What is the expected effect of surgical therapy performed in pockets shallower than 4.2 mm?

Surgical therapy performed in periodontal pockets shallower than 4.2 mm is expected to induce a loss of attachment. This outcome can be attributed to a few key factors inherent in the nature of periodontal surgery and the specific anatomy of shallower pockets.

When surgical procedures are carried out in shallow pockets, the removal of tissue and the manipulation involved can disrupt the soft tissue attachment to the tooth. This disruption may lead to apical migration of the epithelial attachment, which ultimately results in a net loss of clinical attachment level as the tissue may not successfully reattach at the same level post-surgery.

Moreover, the surgical intervention may not be necessary in such shallow pockets since non-surgical measures usually suffice for treatment and healing. This could lead to additional trauma and inflammation, further exacerbating attachment loss.

Other options, such as inducing a gain in attachment or having no effect, do not account for the physiological responses and healing mechanisms associated with surgical treatments in shallower pockets. Thus, based on periodontal treatment protocols and outcomes, the result of surgical therapy in shallow pockets is more likely to lead to a loss of attachment rather than any gain or neutrality in attachment levels.