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.     

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.     

Comparison of four laser types for experimental pain stimulation on oral mucosa and hairy skin

The use of different lasers for stimulation in human experimental pain research has provided a sensitive method for evaluation of thin nerve fiber functions. In this study, sensory and pain thresholds were compared to argon-, copper vapour-, Nd:YAG-, and CO2 laser stimulation on hairy skin and on oral mucosa. The influence on thresholds with respect to laser type, stimulation site, surface colour, and stimulus parameters (laser beam diameter and pulse duration) was investigated. Significant differences in thresholds between the four lasers were found on both surfaces; however, no significant differences existed between thresholds on the skin and on the tongue when the same laser was used. The observations imply that wavelength-dependent optical properties of the stimulated tissue influence on threshold determinations. Furthermore, the results indicate that temporal and spatial summation mechanisms may exist for laser induced warmth and pain perceptions. Laser stimulation may be a new tool for the investigation of origin and genesis of various orofacial pain syndromes.     

Tin: an overlooked contact sensitizer?

Patch tests with metallic tin in 73 nickel-sensitive patients revealed 6 positive allergic reactions. Only 4 doubtful reactions were seen, which makes irritancy unlikely. The relevance and clinical significance of the unexpected finding deserves further evaluation.     

Elbow eruptions in nickel and chromate dermatitis

In 7 patients with nickel or chromate allergy and dyshidrotic hand eczema, we observed symmetric hyperkeratotic lesions on the elbows which ran a similar course to the hand dermatitis.
Histopathological examinations show findings suggestive of lichen simplex chronicus and subacute-chronic dermatitis, but exclude psoriasis.
We conclude that these elbow lesions are a characteristic of systemic allergic contact dermatitis.     

Classification of hand eczema: clinical and aetiological types. Based on the guideline of the Danish Contact Dermatitis Group

Background. No generally accepted classification scheme for hand eczema exists. The Danish Contact Dermatitis Group recently developed a guideline defining common clinical types and providing criteria for aetiological types. Objectives. To test the concepts of this guideline in a group of hand eczema patients. Methods. Seven hundred and ten hand eczema patients were included from seven dermatology clinics in Denmark. The hand eczema was classified into one of five clinical types, with standard photographs as reference. The severity was scored by the physician, who also made a final aetiological diagnosis. Results. Irritant contact dermatitis was most frequent in chronic, dry fissured hand eczema (44.3%), pulpitis (41.7%), and nummular hand eczema (40.9%), whereas allergic contact dermatitis dominated in vesicular types of hand eczema, with recurrent (35%) and few (24.2%) eruptions. Hyperkeratotic palmar hand eczema was the only clinical type that constituted a distinct subgroup; it was found most frequently in older men and had the strongest relationship, although not significant, with non‐specific dermatitis. Conclusions. The relationship between clinical type of hand eczema and aetiological diagnosis fitted with general experience, but no simple relationship was found. This emphasizes that patch testing and exposure analysis are mandatory. Hyperkeratotic palmar hand eczema was identified as a distinct clinical subtype.