Angulated Abutments - A Curve That Sets Everything Straight The Advent of Angulated abutments has facilitated the parallelism of non-aligned implants thereby making the prosthesis fabrication easier. This is particularly useful in clinical situations where anatomic constraints and other reasons compel to surgically position implants at angles that are not favourable for prosthetic rehabilitation. The Advent of Angulated abutments has facilitated the parallelism of non-aligned implants thereby making the prosthesis fabrication easier. This is particularly useful in clinical situations where anatomic constraints and other reasons compel to surgically position implants at angles that are not favourable for prosthetic rehabilitation. However, Angled abutments have their own advantages and limitations. This article reviews the various applications, indications and setbacks of using Angled abutments. A curve that sets everything straight – An ‘esthetic Smile’, with an “Angulated Abutment”!! Introduction of angulated abutments in the field of implant dentistry has revolutionised the possibility of providing the patients with the most desired esthetic smile. The use of angulated abutments in implant dentistry has helped serving a lot of patients with Osseointegrated supported prosthesis as a treatment modality in replacement of the missing natural teeth. A tooth, a portion of a tooth, or that portion of a dental implant that serves to support and/or retain a prosthesis (GPT -8) Implant abutment: Implant abutment is the portion of the implant that supports and/or retains a prosthesis or implant superstructure. An abutment whose body is not parallel to the long axis of the implant. It is utilized when the implant is at a different inclination in relation to the proposed prosthesis NEED FOR ANGULATED ABUTMENTS : An implant may be placed at a different inclination in relation to the proposed prosthesis due to various anatomic constraints in the existing clinical condition. Now, there are several considerations to be kept in mind while placing an implant. These include the Width, Height, Angle of the residual bony ridge, Presence of bony undercuts, Shape of the arch and Maxillo-mandibular relationships. Besides, the location of anatomic structures like the mandibular canal in the mandible and the proximity of the paranasal air sinuses in the maxilla also dictate the implant alignment.1 Any unfavourable clinical conditions can be managed either surgically by means of Bone augmentation procedures, Sinus elevation and Nerve repositioning. Non-surgical means include NEED FOR ANGULATED ABUTMENTS : An implant may be placed at a different inclination in relation to the proposed prosthesis due to various anatomic constraints in the existing clinical condition. Now, there are several considerations to be kept in mind while placing an implant. These include the Width, Height, Angle of the residual bony ridge, Presence of bony undercuts, Shape of the arch and Maxillo-mandibular relationships. Besides, the location of anatomic structures like the mandibular canal in the mandible and the proximity of the paranasal air sinuses in the maxilla also dictate the implant alignment.1 Any unfavourable clinical conditions can be managed either surgically by means of Bone augmentation procedures, Sinus elevation and Nerve repositioning. Non-surgical means include Change in the intended location of implant Insertion/placement of the implant at an angled trajectory 2 Although, ideally the implants should be aligned vertically with the axial forces, and placed parallel to each other and the adjacent teeth, situations may arise where there is a difference between the planned long axis of the implant and the long axis of the planned prosthetic tooth. In such situations compensating strategy of abutment angulation may be used if esthetics, biomechanics and tissue biology favours implant placement at an angled trajectory.3 Besides, angulated abutments facilitate implant placement with greater width and height, avoids surgical intervention, reduces treatment time, reduces cost and allows greater number of patients to be treated, who otherwise cannot be treated using the conventional technique.2 Angulation Issues : Angulated abutments may be prefabricated and are available at varying angulations from 15° to 35° commercially. Several manufacturers offer abutments ranging from 0° to 60°. However, it is advisable to used angled abutments to correct angulations within 15°. Buccolingual Angulations of implants ranging from 0°-15° are easy to correct with preangled components. Angulation greater than 15° may be corrected with either pre-angled parts or custom-made components. A 15° angulation of a prefabricated abutment can create parallelism between adjacent abutments. Additionally, correcting an implant trajectory with a 15° angled abutmen2 Mesiodistal angulation issues can be corrected by reducing the side of the transfer coping. If the angulation is too severe, the clinician may select an angulated abutment based on visual inspection of the implant angulation.2 Mesiodistal angulation issues can be corrected by reducing the side of the transfer coping. If the angulation is too severe, the clinician may select an angulated abutment