Segmental LeFort I osteotomy for management of transverse maxillary deficiency.
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Humans↗
Biomedical subjects
W R Proffit
Publications and source records attributed to W R Proffit.
Influences on the outcome of early treatment for Class II malocclusion.
In the first phase of a randomized clinical trial of early versus late Class II treatment, statistically significant differences were observed between the treatment and observation groups. However, there were wide variations in response. The change in jaw relationship (categorized as the annualized reduction in ANB angle) was favorable or highly favorable in 76% of the headgear, 83% of the functional appliance, and 31% of control (observation only) groups. The patient's initial skeletal severity, age/maturity at the outset of treatment, growth pattern, and cooperation with treatment were examined as possible influences on early growth modification treatment. Correlations between the annualized change in the ANB angle and any of the possible influences were close to zero and not statistically significant. We conclude that there is little to be gained from precisely timing early treatment to specific age/maturity markers and that a favorable reduction in Class II skeletal problems can occur for patients in a broad range of skeletal severity and growth patterns. Cooperation, measured as the number of hours of reported wear, or the clinical assessment of compliance, explained little of the variation in treatment response. The wide variation in growth seen in the untreated patients highlights the importance of well-controlled studies if clinicians are to improve their ability to select children with the greatest chances of a favorable treatment response.
Activator Appliances↗
The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial.
Early treatment for Class II malocclusion is frequently undertaken with the objective of correcting skeletal disproportion by altering the growth pattern. Because the majority of previous studies of growth modification for Class II malocclusion have been based on retrospective record reviews, the efficacy of such an approach has not been well established. In this controlled clinical trial, patients in the mixed dentition with overjet > or = 7 mm were randomly assigned to either early treatment with headgear, or modified bionator, or to observation. All patients were observed for 15 months with no other appliances used during this phase of the trial. The three groups, who were equivalent initially, experienced statistically significant differences (p < 0.01) in skeletal change. There was considerable variation in the pattern of change within all three groups, with about 80% of the treated children responding favorably. Although patients in both early treatment groups had approximately the same reduction in Class II severity, as reflected by change in the ANB angle, the mechanism of this change was different. The headgear group showed restricted forward movement of the maxilla, and the functional appliance group showed a greater increase in mandibular length. The permanence of these skeletal changes and their impact on the subsequent treatment remains to be evaluated.
Analysis of Variance↗
Soft tissue limitations in orthodontics: treatment planning guidelines.
Orthodontists have traditionally viewed structural discrepancies as the major limitation of treatment. In reality, it is the soft tissues that more closely determine therapeutic modifiability. The boundaries of dental compensation for an underlying jaw discrepancy are established by pressures exerted on the teeth by the lips, cheeks, and tongue; limitations of the periodontal attachment; neuromuscular influences on mandibular position; and the contours of the soft tissue facial mask. The ability of the soft tissues to adapt to changes in tooth-jaw relationships are far narrower than the anatomic limits in correcting occlusal relationships. The tolerances for soft tissue adaptation from equilibrium, periodontal, and facial balance standpoints are in the range of 2 to 3 mm for expansion of the mandibular arch and even less for changes in condylar position. Thus, analysis of the soft tissues is the critical step in orthodontic decision making, and this can only be accomplished through physical examination of the patient. Although quantitative measurements cannot be rigorously applied, guidelines for soft tissue assessment, with particular emphasis on facial esthetics, are proposed. From this perspective, a contemporary philosophy of orthodontic practice is offered, with general indications and contraindications for nonextraction, extraction, and surgical treatment.
Adaptation, Physiological↗
A survey of the opinions of orthodontic specialist trainees in the U.K.
A questionnaire survey was carried out to ascertain a profile of orthodontic postgraduates in training in the United Kingdom during 1993. Information about the postgraduates, their programmes and their career plans was collected. Eighty-nine questionnaires were distributed to those enrolled in 13 of the training programmes in the U.K. at that time from which the response rate was 64 per cent. The results can be compared with a similar survey carried out in the United States of America in 1992 (Keith and Proffit, 1994).
Adult↗
The prevalence of facial asymmetry in the dentofacial deformities population at the University of North Carolina.
