Publications by authors named "Nadja Rohr"

24 Publications

  • Page 1 of 1

Fracture load of zirconia implant supported CAD/CAM resin crowns and mechanical properties of restorative material and cement.

J Prosthodont Res 2021 Apr 9. Epub 2021 Apr 9.

Biomaterials and Technology, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel.

Purpose: To test if resin CAD/CAM materials should be considered for zirconia implants and how their mechanical properties affect the fracture load.

Methods: Fracture load of molar crowns of CAD/CAM materials (VITA CAD-Temp [CT], Cerasmart [CS], Lava Ultimate [LU], Pekkton Ivory [PK]) on zirconia implants (ceramic.implant, 4.0 mm) fixed either with no cement, temporary cement (Harvard Implant semi-permanent [HIS]), self-adhesive (VITA Adiva S-Cem [VAS]) or either one of two adhesive cements (Multilink Automix [MLA], VITA Adiva F-Cem [VAF]) was analyzed. The restorative materials were characterized by their flexural strength, fracture toughness, elemental composition and organic/inorganic ratio while compressive strength of the cements was measured.

Results: For the fracture load significantly highest mean values were fo und overall for PK (2921 ±300 N) > LU (2017 ±499 N) > CS (1463 ±367 N) = CT (1451 ±327 N) (p > 0.05). When analyzing the effect of the cement on the fracture load the overall ranking was VAF (2245 ±650 N) ≥ MLA (2188 ±708 N) ≥ VAS (2017 ±563 N) > HIS (1757 ±668 N) = no cement (1595 ±757 N) (p <0.05), meaning fracture load increased with the compressive strength of the cements. Additionally, a linear trend was found between the fracture load and the fracture toughness of the restorative materials.

Conclusions: All restorative materials exhibited fracture load values similar or higher than lithium disilicate tested previously. Fracture load of CT, CS and LU can be significantly increased when an adhesive cement with a high compressive strength is used.
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http://dx.doi.org/10.2186/jpr.JPR_D_20_00051DOI Listing
April 2021

Clinical outcome of metal- and all-ceramic resin-bonded fixed dental prostheses.

J Prosthodont Res 2020 Oct 6. Epub 2020 Oct 6.

Department of Reconstructive Dentistry University Center for Dental Medicine Basel, University of Basel.

Purpose: The aim of this retrospective cohort study was to investigate the long-term outcome of metal- and all-ceramic resin-bonded fixed dental prosthesis (RBFDP) up to 17 years, and to evaluate potential factors influencing the risk for complications.

Methods: Patients who were treated with RBFDP to replace teeth in the anterior or first premolar region in an university setting were identified from electronic records. Data collection comprised dental and periodontal parameters, periapical radiographs, and assessment of the RBFDP. Patient-reported satisfaction was evaluated on visual analog scales (VAS), and 5-year cumulative survival and success rates were calculated. Cox regression models were used to compare metal- versus all-ceramic RBFDPs.

Results: Seventy-one patients with RBFDP replacing 65 anterior teeth and 6 premolars were included with a mean observation period of 56.1 (±42.7) months. RBFDP cumulative survival rate was 86.7% and cumulative success rate 71.7% after 5 years, with no significant difference between metal-and all-ceramic RBFDPs. The risk for RBFDP failure was significantly higher with more than one pontic (OR 6.1; p=0.033), or negative pulp vitality testing of abutments (OR 7.3; p=0.042), while complications tended to be increased with two-wings compared to one-wing RBFDP (OR 5.4; p=0.054).

Conclusions: Metal- and all-ceramic RBFDPs facilitated good long-term results, particularly with one-wing, one-cantilever, and vital abutment teeth.
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http://dx.doi.org/10.2186/jpr.JPR_D_20_00014DOI Listing
October 2020

Viscous behavior of resin composite cements.

Dent Mater J 2021 Jan 8;40(1):253-259. Epub 2020 Oct 8.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel.

The objective of this study was to analyze the viscous behavior during setting reaction of resin composite cements and how it is influenced by temperature. Viscous properties during auto-polymerization at 23°C of three adhesive (Panavia V5 [PV5]; RelyX Ultimate [RUL]; Multilink Automix [MLA]) and three self-adhesive (Panavia SA plus [PSA]; RelyX Unicem 2 Automix [RUN]; Multilink SpeedCem [MSC]) resin composite cements were rheometrically measured. Changes in contact angle and temperature during auto-polymerization were evaluated for each cement at 23°C and 37°C. Rheological analysis and temperature measurements corresponded in terms of curve progression. The tested resin composite cements demonstrated strong variations in their viscous behavior during setting reaction. PV5 and PSA become less viscous at 37°C and then polymerize quickly. For RUL and RUN at 37°C, viscosity rises, and polymerization takes place quickly. MLA and MSC start with high viscosity, then MSC polymerizes very fast and MLA rather slowly.
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http://dx.doi.org/10.4012/dmj.2019-313DOI Listing
January 2021

Efficacy of Plasma-Polymerized Allylamine Coating of Zirconia after Five Years.

J Clin Med 2020 Aug 27;9(9). Epub 2020 Aug 27.

Biomaterials and Technology, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, 4058 Basel, Switzerland.

