Members Lectures

Saving Teeth – Alternatives to Extraction Notes

 Dr David E. Clarke

BVSc, Diplomate AVDC, Fellow AVD, MANZCVSc.

Registered Specialist, Veterinary Dentistry

 TOPICS

Pathology limited to crown

Fractured tooth crown

# enamel only – no dentine exposed or tooth displacement

# enamel and dentine – no pulpal exposure

# complicated – pulp exposure

Enamel hypomineralisation

Periodontally affected tooth

Increased periodontal sulcus or pocket

Gingival recession

Maloccluded tooth

Base narrow or lingually displaced mandibular canine teeth

Anatomy

The healthy tooth is composed of two major parts: the supra-gingival portion that extends above the gingiva and is grossly visible, termed the crown, and the sub-gingival portion that extends beneath the gingiva, termed the root. A central cavity is located within the tooth, termed the pulp canal (located in the root segment) and pulp chamber (located in the crown segment). The pulp, which consists of nerves, blood vessels and connective tissues, is located within the pulp canal and chamber. It provides nutrition and sensation to the tooth. The pulp is surrounded and therefore protected by two hard layers. An inner layer composed of dentine, which is found in both the crown and root, and an outer layer of enamel and cementum. The crown is covered in enamel. The root has an outer covering of cementum. The point where the crown and root meet is termed the cemento-enamel junction.

 

The periodontal ligament is a connective tissue that supports and holds the tooth in the alveolus. The ligament is composed of collagen and elastic fibres arranged in bundles or groups, with one end attaching to the cementum on the tooth root and the other end attaching to the maxillary / mandibular alveolar bone (cribriform plate). The periodontal ligament contains blood vessels, lymphatics and nerves. The gingiva, a stratified squarmous epithelium, is the part of the oral mucosa that covers the alveolar processes and surrounds the teeth. In the majority of animals, after the tooth has erupted to full crown height, the gingiva attaches permanently to the tooth at the cemento-enamel junction. The gingiva can be divided into two regions: the free gingiva (which lies coronal to the epithelial attachment, is mobile, and does not attach to the tooth surface) and the attached gingiva (which lies apical to the epithelial attachment, is not mobile and attaches to the periosteum of the underlying bone). The space created between the free gingiva and the tooth surface is termed the gingival sulcus. In healthy pathogen-free animals, the gingival sulcus is V-shaped and barely allows penetration with a periodontal probe. Once a bacterial population is established within the oral cavity, the sulcus enlarges and the probing depth is normally 0 – 0.5mm in cats and 2 – 3 mm in dogs.

Placing a Bonding Agent or a Composite Restorative

Clean the teeth with an ultrasonic scaler followed by a flour pumice. Remove any unsupported enamel. Apply a 37% phosporic acid to the enamel for 60 seconds tehn remove and wash. Dry with clean air. Apply a thin layer of unfilled resin / bond and air thin then cure with a blue light. If placing a composite consider the colour of the tooth and place with a plastic instrument the composite to the resin. Contour and then cure with a blue light. Smooth with Soflex polishing disks.

Partial Coronal Pulpectomy (Direct pulp capping)

Immature adult teeth with vital pulps, very recent fractures of mature adult teeth, and accidental iatrogenic exposure of the pulp may require endodontic treatment to ensure pulp vitality.

In immature adult teeth, the procedure is termed apexigenesis, where the preservation of vital pulp allows the tooth to obtain normal length and root apex closure. The pulp may be exposed following trauma, or deliberately following removal of the tooth crown as a treatment for orthodontic conditions, such as lingually deviated mandibular canine teeth (base narrow canines). If the exposure is deliberate, the procedure is termed direct pulp capping. After cutting the crown off, using a water-cooled high speed flat diamond bur, the pulp at the site of exposure should appear healthy and bleed on sterile probing. The tooth should be washed with copious amounts of sterile saline and bleeding stopped with gentle pressure with a sterile pledget or a blunt ended absorbent paper point. Once the bleeding has stopped, a dressing of calcium hydroxide or MTA is placed,followed by an intermediate layer (glass ionomer) and then a surface restorative used over this.

When the pulp has been recently exposed in a mature adult teeth, due to trauma, it is termed vital pulpotomy.

Vital pulpotomy is the removal of the coronal portion of the pulp, which aids to remove any surface infection, as well as provides a space for medications. Vital pulpotomy offers a quicker alternative to pulpectomy and leaves the tooth with a vital, healthy pulp.

The clinical steps include:

 

1. Remove about 5mm of coronal pulp. The coronal portion of the pulp is removed using a sterile round diamond bur or curette. Access may be gained via the fracture site.
2. Flush pulp with saline and place a paper point over pulp stump for 5 minutes. Haemostasis is difficult to achieve in healthy pulps, but can be obtained with gentle pressure. If the bleeding persists once the paper point is removed, check for tissue tags.       If bleeding continues for longer than 5 to 6 minutes, then the pulp may be irreversibly inflamed and a complete pulpectomy is needed.
3. Once the bleeding has stopped, a thin 1 mm layer of calcium hydroxide powder or MTA over the pulp to encourage formation of a tertiary dentine bridge.
4. Remove any excess material on the internal walls of your access hole, and place a 1-2mm layer of reinforced glass ionomer cement.       Glass ionomer provides a firm base so that you can place your composite resin without disturbing the calcium hydroxide.
5. Acid etch the dentine and enamel with 37% phosphoric acid etch and rinse off after 30 sec, then dry thoroughly.
6. Place a light cured bond/adhesive.
7. Place your composite restoration in two stages. Firstly place a flowable composite as a base. Then use a hybrid type of composite in 2 mm increments up to the level of your crown amputation or level of the fracture.
8. Finally, finish and smooth the composite with finishing burs in the high speed handpiece. You may also use polishing discs in a slow speed handpiece.

Standard Root Canal Therapy

Standard root canal therapy is indicated for mature adult teeth with long-standing infections; teeth that have discoloured crowns, which suggest internal haemorrhage and pulpal necrosis; or have periapical abscesation confirmed by periapical lucency on radiography.

Standard root canal therapy involves gaining access to the pulp canal (access), removal of all the pulp tissue (debridement), shaping of the root canal, drying the canal and filling the canal (obturation) with a canal sealer and core material and a final restorative placed.

Biological aims:

1. To remove from the root canal and chamber, all organic matter that is capable of decomposing into tissue destructive by- products or that can support bacterial growth
2. To remove or kill all bacteria present in the root canal and chamber.

Mechanical aims:

1. To prepare the root canal, which allows complete three dimensional filling
2. To fill the prepared space with a bio-compatible filling material in order to completely seal the coronal and apical ends of the canal.

Periodontal Disease

Periodontal probes are used to measure the depth of the gingival sulcus and periodontal pockets.

To determine the depth of the gingival sulcus or periodontal pocket, the graduated periodontal probe is placed along the root surface, under the gingival margin, until it reaches the resistance of the epithelial attachment. The depth of the sulcus or pocket is measured in millimetres from the gingival margin to the epithelial attachment. Measurements are made in two to three places on the buccal surface and two to three places on the lingual/palatal surface of each tooth. If the gingiva has receded, then the measurement from the epithelial attachment to the cemento-enamel junction gives the loss of attachment. The depth of the pocket, as well as, gingival recession should be recorded on the dental chart. Healthy periodontal tissues exhibit pocket measurements of 0 – 0.5mm and 2 – 3 mm in the cat and dog respectively. Therefore, measurements of 2mm or greater in cats and 5mm in dogs indicate attachment loss.

