Development of fibre-optic confocal microscopy for detection and diagnosis of dental caries

We report on the development of a fibre-optics-based confocal imaging system for the detection and potential diagnosis of early dental caries. A novel optical instrument, capable of recording axial profiles through caries lesions using single-mode optical fibres, has been developed. The practical study illustrates that miniature confocal devices based around single-mode optical fibres may provide additional diagnostic information for the general dental practitioner.

Removal of partially erupted third molars using an Erbium (Er):YAG laser: a randomised controlled clinical trial

We compared Erbium (Er):YAG laser with a surgical bur for removal of partially erupted lower third molars. Patients were randomised to be treated by either laser or bur. A total of 42 patients (laser = 22; bur = 20) were treated. A greater reduction in the range of mouth opening was found after laser than after bur treatment. Postoperative pain was more common after bur treatment. The duration of operation was considerably longer with laser than with bur. No persistent complications were encountered.

The effect of dentine on fluorescence measurements of enamel lesions in vitro

This study aimed to determine the contribution of the underlying dentine and the enamel-dentine junction to measurements of mineral loss from enamel recorded using quantitative light fluorescence (QLF). Sixteen square blocks (5 x 5 mm) were cut from the labial surfaces of extracted bovine incisor teeth. A dental drill was used to remove dentine and the enamel-dentine junction from half of each specimen. All specimens were embedded in epoxy resin and ground to produce a smooth, flat enamel surface. Half of the enamel surface of the block, perpendicular to where the dentine had been removed, was demineralised for 72 h prior to undertaking QLF measurements from the enamel surface to compare fluorescence loss from different areas of the block. QLF readings taken from lesions with no underlying dentine or enamel-dentine junction were very similar to readings from lesions with underlying dentine. A comparison of the two data sets demonstrated a linear relationship with a gradient of 0.95 and a y intercept of -1.24 (r(2) = 0.936). From these data, the underlying dentine and enamel-dentine junction did not influence mineral loss in enamel measured using QLF.

The influence of three Erbium:YAG laser energies on the in vitro microleakage of Class V compomer resin restorations

OBJECTIVES

To investigate the influence of three Erbium:YAG pulse energies (200 mJ, 240 mJ, and 300 mJ with a 100 mJ dentine finish) on the microleakage of Class V compomer restorations (Compoglass).

DESIGN

In vitro study.

SAMPLE AND METHODS

Sixty-one extracted human premolar teeth were randomly allocated to three groups (according to pulse energy). Each tooth hosted one test cavity prepared with one of the three Er:YAG pulse energies using a pulse repetition rate of 5 Hz and a pulse duration of 250 microseconds, and one control cavity prepared with a conventional diamond bur in a high-speed hand piece. Both cavities were placed at the cervical margin of the tooth and were restored and finished according to the manufacturer's instructions. Each tooth was then stored in 0.12% thymol solution at 37 degrees C for three months, before being thermocycled through water baths between 5 degrees C and 55 degrees C for 240 cycles. Microleakage was assessed using a methylene blue dye penetration technique and was quantified using a score 0 (none) to 4 (to and into the axial wall). The data was analysed using the Kruskal-Wallis and Mann-Whitney U-tests.

RESULTS

Leakage was seen in all groups at both the dentine and enamel margins. There were no statistically significant differences in leakage (P < 0.05) at either the enamel or dentine margins, except for the 240 mJ lased enamel margins. This group performed significantly better than the enamel margins prepared with 200 mJ (P = 0.03) and the 300/100 mJ (P = 0.01) laser energies as well as the conventionally prepared enamel margins (P < 0.001).

CONCLUSION

Cavity preparation with this Erbium:YAG laser did not influence the microleakage of Compoglass restorations adversely. Different pulse energies were required for optimum cavity sealing at the enamel and dentine margins and for different materials.

Influence of Erbium:YAG laser energies on the microleakage of Class V resin-based composite restorations

PURPOSE

To evaluate the influence of three Erbium:YAG laser energies on the microleakage of Class V resin-based composite restorations.

MATERIALS AND METHODS

60 extracted human premolar teeth stored in 0.12% thymol solution were randomly allocated to three groups. Buccal and lingual box-shaped Class V cavities were prepared on each tooth. One cavity served as the control and was cut using a conventional diamond bur in a high-speed handpiece. The test cavity was prepared using a pulse repetition rate of 5 Hz with 1 of 3 pulse energies; 200 mJ, 240 mJ, and 300 mJ with a 100 mJ dentin finish. The cavities were restored with Scotchbond Multi-Purpose and Z100 and were finished immediately before being stored for 3 months in thymol solution at 37 degrees C. Following thermocycling between 5 degrees C and 55 degrees C for 240 cycles and a further 12 hrs storage, the teeth were immersed in a 2% aqueous solution of methylene blue for 24 hrs. They were then sectioned through the mid-point of the restorations in a bucco-lingual plane and dye penetration was scored as 0 (none) to 4 (to the axial wall) for the enamel and dentin margins of both sections. The worst score for each margin was used for statistical analysis using the Kruskal Wallis and Mann-Whitney U tests at P < 0.05.

