A punch is used to make the required numbers of holes depending on the teeth to be isolated. Usually single tooth isolation is all that is required for endodontic treatment. Single-hole punches (Dentsply Ash, Weybridge, Surrey, UK) are available which will cut a neat hole (1.63 or 1.93 mm), while those with a rotatable table (Ainsworth pattern) will cut different sized holes ranging in diameter from 0.5 to 2.5 mm (Fig. 6.4). Whichever is chosen, it is important to ensure that the punch is sharp, so as to produce a clean hole without any residual tags on the rubber dam. Otherwise, the rubber dam will tear when stretched and applied to the tooth. The size of hole that is punched is also important; the ease of application with a larger hole must be balanced by the quality of the seal at the cervical margin.

There are many different designs of rubber dam clamp to cater for every possible situation. However, there are no standards governing the manufacture of rubber dam clamps. ²

Clamps have two uses: first, they anchor the rubber dam to the tooth, and second, they retract the gingivae. In endodontics, anchorage is the main requirement. Most clamps are made from stainless steel; some are made from plated steel, which may be more susceptible to corrosion by sodium hypochlorite. There are also non-metallic clamps made of plastic (SoftClamp, KerrHawe, Bioggio, Switzerland) on the market. Clamps are winged or wingless, retentive or bland (Fig. 6.5). A winged clamp allows the attachment of the rubber dam to the clamp so that both clamp and rubber dam may be applied to the tooth together. Retentive clamps are designed to make a four-point contact with the tooth; they have narrow, curved and slightly inverted jaws, which may displace gingival tissue to grip the tooth below the level of greatest circumference; they are very useful on partly erupted teeth. Bland clamps are less likely to impinge on the gingivae as they have flat jaws, which grip the tooth around its entire circumference. However, they can only be used where a tooth is fully erupted and has a cervical constriction that prevents the clamp from slipping off.

A basic assortment of clamps may consist of the following (Fig. 6.6): Ivory pattern 00, 0, 1, 2A, 9, W8A, 14 and 14A. The wingless W8A, the winged 14 and 14A are for molars, the 2A and 1 for premolars, and the 9 for incisors. A range of lettered Ash clamps, which are generally smaller, may also be used; the winged K and E for molars and premolars respectively, and the wingless EW for incisors and broken down premolars. The EW clamp gives better access than the 9 clamp. The fracture or unexpected dislodgement of a rubber dam clamp is probably the only serious risk associated with rubber dam usage. The risk of inhaling or swallowing the fractured or dislodged clamp may be minimized if it can be retrieved. A length of floss should be tied to one of the holes in the jaw of the clamp and then knotted, it is then wound around the bow of the clamp, threaded through the other hole in the opposite jaw and tied again (Fig. 6.7).

In anterior teeth, it is sometimes possible to secure the rubber dam without the use of clamps. The interproximal spaces may be wedged with wooden wedges, strips of rubber dam or short lengths of specially made latex or non-latex cords (Wedjets, Hygenic, Coltène/Whaledent, Cuyahoga Falls, OH, USA) (Fig. 6.8).

Several types are available including the University of Washington/Stoke, Ivory (Heraeus Kulzer, South Bend, IN, USA) (Fig. 6.9) and Brewer (Dentsply Ash) patterns; the choice is a matter of personal preference. The forceps are used to place, adjust and remove the rubber dam clamp. Some forceps may require adjustment to their working ends prior to first use. If the ends are too large, they need to be reshaped so that it is less difficult to disengage the clamp on the tooth.

The corners of the rubber dam are held apart on a frame, stretched over the patient’s mouth, so as not to obscure the operator’s vision and not to be uncomfortable for the patient. Rubber dam frames come in various sizes and designs; they are shaped so that they do not impinge on the patient’s face. Rubber dam frames are made from either metal or plastic; the latter is lighter, more comfortable and being radiolucent, removal is not always necessary when taking radiographs (Fig. 6.10). Plastic, foldable rubber dam frames (Dentsply Ash) with an articulated joint to facilitate radiography are also available.

