Multivariate comparison of elemental concentrations in human teeth

R-mode factor analysis was applied to characterize the chemical composition of human teeth investigated by particle induced X-ray emission (PIXE), Rutherford backscattering spectrometry (RBS) and X-ray fluorescence (XRF) techniques. The approach developed in this study enabled the separation between essential mineral teeth components and the pollutants deposited in teeth tissues during the human life. The three independent sources of metals incorporated in human teeth were found. The first source, representing about 43% of the variance of the concentration data, was characterized by pollutant elements of power industry emissions. The second factor was loaded with toxic elements of general urban pollution. The third factor represented the tooth source as it contained mainly large fractions of the mineral components of the tooth tissue as Ca and K.     

Scanning electron-microscopic study of pellicle and plaque formation on tetracyclineimpregnated dentin

Abstract — Previous experiments have shown that tetracyclinecs may react with hydrosyapatite, e.g. in enamel and dentin, without losing their antimicrobial capacity. The present paper examines the pattern of pellicle and plaque formation on doxycycline-treated dentin by the use of scanning electron microscopy (SEM). From newly extracted human teeth were prepared standardized dentin slabs, half of which were soaked in aqueous solutions of doxycycline HC1, 10 mg/ml (pH 2.5) for 10 min. Seven volunteers carried doxycycline-impregnated specimens ligated to the buccal surface of a maxillary molar for 2 h, 8 h, 24 h and 120 h, respectively. Untreated control specimens were ligated to the contralateral teeth. After removal from the oral cavity, the dentin slabs were briefly rinsed in water, allowed to air dry and processed for SEM. SEM assessment of the specimens showed that doxycycline-impregnation resulted in a superficial etching of the dentin, a reduced rate of pellicle formation as well as an impairment of pellicle adhesion, and a retarded bacterial plaque formation on the dentin surfaces.     

Early Designs for the Occlusal Anatomy of Posterior Denture Teeth: Part III

Part III of this series of articles, like Part II, reviews the pioneering efforts in the 19th century to improve the quality of artificial teeth. The focus of this article, unlike that of Part II, is specifically modifications in the design of the occlusal anatomy of the 19th century denture teeth, along with the theories of mandibular movement that inspired those modifications. This article concludes the introductory phase of this project, which seeks to unravel the confusing history of the development of (posterior) denture teeth.     

Factors influencing survival of reconstructions. Consensus report of Working Group 2

Abstract: In order to evaluate the level of evidence of factors influencing the survival of reconstructions, systematic reviews of the relevant literature were prepared by a group of rapporteurs. The review papers were circulated to the members of the group before the conference and formed the basis for group and panel discussions. Subsequently, modifications were added to the review papers, and suggestions for consensus statements concerning the following topics were prepared and again critically reviewed in the group and in the plenum: Impact of (i) periodontal disease on the survival of tooth-supported reconstructions, (ii) post-surgical factors as supportive therapy on the survival of implant supported reconstructions, (iii) technical and/or biological complications on the survival of different types of reconstructions, (iiii) material choice for reconstructions on the survival of single crowns and fixed dental prostheses.     

牙根发育不良疾病的研究进展

牙根发育不良疾病是牙齿根部生理性发育出现障碍的疾病。其发病率为1%~10%,乳、恒牙列均可发生,其结果可导致牙根缺如或短根,严重者可造成牙齿过早脱落。国外学者将该疾病统称为短根异常疾病。其发病因素有遗传性疾病、全身性疾病、外源性因素和医源性因素等。     

An imaging routine for assessing the efficacy of instruments used for scaling and root planning

Deposits of dental plaque or calculus are typically quantified using planimetric techniques. However, error is introduced into a quantitative analysis of plaque deposits using these methods, since they require a significant amount of human intervention. The purpose of this study is to describe and validate a computerized imaging routine which has the potential to objectively identify material on dental roots and measure the area covered by these deposits. Dentiform teeth with simulated plaque were videorecorded. A computer routine was developed based on a flood-fill algorithm which analyzed images of the dentiform teeth and determined the amount of simulated plaque on their root surfaces. Results showed that the dentiform teeth and their simulated plaque patterns are duplicated by the imaging routine in a rapid and reliable fashion. The system shows a high degree of accuracy with an average error factor of only 0.58%. As well, the system enables precise reproducibility with an average error factor of only 0.71%.     

