10-year randomized trial (RCT) of zirconia-ceramic and metal-ceramic fixed dental prostheses.

OBJECTIVES: To monitor zirconia-ceramic and metal-ceramic posterior FDPs with respect to survival and technical/biological complication rates. MATERIALS AND METHODS: Fifty-eight patients received 76 3- to 5-unit posterior FDPs. The sites were randomly assigned to 40 zirconia-based (ZC) and 36 metal-based (MC) FDPs. FDPs were examined at baseline (cementation), at 6 months, at 1 year and then yearly up to 10 years. Technical outcomes were assessed using modified United States Public Health Service (USPHS) criteria. Biologic outcomes included probing depth, plaque, bleeding on probing and tooth vitality. Statistical analysis was performed applying Kaplan-Meier (KM) estimation, log-rank, Mann-Whitney and Fisher exact test. RESULTS: During the 10-year follow-up thirteen patients (17 FDPs) dropped out and 6 FDPs in 6 patients (5 ZC,1 MC) were considered catastrophic failures for technical and/or biological reasons. Forty-four patients with 53 FDPs (29 ZC, 24 MC) were available for examination. The median observation period was 10.3 years (ZC) and 10.0 years (MC). The 10-year KM survival estimate of ZC FDPs was 91.3% (95%CI:69.5;97.8) and 100% of MC FDPs. Minor chipping of the veneering ceramic and occlusal wear were found to a similar extent at ZC and MC FDPs. ZC FDPs demonstrated a significantly higher rate of framework fracture, de-bonding, major fractures of the veneering ceramic and poor marginal adaption. Biological outcomes were similar in both groups and between abutment and control teeth. CONCLUSION: At 10 years, ZC and MC posterior FDPs resulted in similar outcomes for the majority of the outcome measures (p > 0.05).

Analysis of Vertical Marginal Adaptation of Zirconia Fixed Dental Prosthesis Frameworks Fabricated by the CAD/CAM System: A Randomized, Double-Blind Study.

PURPOSE: The purpose of this study was to evaluate the marginal adaptation of fixed dental prosthesis frameworks fabricated by computer-aided design/computer-assisted manufacture (CAD/CAM) with three different systems of data acquisition. MATERIALS AND METHODS: A total of 50 specimens were fabricated as follows: using the conventional method (Ni-Cr) (n=10); iTero/industrial milling (Group 1, n=10); Cerec Bluecam/industrial milling (Group 2, n=10); 3S/industrial milling (Group 3, n=10); and Cerec BlueCam/Sirona milling (Group 4, n=10). The specimens were numbered and randomized, and the vertical marginal discrepancy was analyzed. RESULTS: Intraobserver analysis indicated no statistically significant difference (paired t test, P=.822) between periods before and after analysis. The conventional method (321 µm) showed greater discrepancy when compared with the CAD/CAM system (89 µm) (P<.001). The intraoral system showed a lower rate of marginal discrepancy when compared with the extraoral system (3S) (P<.001). The closed system presented a higher marginal discrepancy (114 µm) than the open intraoral system (iTero) at P<.001. In addition, the intraoral system when open showed statistically significant differences in mean marginal discrepancy values compared with the same system in closed condition (P>.05). CONCLUSION: The CAD/CAM systems showed less marginal discrepancy than the conventional method for the fabrication of the frameworks.

Three-Year Analysis of Fixed and Removable Telescopic Attachment-Retained Implant-Supported Dental Prostheses: Survival and Need for Maintenance.

