Comparison of position repeatability of a human operator and an industrial manipulating robot

STATEMENT OF PROBLEM: Implant-supported restorations in the partially edentulous jaw have been performed at the Mayo Clinic for more than 10 years. Clinical performance of the implants and the prostheses should be reported to ensure effectiveness of this procedure. PURPOSE: This retrospective study described results for implant survival, implant fracture rate, prosthetic complications, and design changes that may impact these results. MATERIAL AND METHODS: A retrospective chart review was conducted of all registered implant patients in a large multispecialty medical center. Patients with a partially edentulous jaw who had received endosseous implants to support and retain dental prostheses were included in this review. Implant survival and fracture, prosthetic complications, and demographic data were recorded and analyzed through Kaplan-Meier methods. RESULTS: A total of 1170 implants were placed in four anatomic locations: anterior maxilla, posterior maxilla, anterior mandible, or posterior mandible. Location of implants was shown to have no effect on implant survival (p = 0.7398), implant fracture rates (p = 0.2385), screw loosening (p = 0.8253), or screw fracture (p = 0.2737). Development of new restorative components has resulted in significantly better rates of implant survival without fracture (p = 0.0054), screw function without loosening (p < 0.0001) and screw function without fracture (p = 0.0013). Implant survival seems to have been improved with the new components (p = 0.0513). CONCLUSIONS: Implant survival in this study was independent of anatomic location of implants. Virtually all clinical performance factors were improved by design changes in implant restorative components that were brought to market in early 1991.     

Survival of cylindrical implants in composite grafted maxillary sinuses

PURPOSE: This retrospective study investigated the survival of dental implants placed in the maxilla after composite grafting of the sinus and an average of 55 months of loading. PATIENTS AND METHODS: Maxillary sinuses of 88 patients were grafted with autogenous cancellous bone combined with dense hydroxyapatite particles. After an average healing period of 3.4 months, hydroxyapatite-coated titanium endosseous implants were placed. A total of 388 implants were placed in grafted sinus floors, and 82 were placed in onlay grafted nonsinus position in the canine region. The implants were loaded with overdentures and fixed bridges 4 months (mean) after implantation, with a follow-up for a mean of 55 months. RESULTS: The cumulative implant survival was calculated according to the Kaplan-Meier method. Implant survival from the time of loading was 89% in full reconstructed cases and 90% in partially edentulous cases. The overall cumulative implant survival rate, including the loss in the surgical stage, was 82%. CONCLUSION: Implant loss in composite grafted maxillae after 70 months of follow-up was similar to loss in nongrafted maxillae.     

Clinical evaluations of a porous-surfaced endosseous implant system

Clinical evaluations of a new porous-surfaced implant concept (Endopore) in a large population of fully and partially edentulous patients are reported, and a technique of spreading buccal and lingual plates with osteotomes to place these implants in proximity to the sinus of the posterior maxilla is described. Three-dimensional, interconnecting pores on this implant's bone interface surface give a great surface area for bone engagement. When the maxilla is prepared by this spreading procedure, these implants can be successfully placed in areas having limited available bone. Our success rates are 97.0% for implants stabilizing a mandibular overdenture and 94.8% for implants placed in partially edentulous patients. Many times, sinus lift or other augmentation procedures can be avoided in the maxilla and mandible, allowing for less patient morbidity and for an implant reconstruction that is more affordable for the patient.     

The effect of strenuous versus moderate exercise on the metabolism of proteoglycans in articular cartilage from different weight-bearing regions of the equine third carpal bone

In the present multi-center study, non-submerged ITI implants were prospectively followed to evaluate their long-term prognosis in fully and partially edentulous patients. In a total of 1003 patients, 2359 implants were consecutively inserted. Following a healing period of 3-6 months, the successfully integrated implants were restored with 393 removable and 758 fixed restorations. Subsequently, all consecutive implants were documented annually up to 8 years. At each examination, the clinical status of all implants was evaluated according to predefined criteria of success. Therefore, the data base allowed the evaluation of 8-year cumulative survival and success rates for 2359 implants. In addition, cumulative success rates were calculated for implant subgroups divided per implant type, implant length, and implant location. Furthermore, the actual 5-year survival and success rates could be determined for 488 implants. During the healing period, 13 implants did not successfully integrate, whereas 2346 implants fulfilled the predefined criteria of success. This corresponds with an early failure rate of 0.55%. During follow-up, 19 implants were classified as failures due to several reasons. In addition, 17 implants (approximately 0.8%) demonstrated at the last annual examination a suppurative periimplant infection. Including 127 drop out implants (= 5.4% drop out rate) into the calculation, the 8-year cumulative survival and success rates resulted in 96.7% and 93.3%, respectively. The analysis of implant subgroups showed slightly more favorable cumulative success rates for screw type implants (> 95%) compared to hollow-cylinder implants (91.3%), and clearly better success rates for mandibular implants (approximately 95%) when compared to maxillary implants (approximately 87%). The actual 5-year survival and success rates of 488 implants with 98.2% and 97.3%, respectively, were slightly better than the estimated 5-year cumulative survival and success rates of 2359 implants indicating that the applied life table analysis is a reliable statistical method to evaluate the long-term prognosis of dental implants. It can be concluded that non-submerged ITI implants maintain success rates well above 90% in different clinical centers for observation periods up to 8 years.     

Clinical assessment of olfactory dysfunction in Parkinson''s disease

The possibility of placing endosseous implants in the edentulous maxilla is frequently reduced by inadequate bone volume of the residual ridge. In totally edentulous maxillae with knife-edge conformation, insufficient thickness is frequently associated with insufficient height of the residual ridge in the posterior maxilla because of pneumatization of the maxillary sinuses. This surgical method combines grafting of the maxillary sinuses, onlay grafts on the buccal side of maxillary posterior segments, and sagittal osteotomy of the anterior maxilla with interpositional bone grafts. Five to six months after maxillary reconstruction, Br?nemark implants were placed and, after osseointegration occurred, implant-supported dental prostheses were fabricated. Three patients have been treated with this method and 22 implants have been placed. The mean follow-up after final prosthetic rehabilitation has been 16 months; survival rate has been 100%. Despite the small number of patients and the short follow-up, preliminary results have shown very promising results.     

Long-term follow-up on hydroxylapatite-coated cylindrical dental implants: a comparison between developmental and recent periods

PURPOSE: To compare success rates for dental implants placed from 1985 through 1988 and from 1989 through 1991, and to investigate the factors associated with success or failure. PATIENTS AND METHODS: All hydroxylapatite-coated cylindrical implants placed from 1985 through 1991 were followed yearly. Lifetable survival analyses compared implant success for a "developmental period" from 1985 through 1988 (4 to 8 years follow-up) and a "recent period" from 1989 through 1991 (1 to 4 years follow-up). Reasons for success or failure, time from implant placement to removal related to failure reason, outcome after implant removal, and a morbidity analysis are included. RESULTS: The 7 to 8-year cumulative success rate for all implants placed in the developmental period (maxilla and mandible combined) was 86.5%; it was 84.2% for all maxillary implants and 87.5% for all mandibular implants. The cumulative success rate for all implants placed in the recent period was 97.5%; it was 97.5% for all maxillary implants and 97.6% for all mandibular implants. The difference between the two periods was statistically significant only for the anterior maxilla. Regression analysis on the interval success rates indicates that interval failure did not follow a linear relationship with time. The most common reasons associated with failure were lack of keratinized gingiva, poor oral hygiene, mechanical overload, and malposition. CONCLUSION: Comparison with previously reported cumulative success rates indicated learning curve experiences comparable with other implant systems. Improvements in hardware, surgical and prosthetic techniques, and patient selection have led to an improvement in success rates with the recent period implants.     

Increase in skeletal muscle protein content by the beta-2 selective adrenergic agonist clenbuterol exacerbates hypoalbuminemia in rats fed a low-protein diet

Between 1990 and 1995, 214 implants were placed in 29 maxillae and mandibles of 22 patients following extraction of all residual teeth as a consequence of severe periodontal disease. All patients were discharged wearing immediate dentures. The implants were analyzed with regard to the number per arch, location, length, and diameter. The 5-year cumulative survival rate was 98.5%. The mean number of implants per arch was 7.5 for the maxilla and 7.2 for the mandible. The preferred implant locations were canines, central incisors, lateral incisors, and second premolars in the maxilla; and lateral incisors, first molars, and canines in the mandible. The mean implant length was 14.7 mm in the mandible and 14.5 mm in the maxilla. The mean implant diameter was 3.8 mm in the maxilla and 3.8 mm in the mandible. The results of the present study indicate that immediate implantation for fixed full-arch reconstruction can be considered a viable treatment alternative in patients with severe periodontal disease.     

