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PubMed1996

Resistance to fracture of teeth with various preparations for amalgam.

OBJECTIVES: Advances in dental instrumentation and materials have allowed for increasingly conservative preparations when treating teeth for dental caries. Research has shown that some materials, properly used, can restore teeth to their pre-prepared strength. At the present time, the longevity of these materials is unknown, requiring clinicians to remain committed to conservative methods of tooth preparation. The purpose of this study is to compare the resistance to fracture of teeth prepared with occlusal, mesio-occlusal-distal (MOD) and mesial/distal slot preparations against unprepared control teeth. METHODS: Thirty-two non-carious, non-restored human maxillary premolar teeth were divided into three experimental groups and a control group with eight teeth in each. After preparation, the teeth were loaded to fracture on an Instron Universal Testing Machine, and the results were compared using an Analysis of Variance (ANOVA) followed by Tukey's Studentized Range Test (P < 0.05). Fracture patterns were compared by chi-square analysis at the 0.1 level of probability. RESULTS: There was no significant difference in fracture resistance among the experimental groups, but all were less resistant to fracture than the unprepared control group. The MOD and occlusal groups demonstrated a tendency towards vertical fracture while the mesial-distal slot and unprepared groups tended to a more limited fracture of a single cusp. CONCLUSIONS: Any preparation appears to decrease a tooth's resistance to fracture. Conservative preparation design may affect fracture pattern and enhance options for subsequent restoration.

Analysis of Variance↗
PubMed2001

In vitro microleakage of luting cements and crown foundation material.

STATEMENT OF PROBLEM: Microleakage is a concern for the long-term prognosis of a cemented crown and foundation. PURPOSE: The aims of this investigation were, first, to evaluate microleakage of zinc phosphate cement and resin-reinforced glass ionomer cement under ideal (dry) versus contaminated (wet) conditions, and second, to compare 3 foundations under both ideal and contaminated conditions. MATERIAL AND METHODS: One hundred forty extracted molar teeth were cleaned and mounted. Tooth preparations for complete veneer cast crowns were completed with a chamfer finish line. A mesial surface class II cavity preparation 4 mm wide buccolingually and 2 mm deep was made in each tooth. Seven restorative groups were formed: amalgam/cavity varnish, amalgam/dentinal bonding agent, and composite/dentinal bonding agent, each with dry and contaminated groups, and a seventh group of class II cavity preparations without foundations. Finish lines for crown margins were refined 1.5 mm gingival to the restoration. Artificial crowns were cast in type III gold. Treatment groups were divided into 4 cement groups: dry and contaminated zinc phosphate cement and dry and contaminated resin-reinforced glass ionomer cement. The specimens were thermocycled and immersed in erythrosine B solution for 24 hours. Subsequently, they were rinsed, and their coronal portions were embedded in clear resin. Teeth were sectioned mesiodistally, and standard photomicrographs were made. The microleakage of each restoration and crown was measured. RESULTS: The least foundation microleakage was recorded for amalgam/dentinal bonding agents (ideal group) and composite/dentinal bonding agents (ideal group). The most microleakage was observed within the group without a foundation. In cement groups, the control and experiment sides were evaluated separately but displayed the same order of finding. The least leakage was recorded with resin-reinforced glass ionomer cement (ideal group); the most microleakage was noted with zinc phosphate cement (ideal group). An interaction was demonstrated on the experimental side between cements and the foundations (P=.0001). CONCLUSION: Within the experimental conditions of this study, less microleakage was recorded with resin-reinforced glass ionomer cement (ideal or contaminated) than with zinc phosphate cement (ideal or contaminated). There also was less microleakage evident with a foundation of silver amalgam or composite when a dentinal bonding agent was used under ideal conditions.

Analysis of Variance↗
PubMed1999

Dental burs--what bur for which application? A survey of dental schools.

