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Showing 5 results for Impression Technique
Fabrication of sectional complete denture using metal framework design for a patient with microstomia: a case report
A. Rohanian, Gh. Ommati Shabestari,
Volume 23, Issue 1 (6-2010)
Abstract

Microstomia is defined as an abnormally small oral orifice. Microstomia can occur as a result of trauma from electrical and thermal lesions, chemical burns and trauma from surgeries. Prosthetic rehabilitation of microstomia patients presents difficulties at all stages, from the preliminary impressions to fabrication of prosthesis. For impression procedures different treatment methods have been suggested. Swing hinge and collapsible dentures are used to provide prosthodontic treatment to patients with microstomia. Not only is such a prosthesis difficult to fabricate, but may be expensive. The literature contains reports on the fabrication of sectional denture with the denture pieces connected by different designs. This article describes a simple method of fabricating a 2-pieces denture using removeable partial denture metal framework to connect the sections, for a patient with limited oral opening. Combination of metal framework and sectional complete denture for a patient with limited oral opening is an acceptable, effective and available method.


Accuracy of different abutment level impression techniques in All-On-4 dental implants
Marzieh Alikhasi, Mahnaz Arshad, Hakime Siadat, Susan Rahimian,
Volume 25, Issue 3 (7-2012)
Abstract

Background and Aims: Passive fit of prosthetic frameworks is a major concern in implant dentistry. Impression technique is one of the several variables that may affect the outcome of dental implants. The purpose of this study was to compare the three dimensional accuracy of direct and indirect abutment level implant impressions of ALL-ON-4 treatment plan.
Materials and Methods: A reference acrylic resin model with four Branemark fixtures was made according to All-On-4 treatment plan. Multiunit abutments were screwed into the fixtures and two special trays were made for direct and indirect impression techniques. Ten direct and ten indirect impression techniques with respective impression transfers were made. Impressions were poured with stone and the positional accuracy of the abutment analogues in each dimension of x, y, and z axes and also angular displacement (Δθ) were evaluated using a Coordinate Measuring Machine (CMM). Data were analyzed using T- test.
Results: The results showed that direct impression technique was significantly more accurate than indirect technique (P<0.001).
Conclusion: The results showed that the accuracy of direct impression technique was significantly more than that of indirect technique in Δθ and Δr coordinate and also Δx, Δy, Δz.


Accuracy of implant transfer and surface detail reproduction with polyether and polyvinyl siloxane using closed-tray impression technique
Marzieh Alikhasi, Hakimeh Siadat, Elaheh Beyabanaki,
Volume 26, Issue 4 (1-2014)
Abstract

  Background and Aims: Making accurate impressions of prepared teeth when they are adjacent to dental implants is of great importance. In these situations, disregarding the selection of appropriate impression material and technique, not only can affect accuracy of transferring of the 3-dimentional spatial status of implant, but also can jeopardize the accurate recording of tooth. In the present study, the accuracy of two impression materials with taper impression copings for recording implant position and surface details was evaluated.

  Materials and Methods: One metal reference model with 2 implants (Implantium) and a preparation of three grooves on a tooth according to ADA no. 19 standard was fabricated. 10 medium- consistency polyEther (PE) impressions using custom trays and 10 polyVinyl Siloxane (PVS) putty wash impressions using prefabricated trays with conical impression coping were made. Impressions were poured with ADA type IV stone. A Coordinate Measuring Machine (CMM) evaluated x, y and angular displacement of the implant analog heads and also accuracy of groove reproduction were measured using a Video Measuring Machine (VMM). These measurements were compared to the ones from reference model. Data were analyzed using one-way ANOVA and T-test.

  Results: Putty wash PVS had less linear discrepancy compared with reference model (P > 0.001). There was no significant difference in the surface detail reproduction (P = 0.15).

  Conclusion: Putty wash PVS had better results for linear displacement compared with medium consistency PE. There was no significant difference in surface detail reproduction between the two impression materials.


The influence of implant placement depth on the accuracy of connecting impression transfers to the implants
Hakimeh Siadat, Amin Jabbari, Mohammad Taghi Baghani, Marzieh Alikhasi,
Volume 30, Issue 1 (6-2017)
Abstract

Background and Aims: The exact placement of impression copings in making accurate prosthesis is very important. In some cases, the implants need to be placed deeply subgingival, which could reduce the direct vision and ultimately reduce the precision of impression copings and subsequently, delivered prosthesis. This would be the cause of multiple complications such as delivery of ill-fitting prosthesis. The aim of this study was to evaluate the effect of the dental implant placement depth on the accuracy of impression coping connection by students.

Materials and Methods: This in-vitro and experimental study was conducted by 50 senior dental students. Four implants at different depths (0, 2, 4 and 6 mm) were placed in a model. After learning how to mount impression coping on implants, the students were asked to mount impression copings on all four implants. The samples were examined by an experienced prosthodontist using a magnifier with 4x magnification. Data were analyzed by statistical Cochran test (P<0.05(.

Results: The proper adapting rate of transfer copings, in subgingival implants with the depth of 0, 2, 4 and 6 mm were 100%, 62%, 58% and 20%, respectively. Statistically significant differences were observed between all groups (P<0.001).

Conclusion: The results showed that there was an inverse relationship between the increasing depth of the implants in the gingiva and the dentist’s ability to connect the impression copings properly.


Comparative evaluation of different surfaces fit of digitally fabricated cobalt-chromium copings in two depth of finish lines
Soudabeh Koulivand, Hakimeh Siadat, Safoura Ghodsi, Marzieh Alikhasi,
Volume 31, Issue 4 (1-2019)
Abstract
Background and Aims: Despite the increasing application of intra-oral scanners, the effect of finish line position on gingival margins adaptation is still discussed. The purpose of this clinical study was to evaluate the fitness of cobalt-chromium copings obtained from intraoral scanning in two depth of finish lines.
Materials and Methods: Thirty teeth prepared for single premolar metal-ceramic crowns were included. Fifteen teeth had supragingival and fifteen had sub-gingival finish lines. Digital impressions were made using an intraoral scanner (Trios-3shape). Computer-aided design and computer-aided manufacture (CAD/CAM) cobalt-chromium copings were fabricated from the scan files. The copings were evaluated intraorally and after adjustments, the internal and marginal discrepancy were measured using silicone replicas and a stereomicroscopy. Internal and marginal discrepancies were analyzed using the Multivariate test (P<0.05).
Results: The mean internal and marginal gap were 52.1 and 56.27μ, for supragingival group and 49.72 and 62.98μ for subgingival group, respectively. The evaluation of finish line position showed no significant effect on obtained results (P>0.05).
Conclusion: CAD/CAM chrome-cobalt copings fabricated by digital impressions provided acceptable marginal and internal precision. However, the finish line position had no significant effect on the internal and marginal adaptation.

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