The effect of custom tray material type and fabrication technique on tensile bond strength of impression material adhesive systems

Accuracy and feasibility of 3D-printed custom open trays for impressions of multiple implants: A self-controlled clinical trial

STATEMENT OF PROBLEM

Three-dimensionally printed custom open trays have become a popular option in clinical implant dentistry because of advantages such as individualization, efficiency, and effectiveness. However, clinical evidence on their accuracy and feasibility is lacking.

PURPOSE

The purpose of this clinical study was to evaluate the accuracy and feasibility for impressions of multiple implants by using 3D-printed custom open trays versus conventional custom open trays.

MATERIAL AND METHODS

Twenty-two partially edentulous individuals needing impression making for restorations supported by multiple implants were enrolled. Two types of custom open trays were made for each participant, a 3D-printed tray (test) and a conventional tray (control). With a splinted technique, silicone definitive impressions were obtained with the 2 custom open trays and poured with Type IV dental stone. Impression accuracy (primary outcome) was evaluated by measuring linear distances and the marginal gaps between the implant replicas and verification devices on the test and control casts. Clinical tray fit, impression quality, and cast quality were rated by an independent technician through a visual analog scale (VAS). The fabrication time and cost of the 2 types of custom open trays were recorded. The feasibility of 3D-printed trays was determined from these outcomes. The paired Student t test and Wilcoxon rank-sum tests were used for statistical analysis (α=.05).

RESULTS

For impression accuracy, no statistically significant difference was found between test and control groups (P>.05). In terms of clinical tray fit, impression quality, and cast quality, no statistically significant difference was found (all P>.05). Regarding fabrication time and cost, the test group (57.65 ±6.49 minutes, 0.37 ±0.07 United States dollars [USD]) exhibited superiority over the control group (101.96 ±2.92 minutes, 4.41 ±0.37 USD) (both P<.001).

CONCLUSIONS

Within the limitations of this study, the 3D-printed custom open trays were clinically accurate, efficient, and cost-effective for impressions of multiple implants.

Effects of printing layer thickness on mechanical properties of 3D-printed custom trays

STATEMENT OF PROBLEM

The layer thickness serves as a straightforward and controllable parameter to alter the mechanical properties of 3D-printed custom trays. However, how the printing layer thickness affects the mechanical properties of the trays is not fully understood.

PURPOSE

The purpose of this in vitro study was to investigate the effects and their underlying mechanisms and to optimize the mechanical properties through modulation of the printing layer thickness.

MATERIAL AND METHODS

Polylactic acid (PLA) specimens were 3D-printed with 5 layer thicknesses from 0.1 mm to 0.5 mm. The bond, flexural, and tensile strengths were measured by using a universal test machine. Postfracture interfaces were examined by means of scanning electron microscopy. Additionally, the printing dimensional accuracy was estimated by measuring the size deviations between the printed and virtual specimens, and the printing times were recorded.

RESULTS

With increasing PLA printing layer thickness, the tensile bond strength first increased and then decreased, peaking at a thickness of 0.4 mm. While the flexural and tensile strengths decreased, the printing dimensional accuracy remained constant from 0.1 mm to 0.4 mm and then decreased at 0.5 mm. The printing time sharply decreased as printing layer thickness increased.

CONCLUSIONS

Moderate layer thickness provided the best properties for 3D-printed custom trays.

Compatibility of a Silicone Impression/Adhesive System to FDM-Printed Tray Materials-A Laboratory Peel-off Study

Computer-aided design (CAD) and additive manufacturing (AM) have shown promise in facilitating the fabrication of custom trays. Due to the clinical requirements, custom tray materials should achieve good bonding to the impression/adhesive systems. This study evaluated the retention of three fused deposition modeling (FDM) custom tray materials to a silicone impression/adhesive system before and after gritblasting (GB) by peel-off test. CAD-designed experimental test blocks were printed by FDM using acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol copolyester (PETG), and high impact polystyrene (HIPS), and the reference test blocks were made of a conventional light-curing resin (n = 11). Before and after GB, the surface topography of all tray materials was analysed, and the maximum strength of the test block peeled off from a silicone impression/adhesive system was measured. After GB, the arithmetic mean height (Sa) and the valley fluid retention index (Svi) of the four material groups declined (p < 0.05). The peel-off strength of each of the four material groups significantly decreased by GB (p < 0.05), but no statistical difference could be found among them before or after GB. In all peel-off tests, adhesive failure occurred at the adhesive-impression material interface. The results indicated ABS, HIPS, and PETG could provide sufficient adhesion to the adhesive as the conventional light-curing resin, and GB could reduce the roughness generated by FDM and weaken the bonding between the adhesive and the silicone impression.

Need for a reliable alternative to custom-made Implant Impression trays: An in vitro study comparing accuracy of custom trays versus specialized aluminum stock tray

Purpose

The aim of the present study was to evaluate and to compare the accuracy of implant casts obtained by open tray pick-up impression technique using 2 types of custom-made trays and a specialized aluminum stock impression tray.

Materials and Methods

A heat-cure acrylic resin master model was fabricated. Two implants were placed parallel to each other. Ten impressions were made from each group. Polyvinylsiloxane impression material with single step putty wash technique was used for making all the impressions. The resultant casts obtained were compared to the master models with respect to the distances measured between the reference points using a stereomicroscope. The data obtained was statistically analyzed using one-way ANOVA, Tukey's post hoc procedures, and t-test.

Results

Mean value obtained was 2.012967 cm (±0.007060) for corimplant stock tray, 2.012627 cm (±0.007945) for autopolymerizing acrylic resin tray, 2.010279 cm (±0.006832) for light-cure hybrid composite tray. P value was calculated to be >0.05; hence, there was nonsignificant deviation of observations from standard value in each group.

Conclusion

Statistically insignificant difference was found between the accuracy of casts obtained by the different impression trays. However, light-cure hybrid composite trays showed best results followed by autopolymerizing acrylic resin trays and Corimplant stock tray.

Strain Gauge Evaluation of Transfer Impression Techniques of Multiple Implant-Supported Prosthesis

PURPOSE

This in vitro study assessed the accuracy of multiple implant-level impression techniques (open tray and closed tray) for the fabrication of 3-unit implant prostheses with strain gauge (SG) analysis.

MATERIALS AND METHODS

A polyurethane master model was designed to simulate a clinical situation. Two rigid custom trays were fabricated for the model. The impression material used was polysulfide. Transfer implant impressions were made using 2 techniques; ten tapered copings not splinted (custom closed tray) and ten square copings splinted with acrylic-resin (custom open tray). The improved stone models were allowed to set for 1 hour before being separated from the impression. The superstructures were sprued, invested, and cast with a cobalt-chromium alloy. Four SGs were bonded on the surface of each polyurethane block.

RESULTS

A statistically significant difference was found between the 2 impression techniques tested (P = 0.000). This study found a significant average difference of 144.68 ± 5.53 με for open custom tray and 253.3 ± 16.7 με for closed custom tray.

CONCLUSION

The custom open tray technique was the most accurate impression for multiple implants compared with closed custom tray.

A Comparative Evaluation of Accuracy of the Dies Affected by Tray Type, Material Viscosity, and Pouring Sequence of Dual and Single Arch Impressions- An In vitro Study

INTRODUCTION

The clinician's skill, impression techniques, and materials play a very important role in recording fine details in an impression for accuracy of fixed partial denture prosthesis. Impression of prepared teeth and of the opposing arch can be recorded simultaneously by dual-arch trays, while the full arch metal trays are used for impressions of prepared teeth in one arch.

AIM

To measure and compare the accuracy of working dies made from impressions with metal and plastic dual arch trays and metal full arch trays, for two viscosities of impression material and by changing the sequence of pour of working and non-working sides.

MATERIALS AND METHODS

A balanced design with independent samples was used to study the three variables (tray type, impression material viscosity, and pouring sequence). An impression made by dual arch trays and single arch trays were divided in to three groups (Group A-plastic dual arch tray, Group B-metal dual arch tray, Group C-full arch metal stock tray). Out of these three groups, two groups (Group A and B) were subdivided in to four subgroups each and one group (Group C) was subdivided in to two subgroups. A sample size of 30 was used in each subgroup yielding a total 300 impressions in three groups or ten subgroups. Impressions were made of a machined circular stainless steel die. All three dimensions (Occlusogingival, Mesiodistal, and Buccolingual) of the working dies as well as stainless steel standard die were measured three times, and the mean was used for the three standard sample values to which all working dies means were compared. Statistical analysis used for this study was a 3-factor analysis of variance with hypothesis testing at α =0.05.

RESULTS

With respect to the selection of impression material viscosity statistically significant differences were found in the dies for the buccolingual and mesiodistal dimensions. Metal dual arch trays were slightly more accurate in the mesiodistal dimension in comparison to the plastic trays in reference of tray selection and in view of pouring sequence no differences were observed in occlusogingival dimension but in buccolingual and mesiodistal dimensions nonworking side was more accurate.

CONCLUSION

The gypsum dies produced from the dual arch impressions were generally smaller in all three dimensions than the stainless steel standard die. Plastic dual-arch trays were more accurate with rigid impression material and there was not statistically significant difference for sequence of pouring. Metal dual-arch trays were more accurate with monophase impression material and working side was more accurate. Stock metal full arch trays were more accurate for monophase impression material.

