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Biomedical subjects

A A Caputo

Publications and source records attributed to A A Caputo.

At least 127 records · Page 7Linked to original sources
PubMed1980

Canine retraction with J hook headgear.

Several methods have been described for accomplishing distal movement of canines without losing posterior anchorage. An accepted method in canine retraction is the use of headgear with J hooks. Since it incorporates extraoral anchorage, it is most effective in maximum-anchorage cases. It was the purpose of this study to analyze the distribution of force transmitted to the alveolus and surrounding structures by means of photoelastic visualization, utilizing J hook headgear for maxillary canine retraction. A three-dimensional model representing a human skull was used. This model was constructed with different birefringent materials to simulate bone, teeth, and periodontal membranes. Three different vectors of force were applied representing high-, medium-, and low-pull headgear, which were placed at angles of 40, 20, and 0 degrees to the occlusal plane. The photoelastic analysis was made by means of a circular-transmission polariscope arrangement, and the photoelastic data were recorded photographically. The stress areas created by the three different vectors of force were associated with various degrees of canine tipping. This effect was greater with the low-pull force component than with the medium-pull traction. The high-pull headgear produced the least tipping tendency, being closer to a bodily movemment effect. Further, stresses were transmitted to deeper structures of the simulated facial bones; these regions were the frontozygomatic, zygomaticomaxillary, and zygomaticotemporal sutures.

Alveolar Process↗
PubMed1980

The retentive and stress-distributing properties of a threaded endodontic dowel.

When the Radix Anchor apex was allowed to engage the bottom of the prepared channel, very high apical stresses were generated within the supporting structure. When the coronal flanges engaged the occlusal portion of the model, high lateral stresses occurred in the coronal portion of the channel. These stress concentrations can be avoided by installing the dowel so that only the retentive threads engage dentin. This may be accomplished by "backing off" one half turn when slight resistance to dowel threading is encountered. The Radix endodontic dowel system was more retentive than cemented dowels and less retentive than another dowel which threads into the dentin of the channel wall. The Radix Anchor was more retentive when both diameter and length of imbedment were increased simultaneously.

Crowns↗
PubMed1980

Photoelastic stess analysis of overdenture attachments.

This is a summary of various investigations designed to study the transmission of forces through overdenture abutments to the remaining oral structures: 1. The best design for uniform distribution of occlusal forces to the remaining structures was the conventional design, particularly the amalgam restored abutment. This design, however, provided less effective retention and stability than the other designs. 2. In the group of stud type attachments studied, the Ancrofix transferred stress in a more favorable manner to the remaining structures in the oral cavity when compared to the other stud attachments. 3. The Hader Bar provided more desirable effects to the abutments and remaining structures than did the other tissue bars. 4. The major objective in the choice of an overdenture attachment should be the consideration of how the stress is transferred from these attachments through the abutments and other structures, not the retnetion and stability.

Dental Abutments↗
PubMed1980

Antimicrobial action of dental cements.

It was observed that some of the cements tested had bacteriostatic and/or bactericidal action. The cements listed in decreasing order of effectiveness are (1) zinc oxide-eugenol, (2) silicophosphate, (3) zinc phosphate, and (4) silicate. The two newer cements, polycarboxylate and composite resin, exhibited no measurable antimicrobial action.

Anti-Infective Agents, Local↗
PubMed1980

Effects of surface treatments on the retention of restorative materials to dentin.

The effect of various pretreatments on shear bond strengths between dentin and three restorative materials was investigated. Pretreatments included use of cleansing agents and adhesion promoters in combination. Results indicated that: (1) phosphoric acid (50%) and EDTA (10%) were not effective in improving bonding between restorative materials and dentin; (2) NPG-GMA significantly increased resin-dentin adhesion with Cervident and Simulate resin. Silane adhesion promoter in combination with Fuji provided the greatest resistance to shear forces; and (3) Fuji Type II restorative material demonstrated more resistance to shear forces than Cervident and Simulate resins.

Acid Etching, Dental↗
PubMed1980

Biological implications of dental materials.

Testing of the biologic effects of dental materials has lagged far behind the characterization of their mechanical and physical properties. Various biologic-type tests, whether in vitro or in vivo, have often produced conflicting or confusing data. The objective of this article was to bring together the results of various investigations to form guidelines for the safest use of dental materials. Since many interactions between dental materials and living tissue have not been definitively established, a conservative approach was taken. The clinician who heeds the data summarized for the dental materials presented here will have the greatest probability of obtaining a benign chemical response of soft and hard tissues.

Biocompatible Materials↗
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↗
PubMed1979

Occlusal force transmission by overdenture attachments.

This investigation utilized a composite photoelastic model to examine the load-transfer characteristics of several overdenture attachments. Tissue bar (Hader and King Connector) and stud (extracoronal) attachments (Rotherman, Gerber, and Ancrofix) were studied. The following observations may provide guidelines for the selection of overdenture attachments. 1. The more retentive tissue bar and extracoronal attachments produced higher stress concentrations. 2. Of the tissue bars tested, the Hader Bar produced less torquing forces on the abutment teeth. 3. The Ancrofix appeared to share the forces of occlusion between abutments and the posterior edentulous regions. 4. It must be emphasized that several other factors will also influence the choice of overdenture attachments, such as the judgment of the dentist, economics with respect to the patient, and the availability of laboratory expertise.