Plasma-polymerized allylamine (PPAAm) coatings of titanium enhance the cell behavior of osteoblasts. The purpose of the present study was to evaluate a PPAAm nanolayer on zirconia after a storage period of 5 years. Zirconia specimens were directly coated with PPAAm (ZA0) or stored in aseptic packages at room temperature for 5 years (ZA5). Uncoated zirconia specimens (Zmt) and the micro-structured endosseous surface of a zirconia implant (Z14) served as controls. The elemental compositions of the PPAAm coatings were characterized and the viability, spreading and gene expression of human osteoblastic cells (MG-63) were assessed. The presence of amino groups in the PPAAm layer was significantly decreased after 5 years due to oxidation processes. Cell viability after 24 h was significantly higher on uncoated specimens (Zmt) than on all other surfaces. Cell spreading after 20 min was significantly higher for Zmt = ZA0 > ZA5 > Z14, while, after 24 h, spreading also varied significantly between Zmt > ZA0 > ZA5 > Z14. The expression of the mRNA differentiation markers collagen I and osteocalcin was upregulated on untreated surfaces Z14 and Zmt when compared to the PPAAm specimens. Due to the high biocompatibility of zirconia itself, a PPAAm coating may not additionally improve cell behavior.
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http://dx.doi.org/10.3390/jcm9092776DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7565740PMC
August 2020

Crystal structure of zirconia affects osteoblast behavior.

Dent Mater 2020 07 30;36(7):905-913. Epub 2020 May 30.

Biomaterials and Technology, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel, Switzerland.

Objectives: Different approaches are currently undertaken to structure the endosseous part of zirconia implants. The purpose of the present study was to evaluate how surface roughness and monoclinic to tetragonal phase ratio of zirconia affect cell behavior of human osteoblasts.

Methods: Zirconia discs with five different surface structures were produced: machined; machined heat-treated; polished; polished heat-treated; sandblasted, etched and heat-treated (cer.face 14, vitaclinical). The specimen surfaces were then characterized in terms of monoclinic to tetragonal phase ratio, wettability, roughness and visualized using scanning electron microscopy. To determine the reaction of the human osteoblastic cells (MG-63) to the surface roughness and monoclinic to tetragonal phase ratio of zirconia, cell spreading, morphology, actin cytoskeleton, viability and gene expression of alkaline phosphatase (ALP), collagen type I (COL) and osteocalcin (OCN) were assessed.

Results: Heat-treatment of the specimens significantly improved the surface wettability. With increased surface roughness Ra of the specimens, cell spreading was reduced. Cell viability after 24h correlated linearly with the tetragonal phase ratio of the specimens. Gene expression after 24h and 3 d was comparable on all specimens irrespective their surface roughness or monoclinic to tetragonal phase ratio.

Significance: Smooth zirconia surfaces with a high tetragonal phase ratio revealed best surface conditions for MG-63 osteoblastic cells and may be considered to design the endosseous part of zirconia implants.
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http://dx.doi.org/10.1016/j.dental.2020.04.017DOI Listing
July 2020

Surface structuring of zirconia to increase fibroblast viability.

Dent Mater 2020 06 27;36(6):779-786. Epub 2020 Apr 27.

Biomaterials and Technology, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel, Switzerland.

Objective: The neck area of zirconia implants or abutments is currently either machined, polished and in some cases additionally heat-treated. The aim of the present study was to determine how the surface topography and crystalline structure of zirconia affects the viability of human gingival fibroblasts (HGF-1).

Methods: Zirconia discs with a diameter of 13mm were either polished [Zp], polished and heat-treated [Zpt], machined [Zm], machined and heat-treated [Zmt] or sandblasted, etched and heat-treated [Z14] which is the surface topography of the endosseous part of a zirconia implant. The specimen surfaces were analyzed using scanning electron microscopy (SEM), characterized in terms of monoclinic to tetragonal phase ratio, storage effect on wettability and roughness. The viability and morphology of HGF-1 cells was then tested on all surfaces after 24h.

Results: The effect of the heat-treatment was visualized for the polished specimens with SEM. Contact angle of water was significantly decreased after 2 weeks air storage of the zirconia. Cell viability was significantly higher on smooth surfaces (Zpt, Zm, Zmt) when compared to Z14. HGF-1 cells spread very flat and attached tightly to the smoother surfaces Zp, Zpt, Zm and Zmt while on Z14, cells did not fully extend into the etched morphology of zirconia and stretched over longer distances.

Significance: For the structuring of the neck part of zirconia implants or abutments, a smooth surface with exposed grains might be suggested as the optimal substrate for human gingival fibroblasts. The wettability with water of zirconia decreases with prolonged air storage.
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http://dx.doi.org/10.1016/j.dental.2020.03.024DOI Listing
June 2020

Comparing the mechanical properties of pressed, milled, and 3D-printed resins for occlusal devices.

J Prosthet Dent 2020 Dec 17;124(6):780-786. Epub 2020 Jan 17.

Research Associate, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel, Switzerland. Electronic address:

Statement Of Problem: Comparisons of the material qualities of pressed, milled, and 3D-printed occlusal devices are sparse, complicating informed decisions on material choice.

Purpose: The purpose of this in vitro study was to compare the material properties of pressed, milled, and 3D-printed resins, as well as how these are affected by thermal aging. These data were then used to estimate the likely clinical performance of the tested materials.

