Histomorphometric and removal torque analysis for TiO2-blasted titanium implants. An experimental study on dogs

The aim of the present study was to compare the anchorage of TiO2-blasted screw and cylindrical implants with conventionally used machine-produced screw and cylindrical implants inserted immediately in extraction sockets on dogs. 6 adult mongrel dogs had 3rd and 4th mandibular premolars extracted bilaterally and 24 commercial pure titanium implants were placed immediately in extraction sockets and covered with mucoperiosteum. Each dog had inserted 4 implants: 1 screw implant and 1 cylindrical implant blasted with titanium-dioxide-particles; 1 screw implant and 1 cylindrical implant with machine-produced (m.p.) surface (controls). After a healing period of 12 weeks, 16 implants from 4 animals were used for removal torque test, which demonstrated that significantly higher removal torque force was needed to unscrew the implants blasted with titanium-dioxide-particles, than the normal m.p. implants. The medians for the TiO2-blasted screw and cylindrical implants were > 150 Ncm and 105 Ncm, respectively, while the values for the m.p. implants were 60 Ncm and 35 Ncm, respectively. The SEM investigation demonstrated a high irregularity of the TiO2-blasted surface compared to the machined surface. The Ra and Rz values for surface roughness were higher for the TiO2-blasted implants than for the normal m.p. implants. Histomorphometrically, the arithmetic mean of the direct bone-implant contact fraction was 69%. There was no significant difference in direct bone-implant contact length fraction between TiO2-blasted implants and the control implants. The implants blasted with titanium-dioxide-particles in this study showed a better anchorage than implants with a machine-produced surface. The screw implants showed a better anchorage than the cylindrical implants.     

镧、铈、氟在抑制人离体牙根面脱矿中作用的比较研究

作者采用含镧(La)、铈(Ce)、氟(F)的脱矿液，在体外模拟口腔pH循环变化的环境中对离体人牙根面进行抑制脱钙的实验研究，并采用化学及能谱分析手段，对La，Ce，F在根面的抑制脱钙作用进行定量分析。结果显示，这三种微量元素对根面均有明显的抑制脱钙作用，但F较La、Ce的抑制作用强．该研究还从晶体物理化学角度对La、Ce、F的抑制脱矿作用的机理进行探讨。     

Bacteremia in conjunction with endodontic therapy

Abstract This study characterizes oral microorganisms believed to have spread from the root canal into the blood stream during and after endodontic therapy of teeth with Asymptomatic apical periodontitis. Microbiological samples were taken under aseptic conditions from the root canal of 26 single-rooted teeth in 26 patients. In the endodontic treatment of 13 of the patients (Group 1), the first 3 reamers, sizes 15, 20 and 25, were used to a level 2 mm beyond the apical foramen. In the other 13 patients (Group 2), the instrumentation ended inside the root canal 1 mm short of the apical foramen. Blood samples were taken from the patients during the instrumentation and 10 min after the treatment was completed. Anaerobic microorganisms were isolated from all root canals. In 7 patients of Group 1, Propionibacterium acnes, Peptostreptococcus prevotii, Fusobacterium nucleatum, Prevotella intermedia and Saccharomyces cerevisiae were recovered from the blood. In 4 patients of Group 2, P. intermedia, Actinomyces israelii, Streptococcus intermedius and Streptococcus sanguis were isolated from the blood. Biochemical tests and antibiograms revealed that the isolates from the root canal and blood had identical profiles within the patients, strongly suggesting that the microorganisms isolated from the blood had the root canal as their source.     

The influence of a flexible coating on the bone stress around dental implants

summary The influence of a three-layered flexible coating of Polyactive® on bone stress distribution was investigated by three-dimensional finite element models of mandibular bone, in which a titanium implant (coated or uncoated) was located. Poly-active® is a system of poly(ethylene oxide) poly(butylene terephthalate) segmented co-polymers with bone-bonding capacity. In the case of sagittal and transversal loading, the use of a Polyactive® coating reduced both the minimum principal stress in the bone and the compressive radial stress at the bone-implant interface. However, it raised the maximum principal and the tensile radial stress. In the case of vertical loading, the application of a flexible coating reduced the compressive radial stress at the bone-implant interface around the neck of the implant by a factor of 6.6 and the tensile radial stress by a factor of 3.6. Variations in composition and thickness of the coating did not affect the results significantly.     