RESULTS

When the lased groups were compared, optimum sealing was achieved with energies of at least 240 mJ at the enamel margin and with energies no higher than 200 mJ to finish the dentin margin. However, while all the pulse energies compared favorably to the control group in enamel, a similar result was found only using the 300 mJ, with 100 mJ, finish at the dentin margins.

Effect of pulsed Nd:YAG laser radiation on action potential conduction in isolated mammalian spinal nerves

BACKGROUND AND OBJECTIVE

Dental lasers are claimed to produce analgesia, but the mechanisms and extent of any effects are uncertain. This study investigated the effects of lasing on nerve conduction in isolated nerves.

STUDY DESIGN/MATERIALS AND METHODS

Pulsed Nd:YAG laser energy was applied to spinal nerves in vitro and effects were measured as attenuation of the compound action potential (CAP) evoked by electrical stimulation.

RESULTS

Lasing for 1 minute at 0.3-3.0 W caused a dose-dependent attenuation of all components of the CAP (P < 0.03). With 0.3-1.0 W power, the CAP recovered to > 95% of the control levels 7 minutes after lasing; recovery was incomplete after lasing at > 2.0 W.

CONCLUSION

Isolated nerves were remarkably tolerant of lasing. The degree of nerve conduction block increased with laser power. The data indicate that lasing could diminish sensations, including pain, mediated by peripheral nerves in soft tissues.

Preliminary investigation of a novel carbon dioxide laser for applications in dentistry

BACKGROUND AND OBJECTIVE

A novel pulsed CO(2) laser was examined for its ability to ablate hard dental tissues.

STUDY DESIGN/MATERIALS AND METHODS

Lased human enamel surfaces were viewed using light and scanning electron microscopy for evidence of adverse structural changes. In vitro shear bond strength tests were conducted on composite resin bonded to lased enamel surfaces and compared with conventionally prepared specimens. A thermal camera was used to monitor temperature changes during cavity preparation in tooth slabs to assess likely changes to the dental pulp.

RESULTS

No charring or surface cracks were observed on lased enamel surfaces using both microscopic techniques. Bonding of the lased enamel surfaces to composite resin was not significantly different from the acid-etched control group. For cavities with a remaining dentine thickness of less than 1 mm, the temperature rise was less than 6 degrees C.

CONCLUSION

A novel pulsed CO(2) laser shows promise for cutting cavities in teeth.

Effect of HeNe and pulsed Nd:YAG laser irradiation on intradental nerve responses to mechanical stimulation of dentine

BACKGROUND AND OBJECTIVE

Our study aimed to determine how lasing affected intradental nerve responses to dentine stimulation. Study Design/Materials and Methods Intradental nerve activity was recorded from canine teeth of anaesthetised ferrets. Dentine exposed at the tip of the tooth was stimulated with a glass probe. After determining baseline responses to mechanical stimulation, dentine was lased using a pulsed Nd:YAG laser at 60-150mJ/pulse and 10-30 pulses/sec (total power = 0.3-3.0 W).

RESULTS

The HeNe aiming beam alone and Nd:YAG laser at 0.3 W (+ HeNe) had no effect on intradental nerve responses to dentine stimulation. Lasing at 0.6-1. 5 W could either enhance or suppress intradental nerve responses. Lasing at more than or equal to 2.0 W or repeated lasing at lower intensities depressed intradental nerve responses. Lasing often induced intradental nerve firing.

CONCLUSION

HeNe lasing had no effect on intradental nerve excitability. The Nd:YAG laser could depress intradental nerve responses to dentine stimulation.

Dental materials: 1997 literature review

This review of the published literature on dental materials for the year 1997 has been compiled by the Dental Materials Panel of UK. It continues a series of annual reviews started in 1973. Emphasis has been placed upon publications, which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, ceramometallic restorations and resin-bonded bridges, ceramics, denture base resins and soft lining materials, impression materials, dental implant materials, orthodontic materials, biomechanics and image processing, resin composites, and casting investment materials and waxes). Three hundred and thirty three articles have been reviewed.

