The International Journal of Prosthodontics, 05/2011

Purpose: The aim of this research was to determine the long-term prosthodontic maintenance requirements of mandibular two-implant overdentures using different loading protocols and attachment systems. Materials and Methods: A total of 106 participants were allocated randomly to one of four different implant systems (Steri-Oss, Southern, Straumann, or Brånemark). Three different loading protocols (2, 6, and 12 weeks) were used with six different ball abutment patrices and their respective matrices (Steri-Oss rubber, Straumann gold, Straumann titanium, Brånemark gold, Southern plastic, and Southern gold/platinum). Prosthodontic maintenance events were documented prospectively from baseline until the 8-year recall according to predefined categories. Results: After 6 years, 90 participants attended recall and, thereafter, 68 participants were followed for 8 years. No significant differences were found between the number of prosthodontic maintenance events and the loading protocol used. Steri-Oss rubber matrices had the highest mean number of maintenance events at 32.2 ± 14.5 events, followed by the Brånemark gold matrices at 28.8 ± 12.6 events. The Southern plastic matrices had a significantly lower mean number of maintenance events (8.7 ± 4.2) when compared with all other groups. Over a 6-year period, the matrices with the best longevity were Straumann gold at 3.9 ± 2.1 years. Straumann gold matrices also lasted significantly longer than all other matrices (P .05). Southern gold/platinum, Brånemark gold, and Southern plastic matrices all lasted significantly longer than the Straumann titanium and Steri-Oss matrices (P .05). The mean time to reline for overdentures was 3.37 ± 2.06 years; remaking of overdentures peaked by year 7, with a mean time to remake of 5.81 ± 2.04 years. Conclusion: Early loading protocols do not influence long-term prosthodontic maintenance requirements of unsplinted mandibular two-implant overdentures. By contrast, attachment systems do influence prosthodontic maintenance, particularly with regard to the type of matrices used.

Purpose: This paper aimed to practice evidence-based dentistry by critically appraising relevant evidence to address a common question in prosthodontics. It sought to answer whether the survival and complication rates of all-ceramic fixed dental prostheses (FDPs) were comparable or superior to those of metal-ceramic FDPs, and to use this knowledge to guide clinical decisions. Materials and Methods: A 6S search was conducted. No decision support systems or summaries were available. The journal Evidence-Based Dentistry (zero synopses), Trip database (three synopses, discarded), Cochrane database (three systematic reviews, discarded), MEDLINE OVID (six systematic reviews, one accepted), and Embase (zero systematic reviews) were searched. The selected systematic review assessed the survival and complication rates of all-ceramic and metal-ceramic FDPs. One additional prospective cohort study was considered relevant. Results: The systematic review addressed a well-focused clinical question, but its internal validity was compromised. The search was not systematic; inclusion methodology and impact of study characteristics on results were unclear. The external applicability was limited by compromised internal validity, broad outcome definitions, inaccurate results, and incomplete examination of stated aims. With care, however, the results could be applied to clinical practice. Estimated event rates and 5-year outcomes with a 95% confidence interval were calculated, with the survival rate of metal-ceramic FDPs significantly higher than that of all-ceramic FDPs. All-ceramic FDPs experienced a high incidence of technical failure. The prospective cohort addressed a well-focused clinical question with good internal validity. It compared outcomes of metal-ceramic FDPs provided before and after the introduction of implant therapy. Patient cohorts were clearly defined, similar at baseline, and treated equally. Ten-year Kaplan-Meier cumulative survival with standard errors was reported. Metal-ceramic FDP survival rates were high and significantly improved since the introduction of implants and the decreased use of structurally compromised abutments. Conclusion: The results of the systematic review and prospective cohort were complementary: Metal-ceramic FDPs had high survival, with a significantly greater 5-year survival rate than all-ceramic FDPs. Differences in complications were unknown, but evidence indicated that the complication incidence of metal-ceramic FDPs was lower than that of all-ceramic FDPs. This evidence was directly applicable to the clinical scenario and will help guide clinical decision making.

Purpose: The aim of this research was to explore the relationship between chewing ability and dental functional status, perceived oral health-related quality of life, and a number of background variables in a Vietnamese population. Materials and Methods: The cluster stratified sample consisted of 2,805 dentate subjects aged >= 20 years from urban and rural areas in Southern Vietnam. Chewing ability was assessed using a questionnaire that included questions on perceived difficulty with respect to eight foods and three questions of the Oral Health Impact Profile that were considered relevant. Results: Only a minority reported serious problems with chewing ability (reporting difficult or very difficult to chew). The logistic regression analysis on chewing ability outcomes showed significant relationships between chewing ability and having >= 10 teeth in each arch, having sufficient molar regions (>= 1 molar posterior occlusal pair [POP] bilaterally) for hard and soft foods, and having sufficient premolar regions (>= 3 POPs), especially for hard foods. In the hierarchical functional classification system, likelihood to report complaints on chewing ability appeared to discriminate in the branch ">= 10 teeth in each arch." Likelihood at subsequent levels ranged from approximatel 1.5 to 3. In the branch " 10 teeth in each arch," likelihood did not discriminate because the groups lacked sufficient homogeneity. Conclusions: Chewing ability and oral health-related quality of life were positively correlated. Among all dental and other variables, decreased chewing ability was strongest when correlated with older age categories and not correlated or weakly correlated with sex, socioeconomic status, and residence.

