Dental Extraction in Cats and Dogs

Transcription

1 Veterinary Dentistry Basics : April 2003 Dental Extraction in Cats and Dogs David A. Crossley BVetMed MRCVS FAVD DipEVDC European Veterinary Specialist in Dentistry RCVS Recognised Specialist in Veterinary Dentistry This text is loosely based notes prepared by the author for the British Veterinary Dental Association s basic dentistry courses Sections of this text derive from various other sources as listed under references. Unless otherwise indicated, illustrations are copyright 1994 to 2003 DaCross Services. Indications for extraction There are many possible indications for dental extraction: Developmental abnormalities (deformed or dysplastic teeth) Unerupted teeth (risk of resorption of adjacent tooth roots and dentigerous cysts) Periodontal disease (attachment loss, abscesses, cysts) Chronic stomatitis (the ultimate in dental plaque control) Caries (extensive loss of tooth substance, pulp involvement) Odontoclastic resorptive lesions (loss of tooth substance, exposure of dentine) Complicated crown fracture (pulp exposure or extensive root involvement) Pulpitis (symptomatic - toothache or asymptomatic) Pulp necrosis (causes apical lesions and risk of systemic infection) Periapical lesions (apical periodontitis, abscesses and cysts) Tooth root fracture (longitudinal fractures and unstable transverse root fractures) Retained primary teeth (overcrowding, prevent correct alignment of adult teeth) Overcrowding of primary or secondary dentition (plaque accumulation) Traumatic occlusion (malocclusion leading to hard or soft tissue trauma) Supernumerary teeth (overcrowding, compromised function) Involvement of teeth in neoplasia (en-block resection required, not extraction) Extraction 1

2 Extraction is often not the only option for treating dental disease. The teeth are important to people and those animals that posess them, so the aim of modern dentistry is to maintain a comfortable and functional natural dentition as long as possible using a range of orthodontic, endodontic, restorative and advanced periodontal procedure. Such conservative therapy, however, this is not always practical or affordable. Extraction is always preferred over leaving a significantly diseased tooth untreated. Whilst captive and domestic animals can survive without teeth, providing they are supplied with a diet that does not require chewing, loss of teeth is frequently fatal for wild animals. When treating a wild animal, its survival potential must be taken into consideration: will the treatment reduce feeding efficiency or have a serious adverse effect on the animal s social status? If so, the options are then to maintain it in captivity or euthanasia. Releasing an animal to starve to death is not acceptable. In the case of domestic animals other factors need to be considered, such as the level of care and supervision and the capabilities of the care givers. There are also moral and ethical issues related to requests for cosmetic procedures that are not strictly necessary for the animals wellbeing. PRH / DAC 1994 Apical vessels Root apex Periodontal ligament Root canal Cemento-enamel junction Pulpal chamber Apical delta Alveolar bone Cementum Pulpal tissue Dentine Enamel Basic dental anatomy: Diagram of a two rooted brachyodont tooth from a carnivore. Note that the crown is shorter than the root, the enamel is very thin, the periodontal ligament is narrow and there is an apical delta with many small nerves and fragile blood and lymphatic vessels entering/draining the pulp rather than a single apical foramen as seen in man. Healing following tooth loss When a tooth is lost from its alveolus, whether due to accident, disease or extraction, it leaves a breach in the oral lining tissues. This wound involves the gingiva, periosteum, alveolar bone and any remaining periodontal ligament. Unless the tooth is re-implantated or there is some other surgical intervention, the wound will heal by second intention as commonly described for wounds of skin and subcutaneous tissues. In normal circumstances there is haemorrhage from ruptured gingival, periodontal and apical blood vessels. Some of the blood remains in the alveolus and coagulates forming a protective clot. This may initially completely fill the socket but will contract creating a concave surface. This contraction tends to pull the free gingival margins into the alveolus, thus reducing the area of the Extraction 2

3 deficit in the oral lining within hours of the injury. The inturned gingival margins help to maintain the clot in position and reduce the tendency for contamination from oral debris. The blood clot provides a scaffold on which the cells associated with the healing process can migrate to enter the wound from viable tissues at the periphery. The first few hours immediately following injury (extraction, avulsion etc.) are critical. Cytokines are released, initiating the inflammatory response and attracting neutrophils and later monocytes (macrophages) to eliminate infectious agents and remove wound debris that contaminate the wound. Fibroblasts and endothelial cells are also stimulated to multiply and migrate into the wound, anoxia being a major stimulus for new blood vessel formation and cellular migration. If the initial blood clot is dislodged, healing will be delayed and the damaged tissues will be directly exposed to potential pathogens so that alveolar infection can develop (in man this is known as dry socket and is extremely painful). When it remains in situ, the blood clot is gradually replaced by granulation tissue which is normally highly resistant to infection. The tissue reactions occurring during the first 24 to 48 hours after injury mainly involve various alterations of the vascular bed. After the initial vasoconstriction to control haemorrhage, the blood vessels in the remnants of the periodontal ligament become engorged with blood from which leucocytes migrate and serum proteins (including antibodies and more fibrin) escape into the periphery of the clot. This is the exudation phase of healing. The germinal layer of the surface epithelium at the periphery of the wound exhibits increased mitotic activity and cells start to migrate across the surface of the clot beneath the protective layer of neutrophils that line the exposed oral surface. During the first week of healing, granulation tissue starts to replace the blood clot beneath the advancing epithelium. Fibroblasts deposit networks of collagen fibres whilst capillary ingrowth ensures that these active cells are supplied with metabolites. At this stage changes are seen in the residual periodontal tissue. There is loss of collagen in the wound margins (as is also seen at the margin of skin wounds) and the bony alveolar wall (the cribriform plate, which is seen as the lamina dura on radiography) and the alveolar crest begin to exhibit osteoclastic activity. Epithelial proliferation over the surface of the wound is a more rapid process than healing of the connective tissues, the surface of the socket frequently being covered in 7-10 days if there are no complications, with a normal appearing epithelial surface forming in 2-3 weeks. There is no longer any risk of infection entering the wound from the oral cavity once the epithelium has fully covered the alveolus, however, there may occasionally still be infection within the wound (usually related to residual infected fragments of tooth, bone or calculus). DC 1996 DC 1996 DC 1996 DC DC The sequence of alveolar healing by second intention: Loss of the tooth with haemorrhage and blood clot formation and contraction. The basal layer of the residual junctional and other wound margin epithelium becomes active and cells start to migrate across the blood clot as connective tissue cells enter the blood clot at its margins. Residual periodontal ligament is largely resorbed as granulation tissue is produced to replace th blood clot. Surface epithelialisation is often complete well before granulation tissue fills the socket. Surface epithelium matures within a few weeks. The underlying connective tissues require months to years to mature and remodel, new bone usually being found at the margins within 6 weeks. The lamina dura becomes indistinct with time. Extraction 3

4 DC 2000 DC 2000 DC 1996 DC 1996 DC 2001 As healing progresses, the blood clot becomes increasingly organized as the fibroblasts and new capillaries migrate into the centre of the clot. By the third week, the original blood clot is almost completely replaced by granulation tissue. As this matures the remnants of the periodontal ligament degenerate and the bony walls of the socket are now less distinct due to expansion of existing, and formation of new, fenestrations in the cribriform plate. At this stage trabeculae of new osteoid are being deposited in the maturing granulation tissue which has replaced the blood clot. The trabeculae which form around the whole periphery of the wound and rapidly mineralise to become bone, extend from the socket wall towards the centre of the alveolus where they merge, filling the defect. At this stage the residual walls of the alveolus are becoming indistinct, the extra alveolar trabecular bone merging seamlessly with the new bone within the alveolus. The presence of new bone can usually be detected radiographically by 6 weeks following extraction. There is usually residual radiographic and histological evidence of the prior existence of the alveolus for months to years following loss of adult teeth, however, bone remodelling occurs rapidly during growth and may totally mask evidence of teeth lost by immature animals. The alveolar crest becomes more rounded and recedes further with time, even after the inflammation related to wounding has subsided. The continued loss of alveolar bone occurs because the forces required for its maintenance disappear with loss of the tooth, this often being exacerbated by reduced chewing activity following tooth loss. In the short to medium term, the loss of height of alveolar bone is generally more noticeable when some bone has been lost or removed surgically at the time of injury or extraction when compared with closed extraction or uncomplicated avulsion, however the long term result is generally the same. The additional trauma and associated surgical inflammation arising from preparation of gingival and mucoperiosteal flaps has also been shown to accelerate bone loss, though the author has not noticed any significant differences in the clinical setting. This is probably because flaps are generally used for primary closure of the extraction wound and this offers immediate protection for the blood clot healing tissues. DC 2000 Healing of the extraction socket following primary flap closure. Providing there is apposition of submucosa/gingival connective tissue at the suture line, the epithelium heals rapidly, i.e. within days. The clot is immediately protected and connective healing can progress undisturbed with very little risk of complications. Extraction 4