Basically, there are three methods of application. In the first method, the rubber dam is attached to the clamp, with or without the frame beforehand, and the whole assembly placed onto the tooth. In this method, only winged clamps can be used. Once the clamp is firmly seated, a plastic instrument is used to lift the rubber off the wings to fit against the side of the tooth (Fig. 6.11). In the second method, winged or wingless clamps may be used. The clamp is placed on the tooth and the dam is then stretched over the clamp. If this technique is used, as mentioned earlier, the clamp should be wrapped in dental floss as a precaution against clamp fracture or dislodgement. In the third method, the dam is stretched over the tooth and the clamp, winged or wingless, then placed on the tooth. The assistance of a dental nurse is normally required for this method of application.

If more than one tooth is to be isolated, the rubber is knifed through each succeeding contact point. The rubber is stretched, positioned vertically above the contact point and gently forced through the point. It is important that the rubber remains as a single layer and does not fold over on contact with the teeth. Sometimes knifing is insufficient and the rubber must be forced through the contacts using dental floss. Techniques for placing rubber dam have been reviewed.^{3.4. and 5.} The use of a lubricant on the undersurface of the dam will aid placement; brushless shaving cream or water-soluble tasteless gels are suitable lubricants.

If a tooth is broken-down and there is insufficient tooth structure for clamp placement, there are several ways of managing the problem. It is normally possible to cement an orthodontic band onto the tooth; this transforms a tooth that is difficult to isolate into one that is straightforward. It may alternatively be possible to remove enough soft tissue surgically, or by electrosurgery, to allow a clamp to be placed. Another method is the ‘split-dam’ technique in which clamps are placed on the teeth mesial and distal to it. Three holes are punched in the rubber dam and these holes are joined by cutting through with a pair of scissors. The dam is then stretched over both the mesial and distal clamps, isolating the broken-down tooth. Protection against salivary contamination is aided by the use of a cotton-wool roll placed beneath the dam buccally and an aspirator lingually, plus a caulking agent to stop any seepage. This technique may also be used for cases where bridgework is present.

Following initial access to the pulp space, a safe-ended or non-cutting tip, tapered diamond or tungsten-carbide bur (e.g. Endo Z bur, Dentsply Maillefer, Ballaigues, Switzerland) (Fig. 6.12), can be used to remove the entire roof of the pulp chamber. The non-cutting tip prevents ‘gouging’ of the pulpal floor.

Hand instruments are grouped according to usage and to the classification established by the International Organization for Standardization (ISO). The terminology, dimensions, physical properties, measuring systems and quality control of endodontic instruments and materials are defined by these standards. As a result, endodontic hand instruments, i.e. files, reamers and barbed broaches, are standardized in relation to size, colour coding and physical properties. ⁷ The relevant information on sizing and colour coding for files and reamers are listed in Table 6.1; d₁ is an assessment of the diameter of the working part at the tip end, and is its nominal size; d₃ represents a point at 16 mm from d₁ where the cutting part of the instrument ends. The taper is a constant 0.02 mm per mm of cutting flute; hence also referred to as 0.02 taper. The shape of the tip is variable. The lengths of instruments available are normally 21, 25 and 31 mm. Endodontic hand instruments have been reviewed. ⁸

There have been a number of newer developments in instrument design and technology. Instead of stainless steel, nickel-titanium (NiTi) alloys have been introduced in the manufacture of endodontic instruments. ¹⁶ The NiTi alloys have many interesting properties: a shape memory effect (ability to return perfectly to its original shape), superelasticity (low modulus of elasticity), good biocompatibility and high corrosion resistance. The concept of using NiTi for endodontic instruments came from orthodontics, where its properties have been utilized in the archwires of fixed appliances. The NiTi alloy used in root canal instruments is known generically as Nitinol (Ni for nickel, ti for titanium and nol for Naval Ordinance Laboratory). The manufacture of NiTi endodontic instruments is more complicated than that of stainless steel; the majority of the instruments are machined. ¹⁷

Compared with stainless steel, NiTi instruments have greater flexibility in bending¹⁸ and better resistance to torsional fracture¹⁹ (see later). NiTi instruments have a non-cutting tip and they cannot be easily precurved. Their cutting efficiency is dependent on cross-sectional shape, ²⁰ but is less aggressive compared with stainless steel instruments. ^21,22 NiTi instruments tend to straighten curved root canals less than stainless steel instruments, ²³ producing a more centered, tapered and acceptable preparation. ^24,25 They also have different wear characteristics compared with stainless steel instruments. ²⁶

Many different power-assisted root canal instruments have been developed over the years in the hope of making root canal preparation quicker and to reduce operator fatigue.