The International Journal of Prosthodontics, 03/2003

Purpose: This article describes an original solution for a tooth with an existing cast post and core placed subgingivally. Materials and Methods: The tooth was erupted rapidly using a simplified and easy technique that incorporates fiberotomy during the process of movement. Results: The distal finish line of the core, which was subgingival before movement onset, was elevated, allowing the placement of crown margins on sound tooth structure. Clinical evaluation of the tooth after a period of 4 weeks, during which a provisional acrylic resin crown was used for retention, showed no need for corrective surgery, and fabrication of a metal-ceramic crown (Captek) was begun. Conclusion: When failing to place crown margins on sound tooth structure, the existence of a cast post and core in such a nonrestorable tooth may serve as an anchor in the process of rapid extrusion. Following the need to respect the biologic width and fulfill the obligatory ferrule effect circumferentially, this extrusive treatment modality was applied to meet high treatment standards.

Purpose: The purpose of this study was to determine the influence of two finish line configurations on the marginal accuracy of Procera AllCeram crowns. Materials and Methods: Twenty mechanized specimens of brass were fabricated for complete-coverage crowns. Two finish line designs were used: chamfer and rounded shoulder. AllCeram crowns were fabricated, and the fit of the crowns to the dies was recorded from the buccal and lingual margins. An image-analysis program was used to measure the gap. The results were subjected to statistical analysis using a Student's t test for separate samples and Student's paired t test. Results: No significant differences were observed between the buccal and lingual measurements. When the values of the buccal and lingual measurements were averaged, there were no significant differences in the marginal gap, horizontal discrepancy, or internal adaptation of the axial wall, but there were significant differences in the vertical discrepancy, absolute marginal discrepancy, and internal discrepancy between the two finish line designs. Conclusion: The marginal gap was within the range of clinical acceptability. Some of the variables were influenced by the two finish lines tested.

Purpose: This study investigated the surfaces produced on two commonly used heat-cured acrylic resins by two chairside polishing systems compared to conventional lathe polishing. It used energy dispersive analysis (EDA) and scanning electron microscopy (SEM) to investigate the abrasive materials bonded in the silicone points that are marketed for chairside polishing of acrylic resin. Materials and Methods: Using the three polishing systems (conventional as control, Shofu acrylic polishing system [AcryPoint], and Kenda Queen silicone polisher), three operators polished specimens using a defined protocol. Specimens were subjected to SEM and confocal microscopy. EDA was undertaken on the silicone polishing points. Results: Conventional polishing produced the superior surface, followed by the surfaces produced by the Shofu system and then Kenda Queen. However, both chairside polishing systems produced smoother surfaces on acrylic resin than the surfaces produced by either steel or tungsten carbide burs. Both the Shofu acrylic polishing system and Kenda Queen silicone polisher contain beads of cerium, which is widely used in industry for polishing of glass. Conclusion: Silicone polishing points marketed for polishing of acrylic resin could be used to produce smooth surfaces that have been adjusted with burs where there is no access to a laboratory lathe.

Purpose: This clinical study reports on the results of single molar crowns, three-unit inlay fixed partial dentures (FPD), and complete-coverage FPDs made of the glass-fiber composite system Targis/Vectris with an observation period up to 4.4 years. Materials and Methods: In total, 38 restorations were inserted in 19 patients. Of these, 17 were adhesively fixed three-unit inlay FPDs, five were conventionally cemented completecoverage three-unit FPDs, and 16 were single molar crowns (six adhesively, ten conventionally cemented). The mean observation period was 2.5 ± 1.0 years. Events like fracture of the framework or veneer, loss of cementation, signs of wear, and outward discoloration were noted and rated according to modified Ryge criteria. Results: During the observation time, neither loss of cementation nor framework fracture were noted. However, six facings (36%) of the inlay FPDs fractured. The number of cases with discoloration or wear increased over time for all types of restorations. The wear culminated in fiber exposure of two molar crowns (24 months) and one inlay FPD (54 months). One of the five complete-coverage FPDs was replaced at the request of the patient (discoloration). The cumulative survival rate after 36 months was estimated to be 82% for molar crowns and 72% for inlay FPDs. Conclusion: Fiber-reinforced composite restorations need further improvement of the veneering composites. Because of the increasing wear, discoloration, fractures of the facings, and fiber exposure, fiber-reinforced composites should only be used for provisional restorations.

