This document discusses the importance of circumferential tie and bevels in dental preparations. It defines different types of bevels such as partial, short, long, full, counter, and hollow ground bevels. It also discusses different extensions used in preparations like flares, skirts, collars, and their indications. The ideal requirements of peripheral margins and factors affecting bevel angle are explained. Bevel placement in teeth with facets and their importance in cast restorations is also summarized.

1. By- Dr. Mayank Nahta
Rungta college of dental sciences
and research, Bhilai

2. INTRODUCTION
• The weakest link in any restoration is the tooth restoration
joint or marginal peripheries.
• Every effort should be made to design & prepare these
peripheries to create the most favourable relationship with
the restoration.
• This peripheral marginal anatomy of the preparation is
called “circumferential tie”.

3. Ideal Requisites of Peripheral margins
If the margins ends on enamel,enamel wall should fulfill all
requirements- by Noy
• Enamel must be supported by sound dentin.
• Enamel rods forming the cavosurface margin should be
continuous with sound dentin.
• Enamel rods forming the cavosrface margin should be
covered with restorative material.
• Angular cavosurface margin should be trimmed.

4. BEVELS
• Bevels are flexible extension of a cavity preparation
allowing the inclusion of surface defects,supplementary
grooves,or other areas on tooth surface.
• These are plane of a cavity wall or floor directed away
from the cavity preparation.
• Earlier bevel was placed only on cavosurface
margins and was defined as the roundening off, of
cavosurface margins at an angle.

5. • Now as they are placed at various surfaces of prepared
teeth it is defined as-
“any abrupt incline between the two surfaces of
prepared tooth or between the cavity wall and the
cavosurface margins in the prepared cavity”.
• Bevels require minimum tooth involvement and do not
sacrifice the resistance and retention for the
restoration.

6. • Bevels as part of circumferential tie & are one of the
major retention forms for a cast restoration as it increases
possibility of a direct retentive frictional component
between the casting and the tooth.
• This makes it possible to decrease or eliminate the cement
line by bringing the cast alloy closer to tooth structure.

7. Types of bevels
According to shape and types of tissue involvement they are
divided into six types of bevel :-
1) Partial bevel
2) Short bevel
3) Long bevel
4) Full bevel
5) Counter bevel
6) Hollow ground(concave) bevel

8. Types of bevels (contd.)
They are classified according to surface they are placed .
1)Gingival bevel
2) Occlusal bevel
3) Functional cusp bevel

9. PARTIAL BEVEL
• This type of bevel involves part of the enamel wall , not
exceeding two-thirds of its dimension.
• This is usually not used in cast restorations except to
trim weak enamel rods from margin peripheries.

10. SHORT BEVEL
• This includes the entire enamel wall but not dentin.
• Indicated in Class I alloys specially for type1 & 2

11. LONG BEVEL
• This includes all of the enamel wall, & one-half of the dentinal
wall.
• Its major advantage is that the internal boxed up resistance &
retention features are preserved in this bevel.
• Indicated in first three
classes of cast materials.

12. FULL BEVEL
• This includes all of the dentinal and enamel walls of the
cavity wall or floor.
• Although it is well reproduced by all four classes of cast
alloys, it deprives the preparation of its internal
resistance and retention.
Its use is avoided except in cases
where it is impossible to use
any other form of bevel.

13. COUNTER BEVEL
• When capping cusps to protect and support them, this
type of bevel is used , opposite to an axial cavity wall,
on the facial or lingual surface of the tooth, which will
have a gingival inclination facially or lingually.

14. Hollow Ground (concave) Bevel
• This is the only form which is not in flat plane form.
• This allows more space for cast material bulk , a design
feature needed in special preparations to improve
materials castability retention and better resistance to
stresses.
• These bevels are ideal for class IV and V cast materials

15. • The buccal slopes of the lingual cusps & the lingual
slope of the buccal cusps should be hollow ground to a
depth of atleast 1mm to provide sufficient bulk of
material on these surfaces & to increase the resistance
form.

16. REVERSE BEVEL
• It is placed at the dentinal portion of the cervical wall
towards the axio gingival line angle.
• Reverse bevel at gingival wall will prevent tipping
movements.
• The hydrostatic pressure during cementing a cast
restoration can produce a rotational displacement of the
castings with flat gingival walls.
• This effect is resisted by the reverse bevel resulting in
even seating of the cast restoration.

17. Occlusal bevel
• Bevels create obtuse angled marginal tooth structure,
which is the bulkiest and the strongest configuration of
any marginal tooth anatomy to resist stess.
• Produce acute angled marginal cast alloy substance
which makes it most amenable to burnishing.

18. • In wider cavities, and in deeper ones, they are extended to
improve the taper.
• This design employs the principle of the cone to provide a
snug fit of the casting against the surrounding walls of the
preparation.

