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Class 2 Amalgam Preparation and Restoration


By Harleen Braich

Faculty of Dentistry

University of British Columbia

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CLASS 2 AMALGAM PREPARATION AND RESTORATION

REVERSE CURVE TO MAKE RIGHT ANGLE TO CAVOSURFACE

LINGUAL AND BUCCAL CONTACT S JUST BROKEN

BUCCAL AND LINGUAL WALLS CONVERGING TOWARDS OCCLUSAL

ROUNDED AXIOPULPAL LINE

NO UNSUPPORTED ENAMEL AT GINGIVAL CAVOSURFACE

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CRITICAL REQUIREMENTS FOR A CLASS 2 AMALGAM PREPARATION ON 16MO

1. Buccal lingual contacts just broken. Breaking contacts slightly will allow the amalgam at

those margins to be carved and burnished. It also helps terminate the preparation in self

cleansing area.

2. Gingival contact broken. The gingival contact needs to be broken as caries is always

below the gingival contact.

3. All walls are convergent. The walls need to be convergent occlusally as this provides

additional retention form as well as makes the walls at right angles to the cavosurface.

This provides strength to the amalgam as well as the tooth structure. (Roberson,

ALL INTERNAL LINE ANGLES ROUNDED AND PULPAL DEPTH JUST INTO DENTIN

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Hymann& Swift; 2006)

4. All cavosurfaces are smooth, no unsupported enamel remaining. The external line

angles should be at a butt joint, with no unsupported enamel remaining for resistance

form.

5. Occlusal preparation following the central groove, not more than one third of the occlusal

width. The occlusal preparation should follow the central groove and not be more than

one third of the occlusal width so as to preserve maximum tooth structure and have good

resistance form.( Osborne & Summitt,1999)

6. Reverse S. It establishes the tooth preparation in a form that results in 90 degree

amalgam margin when the amalgam is inserted thus creating greater strength for the tooth

as well as the amalgam.( Roberson, Hymann& Swift; 2006)

7. Axiopulpal line angle is rounded to prevent the stress concentration and to prevent the

fracture of restoration(Powers,2006)

REFLECTIONS ON THE PREPARATION

In the preparation I made, I think that I could have made the reverse curve more

prominent on the buccal wall of the proximal box.

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Along with it I also think that the axiopulpal line angle should have been more parallel to

the gingival cavosurface.

AMALGAM FOLLOWS CONTOUR OF THE TOOTH (TRUE ANATOMY)

PITS IN PROPER POSITION

PROPERLY CONTOURED AND CLOSED CONTACT, NO OVERHANG

PROPERLY SHAPED MARGINAL RIDGE, AT SAME HEIGHT AS ADJACENT TOOTH

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CRITICAL REQUIREMENT FOR AMALGAM

RESTORATION OF 16MO

1. Closed contact. The contact needs to be closed to prevent any food impaction and thus

help reduce bacterial colonisation. It also helps maintain interarch width. Closed contacts

also promote healthy interdental papilla. (Roberson, Hymann& Swift; 2006).

2. Cusps have proper contour. Proper cusp contour is required to maintain occlusal

harmony.

3. Buccal/lingual cusps in proper alignment. The proper alignment of the buccal and

lingual cusps ensures proper arch alignment.

4. Central groove. The central grooves also play an important role in proper arch

alignment.

5. Mesial/distal pits in proper position and well defined.

6. Properly shaped marginal ridge. The marginal ridge should be at the same height as

adjacent ridges so as to maintain proper occlusal harmony

7. In occlusion. Proper cusp and fossa relationship should be maintained so that there are

no detrimental forces on the periodontium.

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8. Proximal surface is flush. There should be no overhangs as they have been strongly

implicated as an etiologic factor in the progression of periodontal disease and are

alarmingly prevalent. In addition to promoting plaque accumulation, they change a non-

destructive sub gingival flora to a destructive one (Brunsvold & Lane; 1990)

9. No marginal voids. A smooth restoration is desirable so that there is no place that acts as

harbour for plaque. Studies have shown association between presence of defective

restorations and manifestation of caries and the incidence of gingival inflammation.

(Albandar, Buischi & Axelsson ;1995)

10. Smooth, no scratches. The finished restoration should be smooth so as to deter the

growth of micro organisms in uneven areas.

REFLECTIONS ON THE RESTORATION

When viewed occlusally the amalgam restoration looks as if it is over extended on the

proximal, but on the other hand I think that I had to do that, so as to maintain and create a

good contact.

PROBLEMS ENCOUNTERED

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In cutting cavities on the maxillary, I always had a problem with the angulation of the bur, which

created a cavity away from the central groove, or too far or close to the ridge, or one wall

convergent and the other divergent, or one wall taller than the other. Slowly I learned to steady

the bur in the right angulation correctly by seeing the angulation in direct vision, rather than in

the mirror before cutting the tooth. Now I always see the angulation by directly placing the bur

onto the tooth every time before cutting onto it. I do not move the angulation of the bur anymore,

but move the mirror instead for proper visualization, thus ensuring correct angulation.

AHA MOMENT

To stabilize while cutting on a tooth I used the ring finger as a rest. I was told at UBC to use the

middle finger as a rest. I tried it in the beginning, felt awkward and went back to using the ring

finger. Once while cutting prep I was not able to stabilise properly and somehow just used the

middle finger as a rest, it really worked wonders for me. I learnt that the more near the rest the

better it will be. So I started to rest with the middle finger, closest to the preparation, sometimes

on the same tooth itself. Since then whenever a very stable or fine movement is desired I use the

middle finger as a rest. This has greatly enhanced my efficiency as well as posture.

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REFERENCES

1. Albandar JM, Buischi YA, Axelsson P. (1995) Caries lesions and dental restorations

as predisposing factors in the progression of periodontal diseases in adolescents. A 3-

year longitudinal study.Vol 66(4):249-54.

2. Brunsvold MA, Lane JJ. (1990) The prevalence of overhanging dental restorations

and their relationship to periodontal disease. J Clin Periodontol.Vol ,17:2,67-72

3. Gardner, K. (2009). Dent 430 Operative Dentistry Manual

4. Osborne JW, Summitt JB. (1999). Extension for prevention: is it relevant today?

American Journal of Dentistry. Vol 11(4):189-96.

5. Powers, J.M., Sakaguchi, R.S., (2006) Craig’s Restorative Dental Materials. (12th ed.)

St.Louis: Mosby

6. Roberson, T., Heymann, H., & Swift, E. (Ed.). (2006). Sturdevant’s Art and Science

of Operative Dentistry (5th ed.). St.Louis: Mosby

7. Summit, J., Robbins, J., Hilton, T., & Schwartz. R. (Ed). (2006). Fundamentals of

Operative Dentistry A Contemporary Approach (3rd ed.). Illinois: Quintessence

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