THE EVOLUTION OF EXTERNAL AND INTERNAL IMPLANT/ABUTMENT CONNECTIONS

CONTINUING EDUCATION 2 5 THE EVOLUTION OF EXTERNAL AND INTERNAL IMPLANT/ABUTMENT CONNECTIONS Israel M. Finger, DDS, MS* Paulino Castellon, DDS Michael Block, DMD Nicolas Elian, DDS FINGER 15 8 SEPTEMBER The indications for implant dentistry continue to increase, enabling the restoration of partially and totally edentulous patients with greater success and predictability. Recent goals for implant dentistry include simplifying the involved procedures, reducing the duration of therapy for the patient and clinician, and enabling the use of conventional prosthodontic techniques for implant-supported restorations. This article reviews key developments in implantology and highlights the various design characteristics of internal abutment connection implants, demonstrating their clinical application in a detailed case presentation. Learning Objectives: This article discusses recent advancements in implant therapy. Upon reading this article, the reader should: Understand the various design characteristics associated with internal abutment connections. Be aware of the clinical application of contemporary implant designs. Key Words: implant, abutment, internal, connection, aesthetics, hex *Professor, Department of Prosthodontics, LSU School of Dentistry, New Orleans, Louisiana. Assistant Professor, Department of Prosthodontics, LSU School of Dentistry, New Orleans, Louisiana. Professor, Department of Oral and Maxillofacial Surgery, LSU School of Dentistry, New Orleans, Louisiana. Director, International Implant Program and Professor, Department of Implant Dentistry, New York University, School of Dentistry, New York, New York. Israel M. Finger, DDS, MS, 1100 Florida Avenue, Box #222, New Orleans, LA 70119 Tel: 504-619-8528 Fax: 504-619-8741 E-mail: ifinge@lsuhsc.edu Pract Proced Aesthet Dent 2003;15(8):625-632 625

Practical Procedures & AESTHETIC DENTISTRY The long-term success of dental implants has been well established in the literature, and numerous investigators have documented the biological factors, surgical procedures, and restorative principles that influence the outcome of implant-supported restorations. 1-3 As a result, implant dentistry has, as a natural extension of Brånemark s initial success with edentulous patients, evolved considerably from the Brånemark protocol that was first introduced to the United States in the 1980s. The indications for implant dentistry have expanded to include the restoration of single or multiple missing teeth. 4,5 As the biological parameters influencing implant function have been appreciably defined, emphasis throughout the industry has shifted to include aesthetics and simplification of treatment as concomitant goals of implant dentistry. 6-8 In all settings, clinicians pursue implant protocols and materials that further expand their use in the fixed replacement of natural teeth. This has contributed in part to the evolution of restoration-driven implant dentistry. 9 This article reviews key developments in implant therapy and highlights the design principles of internal connection implants, emphasizing their application in a clinical presentation. Abutment Connections The original Brånemark protocol required several externally hexed implants to restore fully edentulous arches, linking them together via a metal bar with a fixed prosthesis. 2,10 In this protocol, the external hex design was A Standardshaped screwretained abutment Abutment screw Figure 1A. Illustration of standard abutment for a screwretained implant. 1B. Abutment for a cement-retained restoration. B Straightcementretained abutment Connecting screw Compromised abutment position Buccally inclined implant Figure 2. Premachined abutments can have positioning limitations due to the number of rotational positions within the internal connection implant design. present to help screw the implant into place. In fact, for the fully edentulous, fixed prostheses abutments that were screwed down onto the implants, the hex was not engaged as an antirotation device. 11 When the implants were later placed in single-tooth or partially edentulous cases, the hex had to be used to prevent rotation of the abutment and the single crown. This external hex, which was only 0.7 mm in height, was not designed to withstand the forces directed on the crowns intraorally. 12-15 Therefore, implant manufacturers had to compensate for this by changing the type of screw used (eg, geometry, height, surface area), the precision of the fit over the hex, and the amount of torque used to secure the new screws. These changes have allowed externally hexed implants to be utilized with great confidence, although such efforts still require the clinician to radiographically verify that the abutments are fully seated. New interface designs are utilized on a variety of implants to improve the original external hex implant/ abutment interface. The goals of new designs are to improve connection stability throughout function and placement, and simplify the armamentarium necessary for the clinician to complete the restoration. There are at least 20 different implant/abutment interface variations on dental implants that are cleared for marketing by the FDA (Figure 1). The implant/abutment interface determines joint strength, stability, and lateral and rotational stability. As implant design evolves, different requirements are incorporated into the interface design. 626 Vol. 15, No. 8

