Removable Partial Denture Education in U.S. Dental Schools

PURPOSE: A survey of U.S. dental schools was conducted in 2001 to determine the curricular structure, techniques, and materials used in predoctoral clinical removable partial denture (RPD) programs. MATERIALS AND METHODS: The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 schools returned the completed survey, resulting in a response rate of 82%. RESULTS: Results from this survey show that a large majority of schools are using similar materials in clinical RPDs; for instance, using modeling compound for border molding final impression trays (61%) and using a semi-adjustable articulator for mounting preliminary casts (90%) and final casts (98%). In addition, a large majority of schools are using similar techniques in clinical RPDs, such as border molding the edentulous areas of the final impression tray (80%) and using the altered cast impression technique (59%). A set post-insertion protocol is present for patients who receive partial dentures in the majority of the schools (93%). Only 25% of schools reported incorporating new educational materials such as the use of Portrait artificial teeth at the predoctoral level. Eighteen percent of schools are allowing students to graduate without a set number of RPD clinical requirements as has been traditionally the case. CONCLUSIONS: Predoctoral clinical RPD programs vary from school to school, yet a large percentage of schools agree on many topics.     

Current concepts and techniques in complete denture final impression procedures

PURPOSE: In 2001, a survey of U.S. dental schools was conducted to determine which concepts, techniques and materials are currently prevalent in the teaching of final impression procedures for complete dentures in the predoctoral clinical curriculum. MATERIALS AND METHODS: The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 schools returned the completed survey resulting in a response rate of 82%. RESULTS: Results from this survey show that the majority of schools (71%) teach the selective-pressure technique for final impression making; the majority of the schools (64%) use modeling plastic impression compound for border molding the final impression tray; 39% of the schools do not place vent holes in the final impression tray, 30% of schools place more than one hole and 27% place one hole only; the majority of the schools (98%) are using custom trays for final impressions. Ninety-eight percent of the schools are border molding the custom tray and 70% of schools are using a visible light-cured (VLC) composite resin material to make the trays. Thirty-six percent of the schools are teaching the Boucher impression technique and 34% are teaching the modified Boucher impression technique. CONCLUSIONS: Predoctoral clinical complete denture educational programs agree on many aspects of final impression making, however, there is variability in their teachings regarding the impression philosophy and the materials used.     

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.     

Compatibility of Type IV Dental Stones With Polysulfide Impression Materials

PURPOSE: In the American National Standards Institute/American Dental Association specification no. 19, compatibility of impression materials with dental stones is assessed by the presence of a 20-microns-wide line reproduced on an unmodified calcium sulfate dihydrate cast. In actual dental practice, modified type IV dental stones are used, although little is known of their compatibility with polysulfide impression materials. This study evaluated the compatibility of 6 polysulfide impression materials and 11 modified type IV dental stones. MATERIALS AND METHODS: A line 20 microns wide was etched on four glass dies. Four samples of each combination of impression material and dental stone were prepared according to the manufacturer's directions with an additional 3 minutes for the final setting time. Compatibility was determined by the presence of the reproduced line on the dental stones, as observed under low angle 10 x magnification by four rater groups. RESULTS: The line was reproduced on all of the impression specimens, and the examiners recorded 66 positive identifications of the line on the stone casts out of a possible 1,056 ratings for a total of 6.25% of the specimens. Out of a possible 66 impression-stone combinations, only 18 reproduced the 20-microns line. The combinations reproducing the lines most frequently (75%) were Neoplex with Blue Die Stone (Columbus Dental, St Louis, MO) and Coeflex with Indic Die Stone (Coe Lab Inc, Chicago, IL). CONCLUSIONS: The study showed that many combinations of polysulfide impression materials and modified type IV dental stones did not reproduce the 20-microns line; therefore, not every polysulfide is compatible with every type IV dental stone.     

