[Dental biofilms]

Orodental pathologies are generally classified into two main groups: caries and parodontopathies. They result from polymicrobial infections based on the dental plaque's theory which has constantly evolved. Therefore, the concept of acquired biological pellicle or biofilm has been described and largely elaborated.A bacterial biofilm is a unit of bacterial microcolonies embedded within an exopolymeric matrix and adherent to an inert or living surface. The aim of this paper is to provide a review of the literature with regard to the formation, and composition of the biofilm, as well as to point out the close link that exists between biofilm and dental medicine.

Comparative biology of chronic and aggressive periodontitis vs. peri-implantitis

This review was undertaken to address the similarities and dissimilarities between the two disease entities of periodontitis and peri-implantitis. The overall analysis of the literature on the etiology and pathogenesis of periodontitis and peri-implantitis provided an impression that these two diseases have more similarities than differences. First, the initiation of the two diseases is dependent on the presence of a biofilm containing pathogens. While the microbiota associated with periodontitis is rich in gram-negative bacteria, a similar composition has been identified in peri-implant diseases. However, increasing evidence suggests that S. aureus may be an important pathogen in the initiation of some cases of peri-implantitis. Further research into the role of this gram-positive facultative coccus, and other putative pathogens, in the development of peri-implantitis is indicated. While the initial host response to the bacterial challenge in peri-implant mucositis appears to be identical to that encountered in gingivitis, persistent biofilm accumulation may elicit a more pronounced inflammatory response in peri-implant mucosal tissues than in the dentogingival unit. This may be a result of structural differences (such as vascularity and fibroblast-to-collagen ratios). When periodontitis and peri-implantitis were produced experimentally by applying plaque-retaining ligatures, the progression of mucositis to peri-implantitis followed a very similar sequence of events as the development of gingivitis to periodontitis. However, some of the peri-implantitis lesions appeared to have periods of rapid progression, in which the infective lesion reached the alveolar bone marrow. It is therefore reasonable to assume that peri-implantitis in humans may also display periods of accelerated destruction that are more pronounced than that observed in cases of chronic periodontitis. From a clinical point of view the identified and confirmed risk factors for periodontitis may be considered as identical to those for peri-implantitis. In addition, patients susceptible to periodontitis appear to be more susceptible to peri-implantitis than patients without a history of periodontitis. As both periodontitis and peri-implantitis are opportunistic infections, their therapy must be antiinfective in nature. The same clinical principles apply to debridement of the lesions and the maintenance of an infection-free oral cavity. However, in daily practice, such principles may occasionally be difficult to apply in peri-implantitis treatment. Owing to implant surface characteristics and limited access to the microbial habitats, surgical access may be required more frequently, and at an earlier stage, in periimplantitis treatment than in periodontal therapy. In conclusion, it is evident that periodontitis and peri-implantitis are not fundamentally different from the perspectives of etiology, pathogenesis, risk assessment, diagnosis and therapy. Nevertheless, some difference in the host response to these two infections may explain the occasional rapid progression of peri-implantitis lesions. Consequently, a diagnosed peri-implantitis should be treated without delay.

Characterization of the normal bacterial flora in peri-implant sulci of partially and completely edentulous patients

PURPOSE

To characterize the normal bacterial flora and evaluate the presence of periodontopathogenic bacteria around dental implants and to correlate them with the periodontal flora or, in completely edentulous patients, the alveolar gingival flora.

MATERIALS AND METHODS

Clinical and radiographic parameters were recorded to exclude peri-implantitis in 34 partially edentulous and 19 completely edentulous patients. Partially edentulous patients were subdivided into two subgroups based on the depth of the periodontal pocket: ≤ 4 mm (n = 19) and > 4 mm (n = 15). Microbial samples were collected from peri-implant sulci, the deepest periodontal sulci, and, for completely edentulous patients, from the alveolar gingiva. Predominant aerobic bacteria were determined by microbiologic culturing, and multiplex polymerase chain reaction was used to detect five periodontopathogenic bacteria: Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Prevotella intermedia, and Actinobacillus actinomycetemcomitans.

