Impact of Thermal Cycling on the Vickers Microhardness of Dental CAD/CAM Materials: Greater Retention in Polymer-Infiltrated Ceramic Networks (PICNs) Compared to Nano-Filled Resin Composites

Aim: This study assessed the color and translucency stability of a polymer infiltrated ceramic network (PICN) and compared it with a resin composite (RC) and a feldspathic ceramic (FEL). Methods: Disc-shaped samples of a PICN (Vita Enamic), a feldspathic ceramic (Vitablocks Mark II), and a resin composite (Brava block) were prepared from CAD/CAM blocks. PICN and RC surfaces were finished with a sequence of polishing discs and diamond paste. FEL samples received a glaze layer. The samples were subjected to 30-min immersions in red wine twice a day for 30 days. CIEL*a*b* coordinates were assessed with a spectrophotometer at baseline and after 15 and 30 days of immersion. Color alteration (ΔE00) and translucency parameter (TP00) were calculated with CIEDE2000. Average roughness was measured before the staining procedures. Color difference and translucency data were analyzed with repeated-measures ANOVA and Tukey’s tests. Roughness was analyzed with the Kruskal-Wallis test. Results: Roughness was similar among the experimental groups. All materials had their color alteration significantly increased from 15 to 30 days of staining. PICN reached an intermediate ΔE00 between FEL and RC at 15 days. PICN revealed a color alteration as high as the composite after 30 days. No statistical difference was observed regarding translucency. Conclusion: PICN was not as color stable as the feldspathic ceramic at the end of the study. Its color alteration was comparable to the resin composite when exposed to red wine. However, the translucency of the tested materials was stable throughout the 30-day staining.

Effect of thermocycling and bleaching on the translucency and opalescence of monolithic CAD-CAM dental ceramics.

To investigate the effect of a universal adhesive on the bond strength of composite cements to a polymer-infiltrated ceramic network. Shear bond strength to a polymer-infiltrated ceramic network (Vita Enamic) and to its polymer and ceramic components was assessed on polished surfaces using either a conventional dual-curing resin (RelyX Ultimate) or self-adhesive composite cement (RelyX Unicem 2 Automix). Substrate surfaces were either not pretreated or a silane coupling agent (Vitasil), a universal adhesive (Scotchbond Universal Adhesive), or both were applied. Further, the shear bond strength to polymer-infiltrated ceramic network was evaluated after etching with 5% hydrofluoric acid (Vita Ceramics Etch) of 0, 15, 30, 60 or 120 s without or with application of silane, universal adhesive, or both (n = 10). Statistical analysis was performed using the Kruskal-Wallis test (p < 0.05) followed by post-hoc comparisons with Bonferroni correction. No bond (0 MPa) was formed to the polished polymer-infiltrated ceramic network or to its components for either cement. Application of silane resulted in low mean bond strengths (4 to 5 MPa) to the ceramic. The universal adhesive bonded mainly to the polymer part of the polymer-infiltrated ceramic network. The best bonding performance for both cements was achieved when silane and universal adhesive were applied on the polymer-infiltrated ceramic network. Etching for 30 s or 60 s resulted in the highest mean shear bond strengths for all pretreatment groups (p < 0.05). The best bonding performance of the self-adhesive dual-curing composite cement RelyX Unicem 2 Automix was found on the HF-etched polymer-infiltrated ceramic network. The conventional dual-curing composite cement RelyX Ultimate with Scotchbond Universal Adhesive may bond chemically to the polymer part of the polymer-infiltrated ceramic network. To achieve the highest bond strengths for both cements, the polymer-infiltrated ceramic network should be etched for 30 to 60 s, followed by the application of silane and universal adhesive.