Curing of dental composites by use of InGaN light-emitting diodes

A potential application of blue-light-emitting InGaN LED's as a polymerizing source for dental composite materials is described. We compared a basic LED device with a conventional curing light in vitro to determine the polymerization parameters and to examine the effect of the curing process on the physical properties of these materials. It was determined that an array of six LED's was able to set a range of composite materials more quickly than a conventional light source, with the cured compounds showing similar hardness and material shrinkage parameters but with a lower material temperature rise during the curing process using the array. These findings indicate that a device consisting of several InGaN LED's would be an effective instrument for curing certain light-sensitive materials, particularly dental composites.

Effects of pulsed Nd:YAG laser radiation on action potential conduction in nerve fibres inside teeth in vitro

OBJECTIVE

This study aimed to simulate the effects of lasing dentine on pulpal nerve function.

METHODS

Rat spinal nerve roots were threaded through the prepared pulp canal of a 10 mm long tooth root segment which was mounted in a perspex bath. The protruding ends of the nerve were placed on platinum wire electrodes used to elicit and to record compound nerve action potentials (CAPs). Laser energy (average power = 0.3-3.0 W) was applied to the surface of the root segment using a pulsed Nd:YAG dental laser (dLase 300).

RESULTS

With the laser probe tip placed in static contact with the tooth surface, the nerve CAP was irreversibly abolished within 60 s of lasing at 1.0-3.0 W power. When the laser tip was moved to and fro over the root surface in a scanning mode, similar levels of radiation produced less marked effects. In the latter mode, CAP attenuation increased with increasing power and duration of lasing. After 60 s lasing at 0.3 W, the CAP size was 95% (+/- 5, S.D.) of the prelasing controls value; with 2.0 W the CAP was reduced to 54% (+/- 33). The CAP recovered to 90% of control levels after lasing at powers up to 1.5 W, but reached only 72% of control values after lasing at 2.0 W power.

CONCLUSIONS

Laser radiation applied to dentine caused a dose-dependent block of action potential conduction in nerve fibres in the underlying pulp chamber.

Dental materials: 1996 literature review. Part 2

This critical review of the published literature on dental materials for the year 1996 has been compiled by the Dental Materials Panel of the UK. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, resin-bonded bridges and ceramo-metallic restorations, ceramics, denture base resins and soft lining materials, impression materials, implants materials, orthodontic materials, biomechanics and image processing, resin composites and casting investment materials and waxes). Three hundred and thirteen articles have been reviewed.

Dental materials: 1996 literature review

This critical review of the published literature on dental materials for the year 1996 has been compiled by the Dental Materials Panel of the UK. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, resin-bonded bridges and ceramo-metallic restorations, ceramics, denture base resins and soft lining materials, impression materials, implants materials, orthodontic materials, biomechanics and image processing, resin composites and casting investment materials and waxes). Three hundred and thirteen articles have been reviewed.

Dental materials: 1995 literature review

This critical review of the published literature on dental materials for the year 1995 has been compiled by the Dental Materials Panel of the United Kingdom. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, resin composites, dentine bonding, dental amalgam, endodontic materials, casting alloys, investment materials, resin-bonded bridges and ceramo-metallic restorations, all ceramic restorations, denture base and soft lining materials, impression materials, dental implants, orthodontic materials and biomechanics). Three hundred and thirty articles published in 68 titles have been reviewed.

An evaluation of the Nd:YAG laser in periodontal pocket therapy

The aim of this study was to determine whether the Nd:YAG laser energies of 50 and 80 mJ at 10 pulses per second (pps) were capable of improving the clinical parameters associated with periodontal disease. These energy settings were chosen as previous work indicated that higher values would damage root surfaces and that 80 mJ had an in-vitro bactericidal effect. Eighty periodontally affected sites in teeth scheduled for extraction from 11 patients with adult periodontitis were randomly placed in one of the following four treatment groups: 1. laser treatment at 50 mJ, 10 pps for 3 minutes; 2. laser treatment at 80 mJ, 10 pps for 3 minutes; 3. scaling and 4. untreated control. Probing depth, bleeding on probing (BOP), plaque index, gingival index and gingival crevicular fluid (GCF) volume were measured at baseline and week 6. Baseline subgingival microbiological samples were collected, then repeated immediately after treatment and at week 6 to assess the total anaerobic colony forming units (CFU). Only the scaling group showed a significant reduction in pocket depth and BOP (P < 0.001). The microbial samples taken immediately after scaling and laser at 80 mJ and 10 pps treatments showed a significant reduction in total CFU compared with the baseline (P < 0.01), which was sustained only in the scaling group until week 6. Electron microscopy did not reveal any heat damage on the root surfaces. This study demonstrated that application of Nd:YAG laser pulses of 50 mJ and 80 mJ failed to improve the clinical and microbiological parameters of periodontal disease.

