CAVITY PREPARATION IN PRIMARY TEETHDr. Masar Mohammed
INTRODUCTION BASIC PRINCIPLES IN THE PREPARATION OF CAVITIES IN PRIMARY TEETH CLASS I CAVITIES CLASS II CAVITIES CLASS III CAVITIES CLASS IV CAVITIES CLASS V CAVITIES RECENT CONCEPTS IN RESTORATIVE DENTISTRY
Operative dentistry: Is the art and science of the diagnosis, treatment and prognosis of defects of teeth that do not require full coverage restorations for correction.The aim of pediatric operative dentistry is to maintain the tooth in the dental arch in a healthy state, so as to prevent its loss and the subsequent problems that will result.
Main reasons to control caries in primaryDentition Prevent pain and discomfort. Prevent local infections. Prevent general infections Prevent negative attitudes and promote keeping good oral health Maintenance good mastication, aesthetic and overall well-being Prevent caries in permanent teeth Prevent malocclusion.
ANATOMIC CONSIDERATIONS OFPRIMARY TEETH1. Shorter crown.2. Thinner enamel and dentin.3. Larger pulp and higherpulp horns.4. Enamel rods in cervicalarea directed occlusally.5. Greater cervical constriction.6. Broad, flat proximal contacts.7. Narrow occlusal table.8. Lighter in color.
Prevention is the cornerstone of good management of dental caries in children History taking is fundamental to the execution of restorative care in the primary and mixed dentition. Communication skills are essential in obtaining a child’s co-operation in completing treatment.
In the restoration of primary teeth, we should consider the following factors: The child: age, physical condition, and cooperation among others. Caries degree. Degree of radicular reabsorption of the tooth. Condition of the bone support. Dental material
BASIC PRINCIPLES IN THE PREPARATION OF CAVITIES IN PRIMARY TEETH.The steps in the preparation of a cavity in a primary tooth are not difficult but do require precise operator control
Many authorities advocate the use ofsmall, rounded-end carbide burs in thehigh-speed handpiece for establishing thecavity outline and performing the grosspreparation.they are designed to cut efficiently and yetallow conservative cavity preparationswith rounded line angles and point angles.
The Black’s principles with some modification are basic principles in the preparation of the cavities in the primary teeth. There are three operative steps with the use of the high-speed handpiece:
Opening and conformation of the cavity with the use of the high-speed handpiece. Eliminating the caries of the buccal, lingual, mesial and distal walls with the use of the high-speed handpiece. Eliminate the caries of the pulpal wall with the use of the lower- speed handpiece. The third step will include dentine sterilization and the cement base.
CLASS I CAVITIES Incipient carious lesion in child under 2 years old should be eliminated. Small cavity preparation may be made with a No.329 or No. 330 pear-shaped bur. We should open the decayed area and extend the cavosurface margin only to the extent of the carious lesion. The preparation can be completed in a few seconds.
The outline form should include all pits, fissures and grooves into which a sharp explorer can penetrate.
The pulpal floor should be flat or slightly concave throughout to allow for greater depth of the filling material, for better distribution of stress in the restoration and to avoid endangering the high pulpal horns. The depth of pulpal floor should be established just beneath the dentinoenamel junction (0.5 mm) to avoid pulp exposure.
All the internal line angles should be rounded. The side walls should slightly converge towards occlusal so that the preparation will follow the outer form of the crown. Beside the regular class I cavity preparations done in primary molars, occlusal spot preparations have been recommended.
In such preparations only the carious pits or groove is prepared and the tooth is restored in the usual manner. These preparations are applicable in any of the primary molars with exception of the lower second primary molars in which extension for prevention including all deep pits and fissures is recommended above all, if the child has high caries index
cavity should be covered with calcium hydroxide . A base of polycarboxlate, glass ionomer or rapid-setting zinc-oxide-eugenol cement may then be placed over the calcium hydroxide material to provide adequate thermal pulp protection.
Do not cross the oblique ridge in the upper second primary or first permanent molars and the transverse ridge of the lower first primary molar unless they are undermined with caries. These heavy ridges add support to the tooth.