PURPOSE: The purpose of this retrospective clinical study was to evaluate the clinical outcomes of fixed implant-supported dental prostheses (FISDPs) and removable ISDPs (RISDPs) retained by telescopic attachments, the factors influencing survival, and the type and number of maintenance treatments required during the observation period. MATERIALS AND METHODS: This retrospective clinical study is based on patients who were provided with ISDPs between 2004 and 2010. Patient sex, type of prosthesis, location, opposing dentition, and the effect of continuous follow-up on the probability of a favorable outcome, as well as the number of maintenance treatments, were analyzed. A statistical analysis was performed using the Kaplan-Meier method. RESULTS: A sample of 233 patients with 157 FISDPs and 76 RISDPs supported by a total of 567 implants was randomized and included in the analysis. The mean observation period was 15.9 ± 15.4 months (maximum, 66.0 months). During the observation period, 3.9% of prostheses (7/157 FISDPs and 2/76 RISDPs) ceased to function and 2.3% of implants (13 implants) were lost. The mean survival time was 59.7 ± 2.3 months, with a survival probability of 90.2% after 3 years. Prostheses in the mandible showed significantly higher survival rates than those in the maxilla. Maintenance treatments had to be performed at an earlier stage for patients with RISDPs than for patients with FISDPs. In patients with a conventional removable prosthesis in the opposing arch, the time until maintenance was needed was significantly shorter. CONCLUSION: Within the limitations of a retrospective study, it can be concluded that the FISDPs and RISDPs show equally good survival rates after 3 years in function. RISDPs showed a greater and earlier need for maintenance treatments during the first years in function.

Comparison of accuracy and reproducibility of casts made by digital and conventional methods.

STATEMENT OF PROBLEM: Little peer-reviewed information is available regarding the accuracy and reproducibility of digitally fabricated casts compared to conventional nondigital methods. PURPOSE: The purpose of this in vitro study was to compare the accuracy and reproducibility of a digital impression and cast fabrication with a conventional impression and cast fabrication. MATERIAL AND METHODS: Conventional impressions were made via a 1-step single viscosity technique with vinyl siloxanether material of a typodont master model, and conventional casts were cast from dental stone. Digital impressions were obtained with a digital scanner, and digital stereolithographic models were printed. The typodont and fabricated casts were digitized with a structured light scanner and saved in surface tessellation language (STL) format. All STL records were superimposed via a best-fit method. The digital impression and cast fabrication method was compared with the conventional impression and cast fabrication method for discrepancy, accuracy, and reproducibility. The Levene test was used to determine equality of variances, and a 1-way ANOVA was conducted to assess the overall statistical significance of differences among the groups (n=5, α=.05). RESULTS: No significant statistical difference was found between the digital cast and conventional casts in the internal area or finish line area (P>.05). In addition, there was no statistically significant difference between these 2 techniques for a fixed dental prosthesis or single crown (P>.05). However, statistically significant differences were observed for overall areas of the casts in terms of accuracy (P<.01) and reproducibility (P<.001). Digital impression and cast fabrication were less accurate and reproducible than conventional impression and cast fabrication methods. CONCLUSIONS: No statistically significant difference was found between the digital cast and conventional cast groups in the internal and finish line areas. However, in terms of the reproducibility and accuracy of the entire cast area, the conventional cast was significantly better than the digital cast.

Prevalence of peri-implantitis in patients with implant-supported fixed prostheses.

OBJECTIVE: The purpose of this study was to evaluate periimplantitis prevalence in patients using implant-supported fixed prostheses that did not have any routine maintenance care. METHOD AND MATERIALS: A total of 161 implants (27 patients) were evaluated in patients using implant-supported fixed prostheses. Collected data included information related to patient general health and local factors such as characteristics of implants, time in function, type of loading, positioning, Modified Bleeding Index, bacterial plaque, bleeding on probing (BOP), marginal recession, probing depth (PD), keratinized mucosa, and radiographic bone loss (BL). Factors related to the prostheses were also evaluated. The exclusion criteria were patients that have had any follow-up visit for plaque control of the prosthesis and/or the implants. RESULTS: From a total of 161 implants, 116 (72%) presented without peri-implantitis (PD > 4 mm + BOP + BL > 2 mm) while 45 (28%) had some sign of the disease. Implants placed in the maxilla were 2.98 times more likely to develop the disease (P < .05). Moreover, patients aged ≤ 60 years old were 3.24 times more likely to develop peri-implantitis (P < .05). Another analysis with statistical relevance (P < .05) was that implants with less than 3 mm interimplant distance were three times more likely to have peri-implantitis. There was no statistical relevance considering other analyses. CONCLUSION: It can be concluded that patients aged ≤ 60 years have a greater chance of presenting periimplantitis, as well as for implants positioned in the maxilla and those placed with an interimplant distance < 3 mm.