In a retrospective survey of 1,460 patients evaluated in the Dentofacial Clinic at the University of North Carolina, 495 (34%) were found to have clinically apparent facial asymmetry. When present, asymmetry affected the upper face in only 5% (n = 23), the midface (primarily the nose) in 36% (n = 178), and the chin in 74% (n = 365). The occlusal plane was canted, indicating vertical asymmetry, in 41% (n = 201). Patients with Class II problems, whether or not due to mandibular deficiency, had a 28% prevalence of asymmetry; those with other types of problems (e.g., Class III, long face, Class I) had a 40% prevalence, which is significantly higher than those with Class II occlusions. When the chin deviated transversely, there was an 80% chance that the deviation was to the left. Only in patients with long face was there an equal distribution of left-right chin asymmetry. In the other groups, the prevalence of deviation of the chin to the left approached 90%. These findings are meaningful for clinicians because asymmetry must be identified and planned for prior to initiating treatment.
Face↗
High-resolution observations of human premolar eruption.
Using an optical instrument based on the principle of Moire magnification to obtain resolution of less than 0.1 mu m, eruption of maxillary second premolars was observed during the prefunctional phase of eruption in 10 children. The participants were observed on four occasions for approx. 30 min each, once in the afternoon and once in the evening on two consecutive days. For all participants, a pulsatile movement of the erupting tooth was noted in concert with the arterial pulse. Significant variations in short-term eruption rates and patterns were observed, with a mean rate of 0.28 mu m/min over continuous 20-min periods but a range from -0.91 to 2.29 mu m/min. During most sessions net eruption occurred, but in several of the 30-min periods there was little movement or intrusion. An unexplained cyclic phenomenon was observed consistently, which had a period of 20-50 s and a range of magnitudes from 0.12 to 2.22 mu m. It seems clear that a discontinuous pattern of eruption occurs in short-term as well as longer-term observations.
Arteries↗
The rhythms of human premolar eruption: a study using continuous observation.
New optical technology now allows for precise observation of erupting human premolars. Continuous overnight tracking of an erupting tooth with a video microscope system shows that eruption occurs almost exclusively during the early evening. During the day, slight intrusion is likely to occur. When Moiré magnification is used to provide extremely high resolution (0.05 micrometer), slight movements of the erupting tooth in concert with the arterial pulse can be observed, and a previously unknown cyclic movement with a period of 20 to 50 seconds is seen consistently. Rhythms in skeletal growth and tooth eruption suggest that treatment to influence jaw growth and move teeth may be most effective at specific times of the day.
Bicuspid↗
Soft tissue changes after superior repositioning of the maxilla with Le Fort I osteotomy: 5-year follow-up.
Long-term changes in soft tissue landmark positions were examined in 49 patients following superior repositioning of the maxilla by Le Fort I osteotomy. From presurgery to 1 year, on average the upper lip moved up one third the distance that the upper incisor and point A did, but there was considerable variability. In 25% of the patients the upper lip moved up more than 2 mm, and in 6% it moved up more than 4 mm. As the mandible rotated upward and forward in response to the maxillary movement, soft tissue movements paralleled the adjacent hard tissue movements almost exactly in the absence of genioplasty. From 1 to 5 years postsurgery, in 25% of the patients the maxilla moved downward more than 2 mm, and the mandible rotated down and back, often without relapse of occlusal relationships. In both jaws, long-term changes in soft tissue landmarks exceeded hard tissue changes, meaning soft tissue points tended to move downward even if hard tissue points were stable and moved down more than the corresponding hard tissue points when skeletal changes occurred.
Adaptation, Physiological↗
Orthognathic surgery: a hierarchy of stability.
The stability and predictability of orthognathic surgical procedures varies by the direction of surgical movement, the type of fixation, and the surgical technique employed, largely in that order of importance. The most stable orthognathic procedure is superior repositioning of the maxilla, closely followed by mandibular advancement in patients in whom anterior facial height is maintained or increased. (If facial height is decreased by upward rotation of the chin, stability is compromised). The combination of moving the maxilla upward and the mandible forward is significantly more stable when rigid internal fixation is used in the mandible. Forward movement of the maxilla is reasonably stable, with or without rigid internal fixation, but mandibular setback often is not stable, and downward movement of the maxilla that creates downward rotation of the mandible is unstable. For mandibular setback, the inclination of the ramus at surgery appears to be an important influence on stability. It has been suggested that both interpositional synthetic hydroxyapatite grafting and simultaneous ramus osteotomy improve the stability of downward movement of the maxilla, but this has not been well documented. In two-jaw Class III surgery, the stability of each jaw appears to be quite similar to that of isolated maxillary advancement or mandibular setback. The least stable orthognathic procedure is transverse expansion of the maxilla. Although surgically assisted rapid palatal expansion has been suggested as a more stable alternative to segmental Le Fort I osteotomy, the patterns of movement resulting from the two procedures are different, and differences in stability have not been established.
