Multiunit Abutments Research Articles

In vitro fit of CAD-CAM complete arch screw-retained titanium and zirconia implant prostheses fabricated on 4 implants

Statement of problemComputer-aided designed and computer-aided manufactured (CAD-CAM) titanium and zirconia implant-supported fixed implant prostheses on 4 implants have become popular. The precision and accuracy of their interface fit has not been widely researched. PurposeThe purpose of this in vitro study was to compare the marginal fit of zirconia and titanium implant-supported screw-retained CAD-CAM complete fixed dental prostheses (CFDP) fit with a standardized cast simulating the all-on-4 implant distribution. Material and methodsRepresentation of an edentulous maxilla with 4 multiunit replicas embedded in sites corresponding to the positions of the maxillary first molars and canines was chosen. Multiunit abutments were digitally scanned using scan bodies and a laboratory scanner. CAD software was used to design screw-retained implant-fixed complete prostheses framework, and the file was sent to a milling machine for CAM. Titanium (n=5) and zirconia (n=5) frameworks were milled on 4 implants, and the frameworks were scanned with an industrial computed tomography (CT) scanner while applying the 1-screw test. The direct CT scans were reconstructed to generate a standard tessellation language (STL) file from the voxel data set and transported to volume graphics analysis software from which measurements were extracted. The circular mating surfaces of the corresponding framework interfaces to their representative multiunit abutment replicas on the standard were measured for implant position left maxillary canine (LMC), implant position right maxillary canine (RMC) and implant position right maxillary first molar (RMFM). In addition, color maps were generated to show the marginal discrepancy between the mating surfaces using ±0.500 mm color scale ranges. ResultsThe material type (zirconia or titanium) was not significant for 3D discrepancy measurements (P=.904). However, 3D discrepancy measurement values were significantly different between RMC and RMFM within each group (P<.001). The mean 3D ±SD discrepancy measurement for LMC for titanium was 48.2 ±2.6 μm. The mean ±3D discrepancy measurement for RMC for titanium was 74 ±15 μm and 84.4 ±12.1 μm for zirconia. The mean 3D discrepancy measurement for RMFM for titanium was 102 ±26.7 μm and 93.8 ±30 μm for zirconia. All 3D discrepancy measurements showed values <135 μm. ConclusionsWithin the limitations of the present in vitro study, implant-supported CAD-CAM fabricated titanium and zirconia complete fixed dental prosthesis frameworks showed comparable marginal fit. Three-dimensional microgap measurements of frameworks showed clinically acceptable misfit values. Absolute passive fit was not achieved.

Distortion of CAD-CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks

Statement of problemComputer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated titanium and zirconia implant-supported fixed dental prostheses have become increasingly popular for restoring patients with complete edentulism. However, the distortion level of these frameworks is not well known. PurposeThe purpose of this in vitro study was to compare the 3-dimensional (3D) distortion of CAD-CAM zirconia and titanium implant-fixed screw-retained complete dental prostheses. Material and methodsA master edentulous model with 4 implants at the positions of the maxillary first molars and canines was used. Multiunit abutments (Nobel Biocare) secured to the model were digitally scanned using scan bodies and a laboratory scanner (S600 ARTI; Zirkonzahn). Titanium (n=5) and zirconia (n=5) frameworks were milled using a CAD-CAM system (Zirkonzahn M1; Zirkonzahn). All frameworks were scanned using an industrial computed tomography (CT) scanner (Nikon/X-Tek XT H 225kV MCT Micro-Focus). The direct CT scans were reconstructed to generate standard tessellation language (STL) files. To calculate the 3D distortion of the frameworks, STL files of the CT scans were aligned to the CAD model using a sum of the least squares best-fit algorithm. Surface comparison points were placed on the CAD model on the midfacial aspect of all teeth. The 3D distortion of each direct scan to the CAD model was calculated. In addition, color maps of the scan-to-CAD comparison were constructed using a ±0.500 mm color scale range. ResultsBoth materials exhibited distortion; however, no significant difference was found in the amount of distortion from the CAD model between the materials (P=.747). Absolute values of deviations from the CAD model were evident in the x and y plane and less so in the z direction. ConclusionsZirconia and titanium frameworks showed similar 3D distortion compared with the CAD model for the tested CAD-CAM and implant systems. The distortion was more pronounced in the horizontal and sagittal plane than in the vertical plane.

