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Biomedical subjects

A Shifman

Publications and source records attributed to A Shifman.

At least 19 recordsLinked to original sources
PubMed2002

Effect of wash bulk on the accuracy of polyvinyl siloxane putty-wash impressions.

Variations in the bulk of wash in a putty-wash impression technique can result in dimensional changes proportional to the thickness of the wash material during setting. The purpose of the study was to determine the amount of wash necessary to achieve accurate stone models while using a two-step putty-wash impression technique with polyvinyl siloxane (PVS) impression material. A total of 45 impressions were made of a stainless steel master model, 15 impressions for each wash thickness (1, 2 and 3 mm). The model contained three full-crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring six dimensions (occlusogingival and interabutments) on stone dies poured from impressions of the master model. One-way analysis of variance (ANOVA) showed statistically significant differences amongst the three wash bulk groups, for all occlusogingival and interabutment measurements (P < 0.001). The overall discrepancies of the groups using wash thickness of 1 and 2 mm were smaller than the group with 3 mm wash thickness. Therefore, wash bulks of 1 and 2 mm were most accurate for fabricating stone dies, using PVS impression materials. This can be achieved by using the temporary crown to create the desired wash space in the preliminary putty impression. Wash thickness > 2 mm was inadequate to obtain accurate stone dies.

Analysis of Variance↗
PubMed2001

Diagnostic targeting of temporomandibular disorders.

This article describes a diagnostic chart that is organized for a versatile representation of various conditions of temporomandibular disorders (TMD). It facilitates the grading of disorder severity and visualization of probable mutual effects between groups of disorders. It also enhances the clinician's awareness of potential systemic involvement in TMD by incorporating it into the chart. Comparison of charts completed at consecutive examinations is helpful for the assessment of disorder progression, regression or for the refining of diagnoses.

Diagnosis, Differential↗
PubMed2001

Stress levels for well-fitting implant superstructures as a function of tightening force levels, tightening sequence, and different operators.

STATEMENT OF PROBLEM: Unfavorable stress distribution and occlusal overload have been reported to result in failures ranging from screw loosening to loss of osseointegration. PURPOSE: The purpose of this study was to assess the effect of different tightening forces and sequences, with different operators, on stresses generated on an accurately fitting implant superstructure on multiple working casts made with a splinted impression technique. MATERIAL AND METHODS: The effects of different tightening forces (10 and 20 Ncm) were assessed with the use of 30 stone casts made from a metal master model with a splinted impression technique. Stresses generated were recorded by 4 strain gauges attached to the superior surface of the master framework. A multiple analysis of variance with repeated measures was performed to test for significant differences among the groups. RESULTS: Tightening force values at 10 Ncm ranged from 150.43 to 256 Ncm. At 20 Ncm, microstrain values ranged from 149.43 to 284.37 Ncm. Microstrain values related to the sequence of tightening ranged from 150.8 to 308.43 Ncm (left to right) and 154.63 to 274.80 Ncm (right to left). For the different operators, microstrain values ranged from 100.13 to 206.07 Ncm. No statistically significant differences among the variables of tightening force, tightening sequence, and operators were found ( P >.05). The interaction between groups and strain gauges was also found to be nonsignificant (P >.05). CONCLUSION: The potential of variable tightening force and tightening sequence to generate unfavorable preload stresses can be minimized through use of the splinted impression technique, which ensures an accurately fitting superstructure.

Analysis of Variance↗
PubMed2000

The mandibular first premolar as an abutment for distal-extension removable partial dentures: a modified clasp assembly design.

Sound mandibular first premolars can be used as sole abutments for bilateral distal-extension removable partial dentures, if the denture is designed to minimise the torque applied to the abutment teeth. A simplified modification of the conventional torque-releasing clasp-assembly designs is suggested for these teeth. This modification entails a mesial rest on each abutment tooth connected to the distal proximal plate via a lingual bracing arm. A circumferential clasp arm is optional for buccal retention of the removable partial denture. As with conventional designs, the metal framework is designed to permit some rotational tissueward movement of the distal extension bases, yet not compromise the retention and stability of the prosthesis.

Bicuspid↗
PubMed2000

Speech-aid prostheses for neurogenic velopharyngeal incompetence.

STATEMENT OF PROBLEM: When surgical treatment is not considered an option, prosthetic management of velopharyngeal insufficiency is carried out by means of a speech-aid prosthesis, whereas velopharyngeal incompetence is traditionally managed by a palatal lift prosthesis. Varying degrees of treatment success have been attributed to palatal lift prostheses. PURPOSE: This study introduces the use of nasopharyngeal obturation instead of palatal elevation for the management of velopharyngeal incompetence. METHODS: Seven patients afflicted by neurogenic velopharyngeal incompetence were treated with wire-extension speech-aid prostheses constructed to circumvent the dysfunctional soft palate. The shape of the nasopharyngeal section was functionally molded in speech and swallowing and controlled by video-nasopharyngoscopic examinations. RESULTS: Effective nasopharyngeal obturation with notable improved speech was achieved in all patients. Even though all patients ultimately tolerated the prostheses well, 2 patients denied any improvement in speech with the finalized prostheses. CONCLUSION: Wire-extension speech-aid prostheses used by the patients were an effective treatment approach for velopharyngeal incompetence. Nasopharyngoscopic control is mandatory for maximizing the effect of velopharyngeal closure around the nasopharyngeal section of the prosthesis in function, yet it allows free nasal breathing. Velopharyngeally incompetent patients should be carefully tailored for prosthetic treatment because of contingent noncompliance.

