Implant overdentures retained by self-aligning stud-type attachments: A clinical report

Abstract

The functionality of a new overdenture attachment (LOCATOR R-Tx) was described for different clinical situations: a conventional mandibular implant overdenture (IOD) retained by 2 implants, a straightforward chairside maintenance procedure for replacing a worn LOCATOR (Legacy) attachment with the new LOCATOR R-Tx, and a complex clinical situation with nonideal implant positions with compromised parallelism. The LOCATOR R-Tx is an advance on the existing LOCATOR Legacy attachment and has an improved abutment head design with a more durable surface coating to prevent attachment wear and thereby reduce frequency of maintenance.

Removable prostheses retained by dental implants are successful treatment options with high patient satisfaction, improved comfort, prosthesis stability, and masticatory function compared with conventional dentures. Implant overdentures (IODs) retained by 2 implants significantly improve the Oral Health-Related Quality of Life (OHRQoL) of elderly edentulous patients. The success of IODs and implant-retained removable partial dentures (RPDs) depends on the performance of the attachment system.

Splinted anchorage systems, such as bar attachments, are highly retentive with a fairly low long-term maintenance requirement. However, they have a high initial cost; are difficult to fabricate; and may be complicated to repair, modify, or remake. In contrast, the unsplinted stud anchorage systems such as the spherical anchor or the LOCATOR attachment (Zest IP Holdings, LLC) are straightforward to process and have a low initial cost. Although the LOCATOR attachment is the most widely used attachment for IODs, it has been criticized as being difficult for dependent elders to use. In addition, these attachments are prone to wear and rapid loss of retention and require periodic maintenance visits.

A recently introduced attachment (LOCATOR R-Tx Removable Attachment System; Zest IP Holdings, LLC) overcame some of these drawbacks. The abutment design is intended to provide the same clinical handling as the earlier design but with the benefits of a narrower coronal geometry, an improved surface coating, and greater flexibility in terms of the interimplant angular compensatory mechanism. The purpose of this clinical report was to document the versatility and the ease of use of the new LOCATOR R-Tx attachment in 3 different clinical situations.

Clinical indication #1: mandibular IOD retained by 2 tissue-level implants

A 74-year-old woman was referred for the rehabilitation of her completely edentulous maxilla and mandible. Her chief complaints included inability to eat properly and poor esthetics. Her maximum mouth opening was normal with no evidence of TMJ problems and no history of parafunctional habits. Intraoral and radiographic examinations revealed a moderately resorbed edentulous maxilla and a more severely resorbed mandible. The treatment planned was to rehabilitate the edentulous jaws with a conventional maxillary complete denture (CD) opposing an implant-retained mandibular IOD ( Fig. 1 A, B).

Figure 1
Patient #1 initial situation and abutment selection. A, Intraoral view of edentulous maxilla. B, Intraoral view of edentulous mandible with 2 tissue-level implants ready for loading. C, LOCATOR PLAN abutments in place showing 2-mm gingival cuff height.

The prostheses were fabricated following a 3-visit digital denture protocol, and the patient was first provided with interim trial dentures (AvaDent Digital Dental Solutions Europe; Global Dental Science Europe BV). The trial dentures were worn for a period of 1 month, enabling modifications to be made and allowing the patient to adapt to the new prostheses. Once the patient was accustomed to and comfortable with the trial dentures, implant surgery was planned. By using the mandibular trial denture as a surgical guide, 2 implants (4.1 mm in diameter and 10 mm in length, Regular Neck Tissue Level; Institut Straumann AG) were placed in a single-stage surgery in the mandibular canine region following a standard surgical protocol. After surgery, the mandibular trial denture was relieved sufficiently to not contact the implants and was relined by using a functional impression tissue conditioning material (F.I.T.T.; Kerr Corp). After a healing period of 6 weeks, definitive reline impressions were made by using the trial dentures. The impressions were then scanned and sent to the digital denture manufacturer. The digital dental laboratory incorporated the second set of definitive impressions into the existing denture design and fabricated a set of computer-aided design and computer-aided manufacture (CAD-CAM) fully milled maxillary and mandibular dentures (AvaDent; Global Dental Science Europe BV). The mandibular IOD was milled to include the spaces to accommodate the matrices to be processed intraorally. The definitive CAD-CAM milled dentures were clinically evaluated for retention, stability, fit, extensions, esthetics, and occlusion.