To evaluate the microtensile bond strength of four dental computer-aided design/computer-aided manufactured (CAD/CAM) ceramics after application of four different surface treatments. Four dental CAD/CAM ceramics were tested: feldspathic ceramic (VITABLOCKS-Mark II), polymer-infiltrated ceramic network (VITA ENAMIC), zirconia-reinforced lithium silicate (VITA SUPRINITY), and yttria-stabilized zirconia (VITA YZ T). Four surface treatments were applied: no treatment, 5% hydrofluoric acid-etching, airborne particle abrasion, and tribochemical silica coating. The ceramic blocks were repaired with nanohybrid composite (Tetric N-Collection). Sixteen test groups of 12 specimens were prepared. After thermocycling, microtensile bond testing was performed. The microtensile strengths values were statistically analyzed using two-way analysis of variance and Tukey's post-hoc test. Repaired feldspathic and resin polymer-infiltrated ceramic network ceramics demonstrated superior microtensile bond strengths compared to zirconia-reinforced lithium silicate and yttria-stabilized zirconia. Etched feldspathic and polymer-infiltrated ceramic network ceramics had higher bond strength than the untreated groups. Surface treatments did not affect the bond strength of zirconia-reinforced lithium silicate and yttria-stabilized zirconia with the exception of etching, which reduced the bond strength of yttria-stabilized zirconia. Feldspathic ceramic and polymer-infiltrated ceramic network were repaired with dental composite after surface etching with hydrofluoric acid. Repair of zirconia-reinforced lithium silicate and yttria-stabilized zirconia did not demonstrate promising results. Repair of feldspathic ceramic and polymer-infiltrated ceramic network restorations may be a cost-effective means to promote the longevity of dental restorations. However, zirconia and zirconia-reinforced lithium disilicate restorations do not offer such an option.

Mechanical properties of polymer infiltrated ceramic network (PICN) fall in range between that of resin-based composites and glass ceramics. The aim of this study was to evaluate the mechanical properties of a newly fabricated polymer infiltrated lithium-disilicate network (PILN) and compare it with the commercially available PICN whose ceramic network is feldspathic ceramic (Vita Enamic, Vita Zahnfabrik, Bad Säckingen, Germany). Commercially available lithium disilicate based glass–ceramic CAD/CAM blocks (IPSe.max, Ivoclar, Schaan, Liechtenstien) were ground into a fine powder and used to produce a porous ceramic network (25% porosity). Resin was infiltrated and polymerized to form a dense PILN. Porosity percentage and microstructure were investigated. Single crowns were milled from the newly fabricated PILN blocks and from Vita Enamic then fracture load test was performed. Rectangular specimens were prepared from both materials, afterwards, flexural strength, fracture toughness, brittleness and Vickers’ hardness tests were investigated. Data were analyzed using independent sample-t test and paired sample-t test (n = 12, α = 0.05). Results showed that newly formulated PILN had significantly higher fracture resistance (1640 N) and superior fracture toughness (2.6 MPa m1/2) compared to the control which showed (1103 N) fracture load and (1.7 MPa m1/2) fracture toughness. PILN had lower brittleness index (0.89 μm1/2) than Vita Enamic (1.48 μm1/2) reflecting superior milling qualities. It was concluded that newly fabricated PILN material showed enhanced mechanical properties.

