Presented to referring veterinarian with a complicated crown fracture of maxillary left 3rd incisor tooth from chewing on concrete 3 weeks ago. He was prescribed Amoxycillin 10mg/kg bid and Rimadyl 2mg/kg sid until the tooth could be treated.
HR 148, RR panting, mm pink and moist crt < 2 secs, Mentation: bright and alert, body condition score 4/9, hydration nad, Preanaesthetic blood haematology and biochemistry profile was within normal range. USG 1.035, dipstick pH5, no other abnormalities.
Oral examination revealed a complicated crown fracture (CCF) of the maxillary left 3rd incisor tooth (203) which is defined as a fractured crown with pulp exposure and rotation of maxillary right and left 3rd premolar teeth (107/207)
A good working knowledge of the normal tooth, pulp, and pulp cavity morphology and function is essential in assessing abnormalities and making a logical decision concerning endodontic procedures1. In a dog of this age with a recently erupted permanent dentition, it is expected that the pulp cavity of the third incisor tooth will be quite large. It would also be expected that the apex will be closed, as dogs have an apical delta, where the main root canal divides into a substantial number of multiple accessory canals opening a few millimetres from the apex. There are typically 6-90 of these small delta openings2. Despite Clarke’s study3 which demonstrated a 23.5% success rate following vital pulp therapy 3 weeks after pulp exposure, in an animal with an immature permanent tooth fracture, it is preferable to maintain a vital pulp in order to allow continued dentine deposition and increased strength of the fractured tooth. Dentine is laid down in layers within the pulp cavity as long as the tooth is vital, resulting in the pulp cavity’s gradually decreasing in diameter with age. The chances of this are increased because of the wider pulp canal, the higher numbers of pulpal stem cells and the more efficient apical vascular supply. If pulp vitality is maintained root development can continue along with healing of the coronal pulp wound. Even if the trauma produces an irreversible pulpitis and the pulp becomes necrotic, the pulp canal width may be reduced and the long term strength of the crown will be improved as more dentine is laid down during the months following the procedure.
The main risk in performing vital pulp therapy in a lesion of this duration following pulp exposure is that the infection may have progressed further into the pulp tissue than is removed during the procedure, ie infected pulp is left within the canal post procedure, leaving an irreversible pulpits and eventually pulpal necrosis.
A clear understanding of how inflammation in a low compliance system causes ongoing damage to the pulp becomes critical in the decision making process4. The alternative to partial coronal pulpectomy and direct vital pulp capping is complete pulpectomy procedure (root canal procedure). In removing the entire pulp from the canal, the odontoblasts are also removed or damaged and dentine will no longer be produced to thicken the dentine layer, narrow the pulp canal and as such strengthen the tooth. The endodontic debridement of the root canal will further damage and remove intraradicular and intracoronal dentin and cause changes in collagen cross linking and dehydrate the dentin. Cohen5 quotes a 14% reduction in strength and toughness of endodontically treated molars in people, resulting in a large relatively brittle canal that is more at risk of fracture than a healthy tooth with a vital intact pulp. An aesthetic consideration following complete pulpectomy is discolouration of the tooth due to an immature tooth having limited dentin formation. The decision was made to perform a partial coronal pulpectomy.
Anaesthesia and pain management:
Pre-medication: Buprenorphine 300ug/ml 1.2ml, Acepromazine 2mg/ml 0.25ml, Atropine 0.65mg/ml 3.0ml SC at 1.20pm. Intraveneous cathether placed in right cephalic vein at pre-medication: Hartman’s commenced at 3mls/kg/hr until Induction.
Induction: Ketamine 100mg/ml, Diazepam 5mg/ml 1:1 mix 3ml IV at 2.50pm. During surgery IV fluid therapy maintenance 10ml/kg/hr and continued for one hour post-op
Maintenance: Isoflurane 1-3% in 100% oxygen via a cuffed #10 endotracheal tube
Local nerve block placed using left infraorbital block with 0.5mls 3% mepivicaine (0.015mg) at 3.00pm, Meloxicam 7.2mg SC at 3.45pm
A complete COHAT was performed and a dental chart completed for the whole mouth. The incisor tooth was radiographed confirming a complicated crown fracture and healthy periradicular tissues An infra-orbital nerve block was placed using 0.5ml 3.0% mepivacaine solution in an aspiring syringe and 30g needle.
