Uses of the Infrabulge Clasp
Posted on 12/20/2011
The infrabulge clasp design is most commonly used on distal extension RPDs. One of the primary reasons for this is the requirement of space: to create an effective I-bar, there needs to be adequate edentulous space.
For example, an I-bar design where only one tooth is missing (for example, patient is missing #20 but has #19 and 21), the descending and ascending elements of the i-bar will be so close to each other that they will create a food repository - which could lead to long term oral hygiene issues. If both #20 and #21 were missing, placing an I-bar on #22 would be an effective design as it allows for adequate space of the both ascending and descending elements of the I-bar. With distal extension RPDs, the I-bar is quite effective since there is plenty of room for i-bar as there are no teeth distal to the supporting abutment tooth.
A common I-bar design for distal extension RPDs is the RPI clasp:
R: Rest - mesial occlusal rest emerging from a minor connector in the mesiolingual embrasure
P: Proximal Plate - a guide plate designed on the distal surface of the abutment tooth up to the occlusal third
I: I bar retentive arm placed at the center of the buccal/labial surface of the abutment engaging the undercut.
The Y bar and T bar designs are modifications of the I-bar and usually utilized when additional support is needed on the abutment tooth. One of the T or Y arms is designed as the retentive arm while the other is the reciprocating/bracing arm.
For example, an I-bar design where only one tooth is missing (for example, patient is missing #20 but has #19 and 21), the descending and ascending elements of the i-bar will be so close to each other that they will create a food repository - which could lead to long term oral hygiene issues. If both #20 and #21 were missing, placing an I-bar on #22 would be an effective design as it allows for adequate space of the both ascending and descending elements of the I-bar. With distal extension RPDs, the I-bar is quite effective since there is plenty of room for i-bar as there are no teeth distal to the supporting abutment tooth.
A common I-bar design for distal extension RPDs is the RPI clasp:
R: Rest - mesial occlusal rest emerging from a minor connector in the mesiolingual embrasure
P: Proximal Plate - a guide plate designed on the distal surface of the abutment tooth up to the occlusal third
I: I bar retentive arm placed at the center of the buccal/labial surface of the abutment engaging the undercut.
The Y bar and T bar designs are modifications of the I-bar and usually utilized when additional support is needed on the abutment tooth. One of the T or Y arms is designed as the retentive arm while the other is the reciprocating/bracing arm.
