Sound biologic concepts in orthodontics

Alternative nonsurgical strategies to treat complex orthodontic problems

Patients whose vertical discrepancies are best corrected with both orthodontics and surgery can be placed into two distinct categories. The first category is the group of patients who have short posterior facial heights in conjunction with excessive anterior facial heights. The second category is the group of patients who have the opposite problem, i.e., excessive posterior facial heights and decreased anterior facial heights. Both of these types of malocclusions can best be treated with a combination of orthodontics and surgery. Alternative treatment for these "outer limits" patients require a thorough differential diagnosis, selection of appropriate force systems, and an understanding that nonsurgical treatment will result in compromises. Although these compromises must be accepted these patients can expect treatment results that are esthetically pleasing, highly acceptable for the teeth and supporting tissues, functional, and reasonably stable if a careful differential diagnosis is followed with treatment that uses precise space management with sequential directional force application.

Straight talk about extraction and nonextraction: a differential diagnostic decision

At one stage or another, orthodontics is usually a space management procedure, particularly during the correction of a Class I or Class II malocclusion. Orthodontists use space that is available or create space to correct malocclusions. There are anterior, posterior, lateral, and vertical dimensions of the dentition and its supporting structures. If the muscular balance is normal, the clinician should try to respect these dimensions. The orthodontic clinician should not be an extractionist or a nonextractionist. Rather, the clinician should use differential diagnostic skills and artistic ability to arrive at the most appropriate treatment outcome for each patient.

Clinical ramifications of posterior and anterior facial height changes between treated and untreated Class II samples

Some clinicians have suggested that one primary difference between successful and unsuccessful Class II treatment outcomes is the relative change of anterior and posterior facial heights. Successfully treated cases are claimed to exhibit greater increases in posterior facial height (PFH, articulare to gonion) than in the anterior facial height (AFH, menton to palatal plane). This conjecture was tested here by recalling a treated Class I sample and a treated Class II sample and by comparing the differences found in these samples to an untreated Class II sample at the same ages. The PFH/AFH ratio increased significantly more in the treated Class I and Class II samples during the active phase of treatment than in the untreated Class II sample at the same ages. During the years from posttreatment to recall (mean = 6 yrs), there was a significant increase in the PFH/AFH ratio in the treated Class II sample due to a greater increase in PFH than AFH. This ratio continued to improve after all appliance therapy had been discontinued, and it did not occur in the treated Class I sample nor in the untreated Class II sample. The conclusion was that the patient with a Class II malocclusion, if treated, continues to change favorably over time. This favorable change, in turn, helps maintain the Class II correction.

A comparison of the Ricketts and Tweed-type arch leveling techniques

The purpose of this study was to compare the effectiveness and long-term stability of arch leveling and overbite correction carried out by the Ricketts and modified Tweed techniques. The sample comprised 60 Class II, deep bite, low-angle adolescent nonextraction cases, 30 each from the offices of Robert Ricketts and Fred Schudy, with cephalograms taken before and immediately after treatment and an average of more than 4 years after treatment. Both techniques were successful in overbite correction, producing only minimal increases in mandibular plane angle and anterior facial height. Mandibular incisors in the Ricketts group demonstrated more flaring and anterior bodily movement during treatment, with a greater amount of posttreatment uprighting and overbite relapse than the Schudy group. The Ricketts group demonstrated slightly more than 1 mm of true lower incisor intrusion; this change was relatively stable after treatment. Both techniques produced similar amounts of mandibular molar extrusion during treatment; these changes remained stable after treatment.

First premolar extractions and fixed appliances in the Class II division 1 malocclusion

This cephalometric study investigates the changes in the facial skeleton and dento-alveolar structures which occur during orthodontic treatment of the Class II Division 1 malocclusion by extraction of four first premolars followed by fixed appliances. The Begg and edgewise appliances are compared, and both are contrasted with a group of untreated Class II Division 1 subjects. The main effects of treatment were in the dento-alveolar structures, the changes in the overall facial pattern being small and largely due to extrusion of the molars during overbite reduction. Molar extrusion tended to interrupt forward growth rotation of the mandible, temporarily making it more backwards in direction, and increasing the lower anterior face height. An increase in the posterior lower face height was also noted in the edgewise group. Whilst SN A, and therefore AN B, reduced significantly during treatment, this was probably the result of palatal root torque to the upper incisors. The Begg appliance was more successful than edgewise in this respect.

