Malposed teeth, including flared and crowded incisors, tipped molars, and fractures apical to the alveolar crest, are just some of the problems dentists are confronted with on a daily basis. In response to these challenging problems, simple appliance therapy techniques are an approach to treatment that should be considered.
Many patients are concerned with the appearance of their teeth and request that the dentist improve their aesthetic presentation. Full orthodontic therapy may not be an option, so minor tooth movement should be considered. This article will describe some of the approaches using removable appliances that can give patients the smile they want while providing optimum restorative/prosthodontic care.
REPOSITIONING MAXILLARY ANTERIOR TEETH PRIOR TO PLACEMENT OF VENEERS
Before the introduction of veneers, improvement of anterior aesthetics generally involved preparing teeth for full-coverage porcelain crowns. Removal of significant amounts of tooth structure was the rule, not the exception. Today, porcelain veneers allow dentists to solve a range of aesthetic problems without having to remove large amounts of tooth structure. However, to achieve an ideal result, it is often wise to consider minor tooth movement as a prelude to the restorative phase of care.
|Figure 1. Typical minor tooth movement and veneer case—facial view shows overlapping
central incisor and lateral incisor prior
|Figure 2. Occlusal view showing the labial position of the central incisor. Establishing an acceptable aesthetic result without orthodontic intervention would require endodontic therapy .|
|Figure 3. A simple removable appliance with various springs can be used to reposition teeth prior to placing veneers.||Figure 4. Occlusal view post orthodontics... teeth in alignment and ready for veneers.|
|Figure 5. Occlusal view after veneer placement.||Figure 6. Facial view after minor tooth movement and veneer placement.|
A typical example of minor tooth movement in an adult prior to placement of veneers is illustrated in Figures 1 through 6. This patient presented with a labially positioned central incisor that overlaps the adjacent central incisor and a peg lateral incisor that is lingually placed. After a diagnostic wax-up was completed, 2 options were considered. The patient could have the 4 incisors prepared for crowns (which would have required endodontic therapy for the labially placed central incisor), or he could be treated with minor tooth movement to realign and evenly space the anterior teeth prior to placing veneers. The patient chose the less invasive second option. In this case, a simple Hawley retainer was used with springs to move the central incisors distally, and protrusion finger springs were used to move the lateral incisors labially. (Note: A uniform, internationally accepted method for naming different types of orthodontic springs has yet to be established. They are named according to their function, their direction of force, their form, or their location).1 The total treatment time to align and evenly space the anterior teeth prior to placement of the veneers was 2.5 months.
After the veneers were completed, a Talon splint (Talon Acrylics, Comfort Acrylics) was used as a retainer. This type of retention was chosen because the patient had a history of bruxism. This splint has a dual laminate design with a soft thermoplastic internal layer.2 This internal layer protects against the potentially damaging effects of occlusal pressure points on the porcelain veneers.
CORRECTING MANDIBULAR ANTERIOR CROWDING
One of the most common complaints voiced by adult patients is crowding of the mandibular anterior teeth. Crowding is defined as not having enough space between the cuspids for the lateral and central incisors to be ideally aligned in the arch form. When this occurs, the lateral and central incisors overlap and are forced either labially or lingually. Correcting this problem begins by the dentist carefully evaluating the severity of the crowding and the relationship of the maxillary and mandibular anterior teeth in occlusion. Measuring the amount of crowding is accomplished by comparing the existing space to the space needed to align the anterior teeth. Measuring the existing space is accomplished by measuring the space from the mesial aspect of one cuspid to the mesial of the other. Measuring the required space is accomplished by summing the mesial-distal widths of the central and lateral incisors at their widest point.
When the mandibular anterior crowding is 1.5 mm or less and adequate overjet exists between the maxillary and mandibular anterior teeth to move the mandibular teeth labially, carefully recontouring the interproximal enamel of the 6 mandibular anterior teeth and placing an activated removable appliance (eg, a Spring Hawley) can generally correct this limited degree of crowding.
To fabricate this appliance, the dentist or laboratory technician must first reset the mandibular anterior teeth on the model into the ideal position. This requires that each tooth be adjusted proximally to the same degree that will be required in the mouth. The Spring Hawley retainer is then fabricated to this ideal position.3 It is important to note that on the day of delivery of the appliance—and not before—the interproximal recontouring of enamel is accomplished. This will allow the teeth to move into the ideal position as guided by the appliance.
