Effect of impression holding time and tray removal speed on the dimensional accuracy of impressions for artificial abutment tooth inclined

Odontology - Oral scanners allow dental impressions to be taken in a short time without the use of an impression material. However, it has been noted that high impression accuracy cannot be...     

Drying time of tray adhesive for adequate tensile bond strength between polyvinylsiloxane impression and tray resin material

STATEMENT OF PROBLEM

Use of custom tray and tray adhesive is clinically recommended for elastomeric impression material. However there is not clear mention of drying time of tray adhesive in achieving appropriate bonding strength of tray material and impression material.

PURPOSE

This study is to investigate an appropriate drying time of tray adhesives by evaluating tensile bonding strength between two types of polyvinylsiloxane impression materials and resin tray, according to various drying time intervals of tray adhesives, and with different manufacturing company combination of impression material and tray adhesive.

MATERIAL AND METHODS

Adhesives used in this study were Silfix (Dentsply Caulk, Milford, Del, USA) and VPS Tray Adhesive (3M ESPE, Seefeld, Germany) and impression materials were Aquasil Ultra (monophase regular set, Dentsply Caulk, Milford, Del, USA) and Imprint II Garant (regular body, 3M ESPE, Seefeld, Germany). They were used combinations from the same manufacture and exchanged combinations of the two. The drying time was designed to air dry, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes. Total 240 of test specimens were prepared by auto-polymerizing tray material (Instant Tray Mix, Lang, Wheeling, Il, USA) with 10 specimens in each group. The specimens were placed in the Universal Testing machine (Instron, model 3366, Instron Corp, University avenue, Nowood, MA, USA) to perform the tensile test (cross head speed 5 mm/min). The statistically efficient drying time was evaluated through ANOVA and Scheffe test. All the tests were performed at 95% confidence level.

RESULTS

The results revealed that at least 10 minutes is needed for Silfix-Aquasil, and 15 minutes for VPS Tray Adhesive-Imprint II, to attain an appropriate tensile bonding strength. VPS Tray Adhesive-Imprint II had a superior tensile bonding strength when compared to Silfix-Aquasil over 15 minutes. Silfix-Aquasil had a superior bonding strength to VPS Tray Adhesive-Aquasil, and VPS Tray Adhesive-Imprint II had a superior tensile bonding strength to Silfix-Imprint II at all drying periods.

CONCLUSION

Significant increase in tensile bonding strength with Silfix-Aquasil and VPS Tray adhesive-Imprint II combination until 10 and 15 minutes respectively. Tray adhesive-impression material combination from the same company presented higher tensile bonding strength at all drying time intervals than when using tray adhesive-impression material of different manufactures.     

Effect of wash bulk on the accuracy of polyvinyl siloxane putty-wash impressions

Variations in the bulk of wash in a putty-wash impression technique can result in dimensional changes proportional to the thickness of the wash material during setting. The purpose of the study was to determine the amount of wash necessary to achieve accurate stone models while using a two-step putty-wash impression technique with polyvinyl siloxane (PVS) impression material. A total of 45 impressions were made of a stainless steel master model, 15 impressions for each wash thickness (1, 2 and 3 mm). The model contained three full-crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring six dimensions (occlusogingival and interabutments) on stone dies poured from impressions of the master model. One-way analysis of variance (ANOVA) showed statistically significant differences amongst the three wash bulk groups, for all occlusogingival and interabutment measurements (P < 0.001). The overall discrepancies of the groups using wash thickness of 1 and 2 mm were smaller than the group with 3 mm wash thickness. Therefore, wash bulks of 1 and 2 mm were most accurate for fabricating stone dies, using PVS impression materials. This can be achieved by using the temporary crown to create the desired wash space in the preliminary putty impression. Wash thickness > 2 mm was inadequate to obtain accurate stone dies.     

