Quintessence International, 04/2000

The objective of this article is to introduce a new preparation design that utilizes external axial bevels and a resin placement technique that involves selective application of 2 resins of different viscosity to optimize marginal integrity in large Class II restorations. The rationale behind the intricate application of material and procedural manipulations involved in the delivery of these complicated restorations is discussed.

Traumatic injuries in the permanent teeth of children and adolescents are one of the most frequent causes of dental treatment. The article presents the use of an enamel and dentin adhesive resin system, Syntac, and resin composite materials, Tetric and Variolink, as materials of choice for direct pulp capping after traumatic pulpal exposure (Ellis Class III). Exposed pulp in 10 patients was covered with Syntac and then Tetric and Variolink after etching of dental tissues with phosphoric acid. The follow-up period was from 12 to 48 months. In 1 patient, the treatment was a failure. In the remaining 9 patients, no signs or symptoms of pulpal inflammation or necrosis were observed during the clinical examination.

Objective: The purpose of this study was to conduct a postmortem examination of retrieved failed dental implants to identify design characteristics that may have contributed to premature loss. Method and materials: Forty-five failed implants retrieved from 40 patients with no significant risk factors for implant failure (eg, history of smoking or diabetes) were examined by scanning electron microscopy. All implants were placed by general dentists or periodontists in private practice and had functioned for an average of 4 years. Results: Several design features of currently used implants present plaque-retentive areas. Plaque accumulation occurred along the implant/transmucosal abutment interfaces, transmucosal abutment/prosthesis interfaces, implant-prosthesis interfaces, and on surfaces of the abutment, the implant, and the prosthesis. The size of the microgap between the various components, the degree of surface roughness of the restorations and abutments, the exposure of plasma-sprayed coatings and threaded surfaces of implants, and overcontouring of implant restorations contributed to plaque accumulation and provided an ideal environment for bacterial colonization. Conclusion: These implant features may be key precipitating or exacerbating factors in the development of peri-implant inflammation, predisposing patients to implant failure.

Objective: The aim of this in vitro study was to compare the effects of different exposure values on the image clarity of 3 digital radiographic systems and 1 conventional direct-exposure emulsion x-ray film. Method and materials: Three digital radiographic systems, Digora, RVG, and Sidexis, were compared with the conventional dental x-ray film, Ektaspeed Plus. A medullary bone fragment and human teeth were radiographed with varying voltage, exposure time, and focus-receptor distance. Clinical criteria to evaluate image clarity were detail resolution, sharpness, contrast resolution, and artifacts of the different tooth and jaw structures. Results: The optimal exposure times for digital imaging varied between 0.02 and 0.13 seconds and depended on the objects and the imaging systems. Optimal resolution was obtained when a voltage of 60 kV was used. The focus-receptor distance of 33 to 40 cm resulted in the best contrast and sharpness. Digital images did not always provide the detail resolution or sharpness achieved by conventional radiographs. Conclusion: The recommended exposure time for digital images amounted to approximately half the time needed for conventional film. Digital images had to be modified by adjusting the contrast and brightness to optimize the visibility of the areas to be diagnosed.

Objectives: The purposes of this study were to compare the fluoride ion release from a freshly mixed polyacid-modified resin composite, or 'compomer' (Dyract), and 3 resin-modified glass-ionomer cements (Fuji II LC, Photac-Fil, and Vitremer) and to compare the use of 3 units for measuring fluoride release. Method and materials: Five specimens (3.0 3 2.7 mm) of each material were prepared. The specimens were placed in polypropylene vials with 2 mL of deionized water and stored at 37°C. The solutions were replaced weekly and the levels of fluoride ions were analyzed at days 1, 7, and 30 and subsequently every 28 days for 253 days. Fluoride measurements were carried out using a fluoride ion-selective electrode connected to a pH ion-selective electrode meter. Fluoride ion release was measured in parts per million, micrograms per square centimeter, and micrograms per cubic millimeter. Results: Fuji II LC, Photac-Fil, and Vitremer showed high initial release values, which decreased exponentially and then showed a slow decline during the ensuing time. Dyract released significantly less fluoride ions during the first 84 days than did the 3 resin-modified glass-ionomer cements and maintained this low level of release throughout the study period. The amounts of fluoride ion release measured at any time interval varied with the units of measurement chosen, but the pattern of release remained the same. Conclusion: There was a wide variation in the amounts of fluoride ions released from related products, but the patterns of release were similar and unaffected by the units of measurement used.

Objective: The purpose of this study was to evaluate photoelastically the effects of a cervical tooth structure lesion and its restoration on stress distribution within a tooth. Method and materials: Three-dimensional composite models of a maxillary first premolar with a buccal cervical lesion were fabricated. Two types of cervical lesion were tested: one was wedge shaped and had a sharp line angle at the apex of the lesion, and the other was more rounded and saucer shaped. Vertical loads of 10 lb were applied to the unrestored and restored models at the tip of the buccal cusp, the tip of the lingual cusp, and the center of the occlusal surface. The resulting stresses within the tooth model were monitored and recorded photographically in the field of a circular polariscope arrangement. Results: In the unrestored situation, stress concentrated at the apex of the lesion, regardless of the lesion configuration. However, the sharper, wedge-shaped lesion demonstrated a more severe stress concentration. In the restored situation, stress around the lesion apex and the lingual cervical lesion decreased, while stresses at the gingival and occlusal margins of the lesion increased, compared with the unrestored situation. These tendencies were most obvious when the buccal cusp was loaded. Conclusion: The presence of a cervical lesion changed occlusal load-induced stress distribution and concentrated stress at the apex of the lesion. The shape and dimension of the lesion governed the severity of stress concentration. Restoration of the cervical lesion relieved concentrated stress at the apex of the lesion.