[Seite 133↓]

11  Summary

This work presents four studies dealing with endodontic treatment and microorganisms or microbial cell wall components, respectively.

11.1 Summary of study 1

Lipopolysaccharide (LPS), a cell wall component of Gram negative anaerobic bacteria, has been implicated in the pathogenesis of periapical disease resulting from infected root canals. Calcium hydroxide (Ca(OH)2) has been shown to be an effective medicament in such infections, reducing the microbial titre within the canal. It has been proposed that the therapeutic effect of Ca(OH)2 may also be the result of direct inactivation of LPS. The aim of this study was to investigate whether the toxic potential of an E. coli LPS could be reduced or eliminated by Ca(OH)2. Four concentrations of E. coli LPS ranging from 1-1000 ng/ml sterile water were incubated in duplicate either with 25 mg of Ca(OH)2 or sterile water alone. Controls consisted of Ca(OH)2 without LPS or sterile water only. Monocytes were collected from peripheral blood by centrifuging through a gradient and plated to a specific density. Adherent monocytes were incubated for four days at 37°C with 5% CO2in M199 medium with 10% autologous serum. The different LPS solutions were added to the wells. After four hours the supernatants were collected and quantitatively assayed for TNF—α using an commercial ELISA kit. Statistical analysis was performed with ANOVA. Results indicated that Ca(OH)2 is able to eliminate the ability of an E. coli LPS to stimulate TNF—α production in peripheral blood monocytes (p<0.001).

11.2 Summary of study 2

The aim of this study was to determine the antibacterial effectiveness of either chlorhexidine or calcium hydroxide integrated in gutta-percha points or chlorhexidine or calcium hydroxide delivered as gel or paste, respectively. A total of 70 initially sterile roots with open accesses were carried for one week in the oral cavities of two volunteers. The roots were then removed, samples were taken from the root canals to determine the microorganisms. The roots were medicated with either calcium hydroxide paste, a 5% chlorhexidine gel, a chlorhexidine or a calcium [Seite 134↓]hydroxide containing gutta-percha point, respectively. The accesses were closed with bonding material and the roots incubated for one week. After removal of the antimicrobial agents, roots were again checked for bacterial growth. One thioglycollate soaked paperpoint was then introduced into each canal, roots were incubated for one more week to observe bacterial re-growth. After one week of medication, the absolute bacterial count revealed significantly less bacteria in all test groups compared to the control samples. However, after one and two weeks the application of chlorhexidine-gel and calcium hydroxide paste resulted in significantly more samples without any microbial colonization as compared to gutta-percha point groups and controls.

11.3 Summary of study 3

The aim of this study was to examine whether obturated roots combined with several adhesive and temporary filling materials can be bypassed by bacteria. Standardized cavities were coronally prepared into 130 straight roots mimicing clinical access cavities. After obturation, the roots were assigned to six test and three control groups and coronally sealed with either Clearfil, CoreRestore, IRM, Ketac-Fil or a combination of IRM/wax or Ketac Fil/wax. The roots were then fixed between a top and a bottom chamber each. The top chamber contained soy broth with 108 S. epidermidis CFU/ml, the bottom chamber contained sterile soy broth. For one year, the mounts were checked on a regular basis for turbidity in their bottom chambers indicating bacterial growth. After one year, only 3 out of 19 tested samples from the CoreRestore group and 2 out of 20 samples from the Clearfil group resisted leakage. At termination, there was no significant difference in number of leaking samples among the groups. At the beginning of the experiment, IRM performed worst. Between month 5 and 10, Clearfil showed the least leaking samples, for some months this was statistically significant compared to IRM or Ketac-Fil.

11.4 Summary of study 4

The aim of this study was to examine whether intracanal medication prior to root canal obturation has an inhibitory effect on corono-apical penetration of bacteria. 93 single rooted teeth were instrumented and sterilized with ethylene [Seite 135↓]oxide. They were assigned to three control groups and four test groups. For one week, the roots were dressed with different medicaments: the first group received a 5% chlorhexidine gel, the second was dressed with Ledermix, the third with a fresh mix of calcium hydroxide and water and the fourth group was left unmedicated. After obturation (lateral condensation and AH 26), the roots were fixed between a top and a bottom chamber. The top chamber contained 3ml trypticase soy broth with 108 S. epidermidis CFU´s/ml, whereas the bottom chamber contained sterile trypticase soy broth. For one year, the mounts were incubated at 37°C. They were checked on a regular basis for turbidity in their bottom chambers indicating bacterial growth. None of the test samples leaked for three month. After one year, the calcium hydroxide group had only six leaking out of 20 tested samples whereas the chlorhexidine group had 14 out of 19, the Ledermix group 15 out of 20, and the unmedicated group had 13 leaking samples out of 20 tested. The difference between the calcium hydroxide an the other groups was statistically significant. Ledermix did not perform better than no pre-medication. Chlorhexidine was superior to Ledermix in the second third of the observation period. It may be concluded that under the conditions of this study, calcium hydroxide is considered the medicament of choice to avoid bacterial penetration of the root canal after obturation. The method of sterilizing the teeth prior to integration into the bacterial setup seems to result in prolonged tightness against bacterial penetration.

Reconsidering the results of all four studies it may be recommended to perform multi-visit treatment in case of an infected root canal. A one week intermediate dressing with calcium hydroxide will not only neutralize bacterial LPS, but also reduce bacteria significantly and provide prolonged protection against bacterial penetration after root canal filling. After obturation of the root canal system, it is recommended to quickly provide the tooth with a tight adhesively inserted temporary filling or a definitve restoration to achieve additional protection against bacterial ingress.

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