In periodontal therapy, “guided tissue regeneration” is most successful in treating
1. horizontal bone loss.
2. a 3-walled infrabony defect.
3. a mandibular Class III furcation involvement.
4. a mandibular Class II furcation involvement.

(2) and (4)

(4) only

All of the above.

(1) (2) (3)

(1) and (3)