Shigeru Shoji

Histopathological changes in dental pulps irradiated by CO2 laser: A preliminary report on laser pulpotomy

A study was conducted on the effects of CO2 laser irradiation on the dental pulp. Ten adult mongrel dogs were used. Either focused laser beam (spot size: d=0.15 mm) or defocused laser beam (spot size: d=3.0 mm) was applied to the exposed pulp. The ranges of output power were 3, 10, 30, and 60 W; the ranges of the irradiation periods were 0.1, 0,5, and 1.0 s. Histopathological examination of the pulp was performed immediately after the irradiation. Among the conditions examined, an output of 60 W and an irradiation period of 0.5 s produced the most favorable border between normal and necrotic tissues. No detectable damage was observed in the radicular portions of pulps that were irradiated.

Canal Enlargement by Er:YAG Laser Using a Cone-Shaped Irradiation Tip

To solve the problem of mechanical instrumentation, we developed a cone-shaped laser irradiation tip. This tip delivers 80% of the energy of the laser laterally and 20% of the energy forward. The tip was equipped with a water nozzle. The aim of this study was to examine the effect of Er:YAG laser irradiation using this tip on root canal enlargement and debridement. As a root canal model, a hole (0.5 x 5 mm) was drilled into a bovine dentin block. The tip was inserted into this hole and moved from the apex to the orifice (45 mm/min). The power of 10 mJ x 10 pps caused enlargement of the canal dimension by 106.5%. 20 and 40 mJ x 10 pps caused enlargements of 116.3 and 118.6%. 30 mJ x 10 pps caused the biggest change (129.8%). Scanning electron microscopic observations indicated that the dentin surface after laser preparation appeared cleaner than that obtained after preparation by drilling. This technique may have the advantage of decreasing the preparation time.

A Radio Frequency Identification Implanted in a Tooth can Communicate With the Outside World

A radio frequency identification (RFID) transponder covering the 13.56 MHz band was adapted to minimize its volume so that it could be placed in the pulp chamber of an endodontically treated human tooth. The minimized transponder had a maximum communication distance of 30 mm. In an animal experiment, the transponder was fixed in the cavity of a mandibular canine of a dog. An RFID reader positioned close to the dogs face could communicate with the transponder in the dogs tooth. In certain cases, the system is applicable for the personal identification procedures for hospitalized patients instead of an identification wristband.

Leading a patient to a dental office: the evaluation of pain and stress during the dental treatment using an air-pad sensor system

To ensure the general health of people, every dentist should work toward maintaining the dental health of the public. But most people dislike going to a dental clinic to take treatment. To encourage patients to undergo dental treatment, we should provide them with painless treatment. The purpose of this study is to evaluate patient’s pain and stress during dental treatment using an air-pad sensor to impart painless dental treatment. We have to measure the change of respiration and heartbeat using air-pad sensor. We obtain a low frequency (2–7 Hz) of body vibration using an air-pad sensor. We observe the change in height and width of heartbeat and respiration during the dental treatment. This would help us scientifically determine the pain and stress a patient undergoes during dental treatment.

Stealth authentication by communication with radio-frequency transponder embedded in a tooth

A radio frequency identification (RFID) transponder covering the 13.56 MHz band was adapted to be placed in the pulp chamber of an endodontically treated molar human tooth. In an animal experiment, the transponder could be fixed in the cavity of a mandibular canine of a dog. An RFID reader positioned close to the dog’s face could communicate with the transponder in the dog’s tooth.

Er:YAG and alexandrite laser radiation propagation in the root canal and its effect on bacteria

The goal of the study was to verify differences between the alexandrite and Er:YAG laser energy distribution in the root canal and in the surrounding dentin and bone tissues. For the experiment, two lasers were prepared: the Er:YAG laser (λ=2.94 μm) with a delivery system fluorocarbon polymer-coated silver hollow glass waveguide ended by a special sapphire tip and the alexandrite laser (λ=0.75 μm) with a silicon fiber. The Er:YAG laser was operated in a free-running mode, the length of the generated pulses was 250 μsec and the output energy ranged from 100 to 350 mJ. The pulse length of the free- running alexandrite laser was 70 μsec and the output energy was ranged from 80 up to 200 mJ. For the experiment prepared root canals of molars were used. It was ascertained that the radiation of the alexandrite laser passes through the root canal and hits the surrounding tissue. Nocardia asteroids, Filaments, Micrococcus albus, Lactobacillus sp and Streptococcus sanguis colonies were treated by the Er:YAG or alexandrite laser radiation. The surface was checked by scanning electron microscopy. From the result it follows that the Er:YAG laser destroyed microbial colonies but the differences is in the depth of the affected area.