|Fig1: Caries free beautiful teeth with proper maintenance #|
Arrested caries and remineralization
Pre-Cavitation, or “white spot” caries lesions, can stop when the balance between demineralization and remineralization is changed in favor of remineralization. This could follow the restriction of sucrose, the application of fluoride, or the loss of an adjacent tooth to a proximal caries. This loss of tooth uncovers the area of stagnation and allows proper oral hygiene procedures. The source of the calcium and phosphate for remineralization of the lesion is saliva and plaque. The caries progresses slowly, and even under natural conditions, about 50% of proximal enamel lesions may show no radiographic evidence of progression for 3 years, showing that a small change may be needed to encourage reversal of the process. Although remineralization can bring the mineral content of an enamel lesion closer to that of the original enamel, the deposition is irregular and disorganized at the single crystal level, and the structure of the original enamel cannot be recovered. Despite this, lesions that have incorporated fluoride may be less prone to caries attack than intact enamel. Arrested enamel cavities can remain dull and white or more often discolored due to the incorporation of an extrinsic dye. This is known as inactive lesion or brown spot.
Normal Structure of Dentin
Clinical and Histological Features of Dental Caries
Now we shall describes the clinical features of carious lesions on smooth,
occlusal, and root surfaces. We shall relate the clinical features to their histological
features. We shall consider Enamel and Dentine together, the reasons being:
As a clinician, you will see them in the same way.
You can not understand changes in dentine during caries progression and caries arrest without considering the spread of the enamel lesion.
Changes in Dentine occur before the enamel lesion cavitates. Removal of the biofilm will arrest the lesion in dentine as well as the lesion in enamel.
The lesion, in both enamel and dentine, entirely reflects the activity of the bacterial biofilm.
Before I start talking about the clinical and histological features of dental caries, You must know the
Basic Structure of Enamel
Sound enamel consists of crystals of hydroxyapatite packed tightly together in an orderly arrangement which is known as enamel prisms. The amount of hydroxyapatite ranges between 86 to 95%; the organic component between 1% to 2 % and water between 4% to 12% by volume. The total inorganic content of enamel ranges between 95% to 98% by mass, thats why it looks like crystals.
The crystals are so tightly packed that the enamel gets a glass-like appearance and appears translucent. This is the reason that it allows the varying degrees of yellow colour of the dentine to shine through it. Here, you should know that even though the crystal packing is very tight, each crystal is actually separated from its neighbours by tiny intercrystalline spaces or pores. These spaces are filled with water and organic material. When enamel is exposed to acids produced in the microbial biofilm, mineral is removed from the surface of the crystal which shrinks in size. Thus, the intercrystalline spaces enlarge and the tissue becomes more porous. This increase in porosity can be seen clinically as a white spot.
Lecture Series on Dental Caries
To watch video lectures, click at the following links
In this chapter, you will know about the treatment planning of dental caries. In previous chapter you studies the etio-pathogenesis and clinical characteristics of dental caries. If you have not gone through it, it is advised that you study the previous chapter before proceeding further.
Mechanism of Remineralisation of Enamel
When the oral environment of a person is favourable where the pH is above 5.5 and saliva contains enough calcium and phosphate ions, the remineralisation process of enamel occurs. The supersaturated saliva acts as driving force for remineralisation. In a non cavitated enamel caries lesion, the original crystalline structure of rods remains intact. When it is etched, it acts as nucleating agent for remineralisation. When trace amount of fluoride ions is added to the environment, it enhances the remineralisation process by enhancing the precipitation of calcium and phosphate. The inclusion of fluoride ions results in the formation of fluorapatite crystals in enamel rods which is more resistant to acid attack compared to calcium apatite of the natural enamel rods. Thus, the new enamel becomes resistant to caries process.
This lesson presents basic definitions, terminologies, etiologies, demineralisation-remineralisation of enamel and clinical characteristics of the caries lesion in the context of clinical operative dentistry.
Definitions of Dental Caries and Dental Plaque
Dental caries is defined as a multifactorial, transmissible, infectious oral disease caused primarily by the complex interaction of cariogenic oral flora (biofilm) with fermentable dietary carbohydrates on the tooth surface over time.
Dental plaque is a gelatinous mass of bacteria adhering to the tooth surface. Carious lesions occur only under the plaque. The plaque bacteria metabolises the refined carbohydrate (sucrose mainly) for energy production and produces organic acids as a by product. These acids cause dissolution of crystalline structures of enamel that result in caries lesions of the tooth.