Finger Improved rotational position for preangled abutment Buccal inclination Buccally inclined implant Figure 3. Illustration demonstrates ideal rotational position of a pre-angled implant abutment (GingiHue, 3i Implant Innovations, Inc, Palm Beach Gardens, FL). Figure 4. Preangled abutment in place redirects path of insertion for buccally inclined implant. One of the first internally hexed implants was designed with a 1.7-mm-deep hex below a 0.5-mm wide, 45 bevel. 16,17 Its features were intended to distribute intraoral forces deeper within the implant to protect the retention screw from excess loading, 17,18 and to reduce the potential of microleakage. 14 Internally connected implants also provide superior strength for the implant/abutment connection. 17,19,20 Since the introduction of the internal connection concept, further design enhancements have been made in an attempt to enhance the implant/abutment connection (Table). 21-23 Included in such efforts is the Morse taper, wherein a tapered abutment post is inserted into the nonthreaded shaft of a dental implant with the same taper. 23,24 Other internal connection designs have followed, frequently with variations in their use of joint designs (eg, bevel, butt), or the numbers of hexes present for the restorative phase. 21-23 When using these implant/abutment connections, clinicians had to be mindful of their application in the intraoral environment, an Table Comparison of Internal Connection Systems Nobel Alatec 3i CenterPulse Astra Tech Straumann Biocare Technologies Friadent (Osseotite Feature (Screw-Vent) (Astra) (ITI) (Replace Select) (Camlog) (Frialit 2) Certain) Length of 1.2 mm 2.4 mm 2 mm 3.8 mm 5.4 mm 3.4 mm 4 mm internal connection Type of 6-point 12-point 8-point 3-point 3-point 6-point 6- or 12- retention internal hex conical seal Morse taper internal internal internal hex point (with friction tripod tripod internal hex fit) Verification X-ray X-ray X-ray X-ray X-ray X-ray X-ray or of seating audible click Abutment 60 30 45 120 120 60 30 or 60 positioning PPAD 627

Practical Procedures & AESTHETIC DENTISTRY Figure 5. Preoperative buccal view of the patient s missing left mandibular premolar. Figure 6. Preoperative radiograph of the edentulous space at tooth #20(35). Figure 7. Fabrication of abutment on model for delivery of provisional crown at the time of implant placement. Figure 8. Illustration demonstrates the placement of an implant (Osseotite Certain, 3i, Palm Beach Gardens, FL) into prepared osteotomy. often challenging region due to the involved bone topography, soft tissue contours, rotational forces, and the requisite prosthetic components particularly for aesthetic, single-implant restorations. A new internal connection implant design (eg, Osseotite Certain, 3i Implant Innovations, Inc., Palm Beach Gardens, FL) has recently been introduced to the profession, demonstrating how interface design has continued to evolve. The internal connection implant design incorporates an audible and tactile click when the components are properly seated. This unique feature eases placement for the clinician and may reduce the need for radiographs following placement of the restorative components. The implant s internal connection allows 4 mm of internal engagement, with contact along a significant length that provides lateral stability from off-axis forces. 17,19,20 The deep, 4-mm multilevel engagement zone of this internal connection achieves a precise, secure connection with low torque. No more than 20 Ncm is required to maintain screw retention without loosening. The design of the internal connection allows the height of the screw to be only 1.95 mm from the top of the screw to the seating surface, allowing flexibility in abutment preparation without damaging the head of the screw. From the restorative perspective, an internal connection with retentive features allows the placement of transfer copings and abutments with secure seating and ease of use. The click confirms positive seating and allows the abutment to remain in place in the maxillary arch even prior to placement of the retaining screw. 628 Vol. 15, No. 8

Finger Figure 9. Once a soft tissue flap was elevated, the osteotomy was completed and the 4 mm 11.5 mm implant (Osseotite Certain, 3i, Palm Beach Gardens, FL) was seated. Figure 10. The implant abutment was delivered at the same surgical visit. The site was provisionalized but not loaded at this stage. Figure 11. Clinical view demonstrates the healing around provisional crown at 6 weeks postsurgery. An impression would be taken at 12 weeks postsurgery. Figure 12. Master model shows the position of the prepared abutment and the replication of the soft tissues for fabrication of the definitive restoration. This internal connection design incorporates a 6-point hex and a 12-point, double-hex internal design. The 6-point internal hex provides a stable base for the use of straight abutments. The 12-point, double-hex of the internal connection allows 30-degree increments of rotational flexibility for placement of machined preangled abutments to correct the off-axis emergence of the implant (Figures 2 through 4). This feature provides flexibility for the restorative dentist and enables the surgeon to place the implant in any rotational position without concern for orienting the flats of a hex during surgery. This decreases the involved expenses for the case and simplifies the laboratory and restorative procedures for an implant-supported prosthesis. Additionally, if a provisional crown is fabricated prior to implant placement for delivery at the time of implant surgery (ie, in lieu of a cover screw), the implant can be oriented by the hex flats on the implant placement driver tip. This internal connection design adapts well to abutments that provide a large variety of prosthetic options using the same implant for multiple clinical situations. The audible and tactile confirmation of seating the components into the implant, combined with the 12-point, double-hex design that enables simple alignment for angled abutments, allows ease of placement for the transfer copings and abutments. Case Presentation A 61-year-old female patient presented for the replacement of tooth #20(35) (Figures 5 and 6). The patient s medical and dental histories were unremarkable, and the patient s periodontal status was stable. Clinical PPAD 629

