The International Journal of Prosthodontics, 01/1991

The gradual changes in the skeletal and soft-tissue profile of complete denture wearers resulting from residual ridge reduction were studied using profile cephalometric films obtained from 21 subjects during a 2-year period of denture use. The variables for each observation stage were calculated from 58 digitized reference points. During the first 6 months of denture use, a marked anterosuperior rotation of the mandible as a result of ridge resorption caused a similar profile change of the soft-tissue chin and mandibular lip. Continuing ridge reduction resulted in a marked change of mandibular position at the 2-year stage, leading to a pronounced protrusion of the chin and mandibular lip and a more outward position of the maxillary lip.

This Study evaluated the effect of porcelain surface treatment on the shear bond strength of composite resin to various porcelains and porcelain combinations. A variety of feldspathic porcelains with low and medium alumina content were tested. Porcelain/composite resin samples were stored in 37° C water, thermocycled 1,000 times, and tested in shear. A 3-minute etching using hydrofluoric acid significantly increased the bond strength of most of the feldspathic porcelains with low and medium alumina content. Silane application to all types of etched porcelain had no significant effect on bond strength.

Eleven patients who had only two remaining natural teeth, vital mandibular canines, were treated using experimental 12-unit fixed partial dentures and complete maxillary dentures. The marginal bone support was 60% in one patient and 80% to 100% in the others. The patients were studied for 20 years. After 15 years, seven patients had prostheses that were still functional, two had prostheses that failed, one lost the prosthesis following treatment for oral cancer, and one patient died. Nine of the 22 abutments required endodontic treatment. After 15 years, the fixed partial dentures began to tilt distally and considerable resorption was found under the pontics. The periodontal tissues withstood the increased stress, and the prostheses were stable.

A major problem in the correct diagnosis of pulpal pain is that the associated clinical signs do not predictably correlate with the underlying pathological process. Using conditional probabilities of various pulp conditions from published data, Bayesian Statistical Inference provides the means for deriving a composite probability of the presence of a disease from a multiple set of symptoms. A computer program that can infer a diagnosis for pulpal pain from any combination of 17 clinical symptoms has been developed. From the data, the program provides the computed relative probabilities of a healthy pulp, a saveable pulp, an unsaveable pulp, and a necrotic pulp being present.

Implant-supported posterior restorations must be fabricated following established prosthodontic principles. The need for screw-retained abutments and the narrow diameter of root-form implants dictate additional treatment protocols that fall beyond the scope of conventional prosthodontics. Cemented restorations offer simplicity and good control of morphology, but can only be considered if removal or no reservicing of the restoration is anticipated. Screw-retained restorations allow for reservicing or remediation but necessitate centering of the retaining screw within the occlusal anatomy. When the implant is misaligned, axis problems are solved with preangled copings, custom copings, or double frameworks. The diameter of root-form implants is significantly smaller than posterior natural teeth, and the emergence of the restorations must be progressively flared to achieve proper morphology. Limited interocclusal space and implant placement may dictate restoring posterior teeth as premolars, selecting a short abutment or a nonsegmented (UCLA) abutment, or overlapping the crowns over the soft tissues. The final abutment selection is best assisted with a diagnostic waxing and with provisional restorations anticipating the completed treatment.

Dental shade guides contain a limited selection of colors compared to those found in human teeth. An error in shade selection is thus introduced, since many tooth colors must be defined by approximation to the nearest shade of the guide. The Bioform and Vita Lumin guides, and a combination of the two, were spectrophotometrically compared to the published colors of 335 human teeth. The minimum CIE L*a*b* color difference was calculated for each tooth using each shade guide. The average of these color differences was defined as the coverage error. The Bioform and Vita shade guide coverage errors were not significantly different, but the coverage error was significantly lower when the combination was used. The use of both guides in shade selection is recommended to reduce the coverage error.

Several anatomic relationships existing between the ear and the temporomandibular joint have been proposed to account for the presence of aural symptoms that occur in some patients with temporomandibular joint dysfunction. There are a plethora of functional hypotheses for aural symptoms relating to disturbed functions of the eustachian tube (as well as neuromuscular relationships and neurovascular functions integrating with these hypotheses). Investigators explain the presence of aural symptoms relative to the anatomic relationship of the middle ear to the TMJ as hypothetically due in part to the iny ligament, the sphenomandibular ligament, or the diskomalleolar ligament. This article reviews hypotheses, explanations, and current research on this controversial issue.

The inability to precisely control pore morphology has limited investigations into the exact geometric requirements for optimum ingrowth of bone into porous ceramic implants. A laser machining technique was used to create regular arrays of tubular pores with opening diameters of 75 and 150 microns in sintered hydroxyapatite specimens. Scanning electron microscopy revealed that the size of pores produced in this way is highly reproducible. Heat from the laser beam appeared to produce a fused layer of material, approximately 6 microns thick, around each pore. The nature of this altered material was studied using x-ray diffractometry.

The bond strength of resin-bonded restorations supporting extracoronal precision attachments retaining distal extension removable partial dentures was evaluated. Rigid bars of different lengths were attached to retainers with and without precision attachments. Retainers covering large areas of the teeth and having a generous wraparound design were used, but the teeth were not prepared to enhance resistance form. The retainers without attachments resisted forces as large as 200 N. When less circumferential tooth coverage was used, lower bond strength values were recorded. Four attachments of different loading designs were used. The precision attachments frequently became disengaged before the retainers debonded. Some low bond strengths indicated that there is a measure of unpredictability in the technique.

Rehabilitation of the glossectomy patient is one of the most difficult and challenging problems for the prosthodontist and speech pathologist. The tongue plays an important role in articulation, control of secretions, formation of a bolus, propulsion of the bolus toward the pharynx, clearing the palate, and initiation of the swallow reflex. This paper presents speech and prosthodontic considerations for a patient who underwent a glossectomy and had the additional problem of reduced oral opening.

To better understand patients' relative satisfaction with complete dentures, differences

The author's experience with the swinglock removable partial denture concept is described. This infrequently utilized technique allows the use of undercuts that are unapproachable with other partial denture designs. Indications include missing or weakened key abutment teeth, tooth mobility, aesthetics, economic considerations, and the presence of certain ablative defects following oncologic surgery. The clinician must consider lip position, facial sulcus depth, position of frena, and the periodontal health of potential abutment teeth when considering a swinglock removable partial denture. Specific instructions for blockout, relief, and position of hinge and clasp assemblies should be part of the written laboratory instructions.

Purpose: To determine and compare the frequency of contamination on different sites of healing abutments (HAs) after sterilization with Phloxine B dye on unused and used HAs after sterilization. Materials and Methods: A total of 60 HAs were divided into two test groups: (1) used and sterilized and (2) a control group (unused). The test group was evaluated for contamination after sterilization; the control group did not undergo any procedure. Data were analyzed using SPSS version 22 (IBM). Descriptive statistics were used to determine the frequency of contamination in the different groups and at the different HA sites. Chi-square test was used to evaluate the association of frequency of contamination with the HA site and design. The level of significance was kept at P ≤ .01. Results: The test group showed more contamination compared to the control group. The most contaminated sites were the screw thread and the screwdriver engagement location. Conclusions: HA reuse is cost-effective, but cleaning and sterilization was not effective for these components; thus, HAs need to be reused with caution because they were heavily contaminated when compared to new HAs. Among  the different sites, the screw thread and screwdriver engagement sites were more prone to contamination. HA type did not influence the frequency of contamination.