Removing bacteria from rough surface titanium discs with chlorhexidine and additional brushing with dentifrice.

OBJECTIVES: This in vitro study was conducted: (i) to evaluate the effect of using cotton pellets soaked with chlorhexidine (CHX) on titanium surface roughness; (ii) to assess the removal of Porphyromonas gingivalis (P. gingivalis) from resorbable blast material (RBM) titanium surfaces using CHX pellets; and (iii) to evaluate the effects of additional brushing on bacterial removal efficiency. MATERIALS AND METHODS: RBM titanium discs were treated with CHX-soaked cotton pellets, and change in surface roughness was measured using confocal microscopy. After the titanium discs were incubated with P. gingivalis for 2 days, the discs were cleaned with CHX pellets for 40 s. The quantity of remaining adherent bacteria was measured using crystal violet assay. Additional brushing was performed with dentifrice for a total of 40 s, and bacterial removal efficiency with brushing and dentifrice was evaluated using crystal violet assay and scanning electron microscopy. RESULTS: The changes in surface roughness after treatment were observed by confocal microscopy. Statistically significant decrease in surface roughness was seen in CHX 40-s group (p < 0.05). Cleaning with CHX-soaked pellets resulted in significant decrease in remaining adherent bacteria. Brushing the bacteria-incubated discs with dentifrice reduced adhering bacteria. There were fewer bacteria left on the CHX-pre-treated discs compared with the brushing-only group, but there were no significant differences when compared with the brushing-only group (p > 0.05). CONCLUSIONS: This study clearly showed that burnishing with CHX influenced the RBM titanium surface, and burnishing with CHX pellets and brushing with dentifrice were efficient in removing bacteria from the contaminated titanium surface.

Treatment with various ultrasonic scaler tips affects efficiency of brushing of SLA titanium discs.

PURPOSE: The dental implant surface will be colonized by bacteria once it is exposed to the oral cavity. It is necessary to keep the titanium surface clean to prevent peri-implant diseases. Mechanical instrumentation is widely used, but this may cause damage to the implant surfaces. There is limited information whether surface change resulting from instrumentation influences the adherence of bacteria to the implant surface or influences the ease of removal of bacteria from the titanium surface by daily brushing. Therefore, this in vitro study was performed (1) to evaluate removal of Porphyromonas gingivalis from sand-blasted and acid-etched (SLA) titanium discs after the discs were instrumented by various ultrasonic scaler tips or brushed with a toothbrush with dentifrice using crystal violet assay and scanning electron microscopy (SEM), and (2) to assess the change of surface roughness after the treated discs were brushed with a toothbrush with dentifrice. MATERIALS AND METHODS: SLA discs were treated with various ultrasonic scaler tips and a toothbrush. The titanium discs were incubated with P. gingivalis for 2 days after treatment (ultrasonic scales tips and brush) and then the disc surfaces were brushed for total of 40 seconds (20 seconds, two cycles) with a toothbrush with dentifrice. Differences in adhering bacteria were evaluated using crystal violet assay and SEM. Surface roughness of the treated discs after brushing with dentifrice was measured using confocal microscopy. RESULTS: The change of surface structure was observed after different treatment modalities. Removal of bacteria was increased with the longer time of brushing, and the ultrasonic metal tip group displayed a significantly lower number of bacteria after brushing when compared to other groups. CONCLUSIONS: Within the limits of this study, it may be suggested that when SLA surface is exposed to the oral cavity, it should firstly be treated with metal tips to smoothen the rough surface and thereby reduce attachment of bacteria and facilitate the removal of bacteria by daily oral hygiene procedures.

Decontamination methods to restore the biocompatibility of contaminated titanium surfaces.

PURPOSE: The reaction of cells to a titanium implant depends on the surface characteristics of the implant which are affected by decontamination. The aim of this study was to evaluate the cytocompatibility of titanium disks treated with various decontamination methods, using salivary bacterial contamination with dental pellicle formation as an in vitro model. METHODS: Sand-blasted and acid-etched (SA) titanium disks were used. Three control groups (pristine SA disks [SA group]; salivary pellicle-coated SA disks [pellicle group]; and biofilm-coated, untreated SA disks [NT group]) were not subjected to any decontamination treatments. Decontamination of the biofilm-coated disks was performed by 14 methods, including ultrasonic instruments, rotating instruments, an air-powder abrasive system, a laser, and chemical agents. MG63 cells were cultured in the presence of the treated disks. Cell proliferation assays were performed on days 2 and 5 of cell culture, and cell morphology was analyzed by immunofluorescence and scanning electron microscopy (SEM). A vascular endothelial growth factor (VEGF) assay was performed on day 5 of culture. RESULTS: The cell proliferation assay revealed that all decontaminated disks, except for the 2 groups treated using a plastic tip, showed significantly less cell proliferation than the SA group. The immunofluorescence and SEM analyses revealed that most groups showed comparable cell density, with the exception of the NT group, in which the cell density was lower and bacterial residue was observed. Furthermore, the cells grown with tetracycline-treated titanium disks showed significantly lower VEGF production than those in the SA group. CONCLUSIONS: None of the decontamination methods resulted in cytocompatibility similar to that of pristine SA titanium. However, many methods caused improvement in the biocompatibility of the titanium disks in comparison with the biofilm-coated, untreated titanium disks. This suggests that decontamination is indispensable for the treatment of peri-implantitis, even if the original biocompatibility cannot be restored.

Establishment of a dental license regulation authority is required in Korea: results of the Delphi technique.

PURPOSE: In addition to dental education, a system for the evaluation and management of dental licensing and certification is required to meet the growing societal demand for more competent dentists. In this study, the Delphi technique was used to gather opinions from a variety of professionals on the problems of and remedies for the dental license management system in Korea. METHODS: Delphi surveys were conducted from April 2016 to October 2016 in South Korea. A variety of dental professionals were included and categorized into 3 groups according to their expertise as follows: the basic dentistry group, the clinical dentistry group, and the policy group. The Delphi technique was conducted in 3 rounds of e-mail surveys, each with different questions that probed with increasing depth on the dental license management system. In each successive round, the responses were categorized, scored on a Likert scale, and statistically analyzed. RESULTS: After categorizing the results of the first survey and ranking the results of the second survey using the Delphi technique, regulation by a licensing authority was found to be the most critical issue. This was followed by the license renewal system, continuing education, a tiered licensure system, improvement of foreign license approval, and utilization of retirees, in decreasing order of importance. The third Delphi survey showed a similar ranking, with regulation by a licensing authority being the major concern. Opinions regarding the dental license management system were provided as open-ended responses. The responses of the 3 groups showed statistically significant differences in the scores for the issue of regulation by a licensing authority. After re-grouping into the dentistry group and the policy group, the issue received a significantly higher score in the dentistry group. CONCLUSION: The quality of dental treatment should be managed to protect patients and dental professionals. For this purpose, the establishment of an independent license regulation authority along with legislative changes is required.

Instrumentation With Ultrasonic Scalers Facilitates Cleaning of the Sandblasted and Acid-Etched Titanium Implants.

Mechanical instrumentation is widely used to debride dental implants, but this may alter the surface properties of titanium, which in turn may influence bacterial adhesion and make it more difficult to remove the biofilm. This in vitro study was performed (1) to assess the amount of biofilm formation on a sand-blasted and acid-etched titanium fixture treated with ultrasonic scalers with metal, plastic, and carbon tips and (2) to evaluate how this treatment of titanium surfaces affects implant cleaning by brushing with dentifrice. The titanium fixtures were treated with various ultrasonic scaler tips, and surface roughness parameters were measured by confocal microscopy. Biofilm was formed on the treated fixtures by using pooled saliva from 10 subjects, and the quantity of the adherent bacteria was compared with crystal violet assay. The fixture surfaces with biofilm were brushed for total of 30 seconds with a toothbrush with dentifrice. The bacteria remaining on the brushed fixture surfaces were quantified by scanning electron microscopy. Surface changes were evident, and the changes of the surfaces were more discernible when metal tips were used. A statistically significant decrease in roughness value (arithmetic mean height of the surface) was seen in the 2 metal-tip groups and the single plastic-tip group. After brushing with dentifrice, the treated surfaces in all the treatment groups showed significantly fewer bacteria compared with the untreated surfaces in the control group, and the parts of the surfaces left untreated in the test groups. Within the limits of this study, treatment of titanium fixture surfaces with ultrasonic metal, plastic, or carbon tips significantly enhanced the bacterial removal efficacy of brushing. Thorough instrumentation that smooths the whole exposed surface may facilitate maintenance of the implants.

Who succeeds at dental school? Factors predicting students' academic performance in a dental school in republic of Korea.

The purpose of this study was to examine what cognitive and non-cognitive factors were responsible for predicting the academic performance of dental students in a dental school in the Republic of Korea. This school is one of those in Korea that now require applicants to have a bachelor's degree. In terms of cognitive factors, students' undergraduate grade point average (GPA) and Dental Education Eligibility Test (DEET) scores were used, while surveys were conducted to evaluate four non-cognitive measures: locus of control, self-esteem, self-directed learning, and interpersonal skills. A total of 353 students matriculating at Seoul National University School of Dentistry in 2005, 2006, 2007, and 2008 consented to the collection of records and completed the surveys. The main finding was that applicants who scored higher on internal locus of control and self-efficacy were more likely to be academically successful dental students. Self-directed learning was significantly associated with students ranked in the top 50 percent in cumulative GPA. However, students' interpersonal skills were negatively related to their academic performance. In particular, students' lack of achievement could be predicted by monitoring their first-year GPA. Therefore, the identification of those factors to predict dental school performance has implications for the dental curriculum and effective pedagogy in dental education.

In vitro analysis of the efficacy of ultrasonic scalers and a toothbrush for removing bacteria from resorbable blast material titanium disks.

BACKGROUND: A resorbable blast material (RBM) surface is reported to have a higher bone-to-implant contact percentage than machined surfaces, but modified surfaces with rougher textures have been shown to favor colonization by bacteria and development of peri-implantitis. Therefore, this in vitro study compares the effects of different instruments on surface roughness and removal of bacteria from RBM titanium implant disks. METHODS: RBM titanium disks were treated with various ultrasonic scaler tips and a toothbrush, and change in surface roughness was measured by confocal microscopy. The disks were incubated with bacteria, and instruments made of carbon or plastic, two metal ultrasonic scaler tips, or a toothbrush were used to remove the attached bacteria. The amount of remaining bacteria was evaluated using a crystal violet assay. RESULTS: The change in surface structure following different treatment modalities was analyzed by confocal microscopy. A statistically significant decrease in the arithmetic mean value of RBM surfaces (R(a)) was observed after treatment with an ultrasonic scaler with a metal tip. The use of a metal tip (rather than a carbon or plastic tip) and brushing with dentifrice was more efficient in removing bacteria from the contaminated titanium surface according to the crystal violet assay. CONCLUSION: Within the limits of this study, the use of a metal tip may be effective in removing bacteria from contaminated surfaces.

Calcium hydroxide inactivates lipoteichoic acid from Enterococcus faecalis.

Calcium hydroxide is a widely used endodontic medicament for eliminating viable bacteria and inactivating virulence factors. Enterococcus faecalis, a pathogenic gram-positive bacterium, has been associated with refractory apical periodontitis. Because lipoteichoic acid (LTA) is a major virulence factor of gram-positive bacteria, we examined whether calcium hydroxide could detoxify LTA from E. faecalis. An enzyme-linked immunosorbent assay showed that calcium hydroxide-killed E. faecalis was less potent than heat-killed bacteria in stimulating the release of tumor necrosis factor-alpha by a murine macrophage line, RAW 264.7 (P < 0.05). Pretreatment of LTA with calcium hydroxide remarkably abrogated the ability of LTA to induce the release of tumor necrosis factor-alpha (P < 0.05). Furthermore, calcium hydroxide-treated LTA was not able to stimulate Toll-like receptor 2, which recognizes functionally intact LTA. These results suggest that calcium hydroxide could detoxify LTA, resulting in attenuation of the inflammatory responses to E. faecalis and its LTA.

