Today’s dental patient has extremely high expectations, often asking us to seemingly perform miracles. Sometimes this is unrealistic and just not possible. In the medical world, patients must accept and live with compromises to their health, but some dental patients always seem to expect perfection.
A dentist must be very careful when making the decision to attempt a challenging restoration in the aesthetic zone, especially when the gingival level is directly in the line of vision. The practitioner’s clinical judgment is essential. It is important for the dentist to first perform a complete examination, establish an accurate diagnosis, and assess all treatment possibilities. The clinician should then present all the various treatment alternatives to the patient; educated patients will usually make choices in their own best interest.
Root Caries and Fractures
The incidence of root caries and fractures in the adult population is increasing. Root caries (like other caries) results from the interaction of bacterial plaque, dietary carbohydrates, and a vulnerable tooth surface. The incidence of root decay is influenced by numerous factors such as gingival recession, diet, poor oral home care, and xerostomia caused by medications, chemotherapy, and radiation. The primary causes for root fractures are: (1) occlusal forces, both chewing and parafunctional, that overload the tooth and fracture brittle roots that may have had previous endodontic treatment and large post spaces; and (2) trauma to the teeth by accidents, bruxism, chewing ice, etc. Root fractures are usually untreatable and the teeth condemned for extraction.
To Treat or Not to Treat?
A tooth must be biologically savable in order to attempt to achieve a long-lasting, patient-pleasing restoration. We must first decide if the tooth is treatable and then compare the cost of treatment versus the cost of the alternative choices as well as the prognosis for each. We must assess if the structure of the tooth has sufficient root length, width, wall thickness, and ferrule. A retentive tooth preparation requires a grip on solid tooth structure (ferrule) of at least 2.0 mm and a wall thickness of at least 1.0 mm to allow us to place a post buildup to be able to accommodate the intraoral forces placed on it.1 We must also determine if there is root caries, internal or external resorption, parafunctional habits, evaluate the endodontic and periodontal status and judge if the crown-to-root ratio is suitable to hold a restoration.
There are also aesthetic parameters to observe and follow when working in the aesthetic zone. We must be aware of the tooth position, gingival levels, tooth arrangement, contour, and color. Sometimes these must be intentionally altered even if we are planning to lose the tooth.
A commonly used simple recipe from our dental cookbook is the use of orthodontic extrusion of teeth as a tool to modify gingival and bone levels to recreate aesthetic harmony. Forced orthodontic eruption is a technique for soft- and hard-tissue augmentation, based on osteophysiologic and orthodontic principles. It was first described in the literature by Heithersay2 and Ingber.3 Depending on the forces exerted, orthodontic extrusion is able to alter the position of the gingiva and the underlying crestal bone or can erupt the tooth further out of the bone, allowing us to have a more solid tooth ferrule to work with. Forced orthodontic eruption can be used as a tool to correct infrabony defects, reposition a gingival margin, change a root position, and to achieve a clinical crown lengthening.
There are 2 types of orthodontic extrusion: (1) low intensity extrusion of less than 30 g of force, and (2) high intensity (rapid) extrusion with forces exerted greater than 50 g.
Low intensity orthodontic extrusion, using less than 30 g of force, can produce approximately 1.0 mm of extrusion per week. It stimulates the marginal positioning of the crestal bone and allows the gingiva to follow it. The alveolus, being attached to the root by the periodontal ligament, is in turn pulled along with the movement of the root.
The ability to change the gingival position via the extrusion of teeth gives the clinician the ability to control dental aesthetics.4 Traction forces are placed on the tooth, bringing the crestal bone along with it into a new position. The gingiva follows the vertical movement of the tooth and bone. The presence of the tooth allows us to modify the position of the bone and gumline. The absence of teeth makes these alterations difficult.
