1. DESIGN OF COMPLEX AMALGAM PREPARATION
嘉泉醫大 吉病院 齒科
主任 敎授 金 滿 龍

2. STANDARD PRINCIPLES
Margins 90° (perpendicular) to tangent to carvosurface
Proper clearance: 0.25mm – 0.5mm
Occlusal, axial and gingival walls in dentin

3. EXTENSIONS BEYOND IDEAL
Pulpal and axial extensions beyond ideal; remove round burs or spoon excarvators only

4. EXTENSIONS BEYOND IDEAL

6. Extend beyond ideal depth around tooth at normal depth

7. Provide vertical support for occlusal forces
Avoid inclined planes

8. Provide vertical support for occlusal forces
Convert inclined planes to “steps”

9. HANDLING EXTENSIONS Disto-facial cusp of mandibular molars
Large disto-facial cusp
Small disto-facial cusp
Margin crosses cuspal eminance – cap cusp
Capping disto-facial cusp

10. HANDLING EXTENSIONS

11. CAPPING DISTO-FACIAL CUSP

12. COVERING CUSPS WITH AMALGAM
OFFSETS – THE MOST IMPORTANT SOURCE OF RESISTANCE
If no offsets are present, all the force must be borne by the grooves or pin.

13. Reduce to obtain a minimum of 2mm thickness of amalgam
Reduce flat, perpendicular to occlusal forces.
Leave dentin 0.5mm – 1.0mm higher than pulpal floor to prepare offset
Remove all undermined enamel
(supported by 0.5mm of dentin)

14. RETENTION FEATURES – Slot, pin,cove,well and amalgapin
Slot = a long, narrow retentive factor in a vertical or horizontal wall
Cove = a shallow, round hole in the incisal of class III preparations
Well = a short, deep hole (about 2.0x0.8x0.8mm deep
Amalgapin = a large, deep hole ( mm D X 1.3mm deep) used to replace pins in amalgam restorations

15. Slot 형성

16. PINS IN RESTORATIVE DENTISTRY

17. HISTORY
Dr. Miles Markley in 1958 cemented threaded stainless steel wires, reporting as “pin reinforcement and retention”
Later studies showed that pins increased retention in amalgams, but decreased strength

18. TYPES OF PINS Cemented – pin is 0,002’ smaller than the channel
Friction-locked – pin is 0.001’ larger than the channel
Self-threading (TMS) – pin is ’ larger than the channel

19. General Principles Pins must be stable.
Pins must not perforate into the pulp or periodontal membrane.
Tips of pins will be covered with at least 2mm of amalgam.
Pins will clear matrix brand laterally.

20. General Principles
Pins will not predispose to caring or fracture of tooth structure.
Place so pin is surrounded by 0.5mm-1.0mm of dentin. (Larger pins or non-vital teeth require 1.0mm)

21. General Principles
If pin is close to the DEJ, or if tooth is non-vital
Use smaller pins: regular Minim minikin minuta
Use hand wrench to prevent over-torquing
Monitor torque and seat pin completely
Back off pin ¼ turn

22. General Principles
If pin is close to the DEJ, or if tooth is non-vital
Use cemented pins
Cut groove in pin and “tap”threads in dentin

23. General Principles Must provide flat seat and space around the pin
Allows more complete seating of drill
Allows maximum depth of pin channel
Allows amalgam to flow around the grasp pin
Choose pinhole direction parallel to external surface of tooth, not parallel to long axis of tooth or crown

24. General Principles Choose proper location for pins
Place in area of greatest bulk of dentin
Place mm from the dej to prevent crazing
Place halfway between pulp and external surface of root if gingival margin is in cementum
Avoid furcations and depressions on roots

25. Preparation of pin channels
Prepare in a clean, dry, caries-free field
Use rubber dam to prevent swallowing or aspiration of instruments
Use slow speed, high torque (10:1 contra-angle or torque-increaser)
Keep drill rotating at all times. Never place a drill back into hole unless it is rotating.

26. Preparation of pin channels
Careful maintain the same direction
If pin channel cannot be completed quickly
Check direction of rotation
Use slightly more pressure
Confirm that you are not in enamel
Assume the twist drill is dull and replace

27. If self-threading pins strip and won’t hold
Confirm that all caries has been removed in area of pin channel
Use the next larger drill and pin size
Minuta Minikin Minim regular
Drill the channel deeper (if direction is safe)
Drill to a 3mm depth
Use a 4-5mm twist drill, being very careful no to break
Change to a cemented pin

28. If self-threading pins strip and won’t hold
Avoid the problem by maintaining same angle during drilling, and drill one time only (avoid re-entering the channel)

29. Accidents with pin
Perforation into pulp: fill hole with CaOH and place a pin elsewhere
Perforation in periodontal membrane
Place pin flush with root surface using a hand wrench
Do a gingival flap and cut pin cut off flush with root surface
Fill channel with root canal sealer

30. Accidents with pin Broken drill or pin
If pin is loose, remove it and proceed
If stable, leave the broken pin or drill in place, and place a new one in a different location

31. Avoiding breakage of twist drills
Use only 2mm depth-limiting twist drills
Use only sharp, new drills
Don’t press too hard, especially with smaller diameter drills
Maintain same direction during drilling
Never place a drill into a hole unless is rotating
When using the longer (4-5mm) drills, follow all rules very carefully