Material And Methods: Three pressed (ProBase Cold; Ivoclar Vivadent AG, Palapress clear; Kulzer GmbH, Aesthetic Blue clear; Candulor), 3 milled (Temp Premium Flexible Transpa; Zirkonzahn, idodentine PMMA transparent; Unión Dental S.A., Yamahachi PMMA clear; Yamahachi Dental MFG), and three 3D-printed (Freeprint splint; DETAX GmbH, LuxaPrint Ortho Plus; DMG GmbH, Nextdent Ortho Clear; Vertex-Dental B.V.) resin materials were evaluated. Flexural strength, Martens hardness (HM), Vickers hardness (HV), water sorption, water solubility, and surface topography were analyzed. The tests were carried out after 50 hours of water storage at 37 °C (baseline) and after simulated aging (50 hours of water storage at 37 °C, followed by 20 000 thermocycles [TC] at 5 °C and 55 °C).

Results: At baseline, the mean flexural strength values were 92.8 to 99.5 MPa for pressed, 95.1 to 122.0 MPa for milled, and 19.5 to 91.3 MPa for 3D-printed materials. After aging, these values were 87.6 to 93.5 MPa for pressed, 93.1 to 116.0 MPa for milled, and 13.0 to 63.3 MPa for 3D-printed resins. The mean HM values were 130.1 to 134.1 N/mm for pressed and 130.3 to 158.5 N/mm for milled resins. After aging, the mean HM ranged from 121.6 to 124.2 N/mm for pressed and 116.2 to 149.7 N/mm for milled resins. The mean HV values were 18.2 to 19.9 for pressed and 18.4 to 23.0 for milled resins before aging and 16.9 to 18.7 for pressed and 17.3 to 22.3 N/mm for milled resins after aging. Printed resins could not be measured. At baseline, the mean modulus of elasticity ranged from 4.6 to 4.8 GPa for pressed and from 4.7 to 5.3 GPa for milled resins. For 3D-printed resins, only 1 material could be measured (3.7 GPa). The mean sorption values were 8.6 to 9.2 μg/mm for pressed, 7.9 to 10.5 μg/mm for milled, and 9.2 to 21.2 μg/mm for additive resins. After aging, these values were 21.1 to 22.6 μg/mm for pressed, 20.5 to 23.7 μg/mm for milled, and 19.4 to 45.5 μg/mm for 3D-printed resins. The mean solubility values ranged from 0.3 to 1.4 μg/mm for pressed, 0.4 to 1.7 μg/mm for milled, and -3.5 to 11 μg/mm for 3D-printed materials.

Conclusions: Pressed and milled resins can be considered equivalent in terms of their material properties. Relative to the pressed and milled resins, the 3D-printed resins had lower flexural strength and hardness values and higher water sorption and solubility.
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http://dx.doi.org/10.1016/j.prosdent.2019.10.024DOI Listing
December 2020

HF etching of CAD/CAM materials: influence of HF concentration and etching time on shear bond strength.

Head Face Med 2019 Aug 8;15(1):21. Epub 2019 Aug 8.

Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Mattenstrasse 40, CH-4058, Basel, Switzerland.

Background: The required pretreatment of CAD/CAM ceramic materials before resin composite cement application varies among studies. The aim of the present study was to evaluate the effect of hydrofluoric acid concentration and etching time on the shear bond strength (SBS) of two adhesive and two self-adhesive resin composite cements to different CAD/CAM ceramic materials.

Methods: SBS of two adhesive (Panavia V5, Kuraray, [PV5]; Vita Adiva F-Cem, Vita Zahnfabrik, [VAF]) and two self-adhesive (RelyX Unicem 2 Automix, 3 M Espe, [RUN]; Vita Adiva S-Cem, Vita, [VAS]) cements to four different CAD/CAM materials (Vitablocs Mark II, Vita, [VM]; Vita Enamic, Vita, [VE]; e.max CAD, Ivoclar Vivadent, [EC]; Vita Suprinity PC, Vita, [VS]) was measured. The effect of the surface pretreatment by using two different hydrofluoric acid products (HF5% Vita Ceramics Etch, Vita and HF9% buffered, Ultradent Porcelain Etch, Ultradent Products) were assessed at etching times of 0 s, 5 s, 15 s, 30s and 60s for each cement and restorative material combination (n = 10 per group, total n = 1440).

Results: Significant effects were found for the etching time and cement for all materials with highest shear bond strength for etching times of 60s = 30s = 15 s ≥ 5 s > 0 s and for RUN>PV5 = VAF > VAS (p < 0.05). Etching with HF5% for 5 s to 15 s resulted in higher SBS values, while no differences were observed between HF5% and HF9% buffered when the substrates were etched for 30s to 60s (p < 0.05).

Conclusions: Within the limitations of this study the recommended surface pretreatment of silicate ceramics is HF etching with concentrations of 5% or 9% for 15 s to 60s to achieve highest shear bond strength while the glassy matrix is sufficiently dissolved. The tested resin composite cements can be applied with all tested materials and suggested for clinical application.
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http://dx.doi.org/10.1186/s13005-019-0206-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6686502PMC
August 2019

Influence of bioactive glass-coating of zirconia implant surfaces on human osteoblast behavior in vitro.

Dent Mater 2019 06 16;35(6):862-870. Epub 2019 Mar 16.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel, Switzerland.

