Publications by authors named "Timo O Närhi"

46 Publications

Effect of bioactive glass air-abrasion on Fusobacterium nucleatum and Porphyromonas gingivalis biofilm formed on moderately rough titanium surface.

Eur J Oral Sci 2021 Mar 16:e12783. Epub 2021 Mar 16.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

This aim of this study was to investigate the effects of three types of air-abrasion particles on dual-species biofilms of Fusobacterium nucleatum and Porphyromonas gingivalis, both of which were cultured on sandblasted and acid-etched (SA) titanium discs. Out of 24 SA discs with biofilm, 18 were exposed to either air-abrasion using Bioglass 45S5 (45S5 BG; n = 6), novel zinc (Zn)-containing bioactive glass (Zn4 BG; n = 6), or inert glass (n = 6). The efficiency of biofilm removal was evaluated using scanning electron microscopy (SEM) imaging and culturing techniques. Air-abrasion using 45S5 BG or Zn4 BG demonstrated a significant decrease in the total number of viable bacteria compared to discs air-abraded with inert glass or intact biofilm without abrasion. Moreover, P. gingivalis could not be detected from SEM images nor culture plates after air-abrasion with 45S5 BG or Zn4 BG. The present study showed that air-abrasion with 45S5 or Zn4 bioactive glasses can successfully eradicate dual-biofilm of F. nucleatum and P. gingivalis from sandblasted and acid-etched titanium discs.
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http://dx.doi.org/10.1111/eos.12783DOI Listing
March 2021

Flexural strength and flexural modulus of fiber-reinforced, soft-liner retained implant overdenture.

Int J Prosthodont 2021 Feb 12. Epub 2021 Feb 12.

Purpose: To compare the flexural strength and flexural modulus of soft liner-retained overdentures to ball-and-socket-retained overdentures, as well as to evaluate the effect of using glass fiber as a reinforcement material for soft liner-retained overdentures on such mechanical properties.

Materials And Methods: A total of 80 overdenture specimens were fabricated and divided equally into four groups (n = 20 each): specimens with a metal matrix (group 1); a silicone soft liner matrix (group 2); reinforced with one bundle of unidirectional glass fiber sticks placed above the silicone soft liner matrix (group 3); and reinforced with four layers of bidirectional Stick Net glass fiber weaves placed above the silicone soft liner matrix (group 4). Half of the specimens from each group were stored in water at room temperature (23°C ± 1°C) for 24 hours, while the other half were stored in water at 37°C for 30 days before being subjected to a static 3-point loading test.

Results: After 1 day of water storage, the flexural strength and flexural modulus values of groups 1, 3, and 4 were not significantly different from each other (P = .788, P = .084), but were significantly higher than group 2 (P < .05). Water storage for 30 days significantly decreased the flexural strength and modulus values of group 1 only (P < .001) and not the other three groups (P >.05).

Conclusion: After 30 days of water storage, the flexural strength and flexural modulus values of overdentures retained with a metal housing were not significantly different from those of overdentures retained with a silicone soft liner housing. Placing uni- and bidirectional glass fiber reinforcement above soft liner matrices increases the fracture resistance of a soft liner-retained overdenture.
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http://dx.doi.org/10.11607/ijp.6677DOI Listing
February 2021

Corrigendum to "Biomechanical aspects of reinforced implant overdentures: A systematic review" [J. Mech. Behav. Biomed. Mater. 91 (2019) 202-211].

J Mech Behav Biomed Mater 2021 Feb 16;114:104199. Epub 2020 Nov 16.

Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku, Turku, Finland; Welfare Division, City of Turku, Turku, Finland.

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http://dx.doi.org/10.1016/j.jmbbm.2020.104199DOI Listing
February 2021

Midline denture base strains of glass fiber-reinforced single implant-supported overdentures.

J Prosthet Dent 2020 Sep 18. Epub 2020 Sep 18.

Professor, and Chair of Biomaterials Science Department, University of Turku, Turku, Finland; Chief Hospital Dentist, City of Turku, Welfare Division, Turku, Finland.

Statement Of Problem: The fracture incidence of implant-supported overdentures is more frequent in the area of attachment because of stress concentration and denture deformation in this area. How E-glass fiber reinforcement can address this problem is unclear.

Purpose: The purpose of this in vitro study was to evaluate the influence of unidirectional E-glass fiber reinforcement on the mid-line denture base strains of single implant-supported overdentures.

Material And Methods: An experimental acrylic resin cast was constructed with a single implant placed in the mid-line area and a ball attachment screwed to the implant. Twenty-four experimental overdentures were constructed and divided into 4 groups: group AP fabricated from autopolymerizing acrylic resin without fiber reinforcement, group APF fabricated from autopolymerizing acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix, group HP fabricated from heat-polymerized acrylic resin without fiber reinforcement, and group HPF fabricated from heat-polymerized acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix. A biaxial rosette strain gauge was attached to the incisor areas of each overdenture above the attachment level (Ch1, Ch2) and to a multichannel digital strain meter. A static vertical load of 100 N was applied to the first molar area bilaterally by using a universal testing device during strain measurement procedures. The differences in the mean strain and deflection values among the investigated groups were evaluated for statistical significance using 1-way analysis of variance (ANOVA) with the Tukey post hoc multiple comparison (α=.05).

Results: The type of acrylic resin did not have a statistically significant effect on the mean strain values among groups (P=.350), while the reinforcement did significantly affect them (P<.001). The interaction between reinforcement and acrylic resin was not statistically significant (P=.552). Both strain gauge channels in group APF and group HPF recorded significantly lower strain values by almost 50% than those of group AP and group HP (P<.05).

Conclusions: Unidirectional E-glass fiber reinforcement placed over the residual ridge and implant attachment significantly reduced denture base strains and deformation of single implant-supported overdentures.
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http://dx.doi.org/10.1016/j.prosdent.2020.05.018DOI Listing
September 2020

Effect of bioactive glass air-abrasion on the wettability and osteoblast proliferation on sandblasted and acid-etched titanium surfaces.

