Premature tooth loss, malopposed teeth, tipped molars, posterior bite collapse, and anterior flaring are some of the occlusal problems dentists are confronted with on a daily basis. When challenging problems arise, the general practitioner can choose to refer the patient to a specialist or treat the patient. For the types of problems noted above, the use of appliance therapy can offer a versatile approach to meeting these clinical care challenges. In the past, the term “appliance therapy” referred to the use of simple orthodontic appliances such as space maintainers or Hawley retainers. Today, this term encompasses a broad range of appliances that can be employed in every phase of a patient’s care.
The clinical application of appliance therapy in the general dental practice will be discussed in 3 parts. This part discusses the early treatment of anterior crossbites in children, providing an example of the type of interceptive orthodontics that simple appliance therapy can accomplish. Part 2 will discuss the use of temporary partial dentures, and Part 3 will discuss adjunctive uses of appliance therapy.
DEVELOPMENT OF ANTERIOR CROSSBITES AND ASSOCIATED PROBLEMS IN CHILDREN
The permanent lateral incisors are usually overlapped by, and located palatal to, the permanent central incisors prior to their eruption. If there is insufficient space in the maxillary dental arch during the primary and mixed dentition stages for the permanent lateral incisors to move labially before their emergence, these teeth will change their path of eruption and become palatally positioned in crossbite.1
Some of the more common factors that can contribute to development of a crossbite are (1) trauma to the primary incisors with displacement of the permanent tooth bud, (2) delayed exfoliation of a primary incisor with palatal deflection of the erupting permanent incisor, (3) supernumerary anterior teeth, (4) odontomas, (5) congenitally abnormal eruption patterns, and (6) arch perimeter deficiencies.1
An anterior crossbite should be treated in the primary and mixed dentition. Allowing this malocclusion to persist into the permanent dentition without correction can lead to1-4 (1) labial displacement of the opposing mandibular incisor, (2) exaggerated gingival inflammation and recession of the investing tissues surrounding the mal-opposed teeth, (3) occlusal trauma, (4) enamel abrasion or fractures of the anterior teeth, (5) development of abnormal chewing and swallowing problems, (6) abnormal growth of the maxilla and the mandible, (7) development of a permanent class III dentofacial abnormality, and (8) TMJ dysfunction.
TYPES OF ANTERIOR CROSSBITES IN CHILDREN
There are 3 types of anterior crossbites found in children: (1) simple dental crossbite, (2) functional or pseudo crossbite, and (3) skeletal crossbite. Each category is distinct and has specific diagnostic criteria.
The Simple Dental Anterior Crossbite
Simple dental anterior crossbites are generally the result of the abnormal eruption of the permanent incisors. Various etiologic factors can be involved, including trauma to the primary incisors with displacement of the permanent tooth bud, delayed exfoliation of a primary incisor with palatal deflection of the erupting permanent incisor, supernumerary anterior teeth, odontomas, congenitally abnormal eruption patterns, and an arch perimeter deficiency.1
Patients who have a simple dental anterior crossbite exhibit the following characteristics:
•The crossbite usually involves only 1 or 2 teeth.5
•The facial profile is normal in centric relation and centric occlusion.1
•The anterior-posterior skeletal relationship is normal.1
•The mandible has a smooth arc of closure into an Angle class I molar and cuspid relationship, with a coincident centric relation and centric occlusion.2,6
•An abnormal axial inclination of either the maxillary or mandibular anterior teeth occurs as they erupt, while the other teeth are usually in a normal occlusal scheme.5
THE FUNCTIONAL ANTERIOR CROSSBITE
Patients who have a functional anterior crossbite (pseudo class III)1 exhibit the following characteristics:
•In centric relation or in a relaxed postural position, the patient presents with the normal convex facial profile.
•In centric relation, the opposing incisors generally contact edge to edge with the molars separated, but in an angle class I relation.
•During closing, an early occlusal interference causes an anterior shift of the mandible.
•As the mandible shifts forward into centric occlusion, the incisors are placed into crossbite and the molars into a class III relationship.
•Depending on the severity of the anterior shift when the patient closes into centric occlusion, the patient will either maintain a straight profile or exhibit a concave facial profile.
•The maxillary incisors are generally lingually tipped, and the mandibular incisors may be labially tipped.
•In a pseudo class III, the gonial angle approaches a right angle, with the average near 120°. In addition, a false-normal ANB angle may be present in a pseudo class III.