Objective: The recently developed bioactive glass PC-XG3, which is suitable to coat zirconia implant surfaces with high adhesion strength may reduce the time of osseointegration and the marginal bone loss following implantation. The glass composition has been previously evaluated for cytotoxicity on fibroblast cells, and will now be used to evaluate the cell behavior of osteoblast cells.

Methods: Three different surface morphologies were created with PC-XG3 on zirconia discs. A clinically tested zirconia implant surface as well as polished and machined zirconia served as a reference. Cell viability after 24 h, cell spreading after 30 min and 24 h and the respective morphology of human osteoblasts using scanning electron microscopy were evaluated. Additionally, the corrosive process of PC-XG3 in cell culture medium up to 7 d was measured.

Results: Initial cell behavior of human osteoblasts was not accelerated by the PC-XG3 surface when compared to zirconia. Additionally, it was found that a decreased surface roughness promoted initial cell spreading. Storage in cell culture medium resulted in the accumulation of C and N on the bioglass surface while Mg, Si, K and Ca were decreased and crack formation was observed.

Significance: Since initial spreading quality to a biomaterial is a crucial factor that will determine the subsequent cell function, proliferation, differentiation, and viability it can be assumed that a coating of zirconia implants with this bioactive glass will unlikely reduce osseointegration time.
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http://dx.doi.org/10.1016/j.dental.2019.02.029DOI Listing
June 2019

Chewing simulation of zirconia implant supported restorations.

J Prosthodont Res 2019 Jul 8;63(3):361-367. Epub 2019 Mar 8.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Basel, Switzerland; Vita Zahnfabrik, Bad Säckingen, Germany.

Purpose: To test three potential prosthetic material options for zirconia implants in regard to their mechanical properties, loading and retention capacity as well as to record abrasion after chewing simulation followed by thermocyclic aging.

Methods: Molar crowns (n = 96) of three different computer-aided design/computer-aided manufacturing (CAD/CAM) materials were produced and cemented on zirconia implants (ceramic.implant, Vita) with a diameter of 4.5 mm. Monolithic zirconia (Vita YZ [YZ] with RelyX Unicem 2 Automix [RUN], polymer-infiltrated ceramic (Vita Enamic [VE]) with Vita Adiva F-Cem [VAF] and acrylate polymer (CAD Temp [CT]) with RelyX Ultimate [RUL]. Fracture load and retentive force of the crowns were measured after 24 h water storage at 37 °C and after a chewing simulation followed by thermocyclic aging. Abrasion was recorded by matching stereolithography-data of the crowns obtained before and after chewing simulation. Additionally, the mechanical properties and bonding capabilities of the crown and cement materials were assessed.

Results: Fracture load values were significantly highest for YZ > VE = CT. Retention force values did not differ significantly between the materials. The aging procedure did not affect the fracture load values nor the retention force significantly. Abrasion depth of the crowns was lowest for YZ followed by VE and CT. On unpolished crowns, abrasion of YZ and VE tended to be higher than on polished specimens.

Conclusions: Based on the obtained in-vitro results, all tested materials can be recommended for the use on zirconia implants, although CT is only approved for temporary crowns. The loading and retention capacity of the materials were not significantly affected by aging.
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http://dx.doi.org/10.1016/j.jpor.2019.02.002DOI Listing
July 2019

Loading capacity of CAD/CAM-fabricated anterior feldspathic ceramic crowns bonded to one-piece zirconia implants with different cements.

Clin Oral Implants Res 2019 Feb 29;30(2):178-186. Epub 2019 Jan 29.

Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania.

Objective: This study evaluated the loading capacity of CAD/CAM-fabricated anterior feldspathic ceramic crowns bonded to one-piece zirconia implants with different cements.

Material And Methods: Fifty one-piece zirconia implants were embedded in epoxy resin. The abutment aspect of one implant was optically scanned and a standardized upper canine was designed with CAD-software. Fifty feldspathic ceramic crowns were milled, polished, and mounted on the implants either without any cement, with a temporary cement or with three different composite resin cements after surface pretreatment as recommended by the manufacturers (n = 10). After storage in distilled water at 37°C for 24 hr, specimens were loaded until fracture on the palatal surface of the crown at an angle of 45° to the long axis of the implant and loads until fracture were detected and compared. Compressive strength of the investigated cement materials was determined. Statistical analyses were done with One-way ANOVA followed by post hoc Fisher LSD test (α = 0.05).

Results: The cements revealed significantly different compressive strength values (temporary cement: 37.1 ± 7.0 MPa; composite resin cements: 185.8 ± 21.3, 277.9 ± 22.1, and 389.0 ± 13.6 MPa, respectively). Load-at-fracture values had an overall mean value of 237.1 ± 58.2 N with no significant difference among the composite resin cements (p > 0.05). Fracture load values with the temporary cement or without cement were significantly lower (p < 0.002).

Conclusions: CAD/CAM-fabricated anterior feldspathic ceramic crowns bonded to one-piece zirconia implants provide sufficient resistance to intraoral forces.
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http://dx.doi.org/10.1111/clr.13404DOI Listing
February 2019

Biofilm formation on restorative materials and resin composite cements.