Purpose: The aim of this research was to investigate possible factors behind the desire for and changes in attitude toward implant treatment in a population of middle-aged and older individuals in Sweden. Materials and Methods: In 1989 and 1999, questionnaires were sent to 3,000 residents in Örebro County, Sweden. Response rates were 79% and 68%, respectively. Those responding to both questionnaires yielded a longitudinal study panel. Logistic regression models were done with "desire of implant treatment" and "changes in desire of implant treatment" as dependent variables. Results: Older people, non-city residents, and those with one or several missing and unreplaced teeth changed their desire for implant treatment between study years. Effects of age, residence, and better dental status disappeared during the 10-year study period. Those who were edentulous and those with removable dentures (pseudo R2: 0.17) expressed lower desire for treatment than those with all teeth remaining or only one or a few teeth missing (pseudo R2: 0.24) in 1989. High income significantly increased the probability to desire implant treatment for the study panel at both study occasions (P = .016 and P = .034 for 1989 and 1999, respectively). Conclusions: Factors influencing desire for implant treatment were primarily income and dental status. The influence of young age, urban living, and dental status regarding the subgroup with one or several teeth missing in relation to those with all their teeth disappeared during the 10-year study period.

Purpose: The implant-abutment connection (microgap) influences the peri-implant bone morphology. However, it is unclear if different microgap configurations additionally modify bone reactions. This preliminary study aimed to radiographically monitor peri-implant bone levels in two different microgap configurations during 3 months of nonsubmerged healing. Materials and Methods: Six dogs received two implants with internal Morse taper connection (INT group) on one side of the mandible and two implants with external-hex connection (EXT group) on the other side. One implant on each side was positioned at bone level (equicrestal); the second implant was inserted 1.5 mm below the bone crest (subcrestal). Healing abutments were attached directly after implant insertion, and the implants were maintained for 3 months without prosthetic loading. At implant placement and 1, 2, and 3 months, standardized radiographs were taken to monitor peri-implant bone levels. Results: All implants osseointegrated. A total bone loss of 0.48 ± 0.66 mm was measured in the equicrestal INT group, 0.69 ± 0.43 mm in the equicrestal EXT group, 0.79 ± 0.93 mm in the subcrestal INT group, and 1.56 ± 0.53 mm in the subcrestal EXT group (P > .05, paired t tests). Within the four groups, bone loss over time became significantly greater in the EXT groups than in the INT groups. The greatest bone loss was noted in the subcrestal EXT group. Conclusion: Within the limits of this animal study, it seems that even without prosthetic loading, different microgap configurations exhibit different patterns of bone loss during nonsubmerged healing. Subcrestal positioning of an external butt joint microgap may lead to faster radiographic bone loss.

A high level of clinical skill is required for fabricating a provisional fixed partial denture with fiber-reinforced composite resin (FRC) using either the direct or chairside technique. The freehand approach to restoring missing teeth represents a challenge to the clinician, particularly when shaping and finishing a hygienic pontic. This technical report describes a simplified method for chairside fabrication of a fixed dental prosthesis with FRC. It is based on using a translucent template to guide the buildup procedure and to ensure optimal anatomy and function.

The influence of abutment design on bone resorption around immediately loaded and osseointegrated implants used to support fixed partial prostheses was investigated in a 1-year study. One hundred ten implants were placed in 24 anterior partially edentulous maxillae. The probing depths of each implant were measured 6 and 12 months after abutment placement and analyzed statistically. Total probing depth was 1.75 ± 0.75 mm. There were significant differences between non- and submerged implants with angled abutments and between submerged implants with straight and angled abutments. No significant differences were observed between non- and submerged implants with straight abutments and between nonsubmerged implants with straight and angled abutments. Bone resorption around dental implants is influenced by the abutment design and the associated implantation protocol.