简易印模术对单个前牙烤瓷冠颈缘外观效果的作用观察

目的:观察和探讨两种印模技术对单个前牙烤瓷冠颈缘外观的改善效果。方法:40位患者用简易印模技术制取印模,制作93件镍铬合金烤瓷瓷冠,设为实验组,另35位患者以常规印模技术制取印模,制作71件镍铬合金烤瓷瓷冠,设为对照组。观察两组戴冠当时与两年后的颈缘适合性、颜色、牙龈形态与健康情况。结果:试验组有98%的合金瓷冠具有优良的边缘适合性,仅2件(2%)出现颈缘黑线,与对照组相比有显著差异(P<0.05)。结论:简易印模技术能更好的保证工作区模型的准确度,从而有效地改善了镍铬合金烤瓷冠颈缘的美观与龈组织的健康。     

上前牙倒置阻生拔除后再植的临床体会

为探讨上前牙倒置阻生拔除后再植的可行性，选择上前牙倒置阻生病例15例，经正畸治疗扩展间隙，再经口腔外科手术拔除后再植。结果，86．7％的病例获得良好的治疗效果，无明显松动。认为用拔除后再植术治疗上前牙倒置阻生，能明显改善面形和咀嚼功能，避免了拔牙后再修复。     

Increasing prevalence of penicillinase‐producing Neisseria gonorrhoeae and the emergence of high‐level, plasmid‐mediated tetracycline resistance among gonococcal isolates in The Gambia

Summary One hundred and three strains of Neisseria gonorrhoeae isolated from a periurban STD clinic in The Gambia were studied for antimicrobial susceptibility, plasmid profile, and serogroup using standard procedures. Seventy-nine (77%) were penicillinase producers (PPNG) and fully resistant to penicillin (MIC ≥8 mg/l). One isolate showed chromosomally induced resistance to penicillin (MIC 2 mg/l). None of the isolates was sensitive to tetracycline; 16 (16%) showed intermediate resistance (MICs 1–8 mg/l) and 87 (84%) showed high-level plasmid-mediated resistance (TRNG) (MICs >10 mg/l). This is the first report of TRNG in The Gambia. Only 6 (6%) strains were fully sensitive to trimethoprim-sulphamethoxazole (MIC <8 mg/l); 78 (76%) showed intermediate level resistance (MICs 8–16 mg/l) and 19 (18%) were fully resistant (MIC >32 mg/l). Indications of an increase in MIC to ciprofloxacin and ceftriaxone were found in 6 (6%) and 1 (1%) strains, respectively, although all remained fully sensitive (MICs 0.004–0.03 mg/1 and 0.001–0.015 mg/l). All PPNG and TRNG strains carried the 3.2 MDa and 25.2 MDa plasmids, respectively. All isolates carried the 2.6 MDa cryptic plasmid and 9 (3 PPNG and 6 non-PPNG) carried the 24.5 MDa conjugative plasmid. Forty-four (43%) strains were typed group W1, 58 (56%) W11/111 and 1 had cross-reacting antigens. Because PPNG are frequently encountered and high-level TRNG is now prevalent, the newer cephalosporins and quinolones must now be considered as first-line drugs for the treatment of gonorrhoea in The Gambia.     

Surface topography of enamel and dentine from primary teeth following infrared Nd-YAG laser irradiation: An in vitro study

Data on the effects of laser radiation on primary teeth are scarce. This study investigates the effects of exposing sound enamel, photo-initiated sound enamel, sound dentine and carious dentine of extracted primary teeth to a pulsed neodymium-yttrium aluminium garnet laser (Nd-YAG, wavelength 1.06 μm, pulse length 15μs). Each type of tissue was exposed to three fiuences. Qualitative and quantitative assessments of the irradiated areas revealed that the most marked changes were produced in carious dentine, followed in ranking order by sound dentine, photo-initiated enamel and sound enamel. Evidence of thermal damage to the hard tissues peripheral to the fibre-optic tip, and considerable inter-sample variation were found. The experimental evidence obtained in this in vitro study does not support the clinical use of pulsed laser at 1.06 μm wavelength for cutting primary enamel and dentine.