Orthodontic force systems: technical refinements for increased efficiency

The efficiency of the Begg technique suffers because Class II elastics overwhelm anchor bends, which normally do not yield enough force for vertical control of maxillary incisors. This can be improved by attention to detail and modifications. Bite-opening bends in the arch wires distal to canines and lateral incisors, long (6.5 mm.) mesiogingivally angulated molar tubes, and placement of intermaxillary elastics at the distal ends of the tubes are all helpful. Intermaxillary "check elastics," having one end over the posterior end of the maxillary arch wire, both strands under the end of the mandibular arch wire, and the other end up to the maxillary anterior teeth, reinforce anchor bends and extrude upper and lower molars while keeping them upright. They augment bite opening in Stage I and counteract the adverse affects of the auxiliaries in Stage III.

Effects of intermaxillary elastic traction on orthodontic tooth movement

Intermaxillary elastics are commonly used in orthodontic treatment, yet the exact mechanism by which they effect tooth movement has been unclear. A photoelastic model was produced to stimulate this type of therapy in examples of Class II and III malocclusions. In the open situation, inter-arch activity precipitated occlusal plane rotation; counter clockwise in Class II malocclusion and clockwise in Class III. Comment is made on the force vectors involved when using intermaxillary elastics.

Vertical control: a multifactorial problem and its clinical implications

In this article we have tried to analyze the importance of vertical control in orthodontic cases, as well as the factors affecting it. From the cases presented, it can be assumed that: 1. In vertically growing or nongrowing persons (high-angle cases), the application of proper directional forces becomes extremely critical because a clockwise rotation of the mandible can occur very promptly and is very undesirable. 2. In cases with favorable growth potential, the results may be acceptable, even if the forces applied during treatment are not absolutely controlled; in other words, Mother Nature may often compensate for inappropriate or miscalculated treatment procedures.

The effect of different extraction sites upon incisor retraction

1. From this study, it was found that in cases treated by the Begg technique one can anticipate greater retraction of the anterior dental units in nonextraction (see article) cases, in both types of premolar extraction cases, and in cases, involving extraction of first molars plus first premolars than would be expected on the basis of root surface area resistance values. 2. There is a likely explanation for this. Molars were maintained upright and allowed to move bodily only while incisors were not only moved bodily but often partially tipped as well. 3. The actual mean anterior retraction in first molar extraction cases exhibited a close approximation to the expected mean anterior retraction values in relation to root surface resistance values. 4. Second premolar extraction is one answer to overretraction and has the added edge of creating even less incisor retraction than second premolar extraction. 5. It was also found that the extraction of premolars alone did not result (see article) in a significant change in the increased eruption of the third molars into functional occlusion. A very significant improvement in the rate of sucessful third molar eruption was found in first molar extraction cases and in cases involving extraction of first molars plus first premolars. 6. The mean ages of the patients in the various treatment categories at the start of treatment were similar enough to each other to suggest that age at the start of treatment had no bearing on the success rate of third molar erup tion. Extraction-site selection seemed to be the dominating factor in successful third molar eruption. 7. It was found that the group of cases that exhibited the least amount of anterior retraction also inhibited the least amount of anterior relapse and, conversely, the group of cases exhibiting the greatest amount of anterior retraction also exhibited the greatest amount of anterior relapse. (see article) 8. The nonextraction cases, with no extraction space to close, were treated in the shortest mean time, while the eight-tooth (first molar plus first premolar) extraction cases having the greatest amount of extraction space required the greatest amount of mean treatment time.9. In conclusion, it can be said that changing the location of the extraction site resulted in a change in relative root surface areas of the opposing anchor units in the anterior and posterior segments. There was a definite and predictable change in the amount of anterior retraction achieved by varying the location of the extraction site. This should be considered in the diagnosis, so that a desired treatment goal for the final position of the incisors within the facial profile can be achieved.