impression technique

The accurate impression of the mouth and reproduction of gingiva can be regarded as a record for the production of a cast with optimum fitting and dental restoration. This study investigated the soft tissue accuracy around implant through digital and conventional methods with different viscosities of additional silicone.

An acrylic dentifrice was utilized in the upper right central edentulous area in this study. Moreover, a bone level analogous fixture with a diameter length of 12 and 4.1 mm was inserted in the edentulous area 3 mm below the gingiva parallel to the adjacent central tooth. In total, 30 impressions were made using dentifrice with the help of digital scans (6 times), conventional impressions using a custom tray and regular body additional silicone (12 times), and conventional impressions by a stock tray with putty wash silicone (12 times). Moreover, 6 casts with and 6 casts without gingival masks were prepared using the conventional method before the cast preparation. They were then scanned using the Lab scanner in the STL format. Following that, superimposition of the data and cloud compare software were utilized to compare and evaluate the changes of soft tissue around the implant in each method considering the reference method. The differences between the proposed models and the reference model were recorded, and the data were analyzed in this study.

The result of the Kruskal Wallis indicated no significant differences among the groups in terms of the mean values of the data (p < /em>=0.345).

Regarding the mismatch among the impression methods, the results showed no significant difference in this regard.

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. 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). 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). 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.

An accurate impression of teeth and supporting structure is necessary to restore a lost tooth structure or to replace a tooth with crown and bridge. Although there are various methods for making impression، putty-wash technique is currently preferred since it is simple and does not require a special tray. Silicone elastomeric impression materials have suitable consistency for putty-wash technique and are thus widely used. Considering the existing controversies over the effects of impression technique on the accuracy of restoration، we evaluated the effects of rewash on the accuracy of stone dies produced by a putty-wash technique. In this laboratory study، a model with two metallic dies was used. One die had a horizontal notch as an undercut. Ten impressions were made with spacer and ten impressions with rewash technique. A profile meter with accuracy of one micron was used to measure the dimensions of the produced stone models. The original and produced models were compared by t-test. The mean height of dies without undercut decreased significantly in both groups (11. 69 with spacer، P < 0. 001 and 11. 44 with rewash P < 0. 001). The mean diameter of dies without undercut decreased in both groups (10. 39 with spacer and 10. 27 with rewash) but the difference was only significant using rewash technique (P = 0. 018). The mean distance between two dies increased in both techniques (30. 25 with spacer and 30. 43 with rewash). Again، the difference was only significant using rewash technique (P < 0. 001). The mean diameter of dies below the undercut increased with spacer technique (10. 33; P > 0. 05) and decreased with rewash technique (10. 21; P < 0. 001). The mean height of dies above the undercut decreased significantly in both groups (9. 99 with spacer P < 0. 001 and 10. 21 with rewash P < 0. 001). The impression technique with spacer was more accurate in all dimensions as compared to rewash technique.

Microstomia signifies any significant decrease in the size of the oral aperture. The etiology might include disease، trauma، burns and surgical complications in the peri-oral areas. This article describes a practical method for the treatment of a maxillary-edentulous patient with severe microstomia. The patient was a 40-year-old woman who was completely edentulous in the maxilla، with severe microstomia. Due to reduced mouth opening، all the clinical procedures، from selection of a prefabricated tray for initial impression to designing the final prosthesis، are difficult and it is impossible to use a conventional impression tray and denture in such patients. Implant treatment was not possible for the patient because of financial problems; therefore، complete denture was the best choice. A sectional denture that can be worn and removed easily can be a treatment of choice for such patients. The primary impression in this patient was taken by a sectional tray and putty and wash. The special 2-sectional tray was fabricated for the patient. Then a 2-sectional denture was fabricated by ball attachment and finally was assembled in her mouth by palatal strap frame. In the first fallow-up of the patient after 1 year، she was satisfied with the esthetic and function of the denture، in addition to proper fit and stability of denture، without any traumatic injuries. Sectional dentures that are easily worn and removed can be successfully used for the treatment of patients with microstomia. Complete denture، Impression technique، Microstomia.

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. 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. The results showed that direct impression technique was significantly more accurate than indirect technique (P<0.001). 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.

The success of fixed prosthodontics requires a precise registration of the prepared teeth and finishing line, which necessitates finding to simple technique of impression taking so that an acceptable impression with record of details can be achieved. This research was performed to evaluate the effect of the second wash of Speedex impression material in one- and two-step impression technique on marginal adaptation of the crown. In this in vitro study a laboratory model with two metal dies (similar to the 2nd premolar the 2nd molar) and condensation silicone impression material (Speedex) were used. Impressions were made in four techniques (one-step, one-step with second wash, two-step with 2 mm of space, two-step with a second wash). Each technique was repeated 15 times and 60 impressions were obtained, which were poured with Type IV dental stone. On each die a wax pattern of a three-component bridge was framed and casting was carried out with a metal alloy. The marginal fitness of the frames was viewed and measured under a stereomicroscope at ×100 magnification with a digital micrometer in four areas. The results were analyzed by Tukey test and ANOVA. The least and greatest marginal gaps were observed in the anterior abutment with the two-step technique and the posterior abutment with one-step technique with a second wash (69.56 and 85.59 microns, respectively). The amounts of marginal gaps were clinically acceptable in all the four methods. There were no significant differences between the one-step and two-step techniques (p value = 1) and between one-step technique and two-step technique with a second wash (p value = 0.6). For each four technique the amount of marginal gap was acceptable; therefore, a second wash can be added to the primary wash to achieve more precise impressions with registration of details and finishing line. However, further evaluations are necessary.