Infrabulge Clasps - I Bar, Y Bar or T Bar
Posted on 12/15/2011
Yesterday's blog completed our discussion of the most common suprabulge clasps. We will now move on to discuss the common types of infrabulge clasps - specifically the I bar, Y bar and T bar designs.
The infrabulge clasp design includes the following elements:
1. Infrabulge arm will emerge from the denture base or meshwork from the gingival direction
2. Arm should be 3mm or below the gingival margin
3. Arm should turn up at the abutment margin at a 90 degree angle
4. Tip of the arm should engage an undercut in the gingival third of the abutment tooth
5. Arm should exhibit uniform taper
The advantages of the infrabulge style clasp include:
1. Limited tooth coverage
2. Superior aesthetics as the arm emerges from the gingival
3. Increased retention
4. Decreased torquing forces
5. Improved adjustability compared to the circumferential clasp
The disadvantages of the infrabulge style clasp include:
1. Limited use - cannot be used in the presence of tissue undercuts, shallow vestibule or high frenal attachments.
2. Bracing/Reciprocal action is not equal to the bracing action of the suprabulge clasp design
3. Clasp may not fully disengage from the abutment tooth during removal - causing some pressure on the abutment tooth.
*Portions of this post were adapted from the book: Atlas of Removable Partial denture Design by Dr. Russell J. Stratton and Dr. Frank J. Wiebelt published by Quintessence Publishing Co., Inc. in 1988.
The infrabulge clasp design includes the following elements:
1. Infrabulge arm will emerge from the denture base or meshwork from the gingival direction
2. Arm should be 3mm or below the gingival margin
3. Arm should turn up at the abutment margin at a 90 degree angle
4. Tip of the arm should engage an undercut in the gingival third of the abutment tooth
5. Arm should exhibit uniform taper
The advantages of the infrabulge style clasp include:
1. Limited tooth coverage
2. Superior aesthetics as the arm emerges from the gingival
3. Increased retention
4. Decreased torquing forces
5. Improved adjustability compared to the circumferential clasp
The disadvantages of the infrabulge style clasp include:
1. Limited use - cannot be used in the presence of tissue undercuts, shallow vestibule or high frenal attachments.
2. Bracing/Reciprocal action is not equal to the bracing action of the suprabulge clasp design
3. Clasp may not fully disengage from the abutment tooth during removal - causing some pressure on the abutment tooth.
*Portions of this post were adapted from the book: Atlas of Removable Partial denture Design by Dr. Russell J. Stratton and Dr. Frank J. Wiebelt published by Quintessence Publishing Co., Inc. in 1988.