PURPOSE: The purpose of this study was to survey North American dental schools regarding recommendations for rotary instrumentation for fixed prosthodontic and operative procedures at the predoctoral and postgraduate level. MATERIALS AND METHODS: A 25-question survey was sent to 64 North American dental schools, of which 15 questions specifically related to rotary instrument recommendations. One questionnaire was addressed to the individual at each school having administrative responsibility for teaching tooth preparation techniques. A high response rate was assured by follow-up telephone calls and faxes. The distributions of bur recommendations for both predoctoral and advanced prosthodontic programs were analyzed by chi-squared tests at an a priori alpha = 0.05. RESULTS: Completed surveys were received from 58 of 64 dental schools, a response rate > 90%. Medium grit burs predominate in predoctoral education for gross tooth reduction for fixed prosthodontics, whereas coarse grit burs predominate at the graduate level (p < .05). The use of the diamond bur alone predominates for axial wall refinement, whereas the use of carbide burs or carbide burs in combination with diamond burs prevails for marginal refinement (p < .05). In predoctoral operative dentistry, recommendations for cavity outline form were similar at all dental schools (p > .05) and were principally tungsten carbide (WC) burs. Carbide burs are the instrument of choice for internal walls, but the WC bur alone or in combination with diamond burs is preferred for refining composite margins (p < .05). CONCLUSIONS: There is a broad consensus within North American dental schools on rotary instrumentation used by dental students. There is a greater use of coarser grit burs for gross tooth reduction in fixed prosthodontics at the postgraduate than predoctoral level.

Chi-Square Distribution↗
PubMed2004

Differences between the Cerec-3D software versions 1000 and 1500.

The Cerec-3D software was introduced officially at the IDS 2003 with the version 2.00 R1000. The decisive difference compared with the preceding software generations was that the prepared tooth and the restoration were displayed three dimensionally. Thus, the virtual changes which could be made with the aid of editing tools could also be controlled and seen immediately in 3D. The latest officially available version of the Cerec-3D software version 2.10 R1500 differs in some further developments from the first version 2.00 R1000; these are for example: --If the semiautomatic margin detector is switched off while marking the preparation margin, the alternative intensity image appears instead of the 3D display. --Designing has been decisively improved by the extension of the "Drop" tool (function of continuous application and removal of material). --Under morphologically difficult circumstances, the design proposal can be magnified/reduced in size and repositioned in all spatial directions. --The Parameter setting again permits setting an adhesive gap width specific to the dentist and unit. As an example, the version 1500 software is demonstrated on a simple clinical case in which the occlusion points were defined virtually with the aid of a functional bite registration, eliminating the need for occlusal grinding-in.

Computer-Aided Design↗
PubMed1998

Preimpregnated, fiber-reinforced prostheses. Part I. Basic rationale and complete-coverage and intracoronal fixed partial denture designs.

This is the first of two articles describing the development and use of a continuous fiber-reinforced composite as a framework for the fabrication of fixed partial dentures and splints. The chemical composition and physical structure of the fiber-reinforced composite, along with the progression and development of a variety of fiber-reinforced composite materials, are discussed. Criteria for case selection, tooth preparation, and the clinical and laboratory procedures required for partial- or complete-coverage fixed partial denture fabrication and delivery are described.

Composite Resins↗
PubMed2001

A conservative aesthetic solution for a single anterior edentulous space: case report and one-year follow-up.

Conservative solutions for the restoration of a single edentulous space in the anterior maxilla present an aesthetic challenge to the clinician. Treatment options for tooth replacement include implant placement, a classical fixed partial denture, or a resin-bonded appliance with a metal substructure or fiber-reinforced resin. The resin-bonded Encore Bridge (daVinci Studios, Woodland Hills, CA) offers a restorative solution that is conservative and aesthetic when compared to the required full-tooth preparation in a conventional three-unit fixed partial denture. This case report addresses the indications, preparation guidelines, and restorative procedures for an Encore Bridge.

Adult↗
PubMed2002

Success with inlays/onlays: the seven essentials.

Direct restorative materials have revolutionized the industry over the last several years. They offer the convenience to the patient of a one-visit procedure and they decrease overhead in the dental practice. However, it is essential to remember that direct procedures are not always the treatment of choice. For this reason, we should not discount the need for--or the value of--indirect techniques and laboratory-based procedures, such as inlays and onlays. Fit, form, and function can be more predictable when a procedure involves the ultraprecise workings of the dental laboratory--if the impression-making and other focus areas are given their due significance. This article provides key information about and clinical tips for the seven main facets of inlay/onlay fabrications that will lead to clinical success: diagnosis, tooth preparation, tissue management, impression making, temporization, laboratory communications, and final fit/occlusion.