Phenol/water extract of Treponema socranskii subsp. socranskii as an antagonist of Toll-like receptor 4 signalling.

Treponema socranskii is one of the most frequently found oral spirochaetes in periodontitis and endodontic infections. LPS or glycolipids from bacteria are potent stimulators of innate immune and inflammatory systems. In this study the bioactivity of a phenol/water extract from T. socranskii subsp. socranskii (TSS-P) was analysed. TSS-P showed minimal endotoxicity and no inducing potential for proinflammatory cytokines (TNF-alpha and IL-8) or for intercellular adhesion molecule-1 (ICAM-1) in human monocyte cell line THP-1 cells and primary cultured human gingival fibroblasts. Rather, it inhibited ICAM-1 expression and IL-8 secretion from cells stimulated by the LPS of Escherichia coli and Actinobacillus actinomycetemcomitans, which are known to be Toll-like receptor 4 (TLR4) agonists. However, this antagonistic activity was not shown in cells stimulated by peptidoglycan or IL-1beta. As its antagonistic mechanism, TSS-P blocked the binding of E. coli LPS to LPS-binding protein (LBP) and CD14, which are molecules involved in the recruitment of LPS to the cell membrane receptor complex TLR4-MD-2 for the intracellular signalling of LPS. TSS-P itself did not bind to MD-2 or THP-1 cells, but inhibited the binding of E. coli LPS to MD-2 or to the cells in the presence of serum (which could be replaced by recombinant human LBP and recombinant human CD14). The results suggest that TSS-P acts as an antagonist of TLR4 signalling by interfering with the functioning of LBP/CD14.

Upregulation of intercellular adhesion molecule 1 and proinflammatory cytokines by the major surface proteins of Treponema maltophilum and Treponema lecithinolyticum, the phylogenetic group IV oral spirochetes associated with periodontitis and endodontic infections.

Treponema maltophilum and Treponema lecithinolyticum belong to the group IV oral spirochetes and are associated with endodontic infections, as well as periodontitis. Recently, the genes encoding the major surface proteins (Msps) of these bacteria (MspA and MspTL, respectively) were cloned and sequenced. The amino acid sequences of these proteins showed significant similarity. In this study we analyzed the functional role of these homologous proteins in human monocytic THP-1 cells and primary cultured periodontal ligament (PDL) cells using recombinant proteins. The complete genes encoding MspA and MspTL without the signal sequence were cloned into Escherichia coli by using the expression vector pQE-30. Fusion proteins tagged with N-terminal hexahistidine (recombinant MspA [rMspA] and rMspTL) were obtained, and any possible contamination of the recombinant proteins with E. coli endotoxin was removed by using polymyxin B-agarose. Flow cytometry showed that rMspA and rMspTL upregulated the expression of intercellular adhesion molecule 1 (ICAM-1) in both THP-1 and PDL cells. Expression of proinflammatory cytokines, such as interleukin-6 (IL-6) and IL-8, was also induced significantly in both cell types by the Msps, as determined by reverse transcription-PCR and an enzyme-linked immunosorbent assay, whereas IL-1beta synthesis could be detected only in the THP-1 cells. The upregulation of ICAM-1, IL-6, and IL-8 was completely inhibited by pretreating the cells with an NF-kappaB activation inhibitor, l-1-tosylamido-2-phenylethyl chloromethyl ketone. This suggests involvement of NF-kappaB activation. The increased ICAM-1 and IL-8 expression in the THP-1 cells obtained with rMsps was not inhibited in the presence of the IL-1 receptor antagonist (IL-1ra), a natural inhibitor of IL-1. Our results show that the Msps of the group IV oral spirochetes may play an important role in amplifying the local immune response by continuous inflammatory cell recruitment and retention at an infection site by stimulation of expression of ICAM-1 and proinflammatory cytokines.

Adhesion of oral streptococci to experimental bracket pellicles from glandular saliva.

The aim of this study was to evaluate the functions of bracket pellicles as the binding receptors for Streptococcus mutans and Streptococcus gordonii. Four different types of orthodontic brackets were used: stainless steel, monocrystalline sapphire, polycrystalline alumina, and plastic. The bracket pellicles were formed by incubating orthodontic brackets with fresh submandibular-sublingual saliva or parotid saliva for 2 hours. The pellicles were extracted, and their components were confirmed by gel electrophoresis, immunodetection, and amino acid composition analysis. The roles of the bracket pellicles in the adhesion of oral streptococci were evaluated by incubating tritium-labeled streptococci with pellicle-transfer blots. The results showed that the salivary components adhered selectively according to type of bracket and glandular saliva. The selective adsorption was also proven by the amino acid composition profiles. Among the several salivary proteins, MG2, alpha-amylase, and the acidic proline-rich proteins provided the binding sites for S gordonii. However, none of these proteins in the bracket pellicles contributed to the adhesion of S mutans. These findings suggest that numerous salivary proteins can adhere selectively to the orthodontic brackets, and some of them contribute to the binding of S gordonii.

Use of insertion sequence element IS1126 in a genotyping and transmission study of Porphyromonas gingivalis.

Porphyromonas gingivalis is strongly associated with periodontal diseases and is regarded as one of the risk factors for periodontitis. Insertion sequence element IS1126-based PCR was used to investigate the genetic heterogeneity of P. gingivalis from periodontitis patients and to examine the frequency of the parent-child and spouse-spouse transmission. Two sets of IS1126-specific primers were used for the PCR. The inward primer set (PI1 and PI2), which amplifies the IS1126 fragment of approximately 690 bp, was used to identify P. gingivalis. The outward primer set (PI1RC and PI2RC), which is reverse complementary to PI1 and PI2, respectively, and amplifies the gene fragments between the adjacent IS1126 elements was used to characterize the genotypes of the P. gingivalis strains. PCR of P. gingivalis with PI1RC and PI2RC resulted in the production of two to seven amplicons, which showed a unique electrophoretic pattern in each strain (4 laboratory strains and 37 clinical isolates cultured from 12 patients with aggressive periodontitis). The usefulness of the method for transmission study was confirmed by detecting identical genotypes between the isolates and the plaque samples from which the isolates were cultured and between the plaque samples from different tooth sites in the same patient. Thirty probands with periodontal diseases and their thirty immediate family members were included in the transmission study. In 11 of 14 parent-child pairs (78.6%), P. gingivalis revealed an identical or similar band pattern, whereas 5 of 16 spouse pairs (31.25%) had this similarity. These results show that IS1126-based PCR for genotyping P. gingivalis has a highly discriminating potential with reproducible data and is a simple and reliable method for a transmission study.

Synergistic inhibitory effect of cationic peptides and antimicrobial agents on the growth of oral streptococci.

Although chlorhexidine is one of the most efficacious antimicrobial agents used for the prevention of dental caries, side effects limit its application. The effects of gaegurin 6 (GGN6), an animal-derived cationic peptide, and its derivatives PTP6 and PTP12 on the growth of oral streptococci were investigated to assess the potential of these agents for use in the prevention of dental caries. The minimal inhibitory concentrations of the peptides for inhibition of the growth of oral streptococci (Streptococcus mutans , S. sobrinus, S. sanguis and S. gordonii) ranged from 1.2 to 8.2 muM. The peptides also exhibited marked synergistic antibacterial effects with chlorhexidine or xylitol. The most effective combinations (fractional inhibitory concentration index of 0.5) were xylitol with GGN6 against S. gordonii 10558 and chlorhexidine with either GGN6 or PTP6 against S. sobrinus OMZ-175. These results indicate that cationic peptides alone or in combination with chlorhexidine or xylitol might prove effective for the inhibition of the growth of cariogenic oral streptococci in situ.