Long-Term Bonding Efficacy of CAD/CAM Hybrid Restorative Materials and Universal Adhesives.

OBJECTIVES: In-office and lab milled prostheses are the staple for indirect restorations. It is therefore critical to determine their long-term bonding durability. METHODS: CAD/ CAM blocks of two classes of restorative materials: 1) a nano-ceramic reinforced polymer matrix (NCPM) and, 2) a polymer-infiltrated ceramic network (PICN) were bonded using four different universal adhesives (UA) and silane systems. A lithium disilicate glassceramic (LDS) was used as a reference. The blocks were bisected and bonded with different UA/resin-cement pairs. Bonded blocks were then cut into 1.0x1.0x12.0 mm bar specimens for microtensile bond testing. Half the bars were subjected to bond strength testing immediately and the other half after aging by 50,000 thermal cycles between 5°C and 55°C. ANOVA and post-hoc tests were used to compare mean bond strength among groups. RESULTS: NCPM presented consistently high bond strength regardless of bonding techniques, while the bond strength of PICN and LDS were lower when bonded with UA relative to traditional silanes. The more hydrophilic UA produced higher bond strengths. DISCUSSION: Glass-ceramics exhibited lower bond strength with UA than the conventional etch-rinse-silane techniques. However, UAs preserved bonding interface in the long-term. SIGNIFICANCE: NCPM displayed superior bond strength relative to PICN and LDS regardless of the type of adhesives and bonding techniques.

Patient Satisfaction and Accuracy of Partial Denture Frameworks Fabricated using Conventional and Digital Techniques.

This case report compares a conventional and a digital workflow for manufacturing metal frameworks for maxillary and mandibular removable partial dentures (RPDs). Two sets of maxillary and mandible RPDs were produced. The metal framework of one set of RPDs was produced conventionally using the lost wax casting technique. Intraoralscanning and computer-aided designing (CAD) were used to fabricate the metal frameworks of the other set of RPDs using direct metal laser sintering (DMLS) technology. The accuracy of fit of the two sets of RPDs was evaluated after 3 months using replica models. Patient satisfaction was assessed. Two years later, the fit accuracy of the DMLS prosthesis and patient satisfaction were re-evaluated. The accuracy of fit in the maxillary RPD with the DLMS manufactured metal framework showed better results in all areas except areas of rests (457 vs. 421 µm) and the major connector (850 vs. 512 µm). The mandibular RPD with DLMS manufactured metal framework showed only in the areas of the reciprocal arm and major connector better fit accuracy compared to the conventional RPD. The patient satisfaction with the DLMS manufactured RPDs was rated equally to the conventional one. The use of digital technologies in manufacturing RPDs seems promising regarding accuracy and patient satisfaction.

Comparative Evaluation of Apically Extruded Debris During Root Canal Preparation Using Three Different File Systems Applied Under 2.5% Sodium Hypochlorite or 2% CHX Irrigation.

The chemomechanical cleaning of the root canal system is performed using manual and rotary files. This study aimed to compare the effect of ProTaper, Reciproc and HyFlex rotary files considering 2.5% sodium hypochlorite and 2% chlorhexidine (CHX) as irrigating solutions on apical extrusion of intracanal debris. Single-canal mandibular premolars (N=165) were evaluated. The teeth were divided into 6 experimental groups (N=25) for root canal instrumentation using 3 file systems, (Reciproc, HyFlex and ProTaper) and two irrigation solutions, namely 2.5% sodium hypochlorite or 2% CHX. Fifteen teeth were also assigned into three control groups (n=5) with saline as irrigation solution. Eppendorf tubes were weighed and the teeth were placed inside. The canals were instrumented and the tubes weighed to determine the dry weight of extruded debris. Data were analyzed using one-way ANOVA and Bonferroni test (α=0.05). The mean amount of extruded debris using the sodium hypochlorite solution was significantly higher than other irrigating solutions (p⟨0.001). The mean amount of extruded debris using the Reciproc file system was significantly higher compared to ProTaper and HyFlex (p⟨0.001). The use of the sodium hypochlorite solution, single-file systems and reciprocal movement are associated with higher debris extrusion and might be associated with higher risk of postoperative pain.

