It is useful to consider caries treatment in two historical phases.

Phase 1
  When the enamel caries epidemic began, the disease was thought to be gangrene of the teeth. Gangrene is death of part of the body. If left untreated, a gangrenous area increases in size until the afflicted individual becomes ill and dies. At that time, caries was treated the same as it was treated in other arts of the body – by surgical removal. Extraction was the equivalent of amputation for gangrenous limbs. The surgical specialty of dentistry developed because of the high demand for caries treatment by extraction. Extraction is physically difficult in young people with good periodontal health. However it was effective in eliminating the disease from an individual, because when all of the teeth had gone there could be no further disease.
   When debridement by extraction was the principal method of treatment diagnosis was simple. It was appropriate to respond to patients' symptoms of discomfort or pain and to make the diagnosis of disease at that stage. 'Maintaining the vital force' through good nutrition and good general health was the only preventive strategy available. There is no evidence that this approach was effective because it did not treat the cause of the disease.

   An alternative method of surgical removal, and a simpler one than extraction, was local debridement by cleaning out the decayed area. Many dentists advocated using a small file to abrade away approximal areas of teeth, including the area of the early lesion, to treat the disease. After the file was used the area was left open to saliva. This had some advantages because it was a simple treatment and the decay was slow to recur. But it also had the disadvantages that food tended to lodge between the teeth and the teeth tended to move over time.

   Local removal and then filling the resultant cavity was also attempted. The decay was removed with hand scrapers ('excavators) or rotating burs. The early filings sealed badly and tended to fail within months, or a few years at most, because of continuing disease. Despite the low success rate, some dentists continued to place fillings because they were less difficult and, in a time when there was no local anesthesia, less traumatic for the patient.

   Early fillings were metal - lead, tin or gold. Each of these metals could be pressed or hammered into the cavity. Pure gold was the most difficult of these metals to handle, but tended to last longer if it was very carefully placed and thoroughly condensed. Small bundles of very thin sheets of pure gold, called gold foil, were added one-by-one with tiny instruments and cold welded together using small hammers, called mallets. A mixture of silver and mercury, called dental amalgam, was also used to fill cavities. The mixture is initially soft, so it can be packed into the cavity with only moderate pressure, and because of chemical reactions between the silver and mercury new compounds are formed that set and become hard.

Phase 2
  The concept that caries was gangrene continued well into the 20th Century, and many patterns of care which flow from that concept continue up to the present time.

   The fastidious and systematic refinement of cavity design and filling technologies in the early 1900's, mainly through the work of dentists in North America, changed the nature of caries treatment. Through this work the outcome of the restorative approach was improved until by mid-century it became preferable to extraction. Carefully-placed restorations (which by mid-century included fillings, onlays and crowns) tended to leak less. It became commonplace for restorations to last several years before they failed through continuing disease.

   Complete removal of carious enamel and dentin was thought to be an essential part of successful filling design. Restorative materials did not adhere to teeth. In order for them to stay in place decayed areas had to be modified in shape, with hand or rotary cutting instruments, to make retentive cavity forms. Cavity shapes were also modified to increase the strength of the tooth and restoration. Minimal sizes of cavities were also mandated, so that the junction between the filling and tooth was on areas of the tooth where caries did not usually begin, in the hope that this would result in restorations which would last longer before recurrent decay occurred. This was called 'extension for prevention'. The act of making a restoration therefore usually involved the removal of a substantial amount of tooth structure, often several times more than was actually decayed.

   Preparing large cavities in hard tooth structure with hand cutting instruments (chisels, hatchets and hoes) was very slow and difficult, but it became easier as rotary cutting instruments (rotary burs) were developed and refined. By the 1970's high-speed, air turbine-driven rotary cutting instruments became widely available. It became relatively easy to prepare large cavities using tungsten carbide burs and industrial diamond-impregnated rotary instruments.

Diagnosis in Phase 2
  In phase 1 patients' symptoms were central to diagnosis.
Perhaps unfortunately the main symptom of caries, pulpal pain, develops relatively late, when substantial amounts of tooth structure have been lost. Waiting for pain to develop was not a good strategy if fillings were to be used as the method of treatment. The most successful way to manage caries using filling technologies involved finding the decay early, whether it was new caries (primary caries, on previously unrestored tooth surfaces) or recurrent caries (adjacent to existing restorations).

   Detection became essentially the same as diagnosis. Diagnostic technologies were developed which aided early detection, namely:

• Direct visual inspection
• Indirect vision (using the mouth mirror)
• Auxiliary external illumination
• Transillumination
• The use of sharp explorers (to detect softened enamel, particularly in pits and fissures)
• Radiography
• Separation and the use of floss silk to aid in detection of approximal lesions.

Prevention in phase 2
  In the 1950s the concept that caries was caused by acids produced by bacterial action on residual food on and around the teeth became widely accepted. Brushing teeth after meals to remove residual food was widely advocated as a preventive strategy but had little effect on caries rates. Advising patients to change their food choices and to eat less often was a rational approach, but few individuals took that advice.

   In the 1970s the concept that caries was caused by dental plaque became widely accepted. Patients were advised to brush and floss teeth to remove plaque. The epidemiological discovery that fluoride in the diet would reduce the level of disease was highly significant.
This lead to the demonstration that topical applications of fluoride were similarly effective.
Dietary fluoride supplements in children, water rinses and gels followed rapidly.
The combination of fastidious plaque removal and fluoride use was shown to be effective in reducing caries in individuals and in whole populations.

   The development of polymeric materials which bonded to enamel brought with it the ability to seal fissures. Occlusal fissures are areas of high likelihood for caries initiation in individuals who have the disease. Sealed fissures have a greatly reduced incidence of caries initiation. During this phase, when all individuals were considered to be at risk for caries, placement of fissure sealants in all children and young adults was an appropriate preventive strategy.

Standard of care in Phase 2
   By mid-century the principal method for the treatment of caries had become restoration with “fillings”. Extraction was reserved for the extensively restored tooth which could no longer retain a restoration or which had fractured, or for patients who could not afford restorative treatment.
The accepted standard of care for patients who could afford repeated restoration was to be examined frequently (usually at 6-monthly intervals) using the best aids to detection available. The repeated cycles of tooth restoration resulted in larger and larger restorations. Ideally, this continued until the patient died of old age.

   Improvements in restorative materials, particularly those which adhere to teeth and therefore tend not to leak (e.g. composite resin in some applications, and glass ionomer cement) and those which release fluoride (e.g. glass ionomer cement) increased the longevity of restorations.

   Unfortunately, however, extensively restored teeth sometimes fracture through the root and must be extracted. Fixed bridges and removable dentures were offered to assist patients who had lost because of this style of care and more recently there have been implant supported prostheses.”

   Fixed bridges, removable dentures and implant supported replacements could be offered to assist patients who had lost teeth because of this style of care.
Because virtually the entire population of the industrialized societies had caries (except those who had no teeth), it was appropriate to apply these preventive technologies to everyone with teeth.
'Prevention' was essentially the same for everyone.
'Cure' was not a concept that was used in dentistry relative to caries in this phase, because the only cure for caries was to extract all of the teeth.