Dental Caries: Causes, Classification & Prevention

• Dental caries are progressive irreversible bacterial damage to the hard tooth structure.
• These structures are exposed to the oral environment.
• This damage is characterized by decalcification of inorganic substances.
• This is followed by the destruction of the organic substances in the tooth, forming a cavity.
• Dental caries is not a linear process that begins with acid demineralization of enamel and ends in a clinically detectable lesion, but is a dynamic process.
• This process consists of alternating periods of destruction (demineralization) and repair (remineralization) occuring over a period of time.
• Caries may progress through the enamel, dentin, and pulp, leading to inflammation of the periapical tissues.
• Cariogenic bacteria plus fermentable carbohydrates cause organic acids that affect the tooth.
• Organic acids lead to demineralization of the inorganic portion and destruction of the organic matrix.

Classification of Dental Caries

• Dental caries can be classified according to the:
  • Site of attack (pit & fissure, smooth surface, root, recurrent caries)
  • Rapidity of attack (acute/rampant, chronic, arrested caries)
  • Extent of caries (incipient, cavitated caries)
  • Time of occurrence (primary and recurrent caries)

Pit & Fissure Caries

• Pit and fissure caries occurs:
  • on the occlusal surfaces of molars and premolars
  • on the buccal and lingual surfaces of molars
  • and on the lingual surfaces of maxillary incisors

Smooth Surface Caries

• Smooth surface caries occurs:
  • on interproximal surfaces below the contact area
  • and on the gingival third of the buccal and lingual surfaces of teeth that are not self-cleansing

Root Caries

• Root caries occurs when the root is exposed to the oral environment due to periodontal disease.

Recurrent Caries

• Recurrent caries occurs around the margin or at the base of an existing restoration.
• Recurrent caries is due to inadequate or poor adaptation of the filling material, which produces a leaky margin.

Acute Dental Caries

• Acute dental caries involves rapidly processing caries involving many or all of the erupted teeth.
• It occurs more frequently in children and young adults.

Rampant Caries

• Rampant caries describes the presence of very rapid and extensive carious lesions in the same person.
• It is associated with nursing bottle rampant caries or xerostomia-induced rampant caries, according to the etiology of the condition.
• Other terms for baby bottle caries include baby bottle syndrome, bottle mouth syndrome, and nursing caries.
• Baby bottle caries is a form of rampant caries that affects deciduous teeth.
• It is caused by frequent and prolonged use of a nursing bottle.
• Maxillary incisors are the first teeth usually affected, followed by the first molars but the mandibular incisors often escape because they are covered by the tongue.

Chronic Dental Caries

• Chronic dental caries progresses slowly and tends to involve the pulp later than acute caries and it is most common in adults.

Arrested Enamel Caries

• Arrested enamel caries is when a proximal smooth surface lesion is halted before cavity formation, usually when the adjacent tooth is lost.
• Stagnation area is removed, allowing the lesion to become accessible to plaque control, and remineralization may occur from saliva.

Arrested Dentin Caries

• Arrested dentin caries occurs in lesions with loss of the overlying enamel following extensive lateral spread of caries along the amelodentinal junction.
• The loss of enamel exposes superficially softened carious dentin to the oral environment, where it is removed by attrition, leaving a hard polished surface.
• The dentin is brown-black in color and hypermineralized due to remineralization from oral fluids.

Theories of Caries Etiology

• Theories of caries etiology include:
  • The legend of the worm from an ancient Sumerian text found in 5000 BC
  • Humoral theory
  • Vital theory (18th century)
  • Chemical (acid) theory
  • Parasitic theory
  • Sulfatase theory
  • Proteolytic theory
  • Phosphate theory
  • Complexing and phosphorilating theory
  • Acidogenic (Chemicoparasitic) Theory (Miller's theory 1890)
  • Proteolysis chelation theory

Acidogenic (Chemicoparasitic) Theory

• The most accepted theory of dental caries is the Acidogenic Theory (Miller's theory 1890).
• In this theory, acid formed from the fermentation of dietary substances by oral bacteria leads to decalcification of the tooth substance.
• This causes subsequent disintegration or dissolution of the organic matrix.
• Acids are present in the deeper carious lesions as different microorganisms invade carious dentin.

Proteolytic Theory

• In this theory, the organic or protein elements of tooth (not the inorganic constituents of enamel) are the initial pathways of invasion by microorganisms.
• Caries is essentially a proteolytic process in which microorganisms invade the organic pathways, destroy them, and form acids.
• Structures of enamel having high organic material composition, like enamel lamellae and enamel rod sheaths, serve as a pathway for microorganism invasion through the enamel.

Proteolysis Chelation Theory

• The proteolysis chelation theory was put forward by Schwartz and his co-workers in 1955.
• It involves simultaneous microbiological degradation of the organic components and dissolution of the minerals by the process of chelation.
• The pH of chelation is neutral or alkaline.
• Chelation is a process in which complexing of the metal ions forms a complex substance through coordinate covalent bonds, resulting in a poorly dissociated and weakly ionized compound.