[Treatment of dentin hypersensitivity by means of the Nd:YAG laser. Preliminary clinical study]

The aim of our study is to evaluate the efficiency of the Nd:YAG laser in association with graphite for the treatment of dentinal hypersensitivity. 20 patients suffering of different degrees of this affection were involved. The treatment protocol was: cleaning and drying of the dentinal surfaces, evaluation of the level of pain using a graduated scale (after use of an air spray during 3 sec at a distance of 1 cm from the dentinal surfaces), the treated area was smeared with a graphite paste (graphite mixed to physiologic solution), then irradiated with the Nd:YAG laser until complete removal of the graphite (VSP Mode of 140 microsec, 0,25W, 10 Hz, 300 microm diameter fiber, fluence: 35.39 J/cm2), rinsing and drying followed by a second smearing with the graphite, second lasing, rinsing, drying and a new evaluation of the pain immediately after the treatment and one week later.

RESULTS

The means and standard deviations of the level of pain were 7.34 +/- 0.86 before treatment, 3.24 +/- 1.18 immediately after and 2.07 +/- 0.73 one week after. No anesthetic aspect was noticed after treatment. To conclude, our result revealed significant and immediate pain reduction with respect of aesthetics and the natural aspect of the treated teeth. Our protocol is a promising alternative to the treatment of dentinal hypersensitivity.

[Comparative study on dogs between CO2 laser and conventional technique in direct pulp capping]

Three dogs have been used in this experiment. Class V cavities were made in sixty teeth. A pulpal communication was provoked intentionally in these cavities. Teeth were randomly split in 2 groups (30 teeth for each). On first group, the pulp bleeding was stopped until appearance of coagulum on exposed pulp surfaces by means of CO2 laser irradiation (Output Power: 3 W, Pulse duration: 0.1 sec, frequency: 1 Hz, spot size diameter: 0.3 mm, Energy density: 425 J/cm2). Calcium Dihydroxide was deposited followed by a temporary filling (IRM, Dentsply, De Trey, Germany). In the second group, the calcium Dihydroxide was deposited directly on exposed bleed pulp (conventional technique) followed by the same temporary filling. Ten weeks later, all teeth were extracted and prepared for histological study.

RESULTS

93% of treated teeth preserved their pulp vitality in the group treated with CO2 laser for direct pulp capping versus 82% in the group treated by conventional technique. The average of the thickness of the dentinal bridge newly formed was 391.5 +/- 33 microm for teeth irradiated with laser and 294.1 +/- 28 microm for teeth treated by conventional technique. The thickness of the dentinal bridge newly formed in teeth treated by means of CO2 laser was 33% more important than in those treated by the conventional technique. Statistical analysis showed a significant difference between the averages of values in all groups (p < 0.05). To conclude, CO2 Laser use in the direct pulp capping increases significantly the percentage of pulp vitality preservation and the thickness of the dentinal bridge newly formed after pulp exposition.

[Lasers in general dental practice, an added value]

Laser treatment in promoting dental care is present in many areas and disciplines. Modern practice management implies also the introduction of new technology. As there is evidence of the added value for lasers in different disciplines in dentistry practitioners should not be hold back and not wait for patients demanding for this technology for dental treatment.

[Cavity preparation using an Er:YAG laser in the adult dentition]

Many lasers (i.e., different wavelengths) are available today for clinical applications. Not all lasers are to be used for cavity preparation and removal of carious tissues. Erbiumlasers (Er:YAG and Er,Cr:YSGG) are suitable for these purposes (the wavelengths coincide with the highest absorption peaks of water and hydroxyapatite). The advantages during cavity preparation and caries removal are smear layer free cavity walls, selective and localised removal of tooth substance, a restricted need or the absence of anaesthesia, and cavity walls with a higher acid resistance resulting in a better protection against secondary decay. Possible side effects of erbium lasers with water cooling and used with respect for correct power setting are minimal and can be compared with those of rotary instruments. Erbium laser tooth preparation is now one of the options in the minimal invasive approach. The needs for acid etching has been debated for long. At present it has become clear that acid etching is mandatory to obtain a good adhesion and retention with resin composites.

