The International journal of prosthodontics最新文献

Purpose: The study aims to produce CAD-CAM reference samples for shade communication milled from the material of the restoration zirconia (ZrO2) and zirconia-reinforced lithium silicate (ZLS) and evaluate the color difference with the corresponding conventional Vita Classical (VC) shade tab. Furthermore, it aims to verify the color consistency of the materials.

Materials and methods: Five-five samples were milled out of ZrO2 and ZLS in five different colors and their color parameters were compared with the corresponding VC tabs both visually and digitally. For digital evaluation, images were taken of the samples and VC tabs and analyzed in Adobe Photoshop to extract L*a*b values. Color difference (ΔE00) was calculated using the CIEDE 2000 formula. Multilevel mixed-effects linear regression model was used to derive estimates of the mean ∆E00.

Results: Color difference was significantly higher than 1.8 ΔE00 in the case of all the ZrO2, ZLS A3, B2 and C2 samples. Color difference was also found during the visual comparison. Comparing the same color samples the ΔE exceeded 0.8 in some cases but stayed under 1.8 ΔE00 in every case and showed no color difference visually.

Conclusion: Comparing CAD-CAM samples and VC shade tabs visible and measurable color differences (ΔE00>AT50:50%) were found in the case of all ZrO2 and three out of five evaluated shades of ZLS samples. The color consistency of the blocks was acceptable. Better shade communication thus more reliable shade reproduction is achieved when reference photos are sent with a color sample made from the restoration's material.

Some of the critical clinical challenges encountered in the treatment of adult patients with deep overbite and worn dentition include correction of deep overbite, establishment of an appropriate occlusal vertical dimension (OVD), and maintenance of long-term occlusal stability. Although Angle's Class II division 2-associated deep anterior overbite is common in orthodontic treatment, simple prosthodontic treatment with great improvement of deep anterior overbite and worn dentition is infrequently reported. A 51-year-old man with Class II Division 2 malocclusion presented with hypo-divergent facial pattern, reduced lower facial height, and protuberant lips. Intraoral examination revealed unevenly worn dentition and an Angle's Class II division 2-associated deep and traumatic anterior overbite. Based on the challenges of the presentation, it was imperative to design an protocol to ensure a predictable and favorable prognosis. According to the current protocols, prosthetic treatment of occlusal rehabilitation was applied. Following the 3-month evaluation period using interim prostheses, full-mouth ceramic restorations were completed. Significant post-treatment functional and aesthetic improvements were achieved with resultant stable inter-incisal contacts either immediately after treatment or during the 2-year follow-up period. Full mouth rehabilitation offers brilliant prospects for improved function, enhanced aesthetics, and improved health of the entire stomatognathic system of Angle's Class II division 2 patient associated with deep overbite and worn dentitions.

Purpose: The aim of this article was to present a method for predicting dental materials lifetime, using in vitro thermally accelerated ageing. The technique was tested to compare the behavior of 3 resin base materials for denture.

Materials and methods: Bar-shaped samples of the poly(methyl methacrylate) PMMA based-resin Probase Hot (Probase), CAD/CAM disc Ivobase CAD (IvoCAD) and high-impact resin IvoCAP were aged in artificial saliva for 15, 30, 45, 60, 90, 120 and 180 days at 55°C, 75°C and 90°C. Flexural strength and surface roughness of the 3 resins for each ageing duration and temperature were measured for 3 samples (n=189). Using the time-temperature equivalence principle and the Arrhenius model, a master curve was constructed, the activation energy of the simulated ageing process was calculated and the lifetime of each material was estimated, based on degradation of flexural strength value over time.

Results: The mean initial flexural strength was 87.98 ± 7.37, 79.35 ± 10.01 and 97.31 ± 4.97 MPa for IvoCAD, IvoCAP and Probase, respectively. Activation energies of the ageing in artificial saliva were measured at 81.9, 82.6 and 66.2 kJ/mol, respectively, and average lifetimes at 37°C were estimated at 19.5, 14.4 and 9.2 years.

Conclusion: In this first approach to estimating the in vitro lifetime in artificial saliva of resin-based materials for dentures, the three materials met the expected criteria, validating the estimation method. Therefore, thermally-accelerated ageing and the Arrhenius model could be an interesting tool to add to routine tests used to validate new polymer materials and manufacturing processes.

Purpose: The purpose of this study is to compare the stress distribution between all-on four and all-on six treatment concept with various prosthetics framework materials through finite element analysis.