RESULTS

In all the examined patients, oral streptococci were the most frequent aerobic peri-implant bacteria. The frequency of four periodontopathogenic bacteria in tooth sulci (A actino?mycetemcomitans, P gingivalis, T forsythensis, T denticola) was significantly higher around natural teeth with deeper periodontal pockets, but there was no significant difference in the frequency of the same bacteria in peri-implant sulci in the two partially edentulous subgroups. In contrast, there were no such bacteria in the peri-implant sulci or the alveolar gingiva of completely edentulous patients.

CONCLUSIONS

In healthy peri-implant sulci, oral streptococci constitute the predominant bacterial flora. In partially edentulous patients four periodontopathogenic bacteria were detected around implants, and none of these bacteria were found around implants in completely edentulous patients.

Prevention of biofilm formation on titanium surfaces modified with conjugated molecules comprised of antimicrobial and titanium-binding peptides

Specific binding of antimicrobial peptides to titanium (Ti) surfaces may serve to prevent biofilm formation, leading to a reduction in peri-implantitis. This study evaluated the binding behavior of conjugated molecules consisting of antimicrobial and hexapeptidic Ti-binding peptides (minTBP-1) using the quartz crystal microbalance (QCM-D) technique, and investigated the effect of modification of Ti surfaces with these peptides on the bioactivity of Porphyromonas gingivalis. Four kinds of peptide were prepared: histatin 5 (DSHAKRHHGYKRKFHEKHHSHRGY), minTBP-1 + histatin 5 (RKLPDAPDSHAKRHHGYKRKFHEKHHSHRGY), lactoferricin (FQWQRNMRKVR), and minTBP-1 + lactoferricin (RKLPDAPGGFQWQRNMRKVR). The QCM-D analysis demonstrated that significantly larger increases in peptide adsorption were observed in the conjugated peptides than in antimicrobial peptides alone. In addition, ATP activity in P. gingivalis in peptide-modified specimens significantly decreased compared to that in the Ti control. These results indicate that surface modification with conjugated molecules consisting of antimicrobial and Ti-binding peptides is a promising method for reduction of biofilm formation on Ti surfaces.

[Use of molecular genetic diagnostic methods in periodontology and implantology]

The authors have studied the species-specific composition of major periodontopathogenic bacteria (P. gingivalis, P. intermedia, B. forsythus, A. actinomycetemcomitans, and T. denticola), by applying the Russian reagent kit developed and made by HPF "GENETECH", and some fungi, microorganisms, and viruses among the Moscow Region inhabitants with chronic generalized periodontitis in 2006-2008. The studies have shown it possible to use molecular genetic methods for diagnosis, drug therapy monitoring, and epidemiological studies in periodontology and implantology.

Er:Yag Laser application on titanium implant surfaces contaminated by Porphyromonas gingivalis: an histomorphometric evaluation

AIM

The aim of this study was to evaluate the in-vitro application of Erbium Yag Laser (ERL) on implant surfaces contaminated by Porphyromonas gingivalis (Pg.). Moreover, this study evaluated the surface characteristics of irradiated implants.

METHODS

A total of 60 implants was evaluated (20 for each surface group). Each group was divided in two subgroups composed of 10 implants (test and a control). Implants were contaminated by Pg. reference strains. After proper incubation, test implants were irradiated with ERL. Laser parameters were the following: 2 940 nm wavelength, 20 mus pulse duration, 10 Hz frequency and 30 MJ pulse energy. A periodontal fiber was used to irradiate the implant threads on the axial surface with a 45 degrees angle of incidence and performing apex-crown motions for 16 s. Histomorphometric evaluation of implant surfaces (test and control) was made at different magnifications (1 000x, 6 000x,11 000x). Pg. counts were calculated on a 4 800-mm2 surface utilizing a 10-mm grid. Statistical evaluation was made with Fisher and Student's t test (P<0.05).

RESULTS

No surface alterations on test implants were observed. Counting results showed the following decontamination values: 76.2% for machined test implants, 90.9% for titanium plasma spray implants and 98.3% for sandblasted and etched implants. A minimal residual bacterial presence was observed in all groups.