A New Simplified Beading and Boxing Procedure for Elastic Impression

Beading and Boxing of impression is taught in most dental colleges. The boxing procedure is crucial step to preserve the details of the final impression especially of the vestibular area. This article describes an alternative beading-boxing procedure that is compatible with all impression materials, is efficient, simple, inexpensive, and practicable. Use of commercially available instant adhesive around the border to act as a joining agent between elastic impressions and beading wax or bead made up of base plate wax is advocated in this technique.     

A modified edentulous maxillary custom tray to help prevent gagging

The gag reflex can be a normal, healthy defense mechanism to prevent foreign objects from entering the trachea. During certain dental procedures, however, gagging can greatly complicate the final result, especially during the maxillary complete denture final impression. A modification can be made to the maxillary custom acrylic resin tray to aid in securing a clinically acceptable elastomeric final impression. This modification involves forming a vacuum chamber at the posterior extent of the custom tray to which a saliva ejector tip is embedded. When the saliva ejector is connected to the low-volume evacuation hose, the chamber will trap any excess impression material that might extrude from the posterior border of the loaded tray. This results in a reduced chance of eliciting the patient's gag reflex.     

An alternative method for restoring single-tooth implants

BACKGROUND: Having laboratory technicians prepare soft-tissue casts and implant abutments with or without concomitant removable temporary prostheses during the restorative phase of single-tooth replacement is an accepted practice. It can, however, result in functional and esthetic intraoral discrepancies. CASE DESCRIPTION: Single-tooth implants can be restored with crowns (like those for natural teeth) fabricated at a dental laboratory on casts obtained from final impressions of prepared implant abutments. In the case reported, the restorative dentist restored the patient's single-tooth implant after taking a transfer impression. He constructed a cast simulating the peri-implant soft tissue with final impression material and prepared the abutment on this model. His dental assistant then fabricated a fixed provisional restoration on the prepared abutment. At the patient's next visit, the dentist torqued the prepared abutment onto the implant, took a final impression and inserted the provisional restoration. A crown was made conventionally at the dental laboratory and cemented in place at the following visit. CLINICAL IMPLICATIONS: This alternative method for restoring single-tooth implants enhances esthetics by more accurately simulating marginal gingival architecture. It also improves function by preloading the implant through fixed temporization after the dentist, rather than the laboratory technician, prepares the abutment to the dentist's preferred contours.     

A simple technique to reduce the risk of irreversible gingival recession after the final impression

The chemicomechanical method is the most common tissue displacement technique used to facilitate the final impression for fixed dental prostheses. The article describes a simple technique to minimize the risk of developing gingival irreversible recession because of tissue displacement cords.     

The Results of a Brief Survey of Complete Denture Prosthodontic Techniques in Predoctoral Programs in North American Dental Schools

A brief mail survey of North American dental schools was undertaken to ascertain the current techniques in complete denture prosthodontics regarding preliminary and final impressions, record bases, and denture teeth. Of the 64 schools surveyed, 54 responded (84%). Seventy-four percent of the respondents used only irreversible hydrocolloid (alginate) for their preliminary impressions; 15% used only modeling plastic impression compound. Eighty-one percent used only modeling plastic impression compound for border molding of the final impression tray; 7% used only polyether impression material. Forty-eight percent used only polysulfide rubber (PR) impression material for their final impression material; 4% used only polyether impression material. Only 1 school still used shellac as one of its materials for record bases. Thirty-five percent used only Triad; 35% used only acrylic resin; 24% used both of these materials. Thirteen percent of responding schools used only nonanatomic teeth. The majority (54%) used all three options (nonanatomic, semianatomic, and anatomic). Eleven percent used lingualized occlusion. As compared with a survey performed in 1985, the use of irreversible hydrocolloid as a preliminary impression material, the use of visible light-cured resins for record bases, and the use of anatomic teeth have increased. The use of plastic impression compound for border molding and PR as the final impression material has largely remained the same.     

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...     