Purpose: The purpose of this study was to examine the effects of the occlusal convergence angle of the abutment and the computer's luting space setting on the marginal and internal fit of Cerec 3 computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns. Materials and Methods: Mandibular second premolar all-ceramic crowns were fabricated for nine different conditions using Cerec 3: all combinations of abutments with three different total occlusal convergence angles (4, 8, and 12 degrees) with three different luting space settings (10, 30, and 50 µm). The completed crowns were seated on the abutments, and the marginal gaps were measured. The internal gaps between the crowns and abutments were also measured, using test-fit silicone paste. Results: When the luting space was set to 10 µm, the marginal gaps of the crowns were greater than when it was set to 30 or 50 µm. When the luting space was set to 30 or 50 µm, the marginal gaps ranged from 53 to 67 µm and were not affected by the occlusal convergence angle of the abutment. The internal gaps were within a range of 116 to 162 µm and tended to decrease as the occlusal convergence angle of the abutment decreased. Conclusion: When the luting space was set to 30 µm, crowns with a good fit could be fabricated on the Cerec 3 system, regardless of the occlusal convergence angle of the abutment.

Purpose: In the present prospective study, four different post-and-core systems were evaluated over a period of up to 10 years. Materials and Methods: Fifty endodontically treated teeth in 31 patients were randomized to one of four groups for post-and-core placement: Group 1 received conventional tapered cast posts and cores (n = 14); group 2 received ParaPost system prefabricated gold posts with cast cores (n = 13); group 3 received ParaPost system cast posts and cores (n = 13); and group 4 received Radix-Anchor posts (n = 10). Clinical and radiologic evaluations were made. Results: One post and core in group 2 was functioning well 58 months after placement when the patient died. No posts and cores in groups 1 or 2 had been lost or had any complications, one in group 3 had been lost because of a root fracture after 108 months, and two in group 4 had been lost after 54 and 88 months, respectively, because of loss of retention. The final treatment result for 46 of the 49 remaining posts (30 patients) was successful. The overall failure rate was 6%. There were no statistically significant differences between the four groups. Conclusion: If recommended procedures are strictly followed, posts and cores can serve as abutments for fixed single crowns with satisfactory long-term results.

Purpose: This clinical trial tested the null hypothesis that there would be no difference in prosthetic maintenance for two-implant mandibular overdentures retained by either a bar-clip mechanism or ball attachments. Prosthetic outcomes are reported over 3 years using a six-field protocol. Materials and Methods: One hundred edentulous participants received new maxillary complete dentures and a mandibular two-implant overdenture (IOD), with random assignment to either a bar and metal clip or two ball attachments (titanium alloy matrix and spring) for retention. Eighty-seven subjects were available for follow-up after 3 years. Results: Almost three times as many bar-clip dentures (63%) were rated successful compared to the ball attachment design. Two percent of the participants in each group died over the course of the study, while 15% of the bar-clip and 8% of the ball IOD subjects were lost to follow-up. More than three times as many ball attachment IODs (60%) required retreatment in the form of excessive repairs, and twice as many of the ball attachment design (8%) required replacement. The ball attachment IOD was significantly more likely to require patrix tightening or matrix replacement, while the barclip design was more likely to require activation of the matrix. Conclusion: Using the criteria of a six-field protocol for implant overdenture outcomes, the bar-clip IOD was a significantly more successful prosthesis, requiring less maintenance than the titanium alloy matrix and spring ball attachment IOD employed in this study. The null hypothesis was therefore defeated.

Purpose: The aim of this study was to test the possible elemental release of four different all-ceramic materials in a wear machine to predict results about their long-term behavior in the oral environment. Materials and Methods: Four different all-ceramic materials with different chemical compositions were selected for the wear testing. A total of 20 cylindric samples, five for each ceramic group, were prepared according to the manufacturers¡¯ instructions. These were subjected to two-body wear testing in an artificial saliva medium under a covered unit with a computer-operated wear machine. The artificial saliva solutions for each material were analyzed for the determination of amounts of sodium, potassium, calcium, magnesium, and lithium elements released from the glass-ceramic materials. The differences between and within groups were statistically analyzed with a one-way ANOVA, followed by Duncan tests. Results: The statistical analyses revealed no significant differences among Na, K, Ca, or Mg levels (P >= .05) released from the leucitereinforced groups, while there was a significant (P .05) increase in Li release from the lithium disilicate group. Conclusion: Considerable element release to the artifical saliva medium was demonstrated in short-term wear testing. The lithia-based ceramic was more prone to Li release when compared with other elements and materials.

