Dental caries
This section covers every aspect of the caries process starting from the cause to its prevention and management with emphasis on the risk factors.
1. Why only certain microorganisms have the ability to adhere to the tooth surface?
Certain bacteria have special receptors for adhesion to the tooth surface and they also produce a sticky matrix which contains dextran, an extracellular polysaccharide, that allows them to cohere to each other.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.Swift.JR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications,2002;69
2. Why plaque initiates carious lesions in certain patients and periodontal disease in some patients?
The caries or periodontal disease caused by plaque can be explained by plaque ecosystem. The energy input for plaque is derived from host diet, host saliva, desquamated cells and cervicular fluid. The energy output from the plaque is lost in its metabolic process, production of metabolites, dislodged viable cells and extra cellular polysaccharides. If the plaque community produces large amout of organic acids, caries will develop subjacent to plaque. If the output is largely toxins, protiolytic enzyme and other antigenic materials, periodontal disease will result.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;88
3. Why crystallization of mineral deposits is never seen on tooth surface, inspite of supersaturated level of calcium and phosphate ions in saliva?
“Statherin",a proline rich peptide capable of stabilizing calcium and phosphate ions is present in saliva. This prevents excessive deposition of these ions on the teeth.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;89-90
4. Why incipient lesions that have smooth intact surface become chalky white opacities when dried?
At a pH of 5.0, the surface remains intact while the subsurface mineral is lost. Thus incipient lesion will have a virtually intact surface, but a porous subsurface. When the tooth surface is dried with the stream of compressed air, it removes the subsurface water, leaving air filled voids that render the area opaque and white. When the porous surface is hydrated, the lesion is not detectable clinically because the porous area remains translucent.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;90
5. Why critical pH is considered as 5.5 for tooth surface?
The hydroxyapatite crystals present in the tooth disintegrates into calcium and phosphate ions at pH below 5.5. Hence it is considered as critical pH. When the same tooth surface is remineralized by fluoride, fluorapatite is formed whose critical pH is 4.5. Below a pH of 4.5, the fluorapatite also disintergrates, leading to loss of tooth structure.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;90
6. Why lactobacilli are considered as secondary invaders?
Mutans streptococci, because of their ability to adhere to tooth surface will initiate caries in the presence of sucrose rich diet. On the other hand, lactobacilli have no adhesion ability and will invade the tooth surface only after cavitation. Thus because of more retentive surface area after cavitation, Lactobacilli are probably the most important in the progression of dentinal caries.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;91
7. Why affected dentin does not require removal during operative procedure?
With respect to operative procedures, carious dentin is divided into outer infected dentin and inner affected dentin. The infected dentin is softened dentin contaminated with bacteria and will be stained by caries detector dye, which stains the irreversibly denatured collagen. The affected dentin is softened demineralized dentin, that has not yet been invaded by bacteria. These dentin will not be stained by caries detector dye as they contain reversibly denatured collagen. Thus affected dentin can remineralize, if favourable environment is provided and hence does not require removal during operative procedure.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;100
8. Why an explorer should not be used to diagnose initial caries lesion?
The "catch" felt by the mechanical binding of the explorer tip depends upon factors like the size of the tip of the probe & the surface topography of the tooth than the presence of caries. Hence it is an unreliable procedure to detect pit and fissure caries.And since enamel and dentin can remineralize and repair in all incipient caries lesions in a favourable clinical enviornement, use of explorer tip to probe these non-cavitated lesions will deprive the chance of repair and might convert the non cavitated caries to a cavitated lesion leading to surgical management (restorative procedures). Hence probing should not be done for all initial caries and should only be used to assess the depth of the cavitated caries.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;103-104
9. Why varnish is better than gel or paste for application as a caries preventive agent?
The varnish is easily applied, has more retentive capacity in interdental areas, contains more concentrated active agents and highly safe to apply than any other medium of application.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002
10. What do you mean by extensive caries?
Caries is said to be extensive, when the distance between the infected dentin and the pulp is judged to be less than 1mm or when the faciolingual extent of the defect is up the cuspal lines and these caries requires extensive restorations with amalgam or cast metals.
Ref: Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;687
11. What is contact caries?
The caries that occurs on the proximal surface of the tooth adjacent to a restoration is contact caries.
Ref: Science of Dental Materials, Skinner, Prism books private limited,9th Edn,450
12. What is dental plaque?
A gelatinous mass of bacteria adhering to the tooth surface is termed plaque or the soft, transluscent and tenaciously adherent material accumulating on the surface of the teeth is called plaque.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;67,69
13. What is specific plaque hypothesis?
According to specific plaque hypothesis, the plaque is assumed to be pathogenic only when the signs of associated disease are present.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;68
14. How is the dietary sucrose related to the production of cariogenic plaque?
The single most important factor in producing cariogenic plaque is the high frequency of sucrose exposure. A series of changes occur in the local tooth environment by frequent sucrose intake and it promotes the growth of highly acidogenic bacteria which will lead to caries.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;69
