Transmitted-light plethysmography detects changes in human pulpal blood flow elicited by innocuous tooth cooling and foot heating.

OBJECTIVES: The present study aimed firstly, to investigate whether pulpal circulatory changes elicited by innocuous tooth cooling and foot heating can be monitored with transmitted-light plethysmography (TLP), which detects pulpal blood volume changes, and secondly, to assess the effect of autonomic nervous control on TLP values. DESIGN: Thirty sound permanent maxillary incisors in 30 healthy volunteers (age: 25-35 years) were examined. The photodiode and 525-nm light-emitting diode of a prototype TLP system (J. Morita) were fixed onto the palatal and labial side, respectively, of each tooth with a custom-made acrylic cap. The subjects were stimulated for 10 min by cold (0 °C) water application to the experimental tooth or 30 min by foot heating with a footbath (43 °C). TLP and finger plethysmography were simultaneously recorded before (baseline), during and after stimulation. TLP values and autonomic nerve activity were statistically analyzed using a repeated measures one-way ANOVA followed by Tukey post-hoc test and partial correlation analysis. RESULTS: TLP values decreased significantly after both innocuous stimuli (P < 0.05), and returned to their baseline levels shortly after the removal of the stimuli. There was no significant serial correlation between the autonomic nervous activity and TLP values (P > 0.05). CONCLUSION: TLP was able to monitor the pulpal circulatory changes evoked by innocuous stimuli. Systemic autonomic nervous control mechanisms were not associated with the pulpal circulatory changes, suggesting the involvement of other mechanisms, such as somatosensory-sympathetic nervous control.

Absolute transmitted light plethysmography for assessment of dental pulp vitality through quantification of pulp chamber hematocrit by a three-layer model.

After confirming that the gingival circulation had little effect on transmitted light plethysmography measurement in the upper central incisor in both in vivo experiments and numerical Monte Carlo simulation studies, a three-layer model comprising of a pulp chamber sandwiched between two dentin layers has been introduced to quantify the pulp chamber hematocrit (Hctp) from the measured optical density. Two-flux theory was utilized to derive a mathematical equation for transmitted intensity in terms of tooth dimensions, Hctp, and light-source wavelength. Each layer was assumed homogeneous so as to represent its optical properties by the bulk absorption and scattering constants. The mean error between the Hctp estimate based on the three-layer-model equation and the Hctp actual in the extracted model tooth was -0.00115 with standard deviation (SD) of 0.00733 at 522 nm wavelength, while for 810 nm +0.09157 and 0.02493. The Hctp estimate of the upper central incisor in 10 young volunteers at 522 nm using the three-layer model ranged from 0.002 to 0.061 with the mean of 0.032. The Hctp change reflects blood volume shift in the pulp microcirculation to possibly indicate dental pulp vitality.

Raman imaging of carious lesions using a hollow optical fiber probe.

Raman spectroscopy using a hollow optical fiber probe with a glass ball lens at the distal end is proposed for detection of early caries lesions. Raman spectroscopy on carious lesions of extracted teeth showed that the probe enables measurement with a high signal-to-noise ratio when combined with a ball lens with a high refractive index. The proposed probe and lens combination detects changes in Raman spectra caused by morphological differences between sound and carious enamel. We also obtained a high-contrast image of an early carious lesion by scanning the tooth surface with the probe.

Human pulpal blood flow in different root formation stages measured with transmitted-light plethysmography.

OBJECTIVES: To determine the pulp vitality after traumatic injury, dentists often use pulp sensitivity tests, which can be ambiguous in young permanent teeth with incomplete root formation. Transmitted-light plethysmography (TLP) is a non-invasive objective method that uses a 525-nm LED to detect blood volume change in the pulp. The present study aimed (1) to investigate pulpal blood flow with TLP and optical characteristics in healthy permanent maxillary incisors in different root formation stages, and (2) to assess the influences of body growth of the children and tooth color on the TLP amplitude. DESIGN: Seventy-eight fully erupted maxillary central incisors were divided into four groups, according to the root formation stages. Group 1: root with wide-open apex, Group 2: root completed in length with open apex, Group 3: root with half-closed apex, Group 4: root with complete formation. The TLP amplitude, optical density, electric pulp testing, and cervical tooth color measurements of each group were compared using a one-way analysis of variance followed by the Bonferroni method. The correlation between the weights/heights of children and TLP amplitudes was analyzed using Pearson coefficient. RESULTS: The TLP amplitude was significantly higher in Group 3 than in the other groups. The amplitude was correlated with the weights/heights of children, but not with the tooth color. Optical density and electric sensitivity increased with tooth maturation. CONCLUSION: The amplitude of TLP and optical density may be affected by growth and development in children and indicate changes in the vascular dynamics of the pulp and hard tissue maturation during root formation stages.

Optical-fiber-based laser-induced breakdown spectroscopy for detection of early caries.

A laser-induced breakdown spectroscopy (LIBS) system targeting for the in vivo analysis of tooth enamel is described. The system is planned to enable real-time analysis of teeth during laser dental treatment by utilizing a hollow optical fiber that transmits both Q-switched Nd:YAG laser light for LIBS and infrared Er:YAG laser light for tooth ablation. The sensitivity of caries detection was substantially improved by expanding the spectral region under analysis to ultraviolet (UV) light and by focusing on emission peaks of Zn in the UV region. Subsequently, early caries were distinguished from healthy teeth with accuracy rates above 80% in vitro.