Implant Impressions Research Articles

Comparison of the Accuracy of Biomet 3i Encode Robocast Technology and Conventional Implant Impression Techniques

To compare the accuracy of implant master casts fabricated using Robocast Technology (Biomet 3i) with that of master casts fabricated using traditional transfer (closed-tray) and pick-up (open-tray) techniques. A stereolithographic replica of a Kennedy Class I human mandible was fabricated for use as the master model. Implants were placed into both posterior quadrants (both second premolars and second molars) and set parallel (P) on one side and divergent (nonparallel, NP) on the opposite side. Impressions were made of the master model (patient replica model) with Encode Healing Abutments, open-tray, and closed-tray impression copings. Identical metallic spheres were placed onto each implant analog in the stone master casts, and the casts/spheres were scanned using a digital scanner. Measurements were made between the center points of the spheres and compared to the master model. Data were divided into P, NP, and individual sites, and the differences were analyzed statistically (α = .05). Encode master casts were less accurate than the open-tray casts in NP sites. Encode master casts were less accurate than the open-tray and closed-tray casts in P sites. NP sites demonstrated less accuracy than P sites within the Encode group. Encode master casts were less accurate than the open- and closed-tray casts at the mandibular right second premolar site. The mandibular left second premolar was less accurate than the mandibular right second molar in the Encode group. Within the limitations of this lab-based study and analysis, the Encode technique resulted in master casts that were less accurate than master casts made from traditional open- and closed-tray impression techniques. Further research is necessary before specific clinical judgments can be made.

Evaluation of Accuracy of Complete-Arch Multiple-Unit Abutment-Level Dental Implant Impressions Using Different Impression and Splinting Materials

This in vitro study evaluated the accuracy of multiple-unit dental implant casts obtained from splinted or nonsplinted direct impression techniques using various splinting materials by comparing the casts to the reference models. The effect of two different impression materials on the accuracy of the implant casts was also evaluated for abutment-level impressions. A reference model with six internal-connection implant replicas placed in the completely edentulous mandibular arch and connected to multi-base abutments was fabricated from heat-curing acrylic resin. Forty impressions of the reference model were made, 20 each with polyether (PE) and polyvinylsiloxane (PVS) impression materials using the open tray technique. The PE and PVS groups were further subdivided into four subgroups of five each on the bases of splinting type: no splinting, bite registration PE, bite registration addition silicone, or autopolymerizing acrylic resin. The positional accuracy of the implant replica heads was measured on the poured casts using a coordinate measuring machine to assess linear differences in interimplant distances in all three axes. The collected data (linear and three-dimensional [3D] displacement values) were compared with the measurements calculated on the reference resin model and analyzed with nonparametric tests (Kruskal-Wallis and Mann-Whitney). No significant differences were found between the various splinting groups for both PE and PVS impression materials in terms of linear and 3D distortions. However, small but significant differences were found between the two impression materials (PVS, 91 μm; PE, 103 μm) in terms of 3D discrepancies, irrespective of the splinting technique employed. Casts obtained from both impression materials exhibited differences from the reference model. The impression material influenced impression inaccuracy more than the splinting material for multiple-unit abutment-level impressions.

Effect of Splinting in Accuracy of Two Implant Impression Techniques

Effect of Splinting in Accuracy of Two Implant Impression Techniques

Optical impression method to measure three‐dimensional position and orientation of dental implants using an optical tracker

The aim of this study was to devise an optical impression method that could make impressions of dental implants accurately and rapidly. Four paper markers (4 × 3 mm, 8 × 6 mm, 16 × 12 mm, and 24 × 18 mm) and one titanium marker (8 × 6 mm) were prepared to determine the measuring accuracy of the three-dimensional optical tracker. For a proposed and conventional impression taking method, we compared the reproduction accuracies of the positions and orientations of dental implants and the times to obtain impressions. Finally, we fabricated computer-aided designing (CAD)/computer-aided manufacturing (CAM) superstructure frameworks to determine the adaptation accuracy. The 8 × 6-mm titanium marker was optimal among the prepared markers. Dental implants made by the proposed and conventional impression taking methods had measurement errors of 71 ± 31 μm and 32 ± 18 μm, respectively. The proposed method took a significantly shorter time to obtain an impression than did the conventional method. The connection between the CAD/CAM superstructure frameworks and four implant analogs had uplifts of 55 ± 10 μm, 94 ± 35 μm, 2 ± 1 μm, and 66 ± 3 μm. Our proposed method and fabricated titanium markers enabled us to measure the positions and orientations of dental implants both accurately and rapidly. We then used the reproducible measurement results for the positions and orientations of the dental implants to fabricate CAD/CAM superstructure frameworks within an acceptable accuracy range.

