Noppakun Vongsavan

The sources of laser Doppler blood-flow signals recorded from human teeth

Records of pulpal blood flow obtained from human teeth with a laser Doppler flowmeter include a very large component derived from periodontal and other tissues outside the pulp, but this contamination can be reduced by covering the surrounding tissues with opaque rubber dam. The present experiments were carried out to determine what proportion of the signal obtained with this dam in place is derived from non-pulpal tissues. Recordings were made from 22 healthy, intact upper incisors in 14 individuals (aged 22-40 years) with and without dam under the following conditions: from the intact teeth, after local anaesthesia (LA) and the preparation of a deep cavity in the incisal third of the labial surface of the tooth, and after removal of the pulp and arrest of bleeding. In some cases, a reading was also made after replacing the pulp in the pulp cavity. The rubber dam reduced significantly (P<0.05) the mean blood flow reading from the intact teeth by 73%, from 6.98 arbitrary perfusion units (PU) (+/-1.30 S.D., n=22) to 1.92+/-1.50 PU. After LA and cavity preparation, the mean signal with dam was 1.45+/-0.61 PU (n=16). This fell significantly by 76% to 0.35+/-0.19 PU (n=16) when the pulp was removed but not replaced, and by 43% to 0.98+/-0.36 PU (n=14) when the pulp was removed and replaced in the pulp cavity. The latter condition is thought to reproduce most closely the scattering of light in an intact tooth. The results confirm previous findings that up to 80% of the laser Doppler blood-flow signal recorded from an intact human tooth without rubber dam is of non-pulpal origin. They also show that only approximately 43% of the signal recorded with an opaque rubber dam is from pulp.

Microcirculation and micromorphology of healthy and inflamed gingivae.

Inflammation changes the microcirculatory and micromorphological dynamics of human gingiva. Laser Doppler flowmetry (LDF) and a replica technique for scanning electron microscopy (SEM) were used to examine the facial soft tissues of six maxillary anterior teeth, before and after treatment, in 12 patients exhibiting clinically healthy tissues and in 12 others with moderate gingivitis. All patients received oral hygiene instructions and scaling. The gingiva in the gingivitis group became healthy within 3 months after treatment. LDF results were recorded at the free gingivae, interdental gingivae, attached gingivae, and alveolar mucosae of the six maxillary anterior teeth. The gingival blood flows in the gingivitis group before treatment were significantly different from those in the healthy gingiva group. Flows were restored to the same level as the healthy gingiva, with no significant difference, at P ≫ 0.01, 3 months after treatment. However, there were significant differences among sites during the same period. In addition, blood flow was reduced to a normal level after the inflammation subsided. Initially, the gingival morphology of the inflamed sites exhibited irregular free gingival margins, in contrast to that of healthy gingivae, which were characterized by rounded margins closely adapted to the tooth. One month post-treatment, the gingivae exhibited a wrinkled appearance, but they had reverted to normal micromorphology by 3 months post-treatment. The replica impression technique can be used to record gingival micromorphology both before and after reduction of inflammation.

Pulpal blood flow recorded from human premolar teeth with a laser Doppler flow meter using either red or infrared light.

OBJECTIVE To compare red (635 nm) and infrared (780 nm) light for recording pulpal blood flow from human premolar teeth. DESIGN Recordings were made from 11 healthy teeth in 9 subjects (aged 16-30 years) using a laser Doppler flow meter (Periflux 4001) equipped with both red and infrared lasers. Average blood flow signals were obtained with both light sources alternately from each tooth under five conditions: intact tooth without opaque rubber dam, intact tooth with dam, after injecting local anaesthetic (3% Mepivacaine) (LA) over the apex of the tooth and cavity preparation to almost expose the pulp, after removal and replacement of the pulp, and with the root canal empty. RESULTS With infrared light, the dam significantly decreased the mean blood flow by 80%. Injecting LA and cavity preparation had no significant effect. Removal and replacement of the pulp reduced the mean blood flow by 58%. There was no further change when the pulp was removed. With red light, the dam reduced the signal from intact teeth by 60%. Injecting LA and cavity preparation had no significant effect. The signal fell by 67% after pulp removal and replacement and did not change significantly when the pulp was removed. CONCLUSIONS Opaque rubber dam minimises the contribution of non-pulpal tissues to the laser Doppler signal recorded from premolars. Using dam, the pulp contributed about 60% to the blood flow signal with both red and infrared light. The difference between them in this respect was not significant.

