Dental pulp inflammation; experimental studies in human and monkey teeth

Data from several studies performed during the last 15 years indicate that bacteria and their products are the main etiological factor for dental pulp inflammation. The present series of investigations was conducted in order to determine the irritating effect from various oral bacterial components and restorative measures on dental pulpal tissue and to ascertain reaction patterns of inflamed pulp tissue. The different bacterial materials were tested in an experimental model where the test substance was applied and enclosed in buccal class V cavities prepared in human or monkey teeth. The pulp tissue response was evaluated from tooth specimens after both short (8 hours) and long time (150 days) challenge with the test substance. Intra and extra cellular components from pure bacterial species, cell wall material and a crude mixture of 8 bacterial species were used as representative test materials for oral bacteria associated with growth on or in dentin. Silicate cement restorations were also used as a pulp irritating restorative procedure. The degree of pulpal inflammation was classified according to a descriptive method. In order to obtain a better evaluation method for pulp tissue reactions, a stereo morphometric technique was developed. This method was used in the last study to evaluate the pulp tissue reactions to silicate cement restorations after dentin treatment with calcium hydroxide. The chemotactic effect of the different bacterial materials were also tested in wound chambers implanted in the back of rats. Results from these studies showed that components from different bacterial species had varying capacity to induce pulpal inflammation over cut dentin. The severity of the early inflammatory response was not altered after decomplementation. The tested bacterial products had a similar chemotactic effect on the pulp tissue as on ordinary connective tissue. If the pulp was challenged with bacterial products for a long time period, healing and repair were frequently found, although if the pulp tissue was primary severely inflamed. The inflammatory reactions and repair patterns in human teeth were similar to those of monkey teeth. Treatment of exposed dentin with calcium hydroxide reduced the pulp irritating effect of silicate cement restorations, but induced only limited volumes of irregular secondary dentin formation.