CONCLUSION

The results of the following study showed that ERL application has decontamination effectiveness on different implant surfaces. The modification of laser time application and working parameters could easily determine complete bacterial removal from all the implant surfaces analyzed.

Biofilm on dental implants: a review of the literature

PURPOSE

The aim of this article was to review the current literature with regard to biofilm formation on dental implants and the influence of surface characteristics (chemistry, surface free energy, and roughness) of dental implant and abutment materials and their design features on biofilm formation and its sequelae.

MATERIALS AND METHODS

An electronic MEDLINE literature search was conducted of studies published between 1966 and June 2007. The following search terms were used: biofilm and dental implants, biofilm formation/plaque bacterial adhesion and implants, plaque/biofilm and surface characteristics/roughness/surface free energy of titanium dental implants, implant-abutment interface and plaque/biofilm, biofilm and supragingival/subgingival plaque microbiology, biofilm/plaque and implant infection, antibacterial/bacteriostatic titanium, titanium nanocoating/nanopatterning, antimicrobial drug/titanium implant. Both in vitro and in vivo studies were included in this review.

RESULTS

Fifty-three articles were identified in this review process. The articles were categorized with respect to their context on biofilm formation on teeth and dental implant surfaces and with regard to the influence of surface characteristics of implant biomaterials (especially titanium) and design features of implant and abutment components on biofilm formation. The current state of literature is more descriptive, rather than providing strong data that could be analyzed through meta-analysis. Basic research articles on surface modification of titanium were also included in the review to analyze the applications of such studies on the fabrication of implant surfaces that could possibly decrease early bacterial colonization and biofilm formation.

CONCLUSIONS

Increase in surface roughness and surface free energy facilitates biofilm formation on dental implant and abutment surfaces, although this conclusion is derived from largely descriptive literature. Surface chemistry and the design features of the implant-abutment configuration also play a significant role in biofilm formation.

[Streptococcus mutans colonization on titanium surfaces treated with various fluoride-containing preventive solutions]

Fluoride is a reductive agent and may modify the oxide layer of titanium (Ti) in the transgingival region of dental implants. The low pH and the high fluoride concentration of prophylactic mouthwashes and gels (used in caries prevention) may play a role in this phenomenon. Our main goal was to examine whether changes on the surface structure of Ti caused by high fluoride concentration and acidic pH alter the adherence and the colonization of bacteria. Polished commercially pure Ti discs (CP grade 4, Camlog, Biotechnologies AG, Switzerland) were used in the study. Each sample was treated for 1 hour with one of the solutions: mouthwash containing 0.025% (250 ppm) fluoride, a gel containing 1.25% (12500 ppm) fluoride, and a solution of 1% NaF (3800 ppm fluoride), pH 4.5. The surface structure of the discs was analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The colonization of Streptococcus mutans was studied by scanning electron microscope (SEM) after a 5-day incubation period. The roughness of the treated sample surfaces (Ra), as revealed by AFM measurements, increased 1.3 times for the gel and the mouthwash, and approximately seven folds for the 1% NaF solution, as compared to the control surface. The high fluoride concentration and acidic pH of the gel and the 1% NaF solution resulted in a strong corrosion and a modification of the composition of the Ti surface. The XPS spectra showed the formation of a fluoride containing complex (Na2TiF6) bound strongly to the surface. A correlation was revealed between the roughness of the surface and thickness and maturity of the S. mutans bacterial colonies developed on the modified Ti surface. High fluoride concentration and acidic pH increased the roughness of the Ti surface. Bacterial biofilm colonization on this rough surface proved to be more mature. The amount of bacteria was increased due to the changes in the surface caused by fluoride treatment. The present study indicates that high fluoride concentration in an acidic pH environment may affect the development of a healthy transgingival epithelial junction on the Ti surface. This work was supported by the SIMI-NAS Project of the 5th FWP of the European Commission (Growth Program, GRD3-2001-61801), the Hungarian Ministry of Economy and the EC (GVOP-3.2.1.-2004-04-0408/3.0), the Hungarian Ministry of Health (ETT, 434/2006), and the Hungarian Scientific Research Fund (OTKA F-68440).

