Root-caries risk after periodontal therapy

The incidence of root caries following periodontal therapy is alarmingly high. For that reason, periodontal therapy always should include a strong caries-prevention program.

Trisha E. O`Hehir, RDH, BS

The incidence of root caries following periodontal therapy is alarmingly high. For that reason, periodontal therapy always should include a strong caries-prevention program.

The rate of root caries in adults is reported to be 43 percent to 63 percent. Identified risk factors for root caries include: high salivary levels of streptococcus mutants and lactobacilli, reduced salivary flow and buffering capacity, smoking, and poor oral hygiene.

Researchers use an index to identify the actual rate of root caries. The root-caries index (RCI) is calculated in much the same way a plaque index is scored. The total number of decayed or filled root surfaces is divided by the total number of exposed root surfaces. This number is then multiplied by 100 to determine a percentage. For example: six decayed or filled root surfaces are divided by 60 total, exposed root surfaces. That score of 0.1 is multiplied by 100 to establish a root-caries index score of 10 percent. Reports show average root-caries index rates between 6 percent and 10 percent. Does that compare with what you are seeing in your practice?

Researchers in Holland evaluated 45 periodontal-maintenance patients to determine both the root-caries index and the risk factors for root caries. The average age of the group was 55 years, and the average root-caries index was 8 percent. The average number of root-caries lesions per patients was 4.3 lesions. However, the number of root-surface lesions per patient ranged from 0 to 19.

It is obvious that some people just aren`t susceptible to root caries, while others suffer greatly. Not everyone ends up with recession after therapy, either. In this study, the number of exposed root surfaces ranged from 10 to 119, with an average of 65 per patient.

The researchers thought that those with a history of coronal caries may be the ones most likely to experience root caries, so they looked for a correlation. The average number of coronal caries/fillings was 42, with the actual number ranging from 9 to 83. Surprisingly, the number of coronal lesions a patient had did not correlate with his or her root-caries level.

One correlation the researchers did find was high levels of salivary streptococcus mutant and root-caries incidence. The higher the strep mutant level, the higher the root-caries index. On the other hand, lactobacilli counts did not correlate.

As you might expect, poor oral hygiene was a significant factor. The overall average plaque score was 41 percent, and it ranged from 8 to 88 percent. Breaking down the scores by location, facial surfaces had 29 percent, approximal had 45 percent, and lingual had 50 percent. These are extremely high plaque levels for patients who have undergone periodontal therapy. Root caries seems inevitable under such circumstances.

Other researchers in Belgium wondered if a shift in the bacterial balance after periodontal therapy could result in root caries. It`s a good question! Recession associated with periodontal therapy exposes more root surfaces. If the microbial balance changes, reducing periodontal pathogens and increasing the bacteria responsible for decay, the number of root-caries lesions naturally would increase. To find out, the researchers monitored 10 patients for eight months following treatment.

Volunteers for this pilot study had to have severe disease in the upper right quadrant, with several deep pockets that bled upon probing. Radiographic evidence of loss of half the bone also was needed. The researchers collected bacterial samples from the saliva, dorsum of the tongue, and interproximal areas. All patients received oral-hygiene instructions, together with a new toothbrush and fluoride toothpaste. They all received scaling and root-planing using local anesthesia.

Following therapy, plaque levels were reduced considerably and pocket depths were reduced 0.5 millimeter to 3 millimeters, with an average reduction of 1.6 millimeters. Despite the use of a fluoride toothpaste, a total of 15 new carious lesions developed during the eight-month test period, plus 11 areas of secondary caries around existing fillings. This is most likely attributable to a shift in oral bacteria. The number of streptococcus mutants increased significantly, while the number of periodontal pathogens decreased. Of the 10 test subjects, only one escaped new caries at eight months.

These alarming findings suggest the need for larger studies to more accurately assess the potential of the root-caries problem. Based on what we know today, a strong caries-prevention program should be a part of periodontal therapy. Nutritional counseling, along with effective plaque removal, fluoride rinses, and fluoride and chlorhexidine varnishes, should all be part of the preventive therapy.

References available upon request by e-mail at markh@pennwell.com.

Trisha E. O`Hehir, RDH, BS, is a senior consulting editor of RDH. She also is editor of Perio Reports, a newsletter for dental professionals that addresses periodontics. The Web site for Perio Reports is www.perioreports.com. Her e-mail address is trisha@perioreports. com.

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