Surface accuracy of hydrophilic impressions. 1

The purpose of this study was to examine detail reproducibility and surface roughness of stone models made from silicone, polysulfied rubber, alginate and agar impression materials using stainless steel test block (ISO). In addition, the influence of artificial saliva was studied. The following results were obtained: 1. Silicone impression materials showed the best detail reproducibility of all materials. 2. When artificial saliva was dropped on the stainless steel test block, hydrophilic silicone impression material showed the best detail reproducibility. 3. In the test using artificial saliva, alginate and agar impression materials showed better surface roughness, but poorer detail reproducibility than silicone impression ones. 4. Hydrophilic silicone material indicated the highest detail reproducibility, and the lowest surface roughness in the test using artificial saliva.     

Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions

Abstract— The effect of immersion in six disinfecting solutions on the accuracy of 10 impression materials was investigated. Impressions were taken of a truncated steel cone. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 iron), and after 24 h poured with gypsum. A steel ring fitting the steel cone was placed on the resulting dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and of the impression was calculated to express the inaccuracy. All impressions except some in Blueprint exhibited a net shrinkage, giving rise to too large die stones and incomplete seating of the steel ring. Blueprint impressions, however, occasionally swelled and resulted in too small die stones and "overseating" of the steel ring. The disinfecting solutions had no significant impact on two impression materials. For the remaining eight materials the accuracy was decreased, increased, or unaffected by the immersion. Generally, the accuracy of the alginates investigated were more affected by the disinfecting solutions than were the elastomeric impression materials. The accuracy of the three alginates was drastically impaired by immersion in 70% ethanol, whereas the remaining five disinfecting solutions had a smaller, though sometimes statistically significant, effect on the accuracy. For the elastomeric materials only a few specific combinations of impression material and disinfecting solution reduced the accuracy. Since the control values of accuracy varied, it was concluded that the choice of elastomeric impression material is more critical than the choice of disinfecting agent. As for the alginates, brand as well as type of disinfecting solution have to be considered to obtain an acceptable accuracy of disinfected alginate impressions.     

Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions

The effect of immersion in six disinfecting solutions on the accuracy of 10 impression materials was investigated. Impressions were taken of a truncated steel cone. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 min), and after 24 h poured with gypsum. A steel ring fitting the steel cone was placed on the resulting dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and of the impression was calculated to express the inaccuracy. All impressions except some in Blueprint exhibited a net shrinkage, giving rise to too large die stones and incomplete seating of the steel ring. Blueprint impressions, however, occasionally swelled and resulted in too small die stones and "overseating" of the steel ring. The disinfecting solutions had no significant impact on two impression materials. For the remaining eight materials the accuracy was decreased, increased, or unaffected by the immersion. Generally, the accuracy of the alginates investigated were more affected by the disinfecting solutions than were the elastomeric impression materials. The accuracy of the three alginates was drastically impaired by immersion in 70% ethanol, whereas the remaining five disinfecting solutions had a smaller, though sometimes statistically significant, effect on the accuracy. For the elastomeric materials only a few specific combinations of impression material and disinfecting solution reduced the accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of 3 medicaments on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions.

OBJECTIVE: The purpose of this study was to determine the effect of retraction cord medicaments (aluminum chloride, ferric sulfate, and ferric subsulfate/ferric sulfate) on the dimensional accuracy and surface detail reproduction of polyvinyl siloxane impressions. METHOD AND MATERIALS: Polyvinyl siloxane impressions were made of standardized metal dies (American Dental Association [ADA] specification No. 19) treated with 1 of the 3 retraction cord medicaments. Dimensional accuracy was evaluated by comparing the average length of a line in the impressions to the standard die. Surface detail reproduction was evaluated by viewing the impressions under low-angle illumination at x10 magnification. Reproduction was considered satisfactory if 2 of 3 horizontal lines were reproduced continuously. The dies were also evaluated under the microscope before the impression was made. RESULTS: The medicaments did not significantly effect the dimensional accuracy; mean shrinkage was within ADA guidelines in the treatment groups. All of the medicaments had an adverse effect on surface detail reproduction. These effects were statistically significant compared to the untreated control. CONCLUSION: Although the changes in dimensional accuracy were within ADA guidelines, the surface detail reproduction was modified such that the impression would be considered clinically unacceptable. For optimal results, care must taken to remove all traces of these retraction cord medicaments prior to recording of a polyvinyl siloxane impression.     

