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Early extractions of first permanent molars, done on twenty cases without any orthodontic treatment, have not shown, following the Student's analysis, any statistical difference relative to a pilot group as far as the angles. SN- ANS- PNS, SN-OP, SN-GoGn, FMA, Y-axis are concerned. On the other hand, it has been revealed a closure of the angle ANS- Xi- MP associated with an opening of the mandibular arch.
We investigated the duration of pre-operative orthodontic treatment of patients who had combined orthodontic and orthognathic treatment and examined the variables that influenced this. Records of patients who had undergone such treatment in the past 5 years were collected (n=65) from three consultant orthodontists and one Senior Specialist Registrar/Fixed Term Training Appointment (FTTA). The number of days from placement of the first active orthodontic component to the day that final planning impressions were taken was used to calculate the duration of treatment before the patient was ready for operation. The variables investigated were: sex, age, malocclusion, extractions (excluding third molars), and the clinician. The median duration of pre-operative treatment was 17 months (range 7-47). Only the orthodontist appeared to affect this duration, but this requires further investigation as it may merely reflect variation in other factors such as compliance. We conclude that patients should be informed that the pre-operative phase may last 12-24 months.
In those cases judged to be suitable for treatment by extractions in both arches and the use of upper removable appliances alone, the closure of excess residual space relies on mesial drift of the buccal segments. If opposing residual spaces are unequal in extent, there is a risk that space closure will be incomplete. Two cases are presented where a removable appliance was used to move a buccal segment mesially using a traction screw, and thereby close the excess residual space.
The patient was a 12-year-old girl with a Class I malocclusion characterized by maxillary arch width constriction, dental crowding, and mandibular retrognathia. Treatment goals related to the chief compliant were anterior mandibular repositioning, maxillary arch expansion, and dental alignment. Because the preexisting overjet was minimal and prevented adequate anterior repositioning of the mandible, lower first premolar extraction was recommended to increase the overjet and allow greater anterior repositioning. Treatment was divided into four stages: (1) extraction of mandibular first premolar teeth, alignment, space closure, and an increase in the overjet, (2) anterior mandibular repositioning with a removable plastic Herbst appliance, (3) arch alignment and detailing of the occlusion with full fixed appliances and a tooth positioner, and (4) retainers. At the end of treatment, the patient had an acceptable dental alignment with a Class III molar relationship and an improvement in facial appearance.
Characteristics of the patient, the treatment plan, and the practitioner's office were examined to evaluate causes for variation in the duration of orthodontic treatment. From six offices 118 patients were evaluated. All patients were treated in a single phase with fixed appliances. Appliances were worn for an average of 23.1 months. The mean duration for offices ranged from 19.4 to 27.9 months. Thirty-eight percent of the patients had extractions, and 32% wore headgear. Fifty percent of the variation in treatment duration among patients was explained by a five-step multiple regression equation. The variables entering this equation were (1) number of extracted premolars, (2) number of broken appointments, (3) pretreatment mandibular plane angle, (4) pretreatment ANB angle, and (5) pretreatment Salzmann Index. Observations within each office suggested that the time spent by individual clinicians in detailed finishing, which would not be detected by measures such as the Salzmann Index, was an important source of unexplained variation in treatment duration.
This retrospective cephalometric study examined the facial changes brought about by treatment in 62 Class II division 1 children, using tensor analysis. Thirty-two children were treated with Fränkel appliances, whilst the remaining thirty received premolar extractions, headgear, and conventional Edgewise mechanics. Each child was matched for age and sex with an untreated individual in whom the occlusion was deemed satisfactory and the treatment changes were compared with those expected during normal development. Results indicated that vertical facial development predominated in both treated groups: this exceeded the increase expected in an untreated population . The Fränkel group exhibited the greater gain in lower face height, with changes confined almost entirely to the mandible. Effective mandibular position improved but there was no increase in body length. The incisors were more favourably positioned within the face with similar improvements in the soft tissues. Thus, although facial balance was better following a non-extraction Fränkel approach, control of the vertical dimension was inadequate. The fixed appliance group exhibited a smaller increase in lower facial height and no favourable mandibular development: maxillary retraction was the most striking skeletal alteration. By removing the traditional, fixed, superimpositional framework of the cranial base, tensor analysis highlights vertical and mandibular changes not easily detected by conventional cephalometry.
