Browsing by Subject "Dental Implantation, Endosseous"

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    Microhardness, Strains and Microdamage in Bone Surrounding Endosseous Implants Subjected to Bending Fatigue Loads
    (1999-05) Huja, Sarandeep Singh; Roberts, W. Eugene; Burr, David B.; Christen, Arden G.; Katona, Thomas R.; Garetto, Lawrence P.; McDonald, James L., Jr.
    Intense remodeling occurs in lamellar bone adjacent to osseointegrated endosseous implants. The purpose of this study was to compare microdamage accumulation subsequent to fatigue loading of bone that surrounds an endosseous implant at (a) immediate placement (non-adapted bone) and (b) following a 12 week period of healing (adapted bone). It was hypothesized that there would be less microdamage in the compliant adapted bone than in the older non-adapted bone adjacent to endosseous implants after being subjected to a fatigue protocol. Preliminary studies to measure the microhardness of bone surrounding implants and three dimensional finite element models to quantify the strain environment were required. In addition, a new fluorescent method to quantify microdamage was developed. Titanium endosseous implants (4 mm diameter) were placed into dog mid-femoral diaphyses and allowed to heal for 12 weeks. Block sections of bone, each containing one implant, were cut antero-posteriorly to obtain an implant containing lateral cortex. The medial cortex was used to produce non-adapted specimens by placing a 4 mm diameter titanium rod. Specimens were divided into two groups. Control (n=14 each for adapted and non-adapted, 0 N) and experimental specimens (n=13 adapted and n=14 non-adapted) were loaded in bending for 150,000 cycles at 2 Hz. Specimens were bulk stained with basic fuschin. Histomorphometric methods were used to evaluate crack numerical density, crack surface density and percent damaged area. Microdamage in the non-adapted and adapted specimens was compared using repeated measures ANOVA and Tukey's method at a 95% confidence level. Statistically significant differences (p<0.0001) existed for all measurements between the non-adapted and adapted specimens on the compressive cortices with adapted bone accumulating less microdamage than non-adapted bone. This study suggests that the more compliant adapted bone adjacent to the endosseous implant is relatively resistant to the imposed fatigue loads. The rapidly turning over bone may prevent microdamage accumulation and propagation, thus allowing for the successful adaptation of these implants.
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    Time Course of Osseous Healing at Endosseous Implant Interfaces
    (1992) Tardy, Shelley R.; Roberts, W. Eugene; Garetto, Lawrence P.; Hohlt, William F.; Shanks, James C.; Nelson, Charles
    The purpose of this study was to examine the time course of endosseous implant healing in trabecular bone. Thirty-six, six month old rabbits were used and stratified into three groups of twelve animals (six control, six experimental). Each experimental animal had two implants placed, bilaterally, in the dorsal surface of the nasal bones. Control animals had soft tissue reflection on the left side nasal dorsum and soft tissue reflection with periosteal removal on the right side nasal dorsum. Prior to surgical procedures and implant placement, a series of intravital bone labels were initiated for all animals. The three groups were allowed to heal four, eight, and 12 weeks, respectively. Immediately after euthanizing the animals, torque test procedures were performed on all left side implants. Following histologic processing, analyses were conducted on midfrontal sections of control sites and implants using microradiography, polarized-light microscopy and epifluorescent microscopy. The implants were divided into three regions: supraflange, coronal, and apical. Control sites were separated into cortical and trabecular regions. Within each implant region, the percent woven and lamellar bone was recorded as well as the percent of bone in contact with or near the implant. Osseous remodeling was detected by fluorescent bone labels. Using these markers, data were categorized as old bone, new bone (woven or lamellar), and unmineralized tissue. In control animals, periosteal removal from the rabbits' nasal dorsum had a limited effect on producing noticeable differences in physiologic response compared to the soft tissue reflection-only control sites. The primary responses found in experimental animals were in the coronal implant region. Significantly more new and old bone was present within this region than in the supraflange and apical regions for all healing times. The only significant time factor found was the increased amount of new woven bone in the four week healing group of the coronal and apical regions. Implant geometry, length and the presence of a flange, appears to have been a more significant influence on osseous response than healing time. Little periosteal woven callus and essentially no trabecular response were observed in experimental animals at the time studied. Because of the shortness of the implant (4.0 mm), the most apical portion had limited extension into trabecular anatomy. Limited proximity to osseous tissue in the apical region may explain the lack of trabecular response. The majority of bone and its physiologic adaptation response occurred in the coronal region since this area is more cortical in nature.
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    Trabecular Adaptation to Continuously Loaded Endosseous Implants
    (1993) Bailey, Grant S.; Roberts, W. Eugene; Garetto, Lawrence P.; Baldwin, James J.; Nelson, Charles; Shanks, James C.
    Several studies have shown endosseous implants placed in areas of thick cortical bone to be an effective means of anchorage in complex orthodontic cases. The purpose of this study was to examine the viability of endosseous implants as orthodontic/orthopedic anchorage when placed in this cancellous bone. Eighteen 6-month-old male rabbits were used and stratified into three groups of six animals. Two implants placed (bilaterally) in the dorsal surface of the nasal bones. After a 12-week healing period, the control group (C) had a passive spring placed between the implants, and the 1 Newton constant group (1 NC) received a spring that delivered a constant compressive load of 1N. A 1N load was applied to the progressive load group (3NP) and sequentially increased to 3N over the course of the study. Bone labels were administered throughout the experiment at designated time intervals to provide quantification of the physiologic activity. Following histologic processing, analyses were conducted on midfrontal sections using microradiography and fluorescent microscopy. The implants were divided into three regions: supraflange, coronal, and apical. Within each region the percent woven and lamellar bone was recorded as well as the percent bone in contact with or near the implant surface. Remodeling activity was observed by using fluorescent bone labels. In the sections analyzed using fluorescent microscopy, the regions were further subdivided into zones. Using the bone label data, bone was categorized as old bone, new woven bone, new lamellar bone and marrow space. Within animal, paired t tests revealed no significant difference between right/left implants. Data was pooled and an ANOVA run to test for difference between groups. Few significant differences were seen. Student Newman-Keuls sequential range tests were used to test between region and zone. The coronal region showed trends of more bone overall in the 1NC and the 3NP load groups p < 0.10. The apical region had less bone overall. The fluorescent data showed few significant differences between groups; however, the coronal region showed trends of more bone overall. A RAP effect was observed in the zonal analysis for new lamellar bone. Sutural remodeling was observed at the cortical plate over the nasal suture. A significant trabecular response was not seen in this study; however, the implants in the experimental groups remained stable throughout the study possibly due to the implant design. It was concluded that implants placed in thin cancellous bones are suitable for use as orthodontic/orthopedic anchorage.