ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

PurposeVibration from the high‐speed handpiece may adversely affect the cement layer between a casting and a tooth, causing loss of retention or increased microleakage. This study assessed the effect of crown preparation on retention and microleakage of cemented cast post and cores.Materials and MethodsPost and cores were fabricated for extracted teeth and cemented. Specimens were prepared for crown restorations, varying the preparation time and the rotary diamond instrument used. After thermocycling and immersion in a dye bath, tensile unseating force and linear dye penetration were measured.ResultsIn general, retention decreased with increased severity of crown preparation; however, differences were not statistically significant (α= .05). Although the differing preparation conditions resulted in significant differences in microleakage, no consistent trends were evident.ConclusionsCrown preparation using high‐speed rotary diamond abrasives of cast post and cores luted with zinc phosphate cement had no significant effect on their retention, but had varying effects on subsequent microleakage at the cement‐tooth int

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00116.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A checklist is described that is designed to permit a systematic evaluation of the factors involved in the trial insertion appointment. The checklist aids both the student and the instructor in assuring that items are not overlooked during this important appointment. More equitable grading of the student's preparation and knowledge is facilitated. The checklist also serves as an excellent patient approval form.

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00117.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A simplified method is described for achieving the purpose of the altered cast technique without the inherent laboratory problems of realignment of the metal framework on a modified cast and the extra time involved.

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00118.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

PurposeIn the past it has been difficult to treat soft tissue changes occurring beneath metal frameworks of removable partial dentures or complete dentures using soft reline materials. The main difficulty has been in getting the resilient materials to adhere to the metal. This research investigates the use of microabrading with and without a universal resin bonding system in achieving a clinically useful bond between two soft reline materials and a commonly used base‐metal alloy.Materials and Methods120 disks, 1 inch in diameter, were cast in Ticonium (CPM Industries, Albany, NY). The surface of the disks was finished to a high polish and then evenly microabraded. Four test groups of 15 pairs of disks were established, with two groups receiving Coe‐Soft (Coe Laboratories, Chicago, IL) and two groups receiving Soft Oryl (Teledyne Getz, Elk Grove Village, IL). One group of each reline material had the microabraded surfaces on each disk treated with All Bond 2. Then, 1.2 mm of reline material was placed between each set of disks and allowed to cure. The disks were placed on an Instron machine and a tensile force was applied until bond failure occurred.ResultsAll four groups showed significant bond strengths, with the Soft Oryl groups showing statistically significant higher bond strengths. In both reline material groupings, the groups with only microabrading showed slightly higher bond strengths.ConclusionsSoft reline materials can be made to adhere to base‐metal alloys used in removable prosthodontics with clinically acceptable strengths using microabrading with or without the use of a resin bonding s

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00119.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

PurposeThis study measured the tensile force required to separate a custom implant abutment fixture that had been cast onto a machined component using the Impac custom abutment system (Vident, Baldwin Park, CA). The characteristics of the interface between the cast and machined components were also investigated by scanning electron microscopy x‐ray and energy‐dispersive (JEOL T330A, Peabody, MA) analysis (Kevex Delta Level 1, San Carlos, CA).Materials and MethodsA polycarbonate custom abutment component, attached to a gold alloy component of the abutment, was invested in a phosphate‐bonded investment and cast in a type III gold alloy (Argenco, Argen Precious Metals, San Diego, CA). Eight samples were cast after a burn‐out of 900°F and 13 samples were cast after a burn‐out at 1300°F. The abutment components were pulled in tension in a universal Testing Machine (Instron 4204, Canton, MA) until failure. The interface of as‐cast and failed samples were examined by electron microscopy.ResultsSamples burned out at 1300°F failed at a mean force of 2477 ± 295 N (545 ± 65 Ib), and samples burned out at 900°F failed at a mean force of 2182 ± 91 N (484 ± 20 Ib). Electron microscopy of the interface between the cast and machined components showed retentive tags provided in the design of the machined components. There was also a zone of diffusion between components shown by a zone of void formation within the casting. Failure occurred at the interface of the cast and machined components for all samples.ConclusionsThe cast component was retained by a combination of mechanical and

