Placement of endosteal implants combined with chin bone onlay graft for dental reconstruction in patients with grafted alveolar clefts

CONTEXT: Physical activity and fitness are believed to reduce premature mortality, but whether genetic factors modify this effect is not known. OBJECTIVE: To investigate leisure physical activity and mortality with respect to familial aggregation of health habits during childhood and factors that may enable some individuals to achieve higher levels of fitness. DESIGN: Prospective twin cohort study. SETTING: Finland. SUBJECTS: In 1975, at baseline, 7925 healthy men and 7977 healthy women of the Finnish Twin Cohort aged 25 to 64 years who responded to a questionnaire on physical activity habits and known predictors of mortality. Those who reported exercising at least 6 times per month with an intensity corresponding to at least vigorous walking for a mean duration of 30 minutes were classified as conditioning exercisers, those who reported no leisure physical activity were classified as sedentary, and other subjects were classified as occasional exercisers. MAIN OUTCOME MEASURES: All-cause mortality and discordant deaths among same-sex twin pairs from 1977 through 1994. RESULTS: Among the entire cohort, 1253 subjects died. The hazard ratio for death adjusted for age and sex was 0.71 (95% confidence interval [CI], 0.62-0.81) in occasional exercisers and 0.57 (95% CI, 0.45-0.74) in conditioning exercisers, compared with those who were sedentary (Pfor trend <.001). Among the twin pairs who were healthy at baseline and discordant for death (n=434), the odds ratio for death was 0.66 (95% CI, 0.46-0.94) in occasional exercisers and 0.44 (95% CI, 0.23-0.83) in conditioning exercisers compared with those who were sedentary (P for trend, .005). The beneficial effect of physical activity remained after controlling for other predictors of mortality. CONCLUSION: Leisure-time physical activity is associated with reduced mortality, even after genetic and other familial factors are taken into account.     

Dental prosthetic reconstruction of osseointegrated implants placed in irradiated bone

Deficiency of the sixth component of human complement (C6) has been reported in a number of families from the western Cape, South Africa. Meningococcal disease is endemic in the Cape and almost all pedigrees of total C6 deficiency (C6Q0) have been ascertained because of recurrent disease. We have sequenced the expressed exons of the C6 gene from selected cases and have found three molecular defects leading to total deficiency: 879delG, which is the common defect in the Cape and hitherto unreported, and 1195delC and 1936delG, which have been previously reported in African-Americans. We also show that the 879delG and 1195delC defects are associated with characteristic C6/C7 region DNA marker haplotypes, although small variations were observed. The 1936delG defect was observed only once in the Cape, but its associated haplotype could be deduced. The data from the haplotypes indicate that these three molecular defects account for the defects in all the 38 unrelated C6Q0 individuals we have studied from the Cape. We have also observed the 879delG defect in two Dutch C6-deficient kindreds, but the 879delG defect in the Cape probably did not come from The Netherlands.     

Titanium bone-integrated implants in extraoral facial prosthetic rehabilitation: surgical planning and long-term follow-up

The authors report on their clinical experience in the reconstruction of complex facial deformities using titanium osseo-integrated implants for the retention of soft silicone prostheses. They also evaluate the importance of this surgical technique as a viable alternative to traditional reconstructive procedures using autologous grafts, both in patients with severe osteomuscular defects and corrective surgery of unsuccessful reconstruction operations. The patients who underwent implantation operations were studied by CT 3D and 99m Tc SPECT (Single Photon Emission Computerized Tomography) procedures to evaluate osseo-integration at 3 weeks, 3, 6, 12, 24 months. The study demonstrates that the radiation emission peaks three weeks after surgery with the maximum bone remodeling activity, and after the functional loading of the implants, 3 months after surgery. High uptake past the eight month after surgery has never been detected and must be considered abnormal. SPECT offers the possibility of obtaining a three dimensional reconstruction of the photon emission of selected structures. The use of these nuclear medicine methods in addition to traditional-type radiological procedures introduce new possibilities, although still in the clinical experimentation phase, for the long-term follow-up of the inserted implants in craniofacial rehabilitation.     

Reconstruction of residual alveolar cleft defects with one-stage mandibular bone grafts and osseointegrated implants

PURPOSE: This study evaluates a treatment regimen for reconstruction of residual maxillary alveolar cleft defects consisting of mandibular bone grafting and immediate implant installation. PATIENTS AND METHODS: Sixteen cleft patients (five female and 11 male) had residual cleft defects of the alveolar ridge reconstructed with bone grafts from the mandibular symphyseal region. The bone graft was pretapped at the donor site before fixation in the residual ridge with Br?nemark implants. Twenty implants were installed according to this concept. The period of observation ranged from 36 to 69 months, with a mean of 48 months after implant installation. RESULTS: Five patients developed wound dehiscenses that resulted in total or partial bone graft sequestration. Two implants were lost, one due to sequestration and the other due to mobility at the abutment procedure; 18 implants were still well functioning at the end of the observation period. However, all patients showed significant periimplant bone resorption after this one-stage treatment. CONCLUSION: Because of the observed complication rate, the one-stage procedure may not be optimal for reconstructing residual cleft defects.     

