An Improved All-In-One Attachment System: Two Clinical Case Examples

INTRODUCTION
Ongoing documented success of implant-retained overdentures has revolutionized how patients with fully edentulous arches are treatment planned.¹ Considered the standard of care for those suffering the complete loss of their mandibular teeth, a lower overdenture retained by 2 to 4 implants enhances a patient’s quality of life, satisfaction with treatment, and overall well-being.^2,3

Described as a prosthesis covering and supported by the natural tissues and retained by dental implants, an implant-retained overdenture is considered very successful with a particularly high predictability rate in the mandible.^3-5 Dentists routinely provide implant-retained overdenture rehabilitations in their practices.⁶

In addition to implants of various diameters and lengths, the introduction of many implant abutments and denture attachments enable clinicians to choose the best options for retaining and securing full-arch dentures.⁵ Initially, the implant overdentures were characteristically designed as splinted bars or frames, but studies showed that solitary anchors decreased stress levels at the implant/prosthetic component and reduced stress concentration in the supporting tissues.⁷ Today, solitary or stud anchors, as well as other attachment system designs, are available to provide reasonable stability and retention for implant overdentures.^8,9

Among the abutment/attachment systems available is the LOCATOR Implant Attachment System (Zest Dental Solutions), which has been used by the majority (86%) of prosthodontists in the American College of Prosthodontists and the American Academy of Maxillofacial Prosthetics who were surveyed about common restorative preferences.¹⁰ LOCATOR Attachments with nylon matrices have demonstrated a 90% prosthodontic success rate for more than 3 years, which is higher than other attachments observed during the same period.¹¹ Compared to ball attachments and common dental abutments, the LOCATOR System has also demonstrated better results for loading and masticatory stress6 in addition to the frequency of complications (ie, fewer when compared to ball attachments with retentive anchors).¹² A 3-year study also reported that the LOCATOR System demonstrated better clinical results than other attachments (eg, telescopic crowns, bars) when peri-implant hygiene, cost, prosthodontic maintenance frequency, and the ease of overdenture preparation were evaluated.¹³

The ease and simplicity of using the LOCATOR Implant Attachment System was further enhanced in September 2015, when a more convenient, efficient, and practical removable attachment system was introduced for beta testing (LOCATOR R-Tx Removable Attachment System [Zest Dental Solutions]). Designed for use with endosseous implant-retained overdentures or partial dentures in the mandible or maxilla, the LOCATOR R-Tx is an all-in-one attachment system that includes the appropriate size abutment (that can now be placed using a standard 0.050”/1.25-mm hex drive), denture attachment housing, and all necessary processing components for the case. The following cases illustrate the author’s experience with the LOCATOR R-Tx System during the beta test.

CASE REPORTS
Case 1: Abutment/Housing Replacement
A 73-year-old edentulous female in good health presented with a history of successfully wearing a lower overdenture retained by 3 LOCATOR Attachments in the anterior mandible. Her history with the LOCATOR System was unremarkable, with yearly substitution of the nylon inserts, until recently, when it was apparent that the LOCATOR Abutments were worn, indicating that their replacement was necessary (Figure 1).

Abutment Selection
At the first appointment, the patient’s tissue depth measurements were made by removing the existing LOCATOR Abutments and gauging the sulci with a periodontal probe. Verification of the size and type of implants was made, the appropriate removable attachment system abutments were ordered (LOCATOR R-Tx), and the original LOCATOR Abutments were reattached.

CASE 1 Figure 1. After 9 years of function, the patient’s anterior mandibular LOCATOR Abutments (Zest Dental Solutions) showed signs of wear. Figure 2. The vial cap of the LOCATOR R-Tx Abutment kit (Zest Dental Solutions) was used to carry the abutment(s) and place them onto the implant(s). Figure 3. The LOCATOR R-Tx Abutments were seated in the anterior mandible. Figure 4. The previous attachment housings were removed, and the sites were prepared for picking up the new attachments. Figure 5. In lieu of the Block-Out Spacers supplied with the LOCATOR System, rubber dams were cut for block out and placed with the metal housings for capture in the overdenture. Figure 6. The LOCATOR R-Tx Attachments and Housings, along with the black processing inserts, were secured in the overdenture. Figure 7. The anodized pink metal housings were captured in the overdenture. Figure 8. The pink (medium retention) nylon inserts were used based upon the patient’s previous history with attachments. Figure 9. View of the completed mandibular denture after the access holes were filled.

Abutment and Housing Replacement Protocol
Upon returning for treatment, the worn LOCATOR Abutments were removed using a dedicated driver, and the new removable attachment system abutments were placed. Rather than requiring the setup and use of dedicated armamentarium and instruments, delivery of the LOCATOR R-Tx Abutments was simplified by a plastic carrier handle that is also the lid of the abutment package (Figure 2). Each abutment was hand tightened using a standard 0.050”/1.25-mm implant driver, rather than a part-specific instrument (Figure 3).

