What is restorative dentistry?

Restorative dentistry forms a major part of the workload of general dentistry, being the branch of dentistry involved in treatment of the common dental diseases – dental caries and periodontal disease, and their sequelae, including loss of teeth. Thus the specialty of restorative dentistry includes endodontics, periodontics and prosthodontics. Prosthodontists are also sometimes called ‘conservative clinicians’.

A dental restoration (filling) is used to restore the tooth shape (morphology) and function. Restorations have to be custom-made for every patient, because each patient presents with a unique colour, shape and size of their teeth and relationship of their upper and lower jaws. Each patient also has their own unique aesthetics, depending on the colour, size and shape of their teeth, face and jaws and tone of their facial muscles.

Overview of the role of the dental nurse in restorative procedures

Before Restorative Treatment

• Retrieve case notes, radiographs, consent forms and check medical history.

• Prepare the dental environment, ensuring effective infection control.

• Prepare trolley or tray using aseptic technique.

• Greet and reassure the patient in the waiting area and be their advocate.

• Ensure pre-operative advice has been followed.

• Inform the clinician of any changes/comment from the patient.

• Assist the patient to the dental chair and make comfortable.

• Provide the patient with protective equipment (bib and glasses, Figure 9.1).

• Provide a bowl with water for dentures (if required).

FIGURE 9.1 Protective wear for patients and dental care professionals.

Dental impressions

A dental impression is an accurate representation of part or all of a person’s dentition and adjacent tissue of the mouth. A dental impression is usually made by placing an impression material into the mouth, usually in an impression tray (Figure 9.2). The impression material then sets or hardens so that, when removed from the mouth, it retains the shape of the teeth and/or mouth. It forms a ‘negative’ of a person’s teeth and adjacent soft tissues, which is then used to make a cast or model (Figure 9.3) of the dentition, usually from dental plaster. The model may be used either as a record of the person’s dentition (called a study model) or by the dental technician to make:

FIGURE 9.2 Upper and lower impression trays.

FIGURE 9.3 Upper and lower dental models.

There are several different kinds of impression materials and their properties are described in detail below and in Chapter 12. Impressions are increasingly being made using computers, the basis of CAD–CAM dentistry.

Primary and Secondary Impressions

Primary impressions, which are the initial impressions, are often taken using alginates (p. 214) in a stock impression tray (see Figure 9.4). The resulting cast is then used by the dental technician to make a special tray. Then a secondary impression is made – using a more accurate impression material such as an elastomer (p. 215) – in the special tray.

FIGURE 9.4 Items required for an alginate impression: (A) stock impression trays; (B) scoop for measuring out alginate powder; (C) water measure; (D) plastic mixing bowl with alginate powder; (E) plaster spatula; (F) wax knife; (G) mouth mirror; (H) laboratory prescription (instruction) sheet and label; (I) gauze for keeping the impressions moist; and (J) plastic bag to put the impressions in for sending to the laboratory.

Elastomeric Impression Materials (Elastomers, ‘Rubber Base’)

Elastomers give better impressions (more accurate and stable) than do alginates. There are three main types of elastomers:

• Silicone-based: The silicone base is a paste that comes packaged in tubes. The paste reacts with another material (the chemical reactor), which may be either a paste or a bottled liquid that must be stored in a cool place. This is because it deteriorates after about six months. Varying the amount of chemical reactor changes the setting time of the elastomer. There are two types of silicone impression material depending on the chemical reactor: addition cured (the accuracy of these is very good) and condensation cured.

• Polysulphide: The polysulphide base and its chemical reactor are both provided as pastes packaged in separate tubes. Polysulphide impressions do not require special storage and can be stored indefinitely. Increased relative humidity and temperature shorten both setting and mixing time. The accuracy of polysulphides is good but they have an unpleasant smell (bad eggs) and are messy to use.

• Polyethers: Polyethers have good accuracy but are rather stiff, and this can cause problems, particularly where the preparations are small and narrow or the undercuts deep or multiple. The lower central and lateral incisors are good examples of this. There is a risk of damage to the plaster teeth on the model as the impression is removed from it. For this reason, some technicians are not enthusiastic about the use of polyethers.

Term to Learn

Preparation: a tooth that has been carefully shaped with a dental drill for receiving a crown or filling.

The bases and the chemical reactors of elastomers are usually of different colours. Some products are provided in special mixing syringes. For others, you will need to lay out equal lengths of both the base material and the chemical reactor (catalyst) separately but side by side onto a special polymer paper or parchment pad. The reactor should not touch the base material until everything is ready to mix: then you mix the two pastes with a spatula in the prescribed time, until no streaks remain. A thin uniform layer of elastomer impression material is required to give the most accurate impression, so the materials are used in individually designed (custom or special tray) acrylic trays. You will need to apply a tray adhesive to prevent the impression from pulling away from the tray and distorting. Most elastomer impressions are dimensionally stable if stored dry, and thus they may be sent to the technician without a major risk of dimensional change.

Key Point

Polyether elastomeric impressions will distort if sharing a bag with a damp alginate impression.

Advantages

• Elastomers are flexible and rubber-like once they set, and sufficiently elastic to return to their original shape after slight distortion.

• They do not significantly distort after setting.

• They do not tend to dry out but the cast is still best poured within 30 minutes after an impression is made. This is because some elastomers undergo shrinkage on setting that continues for some time after the impression is made, particularly the condensation silicone type. However, these materials are not subject to syneresis and imbibition because they are hydrophobic (water-hating).