If the patient’s overbite is deep and the mandibular anterior teeth already make contact with the palatal surfaces of the maxillary anterior teeth, the appliance will not promote movement of the teeth into their idealized position regardless of the amount of recontouring or the force exerted, since this contact will simply prevent any labial movement of the mandibular anterior teeth.3 Therefore, it is critical that the dentist evaluate the overbite relationship prior to selecting this treatment approach.
|Figure 7. Orthodontic relapse—mandibular anterior crowding often reoccurs after orthodontic treatment when a patient neglects to wear a retainer.||Figure 8. A Spring Hawley Retainer can be used to correct up to 1.5 mm of crowding.|
|Figure 9. A matrix can be used to bond a retentive wire to each tooth.||Figure 10. Mandibular anterior teeth realigned, with a retentive wire bonded to each tooth.|
In the clinical case shown in Figures 7 through 10, a minimum amount of mandibular anterior crowding was present because the patient did not wear the prescribed retainer after orthodontic therapy. Although the degree of crowding may not appear serious, once the interproximal contact points have been broken, drifting and crowding can worsen over time if left untreated.
Once this minor tooth movement procedure was completed, a laboratory-fabricated indirect matrix was used to bond a retention wire to each tooth. This method of retention is ideal for maintaining the mandibular anterior teeth in their corrected position.4
FORCED ERUPTION PRIOR TO THE PLACEMENT OF AN AESTHETIC RESTORATION
A challenging clinical problem is presented by a patient with a fracture or extensive recurrent caries that extends to or is apical to the crest of the alveolar bone. These teeth often appear to be nonrestorable, but there are several approaches that can be considered for these problems. These range from (1) extraction of the remaining root and placement of a prosthetic restoration to (2) surgical exposure of sound tooth structure to (3) forced eruption of the tooth.5-7
Extraction may appear to be the simplest solution and is indicated if the fracture or caries is extensive. Nevertheless, tooth loss is associated with a decrease in the height and thickness of the alveolar bone. This may compromise the aesthetics of the restorative treatment regardless of whether an implant or fixed partial denture is used.
Surgical exposure of sound tooth structure can also be problematic. The mucoperiosteal flap that allows access to the osseous crest cannot be limited to the involved tooth and must be extended to adjacent teeth for access and establishment of proper contours. Adequate removal of crestal bone and proper contouring may result in the sacrifice of supporting bone on several uninvolved teeth. This can cause root sensitivity, expose furcations, and in some cases can involve the maxillary sinus.7 When crown lengthening is attempted for an anterior tooth, the result may be open embrasures and long clinical crowns.8
An alternate approach is forced eruption of the involved tooth. Forced eruption can be defined as orthodontic movement in a coronal direction through the application of gentle, continuous forces.7 Specifically, when a root segment is forcefully erupted, the forces stretch the gingival and periodontal fibers, producing a coronal shift of gingiva and bone. If accomplished slowly, the gingiva and supporting bone will follow to a position that is coronal to the adjacent teeth. These gingival and osseous changes can help the clinician manage many different restorative problems. For example, after forced eruption, periodontal surgery can be performed, exposing sound tooth structure without sacrificing bone on the adjacent teeth. The soft tissue can then be positioned at a height to blend with the adjacent teeth to produce an aesthetic result.
|Figure 11. In this aesthetically compromised anterior ridge, No. 8 is missing and No. 9 is not restorable. Extraction of No. 9 would create a significant osseous defect.||Figure 12. An active interim partial can be used to forcefully erupt tooth No. 9 while maintaining aesthetics during treatment.|
|Figure 13. Forced eruption extrudes the tooth, bringing the osseous crest in a coronal direction.||Figure 14. Forced eruption completed to idealize the height of the alveolar crest.|
|Figure 15. Three weeks after surgical extraction of the remaining root tip.||Figure 16. Six weeks after extraction of tooth No. 9. The ridge is healed and ready for the placement of a fixed bridge or implants.|
In the example shown in Figures 10 through 16, tooth No. 8 is missing and tooth No. 9 has a vertical fracture. Extraction of tooth No. 9 would cause a decrease in the height and thickness of the alveolar bone, necessitating ridge augmentation surgery to achieve an aesthetic result with a fixed partial denture. Instead, a removable appliance was used to force the eruption of tooth No. 9 and replace tooth No. 8. Once the eruption was accomplished, tooth No. 9 was extracted, and the area was allowed to heal. The eruption was accomplished in 6 weeks.
