Due to the fact that both Kennedys class 1 and 2 involve free end saddles, problems occur as a result of the dentures inability to anchor itself down.

Both classifications must derive support from the remaining teeth and residual ridges, however if designed with unequal forces being distributed over the RPD, rapid destruction of the periodontal tissues may happen with an additional potential of abutment loss.

Rpds must provide equal distribution of forces if not, destruction of the residual ridges will decrease their height, causing rocking to the denture and needing continuous realignments of the denture. All portions of the residual ridge that can provide support should be covered by an accurately fitting denture base. Broad coverage permits favourable distribution of stresses often described as a snowshoe effect.

With the free end saddles in some instances sticky foods may lift denture bases away from supporting tissues. This displacement produces rotation of the rpd on the most posterior abutment, auxiliary rests should be placed as far as is practical from the fulcrum line, rests minimize rotation and aid in retention, these are indirect retainers.

Flexible direct retention is designed to flex or move into an area of greater undercut as forces are applied to the rpd, clasp design is essential as this prevents rocking movement in the denture.

Class 1 must compensate for rotational forces as both saddles are free to move, they must be designed in consideration of-

-        provision of optimum support for the distal extension denture bases,

-        incorporation of flexible direct retention,

-        and provision of indirect retention.

Class 2 gains some retention from the opposite side however must be designed with-

-        must include well-adapted denture base,

-        properly designed direct retention,

-        and appropriately positioned indirect retention.