Posttreatment Stability Research Articles

Spontaneous mandibular arch response after rapid palatal expansion: A long-term study on Class I malocclusion

The purpose of this study was to investigate the spontaneous mandibular arch response to rapid palatal expansion as the sole orthodontic intervention. Particular attention was paid to clinically significant effects and long-term (mean age, 11.3 years) posttreatment stability in 30 Class I malocclusion patients treated during the early and mid mixed dentition. Measurements were made directly on 120 dental casts obtained at 4 assessment stages: pre-expansion (A1), short-term follow-up (A2), progress (A3), and long-term follow up (A4). Comparisons between A1 and A2 showed statistically significant (P < .001) increases for intermolar widths (lingual and occlusal values). During the transition to the permanent dentition, a significant (P < .001) decrease occurred in arch length and arch perimeter. There was a 25% intermolar width (occlusal value) decrease from the initial net gain, whereas the lingual values remained unchanged. Comparisons between A2 and A4 showed an intermolar width (occlusal value) net gain of 50% and a significant (P < .001) decrease for the arch length and arch perimeter. There was remarkable stability in intermolar width (lingual value) and intercanine width (occlusal value), indicating that the increase in the mandibular arch width dimension was in response to the orthopedic effects of rapid palatal expansion in the early and mid-mixed dentition and that the stability was maintained until adulthood.

Stability and predictability of orthognathic surgery

In assessing posttreatment stability in a group of treated patients, most of the change usually occurs in just a few of them. For this reason, it is highly misleading to use statistics based on normal distribution to describe posttreatment changes. With a normal distribution, the mean is the most likely indicator of what a patient would experience, and the clinician tends to think of it in just that way. But if essentially no change occurred in three fourths of the patients who underwent a certain type of treatment, and relatively large changes occurred in the one fourth who experienced change, the mean is highly misleading as an expectation of treatment response.

Stability and predictability of orthognathic surgery.

In assessing post-treatment stability in a group of treated patients, most of the change usually occurs in just a few of them. For this reason, it is highly misleading to use statistics based on normal distribution to describe posttreatment changes. With a normal distribution, the mean is the most likely indicator of what a patient would experience, and the clinician tends to think of it in just that way. But if essentially no change occurred in three fourths of the patients who underwent a certain type of treatment, and relatively large changes occurred in the one fourth who experienced change, the mean is highly misleading as an expectation of treatment response. It is even more misleading to describe stability in terms of the percentage of treatment change that was retained at some follow-up time, as was done in many early articles on stability after orthognathic surgery. Reporting such percentages implies that the amount of relapse is directly related to the amount of treatment change: the more you changed it, the more it would relapse. In dentofacial patients, that almost never is the case. You simply cannot say that 80% of the amount of typical mandibular advancement will be retained, for instance, because, up to 8–10 mm, posttreatment change (in the few patients who experience it) is relatively independent of the amount of advancement. So how should stability data be reported? The best way is in terms of the percentage of the patients who have changes of a given magnitude. From that perspective, responses can be grouped as: Highly stable—less than a 10% chance of significant posttreatment change Stable—less than a 20% chance of significant post-treatment change and almost no chance of major posttreatment change Stable if modified in a specific way (eg, rigid internal fixation [RIF] after surgery) Problematic: a considerable probability of major posttreatment change In the real world, nothing is 100% successful, and high-risk procedures sometimes are quite successful. The clinician needs to know the odds of long-term stability and predictability with the possible treatment approaches, so that this information can guide the choice of treatment. The goal of this article is to put what we know in that context.

A longitudinal index study of orthodontic stability and relapse

Abstract Background: Previous studies of stability and relapse after orthodontic treatment report short-term stability is generally followed by slow relapse to the original condition. What these studies do not report is whether this relapse is continuous or interspersed with periods of improvement or stability. Methods: A subjective 0–10 index of malocclusion was used to record post-treatment stability and relapse over 10 to 12 years following fixed appliance orthodontic treatment of 24 patients. The severity scores were plotted on timelines. Results: Episodes of change, both favourable and unfavourable, were interspersed with episodes of stability. Conclusions: Changes in the first 3 and 12 months post-treatment are indicative of the 10 to 12 years post-treatment outcomes. This index may provide a useful instrument to analyze patients and/or their study models longitudinally.