based on visual inspection of the implant angulation.2 The selection and usefulness of the angled abutment may also depend on the internal mechanism of the implants which may differ for different systems, for e.g. Tri-lobed triangle, hexagon, octagon etc. An Implant, that uses the internal mechanism of a three-lobed triangle, allows only three possible positions to angle the abutment.4 The angle of the abutment can only be positioned in the direction of the base of the triangle i.e. 180° from the apex. Hence, an implant that is surgically placed too far to the lingual and the base of the triangle is in the lingual position, a buccal orientation required to correct the improper angulation cannot be achieved with a prefabricated abutment. In this situation, a custom abutment would be indicated. The concept of measuring the angle of the required abutment at the time of implant insertion was developed in 1986. The latest development of the concept of measuring angles at the time of implant insertion is with a system using a Morse taper to connect the abutment to the implant which makes a finned implant fitted with a 5° tapered wall, one piece abutment post . It provides almost unremovable stability in both straight and angled designs by firm tapping to resist rotation and even removal. Direction indicators ranging from 0 to 37.5 degrees at various increments are available. These fit into the hole within the cover screw to allow the angle of the abutment to be selected. They rotate freely around the longitudinal axes of the implant to an infinite number of rotational points. Angled abutments can also be custom-made wherein the laboratory technicians can fabricate them according to the desired contour required to meet a satisfactory prosthetic outcome. Angled abutments can also be custom-made wherein the laboratory technicians can fabricate them according to the desired contour required to meet a satisfactory prosthetic outcome.5 Direction indicators ranging from 0 to 37.5 degrees at various increments are available. These fit into the hole within the cover screw to allow the angle of the abutment to be selected. They rotate freely around the longitudinal axes of the implant to an infinite number of rotational points. Direction indicators ranging from 0 to 37.5 degrees at various increments are available. These fit into the hole within the cover screw to allow the angle of the abutment to be selected. They rotate freely around the longitudinal axes of the implant to an infinite number of rotational points. Angled abutments can also be custom-made wherein the laboratory technicians can fabricate them according to the desired contour required to meet a satisfactory prosthetic outcome.5 Custom made abutments may be indicated when6 : CAD-CAM technology has also been introduced to enable titanium abutments to be milled to specific requirements. Angled Abutments - Is it a safe Option???? It is an established fact that occlusal loads must be directed as close to the long axis of the fixture as possible. Off-Axis loading can exert heavy stresses on the bone thereby inducing bone resorption around the implant. It is an established fact that occlusal loads must be directed as close to the long axis of the fixture as possible. Off-Axis loading can exert heavy stresses on the bone thereby inducing bone resorption around the implant. Various studies have been conducted to determine the stress on the bone and the prosthetic components following the use of angulated abutments. Studies done using photoelastic stress analysis have shown that straight abutments exerted stress at the apex while angulated abutments manifested stress opposite to the side on which the load was applied. Mesiodistal angulation issues can be corrected by reducing the side of the transfer coping. If the angulation is too severe, the clinician may select an angulated abutment based on visual inspection of the implant angulation.2 The selection and usefulness of the angled abutment may also depend on the internal mechanism of the implants which may differ for different systems, for e.g. Tri-lobed triangle, hexagon, octagon etc. An Implant, that uses the internal mechanism of a three-lobed triangle, allows only three possible positions to angle the abutment.4 The angle of the abutment can only be positioned in the direction of the base of the triangle i.e. 180° from the apex. Hence, an implant that is surgically placed too far to the lingual and the base of the triangle is in the lingual position, a buccal orientation required to correct the improper angulation cannot be achieved with a prefabricated abutment. In this situation, a custom abutment would be indicated. The concept of measuring the angle of the required abutment at the time of implant insertion was developed in 1986. The latest development of the concept of measuring angles at the time of implant insertion is with a system using a Morse taper to connect the abutment to the implant which makes a finned implant fitted with a 5° tapered wall, one piece abutment post . It provides almost unremovable stability in both straight and angled designs by firm tapping to resist rotation and even removal. Direction indicators ranging from 0 to 37.5 degrees at various increments are available. These fit into the hole within the cover screw to allow the angle of the abutment to be selected. They rotate freely around the longitudinal axes of the implant to an infinite number of rotational points. Angled abutments can also be custom-made wherein the laboratory technicians can fabricate them according to the desired contour required to meet a satisfactory prosthetic outcome.5 Custom made abutments may be indicated when6 : CAD-CAM technology has also been introduced to enable titanium abutments to be milled to specific requirements. Angled Abutments - Is it a safe Option???? It is an established fact that occlusal loads must be directed as close to the long axis of the fixture as possible. Off-Axis loading can exert heavy stresses on the bone thereby inducing bone resorption around the implant. Abutment angulation (in degrees) Compressive forces (in microstrains) 0 352 15 942 25 1,126 30 1,246 35 1,325 Results of various studies predict that: Loading an implant on an angled abutment is mostly off-axis which raises concern regarding the detrimental stresses exerted on the bone and the implant. Clinically, angled abutments have been considered as a viable restorative option when implants are not placed in ideal axial positions.7 Various studies have been conducted to determine the stress on the bone and the prosthetic components following the use of angulated abutments. Studies done using photoelastic stress analysis have shown that straight abutments exerted stress at the apex while angulated abutments manifested stress opposite to the side on which the load was applied. Besides, compressive and tensile forces were greater as the abutment angulation increased from 0° to 35°, but the strains produced by them were within the physiologic tolerance of the bone and hence were not detrimental.8 Brosh and colleagues9 used strain gauges to assess the influence of abutment angulation (0°, 15° and 25°) on strains in the bone. They reported that when they compared angled abutments with straight abutments (individual, unsplinted implants); strain gauges demonstrated a threefold increase in compressive strain at 15° and a 4.4 fold increase at 25° when angled abutments were used. Kao and colleagues10 conducted an FEA study and noted that a 15° to 25°abutment angulation compared with a straight abutment increased stress in the crestal cortical bone by 12 percent and 18 percent, respectively. Indications for Angled Implants11 : Single tooth replacement in the frontal region of maxilla Fixed prosthesis on implants for distal extension in the maxilla Fixed dentures on implants in the maxilla Overdentures in the edentulous maxilla Fixed partial dentures on implants in distal extension in the mandible Misjudged direction of preparation for implants Occasional anatomic problems for the placement of straight implants Clinical Guidance2: Direction indicator placed into the osteotomy site which is palatal Abutment with a 150 angulation placed Pre treatment view Post treatment view Treatment planning phase: Angled Abutments considered if they facilitate placing an implant in the proper position eliminating the need for additional procedures and cost During implant insertion: Evaluate implant angulation by placing direction indicators into the osteotomy and correlate to a surgical guide that reflects the desired contour of the definitive prosthesis. This helps to decide if an angled abutment is needed. Additional running room: Implants placed at buccolingual or mesiodistal angulations should be inserted more deeply to permit additional running room. This facilitates the restoration of gradual axial contours. Impression: Closed/ Open tray. Open tray technique is preferred for multiple implants or in implants with divergence of >25° Reduce preload relapse – the clinician should take appropriate steps to reduce the preload relapse. Retighten abutment screws several minutes after initial torque application For long span or full arch restorations – implants can be splinted to compensate for the increased stresses. Avoid undue static stresses after prosthesis insertion: ensure best possible fit before completing prosthetic treatment. Avoid lateral excursions: on teeth that have angulated abutments. Periodic recall: assess the overall occlusion periodically to compensate for time-related changes that may be unfavourable. Advantages of tilting the posterior implants: Compromised bone of the sinus antrum could be circumvented. Cantilever arms can be avoided Large interimplant distance can be created Fewer implants can be used as support for the prosthetic reconstruction Factors that contribute to the high survival rate using the Angulated Abutments are as follows: The implants are placed without surgical compromise of labial or palatal dehiscence. Longer implants can be placed, maximizing the use of the available bone. As a result of the correctly aligned abutments, non stress-inducing, cement-retained restorations can be constructed. Restorations can be constructed, enabling multiple implants to be splinted because of the parallelism that can be achieved for the abutments. Treatment planning is facilitated because complex directional surgical templates are not necessary. Excellent esthetic and functional