Laser digitization of casts to determine the effect of tray selection and cast formation technique on accuracy

STATEMENT OF PROBLEM; Several studies have attempted to determine the ideal combination of dental materials and laboratory techniques to produce the most accurate dental cast. Most have made use of 2-dimensional manual measuring devices, which neglect to account for the dimensional changes that exist along a 3-dimensional surface. PURPOSE: The purpose of this study was to determine the effect of impression tray selection and cast formation techniques on the dimensional change of a dental cast with the use of new, 3-dimensional optical digitizing technology. MATERIAL AND METHODS: Multiple impressions of a machined steel die that resembled a dental arch were made with custom and stock impression trays and vinyl polysiloxane impression material. The impressions were poured in type V artificial dental stone and allowed to set with the tray inverted or noninverted. The steel master die and stone casts were digitized with the Steinbichler Comet 100 Optical Digitizer, which was developed at the Minnesota Dental Research Center for Biomaterials and Biomechanics. Three-dimensional images of the stone casts were aligned to the 3-dimensional image of the master die and analyzed with AnSur-NT software. Multiple measurements of the master die and stone casts were analyzed to determine the accuracy of the 3-dimensional technology and of the impression and cast fabrication techniques. Planar distances between the center of each crown preparation were measured, as were crown heights. Data were analyzed with analysis of variance (P<.05), and root mean square error values were determined. RESULTS: Casts were compared with a total of 45 significance tests, of which only 4 yielded P<.05. There was no pattern to these results, which suggests that they were false-positive findings. CONCLUSION: Results obtained with the use of new optical digitizing technology indicated that neither impression tray type nor cast formation technique affected the accuracy of final casts.     

The Use of Digital Impressions to Fabricate Tooth‐Supported Partial Removable Dental Prostheses: A Clinical Report

Impression making is a critical step in the fabrication of a partial removable dental prosthesis (RDP). A technique is described for making final impressions to fabricate partial RDPs for Kennedy class III patients using a computer‐aided design and computer‐assisted manufacturing digital impression system.     

Antimicrobial effect of 4 disinfectants on alginate, polyether, and polyvinyl siloxane impression materials

PURPOSE: Dental impressions often carry microorganisms that may cause cross infection from patients to dental staff. The aim of the current study was to determine the effectiveness of 4 different disinfectant solutions on 3 commonly used impression materials--alginate, polyether, and polyvinyl siloxane--to establish a protocol for disinfection of these impression materials after clinical exposure and prior to handling in the dental laboratory. MATERIALS AND METHODS: A total of 45 impressions were taken from the maxillary dentate arches of 15 dental staff participants at the Department of Dentistry, Prince Rashid Hospital, Irbid, Jordan. For each participant, 3 successive impressions were recorded in the different impression materials. For each impression, 6 specimens were dissected from 6 different locations and exposed to 6 different regimens: 1 was left untreated, 1 was immersed in sterile water for 10 minutes to serve as a control, and the remaining 4 specimens were exposed to 4 different disinfection treatments (Dimenol, Perform-ID, MD 520, and Haz-tabs). Serial dilutions of the suspension were carried out and counted by the Miles-Misra technique (inoculation on Columbia blood agar for quantification). The dilutions were aerobically incubated at 37 degrees C for 48 hours. RESULTS: The disinfectants were able to completely eliminate microorganisms carried by the impressions. For those undisinfected specimens, the results showed that untreated alginate impressions appear to carry more microorganisms (P < .05) than the other 2 rubber impression materials used in the study. For those specimens immersed in sterile water for 10 minutes (control group), the number of microorganisms eliminated was increased from 62% to 90% compared to those left untreated. CONCLUSION: Impression materials may act as a vehicle for the transfer of microorganisms from the patient's mouth to dental personnel. Impressions should be disinfected to eliminate the risk of cross contamination.     

Predictable preparation, staining, and cementation procedures for chairside CAD/CAM dentistry

Although direct composite resin procedures yield acceptable results when used correctly, if a large quantity of resin is required, complications may arise. In such cases, an indirect protocol must be followed. Numerous CAD/CAM systems, both laboratory and chairside, are available for practitioner use. In a laboratory system, a traditional impression is made and sent to a dental laboratory, where the restoration is fabricated. A chairside system, however, utilizes a digital impression system, and the restoration can then be milled and cemented in a single visit.     