Cementation↗
PubMed2002

[Reactive anxiety in patients during orthodontic treatment with crowns].

Reactive anxiety of patients was evaluated at clinical stages of orthodontic treatment with polymeric crowns. Antistress therapy essentially decreased the number of patients with high reactive anxiety. Measures to control fear are obligatory before tooth preparation and impression making. At the rest stages it is hardly necessary to focus the dentist's and patient's attention at these measures.

Adult↗
PubMed1999

Computer copings for partial coverage.

Partial coverage posterior tooth preparations are very complex surfaces for computer surface digitization, computer design, and manufacture of ceramic copings. The aim of this study was therefore to determine whether the Computer Integrated Crown Reconstruction (Cicero) system was compatible with a proposed partial coverage preparation design and capable of producing ceramic copings. Posterior teeth were prepared for partial coverage copings with deep gingival chamfers in the proximal boxes and around the functional cusps (buccal of mandibular and lingual of maxillary posterior teeth). The nonfunctional cusps (lingual of mandibular and buccal of maxillary posterior teeth) were prepared with broad bevels following the inclined occlusal plane pattern. Optical impressions were taken of stone dies by means of a fast laser-line scanning method that measured the three-dimensional geometry of the partial coverage preparation. Computers digitized the images, and designed and produced the ceramic copings. The Cicero system digitized the partial coverage preparation surfaces precisely with a minor coefficient of variance of 0.2%. The accuracy of the surface digitization, the design, and the computer aided milling showed that the system was capable of producing partial coverage copings with a mean marginal gap of 74 microns. This value was obtained before optimizing the marginal fit by means of porcelain veneering. In summary, Cicero computer technology, i.e., surface digitization, coping design, and manufacture, was compatible with the described partial coverage preparations for posterior teeth.

Bicuspid↗
PubMed2003

Direct adhesive restoration of anterior teeth: Part 2. Clinical protocol.

Contemporary adhesive restorations allow clinicians to deliver minimally invasive, functional, and aesthetic treatment for compromised dentition in the anterior and posterior regions. Part 1 of this article discussed the state-of-the-art relating to composite restorations, both in situations deemed to be relatively uncomplicated and those that are more complicated. This second part discusses the clinical protocol for the placement of direct composite materials as well as the tooth preparation considerations that must be addressed when providing minimally invasive treatment options.

Clinical Protocols↗
PubMed1997

The full coverage restoration in relation to the gingival sulcus.

The full coverage restoration (FCR) and its effect on the periodontium have been the subject of much controversy over the last half century. The conflict relates to whether the margin of the FCR should be placed at or above the gingival crest, or into the gingival crevice. Clinicians and researchers alike have focused their attention primarily on the mechanistic aspects of fixed prosthetic design (i.e., marginal configuration and fit). Although marginal quality and form are factors in the fabrication of the FCR, they alone will not determine periodontal health and restorative success. What determines the success of the FCR is its ability to restore form and function to the masticatory system without adversely affecting its biology. Each technical phase of treatment (i.e., tooth preparation, impression-taking, the provisional restoration, and the final restoration) must be performed within the limits of biologic adaptation. This literature review discusses the scientific evidence regarding FCR margin placement and periodontal health.

Animals↗
PubMed2001

Predictable resin-bonded bridges in general dental practice.

This paper discusses the use of resin-bonded bridges as predictable restorations in general dental practice. The importance and relevance of case selection is stressed. Efforts have been made to discuss ideal design features, creation of interocclusal space and the need to carry out any tooth preparations. In addition, the clinical stages involved are outlined and a brief comparison with conventional bridges and implant-retained prostheses made.

Cementation↗
PubMed2004

Effect of cement types on the tensile strength of metallic crowns submitted to thermocycling.

