Definition An attachment involving two parts: the first half has a ball joint or a similar component cantilevered from the abutment unit; the second part, the socket, is housed within the denture base . This may contain a spring for resilience.
Indications This type of attachment is used in a free-end saddle situation where stress-breaking is a risk . The patrix is connected to the distal abutment to align with the saddle and allow flexion of this portion in relation to the residual dentition.
Advantages The attachment compensates for the differential compressibility of the supporting structures of the denture base, i.e. the mucosa and teeth. The support provided by abutment teeth and oral mucosa is not equal and would result in instability of the denture base during function.
• The extracoronal nature of this attachment results in an altered contour of the abutment tooth which may be difficult to clean .
• Loss or fracture of the spring housed within the matrix could result in the denture sinking and causing possible damage to the supporting structures.
Procedure This type of attachment involves advanced laboratory support and requires careful clinical assessment of the supporting structures and the occlusion.