In Vitro Comparison of Internal and Marginal Adaptation between Printed and Milled Onlays.

STATEMENT OF PROBLEM: Nowadays, milling is still the gold standard for fabricating indirect restorations, but to overcome its disadvantages, there are alternatives, such as 3D printing. PURPOSE: This study aimed to compare the gaps between the prepared tooth and milled and printed onlays fabricated with the same CAD design. It also aimed to determine the gap reproducibility across onlays fabricated by 3D printing and milling. METHODS: A resin tooth was prepared for an onlay. After scanning the preparation, an onlay was designed with proprietary dental software. Next, 22 onlays were milled in a graphene-reinforced PMMA disc (Group 1), and 22 onlays were 3D-printed with a hybrid composite material (Group 2). After that, all fabricated restorations were scanned and superimposed on the scanned prepared resin tooth. Subsequently, a specific software was used to measure the margin, central, and intaglio-located gap between the milled or printed restoration and the preparation. Finally, measurements were compared with a multifactor analysis of variance. RESULTS: The results demonstrated that printed onlays (Group 2) adapted better to the prepared tooth than the milled ones (Group 1) (p < 0.05). The comparison of standard deviations showed the better gap reproducibility of printed onlays (p < 0.05). CONCLUSION: This study concluded that the printed onlays adapted significantly better to the prepared tooth than the milled onlays. Printed onlays also showed significantly better gap reproducibility.

Fabrication of a CAD-CAM combination matrix for trial restorations: A dental technique.

The trial restoration increases outcome predictability in restorative treatments, enhances communication among specialists and patients, and guides tooth preparations. It should reproduce the planned design precisely because many decisions will be made based on the transferred design. Traditionally, a diagnostic waxing design is transferred to the mouth with a flexible silicone matrix. However, a rigid matrix would ensure an accurate transfer of the planned design by avoiding the deformation of the silicone index. A step-by-step technique for fabricating a computer-aided design and computer-aided manufactured (CAD-CAM) rigid matrix relined with polyvinyl siloxane material to fabricate a trial restoration is presented. The technique ensures accurate detail reproduction and dimensional stability, avoiding deformation and ensuring a predictable transfer of the planned design.

Interarch space assessment in edentulous patients rehabilitated with complete removable dentures using open-access software.

BACKGROUND: The interarch space is defined as the vertical space between the edentulous ridge and the occlusal or incisal aspect of the opposing arch. Measuring the interarch space in a patient requiring an implant-supported fixed prosthesis is crucial for determining the prostheses to be used in each clinical situation. Depending on the measurements and other factors, such as the need for lip support or pink esthetics issues, decisions about the most convenient type of implant-supported prosthesis can be taken. Analogic workflow to measure the interarch space can represent a time-consuming and expensive procedure that may lead to inaccuracies. OBJECTIVE: To describe a step-by-step protocol to measure the upper and lower interarch space with open-access software, starting from the digital scan of the patient's complete dentures obtained with an intraoral scanner. METHODS: An extraoral scan (using an intraoral scanner) of the existing complete removable prosthesis is required to assess the interarch space for making an implant-supported prosthesis treatment planning. If the existing complete denture does not fulfill the required functional and esthetic parameters, a complete interim denture, a wax trial denture, or a printed denture prototype should be previously fabricated. The antagonist arch and the intermaxillary record scan also need to be obtained. Finally, all STL files are imported into an open-access software for measuring the interarch space. RESULTS: Open-source software can be used to measure the upper and lower interarch space from existing complete dentures following the step-by-step protocol outlined in this paper. CONCLUSION: Interarch space of edentulous patients rehabilitated with complete dentures can be measured with a 360 degrees scanning of the existing complete denture and open-access software by applying the protocol outlined in this paper. CLINICAL RELEVANCE: The clinician can assess and digitally measure the interarch space of edentulous patients requiring an implant-supported fixed prosthesis using an open access software.

A straightforward protocol for designing an interim hollow shell with open-source software.

