The International Journal of Prosthodontics, 05/1993

The etched-cast restoration was introduced in 1980, and a prospective study was initiated in March 1981 to determine if resin-bonded prostheses would prove to be a long-term alternative to traditional complete and partial coverage restorations. All resin-bonded restorations placed since that time in the author's private prosthodontic practice have been recorded in the study. The success rate of 127 restorations has been 92.9%, with a mean longevity of 5 years and 8 months.

The amount of torque required to loosen screws from three different antirotational screw-retained abutment/implant combinations was compared (with and without adhesive sealant applied) after 6 kg of force was applied during simulated intraoral movements. Movements were generated over two simulated time periods, representing 1 and 6 months. There was no significant decrease (alpha .05) in the torque required to loosen the screws after either time period when using Calcitek Omnilock or Stryker Minimatic. The Core-Vent Bio-Vent specimens, however, exhibited a significant decrease (alpha .05) in the amount of torque required to loosen the screws at the 1-month test period only. The addition of adhesive sealant significantly increased (alpha .05) the amount of torque necessary to loosen the screws only in the Core-Vent specimens.

The clinical usefulness of soft denture-lining materials is well established. This laboratory-based comparative study of a heat-processed silicone (Molloplast-B) and a recently introduced fluoroelastomeric soft lining material (Novus) evaluated absorption behaviour in distilled water; the softness of the materials at different thicknesses, both dry and after immersion in water; and their compatibility with denture cleansers. A significant absorption of water, greater than 5% by weight, was displayed by Novus after 4 months' immersion. The softness of different thicknesses of Novus (up to 1.35 mm) increased significantly upon immersion over the same period when compared to Molloplast-B, which showed no change. Some surface degradation of Novus was evident upon exposure to denture cleansers that was not apparent with Molloplast-B.

This paper presents a combination of several occlusal concepts designed to contribute to the successful use of maxillary dentures in opposition to osseointegrated mandibular prostheses. To ensure a positive outcome when designing such an occlusion, three factors must be considered: patient satisfaction, maxillary anterior bone preservation, and mandibular arch shortening. It is recommended that for centric occlusion the molars have a lingual contact occlusion, the premolars have a buccal contact occlusion, and the anterior teeth have an open occlusal relationship. For an eccentric occlusion, a balanced articulation is favored instead of mutually protected occlusion.

This study reviewed the prosthodontic treatment and aftercare required by 29 patients with 32 implant-supported prostheses (12 fixed and 20 removable) placed on 107 implants. Patients were followed for 4 to 39 months. The majority of implant-supported prostheses (53%) were placed in the mandible. Visual analogue scales were used by the patients to rate their satisfaction with their prostheses and their chewing ability. Approximately one third of the patients studied required three or more relines of their existing dentures between first- and second-stage surgeries, while over half of the definitive implant-supported prostheses required a major adjustment or repair. Removable prostheses required 78% of the total repairs and accounted for 80% of those prostheses that needed repeated repairs. In general, patients were very satisfied with their implant-supported prostheses, but 17% complained of mild speech difficulties and 7% noted slight difficulty in cleaning their fixed prostheses. Overall, the short-term prosthetic management required for the implant-supported prostheses in this study was substantial, particularly with the removable prostheses, and this should be taken into account when evaluating prosthetic options.

A group of 48 patients, all more than 80 years old (mean age 82.7 years) at first implant surgery, who received a total of 254 implants, were followed in one clinical center. Of the exposed implants, 6 of 238 (2.5%) were found to be loose at second-stage surgery, and another 3 implants were lost during the follow-up period. Most patients had minimal postplacement problems, similar to what has been observed in younger patients. However, some patients (10%) experienced obvious problems with general adaptation and muscle control, which has not been observed in younger patients.

This in vitro study evaluated the fracture resistance of all-ceramic crowns as a function of the elastic modulus of the supporting die. All-ceramic crowns were made for dies with three different elastic moduli and two different crown lengths. The occlusal surface was loaded in compression with a 12.7-mm steel ball. The fracture load increased markedly with the increase in elastic modulus. The largest increase was seen when only the occlusal surface of the crown was covered. The characteristic fracture load of the complete-crown restorations was more than double that of the occlusal-cover restorations in the dies with the lowest modulus of elasticity, while for the dies with the highest modulus of elasticity the difference in the characteristic fracture load for the two configurations was not significant.

This research investigated the fatigue life (ie, the number of cycles of a given stress that can be sustained by a sample prior to catastrophic failure) of metal ceramic soldering. One metal ceramic alloy was joined using four postceramic solders and one preceramic solder. All specimens received appropriate heat treatment simulating ceramic application although no porcelain was applied. Five specimens were fabricated for each solder type, and a 35,000 psi (241.4 MPa) fatigue stress was applied to each solder joint during specimen testing. The test variable was the number of stress cycles required to fail each specimen. The postceramic solders exhibited significantly higher fatigue lives than did the preceramic solder. Scanning electron microscope analysis showed that the preceramic solder not only exhibited a larger grain size, but also showed micropores between these grains.

Visible light-polymerized resin composite tabs were bonded to the flattened, acid-etched surface of teeth that were scheduled for extraction. Half of the teeth (group I) were isolated with cotton rolls in conjunction with a saliva ejector. The remaining teeth (group II) were isolated using a rubber dam. Both methods of isolation were used for each patient so that to some extent all patients served as their own controls. Following extraction, all samples were thermocycled 500 times alternating between 6 degrees C and 60 degrees C, after which they were immersed in 5% methylene blue for 4 hours. Each tooth was then mounted in acrylic resin and sectioned on a hard tissue microtome. Microleakage was assessed using a light microscope at x 20 magnification. The use of rubber dam isolation resulted in less microleakage at the enamel resin interface.

Hepatitis B and the acquired immunodeficiency syndrome are serious diseases because of their poor prognoses. The increasing awareness of the latter has highlighted the need for adequate precautions against cross contamination. However, the risk to dental personnel is still far higher from hepatitis B than it is from the human immunodeficiency virus, and the hepatitis virus is more transmissible, especially because it occurs in saliva. The principal potential route of transmission to dental laboratory personnel is via infected impressions. A number of papers have appeared in the literature examining the effects of various disinfecting and sterilising procedures on the accuracy and surface quality of impression materials. This paper reviews this literature and draws upon the findings to recommend a protocol for the handling of impressions to prevent cross contamination.

Three bonding agents were evaluated to determine which were most effective in enhancing the bond of resin composite to stainless steel. A light-activated resin composite was bonded to a total of 60 stainless steel specimens using Panavia, Cover-Up, or Silicoating. Tensile bond strength measurements revealed that all three agents provide a satisfactory means of increasing adherence of the esthetic veneer without decreasing bonding through thermocycling of the specimens. Panavia and Cover-Up were significantly more effective than Silicoating and appear to be easier to use.