Preliminary studies on the phenomenological behaviour of osteoblasts cultured on hydroxyapatite ceramics.

SEM was used to investigate the phenomenological behaviour of osteoblasts towards sintered hydroxyapatite. The osteoblasts were seeded on to porous and dense hydroxyapatite and cultured for 4 to 28 d. They attached and adhered on to the hydroxyapatite surfaces, proliferated and secreted extracellular matrix. No signs of toxicity embarrassment were apparent. It is argued that cell phenomenology seems to be a prerequisite to morphogenesis, and on this premise it is speculated that surface-reactive bone replacement materials owe their compatibility to the ability of their surfaces to interact favourably with the peptides involved in osteomorphogenesis and bone repair.

Interaction of osteogenic cells with hydroxylapatite implant materials in vitro and in vivo.

In a series of scanning electron microscopic studies, the reaction of osteogenic cells to hydroxylapatite (HA) implant materials was investigated in culture and following implantation. Tissue components as found in normal rat and dog bone were identified at the interface in both test systems. In vivo, implant bed cells showed an intimate contact with the HA surfaces. Osteoblasts deposited organic matrix and bone mineral in direct apposition to HA, with no evidence of encapsulation or granulation tissue. The development of such a direct spatial relationship appears to involve mechanisms more encompassing than epitaxis.

Cellular and molecular biological events at the implant interface.

Since implants attain and maintain contact with the body environment through their surfaces, the interfacial interaction between implant bed and implant surface could be a determinant of the implant's performance. This study used osteoblasts to test the ability of different ceramic and metallic surfaces to bind fibronectin and to support cell attachment, adhesion, migration and synthesis of extracellular matrix. The results showed active molecular and cellular interaction between the cells and the surfaces. Extracellular matrix synthesis was demonstrated on surfaces that did not subject the cells to toxicity embarrassment. It is concluded that the surfaces of implants should not be designed to be mere bystanders in the interfacial scenario. Instead they should be conceived with a view to enabling them to interact positively with the molecules responsible for would healing, interfacial tissue morphogenesis and repair.

Comparison of transcutaneous incisions used for exposure of the infraorbital rim and orbital floor: a retrospective study.

One hundred and five patients were investigated for functional and aesthetic impairments following treatment of orbital trauma through subciliary, mid-lower eyelid, or infraorbital incisions. The progress of impairments with time was assessed, and the merits and shortcomings of each of the three approaches were established. The results showed that impairments persisting up to 6 months postoperatively have virtually not receded even after 6 years. The infraorbital incision showed the highest frequency of impairments, followed by the subciliary incision. The mid-lower eyelid incision showed the best results, with an impairment frequency well below those of the other two approaches. This approach seems to combine the advantages of the infraorbital incision with the unnoticeable scar formation associated with the subciliary incision.

Mechanisms and structure of the bond between bone and hydroxyapatite ceramics.

Two assays were carried out to investigate the postulates that dissolution/reprecipitation phenomena and epistaxis are involved in the formation of the bond between sintered hydroxyapatite (HA) and bone. HA was exposed to a physiologic solution and the ions going into solution quantified using inductively coupled plasma (ICP) emission spectroscopy. The HA was retrieved and examined using scanning electron microscopy (SEM). In the second assay, HA was implanted into Alsatian femura. Following retrieval, specimens were prepared and studied with SEM, at magnifications usually reserved for transmission electron microscopy (TEM). In vitro the HA surface composition appeared to shift to the acidic (calcium-deficient) direction. The HA surfaces in both assays underwent a dissolution/reprecipitation degradation of varying severity, forming a recrystallization layer of spherocrystallites. Two modes of bone bonding to implanted HA were identified: (1) bone tissue components bonded to HA via a recrystallization zone similar in structure to the reprecipitation layer in the corrosion assay, and (2) bone tissue components bonded directly to HA crystals with no morphologically discernible signs of dissolution embarrassment. The formation of the bone/HA bond seems to involve dissolution/reprecipitation phenomena. What is believed to be the first morphological evidence of epitaxial growth involvement in the formation of this bond is presented.

Interfacial reactions of osteoblasts to dental and implant materials.

Scanning electron microscopy was used to study the response of osteoblasts to various surfaces including ceramics and glasses as well as steel and titanium. Hydroxylapatite, tricalcium phosphate, bioglass, steel, and titanium supported cell adhesion. However, the toxic effects of the In-Ceram (Vita, Bad Säckingen, Germany), and feldspar ceramic and glaze were severe enough to cause verrucous necrosis that was identifiable after 2 days of culture. After 10 days in culture only the peripheral portions of these specimens were still occupied by cells; the cells in the central portion of the circular specimens had succumbed to necrosis. It was concluded that scanning electron microscopy is useful in identifying the response of cells to materials. Pathologic changes are not recognizable if they are limited to the internal structure of the cell, but readily discernible when they impinge on the morphologic integrity of the cell surface.