BACKGROUND: An interim hollow shell (IHS) is a temporary prosthesis that adapts like a cap over a prepared tooth abutment. Using a conventional protocol to fabricate IHS from casts of the initial situation or the wax-up can be challenging, time-consuming, and sometimes frustrating. A digital workflow makes this process quicker and more convenient. The IHS must be first designed with computer-aided design (CAD), then fabricated with computer-aided manufacture (CAM). Proprietary dental software is commonly used for the design process but needs to be purchased. OBJECTIVE: To describe a step-by-step technique for designing an IHS for posterior relining with open-source software. METHODS: This paper describes a straightforward procedure to design an IHS from a dental scan of the initial situation or a digital wax-up for an esthetic and functional temporary rehabilitation. RESULTS: An IHS can be quickly designed using open-source software by copying an existing restoration or a conventional or digital wax-up. Then, the design can be 3D printed using a biocompatible resin. CONCLUSIONS: The clinician can use open-source software to design IHSs, which are then 3D printed using a biocompatible resin. CLINICAL RELEVANCE: The clinician can design IHSs from a dental scan of the initial situation or a wax-up using open-source software by following the step-by-step protocol outlined in this paper. The restoration can then be 3D printed using a biocompatible resin.

A 3D Finite Element Analysis Model of Single Implant-Supported Prosthesis under Dynamic Impact Loading for Evaluation of Stress in the Crown, Abutment and Cortical Bone Using Different Rehabilitation Materials.

In the literature, many researchers investigated static loading effects on an implant. However, dynamic loading under impact loading has not been investigated formally using numerical methods. This study aims to evaluate, with 3D finite element analysis (3D FEA), the stress transferred (maximum peak and variation in time) from a dynamic impact force applied to a single implant-supported prosthesis made from different materials. A 3D implant-supported prosthesis model was created on a digital model of a mandible section using CAD and reverse engineering. By setting different mechanical properties, six implant-supported prostheses made from different materials were simulated: metal (MET), metal-ceramic (MCER), metal-composite (MCOM), carbon fiber-composite (FCOM), PEEK-composite (PKCOM), and carbon fiber-ceramic (FCCER). Three-dimensional FEA was conducted to simulate the collision of 8.62 g implant-supported prosthesis models with a rigid plate at a speed of 1 m/s after a displacement of 0.01 mm. The stress peak transferred to the crown, titanium abutment, and cortical bone, and the stress variation in time, were assessed.

Protocol for Indirect Restoration Intraoral Scanning Under Dental Dam Isolation: A Dental Technique.

This paper aims to describe an intraoral scanning protocol for indirect restorations utilizing dental dam isolation. This technique consists of the initial scan of both arches and their occlusion. Then, after necessary dental preparation is performed under isolation with a dental dam, intraoral scanning of preparations is performed, maintaining the dental dam in place. The proposed protocol shortens the operative time minimizing clinical factors that can affect the scan accuracy and maximizing preparation margins' visibility, ensuring a stress-free environment. This method can be applied for chair-side dentistry and conventional workflow for sending scans to the laboratory technician.

Protocol for the clinical assessment of passive fit for multiple implant-supported prostheses: A dental technique.

With monolithic materials and the new technologies for framework production, assessment of passive fit before fabrication of the definitive prosthesis or its framework is essential to avoid prosthesis remakes. This article describes an updated clinical protocol to assess passive fit during the prosthesis fabrication process through the systematic use of tactile feel while tightening the retaining screws, the visual or radiographic evaluation when performing the 1-screw or Sheffield fit test, and the torque/time graph obtained during the placement of the implant- or abutment-retaining screws with a torque-controlled surgical motor.

A method for determining the position of the abutment screw of any cement-retained implant-supported prosthesis.

Removing cement-retained implant-supported prostheses may be challenging for clinicians. A method combining a cone beam computed tomography (CBCT) and a digital scan with a virtual surgical planning software program is described to identify the perforation site of a cement-retained implant-supported prosthesis to locate the abutment screw.

Snoring intensity assessment with three different smartphones using the SnoreLab application in one participant.