Disadvantages

• Elastomers are expensive compared with alginates.

• They are more liable than alginates to produce allergic reactions, so should be handled carefully and sparingly.

Uses

Elastomers are used for making impressions of areas containing undercuts, especially for crowns, inlays, bridges, dental implants and removable and fixed partial dentures (see p. 215).

Term to Learn

Dental implant: an artificial tooth root (see Figure 9.24 below) that osseointegrates. Implants are made of inert materials, usually titanium, but zirconia has also begun to be used.

FIGURE 9.24 Schematic drawing of an implant.

Osseointegration: fusion of an implant with the surrounding living bone due to the growth of bone tissue on the surface of the implant material.

Impression Tray Set-Up (Figure 9.4)

Impression trays	To carry impression materials
Impression adhesive	For aiding adhesion of material to tray
Straight handpiece and acrylic trimmer (Figure 9.5)	For adjustment of tray if needed
Impression material
Mixing bowl or pad
Spatula
Shade guide
Laboratory prescription (instruction) sheet and label	For custom instruction to technician
Gauze swabs	For damping and placing over alginate impression
Self-seal plastic bag	For transporting to the laboratory
Mirror	For patient to view their appearance for shade selection and ensuring face is clean

Treatment of caries

Caries prevention is discussed in Chapter 8, both the measures that the patient can take and the measures that the clinician can take (applying dental fissure sealants). Here we discuss the restoration of teeth which have been damaged by caries.

FIGURE 9.5 (A) Acrylic trimmer (B) Straight handpiece.

Repairing damaged or diseased teeth – making a restoration

The Dental Nurse’s Role

Removing the caries

You will need to assist the clinician, mainly by controlling moisture and debris; they remove the caries and prepare the tooth for a restoration (this can be a filling, inlay, crown or bridge).

Moisture control and rubber dam

Moisture control is very important for two reasons:

• To allow the clinician to be able to see clearly what they are doing in the mouth

• Moisture can damage the restoration or its adherence to the tooth (Table 9.1).

TABLE 9.1 Damaging Effects of Moisture on the Setting of Restorations

Materials	Effects of Moisture
Amalgam	Expansion of material
Cement	Fails to adhere to tooth structure; setting time altered
Composite	Fails to adhere to tooth structure
Glass ionomer	Fails to set properly

Moisture control is also crucial in endodontics to prevent spread of infection.

When preparing and placing fillings there are several ways to control moisture (Box 9.2). Use of rubber dam (or dental dam, Figure 9.6) is the most effective.

BOX 9.2 Methods of Moisture Control

• Rubber dam placed on the teeth being treated.

• Aspiration by the dental nurse.

• Saliva ejector in the floor of the mouth.

• Cotton wool rolls placed near the openings of the major salivary gland ducts inside the cheeks, and in the floor of the mouth.

• ‘Dry guards’ placed in the buccal and lingual sulci.

FIGURE 9.6 Rubber dam equipment: (A) rubber dam punch; (B) rubber dam clamp; (C) rubber dam frames; (D) dental floss; (E) a selection of rubber dam clamps; (F) rubber dam sheet; (G) rubber dam napkin; and (H) dry dam.

The rubber dam is a thin square of latex rubber (also available in silicone for latex-sensitive patients). To accommodate the teeth being treated, holes are made in the sheet with a rubber dam punch, and the dam is held in place on the teeth by rubber dam clamps or dental floss (Figure 9.6).

Key Point

The rubber dam isolates the tooth being treated from its environment, retracts and protects the lips and cheeks, and avoids inhalation of small instruments or debris.

You will need to prepare the rubber dam, assist the clinician with placement and use the suction during cavity preparation or endodontics to remove debris, saliva and water. Figure 9.7 shows a selection of suction tips that can be attached to the suction machine and are placed inside mouth.

FIGURE 9.7 A selection of suction tips.

Find Out More

Not all suction tips are suitable for all procedures. Try to match the tips shown in Figure 9.7 with the procedures they are best suited for.

Cavity preparation

Teeth are prepared for the restoration using:

• Burs (Figure 9.8): either in an air-rotor (fast speed) or contra-angle (slow speed) handpiece (Figure 9.9)

FIGURE 9.8 (A) A diamond bur and (B) a steel bur.

FIGURE 9.9 A selection of air-rotor and latch-grip, contra-angle handpieces.

and/or

• Hand instruments such as excavators (Figure 9.10).

FIGURE 9.10 Instruments used for cavity preparation and amalgam restorations: (A) mouth mirror; (B) straight probe; (C) tweezers; (D) excavators; (E) amalgam condensers (pluggers); (F) amalgam burnisher; (G) amalgam carvers; and (H) flat plastic instrument.

The main aim is to remove all of the decayed parts of the tooth but at the same time avoid damage to the underlying dental pulp. Once the clinician has prepared the cavity, the pulp is protected by applying a lining cement with an instrument called a ‘plastic’ (labelled H in Figure 9.10).

Dental cements

Dental cements are used to:

Cements are described in Chapter 12. They are usually prepared by the dental nurse. Several cements are supplied in capsules containing pre-proportioned powder and liquid. These are not only convenient but ensure consistent powder/liquid ratios and thus predictable setting times and ultimately the lining strength.

If cement is supplied in bottle form: