The indications for extraction in the cat include odontoclastic resorptive lesions (FORLs), periapical abscessation (tooth root abscess), advanced periodontal disease, chronic oral inflammatory disease (feline gingivo-stomatitis syndrome), malocclusions, retained deciduous teeth, fractured teeth, supernumerary teeth and some cases of jaw fracture with teeth in the fracture line.
Cat teeth are easily fractured if excessive force is used. This is especially true for teeth affected by FORLs. For this reason, small instruments are used with correct procedures and lots of patience. If an attempt is made to speed up the procedure, the tooth will inevitably break. For the same reason, extraction forceps are only used after the tooth segment is very loose (i.e., just to lift it out).
In aged cats and in some teeth affected by FORLs especially the canines, root ankylosis (tooth root fused to the bone) will often have occurred. These teeth are impossible to extract the conventional way. Radiographs will demonstrate a lack of periodontal ligament space between the root and the alveolar bone. These teeth can be treated using crown amputation provided there is no infection associated with the tooth. A high-speed bur is used to remove the crown and some of the roots of the tooth to below the level of the alveolar crest (in order to allow the gingiva to close over the amputated tooth). If they must be removed completely, the procedure will involve utilizing a muco-periosteal flap technique (see canine extraction).
Perioperative and postoperative pain management are very important considerations with teeth extractions. Analgesia can easily be achieved using regional nerve blocks. These blocks, if performed correctly, will desensitize the region involved which, in turn, reduces intra-operative pain and associated local inflammatory responses to pain stimuli. Apparent post-operative analgesia lasts for several hours as evidenced by the immediate post-anaesthetic behaviour of the cats. The blocks must be given before extraction or surgical trauma.
The technique involves an intra-oral approach to block the maxillary nerve in the pterygo-palatine fossa.
The caudal border of the hard palate is palpated and a 25G needle is bent at 45° to allow a "vertical" insertion of the needle through the soft palate, close to the caudal bony edge of the hard palate. The needle is inserted 5mm palatal to the caudal teeth line (this may pass through the palatine artery at this point) and angled slightly towards the outside of the head (approximately 30° off vertical) to a depth of 5-10mm. After aspiration, 0.3ml of local anaesthetic is injected (I routinely use 2% lignocaine plain). The infraorbital and palatine nerves are blocked with this technique which will afford analgesia to that dental arcade.
This is an extra-oral technique whereby a 25G needle is inserted medially at a point midway between the lower molar and the caudal palpable border of the mandible. It is inserted to a depth of 5mm and, after aspiration, 0.3cc of local anaesthetic is injected.
This will block the inferior alveolar nerve (mandibular nerve) as it enters the mandible.
Incisor Extraction (and Upper Premolar 2)
These are small single rooted teeth with a large root to crown ratio. The roots of cat incisors are approximately 4 times the lengths of the crowns. These are very brittle and delicate teeth. They are very easily broken during attempts at extraction especially if excessive force is used.
A sharp 1mm root tip pick is the only instrument required in order to extract these teeth. It is inserted between the tooth root and the alveolar bone and light rotational forces are applied to fatigue (and tear) the periodontal ligament. Constant force for 30 to 60 seconds is much more effective than constant movement of the root tip pick.
Gradually move around the tooth inserting the root tip pick, rotating and holding for 60 seconds. The instrument will be able to be inserted deeper as the ligament begins to tear. Haemorrhage from the ligament indicates that it is rupturing and aids in "lifting" (= elevating) the tooth from the socket. Once the periodontal ligament attachments have been destroyed, the tooth will be easily removed.
Multi-rooted Tooth Extraction
The principle that is used in extracting multi-rooted teeth is to section them into their individual root components and then remove each section as for a single rooted tooth. This does require knowledge of the relevant anatomy as to root numbers and position of root furcations. Note that the carnassial teeth are not simple two-rooted teeth with a central furcation.
The upper fourth premolar has three roots (2 rostral, 1 caudal) and the lower molar has two roots (a large rostral root and a small caudal) with the furcation approximately two thirds along the length of the tooth.
The technique is to use a fine cutting bur (701 or 556) in a high speed handpiece and section the crown at the furcation of the roots by cutting from the gingival margin towards the crown tip (to avoid iatrogenic damage to the soft tissues). A small elevator or root tip pick can be used to expose the furcation, if needed.
Once the tooth is sectioned, the 1mm root tip pick is again used as for the incisors. With the larger roots, once they have been loosened, the extraction forceps may be used to apply a gentle rotational force to sever the remaining apical periodontal ligament fibres.
Unless damage to the soft tissues has occurred, the extraction sites are not usually sutured. It is important though to ensure that a blood clot occupies the empty socket (to allow rapid healing) as exposed bone leads to a condition known as "dry socket" with associated complications of inadequate healing and persistent infection (dry socket in humans is a very painful condition).
Canine Tooth Extraction
Canine teeth are best extracted surgically using the muco-periosteal flap technique. Even in cases of severe periodontal disease where the tooth can be easily removed, closure of the deficit requires removal of bone.
The gingival margin is removed with size 15 scalpel (to create fresh edges for apposition after extraction) and then diverging full thickness incisions are made rostral and caudal to the tooth from the gingival margin for the length of the root. A diverging flap is required to allow for adequate blood supply. The direction of the incisions is to allow exposure of the bone over the root. This is more difficult for the mandibular canines (full length exposure may not be possible).
The periosteal elevator is then used to lift a muco-periosteal flap off the bone. At the base of the flap, the periosteum is carefully severed (only the periosteum, not the whole flap!) which is evidenced by a sudden ability to stretch the flap past the extraction site. This will ensure minimal tension of the flap when replaced therefore reducing the likelihood of dehiscence.
A round bur (#2 round) in the high speed handpiece is used to remove the bone over the tooth root. An elevator is then used as normal from the palatal side (or lingual side for the lower canines) to remove the tooth. Any rough bony edges are removed with the bur and the flap closed without tension with absorbable sutures (usually 4-0 in the cat). The use of a swaged-on reverse cutting needle will reduce gingival tearing. The periosteum in the flap will ensure rapid bony replacement at the extraction site.
Post-operatively the cat will require very little other than a dietary change for 3 to 4 days. The cat can't be fed anything that will pack into the empty sockets or adhere to the sutures until primary healing has occurred (3 to 4 days in the mouth). It is best to feed small pieces of meat (approximately 3mm pieces) as the sole food source. This is too large to pack into the sockets but small enough that it doesn't have to be chewed. Biscuits, canned food and minced meat are unsuitable.