Phase II: Nonsurgical Adolescent and Adult Cases
The majority of patients receiving orthodontic treatment are either adolescents or adults, and the conditions they present with can range from single tooth crossbites to severe dentofacial deformities. When a patient first presents for treatment, identification of all structural and functional jaw and dental problems must be made during the clinical and radiographic examination. These problems occur in all three planes of space and may include significant dental spacing or crowding, dental or skeletal deep bites, anterior or posterior dental or skeletal open bites, anterior or posterior dental or skeletal crossbites, anteroposterior skeletal or dental malrelationships, and asymmetries of the dentition or skeleton. In addition, many patients also present with other dental problems such as mutilated dentitions and periodontal disease.
The goal of orthodontic treatment is always to address the patient’s chief complaint through the integration of the best research evidence, the clinician’s expertise, and the patient’s values (evidence-based orthodontics). A problem-oriented treatment approach must be used to provide an optimal level of care contingent upon the patient’s desires and resources.
Orthodontic treatment of adolescent and adult patients may include the use of either removable or fixed appliances. Treatment may include jaw orthopedics to restrict anteroposterior maxillary or mandibular growth, orthopedics to enhance maxillary anteroposterior growth or to accelerate mandibular growth, extraction of permanent teeth to eliminate substantial crowding or to camouflage (mask) an underlying skeletal imbalance, maxillary skeletal expansion or maxillary/mandibular dental expansion, orthognathic surgery, and treatment coordinated with other dental disciplines including cosmetic dentistry, prosthodontics, endodontics, and periodontics.
Based upon a systematic clinical and radiographic examination of the patient, the clinician identifies all structural and functional problems of the jaws and dentition. An exhaustive list of these problems is compiled. From this list and the patient’s chief concerns, the goals for treatment are established. Treatment options are composed that address the patient’s chief complaint and all problems on the list. Problems that cannot be addressed are considered treatment compromises and must be discussed with the patient.
2 For any patient with an orthodontic problem, what conditions necessitate referral to an orthodontist?
A good rule of thumb is this: if an orthodontic problem exists in a single dimension and can be treated in 9 months or less, it is a problem that generally can be treated in general practice. Such problems include patients in need of space maintenance, single tooth crossbite correction, and Class I mild alignment problems. On the other hand, patients with multi-dimensional malocclusion problems, skeletal imbalances, and problems that take greater than 9 months to treat are generally best referred to an orthodontist. Remember, the goal is to provide the patient with the highest level of care, and orthodontic care provided to the patient must be to the level of the specialist even if that care is provided by a generalist.
The diagnosis of an orthodontic patient follows a logical sequence of evaluation of facial symmetry and proportions, relationship of the jaws, dental arch length, and irregularities of tooth development, tooth position, and intra-oral soft tissues. The following diagnostic criteria will aid in determining if a patient presents with a single dimension or multidimensional orthodontic problem.
Facial symmetry is noted in the frontal view, seen by looking directly at the patient. Mild variation in symmetry from right to left is normal. Landmarks where marked asymmetry can be noted are the eyes, cheekbones, gonial angles of the mandible, occlusal plane, and midline of the chin. The path of opening of the mandible is also evaluated. Opening paths that are not straight or smooth may foretell mandibular asymmetry or temporomandibular dysfunction. Closing path is evaluated to detect the presence or absence of a functional shift of the mandible into centric occlusion. Marked asymmetry of facial structures or presence of a functional shift signifies referral to a specialist.
Vertical and anteroposterior facial proportions are judged in both the frontal and profile views. Significant protrusion or retrusion of the maxilla or mandible are indications for referral. Vertical proportionality is judged by assessing lip competence and the amount of maxillary incisor crown exposure in relaxed pose. Lack of lip competence in a relaxed pose and/or excessive maxillary incisor show are indications for referral.
Transverse proportions are judged intraorally by the presence or absence of posterior crossbite and/or midline discrepancies. Posterior crossbite involving more than two contiguous maxillary teeth is generally skeletal in nature and is an indication for referral.
The amount of incisor protrusion is judged cephalometrically and by evaluation of lip posture and lip function. The presence of mentalis muscle strain on lip closure is an indication of lip incompetence from incisor protrusion. Excessive lip incompetence and incisor protrusion are indications for referral.
Unusual delay in the eruption of one or more second bicuspids and/or second molars is not an uncommon finding and can lead to significant malocclusion for the patient. These situations should be monitored and referred for evaluation.
Tooth size problems commonly occur that prevent ideal Class I occlusion to be obtained. Patients with abnormal incisor widths (e.g., small maxillary lateral incisors) should be referred for further evaluation.
Tooth drift or displacement out of the line of the dental arch signifies eruption path problems. Correction of malposition requires an understanding of the impact on arch form. If malposition is the result of crowding, then correction will require expansion of the arch or gaining space by extraction or selected tooth width reduction. Overexpansion of the dental arch is prone to relapse. Therefore, a diagnosis of tooth malposition must be accompanied by an understanding of the limitations of arch expansion treatment. Cases in which arch expansion will lead to an improper transverse occlusal plane or excessive incisor protrusion should be referred for evaluation by a specialist.
Tooth displacement that results in anterior or posterior crossbite or anterior overjet may be a clue to an underlying discrepancy between the bony bases of the dental arches. Further diagnosis requires cephalometric and/or orthodontic study model evaluation of the alveolar bases to discover intermaxillary skeletal discrepancies.