A comparative analysis of the accuracy of different direct impression techniques for multiple implants

The aim of this study was to compare the accuracy of different direct implant impression techniques for edentulous arches with multiple implants. Five experimental groups (n = 5) were assembled. Experimental models were created by a direct splinted technique (EG2 to EG5) and a non-splinted technique (EG1). In EG2 and EG3 synOcta impression copings were splinted with an acrylic resin bar, and in EG4 and EG5 with a light-curing composite resin bar. In EG3 and EG5 the resin bars were sectioned, while the other experimental groups were not. Three-dimensional discrepancies were measured by a computerized coordinate measuring machine. Distortion values among the groups were analysed using one-way repeated measures ANOVA. The post hoc Tukey's test was then performed for multiple comparisons. The highest accuracy was obtained in EG2 (mean deviation: 12.70 μm). The acrylic bars demonstrated less deviation (12.70 μm and 22.71 μm) from the master model than the light-curing composite resin groups and the non-splinted group (41.09 μm). The post hoc Tukey's test showed no significant difference among the groups when the effect of splint design on accuracy was investigated. For situations where impressions of multiple implants are to be made, splinting impression copings with acrylic resin demonstrate superior results than the non-splinted technique and splinting with light-curing composite.

Accuracy of Implant Impressions with Different Impression Coping Types and Shapes

Accurate recording of implant location is required so that definitive restorations are properly supported and do not place additional stresses on the implants. Movement of impression copings inside the impression material using an open-tray or close-tray impression technique during clinical and laboratory phases may cause inaccuracy in transferring the three-dimensional spatial orientation of implants intraorally to the definitive cast. Consequently, the restoration may require corrective procedures. This in vitro study compared the accuracy of two different impression techniques with two different impression coping shapes using polyether impression material to obtain precise definitive casts. Two reference acrylic resin models (Technovits 4000, Heraeus Kulzer GmbH & Co., Wehrheim, Germany) with five internal connection implants having different shapes of impression copings (Implantium [Dentium, Seoul, South Korea] and Replace Select [Nobel Biocare AB, Göteborg, Sweden]) were fabricated. Twenty medium-consistency polyether impressions of these models were made with square and conical impression copings of each system using open-tray and close-tray techniques. Matching implant replicas were screwed into the impression copings in the impressions. Impressions were poured with type IV stone, and the positional accuracy of the implant replica heads in x-, y-, and z-axes (represented in [Δr]) and also rotational displacement (ΔΘ) were evaluated using a coordinate measuring machine (Mistral, DEA Brown&Sharpe, Grugliasco, Italy). These measurements (linear and rotational displacements) were compared with the measurements calculated on the reference resin models that served as control, and data were analyzed with a two-way analysis of variance at α = 0.05. Less inaccuracy occurred in less retentive shape impression copings (Replace Select) compared with the more retentive one (Implantium) (p(r) < .001 and p(Θ) < .001), but there was no significant difference between direct and indirect impression techniques (p(r) and p(Θ) > .05). The impression coping shape had more impact on impression inaccuracy than impression technique did. Understanding of the magnitude and variability of distortion when employing certain impression-making methods and impression coping shapes helps the clinician to select a better implant component and impression technique.

Accuracy of implant impressions without impression copings: A three-dimensional analysis

Implant impressions without impression copings can be used for cement-retained implant restorations. A comparison of the accuracy of implant impressions with and without impression copings is needed. The purpose of this study was to evaluate and compare the dimensional accuracy of implant definitive casts that are fabricated by implant impressions with and without impression copings. An acrylic resin maxillary model was fabricated, and 3 implant replicas were secured in the right second premolar, first, and second molars. Two impression techniques were used to fabricate definitive casts (n=10). For the coping group (Group C), open tray impression copings were used for the final impressions. For the no-coping group (Group NC), cementable abutments were connected to the implant replicas, and final impressions were made assuming the abutments were prepared teeth. Computerized calculation of the centroids and long axes of the implant or stone abutment replicas was performed. The Mann-Whitney U test analyzed the amount of linear and rotational distortion between groups (α =.05). At the first molar site, Group NC showed significantly greater linear distortion along the Y-axis, with a small difference between the groups (Group C, 7.8 ± 7.4 μm; Group NC, 19.5 ± 12.2). At the second molar site, increased distortion was noted in Group NC for every linear and rotational variable, except for linear distortion along the Z-axis. Implant impression with open tray impression copings produced more accurate definitive casts than those fabricated without impression copings, especially those with greater inter-abutment distance.