Comparison of five parameters as risk factors for peri-mucositis

PURPOSE

The aim of this study was to identify risk factors for the development of clinical signs of peri-implant mucositis and for the presence of periodontal pathogens and to determine a possible correlation between these clinical signs and the presence of periodontal pathogens.

MATERIALS AND METHODS

In 100 patients, a modified Plaque Index (PI), a modified Sulcular Bleeding Index (BOP), and pocket probing depth (PPD) were recorded. Patients with one implant site that scored positive for PI, BOP, and PPD greater than or equal to 5 mm were considered to have peri-implant mucositis. A sample taken at the implant with the deepest pocket was analyzed for periodontal pathogens. Implant surface roughness, smoking, augmentation at the implant site, type of dentition, and radiation therapy were recorded as possible cofactors in the disease process.

RESULTS

Thirty-one patients showed clinical signs of peri-implant mucositis and, in 25 implant sites, periodontal pathogens were found. Smoking showed a statistically significant correlation with clinical signs of peri-implant mucositis (univariate analysis). For periodontal pathogens at the implant site, the type of dentition was statistically significant. In the multivariate analysis of the clinical signs of peri-implant mucositis, smoking and radiation therapy were significant explanatory variables. Seventy-two percent of the patients showed agreement for finding either clinical signs of peri-implant mucositis and periodontal pathogens or for no clinical signs and no pathogens. The sensitivity for diagnosis of peri-implant mucositis was 45%, and the specificity was 84%.

CONCLUSIONS

Smoking was the most important risk factor in the formation of peri-implant mucositis. Radiation therapy was an explanatory variable for the occurrence of inflammation. Implant surface roughness, augmentation at the implant site, and type of dentition had little influence on clinical signs of peri-implant mucositis. The type of dentition influences the periodontal microbiota at the implant site.

Development of novel implant abutments using the shape memory alloy nitinol: preliminary results

PURPOSE

The development of gap-free abutments is a challenging problem, because the gap between the implant and the abutment, which is a consequence of current manufacturing limitations, can serve as a reservoir for pathogens. This may lead to peri-implantitis, a major cause of implant failure. Therefore, the aim of this study was to design and fabricate a gap-free abutment using a shape memory alloy with improved ability to prevent microleakage at the implant-abutment gap.

MATERIALS AND METHODS

The abutment was designed using the shape memory alloy nitinol and based on mathematical calculations considering the temperature-related, reversible changes to its crystalline alloy structure. The abutment prototypes were tested for their susceptibility to microbes in vitro, under static and dynamic conditions, by contaminating the abutments before assembly using a bacterial solution. Microbacterial tests were performed after cultivation of the implants for 1 week. The results were tested for statistically significant differences using the chi-square test.

RESULTS

The mathematical calculations met the clinical requirements using a contact pressure of 2 3 108 Nm2 with a preload of 1.9 kN on cooled abutments. After recooling, the contact pressure was 1.3 Nm2, allowing for easy disassembly. Microbacterial analysis revealed no penetration of Escherichia coli under static conditions either in the control group or in the prototypes. Under dynamic conditions, however, the prototypes showed significantly reduced bacterial leakage compared to the controls.

CONCLUSIONS

The data presented here demonstrate that dental implants fabricated with gap-free abutments using a shape memory alloy showed significantly reduced bacterial leakage versus conventional implants. This improvement could minimize clinical problems such as peri-implantitis and consequently enhance the long-term success of dental implants.

Regenerative therapy of deep peri-implant infrabony defects after CO2 laser implant surface decontamination

The treatment of a peri-implant infrabony defect is difficult because of contamination of the implant surface and adjacent tissues. This case series addresses the ability of a carbon dioxide (CO2) laser to decontaminate failing implants in 15 patients. Clinical and radiologic data are presented with regard to using the laser in combination with bone grafting and a barrier. Augmentation with autogenous bone grafting material (n = 10) or a xenogenic bone grafting material (BioOss) (n = 9) was used, and bone grafts were covered with a collagen membrane. Clinical and radiologic parameters were evaluated postoperatively. After an observation period of 27 months (+/- 17.83), almost complete bone fill in the peri-implant defect was accomplished. These preliminary clinical and radiologic findings suggest that decontamination of the implant surfaces with the CO2 laser in combination with augmentative techniques can be an effective treatment method for peri-implantitis.

Supra- and subgingival biofilm formation on implant abutments with different surface characteristics

PURPOSE

The aim of the present study was to establish a noninvasive method for quantitative analysis of supra- and subgingival biofilm formation on dental implants considering different surface modifications.

MATERIALS AND METHODS

Patients of both sexes were included. They had to be in generally good health, partially edentulous, and the recipient of at least 1 screw-type implant with an abutment possessing supra- and subgingival areas. Healing abutments were inserted for 14 days. The abutment surfaces were divided into quadrants that were sandblasted, ground, acid-etched, and untreated (with the latter surface as a control). Biofilm formation on the healing abutments was analyzed using scanning electron microscopy, including secondary-electron and Rutherford backscattering-detection methods. Calculation of biofilm-covered surfaces was performed depending on grey-values, considering supra- and subgingival areas. After calculating absolute and relative biofilm-covered surfaces depending on localization, the influence of surface modification on biofilm formation was analyzed.

RESULTS

Fifteen healing abutments were inserted in 11 patients. In all surface properties plaque adhesion in supragingival areas was significantly higher (17.3% +/- 23.1%) than in subgingival areas (0.8% +/- 1.0%). Biofilm accumulation in supragingival areas was significantly increasing by higher surface roughness, whereas this influence was not detected in subgingival areas.

CONCLUSION

The described method is valuable for investigation of supra- and subgingival biofilm adhesion on surface-modified implant abutments. There was a significant influence of surface localization (supra- and subgingival) as well as surface modification on biofilm formation.

Association between transmucosal depth of osseointegrated implants and malodor production

PURPOSE

The aim of the present study was to test the association between transmucosal depth of 2-stage dental implants and malodor production.

MATERIALS AND METHODS

Fifty-nine 2-stage implants were tested in 14 patients. Measurements were conducted 3 to 4 weeks following second-stage surgery. Measurements included healing abutment malodor scored using a subjective scale, volatile sulfide compounds levels measured using a sulfide monitor (Halimeter), and microbial sampling for anaerobic growth and malodor production.

RESULTS

All the malodor-related parameters measured in this study were significantly associated with the transmucosal depth. A significant increase in severity was observed concomitant with the increase in transmucosal depth.

CONCLUSION

Based upon the data from this study of 59 two-stage implants in 14 patients, it appears that transmucosal depth of 2-stage dental implants may be an important factor affecting the presence of anaerobic bacterial population and resulting malodor production within the implant-abutment interface.

A comprehensive and critical review of dental implant prognosis in periodontally compromised partially edentulous patients

OBJECTIVES

The outcome of implant treatment in periodontally compromised partially edentulous patients has not been completely clarified. Therefore, the aim of the present study was to perform, applying a systematic methodology, a comprehensive and critical review of the prospective studies published in English up to and including August 2006, regarding the short-term (<5 years) and long-term (>or=5 years) prognosis of osseointegrated implants placed in periodontally compromised partially edentulous patients.

MATERIAL AND METHODS

Using The National Library Of Medicine and Cochrane Oral Health Group databases, a literature search for articles published up to and including August 2006 was performed. At the first phase of selection the titles and abstracts and at the second phase full papers were screened independently and in duplicate by the three reviewers (I. K. K., S. K., I. F.).

RESULTS

The search provided 2987 potentially relevant titles and abstracts. At the first phase of evaluation, 2956 publications were rejected based on title and abstract. At the second phase, the full text of the remaining 31 publications was retrieved for more detailed evaluation. Finally, 15 prospective studies were selected, including seven short-term and eight long-term studies. Because of considerable discrepancies among these studies, meta-analysis was not performed.

CONCLUSIONS

No statistically significant differences in both short-term and long-term implant survival exist between patients with a history of chronic periodontitis and periodontally healthy individuals. Patients with a history of chronic periodontitis may exhibit significantly greater long-term probing pocket depth, peri-implant marginal bone loss and incidence of peri-implantitis compared with periodontally healthy subjects. Even though the short-term implant prognosis for patients treated for aggressive periodontitis is acceptable, on a long-term basis the matter is open to question. Alterations in clinical parameters around implants and teeth in aggressive periodontitis patients may not follow the same pattern, in contrast to what has been reported for chronic periodontitis patients. However, as only three studies comprising patients treated for aggressive periodontitis were selected, more studies, specially designed, are required to evaluate implant prognosis in this subtype of periodontitis. As the selected publications exhibited considerable discrepancies, more studies, uniformly designed, preferably longitudinal, prospective and controlled, would be important.

Dental implant design and oral and systemic health

Dental implants are now a common treatment for replacing missing teeth, and their success has long been measured by appearance, function, and longevity of placement. Most dental implants provide a natural-looking appearance. However, both patients and dentists should be aware that infectious complications of dental implants may not only affect function and longevity, but also the systemic health of patients. In addition to traditional measures of success, numerous published studies support, as a key outcome, prevention of implants from harboring periodontal pathogens. Known negative outcomes of infection include failure of the implant to integrate with the bone, causing implant loss and possible bone loss. Given the established associations between periodontitis and systemic health, it is possible that infection in and around the implant components may impart risks to systemic health. This article reviews causes for peri-implant infection and implant loss, and evaluates an implant design that decreases the possibility of infection and possible health complications, by preventing bacterial infiltration.

Implant Surface Analysis and Microbiologic Evaluation of Failed Implants Retrieved From Smokers

The aim of this study was to evaluate the microbiota and surface of failed titanium dental implants from 4 manufacturers. Twelve mobile dental implants were retrieved from 10 smokers after 3 to 10 years of functional loading. Before implant removal, microbial samples were taken and evaluated using polymerase chain reaction. After implant removal, analyses of the failed implant surfaces were performed using scanning electron microscopy and energy-dispersive spectrometer x-ray. Periodontal pathogens such as Aggregactibacter actinomycetemcomitans, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Treponema denticola were detected in all implants in different proportions. Surface analysis showed varying degrees of surface roughness between the samples and the presence of proteinaceous material, appearing mainly as dark stains. Foreign carbon, oxygen, sodium, calcium, aluminum, and silicon elements were also found. Although no material-related causes of implant failure were detected, several periodontal pathogens were identified independently of the surface topography or manufacturer.

Infection at titanium implants with or without a clinical diagnosis of inflammation

OBJECTIVES

To assess the microbiota at implants diagnosed with peri-implantitis, implant mucositis, or being clinically healthy.

MATERIAL AND METHODS

Clinical and microbiological data were collected from 213 subjects (mean age: 65.7+/-14) with 976 implants in function (mean: 10.8 years, SD+/-1.5). Forty species were identified by the checkerboard DNA-DNA hybridization method.

RESULTS

Implant mean % plaque score was 41.8+/-32.4%. Periodontitis defined by bone loss was found in 44.9% of subjects. Implant mucositis was diagnosed in 59% and peri-implantitis in 14.9% of all cases. Neisseria mucosa, Fusobacterium nucleatum sp. nucleatum, F. nucleatum sp. polymorphum, and Capnocytophaga sputigena dominated the implant sub-mucosal microbiota and the sub-gingival microbiota at tooth sites. Implant probing pocket depth at the implant site with the deepest probing depth was correlated with levels of Eikenella corrodens (r=0.16, P<0.05), the levels of F. nucleatum sp. vincentii (r=0.15, P<0.05), Porphyromonas gingivalis (r=0.14, P<0.05), and Micromonas micros (r=0.17, P=0.01). E. corrodens was found in higher levels at implants with mucositis compared with implant health (P<0.05). Subjects who lost teeth due to periodontitis had higher yields of F. nucleatum sp. vincentii (P<0.02) and N. mucosa (P<0.05). Independent of implant status subjects with teeth had higher levels of P. gingivalis (P<0.05), and Leptotrichia buccalis (P<0.05).

CONCLUSIONS

At implant sites studied, few bacteria differed by whether subjects were dentate or not or by implant status.

Bacterial colonization immediately after installation on oral titanium implants

BACKGROUND

Information on bacterial colonization immediately after dental implant insertion is limited.

AIMS

(1) To assess the early colonization on titanium implants immediately after placement and throughout the first 12 post-surgical weeks, (2) to compare the microbiota at interproximal subgingival implant and adjacent tooth sites.

MATERIAL AND METHODS

Subgingival plaque samples from implant and neighbouring teeth were studied by checkerboard DNA-DNA hybridization before surgery, 30 min after implant placement, and 1, 2, 4, 8, and 12 weeks after surgery.

RESULTS

Comparing bacterial loads at implant sites between 30 min after placement with 1-week data showed that only the levels of Veillonella parvula (P<0.05) differed with higher loads at week 1 post-surgically. Week 12 data demonstrated significantly higher bacterial loads for 15/40 species at tooth sites compared with pre-surgery (P-values varying between 0.05 and 0.01). Between the period immediately after surgery and 12 weeks at implant sites, 29/40 species was more commonly found at 12 weeks. Included among these bacteria at implant sites were Porphyromonas gingivalis (P<0.05), Tannerella forsythia, (P<0.01), and Treponema denticola (P<0.001). Immediately post-surgery 5.9% of implants, and 26.2% of teeth, and at week 12, 15% of implants, and 39.1% of teeth harbored Staphylococcus aureus. Comparing tooth and implant sites, significantly higher bacterial loads were found at tooth sites for 27/40 species after 30 min following implant placement. This difference increased to 35/40 species at 12 weeks post-surgically.

CONCLUSIONS

Bacterial colonization occurred within 30 min after implant placement. Early colonization patterns differed between implant and tooth surfaces.

Analysis of early biofilm formation on oral implants in man

Biofilm formation on oral implants can cause inflammation of peri-implant tissues, which endangers the long-term success of osseointegrated implants. It has been reported previously that implants revealing signs of peri-implantitis contain subgingival microbiota similar to those of natural teeth with periodontitis. The purpose of the first part of this study was an atraumatic, quantitative investigation of biofilm formation on oral implant abutments; the objective of the second part was to investigate whether Haemophilus actinomycetemcomitans and Porphyromonas gingivalis were present in the crevicular fluid around oral implants. Biofilm formation on 14 healing abutments, inserted for 14 days in 10 patients, was analysed quantitatively by use of secondary-electron and Rutherford-backscattering-detection methods. A 16S rRNA-based polymerase chain reaction detection method was used to detect the presence of H. actinomycetemcomitans and P. gingivalis in the crevicular fluid. For this investigation, samples of sulcus fluid were collected with sterile paper points at four measurement points per abutment. The difference between biofilm coverage of supragingival surfaces (17.5 +/- 18.3%) and subgingival surfaces (0.8 +/- 1.0%) was statistically significant (P < 0.05). By use of universal primers, bacteria were found in all the samples taken, although the two periodontal pathogens were not found in any of the samples. The absence of periodontal pathogens from the sulcus fluid during initial bacterial colonization, despite massive supragingival biofilm formation, substantiates the assumption that cellular adherence of peri-implant tissue by means of hemidesmosoma, actin filaments and microvilli reduces the risk of formation of anaerobic subgingival pockets.

Antibiotic resistance testing of the total implant-associated micro-flora and its pure isolates

OBJECTIVE

The aim of the present study was to examine antibiotic resistant strains among the implant-associated microorganisms in vitro, first as mixed cultures and again as pure isolates for resistance to one of five antibiotics.

METHODS

Samples were taken with sterile paper points from the deepest pocket of one implant per patient (n = 24) to culture the total oral micro-flora. The samples were streaked on agar (Schaedler or BHI) and incubated for 7 d in an anaerobic atmosphere. All colonies were rinsed off the plates, aliquots were added to top-agar. Susceptibility against antibiotics (ampicillin, ampicillin + sulbactam, azithromycin and penicillin, moxifloxacin) was determined using the Etest. Resistant strains were picked, purified and characterized, and the Etests were repeated with a selection of the pure isolates.