Implant-borne single tooth replacement--an illustration and rationale.

This article demonstrates a method for the replacement of a single missing tooth with a dental implant system that can simply and easily be incorporated into a general practice. Recent innovations in implant abutment design and impression procedures have resulted in a technique that is very similar to traditional crown and bridge procedures. This article describes a step-by-step protocol for the restoration of a single missing tooth with an implant-borne, cemented crown.     

Application times for the single-step/double-mix technique for impression materials in clinical practice

Hydrophilicity of unset impression materials underlies changes occurring during working time. Hence, the clinical application time when impression materials contact oral tissues after mixing may play a critical role in successful impressions. The aim of this study was to analyze the clinical time course of impression taking applying the single-step/double-mix technique. Application times of 86 impressions, comprising 265 prepared teeth and 46 implants, taken by 14 different clinicians at a university dental clinic were analyzed. The mean time from loading the impression tray until its final position in the patient's mouth (total application time) was 51.2 seconds; confidence intervals were 46.9 (lower limit) and 55.5 (upper limit). The number of registered teeth and implants did not influence the duration of impression taking. Related to wettability data, several polyvinyl siloxane impression materials show decreased hydrophilicity with respect to estimated application times. The authors suggest considering clinically relevant application times for impression taking in future in vitro studies on physicochemical characteristics of impression materials.     

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.     

An evaluation of DNA yield, DNA quality and bite registration from a dental impression wafer

BACKGROUND: The authors determined the amount and quality of the DNA captured by a bite impression wafer and analyzed any inaccuracies in the impression wafer. METHODS: The authors made bite registrations for subjects aged 7 to 12 years by using a dental impression wafer (Toothprints, Kerr, Orange, Calif.), obtained an oral rinse sample, took cheek cells by using buccal swabs and made an alginate impression to pour a stone model. They extracted and quantified the DNA from the dental impression wafer, mouthwash and buccal swabs by using the Quant-iT PicoGreen (Invitrogen, Carlsbad, Calif.) assay and a real-time polymerase chain reaction (RT-PCR) assay. They compared the stone models and imprints from the wafer. RESULTS: The average amounts of DNA determined by using Quant-iT PicoGreen from the buccal swab, mouthwash and dental impression wafer samples were 113.61, 509.57 and 1.03 micrograms, respectively. The average amounts of DNA determined by using RT-PCR from the buccal swab, mouthwash and dental impression wafer samples were 11.5240, 22.2540 and 0.0279 mug, respectively. The bite registrations and stone models had an average of 14 percent of mismatches. CONCLUSION: The dental impression wafers captured DNA but not in high quantities. They did not produce an accurate representation of the dentition. CLINICAL IMPLICATIONS: The dental impression wafers captured enough DNA to permit amplification. The accuracy of the bite registration was not sufficient for identification purposes. Therefore, dental impression wafers may be useful only as a reservoir for DNA.     

Fabricating an Accurate Implant Master Cast: A Technique Report

The technique for fabricating an accurate implant master cast following the 12‐week healing period after Teeth in a Day® dental implant surgery is detailed. The clinical, functional, and esthetic details captured during the final master impression are vital to creating an accurate master cast. This technique uses the properties of the all‐acrylic resin interim prosthesis to capture these details. This impression captures the relationship between the remodeled soft tissue and the interim prosthesis. This provides the laboratory technician with an accurate orientation of the implant replicas in the master cast with which a passive fitting restoration can be fabricated.     

Management of the flabby ridge: using contemporary materials to solve an old problem

The presence of displaceable denture-bearing tissues often presents a difficulty when making complete dentures. Unless managed appropriately, such 'flabby ridges' adversely affect the support, retention and stability of complete dentures. Many impression techniques have been proposed to help overcome this difficulty. While these vary in approach, they are similar in their complexity, are often quite time-consuming to perform, and rely on materials not commonly in use in contemporary general dental practice. The purpose of this paper is to describe an impression technique for flabby ridges that makes use of polyvinylsiloxane impression dental materials routinely available in general dental practice.