A meta-analysis of implants in partial edentulism

A meta-analytic technique was used to estimate the survival of implants supporting bridges or single crowns in partially edentulous patients. A survey of the literature revealed 66 studies, published between 1986 and 1996. Nine studies on single implants and 10 studies on fixed partial dentures met the inclusion criteria for the meta-analysis. Data from a total of 2686 implants, 570 single crowns (SC) and 2116 in fixed partial dentures (FPD), were analyzed. In order to calculate annual survival rates for individual studies a life-table analysis was conducted. Maximum follow-up time ranged between 1 and 8 years. After 1 year the success rate was calculated to be at least 85.7% for FPD and 97.2% for SC. When the results from the FPD studies were pooled the survival rate was 93.6% after 6-7 years. The corresponding value for SC was 97.5%.     

The dark side of dioxygen biochemistry

The aim of this study was to evaluate the clinical function and long-term prognosis of overdentures retained by a small number of implants in the maxilla and mandible using one of two different attachment systems. Included in the study were all patients referred to specialty clinics in J?nk?ping and Link?ping, Sweden, during the treatment period who needed an overdenture and could be provided with a minimum number of two bilaterally-placed implants. Excluded were patients with bone-grafted jaws, irradiated cancer patients, heavy bruxers, and patients who had lost a fixed prosthesis because of implant losses. The patients were randomly assigned to receive one retentive system, either a round 2-mm-diameter bar with clips or ball attachments (Nobel Biocare). Eighteen overdentures were placed in maxillae and 32 in mandibles, supported by a total of 115 Br?nemark implants. Of the implants placed, 86.1% were continuously osseointegrated. The cumulative implant survival rates after 7 years of loading were 75.4% in the maxillae and 100% in the mandibles. There was no difference in implant survival rate between the attachment systems. Patients with implant losses were characterized by severely resorbed maxillary ridges and inferior bone quality, together with unfavorable loading circumstances such as short implants combined with long leverages. Complications and prosthetic adjustments were mostly resolved early and easily.     

Clinical and microbiological status of osseointegrated implants

Peri-implantitis, an inflammatory response around implants, has a poorly defined etiology and pathogenesis. To better understand the role of specific microorganisms in this disease process, clinical and microbiological parameters were examined in 24 patients with 98 osseointegrated implants. Sites were evaluated for probing depth (PD), plaque/calculus index (PI), gingival bleeding index (GBI), mobility, and crevicular fluid flow rate (CFFR). Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia in subgingival plaque were identified by latex agglutination assays. Clinically, a statistically significant correlation (P < 0.001) was observed between probing depth and the length of time an implant was present. Mobility was also significantly greater (P < 0.001) in the maxillary than in the mandibular implants. Subgingival sites harboring one of the three microorganisms had significantly greater PD, GBI, and CFFR than non-colonized sites. Implants in partially edentulous patients more frequently were colonized with P. gingivalis/P. intermedia than edentulous patients. The incidence of these microorganisms also correlated with fixture longevity. Implants present for 3 to 4 years had a significantly greater frequency of test microorganisms than implants present for 1 to 2 years. These findings suggest that microbial pathogens associated with periodontitis occur more commonly around implants exhibiting gingival inflammation (GBI) and may contribute to peri-implantitis.     

Proteoglycan expression by human trabecular meshworks

The aim of the present study was to clinically assess the peri-implant and periodontal conditions 1 year after placement of oral implants (ITI Dental Implant System) in partially edentulous patients. In all, 127 patients (median age 50 years, range 17 to 79) were examined. They were all treated according to a concept of comprehensive dental care and had received fixed partial dentures (FPD). Significant differences were observed between implants and contralateral control teeth with respect to mean pocket probing depth (PPD) (2.55 mm at implants/2.02 mm at teeth), mean probing attachment level (PAL) (2.97 mm/2.53 mm) and bleeding on probing (BOP) (24%/12%) (Wilcoxon matched pairs sign rank test, P < or = 0.01), whereas mean modified plaque index (0.22/0.30), mean modified bleeding index (0.35/0.44) and mean recession (-0.42 mm/-0.51 mm) did not significantly differ between implants and teeth. Compared to control teeth, the width of keratinized mucosa at implants was significantly smaller at lingual, but not at buccal aspects. Regression analyses showed no significant association between the amount of keratinized mucosa and degree of inflammation. Recession, PPD and PAL were slightly influenced by the amount of keratinized mucosa indicating greater resistance to probing. Grouping the implants according to various lengths, type of fixation of the FPD or combination with natural teeth did not result in statistically significant different clinical parameters, whereas grouping according to different localization within the oral cavity did. For example, the mean PAL in 83 anterior implants was 2.52 mm, whereas 175 posterior implants had a mean PAL of 3.18 mm (Mann-Whitney U-test, P < or = 0.01). Regression analyses between the mean PAL for all implants in each patient and the mean PAL of the corresponding dentition revealed an r2 of 0.23 (P < or = 0.01). Using multiple regression analysis, the mean PAL of the implants showed to be significantly influenced by the combined factors "fullmouth" PII, "fullmouth" BOP and mean PAL of all teeth. The results of this study suggest that in partially edentulous patients the overall periodontal condition may influence the clinical condition around implants and thus reinforces the importance of periodontal treatment prior to and supportive periodontal therapy after the incorporation of osseointegrated oral implants.     