STUDY OBJECTIVES: To compare the assessment of snoring using the SnoreLab application (app) using three different smartphones by one participant to validate SnoreLab as a method for collecting data for studies on the effectiveness of snoring treatment. METHODS: A person from the research group was monitored for 30 consecutive nights with the SnoreLab app using three different smartphones (Xiaomi MI8Pro, Samsung Galaxy Alpha, and BQ Aquaris V). The SnoreLab app instructions were strictly followed, and data were collected from the app. RESULTS: No significant differences were found in the measurements from the three smartphones in the time in bed, all snoring time, snoring percentage, and quiet time. BQ and Samsung smartphones determined significantly more light snoring time than did the Xiaomi smartphone. The Samsung smartphone assessed significantly less loud snoring time than did the Xiaomi smartphone and measured the shortest epic snoring time. The lowest Snore Score was calculated with the Samsung smartphone, the highest with the Xiaomi smartphone. Pearson's correlation coefficients demonstrated a relatively strong relationship between the Snore Score measured with the three smartphones. CONCLUSIONS: Even though there was a relatively strong relationship between the Snore Score measured with the three smartphones by one participant, the observed differences make it difficult to use this index as a method of collecting data for studies on snoring treatment effectiveness when patients use different smartphones; however, the SnoreLab app may be handy to quantify treatment effectiveness for a specific patient, provided the patient always uses the same smartphone.

Comparison of the Marginal Fit of Cobalt-Chromium Metal-Ceramic Crowns Fabricated by CAD/CAM Techniques and Conventional Methods at Three Production Stages.

PURPOSE: The aim of this study was to compare the marginal fit of cobalt-chromium crowns fabricated using conventional casts and computer-aided design/computer-assisted manufacturing (CAD/CAM) techniques at three stages of production: metal coping, after porcelain firing, and after cementation. MATERIALS AND METHODS: A total of 80 metal-ceramic crowns were fabricated using four different techniques: lost wax casting, milling, laser sintering, and milling of a presintered metal block. Marginal fit was measured at each manufacturing stage. RESULTS: The porcelain firing stage improved marginal fit. CAD/CAM techniques resulted in better marginal fit than did conventional casting techniques at all manufacturing stages. CONCLUSION: CAD/CAM techniques improve marginal fit.

In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants.

PURPOSE: In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS: Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS: Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION: Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.

Adhesion of dental porcelain to cast, milled, and laser-sintered cobalt-chromium alloys: shear bond strength and sensitivity to thermocycling.

STATEMENT OF PROBLEM: New technologies have led to the introduction of new materials, so an evaluation of the adhesion of ceramics to these materials is needed. PURPOSE: The purpose of this study was to compare the shear bond strength of dental porcelain to cast, milled, and laser-sintered cobalt-chromium alloys, and to investigate the adhesive bond and failure type after thermocycling, 90 metal cylinders (10 mm diameter and 10 mm height) were prepared from cast (30 specimens), milled (30 specimens), and laser-sintered (30 specimens) alloys. MATERIAL AND METHODS: Ceramic cylinders (2.5 mm diameter and 4 mm length) were fused to the alloy cylinders. For each group, 15 specimens were thermocycled 5500 times at temperatures between 4°C and 60°C before testing. After testing, the specimen surfaces were visually examined to determine the failure mode. Differences in adhesion values according to manufacturing method, testing condition (thermocycling or no thermocycling), and interaction between the factors were evaluated with a 2-way ANOVA. The χ(2) test (95% confidence level) was performed to determine whether the failure mode was associated with the testing condition. RESULTS: Adhesion strengths for the nonthermocycled specimens were 42.79 ±14.14 MPa (cast), 37.56 ±9.18 MPa (milled), and 29.09 ±6.95 MPa (laser-sintered), and, for the thermocycled specimens, 16.52 ±8.96 MPa (cast), 22.21 ±13.25 MPa (milled), and 24.28 ±10.13 MPa (laser-sintered). Two-way ANOVA results indicated no statistically significant differences in adhesion among the manufacturing methods (P=.257), but statistically significant differences were observed according to both testing conditions (P<.001) and interaction between the factors (P=.015). The χ(2) test indicated that the failure mode was not associated with the testing condition (thermocycled, P=.280; nonthermocycled, P=.240). CONCLUSIONS: The porcelain adhesion values for all the materials were adequate for clinical applications. No significant adhesion differences were observed between cast, milled, and laser-sintered specimens, or among thermocycled and nonthermocycled laser-sintered specimens. However, significant adhesion differences were observed among the thermocycled and nonthermocycled cast and the milled specimens.

