Locator versus stress free implant bar attachments for two -implants immediately loaded by mandibular overdentures. A one year randomized study

Abstract

Aim: The purpose of this short-term randomized trial was to study clinical and radiographic outcomes of Locators and stress free implant SFI bar attachments used for two -implants immediately loaded by mandibular overdentures. Material and method: Twelve edentulous participants (6 males and 6 females) received new maxillary and mandibular dentures and wore them for 3 months to increase muscular control. Two fixtures were installed in the canine regions of the mandible and immediately loaded by mandibular overdentures using Locator (group 1) or SFI bar (group 2) attachments. Plaque index (PI), gingival index (GI), probing depth (PD), stability of the implants (IS), and marginal bone resorption (BL) were measured at base line (insertion), 6 and 12 months later. Results: The implant survival was 91.7% and 100% for Locator and SFI bar groups respectively. PI, PD and BL increased significantly with time in both groups. SFI bar group showed significant higher PI and PD than Locator group after 6 and 12 months. On the other hand, Locator group showed significant higher BL than bar group at 6 and 12 months. No significant difference in GI and IS between observation times or between groups was noted. Conclusion: Within limitation of this study, it is concluded that both Locators and SFI bar anchors are recommended for immediately loaded 2 inter-foraminal implants by mandibular overdentures. However, Locators may be favorable regarding improved peri-implant soft tissue conditions and SFI bar may be favorable regarding reduced marginal bone loss around the implants. (1346) Samer Mostafa Ali and Dina Bahgat El Talawy E.D.J. Vol. 67, No. 2 food chewing, enhanced phonation, improved appearance, and better stomatognathic functions than complete dentures 2. Several connectors may be used with overdentures including splinted ones such as bars or individual attachments such as locators, balls, and magnets1. The use of one-stage surgical procedures and immediate loading protocols is one way to simplify implant treatment, short healing time, minimize postoperative discomfort 3, and to provide immediate restoration of mastication and esthetics 4. It is possible that non-splinted implants may be negatively affected by immediate loading because the load is not shared between implants5, i.e. decreased stability and/or marginal bone resorption6. For immediate loading protocol, the effect of attachment on the forces transmitted to bone around implants is a critical factor than for conventionally loaded implants7. The Locator attachment has double retention comes from outer and inner flanges and it has different retention forces with different colors of nylon inserts8, 9. Locator is resilient, and includes a nylon inserts that can be used to remove problems of angulated implants up to 300 10-12. With limited interarch space, locators are used to minimize bulk of the prosthesis13, avoid increase in vertical dimension, and patient dissatisfaction.14. Locator attachments have a low height and can be used with limited inter arch space to avoid denture base deformation and fracture13, 15. In the last decade, stress free-implant bar (SFI bar, Cendres+Metaux SA) was introduced as a ready-made precise round bar that allow chairside adaption for immediate loading protocol 16. This bar connects implants with no soldering or laserwelding. This allows construction of a passive-fit bar17 with reduced corrosion18. Moreover, this bar can be used with individual implant angulations up to 15°19. The bar consists of 2 or 4 ball joints that are connected to implant adapters by screws and tube bar. It can be adjusted to variable interimplant distance. The bar is supplied with 2 types of female part, the E-clips (Elitor precious metal alloy) and the T-clips (all titanium grade IV with nylon inserts)17. Despite these several advantages, the success of SFI bar needs to be investigated in clinical studies19. Reviewing the literature, space requirement of a prefabricated SFI bar on two implants retaining mandibular overdentures was investigated20. However, the clinical performance of SFI for immediately loaded 2 implants assisting mandibular overdenture was not evaluated. Therefore, this study aimed to investigate clinical and radiographic peri-implant tissue responses of Locator and stressfree implant bar (SFI bar) attachments for two -implants immediately loaded by overdentures after 12 months. The authors hypothesis was that no significant difference in the tested outcomes between the 2 attachments. MATERIALS AND METHODS Twelve edentulous patients (6 males and 6 females) who were unsatisfied with retention and stability of their mandibular dentures were selected from this study from the patients attending regularly at the clinic of the prosthodontic department of College of Oral and Dental Surgery of Misr University for Science and Technology. The inclusion criteria are: 1. Sufficient residual bone volume in the intraforaminal area to receive two 3.5 × 11mm implants with sufficient bone quality. Bone quantity and quality and implant position and angulation were verified by preoperative cone beam CT. 2. No history of previous implant surgery. 