Purpose: This study investigated the prevalence of signs and symptoms associated with temporomandibular disorders (TMD) in adults with shortened dental arches in Tanzania. Materials and Methods: The shortened dental arch group comprised 725 subjects with an intact anterior region and zero to eight occluding pairs of teeth posteriorly. They were categorized into five groups according to length and symmetry of the dental arches. A control group of 125 subjects with complete dental arches was included. The subjects were interviewed with questions related to pain and sounds within the temporomandibular joints and restricted mobility of the mandible. Clinical examination consisted of registration of clicking or crepitation of the joints, measuring maximum mouth opening, and assessing occlusal tooth wear. Results: Joint sounds were reported significantly more frequently by subjects with posterior support only unilaterally (17%) and by subjects with no posterior support (10%) compared to other categories of dental arches (3% to 5%). No significant differences were found between categories of dental arches with respect to pain (2% to 9%), restricted mobility of the mandible (0% to 1%), maximum mouth opening 40 mm (0% to 3%), or clicking or crepitation of the joints (12% to 23%). For the younger age group (>= 20 and 40 years), tooth wear occurred significantly more often in subjects with no posterior support. For the older age group (>= 40 years), tooth wear increased significantly with decrease of posterior support. Conclusion: No evidence was found that shortened dental arches provoke signs and symptoms associated with TMD. However, when all posterior support is unilaterally or bilaterally absent, the risk for pain and joint sounds seems to increase.

Purpose: This study aimed to determine if implant-supported overdentures are a long-term economically efficacious therapy for edentulous patients when compared to fixed osseointegrated prostheses. Materials and Methods: Clinical records of 25 patients from two longterm studies (fixed and overdenture) were included in this analysis. A cost minimization analysis from the patient perspective was employed. Direct clinical and time costs incurred over the 9-year period were deflated to 1995 Canadian dollars using the Consumer Price Index. National salary rates by occupation and gender were used to value patients' time, and a sensitivity analysis was carried out to assess the robustness of the results when an equal mean salary rate across treatment groups was assumed. Results: The mean total, clinical, and time costs were significantly higher (P = .05) for the fixed restoration group ($CAD10,748, $CAD10,094, and $CAD654, respectively) when compared to the overdenture group ($CAD3,665, $CAD3,343, and $CAD322, respectively). The initial, maintenance, and clinical visit costs were also significantly higher (P = .05) in the fixed restoration group ($CAD7,567, $CAD2,527, $CAD542, respectively) than in the overdenture group ($CAD2,505, $CAD830, $CAD292, respectively). The sensitivity analysis demonstrated that the time cost for the fixed prosthodontic group ($CAD488 vs $CAD322) was still significantly higher (P = .002), even after an equal mean salary rate was assumed. Conclusion: Overdenture therapy for edentulous patients is a more cost-effective treatment compared to fixed prosthodontic treatment.

Purpose: The aim of this study was to evaluate the effect of different ceramic surface treatments on the tensile bond strength between IPS Empress 2 ceramic framework and Rely X adhesive resin cement, with or without the application of a silane coupling agent. Materials and Methods: One hundred twenty disks were made, embedded in resin, and randomly divided into six groups: group 1 = sandblasting (100 µm), no silanation; group 2 = sandblasting (100 µm), silane treatment; group 3 = sandblasting (50 µm), no silanation; group 4 = sandblasting (50 µm), silane treatment; group 5 = hydrofluoric acid etching, no silanation; and group 6 = hydrofluoric acid etching, silane treatment. The disks were bonded into pairs with adhesive resin cement. All samples were stored in distilled water at 37°C for 24 hours and then thermocycled. The samples were submitted to tensile testing. Results: The use of silane improved the bond strength in relation to the groups in which silane was not applied (P .05). The most effective surface treatment was etching with 10% hydrofluoric acid, both with (25.6 MPa) and without silane application (16.4 MPa); these values showed a statistically significant difference compared to sandblasting with 50- and 100-µm Al2O3. Sandblasting with 50-µm Al2O3, with (11.8 MPa) and without silane (5.4 MPa), demonstrated significantly higher tensile bond strength than sandblasting with 100-µm Al2O3, with (8.3 MPa) and without silane (3.8 MPa). Conclusion: Combined application of 10% hydrofluoric acid and silane enhanced the bond strength between the IPS Empress 2 ceramic framework and resin agent.