We must manage the anterior ridge at the time of extraction to maintain tissue with good interproximal and facial tissue height, as we do not want to lose papillae, creating spaces between the adjacent teeth that are often described as “black triangles.” This is especially critical in patients who have gingival margins that are visible in the direct line of vision.5
The easiest way to maintain gingival aesthetics is to retain a natural tooth or root, because natural teeth stimulate the body to maintain tissue and bone. Before we extract a tooth, we must think about how we will maintain the aesthetics of the anterior ridge. We must maintain the interproximal tissue height in order to retain the interdental papilla. We must maintain the position of the facial free gingival margin in order for the replacement tooth to be in gingival harmony with the adjacent teeth. We must also maintain adequate facial tissue bulk in order for the tissue labial to the tooth to have proper aesthetics.6
There are several alternatives available to us to replace a missing anterior tooth: (1) acid-etched bonded bridge, (2) partial denture, (3) traditional fixed bridge, (4) cantilever bridge, and (5) implant.
Single-tooth anterior implants can be viewed as the most conservative form of treatment available today due to their ability to leave the adjacent teeth unrestored. An understanding by the surgeon and restorative dentist of implant placement and soft-tissue management is the most critical element in their use. There are biological considerations to consider: Is there available bone for an implant? Is there sufficient interroot distance for an implant? Does the patient require and/or consider orthodontics?
Single-tooth implants are especially indicated if the teeth adjacent to the edentulous area do not need restoration, and the natural teeth guide the patient’s occlusion so as not to place excessive occlusal forces on the implant. The use of a surgical placement stent allows the surgeon to maintain the tooth’s incisal edge and the desired free gingival margin position.
If all the aesthetic parameters surrounding an implant site are met, and we believe they can be maintained after extraction, the ideal treatment is to extract the tooth and to place an immediate implant within the envelope of bone. However, when our parameters are not met, or cannot be guaranteed to be maintained after extraction, we can turn to orthodontic extrusion to overbuild the bone and soft tissue. This would then be followed by immediate placement (at the time of extraction) and the placement of a provisional restoration to support the postextraction gingival soft tissue.
Salama and Salama7 described using orthodontic extrusive remodelling to augment both hard- and soft-tissue profiles of potential implant sites. Tooth extractions in the anterior maxilla usually cause defects and deficiencies in the alveolar ridge. Orthodontic extrusive remodeling can create a greater volume of alveolar bone and soft tissue in the vertical and horizontal plane, without the need for further surgical intervention. By stretching the gingival and periodontal ligament fibers, low intensity orthodontic extrusion places tension on the entire alveolar socket, stimulating apposition of the alveolar crest. This conservation of the ridge allows the placement of the dental implant in the exact position and axis of the extracted tooth. Making the diameter of the remaining alveolus smaller by extrusion allows the endosseous implant to be firmly placed at the time of extraction. The implant is able to have more intimate contact with the alveolar bone, making it more stable and for osseointegration to occur earlier. It is much easier to remodel bone and tissue using a patient’s existing tooth than by using additive procedures. The orthodontic eruptive phase usually takes 4 to 6 weeks with a stabilization period of a minimum of 3 months or 4 weeks for every millimeter of extrusion.
Orthodontic extrusion is indicated any time there is facial or interproximal bone loss because, by moving the bone and gingival level coronally, we create a more predictable environment to place the implant.8 Even if some bone is lost following the extraction, by overbuilding the bone in advance, rarely is any bone or gingival grafting necessary and the temporary restoration able to support the tissue. The tooth comes out, the implant goes in, and we place a provisional without occlusal interferences.
Preparing an Aesthetic Implant Site
Orthodontic extrusion can be used to help predict aesthetic harmony in situations where a tooth must be lost. When teeth are broken or decayed under the gumline, the extraction of these teeth may quite possibly leave a defect in the gingiva and bone. Even with current gingival and bone grafting technology, these defects may be difficult and unpredictable to repair. The presence of an existing root gives us the ability to use orthodontic traction, enabling us to alter the position of the gingival crest and underlying alveolar bone. If we overcompensate the position of the gingival crest, we leave ourselves a safety factor if a defect remains after the extraction.9
Diagnosis and Treatment Planning
Our patient presented with a loose post and crown on her upper left central incisor (tooth No. 9). Endodontics had been performed on this tooth due to an accident 25 years earlier when she was a teenager (Figures 1a and 1b). The remaining root was decayed, discolored, internally resorbing, and had very thin supporting walls inhibiting the creation of a retentive ferrule (Figures 2a and 2b).
|Figure 1a and 1b. A loose crown and post on an upper left central incisor.|
|Figures 2a and 2b. The weak and fragile root.|
It was determined that any attempt to salvage this root would be highly unpredictable. It would be unlikely that a new post and crown would last for more than a few years and, after assessing the cost of treatment versus the alternatives and the prognosis for each, it was determined that extraction of the root and placement of an implant was the logical choice.
