Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering.

OBJECTIVE: To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation. MATERIAL AND METHODS: Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05). RESULTS: Mean values (µm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups. CONCLUSIONS: Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Current applications of 3D printing in dental implantology: A scoping review mapping the evidence.

OBJECTIVES: This scoping review aimed to identify the available evidence in the use of 3D printing technology in dental implantology. Due to the broad scope of the subject and its application in implantology, three main areas of focus were identified: (1) customized dental implants, (2) manufacturing workflow for surgical implant guides, and (3) related implant-supported prostheses factors, which include the metallic primary frameworks, secondary ceramic or polymer superstructures, and 3D implant analog models. MATERIALS AND METHODS: Online databases (Medline, Cochrane, Embase, and CINAHL) were used to identify the studies published up to February 2023 in English. Two experienced reviewers performed independently the screening and selection among the 1737 studies identified. The articles evaluated the additive manufacturing (AM) technology, materials, printing, and post-processing parameters regarding dental implantology. RESULTS: The 132 full-text studies that met the inclusion criteria were examined. Thirteen studies of customized dental implants, 22 studies about the workflow for surgical implant guides, and 30 studies of related implant-supported prostheses factors were included. CONCLUSIONS: (1) The clinical evidence about AM titanium and zirconia implants is scarce. Early data on survival rates, osseointegration, and mechanical properties are being reported. (2) 3D printing is a proven manufacturing technology to produce surgical implant guides. Adherence to the manufacturer's instructions is crucial and the best accuracy was achieved using MultiJet printer. (3) The quality of 3D printed prosthetic structures and superstructures is improving remarkably, especially on metallic alloys. However, better marginal fit and mechanical properties can be achieved with milling technology for metals and ceramics.

The effect of a convergent transmucosal neck on soft tissues and radiographic outcomes: a 1-year follow-up randomized controlled trial.

PURPOSE: The aim of this randomized controlled clinical trial was to evaluate peri-implant marginal bone levels (MBLs) and soft tissue dimension changes 1 year after loading. Patients in the control group received bone-level implants, whereas in the test group, tissue-level implants with a convergent transmucosal neck were used. MATERIAL AND METHODS: MBLs were calculated by measuring the distance from the implant shoulder to the first visible bone-to-implant contact using standardized periapical digital radiographs. Baseline (day of loading) and follow-up digital models obtained with an intraoral scanner were used to quantify the changes in the peri-implant soft tissue dimensions with a best-fit algorithm. RESULTS: The difference between final and baseline MBLs showed a mean bone loss of 0.16 ± 0.01 mm in the test group (n = 15) and 0.45 ± 0.09 mm in the control group (n = 14) (p > 0.05). Soft tissue contour at the level of the gingival margin (GM) increased by 1.96 ± 2.69 mm in the test group and 0.65 ± 0.42 mm in the control group (p = 0.167). Both groups showed a coronal displacement of the gingival margin with no significant differences among them. CONCLUSIONS: The present study demonstrated peri-implant hard and soft tissues stability at both implant designs with no significant differences 12 months after loading. CLINICAL RELEVANCE: There is still insufficient scientific evidence to demonstrate the role and advantages of the convergent transmucosal neck on the behavior of the peri-implant soft and hard tissues stability compared to a straight neck in bone-level implants 12 months after loading.

Diagnosis of Interproximal Caries Lesions in Bitewing Radiographs Using a Deep Convolutional Neural Network-Based Software.

The aim of this study was to evaluate the diagnostic reliability of a web-based artificial intelligence program for the detection of interproximal caries in bitewing radiographs. Three hundred bitewing radiographs of patients were subjected to the evaluation of a convolutional neural network. First, the images were visually evaluated by a previously trained and calibrated operator with radiodiagnosis experience. Then, ground truth was established and was clinically validated. For enamel caries, clinical assessment included a combination of clinical-visual and radiography evaluations. For dentin caries, clinical validation was performed by instrumentally accessing the cavity. Second, the images were uploaded and analyzed by the web-based software. Four different models were established to analyze its evaluations according to the confidence threshold (0-100%) offered by the program: model 1 (values >0% were considered positive and values of 0% were considered negative), model 2 (values ≥25% were considered positive and values <25% were considered negative), model 3 (values ≥50% were considered positive and values <50% were considered negative), and model 4 (values ≥75% were considered positive and values <75% were considered negative). The accuracy rate (A), sensitivity (S), specificity (E), positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and areas under receiver operating characteristic curves (AUC) were calculated for the four models of agreement with the software. Models showed the following results respectively: A = 70.8%, 82%, 85.6%, 86.1%; S = 87%, 69.8%, 57%, 41.6%; E = 66.3%, 85.4%, 93.7%, 98.5%; PPV = 42%, 57.2%, 71.6%, 88.6%; NPV = 94.8%, 91%, 88.6%, 85.8%; PLR = 2.58, 4.78, 9.05, 27.73; NLR = 0.2, 0.35, 0.46, 0.59; AUC = 0.767, 0.777, 0.753, 0.701. Findings in the present study suggest that the artificial intelligence web-based software provides a good diagnostic reliability on the detection of dental caries. Our study highlighted model 2 for showing the best results to differentiate between healthy teeth and decayed teeth.

