Clinical status of dentine bonding agents

Dentine bonding agents are an important clinical contribution to modern composite technology. Important differences exist between the first- and second-generation materials which offer complementary advantages. The second-generation materials offer higher dentine bond strengths at the expense of greater chairside complexity. Indications for the use of both types of material are discussed. The role of smear layer and the primed layer is discussed and the connection is made between bond mechanism and clinical techniques. The clinical criteria, such as retention, microleakage and tooth strengthening, are related to the role of the hard tissue bond.     

Oral lichenoid dysplasia: a clinicopathologic analysis

Three women had a diagnosis of oral lichen planus (OLP), which was made on the basis of clinical and histologic features. All three had persistent burning pain associated with large mucosal lesions. Changes in the color (red, red and white, white), configuration, and severity of the lesions were unpredictable and did not correlate well with topical corticosteroid therapy. Only one patient used tobacco (cigarettes)--this patient had recurrent oral candidiasis and was receiving multiple medications. One of the two nonsmokers was a denture wearer with a single episode of candidiasis. After 63, 32, and 56 (mean 50) months, carcinoma developed in all three. In retrospect, the initial biopsy specimens of two patients exhibited lichenoid dysplasia, whereas that of the third showed only lichenoid mucositis. Although speckled erythroplakia was the earliest clinical sign of a classic, nonregressing premalignant lesion, it already signaled the presence of invasive carcinoma. Some early epithelial dysplasias appear to have a robust inflammatory/immunologic response to the antigenically (but as yet not histologically) altered dysplastic epithelium and a high probability of at least temporary resolution. Mucosal erythema of obscure origin displaying spontaneous, usually temporary, partial to complete regression may be common to both purely inflammatory conditions like lichen planus and early epithelial dysplasia. We contend that some, if not most, cases of apparent malignant transformation of OLP likely represent red and white lesions that were dysplastic from their inception but that mimic OLP both clinically and histologically.     

Re-epithelialization of a palatal connective tissue graft transplanted in a non-keratinized alveolar mucosa: A histological and biochemical study in humans

This study was undertaken to evaluate the type of tissue obtained after transplantation of a connective tissue graft, from the same palatal donor site, into a non-keratinized oral mucosa in humans. In 6 human volunteers, a thick palatal epithelio-connective tissue graft was excised, split into two thinner grafts (a thin epithelio-connective tissue graft and a connective tissue graft) and transplanted into controlateral areas lacking keratinized gingiva. The biopsies, excised 3 months post-operatively, were examined using routine histology, immunofluore-scence techniques with different anticy to keratin antibodies and biochemical techniques with non-equilibrium two-dimensional gel electrophoresis. The results show that the epithelio-connective tissue grafts display the histological and biochemical characteristics of keratinized gingiva, whereas the connective tissue grafts expressed features belonging both to keratinized and non-keratinized gingival tissues. It is concluded that the deep palatal connective tissue does not have the full potential to induce non-keratinized epithelial cells to keratinize and that a gingival or palatal connective tissue graft without its overlying epithelium is not likely to yield genuine attached gingiva.     

Infection with a gram-negative organism stimulates gingival collagenase production in nondiabetic and diabetic germfree rats

Experimental diabetes in the rat rapidly produces a shift in the gingival crevicular microflora which is followed, within weeks, by increased production of collagenase by the gingival tissues. To assess the contribution of endogenous (hormonal or metabolic) and exogenous (altered crevicular microflora) factors on this diabetes-induced abnormality in collagenase production, the following series of experiments was undertaken: In each experiment, the germfree rats were housed in two isolators. Half of the animals in both isolators were rendered diabetic (D) with streptozotocin while the remainder were left untreated (non-diabetic (ND) controls). All of the germfree ND and D rats in one isolator of the pair were then infected with either a Gram-positive (S. mitis or A. odontolyticus) or a Gram-negative (Capnocytophaga, A. aclmomycetemcomitans or B. gingivalis) organism. In the other isolator, the ND and D rats were maintained in their germfree state. After 3 wk, the germfree and monoinfected rats were killed and the gingiva (and in one experiment, skin) were dissected. Collagenase activity produced by gingiva in culture (or extracted from gingiva or from skin) was measured using ¹⁴C-collagen fibrils (or [³Hmethyl] collagen molecules) as the substrate. Diabetes increased the collagenolytic activity in the gingiva and skin of the germfree rats. Infecting the germfree rats with a Gram-positive organism had no effect on collagenase activity generated by the gingival explants in the tissue culture system. In contrast, infection with any of the Gram-negative organisms dramatically increased the collagenase activity in the gingival tissues of the ND rats in culture, an effect not seen in the D group of rats using this system. However, monoinfection with B. gingivalis did increase collagenase activity in the extracts of gingiva (but not in skin) from both ND and D rats, with the latter group showing the highest level of enzyme activity. We suggest (i) that experimental diabetes stimulates collagenase production in gingiva by both endogenous (hormonal) and exogenous (bacterial) mechanisms, and (ii) that crevicular Gram-negative organisms stimulate collagenolysis in the adjacent gingival tissues by releasing bacterial products (e.g. endotoxins) which penetrate into the connective tissue and enhance host cell collagenase production.     