Complete treatment of teeth with periodontal pocketts requires sub-gingival scaling and curettage. The term root planing is used to describe scaling of the tooth root. The act of root planing removes plaque, calculus and other foreign matter, i.e. hair, food, from the periodontal pocket, as well as, the superficial layer of endotoxin rich cementum from the root surfaces. The term gingival curettage is used to describe the action of scraping the necrotic epithelial cells, endotoxins and accumulations from the epithelial wall lining the pocket. Gingival curettage is performed using curettes.

The curette is introduced into the periodontal pocket. When the blade reaches the base of the pocket, it is turned to contact the tooth surface. The shank of the instrument should be parallel to the long axis of the tooth for perfect contact of the blade against the root and used with a pull stroke from the depth of the periodontal pocket, with the blade against the tooth root surface. Once calculus, plaque, hair, debris, food, diseased cementum, cementum endotoxins, necrotic and diseased cells have been removed from the pocket, a smooth, glass like sheen should be present on the tooth root. A clean pocket promotes reattachment of the epithelial wall to the tooth root via fibroblastic activity through production of collagen and connective tissues. Local delivery antibiotics, using doxycycline, can be used to enhance this action.

Once the pocket is clean, to prevent accumulate plaque and food entering and to encourage reattachment of the gingiva to the tooth root, a local delivery antibiotic impregnated gel or Consil can be used that stimulate new periodontal ligament and alveolar bone. Doxycycline or clindamycin impregnated polylactic acid polymer gel is placed into the periodontal pocket. The gel adheres to the tooth root, as well as filling the void between the gingival margin and the tooth, thereby preventing plaque and debris entering the periodontal pocket. As the polylactic acid degrades, antibiotic is released, making it available for its antibacterial and anti-collagenase action.

Consil is an osteopromotive bioglass bead, which can be used in periodontal pockets to promote new alveolar bone production and encourage re-attachment of the gingival tissues and periodontal ligament. Consil has the consistency of sand. In the maxilla, Consil can be difficult to keep in situ, so the gingiva must be closely attached to the tooth using purse-string sutures.

Base narrow mandibular canine teeth

Base narrow canine teeth may occur due to retained deciduous canine teeth or may be genetic where the breeders have deliberately bred for a narrow mandible and thus have forced the mandibular canine teeth closer together resulting in traumatic damage to the hard palate.

If the canine teeth have not fully erupted, composite material can be bonded to the cusps of the teeth to guide them into healthy occlusion. The technique is the same as described previously for composite restoration. The composite is contoured so that the tooth erupts into the diastema of caudal to the maxillary canines. As the teeth erupt then move into the position that the composite directs them into.

Crown amputation involves using a high speed diamond tapered bur to cut the crown at the level of the adjacent tips of the incisor cusps. The direct pulp capping (vital coronal pulpectomy technique) has been decribed previously. Orthodontic correction can be achieved by either a maxillary incline plane appliance.

The maxillary incline appliance is anchored to the maxillary canine and lateral incisor teeth. The plate acts as a retention device after the teeth have moved and is quite acceptable to the patient. The incline appliance can be manufactured in acrylic or Protemp Garant within the patients mouth under one general anaesthetic, but often a better appliance can be manufactured in metal or acrylic at an orthodontic lab, but impressions and models are required and thus another anaesthetic is necessary to cement the appliance in the mouth.

If the appliance is modeled in the mouth, wax can be used as a dam and then the acrylic or Protemp Garant is poured onto the hard palate and set. Once it is set, a Goldie bur can be used in a slow speed hand-piece to cut inclines into the appliance at the point where the mandibular canine will contact the appliance and inclined towards the diastema between the 3^rd incisor and canine tooth. The incline can be smoothed using polishing paste or a composite resin. The appliance works because every time the patient closes its mouth, the cusps of the canine teeth contact the incline and force the teeth laterally, until eventually the teeth are forced into the correct occlusal position. The appliance will then act as a retainer. Generally the movement should take a month.