Posterior_Direct_Restorations Salvatore_compressed

Groove evaluation

The essential premise for reliable groove evaluation is that the tooth surface should be clean and accurately observable. After careful cleaning using a high-pressure glycine spray, it is always advisable to observe the grooves using magnifying systems. The possibility of diagnostic error must be considered.5

Magnification systems are an aid for more detailed diagnostic evaluation of grooves. Galilean and prismatic lenses are most commonly used in routine dentistry, but microscopy can be used when the diagnosis is problematic. Once the occlusal surface has been thoroughly analyzed in relation to the patient’s risk rating, it will be possible to decide whether to do nothing, carry out sealing, perform a preventive resin restoration (PRR), or apply a direct bonded restoration (see Table 5-1).

Sealing

Sealing is a preventive procedure to prevent caries lesion formation in deep occlusal surfaces that are difficult to clean. It can reduce caries lesions by up to 51%.2 Filling difficult-to-clean surfaces improves oral hygiene procedures and prevents bacteria proliferating in their ideal habitat.

One of the biggest concerns raised about sealing is the possibility that active caries lesions might be covered. Although there are conflicting views about deliberate sealing of active caries lesions, it has been shown that it is difficult for sealed lesions to grow.6 These findings are reassuring when a practitioner decides to carry out sealing in accordance with the parameters set out in Table 5-1, because sealing could stop the development of an (albeit minimal) early caries lesion that was not identified during clinical evaluation.

The step-by-step procedure for sealing involves:

1.Thorough cleaning of grooves using glycine spray.

2.Removal of aprismatic enamel—which has been shown to be resistant to orthophosphoric acid, leading to an unreliable adhesive bond and loss of sealant.7–9 Preparation must not be aggressive and can be

done with air abrasion, fissurotomy burs, or very small-diameter burs.10

3.A total-etch bonding procedure (37% orthophosphoric acid and bonding system).

4.Light-curing sealant.

Minimally Invasive Cavity Preparation

As shown in Table 5-1, a minimally invasive cavity will be made for exploratory purposes if the grooves are suspect. This minimally invasive procedure involves an exploratory preparation to dispel doubt about grooves that are difficult to diagnose. After cleaning the grooves, they are opened to no more than 1 mm to allow direct assessment of tooth tissue quality. If the cavity is negative, ie, without caries, the exploratory cavity can be sealed (type I PRR)11–13; otherwise, it may be decided to proceed beyond the DEJ and carry out a type III PRR (using restoration material and sealant) or a true Class 1 restoration.

A cavity is negative even when it is pigmented with a black line but cannot be probed by a dental probe. The clinical case described in Fig 5- 4 shows the approach used for an occlusal surface characterized by grooves affected or not by initial demineralization processes with more or less pronounced cavitation.

FIG 5-4 (a) Initial clinical situation. Some grooves are evidently cavitated but others are less clear. (b) The grooves are thoroughly cleaned with a glycine jet and inspected with magnification. (c) Suspect grooves are opened using a very fine flame bur (ie, size 005 or 007) to a depth of no more than 1 mm. (d) Minimal opening shows that some grooves are unaffected by caries while others display caries activity. (e) Minimally invasive Class I cavities are prepared.

Handpieces

There are essentially two types of handpieces used to prepare and finish cavities: a multiplier handpiece (Fig 5-5a) fitted with high-speed burs and a contra-angle handpiece (Fig 5-5b) fitted with low-speed burs. The highspeed turbine allows very high speeds but limited control, so is not recommended as a tool for preparation or for finishing and polishing. Two other useful handpieces are oscillating/reciprocating (Fig 5-5c) and sonic (Fig 5-5d). The nonrotary action of the latter allows certain movements that facilitate cavity preparation and finishing procedures.

FIG 5-5 (a) The multiplier handpiece uses friction-grip (FG) burs and operates at a speed that is a multiple of the contra-angle (generally five times). This is fast enough for diamond burs (to cut the enamel), while the electric motor simultaneously provides great control. The use of a high-speed turbine is not recommended because it does not allow enough control.

(b) The contra-angle (CA) handpiece is fitted with CA burs. It is used with tungsten carbide rosehead burs to remove infected dentin. Rubber and other tips are then used for finishing and polishing. (c) The oscillating handpiece (also referred to as a reciprocating handpiece) moves a diamond file (with one or both working sides) along a single axis to drill a wall in tight spaces. This is an excellent system for modifying a Class 2 cavity in a mesiodistal

direction, removing, for example, horizontal overcontours on a restoration. (d) The sonic handpiece allows high-frequency movement of the diamond inserts, which drill the hard tissue in a selective, conservative manner.

Burs

Figure 5-6 shows a selection of preparation burs for conservative direct restoration of posterior teeth. Although sonic or oscillating tips are sometimes used, those described in Fig 5-6 comprise an essential set to manage almost all cavity preparations in posterior sectors. Note that FG indicates friction grip (high-speed bur, for multiplier handpiece) and CA indicates contra-angle (burs for a contra-angle handpiece).

FIG 5-6 Essential burs. (a) Very small-diameter flame bur (FG; 006–008): used for conservative opening of suspect grooves. (b) Cylindric bur with rounded head (FG; 007– 0014): used for most Class 1 and 2 cavity preparations. (c) Tungsten carbide rosehead bur (CA; 010–020): used to remove infected dentin. (d) End-cutting bur (FG; 012): used to define and finish a cervical step in Class 2 preparations. (e) Fine-grained flame bur (FG; 010): used to finish Class 2 box walls. (f) Arkansas stone (FG): used to smooth the cavity margin. (g) Brownie polisher (CA): used to polish the cavity margin.

Occlusal Cavities (Class 1)

Occlusal cavities (historically defined by Black as Class 1 in terms of topography and treatment type) are the only cavities related to grooves and fissures. All the other classes relate to caries activity on smooth surfaces. This also involves a different caries lesion configuration and propagation rate compared, for example, to interproximal caries lesions. The classic caries lesion topography is a triangle with its tip at the external surface and base at the DEJ. In interproximal caries lesions, however, the external surface is larger, and progression toward the DEJ is slower (ie, triangular topography with base on the external surface and

tip pointing toward the DEJ). As mentioned at the beginning of the chapter, dental preparation aims to remove both caries lesions and undercuts in the cavity, evaluate residual structural factors, and provide restorative material in the necessary thickness.

Essentially two types of burs are used to prepare the cavity:

Diamond cylindric burs with rounded head for a multiplier handpiece (see Figs 5-6a and 5-6b)

Tungsten carbide multiblade round burs for a contra-angle handpiece (see Fig 5-6c)

“THE EXTENT OF PREPARATION ALWAYS DEPENDS ON CLINICAL AND RADIOGRAPHIC ANALYSIS OF CARIES ACTIVITY AND MUST ALWAYS OBSERVE THE PRINCIPLE OF MINIMAL INVASIVENESS.”

The cavity margin is then finished and polished with fine-grained or multibladed burs, stones, or polishers (see Figs 5-6f and 5-6g).

Step-by-step Class 1 preparation

Class 1 preparation (Fig 5-7) follows very specific criteria whether used for treating established caries lesions, reconstruction, or a PRR. As already mentioned, even if the caries lesion is exclusively occlusal, it is advisable to isolate by quadrant (see Fig 5-7a) in order to: