1. IV. TOOTH PREPARATION
A. Definition of Tooth Prep
-Tooth Preparation is the
mechanical treatment of dental
disease or injury to hard tissues
that restores a tooth to its original
form or contour

2. IV. TOOTH PREPARATION
B. Objectives of Tooth Prep
1. Reduction of the tooth in miniature to provide
retainer support
2. Preservation of healthy tooth structure to secure
resistance form
3. Provision for acceptable finish lines
4. Performing pragmatic axial tooth reduction to
encourage favorable tissue response from artificial
crown contours

3. IV. TOOTH PREPARATION
C. Principles in Tooth Prep
1. Preservation of tooth structure
2. Retention and resistance form
3. Structural durability of the restoration
4. Marginal integrity
5. Preservation of the periodontium

4. IV. TOOTH PREPARATION
D. Basic Steps of Tooth Prep
1. Incisal/ Occlusal Reduction
2. Facial Reduction
3. Lingual/ Palatal Reduction
4. Proximal Reduction
5. Gingival Margins/ Finishing Lines
6. Rounding up of Sharp Corners and Line Angles
7. Finishing

5. IV. TOOTH PREPARATION

6. IV. TOOTH PREPARATION

7. IV. TOOTH PREPARATION

8. IV. TOOTH PREPARATION

9. BIOLOGIC
Conservation of tooth structure MECHANICAL
Avoidance of overcontouring Maximum surface area
Supragingival margins Apical extension
Harmonious occlusion Adequate thickness of metal
Protection against tooth fracture Bulk at margins
ESTHETIC
Minimum display of metal
Maximum thickness of porcelain
Porcelain occlusal surfaces
Subgingival margins

10. Depth Guides /
Orientation Grooves
Help dentists in the preparation of teeth
Prevent overreduction as well as
underreduction

11. 1. Incisal/ Occlusal Reduction
 Anterior teeth – 1.5 – 2mm or 2/3 of the
incisal 3rd
 Posterior teeth –
-metal occlusal
1.5-2mm
-metal and porcelain/ fiber reinforced
FC-1.5-2mm
GC-1-1.5mm

12. 1. Incisal/ Occlusal Reduction

13. 1. Incisal/ Occlusal Reduction

14. 1. Incisal/ Occlusal Reduction

15. 1. Incisal/ Occlusal Reduction

16. 2. Labial/ Buccal Reduction

17. 2. Labial/ Buccal Reduction

18. 2. Labial/ Buccal Reduction

19. 3. Lingual Reduction

20. 3. Lingual Reduction
.75 – 1mm amount of tooth reduction

21. 4. Proximal Reduction

22. 4. Proximal Reduction
Degree of Taper
2-5 deg on each side
Average taper of 3 degrees
5-10 degrees combined taper
Average taper of 6 degrees

23. 4. Proximal Reduction

24. 5. Gingival Margins/ Finishing
Lines

25. 5. Gingival Margins/ Finishing
Lines

26. Different Types of Finishing
Lines
Shoulder
Chamfer
Knife edge
Shoulder Bevel
Chamfer Bevel

27. 5. Gingival Margins/ Finishing
Lines

28. Different Levels of Finishing
Lines
Supragingival
Equigingival
Subgingival

29. 5. Gingival Margins/ Finishing
Lines
Is it bad to place margins
subgingivally?

30. BIOLOGIC WIDTH
What is Biologic Width?
It is a band of soft tissue attachment
What is its composition?
It is composed of approximately 1mm
of junctional epithelium and 1mm of
connective tissue fibers.

31. The dentogingival junction includes the gingival sulcus (A-B) approximately 0.8 mm .
The junctional epithelium (B-C) 0.7 to 1.3mm (average 1mm)
The connective tissue attachment (C-D) 1.07mm.
The biologic width (B-D) averages 2mm in occlusogingival height.
D
C
B
A

32. “When you bury the collar,
You attend the funeral of the
periodontium”

33. BIOLOGIC WIDTH
What is its significant clinical implication?
Crown margins can be placed
subgingivally but should not encroach
the Biologic Width.

