Sensory and pain thresholds to orofacial argon laser stimulation in patients with chronic burning mouth syndrome.

OBJECTIVE: Psychophysical assessments of orofacial sensory function were performed in order to investigate neurophysiological aspects of the burning mouth syndrome (BMS). DESIGN: Sensory and pain thresholds to brief argon laser stimulation were determined on six test regions, which included the tip of tongue, the lower lip mucosa and skin, the buccal mucosa, the anterior hard palate, and the dorsum of the hand. SETTING: The experimental examination was performed at the Pain Clinic Unit at the Royal Dental College. PATIENTS: Twenty-three elderly denture-wearing patients diagnosed as suffering from BMS were studied, and a control group included 23 age-, sex-, and denture-matched subjects. The obtained thresholds were compared between groups. RESULTS: Sensory thresholds were significantly higher and ratios between pain and sensory thresholds significantly lower in patients with BMS on all the tested regions. Pain thresholds were significantly elevated on the lower lip skin, the anterior hard palate, and the hand in patients with BMS. At sensory threshold level, a faint pinprick perception was often reported by patients with BMS contrary to a perception of warmth described by control subjects. The intraregional variations in sensory and pain thresholds on the hard palate, the lower lip mucosa, and on the skin were similar in both groups, but differences occurred in sensory thresholds on the tongue in patients with BMS. CONCLUSIONS: The presence of abnormal prepain perceptions and disturbances in the perception of nonnociceptive and nociceptive thermal stimuli applied on both pain-affected and normal regions suggest a perceptual deficit unrelated to specific pathophysiological mechanisms in BMS. However, it appears that a psychological explanation of BMS should be used cautiously, as the present results suggest alterations in sensory function.

Tensile bond strength of resin-bonded non-precious alloys with chemically and mechanically roughened surfaces.

The present study was carried out for investigation of the tensile bond strength of resin-bonded non-precious alloys after their surfaces were roughened by sand-blasting, chemical etching, or sugar crystal impressions. Fifty test specimens were cast in a Ni-Cr (Wiron 88) alloy and 50 in a Co-Cr (Wirobond) alloy. Twenty specimens of each alloy were surface-treated according to the sugar crystal impression method. The remaining specimens were first sand-blasted, and 20 specimens of each alloy were thereafter allocated for chemical etching and divided into subgroups with different etching conditions. The samples were chemically etched in strong inorganic acid solutions. After being etched, the specimens were bonded together in pairs by a chemically-curing resin cement (Panavia EX) with a force of 2 kg/cm2. After cementation, the specimens were stored under humid conditions at 37 degrees C for three wk. Prior to being tested, the specimens were subjected to 1000 thermal cyclings at temperatures between 10 degrees C and 55 degrees C. The tensile bond strength tests showed that Ni-Cr specimens sand-blasted and thereafter etched with a 50% conc. of HNO3 and a 50% conc. of HCl for two min and Co-Cr specimens sand-blasted and etched (conc. HCl for 15 min or three h) or sand-blasted alone resulted in similar high bonding values ranging between 33.3 and 37.2 MPa. Surface roughening with use of the sugar crystal impression method resulted in statistically significant lower bond strength values for both alloys (Ni-Cr, 17.9 MPa; Co-Cr, 10.2 MPa).

Surface roughness of oral mucosa and its reproduction in dental materials.

An even fitting surface is essential to obtain and maintain a healthy oral mucosa in denture wearers. The present study was designed to clarify the relationship between the surface roughness of oral mucosa and its reproduction in the corresponding fitting surface of acrylic dentures. A silicone elastomer/epoxy replica technique was used for rendering the oral mucosal surface accessible to measurements with a stylus-type profile recorder. The method's ability to reproduce roughness with good traceability was tested and verified. Acrylic fitting surfaces made by standard denture-making technique demonstrated roughness values substantially higher than those of the mucosa, stemming from a high inherent surface roughness of dental stone models. To compensate for this, various separating media for stone models were tested as to their ability of reducing surface roughness. One silicone varnish (Silisol, Dreve AG, Germany) produced an acrylic surface with a roughness value comparable to that of the oral mucosa.

