Dental Caries Chapter 2

Plaque Retention and Susceptible Sites

• Any site on the tooth surface that favors plaque retention and stagnation is prone to caries
• Sites that particularly favor plaque retention include:
  • Enamel pits and fissures on occlusal surfaces of molar and premolar teeth
  • Buccal pits of lower molars and palatal pits of upper molars and maxillary incisors
  • Proximal enamel smooth surfaces just cervical to the contact area
  • The enamel at the cervical margin of the tooth, especially in patients with gingival recession
  • The margins of restorations, particularly where there is a wide gap between the restoration and the tooth or where the restoration overhangs the margin of the cavity

Classification of Dental Caries

• Based on tooth surface site:
  • Pit and fissure caries
  • Smooth surface caries
  • Root caries
• Based on tooth surface integrity:
  • Non-cavitated or incipient caries
  • Cavitated
• Based on rate of progression:
  • Acute caries
  • Chronic caries
  • Arrested caries
• Based on whether the caries lesion is new or under restoration:
  • Primary caries
  • Secondary or recurrent caries
• G.V. Black classification:
  • Class I: Caries affecting the pits and fissures of posterior teeth
  • Class II: Caries affecting the proximal surfaces of posterior teeth
  • Class III: Caries affecting the proximal surfaces of anterior teeth, without involving the incisal edge
  • Class IV: Caries affecting the proximal surfaces of anterior teeth, and involving the incisal angle
  • Class V: Caries affecting the cervical one-third of facial and lingual surfaces of all teeth
  • Class VI: Caries affecting the incisal edges of anterior teeth and cusp tips of posterior teeth
• Limitations of G.V. Black classification:
  • Does not include secondary caries
  • Does not include root surface caries
• Kidd and Smith classification:
  • Based on the anatomic site
  • Includes root caries and recurrent caries
  • Does not include the size of the lesion
• Graham Mount's classification:
  • Based on the cavity size and site
  • Does not include root caries or recurrent caries
  • Includes the size of the lesion

Clinical Characteristics of the Caries Lesion

• Characteristics of caries lesion vary according to the surface nature on which the lesion develops
• Three clinical sites for caries initiation:
  • Pits and fissure surfaces of enamel
  • Smooth enamel surface
  • Root surface
• Pits and fissure caries:
  • High susceptibility to dental caries due to their shape
  • Expands as it penetrates into the enamel
  • In cross-section, the gross appearance of a pit-and-fissure lesion is an inverted V (cone shaped) with a narrow entrance and a progressively wider area of involvement closer to the DEJ
  • The dentinoenamel junction is the weakest part of tooth structure
  • When caries reach the DEJ, it spreads laterally along the DEJ and then progresses into dentine in a V-shaped manner
• Smooth enamel surfaces:
  • Less favorable site for dental caries than pits and fissure surfaces
  • Lesions starting on smooth enamel surfaces have a broad area of origin and a conical, or pointed, extension toward the DEJ
  • A cross-section of the enamel portion of a smooth surface lesion shows a V shape (inverted cone) with a wide area of origin and the apex of the V directed toward the DEJ
• Root surfaces caries:
  • Root surfaces are susceptible to dental caries when they become exposed to the oral environment
  • Exposed as a result of gingival recession
  • The root surface is rougher than enamel and readily allows plaque formation in the absence of good oral hygiene
  • The cementum covering the root surface is extremely thin and provides little resistance to caries attack
  • Root caries lesions have less well-defined margins, tend to be U-shaped in cross-section, and progress more rapidly

Progression of Carious Lesion

• The progression of the carious lesion is variable, depending on:
  • The site of origin
  • The conditions in the mouth