[Study of two types of dental implants for immediate loading (expansion implants and locking pin implants) in the Beagle dog]. / Etude de deux types d'implants dentaires pour la mise en charge immediate (implants à expansion et à clavettes) chez le chien Beagle.

Titanium implants have become a treatment of choice for total or partially edentulous patients. The method, however, requires a double surgical time and the placement of the dental prosthesis after a healing phase of 3 to 6 months during which the patients have a toothless mandible with the top of the implants emerging at the gengiva. Immediate loading of standard implants is responsible for micromotions which induce implant failure. New designs of implants would allow an immediate anchoring in the bone, would prevent the shearing forces and would precociously authorize the setting of the prosthesis. We made an experimental study in the Beagle dog. After partial tooth removal, two types of implants were placed (expansion implants and locking pin implants). After 2 weeks, the implants were covered with a gold-palladium prosthesis and left in place during 12 weeks. After sacrifice, a study by resonance frequency (ISQ) and histomorphometry was done. The two types of implants were covered by the same quantity with bone (volume and interface) without interposition of fibrous tissue. The locking pin implants were associated with an increase in the ISQ parameter of stability, higher than that of the expansion implants. The locking pin implant, tested in the dog which has a chewing function close to man, appears interesting for the immediate loading with dental prosthesis.

Image analysis measurements of roughness by texture and fractal analysis correlate with contact profilometry.

Surface properties of a biomaterial are important factors that govern in part its biocompatibility. Among them, surface roughness is now recognized as a very important factor for cell interactions. Surface roughness (Ra) is routinely measured by contact profilometry but other methods are presently usable. We compared two methods (contact profilometry and image analysis of scanning electron microscopic images SEM) on a series of 12 titanium test pieces. The texture analysis of SEM pictures was done by the heterogeneity and run-length methods. Fractal geometry was also used with the "skyscraper" and "blanket" methods providing respectively the D(SKY) and D(BLANK) fractal dimensions. The fractal dimension of the profilometric curve was also computed (D(MINK)). Computer-simulated textures were used to evaluate the pertinence of the algorithms. A significant correlation was found between Ra and all the texture descriptors except heterogeneity. The correlation coefficient was dependent on the microscopic magnification. The fractal dimension of the curve was correlated with D(SKY) and D(BLANK). Run-length, D(SKY) and D(BLANK) were highly correlated, independent of the magnification used, a finding related to the self-similarity of the images. Image texture analysis can be a useful alternative to profilometry with brittle or soft materials or with objects having a complex shape.

Enhanced bone integration of implants with increased surface roughness: a long term study in the sheep.

OBJECTIVES: This study evaluated the quality and the remodeling of bone around commercially pure titanium implants after 3, 6, 12 and 18 month implantation periods in the sheep. METHODS: Twelve animals were implanted in the cortico-trabecular areas of both femurs. Each femur received four implants with a rough surface (type 1) in the right femur and four with a smooth surface (type 2) in the left one. Bone blocks containing the implants were studied by histomorphometry on undecalcified specimens. The amount of bone around implants was measured (bone volume, fractional woven bone volume, bone thickness, contact interface) together with osteoblastic activity (mineral apposition rates, bone formation rates) and resorption activity (eroded surfaces). RESULTS: No significant differences could be observed for the two types of implants between 3 and 6 months. At 12 and 18 months, bone volume and contact interface were still increasing and there was always a tendency for type 1 implants to be associated with higher values. On the contrary, mineral apposition rate, bone formation rates and eroded surfaces decreased in the referent area in contact with the implant; this phenomenon of 'return to the normal' was more evident with type 1 implants. The remodeling process appears to increase bone quality and bone-titanium interface around implants in long term periods. CONCLUSIONS: The net bone quantity necessary to immobilize implants is obtained rapidly but the adapting process to mechanical strength can lead to a small but persistent increase in bone volume around implants. Although the differences between type 1 and type 2 implants were often small or statistically insignificant, the rougher type 1 implants seemed to be associated with stronger bone response.

Effects of roughness, fibronectin and vitronectin on attachment, spreading, and proliferation of human osteoblast-like cells (Saos-2) on titanium surfaces.