5 For there to be first intention healing of a gingival flap, there must be connective tissue contact beneath the epithelium at the suture line. This requires excision or eversion of the free gingival margin and any pocket lining as this has epithelium covering it and epithelium covered surfaces will not heal directly one to the other. In order to free sufficient tissue to enable primary closure there is damage to the underlying tissue, and the resulting inflammation adds to the recession of the alveolar crest, however, in practise this effect appears to be much less that the effect of inflammation from the oral contamination of extraction wounds that heal by second intention. Loss of teeth leads to atrophy of the associated alveolar bone. This can be reduced by subjecting the tissues to appropriate stresses. In man this can be accomplished to some extent by placing implants supporting functional dental prostheses. Whilst it is possible to place implants in animals they have a high failure rate and require meticulous homecare, so are not an acceptable option for bone maintenance. A more practical method of reducing or delaying loss of alveolar bone is the use of a cancellous bone or synthetic graft to fill the alveolus at the time of extraction. A range of synthetic materials are available on the human market, and one (Consil) has been marketed for veterinary use. These are used to fill the socket prior to flap closure. Use of other substances such as haemostatic agents and antibiotics in extraction wounds is more likely to delay healing than assist it. Complications of extraction Tissue devitalisation Wound healing does not always proceed smoothly. The greater the trauma to the remaining tissues the poorer their healing capacity. Gentle, sympathetic tissue handling is required during surgery to preserve their physical and vascular integrity. Inappropriate attempts at closed extraction of large, mechanically retained or ankylosed teeth, frequently result in extensive gingival contusions and lacerations which delay and cause pain during healing. Whilst lacerations can sometimes be sutured, such injuries are largely unnecessary as they can be avoided by thorough preparation and treatment planning. The controlled trauma of preparing and retracting a gingival or muco-periosteal access flap, with or without removal of some of the retentive bone, has minimal effect on healing and it permits protection of the soft tissues during the extraction itself, and the flap can be sutured over the alveolus following extraction to provide immediate protection for the healing tissues. Infection The most common complication of the healing of human extraction wounds is the condition known as dry socket. This is a focal alveolar osteitis which occasionally progresses to osteomyelitis. It occurs when the initial blood clot has been lost or has disintegrated allowing infection to enter the residual periodontal tissues. There is usually a foul odour typical of wounds containing necrotic bone. There is no residual blood supply to the surface of the necrotic tissues which have to be sloughed or resorbed before healing can resume. This can take several weeks. The underlying inflammation sensitises the sensory nerve endings leading to intense pain. The reported incidence is around 2% of all human extractions, being most frequently associated with difficult or traumatic extractions, but it is also known to develop after straightforward extractions. As it is associated with loss of the blood clot before granulation has occurred it usually arises within the first few days after extraction, but has occurred a week or more after the procedure. There have been no reported studies on dry socket in the dog and cat, however clinical cases which strongly resemble the human condition are seen in veterinary practise, most commonly following extraction of the maxillary canine teeth in cats. As the condition is extremely painful, analgesic treatment is indicated. The exposed bone is necrotic and has to resorb or be shed before infection will resolve and healing progress, so healing is extremely slow. Antibiotics make little Extraction 5

6 difference unless there is indication of systemic infection. In most cases little can be done for the patient other than to relieve the subjective signs. Cases need to be monitored closely as sequestration of bone fragments is common. Whilst surgery to debride and remove bone sequestrae appears appropriate, the residual wound is quite likely to succumb to the same infection. Wide surgical excision of the lesion with a margin of healthy tissue (as for tumour excision), leaving only healthy bone is more effective but can rarely be justified for a condition that will usually resolve spontaneously. Less serious infections may also delay healing. The most frequent problem is due to residual fragments of infected tooth, calculus or necrotic bone. These are normally shed through the healing epithelium days to weeks following extraction, this sometimes being accompanied by signs of pain. If such debris and retained root tips are not shed, sequestration is likely with formation of a sinus tract and persistent gingivitis. Failure of ossification Scarring of extraction sockets by healing with fibrous tissue rather than bone is seen occasionally in people and animals, but its incidence in the dog and cat has not been investigated. In human studies, it occurs more frequently when there is extensive loss of periosteum from the alveolar bone during extraction and it is believed that the blood supply from the labial and lingual periosteum is important for normal healing. Fibrous healing is usually a coincidental finding on radiography as it does not cause any clinical signs. Jaw fracture Jaw fracture during dental procedures is most often due to excessively traumatic extraction technique. Failure to detect a pre-existing weakness in the bone, for example from metabolic bone disease, periodontal bone loss, cystic lesions such as dentigerous cysts, and bone involving tumours, significantly increases the risk of complications. A thorough general clinical and both extra- and intra-oral examination is necessary before undertaking treatment. If there is any indication that there could be bone loss then radiography is essential. Whilst the anatomy of many teeth is normal, it is also common to find variations in dental anatomy such as fewer or more than the expected number of teeth or tooth roots, and the presence of dilaceration (bends and other deformities) that complicate extraction. Forewarned is fore-armed, so it is best to routinely obtain radiographs of teeth that require extraction, and whenever possible to get a full mouth series just to be sure no important jaw or tooth pathology has been missed: the weakness may not be at the site of extraction!. Too late!!!! Iatrogenic jaw fracture may occur during physical examination or on opening the mouth for endotracheal intubation, not just during extraction. Breed predisposition and the state of the mouth should alert us to the likelihood of massive bone loss and even a possibility of there being a pre-existing pathological fracture. Rounding of the bone ends occurs within days of fracture at an infected site such as the mesial root of this dog s mandibular first molar tooth. Extraction 6