Load factor control for implants in the posterior partially edentulous segment

There are inherent biomechanical differences in the implant treatment of completely edentulous arches and posterior partially edentulous segments. The partial prosthesis does not benefit from cross-arch stabilization and is, therefore, more susceptible to bending loads. Because of the difference in mobility between teeth and implants, implants may carry a major share of load when mixed with teeth in the same quadrant. However, the frequency of implant overload in posterior partial restorations is low, and, with appropriate treatment planning, overload in these situations is almost always preventable. A checklist procedure is proposed to help the clinician enumerate and evaluate deleterious load factors. By screening patients for such factors in advance, the clinician may identify and avoid potential overload situations when conceiving and fabricating implant-supported posterior partial prostheses. A second checklist, for use at follow-up appointments, lists alarm factors that serve as an early warning of overload once the prosthesis is in place.     

Titanium screw implants for intermaxillary fixation of partially edentulous jaw

Establishment of the best possible relationship between upper and lower teeth is very important when treating jaw fractures and orthognathic deformities in partially edentulous patients. Many surgeons use arch bars and acrylic splints for intermaxillary fixation (IMF) to obtain the best occlusal relationships after the operation. In patients with sufficient teeth, IMF is not so difficult to realize. However, in partially edentulous patients, the available teeth may not be sufficient to apply arch bars or splints. This paper describes a system for IMF of a partially edentulous jaw. Screws made of medical-grade titanium are implanted into the alveolar ridges where two or more teeth are missing. Arch bars or acrylic splints secured on these implants and available teeth can be used safely for IMF. In vitro axial pull-out tests demonstrated that these implants can withstand the traction forces generated by elastics. Five partially edentulous patients, three with mandibular fractures and two with orthognathic problems, were treated with these implants. All patients healed without any complications and with the best possible occlusal relationships.     

Biological factors contributing to failures of osseointegrated oral implants. (I). Success criteria and epidemiology

The aim of this review was to offer a critical evaluation of the literature and to provide the clinician with scientifically-based diagnostic criteria for monitoring the implant condition. The review presents the current opinions on definitions of osseointegration and implant failure. Further, distinctions between failed and failing implants are discussed together with the presently used parameters to assess the implant status. Radiographic examinations together with implant mobility tests seem to be the most reliable parameters in the assessment of the prognosis for osseointegrated implants. On the basis of 73 published articles, the rates of early and late failures of Br?nemark implants, used in various anatomical locations and clinical situations, were analyzed using a metanalytic approach. Biologically related implant failures calculated on a sample of 2,812 implants were relatively rare: 7.7% over a 5-year period (bone graft excluded). The predictability of implant treatment was remarkable, particularly for partially edentulous patients, who showed failure rates about half those of totally edentulous subjects. Our analysis also confirmed (for both early and late failures) the general trend of maxillas, having almost 3 times more implant losses than mandibles, with the exception of the partially edentulous situation which displayed similar failure rates both in upper and lower jaws. Surgical trauma together with anatomical conditions are believed to be the most important etiological factors for early implant losses (3.60% of 16,935 implants). The low prevalence of failures attributable to peri-implantitis found in the literature together with the fact that, in general, partially edentulous patients have less resorbed jaws, speak in favour of jaw volume, bone quality, and overload as the three major determinants for late implant failures in the Br?nemark system. Conversely, the ITI system seemed to be characterized by a higher prevalence of losses due to peri-implantitis. These differences may be attributed to the different implant designs and surface characteristics. On the basis of the published literature, there appears to be a number of scientific issues which are yet not fully understood. Therefore, it is concluded that further clinical follow-up and retrieval studies are required in order to achieve a better understanding of the mechanisms for failure of osseointegrated implants.     

