Starting Points in Treatment Planning
Many factors take part in the planning of orthodontic treatment. A number of these are dealt with here, without pretending to be comprehensive.
Firstly, spontaneous improvements that occur either through natural development of the dentition, or after certain interventions, but without use of appliances, are considered. Interceptive measures are pointed out and matters which should be noticed and implemented are given attention, as are essential factors in choosing the most desirable moment for beginning treatment. The most important sorts of appliances are briefly described. The relationship between the separate entities of the dentofacial complex and their treatment is discussed. The general procedures in planning treatment are set out and the question of whether the dentist should undertake treatment himself, or refer the patient to an orthodontist, is examined.
In particular phases of the development of the dentition, teeth appear to take up abnormal positions. A few examples may elucidate this statement.
Upon emergence of the maxillary central incisors a central diastema is often present, which is mostly spontaneously closed by the time the permanent canines have fully erupted (Fig. 8-1). Parents are frequently disturbed about the initial condition. The linguoposition in which mandibular lateral permanent incisors may emerge, is often considered to be abnormal. The marked domination of the dentition in the as yet immature face of the adolescent can be lacking in beauty. During the intertransitional period a neutro-occlusion of the canines is associated with a slight disto-occlusion of the first permanent molars when the mandibular second deciduous molar is significantly broader mesiodistally than its antagonist, as frequently is the case. Only after the mandibular second deciduous molar is succeeded by the premolar, can the first permanent molars come into neutro-occlusion.
Fig. 8-1 An example of natural dental development of the dentition in a boy, which demonstrates changes in mandibular and maxillary incisors upon emergence.
The two maxillary central permanent incisors, which emerged later, stand far apart and their crowns diverge.
The maxillary lateral incisors have emerged without contact with the centrals; their crowns diverge. The central diastema has become smaller.
E, F At 9 years 1 month the mandibular lateral incisors are fully erupted with their distal surfaces vestibular to the mesial surfaces of the deciduous canines; the mandibular incisors as a group are further labially positioned than their predecessors.
The maxillary lateral incisors have moved further occlusally. There is no contact anywhere between the four incisors. The central diastema has become still smaller.
G, H At 10 years 0 months the mandibular permanent canines have emerged, more vestibularly than their predecessors. Upon exfoliation of the deciduous canines the lateral incisors have improved in alignment. The maxillary permanent canines also have emerged recently; they also take up a more vestibular position than their predecessors. There is now contact between maxillary central and lateral incisors. The central diastema is reduced.
I, J At 12 years 11 months there are good contacts between the mandibular canines and lateral incisors. The mandibular incisors are regularly aligned. The maxillary canines have almost reached the occlusal plane. The central diastema is practically closed. The angulation of the incisors has improved from the moment of emergence till this stage. This process continues.
This series demonstrates the spontaneous improvement in alignment over a period of more than five years, and illustrates that interim irregularities occur which are corrected spontaneously, and therefore should not be treated. The evolution of the frenulum indicated on the maxillary model is worth noting. It remains at its original level while the alveolar process grows caudally past it.
In general, the difference in times of emergence between corresponding maxillary and mandibular teeth is greater than in this example. On average the maxillary teeth emerge about a year later than the mandibular counterparts.
The figures in the photographs indicate the age in years and months.
These examples illustrate situations that do not match the “ideal” picture. They are merely temporary conditions that are part of the development of the dentition and, as such, have no need whatever for treatment.
To interfere in such normal developmental processes in order to “improve” an apparently abnormal situation is irresponsible and displays ignorance. Closing a central diastema (such as that described), or extirpation of the frenulum that frequently runs between those teeth (but usually reduces spontaneously) would in most cases be regarded as malpractice. Not only is unnecessary work performed, but also the patient is burdened for no reason (e.g., time, difficulty with oral hygiene, other disadvantages due to wearing appliances, cost). Another objection is that treatment The will be lengthened if a genuine orthodontic anomaly requires treatment. The unnecessary closure of the diastema would be done at an early age, while possible correction of a genuine anomaly could only be undertaken at a later stage (see also 8.5). Further, it is possible that damage could be done because the roots of the teeth being moved may come into contact with adjacent tooth germs.
