Biological complications with dental implants: their prevention, diagnosis and treatment

Biofilms form on all hard non-shedding surfaces in a fluid system, i.e. both on teeth and oral implants. As a result of the bacterial challenge, the host responds by mounting a defence mechanism leading to inflammation of the soft tissues. In the dento-gingival unit, this results in the well-described lesion of gingivitis. In the implanto-mucosal unit, this inflammation is termed "mucositis". If plaque is allowed to accumulate for prolonged periods of time, experimental research has demonstrated that "mucositis" may develop into "periimplantitis" affecting the periimplant supporting bone circumferentially. Although the bony support may be lost coronally, the implant still remains osseointegrated and hence, clinically stable. This is the reason why mobility represents an insensitive, but specific diagnostic feature of "periimplantitis". More sensitive and more reliable parameters of developing and existing periimplant infections are "bleeding on probing", "probing depths" and radiographic interpretation of conventional or subtraction radiographs. Depending on the diagnosis made continuously during recall visits, a maintenance system termed Cumulative Interceptive Supportive Therapy (CIST) has been proposed.     

Possible regulation of epidermal growth factor-receptor tyrosine autophosphorylation by calcium and G proteins in chemically permeabilized rat UMR106 cells

A model using chemically permeabilized cells was developed to examine mechanisms that regulate protein tyrosine phosphorylation in osteoblastic cells. Using either permeabilized UMR106 osteoblastic or A431 (reference) cells, epidermal growth factor (EGF)-induced cellular tyrosine phosphorylation, and whether there are previously unrecognized interactions between this transduction pathway and Ca2+- or G protein-dependent signalling pathways, were investigated. Both permeabilized cell types, when maintained in non-supplemented cytoplasmic substitution solution (basic CSS), responded to EGF (1-100 ng/ml) with dose-dependent increases in tyrosine phosphorylation. A complex and time-dependent pattern of phosphotyrosine-containing proteins resulted, but the profile of tyrosine phosphorylated proteins was appreciably less complex than in intact cells. Supplementation of basic CSS with MgATP restored the normal complexity of the profiles for EGF-induced tyrosine phosphorylation proteins in both permeabilized cell lines and produced a more sustained accumulation of phosphoprotein products in A431 cells. Adding Ca2+ (< or = 10(-6) M), with or without exogenous MgATP, dose-dependently attenuated EGF-induced tyrosine phosphorylation of EGF receptors (EGFR) and other substrates in UMR106 cells, but was less effective in A431 cells. In both cell types, genistein, an inhibitor of tyrosine kinases, was more effective in attenuating EGF-induced receptor tyrosine phosphorylation in permeabilized cells. Similarly, orthovanadate, an inhibitor of protein tyrosine phosphatases, stimulated the accumulation of phosphoprotein products more effectively in permeabilized cells. Thus, the permeabilization preserves many features of intact cells while facilitating manipulation of intracellular conditions. NaF reproducibly produced a significant vanadate-like action in permeabilized cells that was somewhat stronger than its effect on intact cells. In contrast, the well-known inhibition of tyrosine phosphorylation by phorbol 12-myristate 13-acetate (PMA) was less effective in permeabilized cells than in intact cells; these actions of PMA were Ca2+-dependent. In addition, guanylyl-imidodiphosphate (Gpp(NH)p) attenuated tyrosine phosphorylation in UMR106 cells, and this effect was specifically blocked by guanosine 5'-O-(2-thiodiphosphate) (GDPbetas). These results strongly suggest that there is crosstalk between EGFR-activated tyrosine phosphorylation/dephosphorylation pathways and both Ca2+- and G protein-mediated pathways in UMR106 cells, revealing a previously unrecognized modulation of EGF signalling in osteoblast-like cells that contrasts with the simpler regulatory mechanisms found in A431 cells.     