The mandibular staple bone plate: a long-term retrospective evaluation

PURPOSE: Clinical and radiographic parameters and denture satisfaction were evaluated in a long-term retrospective study of patients treated with the mandibular staple bone plate. PATIENTS AND METHODS: Fifty-six edentulous patients were treated with the mandibular staple bone plate to stabilize their lower denture. The mean evaluation period was 103 months (range, 84 to 139 months). Peri-implant mucosa and bone height were scored, together with quality of the prosthesis and prosthodontic maintenance care. Denture satisfaction was assessed by using two questionnaires. RESULTS: Four staple bone plates were removed during the evaluation period, and one appeared to be fractured. The remaining 51 staple bone plates were functional without any signs of major complications (survival rate, 91%). No further alveolar resorption in the interforaminal region of the mandible took place during the evaluation period. Patients were very satisfied with the prosthetic construction. CONCLUSIONS: The mandibular staple bone plate is a good modality to stabilize the lower denture. However, endosseous implant systems are preferred because of comparable success rates with a more simple operative procedure.     

Mutation analysis and expression of the mottled gene in the macular mouse model of Menkes disease

OBJECTIVES: The purpose of this study was to evaluate the ability of two different panoramic imaging systems to produce cross-sectional images with accurate vertical dimensions of the posterior mandible. STUDY DESIGN: Three partially edentulous human cadaver mandibles were used for this study. On each mandible, three potential implant sites were arbitrarily identified in an area between the mental foramen and the ascending ramus. Each site was imaged using two different panoramic machines. Using each image, the mandible's outline, cortical thickness, and position of the mandibular canal were traced on clear acetate film. The mandibles were then sectioned at each site to serve as a gold standard. The cadaver sections and tracings (corrected for magnification) were measured, recording the overall mandibular height, distance from the crest of the ridge to the superior aspect of the mandibular canal, and the thickness of the cortical bone at the most inferior aspect of the mandible. RESULTS: There were no significant differences between either of the system's image measures and the gold standard when considering the distance between the crest and the mandibular canal. Differences were noted between the systems measures and the gold standard in the assessment of the cortical bone thickness and the overall mandibular height. CONCLUSIONS: Both imaging systems can be useful for vertical measurements of a potential implant site in the posterior mandible.     

Short (6-mm) nonsubmerged dental implants: results of a Multicenter clinical trial of 1 to 7 years

Limited bone height restricts the use of long dental implants, so short implants may be selected in these situations. Recent reports on clinical results with short implants have been negative, however, and have suggested that indications for the use of these implants are limited. To verify these findings, a multicenter study of short ITI implants was carried out. In a 6-year period 253 short implants with a length of 6 mm were placed into 126 patients, who were followed up from 1 to 7 years. Altogether 7 implants were removed; 6 of these were located in the maxilla and 1 in the mandible. The quality of survival was comparable with the clinical results of longer implants from the same implant system. Although the clinical results of these short implants were favorable, it is recommended that they be used in combination with longer implants, especially when used in the less dense bone that is often seen in the maxilla.     

Advanced surgical procedures: bone augmentation

Over the last ten years there has been a significant increase in the range and type of edentulous defects that can be treated using osseointegrated implants. Encouraged by the long-term success of implant reconstructions in the edentulous mandible and maxilla, and the availability of novel implant attachments, clinicians will now undertake more elaborate treatment involving the partially edentate and those with localized or generalized tissue deficiencies. This clinical trend places increasing demands on the predictability, complexity and accuracy of the surgical procedure necessary to allow a successful prosthetic reconstruction. This is especially so when potential implant sites lie in areas of high aesthetic or functional requirements.     

History of the West of Scotland Plastic Surgery Unit: 1940-1986

In this study a comparison is made between intraoral and extraoral radiographical techniques for quantitative measurements of bone density in the edentulous mandible. A phantom model, composed of a dry mandible surrounded by a soft tissue substitute was used. Radiographs were made of aluminium implants of known volumes. Intra- and extraorally placed reference wedges of aluminium or a combination of aluminium and plexiglas were used for the measurement of the aluminium volume of the above-mentioned implants and compared with the real volume. The IBAS image analysis system was used for image processing and measurements. A systematic deficit in the measured volume of 15 to 29% was found. This error was irrespective of the radiographical technique and indicates a constant underestimation of the aluminium volumes. The differential influence of the secondary radiation on the images of the jaw and the wedge is proposed to be a possible cause of this constant underestimation. The intraoral and extraoral techniques do not display significant statistical differences in the levels of validity or accuracy. Obtaining serial intraoral radiographs of adequate quality in the atrophic edentulous mandible can be problematic. It is concluded from this in vitro study that in these cases Oblique Lateral Cephalometric Radiographs may provide a valuable alternative for quantitative image analysis.