Dental caies and tooth decay from A to Z (etiology and treatment)- dental land.

 

Dental caries

Caries is known as dental decay and people see it as cavities. These cavities are formed of holes of variable sizes in the tooth structure when the outer covering layer is demineralized and lost. Scientifically, dental caries is a multifactorial, transmissible infectious disease formed by the complex interaction between bacteria, food substrate, on the tooth surface over time in a continuous dynamic process between demineralization and remineralization.
An imbalance resulting in a shift towards demineralization leads to loss of tooth minerals and destruction of its organic component forming cavities. 
It's diagnosed immediately buy inspection and probing its enamel surface with a sharp instrument to detect catch or diagnosed radiographically by x-ray. Treatment includes removing the affected tooth structure and restoring it with various dental materials. You can prevent it by watching this article 

Key points 

1. Etiology
2. Risk factors
3. Signs and symptoms 
4. Diagnosis 
5. Treatment
6. Prevention

   Etiology

1. Acids: acids cause demineralization of hard mineralized tissue (enamel and dentin) and destruction of 
2. Dental plaque: the plaque at first is a thin, soft layer of bacteria, food debris, mucin and dead epithelial cells (biofilm layer). It is formed on the tooth surface within an hour after cleaning it. By the time (72 hours ) it mineralizes by calcium and phosphate to become hard calculus difficult to be removed by the brush.
3. Cariogenic bacteria: cariogenic bacteria include streptococcus mutants and lactobacillus, which are the most virulent microorganisms. They ferment CHO producing adherent extracellular polysaccharide matrix and acids forming plaque then calculus. 

   Risk factors

1. Inadequate and improper plaque control.
2. Defective crown: there may be developmental defects in the form of fissures and cracks extending deep into the tooth leading to retention of bacteria and good substrate. They are difficult to be cleaned as they are very narrow.
3. Deleterious dietary habits: frequent exposure to CHO and sugars promote the growth of the cariogenic bacteria. Rampant caries, as an example, occurs due to prolonged contact of milk with baby's teeth at bedtime. That's why the bedtime feeding bottle should contain only water.
4.  the tooth surface is more prone to caries when it is poorly calcified, fluoridated, and/or is in an acidic environment. Typically, decalcification begins when the pH falls below 5.5 (eg, when lactic acid-producing bacteria harbor the area or when people drink cola beverages, which contain phosphoric acid)
5.  Reduced salivary flow: more common in elderly that take drugs with this side effect. Also, they are susceptible to root caries due to the gingival recession resulting in exposure of root surfaces to the cariogenic environment.

 Complications 

Tooth decay if not treated, causes further destruction in tooth structure extending to involve the pulp of the tooth causing severe pain. Infection may occur due to the spread of bacteria to periapical tissue causing periapical abscess that may evolve into granuloma and fistula. Premature loss of deciduous teeth is a big problem as it causes loss of space of permanent teeth that may erupt in an incorrect place or remain impacted causing midline shift, teeth malalignment, bad esthetics. All of that may require future orthodontic treatment to be fixed.

                                                           Signs and symptoms 

Caries initially involves only the enamel ( the insensitive outer covering layer) and causes no symptoms. But may appear as black or brown lines on the tooth surface. Caries invading the dentin (sensitive layer) causes pain, first when hot, cold, or sweet foods or beverages contact the affected tooth, and later with chewing or percussion. In this stage, it may appear as an established cavity and hole or even undermined enamel with a grayish color. That's why cavities hurt. Pain can be intense and persistent when the pulp is involved (pulpitis).

Diagnosis

• Direct visual and tactile inspection
• x-rays or special testing instruments

Routine, clinical evaluation (every 6 to 12 mo) identifies early caries when minimal intervention prevents its progression. A thin ball-end probe, sometimes fiberoptic transillumination and special dyes are used, frequently supplemented by new devices that detect caries by changes in electrical conductivity or laser reflectivity. However, x-rays are still important for detecting caries, determining the depth of the carious lesion, and identifying caries under existing restorations 

Treatment

• Restorative therapy(filling material)
• a root canal and crown(endodontic treatment)

Remineralization of teeth

Incipient caries (which is confined to the enamel) should be remineralized by nonsurgical and medical approaches through improved home care (brushing and flossing), cleanings, high-fluoride toothpaste, and multiple fluoride applications at the dental office.

Restoration of teeth

The primary treatment of carious lesion that has entered dentin is by removal by drilling, followed by filling of the resultant defect (cavity).


Fillings for occlusal surfaces of posterior teeth (chewing surfaces), must be composed of strong durable materials, including

• Silver amalgam
• Composite resins
• Glass ionomer

Silver amalgam is composed of silver, mercury, copper, tin, and occasionally zinc, palladium, or indium. 
Amalgam is inexpensive and lasts for about 15 yr. But with good oral hygiene and we'll placement of amalgam using a rubber dam for isolation from saliva, many amalgam restorations last > 40 yr. 

Due to the concern of mercury toxicity and increased interest with esthetics, amalgam use as a filling material has declined. 

Replacing amalgam is not recommended because it is expensive, damages tooth structure, and actually increases patient exposure to mercury. The toxic form of mercury is vapor and it occurs during manipulation and removal. 

Amalgam does not shape any problem to patient and it is a safe material. There is no correlation between mercury in amalgam and that of blood. Amalgam's major disadvantages are less conservative, and bad aesthetics. 
So, it's used mainly for restoring badly decayed posterior teeth.


Composite resins, which provide a more acceptable appearance and better esthetics, have been used in anterior teeth for a long period, where aesthetics are primary and the chewing forces are minimal. 

Some patients want them in posterior teeth as well, and they are now commonly used there. Early-generation composite resins were weak plastic materials. They last less than the half-life of amalgam restoration. 

Also, they suffer from recurrent caries and marginal staining due to its polymerization shrinkage. They had a coefficient of thermal expansion different from that of the tooth causing greater expansion and contraction under thermal changes. 

But the current generation of composites closely resemble enamel hardness and has a lower incidence of recurrent caries than earlier materials and may also last longer.


Glass ionomer, a tooth-colored aesthetic filling, releases, and re-uptakes fluoride when in place, a benefit for patients especially those who are prone to tooth decay. 

It is also used to restore areas damaged by severe brushing and wear. Glass ionomer is less aesthetic than composite and it should not be used on chewing surfaces because it has a high wear rate and low strength.


If decay leaves too little dentin and the remaining tooth structure can not hold a restoration, The missing dentin is replaced by cement, amalgam, composite, or other materials. In many cases, a post must be inserted into a prepared space in one or more roots to support and carry a gold, silver, or composite core, which replaces and restores the coronal dentin. 

This procedure requires a root canal filling (endodontic treatment), in which an opening is made in the tooth and the pulp is removed. The root canal system is thoroughly debrided, cleaned, shaped, and then filled with gutta-percha (obturation material ). 

The outer tooth surfaces are then reduced and prepared so that an artificial crown, usually made of metal, porcelain, or ceramic can be placed and cover the entire tooth. Crowns for anterior teeth are usually made of porcelain or ceramic.

 Prevention 

All that you want to know about the prevention of dental caries and tooth cavitation, you will find in this  link

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