Practice-based evidence from 29-year outcome analysis of management of the edentulous jaw using osseointegrated dental implants.

PURPOSE: The aim of this retrospective study was to summarize practice-based evidence associated with long-term outcomes (>20 years) in the management of edentulous patients. The patient population was managed with implant-supported prostheses, following the original osseointegration protocol, provided over the period from 1983 to 1991 in the group prosthodontics practice at the Mayo Clinic. The data are an example of practice quality assurance monitoring and are used to refine care delivery when needed and to provide information regarding expected outcomes in a shared decision-making interaction with prospective patients. MATERIALS AND METHODS: Two hundred and sixty four patients with at least one edentulous jaw were identified. Of these, 255 completed their care and follow-up at the Mayo Clinic (209 mandible only, 35 maxilla only, 11 mandible and maxilla). Prosthodontic outcomes categorized as anticipated or unanticipated prosthetic and biologic events and the respective interventions required for each were recorded to assess follow-up event dynamics for this care modality. RESULTS: The mean duration of follow-up for 190 of the 255 patients (65 died at a mean follow-up of 12.6 years) was 13.0 years (median 13.6; range 0.3 to 28). At least one prosthetic event was experienced by 148 patients (58%), and 81 (32%) experienced at least one biologic event. Overall, patients experienced 3.8 times more prosthetic events than biologic events. Twenty-four (9%) patients experienced 35 implant failures. Overall survival rates at 20 years were 86% for prostheses, 15% survived free of any event, and 92% experienced survival free of implant failure (95% confidence interval). CONCLUSION: Anticipated and unanticipated prosthetic events occur throughout the life of the hybrid prosthesis. Prosthetic events significantly surpass (four times more) biologic events and occur significantly later in the follow-up. For this patient group, 8.6% (22/255) had implant-supported prostheses remade during follow-up in this patient population. These findings support the recommendation that prosthodontic care for missing teeth be thought of in a "chronic condition" context, recognizing that long-term outcome monitoring to provide realistic care expectations is important for demonstrating care value in oral health promotion.

Occlusion of artificial teeth in partial dentures in the "chewing center"--first exploratory population-based evaluations.

Occlusal performance is a substantial determinant of the quality of dental prosthetic restorations. In the follow-up (SHIP 1) to the Study of Health in Pomerania (SHIP), a representative population of 3300 subjects was studied in the first exploratory evaluation of the occlusion of artificial teeth in the chewing center (first molar region) of partial dentures. A digital analysis of interocclusal records of habitual intercuspation position (ICP) was performed using the Greifswald Digital Analyzing System (GEDAS), a software package that identifies contact points as transparent areas. 562 subjects (280 men aged 61.7 ± 11.9 years and 282 women aged 60.7 ± 10.7 years) had maxillary removable partial dentures (RPDs), and 619 (271 men aged 65.0 ± 11.5 years and 348 women aged 62.4 ± 10.6 years) had mandibular RPDs. Most RPDs were retained with either attachment retainers (11.7% maxilla, 11.7% mandible), cast clasps (38.4% maxilla, 40.7% mandible), telescopes with double crowns (15.7% maxilla, 19.1% mandible), or wrought wire clasps (16.4% maxilla, 8.2% mandible). Some had a combination of different retention elements. The mean number of artificial teeth was 7.8 ± 2.9 in the maxilla and 7.5 ± 3.0 in the mandible. Only the artificial teeth (first molars) in mandibular partial dentures showed differences in the frequency of occlusal contacts between groups (chi-square test). Of these, telescopic crown-retained RPDs had the highest frequency of occlusal contacts (74.4% at tooth 36 and 77.1% at tooth 46), and wrought wire-retained RPDs had the lowest (48.4% at tooth 36 and 45.2% at tooth 46). The results for RPDs with a free-end saddle were comparable and analogous; contact frequencies for those with an interdental saddle did not differ significantly. Notably, the overall frequency of occlusal contacts was greater for tooth 46 (62.9%) than for tooth 36. In conclusion, when replacing teeth in the chewing center, particularly in the mandible, telescopic crown-retained RPDs offer a distinct advantage in terms of occlusal contacts and thus provide better occlusal stability.