The healing abutments were removed, and the height of the peri-implant gingival cuff was measured by using the abutments (LOCATOR PLAN; Institut Straumann AG) ( Fig. 1 C). The gingival cuff height was 2 mm, and the appropriate abutments (LOCATOR R-Tx tissue level RP; Zest IP Holdings, LLC), were selected ( Fig. 2 A, B). The abutments were first hand-tightened on the implants by using a standard hexagonal driver (Zest IP Holdings, LLC) and then tightened to 30 Ncm by using a calibrated torque wrench (Zest IP Holdings, LLC) following the manufacturer’s instructions ( Fig. 2 C). The white block-out spacers (Zest IP Holdings, LLC) were then placed on the LOCATOR R-Tx abutments, and the matrices with the black processing inserts were snapped onto each abutment ( Fig. 3 A). The mandibular denture was then evaluated and adjusted for clearance guided by a silicone material (Fit Checker Advanced; GC Corp) ( Fig. 3 B). The denture was then cleaned and prepared for the intraoral processing of the matrices. Petroleum jelly (Vaseline; Unilever) was applied on the mucosa of the edentulous ridge adjacent to the implants and on the lips to prevent irritation from the autopolymerizing polymethylmethacrylate (PMMA) resin. Care was taken not to contaminate the matrices with the petroleum jelly. The PMMA resin (Unifast; GC Europe N.V.) was mixed and applied on top of the matrices and into the milled housing spaces of the mandibular denture by using a microbrush (3M ESPE) ( Fig. 3 C). The mandibular denture was then inserted, and the patient was requested to occlude into centric occlusion until the PMMA resin had polymerized ( Fig. 4 A). The denture was then removed and inspected. Excess resin around the matrices was trimmed and finished. The black processing inserts were replaced with definitive gray (zero) retention inserts ( Fig. 4 B). Finally, postinsertion and denture hygiene instructions were given to the patient ( Fig. 4 C).

Figure 2
Positioning of LOCATOR R-Tx abutments. A, LOCATOR R-Tx abutment, matrices, and retentive inserts. B, Abutment being positioned and tightened. C, Attachments ready for denture processing.

Figure 3
Space verification. A, White block-out spacers and matrices positioned. B, Silicone material verifying available space. C, Autopolymerizing PMMA resin placed in housing space. PMMA, polymethylmethacrylate.

Figure 4
Matrix processing and definitive result. A, Denture positioned on abutments and patient occluding in centric occlusion. B, Gray (zero) retentive inserts placed after finishing and polishing of processed denture. C, Processed denture in situ.

Indication #2: replacement of a worn out LOCATOR Legacy attachment in a cast RPD

A 67-year-old woman with a cast RPD retained by implants presented with the complaint of loss of retention in her RPD. An intraoral examination revealed that the patient had a Kennedy Class I partially edentulous maxilla with few remaining anterior teeth opposing a restored natural dentition ( Fig. 5 A). Two implants (Regular Neck Tissue Level; Institut Straumann AG) were present in the maxilla’s first premolar regions with LOCATOR Legacy attachments ( Fig. 5 B). The attachments had been in situ for 9 years and presented with severe wear ( Fig. 5 C). The treatment plan was to replace the existing attachments with LOCATOR R-Tx tissue level RP abutments and change the corresponding matrices intraorally in the same visit. The existing LOCATOR abutments were first removed, and the height of the new LOCATOR R-Tx abutment to be used was confirmed with the PLAN abutments ( Fig. 6 A). The 2-mm-high LOCATOR R-Tx abutments were selected, hand-tightened on the implants, and then tightened to 30 Ncm as recommended by the manufacturer ( Fig. 6 B). The existing matrices were then extracted from the RPD by using a housing extractor (Cendres+Métaux SA) ( Fig. 6 C). The white block-out spacer was placed on the LOCATOR R-Tx abutments, and the new matrices were snapped onto the abutments ( Fig. 7 A). Intraoral processing of the matrices into the RPD was performed as described previously ( Fig. 7 B). The patient was satisfied with the retention and the overall result ( Fig. 7 C).

Figure 5
Patient #2 initial situation. A, Intraoral view of initial situation. B, Occlusal view showing Kennedy class I partially edentulous maxilla with implants and LOCATOR Legacy abutments. C, Existing worn LOCATOR Legacy abutments.

Jan 12, 2020 | Posted by in Prosthodontics | Comments Off on Implant overdentures retained by self-aligning stud-type attachments: A clinical report
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