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.     

高强度高应力循环稳定的HDH多孔NiTi形状记忆合金

以氢化脱氢(Hydrogenation dehydrogenation, HDH)钛粉和镍粉为原料制备的多孔NiTi形状记忆合金普遍承载性能与可恢复应变较差. 本研究以NaCl为造孔剂,通过在高真空(10⁻⁴ Pa)下高温(1250 ℃)均匀化烧结制备出了高强度、高应力循环稳定的多孔NiTi合金,研究了不同孔隙率下的微观结构、相变行为、力学性能以及细胞毒性. 研究发现,随着NaCl添加量的增加,样品的孔隙率和孔径增大,同时氧含量略有增加. 在样品中观察到无热处理自发形成的Ni₄Ti₃沉淀相,沉淀相尺寸随样品氧含量增加而增加. 所有样品的马氏体相变均呈现多峰现象,主要归因于非均匀分布的Ni₄Ti₃沉淀相引发的多步相变效应. 孔隙率为14% ～ 37%的多孔NiTi合金的压缩强度为1236 ～1600 MPa. 与其他粉末冶金法制备多孔NiTi合金的抗压强度相比,本研究所获得的合金表现出超高的强度. 样品在8%应变压缩加载–卸载后同时表现出超弹性和形状记忆效应,经加热处理后形状恢复率超过99%. 在循环压缩实验中,多孔NiTi样品在接近8%应变的高应力下承受了50次循环. 样品的残余应变随着周期数的增加而增加. 随着孔隙率的增加,循环结束时的最终残余应变为1.4%、1.55%和1.66%. 低的残余应变说明多孔NiTi样品在高应力压缩环境中具有较好的稳定性,这归因于Ni₄Ti₃沉淀相对基体的强化作用. 使用MC3T3E1 细胞评估了样品的细胞毒性,结果表明多孔NiTi样品具有较低的细胞毒性.     

Stress in bone adjacent to dental implants

Finite element analysis (FEA) was employed to assess patterns of stress in bone adjacent to an implant after application of loads through an attached distal extension cantilever. Under all loading conditions, the highest stresses occurred at the distal cervical bone margin adjacent to the cantilever. In clinical studies, this is not consistently the site of the greatest bone changes seen radiographically. This suggests that extrapolation of FEA studies to clinical implantology should be approached with caution until further data become available on both mechanical properties of bone and patterns of bone remodelling induced by defined functional stresses in mandible and maxillae.     

Guided bone regeneration around dental implants in the atrophic alveolar ridge using a bioresorbable barrier. An experimental study in the monkey

The aim of this study was to evaluate guided bone regeneration (GBR) around dental implants placed in atrophic alveolar ridges using an experimental, nonporous bioresorbable barrier. In 8 Rhesus monkeys, the maxillary canines and lateral incisors were extracted bilaterally and the remaining alveoli were reduced to create atrophic ridges. After a healing period of 3 months, soft tissue expansion was performed using a subperiosteal tissue expander. After 1 month of tissue expansion, and IMZ implant was placed in the atrophic ridge on each side in such a way that its coronal 4 mm to 5 mm remained circumferentially exposed above the bone level. The test implants were covered with a bioresorbable barrier made of poly (D,L-lactid-co-trimethylencarbonate) in a 70/30 ratio, whereas the control implants were covered with a nonresorbable expanded polytetrafluoroethylene (e-PTFE) barrier. The e-PTFE barriers were stabilized with titanium minipins while the bioresorbable barriers were analogously fixed using bioresorbable minipins made of poly (L-lactid-co-D,L-lactid) 70/30. Clinical healing progressed uneventfully in both groups and no soft tissue dehiscences occurred. Histometric and histomorphometric analyses were performed 5 months post surgery. Both test and control implants exhibited direct bone-to-implant contact to variable extents. The mean direct mineralized bone-to-implant contact length fraction was 32% of the total implant length in the test sites and 58% in the control sites. Control sites exhibited significantly greater bone fill compared to the experimental sites (P < 0.001). Histologic observations of test specimens demonstrated a moderate inflammatory reaction related to the degradation and resorption products of the barrier. In conclusion, the nonresorbable e-PTFE GBR barrier was found to be superior to the bioresorbable barriers tested in the present investigation.     

