The purpose of this study was to determine the effect of frequent recall appointments for a professional oral prophylaxis, specificaly for patients with fixed prostheses. By a dental hygienist the prophylaxis was repeated every month for a test group and twice a year for a control group (24 subjects). All patients were reexamined at 6- and 12-month intervals to reevaluate the oral health. This study demonstrated that careful professional cleaning of the teeth of patiens with fixed prostheses once every month is sufficient to maintain satisfactory oral hygiene. For the private practitioner it hardly seems realistic to organize a recall program once every month. However, professional clearning twice a year cannot guarantee oral health in all patients with fixed prostheses. Therefore further examinations over a longer period of time are necessary to determine reasonable recall intervals for the successful establishment and maintenance of oral health.

Adult↗

PubMed1978

[Crown and bridgework prostheses. A survey of the literature].

From 1975 to 1977, 20 dental journals of German, Anglo-American, French and Scandinavian origin were examined for articles concerning crowns and bridges. 286 articles specifically concerned fixed prosthetics, and certain subjects were treated more than others (metal ceramics, relation between restorations and periodontium). It was attempted to give a survey of articles that were clinically oriented, which permitted to reduce the number of articles reviewed.

Crowns↗

PubMed1978

[Periodontal conditions in patients with crowns and bridgework].

A study evaluating supragingival and subgingival placement of restoration margins in 24 patients following periodontal and reconstruction therapy is presented. After 1 year no significant differences in supragingival plaque retention, tooth mobility, and width of attached gingiva were observed between the two types of restorations. The gingiva of those restorations with supragingival termination of margins showed, however, significantly (p less than 0.001) less inflammation. The pocket depth of restored teeth was significantly greater (p less than 0.001) than that of non-restored. It is concluded that whenever feasable, restorations should terminate above the free margin of the gingiva. Every restoration terminating in the immediate vicinity of or in actual contact with surrounding soft tissue is a potential irritant to that tissue and increases the chance of precipitating periodontal disease. It is mandatory that the patients with such restorations participate in a regular dental hygiene recall program where oral hygiene can be evaluated, physiotherapy procedures reviewed and motivation reenforced.

Crowns↗

PubMedDate not supplied

The effect of film thickness and surface texture on the resistance of cemented extracoronal restorations to lateral fatigue loading.

PURPOSE: The aim of the present study was to assess the effect of cement-film thickness and surface texture (roughness) on the resistance of cemented crowns to dynamic lateral loading. MATERIALS AND METHODS: Crown and abutment analogues were cemented using zinc-oxide-eugenol, zinc-phosphate, glass-ionomer, and composite cements. The space left for the cement lute was 0.02, 0.05, 0.1, 0.2, and 0.5 mm. The 3 degrees of surface texture subjected to investigation were (1) polished with up to 4,000-grit paper, (2) sanded using a 1,000-grit paper, and (3) sandblasted with 50-micron aluminum oxide. Testing was conducted according to the staircase procedure. The specimens were subjected to rotational fatigue loading until the cement bond failed or the components reached 1,000,000 stress cycles. RESULTS: The results showed that the relation between cement thickness and resistance to dynamic lateral loading is hyperbolic. For the zinc-oxide-eugenol, the zinc-phosphate, and the glass-ionomer cements increasing surface texture had a moderate effect. For composite cement, sandblasting doubled the resistance to dynamic lateral loading. For both parameters tested (cement thickness and surface texture), the ascending order of resistance was: zinc-oxide-eugenol, zinc-phosphate, and glass-ionomer cements. Crowns cemented with composite cement presented the highest resistance to dynamic lateral loading. CONCLUSION: Within the confines of the present experimental design, it is concluded that (1) decreasing the width of the cement layer increases the resistance to dynamic lateral loading, and (2) texturing the surface of the abutment and the restorations as after sandblasting increases the resistance to dynamic lateral loading.

Cementation↗

PubMedDate not supplied

Mechanics of the implant-abutment connection: an 8-degree taper compared to a butt joint connection.

This paper presents aa comparison between the 8-degree Morse Taper and the butt joint aa connections between an implant and an abutment. Three-dimensional, non-linear finite element models were created to compare the 2 connection principles under equal conditions. The loading configuration was thereby modeled according to a test setup actually used for the dynamic long-term testing of dental implants as required for regulatory purposes. The results give insight into the mechanics involved in each type of connection and are compared to actual findings with the testing machine. The comparison indicates the superior mechanics of conical abutment connections and helps to explain their significantly better long-term stability in the clinical application.

Dental Abutments↗

PubMedDate not supplied

Microstructures of brazings and welds using grade 2 commercially pure titanium.

PURPOSE: Microstructural analyses of commercially pure titanium (CpTi) are scarce. The present report presents the micrographs, fractographs, elemental characteristics, and hardness profiles of brazed joints and weldments using machined rods of CpTi. MATERIALS AND METHODS: CpTi rods were joined using four techniques: laser welding, electric-arc welding, electron-beam welding, and gold- and Ti-filler brazing. The specimens were then subjected to tensile and fatigue loading. After sectioning and patterning, optical micrographs of intact joints were obtained. Fractured surfaces were investigated using scanning electron microscopy (SEM). The joint's composition was determined by SEM-energy dispersive x-ray analysis. Hardness was determined at specific locations using a microindenter. RESULTS: While laser welding left the parent metal's equiaxed structure fairly intact, electric-arc welding, electron-beam welding, and brazing created a heat-affected zone in the vicinity of the joint. The extent and characteristics of the heat-affected zone depended on the amount of heat transferred to the specimens. In this respect, brazing essentially increased grain size and altered their shape. Electron-beam welding augmented this phenomenon, yielding grains that encompassed the full diameter of the joint. Electric-arc welding disrupted the granular pattern and generated highly lamellar/acicular structures. CONCLUSION: Hardness was not a good indicator of mechanical resistance, nor was the joint's structural continuity with the parent substrate. Still, acicular microstructures were characterized by a peculiar behavior in that such joints were highly resistant to tensile stresses while their fatigue strength ranged among the lowest of the joints tested.

