The Scalloped Surgical Guide as an Alternative to Flat Bone Reduction Guide in Full-Arch Implant Restoration.

The goal of this clinical report was to present an alternative to traditional flat bone reduction guides, using a custom-designed 3-dimensional (3D)-printed guide according to the future gingival margin of the planned dentition. A 61-year-old woman with concerns regarding her smile appearance was presented. The initial examination revealed excessive gingival show accompanied by excessive overjet. The dentition was in a failing situation. The proposed treatment plan, relying on the sufficient amount of bone and keratinized tissue, consisted of recontouring of the alveolar ridge and gingiva and placement of 6 implants and an FP-1 prosthesis after extraction of all remaining maxillary teeth. Digital smile design was completed, and a fully digitally guided surgery was planned. This consisted of using 3 surgical guides, starting with the fixation pin guide, continuing with the scalloped hard- and soft-tissue reduction guide, and finally the implant placement template. Following the surgery, the patient received a temporary restoration, and on the 4-month follow-up, a new polymethyl meta-acrylate temporary prosthesis was delivered. The patient's 7-month follow-up is presented in the article. The report of this triple-template guided surgery indicated that digital 3D planning is a considerably predictable tool to properly establish and evaluate future occlusal plane, smile line, and lip support. Scalloped guides seem to be an excellent alternative to conventional bone reduction guides since they require less bone removal and improve patient comfort during surgery.

Accuracy of open-sleeved vs. closed-sleeved static computer-assisted implant systems in immediate maxillary molar implant placement: An in vitro study.

OBJECTIVES: The objective of this study is (1) to compare the accuracy of an open-sleeved static computer-assisted implant system (sCAIS) with a closed-sleeve sCAIS and free-hand approach in immediate implant placement (IIP) of maxillary molar sites and (2) to investigate the influence of socket morphology on these approaches. MATERIALS AND METHODS: Ninety partially edentulous duplicated maxillary models simulating three different molar sockets (type A, B, and C based on Smith and Tarnow's classification) were investigated. Three modalities, including sCAIS with open-sleeves, sCAIS with closed-sleeves, and free-hand approach, were applied separately to 30 models with 120 sockets. A customized Python script automatically measured the deviations between the virtual and actual implant positions for all 360 implants. RESULTS: The 3D deviations of sCAIS were significantly influenced by the socket and sleeve types. Both guided groups exhibited significantly less deviation than the free-hand approach. Type A and C sockets resulted in better implant positions than type B socket sites. In type B sockets, the open-sleeve group achieved significantly less deviation compared to the closed-sleeve group, with respect to apical global (1.34 ± 0.53 vs. 1.84 ± 0.59 mm), coronal horizontal (0.68 ± 0.36 vs. 0.93 ± 0.34 mm), apical horizontal (1.21 ± 0.59 vs. 1.74 ± 0.63 mm), and angular (3.30 ± 1.41 vs. 4.41 ± 1.96°) deviations. CONCLUSIONS: Guided implant surgery significantly reduces deviations during molar IIP compared to free-hand procedures. Furthermore, the use of open-sleeve sCAIS appears to be more effective in minimizing deviations in type B sockets when compared with the closed-sleeve guided system.

Accuracy of Conventional and 3D-Printed Casts for Partial Fixed Prostheses.

PURPOSE: To evaluate and compare the accuracy of conventional and 3D-printed casts using five different 3D printers. MATERIALS AND METHODS: In the control group (CG group, n = 5), five conventional impressions using light- and heavy-body polyvinyl siloxane were obtained from the master model, resulting in five stone models. In the test groups, five different scans were performed by a well-trained and experienced clinician using a TRIOS intraoral scanner. All data were exported in STL file format, processed, and sent to five 3D printers. Five casts were manufactured in each printer group: SG (CARES P20, Straumann); FG (Form 2, Formlabs); WG (Duplicator 7, Wanhao); ZG (Zenith D, Zenith); and MG (Moonray S100, Moonray). Measurements of the accuracy (trueness and precision) of the casts obtained from conventional elastomeric impressions and 3D-printing methods were accomplished using a 3D analysis software (Geomagic Control). RESULTS: The FG group showed the lowest values for trueness (indicating a value closer to real dimensions), which were similar to the SG group only (P > .05). MG, WG, and ZG groups presented higher values and were similar compared to each other. Data on precision demonstrated that all 3D-printed groups showed lower values for precision (smaller deviation) when compared to the CG. CONCLUSIONS: The trueness depends on the chosen 3D printer. All of the tested 3D printers were more precise than cast models obtained from conventional elastomeric impressions.

