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USC/RKH AEGD PROGRAM PRECLINICAL ENDODONTIC PRESENTATION

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AL-RUSHOUD /512 RDS A sharp explorer is then used to check the details of the prepared cavity and to loosen the tooth debris ... Cavity preparation If a cusp ... – PowerPoint PPT presentation

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Title: USC/RKH AEGD PROGRAM PRECLINICAL ENDODONTIC PRESENTATION


1
Amalgam
cavity
preparation
2
  • Dental amalgam has been used in operative
    dentistry for not less than 150
  • years. Almost 80 of single tooth restorations
    are fabricated from amalgam,
  • in view of its numerous advantages, which include

3
Advantages
  • 1- Good adaptability to cavity walls and margins
    ? i.e. provides good seal that prevents
  • 1) Recurrence of caries.
  • 2) Irritation to dentin and pulp.
  • 2- High compressive strength ? minimum 80 MN /
    m2.
  • 3- Low coefficient of thermal expansion when
    compared to other restorative materials ?
  • ? Amalgam ? 25 x 10-6.
  • ? Tooth ? 11.5 x 10 -6.

4
Advantages
  • 4- Indestructible in oral fluids ? i.e. maintains
    marginal seal, proximal contact and contour.
  • 5- Biologically compatible with oral tissues.
  • 6- Convenience of manipulation.
  • 7- Could take and maintain high surface polish
    that increases the strength.
  • 8- Low coast.

5
Disadvantages
  • 4- Thermal conductivity.
  • 5- Dimensional changes during setting ? ? 20 ? /
    cm.
  • 6- Poor esthetic.

6
Fracture
7
INDICATIONS
  • Amalgam should be considered together with
    posterior composite and cast gold as a
    restorative for classes I, II, the distal surface
    of cuspids and class V in posterior teeth.
    Material selection in such cases will depend on

8
A) THE EXTENT OF THE LESION
  • The most suitable indication for amalgam is the
    small and medium sized class I and II cavities
    especially those with four walls and a floor,
    where the amalgam will be confined and not
    subjected to tensile loads.

9
  • Extensive lesions especially those including
    undermined cusps will require cusp capping and
    tooth supported against high loads including
    tensile, where cast gold will serve better.

10
B) ESTHETICS
  • For esthetic-conscious patients, amalgam will be
    objectionable particularly in conspicuous areas
    of teeth and posterior composites may be favored.

11
C) CARIES INCIDENCE
  • Amalgam may be favored if repair or remake is
    likely to include extensions for original
    cavities and for patients with moderately high
    caries incidence being less costly and having
    good sealing ability.

12
D) ECONOMICS
  • Although amalgam restorations cost far less than
    cast gold restorations yet costing per se may not
    be in favor of amalgam in the long run if the
    restoration has to be repeatedly be made. Amalgam
    can also be used for core build-up under full
    crowns.

13
Cavity preparation
  • Cavity preparation for amalgam restoration is
    characterized by ?
  • CSA 90?C.
  • Cavity walls parallel or perpendicular to the
    direction of occlusal force.
  • Enough depth to provide bulk to the material.

14
Cavity preparation
  • If a cusp is undermined and is to be capped with
    amalgam, it must be reduced minimum of 2 mm, to
    provide enough bulk of the amalgam enables it to
    withstand the tensile stresses.
  • The isthmus area shows ? Minimal bucco-lingual
    width.
  • ?
    Axio-pulpal line angle beveled, rounded or
    saucerized to provide
  • a) Elimination of stress concentration
    area.
  • b) Bulk of amalgam.

15
B) DESIGNS OF CLASS I CAVITY PREPARATION
  • Cavity preparation for Class I lesions for
    amalgam restoration. It may be either
  • A- Class I simple cavity.
  • B- Class I buccal pit cavity.
  • C- Class I extension cavity.

