. Curing time was 10 seconds, as recommended by the LCU manufacturers. Measurements were taken 10 times for each sleeve/LCU/tooth position and means (SD) calculated. Data were analysed using three-way analysis of variance (ANOVA). The null hypothesis was that none of the sleeves would, at a 0.1% level, significantly affect the total energy delivered.

RESULTS

All sleeves significantly reduced the total energy delivered (P < 0.001). Cellophane wrap (cling film) had the smallest effect on total energy. Total energy delivered was most strongly influenced by tooth position and LCU model.

CONCLUSIONS

Sleeves significantly reduce the total energy delivered compared to unsleeved LCUs, but to a degree that may not be clinically important. Cling film reduced total energy delivered to a significantly lesser extent than did proprietary bands of sleeve. In order to determine adequacy of delivered total energy, sleeved LCUs should be tested prior to clinical use.

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.

Efficacy of cling film for barrier protection in a dental clinical environment: short communication

Disposable plastic film is sometimes used as barrier protection for items of equipment in the dental surgery. This study was designed to investigate the efficacy of cling film for this purpose. The clinic experiment investigated whether there was a progressive accumulation of bacteria on the dental chair bracket table surface, protected by cling film, during 10 clinical sessions. The results showed that occasional contamination occurred (1—7 cfu/100cm2) but there was no evidence of accumulation of bacteria beneath the cling film. Laboratory experiments in which Escherichia coli, Staphylococcus epidermidis, and Streptococcus sanguinis in suspensions of approximately 3 × 105 cfu/ml were placed on the surface of cling film on agar plates for 30 minutes demonstrated that the organisms were unable to pass through but contaminants from the film were detected on 12/32 plates. We conclude that cling film is effective in this application but could itself potentially be a vehicle for cross-infection.

The Influence of Plastic Light Cure Sheaths on the Hardness of Resin Composite

Disposable sheaths are now recommended as a method of cross infection control when light curing resin composite. However, these sheaths may affect the depth of cure of the resin composite, resulting in a compromise of the mechanical properties of the restorative material.

Effect of Distance from Curing Light Tip to Restoration Surface on Depth of Cure of Composite Resin

Aims

While light-activating composite resins, the light tip may not always be close to the surface of the restoration. This may be intentional in an attempt to create a ramp cure. The aim of this study was to determine the effect of a range of separation distances between the light tip and the restoration surface on the depth of composite cure for different types of light-curing units with a broad range of outputs.

Methods

Three halogen light units, one plasma arc-curing (PAC) light unit and two light-emitting diode (LED) curing lights in clinical use were tested, and a total of 570 restorations cured in a two-part human tooth model at separations ranging from 0 to 15 mm. The tooth was disassembled and depth of cure determined using the scrape test ISO 4049. Light intensity was also measured at each separation distance for each light.

Results

The depth of cure was generally found to decrease as the separation distance increased for all lights at the various cure times. However, the effect of increasing the separation distance was less than anticipated. The depth of cure was also related to the light output.

Conclusions

Depth of composite cure was directly related to intensity and duration of light exposure and inversely related to distance of the light source from the surface for halogen and plasma lights. However, the effect of increasing the separation distance up to 15 mm was less than expected. Altering the separation distance in order to modify the polymerisation characteristics is unlikely to be effective.