A Novel Extended Range Attachment System to Retain Implant Overdentures: A Clinical Report Nadim Z. Baba, DMD, MSD, FACP,1 Fahad A. Al-Harbi, BDS, MSD, DScD, FACP,2 Hamad S. AlRumaih, BDS, MSD, FACP,2 & Abdulkareem AlShehri, BDS, FACP3 1
Advanced Specialty Education Program in Prosthodontics Loma Linda School of Dentistry, Loma Linda, CA Department of Substitutive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 3 King Fahad Medical City, Riyadh, Saudi Arabia 2
Keywords Direct; implant-supported; indirect; Locator abutment; overdentures; partial denture. Correspondence Nadim Z. Baba, DMD, MSD, FACP, Professor, Advanced Specialty Education Program in Prosthodontics, Loma Linda School of Dentistry, 11092 Anderson St., Loma Linda, CA, 92350. E-mail:
[email protected]
Abstract Various attachment systems have been used to facilitate the retention, stability, and support of overdentures. The low profile design, pivoting technology, and durability of the Locator attachment made it one of the commonly used tissue-supported implantretained overdentures. It has been successfully used to retain overdentures as well as partial dentures. This article describes the uses of the new Locator R-Tx abutment and illustrates both the direct and indirect techniques used to process the denture attachment housing into the prosthesis to retain overdentures and partial dentures.
Disclosure: Nadim Z. Baba is a consultant for Zest Dental Solutions. Accepted March 5, 2018 doi: 10.1111/jopr.12907
Dental implants have been effectively used to retain or support maxillary and mandibular overdentures. Several benefits of implant overdentures have been discussed, the most prominent being the psychosocial, anatomical, and functional benefits.1 Various attachment systems have been used to facilitate the retention, stability, and support of overdentures; however, the choice of the attachment depends upon the complexity of the case, the alignments of the implants, the retention value needed, the available vertical and horizontal prosthetic space, and the jaw morphology.2,3 The increase in cost of laboratory fees in addition to the biologic and mechanical complications of splinted retentive mechanisms (i.e., bar) prompted the clinician to consider the use of individual retentive mechanisms in the mandible for overdenture retention.2-5 The most common individual retentive mechanisms are magnets, ball, Dalla Bona, and Locator attachments. A prospective clinical trial compared these attachments and concluded that magnets were more expensive than the other attachments but require low maintenance.6 Other studies7-9 evaluated different retentive mechanisms used for implant-supported overdentures from the standpoint of maintenance needs. They concluded that there was no significant difference regarding postinsertion maintenance between the various attachments; however, the low profile design, pivoting technology, durability, and easeof-use of the Locator attachment has made it one of the pre-
ferred choices for retaining tissue-supported, implant-retained overdentures.3,10-13 The purpose of this article is to describe the new Locator R-Tx attachment and illustrate the direct and indirect techniques used to process the denture attachment housing into the dentures to retain removable complete dentures or partial dentures.
Clinical reports Patient 1: Individual retentive mechanism to retain a mandibular implant-retained overdenture
A 44-year-old Caucasian woman presented to the office for the evaluation of her existing maxillary and mandibular complete dentures. Her chief complaint was, “my dentures are loose specially the lower one, I need adhesive to hold them in place and I don’t like the way they look.” The patient’s medical history and health questionnaire revealed no significant findings. She presented with no medical contraindications to prosthodontic treatment. She is presently under treatment for depression. The patient’s main concern was to determine if it was possible to improve the fit and retention of her maxillary and mandibular
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Figure 3 Use of a calibrated torque wrench to tighten the abutments to 30 Ncm.
Figure 1 Locator R-Tx abutment.
Figure 4 White block-out spacers and attachment housings seated on top of the attachment housing.
Figure 2 Implants with Locator R-Tx abutments in place.
dentures to improve comfort level. She was seeking treatment to have a new set of dentures made that had a natural appearance. At the approximate occlusal vertical dimension (OVD), the patient showed an adequate interarch space. The existing OVD was also appraised (phonetics, swallowing, interocclusal rest space, and facial contours) and found to be proper. The maxillary central incisor midline was correctly aligned with the patient facial midline; however, the mandibular midline was deviated 1.5 mm to the left in relation to the maxillary central incisor midline. The patient stated that the midline shift was made that way at her own request. According to House’s personality classification, the patient was judged to be “exacting.”14 She had reasonable expectations and desires regarding anticipated dental treatment. The residual 2
Figure 5 Creation of a recess site and an undercut using a recess bur.
ridge relationship appeared to have a Class 1 ridge relation, and she revealed a Class III prosthodontic diagnostic index (PDI).15 The patient’s existing complete dentures demonstrated fair esthetics, poor stability and retention, and severe tooth wear. A thorough explanation of all treatment options, their objectives, and limitations were presented to the patient, who consented
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Figure 6 Injection of the chairside attachment processing material in the created recess.
Figure 9 Frontal view of the definitive maxillary complete denture and mandibular implant-supported overdenture.
Figure 7 Denture attachment housing after removal of the processing insert.
Figure 10 Maxillary full-arch view of the preoperative ISRPD.
