David A. Gerard

The response of bone in primates around unloaded dental implants supporting prostheses with different levels of fit

Implant failure as a consequence of prosthetic loading following clinical determination of successful stage I healing is poorly understood. A basic premise of accepted prosthetic protocol is passive connection of multiunit prostheses to the implant support. To better understand mechanical factors related to implant failure, this basic passivity premise was experimentally tested prior to study of functional loading research. The purpose of this preliminary study was to measure the bone response around implants placed in the mandible of baboons that supported prostheses exhibiting two levels of fit and not loaded occlusally. Screw-retained prostheses that exhibited a mean linear distortion of 38 microns and 345 microns made up the fit and misfit groups respectively. The results failed to distinguish a difference in bone response between the two levels of prosthetic fit. Although the finding can be argued as a sample size limitation, the data strongly suggest an opposite response than is clinically expected and, consequently, does not warrant the use of additional animals in this initial study. Because the design of this study does not mimic the clinical application of misfitting prostheses (where dynamic functional loads are superimposed with misfit loads), it cannot be inferred that, in clinical application, fit does not alter the osseointegrated interface. Ongoing investigation of failure due to nonpassive connections under dynamic loading conditions of mastication will help clarify the clinical significance of passivity.

Early Inhibitory Effects of Zoledronic Acid in Tooth Extraction Sockets in Dogs Are Negated by Recombinant Human Bone Morphogenetic Protein

PURPOSEnThis study was conducted with 2 purposes. The first was to determine the effect of a single dose of zoledronic acid (ZA) on the healing of a tooth extraction socket in dogs. The second was to determine if placement of recombinant human bone morphogenetic protein-2 (rhBMP-2)/absorbable collagen sponge (ACS) - INFUSE, (Medtronic, Memphis, TN) into these extraction sockets would inhibit the inhibition on bone healing and remodeling by ZA.nnnMATERIALS AND METHODSnNine adult female beagle dogs (2 to 3 yr old) were placed into 3 groups of 3 dogs each. Group I received 15 mL of sterile saline intravenously; group II received 2.5 mg of ZA intravenously; and group III received 5 mg of ZA intravenously. Forty-five days after treatment, all dogs underwent extraction of noncontiguous right and left mandibular first molars and second premolars. In group I, the right mandibular extraction sockets had nothing placed in them, whereas the left mandibular sockets had only ACS placed in them. In groups II and III, the right mandibular sockets had rhBMP-2/ACS placed in them, whereas the left mandibular sockets had only ACS placed. All extraction sockets were surgically closed. Tetracycline was given intravenously 5 and 12 days later, and all animals were euthanized 15 days after tooth extraction. The extraction sockets and rib and femur samples were harvested immediately after euthanasia, processed, and studied microscopically.nnnRESULTSnA single dose of ZA significantly inhibited healing and bone remodeling in the area of the tooth extractions. The combination of rhBMP-2/ACS appeared to over-ride some of the bone remodeling inhibition of the ZA and increased bone fill in the extraction sites, and remodeling activity in the area was noted. The effects of rhBMP-2/ACS were confined to the area of the extraction sockets because bone activity at distant sites was not influenced.nnnCONCLUSIONSnA single dose of ZA administered intravenously inhibits early healing of tooth extraction sockets and bone remodeling in this animal model. The combination of rhBMP-2/ACS significantly increased bone fill and bone remodeling in these areas, negating much of the effect of the ZA.

Temporomandibular disorders: clinical and laboratory analyses for risk assessment of criteria for surgical therapy, a pilot study.

Temporomandibular disorder (TMD) is a broad category involving dysfunction of the skeletomuscular structures of the head and neck, and the temporomandibular joint (TMJ). A total of 66 patients, 54 with TMD, participated in this study. Group 1 (G1) had 31 patients suffering from early to intermediate stage disease, and no prior surgeries. G1 patients had arthrotomy/meniscectomy performed on the diseased joint(s). Group 2 (G2) consisted of 23 patients with late stage disease. All G2 patients had previously had unsuccessful TMJ surgery and were treated with either a partial or total joint prosthesis. Group 3 (G3) consisted of 12 patients who were clinically and radiographically asymptomatic. Medical histories including inflammatory bowel disease, headaches, vertigo, tinnitus and anemia, as well as surgical tonsillectomies, appendectomies and cholecystectomies, were significantly greater in G1 and G2 when compared to G3. Serological testing included HLA subtype, positive (ANA) antinuclear antibody, erythrocyte sedimentation rate (ESR), anemia profile, hormonal levels of prolactin and estradiol, and rheumatoid factor (RF). HLA frequencies, as well as some serological analyses, were significantly different among the three groups. These findings suggest that surgical failure may be secondary to autoimmune dysfunction with a predisposition to multisystem disease. The utilization of genetic markers, serological testing, and thorough medical and surgical histories should allow the clinician to determine which patients are potentially better surgical risk candidates for treatment of TMD.

HL-60 cell growth-conditioned medium is an effective inducer of myeloperoxidase expression in K-562 human leukemia cells.

K-562 cells were cultured in HL-60 cell growth-conditioned medium (GCM) for up to 96h. Myeloperoxidase (MPO) mRNA was transiently detected by reverse transcription-polymerase chain reaction (RT-PCR) techniques at 12, 24, and 48h. The de novo expression of MPO protein was subsequently detectable by intracellular flow cytometry at 24, 48, 72 and 96h. Immunogold staining and cytochemical analysis demonstrated granularly-sequestered MPO in approximately 40% of HL-60 GCM-cultured cells after 48h of culture. The sequential detection of MPO mRNA and MPO biosynthesis is considered an indicator of serial maturation evocative of myeloblastic cells, and suggest that K-562 cells maintain the ability to differentiate along this lineage.