MOLAR UPRIGHTING TO ENHANCE THE RESTORATIVE OUTCOME
The mesially tipped molar is a common dental problem. This often occurs because the first permanent molar is extracted in childhood due to caries and the second molar tips mesially. In the adult, the first molar can be lost as the result of (multiple) endodontic/restorative failures, extensive caries, caries in the buccal and/or lingual furcation, tooth fracture, and advanced periodontal disease.4 Without timely replacement or provision for space maintenance, the second molar can drift mesially, with the crown tipping in an anterior direction. When this occurs, consequences can include extrusion and migration of adjacent and opposing teeth, uneven marginal ridges, vertical osseous defects, altered coronal-to-gingival form, food impaction, caries, and ultimately posterior bite collapse with loss of the occlusal vertical dimension.7
Some of the restorative challenges presented by a mesially tipped molar include the following7,9,10: inadequate parallelism of abutment teeth; altered occlusal plane; lack of proper interproximal space; root proximity problems; faulty occlusal landmarks; the need for excessive tooth preparation, resulting in pulpal involvement; inadequate space for the pontic; periodontal deformities, including both the hard and soft tissues; a patient’s inability to perform adequate oral hygiene; and bruxism and clenching habits.
Because a tipped molar can have such a profound effect on prosthodontic treatment, molar uprighting is one of the most common orthodontic procedures performed as an aid to restorative therapy.11 However, before proceeding with molar uprighting, a thorough diagnosis is essential, and an appropriate treatment plan should be developed. The following procedures should be included as part of the evaluation:
•Analysis of the dental arches, tooth position, and occlusal plane. Modifications of the occlusal plane may be required. For example, it is often appropriate to adjust an extruded maxillary molar prior to uprighting the opposing mandibular molar.12
•Clinical assessment of the muscles of mastication.13 In the presence of strong musculature, there is an increased likelihood for occlusal trauma to occur to the tooth being uprighted. In this case, use of an appliance with an anterior bite plane is often sufficient to eliminate the occlusal forces. If the musculature is weak, there is a possibility of tooth extrusion during uprighting. This is particularly true when a skeletal open bite is also present. A patient exhibiting both findings would not use a bite plane appliance for disarticulation.13
•A thorough periodontal evaluation is essential, and any required treatment must be completed prior to initiating orthodontic tooth movement. During tooth movement, the area receiving treatment should be kept as free of inflammation as possible. Regular maintenance care is essential throughout treatment. In fact, the frequency of office visits during tooth movement will not be determined by orthodontic adjustments but rather by the need to keep the soft tissues free of inflammation and to prevent crestal bone loss during therapy. Weekly appointments may be necessary.10
•A determination of which teeth can be used for anchorage. When a fixed appliance is used, all of the teeth in the treatment quadrant as far anterior as the cuspid should be included. The cuspid on the contralateral side should also be included by using a heavy stabilizing lingual arch wire.13 With use of a removable appliance, retention and anchorage are accomplished with excellent tissue adaptation, 2 to 3 clasps, and a labial bow to prevent flaring of the anterior teeth.
When molar uprighting is a treatment option, additional restorative dentistry options are available. Instead of avoiding treatment, or using a less than ideal plan, ideal treatment can be provided.
|Figure 17. Molar uprighting to enhance the restoration result. This patient did not wear a retainer after the placement of an implant. The second molar drifted mesially, and the implant was not restorable.||Figure 18. A simple one-screw saggital appliance was used to tip the molar back to its original position and regain the lost space.|
|Figure 19. Occlusal view of the appliance during treatment.||Figure 20. Treatment complete. The second molar has been uprighted and moved distally. The implant can now be restored.|
In the clinical example shown in Figures 17 through 20, the patient was treated with an implant to replace the mandibular first molar. The implant space was not properly maintained with an interim bridge or partial denture, and the second molar drifted and tipped mesially in a period of 8 months. To correct the problem, a removable appliance with an expansion screw was used to upright the molar and reposition it distally. In 4 months, the second molar was in its normal position, and the space needed to restore the implant was reestablished.
