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Biomedical subjects

R J Cronin

Publications and source records attributed to R J Cronin.

At least 19 recordsLinked to original sources
PubMed2005

Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns.

The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate cement using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Crown retention and marginal discrepancy were influenced by the preparation convergence design.

Cementation↗
PubMed2004

Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns.

The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Complete veneer crown retention and marginal discrepancy were influenced by the preparation convergence design.

Cementation↗
PubMed1998

Palatogram assessment of maxillary complete dentures.

Phonetics, esthetics, function, and comfort form the foundation of a successful dental prosthesis. A review of the mechanics of speech as well as common speech problems encountered with a removable maxillary prosthesis are presented. The use of a palatogram to aid the clinician in the assessment and resolution of speech problems associated with a maxillary denture is demonstrated.

Denture, Complete, Upper↗
PubMed1998

Implant use in growing patients. Treatment planning concerns.

The dynamic relationship of dental and craniofacial development to the use of dental implants in a growing patient must be understood before this treatment is initiated. This article describes the three dimensions of maxillary, mandibular, and skeletal growth and their relationship to the placement of dental implants. Recommendations are made for the use of dental implants in the growing individual predicated on the above parameters of growth and development.

Bone Development↗
PubMed1997

An update on fixed prosthodontics.

The practice of fixed prosthodontics has continually evolved as a result of progress in laboratory and biomaterials science, clinical technologies and adjunctive multidisciplinary treatment advancements. This brief review describes those enhancements and how they affect the state-of-the-art practice of fixed prosthodontics.

Dental Abutments↗
PubMed1996

Prosthodontic management of ectodermal dysplasia: a review of the literature.

Ectodermal dysplasia is commonly a difficult condition to manage with prosthodontics because of the typical oral deficiencies and because the afflicted individuals are quite young when they are evaluated for treatment. It is important that these individuals receive dental treatment at an early age for physiologic and psychosocial reasons. This article reviews the literature that pertains to the prosthodontic treatment of the disorder and the review includes considerations in behavior management and timing of treatment.

Anodontia↗
PubMed1995

Refining cast implant-retained restorations by electrical discharge machining.

The UCLA abutment was developed to create implant-retained restorations with ideal contours, excellent esthetics, and minimal vertical space requirements for restorative materials. A major drawback of this abutment is that casting inaccuracies in the lost-wax process are difficult to control. This article describes a method of refining cast implant-retained restorations by use of electrical discharge machining.

Dental Abutments↗
PubMed1993

Maxillary implants and the growing patient.

Maxillary skeletal and dental growth results in dramatic changes in all three dimensions during active growth. Experimental evidence and the behavior of ankylosed teeth suggest that an osseointegrated object remains stationary in the bone surrounding it and does not move or adapt to bone remodeling. Growth changes may result in the burying or loss of implants depending on the placement site. Hence, implants placed in the early mixed dentition have a poor prognosis of continued usefulness through puberty. When placed early, implants may disturb growth or have to be replaced. Implants placed during late puberty or early adulthood have the best change for long-term usefulness.

Adolescent↗
PubMed1992

Restorative considerations for a fixed implant prosthesis using different root form implant systems.

A precise fit at the prosthesis attachment interface is necessary to assure atraumatic loading of the implant fixture. The required high degree of frame accuracy can be more difficult to achieve when a single fixed prosthesis uses different root form implant systems for support. Two clinical protocols are described for these fixed implant prostheses. The first protocol uses a semiprecision attachment for the restorations. The second protocol uses a modified abutment system and a one-piece frame design.

Dental Abutments↗
PubMed1992

Anterior mandibular subapical osteotomy: a useful treatment for patients with severely worn mandibular anterior teeth.

Rehabilitation of patients with severe dental wear is a complex diagnostic and restorative problem. As wear occurs, space for restorative materials is lost, and unique treatment techniques are needed to provide good esthetics and function. Use of orthognathic surgery to reposition mandibular anterior teeth and supporting alveolar bone can create a more ideal environment for restorative procedures.

Alveolectomy↗
PubMed1991

Effect of metal design and technique on the marginal characteristics of the collarless metal ceramic restoration.

This investigation examined the marginal characteristics of the collarless metal ceramic restoration made with two commonly used direct-lift techniques: (1) a porcelain/wax paste and (2) a porcelain/liquid slurry. The metal copings touched the shoulder in half of the groups and were left 0.5 mm short in the other half to comprise the four experimental groups. Marginal seal was evaluated at facial and lingual surfaces on embedded and sectioned specimens for each group. Photo negatives were made of each specimen and projected at a constant magnification so that tracings could be made of the space between the die shoulder and corresponding porcelain. Composite surface measurements were made for each sample with a Zeiss Interactive Digital Analysis System instrument to evaluate porcelain adaptation to the shoulder. The porcelain/liquid groups demonstrated significantly smaller (p less than or equal to 0.05) facial marginal openings than the porcelain/wax groups. The group made with the porcelain/liquid technique with the metal on the die shoulder produced the most consistent overall results. The porcelain/liquid group with the metal off the shoulder had a statistically larger (p less than or equal to 0.05) mean marginal opening from the external margin to a point 0.75 mm to the interior than both techniques with the metal on the shoulder. Lingual marginal adaptation did not vary with each of the four experimental groups.

Crowns↗
PubMed1991

Subpontic osseous hyperplasia: a literature review.

Several incidences of excessive bone growth beneath the pontics of posterior fixed partial dentures have been documented, and this phenomenon has been referred to as subpontic osseous hyperplasia. The clinical, radiographic, and microscopic features are discussed, including the presentation of several etiologies and treatment considerations.

Adult↗
PubMed1988

Immunologic studies in identical twins concordant for juvenile rheumatoid arthritis but discordant for monoclonal gammopathy and amyloidosis.

Identical twins concordant for juvenile rheumatoid arthritis but discordant for monoclonal gammopathy and amyloidosis were the subjects of a study done with mixed leukocyte culture, anti-idiotypic antisera against serum and urinary M component from the amyloid-affected twin, and in vitro estimations of M-component idiotype synthesis by peripheral blood mononuclear cells. Immunohistochemical analysis of renal amyloid deposits in the affected twin showed AL amyloid of the lambda-II variable region subgroup. M-component idiotypes were confined only to the twin with serum and urine M components.

Adult↗