However, the extraction of this decayed and fragile root presented the possibility of creating a large bony defect that would likely be extremely difficult to repair after the extraction. Single-tooth implants placed in aesthetic areas require extreme precision. The fact that this patient displayed gingiva in our direct line of vision made this situation even that much more challenging. A single-tooth implant must be successfully osseointegrated, and in harmony with the adjacent teeth and surrounding hard and soft tissue. The fact that her existing root was still firmly in the alveolar bone allowed for the opportunity to alter the level of bone and gingival using orthodontic extrusion. If the position of bone and gingiva was deliberately overcompensated before extraction, it would help safeguard against a huge defect following the removal of the tooth.
As much as possible of the decay and resorbtion were removed from the remaining root, and then the canal was instrumented to the size of an anterior Super Post No. 3 (Dental Savings Club). This large-diameter fiber post fit intimately into the prepared canal, allowing sufficient orthodontic traction forces to be placed, enabling the root to be extruded. The instrumented canal was first treated with etching gel (Uni-Etch [BISCO Dental Products]) and an adhesive (All-Bond Universal [BISCO Dental Products]). A multipurpose (dual-cure) core and build-up resin (Spee-Dee Build Up Core [Pulpdent]) was injected into the treated canal as a cement. Next, the fiber post was placed into it and light-cured for 30 seconds with a curing light (VALO [Ultradent Products]). We then continued to build up the tooth with the multipurpose core material and allowed it to cure. The tooth was then prepared for a provisional crown. The Spee-Dee Build Up Core material has a glasslike and void-free consistency that cuts like dentin, and it contains flouride. The crown preparation incorporated subgingival margins, creating a definitive ferrule on solid root structure. A provisional crown was then fabricated using a pretreatment template. (Crystal Affinity [CLINICIAN’S CHOICE]) filled with a bis-acryl resin (Luxatemp Ultra [DMG America]). After setting, the bis-acryl resin material was trimmed and coated with Luxaglaze (DMG America). It was then cemented (Fuji Plus Cement [GC America]) to the prepared tooth (Figures 3a and 3b).
|Figures 3a and 3b. The new post build up and permanently cemented bisacryl crown.|
Damon Clear Anterior brackets with a 0.022 slot (Ormco) were bonded from canine to canine and brackets (Speed Brackets [Speed Ortho]) were placed on the posterior and lower teeth; their clip allows for easy wire changes and for all torques to be fully expressed, ensuring accurate angulation of the teeth. Heat-activated high-memory wire (Ormco) was used with gauges increasing from 0.14 to 0.16. Extrusion forces of 16g to 20 g were placed, altering the position of the left maxillary central incisor and its supporting structures. The patient also chose to correct her crowded mandibular incisors. Having the lower arch in ideal position allows the restoration of the maxillary teeth to be much easier since balanced functional forces can be achieved (Figure 4). As the central incisor was extruded, we progressively reduced the lingual surface, allowing the extrusion to occur without any interference from the lower anterior teeth. We migrated the bracket gingivally every second appointment, allowing an extrusion of one mm per month. Once the gingival height was 3mm to 4 mm incisal to that of the adjacent central, the orthodontic forces were eliminated and the root allowed to stabilize in the alveolar bone for 4 months (Figure 5).
|Figure 4. Orthodontic placement with extrusion forces placed on the upper left central incisor.||Figure 5. The completed extrusion, overcompensting the gingival position.|
|Figure 6. Creating an even scallop on the crest of the buccal plate.|
|Figures 7a and 7b. Immediate implant placement 4 mm subgingival allowing for subsequent recession.|
|Figure 8. Allogeneous bone graft placed between the buccal plate and the implant.|
The tooth was then easily extracted and the crest of the buccal plate was reshaped with a No. 4 round bur to create a uniform scallop (Figure 6). A Zimmer Tapered Screw Vent 4.7 mm implant (Zimmer Dental) was placed into the extraction site 4 mm subgingivally out of contact with the buccal plate (Figures 7a and 7b). Allogeneous bone graft (Citagenix) mixed with platelet rich plasma was then grafted between the implant and the buccal plate (Figure 8). The subgingival placement of the implant will compensate for the possibility of the gingival and bone height receding following the extraction and implant. By overcompensating the depth of the implant placement, any further gingival tissue reduction necessary can be simply performed following healing. The implant was judged to have exceptional primary stability and suitable for immediate provisionalization.