CLASS II CAVITIES. These preparations include an occlusal, an isthmus and proximal portion. The outline form of the occlusal step should be dovetail-shaped including all carious pits, fissures, and developmental grooves.
The side walls of the occlusal step should converge from the pulpal wall to the occlusal surface. The pulpal floor should be established just beneath the dentinoenamel junction.
Angles between the side walls and the pulpal floor should be gently rounded. The width of the isthmus should be approximately one-third of the intercuspal dimension of the tooth.
The axio-pulpal line angle should be beveled to reduce the concentration of stresses and provide grater bulk of material in the isthmus area, which is liable to fracture
The greater constriction of primary teeth increases the danger of damaging the interproximal soft tissues during cavity preparation. Extreme care must be taken when breaking through the marginal ridge to prevent damage to the adjacent proximal surface, especially when the bur is revolving at high speed.
The proximal box line angles and walls should converge towards the occlusal. When viewed from the occlusal aspect the resulting axial wall should follow the outline of the original proximal surface.
An axiobuccal and axiolingual retentive groove may be included in the preparation.
The bur is used in a pendulum-swinging fashion to undermine the marginal ridge and at the same time to establish the gingival depth. The gingival seat should be of sufficient depth to break contact with the adjacent tooth. A liner or intermediate base should be placed before the insertion of the silver amalgam.
The amalgam restoration in the Class II cavity needs the use of a matrix retainer. The matrix should be rigid enough to allow adequate packing pressure, ensuring a well-condensed restoration free from an excess of residual mercury.
If the primary molars have an extensive carious lesions, especially first primary molars, should be used a stainless steel crowns, above all, in the first primary molar of a 3 years old child
Indications for use Stainless Steel Crown Restoration of primary molars requiring large multisurface restoration. Restorations in disabled persons or others in whom oral hygienic is extremely poor and failure of other materials is likely.
Restorations of teeth in children with rampant caries.
CLASS III CAVITIES Carious lesions on the proximal surfaces of anterior primary teeth sometimes occur in children whose teeth are in contact and in those children who have evidence of arch inadequacy or crowding. If caries is not extensive, disking by sand paper disc is performed to remove the decay, and then fluoride is applied topically
If the carious lesion not involves the incisal angle, a small conventional Class III cavity may be prepared and the tooth may be restored with glass ionomer or composite resin.
The same basic principles for permanent anterior teeth should be considered in a primary teeth, modified, of course, by the size of the pulp and the relative thinness of the enamel. If it is necessary we modify the Class III cavities with the use of dovetail on the lingual or occasionally on the labial surface of the tooth.
Because of the narrow labiolingual width of the primary incisor teeth, the Class III preparation is very difficult to perform and often needs a labial or lingual dovetail to gain access and aid in retention of the restoration.
The distal surface of the primary canine is a frequent site of caries attack
CLASS IV CAVITIES In these cavities caries involves the incisal proximal angle of the anterior teeth. The principles in the cavity preparation are the same of the cavity preparation in permanent teeth
In regular class IV cavity preparations, composite resin material can be used for restoration.
CLASS V CAVITIES The Class V cavities are realized more frequently in buccal surface of the primary canines. The principles in the cavity preparation are the same of the cavity preparation in permanent teeth, although the depth is not carried more than 1.5 mm.
Walls of preparation converge toward buccal surface of tooth for retention of restoration. When a necessary, retentive groove can be placed along the gingivoaxial and occlusoaxial line angles. Use a No. 1/2 round bur at slow speed. Glass ionomer cement could be used effectively for restoring these cavities.
Pit and fissure sealant is a thin, plastic coating painted on the chewing surfaces of teeth -- usually the back teeth (the premolars and molars) -- to prevent tooth decay. The sealant quickly bonds into the depressions and grooves of the teeth forming a protective shield over the enamel of each tooth.
Indicaations of sealant placement:1. Deep retintive pits and fissures.2. Stained pits and fissures with minmum decalcification.3. No radiographic evidence of proximal caries.4. Factores associated with increased caries incidence.
5. Caries free.6. Possibility of adequate isolation. How Are Sealants Applied?