7 For the jaw to heal it is necessary to remove any infected teeth from the fracture line. However, other teeth that are stable enough to use as splint anchors and teeth that provide stability to fracture itself are best left in situ until healing is complete even if they are otherwise compromised. In practise this means removing all loose teeth and any teeth in the fracture line that have pre-existing endodontic disease. Any other compromised teeth that are not required for splint or wire anchorage should also be removed or treated appropriately. All the remaining teeth require thorough cleaning then jaw stabilisation should be performed in a manner that does not interfere with the blood and nerve supply (i.e. in the mandible the mandibular canal should not be entered) or further compromise the dentition (external fixator pins and hemicerclage wires are not placed through tooth roots). In advanced periodontal disease the best approach is usually to extract all significantly affected teeth and to place a tape muzzle to support the jaw. Production a tape muzzle jaw sling using non-stretch adhesive bandage - darker = adhesive side. the mouth should be able to open sufficiently for the tongue to be protruded rostrally. Support is normally required for around three weeks for unilateral jaw fractures, a longer period sometimes being needed if there has been bilateral fracture. During this time several replacement muzzles will be required as they rapidly become soiled. When the principal of jaw support has been explained to them, many owners will be able to make their own replacements. If there are plenty of remaining teeth and the fracture is towards the rostral maxilla or mandible, then a tooth borne splint is the preferred method of stabilisation as it is placed on the tension surface of the fractured bone. When there is still a substantial amount of bone present an external fixator can be considered, however, this should have acrylic, titanium or carbon fibre fittings to minimise its weight. intra-oral splints can be protected by Preventing the mouth from opening fully by use of a loose fitting tape muzzle jaw sling. The skull and mandible are both composed of thin bone and not supported by being rested on the ground most of the time as are the limbs. Heavy fixators will either rapidly work loose or lead to neck and jaw muscle pain and dysfunction. Providing there are no remaining infected teeth and the blood supply to the fracture/s is intact, functional healing will usually only take 3-4 weeks. Root fracture The roots of extracted teeth should always be checked for evidence of fracture and any remaining root fragments removed. When there is doubt, radiographs are helpful in locating retained root tips. Occlusal views (looking along the sockets rather than across them) give the best chance of identifying small fragments. If there is a high risk of complications in retrieving it, or it already displays evidence of resorption, a non-displaced, non-infected root tip may be left in-situ, Extraction 7

8 radiographed, the owner informed of its presence and the animal monitored. Every effort should be made to remove any dislodged and infected fragments as these are likely to cause further problems. These can usually be accessed through the alveolar bone following raising of a soft tissue access flap. Displaced root tips Care is required when removing fractured roots as they can be displaced into inaccessible compartments such as the mandibular alveolar canal, maxillary sinus or nasal cavity. Whenever feasible these should be located and surgically removed. It is not just root tips that get displaced during attempts at extraction. The bulbous thickening of the apex of this root prevented its extraction and continued inappropriate elevation forced it into the mandibular alveolar canal. Once the location has been conformed radiographically the easiest approach for retrieval is via a lateral soft tissue flap and removal of the bone lateral to the fragment, care being taken to prevent further injury to the mandibular alveolar nerves and blood vessels. Haemorrhage It is wise to question owners for any history of unexplained or excessive bleeding and if suspicions are raised, appropriate tests should be performed prior to undertaking any surgery. A quick and simple test that can be performed on all patients is the bleeding time. On induction of anaesthesia a small stab incision is made into the soft tissue of the inside of the upper lip and the wound observed to see how long it takes for bleeding to stop. The actual time varies depending on stab technique and anaesthetic protocol, however, a useful guide is that if bleeding stops within 2 minutes and pooled blood forms a clot then a bleeding tendency is unlikely. Up to 5 minutes for bleeding to stop can be considered normal. If it takes any longer then care should be taken or the procedure postponed until more precise tests have been performed. Haemorrhage during surgery Haemorrhage may arise from transection of a major blood vessel, e.g. when raising a mucoperiosteal flap close to the infra-orbital or mental foramen. It is essential to know the anatomy of the oral cavity and consequently avoid, or if avoidance is not possible to identify and ligate, these vessels. The main source of haemorrhage from an extraction socket are bone, periosteal and periodontal blood vessels which have been transected during extraction of the tooth. It is usually a diffuse capillary bleed rather than haemorrhage from a discrete vessel. Initial haemostasis occurs within 2-3 minutes following extraction in the healthy individual without any intervention. In situations where prolonged bleeding occurs, application of gentle surface pressure for a few minutes, for example by packing the empty alveolus with moist gauze or a haemostatic dressing, is usually sufficient to stop bleeding. Once haemostasis is achieved gauze is carefully removed. The routine packing of extraction sockets with antibiotics and haemostatic agents is not recommended, as some of these agents carry the potential of evoking a foreign body reaction or will otherwise complicate healing. Whilst bone and synthetic grafts can be used to pack the alveolus these should not generally be used until haemostasis has been achieved. Extraction 8