Allergy to dental materials with special reference to the use of amalgam and polymethylmethacrylate.

The increase in new clinical materials with questionable biological properties and the corresponding increase in awareness in patients to health hazards from dental materials are two important problems of modern clinical dentistry. Based upon evidence from clinical research the hypersensitivity problems related to the use of silver amalgam and acrylic denture base materials are reviewed to define possible risk groups among dental patients. In silver amalgam therapy the main risk group is patients with contact lesions in the oral mucosa adjacent to the restorations, as this group exhibits a high frequency of skin sensitivity to mercury and other base materials in dental amalgam. Among denture wearers a corresponding risk group has been observed among patients with previous allergic diseases and burning mouth syndrome. In these cases a high incidence of skin sensitivity reactions to denture allergens has been observed, usually to methylmethacrylate monomer and formaldehyde. Some possible pathogenic mechanisms leading to a contact allergy of the oral mucosa in these patient groups are discussed.

Variability of argon laser-induced sensory and pain thresholds on human oral mucosa and skin.

The variability of laser-induced pain perception on human oral mucosa and hairy skin was investigated in order to establish a new method for evaluation of pain in the orofacial region. A high-energy argon laser was used for experimental pain stimulation, and sensory and pain thresholds were determined. The intra-individual coefficients of variation for oral thresholds were comparable to cutaneous thresholds. However, inter-individual variation was smaller for oral thresholds, which could be due to larger variation in cutaneous optical properties. The short-term and 24-hr changes in thresholds on both surfaces were less than 9%. The results indicate that habituation to laser thresholds may account for part of the intra-individual variation observed. However, the subjective ratings of the intensity of the laser stimuli were constant. Thus, oral thresholds may, like cutaneous thresholds, be used for assessment and quantification of analgesic efficacies and to investigate various pain conditions.

Hypoalgesic effect of EMLA and lidocaine gel applied on human oral mucosa: quantitative evaluation by sensory and pain thresholds to argon laser stimulation.

Sensory and pain thresholds to argon laser stimulation were used to evaluate the analgesic efficacy and duration of a eutectic mixture of local anesthetics (EMLA) and a 2% lidocaine gel applied topically on the oral mucosa. Application of EMLA for 2 min on the tongue and gingiva increased the pain thresholds by 92.8% and 63.4% respectively. Corresponding values for lidocaine gel were 53.6% and 21.9%. Standardized variation of the EMLA application period (2, 5, and 15 min) produced significantly different analgesic profiles on the tongue but not on the gingiva. Application of EMLA for 5 and 15 min on the tongue and for 2, 5, and 15 min on the gingiva increased the pain thresholds to a predefined analgesic level (2.15 W) for 2 to 25 min. The present experimental model for assessment of oral mucosa pain is suggested to be well-suited for investigations of intraoral analgesia.

Barrier properties of inflamed denture-loaded palatal mucosa to water.

The barrier property of inflamed palatal mucosa to water has been studied in eight adult edentulous persons with a generalized denture stomatitis, by measuring the transmucosal water flow under varying osmotic gradients. Flow rates were registered gravimetrically in solute saturated filter paper discs after 10-min periods of mucosal contact, using solutions with an osmolarity of 0, 0.25, 0.30, 0.38, 0.50 and 0.75 osmol sucrose/l. The histology of the mucosal areas was evaluated from cytologic scrapings, and biopsy material from two persons. The inflow with use of pure water was 2.98 mg/cm2/10 min, being about three and a half times greater than through the intact mucosal surface. The point of isotony of the inflamed mucosa ranged between 0.30 and 0.36 with a mean value of 0.33 osmol/l, thus being of the same magnitude as in plasma and tissue fluid. The observations from the biopsy material were in accordance with earlier histological evidence from generalized denture stomatitis, indicating that the permeability properties of the inflamed mucosa belonged to epithelial cell layers located in the lower part of the spinous layer.

General health factors and denture function in patients with burning mouth syndrome and matched control subjects.

