The interaction of osteoblasts with bone-implant materials: 1. The effect of physicochemical surface properties of implant materials.

This comparative study of various surface treatments of commercially available implant materials is intended as guidance for orientation among particular surface treatment methods in term of the cell reaction of normal human osteoblasts and blood coagulation. The influence of physicochemical surface parameters such as roughness, surface free energy and wettability on the response of human osteoblasts in the immediate vicinity of implants and on the blood coagulation was studied. The osteoblast proliferation was monitored and the expression of tissue mediators (TNF-alpha, IL-8, MMP-1, bone alkaline phosphatase, VCAM-1, TGF-beta) was evaluated after the cell cultivation onto a wide range of commercially available materials (titanium and Ti6Al4V alloy with various surface treatments, CrCoMo alloy, zirconium oxide ceramics, polyethylene and carbon/carbon composite). The formation of a blood clot was investigated on the samples immersed in a freshly drawn whole rabbit blood using scanning electron microscope. The surfaces with an increased osteoblast proliferation exhibited particularly higher surface roughness (here R(a) 3.5 microm) followed by a high polar part of the surface free energy whereas the effect of wettability played a minor role. The surface roughness was also the main factor regulating the blood coagulation. The blood clot formation analysis showed a rapid coagulum formation on the rough titanium-based surfaces. The titanium with an etching treatment was considered as the most suitable candidate for healing into the bone tissue due to high osteoblast proliferation, the highest production of osteogenesis markers and low production of inflammatory cytokines and due to the most intensive blood clot formation.

The influence of implant surface properties on cell adhesion and proliferation.

Interactions of the foreign material of implant and the living tissue on the cell level can cause prolonged healing or, worse, loss of the implant. The cell response to the presence of some implant materials was studied under in vitro conditions. The influence of physicochemical surface parameters on the response of the cells in the immediate vicinity of implants, namely on adhesion, proliferation and synthetic activity of fibroblasts, and on the blood coagulation were compared. The direct contact of tested materials (titanium and Ti6Al4V alloy with various surface treatments, Cr Co Mo alloy, hydroxyapatite-coated titanium, zirconium oxide ceramics, polyethylene and carbon composite) on cell spreading was monitored and the presence of TNF-alpha and IL-8 was evaluated in the cultivation medium. The formation of blood clots was investigated on samples immersed in a well with freshly drawn whole rabbit blood using a scanning electron microscope. The surface free energy was estimated using the measurement of static contact angle. Both the advancing and receding contact angles were measured by the dynamic Wilhemy plate method. Two main groups with extremes in cell viability were established. In the first group the increased polar component of surface free energy, the highest cell density, the lowest inflammatory cytokine production, but no fibres in the clotting blood were found. On the contrary, the second group of materials with a very low polar component of the surface free energy showed distinctly higher expression of inflammatory mediators, low cell proliferation, but faster formation of fibres in the blood coagulum.

Osseointegration of loaded dental implant with KrF laser hydroxylapatite films on Ti6Al4V alloy by minipigs.

This study was performed with the objective of evaluating osseointegration of titanium alloy Ti6Al4V dental implants coated with hydroxylapatite (HA) deposited by a KrF laser. For this a KrF excimer laser and stainless-steel deposition chamber were used. The thickness of the HA films was approximately 1 microm. In this investigation experimental animals minipigs were used; the implants were placed vertically into the lower jaw. After 14 weeks of unloaded osseointegration, metal-ceramic crowns were inserted and, at the same time, fluorescent solution was injected into the experimental animals. Six months after insertion of crowns the animals were sacrificed. The vertical position of the implants was checked by a radiograph. Microscopic sections were cut and ground, and the sections were examined under polarized and fluorescent light using a microscope with a charge coupled device camera. The six month long osseointegration in the lower jaw has confirmed the presence of newly formed bone around all the implants. In the experimental group, which had a laser-deposited coating, the layer of fibrous connective tissue was seen only randomly. In the control group (titanium implant without a cover) the fibrous connective tissue between the implant and the newly formed bone was observed more frequently, but this difference was not significant.

Low-level laser therapy after molar extraction.

OBJECTIVE: The aim of the study was to evaluate effect of the different frequencies of low-level laser radiation (diode 670 nm and Helium-Neon 632.8 nm) on the healing process after human molar extractions. Frequencies of 5 Hz, 292 Hz, and 9,000 Hz were used in experiments. Monitoring of secretory IgA and albumin level in saliva and changes in bone density were used as objective markers of biostimulatory effect. SUMMARY BACKGROUND DATA: From the literature, it is known that if the alveolus is irradiated after extraction along with the lingual and buccal bony wall, faster coagulation, less postoperative discomfort, and quicker healing can be expected. METHODS: Subjective evaluation of therapy was observed using a scale (from -, negative therapeutic effect, to ++++, excellent treatment effect). Changes of secretory immunoglobulin A (sIgA), albumin levels, and bone density were compared in a group of 150 patients (nonlaser therapy, 30 patients). RESULTS: Differences in levels of the saliva markers (sIgA and albumin) were found to be significant when comparing irradiated and nonirradiated groups, and in comparison with those groups irradiated by various modulatory frequencies. Significant differences were observed between the increase of sIgA res. albumin and subjective feelings during treatment. Bone density after extraction and 6 months after surgical treatment was examined using dental digital radiovisiography. No significant differences were detected between bone density in irradiated and nonirradiated groups, perhaps due to our therapy protocol. CONCLUSIONS: The low-level laser has no influence on the process of osseointegration. This effect was observed on fracture healing in rats using He-Ne laser radiation. We found no differences in the bone density when compared to the control group.

Dentin and pulp response to Erbium:YAG laser ablation: a preliminary evaluation of human teeth.

OBJECTIVE: We determined the real effect of Erbium:YAG laser ablation on human teeth in vivo. SUMMARY BACKGROUND DATA: We advocated the idea that overheating of teeth, specially pulp damage can be avoided if correct laser parameters are used. METHODS: We evaluated human premolars scheduled for extraction during orthodontic treatment. Before tooth extraction, an oval cavity preparation was made with a pulsed Er:YAG laser. After extraction, the teeth were decalcified for 6 weeks. Routine staining with haematoxylin and eosin was performed on longitudinal section. One hundred seventy-two sections were prepared and examined in a light microscope. RESULTS: Under Er:YAG laser application, reduction of the dentin layer was observed. Dentinal tubules had a radial course up to the surface. No cracks or structural injury were observed. Inflammatory reaction in the pulp was not found. The vascularity of the pulp was normal. The odontoblasts were of the usual spindle-like or star-like cell shape. The cementum and epithelial attachment were healthy. No changes of structure or indications of inflammation were observed. CONCLUSIONS: The results of this in vivo experiment on human teeth confirm safety of Er:YAG laser ablation of enamel and dentin under the conditions described.