Log in Register

Login to your account

Username *
Password *
Remember Me

Create an account

Fields marked with an asterisk (*) are required.
Name *
Username *
Password *
Verify password *
Email *
Verify email *
Captcha *

Captcha Image Reload image challenge



Authors: Dr. Subashani, Dr. Sunil Dhaded

Abstract:

Over the past 20 years dental implants have contributed to improve the quality of life.1 Abutments are the intermediate devices that affix the final prosthesis to the implant.2 There are many options that govern the selection of abutments. Different types are available to allow for variation in factors like implant position, angulations, depth and soft tissue contours. Plan and choose the best abutment based on clinical scenario and is one of essential of success. Key words: Abutment, intermediate devices, prefabricated abutment, angled abutment.

Introduction:
Figure-1 Figure-2
Abutments attach the crown to the implant and prevent rotation between the components and these intermediate devices extend through the gingival tissues overlying the implants2 (Figure-1). Abutments may consist of one, two or three constituents and these may be either separate or unified. The base, which fits into the antirotational component of implant; the head, serves as prosthetic retainer which protrudes permucosally and the retaining screw which affixes them to implant.

Abutment types:

Palmer classified abutments as standard, preparable, fully customised, computer generated, ceramic and abutments for screw retained crowns. Whereas Crannin classified abutments into: the abutments that engage anti rotational components, custom abutments, abutments for implants with Morse taper interface and abutments that bypass antirotational components. Other classifications based on a) abutment types are Flat topped abutments, tapered shouldered abutments, tapered shouldered variants, abutments for overdenture and direct gold copings. b) Cement retention: angled abutment, angled abutment variants, straight abutments and straight abutment variants. c) Material: Titanium, zirconia, alumina, PEEK and other metal alloys.3

Prefabricated abutments:
Figure-3 Figure-4
prefabricated or stock abutments are manufactured and available in various size and shapes (Figure-2). The best abutment that suits the clinical case is selected.Standard abutments: are used especially in the non-aesthetic zones. It is difficult to achieve good emergence profile with this abutment because of the margin remains supragingival (Figure-3). It allows and can be easy maintained. It is limited to multiunit restoration. Examples of few standard abutments for single restoration are solid abutment, ST abutment, CeraOne.4 Straight abutment: are preferred only when the emergence profile are or can be made parallel. If parallelism is not present between straight abutments, it can be prepared to proper contours by either of these methods:
1) Make an implant transfer impression followed by bench preparation in mouth.
2) Direct preparation in mouth.2 Straight abutments are indicated for replacing single teeth and for large prosthesis up to full arch, implant bone reconstruction (Figure-4).

Angled abutments: angulated abutments are preferred when the implant is at different inclination to the prosthesis. Angulated abutments are available in 15 to 35 degree angulations (Figure-5). The advantage of using angulated abutment is it may compensate for buccolingual and mesiodistal implant angulation problems when an improper jaw relationship exists because of alveolar resorption or skeletal discrepancy.5, 6

Angulated abutments are also preferable in patients with compromised osseosanatomy, the implants may be placed in the most favourable position in relation to quality and quantity of available bone, spatial relationship can be corrected by the engineering and mechanics of prosthesis.
Figure-5
Custom abutments: the individual emergence profile reconstruction can be done by custom abutments. Hence, the crown margin can be positioned few millimetres below the soft tissue margin and it follows the contour of gingival margin (Figure-6).

1. Custom abutments: use of “add-to” abutments which are premachined or standard abutments to which gold or porcelain is added
2. use of CAD-CAM abutments 7
3. use of preparable abutments which are manufactured in bulk material such as porcelain or titanium and which is modified to meet the specific needs
4. Use of copy milling using a scanner and computer assisted manufacturing.


Modifying the prefabricated abutments:
Figure-6 Figure-7


Offers important advantages for long term clinical success of a restoration – Better emergence profile can be created (Figure-7). Distribution of stress and load is better.8-11 Modification of the abutment to match the contour of restoration rather than designing the restoration to match the shape of the abutment Creation of supragingival or sub gingival margins in different cervical areas.

Modifying standard abutments:

Gold or porcelain is added to the standard abutments. One of the example is CeraOne abutment (Nobel bio care) which is a cylindrical titanium abutment and can be modified into an anatomically shaped titanium ceramic transmucosal element. The ceraone abutment is modified with titanium ceramics. CeraOne gold coping is seated onto the modified abutment and it is adjusted to allow for adequate space for metal ceramic crown

Modifying preparable abutments:
Figure-8 Figure-9


These are preferred when the implants are malpositioned. Using these abutments the orientation of the crown relative to the implant can be changed. Few preparable abutments for single tooth restoration are: Ti adapt, ceradapt and solid abutment. (Figure-9) Ceramic abutments: Are manufactured from two high strength ceramic materials that are densely sintered -high purity alumina and yttria -stabilized zirconia.12,13Aesthetic benefit is one of the advantages of using ceramic abutment (Figure-10). When significant angulation changes need to be made ceramic abutments are not prepared because of risk of porcelain fracture.