Midsymphyseal distraction osteogenesis for correcting transverse mandibular discrepancies

Am J Orthod Dentofacial Orthop 2002;121:629-38

The Versatility of Distraction Osteogenesis in Craniofacial Surgery

To review our preliminary results using distraction osteogenesis for the correction of craniofacial deformities and to determine its role in treating anatomic deformities and functional deficits relative to conventional craniofacial surgery. Retrospective clinical review; tertiary care center. Twenty-four consecutive patients were treated with distraction osteogenesis during a 34-month period. Outcomes were compared with preexisting anatomic deformities and functional deficits using records of clinical assessments, photodocumentation, diagnostic imaging, and treatment planning aids. Distraction achieved vs planned distraction based on clinical and radiographic assessment, clinical status of functional deficits before and after treatment, and objective rating of aesthetic improvement. Preliminary results demonstrated good-to-excellent outcome in correcting facial skeletal deformity in 80% of patients. Functional outcomes included resolution or significant improvement of upper airway obstruction in 13 of 14 patients and correction of corneal exposure for all 5 patients with preexisting exorbitism. Correction of malocclusion was less reliable. Problems related to the distraction devices, including failure of the advancement mechanism and fixation, were the most prevalent complications. Distraction osteogenesis represents an exciting new development in craniofacial surgery with several potential benefits, including less invasive surgery, the ability for earlier intervention, and the potential for correction of more severe deformities with improved posttreatment stability. The exact role of distraction osteogenesis relative to conventional techniques requires ongoing assessment.

Nonsurgical management of the anterior open bite: a review of the options

The open bite malocclusion has been described as being of 2 types: dental and skeletal. Proper differentiation is essential in determining the appropriate corrective measures. Dental open bites are generally more responsive to treatment with orthodontics alone, whereas skeletal open bites often require a combination of orthodontics and orthognathic surgery. Patient selection and treatment principles for nonsurgical open bite treatment are discussed, and a review of various methods of treatment for the skeletal open bite is presented. Posttreatment stability and retention concerns are addressed.

An evaluation of the shape of some popular nickel titanium alloy preformed arch wires

The mathematical Beta function is shown to be an accurate planar representation of the natural human arch form defined by the spacial coordinates of the labial and buccal dental/bracket interfacing surfaces in the maxillary and mandibular arches. Graphic planar representations of the corresponding bracket base spacial coordinates of 33 popular preformed nickel titanium arch wires and bracket assemblies were superimposed on each of the relevant maxillary and mandibular natural forms. The arch forms of the preformed nickel titanium arch wires and bracket assemblies did not emulate the natural human arch form. The average mandibular natural human arch form first molar/canine width ratio is 2.38/1; the same preformed arch wire/bracket ratio is 1.87/1. These ratios for the maxillary arch are 1.92/1 and 1.54/1, respectively. The average canine width exceeded the natural canine width by 5.95 mm in the mandibular arch and 8.23 mm in the maxillary arch. The corresponding mandibular first molar and maxillary first molar widths exceeded the natural human first molar arch width by 0.84 mm and 2.68 mm, respectively. These findings have implications with respect to posttreatment stability and facial esthetics. “Round tripping” teeth resulting from subsequent change to stainless steel arch wires to restore a more natural human arch form and size may result in deleterious tissue effects. (Am J Orthod Dentofacial Orthop 1999;116:1-12)

TOOTH STABILIZATION FOR ORTHODONTIC RETENTION

This article reviews stability and retention of the orthodontically treated dentition. Factors and conditions that influence post-treatment stability are discussed. Methods for stabilizing and retaining the occlusion are reviewed.

Occlusal stability after extraction orthodontic therapy in adult and adolescent patients

In this study we compared the posttreatment stability of occlusion in adults and adolescents treated for crowding or maxillary protrusion with four-premolar extractions and edgewise mechanics at an average of more than 4 years out of treatment. The adolescent sample showed a significantly greater posttreatment increase in mandibular anterior crowding than the adult sample. Posttreatment overjet and overbite remained more stable in the adolescents. We noted a correlation between in-treatment expansion and posttreatment narrowing of mandibular intercanine width in the adults. Differences in postorthodontic occlusal changes were noted between the adult and adolescent samples. (Am J Orthod Dentofacial Orthop 1997;112:530-7.)

Tomographic stability of condyle fossa relationships in 40 treated temporomandibular disorder patients

Statement of problem. Condylar position and stability after treatment of 40 temporomandibular disorder patients was studied. Purpose. This study determined pretreatment position and posttreatment condylar stability. Material and methods. Forty temporomandibular disorder patients with symptoms of muscles of mastication pain, temporomandibular joint sounds, attrition, interceptive occlusal contacts, and restricted range of motion were used. Axial corrected midcut sagittal tomograms were made of the 80 temporomandibular joints before treatment. Tracings from the tomograms were used to measure and analyze pretreatment position and posttreatment stability. Results. Pretreatment condyle fossa position was not concentric in 26 of 80 patients (32.5%). Posttreatment condylar position showed no change and was statistically stable. Conclusion. In this study of 40 temporomandibular disorder patients, no statistical change in condylar position was detected. Variable condylar positions were found in the 80 pretreatment axial corrected midcut sagittal tomograms. All patients were asymptomatic after 1 year. (J Prosthet Dent 1998;79:570-4.)

The decision to extract: Part II. Analysis of clinicians' stated reasons for extraction

In a recently reported study, the pretreatment records of each subject in a randomized clinical trial of 148 patients with Class I and Class II malocclusions presenting for orthodontic treatment were evaluated independently by five experienced clinicians (drawn from a panel of 14). The clinicians displayed a higher incidence of agreement with each other than had been expected with respect to the decision as to whether extraction was indicated in each specific case. To improve our understanding of how clinicians made their decisions on whether to extract or not, the records of a subset of 72 subjects randomly selected from the full sample of 148, have now been examined in greater detail. In 21 of these cases, all five clinicians decided to treat without extraction. Among the remaining 51 cases, there were 202 decisions to extract (31 unanimous decision cases and 20 split decision cases). The clinicians cited a total of 469 reasons to support these decisions. Crowding was cited as the first reason in 49% of decisions to extract, followed by incisor protrusion (14%), need for profile correction (8%), Class II severity (5%), and achievement of a stable result (5%). When all the reasons for extraction in each clinician's decision were considered as a group, crowding was cited in 73% of decisions, incisor protrusion in 35%, need for profile correction in 27%, Class II severity in 15% and posttreatment stability in 9%. Tooth size anomalies, midline deviations, reduced growth potential, severity of overjet, maintenance of existing profile, desire to close the bite, periodontal problems, and anticipation of poor cooperation accounted collectively for 12% of the first reasons and were mentioned in 54% of the decisions, implying that these considerations play a consequential, if secondary, role in the decision-making process. All other reasons taken together were mentioned in fewer than 20% of cases. In this sample at least, clinicians focused heavily on appearance-related factors that are qualitatively determinable by physical examination of the surface structures of the face and teeth. They appear to have made primary use of indicators available on study casts and facial photographs and relatively little use of information that is available only on cephalograms or that involves the application of specialized orthodontic theories. (A M J O RTHOD D ENTOFAC O RTHOP 1996;109:393-402.)

Posttreatment Stability of the MCMI-II Personality Scales in Depressed Outpatients

The sensitivity of personality measurement to emotional state has been indicated in several studies. This study explored the effect of depressive state on personality assessment with the Millon Clinical Multiaxial Inventory II (MCMI-II). Posttreatment assessment showed significant decrease in scores on the schizoid, avoidant, self-defeating, and schizotypal personality scales when contrasted with pretreatment assessment. Reduction in scores on the Hamilton Rating Scale for Depression was correlated with reduced scores on the schizoid and the self-defeating scales, and with increased scores on the narcissistic scale. These findings are discussed in respect to methodology, previous studies, and theoretical considerations.

Retention—retainers may be forever

The very word “retain” means “to hold back or hold secure”. From the earliest days of orthodontic tooth movement, many schemes have been proposed to ensure posttreatment stability. The very best research indicates that no solution has been found. A posttreatment routine is recommended. It is suggested that each patient be advised to follow this and further warned that the dental profession does not have any reliable method to predict future dental stability with or without orthodontic treatment.

PET of malignant cerebral tumors after interstitial brachytherapy. Demonstration of metabolic activity and correlation with clinical outcome.

Positron emission tomography (PET) with rubidium-82 (82Rb) and fluorine-18-fluorodeoxyglucose (18F-FDG) was used to diagnose active tumor recurrence and to differentiate this from radiation injury after interstitial irradiation of malignant gliomas. Patients were studied when they presented with radiological or clinical deterioration after an initial period of posttreatment stabilization. Forty studies were performed in 34 patients. The 82Rb was used as a blood-brain barrier tracer to localize the lesion. Uptake of 18F-FDG by the lesion was then compared to uptake by adjacent brain in order to make a diagnosis of active tumor recurrence (higher or equal lesion uptake) or no active tumor (lower uptake). Radiation injury was diagnosed by the exclusion of active tumor. A retrospective clinical diagnosis was established in 38 cases by following the patients' progress for 8 to 142 weeks after the PET study. In two cases, no follow-up diagnosis could be determined. The PET results agreed with the follow-up diagnosis in 15 of 17 cases of active tumor and 17 of 21 cases of radiation injury. Histological examination of surgically resected tissue obtained after the PET study was performed in 18 patients (nine with tumor regrowth and nine with radiation injury). This showed apparently viable tumor as well as necrosis in all cases, regardless of eventual clinical outcome. Some cells from the irradiated volume may appear morphologically intact, but have little or no metabolic or clinical activity. The functional nature of the PET-FDG technique allows diagnosis of tumor activity, which cannot be demonstrated by anatomic imaging studies or by histological examination. The addition of a blood-brain barrier tracer to the 18F-FDG study aids in differentiating normal brain uptake from tumor activity and improves the accuracy of the technique.

