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At least 19 recordsLinked to original sources
PubMed2004

Replacement of missing maxillary canines with dental implants: prosthesis design considerations.

Replacing a missing canine with a dental implant is the optimal treatment plan. The strategic roles canines play in maintaining normal function and the high visibility of these teeth, especially in the maxilla, require a restoration that provides uncompromised function and aesthetics. Eliminating lateral forces on the implant can minimize implant complications, but in young patients (ie, with steep canine guidance) achieving such a goal presents a restorative challenge. This article discusses several considerations (ie, ease of maintenance, retrievability) that will affect the design of the definitive restoration.

Adult↗
PubMedDate not supplied

Finite element analysis of two-abutment Hader bar designs.

Parametric three-dimensional finite element studies were conducted on the Hader bar to determine mechanical properties with respect to bar length, stiffener height, and material properties. Three bar lengths (6, 12, and 18 mm) were analyzed with a 1-mm stiffener height. For the longest bar length (18 mm), two additional stiffener heights were evaluated (2 and 3 mm). In addition, three material types were studied for each of the design cases which represented a selection of alloys commonly used clinically. The model consisted of a representative Hader bar which was constructed of a bar of 1.8 mm diameter. The ends of the bar were fixed to a 2.5-mm diameter coping which was attached to a 1.8-mm diameter root form-type implant, rigidly fixed in a representative block of bone. The bone was modeled as fixed at its distal end to eliminate rigid body motion. A 200-Newton occlusal force was modeled as being transmitted through one, two, or three attachment clips, 5 mm in length, for the three respective bar lengths. The results of these analyses did not predict yielding (failure) for any of the cases studied. Span length and stiffener height were found to play a stronger role in the adequacy of the overall design as compared with changing material properties in the range of alloy stiffness tested. For the span length studies, factors of safety, with respect to static yield strength, ranged from 2.93 to 10.3 and fatigue factors of safety ranged from 1.41 to 3.36.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer-Aided Design↗
PubMed2004

Efficiency considerations for the purely tapered interference fit (TIF) abutments used in dental implants.

A tapered interference fit provides a mechanically reliable retention mechanism for the implant-abutment interface in a dental implant. Understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. In this paper, approximate closed-form formulas are developed to analyze the mechanics of a tapered interference fit. In particular, the insertion force, the efficiency, defined as the ratio of the pull-out force to insertion force, and the critical insertion depth, which causes the onset of plastic deformation, are analyzed. It is shown that the insertion force is a function of the taper angle, the contact length, the inner and outer radii of the implant, the static and the kinetic coefficients of friction, and the elastic modulii of the implant/abutment materials. The efficiency of the tapered interference fit, which is defined as the ratio of the pull-out force to insertion force, is found to be greater than one, for taper angles that are less than 6 deg when the friction coefficient is 0.3. A safe range of insertion forces has been shown to exist. The lower end of this range depends on the maximum pull-out force that may occur due to occlusion in the multiple tooth restorations and the efficiency of the system; and the upper end of this range depends on the plastic deformation of the abutment and the implant due to interference fit. It has been shown that using a small taper angle and a long contact length widens the safe range of insertion forces.

Animals↗
PubMedDate not supplied

Precision of CNC-milled titanium frameworks for implant treatment in the edentulous jaw.

PURPOSE: The purpose of this report was to describe a new technique to fabricate one-piece, implant-supported titanium frameworks by means of a computer numeric-controlled (CNC) milling technique, and to compare the fit of these frameworks with conventional cast prostheses. MATERIALS AND METHODS: The study comprised 20 patients who were provided with 5 standard Brånemark implants each in the edentulous mandible. The fit of the first 10 prostheses with CNC-milled frameworks was measured by means of a 3-dimensional photogrammetric technique. The distortion of the center point of the framework cylinders was measured in relation to the master cast replicas. These measurements were compared with 10 randomly selected routine prostheses with cast frameworks. RESULTS: No significant differences were found between the 2 groups. The 3-dimensional distortion of the cylinders in the completed prostheses ranged from 3 to 80 microns; no passive framework was observed. More distortion was observed in the horizontal plane (x and y axes) as compared to the distortion in the vertical direction (z axis). CONCLUSION: The precision of fit of the first CNC-milled prostheses presented a comparable fit to the conventional cast frameworks. Consequently, this new technique could be a valid option for the routine fabrication of frameworks for implant prostheses.

Computer-Aided Design↗
PubMed2005

Clinical long-term results with 617 Cerec veneers: a nine-year report.

There are no long-term clinical studies concerning the treatment outcome of CAD/CAM generated porcelain laminate veneers. The objective of this study was to conduct a longitudinal evaluation of CAD/CAM fabricated porcelain laminate veneers. A single practitioner placed 715 CAD/CAM generated porcelain laminate veneers produced chairside with the Cerec system on 307 patients between December 1989 and December 1997. 260 patients with 617 veneers were available for recall examination. Forty-seven patients with 98 veneers (13.7%) were unable to be located or return for recall examination. Fourteen restorations had been lost. The Kaplan-Meier survival rate was 94% after up to 9 years (95% confidence interval: 90.7 to 97.8%). Of the surviving restorations, 98% were classified as clinically acceptable after 9 years. 97.3% of the teeth examined tested vital, 96.2% of the veneers were asymptomatic since their production, 98.8% of the veneers were considered successful by the patient. CAD/CAM veneers fabricated with the Cerec System achieved comparable long-term clinical results to those reported for laboratory processed porcelain laminate veneers. The high survival rate and favorable clinical results would support the use of CAD/CAM porcelain laminate veneers in clinical situations similar to those for laboratory processed porcelain veneers. CAD/CAM generated porcelain laminate veneers may provide equally good clinical results and longevity as conventional laboratory-processed porcelain laminate veneers.

Acid Etching, Dental↗
PubMedDate not supplied

Fabrication of titanium implant-retained restorations with nontraditional machining techniques.

Traditional laboratory techniques are being supplemented by modern precision technologies to solve complex restorative problems. Electrical discharge machining combined with laser scanning and computer aided design-computer aided manufacturing can create very precise restorations without the lost wax method. A laser scanner is used to create a three-dimensional polyline data model that can then be converted into a stereolithography file format for output to a stereolithography apparatus or other rapid prototyping device. A stereolithography-generated model is used to create an electric discharge machining electrode via copper electroforming. This electrode is used to machine dental restorations from an ingot of titanium, bypassing the conventional lost wax casting process. Retaining screw access holes are machined using conventional drilling procedures, but could be accomplished with electric discharge machining if desired. Other rapid prototyping technologies are briefly discussed.

Computer-Aided Design↗
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↗
PubMed2005

A computed tomographic scan-derived customized surgical template and fixed prosthesis for flapless surgery and immediate loading of implants in fully edentulous maxillae: a prospective multicenter study.

BACKGROUND: Based on three-dimensional implant planning software for computed tomographic (CT) scan data, customized surgical templates and final dental prostheses could be designed to ensure high precision transfer of the implant treatment planning to the operative field and an immediate rigid splinting of the installed implants, respectively. PURPOSE: The aim of the present study was to (1) evaluate a concept including a treatment planning procedure based on CT scan images and a prefabricated fixed prosthetic reconstruction for immediate function in upper jaws using a flapless surgical technique and (2) validate the universality of this concept in a prospective multicenter clinical study. MATERIALS AND METHODS: Twenty-seven consecutive patients with edentulous maxillae were included. Treatments were performed according to the Teeth-in-an-Hour concept (Nobel Biocare AB, Göteborg, Sweden), which includes a CT scan-derived customized surgical template for flapless surgery and a prefabricated prosthetic suprastructure. RESULTS: All patients received their final prosthetic restoration immediately after implant placement, that is, both the surgery and the prosthesis insertion were completed within approximately 1 hour. In the 24 patients followed for 1 year, all prostheses and individual implants were recorded as stable. CONCLUSION: The present prospective multicenter study indicates that the prefabrication, on the basis of models derived from three-dimensional oral implant planning software, of both surgical templates for flapless surgery and dental prostheses for immediate loading is a very reliable treatment option. It is evident that the same approach could be used for staged surgery and in partial edentulism.

Adult↗
PubMed2000

Clinical long-term results and 10-year Kaplan-Meier analysis of Cerec restorations.

In a private practice, 299 patients were treated with 1010 full-ceramic restorations within a period of 39 months. The inlays and onlays were manufactured using the Cerec technique, and were seated in one single appointment. The clinical success was observed and documented continuously. Re-examination was conducted 9 to 12 years after the placement. According to the Kaplan-Meier method, the probability of survival decreased to 90% (s = 0.018) after 10 years and 84.9% after 11.8 years with no further loss by the final observation at 12 years. Size and outline form did not affect the success rate. Premolars rated better than molars. Vital teeth provided better results than non-vital teeth. The application of dentin adhesive increased the probability of success. Eighty-one failures were recorded during the observation period. The most frequent reason for failures were fractures of ceramic and tooth.

Adolescent↗
PubMedDate not supplied

All-ceramic crowns and preparation characteristics: a mathematic approach.

PURPOSE: The purpose of this investigation was to compare two mathematically calculated preparation parameters, ie, retentive capacity and finish line type, with a visual characterization based on a 3-D projection of the same prepared teeth on a PC screen. MATERIALS AND METHODS: Data from 400 teeth prepared for all-ceramic crowns recorded and manufactured by the Procera system, ie, 100 teeth each of types 11, 13, 14, and 16, were selected. Teeth were visually characterized for retentive capacity as good, acceptable, or insufficient, and type of finish line was characterized as deep chamfer, chamfer, or knife edge. For the mathematic calculations, data points located along vertical lines every 10 degrees around the tooth from finish line to occlusal/incisal midpoint were selected to calculate retentive area, defined as the part of the axial walls with an angle of less than 10 degrees to the preparation midline, and the area at the finish line with an angle of more than 45 degrees to the midline. RESULTS: Significant differences were found between the calculated size of surface areas for all types of prepared teeth visually characterized as having good retention and the two other categories (acceptable and insufficient). The difference between the latter two categories was not significant. Significant differences were also found between calculated surface areas for teeth visually characterized as having a deep chamfer and the two other finish line categories, ie, small chamfer and knife edge, but not between the latter two categories. CONCLUSION: The mathematic program allows a characterization of preparation parameters and may be further developed for use in prospective or retrospective studies of CAD/CAM restorations.

Algorithms↗
PubMed2003

The role of complete denture principles in implant prosthodontics.

During the past 30 years, there has been a growth of implant courses in dental schools at the predoctoral level to meet a burgeoning demand. At the same time, there has been a concomitant reduction in curriculum time devoted to clinical and technical aspects of complete denture construction. There will be a sizable cohort of patients with limited natural dental landmarks seeking implant reconstructions that may be difficult for the general practitioner to restore. This article reviews basic prosthodontic principles and procedures that are important to understand when designing an implant prosthesis.

Dental Occlusion, Centric↗
PubMed2003

Advanced crown and bridge design.

The present article describes the CAD construction procedure of copings, reduced crowns, anatomical crowns, hybrid bridges, and other construction software features contained in the Digident dental CAD/CAM system (Girrbach Dental, Pforzheim, Germany). The individual design of a crown or a bridge framework will, of course, influence the stability and the longevity of the final dental restoration. Especially an anatomically reduced crown framework possesses--in comparison to a simple coping design--several advantages, while for some materials, a full crown design is esthetically not suitable. An anatomically reduced crown design results in a mechanical support of the occlusal cusps, as the high strength framework is mechanically more favorable than the veneering ceramics or composites. Moreover, the reduced construction of the anatomical shape allows the creation of ceramic layers of approximately homogeneous thickness. This has the effect that the residual stresses in the veneering ceramic after the thermal treatment, i.e., several firing and cooling cycles, are minimized. A prerequisite for the computer-aided anatomical construction of crowns is the inclusion of adjacent teeth and the articulation of the opposing jaw. In these terms, the opposing jaw or a bite impression have to be scanned, digitized, and positioned virtually in bite relation. While taking patient-specific articulator parameters into account, a software-integrated "virtual articulator" allows simulation of dynamic occlusion and therefore a computer-aided reduction of interfering contact points.

Computer-Aided Design↗
PubMed1995

Comparison of partial and full crowns as retainers in the same bridge.

The purpose of this study was to assess longitudinally the success of partial and full crown abutment pairs in the same bridges. Fifty patients with a mean age of 45 years (range 22-70 years) were examined during spring 1981 (1-5 year follow-up), 33 of whom were examined a second time during spring 1990 (10-15 year follow-up). The status of the partial crowns, full crowns, and their abutment teeth was assessed using standardized questions, and clinical and radiographic examinations. At the first follow-up examination, all partial and full crowns, and consequently all bridges, were still in use. Before the second follow-up examination one of the full crown abutments had become badly decayed, and the bridge, including the partial crown, had been removed. The failure rate was 0.2% per year for the full crown as a unit, and consequently 0.2% per year for the bridge as a unit.

Acrylic Resins↗