Influence of scanbody design and intraoral scanner on the trueness of complete arch implant digital impressions: An in vitro study.

This study aimed to compare the accuracy of full-arch digital implant impressions using seven different scanbodies and four intraoral scanners. A 3D-printed maxillary model with six implants and their respective multi-unit abutments was used for this study. Seven scanbodies (SB1, SB2, SB3, SB4, SB5, SB6, and SB7) and four intraoral scanners (Primescan®, Omnican®, Trios 3®, and Trios 4®) were assessed. Each combination group was scanned ten times and a dental lab scanner (D2000, 3Shape) was used as a reference. All scans were exported as STL files, imported into Convince software (3Shape) for alignment, and later into Blender software, where their 3D positions were analyzed using a Python script. The 3D deviation, angular deviation, and linear distance between implants #3 and #14 were also measured. Accuracy was measured in terms of "trueness" (scanbody 3D deviation between intraoral scan and desktop scan). Kruskal-Wallis followed by the Bonferroni correction was used to analyze the data (⍺ = .05). The study found statistically significant differences in digital impression accuracy among the scanners and scanbodies (p<0.001). When comparing different intraoral scanners, the Primescan system showed the smallest 3D deviation (median 110.59 µm) and differed statistically from the others, while Trios 4 (median 122.35 µm) and Trios 3 (median 130.62 µm) did not differ from each other (p = .284). No differences were found in the linear distance between implants #3 and #14 between Trios 4, Primescan, and Trios 3 systems. When comparing different scanbodies, the lowest median values for 3D deviation were obtained by SB2 (72.27µm) and SB7 (93.31µm), and they did not differ from each other (p = .116). The implant scanbody and intraoral scanner influenced the accuracy of digital impressions on completely edentulous arches.

Digitally Guided Lateral Sinus Floor Elevation With Simultaneous Implant Placement: 3 Case Reports With Technical Considerations.

A sinus floor elevation via lateral window (LSFE) is one of the most widely used bone augmentation procedures for implant therapy in the posterior area of the maxilla. Locating and preparing a correct opening window on the lateral sinus wall is a key step of this procedure. Conventionally, the surgeon designs and locates the window after the flap is reflected based on the information obtained from cone-beam computed tomography (CBCT) images or other diagnostic aids. Nevertheless, in spite of the advancements in CBCT imaging, clinicians may still experience hardships in situating and procuring meticulous access to the maxillary sinus by using CBCT alone. Therefore, in cases requiring an LSFE simultaneous to implant placement, a maxillary sinus surgical guide has been tested and reported to be the amiable method to be utilized as a conjunct to prevent unpredictable consequences according to its application in implying both the direction for the implant and the location of the lateral window. This article presents 3 clinical cases with a fully digital approach to guide the opening of the lateral wall of the maxillary sinus as well as the simultaneous placement of a single implant in an ideal 3D position. Based on the CBCT images and intraoral scan, a surgical guide was fabricated based on 3D software. During surgery, this teeth-supported template can be placed intraorally, guiding sinus window opening preparation. This technique makes the sinus window opening procedure simple and predictable, reduces surgical time and the risk of complications, and allows the placement of the implant in the ideal 3D position.

Erratum: Sleeveless guided implant placement compared to conventional approaches: An in vitro study at healed sites and fresh extraction sockets.

The following amendments are made to the published article: Int J Oral Implantol (Berl) 2023;16(2): 117-132; First published 9 May 2023.

Volumetric Outcomes of Peri-implant Soft Tissue Augmentation with a Xenogeneic Cross-Linked Collagen Scaffold: A Comparative Clinical Study.

