Written by Allen L. Schneider, DDS Tuesday, 31 October 2006 19:00
Directly proportionate to the increase in the successful use of implants, the saving of healthy roots for use in retaining overdentures has decreased over the past decade. According to Vogel, “With the explosion in use of implants we now see the need for techniques and materials specific to Implant Dentistry rather than an adaptation of existing tooth dentistry procedures to optimize results.”1
Figure 1. A simple Angle Measurement Guide.
Figure 2. Extending posts indicate the highly divergent path of insertion.
However, the perception of added complexity due to an increase in divergent angles when using a combination of root and implant attachments to retain an overdenture further decreases the saving of roots for this purpose. The use of a simple Angle Measurement Guide (Zest Anchors; Figure 1) and the advancement of attachment designs with the ability to accommodate greater angles of divergence have now overcome the challenges of this type of combination case.
The measured angle of divergence dictates the choice of available dental attachments that can be used for an implant or root (Figure 2).
The following is a partial list of overdenture attachments that can be used based upon the degree of angle:
• 0° to 9° implant: Dalbo-PLUS Implant Abutment4 (Attachments International), EDS Implant Abutment (Essential Dental Systems), ERA 0° and 5° Implant Abutment5,6 (Sterngold), Locator Implant Abutment7 (Zest Anchors), O-Ring Implant Abutment8 (Attachments International), Sphero Flex 0° and 7° Implant Abutment9 (Preat Corporation), and many other systems.
• 0° to 9° root: Dalla Bona Root Post (Attachments International), EDS Flexi-Overdenture, ERA 0° and 5° Direct Overden-ture, Locator 0° Root Female,10 O-Ring Root Post, Preci Clix Overdenture8 (Preat Corporation), Sphero Flex Endodontic Post, SPL Titanium Post11 (Rhein83), and many other systems.
• 10° to 19° implant: ERA 11° and 17° Implant Abutment, Locator 10° to 20° Extended Range, Sphero Flex 14° Implant Abutment.
• 10° to 19° root: ERA 11° and 17° Direct Overdenture, Locator 10° Root Female, Sphero Flex 14° Endodontic Post.
• 20° to 25° implant: Locator 10° to 20° Extended Range.
• 20° to 25° root: Locator 20° Root Female.
• 26°+ implant and root: Use of a cast implant bar or root coping with dental attachments surveyed into parallel positions on top.
Figure 3. The Post Drill follows the angle of the root canal.
Figure 4. Guide pins enable the proper selection of post angle before cementing.
Figure 5. The Locator Root Attachments cemented in place.
Figure 6. The implant attachment increased denture retention and stability.
A 68-year-old male presented with loose teeth and failing bridges in his mandible. Several teeth were able to be saved in the lower arch. After endodontic therapy was performed, the crowns were removed from the cuspids in preparation for placing a Locator Root Attachment in each one. The Locator Pilot Drill was used with a slow-speed handpiece to create a post preparation in both cuspid roots, following the root canal to a depth of 6 mm (Figure 3). This was followed by a Locator Spotface Diamond Bur to create an attachment seat into the top of the root surface. Locator Black Parallel Posts were snapped onto the Locator Root Females and tried into the preparations to determine the correct angle of post selection (0°, 10°, or 20°) to be used (Figure 4). The Angle Measurement Guide aided in the determination of the proper post angle to be used. The Locator Root Female posts were then cemented into place (Figure 5) using a strong adhesive resin cement.
An implant with Locator Abutment was placed into the posterior second molar area on the left side of the lower ridge where most of the teeth were missing (Figure 6). This created a triangle of additional support and retention for the partial denture prosthesis.
Figure 7. Black Processing Males aided in accurate try-in procedures.
Figure 8. The Male Removal Tool easily removes the Processing Male.
Figure 9. The final Locator male inserts accommodated the divergent angles.
