预成弹性根管印模桩的研制及应用

目的：研制一种预成的根管印模桩,解决桩核印模的缺损性缺陷。方法：根据预备根管形态和联合印模特点,设计出具有表面嵌合形态的印模桩,应用弹性材料采用注塑成型法制作预成弹性印模桩,通过预成印模桩联合印模材料制取桩核印模。结果：制作出的印模桩表面光滑,与印模材料能够紧密嵌合,与琼脂、藻酸盐印模材联合或硅橡胶印模材制取的桩核印模无缺损性缺陷。结论：研制出预成的弹性根管印模桩,预成的弹性根管印模桩有助于获得完整的桩核印模。     

DTG thermal analyses and viscosity measurements of three commercial agar impression materials

Three commercial agar impression materials, two for clinical uses and one for dental laboratory, were examined for their thermal properties by differential thermogravimetric (DTG) thermal analyses and viscosity measurements. On DTG profiles, an endothermic peak along with weight loss at around 100 degrees C was observed on all three agar impression materials as a result of water evaporation. Two clinical agar impression materials were more susceptible to this trend than the remaining one dental laboratory agar impression material. The viscosity of three agar impression materials could be expressed in the exponential function of temperature. Viscosity at 46 degrees C of one dental laboratory agar impression material far exceeded those of two clinical agar impression materials. Monitoring the viscosity could facilitate the detailed analysis of setting process of agar impression materials upon cooling, and might be useful for future development of agar-based dental impression materials.     

Technique for making flexible impression trays for the microstomic patient

This impression technique can be used for patients in whom routine use of stock impression trays is hindered by microstomia. Putty wash material can be manipulated with minimal effort and time. Placing the completed preliminary impression in a free-flowing mix of dental stone stabilizes the impression material and facilitates boxing and pouring of the impression. The resultant preliminary casts can then be used for diagnostic purposes and for making rigid sectional trays for final impressions.     

全口义齿印模技术的发展现状

全口义齿修复前,需通过可塑性印模材料来复制无牙颌牙槽嵴和周围软硬组织的解剖形态,清晰准确的口腔印模不仅为后续技工制作义齿提供了良好的结构基础,而且是保证最终修复体固位、稳定及功能的关键.现有研究表明,除印模材料、印模托盘、印模操作和印模消毒外,印模技术也是无牙颌印模制取精度的重要影响因素之一.近年来,随着各类牙科材料的...     

An Investigation of the Rheological Properties of 10 Vinyl-Polysiloxane Impression Materials

Purpose The time required for 10 vinyl-polysiloxane impression materials to reach a viscosity of 5000 poise (Tcv) was estimated. This viscosity was selected based on previous work that suggested that an impression material might not be workable if its viscosity exceeded this limit. The effect of variations in the time of placement of the impression materials into a simulated oral-temperature environment was also studied. Materials and Methods The change in the viscosity of the impression materials was recorded with a viscometer at oral temperature. Impression materials were placed at either 20 seconds, 30 seconds, or 40 seconds from the start of mixing. Results There were statistically significant differences in Tcv among various impression materials. Variations in placement time significantly affected the Tcv of six impression materials. Conclusions Knowledge of the viscosity change of an impression material is beneficial in the clinical selection of an impression material.     

A Simplified Approach for Fabrication of a Lightweight Individualized Impression Tray with the Aid of Existing Obturator Prosthesis Using Lost Salt Technique

Maxillary defects resulting from ablative oncologic surgery can be extensive and usually have complex contours. Impression procedures for such defects can be time consuming and cumbersome, challenging the skills of even the most‐experienced clinician. A well‐oriented impression tray with proper extension and adequate contour is essential for successfully capturing the relevant details in impression. This article describes a method using the patient's existing obturator prosthesis to simplify and expedite the fabrication of a lightweight individualized impression tray directly on an irreversible hydrocolloid impression, thus avoiding the preliminary impression procedure for the patient.     

Comparison of vertical movement occurring during loading of distal-extension removable partial denture bases made by three impression techniques.

Although the altered-cast impression technique attains stability and controlled tissue support for distal-extension removable partial dentures, the procedure is time-consuming and technique-sensitive. This study clinically compared the vertical displacement of distal-extension removable partial dentures made from different impression techniques. The impressions studied were the altered-cast impression, an impression made from a border-molded custom tray, and a stock tray irreversible hydrocolloid impression that served as a control. A post hoc analysis, using a Tukey Q-test, exhibited significance (p less than 0.01) between the two impression techniques after intraoral loading was performed. Although statistically significant, the 0.19 mm difference between the impression techniques may or may not be clinically relevant. Additional research is required in this area.     

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口腔印模的质量直接影响修复体的准确性和修复质量。临床常用的口腔弹性印模材料有藻酸盐水胶体印模材料、琼脂水胶体印模材料、硅橡胶印模材料、聚醚橡胶印模材料和聚硫橡胶印模材料。各种材料组成不同,性能各异,临床使用时应根据具体病例,选择合适的印模材料和消毒方法,以获取最佳效果。本文主要介绍了各弹性印模材料性能特点及临床使用注意事项。     

A review of contemporary impression materials and techniques

The contemporary restorative dentist has a host of impression materials available for making impressions in fixed prosthodontics,implant dentistry, and operative dentistry. With proper material selection and manipulation, accurate impressions can be obtained for fabrication of tooth- and implant-supported restorations. This article outlines the ideal properties of impression materials and explains the importance of critical manipulative variables. Available impression materials are analyzed relative to these variables, and several "specialized" impression techniques are described. Special attention is paid to polyvinyl siloxane impression materials because they have become the most widely used impression material in restorative dentistry.     

A wash technique using rubber-base impression material

The rubber-base impression materials are versatile and extremely accurate when the procedures are sound. A simplified technique using a preliminary impression of heavy-bodied material and a final wash impression of light-bodied, rubber-base impression material has been described. This technique reduces considerably the occurrence of voids or defects in the impression and gives good detail. In addition, the preliminary rubber-base impression can be used to construct temporary acrylic resin restorations.     

Prevention of acquired immunodeficiency syndrome and hepatitis B. Part IV: The effect of impression material on glutaraldehyde solution

Immersion of dental impressions in 2% glutaraldehyde has been shown to be an effective disinfection procedure for viral contamination. This study compared the effect of immersing impression materials on the concentrations of glutaraldehyde. Contamination with saliva slightly affected the concentration of glutaraldehyde. Irreversible hydrocolloid impression material markedly decreased the concentration of glutaraldehyde, whereas the immersion of silicone rubber impression material only slightly affected the concentration of glutaraldehyde. Attention should be paid to the concentration of glutaraldehyde solution when irreversible hydrocolloid impression material is immersed in the disinfectant.     

数字化印模在无牙颌中应用的研究进展

数字化印模是一种高效、便捷的新兴印模技术,近年来在固定冠、种植牙,可摘局部义齿中都展现了良好的准确度以及临床疗效,同时简化了临床诊疗的繁琐流程,提高了患者舒适度.无牙颌印模制取一直是临床诊疗的关键与难点,数字化印模在无牙颌患者修复中的应用逐渐增多.该文将从无牙颌数字化印模的分类、准确度研究以及临床扫描策略进行综述,为无...     

Assessment of tissue conditioning materials for functional impressions.

The validity of two types of tissue conditioning materials was studied and compared with that of two commonly used impression materials. The effect of three important factors on the accuracy of the impressions was observed. These factors were thickness of the impression material, time of compression of the impression, and the time interval before pouring the impression. A chrome-cobalt master cast was specially designed and 500 impressions were made and poured, resulting in 900 casts. Conclusions reached from this investigation were that: 1. Visco-Gel and Coe-Comfort tissue conditioning materials can be used as impression materials. 2. The dimensional accuracy of Visco-Gel is better than that of the Coe-Comfort impressions. 3. There is no significant difference between using a tray with a space of 1.5 mm or 3.0 mm for the impression material. 4. The less bulky the impression, the less time is required for compression with fewer inaccuracies. 5. It is preferable to pour the cast in the impression immediately or within 2 hours. 6. Both kinds of materials tested can be used as duplicating materials under certain conditions.     

A laboratory investigation of the accuracy of two impression techniques for single-tooth implants

PURPOSE: This laboratory study investigated the accuracy of four implant impression procedures using two impression techniques and two different materials. MATERIALS AND METHODS: A master model was used to produce 40 different stone casts incorporating laboratory implant or abutment analogues from the different combinations of two impression techniques (the repositioning impression coping technique at the implant level and the pickup impression technique at the abutment level) and materials (President polyvinyl siloxane and Impregum F polyether). Variations in the resulting working casts were measured using the Reflex Microscope to derive distances and angles from the three-dimensional coordinates of optical targets that were attached to a test coping placed on the implant analogue and on a reference device positioned on the occlusal surfaces of the casts. RESULTS: The results showed greater variations in analogue position with the repositioning impression technique than with the pickup technique. The rotational errors were large enough to be of clinical concern. No significant differences were found between polyvinyl siloxane and polyether impression materials for the two tested types of impression techniques. CONCLUSION: The repositioning impression technique at the implant level can produce less predictable results than the pickup technique at the abutment level. The choice of impression material made no significant difference.     

Controlling bacterial contamination of dental impression guns

BackgroundDental impression material handgun cartridge dispensers are contaminated easily during clinical use. The authors attempted to quantify contamination by bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), of impression guns used in an academic dental clinic after five infection-prevention protocols were followed.MethodsThe authors obtained samples from four commercially available impression guns at four specific sites (button, handle, latch, trigger) after routine clinical use, disinfection, steam sterilization (also known as autoclaving), steam sterilization followed by use of plastic impression gun covers and steam sterilization followed by use of plastic impression gun covers and disinfection.ResultsThe authors found that after routine clinical use, bacteria—including MRSA—heavily contaminated the impression guns. After the impression guns underwent disinfection, there was a 6 percent decrease in bacterial counts. The use of steam sterilization achieved sterility without harming the impression guns. Use of steam-sterilized impression guns with plastic impression gun covers decreased bacterial isolates by approximately 60 percent. Use of steam-sterilized impression guns plus covers and disinfection resulted in an approximately 95 percent reduction in contamination.ConclusionsThe use of common infection-prevention methods appears to reduce the bacterial counts, including those of MRSA. Bacterial contamination was lowest after steam sterilization, followed by the use of plastic impression gun covers and disinfection.Clinical ImplicationsUse of contaminated impression guns on successive patients could increase the risk of causing cross-transmission of disease. The use of sterilization, plus plastic impression gun covers and disinfection, for impression guns after each use could be an effective and practical infection-control method for dental practices.     

Comparative evaluation of dimensional accuracy of casts generated from multiple mix impression technique,matrix impression system and dual arch impression technique – An in vitro study

For a successful fixed partial prosthodontics, obtaining an accurate impression for making an accurate cast is of prime importance.In the present study the three fixed prosthodontic impression procedures, multiple mix impression technique, matrix impression system and dual arch impression technique; have been compared in terms of dimensional accuracy. An articulated acrylic resin typodont prepared with reference points was used as a master model. Addition silicon impression materials in various consistencies were used for making impressions. The coordinate measurement machine (Lloyd, Germany) was used for three dimensional measurement of master model and stone casts with an accuracy of 0.0001 mm.As per statistical analysis, all the impressions had a tendency to be oversized in horizontal dimensions and undersized in vertical dimensions. Dual arch impression technique used with flexible disposable plastic tray has found to be less dimensionally accurate as compared to multiple mix impression technique and matrix impression system whereas the other two techniques were comparable to each other.     

A clinical evaluation of the agar alginate combined impression: dimensional accuracy of dies by new master crown technique

PURPOSE: To evaluate the dimensional accuracy of several impression methods including agar alginate combined impression in vivo; the marginal accuracy of stone dies was determined using a new electroformed master crown technique. MATERIALS AND METHODS: Cast cores with knife-edge and chamfer margins and electroformed master crowns were fabricated for 3 patients. Five impressions were taken of each preparation, using agar alginate combined impression and silicone impression materials. Dies were made after impression. The marginal fit of the master crown on each die was analyzed by four-way analysis of variance (ANOVA) and Tukey HSD test (p<0.05). RESULTS: The marginal fit of the master crown on the dies with chamfer margin was better than those with knife-edge margin for agar alginate combined impression. The shape of the margin did not affect the accuracy when silicone impression material was used. CONCLUSIONS: The results suggest that the agar alginate impression method is clinically acceptable for the chamfer margin, but shape of the margin may affect the dimensional accuracy of dies. The shape of the margin does not affect the accuracy of dies when silicone impression was used. Furthermore, the master crown made by electroforming technique could be useful for clinical evaluation of impression methods.     

Impression techniques for implant dentistry

The object of making an impression in implant dentistry is to accurately relate an analogue of the implant or implant abutment to the other structures in the dental arch. This is affected by use of an impression coping which is attached to the implant or implant abutment. This impression coping is incorporated in an impression - much as a metal framework is 'picked up' in a remount impression for fixed prosthodontics. With implant copings the coping is usually attached to the implant or abutment with screws. The impression material used is usually an elastomeric impression material; the two types most widely used and shown to be the most appropriate are polyether and polyvinyl siloxane impression materials.     

A two-stage impression technique for the indirect fabrication of multiple cast dowel and cores.

Making an accurate impression of root canals prepared for cast dowel and cores can be impeded by the number of teeth involved and the working time of the impression material. These factors aside, the technique described can be used to obtain a detailed full-arch impression that precisely captures remaining tooth structure and all canal spaces. The two-stage technique involves first fitting tapered plastic sprues and making individual canal impressions. A full-arch pickup impression is then made to capture the individual canals. This simple and easily correctable procedure ensures an accurate master cast on which dowels and cores can be indirectly made.     

Impression procedure for creating a partial auricular prosthesis

Severe anatomic undercuts associated with tissue remnants or a defect site can often be an obstacle in achieving an accurate impression for a facial prosthesis. This article describes a procedure that overcomes the problems encountered in achieving an accurate impression. The distinct properties of 2 impression materials are applied to create a 3-piece impression that can be reassembled to develop an accurate stone master cast.