Evaluation of Clinical Periodontal Parameters of Abutment Teeth Supporting Distal-Extension Base Removable Partial Dentures: A Cross-sectional Study.

To assess the clinical periodontal status of abutment teeth in regards of different design components of distal-extension removable partial dentures. Subjects (N=100) with acrylic or cobalt-chromium distal-extension removable partial dentures were enrolled and their periodontal parameters plaque and gingival indices [PI, GI], probing depths [PD], clinical attachment loss [CAL] and a mobility index [MI] evaluated. Denture base type, major connector, occlusal rests position, design of direct retainers, retention, stability and denture wearing habits were further evaluated. Acrylic RPDs were associated with higher mean±SE PI [1.70±0.74], GI [1.76±0.55], PD scores [2.47±1.02 mm] and CAL values [4.46±2.11 mm] compared to CO-CR RPDs [p⟨0.05]. For abutments, the PI [1.6±0.83], GI [1.72±0.57], PD [2.32±1.03] and CAL [4.26±2.08] were higher than their non-abutments counterparts [p⟨0.05]. CAL scores were found to be significantly higher for mandibular abutments compared to maxillary ones [P=0.002]. The highest PI [1.83±1.10] and GI [2.00±0.00] scores were associated with lingual bars and horse-shoe connectors, respectively. Full palatal coverage and lingual plates were associated with the highest PD [2.80±0.48] and CAL [4.70±0.37] scores. Acrylic RPDs, type of major connector, wrought wire clasps and distal occlusal rests may be considered as risk factors for periodontal disease progression in distal-extension removable partial denture wearers.

Effect of Thickness and Translucency on Color Change and Masking Ability of Ceramic Materials used for Laminate Veneers.

This study evaluated the effect of the thickness and translucency of lithium disilicatebased glass ceramics on resin composite substrates on color change and masking effect. Laminate veneers were fabricated using IPS e.max CAD (A1) blocks with two different light transmittance values (High translucent [HT], Low translucent [LT]). Slices of two different thicknesses (0.3 mm, 0.5 mm) were obtained (n=10) and laminate veneers were cemented on the resin composite substrates of two different shades (A2, A3.5). The color change (ΔE values) was evaluated with the CIELab color system using a spectrophotometer, while the masking effect was calculated. The data were analyzed using independent-samples t-test and two-way analysis of variance. The ceramic thickness and translucency had a significant effect on final color and masking. When HT was used, and the laminate veneer thickness decreased (0.3 mm), the masking effect in ΔE values were lower (p⟨0.05). The ΔE values (⟩3.7) were clinically unacceptable. With the increase in thickness, translucency of porcelain laminate veneers decreases showing better color masking ability. Veneer thickness seems to be more effective on the restoration's masking ability than the shade of the substrate and translucency. Cinically, in case a 0.5-mm or thinner laminate veneer is planned, tooth color, resin cement and ceramic type should be considered.

Evaluation of New Alkasite Based Restorative Material for Restoring Non- Carious Cervical Lesions- Randomized Controlled Clinical Trial.

Two different restoration materials, an alkasite-based resin composite and a resinmodified glass ionomer cement were used to assess restoration of non-carious cervical dental lesions. This split mouth randomized controlled trial included 40 patients. After randomization both sides of the dental arch were restored with either an alkasite-based (Cention N, Ivoclar Vivadent) or a resin-modified glass ionomer cement (Voco GmbH) restoration. The placed fillings were evaluated by blinded additional operators 1, 6 months and 1 year after to the USPHS criteria (retention, marginal integrity and discoloration, anatomical form and secondary caries). Data were analyzed using Kendall's Coefficient of Concordance test and Chi-square tests using SPSS software (SPSS Inc., Version 20) (P=0.05). As for retention and anatomic form both materials performed similar after one month. However, the retention and anatomic form for alkasite based restorative Cention showed significantly better results after 6 months (p=0.013/p=0.003) and one year (p=0.026/p=0.008). The resin modified glass ionomer restoration showed higher discoloration after 6 months (p=0.025) and one year (p=0.018), while Cention performed better regarding marginal integrity at all time intervals. No secondary caries occurred. Alkasite based restorative materials displayed superior technical, mechanical and aesthetical performance in a follow-up period of one year and can therefore be recommended as an alternative to resin-modified glass ionomer cements.

Immediate and Late Repair of Microhybrid Resin Composites: Effect of Silane Coupling Agent, Universal Adhesives and Photo Polymerization.

This study investigated the effect of silane coupling agent and universal adhesive application on repair bond strength of resin-based composite after bur grinding. Microhybrid resin composite (Charisma Smart) blocks (N=80; 8x8x4 mm3) were prepared, aged (37°C; 1 month), roughened, etched and randomly divided into two groups. Silane was applied to half of the groups (Porcelain Primer, Bisco), before one of the following universal primers/adhesives was applied: a) Scotchbond Universal (3M), b) All-Bond Universal (Bisco), c) G-Premio Bond (GC), and d) Clearfil SE Bond (Kuraray). In each adhesive group half of the group was photo-polymerized. The blocks were repaired with the same size resin composite and segmented into beams. Half of the beams were subjected to micro-tensile bond test (1 mm/min), while the other half was aged (37°C; 6 months) prior to testing. Failure modes were analyzed using Scanning Electron Microscopy (SEM). Data were analyzed using repeated measures of ANOVA, Tukey's post-hoc, and paired t-tests (alpha=0.05). The silane application did not affect the repair bond strength regardless of photo-polymerization of the adhesive resin. The repair bond strength decreased significantly after 6 months when adhesive resin was not photopolymerized (p⟨0.05). Photo-polymerizing universal adhesives might ensure higher repair bond strength and its maintenance after aging.

Evaluating the Bond Strength of a Polymer Infiltrated Ceramic Network to Zirconia Using the Crossbeam Push-Off Method.

Porcelains and glass-ceramics have been used to produce CAD-milled veneers and crowns for zirconia copings and implant-abutments. This study evaluated the bondstrength of a polymer-infiltrated-ceramic-network to zirconia using two adhesive cement systems: Panavia 21 and Multilink Automix. Lithium disilicate and feldspathic porcelain were also tested as reference CAD-On materials. Long beams (3x6x40 mm³) of zirconia and short beams (3x6x15 mm³) of the CAD-On materials were prepared. Zirconia and each CAD-On material were bonded in a crossbeam arrangement and subjected to a modified tensile bond-strength test. Half of the samples in each group (n=10) were tested 5 days after bonding (baseline) and the remaining (n=10) underwent aging (50,000 thermocycles at 5°C and 55°C) prior to bond-strength testing. The effects of material, cement, and aging on the tensile bond-strength were tested using a three-way ANOVA. The reference lithium disilicate/Multilink system showed no significant differences in bond strength compared to polymer-infiltrated-ceramic-network and porcelain. The long-term retention of polymer-infiltrated-ceramic-network was not statistically different compared to the baseline values and the two reference materials. With comparable bond strength between all materials, polymer-infiltrated-ceramic-network is the favorable choice for CAD-On to zirconia copings and implant-abutments due to its superior resistance to fatigue fracture relative to porcelain.

Evaluation of Smear Layer Removal and Antimicrobial Efficacy of HybenX Against Enterococcus Faecalis Biofilm.

To evaluate the antibacterial efficacy of HybenX, an endodontic irrigant against Enterococcus faecalis biofilm and determine its efficacy in removal of smear layer. Forty root canals were inoculated with E. faecalis for three weeks, divided into 4 groups and irrigated with: Group1: 5 ml 2.5% sodium hypochlorite; Group2: 5 ml 2% chlorhexidine gluconate; Group3: 5 ml HybenX; Group4: 5 ml distilled water (control). Dentin shavings were collected and plated on agar plates, followed by colony forming unit (CFU) determination. For smear layer removal examination, 30 single rooted teeth were instrumented and divided into 3 groups and treated with: GroupI: 5 ml of 17% EDTA; GroupII:5 ml of HybenX; and GroupIII: 5 ml of distilled water. Samples were then subjected to SEM examination. All irrigants showed a significant reduction in CFUs compared to the control group (P⟨ .001), but none compared to each other. Regarding smear layer removal in the apical third, EDTA removed smear layer more effectively than HybenX (P = .014). HybenX demonstrated good antimicrobial efficacy against E. faecalis biofilm and removed the smear layer effectively in coronal and middle third of the root canal system. HybenX can be considered as a promising irrigating agent in root canal treatment of infected teeth.

Evaluation of Adhesion Protocol for Titanium Base Abutments to Different Ceramic and Hybrid Materials.

Scientific evidence regarding conditioning of different ceramic and hybrid materials and their bonding on titanium abutments is lacking. Titanium disks (Tritan) (N=450, n=15) were randomly cemented onto five different ceramic and hybrid materials, namely 1. Zenostar T, 2. Lava Ultimate, 3. IPS e.max CAD, 4. Vita Enamic multicolor and 5. G-ceram using three different cements, Panavia 21, TheraCem and Multilink hybrid abutment. Half of all specimens were thermocycled (5000 cycles, 5-55°C), while the other half were kept dry. Macro shear bond testing was conducted using a universal testing machine. Failure types were classified using a digital microscope. Data was statistically analyzed with three-way ANOVA and Tukey HSD post hoc tests. Both the ceramic (P⟨0.0001) and cement type(P⟨0.0001) significantly affected the shear bond strength(MPa), while thermocycling did not (P⟩0.05). The incidence of cohesive (50.34%) and adhesive failures (49.66%) were not significantly different. As for implant superstructures, when ceramics are bonded to titanium bases, the ceramic and cement type both have an impact on the bond strengths along with the conditioning and bonding protocols for each substrate. An equal affinity of the cements tested to the ceramic, hybrid materials and to titanium can be assumed. Combination of zirconia and TheraCem can be recommended for clinical use.

Effect of Thickness and Shade of Resin and Ceramic- Based Hybrid Materials on Color Masking Abilities and Optical Performance of CAD/CAM Materials.

Scientific data analysing color masking abilities of chairside CAD/CAM materials is lacking. The purpose of this in-vitro study was to evaluate the thickness and shade influence of three materials on their optical behaviour. Three materials: a) LD: Lithium disilicate glass ceramic (Emax, Ivoclar Vivadent), b) LDS: Lithium-disilicate-strengthened aluminosilicate glass ceramic (N!ce, Straumann) and c) RNC: Resin Nanoceramic (Lava Ultimate, 3M ESPE) were polished in different shades (A1,A2,A3) and thicknesses (0.1- 1.2mm). Specimens (N=108; n=36 per group) (12x12x1mm3) were positioned on resin composite base (Clearfil AP-X, Kuraray) in shade A3. Spectrophotometric measurements were performed and the parameters thickness, shade and material were analysed using three-way ANOVA, and pairwise T-tests (P-values ⟨ 0.05). Both the shade (p⟨0.001) and the interaction of material in correlation to thickness (p⟨0.001) were significant. Shade value A1-A3 comparisons were significant A1 vs. A2 (p=0.045); A2 vs. A3 (p=0.002); A1 vs. A3 (p⟨0.001)). A significant correlation of the material and thickness was observed when comparing LD and LDS (p=0.007) at the thickness of 0.1-0.4 mm. Masking abilities were influenced by material and thickness choice. Reinforced glass ceramics showed the best results in the smallest thickness tested (0.1-0.4 mm). LDS could be considered as an advantageous alternative in minimal-invasive cases.

Comparison of the Clinical Accuracy of Digital and Conventional Dental Implant Impressions.