outcomes can easily be achieved using conventional restorative procedures. DISCUSSION : As the need for functional and esthetic restorations has increased in the present times, the need to use angled abutments to achieve these goals has also been widely accepted in implant dentistry. The use of angled abutments has simplified the management of clinical situations when implant placement is suboptimal. Although it is the planned prosthesis which determines the orientation and angulation of the implant, the anatomy of the jaws and the morphology of the residual ridges may not permit the implant to be placed as desired. In such situations, angled abutments seem to have an upper hand over the straight abutments as they permit the implant placement in a more ideal location in the bone without compromising the esthetics. Hence, permitting a greater number of patients to be treated with implant therapy. Advantages of Angled Abutment over Straight Abutment : A common point of concern is the management of Off-Axis load exerted on the implant and the bone. But several studies have proved that although stresses exerted on the bone are more with angled abutments when compared with straight abutments, they fall within the physiological tolerance of the bone and hence are not a cause of implant failure. Different component designs of implant systems may affect the distribution of stress and strain on the implant and hence the bone. In general, studies indicate that implants with internal connection show more favourable distribution of forces when compared to external connection and hence may be beneficial to be used with angled abutments. A common complication following implant placement is loosening of the screw that connects each component. This problem is especially common in single implant - supported prosthesis and particularly with those placed in the anterior maxilla. This is because most occlusal loads applied to maxillary anterior teeth are at an angle to the long axis of the implants. Chun et al3 in their study stated that implants with angled abutments showed significantly higher removal torque values(RTVs) when compared to straight abutments in external-hex implants while there was no significant difference in RTVs among abutments in internal-hex implants. There was also no significant difference in the peri-implant mucosal complications and the overall gingival problems were comparable or lower than those with standard abutments.12 SUMMARY : The use of angulated abutments is well established. The concern about survival of implants loaded by means of angled abutments had largely been dispelled. Use of angled abutments has not decreased the survival rate of implants or prostheses in comparison with that of straight abutments. Angled abutments result in increased stress on implants and adjacent bone, but the stresses are usually within the physiological tolerances. Angled abutments do not result in increased episodes of screw loosening when compared to straight abutments. Soft tissue performance around angled abutments is comparable to that of straight abutments. Sometimes, a little tilt can create wonders. This rightly holds true for Angulated abutments. One can create a beautiful smile for someone with the use of Angulated Abutments. REFERENCES : Eger DE et al. Comparison of angled and standard abutments and their effect on clinical outcome: a preliminary report. IJOMI 2000;15:819-823 John Cavallaro, Gary Greenstein. Angled Implant Abutments. JADA 2011;142 (2):150-158. Chun-Yeo Ha et al. The influence of abutment angulation on screw loosening of implants in the anterior maxilla. IJOMI 2011;26:45-55. Nobel Biocare Services AG. Nobel Esthetics Product Catalog. 2005. Eger DE et al. Comparison of angled and standard abutments and their effect on clinical outcome: a preliminary report. IJOMI 2000;15:819-823. Philip G. Kotick, DDS; Barry Blumenkopf.Abutment Selection for Implant Restorations.A number of considerations factor into treatment planning implants. Inside Dentistry.July/August 2011, Volume 7, Issue 7. Xavier E. Saab, Jason A. Griggs John M. Power. Robert L. Engelmeier.Effect of abutment angulation on the strain on the bone around an implant in the anterior maxilla: A finite element study. J Prosthet Dent 2007;97:85-92 Clelland NL, Gilat A. The effect of abutment angulation on stress transfer for an implant. J Prosthodont 1992;1(1):24-28. Brosh T, Pilo R, Sudai D. The influence of abutment angulation on strains and stresses along the implant/bone interface: comparison between two experimental techniques. J Prosthet Dent 1998;79(3):328-334. Kao HC, Gung YW, Chung TF, Hsu ML. The influence of abutment angulation on micromotion level for immediately loaded dentalimplants: a 3-D finite element analysis. Int J Oral Maxillofac Implants 2008;23(4):623-630. Ten Bruggenkate CM, Sutter F, Oosterbeek HS, Schroeder A. Indications for angled implants. JPD 1992;67:85-93. Ming-lun hsu.Tai-Foong Chung.Hung-Chan Kao. Clinical applications of angled abutments - a literature review.chin dent j, 24(1)：15-20, 2005. Home alarm systems Implant Dentist Implant Abutment Dental Implants Prosthetic Masters Degree
Posted on: Fri, 21 Jun 2013 23:33:11 +0000
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