The Accuracy of an Implant Impression Technique Using Digitally Coded Healing Abutments

A healing abutment (Encode) provided with digitally coded information on length and diameter on the top was launched in 2007. So far, no study has evaluated working cast fabrication using impressions of the coded abutments and analogue placement using a robot technique. To compare the accuracy of implant analogue placement in working casts using a robot technique and an impression of Encode healing abutments, with the traditional technique. One acrylic master model was fabricated, provided with two groups of three implant analogues. Encode healing abutments were mounted on the test side and conventional pickup impression copings were inserted on the control side. Fifteen impressions were made with a vinylpolysiloxane material. Implant analogues were placed by a robot on the test side. The center point of each implant analogue fitting surface was measured with a laser measuring machine in the x-, y-, and z-axis, as were also the angular direction of the center axis and the position of the antirotational hex. Two-way analysis of variance was performed using SPSS 17.0; the statistical significance was set at p < .05. Mean center point deviation for the test and control side was 37.4 µm versus 18.5 µm (p = .001) in the x-axis, 47.3 µm versus 13.9 µm (p < .001) in the y-axis, and 35.0 µm versus 15.1 µm (p < .013) in the z-axis. Mean angle error was 0.41 degrees for the test and 0.14 degrees for the control side (p < .001). Mean rotation of the hexagon was 2.88 degrees for the test side and 1.82 degrees for controls (p < .001). Both conventional and robot technique presented low levels of displacement of the implant analogues in all casts. The test technique was less precise, but the difference in accuracy was small, and both techniques are precise enough for single crowns and short-span, implant-supported fixed partial prostheses.

Custom Copings for Accurate Impressions of Multiple Internal Connection Implants

The technique presented facilitates a 1-step final impression and registration of multiple internal connection implants that have an unfavorable proximity. This is achieved by the use of customized impression elements that provide an accurate registration of the implant positions and the maxillomandibular relation. By means of this procedure, problematic implant positions are bypassed and chair-side time is reduced significantly.

Effect of Implant Angulation, Connection Length, and Impression Material on the Dimensional Accuracy of Implant Impressions: An In Vitro Comparative Study

With regard to implant-supported prostheses, to date no technique has been proven to guarantee a completely passive fit of prosthetic frameworks. Several clinical variables may affect the precision of impressions, particularly in the presence of implants. To compare the accuracy of implant impressions made with different materials, lengths of impression coping connections, and not parallel position of the implants. A calibrated testing device allowing reproducible standardized positions was used. Two control groups of master models and eight experimental groups with predetermined undercuts were used to make addition silicon and polyether implant impressions by means of the open-tray pick-up technique. Four reference distances were evaluated on each study cast by using a profile projector and a standardized measurement protocol. The data were statistically analyzed by means of three-factor analysis of variance. The impressions made in the presence of angulated implants were significantly less accurate than the ones made with parallel implants. The tested addition silicon resulted advantageous in presence of nonparallel implants whereas the polyether achieved the best results with parallel implants and standard impression copings. The angulation of the implants may cause strains of impressions, probably because of the higher forces required for the impression removal. Moreover, undercuts negatively affected the impression accuracy. More accurate casts were obtained using the tested addition silicon in the presence of nonparallel implants and using a standard length connection of the copings in the presence of parallel implants, respectively.