Effect of variation of impression material combinations, dual arch tray types, and sequence of pour on the accuracy of working dies: "An in vitro study"

Aims:

To evaluate the accuracy of dies made from dual arch impressions using different sectional dual arch trays, combinations of elastomeric impression materials, and the sequence of pour of dies.

Subjects and Methods:

The dual arch impression materials were grouped into three groups depending on the combination of impression materials used and each group is subdivided into four subgroups. A sample size of 8 in each subgroup yielding a total 96 impressions will be made into three groups of 32 each (Group I, II, and III). Group I constitute impressions made using monophase (M) impression material, Group II constitute impressions made using combination of heavy body and light body (HL), and Group III constitute impressions made using combination of putty and light body (PL). Dies obtained were evaluated with a travelling microscope to measure the buccolingual width of the tooth at the margin by using the sharp corners of the notches as reference points.

Statistical Analysis Used:

Descriptive analysis namely mean and standard deviation, one-way analysis of variance test.

Results:

The results obtained in this study indicate that though not statistically significant, the metal dual arch trays performed better when compared to the plastic trays in reproducing die dimensions.

Conclusions:

From the results obtained, dies poured from combination of heavy body and light body impressions using plastic or metal dual arch trays showed least variation in bucco-lingual dimension from master model.

The bond strength of different tray adhesives on vinyl polysiloxane to two tray materials: an in vitro study

There has been no established chemical bonding between custom tray resin and the elastomeric impression materials without the use of manufacturer's recommended specific tray adhesive. The present study was aimed to compare the bond strength of the manufacturer recommended tray adhesives with the universal tray adhesives using the medium body consistency vinyl polysiloxane (VPS) material and custom tray made of autopolymerising resin and visible light cure (VLC) resin. A total 90 cubicle specimens of autopolymerising resin and 90 specimens of VLC resin were tested for its tensile bond strength. Effectiveness of universal tray adhesive was compared with manufactured tray adhesive. Each of these specimens was then subjected to tensile load in hounsefield universal testing machine at a cross head speed of 5 mm/min and the results were compared and evaluated using one way analysis of variance and post hoc Tuckey's test. Analysis of bond strength revealed that the universal tray adhesive showed better strength and was statiscally significant when compared to the manufacture supplied tray adhesive. Comparison between both the groups, VLC resin showed better bond strength as compared to autopolymerizing resin. Universal tray adhesive had better tensile bond strength than the manufacturers recommended tray adhesive with the medium body viscosity VPS impression material for both autopolymerising and VLC tray resin.

An in vitro study of the bond strength of five adhesives used for vinyl polysiloxane impression materials and tray materials

Although stock trays often provide mechanical retention for elastomeric impression materials, manufacturers typically recommend the use of an adhesive, whether a stock or custom tray is used. The mention of the bond strength on the adhesive packaging is not available, therefore the clinician has no idea whatsoever of the ideal adhesive. The aim of this study was to evaluate the bond strength of three vinyl polysiloxane (VPS) materials, one with a poly(methyl methacrylate) autopolymerizing (PMMA) specimen and another with a light-polymerizing tray material (VLC), using the adhesive recommended by the manufacturer of the impression material, and two universal adhesives. A total of ninety specimens (15 × 15 × 20 mm) were used, 45 specimens were made in PMMA and rest 45 was made in VLC. Five paint-on adhesives (Coltene, Caulk, 3M, universal Zhermack and universal GC) were applied. Three impression materials, Affinis, Reprosil, and 3M, were mixed and injected into a perforated poly vinyl chloride cylinder. Tray specimens were positioned against the open cylinder end in contact with the VPS material. Tensile strength tests were conducted until adhesive separation failure. Mean values and standard errors of the adhesive strength were recorded in MPa for each material combination. GC paint-on universal adhesive provided significantly higher adhesive strength values.

Tensile Bond Strength between Custom Tray and Elastomeric Impression Material

The aim of this study was to investigate how to achieve sufficient and stable adhesive strength between impression material and tray. Impression materials were molded between autopolymerizing resin columns, and tensile strength was measured as a function of these factors: tray storage time (1, 2, 4, 7, and 10 days), adhesive drying time (0, 1, 5, 10, and 15 minutes), and tray surface roughness (air abrasion, bur-produced roughness, and no treatment). Tensile bond strength was not affected by tray storage time throughout the entire evaluation period of 10 days. As for tray adhesive drying time, Reprosil and Exaimplant yielded extremely low values for drying times of 10 minutes or less (P<0.05), while Imprint II and Impregum were not influenced by drying time. Vinyl polysiloxane achieved the highest adhesive strength with bur-produced roughness, which was significantly higher than with air abrasion or no treatment (P<0.05), whereas polyether achieved the lowest value with bur-produced roughness (P<0.05). It was concluded that surface treatment of custom tray should be adapted to the type of impression material used to achieve optimum bond strength.