Comparing effects of tray treatment on the accuracy of dies

The effects of tray treatments on the accuracy of dies from addition silicone impressions were investigated. Tray treatments included custom acrylic resin tray with adhesive, perforated custom acrylic resin tray without adhesive, and perforated custom acrylic resin tray with adhesive. No appreciable differences were found in the complete crowns among the three tray treatments on the first pours. Significant statistical differences observed in the MOD and occlusal inlays were nonetheless of questionable clinical significance. Adhesives are advisable if the impressions are poured repeatedly, however, to minimize accidental separation of the impression from the tray. The second casts were less accurate with complete crowns and MOD inlays when perforated trays were used without adhesives.     

The effect of tray selection,viscosity of impression material,and sequence of pour on the accuracy of dies made from dual-arch impressions

STATEMENT OF PROBLEM: Dual-arch trays are often used to generate impressions of prepared teeth and of the opposing arch simultaneously. There is concern that accuracy of the casts generated with this technique can be affected by the type of tray, viscosity of the impression material, and sequence of pouring the cast. PURPOSE: This study compared the accuracy of working dies made from impressions with metal and plastic dual-arch trays, for 2 different viscosities of impression tray material and by altering which side of the impression was poured first. MATERIALS AND METHODS: Impressions were made of a typodont mandibular arch containing a circular stainless steel crown preparation (standard). There were 3 variables: type of dual-arch tray, impression material viscosity, and order of pour of the impressioned arches. A balanced design with independent samples was used (n=10). Two types of dual-arch trays, plastic (Triple Tray) and metal (COE Impression Tray), and 2 viscosities of addition silicone for the tray were used (Aquasil Rigid and Aquasil Monophase). Type IV gypsum (Fuji-Rock) with a ratio of 20 mL of distilled water to 100 g of powder was hand-mixed for 10 seconds then mixed under vacuum for 40 seconds and poured into the trays while being vibrated. One side of the dual-arch impression was poured with 35 g of stone and allowed to set for 1 hour before the other side was poured with 35 g of stone. The order of pour was randomized, and all casts were allowed to set for 24 hours at room temperature before removal. The dies were measured in 3 dimensions (buccolingual, mesiodistal, and occlusogingival) with a measuring microscope. The gypsum working dies were placed into a custom jig fabricated to permit measurement at a fixed, reproducible position under the microscope. Each dimension of the working dies was measured 3 times, and the mean was used for the sample value. The same 3 aspects of the stainless steel standard were measured multiple times, before and then at the conclusion of measuring all working dies, to arrive at the 3 standard values to which all working die means were compared. The means for the standard used in the statistical analysis were those taken at the conclusion of the study. The intraexaminer variation for measuring the standard was 0.001 mm. A 3-factor analysis of variance was used for the statistical analysis with hypothesis testing at alpha=.05. RESULTS: Statistically significant differences were found with viscosity selection for the buccolingual and occlusogingival dimensions of the working die. The rigid material produced working dies slightly taller (1 microm) than the standard, and those from the monophase material were 4 microm shorter. Regarding tray selection, metal trays were slightly more accurate in the mesiodistal dimension, and when monophase was used in a plastic tray, gypsum dies were nearly 30 microm smaller in the mesiodistal dimension (P<.05). Differences were not detected for sequence of pouring impressions. CONCLUSION: Within the limitations of this study, the monophase material, when compared with the rigid impression material, was most accurate for the occlusogingival and mesiodistal dimensions, although not as accurate in the buccolingual. This buccolingual difference (0.002 mm-0.006 mm) would be clinically inconsequential with the application of die spacer. The rigid impression material was also unaffected by tray selection for the mesiodistal, whereas monophase was affected. When a monophase impression material was used, plastic dual-arch trays yielded gypsum dies which were significantly smaller (0.029 mm) than the ones generated from the metal trays (0.006 mm). Thus rigid impression materials can be recommended for use in dual-arch trays; however, the magnitude of the differences would generally not be clinically significant because they could be compensated for with several coats of die spacer.     