Fully customized abutments:

Implant manufactures have expanded abutment choices, but the use of custom /laboratory fabricated abutment remain common place. UCLA abutment: This type of abutment is preferred to overcome problem of limited interocclusal space, limited interproximal distance, implant angulation and aesthetic problem.14, 15

UCLA abutment

can be used to resolve severe angulation problems (Figure-11).The other application of UCLA abutment, such as free standing or splinted implant supported artificial crown; implant supported fixed partial dentures; custom abutments for cemented restoration and bar attachment for over -dentures.16

Computer generated abutments:
<
Figure-10


These are customized abutments that are produced using a factory process. The use of computer-aided design technology is now available for fabrication of custom abutments. An example of CAD/CAM abutments is the Atlantis™ abutment (Astra Tech Dental). 17-19 Atlantis VAD™ (Virtual Abutment Design) is a patented process using 3D-optimized scanning software to generate an exact virtual image of the upper and lower implant-level model.

Using the Atlantis software, the patient-specific abutments are individually designed from the final tooth shape. Atlantis abutments are available in zirconia, titanium, or gold-shaded titanium (Figure-12). It is also available for all major systems, including Astra Tech, Biomet 3i, Nobel Biocare, Straumann and Zimmer Dental. Use of copy milling using a scanner and computer assisted manufacturing: A custom milled abutment can be fabricated in titanium, alumina or zirconia using a scanner and computer-assisted manufacturing. 15 The process of copy milling is similar to key duplication and the machine has two co-rotating elements.

The advantages of copy milled abutments are:
Figure-11
 
  • Titanium construction for biocompatibility
  • Non-rotating abutment-implant junction
  • Machined fit to the implant
  • Screw tightening to 32 Ncm
  • Alterability so that the margin can be placed at an ideal level to the gingival crest
  • Creation of transitional contours of tissue and emergence profile in the abutment itself.


Choose the abutment that best suits the clinical scenario:

Pre angulated abutment may be used as a treatment of choice when anatomic limitation preclude the axial abutments.20 In cases where in the implant has osseointegrated and is anticipated to function optimally, the restorative treatment option include: abutments with adjustable necks and prefabricated angled abutments or custom abutment.21 When surgical approach is contraindicated the malpositioned implants can be restored using prefabricated, modified or custom made in laboratory.

Conclusion:

Careful planning of the implant position and subsequent bridge design can simplify complications. Various designs and materials of implant abutment are available. Each type presents advantages and disadvantages but the clinical situation is the primary determinant of using one type rather than using the other. ”THE ONLY GOOD IS KNOWLEDGE AND ONLY EVIL IS IGNOREANCE”

References:
Figure-12
 
  1. Renee E. Duff and Michael E.Razzoog.Managment of a partially edentulous patient With malpositioned implants, using all-ceramic abutments and all-ceramic restoration: A clinical report.The Journal Of Prosthetic Dentistry 2006;96:309-12
  2. Crannin AN, Klein M, Simons A. Atlas of oral implantology. Mosby. 2nd edition.
  3. Implant abutment selection a literature review. International journal of oral implantology and clinical research, May –august 2014;5(2)43-49.
  4. Palmer RM, Smith BJ, Howe LC, Palmer PJ. Implants in clinical dentistry. Taylor and Francis
  5. Eger DE, Gunsolley JC, Feldman S. Comparison of Angled and Standard Abutments and Their Effect on Clin.
  6. Misch C.Prosthodontic considerations.contemporary implant dentistry
     
    • Marchack CB, Vidjak FM, Futatsuki V. A simplified technique to fabricate a custom milled abutment. J Prosthet Dent. 2007;98(5):416-7.
    • Kourtis SG. Selection and modification of prefabricated implant abutments according to the desired restoration contour: a case report. Quintessence Int. 2002;33(5):383-8.
    • Bider MW, Misch CE. Force transfer in implant dentistry;Basic concepts and principles.J oral implants 1992;18:264-274.
    • Richter EJ.In vivo vertical forces on implants. International journal of oral and maxillofacial implants 1995;10:99-108.

Add comment


Security code
Refresh