As soon as the process has reached dentin there is an immediate vital response by the odontoblasts and their processes within the dentinal tubules which is assumed as defense reaction.

After reaching enamel dentin junction (EDJ), caries spreads laterally along the junction of least resistance and therefore undermines sound enamel. The established occlusal dentinal lesion is conical in shape with its basis on the EDJ and its apex directed towards the pulp.

Continuous irritation of odontoblasts processes by acids diffusing through the porous enamel or even by bacteria themselves at the stage of enamel destruction activates the pulp/dentin organ in such a way that a region of reactionary or reparative irregular dentin begins to form from the pulpal side.

In addition a mild degree of inflammation in the pulp may occur which is still reversible. But, if the bacterial invasion in the cavity continues, and the irritation of the pulp is persisting, it can cause severe inflammatory changes in the pulp which will not recover.

Hidden caries lesion in some areas which are relatively well protected from mechanical pressure, the layer of clinically intact enamel can be maintained for a long time, so hiding an ongoing demineralization in dentin.

In rare cases, if soft dentin is exposed to attrition () the affected area gradually turned in to a smooth and polished surface, and the caries process may become arrested.

 TYPICAL LOCATION

• Approximal surfaces a defect above the gingival margin, the ridge may be broken and the cavity extends to the occlusal surface.
• Occlusal surfaces a defect located in the pits and fissures and involving surrounding enamel.
• Smooth surfaces above the gingival margin

PATIENT COMPLAINS

• Short  pain as reaction to sweets, thermal agents or mechanical pressure.
• High sensitivity on probing
• Aesthetical discomfort especially in anterior teeth

CLINICAL APPEARANCE a gross cavity full of soft demineralized dentin

1. ACTIVE LESION

·        Light brown and dull ()

·        On smooth surfaces shalow defect close to gingival margin

2. INACTIVE LESION 

·        Dark brown and shiny

·        On smooth surfaces with small distance from gingival margin

 DIAGNOSIS

·        Gentle probing

o       Active lesion feels soft and sticking

o       Inactive feels smooth and hard

·        Radiograph detection conical shape in enamel, EDJ and dentin at varying depth is usually involved too

·        FOTI for approximal surfaces a shadow in the area of a carious demineralization

·        Electrometrical test show normal tooth vitality.

DIFFERENTIAL DIAGNOSIS pulpitis symptomatica, pulpitis asymptomatica, periodontitis asymptomatica