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Biomedical subjects

A A Caputo

Publications and source records attributed to A A Caputo.

At least 109 records · Page 6Linked to original sources
PubMed1983

Antibacterial and mechanical properties of restorative materials combined with chlorhexidines.

Chorhexidine gluconate or chlorhexidine dihydrochloride were added to a composite resin and a glass ionomer restorative material in concentrations of 0, 1, 2, 3, 5, and 10% by weight. Antibacterial activity was measured by inhibition of growth of S. viridans, S. pyogenes, S. mutans, L. acidophilus, and E. coli, for 4 days. Compressive, tensile, and restorative material-enamel adhesive shear strength tests were performed. The addition of chlorhexidine gluconate or chlorhexidine dihydrochloride increased the antibacterial activity of the composite resin and the glass ionomer restorative material and changed the mechanical properties of the restorative materials. The addition of chlorhexidine dihydrochloride resulted in mechanical properties closest to controls.

Bacteria↗
PubMed1982

Experimental force analysis of the contraction utility arch wire.

An experimental apparatus consisting of a metal framework, a strain gauge, and a Wheatstone bridge was used to measure the retraction force delivered to the mandibular incisors by a contraction utility arch wire (0.016 by 0.016 inch blue Elgiloy). The contraction utility arch wire was activated 1 mm. and retraction forces were recorded as the deflection of a point image on an oscilloscope. The results indicated that the retraction forces at the incisor positions were reasonably within an optimal force range to move teeth quickly with minimal tissue damage and discomfort. However, the lateral incisor positions in both ovoid and narrow arch forms received significantly more force than the central incisor positions, and the narrow tapered arch form delivered more retraction force than the ovoid arch form.

Dental Stress Analysis↗
PubMed1982

Observation of orthopedic force distribution produced by maxillary orthodontic appliances.

A three-dimensional anatomic model was duplicated from a human skull, using different birefringent materials to simulate the various craniofacial structures. Individual bones of the midface were fabricated separately and then articulated in their correct sutural relation. One removable and four fixed maxillary appliances were used. The fixed appliances included the Haas, Minne-expander, Hyrax, and quad helix devices. The removable appliance incorporated an expansion screw in a full acrylic palate with appropriate retentive clasps. After the insertion of each appliance, intraoral forces were produced by incremental activation. The model was examined and photographed in the field of a transmission polariscope. Each appliance used produced a different range of load-activation characteristics. This was reflected by the differences in the stresses transmitted through the bones of the craniofacial complex and the effect on the various sutures. Stresses produced by the fixed appliances were concentrated in the anterior region of the palate, progressing posteriorly toward the palatine bone. The Haas, Minne-expander, and Hyrax appliances produced stresses that radiated superiorly along the perpendicular plates of the palatine bone to deeper anatomic structures, such as the lacrimal, nasal, and malar bones, as well as the pterygoid plates of the sphenoid. Similar stress characteristics were seen with the removable appliance. However, increased activation decreased retention of the appliance, thereby lessening the stress. The quad helix appliance proved to be the least effective orthopedic device. Although the effects of palate separation were seen with increased activation, this appliance primarily affected the posterior teeth.

Equipment Design↗
PubMed1982

Stress distribution under high-pull extraoral chin cup traction. A photoelastic study.

Birefringent materials were employed in the fabrication of a model of a human skull with distinct simulants for teeth, bone, and periodontal ligaments. The following observations were made subsequent to the application of force to this model with an extraoral high-pull chin cup: 1. Reciprocal stresses were observed in the posterior portion of the glenoid fossa and the contacting posterior part of the head of the condyle. 2. A tension coil spring representing the external pterygoid muscle applied reciprocal stresses at its insertions in the lateral pterygoid plate on the greater wing of the sphenoid and the anterior aspect of the head of the condyle. 3. Stresses were seen to radiate from the roots and apices of both the maxillary and mandibular posterior teeth. 4. A distinct concentration of stress was noted in the retromolar area of the mandible, away from the dentition, indicating a bending stress. 5. The posterior half of the sigmoid notch, below the anterior aspect of the head of the condyle, displayed a heavy band of stresses. 6. Selected sectioning of the mandible substantiated observations made from the intact hemimandible and also showed evidence of bending in the area corresponding to the head and neck of the condyle.

Dental Stress Analysis↗
PubMed1981

Photoelastic analysis of stress patterns on teeth and bone with attachment retainers for removable partial dentures.

This investigation was designed to evaluate the forces developed in supporting structures by removable partial dentures with attachment retainers. The attachments tested were the (1) Sterngold type 7, (2) Dalbo MK, and (3) Thompson dowel. The study utilized a photoelastic model with stress areas recorded photographically. The results showed that: 1. Splinted abutments are indicated when using the tested attachment retainers. 2. With single abutments, the attachment retainers induced distal force on the teeth which resulted in unfavorable horizontal bone forces. 3. The Dalbo MK attachments produced the most force on the edentulous regions and the least force on the abutment teeth. 4. The Thompson dowel and Sterngold type 7 attachment retainers induced similar stress patterns on single abutments and both produced distal abutment forces. 5. The Thompson dowel induced more favorable stress patterns when the abutments were splinted.