Retention of sealants over carious and sound tooth surfaces

Bacteriologic and clinical studies suggest that sealants can be used therapeutically on incipient caries of the enamel. The present study was designed to explore this approach further by determining whether there is a difference in retention rates on sound or carious tooth surfaces sealed for the first time as well as resealed surfaces. A total of 1766 teeth were sealed for subjects 12-14 yr of age of which 120 were judged to be carious. Mouths were divided sagittally on a random basis and an ultraviolet light activated resin with a filler or an autopolymerizing resin without a filler was placed on contralateral surfaces of all molar and premolar teeth. The effects of sealant type, caries status, arch and tooth type on retention over a 2-yr period were tested using Mantel-Haenszel statistics. At the end of 1 yr, 88% of the teeth sealed with the autopolymerizing resin were judged to be completely intact compared to 82% of the teeth filled with the ultraviolet light resin. At the end of the second year the retention rates were 84% and 75% respectively. The retention rates for carious and sound teeth at the end of both years were almost identical. Overall, premolars had a 15% more favorable retention rate than molars. There were minimal differences between arches although maxillary premolars had approximately a 5% higher retention rate than mandibular premolars. The reverse was true for molar teeth. Retention of sealants at the end of the second year (resealed after 1 yr) was 4% less than comparable teeth sealed initially.     

Viadent, ethanol, and pH effects upon gingival epithelial-like cells, in vitro

Interest has recently been directed towards the use of antiplaque mouthrinses. Most published material concerns the antimicrobial effects of these agents rather than their effects upon oral tissue. This study was conducted to evaluate the effect of a sanguinarine-containing mouthrinse called Viadent upon epithelial-like gingival cells. The cells were grown for 24 hours in supplemented Earle's medium, with and without different Viadent dilutions. Cell counts were made with a hematocytometer. It was found that 50% of the cells were inhibited at 1.2% Viadent. In similar studies, it was found that 70% ethanol and two pH buffers were less toxic than Viadent. Exposure of preformed cell monolayers to Viadent also showed significant inhibition. The relative toxicity of different antiplaque agents may be compared using such cells as a model system. In conclusion, it was observed that Viadent significantly affected gingival cell growth in vitro, that viable cell numbers were greatly reduced by short time exposure, and that the toxic effect of Viadent could only partially be accounted for by ethanol content and/or pH.     

Treatment and disposal of contaminated sharps.

Dentists, like other health care workers, make an overt effort to protect themselves and their employees from infectious agents present in the body fluids of their patients. Of special concern are treatment-generated infectious waste materials, such as sharps. Sharps are items such as needles, sutures, scalpel blades, or broken glass which are capable of puncturing, cutting, or abrading tissue. Needles can cause occupational transmission of hepatitis B and AIDS. This article presents methods to safety store, treat, and dispose of sharps. All suggested procedures comply with current Indiana law, CDC guidelines, and EPA and OSHA regulations.     

The effect of root canal preparation on the shape of the curved root canal

Summary. This study reports the effect of the step-bad enlargement technique of root canal preparation on the shape of the curved root canal of extracted human teeth. This was achieved by superimposing tracings made from photographic prints obtained by radiographs of teeth before canal preparation, after apical preparation and after coronal flaring. After apical preparation, the root canal sometimes demonstrated an hour-glass shape. Flaring the coronal portion of the canal was often successful in opening out the narrowest portion, the elbow, of this hour-glass shape.     

Ultrastructure of lingual enamel epithelium in rabbit permanent incisors

The recent observation that the lingual surface of the permanent rabbit incisor, in contrast to the rodent incisor, is covered with enamel near the initially formed tip, initiated a histologic study of the enamel epithelium in this region. Tooth buds from fetal New Zealand white rabbits aged 27 and 30 days in utero were processed for transmission electron microscopy. Examination of longitudinal and cross-sections revealed a transition of secretory ameloblasts to postsecretory ameloblasts on the facial aspect of the enamel organ. Incisally, the facial ameloblast layer was continuous with postsecretory ameloblasts on the lingual aspect. More apically on the lingual surface, a gradual transition between postsecretory and reduced ameloblasts occurred. This study shows that by day 27 in utero, the ameloblasts on the lingual aspect of the tooth are in the postsecretory and degenerative stages and that, by day 30, the enamel epithelium lingually has been replaced by cementum on the prismatic enamel and by connective tissue.     

Clinical short term study of marginal integrity of resin restorations

The marginal adaptation of 649 Durafill and Silux fillings in beveled and acid etched enamel cavities was assessed in a clinical study. The investigation included Class III with and without lingual extension, Class IV and Class V. The frequency of marginal discoloration and marginal gaps after 15 months was markedly reduced in all Classes when a low-viscous resin was used prior to application of the restorative.