Influence of different cleaning procedures on the shear bond strength of 10-methacryloyloxydecyl dihydrogen phosphate-containing self-adhesive resin cement to saliva contaminated zirconia.

Purpose To evaluate the effect of different cleaning methods on the shear bond strength (SBS) of a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing self-adhesive resin cement to zirconia after saliva contamination.Methods Sixty zirconia specimens were randomly divided into four groups (n=15) according to treatment surface. Except for the control group, all samples were contaminated with saliva and were then rinsed with water-spray and air-dried. Subsequently, the specimens were either treated with a cleaning paste (CP), with argon plasma (AP), or did not undergo an additional cleaning process (WS). An MDP-containing self-adhesive resin cement was applied onto the ceramic surfaces. Specimens were stored in water (24 hours) followed by thermocycling (5°C to 55°C for 10.000 cycles). SBS tests were performed in a universal testing machine, and the results (MPa ± SD) were statistically analyzed using ANOVA and Bonferroni post-hoc test. Fractured surfaces were examined to identify the failure types using a stereomicroscopy and SEM.Results The surface cleaning treatment (p<0.05) significantly affected the results. The highest SBS values were observed in the control group (12.16 ± 1.22 MPa) and were statistically comparable to values for the CP group (11.38 ± 1.65 MPa). The AP group (9.17 ± 1.06 MPa) showed significantly higher bond strength than the WS group (6.95 ± 1.20 MPa), but it showed significantly lower strength than the control and CP groups.Conclusions The CP application was the most effective method in removing saliva contamination. The AP treatment could not restore the SBS to the same level as uncontaminated specimens.

Analysis of Surface Roughness, Fracture Toughness, and Weibull Characteristics of Different Framework-Veneer Dental Ceramic Assemblies after Grinding, Polishing, and Glazing.

PURPOSE: To compare the surface roughness and biaxial flexural strength of dental ceramics obtained after chairside surface modification by mechanical polishing procedures, versus laboratory reglazing. MATERIALS AND METHODS: Discs (16 × 1.5 ± 1.6 mm) (N = 90) of various framework-veneering combinations were fabricated: D/FC: lithium disilicate/feldspathic ceramic; Z/AL: zirconium dioxide/aluminous ceramic; N/FC: noble alloy/feldspathic ceramic; N/FF: noble alloy feldspathic with fluorapatite; B/FC: base alloy/feldspathic ceramic; B/FF: base alloy/feldspathic ceramic with fluorapatite. In each group 10 specimens were ground using a diamond bur (46 µm) and five were polished with silicone-reinforced disc polishers (25 µm). Surface roughness (Ra) was measured using contact profilometry. After thermocycling in artificial saliva (6000 cycles, 5 to 55 ± 5°C), biaxial flexural strength was measured using "piston-on-three ball" test. The data (N) were analyzed using one-way ANOVA, Bonferroni, and Tukey's posthoc tests. Weibull distribution values were calculated. RESULTS: Surface roughness was significantly higher in the ground group only (p < 0.0001). Mean fracture toughness was significantly lower for chipping (RK: 287, HS: 22, ISO: 1099 MPa) than for total fracture (p < 0.05), (RK: 841, HS:64, ISO: 3222 MPa). For chipping, Weibull distribution presented the highest shape value (m) for D/FC (3.82-5.07) and for total fracture for B/FC (3.69-4.6). CONCLUSION: Chairside surface polishing restored veneer ceramic roughness and mechanical strength to the level of glazing. Feldspathic ceramic with fluorapatite presented better polishing results than conventional feldspathic ceramic did. Ceramic fused to metal was more resistant than lithium disilicate or zirconium dioxide framework-veneer assemblies. Lithium disilicate framework veneered with feldspathic ceramic presented more durability against chipping. CLINICAL IMPLICATIONS: After chairside occlusal modifications in the surfaces of cemented all-ceramic or fused-to-metal FDPs, mechanical polishing procedures should always be carried out.

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 Pearson's 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.

In vitro comparison of the accuracy (trueness and precision) of six extraoral dental scanners with different scanning technologies.