A survey of removable partial denture casts and major connector designs found in commercial laboratories, Athens, Greece.

PURPOSE: This survey was conducted to study the prevalence of partial edentulism, the type of removable partial denture (RPD) support, the type of major connectors, and the frequency of their use in relation to the partial edentulism classes encountered, concerning patients in Athens, Greece. MATERIALS AND METHODS: The material comprised 628 final casts for RPDs. Each cast was photographed in a way that would allow the number of existing teeth, the classification of partial edentulism, the RPD support, and the particular parts of the metal framework to be identified. Data collected were analyzed statistically using prevalence tables and the χ(2) test. RESULTS: Two hundred seventy six (43.9%) casts were for the maxilla and 352 (56.1%) for the mandible. The most frequently encountered group was Kennedy class I for both arches, while class IV was the classification least encountered (p < 0.001). Of all RPDs constructed, 96.8% had a metal framework (tooth-borne and tooth/tissue-borne), while 3.2% of the RPDs were frameless (tissue-borne, acrylic dentures). The U-shaped palatal connector (horseshoe) in the maxilla and the lingual bar in the mandible were the most frequently used for all partial edentulism classes, at 55.2% and 95%, respectively. CONCLUSIONS: Analysis of the casts revealed that the type of major connectors selected does not comply with the indications for their applications, considering the lack of dental history and clinical examination. This notes the need for further training dentists and dental technicians in aspects of RPD framework design.

Dental prosthetic status and prosthetic needs of the institutionalized elderly living in geriatric homes in Hyderabad: a pilot study.

INTRODUCTION: To promote oral health among the elderly, we need to know their prosthetic status and prosthetic need. Hence, a survey of prosthetic status and need of elderly inmates of geriatric homes in Hyderabad was done. MATERIALS AND METHODS: A cross-sectional study was undertaken, and 174 subjects aged 60 years and above were examined of which 103 were male and 71 were female (59.2% males and 40.8% females). The oral examination of the study subjects was carried out using basic oral health surveys, WHO 1997 criteria. RESULTS: Majority of the subjects, 73 (70.8%) males and 53 (74.6%) females had no prosthesis. Only 4.6% had complete dentures and 21.1% had removable partial dentures and 10.9% had single/multiple bridges. Need for any prosthesis was (83.5%) male and 63 (88.7%) female subjects and nearly 82. 8% subjects required one-unit prosthesis. CONCLUSION: Dental prosthetic status of people living in geriatric homes is very poor and there is high unmet need for prosthetic care existed among the institutionalized elderly surveyed.

Survival analysis of mandibular complete dentures with acrylic-based resilient liners.

OBJECTIVE: The purpose of this long-term randomised controlled trial was to compare the longevity of dentures constructed using a conventional acrylic resin (CAR) to that of dentures constructed using an acrylic-based resilient liner (ARL). MATERIALS AND METHODS: The follow-up study was essentially carried out by annual telephone calls to each of the 67 participants. The Kaplan-Meier method and life-table analysis were used for univariate analyses. The Cox proportional-hazards test was used as a final model for statistically adjusting predictor variables such as sex, clinician type, mandibular denture type and age at denture delivery. RESULTS: The denture type was likely to affect the survival time of the dentures, while the sex and clinician type were not. The group using acrylic-based resilient denture liners had twice the risk of having shorter denture-survival times than those using conventional acrylic resin dentures. Younger participants were likely to have a reduced risk of having shorter denture-survival times than older participants. CONCLUSION: We conclude that mandibular complete dentures constructed using ARL are twice as likely as dentures constructed using CAR to have shorter denture survival times, mainly because of material deterioration.