Materials and methods: A three-dimensional finite element model of edentulous maxilla was simulated using computerized topographical data of a patient. Four implants were placed according to All-on four concept. In addition to the all-on four concept, two more axial implants were placed in anterior region to create the all-on six concept. Four framework materials were investigated: Cobalt-Chrome (CoCr), Zirconium (Zr), Titanium (Ti) and Polyetheretherketone (PEEK). 100 N load was applied at anterior region, 150 N oblique load was applied at premolars and 200 N oblique load was applied at molars region simultaneously. Principal stresses in bone, the Von Mises stresses in implant and frameworks were calculated and compared.

Results: All-on six concept showed lower von Mises on implant, and framework, and principal stress values on the bone, than all-on four concept. PEEK exhibited highest stress values on bone and implants, while CoCr showed least stress values.

Conclusion: Stress distribution was influenced by the framework materials. The use of framework material with appropriate physical properties on the correct indication might be particularly important in determining the success of the implant-supported prostheses.

Purpose: This study aims to compare the surface roughness (SR), contact angle (CA), surface free energy (SFE), and bacterial adhesion of resin-based materials used in additive, subtractive, and conventional manufacturing techniques.

Materials and methods: This study involved four groups of 23 specimens: Indirect conventional resin composite (ICRC), subtractively manufactured resin composite (SMRC), additively manufactured resin composite (AMRC), and soda-lime-silica glass (SLSG). One specimen per group was analyzed by Energy Dispersive X-ray Spectroscopy (EDS) before polishing. Following the polishing procedure, SR, CA, and SFE were measured. The sterilized specimens were divided into two subgroups for Streptococcus mutans and Streptococcus mitis adhesion. One randomly selected specimen from each group was also reserved for visualization of bacterial adhesion using Scanning Electron Microscopy (SEM), and bacterial adhesion was quantified in the remaining specimens (n=10). Data for SR, CA, SFE, and bacterial adhesion were analyzed using one-way ANOVA, Tukey post-hoc tests, and Pearson correlation (α = .05).

Results: Among the resin groups, the ICRC group had the lowest SR values (P < .001). The higher CA was observed in the SMRC group than AMRC (P = .016). AMRC displayed significantly lower S. mitis adhesion compared to ICRC and SMRC (P < .001 and P = .003, respectively). A positive correlation was found between SR and S.mutans adhesion (R = .455, P < .003).

Conclusion: Resin materials designed for different manufacturing techniques exhibited diverse surface characteristics. Nevertheless, the 3D printable permanent resin demonstrated comparable S. mutans adhesion to that of ICRC and SMRC.

Purpose: To inspect the impact of polyethylene fiber (Ribbond) on the long-span, 3D-printed, interim fixed dental prosthesis regarding fracture strength.

Materials and methods: A stainless steel platform was fabricated to replicate the partial edentulism for a maxillary four-unit fixed dental prosthesis. The prosthesis was fabricated by a Formlabs SLA 3D printer. The specimens were allocated into four groups of 20 each: experimental reinforced Group A (prosthesis with a slot reinforced with fiber); experimental Group B (prosthesis with a slot filled with 3D-printed material), negative control Group C (prosthesis with a slot); and control Group D (full-contour prosthesis). Fracture strength exams were performed with a universal tester. The fracture patterns were examined. A statistical analysis was conducted using one-way ANOVA and Tukey HSD test.

Results: The control group exhibited a significantly higher mean flexural load (D: 306.32 ± 50.76 N) compared to the other groups (A: 194.37 ± 68.02 N; B: 178.25 ± 42.67 N; and C: 156.68 ± 29.73 N; [P < .001]). No differences were identified among Groups A, B, and C. The fracture pattern differed between the nonreinforced Groups B, C, and D and reinforced Group A, with catastrophic failure observed in the nonreinforced group and unseparated failure observed in the reinforced group.

Conclusions: The study findings demonstrate that the incorporation of Ribbond in 3D-printed, interim fixed dental prostheses does not significantly enhance their fracture strength. However, it does lead to a noticeable change in the fracture behavior, shifting from a complete failure to an incomplete fracture pattern.

Purpose: To describe a digital workflow for the management of the emergence profile and the restoration's finishing line on vertically prepared teeth using a digital data set.