ObjectivesThe aim of this in vitro investigation was to assess and compare surface characteristics and nanomechanics of model polymer infiltrated ceramic network (PICN) materials compared to CAD/CAM resin composite blocks. Material and methodsFour model PICN materials sintered at different temperatures (Exp.125, Exp.130, Exp.135 and Exp.155) were investigated along with three CAD/CAM resin composites; Lava Ultimate (LU), Cerasmart (CS) and Grandio Bloc (GB), and one commercial PICN block - Vita Enamic (VE). Forty samples were prepared with dimensions of 14 × 12 × 2 mm for resin ceramic and VE blocks and 15 × 2 mm discs for model PICN materials. All samples were scanned using atomic force microscopy (AFM) (n = 3) at multiple locations and two different scan sizes (20 ×20 µm and 3 ×3 µm). Surface optical gloss (n = 5) at 60° was also determined for all the groups. Data were analysed using one-way ANOVA, and Tukey’s post hoc test (α = 0.05). ResultsResin composite blocks showed smoother surfaces compared to the PICN materials. The average surface roughness values (Ra) ranged from 7.75 nm to 31.21 nm and the gloss value ranged from 56.43 GU to 91.81 GU. The highest surface roughness value was found for Exp.125 (31.21 nm) while LU showed the lowest roughness value (7.75 nm) (the difference being statistically significant: p = 0.001). Variation was noticed in terms of nanomechanical mapping within and between the groups. Images generated from the elastic modulus map values clearly indicated that all PICN materials had more than one phase and very different components. ConclusionsCAD/CAM resin composite blocks exhibited higher gloss and lower roughness values compared to PICN materials. However, both the commercial and model PICN materials showed more stiffness than resin composite with the presence of at least two different phases. Sintering temperature appears to have a significant effect on material topography and nanomechanical properties. The model PICN sintered at 1550 °C showed a comparable range of elastic modulus values to those of enamel.

Polymer-infiltrated ceramic network (PICN) composites are recognized for their mechanical properties, closely resembling natural tooth enamel. However, the low fracture toughness of current PICN materials limits their broader use. This study draws inspiration from the natural enamel rod–sheath architecture to develop bionic PICN composites with an enamel-like structure, enhancing their fracture toughness for dental restorations. By simulating the morphology and arrangement of enamel rods, 3 types of zirconia ceramic scaffolds were designed and manufactured by digital light processing technology, which featured a straight-rod structure, a gnarled-rod structure, or a natural rod distribution structure. The scaffolds were surface treated and resin infiltrated to obtain enamel-structured PICN material, wherein the infiltrated resin formed a rod-sheath structure. With VITA Enamic (VE) as control, the enamel-like composites were characterized in detail for their microstructure, flexural strength, fracture toughness, flexural modulus, friction and wear properties, adhesive properties, and cell compatibility. Results show that the PICN with the natural rod distribution structure had the highest flexural strength and fracture toughness among the 3 PICN composites, but there was no significant difference in their moduli. Its strength and modulus were slightly lower than those of VE, but its toughness was 7.0 ± 0.6 MPa·m1/2, around 7 times that of VE. The fracture mode in the ceramic phase was mainly transgranular, while ductile fracturing of the resin phase contributed to toughening. Furthermore, it exhibited superior wear resistance when compared with VE and bovine enamel. After sandblasting and priming, its bond strength to bovine dentin was comparable to that of VE after standardized treatment. Cytotoxicity assays confirmed high cell viability and healthy morphology. Overall, these results indicate that the newly developed PICN composites offer significant improvement over current dental materials, making them promising candidates for bonded prosthetic applications.

Objectives: The repair bond strength of the composite to a polymer-infiltrated ceramic network (PICN) restoration may vary depending on the repair protocol used and may decrease over time. The aim of this study was to evaluate the effects of different repair protocols and artificial aging on shear bond strength (SBS) of a composite for repair to PICN material. Materials and methods: Artificially aged specimens (5000 thermal cycles between 5°C and 55°C) sliced from PICN CAD/CAM blocks (Vita Enamic) were randomly divided into 5 groups according to the repair protocol applied: 1) TS: tribochemical silica coating-Single Bond Universal 2) ES: etching with hydrofluoric acid (HF)-Single Bond Universal 3) EU: etching with HF-Ultradent Porcelain Repair System 4) GU: grinding with diamond bur-Ultradent Porcelain Repair System 5) GI: grinding with diamond bur-Ivoclar Vivadent Ceramic Repair System. After receiving a composite resin cylinder for repair, specimens were further divided into 2 subgroups considering artificial aging procedure (n=12): baseline/aging (5000 thermal cycles between 5°C and 55°C). SBS tests were performed by using a universal testing machine and failure types were classified as cohesive failure in PICN, cohesive failure in composite, adhesive, and mixed. The SBS data were analyzed with 1-way ANOVA,factorial ANOVA, least signifigance difference, and Duncan tests (α=0.05). Failure modes were calculated as a percentage. Results: The mean SBSs for ES and GU were higher than TS at baseline (p&amp;lt;0.05). After aging procedure, EU and GU showed lower SBS than ES (p&amp;lt;0.05). Aging decreased the SBS for ES, EU and GU compared to baseline (p&amp;lt;0.05). The failure modes in general were observed as cohesive in PICN at baseline, while the only group that showed cohesive failure predominantly was EU after aging. Conclusions: Considering the time-efficiency and effectiveness, etching with HF followed by Single Bond Universal application can be recommended as the intraoral repair protocol for PICN.