Performing soft tissue augmentation (STA) at implant sites to improve esthetics, patient satisfaction, and peri-implant health is common. Several soft tissue grafting materials can be used to increase soft tissue thickness at the second-stage surgery, including human dermal matrices and xenogeneic collagen scaffolds. This study assessed and compared the volumetric outcomes, from second-stage surgery to crown delivery, around implants that received STA with a xenogeneic cross-linked collagen scaffold (XCCS) vs nonaugmented implant sites. Thirty-one patients (31 implant sites) completed the study. Intraoral digital scans were taken at the second stage and prior to crown delivery, and the STL files were imported in an image-analysis software to assess volumetric changes. XCCS-augmented implants showed significantly greater volumetric changes compared to control sites, which showed volume loss. The mean thickness of the XCCS-augmented area was 0.73 mm. There was no difference in patient-reported esthetic evaluations between groups. STA with XCCS provided significantly greater volumetric outcomes compared to nonaugmented sites. Further studies are needed to evaluate the long-term behavior of the augmented peri-implant mucosa and the effects of STA on peri-implant health.

Comparative physical and mechanical properties of a 3D printed temporary crown and bridge restorative material.

Background: The objective was to compare physic-mechanical properties of different materials used for temporary restorations. Material and Methods: Protemp 4/bisacrylic resin, Jet/acrylic resin, and Nexdent C&B/3D-printed resin samples (10mm diameter x 2mm thickness) were analyzed for surface roughness and color stability tests (baseline, after 5 thousand brushing cycles; and after artificial aging in water at 60oC for 24 hours) and Knoop microhardness. All data were checked for normality using Shapiro-Wilk test. Surface roughness and color stability were analyzed using two-way repeated measurements ANOVA, microhardness data was subjected to one-way ANOVA. All tests were followed by Tukey test and were performed with α=0.05. Results: For roughness, material (p=.002), time points (p=.002) and interaction between both (p<.001) were significant. All groups presented similar roughness for measurements of baseline and after brushing. After artificial aging, 3D printed resin showed decreased roughness when compared with other resins, and with its baseline reading. Acrylic resin showed an increase in surface roughness (when compared with measurement after brushing cycles). Considering color stability, only the material (p=.039) and the time (p<0.001) were significant. All groups showed similar color variation before and after artificial aging. There was an increase in color alteration after artificial aging for all groups. Considering microhardness test (p<.001), the 3D printed resin showed the highest values and acrylic resin the lowest. Bysacylic resin was similar to both 3D printed and acrylic resins. Conclusions: The tested 3D printed resins present similar or better properties than other tested temporary materials while being integrated with the digital workflow. Key words:Disinfection methods, hydroxyl radical, environment, surfaces, dentistry.

Effects of crown contour on artificial biofilm removal efficacy with interdental cleaning aids: An in vitro study.

OBJECTIVES: To evaluate the efficacy of various interdental cleaning aids for artificial biofilm removal on different implant-supported crown designs. METHODS: Mandibular models with missing first molar were fabricated and installed with single implant analogs and loaded with crowns of different designs (concave, straight, and convex). Artificial biofilm was made with occlusion spray. Thirty volunteers (periodontists, dental hygienists, and laypersons) were asked to clean the interproximal areas. The crowns were unscrewed and photographed in a standardized setting. The outcome was measured by the cleaning ratio which represents the cleaned surfaces in relation to the area of the tested surface. RESULTS: A significant difference in favor of concave crown (p < .001) on the basal surface was cleaned by all tools, except the water flosser. There was evidence of an overall effect of "cleaning tool," "surface," and "crown design" (p < .0001) except for the "participant" factor. The mean cleaning ratio for each cleaning tool and overall combined surfaces were (in%): dental floss: 43.02 ± 23.93, superfloss: 42.51 ± 25.92, electric interspace brush: 36.21 ± 18.78, interdental brush: 29.10 ± 15.95, and electric water flosser: 9.72 ± 8.14. Dental floss and superfloss were significantly better (p < .05) than other tools in removing plaque. CONCLUSIONS: Concave crown contour had the greatest artificial biofilm removal, followed by straight and convex crowns at the basal surface. Dental floss and superfloss were the most effective interdental cleaning devices for artificial biofilm removal. None of the tested cleaning devices were able to completely remove the artificial biofilm from the interproximal/basal surfaces.

Physical and mechanical properties of four 3D-printed resins at two different thick layers: An in vitro comparative study.

