2024 年 24 巻 1 号 p. 9-11
Purpose: The aim of the present study was to evaluate the irradiance of light-emitting diode (LED) light bulbs seated around the abrasive grinding disc of a wet laboratory cast trimmer for the enhancement of environmental brightness.
Methods: A total of 12 LED light bulbs were set up along the inner framework of a rotary cast trimmer. The irradiance of the bulbs was determined with a spectral radiometer.
Results: The spectral irradiance mean of 12 LED light bulbs in the cast trimmer was 37.3 µW/cm2 and the value was significantly greater than that of the control. The irradiance median of the 9787 LED light bulb varied from 640.3 µW/cm2 for 0 mm distance to 79.4 µW/cm2 for 200 mm distance. Analysis revealed that irradiance was not statistically affected by the bulb-sensor vertical distances within 50 mm.
Conclusion: The working environment, especially brightness, around a dental stone cast placed on the trimmer stage can be improved considerably through the use of the LED light bulbs.
It is difficult for dental technicians to secure brightness around a stone cast placed in a wet rotary cast trimmer. This is due to the structure of the steel framework surrounding the abrasive grinding disc of the cast trimmer. Moreover, the water flow and direction of the rotary disc make it difficult to visualize the cutting surface.
Several articles have reported the relation between working environment and characteristics of dental equipment. The noise level of a cast trimmer was 70-80 dB at the 15-cm distance, which was lower than that of an airborne particle abrader [1]. Goswami et al. [2] later reported that the noise level of a lathe trimmer was higher than that of a vibrator. One of the problems associated with laboratory cast trimmers is insufficient brightness around a stone cast. This is clearly derived from the structure of the metallic framework and rotary disc of the trimmer. Simple methods for removing debris from a stone cast after the use of a cast trimmer have also been described [3]. The application of light bulbs is considered to be useful in the enhancement of at-hand brightness of the cast placed on the working table of the trimmer. Various light sources are candidates for this purpose. Light-emitting diode (LED) light bulbs have been used for both chair-side [4,5,6,7] and laboratory light polymerization units [8,9,10].
Although wet rotary cast trimmers are frequently used in the dental laboratory for trimming stone casts, only limited information is available concerning improvement in the working environment especially as related to brightness around the casts.
The current study used LED light bulbs for the enhancement of the environmental brightness of a cast trimmer. The null hypothesis is that application of LED light bulbs is effective for the improvement in the working environment of a cast trimmer.
A representative wet laboratory cast trimmer and LED light bulbs were selected. Their specifications and model codes are summarized in Table 1.
AssemblyThe assembly of the wet laboratory cast trimmer with and without LED light bulbs is shown in Fig. 1. The bulbs are seated in a piece of irrigation waterproof tape 1-5 m in length. A piece of tape with bulbs in multiples of three can be separated from the originally supplied long tape. The cast trimer used a piece of tape with 12 bulbs. The tape was bonded inside the framework of the trimmer along the rotary cutting disc with a cyanoacrylate adhesive (Feed Instant Glue LV, Feed Co., Ltd., Yokohama, Japan). The bulbs were set at approximately a quarter of the circumference of the cutting disc (Fig. 1). An alternative current adapter was connected to the end of the tape.
Irradiance of the LED light bulbsIrradiance of the LED light bulbs was determined with a spectral radiometer (USR-45, Ushio Inc., Tokyo, Japan). The distance between the light receiving sensor and the LED light bulbs set in the cast trimer is shown in Fig. 2. In addition, irradiance of a single bulb was measured for the bulb-sensor vertical distances of 0, 50, 100, 150, and 200 mm. Measuring conditions are summarized in Tables 2 and 3. Irradiance was determined by 9 replications for each condition.
Statistical analysisThe difference in irradiance determined at the trimmer stage between light-exposed and unexposed conditions was statistically analyzed. In addition, the difference in irradiance of a single bulb measured at the different five bulb-sensor distances was analyzed. Normality was analyzed with D'Agostino-Pearson test. Homoscedasticity, i.e., homogeneity of variance was evaluated with Bartlett's test. Based on the results of normality and homoscedasticity evaluations, data were statistically analyzed further with unpaired t test or Dunn's multiple comparisons test with the value of statistical significance set at P < 0.05 (GraphPad Prism 8.3 software, GraphPad Software, La Jolla, CA, USA).