The teeth were scaled with an ultrasonic scaler and polished with a slow speed cup and paste. The fractured tooth was sterilised using 0.5% chlorhexidine for 60 seconds and a sterile drape placed to isolate the tooth from the oral cavity. Using a sterile tapered diamond bur in a high speed drill with water cooling, 5mm of coronal pulp was removed a-discussion. A high speed water-cooled abrasive diamond bur has been shown to produce the least amount of damage to the underlying tissue during pulp removal7. The amputation site must be clean with no sheds of tissue or dentine debris remaining. Pulpal haemorrhage was an indicator of current pulp vitality. Haemostasis was obtained using an adrenalin impregnated pledget left in contact with the pulp stump for 30 seconds. Once the pledget was removed, the pulp stump is visually checked to ensure hemostasis. A 1mm layer of Biodentine ® was applied to the pulp stump Biodentine® takes 12 minutes to set after which a sandwich glass ionomer layer is used to fill the canal 1mm short of the fractured surface of the crown Glass ionomer is applied to create an hermetic seal to the canal whilst the dentinal bridge forms. The glass ionomer is cured with a blue wave length light. Once cured, the exposed tooth surface is etched with 37% phosphoric acid for 15 seconds , then rinsed with water and gently dried with air from the 3 way syringe. An unfilled composite bond is applied directly to the etched tooth surface with a microbrush, thinned out with gentle air spray and light cured. A composite restorative is then applied to the crown of the tooth to protect the underlying glass ionomer, dentine and to provide normal anatomical structure. Various shades of composite were chosen and placed against the enamel in order to choose the most appropriate shade for this tooth age and quality . The composite restoration is light cured in 2mm increments. The composite restoration is polished, starting with course grade sanding discs and working through to the finest disc to achieve a smooth finish, which reduces accumulation of plaque and calculus. The sanding process is managed with continuous water spray from the 3 way syringe to prevent overheating of the tooth and pulp to decrease concurrent pulpitis. The final smoothness of the restoration and the margin is checked with a dental explorer probe to assess and determine whether there are any overhangs.
- It is usually necessary to remove only a few millimetres of pulp tissue. Tradionally the term pulpotomy in human dentistry implied removal to the cervical line, but this is neither mandatory nor advisable. It is up to the clinician to determine the depth to which tissue is removed which should include all irreversibly inflamed so medications are placed against healthy uninflammed pulp tissue. Cvek has shown that in humans the time between accident and treatment is not critical so long as superficially inflamed tissue is removed prior to treatment6. Clarke published data to demonstrate in dogs that time is directly proportional to treatment success3. The difference could be explained by the species, the different tooth anatomy or physiology, or the knowledge, skill and competence of the clinician.
- Biodentine® is a bioactive dentin substitute with mechanical properties similar to dentin and can replace it in both the crown and the root. It stimulates the pulp cells resulting in the production of reactionary dentin. This leads to formation of a dentin bridge faster and with a greater thickness than similar products have been shown to, optimising the ability to maintain vitality of the pulp canal. The manufacturer Septodont recommend the product for its high-purity, monomer-free mineral ingredients and is high biocompatibility. This creates the optimal conditions for maintenance of pulp vitality, by providing a very tight seal on the dentin surface, thus reducing the risk of postoperative sensitivity and the longevity of the restoration in vital teeth.
- The use of air is important with regard to desiccation of the dentin and damage to the intra-tubular collagen bundles. If a jet of air is forced over the freshly cut surface of dentine, a rapid outward movement of fluid occurs which stimulates the sensory nerve of the pulp producing pain and drawing the odontoblast up into the tubules resulting in their death. The pulp itself is not injured.8,9. Ultimately odontoblasts that have been destroyed are replaced by new odontoblasts that arise from the cell-rich zone of the pulp and begin to produce reparative dentine10. On the other hand, the air causes a collapse of the dentinal collagen which results in a weaker bond strength.
- Cephalexin 740mg slow IV 3.00pm
- Meloxicam 7.2mg SC at 3.45pm.
- Amoxycillin 500mgPO bid q 7 days
- Meloxicam 0.5mg/ml 3.6mg sid q 3 days.
Antibiotics were prescribed as the pulp was exposed for 3 weeks until treatment could be performed, thus there was a high chance the pulp was infected. Non-steroidal anti-inflammatories were prescribed to treat pulpitis.
Post operative review:
Reevaluation in 10 days time to ensure the final composite restoration was intact. The owner was asked to feed soft chunks of meat or food that could be squashed between thumb and forefinger for 90 days.
Further treatment required:
- Radiography of the tooth is recommended 90 days post operatively to assess the formation of a dentine bridge.
- Wiggs RB. Endodontic anatomy, pathology and examination. NAVC Proc 1992:106.
- Hennet P. Apical root canal anatomy in the dog and its significance. Veterinary Dental Forum. 1990.
- Clarke DE : Vital Pulp Therapy for Complicated Crown Fracture of Permanent Canine Teeth in Dogs: A Three Year Restrospective Study. J Vet Dent 2001,18 117-121.
- Syngcuk K : Neurovascular Interactions in the Dental Pulp in Health and Inflammation. J Endo 1990,16/2 48-52
- Wagnild GW, Mueller KI : Restoration of the Endodontically treated Tooth. In: Pathways of the Pulp(Cohen S,Burns RC 1994 Mosby 607-609.
- A clinical report on partial pulpotomy and capping with calcium hydroxide in permanent incisors with complicated crown frctures. J Endod 4:232, 1978
- Granath LE and Hagman G. Experimental pulpotomy in human bicuspids with reference to cutting technique, Acta Odontol Scand 29:155, 1971.
- Bergenholtz G et al. Bacterial leakage around dental restorations: its effect on the dental pulp. J Orla Pathol 11:439, 1982.
- Berggren H. The reactionof the translucent zone to dyes and rasisotopes, Acta Odontol Sacnd 23:197, 1965.
- Bowen RL, Cobb En, Rapson JE. Adhesive bonding of various materials to hard tissues: improvement in bond strength to dentin. J Dent Res, 61:1070, 1982.