Attachments in removable partial prosthesis

by Dr.Hamide Noroozi D.D.S(prosthodontist) 2015

Contents• Definition of attachment • History• Indications of attachments• Classification of attachments• consideration when selecting attachments• brands (Rhein)

Definition:An attachment is a connector consisting of two or more parts.one part is connected to a root , tooth , or implant called female or matrix

and the other part connected to a prosthesis ,called male or patrix

Male attachments Female attachments Patrix Matrix Flange Slot Insert Crypt Key Keyway

Fitting part Receptacle

HistoryWinder (18th century)“Winders design” Screw joint retention

First unilateral fixed detachable type of RPD

Parr (1886) Extracoronal socket attachment

Stair(1886) Telescopic abutment restoration

Ash (1912) Split bar attachment system

Late 19th century :

Dr.Herman, ES Chayes

“T shaped”

Precision Attachment (1906)

“H shaped”

Chayes Attachment (1912)

INDICATION / APPLICATIONS OF ATTACHMENTS

Removable Prosthodontics • As a retainer in a removable tooth supported partial denture • Stress Breakers – Distal Extension Base cases • For movable joints in sectional dentures • As a retainer in overdentures

Fixed ProsthodonticsAs a connector in fixed partial denture construction

(long span bridges)

To overcome alignment problems where abutments have differing path of insertion

IMPLANT PROSTHODONTICS

Implant supported overdenture

They are used for connection between the tooth and the implant

Classification location : intracoronal, extracoronal,stud type, bar ,telescopic

method of fabrication:precision ,semiprecision or custom cast

the mechanism of attachment : rigid ,semirigid , or resilient

capacity for activation: activatable , nonactivatable

Location

Intracoronal• Incorporated entirely within the contour of the crown• Occlusal forces applied close to the axis of rotation• Extensive preparation of abutment• contraindicated in young patient with large pulp• All intracoronal attachments are rigid• Easy to maintain hygiene

Omega BeyelerMcCollum

Bakers attachment Schatzmann attachment Ney attachment

Extracoronal• Positioned entirely outside the crown contour• Normal tooth contour can be maintained• Minimal tooth reduction is necessary• Possibility of devitalizing a tooth is reduced• in distal-extension prosthesis, double abutting is recommended• As a stress breaker and stress director in free end RPD• Difficult to maintain hygiene,positioning at 1mm oclussal to the gingival

margin to preserve access for hygiene and prevent periodontal disease

Dalbo / Dallabona attachment Ceka attachment

Roach attachment (ball and tube attachment) Pin and tube attachment

The alignment of the attachments with a line bisecting the angle between the sagital plane and the middle of the ridges

Stud TypeRadicular :The stud is attached to the metal coping cemented over the prepared abutment, while the housing is embedded in the fitting surface of the denture. e.g :

Ceka ,dalbo stud, Rotherman, Gerber

dalbo stud

Ceka

SCHUBIGER ATTACHMENT

Rotherman

Intra-Radicular:The stud is attached to the fitting surface of the denture and the housing is incorporated in the abutment. e.g : Zest Anchor

matrixmetallic funnel shaped tube

patrix

polyethylene stud

Bar Type Bar Type attachments span an edentulous area and connect abutment teeth,roots or implants.

indications: removable bridge, partial denture,or overdenture

• bar attachments : 1) Bar units - rigid2) Bar joints – permits rotation (clip or sleeve)

• Space requirements vertical: 3 - 6.2mm between abutments: Based on attachment system

Round / circular Oval / egg shaped ‘U’ shaped /

parallel sided bars

Multiple sleeve bar jointsSingle sleeve bar joints

BAR JOINTS

DOLDER BAR

ACKERMANN BAR

CM BAR

It is similar to circular Ackermann bar with diameter of 1.9 mm fabricated with precious and semi-precious alloys recommended for long spans

HADERBAR Helmut Hader in 1960 Available as a prefabricated plastic pattern

Prefabricated plastic pattern are adapted to master cast according to its contour and cast in alloy of choice .