9 Prolonged haemorrhage from inflamed gingival tissue rather than the tissues of the alveolus proper can be eased by placement of a horizontal mattress suture across the alveolus to tense the mucoperiosteum against the alveolar bone and reduce local blood circulation. Such sutures also improve stability of the clot within the alveolus, but care is required to avoid causing ischaemia which will delay healing and promote infection. Haemostatic agents A range of types of haemostatic agent can be used singly or in combination: Gelatin based materials When blood comes into contact with these materials the thrombocytes adhere to the gelatin meshwork and then release thromboplastin which will contribute to the production of fibrin. The material is resorbed over a period of 4-6 weeks and does not usually induce excessive inflammation or foreign body reaction. Cellulose based materials These materials are composed of oxidized cellulose in filamentous form. The mode of action is similar to gelatin based materials. The material is resorbed and does not significantly delay healing or induce a foreign body reaction. Calcium alginate based materials The alginates derived from seaweed can be formed into filaments and woven to form absorbent pads similar to the cellulose based materials. In addition to the adhesion of thrombocytes and initiation of clotting mechanisms, free calcium is released from the alginate ensuring that there is ample available to allow the clotting mechanisms to work. Thrombin Thrombin catalyses the conversion of fibrinogen to fibrin. The commercially available form is manufactured from bovine prothrombin and is commonly available as a powder. It can be applied to the bleeding surface in the powder form or as a solution. Thrombin is inactivated in acid conditions such as found in cellulose haemostatic products. Vasoconstrictors Local vasoconstriction can be achieved by applying adrenalin solution to the bleeding surface, however, great care is required as adrenalin will be absorbed into the circulation and in patients with cardiac problems and those under halothane anaesthesia life threatening arrhythmias may develop. The easiest and safest way of applying it to an extraction socket is packing the socket with gauze soaked in a local anaesthetic containing 1:100,000 adrenalin. Once haemostasis has been achieved the gauze is gently removed. Reactive hyperemia and delayed haemorrhage is a significant risk associated with the use of higher concentrations of topical vasoconstrictors. Bone wax Bone wax is derived from bee s wax. It is pressed firmly into the bone and socket. No attempt is made to retrieve it at a later date. It delays healing. Postoperative haemorrhage Minor haemorrhage may occur postoperatively and usually causes great concern to the owner as the dilution of the blood by the saliva makes the bleed appear much more profuse than it really is. In th vast majority of cases any fresh haemorrhage resolves within a few minutes and no further action is required. It is useful to warn the owner when the patient is discharge that drinking water may become coloured by blood and that blood-tinged saliva may well be seen for a day or two. Behavioural control is advised for several days post extraction, for example: avoidance of excitement and restriction of exercise to avoid peaks of blood pressure that could start haemorrhage, and prevention from excessive chewing and carrying of objects that could disturb the wounds. Extraction 9

10 Prevention of complications The most common indication for extraction in veterinary dentistry is periodontal disease. As extraction is an invasive surgical procedure it is recommended that all periodontal treatment, i.e. supra- and sub-gingival scaling and polishing etc. be performed prior to extraction. The oral cavity then needs to be cleaned of all free-floating debris and rinsed with a suitable surgical disinfectant such as 0.1 to 0.2% aqueous chlorhexidine solution before the extractions are performed. This will prevent contamination of the extraction sockets with infected debris and promote uncomplicated healing of the extraction wounds. The majority of other complications can be avoided by a similarly careful approach to preparation and performance of the procedure. Pre-operative radiography, planning for use of surgical techniques to assist extractions, allowing plenty of time to perform procedures and a patient, gentle technique are paramount. Post-operative care The main considerations immediately post-op are to protect the blood clot, reducing the risk of infection, and to prevent stimulation of secondary haemorrhage. Extraction always involved soft tissue, and frequently bone and periosteal damage, so pain is expected following the procedure. Analgesics In most instances an opiate analgesic will be indicated for intra- and immediate post-operative pain control when extractions are to be performed. The newer non-steroidal anti-inflammatory drugs are the analgesics of choice for longer term post-op pain control providing there are no general contra-indications to their use. At normal therapeutic does these drugs provide sufficient pain relief, with minimal interference to the healing of the extraction wound. Glucocorticoids are contra-indicated During healing as they interfere with both endothelial and fibroblast proliferation as well as surface epithelialisation and predispose to infection, all stages of the healing process are delayed and prolonged by their use. Antibiotics Providing the animal does not have any medical complications antibiotic treatment is rarely necessary for dental extractions providing the oral cavity has been thoroughly cleaned before hand. In cases where there is known organ dysfunction, endocardiosis, immunosuppression or there are permanent surgical implants then a prophylactic dose of antibiotic should be given as part of the pre-anaesthetic protocol, this possibly being repeated after four hours so that an effective level is maintained throughout and for a short period after the procedure. If there is evidence of extensive local infection or marked systemic effects are apparent then a course of an appropriate antibiotic is indicated. Diet and behavioural control It is the authors preference to continue feeding the diet to which the animal is accustomed post extraction, even if it requires extensive chewing as this food will be rapidly cleared from the oral cavity and will not upset the animal s digestion. It is a good idea to restrict exercise and oral activities such as Non-feeding related chewing, carrying of toys, retrieval exercises and tooth brushing for 2-7 days post extraction. During this time an antiseptic mouthwash can be used for plaque control. Toothbrushing should be resumed as soon as possible. Extraction 10

11 Extraction Techniques Extractions should be performed following a proper case workup, including diagnostic radiology and cleaning of the oral cavity to prevent debris, e.g. food remnants, plaque and calculus, from contaminating the extraction socket and potentially interfering with normal healing. There are various combinations of techniques and procedures for tooth removal. En-block resection is one, but this is not generally applicable for dental cases, it being Most suitable for tumour resection. The exact technique or combination of techniques used will depend mainly on the root morphology of the tooth to be extracted. Open versus closed techniques Straightforward extraction of simple rooted teeth can often be performed using a closed technique, i.e. by incising and working within the gingival sulcus without raising a gingival flap, especially if there has already been loss of periodontal attachment. Even extraction of teeth with simple root anatomy can be eased by providing greater access. This is achieved by using an open technique, i.e. by incising the gingiva and raising a full-thickness gingivo-mucoperiosteal flap to expose the labial/buccal and sometimes also the palatal/lingual bone plate. This allows direct visualisation of the alveolar crest and permits removal of some bone to further ease access and directly reduce the amount of periodontal attachment. One of the major advantages of raising a soft tissue flap is that it can then be protected during the rest of the procedure and used for primary wound closure. The minor tissue trauma involved in raising a flap is nothing compared with the gingival bruising and tears commonly caused during closed extraction. Although many teeth have complex anatomy with multiple roots, it is easy to simplify their extraction be sectioning the tooth into single rooted units. In many cases this can be done by creating the simplest of gingival flaps to expose the furcations to provide access for sectioning the tooth and elevation of each of its roots. Some general guidelines for dental extraction: Living tissues should be handled gently Great force is not necessary Patience and gentle technique are much more efficient Start with a clean environment Cut epithelial attachment first Section all multi-rooted teeth into single-rooted segments Sever the attachment of the tooth to the bone Remember the proximity of the nasal chamber, orbit, nerves and blood vessels Avoid leaving root fragments behind Avoid using extraction forceps unless a tooth is completely loose Smooth off sharp bony projections to aid gingival healing Close wounds with a flap when practical Extraction 11

12 Closed extraction technique Use of the closed technique is generally only suitable for extraction of small single rooted teeth. This requires use of a variety of instruments in a wide range of sizes and shapes to fit against the different shapes and sizes of tooth root. Unlike human teeth which are quite robust, dog and cat teeth are more delicate structures, often with long thin roots, particularly when considering the deciduous dentition. A further complicating factor in the latter case is that the adult tooth forms and erupts alongside most deciduous tooth roots, so they become more fragile as they are resorbed. Both the fragility of the teeth and the lack of properly fitting extraction forceps contraindicates their use as a primary means for extraction in dogs and cars. Once a single rooted tooth/tooth segment has been thoroughly loosened then forceps may be of use for the final removal. The chosen instrument should contact the tooth over a large area, rather than having point contacts which concentrate stresses and predispose to crushing and/or fracture. The relative proportions of human (left) and dog (right) teeth. When used for extraction, dental forceps must contact a large surface area to avoid stress concentration and crushing. The most important extraction instruments are elevators and luxators. The traditional (eg. Coupland) dental elevator is derived from a bone gouge/chisel and has a robust working tip that is sharpened with a 45 degree bevel. This is unsuitable for the purpose of severing the periodontal attachment, widening the periodontal space, wedging the tooth across the alveolus and tearing further periodontal attachment, so luxators were introduced. These are thinner tipped ( knife ended) instruments that will penetrate into the narrow (normally under 0.25mm wide) periodontal space to cut periodontal fibres whilst the taper provides a good mechanical advantage reducing the force required to use the instrument. 1 1 A B 1 8 Traditional dental elevators (A) are straight ended bone gouges sharpened at a 45 degree angle (1:1 slope) on the back of the tip. Luxators (B) have a curved tip and a more gradually tapered working end (1:6 to 1:8) that provides a great mechanical advantage. They are sharpened on the front of the working surface. Newer instruments have been introduced combining features of elevators and luxators. These instruments must be sharpened on a frequent basis to maintain their working tips. Extraction 12

13 An elevator, or preferably a luxator, is selected to fit the shape of the particular root surface that is to be worked on (as most roots are not circular in section it may be necessary to use two or more sizes or shapes of instrument on each tooth root) and then worked through the gingival sulcus into the periodontal space using gentle longitudinal pressure and circumferential movements. This cuts the periodontal ligament to the depth reached by the instrument and forces the alveolar bone and tooth apart. CG/DC CG/DC the tips of dental elevators are quite thick compared with the periodontal space so they do not penetrate far. The knife blade taper of luxators allows them to penetrate deeply an cut a greater amount of the periodontal attachment. Elevation/luxation should be repeated around as much of the circumference of the root as possible. Repeated application at different sites starts the tooth rocking in it socket. This action can be increased by inserting the instrument until the tip becomes locked in place and then rotating the handle to apply and maintain additional lateral pressure against the tooth and bone whilst maintaining longitudinal pressure. Tension needs to be maintained for seconds to allow for stretching and tearing of the periodontium. Care is required to avoid applying too great a pressure to the tissues or instruments. The technique requires finesse not brute force! Simple leverage should be avoided as this is likely to damage the fulcrum and other structures. As luxators are made of softer steel than elevators, they will bend quite easily. If this happens, too much force is being used. The large diameter of elevator and luxator handles provides a significant mechanical advantage when the instrument is rotated on its long axis. When the tip is placed between two objects and the handle rotated a large force is produced over a short distance. Great care is required to avoid any transverse movement as simple leverage tends to result in unnecessary damage to both the instruments and tissues. Rotational leverage can also be applied using an elevator horizontally between tooth sections and gently rotating the working end to separate the two. Here it is important to apply the instrument as far apically as possible to reduce the likelihood of tooth fracture. Elevators and Extraction 13