34. IF VIOLATED …
Inflammation
and
Osteoclastic Activity
Bone Resorption
and
Pocket Formation

35. Intacrevicular Margin

36. 6. Rounding up of Sharp
Corners and Line Angles

37. 7. Finishing

38. 7. Finishing

39. Most Common Errors in Tooth
Preparation
Over reduction
Under reduction
Undercuts
Rough tooth preparations
Lack of parallelism
Failure to contour proximal surfaces of
adjacent teeth

40. Type of CVC Facial Lingual Incisal/
Reduction Reduction Occlusal
Reduction
Acrylic Jacket .75-1mm .75-1mm Ant. 1.5-2 mm
Crown shoulder shoulder
Porcelain Jacket 1.2-1.5mm .75 – 1mm Ant. 1.5-2 mm
Crown shoulder shoulder Post.
Porcelain Fused 1.2-1.5 mm .75-1mm FC-1.5-2 mm
to Metal crown shoulder chamfer GC-1-1.5 mm
Fiber Reinforced 1.2-1.5mm .75-1mm
Metal Crown shoulder chamfer
Acrylic Fused to 1.2-1.5 mm .75-1mm Ant. 1.5 – 2 mm
Metal Crown shoulder chamfer Post. 1-1.5 mm
Complete Veneer .75-1mm .75-1mm Post. 1-1.5mm
Metal Crown chamfer
chamfer

41. V. OCCLUSION

42. A joint is a joining together of two bones. The temporomandibular joint (TMJ) is
the articulation between the temporal bone and the mandible. It is bilateral, and
movement of the right and left sides are interrelated and function as a single
unit..
The condyle of the mandible articulates with the mandibular
(GLENOID) fossae of the temporal bone. The specific location is the posterior
slope of the articular tubercle and the anterior portion of the mandibular
(glenoid) fossae. The condyle does not fit into the center of the mandibular
fossae but rests closer to the articular tubercle. The condyle and articular
eminence do not actually touch, the articular disc (meniscus) rests between
them. This disc is a pad of dense fibrous connective tissue that is thickest at the
posterior ends, thinnest in the middle and thicker again at the anterior ends. The
articular disc, in effect, separates the temporomandibular joint into upper and
lower joint spaces. Laterally and medially, the disc is attached to the condyle
itself, so that whenever the condyle glides forward and backward, the disc
moves with it.
The condyle and articular eminence are covered by dense
collagenousconnective tissue, which contains no blood vessel or nerves.
Synovial fluids bathes this structures, providing nourishment and lubrication
that enables the bones to glide over each other without friction.
A thick fibrous capsule surrounds and encloses the entire joint. The

43. disc and capsule are fused anteriorly, and some fibers of the lateral pterygoid
muscle insert into the disc. Posteriorly, the disc and capsule are not directly
attached but are connected by means of a retrodiscal pad, a pad of loose
connective tissue that allows for anterior movement of the joint.
Nerve and blood supply- Innervation is supplied by two nerves, the
auriculotemporal and ,masseteric nerves, which are branches of the mandibular
nerve (V3), blood supply is provided by branches of the superficial temporal and
maxillary arteries.
Movement- TMJ movement within the temporomandibular joint is essentially of
two types: Hinge (swinging) motion and gliding movement.
The condyle of the mandible articulates with the
mandibular (glenoid) fossae of the temporal bone. The
specific location is the posterior slope of the articular
tubercle and the anterior portion of the mandibular
(glenoid) fossae. The condyle does not fit into the center of
the mandibular fossae but rests closer to the articular
tubercle . The condyle and articular eminence do not
actually touch, the articular disc (meniscus) rests between
them. This disc is a pad of dense fibrous connective tissue
that is thickest at the posterior ends, thinnest in the
middle, and thicker again at the anterior ends. The
articular disc in effect, separates the teemporomandibular
joint into upper and lower joint spaces. Laterally and
medially, the disc is attached to the condyle itsel, so that
whenever the condyle glides forward and backward, the
disc moves with it.
The condyle and articular eminence are covered by dense collagenous connective tissue, which contain s no blood vessel or
nerves. Synovial fluid bathes these structures, providing nourishment and lubrication that enables the bones to glide over each
other without friction. A thick fibrous capsule surrounds and encloses the entire joiunt. The disc and capsule are fused
anteriorly....(contiued above)

44. Mandibular movement
Mandibular movement can be broken down into a series of motions that
occur around three axes:
2.Horizontal
This movement, in the saggital plane occurs when the retruded
mandible produces a purely rotational opening and closing movement
around the hinge axis, which extends through both condyles.

45. 2. Vertical
The movement occurs in the horizontal plane when the
mandible moves into a lateral axcursion. The center for this
rotation is a vertical axis extending through the working side
condyle.

46. Sagittal
When the mandible moves to one side, the condyle on the side
opposite from the direction of movement travels forward. As it does, it
encounters the eminentia of the glenoid fossa and moves downward
simultaneously. When viewed in the frontal plane, this produces a
downward arc on the side opposite the direction of movement, rotating
about an anteroposterior (sagittal) axis passing through the other
condyle.

47. Various mandibular movements are comprised of motions occuring about one or
more of the axes. The up and down motion of the mandible is a combination of
two movements...
...There is a purely rotational component
produced by the condyle rotating in the lower
compartment of the temporomandibularjoints.
...There is also some gliding movement in the
upper compartment of the jaw.