Kennedy classification and treatment options: a study of partially edentulous patients being treated in a specialized prosthetic clinic.

PURPOSE: This study was done under the auspices of the Swedish International Development Cooperation Agency, whose aim is to improve living conditions in developing countries, including dental aid. Each year the number of medical staff from the European Union willing to help in developing countries increases, and it is thus important to highlight issues of development. From the Middle Asian region, the Republic of Kazakhstan was chosen. At present, few studies have evaluated the prevalence of various types of partial edentulism in this region, and no research has investigated the prosthetic treatment choice in the various types of partial edentulism. The purpose of this study was to determine (i) the prevalence of various types of partial edentulism in patients seeking dental care and (ii) the type of prosthetic restoration most commonly chosen to treat these patients. MATERIALS AND METHODS: One hundred twelve patient records, together with panoramic radiographs, were studied. Various types of partial edentulism were grouped into four Kennedy classes. Patient records were used to examine which treatment option was chosen for each patient. RESULTS: The most prevalent type of partial edentulism in this patient sample was Kennedy type III, in both the maxilla (50.0%) and the mandible (41.1%). Partial edentulism was most frequently managed by fixed partial dentures (FPDs) in both jaws. Kennedy IV was the least prevalent (7.1% in the maxilla, 5.6% in the mandible) and in most cases treated with removable partial dentures (RPDs) in both jaws. CONCLUSION: Our results are consistent with previous research on the prevalence of Kennedy classes in Kazakhstan. RPDs were the most common type of prosthetic management for partial edentulism.

Dental functional status with and without tooth replacement in a Chinese adult population.

The objective of this study is to investigate the prevalence of missing teeth and prosthodontic replacements in a Chinese adult population using a hierarchical dental functional classification system. A total of 1,462 dentate subjects over 40 years from Shandong Province, China were included and categorized in the functional classification system with and without tooth replacements. Depending on replacements, subjects could be reclassified (promoted) to categories reflecting higher functionality. "Promotions" were considered indicators for prosthodontic effectiveness. Homogeneities after dichotomization into functional categories appeared to be moderate to good. In the "≥10 teeth in each jaw" branch, mean number of teeth and posterior occluding pairs were 27.93 ± 2.74 and 7.10 ± 1.94, respectively. In the branch "<10 teeth in each jaw," these figures were 16.17 ± 5.54 and 1.49 ± 1.45. Fixed dental prostheses (FDPs) added on average 3.5 artificial teeth; 46% of subjects with FDP promoted to a higher functional level. For removable dental prostheses (RDPs), these numbers were 8.5% and 79%, respectively. Promotion value per tooth added was significantly higher for FDPs. The classification system was able to quantify the effectiveness of teeth replacements. It was shown that RDPs were more effective when higher numbers of teeth were replaced, while FDPs were more effective per artificial tooth added.

Palatal and mandibular tori in a Romanian removable denture-wearing population.

OBJECTIVE: To establish the prevalence of palatal tori (TP) and mandibular tori (TM) in a Romanian denture-wearing population in order to see how or if tori influenced the denture design or the treatment planning. BACKGROUND DATA: There are no available data regarding tori in an elderly Romanian population and its implication for treatment planning. It could be considered a local factor influencing the quality of prosthetic treatment. MATERIAL AND METHOD: Tori prevalence was investigated in 251 patients, with an average age of 62years. A statistical analysis was made, using odds ratio (OR) for the distribution related to gender and the Chi-squared test for the differences in prevalence related to age groups. Treatment planning difficulties because of presence of tori were recorded. RESULTS: Frequency of TP was significantly higher in both genders (OR=2.0661 and p=0.0446) and non-significant frequency for distribution between genders for TM (OR=0.9421 and p=0.8273). The differences in age groups showed both tori types have a variable prevalence related to age. The most frequent location for TP was found in the posterior one-third and two-thirds of the palate and for TM in the canine and first premolar area presenting with different sizes. CONCLUSIONS: Tori prevalence in our study group is high and is significantly related to age (p<0.05) having a peak at over 60 years. The preferential site of TP in the posterior palatal area and this location has an impact on decision making in treatment planning for the upper denture.