Influence of bone quality on stress distribution for endosseous implants

The present study examined the influence of bone quality on the transmission of occlusal forces for endosseous dental implants. Employing the finite element method, the study modeled a 3.75 x 10-mm threaded implant placed in a 12 x 11 x 8-mm section of bone. By varying the elastic parameters assigned to the bone elements, four bone quality categories were established. A load of 100 N was applied at the occlusal surface of the restoration at a 30 degrees angle to the vertical axis of the implant. Maximum von Mises stress concentrations (sigma Emax) were observed to be located in the marginal bone at the coronal aspect of the implant fixture in all four cases. Values of sigma Emax were 13.7 MPa for type 1 bone, 15.8 MPa for type 2 bone, 20.1 MPa for type 3 bone, and 26.5 MPa for type 4 bone. Magnitude of the stresses in bone was strongly correlated (r = 0.997) with computed displacement of the implant system. This analysis predicts that placement of implants in bone with greater thickness of the cortical shell and greater density of the core will result in less micromovement and reduced stress concentration, thereby increasing the likelihood of fixture stabilization and tissue integration.     

Advances in osseointegrated implants for dental and facial rehabilitation following major head and neck surgery

Osseointegrated implants can be used to facilitate retention stability and support for facial and intraoral prostheses used to restore head and neck defects. Preliminary studies indicate that in nonirradiated maxillectomy patients the success rates are about 75%. In the reconstructed mandible the results appear to be more favorable--over 90% for implants placed in free nonvascularized bone grafts and over 90% for free revascularized bone grafts. Similar high success rates have been observed for most sites used to support facial prostheses. Success rates for auricular sites exceed 95% and for floor of nose sites success rates exceed 90%. Success rates have been lower (77%) for implants placed in the frontal bone for retention of orbital prostheses. Success rates for irradiated bone sites have been lower and range from 60.4% in the maxilla to 68.6% in facial bone sites. Of greater concern is that most implants placed in irradiated sites are beginning to show signs of impending failure.     

SMS text messages as a prosthetic aid in the cognitive rehabilitation of schizophrenia.

Objective: To evaluate the efficacy of short message service (SMS) text messages as a compensatory aid to improve independence in individuals diagnosed with schizophrenia and cognitive deficits. Design: An ABA withdrawal single-case experimental design was used. Eight men diagnosed with schizophrenia took part in the study; all demonstrated memory or planning problems in everyday life. Results: Five participants completed the entire trial. Four were more successful in carrying out daily activities when receiving prompts, whereas 1 did not profit from the intervention. Conclusion: SMS text messages can be effective in compensating for cognitive impairment in some but not all individuals with schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ketorolac on bone repair: A radiographic study in modeled demineralized bone matrix grafted rabbits

The treatment of instability of the multiply reoperated knee is a complex problem. The causes for failure are numerous and include repeated trauma, insufficient fixation and non-anatomic placement of the graft, inadequate replacement material, isolated anterior cruciate ligament (ACL) reconstruction in complex knee instability or the use of a ligament prosthesis. With every surgical procedure, however, the anatomical and technical conditions become worse. Problems like degenerative changes, joint stiffness and gait abnormalities occur and often become a more focal point than the instability itself. The purpose of this paper is to present the problems and the dilemma of instability of the multiply reoperated knee and the possible solutions. Between 1976 and 1996, a total of 1752 ACL reconstructions were carried out in Munich and Hannover. Of these, 228 (13%) were revision, mostly of failed ACL reconstructions performed elsewhere. Since 1989, we have chosen the severest cases from this group (more than three operations on the same knee) for this study. Seventeen patients were investigated who had undergone up to 25 operations. The mean number of operations was 7. All primary operations were performed in other hospitals. In 10 cases only the ACL reconstruction was performed as a final procedure, mostly in combination with other procedures like medial meniscus replacement, extra-articular stabilization or arthrolysis. In the other cases operations such as osteotomies, arthrodesis or amputation were necessary. The results present the main dilemma in instability of the multiply reoperated knee since they were not successful in all patients. Finally, 15 patients report still having instability, pain or swelling in isolation or in combination. Nine patients were satisfied with their subjective results. Even after the socalled definitive procedures, certain complications arose. The main goal in the treatment of instability of the multiply reoperated knee is to avoid a series of operations, hospitalization and history of illness. General revision surgery for the entire complaint is not the aim of the treatment. The specific problem of the patient should be extracted from the complex situation, and this should be solved with the most limited procedure possible only.     

