roughness study of ytterbium-doped potassium yttrium tungstate [YB: KYW] thin-disk femtosecond ablated dentin

The aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a Ytterbium-Doped Potassium Yttrium Tungstate [YB: KYW] thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances. Twelve extracted human premolars were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick with a cutting machine. The dentin samples were fixed on a stage at focus plane. The laser beam was irradiated onto the samples through a galvanometric scanning system, so rectangular movement could be achieved. After ablation, the samples were examined with a scanning electron microscope and laser three-dimensional profile measurement microscope for morphology and roughness study.With increasing laser fluence, dentin samples exhibited more melting and resolidification of dentin as well as debris-like structure and occluded parts of dentinal tubules. When at the scanning speed of 2400mm/s and scanning distance of 24microm, the surface roughness of dentin ablated with femtosecond pulsed laser decreased significantly and varied between values of dentin surface roughness grinded with two kinds of diamond burs with different grits. When at the scanning speed of 1200mm/s and scanning distance of 12microm, the surface roughness decreased slightly, and the surface roughness of dentin ablated with femtosecond pulsed laser was almost equal to that grinded with a low grit diamond bur. This study showed that increased laser influence may lead to more collateral damage and lower dentin surface roughness, while scanning speed and scanning distance were also negatively correlated with surface roughness. Adequate parameters should be chosen to achieve therapeutic benefits, and different parameters can result in diverse ablation results

Study on knowledge, attitudes, and practice of tobacco control of medical staff in Gansu prov-ince / 中国卫生政策研究

Objective:Through a study on knowledge, attitudes, and practice of tobacco control of medical staff in Gansu Province, the paper aims to analyze the issues of participation, community tobacco control leadership and other aspects that impact the creation of a smoke-free healthcare system in order to provide a basis for the formulation of policies to improve the health professional mechanism of tobacco control. Methods:The stratified cluster sampling method was adopted to select 34 companies, accounting for a total of 805 medical staff as the study population in all kinds of health institutions. A self-designed questionnaire was adopted to investigate their knowledge, attitudes, and practice via on-site self-administered surveys. Results:the medical staff lacks knowledge as to the depth and breadth of damage from the use of tobacco. Although their attitude towards tobacco control is positive, the comprehensive to-bacco control service capabilities are insufficient. Logistic regression analysis showed that tobacco control capabilities of medical staff is related to their attitude toward smoking and whether or not they discourage smoking or asking about smoking . Conclusion:The key to the creation of a smoke-free health system to lead the community in tobacco control is the targeted tobacco cessation knowledge and skills training of medical staff to reduce smoking rates among medical staff and enhance the awareness of administrative staff.

Establishment of database with standard 3D tooth crowns based on 3DS MAX / 生物医学工程学杂志

The database with standard 3D tooth crowns has laid the groundwork for dental CAD/CAM system. In this paper, we design the standard tooth crowns in 3DS MAX 9.0 and create a database with these models successfully. Firstly, some key lines are collected from standard tooth pictures. Then we use 3DS MAX 9.0 to design the digital tooth model based on these lines. During the design process, it is important to refer to the standard plaster tooth model. After some tests, the standard tooth models designed with this method are accurate and adaptable; furthermore, it is very easy to perform some operations on the models such as deforming and translating. This method provides a new idea to build the database with standard 3D tooth crowns and a basis for dental CAD/CAM system.

Computer aided design and manufacturing of the framework of PFM fixed bridge / 生物医学工程学杂志

We have carried out a research on the method for Computer Aided Design and Manufacturing (CAD/ CAM) of the framework of porcelain-fused-to-metal(PFM) fixed bridge. Taking the missing of the mandibular first molar as an example, firstly, we used ATOS II 3D scanner to collect the 3D data of the abutment teeth and used the acquried data to design the coping crowns. Secondly, the relevant standard bridge was selected from the standard bridges database and was deformed inaccordance to the characteristic of the patient. Then it was set to the correct position between the coping crowns automatically based on the restricting lines and faces. Finally, the connector was designed to connect the coping crowns and the bridge based on the touching area. The final product was manufactured by 3-axis NC milling machine. The results of examination showed that the framework of PFM fixed bridge fitted the abutment teeth very well, and the hardness of the connector and the precision of the whole model were feasible and reasonable. The method of designing and manufacturing the framework of PFM fixed bridge from CAD/CAM is practicable, efficient and accurate. It is also an important part of homemade dental CAD/CAM system.