A methodology to study the effects of prosthesis misfit over time: an in vivo model.

PURPOSE: Passive fit of implant-supported superstructures cannot currently be achieved. The aim of this investigation was to create a methodology that can be used to study the effects of prosthesis misfit in humans. MATERIALS AND METHODS: An edentulous patient received two interforaminal implants and a screw-retained bar for the retention of the mandibular denture. A corresponding in vitro model with strain gauges placed mesially and distally, adjacent to the implants, was fabricated to serve as a standardizing control. Over a period of 6 months, a total of 10 measurements on both the in vitro model and in the patient's mouth were conducted with newly fixed strain gauges on the bar. RESULTS: The in vitro experiments showed that no component wear at the abutment-bar interface had occurred and that repositioning of the strain gauges on the bar caused deviations in strain measurements up to 10.55%. In vivo, a reduction in strain development, from 445 to 383 Mum/m, was observed in the initial phase up to 12 weeks after bar insertion. Subsequently, the measurement values increased, and after a period of 24 weeks, they nearly reached the initial strain level (443 microm/m). Only minor changes in strain development of the bar could be detected; these might be a result of limited dynamic loading and the cortical architecture of the surrounding bone. Deviations in measurement accuracy caused by repositioning of the bar strain gauge are a limitation of this technique and should be eliminated in future studies. CONCLUSIONS: The present methodology can be applied to study changes in static implant loading over time in humans.

Patterns and reasons for tooth extraction at the Winterveldt Clinic: 1998-2002.

BACKGROUND: Tooth extraction is the most common form of dental treatment in developing countries despite significant advances in medicine and dentistry. Dental caries, periodontitis, orthodontics, trauma and prosthodontics are the main reasons for extractions. OBJECTIVE: To determine the patterns of tooth extractions and the reasons for these extractions in a primary care dental clinic attached to a dental training institution. METHODS: A descriptive, retrospective and quantitative study design was followed. Data was gathered from 3793 patient files to record the following variables: age, gender, type of tooth extracted and reason for the extraction. RESULTS: Almost 60% of teeth extracted were lower and upper molars. The main reasons for extractions were dental caries (47.9%) and periodontitis (22.6%). CONCLUSIONS: The findings of the study show an urgent need to reverse the trends in extractions and more emphasis should be placed on primary prevention in order to reduce tooth loss.

Survey on use of titanium dentures in Tsurumi University Dental Hospital for 11 years.

PURPOSE: The purpose of this study was to survey the production of titanium dentures in Tsurumi University Dental Hospital and to study the actual use of titanium dentures in our university. METHODS: The survey was based on the metal base dentures produced at Tsurumi University Dental Hospital during an 11-year period between April 1995 and March 2006, with relation to the types of metals used in the dentures, types of dentures, dental condition, and the number of artificial teeth. RESULTS: 1871 metal base dentures were produced in the study period. The dentures consisted of 1290 cobalt-chromium alloy dentures (68.9%), 350 titanium dentures (18.7%) and 231 platinum-added gold alloy dentures (12.3%). Within the titanium denture groups, 132 were complete dentures (37.7%), 55 were complete overdentures (15.7%) and 163 were removable partial dentures (46.6%). JIS type 3 pure titanium was used in the titanium base of 252 dentures (72.0%). The average number of artificial teeth was 10.9, which was the highest among the three types of metal bases, exhibiting significant differences (P<0.01). CONCLUSION: Approximately 32 titanium dentures per year on average were delivered at our university and they were applied to almost edentulous arch compared with the other metal base dentures.

Quality of removable partial dentures worn by the adult U.S. population.