OBJECTIVES: This in vitro comparative study aimed to evaluate the physical and mechanical properties of four 3D-printed resins with two different thickness layers. METHODS: Four printed resins (VarseoSmile Crown Plus, VSC; NexDent C&B MFH, MFH; Nanolab 3D, NNL; and Resilab 3D Temp, RSL) were printed with 50 µm and 100 µm layer thickness, resulting in 80 bars measuring 25 × 2×2 mm. The specimens underwent a Raman spectroscopy for degree of conversion, confocal laser scanning microscopy for surface roughness (Sa), three-point bending test for flexural strength and elastic modulus, and a Vickers hardness test (VHN). Data was tested for normality using the Shapiro-Wilk, two-way ANOVA, and Tukey test (α = 0.05) for statistical analysis. RESULTS: The layer thickness affected all performed tests, but the elastic modulus (p < 0.001). Specimens with 100 µm showed, in general, worse results outcomes than those with 50 µm (p < 0.001). However, within the limitations of this comparative in vitro study, it could be concluded that the tested resins and layer thicknesses directly influenced physical and mechanical properties. SIGNIFICANCE: The physical and mechanical properties of three-dimensional printed restorations can be affected by the layer thickness, which can interfere with the choice of the 3D printing resin for a desired clinical outcome.

Comparison of mechanical properties of 3-dimensional printed and thermoformed orthodontic aligners.

INTRODUCTION: Orthodontic treatment using clear aligners has experienced exponential growth since its introduction in the late 1990s. Three-dimensional (3D) printing has also grown in popularity among orthodontists, and companies have begun to produce resins to directly print clear aligners. This study aimed to examine the mechanical properties of commercially available thermoformed aligners and direct 3D-printed aligners under laboratory conditions and a simulated oral environment. METHODS: Samples were prepared (approximately 2.5 × 20 mm) from 2 thermoformed materials, EX30 and LD30 (Align Technology Inc, San Jose, Calif), as well as 2 direct 3D-printing resins, Material X (Envisiontec, Inc; Dearborn, Mich) and OD-Clear TF (3DResyns, Barcelona, Spain). Wet samples were subjected to phosphate-buffered saline at 37°C for 7 days, whereas dry samples were stored at 25°C. Tensile and stress relaxation tests were carried out on an RSA3 Dynamic Mechanical Analyzer (Texas Instruments, Dallas, Tex) and Instron Universal Testing System (Instron, Norwood, Mass) to calculate elastic modulus, ultimate tensile strength, and stress relaxation. RESULTS: The elastic modulus of dry and wet samples was 103.2 ± 17.3 MPa and 114.4 ± 17.9 MPa (EX30), 61.3 ± 9.18 MPa and 103.5 ± 11.4 MPa (LD30), 431.2 ± 16.0 MPa and 139.9 ± 34.6 MPa (Material X), and 38.4 ± 14.7 MPa and 38.3 ± 8.4 MPa (OD-Clear TF), respectively. The ultimate tensile strength of dry and wet samples was 64.41 ± 7.25 MPa and 61.43 ± 7.41MPa (EX30), 40.04 ± 5.00 MPa and 30.09 ± 1.50 MPa (LD30), 28.11 ± 3.75 MPa and 27.57 ± 4.09 MPa (Material X), and 9.34 ± 1.96 MPa and 8.27 ± 0.93 MPa (OD-Clear TF), respectively. Residual stress of wet samples at 2% strain for 2 hours was 59.99 ± 3.02% (EX30), 52.57 ± 12.28% (LD30), 6.98 ± 2.64% (Material X), and 4.39 ± 0.84% (OD-Clear TF). CONCLUSIONS: There was a significant difference in elastic modulus, ultimate tensile strength, and stress relaxation among the samples tested. Moisture, specifically a simulated oral environment, appears to have a greater effect on the mechanical properties of direct 3D-printed aligners when compared with thermoformed aligners. This is likely to impact the ability of 3D-printed aligners to generate and maintain adequate force levels for tooth movement.

Sleeveless guided implant placement compared to conventional approaches: An in vitro study at healed sites and fresh extraction sockets.