The effect of an Nd-YAG pulsed laser on the cleaning of the root canal and the formation of a fused apical plug

A Neodymium-yttrium aluminium garnet (Nd-YAG) pulsed laser was used in vitro to determine whether various laser energy levels from 0.75 W to 1.7 W at 15 pulses s(-1) (pps) were able to (i) remove debris from the walls of prepared root canals (ii) remove pulpal tissue from unprepared canals and (iii) create a fused apical plug from dentine chips, hydroxyapatite (HAP) or low-fusing dental porcelain. Single-rooted teeth were sectioned at the amelocemental junction and the crowns discarded. The root canals of 50 teeth were prepared chemomechanically and allocated to four groups of 10 teeth for laser treatment. One group was left unlased as a control. After lasing, the teeth were split longitudinally, stained and examined for residual debris. Results showed that there was no statistically significant difference between the groups (P<0.05). A further 20 teeth were not prepared and lased in the coronal one-third of the root canal at different energy levels; five teeth were not lased. The teeth were split and examined as previously. The results showed that lasing cleaned the coronal part of the root canal almost completely of pulpal tissue. In the final part of the study laser energy was applied to dentine chips, HAP and low-fusing porcelain in an attempt to produce a fused apical plug. The laser was unable to melt the dentine chips but some hardening of HAP occurred when combined with blue food-colouring, with or without glycerine, at energy levels of 1.0 W, at 15 pps for 30 s. Superficial hardening of low-fusing porcelain occurred at 1.0 W, 15 pps for 30 s.

A clinical study of pulsed Nd: YAG laser-induced pulpal analgesia

The pulsed Nd: YAG laser is advocated as an alternative means of providing analgesia during routine dental procedures. Since the evidence to support this claim is mainly anecdotal, a clinical trial was carried out using an electric pulp tester (EPT) to measure the extent and duration of any analgesic effect induced by pulsed Nd: YAG laser treatment. A double-blind crossover experiment involving laser and sham treatments was used on 21 subjects. A small (3.6 arbitrary units) but statistically significant increase was observed in the mean responses measured 5 min after laser treatment with 113 mJ pulses at 15 pulses s-1 (pps) for 3 min. The pain thresholds returned to baseline values after 60 min. No statistically significant changes in threshold were found with the sham treatment. The order in which laser and sham treatment was received made no difference to the results.

An evaluation of the effects of an Nd:YAG laser on subgingival calculus, dentine and cementum. An in vitro study

The aim of this study was to evaluate the effects of Nd:YAG laser treatment on subgingival calculus, cementum and dentine, in vitro at different power settings and durations. The study included 2 experiments. In the 1st experiment, 32 extracted teeth with calculus were divided into 8 laser treatment groups. Each tooth was treated on 2, 3 or 4 sites. In the 2nd experiment, 3 extracted cementum covered teeth and 3 extracted root planed teeth with exposed dentine were selected. 1 surface of each tooth was subjected to 8 different laser treatments. In both experiments, all specimens were assessed using scanning electron microscopy. Micrographs were taken from each treated site at x 100 and x 750 magnifications. An arbitrary scale (from 0 to 3) was used to score the degree of damage caused by the laser. Generally, the laser caused greater damage on calculus than either cementum or dentine. Linear regression analysis showed that higher total energy input caused a greater mean damage score on calculus (R2 = 66%, p < 0.001). 3-way analysis of variance showed that for calculus, the power setting, number of pulses per second and the duration of exposure contributed independently to the mean damage score in an additive way. Cementum specimens were not affected by treatment 1 (50 mJ, 10 pps, 1 s), treatment 2 (50 mJ, 10 pps, 5 s), and treatment 5 (50 mJ, 20 pps, 1 s). Dentine specimens were not affected by treatment 1 (50 mJ, 10 pps, 1 s).(ABSTRACT TRUNCATED AT 250 WORDS)

Opto-thermal in vivo monitoring of sunscreens on skin

Opto-thermal transient emission radiometry (OTTER) provides a convenient means for in vivo and in situ monitoring of human or animal skin properties and surface concentrations of topically applied substances, such as drugs and cosmetics. This is illustrated with measurements on the rates of disappearance from skin of a number of commercial sunscreen preparations. The break-up of the physical structure of creams on skin can also be monitored through dynamic phase change phenomena, induced by a laser pulse.