16
CLASS 1 CAVITIES
Definition
These are pit and fissure type cavities that
involve the occlusal surfaces of molars and
premolars, the occlusal 2/3 of buccal and lingual
surfaces of molars, and the palatal pits in
maxillary anterior teeth.
17
  • These are self-cleansable areas. However, they
    may get involved by caries due to their inherent
    defective structure as areas of imperfect
    coalescence of lobes of calcification of these
    teeth. These areas are retentive for food and
    thus invite caries.

18
These lesions are clinically characterized by
  1. A small surface opening which may remain
    unnoticed until the lesion becomes of a
    considerable size.
  2. A conical spread in both enamel and dentin, with
    the bases of cones at the Amelo-Dentinal
    Junction, "A. D."J.
  3. Its rapid burrowing at the dento-enamel junction.
    These lesions may involve one or more surfaces
    and hence a simple or compound cavity should be
    prepared.

19
Application of Principles
A.
Simple occlusal cavities
Designing the Outline Form. The outline form of a
routine class I cavity should describe a
symmetrical design running in sweeping curves
along all pits, fissures, and angular grooves
between the cusps and with a minimum width.
20
  • The mesial and distal margins are placed midway
    between the bottom of the proximal fossae and the
    crest of the proximal ridges and in a direction
    parallel to these ridges.

21
  • The mesial and distal wall should have a slant
    or slight divergence from the pulpal floor
    outward to avoid undermining the marginal ridges.

22
  • In a bucco-Iingual direction, the cavity is
    extended just sufficient to eliminate the
    defective and susceptible tissues. The lingual
    and the buccal wail should be parallel to the
    respective tooth surface.

23
  • It must be reemphasized that the outline form
    for class 1 cavities should be very conservative
    since they involve cleansable areas.
  • It is governed only by the extent of caries in
    both enamel and dentin and the amount of
    extension or need to eliminate pits and fissures
    to secure smooth margins.

24
Again
  • The outline form for simple design of Class I
    cavity preparation should include all carious and
    undermined enamel, all pits and fissures and
    extended to area self-cleansable in the shape of
    multi curves without any
  • sharp line angles.

25
  • Bucco-lingually, it should not extend beyond the
    intercuspal line except if there is caries with
    minimal width of the cavity about 1/4 - 1/3 the
    inter-cuspal distance. Mesio-distally, it should
    be extended mid way between the triangular fossa
    and the crest of the marginal ridge.

26
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27
The resistance form
  • Achieved by maximum conservation of sound tooth
    structure. Also, considering the amalgam as a
    brittle material, cavo-surface
  • margin configuration of 90oC provides both the
    enamel margins and the amalgam restoration with
    enough bulk at margins to resist the fracturing
    forces

28
  • Minimal cavity width and providing bulk of the
    restoration through a cavity depth at level of
    0.2-0.5-mm beyond the DEJ will provide minimal
    surface area of the restoration exposed to the
    occlusal loading force with bulk strength through
    the depth.

29
  • Flat and smooth pulpal floor parallel to the
    occlusal plane will help in proper distribution
    of occlusal forces and provides stability that
    deletes the wedging action of the restoration
    upon the tooth structure. Roundation of axial
    line angles also eliminates stress concentration.

30
Retention form
  • Only retention against axial displacement is
    needed in the form of mechanical undercuts in
    dentin by converging the cavity walls occlusally
    about 5 - 15 from the tooth long axis.

31
Convenience form
  • In simple Class I cavity design, no need for
    convenience in as it is easily seen and
    instrumented.
  • Only, accentuation of cavity walls, line and
  • point angles and selection of suitable sized
    instruments is considered as a satisfactory
    convenience.

32
Removal of Carious Dentin
  • In small size cavities, the carious dentin should
    have been removed during making the cavity
    extensions.
  • In moderately deep and deep cavities, the carious
    dentin is peeled off carefully at the sides using
    large spoon excavators, and then scooped out in
    few and large pieces.
  • Only light pressure in a direction parallel to
    that of the pulp is utilized. This is continued
    until a sound dentin floor is reached.

