Attachment

INTRODUCTION The desire to balance between functional stability and cosmetic appeal in partial dentures gave rise to the development of Precision Attachments The precision attachment is sometimes said to be a connecting link between fixed and removable partial denture as it incorporates features common to both types of construction.
DEFINITION
Precision means quality or state of being precise. Attachment means direct retainer or mechanical device function to retain, support and stabilize dental prosthesis.
Attachment: can be defined as a mechanical device for the fixation, retention, and stabilization of prosthesis. It is a retainer consisting of a metal receptacle and a closely fitting part; the former (the female {matrix} component) is usually contained within the normal or expanded contours of the crown of the abutment tooth and the latter (the male {patrix} component), is attached to a pontic or the denture framework.

CLASSIFICATIONS OF ATTACHMENTS:

Based on method of fabrication and the tolerance of fit:
I. Precision attachments (prefabricated types): are machined devices with high precise tolerances, interchangeable or adjustable, and more expensive than semiprecision attachment.
II. Semiprecision attachments (custom made / laboratory made): are prepared in the dental laboratory, directly casted from plastic or wax patterns with less precise tolerance.
According to their relationship to the abutment teeth:
Intracoronal (Internal attachment).
Extracoronal (External attachment)
Based on stiffness of the resulting joint:
Rigid attachments
Resilient attachments (Non rigid)
Based on geometric configuration and design of the attachment.
Key and Keyway, Interlocks, Ball and socket, Bar and clip / sleeve, Hinge, Telescopic, Push button, Latch, Screw units
Other classification:
1. Intradental: i. Frictional ii. Magnetic
2. Extradental: i. Cantilever attachment. ii. Bar attachment
ADVANTAGES:
Compared to conventional clasp retainers
Improved esthetics and elevated psychological acceptance.
More Hygienic: elimination of food stagnation.
Retention unaffected by crown contour.
Mechanical advantage: reduction of non-axial loading, torqueing forces and rotational movement of the abutment.
In Distal extension base cases Broken stress philosophy:
a. Reduced stress to the abutment
Stress free rotational/vertical movements
Cross arch load transfer and prosthesis stabilization


DISADVANTAGES:
Expensive
Complexity of laboratory and clinical procedure
Wearing of attachment components, it requires periodic maintenance.
Requires high technical expertise (Dentist and laboratory technician).
Requires aggressive tooth preparation
Requires high patients cooperation and manual dexterity.

INDICATIONS / APPLICATIONS

Removable Prosthodontics
As a retainer in a removable tooth supported partial denture in the anterior part of the mouth for esthetic concern.
As a Stress Breaker in free end saddles/Distal Extension Base cases (DEB)
For movable joints in sectional dentures when cantilevered pontic is to be used as abutment
4. Periodontal involvement of the tooth contraindicates rigid FPDs
5. Divergent abutment teeth with high survey lines parallel path of placement.
6. As a retainer in tooth supported over denture
II. Fixed Prosthodontics:
1. as a connector in long span bridges.
2. To overcome alignment problems where abutments have differing path of withdrawal.
III. Implant Prosthodontics:
Implant supported over denture
They are used for connection between the tooth and the implant.


CONTRAINDICATIONS
1. Poor periodontal support.
2. Poor crown to root ratio.
3. Poor oral hygiene habits.
4. Abnormally high carious rate.
5. Inadequate space. An attachment requires a minimum of 4-6 mm vertical space & adequate BL width to incorporate attachment without overcontouring.
6. Compromised endodontic and restorative conditions.








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صناعة /خامس اسنان

د.ايناس م(3)
6/3/2017