Biomedical subjects

A A Caputo

Publications and source records attributed to A A Caputo.

At least 19 recordsLinked to original sources

PubMed1992

Adhesion of resin to casting alloys.

The bond strength of a composite resin bonded to various dental casting alloys with three adhesive systems--Silicoater, Panavia, and Superbond C&B--was investigated. The metal surfaces were treated solely with aluminum oxide blasting before application of the adhesive. Thermal cycling caused a reduction in bond strength for all combinations of the adhesive systems and alloys, but the Silicoater system recorded the greatest bond strength. The 4-META system was equivalent to Panavia system in bond strengths to most metals and exhibited greater strength with others.

Adhesives↗

PubMed1992

Load transfer by a maxillary distal-extension removable partial denture with cap and ring extracoronal attachments.

This study photoelastically compared the stress distribution characteristics of maxillary, bilateral, distal-extension removable partial dentures retained by light and heavy ERA extracoronal attachments. One prosthesis included supporting rests and the other had no rests. Both designs were tested with and without abutment splinting. The most favorable stress distributions were obtained with light retention elements, supporting rests, and splinting of the abutments. In this configuration the attachment prosthesis compared favorably in stress distribution with the maxillary I-bar retained removable partial denture in a previous study that used a comparable maxillae model.

Dental Prosthesis Retention↗

PubMed1992

The retentive and stress distributing properties of split threaded endodontic dowels.

A threaded, parallel-sided endodontic dowel that has a longitudinal split was tested to determine its retention and stress distribution properties. Photoelastic stress analysis revealed high installation stresses unless the dowels were counterrotated. Axial loading created stresses at the threads, with elevated coronal and apical stresses. Even higher coronal stresses were recorded with inclined loads, and shorter dowels generated greater stresses than longer dowels. The retentive values were generally lower than those in comparable studies.

Analysis of Variance↗

PubMed1992

Comparison of load transfer by maxillary distal extension removable partial dentures with a spring-loaded plunger attachment and I-bar retainer.

This study photoelastically compared the stress distribution characteristics of two maxillary bilateral distal-extension removable partial denture designs, one using I-bar retention and the other using a semiprecision spring-loaded plunger attachment. Each prosthesis was subjected to vertical and horizontal extension-base loads. Comparisons were made from photographic recordings of isochromatic fringe distributions. The two retention designs produced comparable stresses with splinting of abutments for the plunger attachment. The attachment-retained prosthesis proved less stable with some loadings. Stress patterns followed three trajectories in the maxilla. A basis for stress distribution comparisons to other maxillary removable partial denture attachments is established.

Analysis of Variance↗

PubMed1992

Microleakage of new crown and fixed partial denture luting agents.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

Adhesives↗

PubMed1992

Endodontic dowel retention with resinous cements.

This study compared the capability of three composite resin cements to sustain a standard endodontic dowel. All of the systems incorporated some form of smear layer removal on the dentin of the endodontic channel. One system that used a methyl ethyl ketone drying agent provided inadequate clinical resistance to dislodgment of 5.4 DaN. A second cementing system that used only smear layer removal resisted loads at 54.7 DaN. The third cementing regimen that included a surface-initiated dentinal adhesive and smear layer removal recorded retention of 77.4 DaN. This study supported the concept that passively cemented dowels with composite resin can be as effective as actively seated dowels.

Acrylic Resins↗

PubMed1991

A new endodontic stabilizer implant device.

A new endodontic stabilizer implant device is presented that can be used immediately after enucleation of large periapical cysts. The force transmission characteristics of this implant were evaluated by means of photoelasticity. The implant served to distribute incisal forces within the supporting structure. Improved stress conditions resulted at the tooth apex and between the apex and the superior border of the implant when the tooth was subjected to apicoectomy.

Apicoectomy↗

PubMed1991

Reuse of silver-palladium ceramic metal.

The effect of various percentages of reused silver-palladium alloy on the bond strength of porcelain was considered. All-new metal and once-cast alloy with the addition of 50% new metal produced the highest bond values. Once-cast alloy with less than 50% new metal produced bond strength values that were significantly lower. When using this silver-palladium alloy, 50% new alloy should be added to each casting button, and buttons with questionable casting history should not be used.

