Histomorphometric comparison of implant anchorage for two types of dental implants after 3 and 6 months' healing in baboon jaws.

STATEMENT OF PROBLEM: A complete understanding of dental implant prognosis requires better knowledge of the bone anatomy after implant healing. Such baseline data are necessary to compare against load-induced changes in anatomy. PURPOSE: The purpose of this article is to describe and compare measures of implant support (percentage [%] integration and percentage [%] bone area) for various implants in baboon jaws after healing times of 3 and 6 months. MATERIAL AND METHODS: Commercially pure titanium (cpTi) and titanium alloy (Ti-alloy) screw-shaped implants were placed in the posterior jaws of 9 female baboons after 2 months of postextraction healing. Specimens were harvested after 3 months (5 baboons: 8 cpTi, 7 Ti-alloy) and after 6 months (4 baboons: 8 cpTi, 8 Ti-alloy). Each implant provided 6 polished horizontal sections for data collection, which was accomplished from digitized images with the IMAGE analysis system (reliability at 1.6%). Three- and six-month data for each parameter were compared with the use of ANOVA (P<.01). RESULTS: The results revealed a significant increase in the % integration (cpTi 39.1 to 56.2; Ti-alloy 40.0 to 55.2) and the % bone area (cpTi 38.8 to 47.9; Ti-alloy 38.9 to 49.2) from 3 to 6 months for both implants. This significant increase was also true for comparisons by jaw for each implant material (P<.01 for overall and by jaw comparisons). CONCLUSION: A time-dependent increase in jawbone anchorage was measured in this nonhuman primate population, and it was shown that the 6-month maxillary data were comparable to the 3-month mandibular data. These results lend support to the clinical strategy of waiting longer to load implants in the maxilla.

Histomorphometric analysis of implant anchorage for 3 types of dental implants following 6 months of healing in baboon jaws.

In an effort to better understand the supporting anatomy for unloaded endosseous dental implants, this study focused on the histomorphometric analysis of 3 different types of implants placed into non-human primate jaws and allowed to heal for 6 months. This report describes data from 24 screw-type dental implants placed in edentulated (2 months healing time) posterior arches of 4 adult female baboons. Three different implants were placed and allowed to heal for 6 months prior to processing for evaluation: commercially pure titanium (n = 8), titanium alloy (n = 8), and titanium plasma-sprayed (n = 8). Circumferential bone-implant interface sampling from 6 regions along the entire length of each implant was obtained for evaluation of percent bone-implant contact (%BIC) and percent bone area (%BA), within 3 mm of the implant. Data were collected (reliability of 1.6% for both parameters) and analyzed by an observer blinded to implant material using IMAGE analysis software for differences between jaws, implant biomaterials, and jaw/biomaterial (analysis of variance, pairwise comparison using least squares method with Bonferroni adjustment). The results indicated that the overall mean %BIC was 55.8 and mean %BA was 48.1. Maxillary and mandibular differences for both parameters were statistically significantly different: %BIC in maxilla 50.8, in mandible 60.8; %BA in maxilla 43.6, in mandible 52.6 (both significant at the P < .05 level). The biomaterial analyses revealed no significant differences between the different implants for %BIC or %BA. The trend observed--that mandibular values were greater than maxillary values for the overall jaw comparisons--was found to be consistent at the jaw/biomaterial level, although the small sample size limited statistical power. These data, along with data from a previous 3-month study, provide insight into baseline supporting anatomy for dental implants.

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.

Differential regulation of interleukin-1alpha and interleukin-1beta in K-562 cells.

Interleukin (IL)-1alpha and IL-1beta are encoded by two separate genes, but both function as comitogens for lymphocyte activation. In this study, we observed K-562 cells to express constitutively mRNA for IL-1alpha, although IL-1alpha was not detected in the growth-conditioned medium (GCM). However, IL-1beta mRNA was not expressed unless the cells had been treated with phorbol myristate acetate (PMA). Both IL-1alpha and IL-1beta were detected in the GCM after the cells had been cultured with PMA, suggesting that IL-1 elaboration required PMA treatment. The K-562 cells treated with PMA differentiated to the myeloblastic stage, as observed by nuclear morphologic properties by electron microscopy. PMA treatment induced de novo expression of CD61 or gpIIIa, a marker associated with megakaryoblasts. These results showed that although K-562 cells constitutively expressed IL-1alpha mRNA, PMA treatment was required for secretion. On the other hand, both the expression and secretion of IL-1beta required treatment with PMA. This study showed that K-562 cells treated with PMA differentiated to the myeloblastic stage and expressed and secreted IL-1alpha and IL-1beta.

Experimentally induced upper facial third fractures in unembalmed human cadaver heads.

Considerable need exists in the transportation industry to develop safety guidelines to protect the head and neck. One of the goals of this study was to produce facial fractures similar to those induced in motor vehicle crashes. Unembalmed cadaver heads were fixed to a supporting device and impacted with a steel pipe. The most common fracture was of the frontal sinus; multiple orbital wall, naso-orbitoethmoid, Le Fort I, II, and III fractures were also produced. Average impact speeds of 7.2 meters per second striking at the supraorbital rims created severe injury to both skull and contents. Energy absorption values accounted for the actual total contact time between head and pipe with tolerance level values measuring the force at specific intervals. The method described may be used to reproduce reliably those forces resulting in the facial fractures seen in the emergency room setting after motor vehicle crashes.

Quantitative histomorphometric description of implant anchorage for three types of dental implants following 3 months of healing in baboons.

Important to the understanding of the dynamics associated with dental implant anchorage over time is a knowledge of the supporting anatomy for common endosseous implants prior to being placed into function. This study followed 20 screw-shaped dental implants placed in edentulated (2 months' healing time) posterior jaws of five adult female baboons. Implants made of three biomaterials were placed and allowed to heal for 3 months prior to processing for evaluation. Percentage integration and bone area data from six horizontal sections along the entire length of each implant were collected and analyzed for differences between jaws, implant biomaterials, jaw/biomaterial, and sections of the implants (ANOVA, pairwise comparison using LSM with Bonferroni adjustment). The results indicated that overall mean percentage integration was 46.5 and mean percentage bone area was 39.9. Maxillary and mandibular differences for both parameters were statistically different (integration: maxillary = 38.1%, mandibular = 56.7%; bone area: maxillary = 35.8%, mandibular = 44.9%; both were significant at the P < .05 level). The biomaterial analyses revealed significant differences for percentage integration between the metal implants and the hydroxyapatite-coated implant (commercially pure titanium = 39.1%, titanium-aluminum-vanadium = 40.0%, hydroxyapatite-coated = 61.5%), but no such difference was noted for percentage bone area (commercially pure titanium = 38.8%, titanium-aluminum-vanadium = 38.9%, hydroxyapatite-coated = 42.3%). Discussion of the relative importance of the two parameters highlights the fact that resistance to functional loads requires establishing and then maintaining an adequate volume of bone, which may have a functionally specific structure based on the mechanical properties of the local jaw environment.

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.

The Christensen prosthesis. A retrospective clinical study.

The objective of this study was to determine if the Christensen temporomandibular joint prosthesis system in an effective alternative in treating patients with severe temporomandibular joint disorders. A total of 69 patients who were not responsive to either nonsurgical or prior surgical treatments were placed into one of three treatment groups depending on the following diagnoses: (1) placement of a glenoid fossa-eminence prosthesis with meniscus retention (22 patients, 40 joints); (2) placement of a glenoid fossa-eminence prosthesis without retention of the meniscus (26 patients, 49 joints); (3) total joint replacement (21 patients, 34 joints). Patients were evaluated immediately before surgery and at regular intervals after surgery for an average of 3.1 years. Success was measured as a significant improvement of function and decrease in pain as measured on a visual analogue scale, as well as improved incisor opening as measured with a Therabite Scale (Lorenz Surgical, Jacksonville, Fla.). Comparison of mean and average pre- and postsurgical values for all groups and criteria showed significant improvement. Results of this study indicate that the Christensen temporomandibular joint prosthesis system may offer a viable method for the treatment of severe temporomandibular joint disease with a high degree of success.

Lowered susceptibility of K-562 cells treated with gamma interferon in serum-free medium to natural killer cell-mediated cytolysis.

K-562 cells grown in serum-free medium were treated with gamma interferon (IFN-gamma) and they became significantly less susceptible to natural killer (NK) cell-mediated cytolysis. To examine if this loss in susceptibility was related to induced differentiation events, the presence of various antigens was determined after induction. There was a coincident expression of class I HLA common antigen, although it is not clear if this is a direct causal relationship. The level of the constitutively expressed myelomonocytic antigen, reactive with anti-Leu-M1, was not affected by IFN-gamma induction and three normally nonexpressed monocytic antigens, defined by monoclonal antibodies, remained unexpressed. IFN-gamma did induce an enhanced expression of IL-2 receptors on K-562 cells after 2 days of treatment but, thereafter, the expression appeared to be suppressed. Electron microscopy of IFN-gamma-treated cells revealed the development of increased surface blebbing and electron-dense cytoplasmic inclusions. These ultramicroscopic changes could not be correlated with definitive differentiation events. We suggest that IFN-gamma treatment of K-562 cells induces class I HLA expression and morphological changes that may be important to differentiation events that render the cells less susceptible ot NK-mediated cytolysis.

Proliferation and differentiation of human myeloid leukemic cells in immunodeficient mice: electron microscopy and cytochemistry.

To study the influence of a biologic environment on cultured human leukemia cells, KG-1, KG-1a, and HL-60 cells were inoculated subcutaneously into newborn nude mice. The cells developed myelosarcomas at the site of inoculation and in lungs and kidneys. KG-1 and HL-60 myelosarcomas were successfully passaged through adult nude mice, whereas KG-1a tumors proliferated only after transplantation into newborn hosts. The human nature of the cells forming myelosarcomas in mice was assessed by chromosomal analyses and detection of cross-reactivity with an antibody to the human leukemia cell line K562. We undertook electron microscopic and cytochemical examinations of the cells proliferating in vitro and in the mice. The granules of KG-1 cells in vivo did not react for acid phosphatase, as observed in vitro, and the HL-60 cells proliferating in mice lost the perinuclear myeloperoxidase (MPO) demonstrated in cultured cells. Although the influence of an in vivo selection of cell subpopulations cannot be ruled out, the enzymatic changes are compatible with induced cell differentiation. Conclusive evidence of differentiation in vivo was observed in the KG-1a cell subline. The undifferentiated KG-1a blasts developed cytoplasmic granules and synthesized MPO during proliferation in vivo. These observations indicate that human leukemia cells from established cell lines proliferate in nude mice and may acquire new differentiated properties in response to the in vivo environment.

Local and metastatic growth and in vivo differentiation of human myeloid leukemia cells transplanted in nude mice.

Cells from the established human myeloid cell lines KG-1, KG-1a, and HL-60, transplanted subcutaneously (sc) into nude mice, developed discrete tumors (myelosarcomas). These myelosarcomas had a host's age-associated pattern of growth identical to that of experimental tumors produced by sc transplantation of cells derived from malignant solid neoplasias. Thus, leukemia cells yielded either localized myelosarcomas at the site of inoculation or a disseminated neoplastic growth after inoculation in adult (more than 4 weeks old) or newborn (1-3 days old) nude mice, respectively. Human myeloid leukemia cells proliferating in the nude mice preserved the human karyotype and a surface antigenic determinant and did not influence the hematopoietic tissues of the host. The KG-1 and HL-60 cell lines consistently attained varying degrees of differentiation along the myeloid series in vitro, and these features were maintained during proliferation in the mice. Furthermore, cells of the variant subline KG-1a, which had a blastic morphology, developed signs of differentiation that were not seen in culture. The presence of readily identifiable markers, such as cytoplasmic granules containing myeloperoxidase, in the cell lines tested makes these models particularly useful for studying the influence of a biological environment on cell differentiation and its influence on tumor growth. These experimental systems are also suitable for investigating the mechanism(s) of metastases and for in vivo experimental therapeutic trials.

Absence of morphological, chromosomal and antigenic changes in the K-562 cell line growing as localized or disseminated tumours in nude mice.

Transplantation of K-562 cells into adult and newborn nude mice led to the development of localized s.c. and disseminated myelosarcomas, respectively. This age-associated, changing pattern of in vivo proliferation of K-562 cells derived from a single aliquot was consistently repeated throughout sequential passages. The only variable in this experimental system was the age of the recipient mice. Not only did the mice have an identical genetic background, but also the transplanted K-562 cells were derived from a single culture passage. As shown by cytological and histological examinations, the characteristic morphology and percentage composition of the subpopulations of the K-562 cell line were preserved in successive in vitro and in vivo passages. The K-562 cells had no prevailing phenotypic traits which could be associated with the growth either in the s.c. tissue or in the viscera. Furthermore, the cells maintained the human karyotype, including their typical chromosomal abnormalities and antigenic determinants, as demonstrated by the binding of a specific antibody, throughout all passages. Our results demonstrate that heterotransplanted K-562 cells may change their behaviour in vivo without undergoing modifications associated with different types of growth. These findings would indicate that the ability of neoplastic cells to proliferate in various environments (metastases) is not the consequence of predetermined cellular characteristics but is functionally conditioned.

Arrest and extravasation of neoplastic cells. An electron microscopy study of serial sections at sequential stages.

The morphological aspects of the arrest and extravasation of malignant cells of human origin (K-562 cell line) in the lungs of athymic (nude) and asplenic-athymic (lasat) mice were studied by electron microscopy examination of serial sections. The specimens were obtained at sequential stages after the sc inoculation into newborn mice of 10(7) malignant cells. K-562 cells (10(5)) were also injected iv into control groups of nude and lasat mice to assess the influence of the route of inoculation on the in vivo behavior of K-562 cells. Our results demonstrated that K-562 cells were arrested and proliferated within the pulmonary capillaries without the participation of platelets or fibrin. The neoplastic cells extravasated by attrition and penetration of the endothelium (rather than by diapedesis) and continued to proliferate in the interstitial tissue of the lung, developing into neoplastic nodules. Following iv injection, K-562 cells induced the formation of platelet-tumor cell aggregates within the pulmonary capillaries. However, under these conditions, the neoplastic cells did not adhere to the endothelium nor did they proliferate or extravasate. These aggregates were flushed out by the circulation, restoring the permeability of the capillaries.