The Skeletal Anterior Crossbite
Patients who have a true skeletal class III, or mesio-occlusion, have skeletal abnormality involving mandibular hypertrophy, a marked shortening of the cranial base or maxilla, or a combination of both.6 Some of the characteristics exhibited by these patients include the following:
•In centric relation, the patient’s facial profile will be straight or concave.1
•In centric relation, there will be a class III molar relationship and an anterior crossbite.1
•In centric occlusion, there will be a class III molar relationship and an anterior crossbite.1
•The arc of mandibular closure remains smooth without any occlusal interferences.1
•During growth, the angulation of the maxillary and mandibular incisors changes relative to the cranial base or occlusal plane, in an attempt to compensate for the skeletal discrepancy.
•Usually the maxillary incisors become labially inclined and the mandibular incisors become lingually inclined.1
|Table. Definitions of Some Cephalometric Terms|
Flush terminal plane—this term is used to define the normal relationship of the maxillary and mandibular primary second molars to each other during the mixed dentition stage of development. During this stage the distal aspects of these molars are flush to each other when the patient is fully intercuspated.
Dental study casts alone do not provide satisfactory information regarding the relationship of the jaws to each other or to the status of the jaws in the craniofacial complex. Obtaining, tracing, and analyzing a cephalometric head film can accomplish this. Listed below are some of the basic cephalometric landmarks used to help clarify the causes of a skeletal and functional crossbite.
Sella—the geometric center of the pituitary fossa.
Nasion—the most anterior aspect of the frontonasal suture.
SN—a line connecting sella to nasion used to represent the anterior cranial base.
Point A—the most posterior point in the concavity between anterior nasal spine and the maxillary alveolar process. Regarded as the anterior limit of the apical base of the maxilla.
Point B—the most posterior point in the concavity between the chin and the mandibular alveolar process. Regarded as the anterior limit of the apical base of the mandible.
SNA—an angle formed by connecting sella, nasion, and point A used to determine whether the maxilla is positioned anteriorly or posteriorly to the cranial base.
SNB—an angle formed by connecting sella, nasion, and point B used to determine whether the mandible is protrusive or recessive relative to the cranial base.
Gnathion (Gn)—a point located by taking the midpoint between the most anterior and inferior points of the bony chin.
Mandibular Plane—a line formed by joining gonion and gnathion SN to GoGn. The mandibular plane angle is formed by relating the mandibular plane to the cranial base. Excessively high or low mandibular plane angles suggest unfavorable growth patterns.
ANB—an angle formed by connecting A point of nasion and B point. This angle represents the anterior/posterior relationship of the maxilla and mandible to the cranial base.
•Cephalometrically, a reduced or negative value for the ANB angle indicates that either the maxilla is relatively retracted or the mandible is positioned anteriorly. If the SNA angle value decreases beyond the standard deviation for the age and gender of the child, and the SNB angle is normal, the dentist should consider that the problem is in the maxillary dental component. If the SNB angle value increases over the standard deviation for the age and gender of the child, then the dentist should consider that the problem is in the mandibular skeletal component.3 (See the Table for definitions of some common cephalometric terms.)
•Another cephalometric characteristic found in a skeletal class III is that the gonial angle is more often obtuse, with a range between 130° and 140° (this results in a long facial appearance). It should also be noted that a high SN-to-mandibular-plane angle can mask a developing class III malocclusion. It is important to emphasize that an in-depth cephalometric analysis is required before treating these cases.3
Before attempting to treat an anterior crossbite, the dentist must determine whether the crossbite is skeletal, functional, or dental in nature. To do this will require a precise clinical and radiographic examination of the patient. The following steps should be included in this examination:
•Evaluate the number of teeth involved in the crossbite and their inclination. In a simple dental crossbite, usually only 1 or 2 teeth are involved. In a functional class III occlusion, maxillary incisors tend to be lingually inclined and the mandibular incisors are labially inclined. In a true skeletal class III, an attempt to compensate for the skeletal discrepancy occurs, and during growth the maxillary incisors usually become labially inclined and the mandibular incisors become lingually inclined.
•Examine the profile. Direct the patient to close the mouth into a rest position with lips together, but with the teeth out of contact. This will allow the clinician to evaluate soft tissues, facial musculature, and overall facial profile for any signs of a skeletal mandibular prognathism.
•Examine the arc of closure. When a patient opens and closes into full occlusion, the arc of closure will either be smooth and uninterrupted, or exhibit an anterior shift to avoid an abnormal incisal interference. A true skeletal class III patient will close in a smooth uninterrupted arc. A patient with a functional crossbite will experience an anterior shift, and a patient with a dental crossbite may or may not shift forward.