A method of fabricating an accurate repositioning device for relocating multiple multiunit abutments

A method of fabricating an accurate repositioning device for relocating multiple multiunit abutments

Accuracy and mechanical performance of passivated and conventional fabricated 3-unit fixed dental prosthesis on multi-unit abutments

PurposeThe aim of this study was to evaluate the fit and mechanical stability of conventional versus passive fitting 3-unit fixed dental prosthesis (FDP) screw-retained on implants. MethodsTwenty acrylic models, each with two embedded implants, were fabricated and functioned as patient-models. Impressions were taken and 20 all-ceramic FDPs were pre-fabricated on the plaster casts. Respectively 10 FDPs were fixed on the plaster casts (group 1) and on the patient-models for passive fitting (group 2). The fit of each FDP was checked on the patient-model by means of visual control (grades 1–10) and microscopic examination. Furthermore, specimens were artificially aged for possible prosthodontic failures, followed by a fracture strength test. ResultsGroup 2 [1.4 (±0.3)] showed significantly (p<0.001) better results in the visual examination of the marginal fit compared to group 1 [6.3 (±2.4)]. The microscopic marginal misfit was 160μm (±80μm) at the abutment margin and 150μm (±80μm) at the axial wall of the abutment for group 1, respectively, 0μm and 0μm up to 17μm for group 2 (p<0.001). No failure of the FDPs could be observed during artificial aging in both groups. The fracture load showed no significant difference (p=0.60) between group 1 [2583N (±664N)] and group 2 [2465N (±238N)]. ConclusionsVisual and microscopic examination detected huge differences in marginal fit between groups 1 and 2. However, no statistically verifiable differences could be detected in long-term stability of implant-supported FDPs irrespective of the fit.

Device for easily measuring of the torque of an implant hand driver

BackgroundAs one of the loads applied in implant dentistry, managing the torque is important for the success of an implant treatment. For this purpose, it is crucial to ascertain the level of torque being exerted with a hand driver. We have developed an adapter that makes it easy to measure torque by using a standard torque wrench in one’s possession, rather than with a torquemeter.ProceduresThe head of an abutment screw is cut into a hexagon and pushed into and fixed to the hexagonal hole (for multi-unit abutments) of a machine driver. With this, a torque wrench adapter and torque wrench are assembled. A hand driver is rotated clockwise to the limit, and the torque value is read.ResultsIt was possible to read the torque value during screw fastening.ConclusionsThis technique makes it easy for each dentist to measure the maximum torque that can be exerted by a hand driver he or she is using. It is even possible to handle different implant systems.

Rehabilitation of edentulous maxillary arch with implant-assisted fixed complete prosthesis using multi-unit straight and angulated abutments

In comparison to an edentate mandible, rehabilitation of a completely edentulous maxilla using osseointegrated implants has always tested the ability of clinician and laboratory technician. Complex anatomy, as well as the biomechanical limitations of the maxillary bone, resists the placement of implant in its ideal location. This article illustrates a two-stage surgical and prosthetic management of edentulous maxilla opposing natural teeth using seven implants. This case report highlights the advantages of multi-unit straight and angulated abutments, torqued onto the implants, over which a cast titanium framework was made for fabrication of implant-assisted fixed complete dental prosthesis (FP-3 prostheses).

Influence of Resin Cements on the Tension Force of Cast Frameworks Made by the Technique of Framework Cemented on Prepared Abutments.

This study evaluated the tension force of cast frameworks made by the technique of framework cemented on prepared abutments using two different resin cements. Forty multi-unit abutment analogs were individually fixed with chemically cured acrylic resin inside PVC cylinders using a parallelometer. Brass cylindrical abutments were tightened to the multi-unit abutments to be used as spacers and then castable UCLA abutments were positioned above. These abutments were cast with Ni-Cr and then divided into 4 groups (n=10): cemented with RelyX U100(r); cemented with RelyX U100(r) and simulation of acrylic resin polymerization process; cemented with Multilink(r); and cemented with Multilink(r) and simulation of acrylic resin polymerization process. Abutments were cemented according to manufacturers' instructions. In a universal testing machine, tensile strength was applied in the direction of the long axis of the abutments at 1 mm/min crosshead speed until displacement of the luted abutments was obtained. The values of maximum tensile force (N) required for the displacement of the luted abutments were tabulated and analyzed statistically by one-way ANOVA with a 95% confidence level. No statistically significant difference was found among the groups (p>0.05). There was an increase in mean tension force when the specimens were subjected to the simulation of acrylic resin polymerization process, but the results did not differ statistically. Both resin cements presented positive results as regards the retention of luted abutments on their respective multi-unit abutments. Both materials may be indicated for the technique of framework cemented on prepared abutments when professionals pursuit better adaptation of implant-supported frameworks.

