LOCATOR R-Tx – Improved & Advanced Removable Attachment System

Joseph J. Massad, DDS, Associate Professor, Department of Prosthodontics, University of Tennessee Health Center School of Dentistry, Memphis, Tennessee, USA

Swati Ahuja, BDS, MDS, Adjunct Assistant Professor, Department of Prosthodontics, University of Tennessee Health Science Center, College of Dentistry, Memphis, Tennessee, USA (sahuja@uthsc.edu)

Russell Wicks, DDS, MS, Professor and Chair, Department of Prosthodontics, University of Tennessee Health Science Center, College of Dentistry, Memphis, Tennessee, USA

David R. Cagna, DMD, MS, Professor, Department of Prosthodontics, University of Tennessee Health Science Center, College of Dentistry

Republished with permission from Dentistry Today

Abstract

Zest Dental Solutions has introduced the next-generation LOCATOR attachment system (LOCATOR R-Tx Removable Attachment System) to improve the angle correction capability of the conventional LOCATOR attachment along with several new features incorporated in the design to improve its clinical performance. LOCATOR R-Tx abutments are restored using the same technique as conventional LOCATOR attachment systems. The purpose of this article is to report a case utilizing LOCATOR R-Tx attachment systems to facilitate fabrication of an esthetic and functional implant-retained, removable, complete denture prosthesis. 

Implant overdentures may be supported and retained using bar and clip attachment systems or through individual, free standing abutment-based attachments. Free standing abutment attachments include balls, magnets, resilient stud attachments, such as the LOCATOR system (Zest Dental Solutions) and ERA (Sterngold), and non-resilient stud attachments such as Ankylos Syncone (Dentsply International).^1-4 Attachment system selection depends on a variety of factors that must be identified early in the treatment sequence. These factors include implant position, desire for cross-arch stabilization, size of the prosthesis, economics, oral hygiene compliance, sore spots tendency, restorative space availability, condition of the prosthesis in the opposing arch, and/or ease of fabrication or repair of the prosthesis.⁴

Bars have been primarily indicated to accommodate non-parallel implant trajectories. However, most bar systems require substantial planning and the fabrication of a bar supported prosthesis is technique sensitive.⁵ They require more vertical restorative space compared to individual stud attachments.⁵ Patients with bar-supported prostheses may be prone to develop mucosal hyperplasia beneath the bar and mucositis around the implants.^6-8 Reduced tissue coverage of individual stud attachments, such as LOCATOR or ERA attachments make them a preferred treatment choice for patients with poor oral hygiene.⁴

LOCATOR attachments were introduced in 2001 and have been used successfully since their inception. They have several advantages including resiliency; self-alignment^9-11  (making it easy for the patient to align and seat the prosthesis  as well as decreasing the wear of nylon retentive inserts due to improper prosthesis placement), dual retention (internal and external)^9-11; ease of replacement of the nylon retentive inserts^{12, 13}, maintenance of oral hygiene⁸; and low-profile¹¹ (3.17 mm for external hexagon implant, 2.5 mm for internal connection). The LOCATOR attachment system has become a popular choice when there is reduced vertical restorative space.⁵ The reduced height of the attachment also decreases the forces to the implant by reducing the lever arm length.¹⁴ LOCATOR attachments make it possible to transform an existing denture to an implant-retained overdenture.^{11, 15} They can be used to support and retain both complete11 and partial removable prostheses.¹⁶ They are compatible with the majority of available implant systems.¹⁷

Implant overdentures using  LOCATOR attachment systems demonstrate a high success rate (over 94.5%)¹⁸ and have  demonstrated superior clinical results compared to ball and bar attachments, with regard to rate of prosthodontic complications and the maintenance of the oral function.¹¹ However, all stud attachments, including LOCATOR attachments, display a significant reduction in retention when used in conjunction with non-parallel implants.^19-21 The manufacturer recommends using the Extended Range (Gray, red, orange or green) LOCATOR inserts to correct up to 20° angulation per implant (40 degrees between two implants). However, the Extended Range Inserts provide only external retention and also wear faster than the Standard Range.^{17, 22} The success of a removable implant restoration primarily depends on the retentive capacity of its attachment to sustain its long-term functionality. 

Recently, Zest Dental Solutions has introduced the next-generation LOCATOR attachment system (LOCATOR R-Tx Removable Attachment System) (Fig. 1) to improve the limitations associated with conventional LOCATOR attachment. In addition to its angle correction capability, several new features have been incorporated to improve its clinical performance.¹⁷ The new features include: a DuraTec® titanium carbon nitride coating, which is aesthetic, harder, and more wear resistant compared to the titanium nitride coating used on conventional LOCATOR abutment; an industry-standard .050-in / 1.25-mm hex drive mechanism, precluding the need of special drivers; a smaller central cavity which decreases food and plaque accumulation; dual-retentive features on the external surface of the abutment; and absence of internal engagement, preventing debris and plaque accumulation within the drive mechanism from impacting proper seating; and a reduction in the coronal abutment dimension, making it easier for the patient to align and seat the prosthesis.¹⁷

The redesigned Denture Attachment Housings (DAH) (Fig. 2) is anodized pink for aesthetics and designed with flats and grooves to resist vertical and rotational movement.¹⁷ It permits 50% increase in pivoting capability and up to 30-degree angle correction per implant as opposed to maximum of 20-degree angle correction per implant with conventional LOCATOR.¹⁷ 

A conventional locator DAH is not anodized and only designed with horizontal grooves to resist vertical movement.¹⁷ Opposed to the conventional LOCATOR, LOCATOR R-Tx offers only one set of inserts (Zero retention -Gray, Low retention -Blue, Medium retention -Pink and High retention -white) (Fig. 3) 

In addition, the LOCATOR R-Tx all-in-one packaging (Fig. 4) provides all the necessary components needed with only a single part number: Abutment, DAH with Processing Insert, Retention Inserts, and Block Out Spacer. 

