Pedodontics…


- Morphology of Primary Teeth

- Isolation techniques

- Cavity preparation for Amalgam, class I

Morphology of Primary Teeth

Objectives:

-Identify and distinguish morphologic differences in primary teeth.

-Apply the knowledge of morphology in clinical procedures for children

Primary Dentition

  • 20 primary teeth as compared to 32 permanent teeth
  • No premolars in the primary dentition
  • The primary molars are replaced by the premolars
  • The permanent molars erupt distal to the primary second molars

General Morphologic considerations

  • Crown
  • Root
  • Pulp

I-Size & Color

  • Smaller
  • MD width of ant. Primary < ant. Permanent teeth
  • MD width of Primary molars > Permanent premolars
  • Bluish-white (Primary) vs grayish-white or yellowish-white (Permanent)

II-Crown

  • Crown form ( MD > OG )

Anterior = cup posterior = square

  • Bulbous crown: Steep Cervical constriction /Prominent cervical bulge

[ G. floor – Matrix type ].

  • Narrow occlusal table: Convergence of buccal & lingual walls.
  • Contact area in primary border, flatter and more gingival

Primary

  • Thin Enamel

Clinical significance: IMP

  1. Early diagnosis of caries
  2. Bur size (recommended bur is no 330 pear shaped )
  3. Sufficient bulk of restoration
  • Enamel rods incline occlusally vs horizontal or apical in gingival 1/3

III- Root

  • Roots are longer & more slender.
  • Crown root ratio bigger in primary teeth.
  • Roots are narrower MD than those of permanent.
  • No root trunk in primary molars
  • Roots of primary molars are widely divergent to accommodate buds of permanent premolars.

IV- Pulp

•Follows the morphology of crown

•Higher pulp horns / mesial

•Pulp chamber is larger in relation to crown size compared to permanent teeth / cavity depth

•Canals of primary molars have many lateral branches and apical ramifications

•Wide apical foramina

•Increased blood supply : typical inflammatory response

•Less nerve fibers : less sensitivity to pain

Summary

Primary teeth have

  • Thinner enamel and dentin layers
  • Pulp horns closer to the outer surface
  • Mesial pulp horn much higher
  • Relatively larger pulps
  • Enamel rods direct slightly occlusally in the cervical area
  • Cervical area is constricted significantly
  • Roots flare as they approach the apex
  • More tortuous and irregular pulp canals

During Cavity Preparation:

  • The depth of the cavity should be less.
  • The width of the cavity should also be less in a deciduous tooth.
  • Care must be taken while preparing the proximal box, as there is risk of pulp exposure at the site of constriction.
  • Care must be taken during cavity preparation, not to extend very deep as there is increased chance of pulp exposure.
  • Enamel beveling at the gingivocavo surface line angle is not required, as no enamel remain unsupported.
  • The proximal box preparation may have to be extended widely to break the contact free.

Isolation techniques

Objectives

•List the advantages and indications for use of rubber dam.

•Use the appropriate rubber dam instrumentation

and application for the child patient.

The objective of isolation is to provide

  • A dry, clean operating field.
  • Access and visibility
  • Improved propertiesof dental

materials

  • Protection of the

patient and operator

  • Improved operating

efficiently.

Different methods of isolation:

•Rubber dam

•High volume evacuator

•Absorbents

•Mouth prop

•Cotton rolls and holders

+ Saliva ejector

RUBBER DAM

•It is used to define the operating field by isolating one or more teeth from the oral environment. The dam eliminates saliva from the operating site and retracts the soft tissue.

Advantages of Rubber dam

  • Clean, dry operating field.
  • Clear access and visibility.
  • Improves properties of dental materials.
  • Protection of the patient and operator.
  • Improves operating efficiency.
  • Prevents aspiration of fluids used.
  • Prevents accidental ingestion of files/reamers.
  • Prevents injury to soft tissue such as tongue, cheek, gingival.
  • Reduced patient's conversation.

Disadvantages of Rubber dam

- Time consumption

- Patient objection

Certain conditions may preclude the use of rubber dam:

- Incompletely erupted teeth.

-Third molar isolation

-Extremely mal-positioned teeth.

-People suffering from asthma, mouth breathers.

Precautions to be taken with using Rubber Dam:

•Patient must not be a mouth breather.

•Clamps used must be tightly secured in place and a floss

thread must be tied to retrieve the clamp if ingested or aspirated.

•The dam should be checked not to cover the nostril.

•Lips should be lubricated to provide drying.

•The clamp must not impinge on the gingival nor traumatize the adjacent teeth.