A total of 30 denture-wearing patients with burning mouth syndrome (BMS) referred to a Pain Clinic Unit and 26 age- and sex-matched control subjects were examined and compared with respect to general health factors and denture function. The study demonstrated a significantly higher frequency of multiple chronic diseases, psychosocial stress factors, and tenderness/pain in masticatory, neck, shoulder, and suprahyoid muscles in patients with BMS. Denture function differed also between the two groups as patients with BMS had significantly less daily use of dentures, reduced tongue space, incorrect placement of occlusal table and increased vertical dimension. Pain interview with the use of the McGill Pain Questionnaire demonstrated that pain in parts of the body other than the oral cavity were reported more frequently and that the intensity of past pain experiences was not rated higher except for pain in the head in patients with BMS. The results suggested a complex interaction between several general health factors, psychosocial stressors and denture dysfunction in order to explain an idiopathic burning pain in the anterior part of the oral cavity. The existence of demonstrable load factors does not seem to support the suggestion that BMS is primarily a psychogenic disorder.

A 12-month study on changes in the barrier properties of denture-loaded palatal mucosa in immediate denture wearers.

The changes of barrier properties and surface cytology of the palatal mucosa during a denture-wearing period of 12 months has been studied in 18 adult subjects. Transmucosal rates of water transport and that of a 1.10 osmol sucrose solution were registered gravimetrically before denture treatment, after 3 months and after 12 months of denture wearing according to procedures described earlier. The keratinization pattern and the leukocyte migration were evaluated from scrapings taken from the palate and the fitting surface of the denture. The clinical appearance was recorded photographically. After 3 months of denture wearing only minor changes in permeability and surface cytology were observed. After 12 months a distinct grouping of the material was possible with regard to permeability reactions, as seven subjects showed no changes, five subjects demonstrated an increased osmotic activity in the palatal mucosa, and six subjects exhibited a severely decreased barrier function. The color photos revealed inflammatory reactions of the palatal mucosa in the latter group. The cytologic observations showed after 12 months a significant decrease in the proportion of anucleated cells in the inflammatory group, but only minor changes in the remaining material.

Changes in the water permeability of palatal mucosa after complete denture treatment.

The water permeability of the human palatal mucosa has been studied in 12 persons with 1 year of full maxillary denture experience and 10 persons without dentures. Transmucosal water transport rates were studied gravimetrically with the use of solutesaturated discs of filter paper in contact with the mucosa, in accordance with earlier described procedures (KAABER 1973a, b). The inflow of water through clinically healthy mucosa was at the same level in both groups. After use of a 1.10 mol sucrose solution a significant increase in the inflow was observed in the denture wearers group, which suggested an increased amount of osmolytes in the mucosal surface. Two denture wearers with a slightly inflamed mucosal surface showed an increased inflow after use of water and a corresponding strong outflow after use of the sucrose solution, indicating a partial loss of the mucosal barrier function.

Skin sensitivity to denture base materials in the burning mouth syndrome.

The significance of sensitizing compounds in the denture base for the etiology of the burning mouth syndrome (BMS) has been studied in 53 denture-wearing persons, seven males and 46 females. Epicutaneous patch tests were performed with standard concentrations of benzoyl peroxide, dibutylphthalate, dimethyl-p-toluidine, formaldehyde, hydroquinone, methylmethacrylate, p-phenylendiamine and with cadmium sulfate, potassium dichromate, cobalt chloride and nickel sulfate. Furthermore, patch testing was performed with filings from the denture mixed with the patient's own saliva. In cases with an inflamed oral mucosa, the presence of hyphae of Candida albicans was assessed by a smear technique. Positive skin reactions were observed in 15 persons to dimethyl-p-toluidine, hydroquinone, formaldehyde, methylmethacrylate, p-phenylendiamine, potassium dichromate, cobalt chloride and nickel sulfate, including three cases with reactions to filings from their dentures, and one patient who after subsequent testing showed skin sensitivity to balsam of Peru. In 12 cases an etiological connection could be traced between the oral symptoms and the denture base, indicating that contact sensitivity to base materials or to allergens and microbial antigens on the denture plate plays a greater role in the pathogenesis of BMS in edentulous persons than previously suggested.

