The International Journal of Prosthodontics, 06/2008

Purpose: To assess, at a 10-year interval, changes in attitudes toward desire for implant treatment among middle-aged and older Swedish subjects with respect to dental status. Materials and Methods: Three thousand subjects, residents of Örebro County, Sweden, were surveyed via the same questionnaire in 1989 and again in 1999 regarding their possible need for and interest in implant-based prosthodontic treatment. Results: One thousand six hundred sixty-five subjects responded to both surveys. In 1989 few respondents indicated an interest in implant treatment, whereas in 1999, 92% of those who had not indicated an interest in the earlier survey now indicated that they desired implant treatment. The cohort reporting having no teeth had a considerable lower increase in desire. Among those who reported a possible treatment need (ie, missing 1 or more teeth and had not had them replaced or those who wore complete dentures), cost was the most commonly cited reason for declining implant treatment. Conclusions: There was a dramatic increase in the interest for implant treatment over the period from 1989 to 1999. Changes in awareness of implant treatment, along with an expansion in the number of qualified providers, may have contributed to this increase.

This in situ study evaluated the Shore A hardness and phthalate concentration of 3 tissue conditioners (Coe-Comfort, Dura Conditioner, Softone) inserted into grooves on 9 maxillary dentures. Data were collected at baseline and after 3, 7, and 14 days of denture use. All materials showed a decrease in phthalate concentration and an increase in hardness over time, but the largest changes occurred during the first 3 days; 59% to 74% of the hardness variability was explained by the phthalate concentration. Overall, Coe-Comfort was softer and had less alteration in its phthalate concentration than Dura Conditioner and Softone up to day 7.

Purpose: The aim of this study was to compare prospective treatment with implant-retained mandibular overdentures (IROs) versus conventional complete dentures (CDs). This paper reports on the study design and 1-year outcomes. Part 2 in this series will report the 7-year outcomes. Materials and Methods: Sixty edentulous patients with severely resorbed mandibles, already using a conventional CD, participated. Thirty patients received an IRO and 30 received a conventional CD. The patients were retrospectively matched for age, gender, and social class. The length of each treatment session was recorded. Both groups provided a subjective assessment of their current dentures, and satisfaction with their new dentures was evaluated using questionnaires focusing on denture-related complaints and a general satisfaction scale. Results: Patients with IROs were more satisfied with the performance of their dentures than those using conventional CDs, especially with regard to subjective fit, looseness, and quality of chewing; however, more clinical treatment was required. The mean time taken by the prosthodontist to construct CDs was 268 minutes, compared to 327 minutes for IROs, to the time of the second review appointment after insertion. Conclusions: Mandibular IROs provided enhanced performance but required more clinical resources.

Grinding intaglio surfaces of ceramic restorations with diamond burs is a common procedure to improve fit. This study evaluated the effects of simulated diamond bur grinding and subsequent veneer firing and glazing on a lithium disilicate glass-ceramic. The results revealed a significant reduction in the roughness and strength of the material after diamond bur grinding, whereas the strength was restored through crack healing and formation of a glass layer after heat treatment. The finding indicates that grinding of lithium disilicate ceramics with diamond burs may introduce flaws and cracks, and therefore subsequent heat treatments, veneer firing, or glazing, are suggested.

The purpose of this retrospective cohort study was to investigate patient satisfaction factors that affect the usage of removable partial dentures (RPDs) using a multivariate analysis. Sixty-seven patients, who had RPDs inserted at the Tohoku University Hospital between 1996 and 2001, participated in this study. Data were collected from patients' clinical records and a questionnaire. Of the 15 factors examined, significant associations were found between RPD usage and pain, color of the artificial teeth, and arrangement of the artificial teeth. These findings suggest that RPD usage is related to patient satisfaction with esthetics and an absence of pain.