The relationship between metallic cast crowns and tensile strength according to cement types submitted to thermocycling was studied. Seventy-two metallic crowns were cast with Verabond II Ni-Cr alloy and cemented in standardized preparations with 10 masculine tapering. Three types of finishing line (45-degree chamfered, 20-degree bevel shoulder and right shoulder) were made with diamond burs on bovine teeth. Twenty-four metallic crowns in each group were randomly subdivided into three subgroups of 8 samples each according to the cement used: SS White zinc phosphate cement, Vitremer resin-modified glass ionomer cement, and Rely X resin cement and were submitted to thermocycling. Retention was evaluated according to tensile load required to displace the metallic cast crowns from tooth preparations with an Instron testing machine. ANOVA and Tukey's test showed a statistically significant difference among luting materials, with greater results for Rely X resin cement (24.9 kgf) followed by SS White zinc phosphate cement (13.3 kgf) and Vitremer resin-modified glass ionomer cement (10.1 kgf). The finishing line types did not influence the tensile resistance of the crowns fixed with the three cements. Increased tensile resistance of metallic crowns fixed on bovine teeth was obtained with resin cement, independent of the finishing line types.

Animals↗
PubMed1998

A new method for casting discrepancy: some results for a phosphate-bonded investment.

OBJECTIVES: An accurate and realistic casting discrepancy method applicable to base metal alloys has hitherto been lacking. The purpose of this study was to develop a method for determining casting discrepancy free of interference from oxide, slag and surface defects, working under realistic conditions. In addition, a variable was sought that could be used for calibrating the casting process to allow for local errors. METHODS: A crown pattern was designed to incorporate circular V-grooves on the margin and the inside surface of the occlusal part for determination of the 'groove root diameter' (GRD) with a measuring microscope. Castings using a phosphate-bonded investment were made to test the effects of 'hygroscopic' expansion, burn-out temperature, powder/liquid ratio and groove location. RESULTS: The tested investment variables showed the expected effects, but the distortion between marginal and pulpal regions was clearly shown, as were interactions between some variables. 'Special liquid' proportion appears to be a good candidate variable for process calibration. CONCLUSIONS: The GRD method was shown to be sensitive and reproducible. It is also applicable to many other casting systems, and in particular to monitoring overall process discrepancy, i.e. from tooth preparation to casting, which is suggested as being the key issue.

Analysis of Variance↗
PubMed2002

Clinical aspects of resin-bonded bridges.

Resin-bonded bridges have emerged as an attractive, minimally invasive prosthodontic option for the restoration of edentulous spaces. Although success rates, determined by retrospective studies, vary greatly, resin-bonded bridges now have success rates approaching those of their cemented counterparts; success is dependent, however, upon appropriate design and careful technique. The metal framework must be rigid and of sufficient surface area to afford secure adhesion to the underlying teeth. Tooth preparation should be restricted to enhancing the bonding area, and it is important that prostheses are designed to maintain axial loading, and guidance upon metal.

Contraindications↗
PubMed1994

[Porcelain onlays].

This article covers the clinical application of feldspathic porcelain onlays. The indication, tooth preparation, try-in and cementation procedures using total etching and the latest concepts in dentin bonding are discussed. When properly executed fired porcelain onlays can meet the highest esthetic demands but they require maximum skills, both of the dental surgeon and of the dental technician.

Acid Etching, Dental↗
PubMed1999

Custom adaptation of an occlusal plane analyzer to a semiadjustable articulator.

The use of a semiadjustable articulator has become more popular for prosthodontic rehabilitation. An occlusal plane analyzer has long been used to assist the operator in the development of an initial mandibular occlusal plane in diagnostic contour casts and later as an integral part of both the contours of the definitive restorations as well as guidelines for the actual tooth preparations. Many manufacturers of semiadjustable articulators offer no such occlusal plane analyzers for use with their instruments. This article describes modifications for the adaptation of an occlusal plane analyzer to the WhipMix 2240 semiadjustable articulator, a possibility heretofore unavailable from any manufacturer.

Dental Articulators↗
PubMed2000

[A hardware and software complex for producing 3D models of the teeth].

A complex of short-basis photogrammetry, methods and software for obtaining and analysis of 3D digital models of relief of dentition and its fragments is presented. This complex is intended for planning and evaluation of tooth preparation and quality of prosthetic treatment. The method was used to assess the correctness of dental shape repair by artificial crowns. The complex can form the base for the CAD/CAM technology.

Calibration↗