Effect of implant design and bioactive glass coating on biomechanical properties of fiber-reinforced composite implants.

This study aimed to evaluate the influence of implant design and bioactive glass (BAG) coating on the response of bone to fiber-reinforced composite (FRC) implants. Three different FRC implant types were manufactured for the study: non-threaded implants with a BAG coating; threaded implants with a BAG coating; and threaded implants with a grit-blasted surface. Thirty-six implants (six implants for each group per time point) were installed in the tibiae of six pigs. After an implantation period of 4 and 12 wk, the implants were retrieved and prepared for micro-computed tomography (micro-CT), push-out testing, and scanning electron microscopy analysis. Micro-CT demonstrated that the screw-threads and implant structure remained undamaged during the installation. The threaded FRC/BAG implants had the highest bone volume after 12 wk of implantation. The push-out strengths of the threaded FRC/BAG implants after 4 and 12 wk (463°N and 676°N, respectively) were significantly higher than those of the threaded FRC implants (416°N and 549°N, respectively) and the nonthreaded FRC/BAG implants (219°N and 430°N, respectively). Statistically significant correlation was found between bone volume and push-out strength values. This study showed that osseointegrated FRC implants can withstand the static loading up to failure without fracture, and that the addition of BAG significantly improves the push-out strength of FRC implants.

Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study.

OBJECTIVE: The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging. METHODS: The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage. RESULTS: At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity. CONCLUSIONS: Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.

In vitro antimicrobial activity of propolis samples from different geographical origins against certain oral pathogens.

Propolis is an agent having antimicrobial properties, however, its composition can vary depending on the area where it is collected. In the present study, the antimicrobial activity of five propolis samples, collected from four different regions in Turkey and from Brazil, against nine anaerobic strains was evaluated. Ethanol extracts of propolis (EEP) were prepared from propolis samples and we determined minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of EEP on the growth of test microorganisms by using agar dilution method. All strains were susceptible and MIC values ranged from 4 to 512 microg/ml for propolis activity. Propolis from Kazan-Ankara showed most effective MIC values to the studied microorganisms. MBC values of Kazan-Ankara EEP samples were ranged from 8 to 512 microg/ml. Death was observed within 4 h of incubation for Peptostreptococcus anaerobius and micros and Lactobacillus acidophilus and Actinomyces naeslundii, while 8 h for Prevotella oralis and Prevotella melaninogenica and Porphyromonas gingivalis, 12 h for Fusobacterium nucleatum, 16 h for Veillonella parvula. It was shown that propolis samples were more effective against Gram positive anaerobic bacteria than Gram negative ones. The organic chemical compositions of EEPs were determined by high-resolution gas chromatography coupled to mass spectrometry (GC-MS). The main compounds of EEPs were flavonoids such as pinobanksin, quercetin, naringenin, galangine, chrysin and aromatic acids such as cafeic acid. Because of increased antimicrobial resistance, propolis may be kept in mind in the treatment of oral cavity diseases.

Effects of different retraction medicaments on gingival tissue.

OBJECTIVE: Exposure of the gingival sulcus and control of hemorrhage are prerequisites to the treatment of cervical lesions and improving the quality of impressions prior to fabricating indirect restorations. Gingival retraction cords saturated with different medicaments are widely used for this purpose. However, the long-term effects of the chemicals in gingival tissues are not clear. The purpose of this study was to compare the histopathologic effects of 2 different retraction solutions in gingival tissue. METHODS AND MATERIALS: In this in vivo study, a solution of 10% aluminum chloride and a solution of 15.5% ferric sulfate were used as retraction medicament in dogs. The saturated cords were allowed to remain in the gingival sulcus of the dogs for 3 minutes. After the removal of the cords, gingival biopsies were taken at 30 minutes, 24 hours, 7 days, and 12 days. For all specimens, histologic evaluation was performed by light microscopy to determine the degree of epithelial loss, alteration of the connective tissue, and inflammation. RESULTS: Histopathologic examination of gingival tissue revealed that the ferric sulfate solution caused significant changes in gingival tissues at the beginning. However, the tissue returned to its normal histologic appearance at the end of day 12. CONCLUSION: The results of this study revealed that the biologic effects of ferric sulfate solution are more satisfactory than aluminum chloride solution. However, both medicaments are reliable and can be used in gingival retraction.

Increased antibacterial activity of zinc polycarboxylate cement by the addition of chlorhexidine gluconate in fixed prosthodontics.

PURPOSE: This study evaluated the antibacterial activity of water-activated zinc polycarboxylate cement with adjunctive 0.12% chlorhexidine gluconate on the subgingival microbiota in fixed partial dentures. MATERIALS AND METHODS: Thirty-six teeth prepared as fixed partial denture abutments in 9 patients were cemented randomly using water-activated zinc polycarboxylate cement (control group) or water-activated zinc polycarboxylate cement, including 0.12% chlorhexidine gluconate (test group). A total of 108 subgingival plaque samples were analyzed at baseline, immediately before permanent cementation (5 weeks), and 8 weeks later (at 13 weeks). RESULTS: In the control group, the subgingival microbiota altered to closely resemble the flora of chronic gingivitis (increased proportions of gram-negative anaerobes such as Prevotella intermedia, Fusobacterium nucleatum) by 13 weeks. In contrast, the microflora at test sites comprised predominantly gram-positive facultative cocci and rods at 13 weeks. CONCLUSION: This study demonstrated that the addition of 0.12% chlorhexidine gluconate may enhance the antimicrobial action of polycarboxylate cements to ensure the maintenance of a microflora compatible with periodontal health, at least up to 13 weeks post-cementation.