Dent Mater 2018 11 13;34(11):1702-1709. Epub 2018 Sep 13.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry, University Center for Dental Medicine, University of Basel, Hebelstrasse 3, 4056 Basel, Switzerland. Electronic address:

Objectives: Monolithic zirconia, polymer-infiltrated ceramic and acrylate polymer cemented with resin composite cement have recently been identified as prosthetic treatment options for zirconia implants. The aim of the present study is to determine in vitro, to what extent bacteria adhere to these materials.

Methods: Disks made of zirconia (Vita YZ [YZ]), polymer-infiltrated ceramic (Vita Enamic [VE]), acrylate polymer (Vita CAD-Temp [CT]), self-adhesive cement (RelyX Unicem 2 Automix [RUN]) and of two different adhesive cements (RelyX Ulimate [RUL] and Vita Adiva F-Cem [VAF]) were produced. The biofilm formation of three bacterial species (Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis) on each material was assessed over 72h using a flow chamber system. The biofilms were quantified by crystal violet staining (optical density 595nm) and visualized using SEM. The inorganic composition of the different materials was analyzed and the wettability of the specimens was measured.

Results: For the restorative materials lowest biofilm formation was found on CT: OD 0.5±0.1, followed by VE: OD 0.8±0.1 and YZ: OD 1.4±0.3. The biofilm formation on resin composite cements was significantly lower on VAF: OD 0.6±0.1 than for RUL: OD 0.9±0.1 and RUN: OD 1.0±0.1. A high wettability of the specimens with saliva/serum mixture tended to result in a higher biofilm formation. Correlations were obtained between the organic/inorganic composition of the materials and the polar/dispersive part of the surface free energy.

Significance: Three-species biofilm formation on restorative and cement materials strongly relies on the materials composition. If the restorative material CT and cement VAF also prevent excessive biofilm formation in a clinical situation should be further investigated.
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http://dx.doi.org/10.1016/j.dental.2018.08.300DOI Listing
November 2018

Correlations between fracture load of zirconia implant supported single crowns and mechanical properties of restorative material and cement.

Dent Mater J 2018 Mar 23;37(2):222-228. Epub 2017 Nov 23.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine, University of Basel.

Zirconia implants that were restored with veneered zirconia displayed severe chipping rates of the restorations in clinical studies. Purpose of this study was to evaluate the fracture load of different zirconia implant supported monolithic crown materials (zirconia, alumina, lithium disilicate, feldspar ceramic and polymer-infiltrated ceramic) cemented with various cements (Harvard LuteCem SE, Harvard Implant Semi-permanent, Multilink Automix, VITA Adiva F-Cem). Flexural strength and fracture toughness of crown materials and compressive strength of the cements were measured. Fracture load values of crowns fabricated from lithium disilicate, feldspar ceramic and polymer-infiltrated ceramic were increased when cement with high compressive strength was used. Fracture loads for zirconia and alumina crowns were not influenced by the cement. Flexural strength and fracture toughness of the ceramics correlated linearly with the respective fracture load when using adhesive cement with high compressive strength. To achieve sufficient fracture load values, cementation with adhesive cement is essential for feldspar and polymer-infiltrated ceramic.
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http://dx.doi.org/10.4012/dmj.2017-111DOI Listing
March 2018

Effect of aging and curing mode on the compressive and indirect tensile strength of resin composite cements.

Head Face Med 2017 Nov 21;13(1):22. Epub 2017 Nov 21.

Division of Materials Science and Engineering, Clinic for Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine, Hebelstrasse 3, CH-4056, Basel, Switzerland.

Background: Resin composite cements are used in dentistry to bond ceramic restorations to the tooth structure. In the oral cavity these cements are subjected to aging induced by masticatory and thermal stresses. Thermal cycling between 5 and 55 °C simulates the effect of varying temperatures in vitro. Purpose of this study was to compare indirect tensile to compressive strength of different cements before and after thermal cycling. The effect of the curing mode was additionally assessed.

Methods: Indirect tensile strength and compressive strength of 7 dual-curing resin composite cements (Multilink Automix, Multilink SpeedCem, RelyX Ultimate, RelyX Unicem 2 Automix, Panavia V5, Panavia SA Plus, Harvard Implant semi-permanent) was measured. The specimens were either autopolymerized or light-cured (n = 10). The mechanical properties were assessed after 24 h water storage at 37 °C and after aging (20,000 thermo cycles) with previous 24 h water storage at 37 °C.

Results: Indirect tensile strength ranged from 5.2 ± 0.8 to 55.3 ± 4.2 MPa, compressive strength from 35.8 ± 1.8 MPa to 343.8 ± 19.6 MPa.

Conclusions: Thermocyclic aging of 20,000 cycles can be considered a suitable method to simulate the degradation of indirect tensile strength but not compressive strength of resin composite cements. The effect of thermocycling and the curing mode on the resin composite cements is material dependent and cannot be generalized.
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http://dx.doi.org/10.1186/s13005-017-0155-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5697404PMC
November 2017

Efficacy of a Universal Adhesive in the Bond Strength of Composite Cements to Polymer-infiltrated Ceramic.

J Adhes Dent 2017 ;19(5):417-424

Purpose: To investigate the effect of a universal adhesive on the bond strength of composite cements to a polymer-infiltrated ceramic network.

Materials And Methods: 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.

Results: 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).

Conclusion: 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.
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http://dx.doi.org/10.3290/j.jad.a39277DOI Listing
January 2019

Fracture behavior, marginal gap width, and marginal quality of vented or pre-cemented CAD/CAM all-ceramic crowns luted on Y-TZP implants.