Evaluation of biochemical validation measures in determination of smoking status

This study was designed to evaluate the use of salivary cotinine, salivary thiocyanate, and expired-air carbon monoxide as biochemical validation measures for assessing the smoking status of adults. The participants were 20 known non-smokers plus 216 admitted smokers and 102 proclaimed quitters participating in a clinical trial of approaches to facilitate smoking cessation. Conventional analytical procedures were utilized. By use of data from known non-smokers and admitted smokers, the sensitivity and specificity of the validation measures were as follows: salivary cotinine, 99% and 100%; expired-air carbon monoxide, 96% and 100%; and salivary thiocyanate, 67% and 95%, respectively. The salivary cotinine and expired-air carbon monoxide tests confirmed smoking cessation for 55% and 74%, respectively, of the proclaimed quitters. The length of time since quitting was significantly related to the results observed with the latter measures. Consideration of these observations along with various practical factors suggests that expired-air carbon monoxide assays may be the validation measure of choice for most clinical trials.     

Effects of citric acid treatment on pedicle flap coverage of localized recession

Citric acid conditioning of denuded roots prior to laterally positioned pedicle flap (LPPF) coverage may increase the likelihood of reattachment, but no controlled studies to determine the efficacy of the procedure in managing naturally occurring defects in humans have been reported. This investigation compared the effects of LPPF root coverage with and without citric acid (pH1) pretreatment in a group of patients with gingival recession and associated denuded roots. Thirty-six patients participated in the study. Eighteen received LPPFs without citric acid pretreatment and 18 received LPPFs with citric acid pretreatment. Gingival recession and sulcus depth were measured preoperatively and 30, 60 and 90 days after the surgical procedure. LPPFs both with and without citric acid pretreatment reduced significantly the amount of exposed root, but no differences between groups were found. For sulcus depth, the 90-day value for the citric acid group was significantly increased over the preoperative level, but no other changes were noted. There appears to be no clinical justification for using citric acid conditioning as an adjunct to LPPF coverage of denuded roots.     

The loss of residual monomer from acrylic orthodontic resins

The paper studies the loss of residual monomer from 6 acrylic orthodontic resins. Gas chromatography was used for the determination of residual monomer in the resin, and ultraviolet spectroscopy for the determination of methylmethacrylate in water. The results showed that high levels of residual monomer were present in orthodontic resins. There was a rapid loss of monomer in the first 24 h of soaking of the specimens in water. This loss continued but shows that high levels of residual monomer remain. It is recommended that in any future Standards Specification there should be an upper limit of residual monomer that is agreed as acceptable.     

Hepatitis C virus infection and lichen planus: a short review

OBJECTIVE: To review the current literature regarding the association of lichen planus (LP) and liver disease, with particular attention to the association of the oral variant of the disease with hepatitis C virus (HCV) infection.
MATERIALS AND METHODS: Available literature of the possible association of LP with systemic disorders, in particular chronic hepatic disease, has been reviewed. RESULTS: LP is sometimes associated with infectious or autoimmune disease and/or neoplasia, however an aetio-logical association between LP and these disorders seems unlikely. A more consistent association exists between LP and chronic hepatic disease. The precise cause of this association is not known. However, in the last 6 years a notable association between HCV infection and LP has been observed, particularly in patients in Spain, Italy and Japan. The pathogenesis of this possible HCV-associated LP is not known, but it may involve a cell mediated response to an altered epithelial antigen.
CONCLUSION: There is now evidence to suggest a significant association between HCV infection and LP in some groups of patients.