Keith E. Thayer

Cast metal, resin-bonded prostheses: A 10-year retrospective study

A sample of 99 resin-bonded prostheses placed over a 10-year period were examined by four clinicians using a standardized criteria sheet. Areas examined included hard tissues, periodontium, retainer and pontic design, retention, the effect of occlusion on framework design and retention rate, and bonding media. The data from 7- and 10-year retrospective studies were compared for meaningful trends. Results showed (1) caries on retainer teeth was 3%, (2) gingival index of the retainer teeth was less than the gingival index of the rest of the mouth (0.7 +/- 0.5 versus 0.9 +/- 0.6), (3) the respective mean probing depths of retainer teeth of 34 patients in the 7- and 10-year studies were 2.2 +/- 0.4 mm and 1.9 +/- 0.7 mm, (4) the debond rate of all the prostheses from all causes was 31%, (5) the debond rate comparing etched metal and perforated retainers from all causes was 32% and 31% [corrected], respectively, and (6) 83% liked the prosthesis; 17% were noncommittal. The authors concluded that the resin-bonded prosthesis may be considered a permanent restoration and a valuable asset in the clinicians armamentarium.

Analysis of Debond Rates of Resin-bonded Prostheses

Debonding rates of 164 resin-bonded prostheses (RBP) placed from 1974 to 1985 were examined at recall. The yearly debond rates were calculated, the cumulative probability of failure was determined for the debonded RBPs, and Weibull distribution parameters were determined. For perforated prostheses, there was a high initial debond rate, followed by slowly decreasing rates for about 5 years. Increasing rates after 5 years indicated the beginning of wearout. The Weibull parameters for the wearout period ofthe perforated prostheses were: characteristic life = 128 (SE = 2) months, modulus = 1.27 (0.06), and threshold parameter = 0. Data were available for etched frameworks for 6 years and showed decreasing debond rates during this time. The characteristic life of the etched bridges was 318 (84) months. The cumulative failure data were also modeled with a cubic polynomial distribution that resulted in a U-shaped hazard function.

Dentinal smearing: An investigation of the phenomenon

/I I n order to prevent damage to the pulp, it is possible that treatment should-be aimed‘ toward a reduction in the permeability of the dentin rather than toward an attempt to stimulate irregular secondary dentine formation.“’ If dentin can be smeared by instrumentation, and if smearing effectively closes the orifices of dentinal tubules, further investigations into its clinical applications are warranted. If the permeability of dentinal tubules can be reduced by smearing, a modification of current concepts of pulpal protection could result when potentially irritative restorative materials are used. For example, if the deleterious effect of the phosphoric acid in zinc phosphate cement could be mediated by an effective chemical barrier, the need for a cavity varnish could be eliminated.‘-’ Hydration of exposed dentin by fluid flow from capillary forces and differential pressure gradients results in restorative materials potentially resting on a moist surface.x-‘7 Obturation of the external orifices of exposed tubules could obviate the problem of adhesion to moist surfaces. Clinically, it would be advantageous if a biomechanical procedure could decrease or eliminate the permeability and the exudation of the fluid tubular contents onto exposed

Complete crowns constructed for an existing partial denture

W hen the prevention of dental disease has failed or trauma has taken its toll of tooth structure, there is no other ethical course to follow than to rehabilitate. The purpose of this article is to introduce another technique for the construction of a complete crown to restore the tooth and meet the demands of an existing partial denture. which the intended tooth retains, supports, and braces. The ideal treatment involves the construction of a complete crown which is properly surveyed and contoured, followed by the fabrication of a new removable prosthesis. The ideal is not always practical. It must be first established that the partial denture is adequate or can be made adequate prior to construction of the complete crown. Further, it must be assumed the tooth in question is restorable. Certain advantages of this technique will become apparent as one employs the DuraLay inlay pattern resin kit.?

Fabrication of temporary crowns and fixed partial dentures

Abstract The methods of temporary crown or bridge fabrication described in this article have some distinct advantages over the use of preformed temporary prostheses. 1. Tooth form and position can more closely duplicate the patients natural teeth. This is very important esthetically in the anterior portion of the mouth. 2. Tooth form can be more closely duplicated for posterior teeth. This allows stabilization of the prepared teeth in anteroposterior as well as occlusal relationships during fabrication of the permanent appliance. 3. Alginate, silicone, and thiokol rubber impression materials can be used, but they are either more inaccurate, costly, or time-consuming to use. It is difficult to remove the temporary protection from some of these impressions without danger of breakage. It is difficult to fabricate the appliance to the correct occlusal relationship when the patient cannot close his teeth into centric occlusion.

A rubber-base impression technique for fixed partial dentures

Abstract Mercaptan rubber is an impression material that can be used for making single or multiple restorations. A knowledge of the properties of the material and the use of a sound procedure aid in obtaining satisfactory and consistent results.

Analysis of Heart Rate in Dogs During Retraction and Impression Procedures

This study recorded heart rates of fasting and nonfasting dogs that had gingival sulci packed with 8% epinephrine-impregnated retraction cords followed by impressions with elastic impression material. No significant increase in heart rate was observed in the retraction and impression procedures.

Restoration of endodontically treated molar with root fracture

The management of an unusual and extreme tooth and root fracture has been presented and discussed. A somewhat unorthodox approach was used in preparing the fractured root surfaces to fit the cast gold crown instead of making a crown to fit a prepared tooth surface. Diagnosis and treatment planning is a key factor in treating unusual patients. All factors must be carefully considered. Condition of adjacent teeth, periodontal support, size and form of remaining tooth structure, and occlusion are all important considerations. With careful and proper study, simple and conservative restorations can frequently be made that will provide excellent service for extended periods of time.

A die transfer technique

R estorative dentistry has been greatly simplified since the advent of elastomeric materials which enable dentists to obtain accurate reproductions of prepared teeth. Impressions for multiple fixed restorations require great skill as all preparations must be completely and accurately recorded. This is particularly difficult with full crown preparations because of extensive subgingival margins. In making an impression of multiple tooth preparations, it is not unusual to find that margins have been inadequately recorded. A second impression is usually made to obtain an accurate reproduction of the prepared teeth. Due to the difficulties encountered in making an impression of several prepared teeth, another defect may be found in the second impression. Performing this procedure repeatedly is frustrating, time-consuming, and discomforting to both the patient and the dentist. In a situation where the first impression is defective, it can be saved and poured in die stone. A second impression is then made to include only the tooth exhibiting a defect in the first impression and at least the occlusal one third of the adjacent teeth. By utilizing the following technique, the defective tooth can be replaced by transferring the die obtained from the second impression to the master cast.