Clin Oral Implants Res 2018 Feb 31;29(2):175-184. Epub 2017 Oct 31.

Department of Periodontology, Endodontology and Cariology, University Center for Dental Medicine Basel, University of Basel, Basel, Switzerland.

Objectives: To investigate the fracture behavior and marginal gap region of CAD/CAM fabricated lithium disilicate (L) and zirconium dioxide (Z) crowns using palatal venting (PV), pre-cementation with custom analogs (CA), or conventional cementation technique (SP) with adhesive cement (A) or resin-modified glass ionomer cement (B).

Material And Methods: Twelve groups (n = 6) were set according to material (L, Z), cement (A, B), and technique (PV, CA, SP). Specimens were thermo-mechanical aged (TML), loaded until fracture (LF) and fracture patterns recorded. Marginal gap width and quality were assessed and compared to replicas obtained before and after TML.

Results: Crown material significantly influenced LF with a mean of 1037.6 ± 282.4 N in L and 5356.3 ± 1207.0 N in Z groups (p < .001). Neither cement material nor cementation method affected the outcome. Fractures occurred along the mesial-distal central fissure in both materials. Gap width before TML was 22.04 ± 13.42 μm for L and 19.98 ± 12.72 μm for Z specimens, with overall no influence of crown material, cement type, or method. Marginal cleanliness just below the polished implant shoulder reached 66.7%-88.9% with A, and 91.7%-100% with B, and tended to increase in all groups during TML indicating a decrease in excess cement. Implant-crown junctions were cleaner with B compared to A (p ≤ .001) and along Z crown surfaces compared to L (p ≤ .007).

Conclusions: Crown venting of lithium disilicate and zirconium dioxide crowns did not affect the fracture load and patterns. Complete cement removal was rare, and the observed particle ablation requires further clinical attention, particularly with submucosal margins.
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http://dx.doi.org/10.1111/clr.13075DOI Listing
February 2018

The effects of crown venting or pre-cementing of CAD/CAM-constructed all-ceramic crowns luted on YTZ implants on marginal cement excess.

Clin Oral Implants Res 2018 Jan 17;29(1):82-90. Epub 2017 Oct 17.

Department of Periodontology, Endodontology and Cariology, University Center for Dental Medicine Basel, University of Basel, Basel, Switzerland.

Objectives: The purpose of this study was to analyze the cement excess produced when cementing CAD/CAM-fabricated lithium disilicate (L) or zirconium dioxide (Z) crowns using adhesive cement (A) or resin-modified glass ionomer cement (B). Three different cementation techniques were applied: palatal venting (PV), pre-cementation with custom analogs (CA), and conventional standard procedure (SP).

Materials And Methods: Seventy-two crowns (36 each material) were assigned to 12 experimental groups depending on the restoration material (L, Z), type of cement (A, B), and cementation technique (PV, CA, SP). Weight measurements were taken during cementation, and the amounts of excess cement, cement retained in crown, and relative excess cement were calculated and statistically analyzed.

Results: A significant direct relation between the amounts of cement applied and excess cement was observed in groups CA and SP. Vented crowns showed least amounts of marginal excess cement (0.8 ± 0.3 μl) followed by CA (4.2 ± 1.1 μl) and SP (8.8 ± 2.5 μl; p < .001). In CA, 32.1% less excess cement (95%CI: 28.4, 35.7) was produced than in the SP group (p < .001), but 27.4% more than in the PV group (95%CI: 23.8,31.0; p < .001). Overall, slightly smaller amounts of adhesive cement (A) than of glass ionomer cement (B) were retained in crowns.

Conclusions: Using crown venting was the most effective measure to reduce the amount of marginal excess cement, followed using a pre-cementation device. To keep the marginal excess cement of one-piece zirconia implants to a minimum, both techniques should be considered for clinical application.
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http://dx.doi.org/10.1111/clr.13071DOI Listing
January 2018

Bacterial colonization of resin composite cements: influence of material composition and surface roughness.

Eur J Oral Sci 2017 08 15;125(4):294-302. Epub 2017 Jun 15.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine, University of Basel, Basel, Switzerland.

So-called secondary caries may develop in the cement gap between the tooth and the bonded restoration. Cement materials with a low susceptibility to biofilm formation are therefore desirable. In the present study, the adhesion of Strepococcus mutans onto three adhesive (Multilink Automix, RelyX Ultimate, and Panavia V5) and three self-adhesive (Multilink Speed Cem, RelyX Unicem 2 Automix, and Panavia SA plus) resin composite cements was evaluated. Previous studies have failed to evaluate concomitantly the effect of both the composition of the cements and their surface roughness on biofilm formation. The presence of S. mutans on cement surfaces with differing degrees of roughness was therefore recorded using fluorescence microscopy and crystal violet staining, and the composition of the cements was analyzed using energy-dispersive X-ray spectroscopy mapping. Biofilm formation on resin composite cements was found to be higher on rougher surfaces, implying that adequate polishing of the cement gap is essential. The use of copper-containing cements (Multilink Automix, Panavia V5, and Panavia SA plus) significantly reduced biofilm formation.
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http://dx.doi.org/10.1111/eos.12355DOI Listing
August 2017

Assessing degradation of composite resin cements during artificial aging by Martens hardness.

Head Face Med 2017 May 19;13(1). Epub 2017 May 19.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine Basel, University of Basel, Hebelstrasse 3, 4056, Basel, Switzerland.

Background: Aim of the study was to verify the efficiency of Martens hardness measurements in detecting the degradation of composite resin cements during artificial aging.

Methods: Four cements were used: Variolink II (VL2), RelyX Unicem 2 Automix (RUN), PermaFlo DC (PDC), and DuoCem (DCM). Specimens for Martens hardness measurements were light-cured and stored in water at 37 °C for 1 day to allow complete polymerization (baseline). Subsequently the specimens were artificially aged by water storage at 37 °C or thermal cycling (n = 6). Hardness was measured at baseline as well as after 1, 4, 9 and 16 days of aging. Specimens for indirect tensile strength measurements were produced in a similar manner. Indirect tensile strength was measured at baseline and after 16 days of aging (n = 10). The results were statistically analyzed using one-way ANOVA (α = 0.05).

Results: After water storage for 16 days hardness was significantly reduced for VL2, RUN and DCM while hardness of PDC as well as indirect tensile strength of all cements were not significantly affected. Thermal cycling significantly reduced both, hardness and indirect tensile strength for all cements. No general correlation was found between Martens hardness and indirect tensile strength. However, when each material was analyzed separately, relative change of hardness and of indirect tensile strength revealed a strong linear correlation.

Conclusions: Martens hardness is a sensible test method to assess aging of resin composite cements during thermal cycling that is easy to perform.
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http://dx.doi.org/10.1186/s13005-017-0142-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5437403PMC
May 2017

Influence of cement type and ceramic primer on retention of polymer-infiltrated ceramic crowns to a one-piece zirconia implant.

J Prosthet Dent 2018 Jan 28;119(1):138-145. Epub 2017 Apr 28.

Professor, Division of Dental Materials and Engineering, Department of Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine Basel, University of Basel, Basel, Switzerland.

Statement Of Problem: The best procedure for cementing a restoration to zirconia implants has not yet been established.

Purpose: The purpose of this in vitro study was to measure the retention of polymer-infiltrated ceramic crowns to zirconia 1-piece implants using a wide range of cements. The effect of ceramic primer treatment on the retention force was also recorded. The retention results were correlated with the shear bond strength of the cement to zirconia and the indirect tensile strength of the cements to better understand the retention mechanism.

Material And Methods: The retention test was performed using 100 polymer-infiltrated ceramic crowns (Vita Enamic) and zirconia implants (ceramic.implant CI) The crowns were cemented with either interim cement (Harvard Implant semipermanent, Temp Bond), glass-ionomer cement (Ketac Cem), self-adhesive cement (Perma Cem 2.0, RelyX Unicem Automix 2, Panavia SA), or adhesive cement (Multilink Implant, Multilink Automix, Vita Adiva F-Cem, RelyX Ultimate, Panavia F 2.0, Panavia V5 or Panavia 21) (n=5). Additionally ceramic primer was applied on the intaglio crown surface and implant abutment before cementation for all adhesive cements (Multilink Implant, Multilink Automix: Monobond plus; RelyX Ultimate Scotchbond Universal; Vita Adiva F-Cem: Vita Adiva Zr-Prime; Panavia F2.0, Panavia V5: Clearfil Ceramic Primer) and 1 self-adhesive cement containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) (Panavia SA: Clearfil Ceramic Primer). Crown debond fracture patterns were recorded. Shear bond strength was determined for the respective cement groups to polished zirconia (n=6). The diametral tensile strength of the cements was measured (n=10). Statistical analysis was performed using 1-way or 2-way analysis of variance followed by the Fisher LSD test (α=.05) within each test parameter.

Results: Adhesive and self-adhesive resin cements had shear bond strength values of 0.0 to 5.3 MPa and revealed similar retention forces. Cements containing MDP demonstrated shear bond strength values above 5.3 MPa and displayed increased retention. The highest retention values were recorded for Panavia F 2.0 (318 ±28 N) and Panavia 21 (605 ±82 N). All other adhesive and self-adhesive resin cements attained retention values between 222 ±16 N (Multilink Automix) and 270 ±26 N (Panavia SA), which were significantly higher (P<.05) than glass-ionomer (Ketac Cem: 196 ±34 N) or interim cement (Harvard Implant semipermanent: 43 ±6 N, Temp Bond: 127 ±13 N). Application of manufacturer-specific ceramic primer increased crown retention significantly only for Panavia SA.

Conclusions: Products containing MDP provided a high chemical bond to zirconia. Self-adhesive and adhesive resin cements with low chemical bonding capabilities to zirconia provided retention force values within a small range (220 to 290 N).
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http://dx.doi.org/10.1016/j.prosdent.2017.02.002DOI Listing
January 2018

Tooth surface treatment strategies for adhesive cementation.

J Adv Prosthodont 2017 Apr 6;9(2):85-92. Epub 2017 Apr 6.

Division of Dental Materials and Engineering, Department of Reconstructive Dentistry and Temporomandibular Disorders, University Center for Dental Medicine, University of Basel, Switzerland.

Purpose: The aim of this study was to evaluate the effect of tooth surface pre-treatment steps on shear bond strength, which is essential for understanding the adhesive cementation process.

Materials And Methods: Shear bond strengths of different cements with various tooth surface treatments (none, etching, priming, or etching and priming) on enamel and dentin of human teeth were measured using the Swiss shear test design. Three adhesives (Permaflo DC, Panavia F 2.0, and Panavia V5) and one self-adhesive cement (Panavia SA plus) were included in this study. The interface of the cement and the tooth surface with the different pre-treatments was analyzed using SEM. pH values of the cements and primers were measured.

Results: The highest bond strength values for all cements were achieved with etching and primer on enamel (25.6 ± 5.3 - 32.3 ± 10.4 MPa). On dentin, etching and priming produced the highest bond strength values for all cements (8.6 ± 2.9 - 11.7 ± 3.5 MPa) except for Panavia V5, which achieved significantly higher bond strengths when pre-treated with primer only (15.3 ± 4.1 MPa). Shear bond strength values were correlated with the micro-retentive surface topography of enamel and the tag length on dentin except for Panavia V5, which revealed the highest bond strength with primer application only without etching, resulting in short but sturdy tags.

Conclusion: The highest bond strength can be achieved for Panavia F 2.0, Permaflo DC, and Panavia SA plus when the tooth substrate is previously etched and the respective primer is applied. The new cement Panavia V5 displayed low technique-sensitivity and attained significantly higher adhesion of all tested cements to dentin when only primer was applied.
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http://dx.doi.org/10.4047/jap.2017.9.2.85DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5397593PMC
April 2017

Evaluation of ISO 4049: water sorption and water solubility of resin cements.

Eur J Oral Sci 2017 04 21;125(2):141-150. Epub 2017 Feb 21.

Department of Rekonstructive Dentistry and Tempomandibular Disorders, Division of Dental Materials and Engineering, University Center for Dental Medicine Basel, University of Basel, Basel, Switzerland.

The aim of this study was to evaluate the water sorption and solubility test design of ISO 4049 for resin cements. Sorption and solubility of six dual-curing resin cements [RelyX Unicem 2 Automix (RUN), Multilink Speed CEM (MLS), Panavia SA Plus (PSA), RelyX Ultimate (RUL), Multilink Automix (MLA), and Panavia V5 (PV5)] were analyzed by storage in distilled water after dual-curing. In addition, sorption and solubility during thermal cycling were assessed with self-cured and dual-cured specimens. After water storage, all cements revealed sorption in the range of 30 μg mm except for PV5, for which sorption was markedly lower (mean ± SD = 20.8 ± 0.4 μg mm ). Solubility values were negative for RUN and RUL (-2.1 ± 0.08 μg mm and -1.9 ± 0.13 μg mm , respectively). All other cements attained positive values in the range of 0.4-0.8 μg mm . Thermal cycling effects were more pronounced. The assessment of water sorption according to ISO 4049 provides reliable results. Solubility results must be interpreted with care because absorbed water may distort the values.
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http://dx.doi.org/10.1111/eos.12339DOI Listing
April 2017

Correlation between flexural and indirect tensile strength of resin composite cements.

Head Face Med 2016 Nov 4;12(1):29. Epub 2016 Nov 4.

Division of Dental Materials and Engineering, Clinic for Reconstructive Dentistry and Temporomandibular Disorders, University Hospital of Dental Medicine, University of Basel, Hebelstrasse 3, 4056, Basel, Switzerland.

Background: To evaluate a potential correlation between flexural strength and indirect tensile strength in assessing the mechanical strength of resin composite cements.

Methods: Flexural strength (n = 5) and indirect tensile strength (n = 5) of 7 resin composite cements (RelyX Unicem 2 Automix [RXU], Panavia SA [PSA], Clearfil SA [CSA], Panavia F2.0 [PF2], Multilink Implant [MLI], DuoCem [DCM], Panavia 21 [P21]) were determined. Specimens were either auto-polymerized or dual-cured (except P21) and stored in water at 37 °C for 1 day prior to measurement. Flexural and indirect tensile strength of 4 cements (RXU, PSA, PF2, MLI) was additionally measured directly after curing and after 96 h water storage at 37 °C.

Results: Except for PF2, dual-cured specimens achieved higher flexural strength than auto-polymerized specimens. In the indirect tensile strength test differences in auto-polymerized and dual-cured specimens were only detected for RXU and DCM. A general non-linear correlation was found between flexural and indirect tensile strength values. However, strength values of auto-polymerized and dual-cured specimens did not generally correlate.

Conclusions: Flexural strength and indirect tensile strength of resin composite cements are correlated. At high strength values the indirect tensile test is less sensitive than the flexural test. The results suggest that the indirect tensile test may only be recommended as a screening test especially for low or medium strength resin composite cements.
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http://dx.doi.org/10.1186/s13005-016-0128-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5096060PMC
November 2016

Loading capacity of zirconia implant supported hybrid ceramic crowns.

Dent Mater 2015 Dec 14;31(12):e279-88. Epub 2015 Oct 14.

Institute for Dental Materials and Engineering, University Hospital for Dental Medicine, University of Basel, Hebelstrasse 3, CH-4056 Basel, Switzerland; VITA Zahnfabrik, 79713 Bad Säckingen, Germany.

Objective: Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type.

Methods: Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05).

Results: The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load.

Significance: Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used.
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http://dx.doi.org/10.1016/j.dental.2015.09.012DOI Listing
December 2015