The position of mandibular third molars was studied in 60 patients from the pedodontic and orthodontic departments at the Federal University of Rio de Janeiro. All individuals received orthodontic treatment with an edgewise appliance following the extraction of first premolars. Examination of superimposed pretreatment and posttreatment cephalometric radiographs led to the observation that mandibular growth is directly related to the positioning of mandibular third molars. Third molar impactions were more likely to occur in cases with a predominance of vertical growth. The larger ascending ramus, the diminution in total length of the mandible and the larger mesial inclination of the crowns also seem to be indicative of third molar impaction.
A thirteen-year-old boy presented with a Class III skeletal tendency in association with severe crowding in both the upper and lower arches. Whilst there was not a frank posterior crossbite, it was felt that the upper arch was narrow and that the lower arch was similarly constricted. Taking this into account along with the fact that his upper lip was flat and the nasolabial angle obtuse, it was decided to pursue a non-extraction treatment, with the aim of providing by expansion an extra 16 mm of space in the upper arch and 8 mm in the lower arch to accommodate the full dentition, and with a view to extracting third molar teeth later. This proved to be successful, albeit over an extended period of time, with active treatment taking nearly three and a half years. A realistic alternative would have been to remove four bicuspid teeth and pursue an orthodontic/surgical approach to treatment. In retrospect, and with the benefit of reviewing his records without surgical intervention, the treatment plan decided upon has been well justified.
We describe a case in which a patient with a class II division I incisor relationship on a skeletal II base was transferred midway through a treatment that consisted of aligning the upper and lower arches with fixed appliance orthodontics in preparation for a mandibular advancement osteotomy. The lower second molars had previously been extracted; the lower third molars were left unerupted and some distance from the lower first molars. To provide a good occlusion at the end of treatment, it was decided to expose and approximate the lower third molars to the distal aspect of the lower first molars with the use of nickel titanium closed-coil springs; this was to be done before the osteotomy.
Discriminant analysis has been used to predict the long-term outcome of treatment in children with Class III malocclusions considered suitable for orthodontic correction by a non-extraction technique. Thirty-four children, whose treatment included the application of headgear to the mandibular dentition, formed the basis of this study. Records were examined at the start of treatment and at least 2 years out of all retention. For 25 of these patients, the treatment outcome was unambiguous and from these data a four-variable discriminant model was generated using a step-wise selection procedure, run under SPSS. This afforded 100 per cent correct prediction of the relapse status of all 25 children. The model provided realistic predictions for the remaining nine cases and for seven out of eight other children considered suitable for treatment without extractions, but by a variety of different techniques. The model was not suitable for the prediction of treatment outcome in children who required extractions: these represented a distinctly different sub-group of Class III individuals. Thus, using four measurements taken from the start of treatment records, the eventual outcome of orthodontic treatment can reliably be estimated, provided that the model is restricted to the sub-group of Class III children for whom it was designed. If the discriminant model predicts that this form of therapy will relapse, an alternative approach may be chosen.
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.
A case report of the orthodontic treatment of a male adolescent with a Class I bimaxillary protrusive malocclusion, complicated by a vertical growth pattern and high mandibular plane angle. Treatment consisted of extraction of maxillary second premolars, mandibular first premolars, use of a transpalatal bar, occipital pull headgear, and light wire mechanics. An acceptable result was achieved, with a decrease in the facial axis, decrease in lip strain, and an attractive full smile. This case report was presented to the American Board of Orthodontics in partial fulfillment of the requirements for the certification process conducted by the Board.
