The International Journal of Prosthodontics, 01/2002

Purpose: The purpose of this study was to compare five different abutment-crown combinations for single implant-supported restorations regarding their capabilities to withstand loads. Materials and Methods: Fifty implants were placed into resin blocks, and the restorations were connected to the implants. The five tested restorations were: (1) metal-ceramic crowns cemented to titanium abutments, (2) In-Ceram crowns cemented to titanium abutments, (3) Celay feldspathic crowns cemented to titanium abutments, (4) In- Ceram crowns cemented to milled ceramic abutments, and (5) Celay feldspathic crowns cemented to milled ceramic abutments. The specimens were loaded at 0- and 45-degree angles to the long axis, and the load values at the moment of failure were recorded using a universal testing machine. Results: The fracture strengths under vertical loading were greater than those under oblique loading. The fracture strengths of metal-ceramic crowns cemented to the titanium abutments were higher than those of all-ceramic crowns cemented on the milled ceramic abutments, regardless of loading direction. There were no differences in the fracture strengths of the ceramic crowns between the two different abutment types under oblique loading. Conclusion: All-ceramic crowns on the milled ceramic abutments were weaker than the metal-ceramic crowns on the titanium abutments under oblique loading.

Purpose: The aim of this in vivo study on dogs was to investigate and compare the inflammatory potential of four different retraction agents on the gingival connective tissue. Materials and Methods: All procedures on eight beagle dogs were performed under general anesthesia: taking oral hygiene measures, placing retraction cords medicated with four chemical agents into the gingival sulci, and taking tissue biopsies. The specimens were evaluated after a 10-minute exposure to chemical agents. The inflammatory response of the connective tissue underlying the sulcular and junctional epithelium triggered by retraction agents was assessed quantitatively. Microscopic images of tissue specimens were morphometrically analyzed using a computer-assisted morphometric method. Results: The most intense inflammatory response in the connective tissue underlying the sulcular epithelium was triggered by astringent retraction agents-Racestyptine in specimens taken after 1 day and 1 week and Rastringent after 1 day (P .05). Tetrahydrozoline-sympathomimetic vasoconstrictor (Visine) was found to have the lowest inflammatory potential. Retraction chemicals produced no significant effects on the connective tissue subjacent to the junctional epithelium. The ratio of the connective tissue area to that of the inflammatory infiltrate showed that 25% aluminum chloride (Racestyptine) was the most aggressive and tetrahydrozoline the least aggressive retraction agent used. Conclusion: All the retraction chemicals tested increased the infiltration with inflammatory cells in gingival connective tissue.

Purpose: The aim of this study was to measure vertical masticatory forces in vivo using a method that should be insensitive to the location of bite force impact. Materials and Methods: Two exchangeable implant abutments were equipped with strain gauges. In nine patients, the abutments were attached to implants supporting three-unit fixed partial dentures (FPD) in one mandibular chewing center. The signals of the two abutments were summed to give a force reading that was independent of the location of force impact along the FPD. In two subjects, an additional strain gauge was fixed under the pontic. With both setups, masticatory forces were measured in chewing of winegum. Results: Total masticatory force displayed by the sum signal proved to be independent of the site of force application. Pontic strain gauges indicated only 42% or 84% of the force measured simultaneously by the corresponding sum signal of the abutments. In all nine patients, a mean total masticatory force of 220 N, with a maximum of 450 N, was found. The single abutments experienced mean loads of 91 N (anterior) and 129 N (posterior), with a maximum of 314 N. Conclusion: Measuring chewing force via bending of a pontic involves the risk of underestimation. Masticatory forces obtained with a method that was insensitive to the site of force application were higher than forces found with some other setups.

Purpose: Dentist-patient verbal communication dimensions on patient satisfaction were investigated in a prosthodontic context, controlling for the age and gender of patients and dentists and the amount of delivered prosthodontic treatment. Two concepts of satisfaction were defined, one for the single visit (satisfaction with care), and one for the overall result (satisfaction with treatment outcome). Materials and Methods: Audio recordings of 61 patients meeting 15 dentists were made in three specialist clinics of prosthetic dentistry. The prosthodontic treatment periods with fixed tooth- or implant-supported prostheses, on average 20 months, were monitored by questionnaires. One visit near the end of each treatment period was audio recorded. The recorded verbal communication was analyzed with the Roter Interaction Analysis System-Dental. Results: Bivariate analysis showed that patients of female dentists were more satisfied in the long-term perspective than patients of male dentists. In logistic multivariate regression models, the verbal communication dimensions information-dentist horizon and information-patient horizon, together with the mouth involvement of the prosthodontics, influenced patient satisfaction with treatment outcome. Conclusion: Patients undergoing extensive prosthodontic rehabilitation should be given the opportunity to ask and talk about their dental health, and dentists should minimize their question-asking and orientating behavior during the encounters to help improve patient satisfaction with treatment outcome.

