Considerations preliminary to the application of early and immediate loading protocols in dental implantology.

In oral implantology, a 3-6 month stress-free healing period is presently accepted as a prerequisite to achieve bone apposition without interposition of a fibrous scar tissue. This protocol was introduced by Brånemark and co-workers in 1977. The aim of the present paper is to review the reasons that led Brånemark and collaborators to require long delayed loading periods. It is shown that the requirement for long delayed loading periods was drawn from the initiation and development periods of their original clinical trial. Demanding conditions were met involving simultaneously: 1) patients with poor bone quality and quantity, 2) non-optimized implant design, 3) short implants, 4) non-optimized surgical placement, 5) non-optimized surgical protocol and 6) biomechanically non-optimized prosthesis. Extrapolation of the requirement for long healing periods from these particular conditions to more standard situations involving refined surgical protocols and careful patient selection might be questioned. Albeit premature loading has been interpreted as inducing fibrous tissue interposition, immediate loading per se is not responsible for fibrous encapsulation. It is the excess of micromotion during the healing phase that interferes with bone repair. A threshold of tolerated micromotion exists, that is somewhere between 50 microns and 150 microns. It is suggested that loading protocols might be shortened through 2 different approaches. The first way would be to decrease stepwise the delayed loading period for free-standing implants below the presently accepted 3-6 months of healing. The second way would be to identify immediate loading protocols that are capable of keeping the amount of micromotion beneath the threshold of deleterious micromotion. Immediate loading protocols for implants-retained overdentures and fixed bridges are reviewed. It is shown that successful premature loading protocols require a careful and strict patient selection aimed to achieve the best primary stability. These various protocols need to be further documented in order to assess their predictability.

Evaluation of combinations of titanium, zirconia, and alumina implants with 2 bone fillers in the dog.

The quality of the tissue-implant interface was evaluated using light and scanning electron microscopy with morphometric analysis. Nine dogs were implanted with 3 types of dental implants (titanium, zirconia, or alumina). A total of 24 dental implants was placed in mandibular bone previously filled with coral carbonate calcium (corail) or hydroxyapatite. The study results in breaking the concept of osseointegration into 2 phases: "osseocoaptation," which concerns only the interface (physical contact between the implants and the bone without interpenetration process), and "osseocoalescence," which relies on an interpenetration of the bioactive material, which almost entirely disappears, being substituted by newly formed bone. There was no significant statistical difference between the 3 types of implants. Both fillings showed good ossecoalescence properties. However, hydroxyapatite led to fibrous encystment, preventing osseocoaptation of implants. In contrast with calcium carbonate filling.

[Parietal grafts in maxillofacial and pre-implant surgery]. / Les greffons pariétaux en chirurgie maxillo-faciale et pré-implantaire.

Due to the recent regulations generated by the diversity of infectious risks, autologous bone is the standard graft material in maxillofacial surgery. Although synthetic biomaterials can be useful, they remain insufficient in many situations. Among the many sites offering graft material, monocortical parietal bone which is accessible within the craniocephalic operative field has distinguishing characteristics due to its membranous embryological origin and its mode of direct ossification which does not include a cartilaginous stage. The proportion of cancellous bone per unit volume is much higher than in enchondral bone (iliac bone, ribs...). These factors are undoubtedly the source of its main qualities--very little resorption and excellent capacity for bony integration--motivating its increasingly widespread use over the past twenty years. We present our experience in a series of patients who underwent surgery between 1992 and 1997. Parietal bone was used for orthognathic, pre-implant or reconstruction surgery after trauma or carcinological trauma. We present a description of the surgical procedures together with morbidity results and compare our findings with those found in large series in the literature, particularly concerning rare neuromeningeal complications. We discuss indications for parietal grafts and their course at the receiver site.

Timing of loading and effect of micromotion on bone-dental implant interface: review of experimental literature.

A significant no-load healing period is the generally accepted prerequisite for osseointegration in dental implantology. The aim of this article was to examine whether this no-load healing period is validated by the experimental literature. In vivo histological data was scrutinized to identify the effect of early loading protocols on the bone-implant interface. Several loading modes were identified. They were categorized into groups according to implant design and the type of prosthetic reconstruction, and by their ability to introduce a distinct magnitude of motion at the interface. Specific histologic responses of early loaded implants (i.e., fibrous repair or osseointegration) were suggested to be directly related to the specific combinations of the above parameters. Early loading per se was not found to be detrimental to osseointegration. Specifically, only excessive micromotion was directly implicated in the formation of fibrous encapsulation. The literature suggests that there is a critical threshold of micromotion above which fibrous encapsulation prevails over osseointegration. This critical level, however, was not zero micromotion as generally interpreted. Instead, the tolerated micromotion threshold was found to lie somewhere between 50 and 150 microns. Suggestions are made for the earliest loading time that achieves osseointegration.