•Note the relative positions of the primary and permanent molars in both centric occlusion and centric relation. In a skeletal class III occlusion, a mesio-occlusion is maintained in both positions. In a simple dental crossbite, a flush terminal plane of the molars will be maintained in both centric relation and centric occlusion. In a functional pseudo class III, there may be a shift from a flush terminal plane to a class III relationship as the mandible closes from centric relation to centric occlusion.6
•Attempt to manipulate the mandible posteriorly to obtain a more favorable relationship with the maxilla. If the incisors can be brought to an edge-to-edge position or nearly so, it indicates that the crossbite is more likely because of a functional rather than a skeletal or dental component.3
•Complete a space analysis by evaluating the patient’s arch width and length. One of the most common mistakes an inexperienced clinician makes when trying to correct a crossbite is to try to move a tooth into position when there is inadequate space. Therefore, before initiating the crossbite correction, always make sure there is adequate space. Correction of this problem may involve reducing the size of primary cuspids, extraction of the primary cuspids, and/or expansion of the arches.
TREATMENT OF ANTERIOR CROSSBITES
Treatment of a Simple Dental Anterior Crossbite
The best treatment of a simple dental anterior crossbite is to prevent the condition from ever occurring. This can be accomplished by taking routine radiographic images of the maxillary incisor region to identify abnormalities such as an odontoma, the delayed exfoliation of a primary incisor, or the presence of a supernumerary tooth. Observing and managing severe arch perimeter deficiency is also essential to prevent a crossbite from occurring.
Once a dental anterior crossbite exists, many methods have been used to correct it. These range from the use of an acrylic incline plane to a reverse stainless steel crown. Even tongue blades have been used to try to “jump” a crossbite.3,4 The key to success is to use an appliance that is both comfortable and predictable. The 3 appliances described below are the most common. All of them work by tipping the maxillary teeth forward so that they are in a normal dental relationship to the mandibular teeth. Once this is accomplished, coordinated growth can occur between the maxilla and the mandible.1
|Figure 1. A Hawley retainer with a recurve spring and posterior coverage can open the bite sufficiently to allow the incisor to advance without occlusal interference.|
The first appliance is a simple Hawley retainer with recurve springs and a posterior bite plane (Figure 1). This is the removable appliance of choice when enough space exists in the arch form to move the teeth in crossbite back into their ideal place in the arch. Activation of the spring in a labial-gingival direction will place direct pressure on the tooth in crossbite and should be done every 4 weeks. The usual design also has a labial bow. This bow diminishes any lip pressure while controlling labial tooth movement. A posterior occlusal bite plane is used to open the bite and allow the incisor to advance without occlusal interference.
|Figure 2. A Schwarz appliance with occlusal coverage can easily regain the space needed to move anterior teeth out of crossbite.|
When space needs to be created for the teeth in crossbite, a simple Schwarz appliance with occlusal coverage will usually suffice (Figure 2). Turning the expansion screw one-quarter turn per week will exert enough force to create a 1-mm increase in arch width per month. Once enough space has been regained, simply activate the springs to move the teeth labially out of crossbite.
|Figure 3. The labial-lingual appliance is excellent for the noncompliant patient.|
The third design is a fixed labial-lingual appliance (Figure 3). This appliance includes a vertical removable lingual arch for ease of adjustment, with a recurve spring to jump the crossbite. As in the removable appliance, the passive labial bow is utilized to diminish any lip pressure during active therapy. This appliance is particularly useful when treating less cooperative patients.
|Figures 4 and 5. The single-tooth anterior crossbite caused by an underdeveloped maxilla.|
|Figure 6. Sample of a Schwarz appliance after treatment has been completed. Occlusal bite plane has been removed and the appliance is used as a retainer.|
|Figures 7 and 8. Anterior crossbite corrected after 4 months of active treatment.|
Regardless of the appliance used, once an appropriate overbite and overjet have been established, the occlusal relationship will usually retain the corrected tooth position. If the tooth is not fully erupted, the bite planes should be removed from the appliance, and the appliance should be worn as a retainer until an appropriate overbite is established (Figures 4 through 8).