The influence of surface roughness and the presence of adhesion molecules in the culture medium were studied regarding cell adhesion, shape, and proliferation of osteoblast-like cells grown on two types of titanium disk. Type I disks were acid etched and type II disks were sandblasted and acid etched. Surface roughness was determined by contact profilometry and scanning electron microscopy. Chemical composition and oxide thickness of the superficial titanium layer were established with energy dispersive X-ray spectrometry, electron spectroscopy for chemical analysis and auger electron spectroscopy. Titanium release in the culture medium was assessed by inductively coupled plasma-optical emission spectrometry. Osteoblast-like cells (Saos-2) were cultured on both types of titanium disks (1) in standard conditions (DMEM culture medium supplemented with fetal calf serum), (FCS), (2) with the culture medium alone (DMEM alone), (3) in the presence of fibronectin or vitronectin (DMEM supplemented with fibronectin or vitronectin). Cultures were also performed in the presence of monoclonal anti-integrin (beta1, alphav) to test the cell adhesion molecules involved in the cell binding to the titanium surface. We found that sandblasting does not modify the chemical surface composition and that titanium represents only 5-6% (in the atom percentage) of surface elements. Release of titanium in the culture medium was found to increase from 24 to 72 hours. In the absence of FCS, fibronectin, or vitronectin, cells appeared scanty and packed in clusters. On the contrary, cells cultured in the presence of FCS, fibronectin, or vitronectin were flattened with large and thin cytoplasmic expansions. The addition of anti beta1 or alphav integrin subunit monoclonal antibody in the culture medium decreased adhesion and spreading of cells, particularly in the presence of fibronectin. Cell proliferation was significantly higher on culture plastic than on both types of disks, but was increased on rough but not on smooth surfaces. These results indicate that a high surface roughness and presence of fibronectin or vitronectin are critical elements for adhesion, spreading, and proliferation of cells on titanium surfaces.

The early remodeling phases around titanium implants: a histomorphometric assessment of bone quality in a 3- and 6-month study in sheep.

The purpose of this study was to evaluate the quality of the bone matrix around commercially pure titanium implants at 3 and 6 months postplacement in sheep. Implants were placed in the corticotrabecular areas of both femurs in 6 animals. Each animal received 4 Euroteknika implants in the right femur and 4 Nobel Biocare implants in the left femur. Bone blocks containing the implants were studied undecalcified after being embedded in methylmethacrylate. Sections were stained with toluidine blue and basic fuchsin. The amount of bone around the implants, the contact interface between the implant and bone, and the mineral apposition rates were measured. The fractional amount of woven bone could be quantified because of its high glycosaminoglycan content. No differences could be observed between the 2 types of implants. Total bone volume did not increase around both types of implants between 3 and 6 months, indicating that ankylosis was rapidly achieved. In contrast, in the area in contact with the implant, the bone-titanium interface drastically increased and the mineral apposition rate decreased. The fractional volume of woven bone around implants was considerably reduced after 6 months. Bone quality around implants was improved at 6 months (volume of woven bone near zero), and true osteonic structures were observed in close contact with titanium. The remodeling process appeared to improve bone quality and increase the bone-titanium interface around implants, while the net bone quantity necessary to immobilize implants was achieved rapidly and remained unchanged.

Does titanium surface treatment influence the bone-implant interface? SEM and histomorphometry in a 6-month sheep study.

Two types of threaded titanium implants (Euroteknika and Nobel Biocare) were compared in a 180-day in vivo experiment in sheep. The implant characteristics were analyzed by scanning electron microscopy and image analysis to determine the roughness index of the surface. Implant specificity appeared through their slightly different chemical composition, their peculiar thread morphology, and their different roughness indexes (0.214 and 0.139, respectively). Implants were placed in the distal part of the tibial diaphysis. Histomorphometric analysis of the bone-implant interface was done on bone sections processed undecalcified. Both types of implants exhibited a similar bony reaction, with haversian bone in close contact with the titanium surface without interposition of fibrous tissue. The interface length percentage covered by bone was not significantly different between the two types of implants.

[Original endosseous implant therapy to resolve the problem of posterior unilateral or bilateral edentulousness of the upper jaw]. / Therapeutique implantologique endo-osseuse originale pour résoudre le probleme de l'édentement postérieur uni ou bilatéral au maxillaire supérieur.

An increased pneumatization of the maxillary sinus and an important alveolar crest resorption usually means a contra-indication to any endosteal implantation unless a grafting of the maxillary sinus is attempted. As early as 1986, a scanner analysis was performed over 200 patients to scrutinize a new anatomical approach of the tubero-pterygoid junction. The maxillary bone, especially the tuberosity is extremely spongious and fragile. On the other side the tubero-pterygoid junction at the boundary of the palatal bone and the two pterygoid wings presents a limited site but essentially cortical, very secure to assure the primary stability of a Brånemark implant. The scanner X-ray enhances the tubero-pterygoid junction and allows to reposition it in the three planes. It mainly consists of superimpositions of computerized coronal and axial tomographs. The scanner computer is providing the right pathway from the tuberosity to the pterygoid process.