Perhaps you should try some spelling variations:
increased periodontal » decrease periodontal (Expand search), increased peritoneal (Expand search), diseased periodontal (Expand search)
periodontal defect » periodontal defects (Expand search), periodontal effects (Expand search), periodontal efeitos (Expand search)
decrease and » decreases and (Expand search), decrease in (Expand search), decrease of (Expand search)
and decrease » and decreases (Expand search), and decreased (Expand search), and increase (Expand search)
to increased » to increase (Expand search), of increased (Expand search), and increased (Expand search)
decrease to » decreased to (Expand search), decrease toc (Expand search), decrease the (Expand search)

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (( decrease _ decrease AND decrease ) OR ( decrease to increased periodontal defect ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( decrease _ decrease and decrease ) OR ( decrease to increased periodontal defect ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease _ decrease and decrease ) OR ( decrease to increased periodontal defect ))*.