Monaco, Carlo

Purpose. This study evaluated the covering properties of lithium disilicate masses with varying translucencies and opacities when applied to discolored abutments, aiming to optimize esthetic outcomes in prosthetic restorations of dyschromic teeth. Materials and Methods. Four resin abutments simulating various discolorations were fabricated. Thirteen lithium disilicate frameworks of high-opacity, medium-opacity, and low-translucency masses were heat-pressed to a uniform thickness of 1 mm. Color parameters (CIE L*, a*, b*) were measured using a spectrophotometer across abutment colors. Color differences (ΔE) were calculated relative to a non-dyschromic reference abutment with different LD frameworks above and statistically analyzed using non-parametric ANOVA and multiple comparisons tests (α=0.05). Results. Significant ΔE differences were found among lithium disilicate masses on dyschromic abutments (p<0.0001). High opacity 2 mass consistently showed the best masking performance, achieving ΔE values below the perceptibility threshold for light abutments but not for darker abutments. Low translucency and medium opacity masses exhibited intermediate results, with higher ΔE values on severely discolored abutments. Conclusions. Lithium disilicate frameworks at 1 mm thickness are insufficient to fully mask dyschromic abutments while maintaining translucency. High opacity 2 mass provided the best masking, but darker abutments required additional opaque veneering. The study highlights the limitations of minimally invasive lithium disilicate restorations for severe discolorations. Furthermore, this study highlighted how, in dyschromic abutment covering, it would be easier to reach a perfect matching with a light color, such as a Vita scale A1 using a high opacity mass of lithium disilicate, rather than with more chromatic colors, which resulted in more difficult to mimic.

Purpose. The purpose of this in vitro study was to evaluate the color stability of resins for complete dentures produced with different technologies after immersion in coffee solution. Materials and Methods. 50 square-shaped specimens were prepared from different resins for complete dentures (n=10): Probase Hot (PH; Ivoclar AG), IvoBase CAD (IBC; Ivoclar AG), Ivotion Dent white (ID, Shade A2; Ivoclar AG), Dima Print Denture Base (DPDB; Kulzer), Dima Print Denture Teeth (DPDT, Shade A2; Kulzer). One side of each specimen was polished according to manufacturers’ instructions (POL) while the other one was left unpolished. (UNPOL) (T0). The specimens were immersed in a coffee solution at 37 °C for 28 days (T28).  During the storage period, the staining solution was replaced every 24 h. The CIELab color. differences (ΔEab) between the different time intervals were evaluated using a live-video. comparative spot digital colorimeter (Smart_Vision). Data were collected and statistically analyzed (p<0.05). Results. The highest color stability was recorded for IBC UNPOL (∆E= 0.32; p<0.05). All specimens scored an acceptable ∆E, except for DPDT UNPOL (∆E= 4.56) which scored significantly lower as compared to all the other specimens (p>0.05). Conclusions. Milled and 3D printed resins for complete dentures demonstrated comparable color stability to traditionally-fabricated materials. Polishing influenced the color stability only in the 3D printed white resin where the unpolished group reached an clinically unacceptable level of color change after staining.

Purpose. This observational study introduces a novel digital technique for analyzing the inclination of the tooth emergence profile and the distance between the bone crest and the cementoenamel junction (CEJ), essential in prosthetic dentistry. Material and methods. The study used cone-beam computed tomography (CBCT) scans from 24 patients, analyzing 57 teeth for emergence profile inclination and 206 teeth for the bone crest-CEJ distance. Digital measures were taken using an implant planning software. Results. The emergence profile] angle varies according to the tooth anatomy. Results indicated an increase in emergence profile angle from an average value of 13° to 19° when simulating prosthetic chamfer preparation, highlighting the importance of maintaining the natural tooth anatomy in restorative procedures. The average distances between bone crest and CEJ were 2.43 ± 1.08 mm on the buccal side, 1.96 ± 0.88 mm on the palatal side, 1.88 ± 1.05 mm on the mesial side, and 1.97 ± 0.92 mm on the distal side. Discrepancies in bone crest heights, particularly at the vestibular reference point, were found, which could affect periodontal health. Conclusion. The research provides a foundation for future studies to refine soft tissue management techniques in dental practice. These findings underscore the needing for a deeper understanding of supracrestal tissues in prosthetic rehabilitation, aiming to enhance the design of anatomical implant abutments and improve patient outcomes.