Microcirculation of the healthy human gingiva

Abstract The purpose of this study was to evaluate the microcirculation in healthy human gingiva. Forty-two adult volunteers with clinically healthy gingiva participated. The ages of this research sample ranged from 20 to 30 years. Periodontal conditions were evaluated and assessed by using the qualitative plaque index, gingival index, gingival bleeding index, tooth mobility, and laser Doppler flow-metry (LDF) on 12 maxillary and mandibular anterior teeth. The LDF data were recorded on the facial aspect of the free gingiva, interdental gingiva, attached gingiva, and alveolar mucosa of 12 maxillary and mandibular anterior teeth, utilizing an acrylic stent to stabilize the probe. This technique was then modified to circumvent contamination by saliva and gingival exudate. Blood flow in the maxillary anterior gingiva differed significantly from that in the mandibular anterior gingiva in interdental gingiva, attached gingiva, and alveolar mucosa, at P < 0.01. The maxillary anterior gingiva, at each point on the stent, showed significant differences in the mean LDF, at P < 0.01. For the mandibular anterior gingiva, the difference was significant only in the alveolar mucosa region.

Sensory Transduction in Human Teeth with Inflamed Pulps

The effects of pulpal inflammation on the sensitivity of dentin to cold (5°C) and negative hydrostatic pressure (−300 mm Hg) stimuli in man were compared, since recent evidence suggests that these stimuli excite different classes of sensory receptors. Dentin was exposed in premolars in 14 participants aged 15-25 years. Stimuli were applied to etched dentin immediately after cavity preparation and after the cavity had been filled with gutta percha for 7 days. This treatment increased significantly the intensity of pain produced by cold, and at the same time decreased that evoked by negative pressure stimuli. Pulpal blood flow was increased in the treated teeth, indicating that their pulps were inflamed. It is concluded that the sensory receptors responsible for the response to cold were probably sensitive to some change other than an outward flow of fluid in dentinal tubules, which would be caused by both forms of stimulus.

A comparison between red and infrared light for recording pulpal blood flow from human anterior teeth with a laser Doppler flow meter

OBJECTIVE To compare red (635 nm) and infrared (780 nm) light for recording pulpal blood flow from human anterior teeth with a laser Doppler flow meter. DESIGN Recordings were made from 7 healthy teeth in 5 subjects (aged 22-55 years) using a laser Doppler flow meter (Periflux 4001) equipped with both red and infrared lasers. Average blood flow signals were obtained with both light sources alternately from each tooth under five conditions: intact tooth without opaque rubber dam, intact tooth with dam, after injecting local anaesthetic (3% Mepivacaine) (LA) over the apex of the tooth and cavity preparation to almost expose the pulp, after removal and replacement of the pulp, and with the root canal empty. RESULTS With infrared light, because of technical limitations, data were obtained for the first three conditions only. The dam significantly decreased the mean blood flow by 82%. Injecting LA and cavity preparation had no significant effect. With red light, dam produced a decrease of 56%, and the resulting signal was reduced by 33% after LA and cavity preparation. The remaining signal fell by 46% after pulp removal and replacement. This contribution of the pulp is similar to that recorded previously with infrared light. There was no significant further change when the pulp was finally removed. CONCLUSIONS The importance of using opaque rubber dam is confirmed. With dam, there is no advantage to using red rather than infrared light, and in each case the pulp contributes less than 50% to the blood flow signal.

Effects of enamel and dentine thickness on laser Doppler blood-flow signals recorded from the underlying pulp cavity in human teeth in vitro.

OBJECTIVE To determine the effect of enamel and dentine thickness on laser Doppler blood-flow (LDF) signals recorded from dental pulp. DESIGN Observations were made on 18 human premolars that had been extracted from young patients during orthodontic treatment. The apical 2/3 of the root was cut off and the remaining pulp removed. Blood flow signals were recorded from the buccal surface of the crown with a laser Doppler flow metre while dilute blood was pumped at 10 ml/min. through a cannula inserted into the pulp cavity. Recordings were made from the enamel surface and at 0.5 mm steps through the enamel and dentine. RESULTS The blood flow signal increased significantly as the cavity depth increased and at 2.0 mm, the median flux signal was more than ten times greater than that obtained on the enamel surface. The backscattered light intensity did not change with cavity depth. CONCLUSION When recording pulpal blood flow from a human tooth with a laser Doppler flow metre, a substantially better signal-to-noise ratio should be obtained by placing the probe on dentine in the floor of a cavity than on the enamel surface.