Copper↗

PubMedDate not supplied

Invisible supragingival crown margins: an in vitro study.

A method of improving the esthetics and seal of porcelain crown margins using composite resin is described. The procedure includes a circumferential shoulder-type preparation located entirely in enamel. To provide adequate space for a thin layer of composite resin to blend gradually into both tooth enamel and porcelain surfaces, the cervical enamel as well as the opposing porcelain butt joint are subsequently beveled. In this study, microleakage analysis and SEM evaluation of the marginal area indicate that the marginal design described can predictably produce an optimal esthetic appearance and marginal seal, contour, and integrity with supragingival ceramic restorations.

Crowns↗

PubMedDate not supplied

Stress fatigue: basic principles and prosthodontic implications.

Clinical evidence indicates that the majority of fractures that occur in prosthodontic structures do so after a period of many years. Such failures generally are not related to an episode of acute overload but result from fatigue failure. This paper reviews the current knowledge of fatigue failure and test methods. An overview of published studies is given, and the authors suggest guidelines for future prosthodontic studies of this nature.

Chemical Phenomena↗

PubMedDate not supplied

Tensile bond strength of gold and porcelain inlays to extracted teeth using three cements.

This in vitro study compared the tensile bond strength of gold and porcelain inlays to extracted molars in standardized cavities. Three cements were used: zinc phosphate, glass-ionomer, and a resin composite cement. The gold inlays were cemented using zinc phosphate or glass-ionomer cement, and the porcelain inlays were luted using resin composite or glass-ionomer cement. Surface treatments included, for gold inlays, either no treatment (zinc phosphate cement) or airborne particle abraded and tinplated (glass-ionomer cement); and for porcelain inlays, either no treatment (glass-ionomer cement) or etched and silane-treated (resin composite cement). Statistical analysis was performed using the Weibull distribution. Results showed no significant differences between gold inlays cemented using zinc phosphate or glass-ionomer cements and porcelain inlays luted using glass-ionomer cements. The bonded porcelain inlays (resin composite cement) showed tensile bond strengths two to three times higher than those obtained for cemented gold inlays.

Composite Resins↗

PubMedDate not supplied

Computer-aided design and transverse strength of screw-retained attachments.

Two commercially available, screw-retained attachments and an experimental attachment were modeled and analyzed by computerized finite element method. Mechanical test specimens were then developed. Cast rectangular bars were fabricated with the attachments or were joined by soldering at midspan as a control. These bars were subjected to three-point loading. The soldered connector was stronger than the three attachment designs, and the experimental attachment was stronger than the two commercial products. There was general agreement between the mechanical and finite element testing. The use of computer-aided technology to design dental devices with improved mechanical properties was demonstrated by this study.

Analysis of Variance↗

PubMedDate not supplied

The relationship between abutment taper and resistance of cemented crowns to dynamic loading.

This study investigated the relationship between abutment total occlusal convergence angle (taper) and the resistance of cemented crowns subjected to dynamic loading. Crown and abutment analogs were placed using zinc-oxide-eugenol, zinc-phosphate, glass-ionomer, or resin composite cement. Total occlusal convergence angles of 2.5, 5, 10, 15, 20, 30, and 40 degrees were used. Dynamic stresses were applied to the luted components until the bond failed or the components reached 10(6) load cycles. The data were analyzed using the staircase technique. The relationship between convergence and resistance was approximately linear for all the cements tested. Crowns luted with resin composite cement were more resistant to dynamic lateral loading than those placed using glass-ionomer or zinc-phosphate cements. Crowns luted with zinc-oxide-eugenol cement presented the least resistance to cyclic lateral stresses.

Cementation↗

PubMedDate not supplied

Fracture resistance of human enamel and three all-ceramic crown systems on extracted teeth.

This in vitro study measured the fracture resistance of intact extracted molars and three types of all-ceramic crowns; feldspathic porcelain, glass-ceramic, and glass-infiltrated alumina. All crowns were of a simplified three-cusp occlusal configuration, and were placed on prepared, extracted third molars. The ceramic crowns were bonded to dentin with a resin composite cement, except for 10 of the feldspathic crowns, which were luted with zinc phosphate cement. The fracture resistances was measured using a spherical steel indenter that contacted the occlusal surface at three points. A total of 40 ceramic crowns and 50 extracted maxillary third molars were tested. The Weibull distribution was used for data analysis. Intact extracted teeth were significantly stronger than all-ceramic crowns. Of the ceramic restorations, the glass-infiltrated alumina crowns exhibited the highest fracture resistance.

Aluminum Oxide↗

PubMedDate not supplied

Implant-supported restorations in the anterior region: prosthetic considerations.

Achieving functional and aesthetic implant-supported restorations in the partially edentulous patient can be particularly challenging when the implant sites are in the anterior region and not in harmony with the adjacent dentition. The learning objective of this article is to focus on presurgical evaluation of anterior implant sites and systematic development of related therapeutic modalities. Utilization of guided bone regeneration and connective tissue grafting predictably facilitates implant positioning that is compatible with required aesthetic restoration and soft tissue contours. Other aspects, such as abutment protection caps with variable emergence profiles, provisional restorations for the development of optimal periimplant soft tissue contours, and fabrication guidelines for different types of prosthetic restorations, are also discussed.

Alveolar Ridge Augmentation↗