33
Planning of Enamel Walls
  • The enamel walls of the cavity should be finished
    free from any loose, short, or undermined enamel,
    and trimmed to meet the tooth surface at a right
    cavo-surface angle.
  • This may be done by sharp and regular-edged
    chisels and hatchets, plane fissure burs, stones,
    or sand-paper discs.
  • All sharp corners in enamel must be rounded, as
    they may contain short enamel rods.

34
Performing of the toilet of the cavity
  • A sharp explorer is then used to check the
    details of the prepared cavity and to loosen the
    tooth debris which are then blasted out with warm
    air.

35
II
Procedure
  • The outline form is performed by first gaining
    access through the enamel to the carious dentin
    floor of the cavity followed by making the
    necessary cavity extensions.

36
  • In case of initial carious lesions, access is
    obtained by employing a small sized round bur.
  • In big carious lesions, access is obtained
    easily by breaking down the undermined enamel
    overlying the carious dentin, using a suitable
    size chisel.
  • In either case, access is started at the most
    defective area of enamel, i.e., a carious pit or
    fissure.

37
  • The bur is held at a right angle to the involved
    surface of, the tooth and light pressure in an
    in-and-out direction is exerted. Cutting is
    continued until the amelo-dentinal junction
    (A.D.J.) is reached.

38
  • The necessary cavity extensions through pits,
    fissures, and deep developmental grooves are made
    using an inverted cone bur held at right angle to
    the surface of the tooth.
  • The bur is rotated, and carefully introduced
    through the opening just obtained, so that its
    weak corners do not touch the enamel and get
    dulled.

39
  • With the bur seated in the cavity just below the
    amelo-dential junction ½ -1 mm. gentle pressure
    is applied in the direction of required
    extension.
  • During cutting, the bur should be kept moving
    in-and-out of the cavity and at right angle to
    the tooth surface. In this way, the bur will
    undermine and lift the cut enamel, and at the
    same time unclog itself.

40
  • Provision of ample resistance and adequate
    retention through boxing of the preparation could
    be obtained.
  • This is obtained by using a fissure bur held
    perpendicular to the surface of the tooth. All
    the line angle in dentin must be squared up hoe
    excavators.

41
B.
Buccal Pit Cavities
  • The outline of these cavities usually describes a
    triangle with its base faming the gingival wall
    and its sides forming the mesial and distal
    walls.
  • The gingival wall is placed at or slightly
    occlusal to the height of contour of the tooth.

42
  • All walls are extended just enough to eliminate
    defective enamel and dentin.
  • The enamel walls are planed in the direction of
    enamel rods and perpendicular to the axial wall.

43
  • Hoe excavators are used to smooth the axial wall
    and make it parallel with the external surface of
    the tooth.
  • It should be re-emphasize that the shape of the
    cavity will be governed by the extension of
    caries, accordingly the outline of these cavities
    may be a rounded or oval in shape.

44
Class I extension cavity
  • Compound or complex Class I cavity design is an
    extension of the occlusal cavity to buccal or/and
    lingual surfaces

45
It is indicated in
  • 1. Deep caries in buccal or / and lingual pits.
  • 2. Deep fissure or groove extended from the
    occlusal to the lingual or / and buccal surfaces.
  • 3. Fissure crossing the oblique ridge in upper
    molars.

46
  • 4. When the remaining oblique ridge in upper
    molars or transverse ridge in lower premolars is
    weak (Fig. 4-4, A and B), it is a must to be
    included in the cavity outline to avoid its
    fracture.

47
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48
The outline form
  • The outline form of compound or complex Class I
    design is the she same as simple Class I cavity
    preparation in addition to extension to include
    the carious or retentive area either buccal
    or/and lingually.