Misfit of pure titanium frameworks: Effect of veneer coverage and spark erosion process

Objective. The purpose of this study was to evaluate the influence of veneer application on the misfit level of implant-supported frameworks. Materials and Methods. Thirty commercially pure titanium (Tritan, Dentaurum, Pforzheim, Germany) frameworks were fabricated from a metallic index containing five Branemark-type multi-unit abutments. Analogs of the abutments were positioned into the framework to manufacture an index for each framework, which permitted the evaluation of the marginal gap caused only by the veneer coverage. The frameworks were grouped (n = 10) in the following manner: (G1) heat-cured acrylic resin (Clássico, Clássico, São Paulo, Brazil); (G2) light-cured resin (Versyo.com, Heraeus Kulzer, Brazil); and (G3) porcelain (Triceram, Dentaurum, Pforzheim, Germany). Marginal refinement with spark erosion was then conducted. The marginal gap was verified before and after the veneer coverage and the spark erosion procedure, following the single screw test protocol (tightening force of 10 Ncm). Data were submitted to an analysis of variance (ANOVA) in a split-plot design for repeated measurements followed by a Tukey test (p = 0.05). Results. The veneer application was associated with a significant increase in the mean misfit values of all groups. The lowest values were presented by G2. After the spark erosion process, the mean misfit value decreased only on G3. Conclusions. Heat-cured acrylic resin and porcelain produced the highest values of marginal gaps, whereas light-cured acrylic resin produced the lowest. In addition, the spark erosion process was effective only in the marginal gap of the porcelain application group.

Implant-supported titanium framework: photoelastic analysis before and after spark erosion procedure

Aim: This study used a photoelastic analysis to evaluate the passive fit of titanium cast laser welding frameworks before and after spark erosion procedure. Methods: A stainless steel cast was used in order to reproduce a human mandible. Five Multi-Unit abutment analogs were attached to this cast and 6 frameworks were produced in commercial pure titanium. The cast was molded and a photoelastic matrix was produced incorporating 5 dental implants with Multi-Unit abutments. All samples were subjected to a laser welding. The precision of adjustments within a range of 0.5 μm was evaluated under microscope observation. The best fitted framework was selected and subjected to a photoelastic analysis (Group I). The tightening of the screws was in 3 predetermined sequences (1,2,3,4,5/ 5,4,3,2,1/ 3,2,4,1,5). Then the same framework was subjected to a refinement by spark erosion technique (Group II) and evaluated by photoelastic analysis. Results: The sequence (3,2,4,1,5) achieved better results in both groups. A larger number of fringes were observed around the median implants in all sequences in both groups. Conclusions : The titanium cast laser welded frameworks processes associated with spark erosion procedure improves significantly the marginal framework adaptation and is effective for its passive fit.

Porcelain application and simulation of firing cycle: effect on marginal misfit of implant-supported frameworks

Aim: Success of implant-supported prostheses is related to the frameworks’ passive fit, hence inaccuracies can generate stress, leading to bone resorption and rehabilitation failure. This study evaluated misfit levels of implant-supported frameworks after different coverage treatments. Methods: Twenty commercially pure titanium (CP Ti) frameworks were manufactured with 5 Branemark type multi-unit abutments. Frameworks were distributed in two groups as follows: G1 - porcelain application (n=10); G2 - porcelain firing cycle simulation (n=10). Using a traveling microscope, marginal misfit was measured before and after undertaking the techniques, following the single-screw test protocol. All data were submitted to ANOVA and Tukey’s test (p<0.05). Results: Initial marginal misfit values were not significantly different, but both groups presented significantly higher misfit values after treatment: G1: 233.99 µm (p=0.0003); G2: 119.75 µm (p<0.0001). In addition, G1 presented higher misfit than G2 (p<0.0001). Conclusions: Porcelain application promoted significantly higher increase of misfit, which indicates that such procedure should be considered on misfit analysis of implant-supported prostheses.

Simplified Methods of Implant Treatment in the Edentulous Lower Jaw: A 3‐Year Follow‐Up Report of a Controlled Prospective Study of One‐Stage versus Two‐Stage Surgery and Early Loading

Interest in the use of one-stage surgery and immediate loading of oral implants has lately been increasing. The aim of this study was to compare the 3-year results of one-stage surgery versus two-stage surgery, early loading versus loading after a 3-month healing period, and the use of one-piece implants versus the use of two-piece implants. The study included 108 patients with edentulous mandibles. Each patient was treated with four Brånemark System implants (Nobel Biocare AB, Göteborg, Sweden) and with full fixed prostheses. Patients were consecutively treated and were distributed in four groups: group A (one-stage surgery), group B (control group with two-stage surgery), group C (one-piece implants), and group D (early loading). In groups A and B Brånemark Standard implants and standard abutments were used. In group C the conical one-piece Brånemark implant was used, and in group D the patients had Brånemark System Mk III implants together with multiunit abutments. All patients were observed for 3 years. Of the 432 inserted implants, 24 were lost. Survival rates in the three experimental groups ranged from 93.2 to 93.3% whereas the survival rate in group B (the control group with two-stage surgery) was 97.5%. The differences between the groups were not statistically significant. The changes in marginal bone level were measured from fixture insertion to the final follow-up at 3 years. The bone loss in group D (early loading) was significantly less than in group B (the control group) whereas there were no differences in marginal bone change between the other groups. Early loading seemed to give good results in the anterior part of the mandible. The survival rate of the early-loaded implants did not significantly differ from that of implants inserted with the conventional two-stage procedure, but the mean marginal bone loss around the surviving implants was less with early loading.