Margins

1
Margins Finish Lines

• Class of 2007
• March 14, 2005
• Brent Fung, D.D.S.

2
Where What is a Finish Line?

• Finish Lines are found at the outermost portion
  of a preparation. Also included is the area at
  and around where the restoration and tooth meet.
  They provide the restoration the best chance for
  long term success by shaping the preparation in
  such a fashion to maximize the strength,
  esthetics, and marginal closure of the
  restoration.

3
Finish Line Determination

• These factors should be considered when choosing
  a finish line
• Restorative Material Requirements
• Bulk Strength
• Optimal Closure Angulation
• Material Esthetics
• Patient Esthetics
• Margin Placement (i.e. Extension)
• Metal vs. Porcelain in Possibly Visible Areas
• Tooth Requirements
• Bulk of Tooth Remaining (Conservative, yet
  Adequate Tooth Preparation)

4
Different Finish Lines

• Shoulder (far left)
• Sloped Shoulder (2nd from right)
• Bevel (not pictured)
• Shoulder-Bevel (far right)
• Chamfer (middle)
• Knife-Edge (2nd from left)

5
Finish Lines

• Shoulder
• Shoulders are finish lines that have an
  angulation of 90 to the external surface of the
  tooth.

6
Finish Lines

• Shoulder
• This configuration imparts strength to materials
  that require maximum bulk at the margin.
  Examples of these materials are Amalgam and
  Porcelain.
• These finish lines require a relatively large
  amount of tooth reduction to accomplish the
  esthetics achieved in porcelain restorations.

7
Finish Lines

• Sloped Shoulder
• Sloped shoulders are finish lines that purposely
  have less than a 90 angulation to the external
  surface of the tooth.
• This special configuration is used in certain
  metal collar situations where axial reduction
  cannot be maximized for porcelain esthetics.
• They are not used with any regularity here at
  USC.

8
Finish Lines

• Bevel
• Bevels are finish lines that purposely end at an
  angulation to the external surface of the tooth.
  The angle and size will change depending on the
  restorative material requirements (bulk
  retention) esthetics.
• Bevels are commonly used with composite materials
  and gold alloy restorations. Composite materials
  use different angles depending on esthetic
  considerations from obtuse to acute and differing
  widths proportionate with the amount of retention
  required of the enamel.

9
Finish Lines

• Shoulder-Bevel
• Shoulder-Bevels are combination finish lines that
  require two steps to complete. The shoulder is
  placed to satisfy the material bulk requirement
  of a gold alloy restoration. Then, a bevel can
  be placed to maximize the marginal closure of the
  restoration.

10
Finish Lines

• Shoulder-Bevel
• Shoulder-Bevels are commonly at USC with gold
  alloy restorations. Gold alloys are typically
  0.65 mm in width at 45 to the external of the
  tooth.
• Bevels are placed with multi-fluted, carbide burs
  like the 281 or 283.

11
Finish Lines

• Shoulder-Bevel
• Detractors say that the extra step in preparation
  after a shoulder is not time efficient. They
  also say that this marginal design isnt
  conservative.
• Advocates of this marginal design say that it is
  exact in its material bulk requirements, gives a
  positive vertical stop upon seating, and done
  well, yields outstanding results.

12
Finish Lines

• Chamfer
• Chamfers are finish lines that only require one
  step to complete. The shape of the bur covers
  the material bulk requirement and the optimal
  angulation of marginal closure. The axial depth
  changes with these burs to accommodate different
  uses.

13
Finish Lines

• Chamfer
• Chamfers are commonly used with gold alloy
  restorations, porcelain restorations of all sorts
  (Veneers, Onlays, PFMs, All-Ceramic Crowns.

14
Finish Lines

• Chamfer
• Detractors say that this margin design say that
  it is hard to measure the axial reduction to
  satisfy material bulk requirements.
• Advocates of this marginal design say it is time
  efficient, easy to place, can yield excellent
  results, satisfies material bulk requirements,
  and is conservative, relatively speaking.

15
Finish Lines

• Knife Edge
• Knife Edge margins are finish lines that meet the
  external of the tooth in a near parallel
  angulation. These margins were more commonly
  used in past years.
• There are no regular indications for use of a
  knife edge margin.

16
Finish Lines

• Knife Edge
• Detractors say that knife edge margins rarely
  satisfy the material bulk requirements for any
  restorative material. Because of this, they
  commonly cause over-contoured restorations
  because the technician doesnt have enough room
  to do otherwise. They can also be very difficult
  to identify, making it difficult to create
  well-fitting indirect restorations.
• Advocates of this marginal design say it is easy
  to place.

17
Summary

• In summary, marginal configuration is dependent
  primarily on the restorative material
  requirements for bulk and strength. Other
  factors include esthetics and tooth requirements.
• Any marginal configuration, used properly, can be
  effective in sealing a margin. Operator choice
  and execution are the most important factors.