Dentine Caries: Acid-tolerant Microorganisms and Aspects on Collagen Degradation.
نویسنده
چکیده
Dental caries is a common disease all over the world, despite the fact that it can be both effectively prevented and treated. It is driven by acids produced by oral microorganisms as a consequence of their metabolism of dietary carbohydrates. Given enough acid challenge, eventually the tooth enamel barrier will be broken down, and the carious lesion will extend into underlying hard tissue, forming a macroscopic cavity in the dentine. In comparison to biofilm on enamel, a dentine carious lesion provides a vastly different environment for the residing microorganisms. The environment influences the types and numbers of microorganisms that can colonize the dentine caries lesion. The overall aims for this thesis are to enumerate and further study microorganisms found in established dentine caries lesions and also to illuminate how host-derived proteolytic enzymes might contribute to this degradation, not only to better understand the caries process in dentine but also to find incitements for new methods to influence the natural progression of caries lesions. In Paper I, the numbers of remaining viable microorganisms after completed excavation using two excavation methods were investigated. Samples of carious dentine tissue were collected before and after excavation and cultivated on different agar media in different atmospheres. Analysis was performed by counting the number of colony-forming units (CFUs). Key findings: The number of remaining microorganisms after excavation was low for both methods, but some microorganisms always remained in the cavity floors even when the cavities were judged as caries free using normal clinical criteria. In Paper II, the acid tolerant microbiota in established dentine caries lesions was investigated. Samples were taken as in Paper I, but on three levels (superficial, center of lesion, floor of lesion after completed excavation). The samples were cultivated in anaerobic conditions on solid pH-selective agar media of different acidity. Key findings: Each investigated lesion harbored a unique microbiota in terms of both species composition and numbers of microorganisms. This indicates that various combinations of aciduric microorganisms can colonize, survive in and probably also propagate dentine carious lesions. We also found that solid pH-selective agars can be used successfully to select acid-tolerant microorganisms in caries lesions. This would preserve their phenotypic traits for further study. In Paper III, the relation between salivary levels of matrix metalloproteinase-8 (MMP-8), salivary levels of tissue inhibitor of MMP (TIMP-1), and the presence of manifest caries lesions in a large number of subjects was investigated. Saliva samples were collected and analyzed for concentrations of MMP-8, TIMP-1 and total protein using immunofluorometric assays, enzyme linked immunosorbent assays and Bradford assays, respectively. Key findings: Subjects with manifest caries lesions had significantly elevated levels of salivary MMP-8 compared to subjects without caries lesions. TIMP-1 was not significant in any case. In Paper IV, a new method for generating bioactive demineralized dentine matrix substrate (DDM) was developed using a dialysis system and two different demineralization approaches (acetic acid or EDTA). The generated DDM was subsequently analyzed for the presence of type 1 collagen, active MMP-8 and hydroxyproline (HYP) levels using SDS-PAGE, ELISA or immunofluorescence assay. Key findings: Both demineralization methods produced a substrate rich in collagen and with preserved MMP-8 activity. This report presents new knowledge on the composition of the acid tolerant dentine caries microbiota from three levels in dentine carious lesions and on the efficacy of operative caries removal on the numbers of viable microorganisms in the caries free cavity using two operative methods. Moreover, the basic mechanisms behind collagen degradation in the dentine caries process are studied from both a clinical and laboratory perspective. The report also provides a reference for further studies on dentine caries microbiology and dentine caries collagen degradation mechanisms, both of which are known only in part.
منابع مشابه
Immunolocalization and distribution of proteoglycans in carious dentine.
BACKGROUND Collagen type I, proteoglycans (PG) and non-collagenous proteins represent important building blocks of the dentine matrix. While different PGs have been identified in dentine, changes in the distribution of these macromolecules with the progression of caries have been poorly characterized. The aim of this study was to compare the immunolocalization of three small collagen-binding PG...
متن کاملBiomimetic Remineralization of Demineralized Dentine Using Scaffold of CMC/ACP Nanocomplexes in an In Vitro Tooth Model of Deep Caries
Currently, it is still a tough task for dentists to remineralize dentine in deep caries. The aim of this study was to remineralize demineralized dentine in a tooth model of deep caries using nanocomplexes of carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) based on mimicking the stabilizing effect of dentine matrix protein 1 (DMP1) on ACP in the biomineralization of dentine. The exp...
متن کاملThe photo-activated antibacterial action of toluidine blue O in a collagen matrix and in carious dentine.
The main aim of this study was to determine the susceptibility to photo-activated disinfection (PAD) of Streptococcus mutans when the organism was present in a collagen matrix--an environment similar to that which would exist within a carious tooth. In addition, the susceptibility to PAD of bacteria present in carious human teeth was also determined. Light was delivered to the collagen and teet...
متن کاملReactivation of inactivated endogenous proteolytic activities in phosphoric acid-etched dentine by etch-and-rinse adhesives.
Auto-degradation of collagen matrices occurs in resin-infiltrated dentine by the slow action of host-derived matrix metalloproteinases. As phosphoric acid-etching inactivates these endogenous enzymes, it is puzzling how hybrid layers created by simplified etch-and-rinse adhesives can degrade in vivo. This study tested the null hypothesis that there are no differences in the relative proteolytic...
متن کاملChemochemical caries removal: a review of the techniques and latest developments.
Chemomechanical caries removal involves the chemical softening of carious dentine followed by its removal by gentle excavation. The reagent involved is generated by mixing amino acids with sodium hypochlorite; N-monochloroamino acids are formed which selectively degrade demineralised collagen in carious dentine. The procedure requires 5-15 minutes but avoids the painful removal of sound dentine...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Swedish dental journal. Supplement
دوره 233 شماره
صفحات -
تاریخ انتشار 2014