A User-Friendly Technique for Replacing Nylon Inserts of a Locator Attachment

Implant-retained overdentures have gained popularity as a viable treatment option for patients with severe residual ridge resorption, neuromuscular disorders, and pronounced gag reflexes and who experience problems related to retention and stability with conventional complete dentures. This is substantiated by the McGill consensus statement, which suggested that the two-implant overdenture should be the first-choice standard-of-care treatment for the edentulous mandible.¹ In comparison to conventional dentures, implant-retained overdentures offer improved retention, stability, and masticatory efficiency and also can enhance a patient's psychological well-being. Further, an implant-supported prosthesis can increase a denture patient's maximum occlusal force by up to 300%.² These prostheses may also be advantageous over fixed implant-supported ones in situations of unfavorable jaw relationships and inadequate bone availability for a fixed prosthesis.^3,4

A variety of available attachment systems are used in conjunction with implant overdentures. These include bar, ball, magnetic, and other resilient attachment systems such as the Locator attachment system. Among these, the Locator attachment system has become prominent due to its self-aligning property, simplicity of use, and minimum height requirement of male inserts within the denture and abutment on the implant or attachment on the overdenture bar.^5-7 The minimum space requirement for Locator systems is 8.5 mm, as opposed to ball attachments, which require at least 10 mm to 12 mm vertical space.⁸ In addition, studies have shown that ball attachments and magnets require more prosthetic maintenance due to wear or fracture of the ball head, activation of the ball matrix, and corrosion or wear of the magnets.^9-12

The Locator attachment system includes a patrix consisting of a titanium nitride-coated cylindrical abutment featuring external and internal undercuts and a matrix formed by a titanium-metal housing (Figure 1) in which interchangeable nylon inserts are located.⁴ The system's standard armamentarium comprises three different types of male inserts with various retentive capacities, with blue, pink, and clear having retention values of 6.67 N, 13.35 N, and 22.24 N, respectively (Figure 2). An extended armamentarium may sometimes be available, which includes grey, red, orange, and green cap-bearing retention values of 0 N, 4.45 N, 8.9 N, and 17.79 N, respectively.

Although Locator attachment systems have shown an implant survival rate of 95.2%, they, too, have specific prosthodontic maintenance requirements and complications like other attachment systems. These include attachment loosening, denture cap-related problems, loss of insert, and implant fracture, with the most frequently reported difficulty being the loss of rvetention owing to the wearing of the nylon inserts, which necessitates the insert's replacement.⁴ Rabbani et al investigated the retentive force reduction and wear of the Locator attachment system with different implant angulations over 6, 12, and 18 months of simulated use and concluded that there was a significant reduction of retentive force of 59% to 70% after 18 months of simulated use (ie, 2,160 cycles).¹³ Similarly, in a retrospective study by Patodia et al on 75 patients, replacement of attachments constituted 63% of the complications encountered.⁴ Another retrospective evaluation by Engelhardt et al on 32 patients over a mean observation period of 4.78 ± 1.72 years reported similar findings.¹⁴

TheLocator system comes with a 3-in-1 Locator core tool designed for replacing the inserts. The core tool consists of a gold-plated implant abutment driver, a male removal tool, and a male seating tool. The removal end of the core tool needs to be loosened a full three turns counterclockwise and then inserted into the denture cap until the sharp end of this tip engages the male insert and is then pulled out of the denture cap, followed by the use of the seating tool to place the new nylon insert into the denture cap. The use of the core tool can be technique-sensitive and cumbersome.

The following proposed technique is a straightforward protocol for replacing Locator nylon inserts in the denture metal housing using a dental explorer and mirror head.

The first step in the technique is to remove the worn-out nylon inserts from the metal housing with the aid of a #23 or similar explorer. The curved end of a dental explorer can engage the nylon insert, which can be pulled out with a twisting action (Figure 3). The metal housing should then be examined for possible damage and cleaned with a soft-bristle brush or air-water spray. Next, the mirror head gets disengaged from the handleby firmly holding the mirror handle with one hand and rotating the mirror head in a counterclockwise direction (Figure 4). The retentive insert (Locator replacement male) is then placed in the metal housing and gets gently pushed with the threaded end of the mirror head so that it engages into the metal housing (Figure 5).

Lastly, the clinician should ensure that the nylon insert is seated snugly within the metal housing. This can be confirmed by a snap sound that will accompany the proper seating of the nylon insert. Proper seating of the nylon inserts within the metal housing can be further confirmed by reseating the prosthesis in the patient's mouth, wherein a proper fit of the prosthesis will indicate proper seating of the inserts.

This technique is relatively simple and uses readily available instruments in the clinic to replace worn-out nylon inserts. This straightforward technique eliminates the need for a Locator core tool for the subsequent replacement of worn-out nylon inserts into the denture metal housing.

Nirmal Kurian, BDS, MDS
Associate Professor, Department of Prosthodontics and Crown & Bridge, Christian Dental College, Ludhiana, Punjab, India; Diplomate, Indian Board of Prosthodontics

Kevin George Varghese, BDS, MDS
Assistant Professor, Department of Prosthodontics and Crown & Bridge, Christian Dental College, Ludhiana, Punjab, India

Samiksha Wadhwa, BDS
Postgraduate Resident, Department of Prosthodontics and Crown & Bridge, Christian Dental College, Ludhiana, Punjab, India

Achsah Ann Thomas, BDS
Postgraduate Resident, Department of Prosthodontics and Crown & Bridge, Christian Dental College, Ludhiana, Punjab, India

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