Purpose: To evaluate the effect of a staining solution on the color stability of resins for complete dentures produced with conventional and digital technologies. Materials and Methods: A total of 60 resin specimens were prepared and divided into six groups of 10 specimens each: Probase Hot (PH; Ivoclar), IvoBase CAD (IBC; Ivoclar), Ivotion Dent (ID; Ivoclar), Ivotion Dent Multi (IDM; Ivoclar), Dima Print Denture Base (DPDB; Kulzer), and Dima Print Denture Teeth (DPDT; Kulzer). One surface of each specimen was polished following the manufacturer’s instructions. The CIELab color differences were evaluated before and after 28 days of immersion in a coffee solution and measured as ∆E using two dental spectrophotometers. One specimen for each group was selected for scanning electron microscopy (SEM) analysis at baseline and at 28 days. Results: Data analysis was performed with Kruskal-Wallis test and post-hoc Dunn test for comparison. Regarding specimens analyzed with VITA Easyshade, IDM white zone (polished and unpolished) scored higher (∆E = 0.87 and ∆E = 1.15, respectively). All milled samples (IBC, ID, IDM pink zone), scored significantly higher compared to PH and DPDT. Regarding SpectroShade, IDM pink zone performed better for both polished and unpolished specimens (∆E = 1.57 and ∆E = 2.07, respectively). ID demonstrated a statistically higher color stability compared to PH and DPDT. Regarding SEM analysis, any difference in surface morphology was observed between baseline and 28-day immersion analyses. Conclusions: Color stability was significantly higher in resin specimens obtained with digital technologies compared to conventional resin specimens afterimmersion in a staining solution.

Purpose: To evaluate the influence of different Co-Cr framework manufacturing techniques on the bond strength between metal and two types of veneering ceramics with and without a metal primer. Materials and Methods: A total of 72 metal specimens were fabricated using the same Co-Cr alloy (Keramit NP, Nobil Metal) with three different techniques: ingots for casting (Keramit NP); disks for CAD/CAM milling (sinergia diskKeramit NP); and powder for selective laser melting (SLM, Keramit NP-S). Each of the 24-specimen groups was divided into two subgroups, according to the application, or lack thereof, of Nobil Metal Bonding (NMB). Two. different veneering ceramic systems were used: Ceramco iC (Dentsply Sirona) and Noritake Super Porcelain EX-3 (Noritake). The bond strength of the metal-ceramic system was evaluated using the three-point bending test and the modality of failure with SEM analysis. Three-way ANOVA with interactions was used to evaluate the influence of the metal production process, the presence or absence of the bonding agent, and the type of veneering ceramic on ceramic-metal adhesion. Results: All specimens exceeded the minimum bond strength of 25 MPa required by ISO Standard 9693-1:2012. The highest values of adhesion were registered for specimens manufactured with casted metal/Noritake veneering ceramic (40.59 ± 7.30 MPa). The lowest values were registered for specimens manufactured with CAD/CAM metal/NMB/ Ceramco iC veneering ceramic (29.47 ± 3.38 MPa). Conclusions: The fabrication method and= the type of veneering ceramic had a significant influence on the mean bond strength. The application of the NMB did not show an influence on bond strength.

Aim: The present in vitro study aimed to evaluate the depth of reading of intraoral scanners (IOSs) within the gingival sulcus. Materials and methods: A knife-edge preparation for a full crown was performed on a Frasaco model. The gingival sulcus of the scanned model was modified using a dedicated software program (Model Creator, exocad DentalCAD 2.4 Plovdiv) by setting the apical width (AW), coronal width (CW), and gingival sulcus depth (D). Two dental models with different gingival sulcus depths (1 or 2 mm) were printed using the digital light processing (DLP) technique. Each model was scanned 10 times. Seven different IOSs were used: Emerald, Trios 3, Carestream 3600, Dental Wings DWIO, CondorScan, True Definition Scanner (TDS), and Cerec Omnicam. Measurements of D values were performed using 3Shape 3D viewer software. The normality of the data distribution was evaluated using the Shapiro-Wilk test (P < 0.05). The nonparametric Levene’s test was used to check for homoscedasticity. The data were statistically analyzed using the Kruskal-Wallis test (α = 0.05) and the Nemenyi test. Results: All IOSs were able to read within the 1-mm–deep gingival sulcus, albeit with some statistically significant differences (P < 0.001). TDS and Trios 3 were able to read within the 2-mm–deep gingival sulcus (P < 0.001). Conclusions: The depth of reading of different IOSs can vary significantly. In the model with a 2-mm gingival sulcus, even in the absence of oral fluids, the depth of reading was incomplete, suggesting that deep preparations into the gingival sulcus are difficult to detect with IOSs. Keywords: intraoral scanner (IOS), gingival sulcus, depth of reading, knife-edge preparation, digital light processing