Marginal adaptation of zirconium dioxide copings: influence of the CAD/CAM system and the finish line design.

STATEMENT OF PROBLEM: Marginal adaptation is essential for the long-term success of dental restorations. Studies comparing the marginal gaps of computer-aided design/computer-aided manufacturing (CAD/CAM) restorations made from conventional and digital impressions are limited. PURPOSE: The purpose of this study was to evaluate the marginal adaptation of zirconium dioxide copings made with 2 different CAD/CAM systems, the Lava All-Ceramic System (scanning definitive dies made with conventional impressions) and the Lava Chairside Oral Scanner (scanning directly from the prepared tooth). In addition, the influences of 2 different finish line configurations were also compared. MATERIAL AND METHODS: Forty human molar teeth were prepared to receive complete crowns. Twenty were prepared with a 90-degree round shoulder and the other 20 with a 45-degree chamfer finish line. Zirconium dioxide copings were fabricated by using CAD/CAM technology. The specimens were randomized; they included 10 teeth with round shoulder and 10 with chamfer finish lines with the Lava All-Ceramic System, and 10 teeth with round shoulder and 10 with chamfer finish lines with the Lava Chairside Oral Scanner. The marginal gaps were measured at 5 points on each side with stereomicroscopy at 40× magnification. Data were analyzed with 2-way ANOVA (α=.05). RESULTS: The mean values of the measured marginal gap for the round shoulder group were 52.66 µm with the Lava All-Ceramic System and 14.98 µm with the Lava Chairside Oral Scanner. The mean values for the chamfer group were 64.06 µm for the Lava All-Ceramic System and 18.45 µm for the Lava Chairside Oral Scanner. Differences were identified when the marginal gaps between the specimens with different CAD/CAM systems were compared. However, differences in the finish line design were identified only between the round shoulder and chamfer with the Lava All-Ceramic System. CONCLUSIONS: Restorations fabricated with the Lava Chairside Oral Scanner displayed smaller marginal gaps than those made with the Lava All-Ceramic System. Nevertheless, all marginal gaps were within the range of clinical acceptability for both groups.

Comparison of the marginal adaptation of zirconium dioxide crowns in preparations with two different finish lines.

PURPOSE: The purpose of this study was to evaluate the marginal adaptation of zirconium dioxide crowns in preparations with two different finish line configurations before and after porcelain firing cycles, after a glaze cycle, and after cementation. MATERIALS AND METHODS: Twenty human molar teeth were prepared to receive full crowns; ten were prepared with a 90° round shoulder and another ten with a 45° chamfer finish line. Zirconium dioxide copings were fabricated using CAD/CAM technology (Lava™ system). They were then veneered with a low-fusing glass-ceramic (IPS e.max® Ceram). Finally, they were glazed and cemented with a resin-composite cement (RelyX™ Unicem, Aplicap™). Measurements for marginal adaptation using stereomicroscopy (40×) were performed at four stages: copings (S1), after porcelain firing cycles (S2), after glazing (S3), and after cementation (S4). One-way ANOVA was used to assess the influence of the finish line design on the marginal adaptation in each stage. Two-way ANOVA with repeated measurements was performed to assess the influence on the marginal adaptation of the porcelain firing cycles, glaze firing cycle, and cementation. RESULTS: The measured marginal gap mean values for the shoulder group (µm) were: 50.13 (S1), 54.32 (S2), 55.12 (S3), and 59.83 (S4). The values for the chamfer group were: 63.56 (S1), 71.85 (S2), 74.12 (S3), and 76.97 (S4). When comparing marginal gaps between specimens with two different finish lines, differences were noticed at the four studied stages (p = 0.0165, p = 0.0027, p = 0.0009, and p = 0.0009, respectively). No differences were manifested in the marginal gap measurements of the shoulder group at the different stages of fabrication (p = 0.4335); however, in the chamfer group, differences were noticed between S1 and S3 (p = 0.0042). CONCLUSIONS: Marginal adaptation was influenced by the finish line design. The firing cycles significantly affected the chamfer group; nevertheless, the marginal gap was within the range of clinical acceptability.