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    • br Discussion The microscopic space between implant and

    2018-10-31


    Discussion The microscopic space between implant and abutment (microgap) facilitates the infiltration of fluids and chemicals i was reading this from tissue fluids and saliva, facilitating bacterial invasion and proliferation [4–6], even in patients with good oral hygiene [1,12,20,22,23]. The bacterial contamination may be eventually correlated with gap sizes or misfits. The level of contamination depends not only on the precision of fit, but also on the degree of the applied micromovement and torque. The incidence of loads and unscrewing of the prosthetic abutment can increase infiltration, whereas optimal adaptation, minimal micromovement and exceptional prosthetic and occlusal planning are factors that can minimize microleakage [8,24]. Several in vitro studies have described the occurrence of bacterial leakage along the implant–abutment interface of systems with different internal connection designs in static or dynamic loading conditions [20,21,25]. Quirynen et al. [26] demonstrated that bacterial invasion of the implant-abutment microgap was detected when fixtures and abutments were assembled and installed in a liquid blood medium inoculated with oral microorganisms. Similarly, Jansen et al. [1] reported microbial leakage of 13 different implant–abutment combinations using E. coli as the indicator bacteria. Callan et al. [27] described moderate to high levels of eight different periodontal pathogenic microorganisms, including A. actinomycetemcomitans and P. gingivalis, colonizing the microgap using DNA-probe analysis. Tesmer et al. [28] assessed the potential risk for invasion of oral microorganisms into the fixture abutment microgap of dental implants with internal Morse-taper connections and the tri-channel internal connection. The 14-day period to observe implant external contamination confirms the study by Koka et al. [29] who verified that subgingival bacterial colonization proceeds in the same time interval. Nakazato et al. [30] however, showed that it takes only 4 h for bacterial colonies to be seen on abutment surfaces. The bacteria infiltration may occur both from an external source to the inner area of an implant and in reverse. This migration of bacteria is probably facilitated through the unavoidable presence of microgaps between the fixture and the abutment components of the assembled system [8,22,31]. The existence of such bacterial leakage is not surprising if one compares the diameter of oral microorganisms (less than 10 μm) with the passive fit between implant components. Binon et al. [32] measured the gap between implants and abutments of different systems and reported dimensions ranging from 20 μm (Implant Innovation) to 49 μm (Nobelpharma AB). The fit between abutment and prosthetic suprastructure shows even larger gaps. A wide variety of microorganisms seem to be able to penetrate along the implant components, ranging from gram positive cocci to gram-negative rods. Some of the identified species (Bacteroides species, Fusobacterium species and Peptostreptococcus micros) have been associated with peri-implantitis [25,27]. Current implant systems cannot completely prevent microbial leakage and bacterial colonization of the inner part of the implant. The penetration of oral microorganisms through the implant abutment interface may produce soft-tissue inflammation and constitute risk to the clinical success of the implants. Loading forces on implants may also contribute to the bacterial colonization of the fixture abutment interface microgap. One disadvantage of the present in vitro study is that loading conditions were not applied. For instance, in an in vitro experiment using loading forces, Steinebrunner et al. [8] evaluated bacterial leakage along the fixture abutment interface microgap and discovered statistically significant differences between five implant systems with respect to the number of chewing cycles and bacterial colonization. Later Nascimento et al. [33] evaluated bacterial leakage of human saliva under loaded and unloaded using DNA check board. Thus, it is important to confirm or contrast the results of the present study using loading conditions.