The aim of this study was to compare the clinical accuracy of digital and conventional dental implant impressions. Two types of implant impressions were made for each case, namely a conventional open-tray impression and a digital implant impression (DII) using a Trios IOS. Master casts were scanned using a D800 laboratory scanner and STL files were retrieved from conventional and digital workflows to be exported for comparison. The distance between center points, angulation, rotation, vertical shift, and surface mismatch of the scan bodies were evaluated and compared between conventional and digital impression techniques. Comparing digital and conventional impression techniques the following factors showed statistically significant differences: distance (73.7±75 µm), angulation (0.42±0.3°), and surface mismatch of scan bodies. The difference in conventional and digital impression techniques as regards to angulation and distance between the implants were associated with distance, angle, and vertical shift differences in scan. The mismatch of the scanned surface of scan bodies was twice higher for the intraoral scanner group. Clinicians should therefore control the implant suprastructures clinically and also using casts (e.g. printed casts) when a digital scan is planned.

In Vitro Static and Fatigue Behavior of Ceramic Occlusal Veneers Using CAD/CAM.

To evaluate fracture resistance of occlusal veneers made of glass-ceramic and zirconia with and without fatigue. Occlusal overlays (N=80; n=10 per group) were milled out of CAD/CAM materials, namely: a)LD:Lithium disilicate glass ceramic, b)LDS:Lithium-disilicate- strengthened aluminosilicate glass ceramic, c)ZLT:Zirconium dioxide ceramic and d)ZMT:Zirconium dioxide ceramic. The overlays were cemented on polymeric duplicates, randomly distributed to aging or non-aging conditions and loaded until fracture. Ultimate catastrophic failure strength(Fmax) and Initial crack formation load(Finitial) values were analysed using two-way ANOVA. For Finitial, material type and aging and their interaction resulted in significant values (p =⟨0.001). Finitial mean±SD values ranged from ZMTa (593 N ±205 N) to LDSb (118 N ±42 N). As for Fmax, the material type significantly affected the outcome (p⟨0.001), while aging type did not show an influence (p=0.795). The non-aged Fmax specimens values presented were: LDSa (877 N ±253 N)⟨LDa (2029 N ±412 N)⟨ZLTa (2049 N ±379 N)⟨ZMTa (2144 N ±333 N), LDSa being significantly lower (p⟨0.001). The aged Fmax values were: LDSb (1313 N ±599 N)⟨ ZLTb (1715 N ±453 N)⟨ZMTb (2018 N ±300 N)⟨LDb (2134 N ±289 N). LDS yielded significantly lower Fmax values without and non-significant less favourable results with aging. The mechanical properties following aging and lack of additional firing makes LDS an interesting restorative material for clinical application.

Evaluation of Smear Layer Removal Using Different Irrigation Methods In Root Canals.

This study evaluated different irrigation methods in smear layer removal from the root canal walls using maleic acid (MA). Maxillary anterior teeth (N=30, n=10 per group) were decoronated, canals were enlarged with Protaper (size F4) and allocated to three groups: EndoUltra: 2.5 ml of 7% MA was irrigated for 30 s, followed by EndoUltra activation for 30 s; EndoSafe: EndoSafe irrigation system was used for 1 minute using 5 ml of 7% MA; Side-vented needle: 30 gauge needle irrigation was performed for 1 min using 5 ml of 7% MA. After SEM analysis, the inter-examiner reliability was verified using Kendall's Co-efficient and data were analyzed using Pearson Chi-Square test. No statistical significant differences were found between the two examiners (p⟩0.05). In intra-group comparison, needle and EndoSafe irrigation demonstrated significantly better smear layer removal at middle third of the root canal system (p⟨0.05) when compared to apical third. In inter-group comparison, smear layer was minimally removed with needle irrigation. In the apical third, EndoUltra group removed smear layer more effectively. Endosafe needle irrigation in combination with 7% MA removed the smear layer in the root canal at best, while the EndoUltra performed the best at the apical third of the root.