Polymer-infiltrated ceramic network (PICN), commonly referred to as 'hybrid ceramic,' represents a unique class of materials that integrate glass-ceramic and polymer. Vita Enamic is the only PICN material available on the market, benefiting from over a decade of clinical use and research. It offers a balance between pure ceramics and direct and CAD/CAM composites, leveraging their advantages while minimizing their disadvantages in the context of severe tooth wear (TW) treatment. PICN exhibits properties that closely mimic tooth tissue, particularly its wear behavior and stiffness, while polymer promotes the material's ability to dampen occlusal stress. The introduction of PICN prompted the One-step No-prep technique for treating severe TW. This noninvasive and straightforward method provides a cost-effective alternative to traditional indirect approaches. The present article reviews the properties of PICN and compares them with other materials used in TW treatment. Clinical cases illustrate the One-step No-prep technique for generalized severe TW and the orthodontic-assisted One-step No-prep technique for localized cases, which is an evolution of the Dahl concept. The clinical and scientific background of PICN as used in the One-step No-prep technique are discussed and the excellent clinical outcomes from various perspectives are highlighted. The article also addresses the limitations of PICN such as the tendency for chipping at thin occlusal borders of posterior restorations and a lower gloss on occlusal surfaces compared with pure ceramics. These limitations do not affect patient satisfaction but could be improved upon. Despite these drawbacks, PICN appears to be suitable for managing TW in a noninvasive way.

To investigate and compare the translucency and color stability of a newly introduced polymer-infiltrated ceramic network (PICN) material (Crystal Ultra) to those of clinically well-established restorative materials. A total of 80 specimens measuring (12 × 14 × 1 mm ± 0.05 mm) were prepared from five CAD/CAM (IPS e.max (IPS), Lava Ultimate (LU), Cerasmart (CS), Vita Enamic (VE), Crystal Ultra (CU)) high translucency (HT) blocks in A2 or equivalent shades. Specimens were randomly allocated into two groups (A and B) (n = 8), and were subjected to 5,000 thermal-cycles (TC). This was followed by one-week immersion of group A specimens in coffee (staining) solution and group B specimens in distilled water. Following immersion, the specimens from both groups were further subjected to 5,000 TC. A spectrophotometer was used to measure the translucency parameter (TP) and color change (ΔE00 ) of the samples using CIELAB color coordinates at baseline, after 5,000 TC, following immersion, and after further 5,000 TC. Color stability was evaluated using the CIEDE2000 formula. Data were analyzed by non-parametric tests (α = 0.05). The TP values of the CAD/CAM materials ranged from 18.0-22.0. Following the initial TC, the changes in TP values were significant for VE (p = 0.012). Coffee immersion and further TC significantly impacted the TP values of PICN (VE and CU) materials compared to glass- ceramics (IPS), and resin nanoceramic (CS and LU) materials (p = 0.012). The comparison between CAD/CAM materials at different intervals showed a significant difference in the TP values (p < 0.01). The materials showed perceptible color changes following the initial TC except for PICN materials which demonstrated acceptable color changes. The major color difference was noticed for the resin nanoceramic specimens immersed in coffee; LU and CS showed higher color changes (ΔE00 = 2.45 and 2.09, respectively) than VE and CU (ΔE00 < 1.8). The translucency of the newly introduced Crystal Ultra PICN material was low compared to the resin nanoceramics and lithium disilicate glass-ceramic. The Crystal Ultra material exhibited better color stability compared to resin nanoceramics, but higher color change when compared with Vita Enamic PICN and lithium disilicate glass-ceramic CAD/CAM materials.

To evaluate the effect of in-office and at-home bleaching agents on color changes (ΔE00 ), translucency (TP00 ), whiteness (WID ), surface roughness (Ra ), and surface topography (Rsk and Rku ) of a resin nano-ceramic and a polymer-infiltrated ceramic network CAD/CAM material. Sixty specimens (6 mm × 7 mm × 1.3 mm) were prepared from Lava Ultimate (LU) and Vita Enamic (VE). The specimens were divided into 6 groups according to the bleaching agents applied (n = 10/group): control, Perfect Bleach Office + (PBO), Opalescence Boost (OB), Perfect Bleach (PB) with 10% and 16% carbamide peroxide and Whiteness Perfect (WP). ΔE00 values were calculated before and after bleaching procedures with a spectrophotometer using the CIEDE2000 formula. ΔTP00 and ΔWID values were calculated for each material. Ra , Rsk , and Rku values of the specimens were evaluated with an Atomic Force Microscope. Two-way ANOVA was used for statistical analyses of the parameters measured after bleaching. For pairwise comparisons, Tukey test was performed. For LU, no statistically significant difference among the ΔE00 values of the groups was observed (p = 1.000). For VE, only WP group presented significantly higher values (2.12 ± 2.66) than the other groups (p < 0.001). For both materials; ΔTP00 values of at-home bleaching groups were significantly higher than in-office bleaching groups and control group (p < 0.001). For VE, ΔWID values did not demonstrate statistically significant difference (p = 1.000); however, for LU, PBO applied group showed statistically higher ΔWID values (3.00 ± 2.38) (p = 0.010) and WP applied group showed lower ΔWID values (0.47 ± 0.31) than the other groups (p = 0.030). For both LU and VE, there was no statistically significant difference among the groups regarding Ra (F = 4.544), Rsk (F = 2.369), and Rku values (F = 2.391) (p = 1.000). All of the VE groups presented Ra values higher than 0.2 µm. The optical properties of LU and VE after bleaching applications were affected by the contact time with bleaching agents rather than concentration. Bleaching procedure had no effect on the surface properties of these materials.

The aim of the present study was to evaluate the fatigue to cyclic and static resistance of indirect restorations with different preparation designs made either of lithium disilicate (LS) or polymer-infiltrated ceramic network (PICN). Eighty-four (n = 84) molars were chosen, endodontically treated, and prepared with standardized MOD cavities. The molars were randomly divided into 6 study groups (n = 14) taking into account the "preparation design'' (occlusal veneer with 1.2 mm occlusal thickness; overlay with 1.6 mm occlusal thickness; adhesive crown with 2 mm occlusal thickness) and the "CAD/CAM material'' (E-max CAD, Ivoclar vivadent; Vita Enamic, Vita). A fatigue test was conducted with a chewing simulator set at 50 N for 1,500,000 cycles. Fracture resistance was assessed using a universal testing machine with a 6 mm diameter steel sphere applied to the specimens at a constant speed of 1 mm/min. A SEM analysis before the fracture test was performed to visually analyze the tooth-restoration margins. A statistical analysis was performed with a two-way ANOVA and a post-hoc pairwise comparison was performed using the Tukey test. The two-way ANOVA test showed that both the preparation design factor (p = 0.0429) and the CAD/CAM material factor (p = 0.0002) had a significant influence on the fracture resistance of the adhesive indirect restorations. The interaction between the two variables did not show any significance (p = 0.8218). The occlusal veneer had a lower fracture resistance than the adhesive crown (p = 0.042) but not lower than the overlay preparation (p = 0.095). LS was more resistant than PICN (p = 0.002). In conclusion, in the case of endodontically treated teeth, overlay preparation seems to be a valid alternative to the traditional full crown preparation, while occlusal veneers should be avoided in restoring non-vital molars with a high loss of residual tooth structure. LS material is more resistant compared to PICN.