Armamentarium

  • Rubber dam sheet
  • clamps
  • Rubber dam forceps
  • Rubber dam punch
  • Rubber dam template
  • Rubber dam holder frame
  • Scissor

Rubber dam material

•made of latex material :

•Size – 5 x 5 inches (Pediatric purpose)

6 x 6 inches (Adult size)

•Thickness – Thin (0.006”)

Medium (0.008”)

Heavy (0.010”)

Extra-heavy (0.012”)

Special heavy (0.014”) Color – green, blue, black, brown.

•It has a dull and bright surface.

•Thicker material resists tear

•The thinner ones pass through the tight proximal contact easily.

Clamps:

- Used to anchor the dam to the posterior

tooth to be isolated.

- Different sizes are available for different teeth.

Rubber dam forceps

Rubber dam punch

Rubber dam template

Rubber dam holder/frame

Placement of rubber dam

Steps involved are:

•Obtaining anesthesia.

•Mark the punch holes – using the template.

•Make punch holes using rubber dam punch.

•Selection of the correct clamp.

•Rubber dam placement (one of the 3 methods):

- Clamp is placed first on the tooth followed by the sheet

- The sheet is placed first followed by the clamp

- Both the clamp and the sheet are placed simultaneously (this is possible when winged clamp is being used).

Cavity preparation for Amalgam, class I

Def:

Cavity preparation is defined as the mechanical alteration of a defective, injured or disease tooth in order to best receive a restorative material which will reestablish a healthy state of the tooth including esthetic corrections where indicated, along with normal form and function.

What are class I lesions?

-Caries in occlusal pits and fissures of posterior teeth

-Caries in the occlusal two-thirds of the facial and lingual of posterior teeth

-Caries in the lingual pits of maxillary incisors

Diagnosing Class I Caries

-Softening at the base of a pit or fissure (WHO).

-Opacity surrounding the pit or

Fissure, enamel appears chalky

when dried.

-Softened enamel that may

-Brown-gray enamel

( caused by lateral spread

of caries into dentin ).

-Radiographic evidence.

INCIPIENT CLASS I CAVITY

•Small carious lesion in the central fossa of primary molars with all other teeth being sound.

•May be made without local anesthetic.

•A No. 329 or No. 330 bur is used.

•Restored with amalgam

or a resin modified glass ionomer.

•A preventive resin restoration

may be done if needed.

PIT OR FISSURE CLASS I CAVITY

Outline form

•should include all fissures, areas of caries, pits and developmental

grooves and should be dovetailed.

•Facial & lingual margins should not extend more than halfway between central groove and cusp tips(one- quarter to one- third of the intercuspal width)

•Leave marginal ridges supported by dentin.

•Keep bur perpendicular to the occlusal plane of the tooth while preparing the outline

The extension of the occlusal portion of the cavity preparation depends on the primary molar involved:

The occlusal portion usually is extended about one half the way across on the primary maxillary and mandibular first molar.

-For the primary mandibular second molar,

extend the step completely across the occlusal surface.

  • The primary maxillary second molar preparation includes

only the nearest occlucal pit.

  • The oblique ridge is not included unless undermined with

carious lesions.

Resistance form

•Proper form prevents fracture

of tooth and restoration during

function.

•Slightly rounded line angles 2.

•Enamel supported by sound dentin.

•Weak tooth structure is removed.

•Amalgam requires a thickness of at least 1.5 mm to prevent fracture of the material (0.5 mm beneath dentino enamel junction 1).

•The walls converge slightly with the greater width at the pulpal floor 3.

IMP.

Retention Form

•Correct retention form ensures that the restoration

will not dislodge due to lifting or tipping forces.

• Facial and lingual walls are parallel or slightly

convergent.

Finish of the enamel walls

The cavosurface angle 4 for amalgam restoration

should be 90-110 degrees.

This is called a butt joint.

Convenience Form

•The cavity allows operator to visualize all remaining caries and to use the proper instruments in the preparation when condensing the amalgam.

IMP.

DEEP-SEATED CLASS I CAVITY

•Plane back the enamel that overhangs the extensive lesion.

•The cavity should extend through out the remaining grooves and anatomical occlusal defects.

•The carious dentine should next be removed with large round burs or spoon excavators.

•Then , the cavity walls should be finished as previously described.

•With deep carious lesions and near pulp exposures, the depth should be covered with a biocompatible base material for adequate thermal protection of the pulp.

Lab Guidelines for Class I

•Mark pits and fissures with a sharp pencil Using a 329 or 330 bur drop to length of bur in a pit.

•Follow fissures at depth of bur.

•Place dove tails mesial and distal.

•Diverge mesial and distal walls.

•Take prep to 1.5 mm depth.

•Smooth walls and floor.

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