PURPOSE: To investigate the accuracy of a novel sleeveless implant surgical guide by comparing it with a conventional closed-sleeve guide and a freehand approach. MATERIALS AND METHODS: Custom resin maxillary casts with corticocancellous compartments were used (n = 30). Seven implant sites were present per maxillary cast, corresponding to healed (right and left first premolars, left second premolar and first molar) and extraction sites (right canine and central incisors). The casts were assigned into three groups: freehand (FH), conventional closed-sleeve guide (CG) and surgical guide (SG) groups. Each group comprised 10 casts and 70 implant sites (30 extraction sites and 40 healed sites). Digital planning was used to design 3D printed conventional and surgical guide templates. The primary study outcome was implant deviation. RESULTS: At extraction sites, the largest difference between groups occurred in angular deviation, where the SG group (3.80 ± 1.67 degrees) exhibited ~1.6 times smaller deviation relative to the FH group (6.02 ± 3.44 degrees; P = 0.004). The CG group (0.69 ± 0.40 mm) exhibited smaller coronal horizontal deviation compared to the SG group (1.08 ± 0.54 mm; P = 0.005). For healed sites, the largest difference occurred for angular deviation, where the SG group (2.31 ± 1.30 degrees) exhibited 1.9 times smaller deviation relative to the CG group (4.42 ± 1.51 degrees; P < 0.001), and 1.7 times smaller deviation relative to the FH group (3.84 ± 2.14 degrees). Significant differences were found for all parameters except depth and coronal horizontal deviation. For the guided groups, there were fewer significant differences between healed and immediate sites compared to the FH group. CONCLUSION: The novel sleeveless surgical guide showed similar accuracy to the conventional closed-sleeve guide.

Bacterial Leakage Evaluation Through DNA-DNA Checkerboard Hybridization Technique in Morse Taper Implant-Abutment Connections: An In Vitro Study.

Purpose: The objective of this in vitro study was to evaluate the activity of local gel containing metronidazole (MN) in the leakage area, which was analyzed by the DNA-DNA checkerboard hybridization method. Materials and Methods: Thirty-six sets of Morse taper/mini-pillar implants were used in this study. These implants were equally divided into the following three groups: MN gel (test group), no MN gel (negative test group), and no gel (control). The gel was prepared with metronidazole (15%). Unstimulated saliva samples were collected, transferred to a Falcon tube, and stored at 37°C. The sets were partially immersed in microtubes containing 300 µL of saliva and were incubated at 37°C ± 1°C for 7 days. Microbial infiltration was evaluated (37 bacterial species and 5 species of Candida). The results were analyzed with Wald-Type, ANOVA, and multiple comparisons analysis between groups. Results: After comparing the quantity of microorganisms, both gel-treated groups (no MN gel and MN gel) had more significant microorganism presence than the control group (P < .001), and no significant result was found between the no MN gel and MN gel groups (P > .05). Regarding the bacteria found, the most common were Aggregatibacter actinomycetemcomitans, Prevotella melaninogenica, Bacteroides fragilis, and Candida tropicalis. Conclusion: Within the limitations of this study, it was concluded that the gel containing metronidazole used in this study was not effective in preventing the infiltration of microorganisms through the Morse taper implant-abutment interface.

Digital planning for two-implant-supported overdenture and bone reduction guide using cone-beam computed tomography: Simple features for predictable outcomes.

The two-implant-supported mandibular overdenture is considered a reliable treatment option to restore masticatory function. Digital planning has been shown to improve the precision and accuracy of the surgical procedure. The outcomes are indeed pertinent to the ideal three-dimentional positioning of the implant placement. Recently, the uses of cone-beam computed tomography (CBCT) and intraoral scan have improved greatly the workflow of digital planning; however, the sophisticated technology caused confusion among clinicians. The purpose of this case series was to exhibit the efficacy of a bone-supported guide in applying simultaneous implant placement and bone reduction, solely based on CBCT data. The bone reduction can therefore be determined accordingly, by adding windows to the guide, allowing the clinician to decide the amount of bone reduction as well as the location for implant placement. This novel surgical guide would not only fit properly on the bone but also provide the benefits of less-invasive surgery and the opportunity to place implants parallel. The  digital workflow described not only simplifies the fabrication process but also yields predictable surgical outcomes.

Cost and effectiveness of 3-dimensionally printed model using three different printing layer parameters and two resins.