CHOOSING AN APPLIANCE FOR COSMETIC MOVEMENT
Most aesthetic tooth movement procedures can be accomplished with either a fixed or a removable appliance. In cases where either appliance will accomplish the result, the following information will help decide which approach is most appropriate.
Fixed appliances are preferred when12 (1) bodily movement of the tooth/teeth is/are needed; (2) wearing brackets and wires on anterior teeth is unacceptable to the patient; (3) the patient has excellent oral hygiene, reducing the risk of caries; (4) there are questions regarding the patient’s willingness to cooperate with the wearing of a removable appliance; and (5) there are enough teeth present for anchorage.
Removable appliances are preferred when12 (1) bodily movement of a tooth/teeth is not required—removable appliances produce a tipping action; (2) aesthetics is important—the patient needs an inconspicuous appliance that can be removed when required; (3) brackets and wires are not appropriate. For example, placing brackets on porcelain veneers or crowns is contraindicated because the bonding process will damage these restorations; (4) the patient does not have adequate anchorage. A removable appliance allows the clinician to use the soft tissue, teeth, and the appliance for this purpose; and (5) the patient is cooperative and responsible (ie, will wear and cleanse the appliance as prescribed and is not likely to lose or break it).
When tooth movement is an integral part of dental care, the dentist has the ability to treat cases that would otherwise be left untreated. With proper evaluation and treatment planning, minor tooth movement procedures are easy and predictable. Prior to initiating a minor tooth movement procedure, the patient should be informed of all possible options, which may include periodontal, orthodontic, and prosthodontic care.
When using a removable appliance for minor tooth movement, plaque control and control of inflammation are essential. This will require regular maintenance visits throughout treatment. In fact, the frequency of visits during tooth movement is often not determined by orthodontic adjustments, but rather by the need to keep the area being treated as free of inflammation as possible. This will reduce the chance of crestal bone loss occurring during appliance therapy.
1. Witt E, Gehrke M, Shaye R. Removable Appliance Fabrication. Chicago, IL: Quintessence Publishers.1988.
2. Veis R, Christian J. The Principles of Appliance Therapy or Adults and Children. Los Angeles, CA; 2002: chap 13, page 13.4.
3. Veis R, Salzer A, Christian J. Manual of Appliance Therapy for Adults and Children. Los Angeles. 1994: chap 8, pages 8-2, 8-33.
4. Moyers RE. Handbook of Orthodontics. Chicago, Ill: Yearbook Medical Publishers; 1980: chap 15, pages 597-599.
5. Johnson GK, Sivers JE. Forced eruption in crown-lengthening procedures. J Prosthet Dent. 1986;56:424-427.
6. Potashnick SR, Rosenberg ES. Forced eruption: principles in periodontics and restorative dentistry. J Prosthet Dent. 1982;48:141-148.
7. Marks MH, Corn H. Atlas of Adult Orthodontics: Functional and Esthetic Enhancement. Philadelphia, Pa: Lea & Febiger; 1989: chap 18, pages 391-412.
8. Oesterle LJ, Wood LW. Raising the root: a look at orthodontic extrusion. J Am Dent Assoc. 1991;122:193-198.
9. Pritchard J. The Diagnosis and Treatment of Periodontal Disease. Philadelphia, Pa: WB Saunders Co; 1979: chap 25, pages 462-503.
10. Brown IS. The effect of orthodontic therapy on certain types of periodontal defects: I. clinical findings. J Periodontol. 1973;44:742-756.
11. Vandarsall R Jr, Swartz M. Adjunctive Orthodontics for the General Practitioner Molar Uprighting. Orange, Calif: Ormco; 1987.
12. Proffit WR, Fields HW. Contemporary Orthodontics. St Louis, Mo: CV Mosby Co, 1986: chap 19, pages 476-483.
13. Khouw FE, Norton LA. The mechanism of fixed molar uprighting appliances. J Prosthet Dent. 1972;27:381-389.
Dr. Veis is a practicing dentist in Los Angeles and a former associate clinical professor of restorative dentistry at the University of Southern California Dental School. He lectures on the integration of appliance therapy into the general practice and is co-author of the text and home study course, “Principles of Appliance Therapy for Adults and Children.” A member of the American Dental Association, the Academy of General Dentistry, the Academy of Dental Sleep Medicine, the American Academy of Gnathologic Orthodontics, and the Academy of Sports Dentistry, he can be contacted at (800) 423-3270 or visit smldent.com.