Positional accuracy of four die tray systems

This study evaluated the positional accuracy of dies with four die tray systems. The die trays were: (1) Accu*trac Precision die system, (2) Model-Tray system, (3) Sterdo Split model tray, and (4) Tricodent One*Cast die tray system. Positional change of the dies was measured by using an Olympus binocular scanning tunneling microscope (STM). Positional change of the dies was the difference between preremoval and postremoval die position. Results show that all four die tray systems are not significantly different in most measurement categories, although the Model-Tray system was significantly different from the other die tray systems in one measurement category.     

Effects of reheating on the accuracy of addition silicone putty-wash impressions

The effect of the relatively high thermal contraction of addition silicones (polyvinylsiloxane) on the accuracy of stone casts was evaluated using the putty/wash relining impression technique and acrylic resin trays. Impressions were made at 37 degrees C and were divided into two groups. One group was poured at room temperature (22 degrees +/- 2 degrees C) and another group was reheated to 37 degrees C before pouring. Measurement of the dimensional changes failed to reveal improved accuracy of the stone casts poured at the same temperature as that reached during impression making. On the basis of this limited sample, it can be concluded that reheating the impression using the putty/wash relining technique did not improve the accuracy of the stone cast.     

Influence of impression material and time on the 3-dimensional accuracy of implant impressions.

OBJECTIVE: To investigate, in vitro, the effect of time on the 3-dimensional accuracy of open-tray implant impression copings made of polyvinyl siloxane and polyether impression materials. METHOD AND MATERIALS: Reference models with 4 internal connection implants were fabricated. Four sets of 71 direct impressions were made with square impression copings using an open-tray technique. One set of impressions was made with polyether material (material A) and each of 3 polyvinyl siloxane materials (materials B, C, and D). Three-dimensional changes in spatial orientation of the implant analogs were measured over 48 hours using an optical measurement device. Deviation values were summed over 4 points and averaged per impression. Global differences were tested with a nonparametric Kruskal-Wallis test followed by pairwise comparisons using the Mann-Whitney U test. RESULTS: The mean dimensional accuracy of implant impressions significantly differed over time (P < .001). Materials A and B were found to produce comparable results, For materials C and D there was a significant increase in deviations, with a maximum increase at 2 hours. Deviations for material C were comparable to materials A and B at 48 hours. Baseline values were not maintained by any material. CONCLUSIONS: Within the limits of this in vitro study, it can be concluded that time cannot be neglected as a factor affecting the accuracy of implant master casts.     

Dimensional accuracy of microcomputed tomography-scanned half-arch impressions

Statement of problem

Accuracy in impression making may be enhanced by digitizing the physical impression directly and thereby be unhampered by errors introduced by gypsum casts.

The effect of tray selection on the accuracy of elastomeric impression materials

This study evaluated the accuracy of reproduction of stone casts made from impressions using different tray and impression materials. The tray materials used were an acrylic resin, a thermoplastic, and a plastic. The impression materials used were an additional silicone, a polyether, and a polysulfide. Impressions were made of a stainless steel master die that simulated crown preparations for a fixed partial denture and an acrylic resin model with cross-arch and anteroposterior landmarks in stainless steel that typify clinical intra-arch distances. Impressions of the fixed partial denture simulation were made with all three impression materials and all three tray types. Impressions of the cross-arch and anteroposterior landmarks were made by using all three tray types with only the addition reaction silicone impression material. Impressions were poured at 1 hour with a type IV dental stone. Data were analyzed by using ANOVA with a sample size of five. Results indicated that custom-made trays of acrylic resin and the thermoplastic material performed similarly regarding die accuracy and produced clinically acceptable casts. The stock plastic tray consistently produced casts with greater dimensional change than the two custom trays.