The existing LOCATOR Housings were removed from the mandibular denture using a trephine bur, and the sites were prepared with several instruments (eg, recess bur, undercut bur, vent hole bur, grind bur, and trim and polish burs) contained in the Chairside Denture Prep and Polish Kit (Zest Dental Solutions) (Figure 4). The recess bur was used to create adequate space for properly luting the new housing. The undercut bur was utilized to lock in and enhance the mechanical retention of the bis-acryl attachment processing resin (Chairside Attachment Processing Material [Zest Dental Solutions]) that would secure the attachment housing. The vent bur was used to make a hole from the bottom of the recess through the lingual wall of the denture, enabling excess resin to flow from the prosthesis and, thus, preventing hydraulic pressure during the pick-up procedure.

The LOCATOR R-Tx kit also includes an anodized pink attachment housing that has nylon inserts specific to the system, and a Block-Out Spacer to prevent undesired resin flow into undercut areas. However, because this case was the author’s first experience with the new system, the decision was made to cut rubber dams, rather than to use the supplied Block-Out Spacers, to extend the range of the block out (Figure 5). In subsequent cases, the supplied spacers proved to be just as effective and less time consuming than using rubber dams.

The housings with black processing inserts were placed on each abutment, and unobstructed seating of the overdenture was confirmed. The occlusion was verified by having the patient close together. The overdenture was removed, and the recess areas were dried completely (Figure 6). Each divot was partially filled with the bis-acryl attachment processing resin, and the overdenture was seated. Next, the patient was instructed to lightly close for proper orientation. Once the resin was completely set, the overdenture was removed, excess pick-up material cleaned away, and the areas polished.

Four retentive nylon inserts of increasing retention levels are included with the system (gray = zero retention; blue = light retention; pink = medium retention; and clear = high retention). Because this patient had a history with medium retention, the pink nylon inserts were used. The black processing inserts were removed using the new LOCATOR R-Tx Retention Insert Tool provided in the kit, and the pink nylon inserts were installed using the reverse end of the same instrument (Figures 7 and 8). The working end of the tool is double-sided for performing insert placement and/or removal.

Final Insertion
The completed LOCATOR R-Tx-converted overdenture (Figure 9) was seated, after which the patient demonstrated competency in easily removing and reseating it. She returned in 2 weeks for a scheduled follow-up and expressed satisfaction with all aspects of the removable attachment system’s performance.

Case 2: New Abutment and Attachment Installation
A 71-year-old edentulous male presented for installation of implant overdenture abutments and attachments. Two new and fully integrated dental implants had been previously positioned properly in the anterior mandible (Figure 10). Healing abutments were removed, and sulci depth was measured using a periodontal probe to determine the appropriate LOCATOR R-Tx Abutments based on this measurement, as well as the type, size, and diameter of the implants. The healing abutments were reseated, the appropriate abutments ordered, and the patient scheduled for the installation appointment.

At the next appointment, the healing abutments were removed and the LOCATOR R-Tx Abutments were then placed using the plastic vial lid (as described in case 1). Each abutment was hand tightened using a standard 0.050”/1.25-mm implant driver and torqued to 25 Ncm per implant manufacturer recommendations (Figure 11). A vinyl polysiloxane (VPS) recording medium (Regisil [Dentsply Sirona Restorative]) was used to identify the abutment positions relative to the intaglio of the mandibular denture. These locations in the denture were then relieved using the recess bur, and undercuts and vent holes were made using the respective instruments contained in the LOCATOR Chairside Kit.

Returning to the patient, Block-Out Spacers were placed over each abutment, and the LOCATOR R-Tx housings with black processing inserts were seated (Figure 12). The denture was then inserted to verify complete seating, and the patient was instructed to close to ensure the occlusion was not affected. The denture was removed and dried, after which pick-up resin (CHAIRSIDE Denture Kit [Zest Dental Solutions]) was injected into the prepared recessed sites. Next, the denture was reseated and the patient was guided into lightly closing to ensure a proper relationship between the upper and lower dentures. Upon the setting of the material, the overdenture was removed, extraneous pick-up resin removed, and the overdenture polished (Figure 13). The black processing inserts were replaced with clear (high retention) nylon inserts, and the patient demonstrated competency in easily and comfortably placing and removing the overdenture. The patient was dismissed and requested to return in 2 weeks for evaluation. At 2 weeks postoperative, he reported complete satisfaction with the result.

