Imperforate titanium shell enclosing recombinant human bone morphogenetic protein-2-induced bone formation for high-profile dental implants in rabbit tibia.

PURPOSE: To evaluate the use of a nonperforated titanium occlusive device over high-profile dental implants in rabbit tibia using recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge (ACS) for augmentation grafting. MATERIALS AND METHODS: Eight New Zealand white rabbits were used for the experiment. All rabbits underwent computed tomography of the right tibia. A custom titanium shell was manufactured for each rabbit using a computer-assisted design to confine the graft. Three high-profile implants were placed in the right tibia of each rabbit; the middle implant was placed 8 mm in supracrestal fashion and the adjacent implants were placed 5 mm in supracrestal fashion. There were 4 groups (n = 2 per group): non-shell control, titanium shell only, titanium shell over buffered collagen, and titanium shell over the ACS enriched with rhBMP-2. The animals were sacrificed after 6 or 12 weeks. Histologic preparation was carried out to evaluate bone formation. RESULTS: After 6 weeks, negligible bone growth was found around the implants. After 12 weeks, there was minimal bone formation around the implants in the control group, whereas in the group treated with ACS enriched with rhBMP-2, the titanium shell was filled with mature bone, which was expressed at the implant surface, the shell's interior, and the exterior surfaces. CONCLUSION: The placement of ACS enriched with rhBMP-2 beneath an occlusive nonperforated titanium shell confining high-profile dental implants resulted in visibly more formation of mature bone.

Island osteoperiosteal flap vitality when isolated from basal bone by silicone interposition: an experimental study in rabbit tibia.

PURPOSE: This study sought to confirm, through histologic evaluation, the vitality and viability of the island osteoperiosteal flap (i-flap) in a rabbit tibia model. MATERIALS AND METHODS: In four rabbits, an osteotomy was performed on the tibial aspect of the right leg. A bone flap was raised, but the periosteal attachment was kept intact. The free-floating i-flap was separated from the rest of the bone by a silicone sheet. The rabbits were to be sacrificed after 1, 2, 4, and 8 weeks and histologic samples examined. RESULTS: All surgeries were accomplished successfully; however, three animals showed fractured tibiae within a few days after surgery and were sacrificed immediately after the fractures were discovered. The fourth rabbit was sacrificed at 4 weeks. Histologic specimens showed vital new bone in the i-flap area and signs of remodeling in the transition zone and the original basal bone. CONCLUSION: The i-flap remained vital. This suggests potential for use in bone augmentation strategies, particularly for the alveolar split procedure.

Recombinant human bone morphogenetic protein-2 confined by an imperforate titanium shell over high-profile dental implants in rabbit tibiae: a pilot bone augmentation study.

PURPOSE: To evaluate the use of a nonperforated titanium occlusive device over a bone morphogenetic protein-2 in an absorbable collagen sponge (BMP-2/ACS) in grafting the bone around high-profile (ie, supracrestal) dental implants in rabbit tibiae. MATERIALS AND METHODS: Eight New Zealand white rabbits were used for the experiment. Two implants were placed in the right tibia of each rabbit, with 4 mm of each implant placed supracrestally ("high-profile" placement) in four groups of two rabbits each: control, titanium shell only, titanium shell over buffered collagen, and titanium shell over BMP-2/ACS. The animals were sacrificed after 3 or 6 weeks. Calcified and nondecalcified histologic preparation was carried out to evaluate bone formation and degree of osseointegration. RESULTS: Three of the eight animals developed tibial fractures. The two BMP-2 test animal tibiae remained intact, with the 3-week specimen showing very little bone formation inside or outside of the titanium chamber and the 6-week specimen showing bone mostly outside of the chamber. CONCLUSION: The placement of BMP-2 beneath an occlusive nonperforated titanium shell next to a high-profile implant did not result in significant bone formation. .

Cholinergic status modulations in human volunteers under acute inflammation.

Cholinergic Status, the total soluble circulation capacity for acetylcholine hydrolysis, was tested for putative involvement in individual variabilities of the recruitment of immune cells in response to endotoxin challenge. Young (average age 26) and elderly (average age 70) volunteers injected with either Escherichia coli endotoxin or saline on two different occasions were first designated Enhancers and Suppressors if they showed increase or decrease, respectively, in plasma acetylcholinesterase (AChE) activity 1.5 h after endotoxin administration compared to saline. Enhancers showed significant co-increases in plasma butyrylcholinesterase (BChE) and paraoxonase (PON1) activities, accompanied by rapid recovery of lymphocyte counts. Young Enhancers alone showed pronounced post-exposure increases in the pro-inflammatory cytokine interleukin-6 (IL-6), and upregulation of the normally rare, stress-induced AChE-R variant, suggesting age-associated exhaustion of the cholinergic effects on recruiting innate immune reactions to endotoxin challenge. Importantly, IL-6 injected to young volunteers or administered in vitro to primary mononuclear blood cells caused upregulation of AChE, but not BChE or PON1, excluding it from being the sole cause for this extended response. Interestingly, Suppressors but not Enhancers showed improved post-exposure working memory performance, indicating that limited cholinergic reactions may be beneficial for cognition. Our findings establish Cholinergic Status modulations as early facilitators and predictors of individual variabilities in the peripheral response to infection.