Dental Alloys↗

PubMed1991

Fixed cantilever splints on teeth with normal and reduced periodontal support.

Photoelastic models were used to visualize stresses developed in teeth and supporting bone by cantilever fixed partial dentures where the most distal abutments had either crater or trough osseous defects. The effects of splinting the periodontally involved teeth to one or more additional sound teeth were studied. It was shown that for a cantilever fixed partial denture with either normal periodontal support, or a distal abutment with a moderate degree of mobility and bone loss, the following can be concluded: (1) occlusal forces on a cantilever fixed partial denture were significantly distributed to only the three teeth closest to the loaded cantilever, (2) optimum stress reduction occurred with the splinting of a periodontally compromised tooth to two periodontally sound teeth. Increasing the number of splinted abutments did not result in a proportional reduction of stress in the periodontium, and (3) no significant cross-arch sharing of occlusal loads was seen.

Alveolar Bone Loss↗

PubMed1991

Glass ionomer bond strength and treatment of dentin with polyacrylic acid.

This investigation compared the effect of smear layer removal using various treatments with polyacrylic acid on the shear bond strength of glass ionomer restorative materials to dentin. Three brands of glass ionomer were applied to prepared dentin surfaces of extracted human molars, after one of four treatments with polyacrylic acid. Samples using dentin surfaces with the smear layer left intact served as controls. Comparison of mean shear bond strength values for all possible combinations of restorative material and polyacrylic acid treatment indicated that samples produced using 25% polyacrylic acid had lower (p less than 0.05) values in some instances. No other significant differences were found when test values were compared with each other or with control values. The authors concluded that removal of the smear layer does not enhance the dentin-glass ionomer restorative bond strength, as has been suggested by other investigators. Scanning electron photomicrographs indicate that treatment with higher concentrations of polyacrylic acid produces higher degrees of dentinal tubular orifice patency.

Acrylic Resins↗

PubMed1991

Bond strength of ceramic brackets with various bonding systems.

The purpose of this investigation was to determine the shear and tensile bond strengths of various ceramic and ceramic-filled brackets in combination with commonly used bonding systems. One monocrystalline, two polycrystalline and one ceramic-filled plastic bracket types were tested in combination with one light-cured and two chemically-cured bonding systems. Bonding procedures were performed on properly prepared human teeth. Shear and tensile tests were performed on an Instron test machine. The shear bond strength of the mono- and polycrystalline ceramic brackets was not affected by the bonding system. There was a difference among bonding systems used with the ceramic-filled plastic bracket. Ceramic-filled plastic and polycrystalline ceramic brackets exhibited the greatest resistance to tensile force, while monocrystalline brackets showed the highest propensity for tensile fracture of the wings.

Acid Etching, Dental↗

PubMed1991

Functional stress modification after high condylectomy surgery.

Surgical removal of the head of the condyles inevitably leads to radical redistribution of loads applied to the mandible. The nature of this redistribution can have important implications on the surgical approach and subsequent reconstructive procedures. The purpose of this investigation was to visualize photoelastically the functionally delivered stresses after high condylectomy surgery. Three identical models of a dentate human mandible were constructed from a photoelastic material. One mandible simulated a unilateral and the other simulated a bilateral high condylectomy. The third mandible had both condyles intact and served as basis for comparisons. Silicone implants were placed on the sectioned condylar heads. The condyles, with the silicone implants, were fitted into simulated fossae and the mandibles were loaded unilaterally and bilaterally. The resulting stresses were observed and photographed in the field of a circular polariscope. Substantial differences in load-generated stresses were observed as a result of both unilateral and bilateral condylectomies, compared to the normal case. The most severe stress conditions occurred with the unilateral condylectomy, where stresses associated with torsion were most evident.

Humans↗

PubMed1991

In vitro toothbrush abrasion and bond strength of bleached enamel.

Vital tooth bleaching is experiencing increased usage because of its convenient application and effectiveness for lightening teeth and stain removal. The purpose of this investigation was to evaluate the effect of bleaching agents on enamel toothbrush abrasion and bond strength.

Analysis of Variance↗

PubMed1991

Load transfer to abutment teeth by two non-metal adhesive bridges.

Recently, two alternatives to the etched metal, Maryland-type bridge have been proposed for anterior applications. These are the all-ceramic bridge and the composite resin framework, ceramic veneered pontic bridge. Both designs use acid-etched winged retainers for adhesion. The purpose of this study was to evaluate the load transfer to abutment teeth by these two designs using photoelastic modeling.

Composite Resins↗

PubMed1990

Effects of disinfectants on dimensional accuracy of impression materials.

There is a continuing concern over the potential for cross-contamination of viral infections such as AIDS by means of dental impressions. This investigation compared the effects of various viricidal agents on the accuracy of irreversible hydrocolloid and silicone impressions made of single-unit and full mandibular arch models. Measurements on casts made from the treated impressions were compared with the corresponding measurements on casts made from untreated impressions. The results of this study led to the conclusions that there was no preferred disinfectant with respect to dimensional stability for the irreversible hydrocolloid, condensation silicone, or vinyl polysiloxane impression materials tested, and there was no difference in the accuracy of the casts obtained either by spraying with or immersion in any of the disinfectants tested. Therefore using the disinfectants described with either the immersion or spray techniques will not significantly affect the dimensional accuracy of cats made from treated impressions.

Aerosols↗

PubMed1990

Effect of opaque porcelain application on strength of bond to silver-palladium alloys.

The opaque porcelain layer for porcelain-fused-to-metal restorations is critical for success. This investigation examined opaque porcelain application using one- and two-layer techniques with respect to their effect on the strength of bond to three silver-palladium alloys. There were no significant differences in the flexural bond strengths of the three alloys for the one- and two-layer opaque application techniques. With respect to bond strength, these results afford flexibility in the choice of the one- or two-layer techniques.

Dental Alloys↗

PubMed1990

Altered corrosion resistance from casting to stainless steel posts.

Heat treatment during the burnout procedure may cause corrosion of the stainless steel post. This study was undertaken to determine whether alteration of the corrosion resistance of stainless steel posts occurs as a result of various simulated burnout procedures. Stainless steel posts were divided into five groups of five posts: group 1, control; 2, gypsum-bonded investment, bench cooled; 3, gypsum-bonded investment, quenched; 4, phosphate-bonded investment, bench cooled; and 5, phosphate-bonded investment, quenched. The posts were placed in individual containers of Ringer's solution and observed at 30, 180, and 600 days. Scanning electron microscopy, energy dispersive x-ray spectroscopy, optical emission spectroscopy, and optical microscopy were used to evaluate the posts qualitatively and quantitatively. Investment and heat treatment altered the metallic structure of stainless steel posts. Prefabricated posts submitted to simulated burnout procedures had a noticeable reduction in corrosion resistance. Direct casting to stainless steel posts is contraindicated.

Corrosion↗

PubMed1979

Adhesion of mesh-base direct-bonding brackets.

The bond strength of mesh-base and metal-base brackets to human enamel was investigated for different adhesive systems. The bond strengths were determined by means of tension, shear, and torsion tests. The data were statistically analyzed and the following conclusions were drawn: 1. An adhesive system (bracket base and adhesive) cannot be selected on the basis of one test (tension, shear, or torque) alone. The various systems generally ranked differently, depending upon the test method utilized. 2. Mesh-base brackets were more retentive than the metal-base brackets in tension, while metal-base brackets were more retentive in shear. 3. For the metal-base brackets, Bond-Eze was the most retentive material, Adaptic and Orthomite followed narrowly behind, and Genie was the least retentive. 4. For the mesh-base bracket in tension and shear, Bond-Eze, Adaptic, and Solo-Tach were the most retentive materials when used with the 60-mesh base, and Genie was the least retentive. Torsion values were not useful because of a large number of bracket wing failures.

Adhesiveness↗