[Lasers: principles, characteristics and tissue interactions]

Since their appearance in 1960, lasers have been considered useful light sources for medical applications. Laser light is monochromatic, the bundle is parallel and can be directed and focussed, as a result of which very high energy densities can be achieved. Several applications in dentistry have been investigated over the past decades. This article describes the physics behind lasers, the characteristics of the laser beam and overviews the laser wavelengths currently used in dentistry. The different interactions between the laser beam and the target are explained.

[Preprosthetic surgery of the edentulous maxilla: vestibular deepening with the aid of the CO2 laser]

Vestibular deepening for maxillary edentulous patients is mainly indicated once instability cannot be reached due to important bone resorption. Vestibular deepening with CO2 super-pulsed laser enhance, in a bloodless environment, sustentation as well retention of those full dentures in good operative conditions as compared with conventional techniques.

[Use of laser Doppler flowmetry in dentistry]

An early determination of pulpal vitality is crucial with respect to a correct differential diagnosis of revascularisation or necrosis and its treatment. The use of sensibility tests (cold, heat, electrical pulp test) in combination with X-ray are commonly promoted. However these tests are arbitrary, based on sensations and therefore not always reliable. In such situation the registration of 'real' pulpal blood flow and hence pulp vitality will be more than an added value. The most studied and well documented method is laser Doppler flowmetry (LDF) as it is non invasive, direct and objective. In this article we describe blood flow, LDF and its characteristics, advantages and disadvantages of this method and the newest developments regarding LDF. Despite a low implementation of LDF in Belgium, this technique proved to belong indisputable to the basic assets of a dental clinic. A number of cases are described to demonstrate the efficacy and added value of LDF in assessing tooth vitality.

["Power bleaching" with the KTP laser]

The most important constituent of the bleaching process is the hydrogen peroxyde. The bleaching effect is the result of a change in the chemical structure of organic molecules in the teeth. Different bleaching techniques are described on the basis of the concentration of the hydrogen peroxyde used and on the basis of the different methods of application. It has been demonstrated that a faster change in colour can be obtained when bleaching is performed in combination with a light source i.e. power bleaching aiming for a more in depth change of colour. Different investigations have demonstrated that negative effects associated with bleaching agents are seen earlier when light sources have been used as accelerators. So, light activation may not lead to 'heating of the pulp'. Different types of laser bleaching have been described, though, not all of them will lead to the desired result. There is only one exception at present and this is the KTP-laser bleaching with the Smart Bleach gel. The specific laser-tissue interaction is the result of different activation processes of the hydrogen peroxyde in the gel: as a result of the interaction with the laser a photocatalytic effect is induced (i.e. the activation of the gel by means of light--this is also referred to as a photochemical reaction), a limited photothermal effect (light absorption may result in a certain heating of the gel). The light activated gel also has an alkaline pH, which favours the ionisation of the hydrogen peroxyde into perhydroxyl ions (these are the most reactive free radicals). It is also possible to directly cut the tetracycline molecules (a good absorption of light by the tetracycline molecules at 532 nm). This will result in better decolouration of tetracycline stained teeth. This last process is described as direct photobleaching. It also needs to be emphasized that bleaching with a laser can only be performed by a dentist who has acquired a substantial knowledge on laser-tissue interaction and laser physics, and who follows accurately the requested bleaching procedure. Furthermore, whatever the opinion might be, tooth bleaching is a medical dental procedure on biologic tissues and hence this procedure can only by dentists.

[Inter-university cooperation in Flanders--an academic point of view on peer review]

Peer review as a possibility for discussion among practising dentists was introduced in Belgium in 1998 in the framework of a quality ensuring program. The 'Interuniversitary Cooperation', an initiative of Flemish universities active in teaching, research and patient treatment in dentistry has been involved in this program since its beginning to set up a dialogue between academia and dental practitioners and to gather information on scientific and educational matters. In this article the principles and organisation are described and thought is given to the attitude of the participants and future possibilities.