The cariostatic potential of cheese: cooked cheese-containing meals increase plaque calcium concentration

OBJECTIVE: Eating cheese by itself increases plaque calcium concentration - which is probably one mechanism of the well-established action of cheese in reducing experimental caries. The objective of the present study was to determine whether consumption of cheese as part of a cooked, mixed meal (ie as it is habitually consumed) is able to increase plaque calcium concentration. DESIGN: Plaque samples were obtained from 16 adult volunteers before and 5 minutes after consumption of either a 15 g cube of cheese, one of two cheese-containing test meals, or one of two control meals. Each subject tested each of the four meals on a separate occasion. Plaque calcium concentration was measured using atomic absorption spectrophotometry. RESULTS: The test meals increased plaque calcium concentrations to a significantly greater magnitude than the control meals (P < 0.05). A non-significant trend was observed towards a larger magnitude of change in plaque calcium concentration in the 8 subjects with the lowest, compared with the 8 subjects with the highest baseline concentration. CONCLUSION: The findings suggest that cheese-containing meals increase plaque calcium concentration and thus probably protect against dental caries.     

Evaluation of antibacterial activity of three dentin primers using an in vitro tooth model

This study compared the antibacterial activities of three dentin primers and investigated a newly designed experimental system using a bovine tooth model method for evaluating antibacterial activity by comparing this method with a conventional disk diffusion method. The antibacterial activities of SA primer in Clearfil Liner Bond, LB primer in Clearfil Liner Bond II, and ED primer in Panavia 21 were evaluated using the conventional disk diffusion method. The 50 microliters aliquot of each primer was applied to three sterilized paper disks, then placed onto Tryptic Soy agar plates already inoculated with Streptococcus mutans. After anaerobic incubation for 48 hours, the diffusion of antibacterial components was determined using the inhibition zone produced around the paper disk. The diameter of the inhibition zones was measured and the average calculated. Standardized cavities (diameter 5.0 mm, depth 3.0 mm) were prepared on the labial surfaces of bovine teeth and inoculated with S mutans (10(6) CFU/microliter) following sterilization by 60Co gamma rays (50 KGy). The teeth were divided into four groups: SA primer, LB primer, ED primer, and a control group. Except for the control teeth, the cavity preparations were treated with the respective dentin primers, and then firmly sealed with a temporary sealing material. The teeth were placed in bottles containing melted Tryptic Soy agar. Five ml of Tryptic Soy broth was then added to the surface of the hardened Tryptic Soy agar. After 1 week's incubation of the teeth in the bottles at 37 degrees C, the number of bacteria remaining in each cavity was counted, except for eight specimens, which were used for SEM observation. The ED primer showed the widest inhibition zone in the disk diffusion test, which was significantly different from the other primers. Using the bovine tooth model, all dentin primers showed antibacterial activity, with significant differences found among the four groups. The results indicated that ED primer had the strongest antibacterial effect among the three primers.     

Effect of soaking in Hank's balanced salt solution or milk on PDL cell viability of dry stored human teeth

Abstract— This study was designed to evaluate the effect of soaking in either Hank's balanced salt solution (HBSS) or milk on peri⁻odontal ligament (PDL) cell viability in avulsed teeth. Dry storage times of 30, 60, and 90 min were evaluated. PDL cell viability was determined after removal of the cells from the root surfaces of extracted teeth using a modification of the procedure described by Nakashima (Arch Oral Biol 1991;36:655–63). After trypsinization and subsequent treatment in collagenase, the cells were stained with trypan blue, and viable and non-viable cells were counted using a hemocytometer and converted to percentages for statistical comparison. The results of this study demonstrated no significant difference in the number of viable cells with or without soaking in HBSS or milk at any of the dry storage times. In addition, there was no significant difference in PDL cell viability between the 30-and the 60-min dry periods. Although the soaking procedure had no obvious negative consequence, no simcant improvement in PDL cell viability by the addition of this step was demonstrated under the conditions of this study.     

Alveolar bone growth in response to endosteal implants in two patients with ectodermal dysplasia

The occurrence of alveolar bone growth after placement of endosteal mandibular implants in two edentulous children is reported. The fact that alveolar bone growth occurred in the absence of natural teeth suggests that its growth and preservation is dependent upon biomechanical factors rather than the presence of teeth, as is traditionally thought.     