Time-saving method for the fabrication of a definitive cast for an implant-supported prosthesis

Conventional methods for fabricating an implant-supported overdenture or an implant-supported, fixed complete denture involve a series of patient visits. Because these visits occur in sequence, each visit depends on the accuracy of the previous visit and influences the accuracy of subsequent visits. Any procedural errors during these visits could compromise the fit of the definitive prosthesis. 1,2 The first step in achieving an accurately fitting, passive prosthesis requires capturing the 3-dimensional intraoral relationship of the implants with an impression. The accuracy of this impression procedure has an essential role in the prosthesis-implant adaptation. 3-5 Although several strategies have been suggested to enhance precision when making the definitive impression and cast for an implantsupported prosthesis, 6 it appears that absolute accuracy is currently not attainable. 7,8 A number of implant impression techniques have been described. 9,10 Most implant impression techniques have 1 feature in common, whereby impression material is present between the implant impression copings and the custom tray. The presence of this impression material produces resiliency in the system, and this lack of a rigid connection to the tray may result in an inaccurate cast. This article describes a time-saving, step-by-step technique designed to achieve 4 objectives with accuracy in a single clinical visit: (1) impression of the soft tissue, (2) impression and position of the implants, (3) registration of the maxillo-mandibular relationships, and (4) arrangement of the artificial teeth. The use of a verification jig 11 has confirmed the accuracy of this impression method.

Use of wax spacers for putty-wash impression of implant snap-on impression copings

Use of a custom tray with elastomeric impression material or a stock tray with a putty-wash method is recommended for making an impression of dental implants.1,2 For impressions of the transfer impression assembly, including the impression coping and positioning cylinder, a stock tray with putty impression material must be used to register an unmodified solid abutment.3 When abutments are prepared to provide adequate space for the restoration, relief of the putty impression material must be accomplished to provide sufficient space for the wash material.

An evaluation of impression techniques for multiple internal connection implant prostheses

Movement of impression copings inside the impression material using an open-tray impression technique during clinical and laboratory phases may cause inaccuracy in transferring the 3-dimensional spatial orientation of implants intraorally to the definitive cast. Consequently the restoration may require corrective procedures. This in vitro study evaluated the accuracy of 3 different impression techniques using polyether impression material to obtain a precise definitive cast for a multi-unit implant restoration with multiple internal connection implants. A reference acrylic resin model with 4 internal connection implants (3i Implant Innovations) was fabricated. Forty-five medium-consistency polyether impressions (Impregum Penta) of this model were made with square impression copings using an open-tray technique. Three groups of 15 specimens each were made with different impression techniques: in the first group, nonmodified square impression copings were used (NM group); in the second group, square impression copings were used and joined together with autopolymerizing acrylic resin before the impression procedure (R [resin] group); and in the third group, square impression copings previously airborne-particle abraded and coated with the manufacturer-recommended impression adhesive were used (M [modified] group). Matching implant replicas were screwed into the square impression copings in the impressions. Impressions were poured with ADA type IV stone (New Fujirock). A single calibrated examiner blinded to the nature of the impression technique used examined all definitive casts to evaluate the positional accuracy (mum) of the implant replica heads using a profile projector (at original magnification x10). These measurements were compared to the measurements calculated on the reference resin model which served as control. Data were analyzed with a 1-way analysis of variance at alpha=.05, followed by the Student Newman-Keuls test (alpha=.05). The data obtained with the profile projector revealed significant differences within the 3 impression techniques ( P <.001). The Student Newman-Keuls procedure disclosed significant differences between the groups, with group R casts being significantly more accurate than group NM and group M casts ( P =.05). The mean distance (+/-SD) between the posterior implants compared to the reference acrylic resin model was 18.17 mum (+/- 6.4) greater for group R casts, 41.27 mum (+/- 8.4) greater for group M casts, and 46.21 mum (+/- 8.9) greater for group NM casts. Distances between the anterior implants were also greater than those recorded on the reference model. The distance was 15.23 mum (+/- 5.9) greater on group R casts, 38.17 mum (+/- 8.3) greater on group M casts, and 43.23 mum (+/- 8.7) greater on group NM casts. Within the limitations of this study, improved accuracy of the definitive cast was achieved when the square impression copings joined together with autopolymerizing acrylic resin were used to make an impression of multiple internal connection implants.

Impression technique for arches requiring both implant and natural tooth restorations.

Implant impression copings reduce access to prepared teeth during the impression-making process. If the impression copings and teeth are in close proximity, it may be difficult to extrude impression material circumferentially around the margins of the tooth preparations. A technique is described that allows the impressions of the prepared teeth to be made without the implant impression copings interfering. The advantages and disadvantages of the technique are discussed.