STATEMENT OF PROBLEM: When 3-dimensional printing casts, the operator can change the type of resin and the printing layer thickness, reducing the fabrication time. However, how these parameters affect the accuracy of 3-dimensionally printed casts is unknown. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of 3-dimensionally printed casts by using a stereolithography (SLA) 3-dimensional printer (Forms2) with 3 different layer thickness (25, 50, and 100 µm) and 2 different resins (Gray and Cast) and by comparing the time to obtain each cast. MATERIAL AND METHODS: One master cast was scanned, and a single file was printed several times. The printed casts were then scanned by using a laboratory scanner. The standard tessellation language (STL) files provided by the laboratory scanner were superimposed and compared by using a software program (Geomagic Control; 3D Systems). The 2-way ANOVA test was used for the trueness evaluation, followed by the Tukey test to identify differences among the groups (α=.05). RESULTS: No statistically significant differences in accuracy were found among the 3 different layers for either resin (P>.05). Printing time doubled as layer thickness decreased. CONCLUSIONS: This study showed that when printing casts, the fastest printing settings can be used without losing accuracy and that the laboratory digital workflow can be accelerated with selection of the resin and cast layer, as the type of resin and layer thickness did not influence the quality of the casts.

Accuracy of partially and fully guided surgical techniques for immediate implant placement: An in vitro assessment.

STATEMENT OF PROBLEM: Optimal implant positioning is essential to achieving predictable results. Computer-guided surgery has been reported to be an accurate technique for implant placement in healed sites, but the accuracy of guided techniques for immediate implant placement into fresh sockets is still unclear. PURPOSE: The purpose of this experimental randomized split-mouth study in pig jaws was to determine the accuracy of partially and fully guided surgical techniques for immediate implant placement into fresh sockets and to compare 2 different methods of implant position deviations analysis. MATERIAL AND METHODS: Twenty implants were installed in 10 pig jaws using 2 different techniques: partially guided (n=10) and fully guided (n=10). Cone beam computed tomography and digital scanning were performed before and after the surgical procedure to plan the virtual implant position and fabricate the surgical guide, as well as to determine implant position deviations. Two methods were used to evaluate implant deviations: tomographic and digital scanning. The Shapiro-Wilk test of normality was used. Deviation comparisons were carried out by using paired t tests (α=.05), and intraclass correlation coefficient (ICC) was computed to assess the agreement between the 2 methods of implant deviation analysis. RESULTS: In the tomographic analysis, the partially guided technique resulted in significantly higher global apical and lateral coronal deviations (2.25 ±0.59 mm; 0.96 ±0.55 mm) than fully guided (1.52 ±0.89 mm; 0.75 ±0.52 mm) (P<.01 and P<.05, respectively). The analysis performed using digital scanning showed significantly higher angular, global apical, and lateral apical deviations in the partially guided (6 ±3.28 degrees; 2.49 ±1.03 mm; 2.16 ±1.07 mm) technique than in the fully guided (3.32 ±1.84 degrees; 1.5 ±0.58 mm; 0.98 ±0.67 mm) (P<.05). An ICC of 0.522 between the 2 methods of implant deviation analysis was obtained. CONCLUSIONS: The partially guided technique was less accurate than the fully guided technique for immediate implant placement into fresh sockets. A moderate concordance was observed between cone beam computed tomography and digital scanning analyses, suggesting that more studies are required to validate and to define the most reliable method of measuring implant deviation.

Assessment of Deviations of Implants Installed with Prototyped Surgical Guide and Conventional Guide: In Vitro Study.

OBJECTIVE: The study aimed to assess the angular and linear deviations of implants installed in mannequins aided by surgical guides produced with the techniques of dual tomography (DT), model-based tomography (MT), and nonprototyped guide. MATERIALS AND METHODS: Implants were installed in mannequins of a partially edentulous maxilla and divided into three groups: Group C (n = 20), implants installed using the conventional technique with flap opening and conventional guide; Group DT (n = 20), implants installed using guided surgery with the dual tomography technique; and Group MT (n = 20), implants installed using the model-based tomography technique. After implant installation, the mannequin was subjected to a computed tomography (CT) to measure the linear and angular deviations of implant positioning relative to the initial planning on both sides. RESULTS: There was a higher mean angular deviation in group C (4.61 ± 1.21, p ≤ 0.001) than in groups DT (2.13 ± 0.62) and MT (1.87 ± 0.94), which were statistically similar between each other. Similarly, the linear deviations showed group C with the greatest discrepancy in relation to the other groups in the crown (2.17 ± 0.82, p = 0.007), central (2.2 ± 0.77, p = 0.004), and apical (2.34 ± 0.8, p = 0.001) regions. CONCLUSION: The techniques of DT and MT presented smaller angular and linear deviations than the conventional technique with the nonprototyped guide. There was no difference between the two-guided surgery techniques.