Humans↗
The application of Moire magnification to high-resolution studies of human premolar eruption.
The optical phenomenon of Moire magnification can be used to provide real-time measurements of the position of an erupting human premolar, with a resolution of 0.1 micron or better. A new instrument for this purpose, which allows repeated measurements in the same individual, is described. Cyclic changes in the position of the erupting tooth in concert with the heartbeat, with a magnitude of 0.05-0.35 micron, can be discerned. An unusual cyclic rhythm, with a period of 20-50 s, was observed.
Bicuspid↗
The daily rhythm of tooth eruption.
A video microscope system, which can resolve tooth movements to 1 to 2 microns, was used to monitor the eruption of 17 human maxillary second premolars in the prefunctional phase. Eruptive movement was detected by the change in position of an optical ruling on the erupting tooth relative to a reference ruling on the occluding adjacent teeth. Eruption was observed as the teeth erupted toward the occlusal plane over approximately a 41-hour period, from late Friday afternoon until Sunday noon. Half hourly observations were made during a 6 to 8-hour continuous laboratory session, which was during the day (9 AM to 5 PM) for nine of the subjects, and during the evening (5 to 11 PM) for eight. A similar pattern of eruption was seen for all subjects. The tooth intruded from before to after dinner on the first day, erupted significantly overnight, ceased eruption and approximately maintained its position during the next day, and erupted again during the second night. On the average, a slight intrusion was observed during the day, and statistically significant intrusion was associated with breakfast and dinner. Eruption occurred during the evening observation period, and the rate of evening eruption was significantly greater in children who were supine and relaxed than those who were upright and active. The 24-hour eruption rate was slower for teeth that were within 1.5 mm of the occlusal plane. The circadian eruption rhythm may be related to fluctuations of hormonal levels that affect metabolic activities within the periodontal ligament. It is also possible that a transient reduction in pressures by the cheeks, lips, and tongue during periods of rest allows eruption to occur then.
Adolescent↗
Communication in orthodontic treatment planning: bioethical and informed consent issues.
Orthodontic treatment planning is an interactive process in which the patient or parent and the orthodontist serve as co-decision makers. As in most partnerships, there is a natural tension between the orthodontist and the patient because of differences in their frames of reference. The orthodontist generally is influenced more by the objective findings (the problem list), whereas patients are guided more by subjective issues related to their perceived needs, desires, and values. The art of careful probing and listening to the patient as part of the treatment planning process is an essential skill. One of the most difficult situations in contemporary orthodontics is presented by the patient with a jaw discrepancy for which the alternative treatments are orthodontic camouflage through dental compensation or surgical-orthodontic correction. Computer imaging to simulate the probable treatment outcomes can facilitate communication about these alternatives by eliminating misconceptions. Full disclosure and the consideration of all viable treatment alternatives have great benefits from a risk management standpoint, in addition to their bioethical merits.
Adolescent↗
The duration and sequencing of surgical-orthodontic treatment.
A review of surgical-orthodontic patients treated through the University of North Carolina Dentofacial Program indicated that the duration of surgical treatment was roughly comparable to that of nonsurgical orthodontics for most patients; there was a greater chance of very long treatment when surgery was involved. Treatment times differed significantly among patients whose orthodontic treatment was done in the faculty practice, university clinic, or outside the university. Median treatment times were 18, 24, and 28 months, respectively, for the three practice settings, but some patients in each group underwent more than 48 months of treatment. After 1 year of presurgical treatment, two thirds of the faculty practice patients, but only one third of the clinic and private practice patients, were ready for surgery. Postsurgical orthodontic treatment of patients attending the faculty practice also was completed more quickly: appliances were removed within 9 months from 83% of faculty practice patients, 71% of clinic patients, and 53% of private patients. Guidelines for efficient management of surgical-orthodontic patients are presented.