Purpose: This study was designed to investigate potential discrepancies between the depth and width of the mandibular denture anterior lingual flange and the alveolingual sulcus and to measure the changes in retention when flange lengths were modified to optimal dimensions in a sample population of elderly edentulous subjects. Materials and Methods: The anterior lingual flange and alveolingual sulcus were measured in 66 randomly selected elderly Taiwanese denture patients. The length and width of corresponding regions of the anterior lingual flange and alveolingual sulcus were compared. Mandibular denture retention was recorded and compared prior to and following modification of the anterior lingual flange with border molding. Results: A significant statistical difference existed between the mean anatomical dimensions of the alveolingual sulcus and the corresponding denture flanges. Following functional border molding, the mean retention of the mandibular denture increased in a statistically significant manner. Conclusion: The discrepancies between the anterior lingual denture flange and alveolingual sulcus dimensions appeared to significantly diminish mandibular denture retention and reinforce the value of proper flange extensions in the sublingual region.

Purpose: The influence of resilient support of abutment teeth on the fracture resistance of all-ceramic three-unit fixed partial dentures (FPDs) was tested in this study. Materials and Methods: Three groups (n = 8) of glass-infiltrated, alumina-based, all-ceramic FPDs that were adhesively bonded to human molar teeth were investigated. In control group A, teeth that were rigidly inserted in polymethyl methacrylate (PMMA) resin were used for thermocycling and mechanical loading (TCML), as well as for fracture testing. In group B, TCML was conducted on teeth that had their roots covered with a polyether layer. After TCML, the polyether layer was removed entirely, and the teeth were rigidly fixed in PMMA for fracture testing. In group C, teeth roots remained covered with a polyether layer during TCML as well as during fracture testing. Using a resilient attachment, tooth mobility was determined in axial, buccal, and oral directions. Results: Mean tooth mobility was 76 ± 4 µm in the axial direction, 278 ± 41 µm in the buccal direction, and 128 ± 17 µm in the oral direction. Group C showed the lowest mean fracture strength (polyether during both TCML and fracture testing) of 523 N. For group B (polyether during TCML but not during fracture testing), a fracture strength of 676 N was found, and for control group A (rigidly embedded teeth), it was 919 N. Conclusion: These results confirmed the influence of resilient attachments on the aging process and fracture strength testing of FPDs. Fracture resistance was significantly reduced when this particular interface was used in both TCML and fracture testing.

The aim of this research was to compare the accuracy outcomes of open- and closed-tray implant impressions for partially edentulous patients. Eleven partially edentulous spaces in seven patients with two existing implants for fixed partial dentures were included. Group I (closed-tray) and group II (open-tray) were compared using microcomputed tomography scanning. No statistically significant differences were found between the closed- and open-tray techniques (P = .317). The subjective evaluation of patient comfort showed no differences with either impression technique. There were no differences seen between open- and closed-tray impression techniques in partially edentulous patients when implants had less than 10 degrees of angulation.

Purpose: The objectives of this study were to investigate the nature of recently published prosthodontic literature, to investigate the types of collaboration and funding as well as their relationship, and to analyze the associations between collaboration and extramural funding. Materials and Methods: Three peer-reviewed prosthodontic journals were used for the analysis of articles published in 1998, 2003, and 2008. The articles were analyzed based on associations between the type of article, type of original research, collaboration, and funding. The chi-square test and logistic regression were used for data analysis (α = .05). Results: From 998 articles, a significant decrease in reviews (P .001) and an increase in case reports (P = .001) were observed. Articles regarding dental materials ranged from 53% to 58% of the total original research, and the amount of collaboration among disciplines (P = .012), institutions (P .001), and countries (P = .014) increased from 1998 to 2008. Most studies (77.5%) did not report funding, and articles related to dental materials had the most collaboration and funding. Dental materials (48%), clinical care (37%), and education/public health research (7%) were supported by private companies, and biomedical and translational studies were mostly supported by a university (13%) or the government (7%). A strong association was noted between collaboration (P = .010), extramural funding, and original research, especially related to education/public health (P .001), clinical care (P = .013), and dental materials (P = .004). Conclusion: An increase in original research and collaboration was observed from 1998 to 2008. Studies that reported funding remained constant. A strong association with collaboration and funding was observed, along with studies involving clinical care, education, public health, and dental materials.

The aim of this research was to quantify the strain development of three-unit implant-supported fixed partial dentures (ISFPDs) copy milled from zirconia ceramic. Three ISFPD groups (n = 10) were fabricated by means of casting, copy milling, and computer-aided design/computer-assisted manufacturing (CAD/CAM) to fit an in vitro model with two implants. During cementation of the restorations, the emerging strains were recorded using strain gauges attached to the cast material mesially and distally adjacent to the implants. Absolute mean strain development ranged from 85.39 µm/m to 326.83 µm/m at the different strain gauge locations. Fabrication method had a significant effect on strain development (multivariate analysis of variance, P = .011), with the cast restorations showing the highest strain development and the CAD/CAM-fabricated ISFPDs showing the lowest. Copy milling leads to ISFPs that are more precise than cast restorations but less precise than CAD/CAM-fabricated restorations.