Tooth preparation basics

1. GOOD AFTERNOON

2. PRESENTED BY: Aneesah khathoon P.I

3.  Mechanical alteration of a defective, diseased
or injured tooth to best receive a restorative
material to re-establish:
◦ The Normal Form
◦ Function &
◦ Esthetics of the tooth

4.  CONVENTIONAL PREPARATION
◦ Eg: For Amalagam, cast metal, ceramic
 MODIFIED PREPARATION
◦ Eg; For Composites, GIC

5.  CLASS I
◦ All pits & fissures including
 Occlusal surfaces of posterior teeth
 Occlusal 2/3rds of facial & lingual surfaces of Molars
 Lingual pits of maxillary incisors
 CLASS II
◦ Proximal surfaces of posterior teeth

6.  CLASS III
◦ Proximal surfaces of anterior teeth without
involving the incisal angle
 CLASS IV
◦ Proximal surfaces of anterior teeth involving the
incisal edge

7.  CLASS V
◦ Gingival 1/3rd of facial & lingual surfaces of all teeth
 CLASS VI
◦ Incisal edge of anterior teeth & occlusal cusp tips of
posterior teeth

8.  Caries extent
 Occlusion
 Pulpal
involvement
 Esthetics
 Patient’s age
 Gingival status
 Anesthesia
 Bone support
 Patient’s desires
Enamel rod direction
Extent of old restorative
Contours
Pulp protection
Economics
Bur design
Fracture line
Tooth anatomy
Ability to isolate areas
Material limitations

10. ◦ The locations the peripheries of the completed
tooth prep will occupy on tooth surfaces
 Internal outline form
 External outline form
◦ Preparing an initial depth of 0.2-0.5 mm pulpally of
DEJ or 0.8 mm pulpally to normal root surface
position

11.  PRINCIPLES:
◦ All unsupported & weakened enamel should be
removed
◦ All faults should be included
◦ All margins should be placed in a position to allow
finishing of margins of restorations
 FEATURES:
◦ Preserving cuspal strength
◦ Preserving marginal ridge strength
◦ Minimising facio-lingual extensions
◦ Connecting 2 close defects (<0.5mm) or tooth
preps.
◦ Restricting the depths of the preps into dentin

12.  The shape & placement of the preparation
walls that best enable the remaining tooth
structure & the restoration to withstand,
without fracture, the masticatory forces
delivered principally along the long axis of
the tooth.

13.  FEATURES & PRINCIPLES:
 Relatively long horizontal floors
 Box-like shape
 Inclusion of weakened tooth structure
 Preserving cusp & marginal ridge
 Rounded internal line angles
 Adequate thickness of restorative material
 Reduction of cusps for capping

14.  Shape and form of preparation that prevents
displacement or removal of restoration by
tipping & lifting forces for non-bonded
restorations

15.  FEATURES:
 In Amalgam restorations
◦ Occlusal convergence
◦ Divergence of dovetail
 For Composite
◦ Micromechanical bonding to tooth

16.  Shape or form of the preparation that
provides for adequate observation,
accessiblity & ease of operation in preparing
& restoring he tooth

17.  FEATURES:
 Mod of cavo-surface margins for ease of
placement of restorative material
 Extension of buccal & lingual walls for
visibility & access to deeper portions of cavity
 Proximal lesions can be inspected from facial
or lingual embrasures in a tooth with wide
accessible embrasures & intact marginal ridge

18.  Elimination of any infected carious tooth
structure or faulty restorative material left in
tooth after initial preparation
 Spoon excavators/carbide burs

19.  Pulp irritation causes
◦ Heat generated by rotary instruments
◦ Some ingredients in various materials
◦ Thermal changes conducted through restorative
materials
◦ Forces transmitted through materials, to dentin
◦ Galvanic shock
 Liners & bases are used

20.  Mechanical features
◦ Retention grooves
◦ prep extensions
◦ Skirts
◦ Beveled enamel margins
 Placement of etchant, primers or adhesiveon
prepped walls
◦ Enamel wall etching
◦ Dentin treatment

21.  Further development of degree of surface
smoothness or roughness that produces the
max effects of a restorative material
 FEATURES:
◦ Design of the cavosurface angle
 90° cavosurface angle
 Bevelling of cavosurface angle
◦ Degree of smoothness or roughness of the wall

