Class III Restoration Techniques
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Questions and Answers

What is the primary purpose of placing a groove at the junction of the axial and external walls?

  • To provide a channel for dental materials
  • To create a seal against the tooth structure
  • To increase tooth sensitivity
  • To enhance retention and resistance form (correct)

    • When might a beveled conventional Class III restoration be indicated?

  • When there are no existing restorations present
  • When replacing an existing defective restoration (correct)
  • When caries is confined to the lingual surface
  • When caries is only found on the incisal edge

    • What should be done first when restoring adjacent carious lesions?

  • Develop the larger outline form first (correct)
  • Insert restorative material for both lesions simultaneously
  • Prepare the secondary healing area first
  • Develop the smaller outline form first

    • Which bur size is typically used to enlarge the opening for caries removal?

    <p>Round bur No. 1/2</p> Signup and view all the answers

    What is a critical aspect to consider regarding the external walls of a cavity preparation?

    <p>They must extend to sound tooth structure</p> Signup and view all the answers

    What is a modification for the conventional cavity design when the carious lesion is small?

    <p>Avoid gouging into the subgingival area</p> Signup and view all the answers

    What is the correct angle for the bevel in a beveled conventional preparation?

    <p>45 degrees to the cavo-surface</p> Signup and view all the answers

    What is the primary reason for making lingual access undesirable when teeth are irregularly aligned?

    <p>It complicates instrument access to the caries</p> Signup and view all the answers

    What is one advantage of incorporating a bevel at the cavosurface?

    <p>It allows for a stronger enamel to resin bond.</p> Signup and view all the answers

    What is the recommended depth for creating an axial wall into the dentin/DEJ?

    <p>0.2 mm</p> Signup and view all the answers

    What characterizes the shape of the axial wall in this preparation?

    <p>The axial wall follows the external contour of the tooth.</p> Signup and view all the answers

    Why should infected dentin be completely removed during preparation?

    <p>To ensure complete retention of the restoration.</p> Signup and view all the answers

    What shape do preparation walls have in Modified Class III cavities?

    <p>Concave or scooped.</p> Signup and view all the answers

    What is a key requirement for the preparation angle in Modified Class III cavities?

    <p>An external angle of 90 degrees or more.</p> Signup and view all the answers

    What instrument is recommended for removing remaining infected dentin?

    <p>A round bur or small spoon excavator</p> Signup and view all the answers

    What is a primary design consideration for Modified Class III cavity preparations?

    <p>To be as conservative as possible.</p> Signup and view all the answers

    What specific angle should the No.¼ bur be positioned at when preparing the groove retention form?

    <p>Bisecting the junction angle</p> Signup and view all the answers

    What is the minimum remaining wall dimension required to prevent fracture during groove preparation?

    <p>0.25 mm</p> Signup and view all the answers

    When should a tapered fissure carbide bur be used during tooth preparation?

    <p>When preparing an outline form</p> Signup and view all the answers

    What is the recommended depth for the initial preparation of a beveled conventional restoration?

    <p>0.75 mm</p> Signup and view all the answers

    How should the handpiece be positioned relative to the bur's long axis during preparation?

    <p>Perpendicular to the external surface</p> Signup and view all the answers

    Which bur is recommended for limited access interproximally or gingivally?

    <p>No. 1 or 2 round bur</p> Signup and view all the answers

    What should be performed after cleaning the carious lesion or defect during preparation?

    <p>Inspection for approval</p> Signup and view all the answers

    What type of restoration is indicated for a newly formed large carious lesion?

    <p>Beveled conventional preparation</p> Signup and view all the answers

    What is a key feature of the conventional Class IV restoration?

    <p>It requires groove retention form when extended onto the root.</p> Signup and view all the answers

    Which type of Class IV restoration is used for large proximal areas including the incisal surface?

    <p>Beveled conventional Class IV</p> Signup and view all the answers

    What technique is recommended before preparing a tooth for a Class IV restoration?

    <p>Preoperative impression for contouring.</p> Signup and view all the answers

    Which of the following is a retention feature for composite material in Class IV preparations?

    <p>Dovetail extensions.</p> Signup and view all the answers

    When might a conventional Class IV restoration be indicated?

    <p>When the restoration extends onto the root.</p> Signup and view all the answers

    What challenge may arise during shade selection for large Class IV restorations?

    <p>Normal dentin color may be difficult to replicate.</p> Signup and view all the answers

    In the context of large Class IV preparations, where are rounded undercuts typically placed?

    <p>Along line angles and into point angles.</p> Signup and view all the answers

    Which feature is NOT associated with modified Class IV restorations?

    <p>Less retention than conventional designs.</p> Signup and view all the answers

    What is one disadvantage of pin retention in anterior teeth?

