5: Intracoronal Restorations for Posterior Primary Teeth

Chapter 5

Intracoronal Restorations for Posterior Primary Teeth

Aims

The aim of this chapter is to discuss the intracoronal restoration of carious primary teeth. In addition, the clinical relevance of the anatomical differences between the primary and permanent dentitions are highlighted.

Outcome

After reading this chapter, the practitioner should feel able to perform modern operative approaches to caries removal and intracoronal restoration of primary molar teeth and understand how these relate to the morphology of primary molars.

Introduction

Parents and dentists alike are keen to avoid the spectre of toothache in a child. Primary teeth have a key role to play in the future development of both occlusal development and in the acceptance of the child by their peers. The anatomical form of primary teeth, especially primary molars, means that caries can cause changes in the pulp faster than in permanent teeth. Fortunately the restorative techniques are simpler compared to permanent teeth and profit from primary tooth morphology.

Anatomy

The anatomical differences between primary and permanent teeth are illustrated in Fig 5-1. Compared to a permanent tooth, the anatomy of a primary tooth can be summarised as follows:

  • The enamel is thin, lighter in colour and easier to cut with a bur compared with enamel of permanent teeth.

  • The crown is bulbous, especially towards the cervical area.

  • There is a marked cervical constriction apical to the cervical bulge.

  • In molars, the occlusal table is narrow in a buccolingual direction.

  • The pulp horns extend high into the anatomical crown.

  • The enamel rods are inclined occlusally in the cervical region.

QE14_Hosey_fig062.jpg

Fig 5-1 The anatomy of primary teeth.

Although the principles of caries removal in primary teeth are essentially the same as those for the permanent dentition, there are some differences that are important clinically. These are summarised in Table 5-1.

Table 5-1 Clinical significance of primary toth anatomy
Crown Morphology Clinical Significance
Thinner enamel
  • Short distances for caries to penetrate

  • Small burs used

  • Pulp horns near the enamel surface

Cervical bulge with gingival constriction
  • Tendency to make floor of box too deep

  • Forced to re-establish floor by moving axial wall towards pulp

Narrow occlusal table
  • Cusps can be weakened by over-extending buccolingual dimensions

Broad contact areas located gingivally
  • Buccal and lingual walls of a box need to clear contact especially near floor of the box

Large pulp horns sited below cusps
  • Isthmus must be narrow to avoid pulp exposure

  • To reduce failure of restorative material, pulpoaxial line angle may be deepened to increase bulk of material

Gingival third of enamel prisms incline occlusally
  • No need to bevel cavosurface as enamel rods on floor of box will be supported

Indications for Restoration

A minimal restoration, placed with relative ease when the lesion has just penetrated dentine and cavitated, can avoid the need for a larger restoration or even extraction later. In this way, dental operative procedures can be kept simple and used in combination with preventive care to ensure a positive attitude to dentistry and life-long oral health.

Primary teeth are restored in order to:

  • Prevent pain and sequelae, such as irreversible pulpitis and infection.

  • Avoid extraction in certain medical conditions (e.g. bleeding disorders).

  • Avoid extractions in anxious children.

  • Preserve masticatory function.

  • Maintain an intact arch (primary dentition).

  • Provide space maintenance (mixed dentition).

  • Maintain anterior aesthetics.

Sequential Planning

For most children, a period of acclimatisation is required before embarking upon a restorative approach. Remember to use language that is appropriate to the age of the child. In the very young, access for caries removal can be improved by the use of miniature burs in a miniature handpiece. If a child has experienced caries in the primary dentition, you should consider fissure sealing the first permanent molars upon eruption.

Cavity Preparation

In general, the same principles and approach apply to the preparation of primary teeth as for the permanent dentition, but there are several factors worthy of consideration when treating dental caries in primary teeth: moisture control, the longevity of restorative materials, the extent of the caries in relation to the pulp horns and the cooperation of the child.

Moisture Control

Ideally, this should be achieved using dental dam isolation, but lack of cooperation may lead to compromise. Good moisture control can be achieved using small saliva ejectors, cotton wool rolls and dry guards (Fig 5-2).

QE14_Hosey_fig064.jpg

Fig 5-2 Equipment used to obtain moisture control (a) suction and saliva ejectors. (b) Cotton wool rolls and dry guards.

Choice of Material and Durability of Restorations

When placing a restoration in a primary tooth the dentist has to decide whether the filling is to last the lifetime of the tooth or if it is a temporary restoration that she/he expects to eventually replace. This choice is dependent on various factors, not least the expected longevity of the tooth. Nevertheless, in terms of durability the selection of materials can be summarised as follows:

  • Plastic restorations, such as amalgam, composite resins and glass ionomer cements perform best in one or two surface restorations. The glass ionomer materials have the advantage of directly adhering to tooth structure. They also release fluoride, although the clinical significance of this is unproven.

  • The newer resin-modified glass ionomer cements and compomers have the advantage of directly adhering to tooth tissue and a command set due to the resin component. This may be helpful when dealing with a wriggly child.

  • The more recent resin-modified glass ionomers and viscous glass ionomers have the advantages of glass ionomer but with improved strength.

  • The compomers appear to have survival rates similar to amalgam in class II cavities and have the advantage of adhering to tooth tissue via bonding agents.

  • The recommended restoration for primary molars with two or more carious surfaces is the preformed metal crown (stainless steel crown), and these restorations outperform other materials in all but the smallest of single surface restorations.

Two main factors affect the choice of material – those relating to the tooth to be restored and factors pertinent to the patient.

Tooth factors

  • The extent of the carious lesion (linked with durability).

  • The cavity shape after caries removal (e.g. method of retention, maintaining healthy tooth tissue).

Patient factors

  • Efficacy of isolation and moisture control (moisture-sensitive techniques).

  • Caries rate (temporise initially to obtain caries control).

  • Aesthetic expectations.

Caries in Primary Posterior Teeth

These can be put into the following subcategories:

  • Pit and fissure caries.

  • Approximal caries with pit and fissure caries.

  • Approximal caries without pit and fissure caries.

Useful Instruments for Caries Removal

  • Small sharp excavators.

  • Slow speed: round and flat fissure steel burs.

  • High speed: small round and straight diamond burs.

Pit and Fissure Caries

Occlusal pit and fissure caries removal is shown in Fig 5-3.

QE14_Hosey_fig066.jpg

Fig 5-3 Occlusal pit and fissure caries removal. (a) Occlusal caries into dentine. (b) Access through carious enamel to carious dentine via straight diamond or steel flat fissure bur. (c) Caries removal leaving unsupported enamel, which should be removed. (d) Outline of cavity with a flat, slightly concave floor and walls diverging from the occlusal to provide retention for amalgam. (e) Outline is smooth without sharp angles and extends to include carious tissue only.

Access

  • Penetrate the occlusal surface within the carious area just into dentine (to a depth of 1.5mm x 0.5mm into d/>

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Jan 17, 2015 | Posted by in Pedodontics | Comments Off on 5: Intracoronal Restorations for Posterior Primary Teeth
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