Francisco Martínez-Rus

Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings.

STATEMENT OF PROBLEM Marginal fit is an important factor for the long-term success of ceramic restorations; however, it is difficult to compare results from studies on marginal accuracy of zirconium oxide-based restorations that used various computer-assisted systems, because different methods were used to obtain the data. PURPOSE The purpose of this study was to analyze the effect of different manufacturing techniques on the marginal adaptation of zirconia ceramic copings. MATERIAL AND METHODS An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). Ceramic copings (n=10) were fabricated on the LCP models using the following systems: glass-infiltrated zirconia-toughened alumina (In-Ceram Zirconia) and yttrium cation-doped tetragonal zirconia polycrystals (In-Ceram YZ, Cercon, and Procera Zirconia). The absolute marginal discrepancy of the cores was assessed by using an image analysis system. The data were analyzed using 1-way ANOVA and Scheffés test (α=.05). RESULTS The mean marginal openings were 29.98 ± 3.97 μm for the In-Ceram Zirconia group, 12.24 ± 3.08 μm for the In-Ceram YZ group, 13.15 ± 3.01 μm for the Cercon group, and 8.67 ± 3.96 μm for the Procera group. Significant differences were found among the 4 systems (P<.05). CONCLUSIONS The marginal accuracy achieved for the 4 zirconia-based ceramic crown systems analyzed was within the range of clinical acceptance (120 μm).

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions based on wavefront sampling technology

OBJECTIVE The aim of this study was to compare the fit of ceramic crowns fabricated from conventional silicone impressions with the fit of ceramic crowns fabricated from intraoral digital impressions. METHODS Twenty-five participants with 30 posterior teeth with a prosthetic demand were selected for the study. Two crowns were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group) and the other crown was fabricated from a conventional two-step silicone impression (CI group). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone. Each crown was embedded in acrylic resin to stabilise the registered interface and then cut in 2mm thick slices in a buco-lingual orientation. The internal gap was determined as the vertical distance from the internal surface of the crown to the prepared tooth surface at four points (marginal gap, axial gap, crest gap, and occlusal fossa gap) using stereomicroscopy with a magnification of 40×. Data was analysed by using Wilcoxon signed rank test (α=0.05). RESULTS Internal adaptation values were significantly affected by the impression technique (p=0.001). Mean marginal gap was 76.33 ± 65.32 μm for the crowns of the IDI group and 91.46 ± 72.17 μm for the CI group. CONCLUSION All-ceramic crowns fabricated from intraoral digital impressions with wavefront sampling technology demonstrated better internal fit than crowns manufactured from silicone impressions. CLINICAL SIGNIFICANCE Impressions obtained from an intraoral digital scanner based on wavefront sampling technology can be used for manufacturing ceramic crowns in the normal clinical practice with better results than conventional impressions with elastomers.

Accuracy of a digital impression system based on active wavefront sampling technology for implants considering operator experience, implant angulation, and depth.

BACKGROUND There is a scarce knowledge on the accuracy of intraoral digital impression systems for dental implants. PURPOSE The purpose of this study is to evaluate the accuracy of a digital impression system considering clinical parameters. MATERIALS AND METHODS A master model with six implants (27, 25, 22, 12, 15, 17) was fitted with polyether ether ketone scan bodies. Implant no. 25 was placed with 30° mesial angulation in relation to the vertical plane (y axis), and implant no. 15 was positioned with 30° distal angulation. Implant no. 22 was placed 2 mm and no. 12, 4 mm below the gingiva. Experienced (n = 2) and inexperienced operators (n = 2) performed scanning (Lava Chairside Oral Scanner; 3 M ESPE, St Paul, MN, USA) at standard and high accuracy mode. Measurements involved five distances (27-25, 27-22, 27-12, 27-15, 27-17). Measurements with high accuracy three-dimensional coordinated measuring machine (CMM) of the master model acted as the true values. The data obtained were subtracted from those of the CMM values. RESULTS Experience of the operator significantly influenced the results (p = .000). Angulation (p = .195) and depth of implant (p = .399) did not show significant deviation from the true values. The mean difference between standard and high accuracy mode was 90 μm. CONCLUSIONS With the active wavefront sampling, technology-based digital impression system training seems to be compulsory. Impressions of angulated implants may diminish the accuracy of the impression, yet the results were not significant.

Marginal discrepancy of monolithic and veneered all-ceramic crowns on titanium and zirconia implant abutments before and after adhesive cementation: a scanning electron microscopy analysis.

