1 What is a “problem-oriented” approach to treatment?

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.

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.^3,4 Studies have shown that 76% of patients can be treated without extraction in the mandibular arch if an LLHA is used to save this excess (leeway) space and the clinician is willing to accept no more than 1 mm of arch length expansion.^5,6 The drawback of using a LLHA is that the leeway space cannot be used by the mandibular first molars to shift mesially into a Class I molar relationship if they are in an end-on position with the maxillary first molars. Thus, in Class II molar relationship or “end-to-end” molar relationship, the use of the leeway space to improve crowding is limited by the amount of mesial movement of the mandibular first molars to gain a Class I molar relationship.

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.⁷

5 What factors are considered in the decision to extract permanent teeth for a Class I patient?

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.

6 What factors are considered when choosing which teeth to extract?

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 replacement⁸) results in only 2.7 mm more arch length compared with controls (2.7 mm less late arch crowding after the third molars have erupted).⁹ This amount of space gained from extraction is similar in magnitude to that which could be gained by interproximal reduction. Furthermore, success of the second molar extraction approach depends on third molar eruption path and timing, both of which are not as predictable as the amount of arch length to be gained by interproximal reduction for a particular patient.

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?

Generally there are only three ways to treat marked anteroposterior differences in interjaw relationships:

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.

10 Considering the orthopedic approach to treating Class II malocclusions caused by small mandibles, do functional appliances (Bionators, Activators, Frankels, Herbst, Twin Block, etc.) grow mandibles beyond their inherent length?

There is no evidence that functional appliances increase mandibular growth beyond that normally/>