    <p>It may lead to perforation into the pulp or external surface.</p> Signup and view all the answers

    Why is the placement of an arbitrary dovetail extension not commonly used?

    <p>It enhances restoration strength but is less conservative.</p> Signup and view all the answers

    What is the primary method of retention in composite restorations?

    <p>Micromechanical bonding to tooth structure.</p> Signup and view all the answers

    What depth should the initial axial wall for Class IV lesions be established at?

    <p>0.5 mm into dentin.</p> Signup and view all the answers

    What is typically the objective when preparing for a Class IV restoration?

    <p>To remove as little tooth structure as possible.</p> Signup and view all the answers

    What factor can provide additional retention in a restoration?

    <p>Increasing the width of the enamel bevels.</p> Signup and view all the answers

    What is the role of Ca OH liner in the restoration process?

    <p>To act as an antimicrobial barrier.</p> Signup and view all the answers

    What is the ideal angle for preparing a gingival retention groove?

    <p>At an angle bisecting the DEJ junction</p> Signup and view all the answers

    Study Notes

    Class III Restoration

    • The groove is placed at the junction of the axial and the external walls.
    • The carious lesion is positioned facially.
    • Teeth are irregularly aligned, making lingual access undesirable.
    • Extensive caries extent into the facial surface.
    • Faulty restoration that was originally placed at the facial surface.
    • When restoring approximating carious lesions or faulty restorations on adjacent teeth at the same appointment, if one lesion is larger, (more extended outline form), than the other, then the larger outline form is developed first.
    • The second preparation can be more conservative because of the improved access provided by the larger preparation.
    • The reverse order would be followed when the restorative material is inserted.
    • Depending on the extent of the preparation to be restored, there are three designs:
      • Conventional: When caries is entirely on tooth surface
      • Beveled Conventional: When the cavity is large and enamel margins bevel is given at an angle of 45 degrees to the cavosurface
      • Modified: When the carious lesion is small

    Conventional Class III

    • Indicated for replacing an existing defective restoration in the crown portion of the tooth
    • When restoring a large carious lesion for which the need for increased retention and/or resistance form is anticipated.

    Lingual Access

    • Use a round bur No. 1/2, 1. 2 depending on the size of the caries to enlarge the opening sufficiently to allow for caries removal.
    • Extend external walls to sound tooth structure using a straight bur.
    • Extend the gingival and incisal walls up to extent of caries or location of old restoration.
    • Unless necessary, DO NOT:
      • Include the proximal contact.
      • Extend into the facial surface.
      • Extend subgingivally.

    Advantages of Enamel Bevel

    • The ends of the rods are more effectively etched than otherwise only the sides of the enamel rods are exposed.
    • Increase in etched surface area results in a stronger enamel to resin bond, which increases retention of the restoration and reduces marginal leakage and marginal discoloration.
    • Incorporation of cavosurface bevel may enable the restoration to blend more esthetically with the coloration of the surrounding tooth structure.

    Lingual Access Steps After Enlarging the Opening

    • Create an axial wall depth of 0.2mm into the dentin/DEJ (approximately 0.75-1.25mm depth)
    • Axial wall is convex, following the external contour of the tooth.
    • Remove all remaining infected dentin, using a round bur or small spoon excavator.
    • Remove friable enamel at the margins.
    • If necessary, prepare retention [grooves or coves), prepare it along the gingivaxial line angle, and sometimes at the incisoaxial line angle 25 mm with a round bur.

    Modified Class III

    • Most used type of cavity preparation
    • Indicated for small and moderate lesions or faults.
    • Designed to be as conservative as possible.
    • Preparation walls have no specific shapes or forms other than an external angle of 90 or more degrees
    • Preparation design appears to be scooped or concave

    Class IV Restoration

    • Class VI: Caries affecting cusp tips of molars, premolars, and
    • Occlusal factors may dictate a more conventional tooth preparation form, with more resistance form features and secondary, resistance form features.
    • Proper shade selection may be more difficult for large Class IV restorations that don't have normal dentin color.
    • Prewedging before tooth preparation would benefit the effort to restore the proximal contact.
    • For large class IV lesions or fractures, a preoperative impression may be taken to be used as a template for developing the restoration contours.
    • In addition to the etched enamel margin, retention of the composite restorative material in this type of tooth preparation may be obtained by:
      • Groove or other shaped undercuts
      • Dovetail extensions
      • Threaded pins
      • Combination of these

    Types of Class IV Preparations

    • Conventional Class IV
    • Beveled Conventional Class IV
    • Modified Class IV

    Conventional Class IV

    • Has few indications except for any portion of the restoration extending onto the root.
    • Designed with 90 - degree cavosurface margin and requires groove retention form when extended onto the root

    Beveled Conventional Class IV

    • For restoring large proximal areas that also include the incisal surface of an anterior tooth.
    • Gingival and incisal retentive undercuts may be indicated.
    • In large class IV preparations similar to the undercuts used in the class III preparations are placed in which rounded undercuts are placed in the dentin along line angles and into point angles where ever possible.
    • An arbitrary dovetail extension onto the lingual surface of the tooth may enhance the restoration's strength and retention, but it is less conservative and not used often.

