D262Division of Orthodontic & Paediatric Dentistry University of Western Ontario Dr. Sahza Hatibovic-Kofman
PRIMARY DENTITION ANATOMY AND CAVITY PREPARATION 2004-2005
GENERAL OBJECTIVES: To present the anatomy of primary teeth and key anatomical differences
between primary and permanent teeththat influence cavity preparation.
SPECIFIC OBJECTIVES:(1) Describe the general morphological differences between primary and permanent teeth and their clinical implications. Identify special features and location of the roots of primary teeth. Comment on clinical applications. Describe the general morphology of the dental pulp, location of the pulp horns and orifices of canals in the primary teeth. Comment on clinical considerations.
Specific Objectives (continued):(4) Identify histological differences between the pulp of primary and permanent teeth and the clinical relevance. Identify the reason for most restorative problems in paediatric dentistry. Describe the principles of operative dentistry. Describe the steps for preparation and restoration of Class I and Class II amalgam restorations.
(5) (6) (7)
Specific Objectives (continued):(8)(9)
Describe common errors in Class I and II restorations. Describe the differences in cavity preparation when composite is used as a restorative material for primary teeth.
Most problems in paediatric dentistry occur because of
failure to prepare and restore the teeth in a way that takes into account their: ANATOMIC or MORPHOLOGIC structural characteristics and limitations.
ANATOMIC CONSIDERATIONS OF PRIMARY TEETH1.2.
Crowns of primary teeth are smaller, and more bulbous than permanent teeth.Both lingual and buccal walls of the primary teeth taper occlusally, therefore the occlusal surface is quite narrow. Primary teeth demonstrate greater cervical constriction and have more prominent cervical enamel contour than permanent teeth.
Anatomic considerations (continued)4. 5. Primary teeth have thinner enamel and dentin than permanent teeth. The pulp of primary teeth are larger in relation to the crown than permanent teeth. The pulp horns of primary teeth are closer to the outer surface of the tooth than for permanent teeth.
The MESIOBUCCAL pulp horn is the most prominent.
Anatomic considerations (continued)6. 7. 8. Fine canals. Thin pulpal floor. The roots of primary teeth are long, slender and curved. Interradicular space can accommodate the developing permanent tooth. In primary teeth the enamel rods of the gingival third of the crown extend in an occlusal direction. The rods of the permanent teeth extend in a cervical direction.
Anatomic considerations (continued)10.11.
Primary teeth have broad, flat proximal contact areas. Primary teeth are whiter in colour than their permanent successors.
PRINCIPLES OF OPERATIVE DENTISTRYGain access.Establish outline form Eliminate caries. Establish resistance and retention form. Refinement and debridement of the cavity.
RESTORATIVE TRAY - SPEC1. 2. 3. 4. 5. 6. 7. 8. Mirror Explorer Cotton pliers Small spoon Large spoon Hatchet Small condensor Large condensor
Restorative Tray (continued)9. 10. 11. 12. 13. 14. T-3 (Beaver tail) Discoid-cleoid Burnisher G-38 (gold knife) PFI (black felt) Syringe
INFORMATIONIn order to provide the best care for the child patient and teach excellence, we, at the childrens clinic, have decided to use toothcoloured materials and stainless steel crowns as a first choice of treatments. Occasionally other materials will be used according to the medical indications and/or child/guardian demand.
Montreal, November 27, 2000It was very refreshing for us, as clinicians, to hear from a university professor that the University of Western Ontario actually teaches dental materials and techniques that are up-to-date, in order to prepare the students to
the challenges of everyday clinical dental pediatricpractice. J. Victor Legault Quebec Assoc. of Pediatric Dentists
Information (continued)Currently, there are four conventional and two hybrid restorative materials available for the restorations in primary teeth. Conventional materials: 1. 2. 3. 4. Stainless steel crowns (SSC). Amalgam. Composite resin. Glass ionomer cement (GIC).
Information (continued)Hybrids:1. Resin-modified glass ionomer cement (RMGIC). 2. Polyacid-modified resin composite materials (PMRC), compomer.
Information (continued)The restorative material for primary teeth should possess the following properties: be biocompatible join a strong adhesive bond to reminded tooth strengthen residual tooth structure easy handling characteristic be economical
Information (continued)Amalgam is good material and has been used successfully for about 200 years, but tooth coloured materials accompanied with the bonding systems offer advantages over dental amalgam in: Preservation of healthy tooth structure. Today literally we can restore a tooth by removing only decayed structure. To accommodate amalgam a lot of healthy tooth structure has to be removed to provide mechanical retention of the restoration.
