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Journal of Oral Science & Rehabilitation No. 1, 2018

B a c t e r i a l c o l o n i z a t i o n o n d i f f e r e n t a b u t m e n t m a t e r i a l s Fig. 2 not printable Fig. 2 Microbial growth observed after the 3 cleaning treatments tested for the 4 abutment types. The bar graphs display the means and standard deviations obtained. Statistical analysis showed significant differences in microbial abatement with P values of 0.02 (S. haemo- lyticus), 0.02 (S. pyogenes) and 0.0003 (E. coli). Abutment A: titanium abut- ment without anodization; Abutment B: gold hue anodized titanium abutment; Abutment C: pink hue anodized titanium abutment; Abutment D: zirconia abutment. Discussion Abutment decontamination is considered an important factor for long-term dental implant survival. Moreover, chlorhexidine has been widely investigated for its unique properties of inhibiting bacterial growth on titanium sur- faces.15 In the present study, chlorhexidine’s decontamination properties were confirmed, and the degree of bacterial inhibition was compara- ble between all of the abutments considered. S. haemolyticus, S. pyogenes and E. coli were not able to grow on either anodized or nonanod- ized titanium abutments after treatment with chlorhexidine. They were able to partially grow after treatment with sterile water. This is in accor- dance with previous studies,20, 21 which reported the reduction of S. pyogenes on titanium discs after ultraviolet irradiation. However, uncommon oral bacterial populations were used in this study, because they were easier to stain, but, above all, because they express one of the highest adhe- siveness ratios and present the worst possible conditions for the decontamination methods.22 The group contamination (abutment immersed in a bacterial solution and then seeded on the culture plate) showed a surprisingly lower amount of bacterial growth on culture plates compared with bacterial suspension (growth up to second and third quadrants, respectively). This finding shows that titanium surfaces, with and without anodization, and zirconia surfaces behave similarly regarding bacterial adhesion (P < 0.05). These results are in accordance with those of recent studies,23 confirming that zirco- nia and titanium alloy surfaces have comparable properties regarding bacterial adhesion. One limitation of the present study stays in the in vitro conditions used to determine the micro- bial abatement. It would be desirable to assess the same conditions in a dynamic environment such as the oral microbiota. Nevertheless, this study shows evidence that the abutment sur- faces have inhibitory capabilities against 3 dif- ferent microbial species, including Gram- positive and Gram-negative bacteria. This study shows also that a low concentration of chlorhexidine is effective in eliminating microbial contamination from different types of abutments. Moreover, Yamane et al. investigated bacte- rial affinity to titanium and zirconia discs and found no statistically significant adhesion differ- ences.18 Interestingly, the bacterial count after 4 days of contamination was similar to those pre- sented in this study (between 8 and 9 Log CFU).18 Bacterial adhesiveness can be influenced by the surface roughness: The rougher the surface, the greater the bacterial adhesiveness.24 All of the abutments used for the study were prefab- ricated. This fact may be a limitation of the study. In fact, clinically, all abutments placed in the patient undergo a dental technician process that increases the surface roughness character- istics, regardless of the final polishing that is applied. It would be of interest to test the same abutments after preparation. Regarding clinical implications, further stud- ies should test the optimal chlorhexidine con- centration and especially application time to better determine good clinical practice. More- over, the clinical procedure during maintenance with a PTFE curette or rubber cup could modify the titanium abutment surface configuration, leading to an increased roughness, greater bac- terial adhesion and a potentially more difficult cleaning procedure.25 Journal of Oral Science & Rehabilitation Volume 4 | Issue 1/2018 35

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