    Pin Retention

    • Pin retention is sometimes necessary but is discouraged for some reasons:
      • Placement of pins in anterior teeth involves the risk of perforation either into the pulp or through the external surface.
      • Some pins may corrode because of microleakage of the restoration, resulting in significant discoloration of the tooth and restoration.
    • despite these disadvantages, when a large amount of tooth structure is missing, pin retention may be necessary to retain the composite restoration.
      • Characterized by an outline form that occurs when the preparation walls are prepared as much as possible perpendicular or parallel to the long axis of the tooth.
      • Which results to a design that provides greater resistance to biting forces that could cause fracture of the tooth or restorative material.
      • Done by using an appropriate size of round carbide bur or diamond instrument at high speed with air - water coolant.
      • Objective is to remove as little tooth structure as possible, all weakened enamel is removed and initial axial wall depth is established at.5mm into dentin. Excavate any remaining infected dentin.
      • If necessary, a Ca OH liner and RMGI base are applied, bevel is prepared.
      • Placement of retention form which is primarily provided by micromechanical bonding of the composite to the tooth structures.
      • Additional retention may be obtained by increasing the width of the enamel bevels or placing retention undercuts, if this is necessary, gingival retention groove is prepared using a No.
      • 14 round bur, prepared.2mm inside the DEJ at a depth of.25 mm.at an angle bisecting the junction of the axial wall and gingival wall.
      • Sometimes, preparation of groove retention form
      • Prepared with No.¼ bur along the full length10-11/23 gingivoaxial and incisoaxial(occlusoaxial) he angle with.25 mm.in depth into the external walls and next to the axial wall at an angle that bisects the junction between the axial wall and gingival or incisal wall.
      • This should leave between the groove and the margin, sufficient remaining wall dimension of.25 mm to prevent fracture.
      • While preparing the grooves it should be observed that the remaining wall dimension is equal to the half diameter of the bur head, 0.5 mm.
      • The preparation is then cleaned, if indicated and inspected for approval.

    Modified Class IV

    • For small or moderate Class IV lesions or traumatic defects.
    • Objective is to remove as little tooth structure as possible, while removing the fault and providing for appropriate retention and resistance forms.
    • An appropriate size round bur or diamond instrument is used at high speed with air - water coolant.
    • If necessary, a Ca OH liner and RMGI base are applied, bevel is prepared.
    • Placement of retention form which is primarily provided by micromechanical bonding of the composite to the tooth structures.
    • Additional retention may be obtained by increasing the width of the enamel bevels or placing retention undercuts, if this is necessary, gingival retention groove is prepared using a No.
    • 14 round bur, prepared.2mm inside the DEJ at a depth of.25 mm.at an angle bisecting the junction of the axial wall and gingival wall.
    • Sometimes, preparation of groove retention form
      • Prepared with No.¼ bur along the full length10-11/23 gingivoaxial and incisoaxial(occlusoaxial) he angle with.25 mm.in depth into the external walls and next to the axial wall at an angle that bisects the junction between the axial wall and gingival or incisal wall.
      • This should leave between the groove and the margin, sufficient remaining wall dimension of.25 mm to prevent fracture.
      • While preparing the grooves it should be observed that the remaining wall dimension is equal to the half diameter of the bur head, 0.5 mm.
      • The preparation is then cleaned, if indicated and inspected for approval.

    Conventional Class IV

    • For portion of carious lesion or defect entirely or partially on facial or lingual root surface of a tooth.
    • A tapered fissure carbide (700, 701 or 271) or similarly shaped diamond is used at high speed with air water spray.
    • If access interproximally or gingivally is limited, a no. 1 or 2 round bur or diamond may be used to prepare the tooth.
    • With tapered fissure bur, entry is made at 45- degree angle to the tooth surface by tilting the handpiece distally.
    • As cutting progresses distally, one maneuvers the handpiece in such a manner that the bur's long axis is perpendicular to the external surface of the tooth during preparation of the outline form which should result in 90 - degree cavosurface margins.

    Beveled Conventional Class IV

    • Initial preparation should have axial depth of.75mm.
    • Any infected dentin retained in the initial axial wall is removed during the final stage of the tooth preparation.
    • Has beveled enamel margins and indicated for replacement of an existing, defective class V restoration that initially used a conventional preparation or for a large new carious lesion.
    • A.75 mm. axial depth is initially placed and the final preparation is cleaned, inspected, and prepared as outlined above.

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