49
  • It may be extended with step, forming axial wall
    and gingival floor, or without step, in
  • cases showing extended caries or fissure at the
    level of the pulpal floor.
  • The formed step will provide inclusion of the
    carious or retentive area without
  • endangering the pulp.

50
Resistance form
  • The same features of resistance form as simple
    Class I is performed in addition to roundation
    of axio-pulpal line angle to prevent stress
    concentration and to provide bulk to the
    restoration at this critical area.

51
  • The axial wall direction should be parallel to
    the corresponding external tooth
  • surface,
  • i.e. convex, in order to prevent pulp exposure
    and provide uniform thickness of the restoration.

52
  • Axial retention in the form of mechanical
    undercuts in dentin, the same as simple Class I,
    in addition to occlusal lock against lateral
    displacement. Extension for retention to the
    other opposing surface to
  • provide lateral retention in extensive cavities.

53
Convenience form
  • When the cavity design becomes compound or
    complex Class I preparation no need for extra
    convenience than that of simple Class I cavity as
    the extension portion is also easily seen and
    reached.

54
Finishing of enamel walls
  • The enamel wall should take the same direction of
    enamel rods without undermining or weakening with
    cavo-surface margin of 90.

55
  • The mesial and distal walls of the extension will
    be completely parallel to each other and to the
    long axis of the tooth,
  • while the gingival floor of the extension portion
    will be slightly slanting gingivally to be in the
    same direction of enamel rods.

56
Designs of Class II cavity preparation
  • Class II cavity preparation for amalgam
    restoration mat be
  • 1. Class II compound or complex cavity with
    proximal step.
  • 2. Class II compound or complex cavity without
    proximal step.
  • 3. Class II simple cavity.

57
1. Class II compound or complex cavity with
proximal step
  • Compound or complex Class II cavity preparation
    with step consists of three portions, occlusal,
    isthmus and proximal portion.
  • The isthmus portion is defined as the narrowest
    connection between the occlusal and proximal
    portions of class II compound or complex cavity.

58
  • The outline of the isthmus portion should be
    extended to involve all the carious enamel and
    dentin and place the cavity margins in area
    self-cleansable with freeing of the proximal
    contact area.

59
  • According to the occlusal anatomy of the tooth,
    the position and size of the proximal contact
    area and width of the embrasure, the isthmus
    outline form may follow one of the following
    Ingrhams lines

60
  • These lines may be straight in case of small
    contact area,
  • uniform in case of normal sized contact area .
  • or reverse curve in case of broad or wide
    contact area.

61
  • The reverse curve outline will be followed in the
    buccal wall more than the lingual as the contact
    area is much more shifted buccally.
  • The width of the cavity at isthmus should be
    narrow bucco-lingually as much as possible, about
    1/4 the inter-cuspal distance. The occlusal
    outline is similar to that of Class I cavity
    preparation

62
  • The proximal outline should be extended enough to
    ensure involvement of all carious enamel and
    dentin, freeing the proximal surface out of
    contact lingually, buccally and gingivally and
    placing the cavity margins in the embrasures to
    be in area selfcleansable.

63
  • The axial wall is about 0.5 0.8-mm away from
    the DEJ to provide enough bulk of the
    restoration.
  • The axial wall should be in a direction parallel
    to the external proximal tooth surface,
  • i.e. it will be either straight or convex to
    provide enough uniform bulk of the restoration
    and protection of the pulp against traumatic
    exposure.

64
  • It is preferable to complete the proximal outline
    before breaking the marginal ridge and proximal
    enamel plate (Proximal ditch cut) (Fig. 4-6,
  • 7 and 11, A and B).

65
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66
This will provide
  • 1. A guide to proximal design.
  • 2. Protection of the proximal surface of the
    adjacent tooth from rotary instrument.
  • 3. Save time and effort.
  • 4. Reduce heat generation as cutting in enamel
    produces much more heat generation.