[Direct and indirect effects of medication (including chemotherapy) and irradiation on the pulp]

A direct or indirect effect of the intake of medication on the pulp itself has not yet been described in the literature. The effect of local anesthetics on the pulp, on the other hand, has been documented. Although local anaesthesia has been employed in dentistry for many years, most investigations of its action have only considered the effect on the nerves within the pulp using traditional methods. Recently it has become clear that the nerves and blood vessels of the pulp do not act in isolation but are closely related. In this respect it has been shown that there exists a direct relationship between the length of the flow cessation and the concentration of vasoconstrictor used. Therefore care should be taken when using vasoconstrictors especially where pulpal injury is apt to occur when dental procedures such as full crown preparations are performed immediately following a ligamental injection. The anaesthetic efficacy of intraosseous injection is well documented. The effect, however, on the dental pulpal circulation still remains subject of further investigation. Radiotherapy involving the oral cavity and salivary glands and chemotherapy (in a lesser degree) induce alterations in the oral tissues and the salivary gland functions. Some of these side effects are transient. However there are side effects such as the xerostomia which are very drastic for the dentition resulting in radiation caries and dental hypersensitivity. Tooth anomalies in the developing dentition are also described. Due to the rapid progression of the radiation caries a monitoring of the oral cavity with strict application of preventive measurements and systematic follow-up can reduce the incidence of the complications. Unfortunately most of the patients belonging to this group consult with the complications of their radiotherapy and chemotherapy. In this respect endodontic treatment of the severely decayed teeth is an important part of dental treatment. Moreover, extraction is regularly contraindicated as osteoradionecrosis is then one of the major sequels.

[The importance of apical and coronal leakage in the success or failure of endodontic treatment]

The present paper reviews the literature and gives the evidence that apical and coronal leakage of the root canals may lead to failures of the root-canal therapy. It becomes clear that none of the present-day root canal sealers may hermetically seal "the root canal wall--gutta-percha filling interface". In this respect the importance of perfectly sealing coronal restorations (both temporary and permanent) is emphasized.

[The use of glass ionomer cements in endodontics]

Glass ionomer cements are currently used in endodontic therapy for sealing root canals (orthogradely and retrogradely), for sealing and restoring the pulp chamber, for repairing perforations and root resorption defects, and, rarely, for treating vertically fractured teeth. The successful use of these cements is the result of their particular characteristics: a chemical bond to dentin, which enhances the seal of the root canal and the reinforcement of the tooth; a good biocompatibility in the periradicular area and a fluoride release without loss of strength of the material. The fluoride release imparts an antimicrobial effect to combat root canal infection and attributes to bone mineralization after surgery. The present paper reviews the literature regarding the various applications of glass ionomer cements in present-day endodontics.

Reliability of laser Doppler flowmetry in a 2-probe assessment of pulpal blood flow

OBJECTIVE

The reliability of using 2 probes with laser Doppler signals when adjacent teeth are being measured simultaneously to determine pulpal blood flow is unknown. The purpose of this study was to determine whether 2 probes are more reliable than 1 in a single-tool assessment.

STUDY DESIGN

Tooth pulp vitality was studied in 19 adults through use of laser Doppler flowmetry tests. In each subject, testing was carried out on 2 successive occasions with 2 probes positioned on the maxillary central incisors.

RESULTS

Significant mean differences of 31% for blood flux and 96% for concentration were found between the 2 probes, although they shared equal coefficients of variation. The reproducibility for each probe was found to be consistent, and the probes were highly correlated with each other. Flux and concentration, however, were not systematically correlated.

CONCLUSIONS

Simultaneous measurements with 2 probes were clearly more reliable. The necessity for a calibration control was evident.

[Dental care in autism]

The syndrome of autism is not characterized by typical orofacial features. Regarding caries experience, no differences with the normal population are found. The dental health situation on the other hand, depends upon the care devoted to oral hygiene and when necessary, upon the auxiliary help of parents and educators. As far as dental care is concerned, the autistic patient is inherently unresponsive to demonstrations, resists eye-to-eye contact and will frequently resist any effort to establish personal contacts with the dental personnel. Patient management will therefore be qualitatively different from person to person and shall be based on a unique management of the behavioral characteristics. Where the classical 'tell, show, do"-method fails, the 'tell, show, FEEL, do"-method will lead to a successful approach.