Temporalis myofascial flap in maxillofacial reconstruction: clinical and histological studies of the oral healing process

Objectives—To report our experience with temporalis myofascial flaps (TMF), describe the healing process of uncovered flaps in the mouth, and the histology of the repaired mucosa in the long term. Design—Prospective clinical and histological study. Subjects—36 patients who received a TMF over a 6.5 year period for serial assessment of the oral healing, 24 patients whose scars over the reconstructed area were assessed clinically, and 11 whose repaired mucosa was assessed histologically. Main outcome measures—To follow the clinical process of oral healing of the TMF and describe the repaired mucosa healed over the flap. Results—The uncovered TMF in the mouth healed gradually starting with an acute inflammatory phase, going through chronic inflammatory and proliferative phases with eventual epithelialisation of the oral mucosa. There were no major complications. The healed mucosa showed mild scarring in 70% of cases and the repaired mucosa had characteristic histological features that were distinct from the normal mucosa. Conclusion—The TMF is an extremely reliable and versatile flap for maxillofacial reconstruction which heals gradually with eventual coverage by mildly scarred repaired mucosa.     

Galvanic corrosion and cytotoxic effects of amalgam and gallium alloys coupled to titanium

The aim of this study was to examine and compare the galvanic corrosion of a conventional, a dispersed high-copper, and a palladium-enriched spherical high-copper amalgam and a gallium alloy coupled to titanium in saline and cell culture solutions, and to evaluate the effects of the couples on cultured cells. The potentials and charge transfers between amalgams and titanium were measured by electrochemical corrosion methods. Cytotoxicity of the couples, as indicated by the uptake of neutral red vital stain, was determined in 24-h direct contact human gingival libroblast cell cultures. Results of this study indicated that before connecting the high-copper amalgams to titanium, the amalgams exhibited more positive potentials which resulted in initial negative charge transfers, i.e. corrosion of titanium. However, this initial corrosion appeared to cause titanium to passivate, and a shift in galvanic currents to positive charge transfers, i.e. corrosion of the amalgam samples. Lower galvanic currents were measured for the amalgam-titanium couples as compared to the gallium alloy-titanium couple. Coupling the conventional or the palladium-enriched high-copper amalgams to titanium did not significantly affect the uptake of neutral red as compared to cells not exposed to any test alloy. However, significant cytotoxic effects were observed when the dispersed-type high-copper amalgam and the gallium alloy were coupled to titanium. Even though the corrosion currents measured for these couples were less than gold alloys coupled to amalgam, these results suggest there is the potential for released galvanic corrosion products to become cytotoxic. These data warrant further investigations into the effects of coupling amalgam and gallium alloys to titanium in the oral environment.     

Effects of repeated scaling and root planing and/or controlled oral hygiene on the periodontal attachment level and pocket depth in beagle dogs

This study was performed to evaluate the effect of initial and/or repeated subgingival scaling with or without controlled oral hygiene on the level of periodontal attachment and pocket depth in Beagle dogs. furthermore, the effect of repeated scaling on the progression of naturally developed periodontitis was to be determined. At baseline, and at 1,6,12,24 and 36 months clinical parameters for plaquen deposits (PII), calculus (CI), gingival health (GI) periodontal attachment from the cementoenamel junction (CEJ) and pocket depth were recorded by the same examiner. Eight healthy Beagles, 3 1/2–6 years of age with moderate naturally developed periodontal desease were divided into experimental and control animals. In the experimental group, 4 dogs received a thorough scaling and root planing at the start of the experiment. thereafter the experimental dogs were subjected to daily toothbrushing and a rubber cup and pumice prophylaxis every two weeks. The remaining 4 control dogs were not subjected to any oral hygience measures. Two quadrants diagonally opposed in each animal (experimentaal and control) were scaled and root planed every six months. In the experimental group a significant increase in attachment level was maintained throughout the study. Initial scaling followed by oral hygiene reduced pocket depth singificantly and pocket reduction was maintained over the three year period. Repeated scaling did not influence the mainternance of the attachment level or the reduction in pocket depth in the experimental group. The control animals continued to lose attachment and pocket depth increased during the study. Scaling every six months without oral hygience resulted in loss of attachment and increase in pocket depth, although the rate of attachment loss was retarded. It is concluded that following initial scaling conticuous removal of bacterial plaque is essential for the maintenance of periodontal attachment. In moderate periodontal disease the levels of attachments may be maintained without surgical therapy.