Retained deciduous teeth and base narrow canines are genetic in origin. Base narrow lower canines are argued to be a developmental defect or the result of retained deciduous canine teeth. The developing permanent canine tooth buds are genetically misplaced medially; therefore, they are not in position to induce resorptive action on the primary canine root structure. The result is retention of the primary canine and eruption of the permanent canine medial to the retained primary canine.
Brachygnathism, maxillary retrognathism and excessive anisognathism are genatic factors linked to base narrow canines. Clinical presentation is both primary and secondary canine teeth present at the same time. The adage of “No two teeth of the same kind present at the same time” holds true. Retained primary canines, especially base narrow primary canines should be removed but their removal will not result in a correction of the base narrow permanent canine into a proper occlusion. Interceptive extractions of the primary canines are rarely successful.
Base narrow lower canines produce varying degrees of tissue trauma, with possible oro-nasal fistula formation. Ethical considerations always play a part in the orthodontic correction of canine dentition. Base narrow canines cannot be ignored. The relief of soft tissue trauma is paramount. No therapy, when the client will comply, is malpractice.
Select cases, where the base narrow canines are locked directly medial to the upper canine teeth or are in a very difficult position to move into alignment without extensive orthodontics or extraction of restrictive dentition, can be treated with calibrated coronal amputation and vital pulpotomy. This will relieve palatal trauma. However, vital pulpotomies can fail, resulting in additional endodontic therapy. Orthodontic therapy, when possible, is the treatment of choice. Orthodontics insures proper canine function and endodontic vitality.
There are four basic orthodontic procedures for the correction of base narrow canines:
1. Direct or indirect acrylic palatal bite plane. (Tissue supported).
2. Unilateral or bilateral metallic bite planes. (Tooth supported).
3. Custom cast appliances.
4. Chemically cured composite bite planes.
The use of dental composites for base narrow canine correction began as an offspring of dental acrylics used to construct a palatally placed bite plane. The problem with dental acrylics was the difficulty in construction. Dental acrylics were applied as a powder and liquid applied in increments. Confinement of the acrylic mixture until it was polymerized was technique sensitive. The next advancement in bite plane construction was with light cured acrylic. Light cured acrylic can be placed in sheets two mm thick and light cured. This required many applications of light cured acrylic to perfect a suitable bite plane. Retention of light cured acrylic bite planes was often difficult.
The first successful composite bite plane was constructed with light cured dental composite. With this procedure, the upper canine and incisors are first acid etched with orthophosphoric acid and a universal bond lightly placed over the acid etched teeth and light cured. Light cured composite is placed over and around the canine and the three incisors on the affected side. A ramp or incline plane is built between the canine and incisors. The problem with this technique is that light cured composite, like light cured acrylic, must be cured in 2 mm increments, necessitating many applications of the composite. However, the end product is very workable and retentive, but costly.
Approximately six years ago, a new chemically cured composite was detailed at my human dental office. This human product was developed as a temporary crown and bridge material. The composite is packaged in a two-compartment canister, a base component in one compartment and a catalyst in the other. The canister is loaded into a delivery syringe called a Garant. This resembles, and functions similar to, the caulking guns employed by carpenters. As the syringe is compressed, the base and catalyst are driven through a mixing tube and expelled, mixed and ready to apply.
One of the first chemically cured temporary crown and bridge products introduced to the dental market was Protemp Garant by ESPY Inc. The composite is non-exothermic in normal applications thereby eliminating the exothermic tissue damage created by dental acrylic. The composite is stronger that acrylic and not nearly as difficult to apply. The composite does not run extensively and is easier to confine to the designed area. I initially began to use Protemp for non-invasive mandibular fracture reduction. Its use as an incline plane for base narrow canines was quickly adopted.
The procedure for construction of a composite bite plane with Protemp is rather simple. A Protemp bite plane is constructed similar to the light cured composite procedure, only the entire bite plane can be place at one time and shaped after the Protemp polymerizes. Another benefit of the Protemp is that additional composite can be placed over the initial composite placement. This is often needed to extend the composite bite plane, to reinforce selected areas, or repair defects. The composite completely bonds to itself.
The upper canine and incisors are acid etched and air-dried. However, bond is not placed over the canine and incisors. The etching is performed only to create a more retentive surface to the teeth. After acid etching, the teeth must be kept free of salivary contamination. Saliva will re-mineralize the enamel, removing the etched surfaces. Protemp is placed around the upper canine incisors and over the medial palatal area in between the canine and incisors on the affected site.
After the composite has polymerized, the incline plane is fashioned with rotary diamonds or acrylic burs in a dental high-speed and low-speed hand piece. Care must be taken to create an incline plane that is medial enough to engage the lower canine when closing. An incline plane of 45 degrees is adequate. A steep incline plane makes it difficult for the dog to create pressure when closing. All rough edges of the composite are reduced at the same time as establishing the incline plane.
There are many dental manufacturers making chemically cured composite for human temporary crown construction. Most are mixed and delivered in the same fashion as Protemp. All seem to be satisfactory for both mandibular fracture reduction and bite plane construction. All are employed with similar results.
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