Practical Procedures & AESTHETIC DENTISTRY examination revealed multiple sound restorations. Radiographic and clinical examination revealed 13 mm of bone superior to the inferior alveolar canal and 6 mm of crestal width, thus adequate for placement of a dental implant. There was 3 mm of attached keratinized gingiva present on the edentulous crest. A single-tooth, implantsupported restoration was recommended to the patient. The patient was advised of different treatment options. As tooth #19(36) had a sound restoration and #21(34) did not have prior restorations, the patient decided that an implant-supported restoration would be the treatment of choice. The treatment plan consisted of implant placement and immediate provisionalization, which would be followed by placement of a cementretained, metal-ceramic crown restoration approximately three months after implant placement. Figure 13. Occlusal view of the implant site following two months of healing. Note the height and contour of the gingival tissues. Surgical Phase Diagnostic casts were mounted, and a waxup of the planned restoration was fabricated. Based on a periapical radiograph, an analog of the implant was placed into the diagnostic cast to place the top of the implant level with the bone. A fixed abutment (GingiHue Post, 3i, Palm Beach Gardens, FL) was placed into the implant analog, and the abutment was prepared in the laboratory. A hollowed acrylic denture tooth was retrofitted to the implant abutment, leaving 0.5 mm of clearance at the mesial and distal marginal ridges. A surgical guide template was made on the diagnostic model with the analog present to guide the surgical placement of the implant (Figure 7). The implant selected was 4 mm in diameter (due to the 6-mm crestal width) and 11.5 mm in length. After administration of local infiltration anesthesia, a crestal incision was made with a vertical release to expose the crestal bone. The drilling sequence recommended by the manufacturer was followed for single-stage implant placement, and an internal connection implant (Osseotite Certain, 3i, Palm Beach Gardens, FL) was placed level with the crestal bone (Figures 8 and 9). The prepared abutment was placed (Figure 10), and the provisional crown was tried in place. After determining that a minimal occlusal clearance of 0.5 mm was present in all excursions, the abutment was tightened, and the crown Figure 14. Try-in of the prepared implant abutment. Accurate fit was verified by an audible click and eliminated the need to verify with radiographs. Figure 15. Buccal view demonstrates the insertion of the gold abutment screw (Gold-tite, 3i, Palm Beach Gardens, FL). 630 Vol. 15, No. 8

Finger was secured with temporary cement. The incisions were closed using 4-0 chromic sutures on a tapered needle. The patient was placed on antibiotics for 7 days, and mild analgesics were prescribed. Figure 16. Buccal view shows the use of the square driver to facilitate seating of the abutment in the implant. Restorative Phase Following a 6-week healing period, the patient was recalled for evaluation (Figure 11). Clinical and radiographic examination revealed healthy gingival tissue, no radiolucencies, and no evidence of clinical mobility. At 12 weeks, the provisional crown and abutment were removed. An impression for the fabrication of the definitive restoration was made using a transfer-type, implant impression coping, with the audible click confirming proper transfer coping seating. A soft tissue cast was poured, and the depth of the gingival sulcus gauged on the cast. The angulation of the implant was evaluated and a new abutment selected. Once the abutment was prepared to ideal dimensions, a porcelain-fused-to-metal crown was fabricated and delivered within 2 weeks of impression making approximately 14 weeks following implant placement (Figures 12 through 18). Periodic recall of the patient confirmed successful integration of the implant within the patient s mandible and the adaptation of the gingival contour to the definitive restoration. Figure 17. Eight-week postrestoration radiograph of the fullcoverage porcelain-fused-to-metal crown. Conclusion The success of implant dentistry has increased its popularity as a restorative option for the treatment of edentulous patients. Its indications, once limited to edentulous mandibles, have been expanded to include single-tooth replacement and the reconstruction of both partially and fully edentulous mandibular and maxillary arches. While clinicians continue to identify grafting procedures, surgical protocols, and implant materials that simplify the application of implant dentistry, the results to date are promising. This presentation has reviewed the evolution of internal implant/abutment connections and internal connection implants, focusing principally on the latest advances currently available to the clinician. Figure 18. Buccal view of the definitive implant-supported restoration harmoniously integrated with the natural dentition. Acknowledgment The authors receive research support from 3i Implant Innovations, Inc. PPAD 631

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