STATEMENT OF PROBLEMS: Research-based assessments of the quality of removable partial dentures (RPDs), especially within a large patient population, are lacking. PURPOSE: This study evaluated the prevalence and quality of RPDs by use of the National Health and Nutrition Survey (NHANES III) data set. MATERIAL AND METHODS: Estimates of the health and nutritional status of the American population were obtained from the NHANES III data set (1988-1994). Calibrated dentists performed dental examinations on 17,884 adults. If the subject wore an RPD, its quality was assessed with 5 criteria: integrity, tooth wear, the presence of temporary reline material or adhesive, stability, and retention. In this study, the data on RPD defects were used to assess the prevalence of problems. The original population was divided into 4 subgroups: paired RPD data = subjects wearing both maxillary and mandibular RPDs (n = 600 prostheses, 300 maxillary and 300 mandibular); single RPD data = subjects with only one RPD (n = 1003 prostheses, 511 maxillary and 492 mandibular); maxillary versus mandibular RPD data = all subjects with all RPDs (n = 1603 prostheses, 811 maxillary and 792 mandibular); and pooled RPD data = all subjects with a single RPD plus subjects with 2 RPDs, counting only the RPD with the most defects (n = 1303 prostheses, 674 maxillary and 629 mandibular). The subjects were analyzed with descriptive statistics. The distribution of defects in the RPDs was examined for possible associations with chi(2) tests. The paired data for patients with both maxillary and mandibular RPDs were analyzed with Wilcoxon signed rank tests. The prevalence of RPDs as a function of patient age and the association between RPD defects and patient age were analyzed with chi(2) tests. The results were considered highly significant at P<.0001 and significant at P<.05. RESULTS: Of the 17,884 adults who underwent a dental examination, 1306 had RPDs. Three patients were excluded because their records were incomplete, leaving 1303 patients available for analysis. Most of the prostheses examined (65%) had at least 1 defect. Lack of stability was the most prevalent single defect. Distinctions in the type and prevalence of defects were observed between mandibular and maxillary RPDs. Mandibular RPDs had significantly more problems related to retention, whereas maxillary RPDs had significantly more problems related to the presence of reline material and to integrity defects. Tooth wear defects were significantly associated with patient age (P<.0001). Only one third of the RPDs were considered satisfactory according to NHANES III criteria. CONCLUSION: A review of the database used in this study indicated that, in spite of a decline in tooth loss, RPDs are still used in all age cohorts, including young adults. A large number of RPDs were found to have defects.

Accuracy of three corrective techniques for implant bar fabrication.

STATEMENT OF THE PROBLEM: Numerous articles emphasize the importance of passivity of implant-prosthetic component interfaces. Nonpassive interfaces can lead to bone loss, abutment fracture, and connecting screw breakage. PURPOSE: The purpose of this study was to evaluate 3 postcasting techniques for the correction of non-passive fit between a cast bar superstructure and its interface with an implant abutment. MATERIAL AND METHODS: Thirty implant Hader bars were fabricated based on a metal model composed of two 3.8/4.5 HL PME titanium implant abutments. Initial measurements were collected on the y-axis of the left implant abutment-bar interface by using a M2001ARS toolmaker microscope. Means were calculated from buccal, distal, and lingual measurements on each specimen. Ten specimens were sectioned, indexed, and corrected by casting the same alloy (group 1). Ten specimens were sectioned, indexed, and corrected by soldering (group 2). The last 10 specimens were submitted to 2 cycles of electrical discharge machining on a MedArc M-2 EDM machine (group 3). Postcorrection measurements were collected on the 3 groups. A 1-way ANOVA and a Tukey-Kramer test at a 0.05 significance level were performed on the 3 groups after the corrective techniques. RESULTS: Initial gap means were 192 microm for group 1, 190 microm for group 2, and 198 microm for group 3. There was a significant difference (P<0.05) in gap means between group 1 (15 microm) and group 2 (72 microm) as well as between group 2 and group 3 (7.5 microm) after each correction technique. No difference was detected between group 1 and group 3. CONCLUSION: The electrical discharge machining group resulted in the smallest mean gap distance of 7.5 microm, thus meeting the criteria of passive fit (within 10 microm) described in the literature.