Accuracy of conventional and 3D printed casts for partial fixed prosthesis.

PURPOSE: To evaluate and compare the accuracy of conventional and 3D-printed casts using five different 3D printers. MATERIALS AND METHODS: In the control group (CG group, n = 5), five conventional impressions using light- and heavy-body polyvinyl siloxane were obtained from the master model, resulting in five stone models. In the test groups, five different scans were performed by a well-trained and experienced clinician using a TRIOS intraoral scanner. All data were exported as an STL file format, processed, and sent to five 3D printers. Five casts were manufactured in each group: SG (CARES P20, Straumann); FG (Form 2, Formlabs); WG (Duplicator 7, Wanhao); ZG (Zenith D, Zenith); and MG (Moonray S100, Moonray). Measurements of the accuracy (trueness and precision) of the casts obtained from conventional elastomeric impressions and 3D-printing methods were accomplished using a 3D analysis software (Geomagic Control). RESULTS: The FG group showed the lowest values for trueness (closer to real dimensions), which were similar to the SG group only (P > .05). Groups MG, WG, and ZG presented higher values and were similar compared to each other. Data on precision demonstrated that all 3D-printed groups showed lower values for precision (smaller deviation) when compared to the control group. CONCLUSION: The trueness depends on the chosen 3D printer. All of the tested 3D printers were more precise than cast models obtained from conventional elastomeric impressions.

Can postpolymerization for 3D-printed interim restorations be improved?

STATEMENT OF PROBLEM: Postpolymerization methods influence the properties of 3-dimensionally (3D) printed materials. Nevertheless, it is a time-consuming step that could lead dentists to avoid the chairside use of 3D printing. Information assessing the impact of different postpolymerization workflows on flexural strength and color stability is sparse. PURPOSE: The purpose of this in vitro study was to analyze the impact of different postpolymerization methods on the flexural strength and color stability of 3D-printed resins used for interim restorations. MATERIAL AND METHODS: Three resin materials: CT (Cosmos Temp; Yller Biomaterials), DT (Denture Teeth; Formlabs), and CB (C&B MFH; NextDent) were submitted to 4 methods of postpolymerization: a Form Cure polymerization chamber (FC) (Form Cure; Formlabs), a broadband LED device (Valo Grand; Ultradent Products, Inc) operating at 1000 mW/cm2 for 2 different polymerization times (40 seconds/V40 or 120 seconds/V120), and a custom-made polymerization chamber with a 24 W UV LED Strip (CC). The specimens were assessed for flexural strength using an universal testing machine immediately after polymerization or after 10 000 thermal cycles, and the color stability was evaluated using a spectrophotometer at baseline, after 7 days in dark, dry storage at 37 °C and after 24 hours of artificial aging in water at 60 °C. The data were evaluated using 3-way ANOVA (flexural strength) and 3-way repeated measurements ANOVA (color stability), followed by the Tukey HSD test (α=.05). RESULTS: Flexural strength showed significant differences for resin, postpolymerization method, time, and for the interaction between all effects. CT showed the highest overall flexural strength, while DT showed the lowest. In general, V120 produced specimens with higher flexural strength. Thermocycling did not reduce flexural strength except for CB polymerized with FC and V120, and DT polymerized with V40. For color stability, significant differences were found for resin, postpolymerized method, time, and for the interaction between all effects. The highest ΔE values were observed for DT polymerized using V40 after artificial aging. The lowest values were observed for the same resin but polymerized using V120 after 7 days in dark, dry storage at 37 °C. CONCLUSIONS: Postpolymerization with the broadband LED device for 120 seconds can produce specimens with higher flexural strength values and higher color stability when compared with the other postpolymerization workflows tested in this study.