Treatment of a Functional Anterior Crossbite
Treatment of a functional anterior crossbite should be undertaken as soon as possible to eliminate the mandibular shift that accompanies this problem. This is important because this shift subjects the incisors to abnormal occlusal interferences, and over time, the forward positioning of the mandible may alter the patient’s facial growth, resulting in a skeletal class III pattern.1
Similar to the treatment of a dental anterior crossbite, the most appropriate way to treat a functional anterior crossbite is to correct the etiology before it becomes a clinical problem. To do this, simply identify the early occlusal interference responsible for the anterior shift of the mandible and eliminate it. For example, mandibular primary cuspids are often the most common area of interference causing a functional shift. A simple adjustment of the cusp tips with a rotary diamond is often all that is needed to correct the problem.
|Figure 9. Maxillary anterior saggital appliance.|
However, once a functional crossbite exists, a predictable correction can be obtained with the maxillary anterior sagittal appliance (Figure 9). Here, the entire anterior segment can be moved labially with an expansion screw placed 90° to the maxillary incisors. The labial arch wire moves with the segment as a unit while using the posterior teeth for anchorage and retention.
|Figures 10 and 11. Early occlusal interference of the primary cuspids causes a mandibular shift leading to lingually locked anterior teeth.|
|Figure 12. Maxillary anterior sagittal appliance with occlusal coverage can be used to move an entire anterior segment labially.||Figure 13. Functional anterior crossbite corrected after 3 months of active treatment.|
A posterior bite plane is necessary when the anterior teeth are lingually locked behind the mandibular incisors. Activation is achieved by opening the expansion screw one-quarter turn per week. This will advance the incisor segment 1 mm per month. As in the simple dental anterior crossbite, once an appropriate overbite and overjet have been established, the occlusal relationship will usually retain the corrected tooth position. If the tooth is not fully erupted, the bite planes should be removed from the appliance, and the appliance should be worn as a retainer until the correct overbite is established1 (Figures 10 through 13).
Treatment of a Skeletal Anterior Crossbite
There is no simple orthodontic correction for a skeletal anterior crossbite. A clinician with specialized orthodontic training should treat such a patient. The first step in treating a skeletal anterior crossbite is to conduct a differential diagnosis of the location of the skeletal problem. A careful clinical assessment along with a cephalometric analysis is commonly used to differentiate between a maxillary retrusion and a mandibular protrusion.
Early treatment of the class III involving mandibular excess is generally avoided. The treatment of choice for this skeletal problem is comprehensive orthodontics and/or orthognathic surgery when growth is complete.
|Figure 14. Bonded maxillary face mask expansion appliance.|
Early dental orthopedic treatment using a fixed rapid palatal expansion appliance with a protraction headgear is the treatment of choice for patients presenting with a retruded maxilla (Figure 14). Turning the screw in this appliance one-quarter turn daily will result in 1 mm of expansion every 4 days. This expansion should be started at least 1 week before starting a protraction force as it initiates a cellular response in the sutures of the midface and will allow a more positive reaction to the protraction force. This treatment has been shown to be most effective in the early mixed dentition. Therefore, early recognition and referral are essential for treatment success.
This article has discussed the types, characteristics, and etiology of anterior crossbites in children and the use of appliance therapy to treat these conditions. Before treatment is initiated, the clinician must determine whether the crossbite is dental, functional, or skeletal in nature. Prevention is an important part of the general management of patients who are at risk for developing an anterior crossbite, but if a crossbite exists, the appropriate use of appliance therapy can achieve desired treatment outcomes in many cases.
It may not be your obligation to treat, but it is your obligation to diagnose. This statement is particularly true when it comes to the recognition and treatment of anterior crossbites. With proper diagnosis, the general dentist and the pediatric specialist can successfully treat simple and functional crossbites. This by no means obligates the clinician to do so. A healthy working relationship with an orthodontist will allow proper decisions to be made regarding where treatment is accomplished.
1. Major PW, Glover K. Treatment of anterior cross-bites in the early mixed dentition. J Can Dent Assoc. 1992;58:574-579.
2. Graber TM. Orthodontics: Principals and Practice. Philadelphia, Pa: W.B. Saunders Co; 1972:833-847, chapter 17.
3. Payne RC, Mueller BH, Thomas HF. Anterior cross bite in the primary dentition. J Pedod. 1981;5:281-294.
4. Croll TP. Fixed inclined plane correction of anterior cross bite of the primary dentition. J Pedod. 1984;9:84-94.
5. McEvoy SA. Rapid correction of a simple one-tooth anterior cross bite due to an over-retained primary incisor: clinical report. Pediatr Dent. 1983;5:280-282.
6. Moyers RE. Handbook of Orthodontics. 3rd ed. Chicago, Ill: Yearbook Publishers Inc; 1973:564-577, chapter 15.
Dr. Veis is a practicing dentist and a former associate clinical professor of restorative dentistry at the University of Southern California Dental School. He is known for his 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, Dr. Veis currently maintains a private practice in Los Angeles, Calif. He can be contacted at (800) 423-3270 or smldent.com.