Effectiveness of metal surface treatments in controlling microleakage of the acrylic resin-metal framework interface.

STATEMENT OF PROBLEM: Microleakage at the junction between the metal alloy and acrylic resin in a removable partial denture may result in discoloration, fluid percolation, and acrylic resin deterioration. The junction between a metal alloy and acrylic resin is an area of clinical concern. Failure of a removable partial denture may be linked to this interface. Enhancing resistance to microleakage at this interface may improve the long-term union between the 2 materials. PURPOSE: This investigation was designed to determine the effects of various metal surface treatment protocols on microleakage and bond strength between the metal alloy and acrylic resin used in the fabrication of a removable partial denture. MATERIAL AND METHODS: Ninety-six nickel-chromium-beryllium alloy specimens were randomly divided into 8 groups. After adaptation of baseplate wax, each specimen was invested. Subsequent to wax removal, each specimen was divided into a control half and an experimental half. Air abrasion, tinplating/oxidation, and silanation were evaluated individually and in all combinations. Heat-polymerized acrylic resin was processed against all specimens before storage in distilled water at 37 degrees C for 72 hours. Each specimen then was thermocycled in distilled water (3000 cycles) before immersion in sodium fluorescein dye for 24 hours. Counting grids that exhibited dye penetration under ultraviolet light exposure allowed assessment of microleakage. RESULTS: Air abrasion resulted in a significant decrease in microleakage when used individually and in all combinations (P<0.05). All experimental combinations that did not involve air abrasion demonstrated no significant reduction in measured microleakage between the experimental and control sides. Tukey's pair-wise comparison of the difference in the mean number of squares exhibiting microleakage between the control and treated sites for each experimental group revealed a significant difference, based on the involvement of air abrasion. Groups involving air abrasion did not differ significantly from each other (P<0.05). In addition, no significant difference was detected between groups not involving air abrasion (P<0.05). CONCLUSION: Air abrasion, alone and in combination with tinplating/oxidation and with silanation, resulted in a significant reduction in microleakage between the metal alloy and acrylic resin.

In vivo force measurements on maxillary implants supporting a fixed prosthesis or an overdenture: a pilot study.

STATEMENT OF PROBLEM: In this preliminary study, an attempt was made to measure in vivo forces simultaneously on 5 maxillary implants with different types of superstructure. MATERIAL AND METHODS: Force measurements were carried out on 1 test patient with 5 ITI implants in the edentulous maxilla. A screw-retained fixed complete denture and an overdenture were fabricated for comparative measurements of forces. The overdenture could be mounted to 2 different types of bars. The measuring method was used with piezo-electric force transducers that were directly mounted onto the implants. This allowed for simultaneous measurements of forces in 3 dimensions, ie, in axial and transverse directions. Static and functional forces such as maximum biting (clenching), biting on a bite plate, and chewing food were registered. All measurements were repeated in the same way 2 years later. RESULTS: The registered forces exhibited similar force patterns with both types of superstructure and both types of bars for overdenture connection. The force magnitudes were significantly different for the 3 dimensions (P<.05) with highest forces along the implant axis. On the posterior implants, force magnitudes were significantly higher (P<.05) than on the anterior implants in all 3 dimensions. On the anterior implants, under some test conditions, the transverse force components reached up to 100% of the axial force or even exceeded it during the chewing of food. During maximum biting, no upward force (tensile force) was found on any implant with the fixed complete denture, but upward force was found on one anterior implant with the overdenture. When chewing food, small force magnitudes in upward directions were regularly found with both superstructures. The force patterns between the first and second registrations showed similar trends, and no obvious differences were found. CONCLUSION: From these results it was concluded that similar patterns of force transmission onto the implants are observed with a fixed complete denture and an overdenture connected to maxillary implants. The bar design did not significantly influence the force pattern.