Quintessence International, 05/1998

The Procera System embraces the concept of comupter-assisted design and computer-assisted machining to fabricate an al-ceramic crown composed of a densely sintered, high-purity aluminum oxide coping combined with a compatible veneering porcelain. Strength, precision of fit, color stability, cementation, and wear characteristics are among the many factors that concern clinicians when fabricating all-ceramic restorations with this new crown system. This article presents, in summary form, the data from the many studies on Procera AllCeram crowns that have been conducted at clinical and laboratory centers around the world. The evidence reported in these studi es clearly demonstrates that the Procera AllCeram crown represents a combination of computer technology and creativity for which a positive prognosis can be made. Today its application is restricted to single crowns; however, with continued development, multiple unit all-ceramic anterior and posterior fixed partial dentures are clearly in the future.

This article describes a new injection technique for the maxillary arch that achieves pulpal anesthesia of the central incisor through the second premolar without collateral anesthesia of the face and muscles of expression. This palatal injection can be delivered easily, consistently, and vitually imperceptibly with a recently introduced computer-controlled local anesthesia delivery system. The anterior (AMSA) middle superior alveolar block, is a single-site injection requiring less than one cartridge of anesthetic and is ideal for maxillary esthetic restorative dentistry because it does not distort the smile line. A clinical example is also presented.

Selecting the optimum prefabricated post-and-core system can be a complex and imprecise exercise for the restorative dentist. First, no single prefabricated post-and-core system fits all situations. Second, the vast number of post-and-core components currently on the market complicates the selection process. Finally, useful biomechanical criteria for evaluating prefabricated post-and-core components are difficutl to quantify. The prefabricated post-and-core system consists of three components: the post, a core material, and a luting cement. Each combination of component types is a potential system alternative. This article presents useful biomechanical criteria, based on current restorative guidelines, for evaluating the basic components of any prefabricated post-and-core system.

Objective: This practice-based study involved private practitioners who reported on the location of 1,100 sites of clinically diagnosed secondary caries. Method and materials: The secondary caries was noted on schematic diagrams on which the clinicians made an outline of the restoration and marked the location of the caries with a red pen. The secondary caries was classified as being located gingivally, occlusal/incisally, or at any other location of the restoration. Results: Overall, 80% to 90% of the clinically diagnosed secondary caries was reported to be located gingivally, irrespective of the type of restoration or restorative material employed. Class II restorations, analyzed separately, showed a slightly higher relative proportion of occlusal secondary caries on resin composite (16%) than on amalgam (8%) restorations. Conclusion: A number of patient, operator, and material factors may contribute to the development of secondary caries and in the differential diagnosis of marginal discrepancies, including secondary caries, at the gingival area of restorations.

Since reports of the mad cow disease epidemic in Great Britain erupted in the international press, sensational and intimidating articles about the risk that bovine spongiform encephalopathy and related diseases may pose to humans have appeared. The bad news is that compelling scientif ic evidence suggests so-called prion disease can and has infected humans, although the overall risk appears to be low. Furthermore, at present, there is no reliable antemortem diagnosis, specific treatment, or vaccine to prevent the disease. The agent thought to be responsible for this unusal class of disease is a rogue protein (called a prion) that, unlike all other agents known to cause infectious disease, contains neither DNA nor RNA. According to a popular hypothesis, normal membrane-associated prion proteins undergo conformational changes that can cause disease. The bad prion forms cause holes or a spongy appearance in the brain in all disease variants, hence the generic designation of spongiform encephalopathy. The good news is that risk for exposure to prion disease is exceedingly remote in the dental practice and that current universal infection control procedures are probably sufficient.

A severely resorbed maxilla was reconstructed utilizing a combined surgical technique that included the placement of a horseshoe-shaped bicortical calvarium onlay graft, fixed by six endosseous implants. Two more implants were placed in t he pterygoid process to support and stabilize the prosthesis. The dentition was rehabilitated with a fixed implant-supported hybrid prosthesis.

Objective: The effects of time, surface preparation, and use of a bonding agent on the ability to bond amalgam or resin composite to amalgam were studied. Method and materials: Cylindrical amalgam specimens were prepared in a split die (32 groups of 10 each). The 32 groups were divided into two groups of 16 each: amalgam bonded to amalgam and resin composite bonded to amalgam. One half of each group of 16 was bonded within 1 hour after the initial condensation (fresh) and the other half was bonded after 21 days' storage in physiologic saline (old). Four bonding methods (control [no bonding agent], Advance, All-Bond 2, or Amalgambond Plus) were each utilized on one abraded group (air abrasion with 50-um aluminum oxide) and one unabraded group. After an additional 21 days of storage, bond strengths were measured with a three-point flexure test. Solid amalgam cylinders were also tested. Results: Solid amalgam control cylinders exhibited mean bond strengths 10,000 psi greater than any of the bonded specimens. Among specimens of amalgam bonded to amalgam, those that were abraded after 21 days and used no bonding agent showed a significantly greater bond strength than did specimens utilizing any of the other combinations of the selected independent variables. Among specimens of resin composite bonded to amalgam, those bonded after 21 days and utilizing a bonding agent exhibited significantly greater bond strengths than did speicmens utilizing any of the other combinations of the selected independent variables Conclusions: The results of this in vitro study suggest that the strength of a repaired amalgam is only about 40% of that of an unrepaired amalgam. They also indicate that the strongest repair of amalgam using additional amalgam material may be accomplished without the use of any bonding agents utilized in this study. When adding resin composite material to amalgam, the resin composite should be added after the amalgam has had adequate time to set, and the use of a bonding agent increases the strength of the repair.