CASE 2 Figure 10. Healing abutments on 2 new osseointegrated dental implants in the anterior mandible. Figure 11. The selected LOCATOR R-Tx Abutments were secured into place. Figure 12. The Block-Out Spacers (provided in the CHAIRSIDE Denture Kit [Zest Dental Solutions]) and anodized metal housings were placed for capture in the overdenture. Figure 13. View of the completed mandibular overdenture intaglio surface with the clear (high retention) nylon inserts in place.

CLOSING COMMENTS
During beta testing and the treatment of the 2 patients as reported herein, the new LOCATOR R-Tx Removable Attachment System was observed by the author to be comfortably familiar to the older LOCATOR Attachment System, yet simpler and decidedly improved in terms of insert replacement inventory, delivery, and maintenance, and reported abutment alloy strength enhancements for increased wear resistance (ie, from multiple layers of titanium nitride and titanium carbon nitride). Using the attached vial lid from the double-sided package to deliver the abutments to the implant site proved to be very efficient, particularly since it provided a firm grip for seating. The ability to tighten the abutment with the most common, standard hex driver (as opposed to the dedicated driver required for those in the previous LOCATOR System) was a significant improvement in simplicity. The separate vial compartment on the other end of the package for the retentive components was user-friendly, providing storage for unused inserts (which are significantly less due to the elimination of the center plunger). The new pivoting insert/housing assembly provides up to 30° angle correction (a total of 60° between 2 implants) and appeared to provide appropriate overdenture retention. Simultaneously, the dual engagement external geometry also provided significant retention while promoting easier seating alignment for patients. In fact, both patients returned only positive reports regarding overdenture retention and stability.

References

1. Feine JS, Carlsson GE. Implant Overdentures: The Standard of Care for Edentulous Patients. Hanover Park, IL: Quintessence Publishing, Inc; 2003.
2. Melilli D, Rallo A, Cassaro A. Implant overdentures: recommendations and analysis of the clinical benefits. Minerva Stomatol. 2011;60:251-269.
3. Vahidi F, Pinto-Sinai G. Complications associated with implant-retained removable prostheses. Dent Clin North Am. 2015;59:215-226.
4. The glossary of prosthodontic terms. J Prosthet Dent. 2005;94:10-92.
5. Assaf A, Chidiac JJ, Daas M. Revisiting implant-retained mandibular overdentures: planning according to treatment needs. Gen Dent. 2014;62:60-64.
6. Cicciù M, Cervino G, Bramanti E, et al. FEM analysis of mandibular prosthetic overdenture supported by dental implants: evaluation of different retention methods. Comput Math Methods Med. 2015;2015:943839.
7. Barão VA, Delben JA, Lima J, et al. Comparison of different designs of implant-retained overdentures and fixed full-arch implant-supported prosthesis on stress distribution in edentulous mandible—a computed tomography-based three-dimensional finite element analysis. J Biomech. 2013;46:1312-1320.
8. Coleman AJ, Tompkins KA, Evans JH. Restorations using osseointegrated implants with resilient attachments. Compend Contin Educ Dent. 1997;18:384-390.
9. Setz I, Lee SH, Engel E. Retention of prefabricated attachments for implant stabilized overdentures in the edentulous mandible: an in vitro study. J Prosthet Dent. 1998;80:323-329.
10. Cardoso RC, Gerngross PJ, Dominici JT, et al. Survey of currently selected dental implants and restorations by prosthodontists. Int J Oral Maxillofac Implants. 2013;28:1017-1025.
11. Mackie A, Lyons K, Thomson WM, et al. Mandibular two-implant overdentures: three-year prosthodontic maintenance using the Locator attachment system. Int J Prosthodont. 2011;24:328-331.
12. Cristache CM, Muntianu LA, Burlibasa M, et al. Five-year clinical trial using three attachment systems for implant overdentures. Clin Oral Implants Res. 2014;25:e171-e178.
13. Zou D, Wu Y, Huang W, et al. A 3-year prospective clinical study of telescopic crown, bar, and LOCATOR Attachments for removable four implant-supported maxillary overdentures. Int J Prosthodont. 2013;26:566-573.

Dr. Montana received his DDS from the University of Southern California (USC) School of Dentistry in 1987 and completed his certification in advanced prosthodontics at USC in 1989. He maintains a private practice in Tempe, Ariz, with an emphasis on fixed, removable, and implant prosthodontics. He is a member of the American College of Prosthodontists, the Academy of Osseointegration, the Academy of Fixed Prosthodontics, the Pacific Coast Society for Prosthodontics, the ADA, and the Arizona Dental Association. He has lectured internationally on the topics of implant, fixed, and removable prosthodontics. He can be reached at (480) 820-2901 or via email at markmontana@mac.com.

Disclosure: Dr. Montana reports no disclosures.

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