Clinical effects of glazing denture acrylic resin bases using an ultraviolet curing method.

Control of denture plaque accumulation is essential to obtain and maintain a healthy oral mucosa in denture wearers. The present study was designed to study the effect on denture plaque accumulation and denture stomatitis of coating the fitting denture surface by a glaze. Twenty-one subjects wearing complete dentures participated in the study. Glazing of the denture surface was performed using a Perma Cure System. Plaque accumulation was studied clinically and using a semiquantitative microbiologic technique. Plaque accumulation on the glazed and the non-glazed halves of the fitting denture surface was compared after 1 wk. There was significantly less plaque on the glazed half of the denture (P less than 0.001), and the calculated number of CFU of bacteria/cm2 was significantly lower from the test area of the glazed half than from the test area of the non-glazed half of the denture (P less than 0.001). When the patients were re-examined 1 month after the entire fitting denture surface had been glazed plaque scores, yeast scores and number of CFU of bacteria/cm2 were not significantly different from those observed before glazing. There was a reduction of the erythema of the palatal mucosa in 14/19 patients with denture-induced stomatitis. The study indicates that coating of the fitting denture surface by a glaze may be a means to improve denture cleanliness; however, the present glazing system should be further developed to produce a more uniform glazing.

Vertex potentials evoked by nociceptive laser stimulation of oral mucosa: relationship to stimulus intensity.

The present study investigated the relationship between stimulus intensity and size of vertex potentials (VPs) and methods for quantification of VPs elicited by nociceptive argon laser stimulation of the oral mucosa. VPs were evoked by warning and self-triggered stimulation of the tongue and hand. A significant increase was found in amplitude, power, and root-mean-square (RMS) values of the averaged VPs as the intensity of the laser stimuli increased. The latency of the major negative peak decreased significantly with increased stimulus intensity. The use of a warning light stimulus prior to the laser stimulus elicited a visually evoked vertex potential, which served as a control. The power and RMS values of the VPs elicited by warning stimulation of the tongue showed the largest increase and only a small variation when calculated in the 0.2 to 0.7 seconds time interval.

Oral mucosal analgesia quantitatively assessed by argon laser-induced thresholds and single-evoked vertex potentials.

The aim of this study is to quantitate the efficacy of a new topical anesthetic applied to the oral mucosa. Nociceptive pinprick thresholds and single-evoked vertex potentials (VP) elicited by high-intensity argon laser stimuli are used as measures of analgesia. After 5 minutes of occlusion (Orahesive Oral Bandages, ConvaTec) with a eutectic mixture of local anesthetics (EMLA cream, Astra), nociceptive pinprick thresholds on the tongue and gingiva are higher than those taken during nonocclusion. In a double blind-placebo controlled experiment, VPs were elicited every 1 minute for 19 minutes by single laser stimuli applied to the mucosa of the lower lip. After occlusion with EMLA cream for 3 minutes, VPs were significantly reduced when compared to those with placebo cream. One minute after removal of the EMLA cream, the spectral power of the single-evoked VP decreased significantly by 63.3%, the root-mean-square amplitude decreased by 42.7%, and the subjective pain perception (estimated on visual analogue scales) decreased by 88%. A significant reduction in single-evoked VPs was detected until 13 minutes after the removal of the EMLA cream. Oral mucosal analgesia may be quantitated by argon laser-induced nociceptive pinprick thresholds and single-evoked VPs.

Marginal fit of porcelain and indirect composite laminate veneers under in vitro conditions.

The purpose of the present study was to compare the marginal adaptation of indirect composite and porcelain veneers in vitro using transmitted-light microscopy. A preparation with a marginal chamber finish for a veneer was performed on 10 extracted molars after which 5 composite and 5 porcelain veneers were made and fitted using self- and light-cured microfill composite resin. Three longitudinal and 3 horizontal sections were cut in each preparation with the light microscope. Although the absolute marginal discrepancy at the cervical location had the highest statistical significance in the composite veneer group, the composite and porcelain veneers, in general, demonstrated a similar absolute marginal discrepancy and thickness of luting agent with average values from 50 microns to 195 microns for the two parameters. A considerable amount of excess of luting agent was furthermore observed in both groups of veneers, being most pronounced in the composite veneers.

