Scattering of laser light directed onto the labial surface of extracted human upper central incisors

doi:10.1016/S0099-2399(99)80286-6

Journal of Endodontics

Volume 25, Issue 7, July 1999, Pages 483-485

https://doi.org/10.1016/S0099-2399(99)80286-6 Get rights and content

The purpose of this study was to evaluate the scatter of light through human teeth with laser Doppler flowmetry. An optical probe (probe 1), which mounted two optical fibers (one for light illumination and another for the measurement of backscattered light intensity) was placed on the labial surface of the extracted teeth. Another optical probe (probe 2) for the measurement of transmitted-light intensity was placed either on the mesial, distal, or palatal surface or in the canal of the teeth. The light intensity at probe 1 was stable, irrespective of the location of probe 2, whereas the transmitted light intensity at probe 2 tended to increase as probe 2 moved to more incisal positions on the mesial, distal, and palatal tooth surfaces. The results indicate that the light scatters to a wide area outside the tooth and provides information regarding the surrounding tissue blood flow.

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Cited by (22)

A Diagnostic Accuracy Study of Laser Doppler Flowmetry for the Assessment of Pulpal Status in Children's Permanent Incisor Teeth
2019, Journal of Endodontics
The aim of this study was to assess whether laser Doppler flowmetry is more accurate than the conventional pulp sensibility tests (electric pulp test and ethyl chloride) in assessing the pulpal status of permanent anterior teeth in children and to identify the laser Doppler flowmetry’s Flux cut-off threshold.
A cross-sectional diagnostic accuracy study with randomization was performed and included 74 participants (8- to 16-year-old children). Participants had 1 maxillary central or lateral incisor with either a completed root canal treatment or an extirpated pulp and a contralateral tooth with vital pulp. Outcome measures included the sensitivity, specificity, and predictive values as well as the repeatability of all tests.
A significant difference between the Flux values for teeth with vital and non-vital pulps was found. The cut-off ratio for laser Doppler flowmetry was 0.6, yielding a sensitivity of 53% and a specificity of 33%, which were lower than the values of the electric pulp test (sensitivity = 83.8%–94.6% and specificity = 89.2%–97.6%) and ethyl chloride (sensitivity = 81.1%–91.9% and specificity = 73%–81.1%). The repeatability of laser Doppler flowmetry, electric pulp testing, and ethyl chloride were 0.85, 0.86, and 0.81, respectively.
Laser Doppler flowmetry was unable to differentiate between teeth with vital and non-vital pulps. The results of this study showed that there was a high probability for false results. Further development of laser Doppler flowmetry in assessing pulpal blood flow would be required before it could be recommended for clinical use, especially in children.
Effects of magnitude of intrusive force on pulpal blood flow in maxillary molars
2015, American Journal of Orthodontics and Dentofacial Orthopedics
Citation Excerpt :
In a study examining the effects of power increases on signals recorded from teeth, Sasano et al16 found that first premolars gave no signal at laser outputs of 2, 5, 7, or 10 mW; they suggested that the thick dentin prevented the photons from deeply penetrating and passing through the tooth toward the receiving fiber. In contrast to this assertion, Vongsavan and Matthews17 found that LDF could pass through enamel and dentin of 2 to 3.5 mm in thickness to measure blood flow in dental tissues, and Ikawa et al18 showed that laser light was capable of penetrating roots at a depth of 6 mm. In our study, at no time during any observation period was there an absence of PBF, indicating that enamel thickness is not a significant issue in measurement.
In this study, we aimed to evaluate and compare blood-flow changes in the pulp tissues of maxillary molars over a 6-month period after orthodontic intrusion using different magnitudes of force.
Twenty patients were randomly divided into 2 groups (n = 10) according to the amount of intrusive force applied. An intrusive force of either 125 g (light) or 250 g (heavy) was applied to the overerupted maxillary first molars using mini-implants; no force was applied to the contralateral molars. Laser Doppler flowmetry was used to measure pulpal blood flow (PBF) at baseline and during intrusion at 24 hours, 3 days, 7 days, 3 weeks, 4 weeks, 3 months, and 6 months. The data were analyzed with the Mann-Whitney U and Wilcoxon signed rank tests, with P <0.05 considered statistically significant.
PBF decreased significantly at 3 days and continued to remain suppressed until 3 weeks, after which a gradual trend of recovery was observed until 3 months, when the levels returned to near those measured before intrusion. When the data were analyzed with regard to the amount of applied force, significant differences were observed between the 2 groups only at 3 and 7 days.
These findings demonstrate that despite slight regressive changes in pulpal tissue over the short term, PBF values tend to return to their initial levels within 3 months, indicating that changes observed in PBF are reversible, even during radical intrusions of molars with 125 and 250 g of forces.
Improvement of the detection of human pulpal blood flow using a laser Doppler flowmeter modified for low flow velocity
2014, Archives of Oral Biology
Human pulpal blood flow (PBF) signals as measured by laser Doppler flowmeter (LDF) decrease with age. Although this decrease is considered to be due in part to slow blood flow, information regarding this velocity in humans has been lacking. The aims of the present study were to estimate the blood flow velocity in human dental pulp and to evaluate the validity of LDF modified for the measurement of slow blood flow.
Mean blood flow velocities at the upper central incisor, gingiva, fingertip and forearm of 28 volunteers (mean age: 38.6 years old) were estimated using LDF with a frequency analyser. Blood flow signals at these measurement areas were recorded using two different LDFs: (a) one with a standard blood flow range; and (b) one modified for low blood flow velocity.