RESULT

The majority of the mixed cultures (67 - 100 %) showed complete antibiotic resistance. No association with clinical parameters like pocket depth, bleeding on probing or insertion of implants into transplanted bone could be found. Smoking and the surface of the implant also had no influence. 23 % of the 597 resistant colonies contained only yeasts, mostly isolated from irradiated tumour patients. Of the 458 resistant bacteria, the majority were Gram-positive cocci or rods. Staphylococci and M. micros were detected occasionally. The resistance for the 138 selected pure isolates was in most cases lower than for the total micro-flora, irrespective of the antibiotic.

CONCLUSIONS

The higher resistance of the total flora might be explained by synergistic interactions between its members.

Inflammation associated with implants with different surface types

OBJECTIVES

The aim of this study was to determine the nature of the inflammatory infiltrate associated with different transmucosal implant surfaces in dogs.

METHODS

Three experimental and one control single-stage implants were randomly placed on each side of the jaw in eight dogs. The transmucosal portion of the test implants consisted of an acid-etched surface (type A), a machined surface with a circumferential groove (type C) and a surface prepared by mild anodic oxidation (type D). The control was a standard machined surface (type B). In order to determine the response to the different surfaces, plaque control was carried out twice weekly following placement of the implants for the entire period of the experiment. At 6 months, gingival biopsies and plaque samples were obtained. The area of inflammatory infiltrate and the nature of the infiltrating cell types were determined using immunohistology. Real-time polymerase chain reaction was used to identify putative periodontal pathogens.

RESULTS

Inflammatory infiltrates were associated with all implant surfaces and were commonly found subepithelially and perivascularly. T cells were the predominant infiltrating cell type in all lesions, associated with the different surfaces. In all lesions the CD4 : CD8 ratio was approximately 2 : 1. Statistical analysis showed that the type C surface (machined surface with a groove) had significantly larger inflammatory infiltrates than the type B surface (machined surface without a groove; P<0.05). No statistically significant differences were found with respect to the size of the inflammatory infiltrates or in terms of the nature of infiltrating cells. However, despite the intensive plaque control regime, plaque was present on all implant surfaces at the time of biopsy 6 months after placement. All implants had similar numbers of Tannerella forsythia, Fusobacterium nucleatum and Porphyromonas gingivalis. Actinobacillus actinomycetemcomitans, was not detected in any sample.

CONCLUSIONS

These results suggest that the development of inflammation associated with implants is independent of surface type, but is nevertheless associated with the presence of plaque. The different surfaces had no influence on the nature of the infiltrate, with T cells being the predominant cell type in all lesions. Finally, the different implant surface types seemed not to influence the peri-implant microbiota. However, the presence of the circumferential groove tended to be associated with larger infiltrates. Whether this is due to increased plaque accumulation remains to be determined.

In vitro sealing ability of two materials at five different implant-abutment surfaces

BACKGROUND

The aim of the present study was to test the sealing ability of two materials at five different implant-abutment surfaces.

METHODS

In the first phase, 2 mul brain-heart infusion (BHI) broth was deposited into the implant wells and glass culture tubes. A varnish or silicon sealant was applied at the cervical implant portion of experimental groups. The control group remained unexposed. The abutments were torque-tightened to 20 Ncm with a manual torque driver. Implants were immersed in 4 ml BHI broth at 37 degrees C for 2 hours to exclude contamination. In the second phase, 100 mul Enterococcus faecalis American Type Culture Collection (ATCC) strain 29212 was deposited into the glass culture tubes. After periods of 7, 14, 21, 35, 49, and 63 days, the sealing capacity was checked. Abutments were removed, and a sterile paper cone collected material inside implant bodies. This material was transferred to new tubes with BHI to verify the presence of cloudy broths within 24 to 48 hours.

RESULTS

There were no statistically significant differences between the two materials for each time period (Fisher exact test; P >0.05). Group E showed the least level of sealing ability (six implants contaminated), whereas group T showed the highest level (only two implants).

CONCLUSIONS

1) Materials tested were not able to prevent contamination over 63 days. 2) Bacterial contamination was verified after 14 and 35 days in the control and experimental groups, respectively. 3) Although materials tested had demonstrated similar sealing capacities, dental implants showed bacterial contamination regardless of their external or internal hexagonal configurations.