[The formulation of glass ionomer cements and the amount of fluoride]

The glass-ionomer cements (GIC) were developed in the late sixties. The set cement is the result of an acid-base reaction between an ion-leachable glass (the base) and a poly (alkenoic acid). Through the years, the number of applications of these GIC has increased steadily. The evolution has to be referred to the fact that the composition of both acid and base can be changed considerably. This has resulted in the marketing of GIC with different physical and chemical formulations. Furthermore resin-modified GIC were introduced in the late eighties. One of the major GIC advantages remains the fluoride release. The fluoride in GIC is a component of the material itself and is not added afterwards. Beneficial for the GIC in this respect is that the released fluoride is not of structural importance in the set cement. Furthermore the fluoride release does not result on itself in a reduction of physical properties or an increase in porosity.

[Evaluation of the long-term release of fluorides from type II glass ionomer cements with conventional setting reactions]

As a part of a fundamental investigation on the fluoride release of glass ionomer cements (GIC), this study investigates the operator dependency of the fluoride release. In this respect the GIC fluoride release of a classical powder-liquid based system (Fuji II) and a capsule-based system (Fuji Cap II) in water during 14 days was determined on the hand of 5 specimens per formulation, made by 5 different operators. The data reveal that the variance on the fluoride release as well as the mean fluoride release at a given time are independent of the operator for both Fuji II and Fuji Cap II. In order to derive fundamental factors affecting the GIC fluoride release, the long-term fluoride release of 10 conventional setting type II GIC is investigated. In this respect the fluoride release profiles (FRP) of each of 5 cylindrical specimens (d = 6 mm, h = 3 mm) of Fuji II (FP), Fuji Cap II (FC), Miracle Mix (MM), Chemfil II (CP), Chemfil II in caps. (CC), Chelon-Fil (CF), Ketac-Fil (KF), Shofu II (SH), Chelon-Silver (CS) and Ketac-Silver (KS) were determined. The specimens were made according to the manufacturer's instruction and equilibrated at 37 degrees C in 25 mL distilled water up to 140 days. The water was regularly renewed and the fluoride concentration [F] of the equilibrated solution determined. A Multivariate Data Analysis of the [[F], t]-profiles on the basis of Principal Component Analysis (PCA) reveals that the FRP can be classified into 4 distinct groups: [CS,KS,FP]-[FC,CC]-[CF,KF] and [MM], leaving SH and CP apart as unclassifiable. When the cumulative amount of fluoride released ([F]c) for each individual sample is calculated and fitted as a function of time, a regression analysis shows that [F]c is most adequately fitted (r > 0.99) by [F]c = [F]I/t+t1/2 + beta, square root of t, indicating that 2 kinetic processes are responsible for the FRP. A comparison of the parameters of this equation ([F]I, t1/2 and beta) shows that the physicochemical rationale for this classification of the GIC conforms to differences in the kinetics of these processes. From the classification, it becomes apparent that different formulations can result in the same FRP.

[The formulation of glass ionomers and their degree of fluoride]

The glass-ionomer cements (GIC) were developed in the late sixties. The set cement is the result of an acid-base reaction between an ion-leachable glass (the base) and a poly (alkenoic acid). Through the years, the number of applications of these GIC has increased steadily. The evolution has to be referred to the fact that the composition of both acid and base can be changed considerably. This has resulted in the marketing of GIC with different physical and chemical formulations. Furthermore resin-modified GIC were introduced in the late eighties. One of the major GIC advantages remains the fluoride release. The fluoride in GIC is a component of the material itself and is not added afterwards. Beneficial for the GIC in this respect is that the released fluoride is not of structural importance in the set cement. Furthermore the fluoride release does not result on itself in a reduction of physical properties or an increase in porosity.