Information (continued) Repairability. Esthetics. Release of fluoride. Our students are performing high quality care for the child patient and will be using the most current tooth-coloured materials.
GUIDELINES for Usage of theRestorative Materials in Mixed DentitionFirst step in restorative dentistry is to perform good caries diagnosis and elimination of the lesion.
Under diagnosis = misdiagnoses.In the SPEC clinic after visual diagnosis, we will use regularly light caries detector DIAGNOdent and/or dye caries detector Seek and Sable.
STATE OF THE TOOTH Caries free primary and permanent teeth Small decalcification
TREATMENT Pit and fissure sealants
Bur preparation or air abrasion - pit and fissure sealants Cavity preparation, and use caries seek and restore it with composite
Small lesion in dentin occlusally
STATE OF THE TOOTH MO or DO
TREATMENT Conservative preparation without extensions for prevention and use combination of flowable and filled composite. Conservative cavity preparation and glass ionomer cement.
DO or MO next to permanent tooth if exfoliation will occur within two years.
Guidelines (continued) Multi surface lesions and teeth after pulp therapy will be restored with stainless steel crown (SSC).
STEPS FOR PREPARATION AND RESTORATION OF CLASS I AMALGAM RESTORATIONS Administer appropriate anaesthesia and place the rubber dam. Using a No. 330 bur gain access and penetrate into the tooth to a depth of 0.5 mm into dentin. Removal all carious dentin by using large, round bur. Provide retention and resistance by making cavity surface parallel with its external surface.
Steps Class I (continued) Smooth the enamel walls and refine the final outline form with No. 330 bur. Place pulp protection as needed. Place and condense amalgam. Carve amalgam. Burnish the carved amalgam when it has begun its initial set and resists deformation. Remove the rubber dam and check the occlusion.
COMMON ERRORS WITH CLASS I AMALGAM RESTORATIONS Not including all susceptible fissures. Preparing the cavity too deep. Undercutting the marginal ridges. Carving the anatomy of the amalgam too deep. Not removing the amalgam flash from the cavosurface margins. Undercarving, which leads to fracture of the amalgam from hyperocclusion.
STEPS FOR PREPARATION AND RESTORATION OF CLASS II AMALGAM RESTORATIONS Administer appropriate anaesthesia and place the rubber dam. Place a wooden wedge in the in interproximal area. With No. 330 bur in the high speed turbine handpiece, prepare the occlusal outline form at the ideal depth.
Steps Class II (continued) To prepare the proximal box, use the same bur moving it buccolingually in a pendulum motion and in a gingival direction. The contact should be broken between the adjacent tooth gingivally, buccally and lingually. Remove any remaining caries. Round axiopulpal line angle. Remove any unsupported enamel off the buccal, lingual and gingival walls.
Steps Class II (continued) Place pulp protection if necessary. Remove the wedge, place a matrix band, and reinsert the wedge. Condense amalgam. Carving of the occlusal portion is performed with a small carver. The marginal ridge can be carved with the tip of the explorer. Remove the wedge and the matrix. Gently floss the interproximal contact. Burnish the restoration. Remove the rubber dam and check occlusion.
PROCEDURE OF CLASS II CAVITY PREPARATION FOR COMPOSITE RESTORATION1. A local anaesthetic will be administered in the usual fashion and in the appropriate amount to ensure adequate anaesthesia during the procedures. A rubber dam will be used routinely. Wooden wedges will be inserted in the proximal areas to maximize the protection of gingiva and the adjacent tooth, and protection from tearing the rubber dam by bur.
Procedure Class II(continued)4. The outline form of the cavity preparations will be conservative as presented in the picture. No flaring buccal and lingual walls of the proximal box. Caries has to be completely removed, please use seek and sable. The line angles will be rounded slightly, but the cavity will not be extended for prevention. Do not remove healthy and unsupported enamel.
5. 6. 7.
Procedure Class II(continued)9. 10. Rinse the cavity. A cure-thru celluloid matrix band or onmi-paedo matrix will be inserted firmly into place. Acid etch the cavity for 25 seconds. Rinse it for 20 seconds. Rub in one bottle bonding system, air dry and cure for 10 seconds. Apply flavable composite on the edges cure it.