67
  • 5. Enamel wall in the direction of enamel rods.
  • 6. CSA 90.
  • 7. Freeing of the contact area with maximum
    conservation of the tooth structure.

68
Resistance form
  • Resistance of isthmus portion is achieved by
    minimal width of the cavity bucco-lingually about
    ¼ the inter-cuspal distance.
  • This will provide decrease in the surface area of
    restoration subjected to the occlusal stresses.

69
  • Roundation, beveling or saucerization of the
    axio-pulpal line angle, to provide removal of
    sharp axio-pulpal line angle that acts as stress
    concentration area and increased bulk of
    restoration at isthmus area

70
  • Reverse curve in case of wide proximal contact
    area will provide maximum conservation of the
    sound tooth structure during freeing of the
    contact, removal of all undermined enamel and
    correct cavo-surface configuration of 90

71
  • Resistance of proximal portion is achieved by
    performing cavosurface configuration of 90.
  • The gingival floor should be smooth, flat and
    parallel to the pulpal floor and the occlusal
    plane.

72
  • The axial wall should be parallel to the external
    proximal tooth surface and be at 0.5-0.8-mm away
    from the DEJ, To provide uniform bulk of the
    restoration.

73
  • The buccal and lingual walls should be parallel
    to the direction of the corresponding surfaces to
    avoid weakening of cusps.
  • In general, the proximal portion should be a box
    form.

74
Retention form
  • Axial retention features includes,
  • 1) mechanical undercuts by preparing the cavity
    walls slightly converging occlusally, 2) the
    inverted truncated cone shape of the proximal
    portion,
  • 3) proximal axial grooves
  • 4) pin retention in extensive cavities placed in
    the gingival floor.

75
Retention form
  • lateral retention features includes
  • 1) dove tail, which is considered as extension
    for retention in premolars, considered extension
    for prevention that provides retention also in
    molars
  • 2) occlusal lock.
  • 3) proximal axial grooves.
  • 4) pin retention in extensive cavities.

76
  • Proximal axial grooves are cut in the axio-buccal
    and axio-lingual line angles, in the expense of
    buccal and lingual walls rather than the axial
    wall to avoid pulp exposure. They should extend
    from the gingival floor in occlusal direction up
    to the level of the pulpal floor.

77
  • These grooves are wider internally than
    externally and wider gingivally than occlusally.
  • They are prepared using small round bur or small
    tapered fissure bur

78
Convenience form
  • Cutting an occlusal cavity is considered as a
    convenience form as it provides accessibility to
    the proximal portion.
  • The axial wall should be parallel to the tooth
    long axis in occluso-gingival direction to allow
    instrumentation up to the depth of the proximal
    portion..

79
  • Also, accentuation of cavity walls and margins,
    roundation of line angles and selection of
    suitable sized instruments are important
    convenience features

80
Buccal and Lingual Extensions
C.
  • In case of occluso-buccal and occluso-lingual
    cavities extensions are made through the fissures
    and towards the respective surfaces.
  • The cutting is done in dentin at the
    amelo-dntinal junction using a 56 bur until the
    ocdusal ridge is undermined and removed.

81
  • If the caries is still gingival to the level of
    the pulpal seat, a step is indicated a 330 or
    56 but is used to cut the dentin at the
    amelo-dentinal junction, applying pressure in a
    gingival direction and at the same time moving
    the bur mesio-distally.

82
  • The enamel thus undermined, is broken down with
    chisels.
  • Retention grooves are then cut in dentin along
    the axio-mesial and axio-distal line angles. The
    cavity walls and margins are finished as
    previously described.

83
  • In case of deeply-seated caries, where removal of
    the carious dentin will leave a round cavity
    floor, flattening of which to obtain the required
    resistance form, will expose the pulp.

84
The following technique is used
  • The cavity floor is covered with a sub base of
    calcium hydroxide, followed by a base of glass
    ionomer cement which fills it to the routine
    cavity depth.

85
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