Table 1 Equipment and materials used
| Equipment / trade name | Manufacturer / trader | Specification* | Model code |
|---|---|---|---|
| Wet rotary cast trimmer | |||
| Arrow Model Trimmer Custom 700 | Tokyo Dental Industrial Co., Ltd., Tokyo, Japan | current consumption: 6.0 A / 5.4 A (50/60 Hz); motor: AC 100 V, 250 W, 50/60 Hz, 1,500/1,800 rpm | oneA PC-251 |
| LED light bulbs | |||
| Waterproof Tape LED 5050 | LED Paradise / Peace Corp., Koshigaya, Japan | Fully waterproof Grade IP68; LED type: 5050 3chip SMD; number of LEDs: 60/m; rated power: 14.4 W/m; input voltage: DC 12 V; Luminous color: RGB | 9787 |
| AC adapter | |||
| Anthin AC Adapter | LED Paradise / Peace Corp. | input voltage: AC 100-240 V 50/60 HZ; output voltage: DC 12 V; output current: 1.5 A | APS318-1215 |
| Spectral radiometer | |||
| Ushio Spectral Radiometer | Ushio Inc., Tokyo, Japan | interval: 100 s; cumulative time period: 6,664 ms; wavelength range: 400-800 nm | USR-45 |
*Information from the package insert
A total of 12 bulbs were seated. Lighting: a, off; b, on
| Lighting | Distance | D'Agostino-Pearson test | Irradiance (µW/cm2) | Unpaired t test |
|
|---|---|---|---|---|---|
| P value | mean | SD | P value | ||
| on | 117 mm, 20 mm | 0.9944 | 37.3 | 0.5 | P < 0.0001 |
| off | 0.5622 | 6.2 | 0.1 | ||
| Distance | D'Agostino-Pearson test | Irradiance (µW/cm2) | Dunn's multiple comparisons | ||||
|---|---|---|---|---|---|---|---|
| P value | median | IQR | 50 mm | 100 mm | 150 mm | 200 mm | |
| 0 mm | 0.8018 | 640.3 | 1.9 | NS | S | S | S |
| 50 mm | 0.3181 | 196.7 | 0.1 | NS | S | S | |
| 100 mm | 0.4380 | 134.7 | 0.1 | NS | S | ||
| 150 mm | 0.3157 | 100.3 | 0.2 | NS | |||
| 200 mm | 0.6526 | 79.4 | 0.1 | ||||
Lighting: a, off; b, on
Figure 3 shows spectral irradiance determined with a spectral radiometer. Maximal irradiance for the 9787 LED light bulbs was recorded with the 450 nm wavelength. Table 2 presents irradiance of the 12 LED light bulbs seated in the cast trimmer. The irradiance mean at the measuring point (Fig. 2) exposed with 12 light bulbs was 37.3 µW/cm2, whereas irradiance without light exposure was 6.2 µW/cm2. D'Agostino-Pearson test revealed both conditions passed the normality test (P > 0.05). The results were therefore analyzed with unpaired t test. The difference between the two conditions was significant (P < 0.0001).
The irradiance of a single LED light bulb was next determined, and the results are shown in Table 3. Irradiance median of the 9787 LED light bulb was 640.3 µW/cm2 for 0 mm distance, 196.7 µW/cm2 for 50 mm, 134.7 µW/cm2 for 100 mm, 100.3 µW/cm2 for 150 mm, and 79.4 µW/cm2 for 200 mm, respectively. Analysis revealed that irradiance was not statistically affected by the bulb-sensor vertical distances within 50 mm.
Figure 4 compares brightness of a stone cast set on the working table of the wet rotary cast trimer with and without lighting. Improvement in at-hand brightness is clear through the placement of 12 light bulbs.
LED light bulbs effectively enhanced brightness around the stone cast placed on the trimmer stage. It is clear that improvement in brightness improves the safety of the working environment in the dental laboratory.
The selection of light bulbs is an important issue in the current project. Safety of light source must be secured for the assembly. A red-green-blue (RGB) light source was selected due to reduced energy distribution of short wavelength (Fig. 3). RGB-LED light source has been used as a light source for both intraoral and laboratory polymerization apparatus [4,5,6,7,8,9]. A flexible and waterproof substrate was essential for the current assembly. Application of the LED 5050-9787 bulbs made it possible to set up the rounded 12-bulb system. Adhesive ability under wet conditions was required for seating the waterproof tape. Although cyanoacrylate adhesive was used for bonding the tape to the trimmer framework, double-coated tape, or bolts and nuts are also applicable for fixing the tape.
The irradiance of the light bulbs clearly influences the working environment of the dental laboratory. The current experimental results showed that irradiance under the LED light exposure is influenced by the distance between light bulb and spectral radiometer. Brightness around a dental stone cast placed on the trimmer stage improved considerably with the use of the LED light bulbs. The probability of finger injuries and excessive cast grinding during the trimming procedure will be reduced with the use of the LED light bulbs.
IQR: interquartile range; LED: light-emitting diode; NS: not significant; RGB: red, green, blue; S: significant; SD: standard deviation
Not applicable
Not applicable
This project received no funding.
KK: conceptualization, investigation, methodology, data curation, formal analysis, visualization, writing; HK: conceptualization, methodology, formal analysis, writing, review, editing, supervision; HI: conceptualization, methodology, formal analysis, writing, review, editing, supervision. All authors read and approved the final version of the manuscript.
2) HK: NA, NA
1) HI*: imai.hideyuki@nihon-u.ac.jp, https://orcid.org/0009-0009-4569-4978
The authors express their appreciation to the faculty members of Nihon University School of Dentistry for instruction concerning experimental methodology. Problems concerning the current project was reported at the Dental Practice Clinical Needs Online Matching Meeting, Japanese Dental Science Federation, January 23, 2021.
Data generated and analyzed are available from the corresponding author on reasonable request.