STATEMENT OF PROBLEM: The fabrication of prosthetic restorations using computer-aided design and computer-aided manufacturing (CAD-CAM) procedures depends on scanning surfaces. However, limited information is available regarding the effect of extraoral scanning systems on the accuracy of the fabrication process. PURPOSE: The purpose of this in vitro study was to evaluate and compare the accuracy (trueness and precision) and resolution of 6 CAD-CAM extraoral scanners by comparing features and scan technology. MATERIAL AND METHODS: A master die was fabricated to simulate a dental preparation. The die was measured with a coordinate measuring machine (CMM) to obtain an accurate digital CAD reference model (CRM). The master die was then scanned 10 times with 3 structured light scanners, 2 laser scanners, and 1 contact scanner. The resulting laboratory scan data (LSD) were converted to a stereolithography (STL) format. The discrepancies between measurements were compared 3-dimensionally and at 3 selected areas of a virtual sagittal cut using CAD software. The Kruskal-Wallis 1-way analysis of variance was first performed to compare scanners and then to group data according to scanner type. The Spearman rank correlation coefficient was used to test the association between resolution and all other variables (α=.05). RESULTS: For all 6 scanners, the mean resolution value was 133.9 (SD 93.9) points/mm2. The value for trueness was 38.8 (SD 6.2) µm and for precision 45.5 (SD 4.8) µm. Trueness values were 20.3 µm (SD 32.7) at the axial surfaces, 46.6 µm (SD 25.9) at the margin of the preparation, and 55.8 µm (SD 29.3) at the center of the occlusal groove. The ZENO Scan was the most accurate and precise of the 6 scanners for most of the variables measured. CONCLUSIONS: The reliability of CAD-CAM scanners is not affected by a specific technology (light, laser, or contact) but by definite parameters. In addition, the entire scanning procedure is more accurate if the scanned surfaces are smooth and regular.

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions.

OBJECTIVES: The aim of this study is to compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions. METHODS: Twenty patients with 26 posterior teeth with a prosthetic demand were selected for the study. Two crowns (Straumann-Zerion) were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group; Cadent-iTero), and the other crown was fabricated from a conventional one-step silicone impression (CI group; Express Penta Putty and Body Light). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone (Express Ultra Light Body). Each crown was embedded in resin to stabilize the registered interface, cut in 2-mm-thick slices in a buco-lingual orientation. Internal misfit was measured in microns using stereomicroscopy with a magnification of ×40. Measurements were taken at different landmarks: margin, chamfer angle, axial, crest, and occlusal fosse. After checking for normality, data was analyzed using paired Student's t test (α = 0.05). RESULTS: Fit values were significantly affected by the impression technique (p = 0.000). Mean internal misfit and mean marginal misfit were 111.40 µm (SD = 54.04)/80.29 µm (SD = 26.24) for the crowns of the IDI group and 173.00 µm (SD = 92.65)/133.51 µm (SD = 48.78) for the CI group. CONCLUSION: All-ceramic crowns fabricated from intraoral digital impressions with parallel confocal technology demonstrated a clinically acceptable internal and marginal fit as conventional impression. CLINICAL SIGNIFICANCE: Intraoral digital impressions as initial step to the digital workflow could further improve the marginal adaptation of all ceramic single crowns. TRIAL REGISTRATION: http://www.isrctn.com/ISRCTN16111844.

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 µm, than the second quadrant, -116 ± 103 µm. 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.

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.

Accuracy of a digital impression system based on parallel confocal laser technology for implants with consideration of operator experience and implant angulation and depth.

PURPOSE: To evaluate the accuracy of a digital impression system based on parallel confocal red laser technology, taking into consideration clinical parameters such as operator experience and angulation and depth of implants. MATERIALS AND METHODS: A maxillary master model with six implants (located bilaterally in the second molar, second premolar, and lateral incisor positions) was fitted with six polyether ether ketone scan bodies. One second premolar implant was placed with 30 degrees of mesial angulation; the opposite implant was positioned with 30 degrees of distal angulation. The lateral incisor implants were placed 2 or 4 mm subgingivally. Two experienced and two inexperienced operators performed intraoral scanning. Five different interimplant distances were then measured. The files obtained from the scans were imported with reverse-engineering software. Measurements were then made with a coordinate measurement machine, with values from the master model used as reference values. The deviations from the actual values were then calculated. The differences between experienced and inexperienced operators and the effects of different implant angulations and depths were compared statistically. RESULTS: Overall, operator 3 obtained significantly less accurate results. The angulated implants did not significantly influence accuracy compared to the parallel implants. Differences were found in the amount of error in the different quadrants. The second scanned quadrant had significantly worse results than the first scanned quadrant. Impressions of the implants placed at the tissue level were less accurate than implants placed 2 and 4 mm subgingivally. CONCLUSIONS: The operator affected the accuracy of measurements, but the performance of the operator was not necessarily dependent on experience. Angulated implants did not decrease the accuracy of the digital impression system tested. The scanned distance affected the predictability of the accuracy of the scanner, and the error increased with the increased length of the scanned section.