As a general rule, nature should be given an opportunity to achieve spontaneous improvement. This applies as much to allowing normal development of the dentition to proceed at its own pace as it does to permit natural corrections to occur through changes that take place when factors are eliminated (interceptive measures) which had otherwise disturbed the normal processes.
If the term “prevention” means the specific measures which are taken at the appropriate time by which it is possible to avoid the onset of a certain illness or abnormality, there is little possibility of prevention in orthodontics.312 However, there are possibilities to intervene in certain developments so that they proceed more favorably, and these are described as interceptive measures.
Occasionally, interceptive measures can be taken without previously performing a comprehensive investigation and collecting records. In particular cases, it would be irresponsible to interfere until study models and radiographs have been made and analyzed. The temptation of “minor intervention” is great; the negative effects of it can be significant, certainly when the further development is not followed closely.
Experience is invaluable interceptive orthodontics. This experience is more easily added to if different stages are recorded with study models. “Just doing something” is irresponsible. One should continue to carefully weigh up the consequences of intervention, always following up the results of such action.
Some examples of interceptive measures, for which it is essential to first assemble proper records, and other measures for which records are not necessary, are set out below. The latter are dealt with first.
After giving up a thumb sucking habit, the open bite will decrease spontaneously and eversion of the maxillary incisors can reduce. (The psychological drawbacks of attempting to stop such a habit under compulsion are not discussed here; success demands subtlety, kindness and understanding.)
Deciduous teeth which remain too long in the jaw can interfere with the proper disposition of successors that already have emerged. Extraction of the persisting deciduous teeth usually results in spontaneous improvement of the successors. A lateral forced bite can sometimes be easily corrected if interfering deciduous canines and molars are ground clear at an early stage.
Slicing the mesial of deciduous molars, in particular the mandibular second deciduous molar, can lead to an improvement of crowding in the permanent teeth positioned mesial to them.175 However, one has to be sure that the successors are present.
Preventing caries in deciduous teeth or timely restoration of cavities limits the risk of undesirable reduction in available dental arch length (secondary crowding). Caries can result in reduction of mesiodistal diameter, loss of crowns, or extraction. Adjacent teeth can drift into the space created. Premature loss of mandibular deciduous molars does not always have undesirable consequences; losing maxillary deciduous molars, however, usually does have untoward effects, especially if the second deciduous molar is concerned. The provision of space-maintainers as an interceptive measure should be selective; in most cases they are unnecessary.395 It often is preferable to use a space-regainer at a later time, certainly when active orthodontic treatment would be needed for other reasons.
Extraction of a maxillary first deciduous molar can lead to accelerated eruption of its successor. In cases in which the as yet unemerged permanent canine and the first premolar are close to each other (small middle section of the apical area), this extraction can result in a distal movement of the canine crown because the relatively wide premolar crown descends relatively fast and its narrow root takes less room. This early distal movement of the canine permits a spontaneous improvement in the position of the lateral incisor. If one is considering such an intervention, or such ones as are described next, then appropriate records should be collected.
Timely removal of supernumerary teeth (e.g., a fifth mandibular incisor) provides conditions for a spontaneous correction of the anomalous situation. The same applies to an emerged mesiodens, in which a periapical radiograph suffices.
Whenever it is decided to provide orthodontic treatment that involves removal of permanent teeth, an effort should be made to take advantage of the spontaneous improvements that follow the extractions. This happens by leaving the teeth adjacent to the extraction space free to establish a new position, albeit under regular supervision. Occasionally, ample time can be allowed after extraction before it is necessary to fit appliances. In few cases active treatment may even be abolished. Similar consideration can be given to cases of agenesis of mandibular second premolars, in which at an early age orthodontic closure of the space that will result from loss of the deciduous molars, is indicated. Timely extraction of the second deciduous molar (possibly first use hemisection and extraction of the distal half only) permits migration of the first permanent molar, resulting in at least part of the space closure. However, this procedure is not an interceptive measure in the true sense, although it does make use of the phenomena that occur in genuine interception.