48. When the mandible slides forward so that the maxillary and
mandibular teeth are in an end to end relationship, it is in a protrusive
position. Ideally, the anterior segment of the mandible will travel a path
guided by contacts between the anterior teeth.

49. Mandibular movement to one side will place it in a working, or
laterotrusive relationship on that side and a nonworking or mediotrusive
relationship on the opposite side;e.g., if it moves to the left, the left side is
the working side, and the right side is the nonworking side. In this type of
movement, the condyle on the nonworking sidewill arc forward and
medially (A). Meanwhile, the condyle on the working side will shift
laterally and usually slightly posteriorly (B). This bodily shift of the
mandible in the direction of the working side was first described by
Bennet.
The presence of an immediate
or early side shift has been
reported in 86% of the
condyle studied. In addition to
demonstrating the
predominant presence of early
side shift, Lundeen and Wirth
have shown its median
dimension to be approximately
1.0, with a maximum of
3.0mm. Following the
immediate side shift, there is
gradual shifting of the
mandible.

50. The determinants of mandibular movement
The two condyles and the contacting teeth are analogous to the three legs of
an inverted tripod suspended in the cranium.
The determinants of the movements of that tripod are:
-posteriorly, the right and left temporomandibular joints;
-anteriorly, the teeth of the maxillary and mandibular arches;
- And overall, the neuromuscular system.
The dentist has no control over the posterior determinants, the temporomandibular
joints.they are unchangeable.
However, they influence the movements of the mandible, and of the teeth, by the paths
which the condyles must travel when the mandible is moved by the muscles of
mastication. The measurement and reproduction of those condylar movements is the
basis for the use of the articulator.
The anterior determinant, the teeth, provides guidance to the mandible in several ways.
The posterior teeth provide the vertical stops for mandibular closure. They also guide
the mandible into the position of maximum intercuspation, which may or may not
correspond with the optimum position of the condyles in the glenoid fossae. The
anterior teeth (canine to canine) help to guide the mandible in right and left lateral
excursive movements and in straight protrusive movements.
Dentists have direct control over the tooth determinant by orthodontic movement of
teeth; restoration of the occlusal surfaces ;and equilibration, or selective grinding, of
any teeth which are not in harmonious relationship. Intercuspal position and anterior
guidance can be altered, for better or for worse, by any of these means.

51. The Determinants of Occlusion
The closer to a determinant that a tooth is located, the more it will be
influenced by the determinant. A tooth placed near the anterior region
will be influenced greatly by anterior guidance, and only slightly by the
temporomandibular joint. A tooth in the posterior region will be
influenced partially by the anterior guidance.
The neuromuscular system,
through proprioceptive nerve
endings in the periodontium,
muscles, and joints, monitors the
position of the mandible and its
paths of movement. Through
reflex action, it will program the
most nearly physiologic paths of
movement possible under the set
of circumstances present. Dentist
have indirect control over this
determinant. Procedures done to
the teeth may be reflected in the
response of the neuromuscular
system.

52. The Determinants of Occlusion
Condylar Guidance
Anterior/Incisal Guidance
Occlusal Plane
Occlusal Curve
Cusp Height

53. The Determinants of Occlusion

54. The Types of Occlusal
Interferences
Centric Interference
Working Interference
Non-Working Interference
Protrusive Interference

55. One of the objectives of restorative dentistry is to place the teeth in harmony
with the temporomandibular joints. This will result in minimum stress on the
teeth, and only a minimum effort need be expended by the neuromuscular
system to produce mandibular movements.
When the teeth are not in harmony with the joints and with the movements of the
mandible, an interference is said to exist.
Occlusal interferences
Interferences are undesirable occlusal contacts which may produce deviation
during closure to maximum intercuspation, or which may hinder smooth
passage to and from the intercuspal position. There are four types of occlusal
interferences:
5.Centric
7.Working
9.Nonworking
4. Protrusive

56. The centric interference is a premature contact which occurs when the mandible
closes wit the condyles in a retruded, superior position in the glenoid fossa.
It will cause deflection of the mandible in a forward and/ or lateral direction.

57. A working interference may occur when there is contact between the maxillary
and mandibular posterior teeth on the same side of the arches as the direction
in which the mandible has moved. If that contact is heavy enough to disclude
anterior teeth, or interfere with the smooth progress of the nonworking side
condyle, it is an interference.

58. A nonworking interference is an occlusal contact between maxillary and
mandibular teeth on the side of the arches opposite the direction in which the
mandible has moved in a lateral excursion. The nonworking interference is of a
particularly destructive nature. The potential for damaging the masticatory
apparatus has been attributed to changes in the mandibular leverage, the
placement of forces outside the long axes of the teeth, and disruption of normal
muscle function.