Purpose: To describe the treatment of malpositioned implants in the esthetic area using the angulated welded abutment (AWA) approach together with peri-implant soft tissue surgery. Materials and Methods: A clinical case with extreme buccal angulation of two implants in the anterior maxilla was used to illustrate the AWA technique. After implant impression-taking, digital analysis was used to determine the ideal prosthetic angulation of the abutment and the ideal position of its screw hole in relation to the gingival margin of the adjacent teeth. The AWA was designed in two combinable components that were meant to be welded together. Before the welding process, an angulated screw was included in the abutment. Since the angulated screw was inside the abutment, the screwdriver hole could be designed as narrow as possible and put in an ideal position. After periodontal and peri-implant surgery were carried out, the AWA was applied to the implants. Results: The AWA allowed correction of the prosthetic axis. Moreover, relocation of the screw hole allowed the gingival tissue to creep over the abutment. In this way, a new esthetic restoration can be placed after the mucogingival surgery. Conclusion: The excessive misangulation of the implants was efficiently recovered. Further studies are needed to evaluate long-term clinical success, and standardization of this technique is required for routine clinical use.

Purpose: To describe the possible adverse effects of sodium hypochlorite (NaOCl) solutions, highconcentration alcohol solutions, and povidone-iodine products indicated for disinfection of inanimate surfaces against human coronavirus of the severe acute respiratory syndrome (SARS-CoV) on prosthesis materials, including zirconia, lithium disilicate, and acrylic resin. Materials and Methods: A systematic literature research was conducted in the SCOPUS, PubMed/Medline, Web of Science, EMBASE, and Science Direct databases from January 2010 to February 2020 using a combination of the following MeSH/Emtree terms and keywords: “sodium hypochlorite”; “alcohol”; “ethanol”; “povidone-iodine”; “dental ceramic”; “zirconia”; “lithium disilicate”; and “acrylic resin”. Results: A total of 538 studies were identified in the search during initial screening, 44 were subject to full-text evaluation, and 24 fulfilled the inclusion criteria. Seven articles on zirconia and lithium disilicate investigated the effect of NaOCl (0.5% and 1%), 96% isopropanol, and 80% ethanol on bond strength after saliva contamination. The remaining articles evaluated color alteration, surface roughness modifications, decrease in flexural strength, and bond strength of all cleaning agents on acrylic resin. Conclusion: NaOCl solution (1%) for 1 minute is recommended to reduce SARSCoV infectivity and to minimize the risk of cross-contamination through prosthetic materials. An increase in surface roughness and color alteration on acrylic resin were recorded using 1% NaOCl, but without any clinical significance. A decrease in bonding strength was determined after using 1% NaOCl, 96% isopropanol, or 80% ethanol solutions on lithium disilicate. Silanization before the try-in procedure and the application of a second layer of silane after cleaning methods are recommended to improve the bond strength.

Purpose: To evaluate the influence of the crown-to-implant ratio (CI) on marginal bone loss (MBL) around short dental implants placed in the posterior mandible. Materials and Methods: All patients treated with short implants (7-mm length) in the posterior mandible between 1994 and 2003 at the Dental Clinic of the Department of Neuroscience of the University of Padua (Italy) were retrospectively included in the analysis. MBL and clinical CI (cCI) were measured on the radiographs. Implant characteristics including implant diameter, prosthetic type, retention mode, antagonist type, veneering material, and implant surfaces were retrieved from local medical records. A generalized linear mixed model was estimated to identify the predictors of MBL. Results: A total of 108 dental implants placed in 51 patients were included in the analysis. Mean follow-up was 16 years (range: 11 to 20 years). Mean cCI was 2.21 (SD = 0.31) with a mean crown height of 10.86 mm (SD = 0.99). Mean MBL was 1.42 mm (SD = 0.38). At multivariable analysis, cCI ≥ 2 was associated with higher MBL (regression coefficient: 0.27; 95% CI: 0.15 to 0.40), while implant characteristics, follow-up, and site were not associated with MBL. The effect of a cCI ≥ 2 was estimated in an increase of 0.28 mm in MBL (95% CI: 0.14 to 0.43 mm). Conclusion: Higher cCI was associated with greater MBL of implant-supported fixed dental prostheses in short dental implants placed in the posterior mandible, while implant characteristics, follow-up, and site were not associated with MBL. However, the increase of 0.28 mm of MBL in patients with a cCI ≥ 2 may not be clinically relevant. Keywords: crown-to-implant ratio, implant-supported dental prosthesis, marginal bone loss, prosthetic parameters, short implant