It is stressed that extraction of deciduous canines is not an interceptive measure. While it is true that an improvement in alignment of irregular incisors will follow by taking this measure, the effect on the further development of the dentition, and especially the elimination in arch widening due to the extractions, is very unfavorable. The available space for the permanent canine is subsequently much too small. Extraction of deciduous canines without careful planning of further treatment with appliances is irresponsible. This applies particularly to the mandible, where it is seldom possible to secure a good result after extraction of deciduous canines unless fixed appliances are used.
In general practice one has the opportunity to regularly check the development of the dentition. In this, a number of phenomena should be observed, and it is wise to collect records of those observations.
With a small middle section of the maxillary apical area, the first permanent molar in its eruption can cause resorption of the distal root of the second deciduous molar. It ceases to erupt when the enamel of the deciduous molar is encountered (it does not resorb). For continuation of the eruption, the hindrance should be eliminated either by extracting the deciduous molar, or (when only a limited amount of space is needed) by tying a brass ligature between both teeth and increasing its tension over a period by twisting it tighter, or by placing a separation spring.
Sometimes lateral deciduous incisors or deciduous canines are lost prematurely because their roots are resorbed during the eruption of respectively the central, or lateral permanent incisors. This is usually a symptom of a small anterior section of the apical area and an indication that severe crowding will occur later. In the maxilla the premature loss is usually bilateral, but in the mandible it is often on one side only. This difference is related to the absence of a median suture in the mandible. In the maxilla this suture impedes any movement of the central incisors within the alveolar bone across the midline, but due to its absence in the mandible no such midline constraint exists. In cases where unilateral loss of mandibular canines has occurred, or is about to occur, extraction of the corresponding tooth on the other side is often indicated in order to inhibit further tilting of the mandibular incisors towards the side of the early loss, as well as to provide an opportunity for spontaneous correction to occur. However, the grave disadvantages of loss of the deciduous canines (as already described) remain operative.
In many dentitions in which second deciduous molars are still present, their opposing distal surfaces lie in one plane. Consequently, the mesial surfaces of the first permanent molars also lie in one plane and a cusp-to-cusp occlusion for the first permanent molars results. In about 70% of the cases a neutro-occlusion results after emergence of the second premolars; in about 30% a disto-occlusion.13 One does well to follow the development of cusp-to-cusp molar occlusions with care and interfere when indicated.
The timely diagnosis of agenesis of maxillary lateral incisors (palpation) is especially important in cases with neutro-occlusion because in that case one can choose, as a solution, to displace mesially the teeth in the pertinent quadrants. Early extraction of the maxillary second deciduous molar in such cases can simplify the later treatment because the first permanent molar can usually already migrate mesially. Incidentally, with agenesis of maxillary lateral incisors, the permanent canine occasionally erupts mesial to the persistent deciduous canine. When that permanent canine has emerged in the desired position in contact with the central incisor, one must decide if the deciduous canine and should be retained temporarily, or for as long as possible.
At an early age, an undesirable location of the permanent canines can be detected by palpation. This condition is rather often encountered, particularly in the maxilla, but if it is only discovered some time after the contralateral tooth has emerged, then the most favorable time to begin the complex and time consuming treatment has already gone.
One should also be able to detect, by palpation, permanent canines which are forming far mesially in the maxilla close by the root of the lateral permanent incisor, which it may even overlap. This can be a reason for intervention at an earlier age than one normally would consider appropriate.
With severely hypoplastic crowns of first permanent molars, one should decide in good time (i.e., before emergence of the second permanent molars) to conserve or to extract the first molars. If one resorts to extraction, then the sequence and time of extraction must be carefully chosen. Generally, extraction of the mandibular molars should precede that of the maxillary molars.172
In cases with severe crowding, and especially with markedly small posterior sections of the apical area in the mandible, it can be desirable to establish at an early age whether the mandibular third molars are forming. One can then contemplate enucleation when they are not yet, or at least are only very slightly calcified. The germs are then found to be still in the anterior portion of the ascending ramus above the occlusal plane of the mandibular teeth. In this situation they are relatively simply removed surgically.320
There are probably but few situations in which an interceptive intervention is all that is needed. Some aspects of a developing anomaly can occasionally be guided, but very seldom will the effect be such that later on the use of orthodontic appliances will no longer be indicated.
