Winner 2001 - The IADR.CED Visiting Scholar Stipend

 Zeynep Ergücü

2002 IADR-CED VISITING SCHOLAR STIPEND

Stipend Recipient :             Dr. Zeynep ERGÜCÜ, Izmir, TURKEY

Hosted by             :           Prof. Gottfried SCHMALZ , Regensburg, GERMANY

Duration of the stay:   May 01^st -November 01 ^st  , 2002

Research topics       :  

·        Effects of dentin on the antibacterial activity of various dentin bonding agents

·        Monitoring the cytotoxicity of composite luting cements in a dentin barrier test

Research Methods :

·        The antibacterial effects of Prime & Bond NT, Prime & Bond NT without fluoride, Gluma Comfort Bond, ABF, Xeno CF II, HEMA, TEGDMA and 0.2 % chlorhexidine (positive control) were tested against Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus acidophilus using the standard agar diffusion method. Additionally, bovine dentin disks (200µm and 500µm thickness) were placed between the bacteria and the test substances. From dentin bonding agents the non-polymerized components, as well as the polymerized system were tested. After incubation for 24 h (S. mutans and S. sobrinus) or 48 h (L. acidophilus) at 37°C with 5 %CO₂ the diameters of the inhibition zones were measured.

• The cytotoxicity of composite luting cements was investigated by a dentin barrier test.

Three dimensional cultures of SV40 transfected pulp derived cells were transferred into an in vitro dentin barrier test device with dentin slices of 200 and 500 mm thickness. After 24 h incubation at 37°C test materials were applied into the cavity part of the device. Ceramic inserts (Cerafil, Brassler) were luted to the dentin with (1) Variolink II/Excite (Vivadent) or (2) RelyX Unicem (3MEspe). A light curing glass ionomer cement (Vitrebond, 3MEspe) was used as reference material and an A-silicone impression material (President, Coltene) as negative control (100% cell vitality). The pulpal part of the device was perfused with cell culture medium. After 24h exposure, cell survival was measured by MTT tests, and 10 cultures per material were statistically analyzed (Mann-Whitney-test, a=0.05).

Results of the Studies:

• Effects of dentin on the antibacterial activity of various dentin bonding agents

It was observed that dentin reduced the antibacterial activity of chlorhexidine and of dentin bonding agents significantly. The effect of the latter might  be considered to be limited to the superficial dentin after curing.

·        Cytotoxicity of composite luting cements in a dentin barrier test

With a residual dentin barrier of 500 mm the tested composite luting cements may not alter biologically the dental pulp on a short term basis. With a very thin dentin layer, both test materials affected the cells with the self-adhesive material being less toxic and pulp protection is still recommended.

Submitted Abstracts:

Two abstracts were submitted for the 81^st General Sesssion of the International Association for the Dental Research (June 25-28, 2003, Göteborg, Sweden).

·        Paper Submission # 2662 ( Abstract enclosed)

Effect of dentin on the antibacterial activity of dentin bonding agents (G. Schmalz, Z. Ergücü, K.A. Hiller) 

·        Paper Submission # 2391 (Abstract enclosed)

Cytotoxicity of composite luting cements in a dentin barrier test (G. Schmalz, Z. Ergücü, K.A. Hiller)

2662 Effect of Dentin on the Antibacterial Activity of Dentin Bonding Agents

G. SCHMALZ¹, Z. ERGUCU², and K.-A. HILLER¹, ¹ University of Regensburg, Germany, ² Ege University, Bornova/Izmir, Turkey

Objectives: The antibacterial activitiy of different dentin bonding agents was compared and the effect of dentin on the antibacterial activity was evaluated.

Methods: The antibacterial effects of Prime & Bond NT, Prime & Bond NT without fluoride, Gluma Comfort Bond, ABF, Xeno CF II, HEMA, TEGDMA and 0.2 % chlorhexidine (positive control) were tested against Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus acidophilus using the standard agar diffusion method. Additionally, bovine dentin disks (200µm and 500µm thickness) were placed between the bacteria and the test substances. From dentin bonding agents the non-polymerized components, as well as the polymerized system were tested. After incubation for 24 h (S. mutans and S. sobrinus) or 48 h (L. acidophilus) at 37°C with 5 %CO₂ the diameters of the inhibition zones were measured.

Results: Without dentin, ABF Primer showed growth inhibition for all bacterial strains used. Xeno CF II inhibited the growth of S. mutans and S. sobrinus, while Prime & Bond NT had an inhibitory effect on S. sobrinus only. ABF Bonding inhibited colony formation of L. acidophilus. Prime & Bond NT without fluoride, HEMA and TEGDMA did not have any antibacterial effects in this test system. Dentin disks of 500µm thickness reduced the inhibitory effect of chlorhexidine to 23-54 % compared to direct application. ABF Primer (non-polymerized) produced inhibition zones against all tester strains regardless of dentin disks interposed or not. Xeno CF II did not produce any inhibition zones when applied on 200µm thick dentin. After polymerization, the ABF system did not inhibit bacterial growth, if it was separated from the bacteria by a dentin disk of only 200 µm.

Conclusions: Dentin reduces significantly the antibacterial activity of chlorhexidine and of dentin bonding agents and the effect of the latter may be considered to be limited to the superficial dentin after curing.

81st General Session of the International Association for Dental Research (June 25-28, 2003)

2391 Cytotoxicity of Composite Luting Cements in a Dentin Barrier Test

G. SCHMALZ¹, Z. ERGÜCܲ, and K.-A. HILLER¹, ¹ University of Regensburg, Germany, ² Ege Universitesi, Izmir, Turkey

Composite luting cements are applied onto the cut dentin and thus the risk for the dental pulp has to be assessed.

Objective: To evaluate the cytotoxicity of a new self-adhesive composite luting material containing new monomers in comparison with a known material in a dentin barrier test simulating the in vivo situation.

Methods: Three dimensional cultures of SV40 transfected pulp derived cells (Schmalz et al., J Dent Res 78: 522, 1999) were transferred into an in vitro dentin barrier test device with dentin slices of 200 and 500 mm thickness. After 24 h incubation at 37°C test materials were applied into the cavity part of the device. Ceramic inserts (Cerafil, Brassler) were luted to the dentin with (1) Variolink II/Excite (Vivadent) or (2) RelyX Unicem (3MEspe). A light curing glass ionomer cement (Vitrebond, 3MEspe) was used as reference material and an A-silicone impression material (President, Coltene) as negative control (100% cell vitality). The pulpal part of the device was perfused with cell culture medium. After 24 h exposure, cell survival was measured by MTT tests, and 10 cultures per material were statistically analyzed (Mann-Whitney-test, a=0.05).

Results: With 500 mm dentin, cell survival rates for Variolink II/Excite (111%) and RelyX Unicem (94%) were statistically not different from the negative control, but from the reference material (75%). With 200 mm dentin, cytotoxicity of all test materials significantly increased. Both luting cements were significantly less toxic than the reference material (26%). RelyX Unicem (77%) was significantly less toxic than Variolink II/Excite (56%).

Conclusions: With a residual dentin barrier of 0.5 mm the tested composite luting cements may not alter biologically the dental pulp on a short term basis. With a very thin dentin layer, both test materials affected the cells with the self-adhesive material being less toxic and pulp protection is still recommended.

81st General Session of the International Association for Dental Research (June 25-28, 2003)