Comparison of the Accuracy of Two Transfer Caps in Positional Transmission of Palatal Temporary Anchorage Devices: An In Vitro Study

The aim of this study was to compare the positional information transfer accuracy of palatal temporary anchorage devices (TADs) of two different brands of transfer caps: PSM and Leone. Thirty plaster casts of maxillary dental arches were chosen for master models. A couple of Leone TADs were inserted in each master model. For each master model, two analysis models were created: using two transfer caps, Leone and PSM, the impressions were taken, the analogues were connected on the transfer caps, and the casts were poured. Using digital methods and equipment, such as a 3D scanner, a 3D analysis and a comparison of the accuracy of the two transfer caps in transferring the positional information of the TADs was then made. The data obtained were analyzed using the Mann-Whitney U-test at a significance level of α = 0.05. PSM transfer caps showed higher error frequency in almost all measurements. Only two measurements had a larger error in the analysis models made with Leone transfer caps. The Mann-Whitney U-test found a significant difference between the error levels of TADs found in the analysis models created with PSM transfer caps. Leone transfer caps showed greater reliability in TADs positional information transmission.

The Accuracy of Open-Tray vs. Snap on Impression Techniques in A 6-Implant Model: An In Vitro 3D Study

To compare the three-dimensional accuracy of an open-tray and two snap on impression techniques (with and without connecting the plastic caps of the snap on impression transfers) in a full arch 6-implant model, a reference acrylic resin model of the maxilla with six implants was fabricated. Prominent geometrical triangles, in the palate area, served as reference points for a digital overlap between scans. Three impression transfer techniques were evaluated and compared: open-tray direct impression (DI), snap on impression (SpO), and connected snap on impression (SpOC). Polyether impression material was used to make 30 impressions (n = 10), and the master model and all casts were digitally scanned with a laboratory optical scanner. The obtained 3D data were converted and recorded as STL files, which were imported to a 3D inspection software program. Angular deviations (buccal, occlusal and interproximal planes) between the study casts and the reference model were measured. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey post hoc test, with 0.05 used as the level of significance. The 3D angular deviations from the master model revealed no significant differences between the DI and SpO impression groups, but there were significant differences in the SpOC impression group, particularly in the buccal and occlusal planes. In all groups, the 3D angular deviation between the most distal scan abutments on each side of the model was significantly different from all other areas when compared to the master model. Within the limits of this study, it is possible to conclude that the indirect closed tray snap on impression technique with unconnected plastic caps exhibited the same three-dimensional accuracies as the direct open tray technique. The indirect closed tray snap on impression technique with connected plastic caps was less accurate than either the indirect closed tray snap on impression technique with unconnected plastic caps or the direct open tray technique. In the case of full arch implant supported prostheses, inaccuracies may be expected in the most distal implants for all the three impression techniques evaluated in this study. Further in vitro and in vivo research is required.

Effect of implant angulation and depth on the accuracy of casts using the open tray splinted impression technique

The purpose of this study was to evaluate the accuracy of open tray dental implant impressions when the implants are placed with varying implant angulations and depths. Four partially edentulous models were fabricated using photopolymer resin, each having different angulation and depth of the implant analogs. A total of forty open tray elastomeric impressions were made which were poured in type IV die stone (n = 10). These casts were evaluated and compared for accurate reproduction of the spatial orientation of the implant analogs in the models using digitization in three dimensions. The results were analyzed using the independent T test. Statistically significant differences were observed when the casts were compared with their respective master models. These casts had the implant replicas placed deeper within the replicated soft tissue. Making accurate impressions in partially edentulous situations with dental implants placed with varying depth and angulation is critical and clinically demanding. There is a need for future in vivo research to identify methods and materials, exploring digital impression techniques as well, in order to make precise impressions.

Comparison of the accuracy of different impression procedures in case of multiple and angulated implants : Accuracy of impressions in multiple and angulated implants

Background

There is no consensus in the literature regarding the impression procedures in the presence of multiple and angulated implants.

Methods

Three maxillary master models with 6 implants bilaterally positioned in anterior, premolar and molar regions were fabricated. In model 1, all implants were placed in parallel; in models 2 and 3, anterior implants were buccally inclined and posterior implants were distally inclined in 10- and 20-degrees, respectively. Three different impression copings (hexed, non-hex, multi-unit) and two different impression techniques (splinting and non-splinting) were tested. A total of 180 impressions (n = 10 per group) were made using mono-phase vinyl poly-siloxane. Master models and duplicate casts were scanned by a 5-axis laboratory scanner and data were transferred to a software program for the alignment of master and duplicate copings. Coronal and angular deviations were calculated, and data were statistically analyzed.

Results

For angulated models, the lowest deviation values were detected at the splinted non-hex coping group (P < 0.05).

Conclusions

Implant angulation, impression coping type, and splinting the impression copings had significant effects on the accuracy of impressions.

Trial registration

Not applicable.

Three-dimensional accuracy of different impression techniques for dental implants

Background:

Accurate impression making is an essential prerequisite for achieving a passive fit between the implant and the superstructure. The aim of this in vitro study was to compare the three-dimensional accuracy of open-tray and three closed-tray impression techniques.