Preservation of alveolar bone in extraction sockets using bioabsorbable membranes

The purpose of this study was to evaluate the clinical effectiveness of a bioabsorbable membrane made of glycolide and lactide polymers in preserving alveolar ridges following tooth extraction using a surgical technique based on the principles of guided bone regeneration. Sixteen patients requiring extractions of 2 anterior teeth or bicuspids participated in the study (split-mouth design). Following elevation of buccal and lingual full-thickness flaps and extraction of teeth, experimental sites were covered with bioabsorbable membranes; control sites did not receive any membrane. Titanium pins served as fixed reference points for measurements. Flaps were advanced in order to achieve primary closure of the surgical wound. No membrane became exposed in the course of healing. Reentry surgeries were performed at 6 months. Results showed that experimental sites presented with significantly less loss of alveolar bone height, more internal socket bone fill, and less horizontal resorption of the alveolar bone ridge. This study suggests that treatment of extraction sockets with membranes made of glycolide and lactide polymers is valuable in preserving alveolar bone in extraction sockets and preventing alveolar ridge defects.     

Testing bone implants in cell lines and human osteoblasts]

An innovative technology, BladderScan, was introduced to reduce urinary tract infections and care costs in hospitalized adults. Evaluation revealed reductions in infection rates and overall benefits exceeding costs.     

Numerical studies of the effect of prosthetic implants on the strain energy density distribution in the femur

In this study the distribution of the strain energy density (SED) in the natural femur as well as changes of it due to the implantation of an artificial hip joint has been investigated. Because of recently published theoretical considerations the volume related SED was used to describe the respective biomechanical loading situation completely. By means of parameter variation different load cases were simulated. The calculated SED-distributions were compared with the respective results of the natural femur. Thus, the known reasons of failures of hip joint prostheses has been proofed numerical. It was shown that the SED is a suitable mechanical parameter to simulate bone remodeling after hip joint replacement.     

Prevention of bone loss by percutaneous estradiol implants in ovariectomized rats

This study was conducted to investigate whether hydroxyapatite (HAP) is appropriate as a percutaneous drug carrier for estradiol (E2) for the suppression of bone loss. Ten-week-old female Sprague-Dawley rats were subjected either to bilateral ovariectomy (OVX) or to sham surgery (control). Ovariectomized rats were implanted percutaneously with E2-HAP disks containing low, medium or high doses of estradiol (50, 250, or 500 micrograms E2/rat, respectively). Ovariectomized rats without implant and OVX rats implanted only with HAP served as additional controls. All rats were sacrificed 90 days after surgery. At the end of the experiment, bone mineral density of the lumbar spine was measured by dual energy X-ray absorption, and serum E2 was assayed by radioimmunoassay. The bone mineral density of OVX and HAP-treated OVX rats decreased by 18% compared to sham surgery rats, but decreased by only 13, 7, and 3% in rats treated with 50, 250, and 500 micrograms E2/rat, respectively. The in vitro release of E2 from E2-HAP devices was determined by an HPLC method. Estradiol release from the HAP devices followed almost a zero-order kinetics. Estradiol remained intact in E2-HAP implants for up to six months when stored at 5, 25, and 40 degrees C. This study indicates that E2-HAP implants are effective in suppressing bone loss in the spine of OVX rats in a dose-dependent manner.     

Sequestration of the alveolar bone by invasive aspergillosis in acute myeloid leukemia

Compared to non-invasive aspergillosis, invasive aspergillosis in the region of the mouth, jaw and face has rarely been reported. It occurs particularly often in the presence of haematological oncological illness. The case of a patient suffering from acute myeloid leukemia is described; he contracted invasive aspergillosis of the lungs and the alveolar processes in the course of chemotherapeutic treatment. All the alveolar processes in the region of the premolars and molars were demarcated and had to be removed by sequestrectomy. The therapy of invasive aspergillosis should be carried out within the framework of intensive interdisciplinary treatment. In addition to systemic and local antimycotic therapy, the debridement of necrotic hard and soft tissue was necessary.     

Available bone is the foremost criterion in the insertion of endosteal implants

The foremost criterion in the insertion of endosteal implants is bone availability. Implant dentists should consider first the amount of available bone of the edentulous ridge where the endosteal implant will be inserted. A common error and cause of many implant failures is the dentist's use of an implant modality which is not indicated for the density and morphology of the available bone in the edentulous ridge. Implant modality/system is not the primary criterion in the insertion of endosteal implants. Before the dentist inserts an endosteal implant, he should gauge or measure the amount of bone where the implant is intended to be placed. It should be measured in width, height, length, trajectory, and implant-crown ratio. After recording the measurements of the available bone, these should be placed in different categories to serve as guides in implant selection. If there is not enough bone for the endosteal implant, bone modification should be performed. This can be done either by osteoplasty or ridge augmentation with the use of bone grafting materials. Aside from the amount of available bone in the edentulous ridge, another very, very important thing that should be considered is the quality or its density. Any biocompatible implant demonstrates some osseointegrated surfaces depending upon the bone type into which it is placed and the loads placed upon it. Implant body must exhibit a macrogeometry suitable for acceptable levels of force transfer to the surrounding tissues as well as for implantation into a bony site of a particular anatomic size.