Locator Impression Copings were snapped onto the 3 attachments and picked up in an impression. After placing Locator Analogs into the copings, the master cast was fabricated to create an exact duplication of the position of the Locator Attachments. The metal framework for the partial denture was formed around the Analogs, leaving enough room for the Locator Cap Males. Using procedures outlined in a previous article,3 an Eclipse [DENTSPLY Trubyte] record base was constructed that incorporated Locator Denture Cap Males into the baseplate to record centric relation and vertical dimension. A micro-etching unit (Macrocab [Danville Materials]) was used to create a better adhesion texture on the superior surface of the Locator male’s metal housing. Then a special primer material for extra strength in bonding denture resin to metal (METALPRIMER II [GC America]) was painted onto the etched metal attachment housing for secure acrylic resin retention to the Locator Cap Males. Use of the Locator Black Processing Males in the record base (Figure 7) provides stability that allows the clinician to more accurately record jaw records and perform more precise try-in procedures. Additionally, the clinician can evaluate how the final denture will fit much earlier in the process. After the wax try-in with written approval by the patient, the laboratory went ahead with the final processing of the acrylic Locator partial denture.
With the processing of the partial denture and polishing of the underside completed by the dental laboratory, a newly designed Locator Removal Tool (Figure 8) was used to remove the black processing liners from the metal caps. This new Locator Removal Tool is a big improvement over the previous hook tool because it has a sharp, 360° circumference edge that easily grabs and pulls out the black processing liner. The new tool tip is then removed from the Locator Core Tool, and the original Male Seating Tool is used to seat the final nylon retentive liners. Due to the measured angulation difference of greater than 10° between the pair of anterior Locator Root Females, the posterior Locator Implant Abutment, and the remaining dentition, the light retention Locator Extended Range Red Male inserts were used in the anterior to accommodate the variance in the path of insertion for the partial denture (Figure 9). The Locator Extended Range Male has been verified to successfully handle divergence up to 20° for a single attachment and 40° between 2 attachments.
Figure 10. The end results in a full smile.
Advanced designs in dental attachments have improved the ability of the clinician to restore more advanced overdenture cases successfully, including those with highly divergent supporting structures. The choice of an attachment according to its ability to accommodate properly the measured angle of divergence and function is critical to the successful outcome of the case.
In the case described, the patient had severely compromised dentition in the mandibular arch. A combination root and implant Locator Attachment-retained partial denture replaced the missing teeth. This restorative approach offered a simplified solution to successfully overcome the attachment divergence challenges that existed (Figure 10).
1. Vogel R. Emerging trends in implant dentistry: increased precision and productivity through ideal laboratory/doctor interaction. Spectrum Dialogue Magazine. Jul/Aug 2004:44-50.
2. Mijiritsky E, Ormianer Z, Klinger A, et al. Use of dental implants to improve unfavorable removable partial denture design. Compend Contin Educ Dent. 2005;26:744-752.
3. Schneider A. Placement of an implant-stabilized complete denture: a case report. Pract Proced Aesthet Dent. 2004;16:579-582.
4. Rignon-Bret C, Rignon-Bret J-M. Implant retained removable full lower dentures. Spectrum Dialogue Magazine. Jul/Aug 2005:92-93.
5. Dario LJ. A maxillary implant overdenture that utilizes angle-correcting abutments. J Prosthodont. 2002;11:41-45.
6. Coleman AJ, Tompkins KA, Evans JH. Restorations using osseointegrated implants with resilient attachments. Compend Contin Educ Dent. 1997;18:384-390.
7. Kurtzman GM, Schneider AL. Res-toration of divergent implants with removable prosthesis and the locator attachment. Spectrum Dialogue Magazine. Mar/Apr 2004:34-38.
8. Bambara GE. The attachment-retained overdenture. N Y State Dent J. 2004;70:30-33.
9. Storni G, Lindberg G. Removable over-denture prosthesis: a complete prosthesis on four non-parallel implants using direct attachments with self-paralleling movable spheres. Spectrum Dialogue Magazine. Jan/Feb 2004:64-67.
10. Pavlatos J. The root-supported overdenture using the Locator overdenture attachment. Gen Dent. 2002;50:448-453.
11. Storni G, Lenzarini C, Lindberg G. Removable over-denture prosthesis: a complete prosthesis on three devitalized roots in the maxilla using direct Titanium posts with fixed retentive micro spheres diameter 1.8 mm. Spectrum Dialogue Magazine. May/Jun 2004:32-36.
The author wishes to acknowledge Hermanson Dental Laboratory for its expertise and help in documenting this case. He would also like to thank Joseph M. Arzadon, MD, DDS, the oral surgeon on this case.
Disclosure: Dr. Schneider receives an honorarium when lecturing for GC America, Zest Anchors, and Danville Materials.
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