The frequency range of the Doppler shift measured at the teeth with an opaque rubber dam was the narrowest (median: 4.3 kHz) among all of the measurement areas. The estimated mean blood flow velocity was the slowest at the teeth with a dam (median: 0.18 mm/s). LDF for low blood flow velocity detected larger and clearer pulsatile blood flow signals from the teeth with dams than did standard LDF.
The present results indicate that the velocity of PBF in humans is very low and that LDF modified for the measurement of slow blood flow is appropriate for PBF measurement in humans.
Influence of light transmittance and background reflectance on the light curing of adhesives used to bond esthetic brackets
2007, American Journal of Orthodontics and Dentofacial Orthopedics
Introduction: The objectives of this study were to determine the correlation between diffuse light transmittance (DLT) of esthetic brackets and the degree of cure (DC) of light-cured adhesives after direct irradiation, and to evaluate the influence of background reflectance. The influences of curing unit and irradiation time were also determined. Methods: The DLT of 4 ceramic and 4 plastic brackets was measured. Two reference light-curing protocols (cured over a glass slab; mean reflectance, 14.7%) and 4 experimental protocols (cured over bovine tooth slab; mean reflectance, 66.5%) were followed with 3 curing units: halogen, plasma arc, and light-emitting diode. The DC of 2 adhesives was calculated based on Fourier transform infrared spectroscopy. Two-way analysis of variance for the DC was performed (P = .05). The Pearson correlation between the DC and the DLT was determined. Results: Mean DLTs were 44.9% to 75.9%. DC varied by bracket and curing protocol (P <.05) and also by adhesive. In the experimental protocols, there was no significant linear correlation between the DLT and the DC in both adhesives except 1 among 8 groups. The difference in reflectance of background influenced DC (P <.05). Conclusions: Based on this clinically simulated model, it was confirmed that the reflectance of the background tooth influenced the DC, instead of the DLT of a bracket. The interaction of the DLT and the reflectance of the background tooth on the light curing of adhesives should be studied further.
Penetration depth of laser Doppler flowmetry beam in teeth
2005, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology
The aim of this study was to determine the penetration depth of laser light in teeth for contact and noncontact probe tip.
Fifty-one freshly extracted human mature maxillary and mandibular single rooted teeth were selected for the study. A laser Doppler flowmeter was used as a laser source. A digital camera was used to take pictures (with “night shot” mode in total darkness). When probe tip was in contact and when it was 1 mm away from the tooth, the depths of the areas illuminated in high and low density were measured.
In contact probe, root was illuminated to 4.28 ± 0.14 mm depth with high density and 13.27 ± 0.27 mm depth with low density. In noncontact probe, 4.36 ± 0.16 mm with high density and 13.28 ± 0.30 mm with low density of illumination were seen on the root. Between contact and noncontact probe situations the difference was not statistically significant in the depth of illumination. On the other hand, in both groups the difference between areas illuminated in high and low density was statistically significant (P < .05).
Contact or noncontact of the probe on tooth surface did not show any significant difference in light penetration. Besides, we think that, for the present, it is impossible to eliminate the contamination from periodontal tissues completely even if the necessary precautions (periodontal paste etc.) are taken.
Effect of gingiva on laser doppler pulpal blood flow measurements
2004, Journal of Endodontics
The purpose of this study was to evaluate the effect of labial and palatinal gingiva on laser Doppler pulpal blood flow measurements. Twenty upper central incisor teeth determined to be vital from 20 volunteers were included into the study. To stabilize the probe, a laboratory-made acrylic splint positioned the probe labially on the cervical third of the tooth crown. We collected measurements without any gingival covering, and under three conditions: after application of an opaque paste on the labial gingiva, the palatal gingiva, or both the labial and palatal gingiva. The measurement values decreased 46% when there was opaque paste on labial gingiva, 10% on palatinal gingiva, and 63% on both. The decrease in the values when there was an opaque paste on palatinal gingiva was not statistically significant (p > 0.05). The differences between all other groups were statistically significant (p < 0.05). In these measurements, the contribution of labial gingiva to laser Doppler pulpal blood flow measurements is more than that of palatinal gingiva.

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^*: This research was supported in part by a Grant-in-Aid for Scientific Research (No. 09307042) from the Ministry of Education, Science, and Culture, Japan.

^**: M.I. and N.V. received a Grant-in-Aid from the Japan Association of the Promotion for Science.

¹: Drs. Ikawa and Horiuchi are affiliated with the Department of Endodontics and Periodontics, Tohoku University School of Dentistry, Sendai, Japan.

²: Dr. Vongsavan is assistant professor, Department of Physiology and Biochemistry, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.

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Scattering of laser light directed onto the labial surface of extracted human upper central incisors*,**

Arch Oral Biol

Arch Oral Biol

Arch Oral Biol

Non-invasive recording of blood flow in human dental pulp

Endod Dent Traumatol

Laser Doppler flowmetry in assessing vitality in luxated permanent teeth

Int Endod J

Restored vitality in luxated teeth assessed by laser Doppler flowmeter

Endod Dent Traumatol

Pulpal blood flow in immatured permanent teeth after luxation injuries

Jpn J Pediatr Dent

A new method for the non-invasive measurement of pulpal blood flow

Int Endod J

Efficacy of laser Doppler flowmetry in determining pulp vitality of human teeth

Endod Dent Traumatol