Advantages of bar attachments : • Rigidly splint the teeth • Provides good retention, stability and support • Provides cross arch stabilization• Positioned close to the alveolar bone (exhibit less

leverage)

Disadvantages : Bulk of bar Plaque accumulation Soldering procedureWeakness of the denture baseRequire to the adequate space

Telescopic Prosthesis Classification and definition: Telescopic crowns were initially introduced as retainers for RPDs and OverdenturesIndications: Unparalleled abutments Uneven spaces between abutments Useful for obturators

Advantages: Increased Retention and stability

Disadvantages: Bulky crowns

Telescopic Prosthesis Procedure• Inner copings and outer Copings • Need 4mm vertical wall for copings• 0.5-1 mm thickness of Gold coping• 0.15 mm thickness of non-precious• Shoulder preparation of 1.5 mm thickness• Require conical taper for coping 1 to 9 degree• Path of insertion

Method of fabrication

Precision Attachments• prefabricated components are machined in special

metal alloys • maximum dimensional tolerance of 0.01 mm• hardness of alloys is controlled• less wear • standard parts which allows the components to be interchangeable

Semi-Precision• fabricated by the direct casting of plastic ,wax,or refractory

patterns • less accurate than the precision attachment• allow up to 15 degrees (or more) of rotational movement and up to

600 microns (or more) of vertical movement.• In removable partial denture cases, they are cast with the crown or splint and are placed outside the contours of the teeth • advantages: easy fabrication ability to be cast in a wide choice of alloyslower cost

Material Alloys precious alloys: Gold Titanium

non-precious alloys : Cobalt-chromium (co-cr) Nickle-chromium (Ni-cr)

plastic material polyamid (nylon) teflon (polytetrafluoroethylene) polyvinyl chlorine(PVC) Bakelite Lustrex(poly-styrene)

HOW TO attach the components to the framework :• The soldering techniqueThe soldering is the most used procedure to fix prefabricated attachments

• The cast-to technique

insert a component of the attachment (generally the female) directly in the position desired in the wax or resin cap and casting together.

Custom- cast Attachments

Mechanism of attachments

Rigid• rigid mechanism only allows for insertion and removal movements of

one of its components• when RPD is completely seated ,rigid attachment prevent all types of

movement between matrix and patrix• all masticatory forces transmitted to the abutment teeth• in distal-extensions ,in which the lever forces transmitted to the

abutment teeth are grater, the splinting of two or more abutments is recommended

• promotes greater stability in the removable denture

• Rigid attachments Roach

Pin and Tube

Stabilex

Semi-Rigid the semi-rigid attachment allows limited movement between matrix and patrix when a removable denture is fully seated

these movements generally rotational only a portion of masticatory forces transmitted to the abutment teeth

Resilient the resilient attachment allows free movement between the patrix and matrix when the removable prosthesis is fully seated

these movements are mechanically limited by the height of the ridges masticatory forces are mostly transmitted to the ridge

•Resilient attachments Dalbo

ERA

O-ring

Activation

Activatable after a certain time of usage , most attachments will exhibit partially reduced or totally lost retention

this type of attachment can be activated with a feature designed specifically for this purpose such as screws, fissures, vertical or horizontal blades

Nonactivatable nonactivatable attachments do allow a simple swap of their components after a certain time in the oral environment ,plastic material components lose their physical properties;therefore, they should be change every year

Retention Frictional

• resistance to the relative motion of two or more surfaces in intimate contact with each other

• Beyeler attachment is a good example • if attachments are over -polished , frictional retention may be lost

• Mechanical

• Frictional and Mechanical

• Magnetic

Magnet as attachments since 1950 to retain maxillofacial prosthesis

Overdenture Application: Magnets are attached to roots and overdenture

CONSIDERATIONS WHEN SELECTING ATTACHMENTS

Condition of periodontal supportWhen teeth are strong, or can be made strong through splinting, non-resilient designs are the connectors of choice.

Condition of residual ridge A residual ridge showing evidence of rampant resorption generally contraindicates resilient designs.

Opposing archTwo resilient prostheses should generally not oppose each other, as two mobile occlusal planes will impair chewing efficiency.

Vertical height (measured from soft tissue papilla to the occlusal surface)Every attachment has a minimum height requirement; for example, most intracoronal designs require at least 3.5mm and preferably more.

Size of abutments A large pulp chamber or very small mesiodistal dimension may contraindicate an intracoronal design.

Number of abutmentsDouble abutting distal extension cases is always a good idea; however, when not possible, resilient designs are preferred to de-emphasize the supportive role of the abutments.

Position of abutments

Patient dexterityExtracoronal attachments are generally a bit easier to insert than intracoronal. Of the intracoronal designs, tapered attachments are easier than parallel- walled attachments.

Alloy from which the abutment crown will be madeSome attachments must be used only with precious metal. Others only with non-precious alloys.

Space

Minimum attachment length 4mm

Inadequate attachment length < 4mm

Maximum attachment length 6-7 mm

Axial space requirement Sufficient clinical crown length – for minimum of 4mm attachment length

Buccolingual space requirement

an additional 1mm should be added to the buccolingual measurement for metal precision

attachments to allow for the casting alloys

mesiodistal measurements are critical for intracoronal attachments,since a box preparation is required.

Rhein attachments

Thank You