Figure 8 Placement of the medium retention insert.
to the proposed treatment that included placement of two endosseous implants in the mandibular anterior sextant, and fabrication of a new maxillary complete denture and a mandibular implant-retained complete denture. Following implant placement (RC Bone level; Straumann, Andover, MA) and osseointegration, the healing abutments were removed, a periodontal probe was used to measure the
Figure 11 Full-arch view of the maxilla with existing attachments in place.
height of the gingiva at the highest point, and the cuff height of the Locator R-Tx abutments that corresponds to these measurements was selected accordingly (Fig 1). The abutments were hand tightened on the implants using a .050”/1.25 mm hex driver, and radiographs were taken to confirm the abutments were seated on the implants. A calibrated torque wrench
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Figure 12 Placement of Locator R-Tx abutments on the implants.
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Figure 15 Placement of final retention inserts in the housings.
Figure 16 Frontal view of the definitive maxillary ISRPD. Figure 13 Impression copings secured firmly in place.
Figure 14 Finalized virtual framework design.
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(ITL Dental, Irvine, CA) was used to tighten the abutments to 30 Ncm. A white block-out spacer was placed around each abutment followed by a firm seating of the denture attachment housing (Figs 2 to 4). A vinyl polyether silicone (Fit TM Checker Advanced, GC America Inc.; Alsip, IL) was injected into the intaglio surface of the mandibular denture and used to mark the areas where the denture will need to be relieved to allow space for the housings to be picked up. A recess site and an undercut were created using a recess bur followed by an undercut bur. A venting bur was then used to create a 1.0 mm lingual hole to allow for excess of attachment processing material to vent during the pick-up of the metal housings. The denture attachment housings were air-dried, and the chairside bis-acrylic attachment processing material (CHAIRSIDE; Zest Dental Solutions, Carlsbad, CA) was spread around the whole circumference of each housing and in the recesses created in the intaglio of the complete denture, which was then seated on top of the housings with minimal pressure. The attachment processing material was light cured for 30 seconds, the denture disengaged from the abutments, and the excess material removed with the use of a round carbide grinding bur (#09583, CHAIRSIDE Denture prep and polish kit; Zest Dental Solutions). Excess acrylic material still available on the lingual of the denture was removed and the denture polished. The black C 2018 by the American College of Prosthodontists Journal of Prosthodontics 0 (2018) 1–7 ⃝
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processing inserts were removed with the insertion tool; it is recommended to start with the lowest retentive retention inserts and then change them according to the patient retention needs. The chosen retention inserts were positioned into each denture attachment housing and the dentures seated. The patient was then given the appropriate homecare maintenance instructions (Figs 5 to 9). The patient returned at 24 hours and 1 week postplacement for evaluation and adjustments. She reported a high degree of satisfaction with the esthetic outcome, function, and comfort level of the treatment provided. She was extremely happy with her new appearance and smile. Patient 2: Individual retentive mechanism to retain a maxillary implant-retained removable partial denture
A 78-year-old Caucasian woman presented to the office for the evaluation of her existing maxillary implant-supported removable partial denture (ISRPD). Her chief complaint was, “my dentures don’t hold on to the attachments anymore and they have a hole in them.” The patient’s medical history and health questionnaire revealed no significant findings. She presented with no medical contraindications to prosthodontic treatment. She is presently under treatment for high blood pressure and diabetes. The patient wore a maxillary ISRPD supported by two custom-made bars, one on implant area #5 and one on implant area #13 (RC Bone level; Straumann, Andover, MA) incorporated with semi-precision attachments. Her existing ISRPD demonstrated fair esthetics, poor stability and retention, and severe tooth and acrylic wear (Figs 10, 11). She was seeking treatment to have a new maxillary ISRPD made with better fit and retention. Following a thorough explanation of all treatment options, their objectives and limitations, the patient consented to the proposed treatment that included replacement of her two cast bars and semi-precision attachments, and fabrication of a new maxillary ISRPD. The custom-made bars with semi-precision attachments were removed, and a periodontal probe was used to measure tissue depth from the seating surface of the implant to the highest point of the gingiva and the abutments ordered accordingly. The selected abutments were screwed into each implant using the hex drive and torqued to 30 Ncm using a calibrated torque wrench. Two impression copings were placed on each abutment and secured firmly (Figs 12, 13). A maxillary stock impression tray was selected, tried in the patient’s mouth, and trimmed or extended with wax to ensure all desired anatomic areas were covered. A thin layer of a light-body wash poly(vinyl siloxane) (PVS) impression material was applied around the circumference of each impression coping, and a definitive impression was made with the use of a heavy-body PVS impression material (Aquasil; Dentsply Caulk, Milford, DE). After the impression was removed, the analogs were inserted in the impression copings, and the definitive impression was boxed and poured using vacuum-mixed Type III dental stone (Microstone; Whip Mix Corp., Louisville, KY). A record base with occlusal rims was fabricated and adjusted, and the casts were mounted on a semi-adjustable articulator using a facebow
and a centric relation record. The definitive cast was scanned in a laboratory scanner (DW 7series; Dental Wings Inc., Montr´eal, Canada). The scanned information was exported for digital preparation and surveying of the cast using the RPD CAD module. The virtually designed framework was finalized and prepared for printing, and the file was sent to the printer for the creation of wax or resin pattern. The printed pattern was then sprued, invested, and cast in cobalt-chromium (Wironium, Bego USA Inc, Lincoln, RI). After the metal framework try-in, conventional methods, including denture tooth set-up, were used to fabricate the RPD. The teeth and acrylic were processed on the cast poured from the definitive impression. After processing, the black processing inserts were removed from the denture attachment housings, and the selected final retention inserts were placed in the housings and the denture inserted (Figs 14 to 16). The choice of the inserts depends on the amount of desired retention and the dexterity of the patient. It is recommended to start with low-retention inserts to allow the patient to get familiar with their new overdentures. A higher retention insert could be used subsequently at the postinsertion visit if the patient requests it. The patient returned at 24 hours and 1 week postplacement for evaluation and adjustments. She reported high degree of satisfaction with the esthetic outcome, function, and comfort level of the treatment provided. She was extremely happy with his new appearance and smile.