14 luxators should not be used as simple levers. Simple leverage should be avoided, there is little place for it in dental extraction due to the high risk of damage to adjacent tissues (and the instrument itself). A few minutes of elevation/luxation should result in a significant degree of tooth mobility. If this is the case then gentle rotational pressure can be applied using forceps. Pressure should be held for a while then reversed and held again, both rotationally and in an intrusive and extrusive motion. If the tooth is not loosening as expected then an open approach should be used and the pre-operative radiograph re-assessed for evidence of complicating factors such as root curvature, extra roots and ankylosis. Deciduous teeth These teeth are difficult to extract since the root is long relative to its diameter and often partially resorbed. Closed extraction technique is similar to that already described for small single rooted teeth, however an even more gentle technique is needed. A further consideration is the need to avoid damage to any adjacent permanent teeth or tooth buds adjacent to the deciduous teeth. The elevator or luxator should not be inserted between the deciduous tooth and its developing permanent counterpart as this will Result in iatrogenic damage to the permanent tooth. Extraction of damaged or retained deciduous teeth, particularly the canines, is often easier and safer using an open technique. Open extraction An open technique can be applied to any tooth and it can be advantageous even where a closed extraction can be performed without difficulty as the gingival flap can be used to close and protect the alveolus at the end of the procedure. Preparation Extraction is a surgical procedure and so requires appropriate preparation of instruments and equipment as well as the surgical site. It should be checked that all the required instruments and equipment are sterilised and ready for use before starting the procedure.the teeth and oral cavity need to be thoroughly cleaned and disinfected prior to extraction. Once the teeth have been scaled and polished, all debris should be washed from the oral cavity and the entire lining and endotracheal tube, tube ties and the lips and surrounding skin that will be handled during surgery soaked in a dilute (0.1 to 0.2%) aqueous chlorhexidine solution, allowing several minutes contact time for best effect. It is wise to review the pre-operative radiographs at this stage, Raising gingivo-mucoperiosteal flaps The first stage in open extraction is to determine the size, shape and extent of the flap that will be required. The flap design should not compromise wound closure or other tissues and ideally it should permit flap extension should this prove necessary. In planning access flaps it is necessary to predict the amount of bone removal required to enable extraction so that the lines of releasing incisions will not end up over bony defects as unsupported suture lines are more prone to wound breakdown. Extraction 14

15 As flaps heal from their underside to th tissue to which they are apposed, the length of releasing incisions is not a factor. As with other soft tissue flaps, and particularly those of skin, the base of the flap should be sufficient to provide an adequate blood supply to all extremities of the flap. Much of the blood supply enters the gingiva via vessels running from the oral lining mucosa in a direction perpendicular to the mucogingival line, so any releasing incisions should also run in this direction to avoid areas of ischaemia. Providing the vasculature is not compromised, long gingivo-mucoperiosteal flaps can be raised, however, broad based flaps are preferable. Once the incisions have been made a sharp periosteal elevator can be used to carefully lift the gingiva/periosteum from the alveolar bone. Once the mucogingival line has been reached the process becomes easier as the periosteum here is less firmly attached compared with that below the attached gingiva. Closing flaps Once the tooth has been extracted and the exposed bone smoothed the flap is used to close the alveolus and protect the wound from the oral environment. When th flap is of insufficient length it can be extended and advanced by one or both of increasing the length of the releasing incisions and/or cutting the periosteal layer on the underside of the flap. The labial/buccal and palatal/lingual gingiva are apposed in a tension free manner using a synthetic monofilament absorbable suture material with a swaged on reverse cutting needle, any releasing incisions also being closed. Monocryl (Ethicon) is a suitably rapidly absorbable monofilament material, 1.5 or 2 metric sizes being good for most dogs and 1 or 1.5 metric for cats. In situations where healing is likely to be delayed and following major surgical resections a longer acting material such as PDS (Ethicon) may be preferred. Braided sutures are not suitable for intra-oral use as there is significant wicking of saliva containing bacteria and food remnants into the underlying tissues with associated infection and a marked inflammatory response. When complete closure without tension is impractical it is best to close as much of the wound as can be managed tension free and to leave the remainder to heal by second intention. On completion of suturing the flap should be gently compressed against the underlying tissues for 2-5 minutes using a damp swab. This extrudes any blood clots, ensures that the flap is properly apposed and permits fibrin to bond the layers together. Extracting the teeth Once the gingival or gingivo-mucoperiosteal flap has been raised to beyond the area involved, the teeth can be sectioned into single rooted segments and if appropriate the bulk of the crown reduced to facilitate direct access to the periodontal space. Elevation/luxation can be performed immediately if it is likely that the tooth roots can be loosened easily. Where large and ankylosed teeth are concerned, the labial/buccal bone plate overlying the roots can be sectioned or removed. Initially, only sufficient bone is removed to expose the coronal third of the root prior to implementing luxation. Should this prove difficult, the bone removal can be extended further, even as far as the apex, for many teeth, should this prove necessary. In certain cases it is also possible or preferable to remove bone of the lingual aspect of the mandible. Whenever possible removing bone on both medial and lateral aspects should be avoided as this leaves a seriously weakened jaw. Care is required if bone has to be removed on the palatal aspect of maxillary teeth due to the close proximity of the nasal cavity. The method of bone removal should be as tissue friendly as possible. Bone chisels and gouges are very efficient in thin or immature bone and properly maintained dental elevators and luxators can be used for this purpose. Rongeurs can also be used, but are less efficient, it being difficult to get them to bite into the bone alongside tooth roots. Thick, hard bone is best removed using power equipment. A round headed surgical bur in a low-speed handpiece is very effective for sculpting Extraction 15

