From time to time it may be prudent to review index fragementation on the CRM database. High levels of fragmentation may impact on performance. Fragmented indexes can be sorted out by reorganizing or rebuilding.
This Microsoft article explains the options http://msdn.microsoft.com/en-us/library/ms189858.aspx.
This article has SQL code that finds all indexes that are fragmented by more than a certain amount and then runs either a rebuild or reorganize depending on the level of fragmentation http://msdn.microsoft.com/en-us/library/ms188917.aspx.