In an effort to improve the safety of surgery, we investigated the incidents related to surgery using a laser or an electric scalpel, not to mention other equipment.
The subjects included in this study were 86 cases who experienced incidents related to their surgery that we found in the reports of the Japan Council for Quality Health Care. We searched for a breakdown of the medical equipment used and the influence on the patient, and analyzed the causes of the incidents to determine whether new recommendations might reduce the risk of incidents.
The breakdown of the medical equipment included 61 electric scalpels, 11 light sources, 7 radio wave cautery devices, 5 lasers, and 2 supersonic wave coagulation incision devices. The incidents were 46 burns, including 18 with no adverse outcomes, 8 cases with a foreign body left after surgery, 6 cases of damage to a proximal organ, 3 cases with perforations and 5 other incidents. The causes were 33 errors in the use of the equipment, 20 malfunctions and/or damage to the equipment, 17 cases of sudden ignition, 9 cases in conjunction with the use of a counter electrode plate, and 7 other causes.
Many incidents were related to the use of a heat source apparatus, such as an electric scalpel or laser. Because most incidents were due to a lack of knowledge and recognition, taking countermeasures including increased education may be able to prevent the majority of incidents.
Medical workers can reduce incidents by recognizing the risks, increasing their knowledge about the devices and sharing countermeasures as a team.

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We have reported pain relieving effects and blood flow changes in dental pulp by laser irradiation. The aim of this study was to investigate the threshold of thermal sensation and blood flow in dental pulp by low-power Nd:YAG laser irradiation to the mental foramen.
Materials and Methods: Medical staff of Tsurumi University School of Dental Medicine with normal right lower canines received low-power Nd:YAG laser irradiation on the left mental foramen. Blood flow and the threshold of thermal sensation at the right lower canine were measured and compared with those at rest.
Results: Nd:YAG laser irradiation to the left mental foramen elevated blood flow in the dental pulp below the right lower canine (p < 0.05). After irradiation, the blood flow decreased rapidly and became equal to that at rest. The threshold of thermal sensation was also elevated by laser irradiation (p < 0.05).
Discussion: Nd:YAG laser irradiation on the mental foramen resulted in increases of blood flow in the dental pulp and the threshold of thermal sensation, suggesting that it may be effective, for example, for relieving pain by suppressing the sympathetic nerve.

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The clinical examination of dental caries is usually conducted by visual inspection and tactile palpation in conjunction with radiographic examination. Last year, a new device for diagnosis, DIAGNOcam received pharmaceutical approval in Japan. In this apparatus, laser diode light (wavelength 780 nm) is transmitted from bone to tooth, and the images are captured by a charged-coupled device. The detection of dental caries is based on the changes in the contrast of the obtained images compared with that of healthy tooth substances. Recent reports have indicated that this new device has an advantage of no radiation exposure and is effective for caries examination of permanent dentition. However, there is little data available on its efficacy for caries examination of primary teeth. The aim of this study was to evaluate the clinical efficiency of the DIAGNOcam in caries examination of primary teeth. We analyzed eight primary teeth from four individuals, and found that the DIAGNOcam was useful for caries examination of primary teeth. However, the initial caries was not clearly identified. This clinical study revealed that the DIAGNOcam is a useful tool for caries detection in primary as well as permanent teeth.

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Transmitted-light plethysmography (TLP) is an optical technique to detect circulatory changes in pulp tissue. It has been reported as overcoming the disadvantages of electrical pulp testing in terms of objectivity and invasiveness. In a previous study, we reported the applicability of the TLP system with a 525 nm light-emitting diode (LED) to traumatized young permanent and deciduous teeth. The system works by detecting the pulsation intensity of light transmitted through a tooth and visualizing the pulpal blood flow synchronized with the heartbeat. During the clinical follow-up, we found that TLP pulse amplitudes and pulse shape characteristics change gradually due to the pathological condition. However, the origins of tooth plethysmograms were not fully understood because of the structural specificity of teeth. In this study, multiwavelength optical plethysmography was used to examine the light transmission properties of teeth to clarify the effects of physiological parameters such as the blood volume and SO₂ on the pulsation of TLP pulse waves. The results indicated that the optical process in teeth mainly depended on the blood cell concentration (Hct_p), light attenuation by the hard tissues, and the light source wavelength. Clinically, it was assumed that the changes in blood vessel density, pulpal blood volume, and pulp chamber size associated with subjects' ages or pathological conditions might affect TLP pulse waves. We also demonstrated the applicability of pulse oximetry to dental pulp using an in vitro blood circulation model. The LEDs with 470 nm and 590 nm wavelengths showed high sensitivity to the blood SO₂ level. R values calculated from pulsatile/nonpulsatile component ratios of two different wavelengths were significantly correlated with the pulpal SO₂, indicating the possibility of pulpal blood SO₂ measurement. The present results indicate that TLP pulse waves potentially provide additional information to diagnose the circulatory status of the pulp in relation to pathological conditions of the dental pulp.

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Optical coherence tomography (OCT) constructs images through the wave interference that occurs when backscattered light from a sample is coupled with a reference light. OCT visualizes differences in the tissue's optical properties, which includes the effects of both optical absorption and scattering. In particular, swept-source OCT (SS-OCT) can construct images through the ultrahigh-speed scanning of the time-encoded wavelength of a near-infrared laser. The purpose of this study was to apply this technology in the practice of dentistry for imaging teeth and composite restorations, which may facilitate the clinical diagnosis of caries and tooth cracks, as well as the evaluation of existing restorations in the future.
The SS-OCT images obtained by intraoral scanning that involved sound or slightly demineralized enamel up to the deep dentin caries were examined and compared with those of the radiographs. In SS-OCT, sound enamel is almost transparent at the SS-OCT wavelength range or upper near-infrared region around 1,300nm. In caries lesions, the signal generally increases and the demineralized region appears brighter on the grayscale SS-OCT images, because of the formation of numerous submicron-size defects resulting from demineralization in carious lesions. If the caries penetrates into dentin, the penetration depth of the bright zone observed in SS-OCT extends beyond the DEJ level. In some cases, lateral expansion of the caries lesion creates micro gaps along the DEJ, where strong reflection occurs.
Cracked teeth have been a diagnostic challenge because of the difficulty in locating crack lines on incomplete tooth fractures. Since a crack has an unpredictable prognosis, including extraction, accurate diagnosis regarding the size and localization of the crack is required to determine the most appropriate treatment technique. We examined SS-OCT as a diagnostic tool for tooth cracks, and this methodology proved capable of providing clear imaging of tooth cracks, including information on penetration depth.
Since OCT is an optical imaging modality, its principal disadvantage is that the light attenuation from scattering by tissue limits the image penetration depth. Also, images obtained in OCT are significantly influenced by the optical properties of biological structures, e.g. the refractive index, which determines light refraction and light speed. However, OCT is a promising imaging technology in dentistry, because it performs real-time cross-sectional imaging of the tissue microstructure without the need for radiation dosing.

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