16 the bone, however, copious saline irrigation is needed to keep it cool and to wash away the swarf. High speed dental equipment with water irrigation can be used for small areas of bone removal but this will both devitalise tissue (water is cytotoxic to connective tissues) and introduce infection (contaminated air and water are sprayed into the wound). At the end of the procedure it is important to remove as much powdered bone debris as possible as it causes a significant inflammatory response. Following bon removal the tooth is loosened by severing the remaining accessible periodontal attachment working fine elevators or luxators between the tooth root and the bone. Instruments should not be inserted between a deciduous tooth and the developing permanent tooth or tooth bud as already mentioned. Once the tooth is loose it can be lifted from its socket. When the entire lateral alveolar wall has been removed the tooth can be extracted laterally. After removing the teeth, any sharp bony prominences should be smoothed using rongeurs, bone rasps or a bur, and the area thoroughly cleaned of debris (avoiding dislodging blood clots from the depths of extraction sockets). The access flap can then be closed over the extraction socket as already described.. Extracting canine teeth The canine teeth can be difficult to extract due to their size and anatomy David A. Crossley Outline of extraction technique: Raise an access flap extending from the third incisor to the distal edge of the second premolar Make a short rostral releasing incision extending just beyond the mucogingival line Ensure that this incision is not over the tooth root to avoid consequent suturing over dead space. In the maxilla ensure that the incision does not extend beyond the nasal rim of the premaxilla Make a longer caudal releasing incision at the distal edge of the second premolar, approaching the level of the canine tooth apex Use a periosteal elevator to lift the gingiva and periosteum off the bone and fold the flap back to expose the full buccal bone plate over the canine tooth root Ensure that the neurovascular bundles exiting at the mental/infra-orbital foramen, is not transected while raising the flap The full thickness of the buccal bone plate is cut, penetrating into the periodontal space to between a Extraction 16

17 third and full root length using a round or taper fissure bur in a low speed handpiece with copious saline irrigation. The bone plate does not need to be removed. If a handpiece is not available a small bone chisel can be used Create a gutter around the exposed tooth root to permit placement of an elevator/luxator Apply the elevator mesially and distally in the gutter using rotational leverage to loosen the tooth. In the maxilla do not insert the elevator on the palatal aspect of the tooth as this will either tip the apex of the tooth medially forming an oronasal communication, or the elevator itself will puncture the nasal cavity. In either case there is the risk of fistula formation The tooth is finally extracted by lifting the loosened root out of the socket If necessary the bone is smoothed and the socket is curretted and flushed to remove any debris and ensure fresh haemorrhage for The formation of an adequate blood clot The flap is then replaced and fixed without tension using thin monofilament resorbable sutures, being gently compressed in position for several minutes Extraction of large multi-rooted teeth The dog s carnassial teeth can also be difficult to extract, however, by following the principles already outlined, i.e. raising access flaps, sectioning into single rooted segments, bone removal and patient elevation/luxation followed by flap closure, it is usually possible to remove them with minimal effort and obtain rapid and comfortable healing DaCross Services DaCross Services DaCross Services It is not always necessary to raise a large access flap. Exposure of the furcation, sectioning of the tooth and removal of a little bone will permit extraction using standard elevation/luxation and rotational leverage techniques in many cases. If a root does nor loosen as expected, the flap can be extended by making a releasing incision an further bone removed. In th case of the palatal root of the maxillary fourth premolar, bone can be removed lateral to the root to about half its length working through the alveolus of th mesiolateral root. Care is required as the infraorbital canal runs between the tips of these two tooth roots. Extraction of feline teeth The teeth of domestic cats are much smaller and more delicate than those of dogs, so greater care is required during their extraction in order to avoid root fracture. The same techniques can be used for extracting cat s teeth as previously described, however, a modification of the technique may be beneficial. Pre-operative radiography is strongly recommended to allow detection of resorptive lesions, ankylosis and bulbous root tips, which are all commonly found affecting the roots of cat teeth. This permits advanced planning of the surgery to obviate these problems. As it is difficult to avoid accidentally applying leverage to the crowns during elevation (fracturing the roots below the alveolar crest) it is preferable to remove the bulk of the crown before attempting extraction. It is possible to go a stage further and, after raising gingival flaps either side of the teeth to be extracted, to amputate the crowns completely, also removing 1/2 to Extraction 17