The role of cadmium as a skin sensitizing agent in denture and non-denture wearers.

Positive patch test reactions to cadmium were observed in 8 out of 21 denture wearing persons with burning mouth sensations during 1979 and 1980, and in 13 of 125 consecutive outpatients being routine tested at the Dermatological Department in late 1980 and early 1981. Retesting 17 of these patients after at least 3 months delay with 2.0% cadmium chloride and 2% cadmium sulphate in water showed only 7 with a definite positive reaction. At serial dilution of cadmium sulphate, only 1 person reacted to a 1% aqueous solution. An exposure to cadmium could in 1 case be traced back to a 2-year period of work in a PVC plant, while in the remaining 6 cases the most probable exposure factor seemed to be chronic heavy cigarette smoking. The observations did not lend support to the pink acrylic denture base material being a relevant cadmium exposure factor.

Vertex potentials evoked by nociceptive laser stimulation of oral mucosa: a comparison of four stimulation paradigms.

A new method for quantitative assessment of oral mucosal nociception and analgesia has been introduced using vertex potentials elicited by nociceptive argon laser stimuli. Four different stimulation paradigms (long, random, warning, and self-triggered) were compared to determine which technique elicited the most reproducible vertex potentials. A warning stimulation paradigm applied on the tongue and hand elicited vertical potentials with smaller amplitudes, lowest intraindividual coefficient of variation (16.5% and 7.9%, respectively), and highest reproducibility. The latency of the major negative peak was not affected significantly by different stimulation paradigms. The high reproducibility of vertical potentials elicited by the warning stimulation may be ascribed to a standardized psychological state of the subjects.

Influence of oral hygiene on the mucosal conditions beneath bridge pontics.

The purpose of the present study was to elucidate the relationship between the oral hygiene at the bridge pontic and the inflammatory changes in the adjacent mucosa. The study consisted of three 4-wk periods with different hygienic measures: 1) no oral hygiene around and beneath the pontic, 2) thorough hygiene using toothbrush and toothpicks and 3) thorough hygiene using a toothbrush and dental floss every day. The amount of accumulated bacterial deposits on the pontic and the inflammation in the pontic area were estimated using quantitative microbiologic tests, and clinical and histologic examinations. When dental floss had been used the mucosa was healthy while it showed mild or moderate inflammation after the other experimental periods. There was a high correlation between the amount of mucosal exudate and the inflammation in the mucosa as measured by a modified Gingival Index. Daily use of dental floss resulted in a significantly lower number of microorganisms per mm2 compared with the other hygienic measures. Histologic sections of the biopsies showed changes in form of parakeratosis with thinning or loss of stratum corneum. The investigations have demonstrated that insufficient oral hygiene is an important factor in the development of inflammatory changes in the oral mucosa beneath bridge pontics. Regular use of dental floss ought to be a part of the oral hygiene regimen in patients wearing fixed bridges.

Influence of pontic material on alveolar mucosal conditions.

The purpose of the present study was to investigate plaque accumulation and inflammatory changes in the mucosa beneath fixed bridge pontics of various materials, in patients cleaning the infrapontic space daily. Fixed bridges with a tight but non-compressive contact to the mucosa in the pontic area and with interchangeable test specimens placed in the pontic base were constructed for five patients. During 4-wk periods the following materials were tested: alloys with a high or a low gold content, silver-palladium, cobalt-chromium, nickel-chromium and also a dental porcelain or a composite restorative resin. Between the test periods a "sanitary pontic" was used to enable recovery of the alveolar mucosa. Clinical examinations including exudate measurements demonstrated that the alveolar mucosa remained healthy irrespective of the material used when the dental floss was used regularly. The amount of plaque on the test specimens of the seven dental materials showed no consistent differences. The composition of the bacterial deposits showed no regular pattern. This investigation has demonstrated that patients maintaining a high standard of oral hygiene are able to prevent the development of inflammatory changes in the alveolar mucosa in contact with fixed bridge pontics irrespective of the pontic material used.