Purpose: The effect of two levels of prosthesis misfit on prosthetic screw stability was evaluated. Materials and Methods: Two levels of vertical discrepancies-100 and 175 µm-were introduced between an implant-supported complete denture and the terminal abutment. An implant-supported complete denture without vertical discrepancy served as a control. Cyclic load was delivered vertically on the cantilever portion of the prosthesis next to the terminal abutment for 48 hours for each trial. A total of seven sets of new screws were tested for each level of fit. Results: The results revealed significant prosthetic screw instability at both the 100- and 175-µm levels of discrepancy. Conclusion: Vertical discrepancies of 100 and 175 µm introduced between an implant-supported fixed complete denture and the terminal abutment resulted in significant prosthetic screw instability.

Purpose: The purpose of this study was to investigate the prevalence of the clinical signs and symptoms of temporomandibular disorders (TMD) and the relationship between occlusal factors, parafunctional habits, and TMD in a young adult nonpatient population. Materials and Methods: A questionnaire including data from a history and clinical functional examination was used in the study. All 230 subjects were male recruits, from 19 to 28 years of age (mean 21.3 years). Results: Thirty-eight percent of the subjects reported at least one symptom, while in 45% of the subjects at least one sign of TMD was recorded. Temporomandibular joint clicking (40%) and pain on palpation (34%) were the most commonly recorded signs. Multivariate logistic regression analysis showed several weak but statistically significant correlations between the occlusal factors, parafunctional habits, and TMD in this nonpatient population. TMD signs were thus weakly correlated with malocclusion traits (angle Classes II/1, II/2, III, and cross bite), interferences in retruded contact position, midline discrepancy >= 2 mm, = 10 contacts during maximal biting pressure, nonworking-side interferences, horizontal overlap >= 5 mm, and parafunctional habits (teeth clenching and teeth grinding). Conclusion: Some association between occlusal factors and TMD signs was found. However, this association cannot be considered unique or dominant in defining subjects with TMD in the population.

Purpose: This study attempted to (1) clarify the factors influencing the clinical composite assessment of denture-supporting tissues in edentulous patients by experienced prosthodontists and (2) develop a method for quantitative assessment of supporting tissue. Materials and Methods: Seven three- or four-grade scales for clinical factors were used to evaluate supporting tissue in 317 complete denture patients. The general assessment of supporting tissue was conducted with a 10-point scale. The contribution of each grade of the seven factors to the general assessment level was determined by a multiple regression analysis. Results: Based on the contributions of the seven factors, a method for quantitative assessment of supporting tissue was established, category scores for these factors were calculated, and the sums of the category scores were converted to an integer between 0 and 100. The resulting quantification score was closely correlated with the general assessment of the supporting tissue by experienced prosthodontists. Conclusion: The factors influencing the clinical composite assessment of denture-supporting tissues in edentulous patients by experienced prosthodontists were clarified. The quantitative assessment method developed in this study is simple and might be used for preoperative diagnosis and treatment planning.

Purpose: The purpose of the present study was to investigate the effect of roughening the denture base surface on the tensile and shear bond strengths of a poly(dimethylsiloxane) resilient lining material (Molloplast-B) bonded to a heat-cured acrylic resin denture base material. These measured bond strengths were compared to those obtained by packing the soft lining material against poly(methyl methacrylate) (PMMA) denture base acrylic resin dough. Materials and Methods: Three groups of 10 specimens each were constructed for both tensile and shear tests. In the first group, Molloplast-B was packed against cured PMMA denture base surface. In the second group, Molloplast-B was packed against cured PMMA denture base whose surface had been roughened with an acrylic bur. In a third group, Molloplast-B was packed against PMMA denture base acrylic resin dough. Results: Molloplast-B exhibited significantly higher tensile and shear bond strengths when packed against acrylic resin dough. Roughening the denture base surface prior to the application of Molloplast-B had a statistically significant weakening effect on tensile bond strength compared with the smooth surface and the acrylic resin dough. For the shear bond strength, roughening the surface produced a nonsignificant increase compared with the smooth surface, but the bond was weaker than when packed against acrylic resin dough. Conclusion: Significant differences in tensile and shear bond strength were recorded between the three methods used to bond Molloplast-B to denture base material.