PURPOSE To evaluate the marginal discrepancy of monolithic and veneered all-ceramic crown systems cemented on titanium (Ti) and zirconia implant abutments. MATERIAL AND METHODS Sixty customized implant abutments for a maxillary right central incisor were fabricated of Ti and zirconia (n = 30 of each) for an internal-connection implant system. All-ceramic crowns were fabricated using the following systems (n = 10 per group): monolithic with computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD), pressed lithium disilicate (PLD), or CAD yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP). The frameworks of the PLD and Y-TZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were cemented to their implant abutments, and the absolute marginal discrepancy of the gap was measured before and after cementation. Data were analyzed statistically. RESULTS Marginal discrepancies were significantly influenced by the crown system and by cementation, but the material did not significantly affect the results. Interaction terms were not significant. Y-TZP crowns on both Ti and zirconia abutments presented the smallest mean marginal discrepancies before (52.1 ± 17 μm and 56.2 ± 11 μm, respectively) and after cementation (98.7 ± 17 μm and 101.8 ± 16 μm, respectively). Before cementation, MLD crowns showed significantly larger mean marginal openings than PLD crowns on both Ti and zirconia abutments (75.2 ± 12 and 77.5 ± 13 μm for MLD, 52.1 ± 17 μm and 69.7 ± 8 μm for PLD, respectively). After cementation, both Ti and zirconia abutments with MLD crowns (113.5 ± 12 μm and 118.3 ± 14 μm, respectively) showed significantly larger values than with PLD crowns (98.7 ± 17 μm and 109.4 ± 9 μm, respectively). CONCLUSIONS Manually veneered Y-TZP crowns demonstrated more favorable marginal fit on both Ti and zirconia implant abutments before and after cementation compared to those of MLD and PLD.

Accuracy of a Digital Impression System Based on Active Triangulation Technology With Blue Light for Implants: Effect of Clinically Relevant Parameters.

Purpose:To evaluate the accuracy of a digital impression system considering clinical parameters. Materials and Methods:A master model with 6 implants (27, 25, 22, 12, 15, and 17) was fitted with polyether ether ketone scan bodies. Implant no. 25 was placed with 30° mesial angulation and no. 15 with 30° distal angulation in relation to the vertical plane (y axis). Implant no. 22 was placed at 2 mm and no. 12 placed 4 mm below the gingiva. Experienced (n = 2) and inexperienced (n = 2) operators performed the scanning (CEREC system). Measurements involved 5 distances (27–25, 27–22, 27–12, 27–15, 27–17). Measurements with coordinated measuring machine of the master model acted as the true values. Results:The experience of the operator affected the accuracy. Operator 3 (inexperienced) performed better than the rest. Angulation and implant depth did not affect the accuracy results. The position of the camera affected the accuracy of the system. The first scanned quadrant had significantly smaller error, −17 ± 26.3 &mgr;m, than the second quadrant, −116 ± 103 &mgr;m. Conclusions:Digital impressions with CEREC Bluecam system can be a feasible alternative for challenging cases where angulation and depth of the implants are present. The accuracy of the CEREC system for the first scanned quadrant is high, and it decreases when completing a full arch.

Accuracy of two digital implant impression systems based on confocal microscopy with variations in customized software and clinical parameters.

PURPOSE To evaluate the accuracy of two digital impression systems based on the same technology but different postprocessing correction modes of customized software, with consideration of several clinical parameters. MATERIALS AND METHODS A maxillary master model with six implants located in the second molar, second premolar, and lateral incisor positions was fitted with six cylindrical scan bodies. Scan bodies were placed at different angulations or depths apical to the gingiva. Two experienced and two inexperienced operators performed scans with either 3D Progress (MHT) or ZFX Intrascan (Zimmer Dental). Five different distances between implants (scan bodies) were measured, yielding five data points per impression and 100 per impression system. Measurements made with a high-accuracy three-dimensional coordinate measuring machine (CMM) of the master model acted as the true values. The values obtained from the digital impressions were subtracted from the CMM values to identify the deviations. The differences between experienced and inexperienced operators and implant angulation and depth were compared statistically. RESULTS Experience of the operator, implant angulation, and implant depth were not associated with significant differences in deviation from the true values with both 3D Progress and ZFX Intrascan. Accuracy in the first scanned quadrant was significantly better with 3D Progress, but ZFX Intrascan presented better accuracy in the full arch. CONCLUSION Neither of the two systems tested would be suitable for digital impression of multiple-implant prostheses. Because of the errors, further development of both systems is required.