Eur J Oral Sci 2020 04 10;128(2):160-169. Epub 2020 Mar 10.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

The aim of this study was to evaluate the hydrophilicity, surface free energy, and proliferation and viability of human osteoblast-like MC3T3-E1 cells on sandblasted and acid-etched titanium surfaces after air-abrasion with 45S5 bioactive glass, zinc-containing bioactive glass, or inert glass. Sandblasted and acid-etched titanium discs were subjected to air-abrasion with 45S5 bioactive glass, experimental bioactive glass (Zn4), or inert glass. Water contact angles and surface free energy were evaluated. The surfaces were studied with preosteoblastic MC3T3-E1 cells. Air-abrasion with either type of glass significantly enhanced the hydrophilicity and surface free energy of the sandblasted and acid-etched titanium discs. The MC3T3-E1 cell number was higher for substrates air-abraded with Zn4 bioactive glass and similar to that observed on borosilicate coverslips (controls). Confocal laser scanning microscopy images showed that MC3T3-E1 cells did not spread as extensively on the sandblasted and acid-etched and bioactive glass-abraded surfaces as they did on control surfaces. However, for 45S5- and Zn4-treated samples, the cells spread most at the 24 h time point and changed their morphology to more spindle-like when cultured further. Air-abrasion with bioactive glass and inert glass was shown to have a significant effect on the wettability and surface free energy of the surfaces under investigation. Osteoblast cell proliferation on sandblasted and acid-etched titanium discs was enhanced by air-abrasion with 45S5 bioactive glass and experimental Zn4 bioactive glass compared with air-abrasion with inert glass or no air-abrasion.
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http://dx.doi.org/10.1111/eos.12683DOI Listing
April 2020

Air Abrasion With Bioactive Glass Eradicates Biofilm From a Sandblasted and Acid-Etched Titanium Surface.

J Oral Implantol 2019 Dec 19;45(6):444-450. Epub 2019 Sep 19.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Finland.

is able to form a high-affinity biofilm on material surfaces. has also been detected around infected implants. Bioactive glasses (BAGs) have been shown to possess antibacterial effects against and other microorganisms. This in vitro study was performed to investigate the influence of BAG air abrasion on biofilm on sandblasted and acid-etched titanium surfaces. Sandblasted and acid-etched commercially pure titanium discs were used as substrates for bacteria (n = 107). The discs were immersed in an solution and incubated for 21 hours to form an biofilm. Twenty colonized discs were subjected to air abrasion with Bioglass 45S5 (45S5 BAG), experimental zinc oxide containing BAG (Zn4 BAG), and inert glass. After the abrasion, the discs were incubated for 5 hours in an anaerobic chamber followed by an assessment of viable cells. Surface morphology was evaluation using scanning electron microscopy (n = 12). The thrombogenicity of the glass particle-abraded discs (n = 75) was evaluated spectrophotometrically using whole-blood clotting measurement at predetermined time points. Air abrasion with 45S5 and Zn4 BAG eradicated biofilm. Significantly fewer viable cells were found on discs abraded with the 45S5 or Zn4 BAGs compared with the inert glass ( < .001). No significant differences were found in thrombogenicity since blood clotting was achieved for all substrates at 40 minutes. Air abrasion with BAG particles is effective in the eradication of biofilm from sandblasted and acid-etched titanium surfaces. Zn4 and 45S5 BAGs had similar biofilm-eradicating effects, but Zn4 BAG could be more tissue friendly. In addition, the steady release of zinc ions from Zn4 may enhance bone regeneration around the titanium implant and may thus have the potential to be used in the treatment of peri-implantitis. The use of either BAGs did not enhance the speed of blood coagulation.
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http://dx.doi.org/10.1563/aaid-joi-D-18-00324DOI Listing
December 2019

Fatigue resistance of a simulated single LOCATOR overdenture system.

J Prosthet Dent 2019 Dec 12;122(6):557-563. Epub 2019 Apr 12.

Professor, and Chair of Biomaterials Science Department, University of Turku, Turku, Finland; City of Turku, Welfare Division, Turku, Finland.

Statement Of Problem: The incidence of fracture in a single-implant overdenture base increases in the region adjacent to the fulcrum implant.

Purpose: The purpose of this in vitro study was to evaluate the effect of bidirectional woven electrical glass (E-glass) fiber reinforcements on the fatigue resistance of a simulated single LOCATOR-retained overdenture.

Material And Methods: Test specimens with a centrally positioned metal housing for a LOCATOR stud attachment were fabricated from autopolymerizing acrylic resin. Specimens for the control group were fabricated without glass fiber reinforcements. The 4L group specimens had 4 layers of E-glass fiber weaves and were divided according to the fiber location into the following 3 subgroups: 4L-A with 4 fiber layers above the metal housing; 4L-N with 4 fiber layers adjacent to the metal housing; and 4L-A+4L-N with 4 fiber layers above and 4 fiber layers adjacent to the housing. Specimens were stored in distilled water for 1 week at 23 °C before cyclic fatigue testing at 10 000 cycles by using a staircase approach (n=12). The results were analyzed with 1-way ANOVA and the Tukey multiple comparisons post hoc analysis (α=.05). A 2-way ANOVA (α=.05) was conducted to detect the effect of fatigue cyclic loading and the position of the fiber layers and their interaction on the fatigue resistance.

Results: The results of the investigated compressive fatigue limits for the test groups were 190 ±15.9 N for the control group, 265 ±15.9 N for the 4L-A subgroup, 220 ±15.9 N for the 4L-N subgroup, and 275 ±15.9 N for the 4L-A+4L-N subgroup. A nonsignificant difference was found for creep values between the control group and reinforced subgroups (P>.05). The postfatigue flexural strength values in the 4L-A and 4L-A+4L-N subgroups were significantly higher than those in the control group (P<.001) and the 4L-N subgroup (P=.004 and P=.005). However, no significant difference was found in postfatigue flexural strength between the control group and the 4L-N subgroup (P=.828).

Conclusions: Placing 4 layers of bidirectional E-glass fiber weaves above the metal housing can increase the fatigue resistance and the postfatigue flexural strength of single LOCATOR-retained overdentures.
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http://dx.doi.org/10.1016/j.prosdent.2018.11.013DOI Listing
December 2019

TiO-Modified Zirconia Surface Improves Epithelial Cell Attachment.

Int J Oral Maxillofac Implants 2019 Mar/Apr;34(2):313-319

Purpose: Good cell adhesion is an important prerequisite for soft tissue attachment on implant abutment or crown surfaces. The aim of this study was to evaluate the adhesion and proliferation of human epithelial cells on sol-gel-derived TiO-coated and noncoated zirconia.

Materials And Methods: Altogether, 56 zirconia disks (Z-CAD, Metoxit) were fabricated for this study. Half of the disks were coated with a sol-gel-derived TiO coating (MetAlive, ID Creations). The rest of the disks were noncoated and formed the control group. Surface properties of the disks were characterized by contact angle measurements and surface free energy (SFE) calculation. The cell adhesion was tested by cultivating epithelial cells (20,000 cells/cm) on the experimental disks for 1, 3, 6, and 24 hours, after which the fluorescence of the samples was measured (BioTek synergy HT). The amount of cells was detected by comparing the fluorescence value to the standard curve. In addition, the proliferation was studied by growing epithelial cells (25,000 cells/cm) for 1, 3, and 7 days. The number of cells was calculated by defining the absorbance of the samples (Multiskan EX, Thermo Labsystems), followed by a comparison with the standard curve. Finally, the samples were processed for light microscopy.

Results: TiO-coated disks were significantly more hydrophilic with higher total SFE than noncoated disks (P < .05). The amount of epithelial cells was greater on TiO-coated disks than on controls after 24 hours (P < .05). Regarding cell proliferation, the difference was statistically significant (P < .05) on days 3 and 7. Light microscope evaluation confirmed viable cells, which were in immediate close contact with both substrate surfaces. The cell layers on the coated disks appeared to be more uniform and cell rich than the layers on noncoated disks.

Conclusion: This study indicated that TiO coating improves epithelial cell attachment and proliferation on zirconia surfaces. This has good potential to enhance formation of the epithelial junction to the coated zirconia surfaces.
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http://dx.doi.org/10.11607/jomi.6862DOI Listing
May 2019

Early Biofilm Formation on UV Light Activated Nanoporous TiO Surfaces .

Int J Biomater 2018 22;2018:7275617. Epub 2018 Nov 22.

Professor, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Finland.

Purpose: To explore early biofilm formation on hydrothermally induced nanoporous TiO surfaces and to examine the effect of UV light activation on the biofilm development.

Materials And Methods: Ti-6Al-4V titanium alloy discs (n = 40) were divided into four groups with different surface treatments: noncoated titanium alloy (NC); UV treated noncoated titanium alloy (UVNC); hydrothermally induced TiO coating (HT); and UV treated titanium alloy with hydrothermally induced TiO coating (UVHT). plaque formation was studied in 10 healthy, nonsmoking adult volunteers. Titanium discs were randomly distributed among the maxillary first and second molars. UV treatment was administered for 60 min immediately before attaching the discs in subjects' molars. Plaque samples were collected 24h after the attachment of the specimens. Mutans streptococci (MS), non-mutans streptococci, and total facultative bacteria were cultured, and colonies were counted.

Results: The plaque samples of NC (NC + UVNC) surfaces showed over 2 times more often when compared to TiO surfaces (HT + UVHT), with the number of colonized surfaces equal to 7 and 3, respectively.

Conclusion: This study suggested that HT TiO surfaces, which we earlier showed to improve blood coagulation and encourage human gingival fibroblast attachment , do not enhance salivary microbial (mostly mutans streptococci) adhesion and initial biofilm formation when compared with noncoated titanium alloy. UV light treatment provided Ti-6Al-4V surfaces with antibacterial properties and showed a trend towards less biofilm formation when compared with non-UV treated titanium surfaces.
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http://dx.doi.org/10.1155/2018/7275617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282137PMC
November 2018

Biomechanical aspects of reinforced implant overdentures: A systematic review.

J Mech Behav Biomed Mater 2019 03 11;91:202-211. Epub 2018 Dec 11.

Department of Biomaterials Science and Turku Clinical Biomaterials Centre-TCBC, Institute of Dentistry, University of Turku, Turku, Finland; Welfare Division, City of Turku, Turku, Finland.

Purpose: The purpose of this systematic review was to investigate the effect of reinforcement on the mechanical behaviour of implant overdenture (IOD) bases and its cumulative biological effect on the underlying supporting structures (implants and the residual ridge).

Material And Methods: The required documents were collected electronically from PubMed and Web of Science databases targeting papers published in English that focused on denture base reinforcement for IOD prostheses in order to recognize the principal outcomes of reinforcement on the mechanical and biological properties of overdentures. Such biological outcomes as: strains on implants, peri-implant bone loss, residual ridge resorption, and strain on the residual alveolar ridge.

Results: A total of 269 citations were identified. After excluding any repeated articles between databases and the application of exclusion and inclusion criteria, only 13 publications fulfilled the inclusion criteria. Three publications investigated the mechanical properties of fibre and/or metal-reinforced implant overdentures while another 3 articles investigated the effect of metal reinforcement on stress distribution and strains transmitted to the underlying implants. In addition, 3 in vitro studies investigated the effect of metal reinforcement on overdenture base strain and stresses. Stress distribution to the residual ridge and strain characteristics of the underlying tissues were investigated by 2 in vitro studies. Five clinical studies performed to assist the clinical and prosthetic maintenance of metal-reinforced IOD were included. Data concerning denture base fracture, relining, peri-implant bone loss, probing depth, and implant survival rates during the functional period were extracted and considered in order to evaluate the mechanical properties of the denture base, residual ridge resorption and implant preservation rates, respectively.

Conclusion: The use of a denture base reinforcement can reduce the fracture incidence in IOD bases by enhancing their flexural properties and reducing the overdenture base deformation. Strains on the underlying supporting structures of overdenture prostheses including dental implants and the residual ridge can be decreased and evenly distributed using a metal reinforcement.
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http://dx.doi.org/10.1016/j.jmbbm.2018.12.006DOI Listing
March 2019

Load-bearing capacity of simulated Locator-retained overdenture system.

J Prosthet Dent 2018 Oct 29;120(4):558-564. Epub 2018 Jun 29.

Professor and Chair of Biomaterials Science Department, University of Turku, and Chief Dentist, City of Turku Welfare Division, Turku, Finland.

Statement Of Problem: Acrylic resin overdenture bases usually fracture because of stress concentrations at the area of the abutments.

Purpose: The purpose of this study was to evaluate the reinforcing effect of bidirectional woven electrical glass (E-glass) fiber weaves with a different number of layers and different locations on the load-bearing capacity of simulated Locator-retained overdenture specimens.

Material And Methods: Test specimens with a centrally located metal housing for a Locator stud attachment were fabricated from autopolymerizing acrylic resin (polymethylmethacrylate based) and reinforced with bidirectional woven E-glass fiber layers. The control group specimens were fabricated without fiber reinforcement. The 2L group had 2 layers of E-glass fiber weaves and was divided according to the fiber location within the specimens as follows: 2L-A subgroup with 2 fiber layers above the metal housing; 2L-N subgroup with 2 fiber layers adjacent to the housing; and 2L-A+2L-N subgroup with 2 fiber layers above and 2 fiber layers adjacent to the housing. The 4L group had 4 layers of E-glass fiber weaves and was divided according to the fiber location as follows: 4L-A subgroup with 4 fiber layers above the housing; 4L-N subgroup with 4 fiber layers adjacent to the housing; and 4L-A+4L-N subgroup with 4 fiber layers above and 4 fiber layers adjacent to the housing. Dry specimens were submitted to a 3-point static loading test, and the mean flexural strength, flexural modulus, and strain values were analyzed with 1-way ANOVA and Tukey post hoc tests (α=.05). Two-way ANOVA was conducted to detect the influence of the number and location of the reinforcing layers (α=.05).

Results: The results revealed a significant difference (P<.001) in flexural strength values between the control group (92.4 ±14 MPa) and the 2 subgroups, 4L-A (116 ±7.3 MPa) and 4L-A+4L-N (117.1 ±6 MPa), with a significant effect only from the number of the reinforcing layers (P<.001) and not the location (P=.153). No significant differences were found with flexural modulus (P=.195) and strain values (P=.174) among the tested groups.

Conclusions: The load-bearing capacity of a Locator-retained overdenture can be significantly increased by placing 4 layers of bidirectional woven E-glass fiber weaves either only above the metal housing or in both locations above and adjacent to the metal.
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http://dx.doi.org/10.1016/j.prosdent.2018.04.009DOI Listing
October 2018

Effect of ultraviolet light treatment on surface hydrophilicity and human gingival fibroblast response on nanostructured titanium surfaces.

Clin Exp Dent Res 2018 Jun 11;4(3):78-85. Epub 2018 Jun 11.

Department of Prosthetic Dentistry, Stomatognathic Physiology University of Turku Turku Finland.

This study was designed to investigate the effect of nanostructured TiO coatings on human gingival fibroblast and to explore the influence of ultraviolet (UV) light on surface wettability and cellular response. Ti-6Al-4V titanium alloy discs ( = 96) were divided into three groups: a sol-gel-derived MetAlive™ (MA) coating; hydrothermal (HT) coating; and a non-coated (NC) group. Forty-eight titanium substrates were further treated with UV light for 15 min. The water contact angles of the substrates were measured using the sessile drop method. Human gingival fibroblasts were used to evaluate the cell adhesion strength and cell proliferation on experimental surfaces. The strength of cell adhesion against enzymatic detachment was studied after 6 hr of adhesion using gentle trypsinization for 15 min at room temperature. A fluorescence microscope was used for cell imaging (Zeiss-stereo-lumar-v12), and images were analyzed for cell counting, and the percentage of detached cells were calculated. The proliferation of cultured cells up to 10 days was determined according to the cell activity using Alamar Blue™assay. The HT group had the lowest contact angle value (31.1°) followed by MetAlive™ (35.3°), whereas the NC group had the highest contact angle (50.3°). After UV light treatment, all surfaces become considerably more hydrophilic. There was a significant difference in the amount of adherent cells between sol-gel and HT groups when compared with the NC group ( < .05) with detachment percentages of 35.8%, 36.4%, and 70.7%, respectively. All substrate types showed an increase in cell proliferation rate until 10 days. It can be concluded that nanostructured titanium oxide implant surfaces, obtained by sol-gel and HT coating methods, enhance the surface wettability and improve human gingival fibroblast function in terms of adhesion and proliferation rate when compared with non-coated surfaces. UV light treatment clearly enhances the wettability of all titanium surfaces.
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http://dx.doi.org/10.1002/cre2.108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6010723PMC
June 2018

Fracture Strength and Precision of Fit of Implant-Retained Monolithic Zirconia Crowns.

J Oral Implantol 2018 Oct 15;44(5):330-334. Epub 2018 May 15.

1   Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

New monolithic zirconia materials can be used to fabricate full-contour fixed dental prostheses with the computer-aided design/computer-aided manufacturing (CAD/CAM) method. The aim of this study was to examine the fracture strength and precision of fit of screw-retained monolithic zirconia crowns made directly on implants or by cementing on prefabricated titanium (Ti) bases. Monolithic screw-retained implant crowns (n = 6) were produced by CAD/CAM method using partially (PSZ) and fully stabilized (FSZ) zirconia. Industrially produced zirconia crowns were used as a reference. A lateral incisor study model was made onto an implant replica. Crowns were produced either directly on the implant or through cementing on a prefabricated titanium base (PSZ+Ti, FSZ+Ti). The crowns were tightened to implant replicas with a torque of 35 Ncm. The gap between the replica and the abutment or crown was measured from ×400 scanning electron microscope images for precision of fit. Mechanical testing until failure was completed with a universal testing machine with loading angle of 45°. Statistical analysis was performed (analysis of variance). Mean (±SD) failure loads were 259 ± 23 (PSZ), 140 ± 13 (FSZ), 453 ± 25 (PSZ+Ti), 439 ± 41 (FSZ+Ti), and 290 ± 39 (Procera). Mean (±SD) gap values were 2.2 ± 0.2 (PSZ), 2.5 ± 1.0 (FSZ), 7.0 ± 1.0 (PSZ+Ti), 7.7 ± 1.6 (FSZ+Ti), and 6.7 ± 1.7 (Procera). Monolithic zirconia crowns with a Ti base clearly show higher fracture strengths than the crowns fixed directly on the implant surface. Better marginal fit can be achieved with direct zirconia crowns than with crowns on a titanium base or industrially produced zirconia crowns.
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http://dx.doi.org/10.1563/aaid-joi-D-17-00249DOI Listing
October 2018

Ultraviolet photofunctionalization of nanostructured titanium surfaces enhances thrombogenicity and platelet response.

J Mater Sci Mater Med 2018 May 4;29(5):56. Epub 2018 May 4.

Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, Turku, Finland.

The purpose of this study was to evaluate blood and platelet response to nanostructured TiO coatings and to investigate the effect of Ultraviolet (UV) light treatment on blood clotting ability, platelet activation and protein adhesion. Ti-6Al-4V titanium alloy plates (n = 138) were divided into three groups; a sol-gel derived MetAlive coating (MA); hydrothermal coating (HT); and a non-coated group (NC). Sixty nine titanium substrates were further treated with UV light for 1 h. The thrombogenicity of the titanium substrates was assessed using fresh human blood with a whole blood kinetic clotting time method. The platelet adhesion test was conducted to evaluate the morphology and adhesion behavior of the platelets on the titanium substrates. Human diluted plasma and bovine fibronectin were used to evaluate protein adsorption. Total clotting time for the UV treated HT, MA and NC titanium substrates was almost 40 min compared to 60 min for non-UV substrates, the total clotting time for the UV treated groups were significantly lower than that of the non UV NC group (p < 0.05). UV light treatment had significantly enhanced coagulation rates. The HT and MA substrates presented more platelet aggregation, spreading and pseudopod formation in comparison with the NC substrates. UV treatment did not affect the platelet activation and protein adsorption. This in vitro study concluded that nanostructured titanium dioxide implant surfaces obtained by sol-gel and hydrothermal coating methods increased coagulation rates and enhanced platelet response when compared with non-coated surfaces. UV light treatment clearly improved thrombogenicity of all examined Ti-6Al-4V surfaces.
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http://dx.doi.org/10.1007/s10856-018-6067-zDOI Listing
May 2018

Optical Properties and Failure Load of Thin CAD/CAM Ceramic Veneers.

Eur J Prosthodont Restor Dent 2017 06;25(2):86-92

Department of Prosthetic Dentistry and Stomatognathic Physiology, Lemminkäisenkatu 2, FI-20014 University of Turku. FINLAND.

This study aimed to compare optical properties and failure load of leucite (IPS Empress CAD LT) and lithium disilicate glass ceramic (IPS e.max CAD LT) materials in incisor veneers. Four groups of veneers were made on 36 bovine incisors with Cerec 3D milling unit (n=9/group): 0.5 and 0.3 mm thick leucite glass and 0.5 and 0.3 mm lithium disilicate glass veneers. The optical features were measured with CM-700d spectrophotometer using white and yellow try-in pastes. Differences were determined by means of ΔE value and luminance. The bovine teeth with veneers were mounted on acrylic resin blocks (Palapress, Heraeus Kulzer) and static loading test was conducted (LR30K plus, Lloyd Instruments). The color difference of veneers could be noticed with yellow and white cements when the material thickness increased from 0.3 to 0.5 mm (leucite ΔE yellow 4.4, white 6.0; lithiumdisilicate ΔE yellow 2.1, white 4.1). Both materials showed similar failure load with 0.5 mm veneers (leucite 1906 +/-319 N; lithiumdisilicate 2098 +/- 309 N). The failure load of 0.3 mm thick lithium dilisilicate veneers (2002 +/- 427 N) was comparable with the 0.5mm veneers. Ultrathin lithium disilicate glass ceramic veneers (0.3 mm) could be a potential option for clinical use.
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http://dx.doi.org/10.1922/EJPRD_01677Maunula07DOI Listing
June 2017

Surface roughness and the flexural and bend strength of zirconia after different surface treatments.

J Prosthet Dent 2016 Oct 5;116(4):577-583. Epub 2016 May 5.

Laboratory Manager, Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; and Senior Lecturer, Turku University of Applied Sciences, Faculty of Health and Well-being, Turku, Finland.

Statement Of Problem: Different surface treatments are commonly used during the fabrication of zirconia fixed dental prostheses. However, such treatments can affect the properties of the zirconia framework material.

Purpose: The purpose of this in vitro study was to determine the effect of different surface treatments on the surface roughness and flexural and bend strength of zirconia.

Material And Methods: Seventy-two zirconia disks (n=8) and 72 zirconia bars (n=8) were sintered and divided into 9 groups for different surface treatments: sintered control, airborne-particle abraded with 50-μm aluminum oxide, airborne-particle abraded with Rocatec soft (30 μm), airborne-particle abraded with Rocatec (105 μm), grinding dry with a micromotor, turbine grinding under water cooling, grinding with silicon carbide paper, diamond paste polishing, and steam cleaning. The biaxial flexural strength of the disks (diameter 19 mm, thickness 1.6 mm) and 3-point bend test of the bars (thickness 2 mm, height 2 mm, length 25 mm) were measured dry at room temperature. One-way ANOVA followed by the Tukey HSD test (α=.05) and Pearson correlation test were used for statistical analysis.

Results: Airborne-particle abrasion and silicon carbide paper grinding increased the flexural and bend strength of zirconia specimens (P<.05). The 3-point bend test gave 20% to 30% higher strength values than the biaxial test, but a strong correlation was shown between the test types. Surface roughness had a statistically significant negative effect on the strength values in the 3-point bend test.

Conclusions: The surface treatments tested affected the strength and surface roughness of zirconia framework material.
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http://dx.doi.org/10.1016/j.prosdent.2016.02.018DOI Listing
October 2016

Complete-arch implant-supported monolithic zirconia fixed dental prostheses: A systematic review.

J Prosthet Dent 2016 Jun 23;115(6):672-677.e1. Epub 2016 Jan 23.

Associate Dean for Research and Department Head, Oral Biology, University of Illinois at Chicago, College of Dentistry, Chicago, Ill. Electronic address:

Statement Of Problem: Monolithic zirconia prostheses are emerging as a promising option in the implant-based rehabilitations of edentulous patients, yet their clinical performance is not fully documented.

Purpose: The purpose of this systematic review was to assess the clinical performance of complete-arch implant-supported monolithic zirconia fixed dental prostheses.

Material And Methods: The electronic databases PubMed, Science Direct, and Cochrane Library were searched for clinical studies on complete-arch implant-supported monolithic zirconia fixed dental prostheses. Human studies with a mean follow-up of at least 1 year and published in an English-language peer-reviewed journal up to June 2015 were included. Two independent examiners conducted the search and the review process.

Results: The search generated 903 titles. Eighteen qualifying studies were retrieved for full-text evaluation. Nine studies were included on the basis of preestablished criteria. Eight studies reported satisfactory clinical and esthetic outcomes. One study demonstrated prosthesis failure. Clinical studies are lacking on the long-term outcome of complete-arch implant-supported monolithic zirconia prostheses.

Conclusions: Complete-arch dental implant restoration with monolithic zirconia is associated with high short-term success. Despite the many advantages and short-term favorable reports, studies of longer duration are necessary to validate the broad application of this therapy.
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http://dx.doi.org/10.1016/j.prosdent.2015.08.025DOI Listing
June 2016

Impact of gastric acidic challenge on surface topography and optical properties of monolithic zirconia.

Dent Mater 2015 Dec 20;31(12):1445-52. Epub 2015 Oct 20.

Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre (TCBC), University of Turku and City of Turku, Finland; Clinic of Oral Diseases, Turku University Central Hospital, Turku, Finland.

Objective: To evaluate the surface topography and optical properties of monolithic zirconia after immersion in simulated gastric acid.

Materials And Methods: Four partially stabilized (PSZ) and one fully stabilized (FSZ) zirconia materials were selected for the study: Prettau (PRT, Zirkonzahn), Zenostar (ZEN, Ivoclar), Bruxzir (BRX, Glidewell), Katana (KAT, Noritake) and FSZ Prettau Anterior (PRTA, Zirkonzahn). IPS e.max (Ivoclar) was used as a control. The specimens (10×10×1.2mm, n=5 per material) were cut, sintered, polished and cleaned before immersed in 5ml of simulated gastric acid solution (Hydrochloric acid (HCl) 0.06M, 0.113% solution in deionized distal water, pH 1.2) for 96h in a 37°C incubator. Specimens were weighed and examined for morphological changes under scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Surface roughness was evaluated by a confocal microscope. Surface gloss and translucency parameter (TP) values were determined by a reflection spectrophotometer before and after acid immersion. The data was analyzed by one-way ANOVA followed by Tukey's HSD post hoc test (p<0.05).

Results: PRTA displayed the most weight loss (1.40%) among the zirconia specimens. IPS e.max showed about three times more weight loss (3.05%) than zirconia specimens as an average. SEM examination indicated areas of degradation, bead-like shapes and smoothening of the polishing scratches after acid immersion. EDX displayed ion interactions and possible ion leaching from all specimens. Sa and Sq values for PRTA, ZEN and IPS e.max were significantly lower (p<0.05) after acid immersion. TP values increased significantly for PRT, ZEN and IPS e.max (p<0.05), while the surface gloss of ZEN, PRTA and IPS e.max increased (p<0.05).

Significance: Monolithic zirconia materials show some surface alterations in an acidic environment with minimum effect on their optical properties. Whether a smoother surface is in fact a sign of true corrosion resistance or is purely the result of an evenly progressive corrosive process is yet to be confirmed by further research.
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http://dx.doi.org/10.1016/j.dental.2015.09.010DOI Listing
December 2015

The effect of staining and vacuum sintering on optical and mechanical properties of partially and fully stabilized monolithic zirconia.

Dent Mater J 2015 ;34(5):605-10

Department of Prosthetic Dentistry and Biomaterials Science, Institute of Dentistry.

The effect of staining and vacuum sintering on optical properties and the bi-axial flexural strength of partially and fully stabilized monolithic zirconia (PSZ, FSZ) were evaluated. Disc-shaped specimens divided into three subgroups (n=15): non-stained, stained and non-stained with vacuum sintering. After staining and sintering, optical properties were evaluated using a reflection spectrophotometer and bi-axial flexural strength was tested using the piston-on-three balls technique. Statistical analysis was performed using multivariate analysis of variance (MANOVA) followed by post-hoc Tukey's tests (p<0.05). Staining decreased translucency parameter (TP) values of FSZ (p<0.05). Sintering under vacuum enhanced TP values for PSZ (p<0.05). Staining enhanced surface gloss for both types of zirconia (p<0.05). Staining increased bi-axial flexural strength of FSZ (p<0.05), while it decreased the strength of PSZ (p<0.05). Sintering under vacuum provided minimal benefits with either type of zirconia.
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http://dx.doi.org/10.4012/dmj.2015-054DOI Listing
January 2017

Load-Bearing Capacity of Fiber-Reinforced Composite Abutments and One-Piece Implants.

Eur J Prosthodont Restor Dent 2015 Jun;23(2):62-9

Fiber-reinforced composites (FRC) can potentially help in a physiologic stress transmission due to its excellent biomechanical matching with living tissues. Novel one-piece FRC implants and abutments with two different fiber orientations were loaded until failure to assess the load-bearing capacity, fracture patterns, and precision of fit. The one-piece FRC implants showed significantly higher load-bearing capacity compared to FRC abutments regardless of the fiber orientation (p < 0.001). For FRC abutments, bidirectional abutments showed significantly higher loads compared to unidirectional abutments (p < 0.001). The type of structure and fiber orientation are strong determinant factors of the load-bearing capacity of FRC implants and abutments.
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June 2015

Optical properties and light irradiance of monolithic zirconia at variable thicknesses.

Dent Mater 2015 Oct 18;31(10):1180-7. Epub 2015 Jul 18.

Turku Clinical Biomaterials Centre (TCBC), University of Turku, Turku, Finland; Department of Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland.

Objectives: The aims of this study were to: (1) estimate the effect of polishing on the surface gloss of monolithic zirconia, (2) measure and compare the translucency of monolithic zirconia at variable thicknesses, and (3) determine the effect of zirconia thickness on irradiance and total irradiant energy.

Methods: Four monolithic partially stabilized zirconia (PSZ) brands; Prettau® (PRT, Zirkonzahn), Bruxzir® (BRX, Glidewell), Zenostar® (ZEN, Wieland), Katana® (KAT, Noritake), and one fully stabilized zirconia (FSZ); Prettau Anterior® (PRTA, Zirkonzahn) were used to fabricate specimens (n=5/subgroup) with different thicknesses (0.5, 0.7, 1.0, 1.2, 1.5, and 2.0mm). Zirconia core material ICE® Zircon (ICE, Zirkonzahn) was used as a control. Surface gloss and translucency were evaluated using a reflection spectrophotometer. Irradiance and total irradiant energy transmitted through each specimen was quantified using MARC® Resin Calibrator. All specimens were then subjected to a standardized polishing method and the surface gloss, translucency, irradiance, and total irradiant energy measurements were repeated. Statistical analysis was performed using two-way ANOVA and post-hoc Tukey's tests (p<0.05).

Results: Surface gloss was significantly affected by polishing (p<0.05), regardless of brand and thickness. Translucency values ranged from 5.65 to 20.40 before polishing and 5.10 to 19.95 after polishing. The ranking from least to highest translucent (after polish) was: BRX=ICE=PRT
Significance: Brand selection, thickness, and polishing of monolithic zirconia can affect the ultimate clinical outcome of the optical properties of zirconia restorations. FSZ is relatively more polishable and translucent than PSZ.
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http://dx.doi.org/10.1016/j.dental.2015.06.016DOI Listing
October 2015

Degree of conversion of dual-polymerizing cements light polymerized through monolithic zirconia of different thicknesses and types.

J Prosthet Dent 2015 Jul 14;114(1):103-8. Epub 2015 Apr 14.

Professor, Department of Prosthetic Dentistry, University of Turku, Institute of Dentistry and Clinic of Oral Diseases, Turku University Central Hospital, Turku, Finland.

Statement Of Problem: Monolithic zirconia restorations are increasingly common. Dual-polymerizing cements have been advocated for cementation. The opacious nature of zirconia restoration can attenuate light, compromising optimal resin polymerization and eventually restoration debonding.

Purpose: The purpose of this in vitro study was to evaluate the influence of material thickness on light irradiance, radiant exposure, and the degree of monomer conversion (DC) of 2 dual-polymerizing resin cements light-polymerized through different brands of monolithic zirconia.

Material And Methods: Dual-polymerizing resin cements (RelyX Ultimate; 3M-ESPE, and Variolink II; Ivoclar, Vivadent) were mixed according to the manufacturers' instructions with a film thickness of 40 μm, placed under a 10 × 10 mm specimen of monolithic zirconia (Prettau Anterior by Zirkonzahn, Katana by Noritake, BruxZir by Glidewell, and Zenostar by Wieland) and a zirconia core control (ICE zirkon by Zirkonzahn) at various thicknesses (0.50, 1.00, 1.50, and 2.00 mm, n = 5 of each thickness). Each specimen was irradiated for 20 seconds (RelyX Ultimate) and 40 seconds (Variolink II) with Elipar S10 (3M-ESPE, 1200 mW/cm(2)). The amount of irradiance and radiant exposure was quantified for each specimen. Fourier transform infrared spectroscopy was used to measure the DC from the bottom surface of the resin. Statistical analysis was performed with 2-way ANOVA and post hoc Tukey honest significant difference (HSD) tests (α = .05).

Results: Light irradiance and radiant exposure decreased as the thickness of the specimen increased (P < .05) regardless of the brand. The ranking from least to highest was BruxZir < ICE zircon = Wieland < Katana = Prettau Anterior. The zirconia brand, thickness, and cement type had a significant effect on the DC (P < .001). The DC decreased significantly as the thickness of the zirconia increased (P < .001). Katana and Prettau Anterior showed the highest DC and BruxZir showed the lowest.

Conclusion: The thickness of zirconia affects the DC of resin-based cements. The DC of the resin cements differed significantly between cements and among zirconia brands. More polymerizing time may be needed to deliver sufficient energy through some brands of zirconia.
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http://dx.doi.org/10.1016/j.prosdent.2015.02.007DOI Listing
July 2015

Fiber glass-bioactive glass composite for bone replacing and bone anchoring implants.

Dent Mater 2015 Apr 29;31(4):371-81. Epub 2015 Jan 29.

Laboratory of Inorganic Chemistry, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.

Objective: Although metal implants have successfully been used for decades, devices made out of metals do not meet all clinical requirements, for example, metal objects may interfere with some new medical imaging systems, while their stiffness also differs from natural bone and may cause stress-shielding and over-loading of bone.

Methods: Peer-review articles and other scientific literature were reviewed for providing up-dated information how fiber-reinforced composites and bioactive glass can be utilized in implantology.

Results: There has been a lot of development in the field of composite material research, which has focused to a large extent on biodegradable composites. However, it has become evident that biostable composites may also have several clinical benefits. Fiber reinforced composites containing bioactive glasses are relatively new types of biomaterials in the field of implantology. Biostable glass fibers are responsible for the load-bearing capacity of the implant, while the dissolution of the bioactive glass particles supports bone bonding and provides antimicrobial properties for the implant. These kinds of combination materials have been used clinically in cranioplasty implants and they have been investigated also as oral and orthopedic implants.

Significance: The present knowledge suggests that by combining glass fiber-reinforced composite with particles of bioactive glass can be used in cranial implants and that the combination of materials may have potential use also as other types of bone replacing and repairing implants.
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http://dx.doi.org/10.1016/j.dental.2015.01.003DOI Listing
April 2015

In vitro assessment of the soft tissue/implant interface using porcine gingival explants.

J Mater Sci Mater Med 2015 Jan 15;26(1):5385. Epub 2015 Jan 15.

Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, 20520, Turku, Finland,

The biologic seal of peri-implant soft tissue is crucial for long-term prognosis of oral implants. This in vitro study describes a novel tissue culture model using porcine gingival explants to evaluate the soft tissue/implant interface. Two different types of substrates were investigated: (a) plain polymer: BisGMA-TEGDMA (50-50 %) and (b) unidirectional fiber-reinforced composite (FRC). Porcine gingival explants were obtained from a local slaughterhouse. The experimental implants (n = 4) were inserted into the middle of freshly excised porcine gingival explants and cultured at the air/liquid interface up to 14 days. Porcine gingival explants with no implants served as baseline controls. The specimens were fixed and processed for the preparation of undecalcified samples. Histological analysis of the soft tissue/implant interface was carried out using a light-microscope. Microscopic evaluation suggests that the gingival explants established epithelial and connective tissue attachment to both implant types over the incubation period. FRC surfaces seemed to have a favorable tissue response with a sign of an outward epithelial migration. However, tissue degeneration was observed at the end of the experiment. In conclusion, this in vitro model maintains mucosal viability and ability to histologically evaluate soft tissue attachment to biomaterials rendering it a time efficient and cost effective model that may reduce the need for animal experiments.
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http://dx.doi.org/10.1007/s10856-015-5385-7DOI Listing
January 2015

Enhanced osteogenicity of bioactive composites with biomimetic treatment.

Biomed Res Int 2014 9;2014:207676. Epub 2014 Apr 9.

Department of Prosthetic Dentistry, University of Turku, Lemminkäisenkatu 2, 20520 Turku, Finland ; Turku Clinical Biomaterials Centre, University of Turku, Itäinen Pitkäkatu 4B, 20520 Turku, Finland ; Clinic of Oral Diseases, Turku University Central Hospital, Lemminkäisenkatu 2, 20520 Turku, Finland.

Purpose: This study aimed to explore if initiation of biomimetic apatite nucleation can be used to enhance osteoblast response to biodegradable tissue regeneration composite membranes.

Materials And Methods: Bioactive thermoplastic composites consisting of poly(ε-caprolactone/DL-lactide) and bioactive glass (BAG) were prepared at different stages of biomimetic calcium phosphate deposition by immersion in simulated body fluid (SBF). The modulation of the BAG dissolution and the osteogenic response of rat mesenchymal stem cells (MSCs) were analyzed.

Results: SBF treatment resulted in a gradual calcium phosphate deposition on the composites and decreased BAG reactivity in the subsequent cell cultures. Untreated composites and composites covered by thick calcium phosphate layer (14 days in SBF) expedited MSC mineralization in comparison to neat polymers without BAG, whereas other osteogenic markers--alkaline phosphatase activity, bone sialoprotein, and osteocalcin expression--were initially decreased. In contrast, surfaces with only small calcium phosphate aggregates (five days in SBF) had similar early response than neat polymers but still demonstrated enhanced mineralization.

Conclusion: A short biomimetic treatment enhances osteoblast response to bioactive composite membranes.
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http://dx.doi.org/10.1155/2014/207676DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4000935PMC
December 2014

In vitro blood and fibroblast responses to BisGMA-TEGDMA/bioactive glass composite implants.

J Mater Sci Mater Med 2014 Jan;25(1):151-62

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A-glycidyl methacrylate-triethyleneglycol dimethacrylate (BisGMA-TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%-TEGDMA 50 wt%), (b) BAG-composite (50 wt% polymer + 50 wt% fraction of BAG-particles, <50 μm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood-clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay™. The BAG-composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG-composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG-composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG-particles enhances fibroblast and blood responses on composite surfaces in vitro.
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http://dx.doi.org/10.1007/s10856-013-5040-0DOI Listing
January 2014

Biofilm medium leads to apatite formation on bioactive surfaces.

J Appl Biomater Funct Mater 2013 Sep 13;11(2):e95-8. Epub 2013 Sep 13.

Department of Periodontology, Institute of Dentistry, University of Turku, Turku - Finland and Turku Clinical Biomaterials Centre - TCBC, University of Turku, Turku - Finland.

Purpose: When investigating apatite formation on biomaterial surfaces, simulated body fluid (SBF) is used as an in vitro solution, however, it does not provide an appropriate environment for the growth of bacterial biofilm. The aim of the present study was to compare the bioactivity in terms of apatite formation on two bioactive glass (BAG) composite surfaces using both SBF and bacterial-biofilm growing medium (BM).

Methods: Polymer composite substrates with different percentages of BAG-particles (50% and 75% by weight) were prepared. Plain resin substrates were used as a negative control. The substrates were immersed in SBF and BM for 3 days. The surface and, subsequently, the cross-sections of the substrates were examined with scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDS).

Results: All the investigated BAG-composite surfaces showed apatite formation after immersion in SBF and BM liquid media.

Conclusions: The use of BM is a promising method for studies involving simultaneous biofilm growth and apatite formation on bioactive surfaces.
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http://dx.doi.org/10.5301/JABFM.5000154DOI Listing
September 2013

Blood and fibroblast responses to thermoset BisGMA-TEGDMA/glass fiber-reinforced composite implants in vitro.

Clin Oral Implants Res 2014 Jul 16;25(7):843-51. Epub 2013 Apr 16.

Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Centre-TCBC, University of Turku, Turku, Finland; Finnish Doctoral Program in Oral Sciences-FINDOS, Institute of Dentistry, University of Turku, Turku, Finland.

Objectives: This in vitro study was designed to evaluate both blood and human gingival fibroblast responses on fiber-reinforced composite (FRC) aimed to be used as oral implant abutment material.

Material And Methods: Two different types of substrates were investigated: (a) Plain polymer (BisGMA 50%-TEGDMA 50%) and (b) FRC. The average surface roughness (Ra) was measured using spinning-disk confocal microscope. The phase composition was identified using X-ray diffraction analyzer. The degree of monomer conversion (DC%) was determined using FTIR spectrometry. The blood response, including the blood-clotting ability and platelet adhesion morphology, was evaluated. Fibroblast cell responses were studied in cell culture environment using routine test conditions.

Results: The Ra of the substrates investigated was less than 0.1 μm with no signs of surface crystallization. The DC% was 89.1 ± 0.5%. The FRC substrates had a shorter clotting time and higher platelets activation state than plain polymer substrates. The FRC substrates showed higher (P < 0.01-0.001) amount of adhered cells than plain polymer substrates at all time points investigated. The strength of attachment was evaluated using serial trypsinization, the number of cells detached from FRC substrates was 59 ± 5%, whereas those detached from the plane polymer substrates was 70 ± 5%, indicating a stronger (P < 0.01) cell attachment on the FRC surfaces. Fibroblasts grew more efficiently on FRC than on plain polymer substrates, showing significantly higher (P < 0.01) cell metabolic activities throughout the experiment.

Conclusions: The presence of E-glass fibers enhances blood and fibroblast responses on composite surfaces in vitro.
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http://dx.doi.org/10.1111/clr.12151DOI Listing
July 2014

Ectopic bone formation in and soft-tissue response to P(CL/DLLA)/bioactive glass composite scaffolds.

Clin Oral Implants Res 2014 Feb 29;25(2):159-64. Epub 2012 Oct 29.

Department of Prosthetic Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Turku Clinical Biomaterials Center, Turku, Finland.

Objectives: To characterize biological response to subcutaneously implanted macroporous poly(ε-caprolactone/D,L-lactide)-based scaffolds, and to evaluate the effect of bioactive glass (BAG) filler and osteogenic cells to the tissue response and ectopic bone formation.

Material And Methods: In the first part of this study, six different scaffold types were screened in a rat subcutaneous implantation model. The polymer scaffolds with 70/30 caprolactone/lactide ratio and corresponding composites with < 45 μm BAG filler size were chosen for the further ectopic bone formation assay. The scaffolds were loaded with differentiating bone marrow stromal cells and implanted subcutaneously in syngeneic rats.

Results: With plain scaffolds, only mild foreign body reaction with no signs of gross inflammation was observed after 4 weeks of implantation. Furthermore, the scaffolds were fully invaded by well-vascularized soft connective tissue. Overall, all the tested scaffold types showed an appropriate host response. With cell-seeded scaffolds, several loci of immature mineralizing tissue and small amounts of mature bone were observed after 4 weeks. The incidence of mature bone formation was two and four in polymer scaffolds and composites, respectively (n = 8). After twelve weeks, mature bone was observed in only one polymer scaffold but in seven composites (n = 8). Excluding bone formation, the host response was considered similar to that with cell-free scaffolds.

Conclusions: Plain scaffolds supported the ingrowth of well-vascularized fibroconnective tissue. Furthermore, cell seeded composites with BAG filler showed enhanced ectopic bone formation in comparison with corresponding neat polymer scaffolds.
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http://dx.doi.org/10.1111/clr.12051DOI Listing
February 2014

In vivo evaluation of bioactive glass-based coatings on dental implants in a dog implantation model.

Clin Oral Implants Res 2014 Jan 19;25(1):21-8. Epub 2012 Oct 19.

Department of Biomaterials, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.

Objectives: Although titanium is commonly used as a favorable bone implant material due to its mechanical properties, its bioactive and osteoconductive capacity is relatively low. Calcium phosphate ceramics, predominantly hydroxyapatite (HA), have been frequently used for coating purposes to improve the bioactive properties. In view of the suggested osteopromotive capacity of bioactive glasses (BGs), this study aimed to evaluate the effect of BG incorporation into HA coatings on implant performance in terms of bone contact and bone area.

Materials And Methods: A total of 48 screw-type titanium implants with magnetron sputter coatings containing different ratios of HA and BG (HA, HABGLow, and HABGHigh; n = 8) were placed into the mandible of 16 Beagle dogs. After 4 and 12 weeks, their performance was evaluated histologically and histomorphometrically. Peri-implant bone area percentage (BA%) was determined in three zones (inner, 0-500 μm; middle, 500-1000 μm; and outer, 1000-1500 μm). Additionally, bone-to-implant contact (BIC%) and first bone-implant contact (1st BIC) were assessed for each sample.

Results: After 4 weeks, bone-to-implant contact for the HA- and HABGLow-coated groups was significantly higher (P < 0.05) than for the HABGHigh coatings. Mean values for overall BA% showed comparable values for both the HABGLow (58.3%)- and HABGHigh (56.3%)-coated groups. Data suggest that the relative BA around the HA-coated implants (67.8%) was higher, although this was only significant compared to the HABGHigh group. After 12 weeks, all three groups showed similar bone-to-implant contact and no differences in BA were found.

Conclusions: The incorporation of BG into HA sputter coatings did not enhance the performance of a dental implant in implantations sites with good bone quality and quantity. On the contrary, coatings containing high concentrations of BG resulted in inferior performance during the early postimplantation healing phase.
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http://dx.doi.org/10.1111/clr.12060DOI Listing
January 2014