Crowns↗
PubMed1981

In vitro analysis of self-shearing retentive pins.

Combining stress, analysis, microscopic examination, mechanical testing of the shear mechanism, and retention of the Reten Pin leads to the following conclusions: 1. The suggested 0.006 inch pin-channel mismatch induces high lateral and apical stresses. Microscopically, this was seen to correlate with injury to the dentin. 2. The degree of retention was increased by using a smaller pin-channel mismatch. This correlates with smaller stresses and reduced dentinal damage. 3. The shear mechanism acts in a uniform manner, with a relatively small variation from the mean. It is suggested that for the best results the manufacturer should supply larger twist drills and pins with a somewhat deeper self-shearing groove to minimize apical involvement during shearing of the handle from the pin.

Dental Pins↗
PubMed1981

Type III gold alloy complete crowns cast in a phosphate-bonded investment.

A phosphate-bonded investment and a calcium sulphate-bonded investment were evaluated for the surface smoothness and marginal fit they impart to type III gold castings. The phosphate-bonded investment was used with burnout temperatures of 900 degrees F and 1,300 degrees F. The results of this study lead to the following conclusions: 1. The marginal fit with the phosphate-bonded investment method was superior to that obtained with the calcium sulphate-bonded investment. 2. Surface roughness was greater for the castings made with the phosphate-bonded investment when measured with SEM photographs and visual observation. 3. The phosphate bonded-investment increased the incidence of nodules on the surface of the castings. 4. No correlation was demonstrated between marginal fit and surface roughness or the incidence of nodules on the castings.

Calcium Sulfate↗
PubMed1981

Photoelastic stress analysis of hemimandibulectomy bone reconstruction devices.

The results presented show the relative importance of muscle force and occlusal resistance locations and prosthesis/hemimandible interface length. For the prosthesis design used, the addition of muscle function on the prosthesis side has little effect upon bone stress. However, occlusal resistance on the prosthesis side produces much more stress in the bone than other resistance positions. Stress produced by the shorter prosthesis is higher at the areas of bolt/bone interface than for the long prosthesis. However, superimposed inherent stress patterns somewhat obscured the comparison with longer prostheses.

Dental Stress Analysis↗
PubMed1981

The condyle as a stress-distributing component of the temporomandibular joint.

Even though the temporomandibular joint is loaded in function, it often arthroses under heavy use. The effects of stress to the joint are not well understood. This study utilized three-dimensional photo-elastic stress analysis to visualize the intensity and direction of stress within the mandibular condyle generated by various occlusal forces. Functional stress were shown to concentrate in the condylar neck, but were reduced within the condylar head due to its elliptical shape. Stress directions within the condyle were found to be non-preferential, varying with different mandibular positions. This supports the idea that the condyle is designed to receive light varied forces rather than heavy, cyclical unidirectional forces.

Humans↗
PubMed1981

Distribution of stress patterns in the human zygomatic arch and bone.

A three-dimensional photoelastic model was reproduced from a human skull. The insertions of the superficial and deep portions of the masseter muscle and the temporalis fascia were simulated with leather bonded to the appropriate areas. The following loading conditions were employed: (1) bilateral loading of the masseter muscle; and (2) bilateral loading of the masseter muscle together with a bilateral occlusal load. Ther stress freezing technique was used to lock the resulting stress patterns into the model skull. The stress trajectories were observed and photographed in a circular polariscope. The results suggest that the major stress trajectories to the zygomatic bone and arch follow an alveolo-maxillary-zygomatic-temporal direction. Stresses were highly concentrated in the zygomatic process of the temporal bone. Generally, the stresses were concentrated in those areas of the bone where architectural reinforcement had been demonstrated by other methods.

Dental Occlusion↗
PubMed1981

Influence of a ferric chloride mordant solution on resin-dentin retention.

The effects of ferric chloride mordant solution, two cleansing solutions, and three chemical adhesion promoters were examined on resin-dentin adhesion. Adhesion was increased with the use of ferric chloride solution. An NPG-GMA or butyl acrylate-acrylic acid copolymer type of adhesion promoter also increased resistance to shear separation.

Acrylic Resins↗
PubMed1981

Fracture toughness of human enamel.

A microindentation technique was employed to estimate the fracture toughness of human enamel. A pattern of increasing fracture toughness values existed from incisal to cervical in incisor enamel. Statistical analysis indicated that the molar enamel was more brittle than either the canine or incisor enamel. It was observed that the cracks emanating from the corners of an indentation propagated preferentially, with the weakest path of fracture usually extending along the cervical-incisal axis.

Dental Enamel↗