concepts in amalgam preparation/ dental implant courses

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INDIAN DENTAL ACADEMYLeader in continuing Dental Education

Concepts In Tooth Concepts In Tooth Preparation For Preparation For AmalgamAmalgam

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INTRODUCTION Tooth preparation Need for the restoration Objectives of tooth preparation Factors affecting tooth preparation


Concepts G.V. Black's concept(1891) Prime’s concept(1928) Bronner’s concept(1930) McGehee’s concept(1936) Markley’s concept(1951) Vale’s concept(1956) Gilmore concept(1964) T. Fusayama’s concept(1971) Rodda(1972) Almquist, Cowen & Lambert(1973) Knight(1984)


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G.V. Black's concept Extension for prevention(1891, published

in dental cosmos entitled “The management of enamel margins)

Basic idea was to prevent the recurrence of dental decay by placing the margins of restorations along the lines that would be cleansed by the normal excursion of food(Black,1924).


If the tooth requires wide cutting to meet this criterion, then tooth substance to be sacrificed.

Proximal area of high risk of decay has specific boundaries (Black, 1904)

buccal & lingual- embrasures Occlusal- contact point Cervically- position of

healthy gingiva www.indiandentalacademy.com

Extension in incisors and canines

Margin well away from the contact area

This does not mean to make the cavosurface margin conspicuous


Extension in molars and premolars Same and extension determined

by the anatomy of the embrasure.

Extension sufficient so that buccogingival and linguogingival cavosurface point angles covered by free margin of gingiva.

Buccal groove & another sharp grooves included in the preparation.


Extension of gingival third cavities

Free gingiva retracted so that cervical margin of the finished restoration covered by free marginal gingiva.

Mesiodistal extension up to the angles of the tooth classified as immune area.


Black’s instrumentation

Inverted cone bur for initial outline form followed by use of hatchets & chisels to remove the unsupported enamel.


Oppositions to the concept Rodrigues Ottlengui(1901) apologized in 1910 for opposition.

Edmund Kells (1926) accepted concept theoretically while no area on the tooth is always immune to decay.


Prime’s concept

Proposed very conservative cavity preparation

Narrow, shallow occlusal step, triangular proximal boxes and narrow gingival walls inclined to the axial for retention.


Bronner’s concept

Proximal outline converged occlusally as area between the marginal ridge and contact point is seldom the seat of decay.

Proximal area be self retentive.

Suggested that the proximal extension be determined by the profile of the narrow of the two teeth in contact.Also Black’s principles of preparing class 4 cavities be applied to the preparation of class2 cavities.


McGehee’s concept(1936)

In Individuals with good oral hygiene conservative preparation.

Buccal & lingual margins converged toward the occlusal as compared to Black’s ones.


Markley’s concept(1951)

Rounded internal line angles

• Occlusal walls that were parallel to the enamel prism

• Constricted occlusal outline

• Proximal margins extended only far enough for access

• Proximal retention just within the dentine

• Beveled axiopulpal line angle


Gilmore concept(1964)

Recommended narrow occlusal outline and rounded internal line angles.

Recommended proximal clearance from the adjacent tooth be limited to 0.5mm compared to Black proposed the range of 0.8 to 1.2mm.


T. Fusayama’s concept(1971) Very conservative approach Advocated cavity preparation limited to

enamel without retention in dentin for amalgam restoration of pit & fissures.

Narrowest tungsten carbide bur (no. 56) diameter 0.81mm.

cavity depth 1mm and width 0.9mm depth may be more if occlusal surface

presents high cusps.


T. Fusayama’s concept(1971)

Very conservative approach

Advocated cavity preparation limited to enamel without retention in dentin for amalgam restoration of pit & fissures.

Narrowest tungsten carbide bur (no. 56) diameter 0.81mm.

cavity depth 1mm and width 0.9mm

depth may be more if occlusal surface presents high cusps.


Rodda(1972)

Narrow occlusal outline and an ‘S’ shaped curve cut in the buccal wall to produce a 90 degree relationship of the buccal wall to the cavosurface.

Rounded internal line angles and occlusal convergence of proximal walls.


Almquist, Cowen & Lambert(1973)

Concluded that if patients are taught to clean their teeth thoroughly, there would be no need to extend the cavity margins more than required.

Proposed ‘Slot’ preparation.


Knight(1984)

Proximal caries removed through that access.

Proposed the Tunnel preparation If the marginal ridge is intact no need to cut it.Occlusal access prepared 2-3mm from the marginal ridge.


Vale’s experiment(1956)

occluso-proximal preparation of tooth with differing crossing dimensions at the marginal & crossing ridges.

Teeth subjected to measured occlusal loads


Results

TYPE AND NUMBER OF RIDGES INVOLVED

LOSS IN RESISTANCE FORM

OCCLUSO-PROXIMAL WIDTH

1/4 1/3 1/2 ONE

TWO

MARGINAL RIDGE

MARGINAL RIDGES

CROSSING RIDGE

10%

15%

20%

35%

15%

35%

40%

45%

45%


conclusion If G.V. Black was alive today he would

have modified his cavity preparations due to improvement in materials & techniques. We still do not violate his basic rules, but have simply brought them up to date. We are no longer practicing a radical extension for prevention, but have changed the slogan to “constriction for conviction”.


References

Sturdvent et al. Art and science of operative dentistry. 4th edition.

Marzouk M.A et al. operative dentistry: modern theory and practice.

DCNA, Operative Dentistry April 1976. DCNA, Restorative Dentistry April 1985. Sigurjons H. extension for prevention: historical development

and current status of GV Black’s concept. Operative Dentistry 1983;8:57-63.

Markley MR. Silver amalgam. Operative Dentistry 1984; 9:10-25.

Childers JM. Approximal retentive grooves in cavities prepared for amalgam: a historical and current assessment. Operative Dentistry 1985;10: 100-103.

Fusayama T. cavity preparation & amalgam restoration in enamel: Journal of Prosthodontics 1971:657.


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