Pocket Depth and Surgical Indications

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The Perio Perspective

The Magic Number

No one wants surgery. Since our patients, like us, naturally resist surgery, it is important to know when it makes sense, and what the risks are if it is not done.

An accumulating body of clinical research offers guidance when we discuss periodontal surgery with our patients. Obviously, the majority of patients with periodontal disease (PD) will be treated initially with scaling and root planing (SRP), re-evaluated at six weeks, and scheduled for a 3-month maintenance program. When is this not sufficient?

PD, like most diseases, progresses at a variable rate. The rate depends on many factors specific to each patient, including smoking, oral hygiene, stress, immune response, and types of subgingival bacteria present in pockets. But one determinant has repeatedly been shown to correlate with risk of deterioration: pocket depth.

In the 1980s and 90s, the first well-designed clinical research on PD implied that debridement was the key to successful treatment, regardless of pocket depth. This led to an emphasis on SRP – often repeated every few years – and on open flap debridement (“open clean-out”) surgery, and away from osseous (“pocket elimination”) surgery. This was a welcome development, since more conservative treatment was quicker, simpler to perform, and less likely to expose roots and embrasures. However, this body of research did not assess the stability of treatment results by residual pocket depth. Since then, this analysis has been done (Matuliene, G. et al, J Clin Perio 35(8): 685, 2008 and Teles, R et al, J Clin Perio 45(1): 15, 2018). Residual pockets of 4 mm or less are unlikely to deepen, but the risk increases significantly in 5 mm pockets and continues increasing with each additional millimeter of depth. Pockets 5 mm deep have triple the risk for disease progression and an eight-fold increase in risk for loss of the affected tooth. Risk of tooth loss increases by a factor of 11 for 6 mm pockets and by a factor of 64 for 7 mm pockets. So the magic number for proceeding to surgery is 5.

Several determinants affect risk in addition to pocket depth. These include:
  • Tooth position: 25% of molars with deep pockets deteriorate in one year, versus 10% of incisors
  • Oral hygiene and compliance with maintenance schedule
  • Smoking
  • Patient’s overall disease severity: deterioration clusters in patients with a history of more aggressive and widespread disease
  • Presence of inflammation (bleeding on probing)

The importance of pocket depth as a predictive factor may be explained in part by the large difference in bacterial species when comparing shallow and deep pockets (Perez-Chaparro, P, et al, J Clin Perio 45(1): 26, 2018).
Achieving pocket depths of 4 mm or less becomes more difficult as pocket depth increases. So the ideal time to proceed with surgery is for probing depths of 5-6 mm, especially for posterior teeth. And in contrast to the trends of the previous century, treatment should be aimed at pocket elimination, either by osseous resective surgery or by regenerative (grafting) surgery. Once SRP has been completed, repeated SRP, LANAP, or subgingival antimicrobials offer little predictable benefit for residual pockets. Unfortunately, for patients with residual pockets after SRP, there is no magical cure. Only the magic number: 5.

Amy and David