Discussion Implant overdentures provide many psychosocial, functional, and anatomic benefits for patients who have lost all their teeth.1 They have also been found to be more gratifying for edentulous patients than a mandibular complete denture.16 The placement of two interforaminal implants and the use of abutments to retain the denture increases stability and improves the biting force of the mandibular overdenture compared to conventional denture wearers.17 A variety of attachments can be used, depending on the retention requirements, preference of the dentist, and financial limitations of the patient.18 The Locator R-Tx abutment design presents with several improvements to the original Locator abutment and provides the clinician with a redesign that helps improve patient care. The new design permits movement about all axes, thereby reducing the amount of load applied to the implant and the supporting bone. With time, bone resorption under the distal extensions allows the overdenture to pivot in all directions, causing wear of the abutments, wear of the inserts, and/or breakage of the overdenture. While individual attachments can be used on multiple implants with divergent angulations in the bone, the attachments function best and wear is minimized when the implants are parallel to one another; however, the existing bone form may not permit parallelism of multiple implants, particularly in the maxilla, where the residual ridge often has a facial flare to the bone. The new Locator is designed with a dual retentive surface and a narrower coronal geometry of the abutments that allows for an increase in the pivoting capabilities of the housing and allows up to 60° diversion between the implants. This is a great improvement over the legacy Locator that allowed up to 40°
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diversion between implants when extended range inserts were used. The pivoting capability also helps reduce the damage to the retention inserts when the implants are misaligned. With the original Locator, clinicians were often faced with food debris being lodged in the tripod on the top of the abutment, causing the patient to complain about the lack of retention and the lack of ability to seat their dentures in place. The replacement of the tripod or drive mechanism with a small cavity of the hex drive permits simplified placement of the abutment and minimizes the accumulation of food in the recess. The retention provided by the inserts engaging the tripod is now provided by a dual retentive surface. The industry standard hex drive mechanism allows the treating dentist to use any brand of 0.050” screwdriver they have in the office. The attachment housing has been redesigned and subjected to pink anodization to reduce the chance of the grey color of the housing showing through acrylic. Flat grooves were added on the cameo surface of the housing to resist vertical and rotational movement of the housings in the dentures after they have been picked up. On the intaglio surface, a circumferential channel was carved to enhance the pivot range of motion of the inserts. It allows up to 60° diversion between two implants. A need for !2 mm of acrylic resin surrounding the retentive mechanism to prevent denture base fracture should be considered. One advantage of the Locator R-Tx abutment when compared to other individual retentive mechanisms is its reduced vertical height, which is beneficial when vertical space is limited to avoid having a thin layer of resin on top of the abutments. The most common type of complications that occurs with implant overdentures is the fracture of the prosthesis.19 When patients are capable of producing high functional forces, when they have a history of complete denture fracture, or when they desire a maxillary palateless overdenture, the authors highly recommend the incorporation of a metal framework into the denture base to reinforce the overdenture. When compared to the previous Locator, the Locator RTx abutment has been coated with multiple layers of titanium carbon nitride (TiCN) and titanium nitride, which render the abutment pink mimicking the gingival color. As a result of these coated layers, the abutment is harder, and has improved wear resistance and reduced surface toughness when compared to the previous Locator abutment.20,21 Systematic reviews of ISRPD reveal that despite some complications such as the need for reline, replacement of retention inserts, or fracture of the acrylic denture base, to name a few, present with a high survival rate.22,23 However, short-term retrospective studies demonstrated that ISRPD as a treatment modality provides the patient with a low-cost treatment plan, masticatory improvement, and a clear effect on oral health related quality of life.24-29
Conclusion This purpose of this clinical report is to illustrate the direct and indirect techniques used with the Locator R-Tx abutment to process the denture attachment housing into the dentures to retain overdentures or partial dentures. The enhanced abutment and housing design allows more predictable an6
gle correction, an enhanced range of motion, and a pink anodized surface; however, the same processing technique used with the previous generation of this abutment is still the same.
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