SELECTION OF ABUTMENT

TEETHSubmitted by: Lana Michael IVth year

DEFINITION An abutment can be defined

as a tooth, portion of a tooth or that portion of an implant used for the support of a fixed or removable prosthesis.(GPT)

Abutment plays a crucial role in accepting the load acting on a fixed partial denture.

The choice of abutment is important because it has to withstand both the forces acting on it and on the pontic.

FACTORS INFLUENCING THE CHOICE OF AN ABUTMENT

ToothGingivo-

periodontal complex

Root

• Location• Position• Form• Condition

• Crown-root ratio

• Root configuration

• Gingiva• Periodontium

LOCATION, POSITION AND CONDITION OF THE TOOTH

Characteristics of the preferred abutment: Teeth adjacent to edentulous spaces Teeth with grossly decayed crowns that can be

restored with a full veneer crown Modifications like dowel core and pin retained

amalgam restorations-needed to restore crown morphology in grossly destructed teeth

Vital teeth are preferred, though endodontic teeth can be used

Pulp capped teeth cannot be used as they are always under risk of RCT

CROWN-ROOT RATIO The ratio between the length of crown and

length of root should always be less than one The length of crown indicates the length of

tooth structure above the crest of alveolar bone

Ideally, the crown ratio should be 2:3 Ratio up to 1:1 is acceptable

ROOT CONFIGURATION The forces acting on tooth are transferred to

supporting bone through the root. The shape of the root determines the ability of

the abutment to transfer the masticatory load to the supporting bone.

Facts: Roots with greater labiolingual widths are

preferred Roots with irregular curvature are preferred

Teeth with longer roots serve as better abutments

Tooth with conical roots can be used for short span fixed partial denture

ROOT SUPPORT The supporting alveolar bone should be

healthy It should have good trabecular

architecture and shows no sign of bone defects or bone loss

Intra-oral radiographs should be used to evaluate bone architecture

The alveolar bone support is one of the most important factors that aid to evaluate an abutment

PERIODONTAL LIGAMENT AREA

It can be used as a measurement or scale to determine the potency of the abutment

Tylman stated that the two abutment teeth could support two pontics

Johnston et al improvised Tylman’s statement and proposed the famous Ante’s law

ANTE’S LAW The sum of the pericemental areas of the

abutment teeth should be equal to or greater than the tooth to be replaced

The periodontal area of the abutment should be calculated and if it is not sufficient then an additional tooth should be used as a secondary abutment

ASSESSMENT OF PULPAL HEALTH

Usually unrestored abutments are preferred If caries is present, regular preparation can

be done If large caries lesions are present they should

be scooped out and can be used for additional retentions

If the abutment tooth has a carious lesion with pulpal involvement the RCT is advised. RCT not advised for abutments with periapical lesion