Academic Medical Centers↗
Trends in surgical treatment of Class III skeletal relationships.
A review of a surgical-orthodontic database revealed striking changes in the surgical treatment of skeletal Class III problems. After its development, ramus osteotomy for mandibular setback became the standard procedure and was still used in nearly half the patients treated in 1978 to 1985. Between 1985 and 1990, the number of isolated mandibular setback procedures dropped sharply, while the number of maxillary advancements nearly doubled. The number of patients undergoing combined maxillary and mandibular surgery also increased. In 1990 to 1992, isolated mandibular setback was used in fewer than 10% of the patients, while maxillary advancement was used in more than 40% of the patients. The changes were influenced by improvements in surgical techniques, the demonstration that maxillary advancement is unlikely to cause speech problems in noncleft patients, and documentation that better esthetics and stability can be achieved with maxillary than with mandibular surgery.
Adolescent↗
Long-term stability of two-jaw surgery for treatment of mandibular deficiency and vertical maxillary excess.
Changes in cephalometric landmark positions and relationships were evaluated more than 5 years postsurgically in 26 patients whose long-face condition had been treated with a combination of superior repositioning of the maxilla and mandibular advancement. All the patients had a least 2-mm surgical intrusion of the maxilla and 2-mm lengthening of the mandible with wire osteosynthesis, maxillomandibular fixation, and skeletal suspension wires. On the average, a small amount of downward and backward rotation of the mandible occurred long term. The mean change in overjet was less than 1 mm. Most of the changes occurred in a minority of the patients: 20% of the group had 2 to 4-mm downward movement of menton, and the mandibular plane angle increased more than 2 degrees in 25% of the patients. On clinical evaluation, a tendency toward opening of the bite beyond 1 year postsurgery was noted in 5 of the 26 patients (19%), and one patient had a greater than 4-mm decrease in overbite. The condylion-pogonion distance decreased 2 to 4 mm in three patients, two of whom had shown greater than 4-mm shortening of this distance during the first postsurgical year. It appears that long-term shortening of the condylar process is not a highly prevalent problem, but changes of 2 to 4 mm in condylion-pogonion associated with modest clinical relapse may occur beyond 1 year postsurgery in 5 to 10% of these two-jaw surgery patients.
Adolescent↗
Orthodontic training: the residents' perspective.
A survey was carried out at the Graduate Orthodontic Residents' Conference at the University of Michigan, Ann Arbor in August 1991. Questionnaires were distributed to the attending residents who included representatives from 41 of the 51 orthodontic programs in the United States at that time. Of the questionnaires 81% were completed and returned by residents at the schools. Information was gathered relating to the residents themselves, as well as their programs, educational backgrounds, and career plans. The assimilated opinions of the residents on various aspects of their training are presented.
Adult↗
Forty-year review of extraction frequencies at a university orthodontic clinic.
In a review of consecutive charts at 5-year intervals from the orthodontic clinic at the University of North Carolina, the number of patients with extraction of all four first premolars increased from 10% in 1953 to 50% in 1963, remained at 35% to 45% until the early 1980s, then declined sharply to the 1950s level by 1993. Extraction for camouflage of Class II malocclusion (maxillary first premolars alone or maxillary first-mandibular second premolars) reached 16% in 1968, then declined, but not as dramatically, and presently is as frequent as the extraction of four first premolars. The rate of extraction of other teeth, done for a variety of individual reasons, has remained almost constant at about 15% for the past 40 years. Thus the total extraction percentage was 30% in 1953, peaked at 76% in 1968, and declined again to 28% in 1993, with almost all the change in the percentage of four first premolar extractions. The increase in first premolar extractions occurred primarily in a search for greater long-term stability; the recent decline seems due to a number of factors. Greater concern about the impact of extraction on facial esthetics, data to suggest that extraction does not guarantee stability, concern about temporomandibular dysfunction, and changes in technique all seem to have played a role. With appropriate orthodontic mechanics, many patients with Class I crowding can be treated satisfactorily with or without premolar extraction.
Academic Medical Centers↗