[Ceramic implants to benefit complete lower dentures]. / Les implants en céramique au secours de la prothèse totale inférieure.

In our Department of implantology, 141 ceramic implants were put in place with the objective of stabilizing a complete mandibular prosthesis in 39 patients. Despite the small number of cases reported, statistical analysis was informative because of the homogeneity of the conditions: the same indication for a prosthesis; the same operator for the surgery as well as the prosthesis; The very good follow-up with all but 2 patients having been monitored regularly. In addition to the finding that our results are practically superposable on those obtained with titanium implants over the same period of time. We share our experience with ceramic materials; dispel their reputation of fragility, especially since the advent of zirconium; and emphasize the simplicity of these "artificial roots" that can be use without prefabricated and costly intermediate parts.

[Anatomo-radiological study of edentulous jaws prior to implant placement]. / Etude anatomo-radiologique des maxillaires de l'édenté en vue de la mise en place d'implants.

In the case of a total loss of teeth, a conventional understanding of descriptive anatomy is no longer sufficient. It does not take into account: The principles of osteo-architecture allowing the distribution of different types of bone structure (Haversian, spongy, papyracious) to be understood; The mechanisms of bone resorption; The new anatomical relationships created by such resorption.

[Contribution to the experimental study of endosseous sintered ceramic implants]. / Contribution à l'étude expérimentale des implants endo-osseux en céramique frittée.

The authors present the preliminary results of an experimental study of the biocompatibility of materials used in oro-maxillo-facial surgery (filling in of detects and implants). These preliminary results concern sintered ceramic implants and confirm their good acceptability by soft tissues and bone.

Is osseointegration a requirement for success in implant dentistry?

The term 'osseointegration' was coined in 1977. This term gained popularity and has been extensively used, but with various and diverging meanings; therefore, there is a strong need to redefine it. We propose a definition of the concept of osseointegration grounded on a physical basis. Since bioactive biomaterials are more strongly integrated than inert ones (e.g. titanium or alumina), and since osseointegration is a word implying strong bonding, we propose to devote the use of the concept of osseointegration for materials which are most successfully integrated into bone, i.e. when the bone/implant interface is a diffuse interface with full chemical bonding, such as for bioactive biomaterials. If the bone/implant interface is a sharp one, the concept of osseointegration is no longer relevant and we propose use of the term 'osteal integration', i.e. for inert biomaterials, such as titanium and alumina. Based on this proposition, we assert that osseointegration is not a requirement for success in implant dentistry.

[Criteria for choosing an endosseous implant. Clinical and fundamental results concerning sintered ceramic implants]. / Critères de choix d'un implant endo-osseux. Résultats cliniques et fondamentaux concernant les implants en céramiques frittées.

In our opinion, the primary criteria are: absence of severe residual lesions in case of failure of the implant, implant material with demonstrated biocompatibility and which does not interfere with modern medical imaging techniques (CAT-scan, NMRI); ceramics meet this criteria, an implant morphology allowing for perfect initial stabilization, sparing of tissue and good distribution of transmitted forces to bone, an easy, accurate and nontraumatic implantation technique, the possibility of connecting the implant to fixed or movable structures by precision prefabricated accessories, dismantlable if possible, convincing animal experiments and clinical results in large series with a follow-up of more than 10 years.

[Restoration of the alveolar crest with a biomaterial filler. A clinical and histological study]. / Restauration de crête alvéolaire par biomatériau de comblement. Etude clinique et histologique.

The implantation of biocompatible hydroxyapatite is used for human mandibular ridge augmentation in edentulous patients. Histologically, we studied such a material after a long period of implantation (1 1/2 to 2 years) in two patients. The histologic study showed a narrow meshed net of collagen tissue surrounding the hydroxylapatite particles. In the periphery of that tissue, we could see an osteogenesis: the bony trabeculae thus formed firstly were made of an immature bony matrix with an irregular "woven" pattern; secondarily, a mature bone, quite similar to the normal bone, occurred. In our two observations, there was an unusual inflammatory reaction characterized by cellular infiltration of lipophages, lymphocytes and plasma cells in the connective tissue and in one case by a true ischaemic necrosis with granuloma and bacteria. In spite of that inflammation, the whole material was well tolerated, without foreign-body granuloma. Such a granuloma was only found in superficial areas of the gingiva, around extruded particles of the biomaterial.