Purpose: The aim of this retrospective study was to investigate the longevity and clinical performance of fixed partial dentures (FPD) 30, 20, and 10 years after insertion. Materials and Methods: A total of 289 FPDs were inserted in 1966/67, 1976/77, and 1986/87. For patients with FPDs presumably still in function, an evaluation according to the CDA criteria was made. Results: For 64 of the FPDs (22%), no information was available. Seventy-nine patients with 94 FPDs (33%) were clinically examined, and 44 of the FPDs (15%) were reported to be still in function by the patients' current clinicians. The remaining 87 FPDs (30%) were considered lost to follow-up. These FPDs had either been removed for various reasons-in most cases dental caries, lost retention, or fractured abutment teeth-or the patient could not be contacted. Eighty-four percent of the FPDs inserted in 1966/67 were still in function after 20 years, compared to 64% of those inserted in 1976/77. Apart from an increase in wear and discoloration, the oldest FPDs had excellent marginal fit and anatomic shape. Conclusion: The survival rate of 30-year-old FPDs was high; 53% remained in function after 30 years. Based on the CDA criteria, 78% of the restorations were rated satisfactory in all subgroups. The FPDs placed in 1966/67 obtained the highest ratings in color, anatomy, and margin integrity.

Purpose: This study investigated the effect of coronal preparation by high-speed handpiece on the retention of cemented cast posts and cores. Materials and Methods: Cast posts and cores were fabricated for 90 extracted single-rooted human teeth cemented with zincphosphate cement and randomly divided into six groups of 15 specimens each. The six groups were matched randomly two by two, such that one of each of the matched groups was subjected to a 4-minute period of high-speed preparation of the cores. Castings from the first pair (1 and 2) were subjected to an axially directed removal force using a universal testing machine 15 minutes from the start of cement mixing; castings from the second (3 and 4) and third (5 and 6) pairs were tested at 1 hour and 24 hours, respectively, having been stored in water at 37°C for the waiting periods. The forces required for dislodgment of posts from their prepared spaces were recorded. Data were statistically analyzed using two- and one-way ANOVA and the Student's t test. Results: The results showed increased mean retentive strengths of posts as the time to testing increased for both unprepared and prepared groups. Significantly higher mean retentive strengths of posts were recorded for unprepared compared to prepared groups tested at 15 minutes and 1 hour after cementation. Conclusion: High-speed preparation had a significant negative effect on the retentive strengths of posts tested at 15 minutes and 1 hour after cementation, but not on those tested at 24 hours.

Purpose: This retrospective study radiologically investigated alveolar bone resorption in the edentulous maxilla in patients with implant-supported mandibular overdentures. Materials and Methods: This study consisted of 35 healthy, completely edentulous patients with a mean age of 59.7 years. They had received two implants between the mental foramina. New bar-retained mandibular overdentures and maxillary complete dentures were fabricated. Standardized panoramic radiographs taken subsequent to loading and at annual recall visits for up to 8 years were measured for alveolar bone loss in the maxilla. Bone areas and areas of reference not subject to resorption were measured with a planimetry program. The proportional value between both was expressed as a ratio (R). Bone loss was expressed as a change in R between two time points. Differences in the resorption rate between the anterior and posterior parts of the maxilla were investigated. Results: Residual ridge resorption continued during the follow-up period and revealed high individual variability. With a range of 5% to 11% (median) loss in the original bone height, it was significantly (P .031) more pronounced in the anterior than posterior maxilla (2% to 7%) from the second through eighth years. Regression analysis of the medians revealed a relatively high correlation between time and bone loss in both anterior and posterior parts of the maxilla. Conclusion: The anterior anchorage of mandibular overdentures by means of two implants and an ovoid bar was associated with slightly higher resorption in the anterior than in the posterior part of the edentulous maxilla.

Purpose: The purpose of this investigation was to compare two mathematically calculated preparation parameters, ie, retentive capacity and finish line type, with a visual characterization based on a 3-D projection of the same prepared teeth on a PC screen. Materials and Methods: Data from 400 teeth prepared for all-ceramic crowns recorded and manufactured by the Procera system, ie, 100 teeth each of types 11, 13, 14, and 16, were selected. Teeth were visually characterized for retentive capacity as good, acceptable, or insufficient, and type of finish line was characterized as deep chamfer, chamfer, or knife edge. For the mathematic calculations, data points located along vertical lines every 10 degrees around the tooth from finish line to occlusal/incisal midpoint were selected to calculate retentive area, defined as the part of the axial walls with an angle of less than 10 degrees to the preparation midline, and the area at the finish line with an angle of more than 45 degrees to the midline. Results: Significant differences were found between the calculated size of surface areas for all types of prepared teeth visually characterized as having good retention and the two other categories (acceptable and insufficient). The difference between the latter two categories was not significant. Significant differences were also found between calculated surface areas for teeth visually characterized as having a deep chamfer and the two other finish line categories, ie, small chamfer and knife edge, but not between the latter two categories. Conclusion: The mathematic program allows a characterization of preparation parameters and may be further developed for use in prospective or retrospective studies of CAD/CAM restorations.