22.  To free the prep of visible debris with water
from the Syringe & then to remove the visible
moisture with a light burst of air from the
Syringe
 Desensitizers:
◦ 5% Glutaraldehyde
◦ 35% 2-hydroxymethylmethacrylate

23.  FACTORS To be considered
◦ Smaller tooth dimension of the deciduous dentition
◦ The thin enamel covering teeth
◦ Broad contact areas
◦ Narrow occlusal table

24.  Due to narrow occlusal table, isthmus
shouldnot be more than 1/3rd the inter-
cuspal distance for small carious lesions.
 Depth: Not more than 0.5mm in dentin.
 Pulpal floor: Flat; any remaining carious
lesions removed with round bur.

25.  Broad contact areas gingival floor of proximal
box should be wide, to place the margins in self-
cleansing areas.
 Box Converge occlusally with buccal & lingual
wall IIing the external tooth surface.
 Box wall should meet the occlusal wall in a
straight line.
 Wall-X flare
 Isthmus should not exceed 1/3rd the inter-cuspal
width in 1° molars.
 Axio-pulpal line angle rounded, tunneled,
grooved(for bulk)

26.  Strength of amalgam at isthmus: by
adequate depth of preparation.
 Retention: Improved by a U shaped retention
groove along the amelodentinal junction of
box
 Mand. Primary I Molars: When cavity exceeds
ideal prep, an overlay of disto-buccal cusp is
prepared.
 Gingival Seat: X Bevel at cervical area, rather
follow enamel rod inclination.
 If depth of lesion is farther gingivally, axial
wall should follow external surface contour.
 Box should allow the passage of explorer tip
between the margins & adj. tooth.

27.  When contact is open: outline is ; Base
towards gingival aspect of cavity.
 Gingival cavity wall is inclined occlusally to
the enamel rod direction
 Retention pits can be placed at the axio-
bucco-gingival & axio-lingo-gingival point
angles.
 Dovetail may be placed at the mid. 1/3rd of
lingual surface of tooth.

28.  Cavity designs:
Dictated under the site & extent of lesion &
not by any preconceived notion of mech.
Interlocking patterns.
Expectation of extending out to the caries free
area
 1st choice of restorative: One with some º of
biological activity Remineralisation &
healing.
 Only the part of crown irretrievably
degenerated should be removed.
 1st aim of restoration: eliminate any surface
cavitations resulting in caries.

29.  Pre-requisites:
◦ 90º junction b/n amalgam & tooth
◦ Mech. Retention form
◦ Adequate thickness of Amalgam
 BOX-ONLY:
◦ For posterior tooth where proximal surface requires
restoration but occlusal surface is normal.
◦ No occlusal steps
◦ More conservative

30.  TUNNEL
◦ Joins an occlusal lesion with proximal lesion by
means of prepared tunnel under the involved
marginal ridge.
◦ Marginal ridge intact.

31.  BOX-ONLY:
◦ Prepared structure is etched or primed
◦ Advcated: RMGI liner under composite
 TUNNEL:
 SANDWICH TECHNIQUE:
◦ RMGI is used as a flowable composite liner under
some Composite restoration

32.  COMPOSITE:
1. no
2. Bonding, grooves
3. Same for large preps,
special form for
moderate & small
4. No
5. Ca(OH)2 also used:
RMGI on root extns.
6. >1.5mm
 AMALGAM:
1. 1º retention form:
Converge occlusally
2. 2º Retention form:
Grooves, slots, locks,
pins
3. Resistance form: Flat
floor, rounded
angles, box shape
4. Base indication: 2mm
b/n pulp & amalgam
5. Liner: Ca(OH)2
6. Initial pulpal depth:
1.5mm

33.  COMPOSITE:
1. Same
2. Axial wall of 0.2mm
inside DEJ
3. Only on extensive
Class Iis
4. Cavosurface
angle:>90º
 AMALGAM:
1. Occlusal step: Same
as Class I
2. Proximal box: Axial
wall of dentinal depth;
Crown:0.5-0.6
Root:0.75-0.8
3. Beveling on gingival
margin
4. Cavosurface angle: 90

34. THANK YOU!