Scaling is a procedure that aims to remove dental deposits (primarily calculus) from the tooth surface. Scaling should include both supragingival and subgingival instrumentation. Subgingival debridement (i.e. subgingival scaling and root planing) is the most important procedure in professional periodontal therapy. Root planing involves the removal of the superficial layer of toxin-laden cementum from the root surface. If periodontitis is present and subgingival debridement is omitted, the treatment will be useless in terms of health management and will be nothing more than 'cosmetic' as most of the disease process occurs below the gingiva.
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Ultrasonic and sonic equipment
In general, sonic and ultrasonic scalers should only be used above the gum line (Gorrel & Robinson, 1995). All power-driven units generate heat and need constant water cooling at the working tip to avoid iatrogenic damage to the tooth and its supporting tissues. The cooling water will not reach the oscillating tip of most instruments inserted into a periodontal pocket, which may result in thermal damage to the tissues. However, new tips for subgingival use, characterised by a smaller tip size and a modified cooling system, have recently been introduced (Petersilka & Flemming, 2002). These instruments should be used with caution, as over-instrumentation and damage to the periodontal tissues is still possible.
Sonic scaler handpieces operate via compressed air from the dental unit and vibrate with frequencies in the range of 6-9kHz, with the tip oscillating in an almost circular motion.
Ultrasonic scalers vibrate at a much higher frequency, in the range of 20-45 kHz. The tip vibration is either generated by a magnetostrictive mechanism or by a piezoelectric mechanism. In magnetostrictive scalers, the tip of the hand piece oscillates in an elliptical motion, whereas the oscillating motion of piezoelectric scalers is strictly linear (Petersilka & Flemming, 2002).
The use of rotary scalers (e.g. Roto Pro burs, used in a high speed dental handpiece) should be avoided, since it is impossible to scale teeth with them without causing severe damage to the tooth surface (Gorrel & Robinson, 1995).
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All power-driven instruments need to be used with caution, because if used incorrectly they can easily damage a tooth and its supporting tissues. Copious cooling water at the working tip is essential to avoid heat damage of the tissues. The aerosol that is produced is loaded with bacteria. Therefore, protective measures must be taken, both for the operator, who should wear a good surgical mask and goggles and for the animal that should be protected with a throat pack and eye ointment.
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Numerous scalers are marketed, with working tips of different shapes and sizes. The most useful is a sickle or universal insert. The working surfaces are the sides of the tip.
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Correct use of Sonic/Ultrasonic equipment (fig. 1):
– Use copious amounts of water to cool the working tip at all times. Heat may cause irreversible pulpitis and pulp necrosis.
– Use the side rather than the tip of the insert, with feather-light pressure and continuous gentle wiping motion. Never place the working surface of the tip at an angle of 45° or more to the tooth surface, since this will cause overheating and damage of the tooth surface. Ideally, the working surface should be placed flat on the tooth surface (i.e. parallel to the tooth surface). When using subgingival inserts for cleaning the root, only an absolute parallel angulation to the root surface is considered safe if used for a short period of time (Petersilka & Flemming, 2002).
– Even with good water cooling, all sonic and ultrasonic equipment will generate some heat. It is therefore advised to use these instruments for short periods of time, scaling each tooth for less than 15 consecutive seconds. If more time is needed to complete the procedure, it is recommended to work on other teeth before returning to further scale the tooth.
– Subgingival debridement may need to be supplemented with hand-instrumentation, even if power-driven equipment especially designed for subgingival work is used.
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Fig.1 : Correct use of sonic/ultrasonic equipment: the side of the tip is used in a constant wiping motion over the tooth surface. © Verhaert
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Hand instruments (scalers and curettes)
Scalers and curettes are composed of a working part or blade, a shank and a handle (fig.2). The cutting edges of the blade are centred over the long axis of the handle for proper balance of the instrument (Rylander & Lindhe, 1997). A wide variety of scalers and curettes are available and every operator may choose his/her own favourite type (fig.3). Scalers and curettes should be sharpened before each use. Scalers and curettes are held in a modified pen grip (i.e. as one would hold a pen) with the tip of the middle finger on the shank, close to the end of the instrument and with the ring finger and/or little finger used as a finger rest on the animal (Pattison et al, 2002). The finger rest is usually placed on a neighbouring tooth, or even on the treated tooth (fig.4).
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Fig. 2 : Basic design of scaler and curette. The blade is the working part of the instrument.
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Fig. 3 : Two Kaplan scalers (left), a Synthette universal curette and a mini Gracey curette (right)
The scalers are more bulky, and have a sharply pointed tip. The curettes have a rounded toe. © Verhaert
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Fig. 4 : Use of hand instruments: modified pen grip with finger rest.
4a : finger rest on neighbouring teeth
4b : finger rest on treated canine tooth. © Verhaert
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Scalers
Sickle scalers are the most widely used scalers in veterinary dentistry. The blade has a flat surface and two cutting edges that converge in a sharply pointed tip, so that the scaler is triangular in cross section (fig.5). Sickle scalers are used with a pull stroke, directed away from the gingival margin.
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Fig. 5a: Blade design of scaler and curette. The blade of a scaler is triangular in cross section, whereas the blade of a curette is semicircular in cross section
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Fig. 5b : Blade design of scaler and curette. Close-up view of the blade of a scaler (left) and a curette (right).
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Curettes
The curette is the instrument of choice for removal of subgingival calculus in deep pockets, for root planing altered cementum and for removing soft tissue lining the periodontal pocket. It can also be used to remove supragingival calculus.
Curettes have a blade with two cutting edges and a rounded toe, so that in cross section the curette is semicircular with a convex back (fig.5). A curette is finer than a sickle scaler and has no sharp points other than the cutting edges of the blade. Length and angulation of the shank and dimensions of the blade differ between different types of curettes. For correct use of these different types of curette, special training and understanding of the design are required.
The curette is inserted into the gingival sulcus or periodontal pocket with its curved, non-cutting side (back) against the gingiva and the face, delimited by the cutting edges, facing the root. Once the instrument touches the base of the pocket, it is turned slightly so that the cutting edges engage the root surface and the pocket lining (fig.6). The instrument is then pulled out of the sulcus or pocket. This movement is repeated circumferentially around the root, using overlapping strokes. Especially in furcation areas, horizontal and oblique strokes are also used. This procedure should finally result in a clean, smooth root surface.
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Over-instrumentation should be avoided: if the cementum is completely removed, the dentinal tubules become exposed resulting in tooth sensitivity.
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Fig. 6 : Subgingival scaling and root planing:
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 6.a : The curette is inserted in the sulcus or pocket with its curved, non-cutting back against the gingiva and the cutting edges facing the root.
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 6.b : Once the instrument touches the base of the pocket, it is turned slightly so that the cutting edges engage the root surface and the pocket lining.
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