[Maxillar osteonecrosis associated with bisphosphonate treatment and dental implants]. / Ostéonécrose maxillaire sous bisphosphonates et implants dentaires.

INTRODUCTION: Bisphosphosnates are reference products used to treat osteoporosis, malignant bone disease, Paget's disease, and hypercalcemia. However these drugs seem to induce osteonecrosis of the jaws. This osteonecrosis is frequently observed and must be evoked in patients presenting with oral ulceration under bisphosphonate therapy. OBSERVATION: We report the case of a long-term fully dental implanted patient treated by bisphosphonates who presented a maxillar ostenecrosis with no previous radiotherapy. DISCUSSION: The risk factors and mechanism of this induced osteonecrosis are described. But could long term osseo-integrated dental implants be a triggering factor?

[The transitional bridge in early implant loading: history, design, installation, perspectives]. / Le bridge transitoire lors de la mise en charge précoce: historique, conception, mise en place, évolution.

The progress made in implantology since the work of Pr. Branemark has led to the development of early functional implant loading. This satisfies one of our patients' primary goals: restoration of fixed dentition as quickly as possible. This article describes the history, design, installation technique, and perspectives for the transitional prosthesis, the most important component of this early loading concept.

A novel spectrofluorometric technique for specific biocompatibility testing of implantable materials by cell culture. Report on use for multiparameter analysis of human osteoblasts cultured on commercially pure titanium and hydroxyapatite.

The authors describe a novel spectrofluorometric technique based on double-labelled fluorescence imaging using immunoconjugates labelled with fluorochromes. Following isolation and characterization, cells are seeded on the surface of disks of the material(s) to be tested. After application of a primary antibody and an antibody bearing a fluorochrome, the signal emitted by the molecules in the extracellular matrix on the surface of the test disks is measured by spectrofluorimetry. Measurement is thus independent of the surface characteristics of the test material. Measured values are compared with pre-established standard curves. This technique facilitates determination of the characteristic molecules expressed by a given cell type,thus allowing accurate evaluation of the response of pertinent biological samples to implantable biomaterials.

Immediate function of cortically anchored disk-design implants without bone augmentation in moderately to severely resorbed completely edentulous maxillae.

The completely edentulous maxilla remains a challenge in implant dentistry. Conventional two-stage surgical techniques require two independent invasive surgeries separated by a 5-6-month healing period. In addition, an increased risk of trauma to the implant-bone interface may be caused by a removable transitional complete denture during the interim submerged period, which can compromise implant success or increase crestal bone loss around the implants during initial bone healing. The purpose of this clinical trial was to evaluate the safety and efficacy of immediately loading a fixed implant-supported prosthesis without bone augmentation in moderately to severely resorbed, completely edentulous maxillae. Over a 41-month period, 783 titanium implants (627 laterally inserted disk implants, with or without 156 axially inserted Structure implants) were placed in 72 consecutive patients with completely edentulous maxillae using an immediate loading protocol. After 6 months of function, the fixed restorations were removed and each implant status was verified using radiographs, Periotest evaluations, clinical osseointegration criteria, and torque testing at 20 N-cm. Six months postoperatively, 98% of the implants were radiologically and clinically osseointegrated. Fifty-six gold screws (7%) required retightening after 10 months, but no screw fractures occurred during this study period. The postrestorative follow-up of these patients ranged from 6 to 48 months. As of this report, all of the fixed prostheses remain functional, and no additional implants have been lost. This clinical trial demonstrates that immediate loading of nonsubmerged, laterally inserted disk-design implants may provide adequate primary anchorage and longterm osseointegration in completely edentulous maxillae. The initial multicortical anchorage afforded by the disk-design implant in this study, coupled with biomechanical splinting of the disks (sometimes with more traditional root-form design implants) using a rigid prosthesis, permits a one-stage predictable implant procedure offering rapid restoration of patients to masticatory function.

Characterization of endosteal osteoblasts isolated from human maxilla and mandible: an experimental system for biocompatibility tests.

Fragments of cancellous and cortical bone from human maxilla and mandible were cultured by the explant technique. Cells isolated by trypsinization of primary cultures were characterized as osteoblasts on the basis of intracellular alkaline phosphatase activity, the constituents of the extracellular matrix, and response to human parathormone (PTH). In culture, the osteoblasts often gave rise to superposed clumps of large cells whose cytoplasm contained endoplasmic reticulum, numerous mitochondria, vacuoles, and a dense network of intermediate filaments, often at the level of the plasma membrane. In the presence of vitamin C and 1,25-dihydroxyvitamin D3, the osteoblasts produced an extracellular matrix composed of collagen type I and various non-collagenous proteins, including osteocalcin. Biochemical test results were comparable to those reported for osteoblasts of other origins (rat calvaria, human iliac crest), and namely elevated intracellular alkaline phosphatase activity and cAMP accumulation in response to stimulation by human PTH (1-34). Osteoblasts isolated in this manner were cultured in the presence of pure titanium disks to determine the effects of exposure to this metal. Electron microscopy revealed few significant differences in cell growth and specific enzyme activity compared to control osteoblasts grown on plastic dishes, reflecting the excellent biologic and biochemical relationship between the osteoblasts and pure titanium. This experimental system thus appears suitable for biocompatibility studies, and in particular, evaluation of dental implants.

[The implant denture in the laboratory]. / La prothèse implantaire au laboratoire.

The authors analyzed the numerous devices and prosthetic kits currently available for implant prosthodontics. Existing systems can be classified into two fundamentally different categories: the gold ring cylinder (or its equivalent in resin for casting) and the prosthetic abutment core or post concept. The former is based on connection of two nearly flat, horizontal surfaces by means of a screw, which avoids problems of parallelism; the latter can be likened to insertion of one part into another, like a crown that slides along the vertical axis of an abutment, with connection being obtained by cementation and/or screwing. Prosthetic abutment core or post: Whether monoblock or multiblock, the implant core or post is very similar to a conventional metallic abutment. Construction of the implant prosthesis is generally no problem when parallelism has been respected during surgery; if problems are encountered with parallelism, options include: 1. Adjustment of the abutment core by grinding, 2. Use of a telescope to achieve parallelism, 3. Use of a bendable prosthetic abutment core, 4. Use of a prosthetic abutment core preangulated 10 degrees-20 degrees, 5. A combination of the above solutions. The implant prostheses may be screwed, cemented or clipped in position. Gold ring cylinder concept The gold ring cylinder (or its equivalent in resin for casting) theoretically eliminates problems of parallelism, but at the same time restricts the implant prosthesis to screw techniques. A special protocol is required for the impression and construction of the prosthesis. Impression with plaster is often the best method for total edentulism whereas "open" impression trays are advisable for partial prostheses. In the laboratory, use of a machined gold ring cylinder provides optimum precision, but intra-oral verification remains necessary. Implant prosthodontics unquestionably represent a new type of "know how": both the dentist and the dental lab technician must acquire the necessary training and adapt their work routines.