15. How do the microorganisms survive in the oral cavity?
The microorganisms that have the ability to adhere to a surface only can survive in the oral cavity.those which cannot adhere or free floating micro organism are cleared from the mouth by salivary flow and frequent swallowing. The streptococci are able to adhere to the mucosa and the tooth structure through special receptors for adhesion.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;69
16. What are the tooth habitats favouring the pathogenic plaque accumulation?
• Pits and fissures
• Smooth enamel surfaces immediately gingival to the proximal contacts and gingival one third of the facial and lingual surfaces of the clinical crown
• Root surfaces near the cervical line
• Sub gingival areas
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;80
17. Why are the smooth enamel surfaces considered to be the second most susceptible areas to caries?
The proximal smooth enamel surfaces are relatively free from the effects of mastication, tongue movement and salivary flow. The topography of the tooth surface, the size and shape of the gingival papillae and the oral hygiene of the patient determine the plaque community on the proximal surfaces. A rough proximal surface due to caries, non carious defect or a defective restoration will not allow adequate plaque removal. This results in retention of plaque and occurrence of caries or periodontal disease at the site.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;83
18. Why do proximal root surface caries occur?
The proximal root surface caries is unaffected by the hygiene procedures since it may have a concave anatomic surface contour and an occasional roughness at the enamel termination. These when combined with gingival recession and exposure of the root to oral environment, caries producing plaque forms and caries occur on the root surfaces.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;84
19. Why is root caries alarming?
Caries of the root is alarming because it has a rapid progression comparatively, it is often asymptomatic, it is closer to the pulp and it is more difficult to be restored.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;85
20. What is incipient caries and how is it diagnosed?
The initial carious lesion limited to the enamel is incipient caries. It has an intact surface and a porous sub surface. When the intact surface is dried, it becomes chalky white opacities because of the removal of subsurface water, leaving air filled voids. Again when the area is hydrated, it is not detectable.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;90
21. What is turbid dentin?
Turbid dentin is a zone in carious dentin which is invaded by bacteria and there is a marked widening and distorsion of dentinal tubules filled with bacteria. Mineral content is less and there is irreversibly denatured collagen. This zone will not self repair or can be re mineralized. It should be removed before restoration.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;99
22. 11. Why are Streptococcus mutans considered as the primary causative agent for initial coronal caries?
Streptococcus mutans are the primary causative agents for initial coronal caries because
• They adhere to the enamel
• Produce and tolerate acid
• Survive in a sucrose rich environment
• Produce bacteriocins, which kill off the competing organisms.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;101
23. Why is binding of the explorer tips in the pits and fissures is not an indication to diagnose caries?
Though cavitation at the base of the pits and fissures can be detected by binding of an explorer tip, mechanical binding of an explorer may also occur due to non carious causes like shape of the fissure, sharpness of the explorer or the force of application. So it is not indicative of a carious lesion.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;104
24. What are the criteria for diagnosing pit and fissure caries?
Along with the discoloration of pits and grooves and binding of the explorer tip, three more additional criteria have been developed which are:
• Softening at the base of the pit and fissure
• Opacity surrounding the fissure which indicates undermined or demineralised enamel
• Softened enamel that may be flaked away by the explorer
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;104
25. How is carious pulp exposure and mechanical pulp exposure treated?
In carious pulp exposure, infection of the pulp has already occurred and pulp removal is indicated. Whereas in a mechanical exposure, where the exposure occurs in the normal dentin, bacterial contamination due to salivary contact does not occur and hence pulp capping can be done.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;120
26. What are caries control restorations?
Caries control is an intermediate step in restorative treatment where teeth with questionable prognosis are treated to stop the progression of dentin demineralization and to determine the response of the pulp doing a permanent restoration.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;126
27. What is the main advantage of caries control restorations?
Before placing a permanent restoration, the caries control procedure provides time for the pulp to recover, allowing a better assessment of the pulpal status.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;127
28. When is a caries control procedure indicated?
Caries control procedure is indicated when there is an extensive caries that pulpal sequelae will occur very soon, when the nidus of the infection in the patient’s mouth has to be removed and when the teeth has a questionable prognosis.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;127
29. In deep caries, why is the use of high speed handpiece contraindicated?
Fine tactile discrimination is required for removing the caries completely and hence the use of high speed handpiece is contraindicated in deep caries removal.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;128
30. When can the soft infected dentin be left while removing the carious lesion?
Normally, soft infected dentin is removed during caries control procedures. But in asymptomatic teeth with deep lesions, the soft dentin nearest to the pulp may be left since complete excavation may result in pulpal exposure.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;128
31. What is the role of calcium hydroxide in indirect pulp capping?
The soft dentin near the tooth pulp is retained in some cases which will otherwise result in pulpal exposure during excavation. This area is covered with calcium hydroxide overwhich a temporary restoration is placed. The calcium hydroxide promotes reparative dentin bridge formation over the area and it usually occurs in 6-8 weeks and evident radiographically in 10-12 weeks.
Ref:Theodore.M.Roberson,Harald.O.Heymann,Edward.J.SwiftJR.Sturdevant's Art and Science of Operative Dentistry.Mosby publications;2002;128