Using stereophotogrammetric technology for obtaining intraoral digital impressions of implants.

BACKGROUND: The procedure for making impressions of multiple implants continues to be a challenge, despite the various techniques proposed to date. The authors' objective in this case report is to describe a novel digital impression method for multiple implants involving the use of stereophotogrammetric technology. CASE DESCRIPTION: The authors present three cases of patients who had multiple implants in which the impressions were obtained with this technology. Initially, a stereo camera with an infrared flash detects the position of special flag abutments screwed into the implants. This process is based on registering the x, y and z coordinates of each implant and the distances between them. This information is converted into a stereolithographic (STL) file. To add the soft-tissue information, the user must obtain another STL file by using an intraoral or extraoral scanner. In the first case presented, this information was acquired from the plaster model with an extraoral scanner; in the second case, from a Digital Imaging and Communication in Medicine (DICOM) file of the plaster model obtained with cone-beam computed tomography; and in the third case, through an intraoral digital impression with a confocal scanner. RESULTS: In the three cases, the frameworks manufactured from this technique showed a correct clinical passive fit. At follow-up appointments held six, 12 and 24 months after insertion of the prosthesis, no complications were reported. CONCLUSIONS: Stereophotogrammetric technology is a viable, accurate and easy technique for making multiple implant impressions. PRACTICAL IMPLICATIONS: Clinicians can use stereophotogrammetric technology to acquire reliable digital master models as a first step in producing frameworks with a correct passive fit.

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.

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 (α = 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.

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.

Fracture resistance of crowns cemented on titanium and zirconia implant abutments: a comparison of monolithic versus manually veneered all-ceramic systems.

PURPOSE: To evaluate the fracture resistance of all-ceramic crowns cemented on titanium and zirconia implant abutments. MATERIAL AND METHODS: Customized implant abutments for maxillary right central incisors made of titanium (Ti) and zirconia (Zr) (n=60, n=30 per group) were fabricated for an internal connection implant system. All-ceramic crowns were fabricated for their corresponding implant abutments using the following systems (n=10 per group): (1) monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD); (2) pressed lithium disilicate (PLD); (3) yttrium stabilized tetragonal zirconia polycrystal (YTZP). The frameworks of both PLD and YTZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were adhesively cemented to their implant abutments and loaded to fracture in a universal testing machine (0.5 mm/minute). Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test (α=0.05). RESULTS: Both the abutment material (P=.0001) and the ceramic crown system (P=.028) significantly affected the results. Interaction terms were not significant (P=.598). Ti-MLD (558.5±35 N) showed the highest mean fracture resistance among all abutment-crown combinations (340.3±62-495.9±53 N) (P<.05). Both MLD and veneered ceramic systems in combination with Ti abutments (558.5±35-495.9±53 N) presented significantly higher values than with Zr abutments (392.9±55-340.3±62 N) (P<.05). MLD crown system showed significantly higher mean fracture resistance compared to manually veneered ones on both Ti and Zr abutments (P<.05). While Ti-MLD and Ti-PLD abutment-crown combinations failed only in the crowns without abutment fractures, Zr-YTZP combination failed exclusively in the abutment without crown fracture. Zr-MLD and Zr-PLD failed predominantly in both the abutment and the crown. Ti-YTZP showed only implant neck distortion. CONCLUSIONS: The highest fracture resistance was obtained with titanium abutments restored with MLD crowns, but the failure type was more favorable with Ti-YTZP combination.

Influence of CAD/CAM systems and cement selection on marginal discrepancy of zirconia-based ceramic crowns.

PURPOSE: To analyze the effect of ceramic manufacturing technique and luting cement selection on the marginal adaptation of zirconium oxide-based all-ceramic crowns. METHODS: An extracted mandibular first premolar was prepared for a complete coverage restoration and subsequently duplicated 40 times in a liquid crystal polymer (LCP). All-ceramic crowns (n = 10) were fabricated on 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 restorations (n = 5) were cemented on their respective dies with glass-ionomer cement (Ketac Cem Aplicap) and resin cement (Panavia 21). The absolute marginal discrepancy of the crowns was measured before and after cementation by scanning electronic microscopy at 160 points along the circumferential margin. The data were analyzed using one-way ANOVA for repeated measures and for independent samples, Scheffé's multiple range post hoc test, and Student's t-test (alpha = 0.05). RESULTS: There were statistical differences in the mean marginal openings among the four all-ceramic systems before and after luting (P < 0.0001). The Procera restorations had the lowest pre- and post-cementation values (P < 0.0001). A significant increase in the marginal gap size caused by luting media occurred in all tested groups (P < 0.0001). Resin cement resulted in larger marginal discrepancies than glass-ionomer cement (P < 0.0001).