Purpose: The aim of the present study was to examine the marginal integrity of a composite veneer, Artglass, in comparison to a ceramic veneer, IPS Empress, by using two different luting agents. The study also aimed to evaluate the effect of grit blasting on marginal integrity of IPS Empress ceramic veneers. Materials and Methods: A total of 42 human maxillary incisors were used to construct 14 veneers for each experimental group: (1) Artglass veneers, (2) IPS Empress veneers with grit blasting, and (3) IPS Empress veneers without grit blasting. Veneers were luted with Variolink II High Viscosity and Variolink Ultra. The restored teeth were sectioned buccolingually and mesiodistally, and marginal gap width measurements were made at 200X magnification. The data were statistically analyzed with analysis of variance. Results: The mean marginal gap width varied from 105 to 182 µm. No significant differences were recorded between the marginal gap widths in relation to different types of veneers or luting agents. However, significantly higher marginal discrepancies were observed for the incisal margins of IPS Empress veneers without grit blasting. Conclusion: In view of the higher marginal discrepancy of IPS Empress veneers divested without grit blasting, the use of this alternative technique was not beneficial. The use of a highly filled resin luting agent (Variolink Ultra) did not cause an increase in marginal gap widths of the veneers.

Purpose: The aim of the present article is to review some of the technical treatment options for implant prostheses restoring the edentulous mandible, mainly based on the Brånemark system. Materials and Methods: Clinical and technical aspects are discussed for the three established concepts: (1) implant-supported fixed prosthesis, (2) removable implantsupported overdenture, and (3) combined implant-retained and soft tissue-supported overdenture prosthesis. Results: The framework of an implant-supported fixed screwretained prosthesis can be processed in gold, Co-Cr alloy, or titanium with casting, laserwelding, or milling techniques. To improve the stability and retention of a conventional complete denture, one to four implants are indicated, and unsplinted (single attachments) or splinted designs (bar systems) can be applied. The design of the overdenture prosthesis must be carefully planned according to the requirements to ensure adequate stability and optimal form, contour, and esthetics, and the patient's best comfort. Conclusion: A large variety of different treatment modalities exist for both the fixed and removable mandibular implant prosthesis. Clinical and technical aspects should be considered at the beginning of the treatment to: (1) select the optimal implant position, (2) establish an adequate number of functional units, (3) select the appropriate retainers, and (4) apply the best technique for framework processing and veneering.

Purpose: The aim of this study was to analyze color parameters and color compatibility of two randomly chosen Vita shade guides, as well as to propose possible clinical guidelines. Materials and Methods: Data were recorded using a colorimeter set to standard illuminant source C and the CIE L*a*b* system. A custom adapter system, which allowed a measuring area at the middle third of the tabs, was produced. Each of 42 tabs was recorded one time each on three different days. Color distribution was examined in diagrams whose coordinates were L*a*b* and L*C*H° color coordinate pairs. Color coordinate ranges and coverage error were examined using the corresponding equations and statistical methods. Results: The method repeatability was approximately ΔE* = 0.1. Color difference ranges of Vitapan Classical and Vitapan 3D Master were 14.3 and 19.2, respectively. Color coordinate ranges of Vitapan Classical were as follows: ΔL* = 12.8; Δa* = 1.7; Δb* = 9.0; ΔC* = 9.0; and ΔH° = 7.4. Corresponding values for Vitapan 3D Master were ΔL* = 15.3; Δa* = 3.4; Δb* = 16.3; ΔC* = 16.6; and ΔH° = 10.5. Coverage error of Vitapan 3D Master to Vitapan Classical was 1.4 ± 0.6, while vice versa it was 2.0 ± 1.5. Conclusion: Compared to Vitapan Classical, chromaticity ranges of Vitapan 3D Master were extended in the desired directions: hue was extended toward yellow-red, and saturation was extended toward more saturated tabs. Compared to Vitapan Classical, Vitapan 3D Master tabs were more uniformly spaced. The examined shade guides were found to be color compatible.

Purpose: The present study was carried out to evaluate Cerana Class I and II tunnel preparations in combination with Cerana inlays. Materials and Methods: Sixty- eight patients were treated with 89 Cerana restorations, 53 in the maxilla and 36 in the mandible. Of these, 47 were Class I and 42 were Class II. The restorations were examined after 1, 2, and 3 years by the author together with the treating clinician. For the evaluation, the California Dental Association quality evaluation system was used. Results: At the 3- year recall, 59 (66%) restorations were examined. One restoration had been exchanged after 1 week, and 10 (11%) restorations had fractured before the 3-year follow-up. A total of 19% of the marginal ridges had fractured over the 3 years. These fractures were in connection with Class II tunnel preparations, except for one Class I filling. All of the Cerana inlays had acceptable marginal adaptation. Marginal discoloration was seen around 8% of the restorations. The color match was excellent, and the majority of the restorations had a smooth surface. Caries was seen in five teeth, three in connection with fractured marginal ridges. Conclusion: The results indicate that Cerana is an alternative to composite resin restorations in Class I situations, but should be avoided in connection with Class II tunnel preparations.