Effect of the topical application of 50% lignocaine hydrochloride on the sensitivity of dentine in man

OBJECTIVE To determine the effect of topical applications of 50% (w/v) lignocaine HCl on the sensitivity of human dentine. DESIGN The experiments were carried out on 12 premolars scheduled for extraction as part of orthodontic treatment in nine subjects (ages: 16-29 years). Dentine was exposed by cutting a cavity at the tip of the buccal cusp of each tooth, and etched with 35% phosphoric acid. The sensitivity of the exposed dentine to probing and air-blast stimuli was assessed before and after applying either 50% (w/v) lignocaine HCl solution or distilled water to the exposed dentine for 10min. Changes in the sensitivity of the dentine were monitored for up to 160min. The subject indicated the intensity of any pain produced by marking a 100mm visual analogue scale (VAS). RESULTS Before treatment, both forms of stimulus evoked pain in all the teeth. The median VAS score with probing was 40mm and, with air-blast stimulation, 30mm. 50% lignocaine HCl produced a progressive fall in these scores and after 30min there was no response to either probing or air-blast stimulation. The responses started to return 30-160min after the lignocaine had been washed off. Water had no effect. CONCLUSIONS Lignocaine will diffuse into exposed dentine and block the pain evoked by probing and air-blast stimuli provided that a sufficiently steep diffusion gradient is created. A topical application of a 50% (w/v) solution of lignocaine HCl for 10min will anaesthetise dentine within 30min.

The synthesis and characterization of a novel potassium chloride-fluoridated hydroxyapatite varnish for treating dentin hypersensitivity

Dentin hypersensitivity is treated using materials that occlude the dentinal tubules or release potassium ions that induce nerve desensitization. In this study we formulated a novel varnish containing potassium chloride and fluoridated hydroxyapatite and evaluated its physical properties and cytotoxicity. Potassium ion release from the varnish was measured. Dentin permeability was evaluated by measuring the hydraulic conductance of etched dentin discs treated with the varnish. The direct contact test and MTT assay were performed to evaluate the varnishs cytotoxicity. We found that the varnish released potassium ions over 6 h, and demonstrated a statistically higher reduction in dentin permeability compared to commercial fluoride varnish or control. Dentin disc scanning electron microscopy images demonstrated occluded dentinal tubules in the novel varnish group after brushing. The cytotoxicity tests indicated the varnish was biocompatible with gingival and pulpal fibroblasts. We propose the novel varnish is a potential material for use in hypersensitivity management.

Effects of the iontophoresis of lignocaine with epinephrine into exposed dentine on the sensitivity of the dentine in man

OBJECTIVE To determine the effects of the iontophoretic application of lignocaine and epinephrine to exposed dentine on the sensitivity of the dentine in human subjects. DESIGN The experiments were carried out on 13 healthy premolars (13 subjects) that were scheduled for extraction. Dentine was exposed at the tip of the buccal cusp by cutting a cavity which was etched with 35% phosphoric acid. The sensitivity of the dentine was tested with probing and air blast stimuli. The subject indicated the intensity of any pain produced with a score of 0-100. In 7 teeth, the cavity was filled with a solution containing 20% (w/v) lignocaine HCl and 0.1% (w/v) epinephrine HCl, and an iontophoretic current of 120 μA was passed for 90s. The sensitivity of the dentine was tested before and immediately after the treatment and then at 10 min. intervals for 40 min. Pulpal blood flow was recorded at each stage. Control experiments were carried out on 6 teeth using a solution containing only the epinephrine. RESULTS The lignocaine plus epinephrine solution completely blocked the pain produced by both forms of stimulus immediately, and this continued for at least 40 min. It also produced an immediate fall in pulpal blood flow that also lasted for at least 40 min. The epinephrine solution had the same effect on pulpal blood flow but no effect on dentine sensitivity. CONCLUSIONS The topical application of 20% lignocaine and 0.1% epinephrine, with an iontophoretic current of 120μA for 90s, will anaesthetize exposed, normal, dentine.