Purpose: This study describes a mechanical chewing simulator that is able to reproduce mandibular movements in 3 dimensions and the forces exerted during mastication. The aim of this work was to validate the described device, which can be used to test the ability of different restorative materials to withstand stress. Materials and Methods: To validate the masticatory robot, 5 identical samples for each of 3 different restorative materials (an acrylic resin, a composite resin, and a glass ceramic) were created. Each sample underwent 5 minutes of chewing in the robot. The forces transmitted to the simulated peri-implant bone were collected. Two-way analysis of variance was used to evaluate the results. Results: There were significant differences between the materials, and internal comparisons also showed significant differences (P .0001). Conclusion: The different elastic moduli of the restorative materials significantly affected stress transmission at the simulated bone-implant interface, and the masticatory robot was able to identify this difference. The very low levels of variation confirm the precision of the machine during data collection and validate the reliability of the method, showing effective repeatability of the tests.

Because of their strength, zirconia ceramics may be used to restore removable partial denture abutments. This carries the advantages of elimination of the galvanic current between primary and secondary copings, along with thermal protection of abutment teeth. This article describes the fabrication of zirconium primary copings to provide retention for a mandibular telescopic overdenture.

The aim of this study was to compare the effect of location and number of implants on the retention and stability of magnetically retained mandibular overdentures. Four groups of such prostheses were classified according to number and position of the implants in the canine, premolar, or molar regions. Significant differences in retention were observed when 6 magnets were used (4.66 ± 0.45 N), whereas the lowest retention was obtained with 2 magnets (2.1 ± 0.43 N). Only oblique stability was improved significantly when the number of implants was increased.

Purpose: The aim of the present study was to evaluate the prosthodontic maintenance required for mandibular overdentures supported by 4 implants and splinted with either a round bar and resilient overdenture anchorage or a milled bar with rigid anchorage over a 5-year period. Materials and Methods: In a randomized prospective trial, 51 edentulous patients received 4 mandibular interforaminal implants to support an overdenture and maxillary complete dentures. For the implant-supported overdentures (IODs), bar architecture and denture stabilization were chosen randomly; 25 patients received round bars (group 1) and resilient anchorage and 26 patients received milled bars (group 2) and rigid anchorage. The prosthodontic maintenance required for the IODs and opposing dentures were evaluated during a 5-year follow-up period and compared between the 2 retention modalities used for IODs. Results: Forty-six patients (22 in group 1, 24 in group 2) were available for a 5-year follow-up (dropout rate: 9.8%). Prosthodontic maintenance efforts were significantly greater (P .01) with the round bar design (group 1) than with the overdentures stabilized with milled bars (group 2). In group 1, prosthodontic maintenance efforts were more frequent in the early phase of use (1 to 2 years), as compared with an evenly distributed incidence over the 5-year period with the rigid milled bar system. Major prosthetic complications (IOD remaking, bar fracture) were only seen in cases without metal-reinforced frameworks (group 1). Conclusion: When 4 interforaminal implants are used to anchor mandibular overdentures, the design of the anchorage system will significantly affect prosthodontic maintenance efforts and complication rates. Rigid anchorage using milled bars and a metal-reinforced denture framework required less prosthodontic maintenance, ie, for clip activation/fracture, than resilient denture stabilization using multiple round bars without a rigid denture framework.

This study evaluated the concept of computer-aided design of anterior teeth by integrating morphologic information about the mirrored contralateral teeth. With the aid of a digital 3-dimensional tooth library, ipsilateral teeth were automatically mirrored, rotated, and translated to fit in the locations of the contralateral teeth. The reconstruction outcomes were evaluated via 3-dimensional similarity measures, measurements of approximal and antagonistic relationships, and visual ratings of experts. Metric and visual judgments indicate that integrating the shape of a symmetrically located contralateral anterior tooth seems to be a suitable base concept for computer-aided design of anterior restorations.