A plastic temporary abutment (Zimmer Dental) was prepared and screwed directly to the implant (Figures 9a and 9b). A new bis-acryl provisional was then fabricated using the template of the original tooth. This immediately loaded provisional did not have any contact in centric occlusion or in any excursive movement, allowing no force to be placed on it. The patient was advised to avoid biting in this area. The immediate placement of the provisional satisfied the patient as she did not feel toothless, and it gave us the ability to align and preserve the patient’s tissue levels and gingival papilla (Figures 10).
|Figures 9a and 9b. Preparation of the plastic temporary implant abutment.|
|Figure 10. The immediately loaded provisional is short incisally and gingivally allowing no centric or excursive contact.|
After allowing 6 months for implant integration, gingival healing and adaptation, the transitional post and provisional crown were removed, and impressions, bite registration, and shade selection taken for the final all-ceramic restoration. A series of intraoral photographs illustrating the nuances of the internal coloration and transparencies of the adjacent incisors was forwarded to the dental laboratory team.
An Atlantis zirconia abutment (DENTSPLY Implants) was milled, allowing the creation of all ceramic crown for maximum aesthetics (Figure 11a and 11b).
The Atlantis abutment was then waxed to create the design for a lithium disilicate all-ceramic crown (IPS e.max [Ivoclar Vivadent]). An LT BL2 ingot was pressed, and then cut back to accept incisal and cervical characterization. The IPS e.max Ceram Essence Essence stain kit’s (Ivoclar Vivadent) E15 profundo was placed on the incisal third and the cervical third received shade 010 terra-cotta. Delicate white staining was placed to simulate fine internal fissures using IPS e.max Ceram shade 0. A wash firing sealed the colors. EO2 e.max Ceram was then built up the body, giving an opal effect to subdue the internal staining. EO1 e.max Ceram was placed in the incisal portion for a transluscent effect. The porcelain then received another firing. A further cutback of 0.2 mm accomodated the placement of IPS e.max Ceram Dentin 020 in the cervical third and IPS Empress Universal Shade Incisal 2 violet with a touch of mamelon porcelain enhanced the incisal third. The crown was then fired for the final finish and glaze.
|Figures 11a and 11b. The Atlantis zirconia abutment and e.max crown.|
|Figures 12a and 12b. The Atlantis zirconia abutment torqued and sealed.|
|Figure 13. The final e.max restoration.||Figure 14. A difficult challenge being successfully met.|
When the final post and crown was delivered from the dental laboratory team, it was assessed to be sure it satisfied the parameters of our lab photos and provisional model. The patient was then called for the restoratove delivery appointment.
The Atlantis abutment (DENTSPLY Implants) was torqued to the implant (Zimmer Dental) (Figure 12a and 12b). The access opening was closed using teflon tape covered with composite resin. The lithium disilicate crown (IPS e.max) was then permanently cemented (Fuji Plus [GC America]) 9Figures 13 and 14). The excess cement was meticulously removed, and then a radiograph taken to ascertain that no excess cement remained.
Our patient was delighted with the final restoration, with her expectations totally satisfied. She could not differentiate the all-ceramic crown from her natural teeth.
The combination of meticulous treatment planning together with special chemistry among patient, dental team, and laboratory ceramist usually is common to our most successful cases. This magic combination often enables even the most difficult aesthetic challenges to seem to be easily accomplished.
Dr. Mechanic would like to thank his exceptional team: Dr. Brita Nadeau (orthodontics), Dr. Eric Chatelain (implantology), Sophie Labelle (chairside assistant), and Mr. Bassam Haddad, Vivaclair Dental Lab (ceramics).
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Disclosure: Dr. Mechanic reports no disclosures.