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00120.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

PurposeOcclusal forces concentrate at the cantilevered section(s) of fixed implant‐supported prostheses. Investigators in early clinical applications of these prostheses described fractures of the metal alloy framework at the cantilevered‐distal abutment junction. Improved performance was noticed when the framework's cross‐sectional area was increased and the metal alloys used had an increased tensile strength and elastic modulus. Long‐term service of a cantilevered implant‐supported prosthesis is directly dependent on the fatigue life of the metal alloy framework. Two fatigue durability factors that are alterable by the technician/clinician are the framework material and the cross‐sectional design of the structure. These factors can increase rigidity and alter the stress distribution through the framework. The importance of cross‐sectional design on the rigidity may become more critical in situations with decreased intermaxillary space, especially if lengthened cantilevers are required or patients show discernible parafunctional habits. The theoretical aspects of beam deflection and the cross‐sectional design of cantilevered structures under stress were investigated in this study. A subsequent report will provide results from experimental evaluations of designs similar to those assessed in this study.Materials and MethodsThe cross‐sectional designs considered are anL, I, Uand a nearly elliptical‐shaped configuration. The size of the framework was determined by approximating the total cross‐sectional space available for the restoration, minus the space required for artificial teeth in severe restrictions. All theoretical and actual specimens were modeled within these confines. Some allowance for the contours of the inferior surface of the artificial teeth was made to optimize the dimensions of each framework. Calculations enabled comparison of relative deflection and stress characteristics of each design group and predictions of fatigue durability.ResultsThe displacements of each cantilever were found to be dependent upon the heights of each framework. As evaluated, theLand elliptical designs experienced larger maximum end deflections than theI‐andU‐shaped designs. The maximum normal stresses were observed to be less in theIand elliptical sections than in theUandLsections.ConclusionsThe space restrictions for limited intermaxillary conditions reveal that theIcross‐sectional design may provide the least displacement and smallest maximuim normal stress under conditions in which each framework is subjected to an identical load. Each of the framework cross sections considered, however, is a viable candidate for use. The effectiveness of any particular shape in an intraoral environment cannot be easily assessed from the simple statical analysis. Limitations of the predictability with statical analysis as opposed to actual mechanical testing or in vivo use was noted. Less severe space restrictions would probably improve the estimated perfo

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00121.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

PurposeDimensional change and wettability were determined for three addition silicones and a polyether impression material after disinfection by immersion for two 30‐minute cycles in 2% acid‐potentiated glutaraldehyde.Materials and MethodsContact angles of water on disks were measured on a goniometer. Dimensional change was determined by change in distance between two reference lines. Contact angle (degree) and dimensional change (percent) of five samples were measured after 0‐, 30‐, 60‐, and 1,440‐minute intervals of storage in air and disinfectant.ResultsThe contact angle in air increased for two addition silicones and remained constant for the remaining materials. In disinfectant, the contact angle increased for all four materials, with the contact angle of the polyether increasing the least. In air, dimensional change decreased significantly for an addition silicone and a polyether. In disinfectant, the dimensional changes of the addition silicones were not significant, but the polyether increased in dimension after 1,440 minutes.ConclusionsTwo 30‐minute cycles of disinfection in 2% acid‐potentiated glutaraldehyde reduced wettability, but had little effect on the dimensional change of the addition silicones and po

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00122.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Presentation technology is available, and it does not have to be expensive. This article describes computer hardware and software concepts for graphics use, and recommends principles for making cost‐effective buying decisions. Also included is a previously published technique for making custom computer graphic 35‐mm slides at minimal expense. This information is vital to anyone lecturing without the support of a custom graphics laborat

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In Part 1 of this two‐part literature review, the biomechanics of cantilever fixed partial dentures are reviewed. Theoretical constructs of implant biomechanics with special emphasis on implant‐supported cantilevers are also discussed. Finally, an overview of the literature regarding occlusal forces generated by patients with implant‐supported prostheses is pres

ISSN:1059-941X    

DOI:10.1111/j.1532-849X.1994.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY