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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 Introduction Dental implants have become a common choice for edentulous sites, and implant survival rate has been demonstrated to be extremely high.1, 2 For these reasons, attention has switched to different aspects, such as esthetic outcome, including shape and shade of the surrounding tissue, and benefits of different prosthetic mate- rials. In recent years, periimplantitis has been extensively analyzed as bone loss has been expe- rienced around many different implants due to different factors.3 Among these factors, prosthetic compo- nents have been included as possible causes of periimplant bone loss. In particular, different materials might have different effects on periimplant soft and hard tissue and on differ- ent patterns of bacterial plaque accumulation. Titanium has been described as an optimal material, since it combines adequate precision, strength and biological compatibility.4 While not much difference in the reaction of periim- plant soft and hard tissue to titanium and zir- conium is present, the literature shows that titanium and zirconia are slightly superior to gold as abutment materials,5, 6 even if few clin- ical differences have been reported.7 In recent years, all-ceramic restorations have become popular owing to their esthetic advantages concerning the soft tissue.8, 9 A more natural outcome with the utilization of a ceramic abut- ment compared with a metal or titanium abut- ment has been well documented in various clinical and in vitro trials, especially when deal- ing with thin periimplant tissue.10–12 The utili- zation of pink-colored abutments and colored implant heads has also been suggested.13 Hence, titanium anodization or nitride coating has been proposed as a method to improve the esthetic result.14 Recently, great emphasis has been placed on the decontamination of the prosthetic compo- nents in order to exclude any possible source of bacterial colonization. The effect of chlorhexi- dine in disrupting and preventing plaque biofilm formation has been widely investigated.15, 16 Pre- vious studies have compared bacterial adhesion affinity to discs and abutments made of titanium or zirconia.17, 18 Moreover, a wide range of clean- ing methods have been proposed for abutment decontamination.15, 19 No evidence is present regarding contamination and decontamination of anodized abutments. The aim of this in vitro study was to analyze the amount of bacterial colonization and to evaluate the efficacy of microbial removal of 2 different detersion pro- tocols on different abutment materials. Materials and methods Microbiological analysis of bacterial adhesion and colonization of abutments was carried out in December 2015 at the Department of Micro- biology, University of Padua, Padua, Italy. Four different abutments were analyzed: 1 machined Grade 5 pure titanium abutments without anodization; 2 machined gold hue anodized titanium abut- ments; 3 machined pink hue anodized titanium abut- ments; and 4 zirconia abutments with titanium connectors (all by Sweden & Martina, Due Carrare, Italy). Initially, each sterile abutment was contaminated with 3 × 108 colony-forming units (CFU) per mL of 3 different bacterial types (Staphylococcus hae- molyticus, Streptococcus pyogenes and Escherichia coli), representing Gram positive and Gram nega- tive bacteria. This condition simulates a possible condition of bacteria accumulation in the oral tract. Five minutes after the bacterial contamina- tion, the abutments were accurately removed from the suspension with sterile forceps and divided into 3 groups of treatment: The abut- ments of the first group were not subjected to any decontamination treatment; the abutments of the second group were rinsed for 10 min with sterile water; the abutments of the third group were incubated for 10 min in a 0.05% chlorhex- idine solution. All of the samples were collected with sterile cotton swabs and plated on Colum- bia agar and 5% sheep blood, MacConkey agar and Chocolate agar plates (Becton Dickinson, Franklin Lakes, N.J., U.S.) using the dilution streak technique. The first quadrant was streaked with the cotton swab, and the succes- sive ones using a 10 µL bacteriological loop in order to dilute the initial inocula. A volume of 10 µL of the initial supersaturated bacterial solu- tion was plated separately as a positive control. Plates were incubated at 37 °C, and the microbial abatements were measured by observing micro- bial growth in each plate at 24 and 48 h. All of the tests were repeated 3 times after abutment cleaning and sterilization under the same conditions. Differences between decon- tamination treatment groups were statistically Journal of Oral Science & Rehabilitation Volume 4 | Issue 1/2018 33