Materials and methods: Three scans (the prepared teeth the day of the preparation, the provisional restoration placed on the preparation after soft tissue maturation, and the provisional restoration outside of the oral cavity) were combined under a common data set to provide the necessary information to design the final restoration.

Results: The digital technique presented can facilitate the implementation of the vertical preparation, because the desired finish line can be defined by the clinician and be transferred predictably to the dental lab. The current approach provides an alternative gingival management method, taking advantage of the displacement of soft tissue after vertical preparation.

Conclusions: Positioning of the final finishing line on vertically prepared teeth, management of soft tissue, and fabrication of the final restoration can be facilitated with this approach, combining a digital data set that has been obtained during a distinct phase of the treatment.

Purpose: To investigate the microscopic structure and fracture toughness of two pressable glass-ceramics-GC Initial LiSi Press (LiSi) and IPS e.max Press (e.max)-with different levels of translucency.

Materials and methods: Two groups each of LiSi and e.max, with medium opacity and high translucency levels, were examined. The crystal morphology of acid-etched specimens was observed under a scanning electron microscope (SEM). Six specimens in each group were fabricated in a square shape (12 ' 12 ' 1.5 mm) to measure translucency parameters (TP) using a spectrophotometer. Ten bar-shaped specimens in each group with dimensions of 23 x 2 x 4 mm were used to determine the fracture toughness (KIc) by a surface crack in flexure (SCF) using a universal testing machine. One-way ANOVA and Scheffe post-hoc tests were used for statistical analysis.

Results: LiSi showed fine dense crystals 1 to 1.5 μm in size, while e.max showed long rod-shaped crystals 3 to 4 μm in size. The TP values of all specimens coincided with their translucency levels. There was no statistical difference in the KIc between different translucency for both ceramics (P < .05). However, the KIc of e.max was significantly higher than that of LiSi at both translucency levels. As a result of larger and longer crystals, e.max provided better crack deviation mechanism to resist the fracture.

Conclusions: Within the limitations of this study, the translucency levels of both lithium disilicate ceramics did not affect the fracture toughness of the materials. The fracture toughness of e.max was statistically higher than LiSi.

Purpose: To assess wear, fatigue, and fracture resistance of different CAD/CAM onlays milled from monolithic zirconia (ZR), hybrid ceramic (EN), and lithium disilicate (LS) when used as abutments for removable partial denture frameworks fabricated from acetal resin (AR) or cobalt-chromium (Co-Cr).

Materials and methods: Standard onlays and RPD framework were designed and milled using CAD/CAM. Onlays were cemented with resin cement to identical teeth models. The RPD's occlusal rest surface and the ceramic onlays' rest seats were both 3D scanned before and aPer 750,000 mechanical load cycles (50 N) and 8,000 thermal cycles (5° to 55°C) in a chewing simulator. The volumetric loss was measured using 3D-image processing software, and the failure of the samples was detected using a stereomicroscope. The fracture resistance was tested by loading to failure in a universal testing machine. The fatigue failure results were analyzed with Fisher exact probability test, and the wear and fracture resistance data were analyzed using twoway ANOVA and Bonferroni post-hoc test (P < .05).

Results: A significant difference (P < .05) was found between the tested experimental groups in wear, fatigue, and fracture resistance. Zr/Co-Cr combinations exhibited the least wear and the highest fatigue and fracture resistance (P < .05), while the highest wear and least fatigue and fracture resistance were recorded for the EN/AR group (P < .05).

Conclusions: Zr onlays demonstrated a conserva+ve treatment option with superior mechanical behavior when used as an onlay abutment, regardless of the RPD framework material used. The AR framework is not recommended in the posterior region for removable partial dentures.

Purpose: To investigate the effect of BruxZir Steel treatment on the fracture resistance of zirconia threeunit bridges prepared using 5Y-PSZ-based zirconia blanks.

Materials and methods: Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Fracture resistance was analyzed with dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir Steel) was compared to the sintered control restoration (untreated cementation surface). Finite element analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load.

Results: The fracture resistance of the test restorations was significantly higher than that of the control restorations for all manufacturers considered in this study (P < .05). Furthermore, the restoration made of BruxZir Esthetic treated with BruxZir Steel had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blanks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir Steel treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of the BruxZir Steel-treated sample compared to the control.

Conclusions: The fracture resistance of 5Y-PSZ-based BruxZir Steel-treated three-unit bridges was significantly higher (min = 30%, max = 198%) than the control.