Abstract The history of causality between oral microbiota and oral diseases returns back in its roots to 1884. Though the theory was non-specific, oral diseases were related to the overall accumulation of dental plaque. Since the establishment of dentistry as a separate health care profession in the late 19th century, it concentrated on the treatment of oral diseases and prevention of their occurrence by preventing plaque accumulation in ecological niches. The idea of eliminating artificial ecological niches to eliminate the accumulation rate, by increasing the used materials adaptation appeared with the first leakage test in 1912. Since then, leakage testing models were developed to investigate this phenomenon. The acceptance of these models over the years has changed due to their shortcomings in addition to the application of improper methods/materials which led to faulty conclusions. The aim of this thesis is to develop a testing method which can overcome the disadvantages of the previously known leakage and permeability methods and at the same time can be applied in different dental disciplines. More specifically, the first study used a tooth model with different dentinal wounds sizes, to evaluate the new method for its repeatability, detection limit as well the correlation of the infiltrated fluid volume to the pressure difference change over time. A second study that utilised extracted third molars with class I preparation were used to verify the influence of bonding on the sealability of different restorations and at the same time to compare the new system to the well-known SEM marginal surface analysis as well as the Fuchsin permeation test. In another study, root canals with simple and complicated root canal anatomies were used to correlate the measured leakage values as determined with the new method to the root canal volumes sealed with a root canal filling. For the last two studies, three implants systems of different designs, but almost the same dimensions, were used to compare the new method measured values to the substrate (endotoxin like) and bacterial leakage tests. These were also used to investigate the influence of thermo-mechanical loading on implants leakage. The idea of the new testing method is based on measuring the pressure difference change established between two chambers with the sample held in between, the capability of the sample to maintain a tight seal between the chambers contributes to the sample’s leakage indirectly. Simultaneously, the permeated fluid volume through the sample is measured as a direct indicator of the sample leakage status. The results showed a high repeatability, low detection limit, a high correlation of the penetrated fluid volume to the rate of difference change over time and a proper response of the measured permeation in correlation to the dentinal wound size. It also proved the embedding used to be reliable over time with almost no change in its efficiency after multiple measurements. The importance of bonding in preventing leakage was clearly noticeable when testing different restorative materials and protocols. Correlation between different tests applied was in the favour of the new method to the gold standard (Fuchsin penetration test) over the traditional SEM marginal surface analysis. The different implant systems tested showed consistent performance patterns for both testing conditions (under static conditions and under dynamic conditions), where nonsignificant changes in their measured leakage values could be noticed after the thermo-mechanical loading. The new method showed a consistent correlation to the bacterial leakage patterns as indicated by the day at which leakage was observed under all tested conditions. This correlation was missing once comparing both testing methods to the substrate (endotoxin like) leakage testing method. The new method, proved itself to be reliable and correlates well to the most acceptable leakage/permeation testing methods.
Abstract The history of causality between oral microbiota and oral diseases returns back in its roots to 1884. Though the theory was non-specific, oral diseases were related to the overall accumulation of dental plaque. Since the establishment of dentistry as a separate health care profession in the late 19th century, it concentrated on the treatment of oral diseases and prevention of their occurrence by preventing plaque accumulation in ecological niches. The idea of eliminating artificial ecological niches to eliminate the accumulation rate, by increasing the used materials adaptation appeared with the first leakage test in 1912. Since then, leakage testing models were developed to investigate this phenomenon. The acceptance of these models over the years has changed due to their shortcomings in addition to the application of improper methods/materials which led to faulty conclusions. The aim of this thesis is to develop a testing method which can overcome the disadvantages of the previously known leakage and permeability methods and at the same time can be applied in different dental disciplines. More specifically, the first study used a tooth model with different dentinal wounds sizes, to evaluate the new method for its repeatability, detection limit as well the correlation of the infiltrated fluid volume to the pressure difference change over time. A second study that utilised extracted third molars with class I preparation were used to verify the influence of bonding on the sealability of different restorations and at the same time to compare the new system to the well-known SEM marginal surface analysis as well as the Fuchsin permeation test. In another study, root canals with simple and complicated root canal anatomies were used to correlate the measured leakage values as determined with the new method to the root canal volumes sealed with a root canal filling. For the last two studies, three implants systems of different designs, but almost the same dimensions, were used to compare the new method measured values to the substrate (endotoxin like) and bacterial leakage tests. These were also used to investigate the influence of thermo-mechanical loading on implants leakage. The idea of the new testing method is based on measuring the pressure difference change established between two chambers with the sample held in between, the capability of the sample to maintain a tight seal between the chambers contributes to the sample’s leakage indirectly. Simultaneously, the permeated fluid volume through the sample is measured as a direct indicator of the sample leakage status. The results showed a high repeatability, low detection limit, a high correlation of the penetrated fluid volume to the rate of difference change over time and a proper response of the measured permeation in correlation to the dentinal wound size. It also proved the embedding used to be reliable over time with almost no change in its efficiency after multiple measurements. The importance of bonding in preventing leakage was clearly noticeable when testing different restorative materials and protocols. Correlation between different tests applied was in the favour of the new method to the gold standard (Fuchsin penetration test) over the traditional SEM marginal surface analysis. The different implant systems tested showed consistent performance patterns for both testing conditions (under static conditions and under dynamic conditions), where nonsignificant changes in their measured leakage values could be noticed after the thermo-mechanical loading. The new method showed a consistent correlation to the bacterial leakage patterns as indicated by the day at which leakage was observed under all tested conditions. This correlation was missing once comparing both testing methods to the substrate (endotoxin like) leakage testing method. The new method, proved itself to be reliable and correlates well to the most acceptable leakage/permeation testing methods.