AIM:The aim of this study was to investigate the pattern of light transmission through teeth of different species and to examine laser light propagation within enamel from various animal sources.METHODOLOGY:Sectioned teeth from five species--pig, horse, sheep, cat and rat--were evaluated. Samples were illuminated individually by a helium-neon laser light from the buccal surface using a probe 0.5 mm in diameter placed at varying angles between 60 and 120 degrees C. The pattern of light transmission was observed macroscopically. Further evaluation of laser light transmission in enamel was achieved using confocal microscopy.RESULTS:In each species, light was transmitted through the tooth to the pulp, but in the cat and the rat, light was also transmitted to the far side of the tooth. Despite the different patterns of enamel in the species, light was transmitted through enamel to dentine.CONCLUSION:Light from a laser Doppler probe appeared to reach the dental pulp in all the species: however, in the mammals with smaller teeth, light may also have been able to reach the periodontium and thus the reflected signal may not be entirely of pulpal origin.

This study examined the transmission of helium neon laser light in 20 dog and human teeth. The effect of probe position and angulation was observed both macroscopically and at a microscopic level using confocal microscopy, In all teeth in both species, laser light was transmitted through teeth to the pulpal surface with the light following the path of the enamel prisms and dentinal tubules, Probe angulation did not affect the pattern of light transmission, nor did probe position; however, the position of the probe on the tooth surface determined which section of the pulp was illuminated, Enamel and dentine together are able to collect and distribute light within the tooth, with both enamel prisms and dentinal tubules acting as optical fibres.

Laser Doppler flowmetry has been shown to be useful in assessing blood flow in teeth. This study investigated the effect of probe design and bandwidth on laser Doppler readings from vital and root-filled teeth using an 810 nm light source, and established the sensitivity and specificity of each probe/bandwidth combination. Readings were taken from 20 human subjects with a root-filled tooth and a vital contralateral tooth using each of the probes with 0.125 mm, 0.375 mm and 0.5 mm fibre separations and three bandwidths (3.1 kHz, 14.9 kHz and 20 kHz). Ten pairs of traces from each group were examined by 10 trained observers who indicated whether the traces had come from a vital or root-filled tooth. The sensitivity and specificity of each combination were calculated from the accuracy of their replies. This was repeated for five observers but with additional information from Fourier analysis. Median readings from vital teeth were higher than those from root-filled teeth for all combinations. This difference was only significant at the 95% confidence level for the 0.5 mm probe with the two lower bandwidths. The 0.125 mm fibre separation probe showed good specificity. The other two probes had better sensitivity but poor specificity. The best specificity and sensitivity was shown by the 0.5 mm probe/3.1 kHz bandwidth combination. All sensitivities and specificities increased when additional information from Fourier analysis was available, but the 0.5 mm probe/3.1 kHz combination still had the best sensitivity and specificity.

The aim of this study was to investigate the effect of wavelength and bandwidth on laser Doppler flowmeter signals from vital and root-filled teeth, and to establish their sensitivity and specificity. Twenty human subjects were recruited, each with a vital tooth and the contralateral tooth root filled but not restored apart from the palatal access cavity. Readings were taken from these teeth for 3 min at 20 Hz for each of 3.1 kHz, 14.9 kHz and 22.1 kHz bandwidths using a modified laser Doppler blood flow monitor which permitted simultaneous recording using 810 nm and 633 nm light sources with a probe of four optical fibres with 0.25 mm separation. Ten traces from each combination of variables was examined by 10 trained observers who indicated if the traces came from vital or root-filled teeth judged by the amplitude and regularity of pulsatility of the trace. From the accuracy of their replies, sensitivity and specificity were calculated. Median flux values were higher for vital teeth than for root-filled teeth and for the 810 nm wavelength than for the 633 nm wavelength. Flux values increased with wider bandwidth using the 810 nm light source. With the 633 nm light source, the highest flux values were recorded using the 3.1 kHz bandwidth. Using the Mann-Whitney U test, there was a highly significant difference between readings from vital and root-filled teeth for the 3.1 kHz/810 nm wave length combination (p<0.003) and a significant difference for the 3.1 kHz/633 nm wavelength group (p<0.02). Comparison of other groups showed no significant difference (p>0.05). The 810 nm wavelength showed good sensitivity but poor specificity at 14.9 and 22.1 kHz bandwidths. The 633 nm wavelength showed good specificity, but poor sensitivity, at 14.9 and 22.1 kHz bandwidths. The 3.1 kHz bandwidth showed the best sensitivity and specificity for both wavelengths. Sensitivity and specificity were increased if the results of fast Fourier analysis were considered in addition to observations of flux values and pulsatility of traces. The 810 nm/3.1 kHz combination offered the greatest sensitivity and specificity as a test to distinguish between root-filled and vital teeth. This combination was best when the results of Fourier analysis were considered in addition to visual observations.

This study investigated the effects of inferior alveolar nerve block anaesthesia using 2% lignocaine with 1:100,000 or 1:80,000 adrenaline on pulpal blood flow in mandibular molar and canine teeth in 10 human subjects by laser Doppler flowmetry. The duration of pulpal anaesthesia in the teeth using electric pulp testing was also investigated. The injection of 2 ml of 2% lignocaine with 1:100,000 adrenaline caused a decrease in pulpal blood flow in both teeth in every subject. The mean pulpal blood flow in the canine tooth at 15 min was 58% of the baseline value whilst that in the molar was 76%. These values were not significantly different from the reduction in pulpal blood flow produced by 2% lignocaine with 1:80,000 adrenaline. Both solutions produced a reduction in blood flow that was of shorter duration than pulpal and soft tissue anaesthesia, and of shorter duration in the molar tooth compared with the canine. When 2% lignocaine with 1:100,000 adrenaline was injected, the mean reduction of blood flow was of shorter duration (canine, 60 min; molar, 42 min) than following 2% lignocaine with 1:80,000 adrenaline (canine, 93 min; molar, 72 min); these differences in reductions were statistically significant (P < 0.05). Using 2% lignocaine with 1:100,000 adrenaline, the mean duration of pulpal anaesthesia was 76 min in the canine tooth compared with 58 min in the molar tooth. Full soft tissue anaesthesia lasted for 117 min. These values were reduced significantly when compared with the lignocaine solution containing 1:80,000 adrenaline (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The aims of this study were to investigate the effects on pulpal blood flow and anaesthesia in mandibular teeth during inferior alveolar nerve block anaesthesia using 2% lignocaine with 1:80,000 adrenaline in 10 adult human subjects. Local anaesthetic solution was delivered close to the inferior alveolar nerve at the mandibular foramen using a standardized nerve block technique. The pulpal blood flow of the canine and first permanent molar was monitored by a laser Doppler flowmeter. At selected times pulpal anaesthesia was tested with an electric pulp tester. The injection of 2 ml of solution caused a decrease in pulpal blood flow in both teeth in every subject. The reduction in blood flow was of shorter duration than pulpal and soft tissue anaesthesia. A period of increased blood flow following the period of reduction was noted in several subjects. The mean reduction in pulpal blood flow in the canine at 15 min was 48% and lasted for a mean of 93 min. In contrast, the mean reduction in pulpal blood flow in the molar at 15 min was 25% and of 72 min mean duration. The mean duration of pulpal anaesthesia was 114 min in the canine compared with 88 min in the molar. Full soft tissue anaesthesia lasted for a mean of 151 min, whereas complete recovery took 255 min. This study indicated that lignocaine and adrenaline in block anaesthesia acted not only at the site of injection but also within the individual teeth.