The cases presented here clearly demonstrate that the removal of second permanent molars can be effective in many cases where removal of first or second bicuspids would otherwise be recommended. Third molars can be useful components of the dentition. The Author has found that when the proper diagnosis is made and the extraction of second molars is recommended, third molars will assume their position in juxtaposition to the first permanent molar in over 75% of the cases. Although we used several methods of measuring developing mandibular third molars, we were unable to predict accurately and consistently which teeth would erupt in the proper upright position (Fig. 10). With rare exception, maxillary third molars will erupt uneventfully, but in the mandibular arch there is a much greater possibility that it may be necessary to upright or reposition the third molars.
The benefits of lower second molar extraction are substantially reduced if the third molar fails to erupt into a satisfactory position. The selection criteria offered by the literature have been tested in a sample of 51 patients. Prediction is uncertain and cases should be followed until such time as a satisfactory third molar position has been achieved. Failure may be unilateral and more often on the right side. The need for follow-up treatment is subjective but may be as many as one in five patients.
Extracts of the Chinese medicinal plant, Tripterygium wilfordii, cause reversible infertility in male animals. Sub-fractionation studies have now revealed that the plant extracts contain a number of compounds which are potent antifertility agents in male mammals, including the diterpenes triptolide and tripdiolide and an isomer of the latter. A triptolide, 12,13-chlorohydrin, which is a transformation product formed reversibly by interaction of triptolide with HCl, was also found to be active.
Condylar position in 17 patients whose Class II treatment (14 with edgewise appliances and 3 with Begg appliances) included extraction of the maxillary first premolars and in 17 control patients was compared by means of corrected tomography. The condyles in both groups were in an anterior position, and there were no statistical differences between the groups. In addition, no statistical correlation was found when the posttreatment bite depth, interincisal angle, and maxillary incisor inclination were correlated with condylar position. Thus, as determined in this study, condylar position was unrelated to treatment, bite depth, interincisal angle, and maxillary incisor inclination.
Three controversial interrelated aspects of orthodontics have been reviewed: retention, the effect of third molars on lower anterior crowding, and extraction and nonextraction orthodontic treatment. Recent studies have shown that unacceptable lower anterior crowding occurs in 90 per cent of well-treated extraction cases. The implication is that nonextraction cases should be 90 per cent or higher. In view of our present general inability to identify the 10 per cent that will remain acceptable, some form of indefinite retention is advised. A literature review of the effect of third molars on lower anterior crowding finds strong opinions on both sides of the issue. Similar studies often show dissimilar conclusions, particularly when observing cases of third molar extraction or agenesis. Certainly the problem is multifactorial; however, the vast bulk of the evidence indicates that the third molars play an insignificant role in lower anterior crowding. Extraction of teeth for orthodontic treatment prior to 1900 was prevalent and indiscriminate. From the turn of the century to the mid-thirties Angle moved the specialty away from extractions to a relatively rigid nonextraction treatment philosophy. Dissatisified with relapsing Class II cases, recurrence and aggravation of crowding, and what he felt were bimaxillary full faces, Tweed and others, circa 1935, redirected the profession back to extractions with a more disciplined approach to treatment by the removal of four first premolars. Fifty years later we have found that extraction treatment and uprighting lower incisors does not prevent long-term postretention crowding and that flattened profiles are not always esthetically desirable. Earlier treatment of maxillomandibular basal discrepancies by old and new treatment philosophies and mechanics have produced more stable nonextraction corrections. Better control of leeway space and a reduction in caries has helped reduce the amount of lower anterior flaring that was seen in the nonextraction cases in the first third of the century. These reasons have moved the specialty of orthodontics to a mixed but more nonextraction-oriented approach to treatment.
Pretreatment, end of treatment, 10-year postretention, and 20-year postretention records of 31 four premolar extraction cases were assessed to evaluate stability and relapse of mandibular anterior alignment. Crowding continued to increase during the 10- to 20-year postretention phase but to a lesser degree than from the end of retention to 10 years postretention. Only 10% of the cases were judged to have clinically acceptable mandibular alignment at the last stage of diagnostic records. Cases responded in a diverse unpredictable manner with no apparent predictors of future success when considering pretreatment records or the treated results.