Adult↗
PubMed1999

Further aspects of design for distal extension removable partial dentures based on the Kennedy classification.

A supplement to the Kennedy classification of partially edentulous arches for restoration with removable partial dentures has been suggested. Factors affecting denture design relating to the position of the abutment teeth, the symmetry of the edentulous distal extensions, the arch form and the cross-sectional shape of the residual ridges have been discussed and classified. An understanding of the movement of the denture bases in relation to the influence of these factors makes for a rational approach to removable partial denture design and the treatment of complications observed clinically in removable partial denture wearers.

Alveolar Process↗
PubMed1998

Posterior bite collapse--revisited.

Although there are different definitions of posterior bite collapse, only the classical definition of Amsterdam provides a definite diagnosis and treatment plan. This situation entails a subtle loss of the occlusal vertical dimension with resultant flaring of the maxillary incisors. Other causes for flaring, such as derangements of form and functions of lips and tongue, bruxism, habits, as well as the presence of advanced periodontal disease or malocclusions, should be ruled out before the diagnosis of posterior bite collapse can be made. The complexity of differential diagnosis is illustrated with three case reports.

Adult↗
PubMed1996

Prosthodontic treatment for the Applegate-Kennedy class V partially edentulous patient.

Concomitant loss of a canine and adjacent teeth usually occurs in the maxilla as a result of trauma in youngsters with well-preserved dentition or as an outcome of surgical excision of a localized pathosis in that area. It is postulated that in Applegate-Kennedy class V partially edentulous situations, the remaining anterior teeth in the maxilla should not be used as abutments for removable partial dentures. The stability of the prosthesis is maintained by counterresisting the occlusal forces exerted on the restored arch-curve by use of a posteriorly directed path of placement for the prosthesis.

Cuspid↗
PubMed1996

Anterior implant-supported overdentures.

Retention of complete mandibular dentures can be successfully achieved by means of an implant-retained or natural tooth-retained bar and clip system in the anterior segment of the mandible. The same design principles hold true for both methods of anchoring the retentive bar. These retentive elements must be constructed to allow some freedom of movement around a fulcrum line designed to be perpendicular to the sagittal plane.

Dental Prosthesis, Implant-Supported↗
PubMed1994

Use of complete dentures to stabilize a segmentally resected mandible: a clinical report.

Although edentulous patients with a midline segmental resection of the mandible can rarely be treated prosthodontically, this patient's dental condition was managed with some success. This success may be related to preservation of the floor of the mouth with graft. By maximum extension of the denture borders and an interlocking occlusion, a mutual stabilization of the residual segments and the denture was achieved in the static condition, which improved swallowing, control of drooling, and self-esteem. Because of the independent muscle function of each side of the mandible, mastication could not be restored adequately.

Chin↗
PubMed1994

Implant-retained mandibular overdentures: a simplified, cost-effective treatment approach.

The use of implant-retained complete overdentures is a viable treatment modality in compromised patients. Use of two separate implants in the mandible enhances the retention and stability of the denture, which is still mainly supported by soft tissues. A technique for clinical fixation of the internal attachment to a laboratory-rebased and tissue-loaded mandibular overdenture is described. The advantages, disadvantages, and the rationale of the treatment are presented.

Dental Abutments↗
PubMed1993

Simplified fabrication of orbital prostheses using posterior attachment for the artificial eye.

The ocular component of an orbital prosthesis can be held firmly during fabrication by attaching a plastic needle cover with autopolymerizing acrylic resin to the posterior surface of the eye in the wax-sculpted prosthesis. This index is subsequently embedded in the master cast. Compared with other techniques described in the literature, this technique spares the corneal surface of the artificial eye and allows duplicate fabrication of silicone orbital prostheses in nonmetal durable molds.

Acrylic Resins↗
PubMed1992

Index to reposition the metal framework accurately on the altered cast.

The relieved portion of a master cast below the major connector of a cast removable partial denture framework can be filled with dental stone to act as a third point of reference when the framework is reseated in an altered cast procedure. With this simple procedure, an index is formed that will allow accurate repositioning of the metal framework on the altered cast.

Calcium Sulfate↗
PubMed1990

Clinical applications of visible light-cured resin in maxillofacial prosthetics. Part I: Denture base and reline material.

A visible light-cured resin system enables the dentist to accomplish chairside relining of removable prosthesis. The material is pliable and can be initially cured in the mouth with the regular hand-held visible light. A special unit is needed to completely cure the material, which thereafter is comparable in quality to heat-polymerized acrylic resin. The value of this system for the practice of maxillofacial prosthetics is demonstrated by the ease of relining of various devices and obturator prostheses.

Acrylic Resins↗
PubMed1989

The labial endodontic access: a rational treatment approach in anterior teeth.

Labial endodontic access is an alternative to the conventional lingual endodontic access in permanent teeth. The labial approach facilitates visibility and provides direct access to the root apex. Current restorative procedures offer improved methods to overcome the esthetic impairment resulting from this approach. Labial access is especially beneficial for patients with limited mandibular opening. Other indications are in Angle's class II division 2 dentitions or in teeth with resin-bonded cast restorations. Anatomic studies for the single tooth that corroborate the labial endodontic approach are reviewed.

Cuspid↗