Materials and Methods:

Three acrylic resin mandibular master models with four parallel implants were used: Biohorizons (BIO), Straumann tissue-level (STL), and Straumann bone-level (SBL). Forty-two putty/wash polyvinyl siloxane impressions of the models were made using open-tray and closed-tray techniques. Closed-tray impressions were made using snap-on (STL model), transfer coping (TC) (BIO model) and TC plus plastic cap (TC-Cap) (SBL model). The impressions were poured with type IV stone, and the positional accuracy of the implant analog heads in each dimension (x, y and z axes), and the linear displacement (ΔR) were evaluated using a coordinate measuring machine. Data were analyzed using ANOVA and post-hoc Tukey tests (α = 0.05).

Results:

The ΔR values of the snap-on technique were significantly lower than those of TC and TC-Cap techniques (P < 0.001). No significant differences were found between closed and open impression techniques for STL in Δx, Δy, Δz and ΔR values (P = 0.444, P = 0.181, P = 0.835 and P = 0.911, respectively).

Conclusion:

Considering the limitations of this study, the snap-on implant-level impression technique resulted in more three-dimensional accuracy than TC and TC-Cap, but it was similar to the open-tray technique.

Effect of Splinting on Dimensional Accuracy of Impressions Made of Implants with Different Subgingival Alignments

PURPOSE

Placement of implants at deeper levels of gingiva is sometimes inevitable because of issues like esthetics or bone availability. The accuracy of impressions may be affected in these situations. The aim of this in vitro study was to evaluate the effects of splinting and length of impression copings on the accuracy of impressions made of deeply placed implants.

MATERIALS AND METHODS

A metal model with two parallel implants (Implantium; Dentium) was fabricated. One hundred and twenty impressions were made using the direct impression technique with and without splinting the impression copings (using short and long impression copings). Impressions were made of implants at three subgingival levels (1, 3, and 6 mm) using regular viscosity poly(vinyl siloxane). The impressions were poured with type IV dental stone. Displacements in the x, y, and z axes, as well as rotational discrepancies and interimplant distances were measured with a coordinate measuring machine. Data were analyzed with Kruskal-Wallis, Mann-Whitney, and nonparametric adjusted rank transform tests.

RESULTS

There was less rotational displacement using longer impression copings at different subgingival positions of the implants, either with splinted or nonsplinted direct technique (p < 0.05). Also, the nonsplinted technique produced more accurate impressions at different apico-coronal levels of implants than the splinted technique using short impression copings (p < 0.05).

CONCLUSIONS

According to the findings of this study, longer impression copings yielded better results than shorter ones in both splinted and nonsplinted techniques. Also, nonsplinted short impression copings produced more accurate impressions than splinted short impression copings.

Accuracy of different impression materials in parallel and nonparallel implants

BACKGROUND

A precise impression is mandatory to obtain passive fit in implant-supported prostheses. The aim of this study was to compare the accuracy of three impression materials in both parallel and nonparallel implant positions.

MATERIALS AND METHODS

In this experimental study, two partial dentate maxillary acrylic models with four implant analogues in canines and lateral incisors areas were used. One model was simulating the parallel condition and the other nonparallel one, in which implants were tilted 30° bucally and 20° in either mesial or distal directions. Thirty stone casts were made from each model using polyether (Impregum), additional silicone (Monopren) and vinyl siloxanether (Identium), with open tray technique. The distortion values in three-dimensions (X, Y and Z-axis) were measured by coordinate measuring machine. Two-way analysis of variance (ANOVA), one-way ANOVA and Tukey tests were used for data analysis (α = 0.05).

RESULTS

Under parallel condition, all the materials showed comparable, accurate casts (P = 0.74). In the presence of angulated implants, while Monopren showed more accurate results compared to Impregum (P = 0.01), Identium yielded almost similar results to those produced by Impregum (P = 0.27) and Monopren (P = 0.26).

CONCLUSION

Within the limitations of this study, in parallel conditions, the type of impression material cannot affect the accuracy of the implant impressions; however, in nonparallel conditions, polyvinyl siloxane is shown to be a better choice, followed by vinyl siloxanether and polyether respectively.

The Effect of Implant Angulation on the Transfer Accuracy of External-Connection Implants

BACKGROUND

Accurate recording of implant location is required in every implant-supported prostheses. Implant angulation, which is inevitable in various clinical situations, could affect the impression accuracy.

PURPOSE

The purpose of this in vitro study was to compare the transfer accuracy of straight and tilted implants of All-on-4 protocol with implant or abutment level impression making and different techniques of direct and indirect.

MATERIALS AND METHODS

One reference model of edentulous maxilla with four external connection implants (Brånemark) inserted according to All-on-4 protocol was made. Forty impressions of this model were made at implant (groups 1 and 2) or abutment (groups 3 and 4) levels with different techniques of direct or indirect, respectively. Impressions were poured with type IV dental stone. Coordinate measuring machine was used to record x, y, and z coordinates and also angular dislocation of implants. These measurements were compared with the equals calculated on the reference model. Data were analyzed with univariate analysis of variance and t-test at α = 0.05.

RESULTS

The results showed that abutment level impression making (groups 3 and 4), either with direct or indirect technique, produced the same results for straight and tilted implants of Δr variable (p > .05), though in implant level groups (groups 1 and 2), it was statistically significant (p < .05). However, only implant level impression making with direct technique (group 1) had the same results of angular accuracy for straight and tilted implants.

CONCLUSION

Impression technique (direct or indirect) had significant effect on the impression accuracy of tilted implants, and direct technique produced less inaccuracy. Also, abutment level impressions showed more accuracy than implant level impressions.