The research and development of CAD-CAM system in restorative dentistry / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To develop a dental CAD/CAM system with the autonomic intellectual property.</p><p><b>METHOD</b>28 standard teeth crowns were scanned using a newly 3-D laser scanner. As a development platform the Matlab 5.3 were used to process the acquired data, also be used to define the characterized areas on the surfaces of the crowns and to change the crowns form. The software of Surfacer 10.5 to develop a new CAD software for fixed prosthetics, and the 3.5 axis numerical controlled machine to manufacture the prosthetics were used.</p><p><b>RESULT</b>It is the first time, the 3D graphic data bank of Chinese teeth crowns with a standard form was established. A software of the occlusal adjustment and the form modification were developed. It is also the first time, the authors realized the whole process to use the CAD-CAM for the manufacture of a crown.</p><p><b>CONCLUSION</b>The successful result shows, that we have already mastered well the base theory, the mathematics method, the technology of a CAD-CAM system. It provides the basics for the future development.</p>

A study on the stability and reliability of 3D laser cranio-maxillofacial reconstruction / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the stability and the reliability of the first 3D laser cranio-maxillofacial reconstruction system in China.</p><p><b>METHODS</b>The same 3D laser scan image of a head plaster model was measured twice three weeks before and after. That head cast was also scanned and reconstructed twice three weeks before and after, and then the 3D images were measured. To the same head cast we compared the laser measurement with the direct manual measurement. The statistical analysis of measurements was made using the paired t test.</p><p><b>RESULTS</b>There was no significant difference between two sets of measurements on the same image (P > 0.05). The difference in the measurements was not significant between two reconstructed images of the same model (P > 0.05). And there was also no significant difference between the measurements by laser and by hand (P > 0.05).</p><p><b>CONCLUSIONS</b>The recognition of the author to the 3D laser scan image is reliable. The laser scanning system has a good stability and reliability and can be used in clinical study preliminary.</p>

A preliminary study on the design of removable partial denture framework using CAD method / 实用口腔医学杂志

Objective:To investigate the feasibility of 3-D computer aided design(CAD)for the framework of a mandibular Kennedy Class Ⅱ,Modification 2 arch.Methods:In terms of the principle of clinical design,the 3-D framework was built with the technique of mixed model of points cloud,curves and surfaces on the reconstructed model of a partially edentulous cast,including the tissue surfaces and polishing surfaces of every component,such as clasp,rest,lingual bar and mesh construction,etc.Results:Preliminarily,a CAD method for 3-D RPD framework design was established and a individualized RPD framework 3D geometric model was set up.Conclusion:CAD for RPD framework design based on the mixed model of points cloud,curves and surfaces is feasible.

A algorithm for 3D reconstruction of artificial teeth / 实用口腔医学杂志

Objective: To reconstruct three dimension (3D) model of a rtificial tooth and to establish standardized 3D artificial teeth graphic datab ase. Methods: Artificial teeth were incised with CGI autom atic cross section scanning instrument, then data points were picked up from e ach parallel layer contour of incised tooth, and 3D stereo models of artificia l tooth were retrieved using 3D reconstruction techniques. Results: 3D graphic models of 28 artificial teeth were established.The models may represent the graphic feature of the teeth. Conclusion: The present technic is feasible in the establishment of 3D graphic models of artificial tooth.

Establishment of artificial tooth coordinate for full denture / 实用口腔医学杂志

Objective:To establish three-dimension (3D) rectangular coordinate and to obtain relevant parameters of artificial tooth morphology for full denture.Methods:An artificial teeth coordinate was defined based on artificial tooth feature points, which were measured using 3D coordinate-measure-machine.Results:The 3D coordinate of 28 artificial teeth was established and the tooth parameters in the coordinate were obtained.Conclusion:The definition of artificial tooth coordinate using mathematic language is a based work of CAD full denture.