59. The protrusive interference is a premature contact occurring between the
mesial aspects of the mandibular posterior teeth and the distal aspects of
maxillary posterior teeth. The proximity of the teeth to the muscles and the
oblique vector of the forces make contacts between opposing posterior teeth
during protrusion potentially destructive.

60. The protrusive interference is a premature contact occurring between the mesial
aspects of mandibular posterior teeth and the distal aspects of maxillary
posterior teeth. The proximity of the teeth to the muscles and the oblique vector
of the forces make contacts between opposing posterior teeth during protrusion
potentially destructive.

61. There may be anis lowered, the
If the threshold occlusal
disharmony which versus pathologic occlusion
disharmony
Normal had been
(shaded bar) which ismay ideal,
previously tolerated not produce
but which only slightlyby the normal of the population is
symptomsis tolerated more than 10%
In in the patient. (a
patient there complete a pathologic
occlusion can become harmony between the teeth and the
because it is below his
threshold ofSimple muscle joints. Only in that small group
occlusion). perception and
temporomandibular
discomfort. teeth give waymaximum intercuspation when
hypertonicity may achieve to muscle
do the
spasm, the mandible headaches and position with the
with chronic is in a retruded
localized tenderness. optimal superior retruded position in
condyles in the
the fossae.
Treatment is then
then rendered by 90% of the population,And position of
In the other nearly the
then decreasing or
eliminating the
first raisingintercuspation is 1.25+mm forward of the retruded
maximum the disharmony
patient’s
position.
threshold,

62. ARTICULATORS
-is a mechanical device which of the simulates
the movements of the mandible
The principle employed in
the use of articulators is the
mechanical replication of the
paths of movement of the
posterior determinants, the
twmporomandibular joints.
The instrument is then used
in the fabrication of fixed
and removable dental
restorations which are in
harmony with those
movements.

64. As the mandible closes around the hinge axis ( m h a ), the
cusp tip of each mandibular tooth moves along an arc

65. The large dissimilarity between the hinge axis of the small
articulator ( a h a ) and the hinge axis of the mandible ( m h a ) will
produce a large discrepancy between the arcs of closure of the
articulator (broken line) and of the mandible (solid line).

66. A major
discrepancy
exists between the
nonworking cusp
path on the small
articulator (a) and
that in the mouth

67. The dissimilarity between the hinge axis of the full size
semi-adjustable articulator ( a h a ) and the mandibular hinge axis
( m h a ) will cause a slight discrepancy between the arcs of
closure of the
articulator
(broken line)
and of the
mandible
(solid line)

68. There is only a slight
difference between cusp paths
on a full size articulator
(c)and those in the mouth
(m), even though the cast
mounting exhibits a
slight discrepancy

69. The condyle travels a curved path in mandibular movements ( A )
This is reproduced in semi-adjustable articulators as a straight
path ( B ).

70. ..However, the angle changes between an open (C) and a closed
(D) nonarcon instrument <a3 not equal to <a4. For the amount of
opening illustrated, there would be a difference of 8 degrees
between the condylar inclination at an open position ( where the
Thearticulator settings are adjusted ) and a closed position (at which
angle between the condylar inclination and the
.
Occlusal plane of is used ).
the articulator the maxillary teeth remains
constant between an open (A) and a closed (B)
articulator <a1=<a2.

71. Transfer of the tooth hinge-axis relationship
Two caliper-style face-bows are in
use at the present time:
the Quick mount Face-bow
When a precision face-bow transfer is made,
both side arms are adjusted so that the stylus
at the end of each arm is located over the
hinge axis (arrow). A third reference point,
such as the plane indicator shown here, is
used.
An air activated pantograph for
recording mandibular movements
the Slidematic Face-bow

72. Different Styles/Schemes of
Occlusion
Fully Bilateral Balanced Occlusion
Unilateral Balanced Occlusion
– (Group Function)
Canine Guidance
– (Mutually Protected Occlusion)

73. FULLY BILATERAL BALANCED OCCLUSION

74. UNILATERAL BALANCED OCCLUSION
( GROUP FUNCTION )

75. CANINE GUIDANCE
( MUTUALLY PROTECTED OCCLUSION )

76. Definition of Terms:
*Centric Relation
*Centric Occlusion – Centric Relation of
Occlusion
*Maximum Interdigitation / Intercuspation
* Vertical Relation
• Vertical Dimension/Relation at Rest
• Vertical Dimension/Relation of Occlusion
• Interocclusal Distance/ Freeway Space
*Bennett Movement
*Protrusive Movement

78. Movements

79. The Axes of Mandibular
Movements

80. The Axes of Mandibular
Movements

81. The Types of Occlusal
Interferences