3. Absence of local inflammation and oral mucosal diseases. 4. Sufficient inter-arch space. The exclusion criteria were: 1. History of radiotherapy in the head and neck region. LOCATOR VERSUS STRESS FREE IMPLANT BAR ATTACHMENTS FOR TWO -IMPLANTS (1347) 2. Metabolic diseases such as diabetes mellitus. 3. Liver and heart diseases and blood disorder. 4. A history of preprosthetic surgery. 5. Severe maxillomandibular skeletal discrepancy. 6. Excessive parafunctional activity. 7. Smoking habit and uncooperative patients. Patients were randomly classified into 2 groups using random numbers generated in excel sheet (Microsoft office) with equal gender distribution in each group: Group I (G1); included 4 patients who received Locator retained mandibular overdentures, and group II (G2); included 4 patients who received SFI bar retained mandibular overdentures. All patients informed about treatment protocol and merits and all of them signed an informed consent. The Local ethical committee of the faculty approved the study protocol (ETH 30). Surgical and prosthetic procedures Conventional upper and lower dentures were made using standard procedures21. Semi-anatomic acrylic resin teeth (Acrostone-Egypt) were arranged in bilateral balanced occlusion. The patients wear the dentures for 3 months to increase neuro muscular adaptation and necessary adjustments were made. A radiographic stent and cone beam CT (CBCT, i-CAT Vision®, USA) was made. Duplicate lower denture was used as a radiographic stent. Gutta purcha were fixed to polished surface of the denture22. A tissue supported surgical guide was constructed by prototyping technology using 3D imagebased software (OnDemand3DApp Software; CyberMed Inc). A surgical kit including sleeves and standardized drills (supplied by the radiologist) was used for osteotomy preparation. The guide was fixed in the mandibular bone using anchor pins. For both groups, 2 implants (Neoss Ltd., Harrogate, England) were inserted inter-foraminally in the canine region using one-stage non-submerged flapless protocol. The osteotomy sites were prepared following the drilling sequence provided by the manufacturer’s surgical universal kit. During the implant insertion, a minimum 35 Ncm value of insertion torque was achieved 23. Immediately after implant insertion, Locator abutments (group 1) and SFI bar abutments (adapters) (group 2) were threaded to the implants with a 30 N/cm torque. For group 1 (Locators) sufficient relieve was provided in the mandibular dentures over abutments to provide a space for the attachment. The Locator metal housings were attached to the abutments. A circular small pieces of rubber dam and white blocking rings were snapped on the locator abutments to prevent flow of the acrylic resin in the undercuts of the abutments. The metal housings with processing inserts were attached to the lower denture using self-cure acrylic resin while the participants close in retruded contact position (fig 1). After finishing and polishing, the processing inserts were replaced by blue nylon insert (extra light retention). Excess acrylic resin around the abutments was removed to avoid unnecessary loading of the implants and the denture was finished and polished. For group 2 (SFI bar), the implant adapters (bar abutments) of the SFI-Bar® (Cendres + Metaux, Biel/Bienne, Switzerland) were screwed to the implants and tube bars were screwed to the implant adapter by using screw driver. The ball joint on one side was fixed with screws. The tube bar and tube bar gauge on the other side was slide onto the pin of the ball joint until the gauge could be fitted onto the other implant adapter and screwed. The tube bar was sectioned with disc. The shortened tube bar was slide onto the pin and retightened tension-free. Two plastic clips (red, light retention) were inserted in the metal housings and fastened to the bar intraorally. Sufficient relieve in the fitting surface of mandibular dentures was made using disclosing media till no contact was present between the denture and the sleeves of the bars. The space under and around the bars was blocked out with wax. The metal housings and retentive clips were picked up intraorally to ensure passive fit (fig2). The overdentures were (1348) Samer Mostafa Ali and Dina Bahgat El Talawy E.D.J. Vol. 67, No. 2 delivered to the patients immediately after implant placement, and soft diet and 2-weeks regular recall visits for adjustments were scheduled all over the study period. Hygiene instructions were given to patients. All patients administered antibiotics (1 g of amoxicillin and clavulanic acid/ 2 times per day) and Anti-inflammatory drugs (Cataflam 50 mg/ 3 times per day) and mouth rinse with a 0.12% chlorhexidine digluconate (for 7 days). Implant related outcomes A) Clinical