Purpose: To assess the value of removable partial dentures (RPDs) in subjects with shortened dental arches (SDAs) with regard to quality of life. Materials and Methods: Subjects from 2 university dental centers (82 men, 78 women; mean age: 54 ± 18 years) were categorized into the following groups: (1) SDA with intact anterior regions (SDA-1, n = 44); (2) SDA and interrupted anterior region (SDA-2, n = 21); (3) SDA (intact anterior region) extended with distal-extension RPD (RPD-1, n = 25); (4) subjects with interrupted SDA and interrupted anterior region treated with RPD (RPD-2, n = 32); or (5) complete dental arches (CDA, n = 38) as a control. All subjects underwent a short clinical examination and completed 2 structured questionnaires: the Oral Health Impact Profile (OHIP-49) and the Short-Form Health Survey (SF-36). Recorded clinical variables included: teeth present (yes/no), replacement by RPD (yes/no), and number of occlusal units. Age-dependent outcomes were adjusted to outcomes for the age of 60 years. Linear regression models were used to assess differences between the groups. Results: Reliability and validity were good for all subscales. For OHIP, the investigation groups had significantly higher scores (more complaints) than CDA for the subscales "functional limitation," "psychologic discomfort," and "physical disability." Of the 4 investigation groups, SDA-1 subjects had the lowest mean scores. SF-36 scores showed less prominent and less conclusive differences between investigation groups and CDA subjects. SDA-2 subjects showed worse health, with significantly lower scores than RPD-2 subjects for "vitality," "social function," and "mental health." For pure SDA subjects (SDA-1) there was a significant positive effect for "number of occlusal units" in 5 of the OHIP subscales and 2 of the SF-36 subscales. Conclusion: From a quality-of-life perspective, patients with SDAs perceive benefits from RPDs only if anterior teeth replacements are included. In contrast, in subjects with uninterrupted SDAs, where only posterior teeth were replaced by distal-extension RPDs, such benefits could not be demonstrated.

Purpose: Disinfection of dental impressions is an indispensable procedure for the control of cross-contamination; however, there is limited information on the efficacy of disinfection under clinical conditions. The objective of this study was to clinically evaluate the disinfection efficacy of commercially available agents in removing oral pathogens from patient-derived impressions. Materials and Methods: Impressions from 54 patients were divided into groups and either left undisinfected or underwent 1 of 5 disinfection treatments: (1) 2% glutaraldehyde (GA), (2) 1% sodium hypochlorite (SH), (3) 0.25% benzalkonium chloride (BC), (4) 1 ppm ozonated water (OW), or (5) the Hygojet/MD520 system (HJ). An impression culture technique using a brain heart infusion agar medium was used to visualize the microbial contamination on the surface of the impression cultures. The persistent presence of oral pathogens on the impression cultures was examined using selective isolation agar plates. Results: The isolation frequencies of streptococci, staphylococci, Candida, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa species from undisinfected impressions were 100%, 55.6%, 25.9%, 25.9% and 5.6%, respectively. Disinfection with HJ and BC removed the microorganisms with the greatest efficacy, followed by GA, SH, and OW. Potential bacterial contamination could be detected even after disinfection had been performed. Combined use of BC plus GA or SH removed oral pathogens almost completely from dental impressions. Conclusions: This investigation showed that potential contaminants are still present, even after general disinfection procedures. Therefore, either HJ or the combined use of BC with GA or SH is recommended for clinical and laboratory use.

Many clinical studies have reported high survival rates for tilted implants. However, tilted implants transmit increased stress to bone when compared to vertically placed implants. Theoretical (computer-based), laboratory, and clinical studies are warranted to effectively address this issue. In this study, a 3-dimensional finite element analysis was performed to analyze the stress values surrounding tilted versus vertical implants. The results revealed laboratory and biomechanical evidence that distal tilting of implants, splinted in full fixed prostheses without cantilevers, reduced the amount of stress generated around the peri-implant bone when compared to the levels of stress seen in peri-implant bone with vertical implants and cantilevered segments in similar full fixed prostheses.