The dual-sided LOCATOR R-Tx tool (Fig.5) permits easy insertion and removal of the retention insert.¹⁷ Metal slot feature on the back of the tool allows the clinician to disengage a retentive insert with minimal risk of tearing gloves.¹⁷ 

A recent CR report stated that 100% of CR Project Directors would incorporate the LOCATOR R-Tx into their practice and all of them (100%) rated it excellent or good and worthy of trial by colleagues.²³ LOCATOR R-Tx abutments are restored with the same restorative technique used for conventional LOCATOR attachment systems.¹⁷ The purpose of this article is to report a case utilizing LOCATOR R-Tx attachment systems to facilitate fabrication of an esthetic and functional implant-retained removable prosthesis. 

Case Report

A 46-year-old Caucasian female patient presented to the author’s clinic for restoration of 4 maxillary and two mandibular implants (teeth #6, #9, #11 #13, #19 and #20 locations) (Fig. 6). The implants were planned by the restorative dentist and placed by the oral surgeon. 

5 implants were initially planned and placed in the maxillary arch (teeth #4, #6, #9, #11 #13 locations), but implant in location of tooth #4 failed and it had to be removed. 

The oral hygiene of the patient was good. The patient’s medical history was noncontributory. The patient was very esthetic conscious and desired a simple, easy to clean and retentive maxillary restoration.

The mandibular implants were restored with porcelain fused to metal screw-retained crowns which helped establish the mandibular occlusal plane (Fig. 7). An implant-supported overdenture was planned for the maxillary arch. The maxillary implants had a 30-35 degrees divergence, making it challenging to use conventional stud attachments (Fig. 8). 

The newly introduced LOCATOR abutments (LOCATOR R-Tx, Zest Dental Solutions), were chosen to help manage the divergence between the implants. The following procedures were accomplished to fabricate and deliver the definitive prosthesis:

The healing abutments were removed and a maxillary open tray impression was made using direct transfer copings (Fig. 9), yielding an implant level tissue cast (Fig. 10). 

Following this impression, the healing abutments were re-attached to the maxillary implants. An additional impression was made to generate a mandibular cast. Maxillo-mandibular jaw relationship records (Face bow record, Protrusive record and Centric relation record) were registered and the casts were mounted on a semi-adjustable articulator (Whip Mix 2240, Whipmix, Louisville, KY, USA). A wax trial denture procedure was accomplished to evaluate fit, form, occlusion and esthetics (Fig. 11). 

LOCATOR R-Tx abutments (heights chosen based on mucosal thickness) and the DAHs were attached to the implant analogs on the maxillary cast. The mounted casts, and wax trial denture were sent to the laboratory along with detailed instructions for fabrication of the removable dental prostheses incorporating a metal framework.  The framework was designed to accommodate the DAHs which were to be integrated into the prosthesis via a chairside pick-up procedure. The finished maxillary implant-supported removable dental prostheses incorporating a metal framework was returned from the laboratory (Fig. 12) and evaluated in the patient’s mouth. The fit, form and occlusion was evaluated, and the prosthesis was adjusted, finished and polished as needed.  

The healing abutments were removed from the mouth and the LOCATOR R-Tx abutments (retrieved from the laboratory) carefully attached to the implants and torqued as per the manufacturer specifications (Fig. 13). A radiograph was taken to confirm the complete seating of the abutments (Fig. 14). The DAHs (also retrieved from the laboratory) were seated over the abutments (Fig. 15). 

The prosthesis was tried in the patient’s mouth to reverify the fit, occlusion and to ensure that there was no contact of the DAHs within the recesses created in the prosthesis. The recesses were roughened and sandblasted and the denture attachment housings were cleaned and dried. A metal bonding acrylic agent (UBAR Metal Bonding Cold Cure, Protech) was applied to the recesses and the denture attachment housings were picked up directly utilizing an auto-polymerizing resin material (CHAIRSIDE Attachment Processing Material, Zest Dental Solutions) as per the manufacturer recommendations. The prosthesis was adjusted, finished and polished as needed. 

The black processing inserts were removed and replaced with pink retention inserts with the LOCATOR R-Tx tool (Fig. 16). The prosthesis was seated in the mouth. The patient was very pleased with her prosthesis (Fig. 17). The patient was given home care instructions regarding the hygiene and maintenance of the prostheses and placed on a biannual recall schedule.

Summary

Ongoing research and development has led to the innovation of the LOCATOR R-Tx attachment system. Additional patients have been successfully treated using the new attachments (Fig. 18, Fig.19). This article compares the features of the LOCATOR R-Tx with the conventional LOCATOR attachment system.  

It also includes angulated implant case  presentation including clinical and laboratory steps for the fabrication of a metal reinforced overdenture prosthesis incorporating LOCATOR R-Tx attachments.

References

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Dental News March 2020 Issue

Republished with permission from Dentistry Today