Purpose: The purpose of this study was to compare clinicians' ratings of the state of oral tissues and their satisfaction with treatment to edentulous patients' ratings of treatment success after provision of mandibular implant overdentures or conventional dentures. Materials and Methods: Sixty subjects randomly received either mandibular overdentures retained by two implants (n = 30) or new conventional mandibular complete dentures (n = 30). All were given new conventional maxillary dentures. Baseline measures included clinical evaluation of the oral soft and hard tissues. Patients rated their general satisfaction before and after treatment, as well as their satisfaction with stability, speech, and esthetics on visual analogue scales. The treating prosthodontist rated the dentures for the same categories. Patient and clinician ratings were compared using correlations, t tests, and linear regression. Results: None of the clinical variables were significantly correlated with patient satisfaction before or after treatment. The prosthodontist rated mandibular implant overdentures significantly better than conventional dentures regarding general satisfaction, stability, speech, and esthetics. Implant overdentures were also easier to fabricate (P .0001). The prosthodontists' scores were not significantly correlated with patient scores for any question. Conclusion: Clinicians' assessments of the quality of denture-supporting tissues are poor predictors of patient satisfaction with mandibular implant or conventional prostheses. Prosthodontists and patients both rate mandibular implant overdentures as significantly superior to conventional dentures, but patients and clinicians do not usually agree when evaluating individual prostheses.

Purpose: The aim of the study was to evaluate associations among prosthetic status, socioeconomic factors, and general health of subjects aged 55 to 79 years. The data were taken from the Study of Health in Pomerania (SHIP). Materials and Methods: Socioeconomic information (age, sex, education level), medical information (number of diseases), and details on smoking and alcohol consumption were obtained. Prosthetic status in the maxilla and mandible was classified into complete denture (CD), removable partial denture (RPD), >= 10 natural teeth or teeth replaced with fixed prosthodontics (10T+), and = nine natural teeth including fixed prosthodontics (9T-). Results: The data of 1,877 subjects were evaluated. CDs in the maxilla were more frequent than in the mandible. RPDs were more frequent in the mandible and in the group aged 65 to 74 years. Of the individuals with a low education level, 47% had a CD in the maxilla, and only 21% had 10T+. However, of subjects with a high education level, 22% had a CD in the maxilla, and 54% had 10T+. The odds ratio of having a CD in the maxilla increased to 11.9 at the age of 75 to 79 years, compared to 0.6 at the age of 55 to 59 years. Logistic regression analyses showed that the risk of wearing a CD was significantly associated with old age, low education level, low income, smoking, and alcohol abuse, whereas the number of diseases (used as an indicator of general health) was not. Conclusion: Alcohol abuse, smoking, low education level, low income, and old age were significant predictors of wearing CDs.

Purpose: This clinical study evaluated the behavior of inlay fixed partial dentures (IFPD) with conventional and modified framework designs over a period of 12 to 48 months. Materials and Methods: Forty-one glass fiber-reinforced composite IFPDs were made to replace one missing maxillary or mandibular tooth. The frameworks were made only with parallel fibers in 19 restorations (group 1) and built with parallel and woven fibers modifying the design of the pontic element in 22 IFPDs (group 2) according to the manufacturer's instructions. All restorations were evaluated by color match, marginal discoloration, secondary caries, surface texture, marginal adaptation, fracture, and postoperative sensitivity. Results: Three partial adhesive-cohesive veneering composite fractures occurred in the pontic element in group 1 after 3, 4, and 8 months, respectively. One cohesive fracture occurred in an abutment in group 2 after 46 months. Group 1 showed a 16% fracture failure rate; group 2 showed a 5% failure rate. However, no statistical difference was detected between the groups. IFPDs received the highest score at the following rates: color match 71%, marginal discoloration 96%, secondary caries 99%, surface texture 88%, marginal adaptation 98%, fracture 90%, and postoperative sensitivity 100%. Statistical analysis indicated significant deterioration of color match from baseline to last recall. Conclusion: There were nonsignificantly fewer fractures of the veneering composite with the modified design of the framework than with the conventional design. Repair of the fractured veneer of IFPDs may lengthen the lifespan of the restorations, but it is advisable only for slight damage.

Purpose: This article presents a new treatment protocol in maxillofacial prosthodontics. Materials and Methods: A case report of a patient suffering from an orbital defect after tumor resection is presented. To explain the treatment protocol, the procedure of fabricating an implant-retained orbital prosthesis for this patient is discussed. Results: After tumor resection, implants were placed and a prosthesis was made based on both a CT scan and computer-supported technology. Conclusion: The integration of several existing techniques in and outside the field of maxillofacial prosthodontics led to a treatment protocol that was shown to be beneficial in the presented case and others.