Retention and Post-Treatment Stability in the Adult Dentition

Post-treatment changes that occur in the supporting apparatus must be considered in the design and time of use of retention devices. Of equal importance is establishing the methodology of retention prior to initiating active orthodontic therapy. The different types of retainers that are best used are reviewed.

Anterior open-bite malocclusion: A longitudinal 10-year postretention evaluation of orthodontically treated patients

Long-term response of the anterior open-bite malocclusion was evaluated in forty-one white subjects who had undergone orthodontic treatment and were out of retention a minimum of 9 years 6 months. The purpose of the study was threefold: (1) to make cephalometric comparisons between a sample of open-bite patients and a sample with normal cephalometric standards, (2) to evaluate treatment and posttreatment changes that occurred in treated open-bite patients, and (3) to search for predictors and associations of value. Changes occurring across time in the open-bite patients were analyzed by computer means using pretreatment, posttreatment, and long-term cephalometric radiographs and dental casts. An analysis of subgroups was reviewed to compare dentoalveolar and skeletal relationships of both stable and relapse groups. More than 35% of the treated open-bite patients demonstrated a postretention open bite of 3 mm or more, with the relapse subgroup demonstrating across-time, less mandibular anterior dental height, less upper anterior facial height, greater lower anterior facial height, and less posterior facial height. Neither the magnitude of pretreatment open bite, mandibular plane angle, nor any other single parameter of dentofacial form proved to be a reliable predictor of posttreatment stability.

The Rationale for Various Modes of Retention

In addition to the specific aspects of retention mentioned previously, other factors may promote postorthodontic relapse. The seasoned clinician must therefore be aware of any and all variables that may potentially affect the stability of the treatment result. For example, identification and elimination of the etiology of the malformation will enhance the potential for stable treatment. If an anterior open bite deformity is caused by thumb sucking, stability of the corrected open bite can usually be achieved if the child can eliminate the habit. If the habit is not controlled, there is little likelihood that the open bite correction can be maintained. Similarly, successful long-term closure of a maxillary midline diastema will depend primarily on identification and elimination of its etiology. Other factors that may influence posttreatment stability should be considered in the original treatment plan. For example, severe mandibular incisor irregularity may necessitate the extraction of an incisor tooth to avoid potentially unstable expansion of the anterior area of the dental arch. Adherence to accepted principles of good orthodontic therapy are also of importance for posttreatment stability. Proper axial inclination of anterior teeth may assist in preventing recurrence of deep overbite, and proper axial inclination of teeth adjacent to extraction sites may help prevent the reopening of these spaces. Maximum interdigitation of posterior teeth may not insure against the relapse of a class II malocclusion, but failure to achieve good interdigitation will certainly leave the dentition more susceptible to relapse. In 1907, Angle wrote: “After malposed teeth have been moved into the desired position, they must be mechanically supported until all of the tissues involved in their support and maintenance in their new positions shall have become thoroughly modified, both in structure and function to meet the new requirements.” 1 While it is clear that normal function and long-term retention will not necessarily prevent relapse of some aspects of a particular malocclusion, proper retentive procedures will enhance the stability of the corrected malocclusion if supported by good treatment planning and active therapy.

The long-term effect of high pull headgear on the incisor region of the maxilla

A longitudinal study of the influence of high pull traction on the upper incisor segment was studied in six consecutive cases aged between 11 and 16 years. Cephalometric measurements on lateral skull radiographs were used to evaluate the effects of treatment and post-treatment stability with regard to the vertical position of the upper incisors, the upper anterior facial height and the inclination of the maxilla in relation to the anterior cranial base. The development of the upper facial height during this investigation is presented in percentile diagrams. The results show that: 1. High pull traction applied to the upper incisor segment, with two exceptions (A.A. and A.E.) was found to have a permanent orthopaedic effect on the upper anterior facial height. 2. High pull traction had very little effect on the inclination of the maxilla relative to the anterior cranial base. 3. Long-term intrusion of the upper incisors was found in all cases.

Continuous versus intermittent extraoral traction: An experimental study

E xtraoral traction to the maxilla has proved to be clinically effective in the correction of anteroposterior discrepancies in occlusion. Recently, the effect of such traction on the bones of the craniofacial complex has also been recognized.5y i, 9, I*, 13, l6 In all previous experimental studies, with one exception,16 extraoral traction to the maxillas of monkeys has been achieved with continuously applied force (24 hours per day). However, the intermittent application of ext,raoral traction is a common clinical procedure, and investigation is indicated to compare different force-application schedules. This article will describe the treatment effects and the posttreatment stability of extraoral high-pull traction applied to the maxilla of Macaca nemestrina on an intermittent versus a continuous schedule. Duration of force application is the independent variable of study.