Adolescents still in the late mixed dentition should be evaluated for available leeway space. In general, planned future non-extraction treatment can be facilitated considerably with maintenance of the leeway space in the mandible. There are several published analyses that aid in the determination of arch length available in the late mixed dentition.< ?xml:namespace prefix = "mbp" />
3 A class I adolescent patient in the late mixed dentition presents with mild mandibular anterior crowding. Assuming that the mandibular second premolars are present but unerupted below the primary second molars, how much space can be gained to spontaneously align the mandibular incisors by placing a lower lingual holding arch (LLHA)? What percentage of Class I molar cases, with mandibular incisor crowding, can be corrected by placing an LLHA before the primary second molars are exfoliated? What is the drawback of using an LLHA?
The primary second molars are wider in mesiodistal dimension than their permanent premolar successors. As a result of this size difference, approximately 3.4 to 5 mm of total space can be gained for alignment of the mandibular anterior teeth by placing an LLHA.
4 What is interproximal reduction (also termed “stripping”), and when could it be used in Class I crowded patients?
Interproximal reduction is the removal of interproximal enamel to make space to align teeth. In primitive humans whose diets consisted of coarse hard foods, interproximal enamel was naturally worn with chewing over time. In theory, this is due to significant movement of teeth and abrasion at interproximal contact points as a result of this tooth movement. In contrast, modern humans with softer diets experience significantly less wear of interproximal enamel over the average human life span. In fact, there is far more enamel present on the sides of human teeth than will ever be worn away during a lifetime of chewing. Therefore, some of this enamel can be removed without detriment to the long-term health of the teeth. Interproximal reduction is a treatment option for Class I malocclusions with crowding of 1 to 5 mm.
However, interproximal reduction requires proper instrumentation and careful technique to maintain adequate tooth enamel and interproximal surface contour. For many years stripping was restricted to anterior teeth. Later, air rotor stripping (or ARS) was introduced to remove interproximal enamel from posterior teeth.
For a Class I patient, the primary consideration for extraction of permanent teeth is the amount of crowding in the dental arch. If there is significant crowding in a dental arch, extraction of permanent teeth is generally considered reasonable. However, other factors must also be considered. In particular, the inclination of the incisors as viewed in the sagittal plane on a cephalometric radiograph, an assessment of the lip posture, and the status of the periodontium should be considered.
If the anterior teeth are inclined severely to the labial and the patient’s lips are pushed forward as a result, the option of tooth extraction (even in the presence of less crowding) should be considered. Extraction will permit uprighting the anterior teeth and reduction of lip protrusion. Conversely, if the anterior teeth are inclined to the lingual, tipping these teeth to the labial to increase the dental arch length can allow correction of considerable crowding without extraction. In this case, the periodontium of the mandibular anterior teeth must be assessed with regard to thickness of the attached gingival tissue both incisogingivally and faciolingually. Tipping incisors that are invested in thin attached gingival tissue in an anterior direction can result in loss of periodontium.
Once a decision to extract teeth has been made, dental arch symmetry is an important consideration when choosing which teeth to extract. Generally, in Class I malocclusions, dental arch asymmetries are not severe. The treatment goal is to place the permanent canines in a symmetric position bilaterally relative to the skeletal midline of the arch. As such, extraction choices for Class I molar malocclusions involve two paired teeth in each arch (i.e. two upper first premolars and two lower first premolars). However, significant dental arch asymmetries may call for an asymmetric extraction choice in order to reach a symmetric finished result. In making this decision the choice for upper and lower teeth on each side of the arch should be paired to allow maintenance of the Class I relationship during treatment mechanics to close the extraction spaces (e.g., upper and lower right first premolars and upper and lower left second premolars).
7 Does extraction of four second molars instead of four premolars make sense for a crowded Class I patient?
Premolars are typically extracted when significant crowding and/or protrusion exists in the anterior of the arch. Extraction of mandibular first premolars provides approximately 14 mm of space, allowing alignment of the anterior teeth and/or reduction of their labial inclination. Mandibular second molar extraction (i.e., second molar extraction/third molar replacement
8 What factors should be considered when making a decision to treat a patient with a Class II molar malocclusion or to refer the patient to a specialist?
The most important factor to consider in a patient with a Class II molar malocclusion is the contribution of intermaxillary jaw position to the interarch Class II relationship of the dentition. Imbalance between the forward growth of the maxilla and the mandible warrants referral to a specialist. Patients who have mild to moderate interjaw imbalance can be treated by the general dentist provided the practitioner has a thorough understanding of facial growth and the application and treatment outcomes of appliances that modify facial growth.
9 If a patient presents with a Class II molar malocclusion and a marked difference in anteroposterior interjaw relationship, what are the major choices for treatment? On what diagnostic criteria are the choices based?
Orthopedic treatment is an attempt to modify the growth of the jaw(s) by placing forces against a jaw during facial growth. For instance, a headgear applies a force against the maxilla to restrict its forward growth, and a chin cup applies a force against the chin to restrict the forward growth of the mandible.
Placing dental compensations (masking) is an attempt to camouflage the underlying jaw problem without addressing the skeletal problem itself. Various extraction patterns can be used to move the teeth into more acceptable positions (e.g., reduce overjet) and thereby mask the underlying skeletal problem without actually modifying the jaw position. Surgery is generally used to treat moderate to severe jaw size imbalances in patients whose discrepancies are beyond correction that is obtainable with camouflage or growth modification, or in patients who have completed growth. The decision to use any of these three approaches is based upon many factors, the most important of which are the severity of the jaw imbalance, the severity of the Class II interarch relationship, the growth status of the patient, and the patient’s goals.