Alveolar Process↗
PubMed1979

Surface smoothness and marginal fit with phosphate-bonded investments.

Two phosphate-bonded investments and one calcium sulfate investment were evaluated for the surface smoothness and marginal fit they impart to gold castings. A modified technique was also evaluated for each phosphate-bonded investment, where the silica sol was not diluted and the spatulation time was reduced. The results of this study lead to the following conclusions: 1. The marginal fits obtained with all four phosphate-bonded methods were comparable to each other and superior to that obtained with the calcium sulfate investment. 2. The presence of nodules on the surface of the castings was more prevalent with the phosphate-bonded investments. However, this effect was not statistically significant. 3. Clinical assessment of the roughness of the castings revealed that all the methods tested produced clinically acceptable castings. 4. Visual observation by five dentists revealed that both the recommended and modified techniques for one of the phosphate-bonded investments (Ceramigold) produced a smoother surface than any other investment tested. Rating of scanning electron microscope photographs (X600) revealed no difference in the surface roughness between any of the castings. Consequently, no definitive relation between investment type or technique and surface roughness was established. 5. No correlation was demonstrated between surface roughness, as evaluated by either clinical observation or scanning electron microscope photography, and marginal fit of the castings.

Dental Alloys↗
PubMed1979

Effectiveness of porcelain repair systems.

The study indicates that the repair system using a bonding agent with acrylic resin is significantly stronger than the repair system using a specific composite resin. On the basis of this study, the acrylic resin repair system has the best potential for clinical success in porcelain-to-porcelain repairs.

Acrylic Resins↗
PubMed1979

Dowel retention with glass-ionomer cement.

The retentive capacity of the Whaledent Parapost system utilizing ASPA cement was compared at two lengths, three diameters, and with respect to the effect of both medication and citric acid pretreatment. The greatest single factor influencing retention was embedment depth into dentin. No significant differences were observed between the retention values for medicated and unmedicated teeth. Finally, no increase in retention was noted over previously reported values for zinc phosphate, carboxylate, and epoxy resin cements. The glass-ionomer cement tested offers no advantage for post retention.

Acid Etching, Dental↗
PubMed1979

Color stability of temporary restorative materials.

In this study it was shown that: 1. There was a statistically significant initial color difference in materials labeled shade 65. 2. Rough materials darkened significantly more than polished materials. 3. There was not statistically significant over all difference in the amount of staining between air-cured and pressure-cured samples. 4. The methyl methacrylates materials demonstrated that least darkening, followed closely by the ethyl-methyl methacrylate material. The vinyl-ethyl methacrylate material darkened consistently more in 14 and 30 days and significantly more at 60 days. The epimine material was consistently the least color stable and showed a significantly greater amount of darkening.

Absorption↗
PubMed1979

Effects of orthodontic intermaxillary Class III mechanics on craniofacial structures. Part I - photoerlastic analysis.

The relation between active growth and induced anatomic changes was examined using photoelastic stress techniques. The following can be concluded from this investigation: 1. Utilization of Class III mechanics on the photoelastic skull affected the zygomaticotemporal, zygomaticofrontal and frontomaxillary sutures. 2. The stress trajectories observed in the mandible lead to the conclusion that Class III traction affects mandibular growth and opening, as well as condylar repositioning. 3. Evidence of stress was observed in a section of the condyle due to the external pterygoid muscle. 4. The stress concentrated at the outer surface of the pterygoid plate was due to the action of the external pterygoid muscle. 5. The effect of the simulated Class III traction created concentrations of stress mesial and distal of the second molars and at the apical and midroot areas of first molars.

Facial Bones↗
PubMed1979

Effects of orthodontic intermaxillary class III mechanics on craniofacial structures. Part II - computerized cephalometrics.

The relation between active growth and induced anatomic changes was examined using a computerized cephalometric analysis of ten Class III cases treated with intermaxillary traction. The following can be concluded from this investigation: 1. Mandibular growth was redirected and mandibular opening was observed due to maxillary molar extrusion and counterclockwise rotation of the maxilla. 2. Condylar repositioning was noted to occur in all cases due to the effect of the external pterygoid muscle and a possible translatory movement during mandibular rotation. 3. Counterclockwise palatal development occurred in most of the treated cases through vertical action of the Class III mechanism. 4. The effect of the Class III traction was also observed in the mandibular incisor and molar teeth. The incisors retruded and the molars either were located in the predicted position or farther distally. 5. The soft tissue profile was less concave than the predicted value due to less mandibular growth and more retruded incisors in the treated cases. 6. Evidence was shown that a positive relationship exists between computerized cephalometrics and photoelastic techniques in the analysis of ten treated cases. This relationship is based on the fact that specific changes which took place during treatment were found to be consistent with the results of the photoelastic analysis.

Cephalometry↗