Final answer:
The single best criterion for evaluating the success of scaling and root planing procedures is the reduction in pocket depth. Hence, option 1 is correct.
Step-by-step explanation:
The single BEST criterion for evaluating the success of scaling and root planing procedures is the reduction in pocket depth.
Pocket depth refers to the space between the gum line and the tooth. In gum disease, pockets form as the gums recede, allowing bacteria to accumulate and cause further damage. By reducing pocket depth through scaling and root planing, the treatment is helping to restore the health of the gums and prevent further progression of the disease.
Improvement in gingival bleeding, decrease in tooth sensitivity, and increase in tooth mobility are also important indicators of treatment success, but the reduction in pocket depth is considered the best criterion as it directly measures the improvement in gum health.