Posterior_Direct_Restorations Salvatore_compressed
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PHOTOGRAPH BY STANISLAV GERANIN, POLTAVA, UKRAINE.
5
Cavity Preparation
Principles of Cavity Preparation
Cavity preparation, the procedure used to remove demineralized enamel and infected dentin consists of four steps:
1.Opening a cavity or removing a poorly fitting restoration
2.Removing infected dentin
3.Evaluating residual tooth tissue and removing unsupported or structurally compromised enamel
4.Finishing cavity margins
The extent of preparation always depends on clinical and radiographic analysis of the caries lesion (Table 5-1). The clinician will shape the cavity based on the extent of the lesion and in keeping with the principle of minimal invasiveness. This chapter discusses the various levels of tooth preparation according to the type of caries lesion and patient risk level.
TABLE 5-1 Treatment options based on the initial clinical situation
Clinical situation |
Therapeutic options |
|
|
Unpronounced occlusal anatomy, no active |
No treatment |
lesions, good oral hygiene |
|
|
|
Very pronounced occlusal anatomy, no active |
None for adults |
lesions, good oral hygiene |
Sealing if the patient is young2 |
Pronounced occlusal anatomy with suspect |
Ultraconservative opening of grooves for |
grooves in patients at risk (eg, pigmented, |
diagnostic purposes (preventive resin |
discolored grooves) |
restoration [PRR]) |
|
In the absence of caries: |
|
restoration/sealant |
|
If caries present: Class 1 restoration |
|
|
Small, medium, and large occlusal caries |
Class 1 restoration |
lesions |
|
|
|
Areas of interproximal demineralization |
Remineralizing maneuvers and aids |
|
Infiltration method (only in strict |
|
accordance with guidelines) |
|
Class 2 restoration with direct access, |
|
preserving the marginal ridge |
|
Class 3 restoration with removal of |
|
marginal ridge |
|
|
This chapter would have looked very different before the advent of dental bonding.1 The principles of tooth preparation for direct bonded restorations have evolved because of increased knowledge and application of caries prevention as well as dental bonding and the improved mechanical performance of contemporary bonding materials. Nowadays, the principles of cavity preparation are simpler than in the past. The requirements are as follows:
Removing carious dental tissue
Removing unsupported healthy tooth to prevent its mechanical breakdown during function
Preparing space required for the restoration material, respecting the dental structural requirements and minimum thicknesses for the material in question
With the phasing out of amalgam and gold preparations, the following concepts have disappeared:
Extending preparations into healthy adjacent grooves
Accessory mechanical retention areas (swallowtails, dovetails, etc)
Occlusal convergence 
Using retention pins
Dental bonding has changed the preparation and restoration of small,
medium, and large caries-related cavities and assumed a fundamental role in treatments on the borderline between primary and secondary prevention: minimally invasive seals and tooth preparations.
The level of destructiveness involved in treatment depends on the initial clinical situation2 (see Table 5-1). A relatively unpronounced occlusal anatomy without any diagnostic problems does not require any type of treatment. Clinical case management becomes more complicated if grooves are more pronounced. No treatment will be performed in a patient without active lesions, while it will be prudent to perform minimally invasive treatment if the individual has a medium or high risk profile.3
Types of Grooves
The anatomy of molar and premolar occlusal surfaces is highly variable in terms of groove and pit depth. The enamel anatomy can be more or less pronounced and more or less complete, and this can generate grooves and fissures that are particularly subject to caries. Arhatari et al4 used microcomputed tomography (microCT) to show how deep and variable grooves and pit anatomy can be (Fig 5-1). Longitudinal sections through teeth show variable anatomies (open and closed V-shaped, dropshaped, I-shaped; Fig 5-2).
FIG 5-1 Result of 3D microCT reconstruction of the pits and fissures of a molar. Note the extreme depth, steepness, and small size. The base of these pits inevitably lies close to the dentinoenamel junction (DEJ), which predisposes the patient to rapid development of caries if they are damaged. (Courtesy of Benedicta D. Arhatari, ARC Centre of Excellence in Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe University, Victoria, Australia, and Maurice White, Supertooth NDK, Victoria, Australia.)
FIG 5-2 (a) Open V-shaped groove. (b) Closed V-shaped groove. (c) Drop-shaped groove.
(d) I-shaped groove
Under anatomical conditions favoring plaque accumulation and where the enamel on the base of the groove is thin, any newly established caries activity would lead to sudden spread of the caries lesion. It is therefore imperative to be able to effectively evaluate groove types (Fig 5-3).
FIG 5-3 (a to h) Different types of grooves with varying depths, prognoses, and extent of demineralization.