CAD-CAM resin-ceramic material wear: A systematic review

BackgroundImplant and superstructure provide a complex system, which has to withstand oral conditions. Concerning the brittleness of many ceramics, fractures are a greatly feared issue. Therefore, polymer-infiltrated ceramic networks (PICNs) were developed. Because of its high elastic modulus, the PICN crown on a one-piece zirconia implant might absorb forces to prevent the system from fracturing in order to sustain oral forces. Recommendations for the material of superstructure on zirconia implants are lacking, and only one study investigates PICN crowns on these types of implants.Accordingly, this study aimed to examine PICN crowns on one-piece zirconia implants regarding bond strength and surface wear after long-term chewing simulation (CS).MethodsTwenty-five hybrid ceramic crowns (Vita Enamic, Vita Zahnfabrik) were produced using computer-aided design/computer-aided manufacturing (CAD/CAM) technology and adhesively bonded (RelyX™ Ultimate, 3M ESPE) to zirconia implants. Twenty of the specimens underwent simultaneous mechanical loading and thermocycling simulating a 5-year clinical situation (SD Mechatronik GmbH). Wear depth and wear volume, based on X-ray micro-computed tomography volume scans (Skyscan 1172-100-50, Bruker) before and after CS, were evaluated.All crowns were removed from the implants using a universal testing machine (Z010, Zwick GmbH&Co.KG). Subsequently, luting agent was light microscopically localized (Stemi 2000-C, Zeiss).With a scanning electron microscope (SEM, Phenom™ G2 pro, Phenom World), the area of abrasion was assessed.ResultsAfter CS, none of the tested crowns were fractured or loosened.The maximum vertical wear after CS was M = 0.31 ± 0.04 mm (mean ± standard deviation), and the surface wear was M = 0.74 ± 0.23 mm3.The pull-off tests revealed a 1.8 times higher bond strength of the control group compared to the experimental group (t(23) = 8.69, p < 0.001).Luting agent was mostly located in the crowns, not on the implants.The area of abrasion showed avulsion and a rough surface.ConclusionsPICN on one-piece zirconia implants showed high bond strength and high wear after CS.

To introduce a novel approach for full-mouth rehabilitation of severely worn dentition using polymer-infiltrated ceramic network (PICN) computer-aided-design and manufacturing (CAD-CAM) restorations, without tooth tissue preparation and provisional phase. Three patients with generalized tooth wear, suffering from dental pain, masticatory dysfunction, bruxism and neck and back pain, were selected and treated in collaboration with physiotherapists. Occlusal analyses were performed and full-mouth diagnostic wax-ups were designed on the basis of estimated tissue loss. Deficient direct restorations were replaced and low-thickness PICN (Vita Enamic) restorations (up to 0.2 mm) were CAD-CAM designed from wax-ups, milled, tried-in and then bonded within two consecutive days. To mask palatal veneers, either buccal direct composites or glass-ceramic veneers were later performed. An occlusal splint was realized. Clinical results were shown to be successful after a follow-up of 22, 18, and 13 months, respectively. The absence of provisional phase did not engender any inconveniences. Patient reported outcomes were very positive, showing a reduction in neck and back pain and a well-being increase. The proposed protocol is particularly minimally invasive and straightforward compared to classical techniques. PICNs exhibit several advantages compared to other materials. Preliminary results of this multidisciplinary approach are promising but deserve further clinical research. The development of CAD-CAM technologies offers the possibility of improving treatment of severe worn dentition, reducing chairtime and need of tooth tissue preparation, and introducing a new class of composite materials (hybrid ceramics), which exhibit interesting properties for this indication. The influence of the proposed multidisciplinary approach, particularly the collaboration with physiotherapists, needs to be further explored with respect to treatment of associated symptoms, such as masticatory muscles hypertrophy and neck pain.