19. FUNCTIONAL CUSP BEVEL
• It is additional removal of tooth structure in a cavity
preparation.
• A wide bevel placed on the functional cusp provides
space for an adequate bulk of metal in an area of heavy
occlusal contact.

20. • Functional cusp bevel increases the thickness of thin
occluso-axial junction of the restoration.
 Angulation-45 degree
 USE- Provides additonal thickness for the material which
is necesaary because these are the maximum load
bearing areas. So,
large bevel is given
which will help to bear
excess load without
fracture.

21. LOCATION-
• Its prepared on the palatal cusp of maxillary
teeth.
• Buaccal cusps of mandibular teeth.

22. Lack of functional cusp bevel may produce
several problems-
1. May result in over contouring and poor occlusion.
2. Over inclination of the buccal surface will destroy
excessive tooth structure reducing retention.

23. GINGIVAL BEVEL
• Weak enamel is removed.
• Bevel results in 30° angle at the
gingival margin that is burnishable
because of its angular design

24. • A lap sliding fit is produced at the gingival margin which
help in improving the fit of casting in this region.

25. • Increased to bevel E.rods which inclines towards the
cusps.
• Angle of bevel is decreased with increase in steepness of
the cusps
• Increased bevel angulations is necessary for a direct wax
patterns as more marginal bulk is required.
• Bevel angulations should be increased to include remotely
located defects, supplementary grooves or decalcifications
on the occlusal surface.
Factors affecting bevel angle

26. • Bevel angulations should be increased to include
remotely located defects, supplementary grooves or
decalcifications on the occlusal surface.
• In wider cavities and in deeper ones, they are extended to
improve the taper & reduce frictional components for
easier material manipulation.
• Bevel on the occluding surface of the tooth produces thin
feather edges in gold casting which are subject to injury
by attrition and excessive forces during mastication.

27. • As conditions require the occlusal width of the
preparation to be extended bucco lingually the
degree of the occlusal bevel must be increased.
• This increase will result in the forces of occlusion driving
the margin of the casting into closer apposition to the
tooth structure.

28. FLARES
Primary Secodary Reverse secondary flare Skirt
Collar

29. FLARES
• Flares are flat or concave peripheral portions of the facial
and lingual proximal walls in intra coronal preparations.
• Flare are of 2 types-
1. Primary Flare 4. Skirt surface
2. Secondary Flare 5. Collar extensions
3. Reverse secondary Flare

30. • PRIMARY FLARE-
• It is the conventional and basic part of the circumferential
tie facially & lingually.
• It is similar to long
bevel formed of
enamel & a part of
dentin.

31. • They may be hollow ground if they preparation is for
non-noble alloys or cast ceramics.
• Primary flare always have a specific angulation
i.e., 45 degree to the inner dentinal wall.

32. Function-
• Perform the same functions as bevels.
• They can bring the facial & lingual margins of the cavity
to cleansable-finishable areas.
Indications-
• Indicated for any facial or lingual wall of an intracoronal
cavity preparation.
• If they fulfill the the objectives of preparation circu
-mferential tie than secondary flare is not required.
• If not secondary flare is placed peripheral to primary
flare.

33. SECONDARY FLARE
• It is a flat plane superimposed peripherally to a primary
flare.
• Sometimes it is prepared in a hollow ground form to
accommodate materials with low castability.
• Unlike primary flare secondary flare may have different
angulations, involvement & extent, depending upon their
function.

34. • Indications-
• In very widely extended lesions bucco-lingually, the buccal
and lingual tooth structure will be badly thinned ; primary
flare will end with acute angled marginal tooth structure
with unsupported enamel.
• A superimposed secondary flare is prepared in such
cases which create the needed obtuse anglulation
with the marginal tooth strucutre.

35. • In broad contact areas or malposed tooth the primary
flare will not bring the facial and lingual margins to
finishable cleansable areas.
• In such cases a secondary flare is placed peripheral to
primary flare.This will be accompalished without
changing the 45 degree angulation of the primary flare.

36. • In ovoid tooth undercuts are present occluso apically.
Cast restoration prepared in an indirect tech. for this
prep. will result in marginal failure to eliminate this
secondary flare superimposed over a primary flare is
given.

37. REVERSE SECONDARY FLARE
• These are the extension of secondary flare.
 INDICATIONS -
• Indicated to include facial or lingual defects beyond the
axial angle of the tooth.
• To eradicate severe peripheral marginal undercuts which
have not been removed by the maximum angulation
& extent of a secondary flare.

38. • Needed to add to the retentive capability of the
restoration proximally. Also to fulfill the objectives of
secondary flares in extremely wide cavities or contact
areas.
• For encompassing an axial angle for reinforcing and
supporting reasons.
• Contraindicated in class IV & V cast materials.

39. FEATURES
• Reverse secondary flare can be added to a cavity
instead of a secondary flare i.e., superimposed directly
over primary flare, if secondary flare do not fulfil the
objective (wide lesion or contact area,rotation).
• Also, in cases if secondary flares fulfill only a part its
objective e.g., open the contact area then the reverse
secondary flare fulfil rest of the objective e.g.,provide
obtuse angle marginal tooth structure.

40. • It ends on the facial and lingual surface with a knife edge
finish line, its extent should not exceed the height of
contour in mesi-distal direction & tip of the cusps.
• The reverse angulation of this flare has no limitation till it
does not create any undercuts in the occluso apical path
of the cavity.

41. SKIRT
• This is more extensive surface extension then the reverse
secondary flare.
 INDICATIONS-
• To involve defects with more dimensions (depth) than
those that can be invovled in a reverse secondary flare.
• To impart resistance & retension on a cast restoration
instead of missing or shortened opposing facial or
lingual walls.

42. • Indicated in facial & lingual tilted tooth, in order to restore
the occlusal plane.They will allow for the bulk, resistance,
& retention of the additional occlusal cast material required
in bulding the occclusal table.In such condition skirt is
prepared at the side towards which teeth is tilted.

43. FEATURES –
• Prepared to include facial & lingual surfaces near the axial
angle to a depth of –
0.5-1mm- class I & II alloy
1.5-2mm- class III, IV,V
• Max. depth should be at the junction of the surface
extension with cavity preparation.
• Sometimes preferable to terminate skirt in mesially
or distally in a vertical groove

44. • Depth of this groove
Class I-IV 1-2mm, 2 mm or more for ceramics.
• It should be short of gingival finish line.
• Skirt will terminate mesially & distally in-
Class I,II,III – Chamfer line
Class IV &V- End in hollow ground bevel or in rounded
shoulder.

45. • Since its prepared on the convexities there are chances of
undercuts.So the axial reduction should be parallel to the
cavity preparation.
• All the interveining cusps b/w the cavity wall proper & skirt
should be prepared the same way as the capped cusp.
• For Class I-IV alloys the intervening facial or lingual wall
proximally between the cavity preparation and the
skirt should have box portion and the primary flare.

46. • These features will minimize tooth structure loss and
locking property for the restoration.
• These cusp formed completely of dentin and should have
2mm bulk.
• Skirt should terminate shy of the cusp tip or past it.
• If skirt is used to change the contact and contour of the
tooth it should be extended far enough on facial and lingual
surfaces to create sufficient retention.
• For tilted tooth it should be extended far enough on facial
and lingual surface proximally away from the direction of tilt.

47. COLLAR
• This type of extension involvemore surface area and depth.
• 2 types
1. Cuspal collar
2. Tooth collar
• Cuspal collar- involves facial or lingual surfaces of one cusp
only in a multicusped tooth.
• Tooth collar- involve entire facial or lingual
surfaces of the tooth.

48. Indication-
• Help in retention and resistance when entire cusp is lost
prior to tooth preparation or when it is necessary to
remove it due to excessive undermining.
• Helps in retention in shortened teeth.
• Help in enhancing the support for endodontically
treated teeth.

49. • used in places where pins are contraindicated.
• For cast material with low castability.
• Used for areas in a cast alloy restoration to be veneered
by fused porcelain, an collar can accommodate both
porcelain and alloy and facilitates marginal seating of
castings cicumferential tie.

50. FEATURES
• With the depth of 1-2mm,collar ends gingivally in a
bevelled shoulder finish line.
• Class IV bevelled portion should be hollow ground & for
ceramics bevelled in rounded & exaggerated fashion or
have no bevel.
• The interveining cusp should be
should be preserved same as
with the skirt.

51. • If tapering is necessary than, collars have less taper than
skirt towards cavity preparation.This improves retention in
these shortened teeth.
• There should be definite line angle gingivally,at the
junction of the bevelled shoulder with the axial collar.
Shoulder portion of the collar should be parallel to the long
axis of the tooth.
• Bevel is given to the shoulder for better marginal seating
of the cast restoration.

52. BEVELS IN TEETH WITH FACET
• Esthetics, conservation of tooth structure, and
requirements for retention may demand that an occlusal
cavo-surface margin be left in a faceted area in the
region of the height of the tooth cusp.
• In these instances, the degree of bevel must also be
considerably greater than15 °In this manner, the
direction of bevel will result in the forces of occlusion
driving the margin of the casting into closer apposition to
the tooth.

53. • The lower bicuspid teeth offer the most common
example of this exception.
• It may be advisable in many instances to eliminate
complete coverage of excessive extra-coronal facets on
these teeth which result from excessive over-bite of the
buccal cusp of the maxillary bicuspid teeth with no
overjet

54. BEVEL IN CAST RESTORATION
• Bevel on the occluding surface of the tooth produces thin
feather edges in gold casting which are subject to injury
by attrition and excessive forces during mastication.