Irresponsibly executed “interceptive” interventions can make an anomaly worse and either complicate later treatment, or even make it necessary. Interceptive measures should be an integral part of longitudinal guidance, supported by a good knowledge of the development of the dentition, and should not be a casual, local incident.
Finally it is stressed again that the above measures should always be followed by accurate checks in order to evaluate the consequences and to engage in more active therapy when indicated.
The choice of the most suitable moment to commence treatment should be made so as to minimize the treatment duration, the damage to the masticatory apparatus, and the load treatment imposes on the patient and his circle.
Proper treatment timing should maximize the efficiency of the operation and provide the best possible end result. These objects are best realized when one takes the most advantage of the development of the dentition, facial growth, and the “adaptability of skeletal tissues”.396
In most Class I anomalies with crowding, it is advisable to begin treatment during the later phase of the second transitional period (i.e., when the second deciduous molars are still present and the second permanent molars have not yet emerged). One can then use, for treatment purposes, the additional space that becomes available on exfoliation of the second deciduous molar; moreover, the undesirable mesial migration of the first permanent molars which accompanies the emergence of the second molars can be deliberately opposed. (Fig. 8-2). In addition, the unfavorable sequelae to certain emergence sequences in the posterior segments can be nullified.232 394 The treatment can be finished shortly after the completion of the eruption of the canines and premolars.
An advantage of starting treatment in the second transitional period, rather than earlier, is that a great deal of the development of the dentition and growth of the face has already taken place, which in turn removes some of the uncertainties in assessing therapeutic possibilities.41 Above all, it appears that if one waits, the anomalies identified at an earlier age sometimes correct themselves to such an extent that it no longer is sensible to treat them.46 To plan and execute good orthodontic treatment at an early age is relatively difficult, it requires good understanding of complex biological processes. The forecasting of what development may be expected, and of the reaction to treatment, is by no means simple.142 268 With many mild Class II/1 anomalies (a disto-occlusion of a half premolar crown width), it is unnecessary to begin treatment earlier than that detailed above. The maxillary first permanent molars can, if necessary, be moved a little distally before the second molars emerge. The facial skeleton needs minimal influence due to the limited extent of the anomaly. Premolars and permanent canines can assume a correct occlusion after emergence, thus consolidating the result achieved. Should treatment coincide with accelerated growth of the face, this can be a favorable additional factor, though it is by no means essential.178 396 Some girls experience the puberal growth spurt in the second transitional period, but boys seldom do as their spurt comes later in relation to their dental development.
Serious Class II/1 anomalies (a disto-occlusion of an entire premolar crown width) have to be placed under treatment at an early age because it is unlikely that later on the desired result can be reached, or can only be achieved at the cost of much extra effort. Moreover, in such cases, there is often an increased risk of accidental damage to the incisors which in itself is a strong indication for early treatment. Further, subsequent to the transition to permanent incisors, the lower lip frequently comes to lie against the palatal surfaces of the maxillary incisors with all its undesirable consequences. By treating such cases (preferably with functional appliances) during the intertransitional period, a great change can be achieved in a short time.143 253 396 406 However, the total treatment time will mostly be extensive as treatment usually cannot be completed before the premolars and permanent canines are in solid occlusion.
With Class II/2 and Class III anomalies it can also be desirable to begin treatment before the second transitional period. The severity of the anomaly is usually what decides the issue. With a Class III anomaly due to excessive forward growth of the mandible, there is always a risk that treatment will fail eventually. The treatment often takes a long time, and is usually started early, though the anomaly may still require surgical correction, possibly with additional pre and postsurgical orthodontic alignment, to secure a good result. Class III anomalies with a clearly underdeveloped middle face need treating very early on, preferably while still in the complete deciduous dentition, using ventral traction on the maxilla.
If, due to circumstances, one is compelled to treat severe Class II/1 anomalies just in or after the second transitional period, success can often still be obtained through using functional appliances and extra-oral traction in combination (see 8.6.5). Sometimes this approach achieves a great improvement in a relatively short time. In such cases the adaptability is, as it were, called upon twice. If by chance the adolescent growth spurt coincides with the treatment period, then the effect can be surprisingly good.
It is not advisable with Class II/1 anomalies to wait for the adolescent growth spurt before instituting facial orthopedic therapy.178