Accuracy of Definitive Casts Using 4 Implant-Level Impression Techniques in a Scenario of Multi-Implant System With Different Implant Angulations and Subgingival Alignment Levels

Purpose: To evaluate the effect of various implant-level impression techniques on the accuracy of definitive casts for a multiple internal connection implant system with different implant angulations and subgingival depths. Material and Methods: Six tapered Screw-Vent implants were placed in a reference model with different angles (0, 15, and 30 degrees) and subgingival positions (0, 1, and 3 mm). Twenty medium-consistency polyether impressions of this model were made with 4 techniques (n = 5 per group): (1) indirect technique, (2) unsplinted direct technique, (3) acrylic resin-splinted direct technique, and (4) metal-splinted direct technique. Impressions were poured with type IV dental stone. The interimplant distances were measured for casts using a coordinate measuring machine and the deviations compared with the reference model were calculated. Data were analyzed using intraclass correlation coefficient, ANOVA and Bonferroni test (&agr; = 0.05). Results: Four impression procedures showed significant differences (P = 0.0001). Only group 4 casts showed no significant differences in comparison with the reference model (P = 0.666) (ANOVA repeated measures). Conclusions: The impression procedure affected the accuracy of definitive casts. The metal-splinted direct technique produced the most accurate casts, followed by acrylic resin-splinted direct, indirect, and unsplinted direct techniques.

A Clinical Study Assessing the Influence of Anodized Titanium and Zirconium Dioxide Abutments and Peri-implant Soft Tissue Thickness on the Optical Outcome of Implant-Supported Lithium Disilicate Single Crowns

PURPOSE To assess the influence of anodized titanium and zirconium dioxide abutments and peri-implant soft tissue thickness on the optical outcome of implant-supported lithium disilicate single crowns. MATERIALS AND METHODS Twenty patients with a missing maxillary single incisor, canine, or first premolar received an endosseous implant after a two-stage surgery protocol. After healing and soft tissue conditioning, peri-implant soft tissues were reproduced in the impression, and the thickness was measured. Customized abutments were made of titanium, gold-anodized titanium, pink-anodized titanium, and zirconium dioxide. The definitive prosthesis was a lithium disilicate crown stratified by feldsphatic porcelain. Customized abutments were screwed (35 Ncm), and the crown was temporarily placed on the abutment with a try-in paste. Color measurements were made using a spectrophotometer. CIELab color scale was employed following the formula: ΔE = (ΔL)² + (Δa) ² + (Δb) ². Data were analyzed using repeated-measures analysis of variance (ANOVA), Bonferroni and Pearsons correlation tests (α = .05). RESULTS Abutment material type significantly affected the ΔE values at both the peri-implant soft tissue (P = .0001) and coronal level (P = .001). The lowest ΔE values were obtained with zirconia abutments at both soft tissue (6.06 ± 3.2) and coronal level (5.76 ± 2.9) compared with those of other abutments (soft tissue: 8.96 ± 3.1 to 11.56 ± 3.4; coronal: 8.66 ± 6.1 to 10.42 ± 6.3). Mean soft tissue thickness (1.63 ± 0.64 mm) affected the ΔE values at the peri-implant soft tissue level for only titanium and pink-anodized titanium abutments (P = .024 and P = .048, respectively). In all conditions, correlation coefficients between ΔE and the abutment materials were higher for titanium (r = -0.544; P = .024) and the least for zirconia (r = -0.313; P = .238) and gold-anodized titanium (r = -0.393; P = .119) abutments. CONCLUSION All abutment types demonstrated noticeable color difference at both the soft tissue and coronal levels. Zirconia abutments showed the lowest ΔE values at both measurement zones. Soft tissue thickness did not affect the ΔE values at the peri-implant soft tissue level.

Prosthodontic Considerations in the Implant‐Supported All‐Ceramic Restoration of Congenitally Missing Maxillary Lateral Incisor: A Clinical Report

The congenitally missing maxillary lateral incisor is the most common agenesis in the anterior region. There are several treatment options for this anomaly, which causes severe deficiencies: orthodontic space closure, tooth-supported restoration, or single-tooth implant. Each of these solutions has a high degree of success if used in the correct situation. An implant-supported restoration with an interdisciplinary approach provides a predictable outcome. This article describes the treatment of a patient with agenesis of the maxillary left lateral incisor. After orthodontic space management, it was decided to restore the tooth with an all-ceramic crown cemented on a zirconia custom abutment, which fractured after only 6 weeks of service. Fractographic analysis revealed that the failure was due to over-reduction of the buccal wall to correct the labial emergence of the implant. Zirconia abutments should be designed with even wall thicknesses of at least 0.8 mm to avoid areas that may compromise functional success.