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Orthodontic relapse in subjects with varying degrees of anteroposterior and vertical dysplasia.

Fifty seemingly well-treated orthodontic cases were studied by means of pretreatment, posttreatment, and postretention dental casts, lateral cephalograms, and other orthodontic records. The sample was restricted to cases exhibiting anteroposterior and/or vertical dysplasia as revealed by pretreatment dental casts. The sample was divided into a stable group and a relapse group. Each group contained twenty-five cases. A double-blind design was used. The raw data were analyzed by the stepwise discriminant analysis and by the multivariate analysis of variance. On the basis of the results obtained from this study, the following conclusions can be drawn: 1. In seemingly well-treated orthodontic cases, relapse or stability can neither be predicted nor judged from one set of records alone. 2. Relapse or stability of an orthodontic case can be predicted by comparing the posttreatment variables with the pretreatment variables. 3. Relapse or stability of an orthodontic case can be judged by comparing the postretention variables to the posttreatment variables. 4. The PP-GoGn angle and the mandibular intercanine width are the two most important variables associated with orthodontic relapse. 5. Changing the PP-GoGn angle, either by treatment or by growth, was associated with relapse. In other words, changes in the PP-GoGn angle tended to be unstable. This suggests that decreasing the PP-GoGn angle should be avoided. 6. In both the stable and the relapse groups, the mandibular intercanine width decreased postretention. This decrease was associated more with the relapse group than with the stable group. 7. The mandibular intercanine width tended to relapse toward its original pretreatment value. This suggests that, at the end of active treatment, the mandibular intercanine width should be maintained as originally presented. 8. There was no significant interaction between orthodontic relapse (or stability) and Angle Class I and II cases. 9. There was no significant interaction between relapse (or stability), of an orthodontic case, and the sex of the patient. 10. There was no significant interaction between orthodontic relapse (or stability) and whether or not extraction was included as a part of the mechanotherapy. Thus, the pretreatment deep overbite is not necessarily a contraindication to extraction.

Analysis of Variance↗

Genetic analysis of occlusal variation in twins.

Orthodontists usually assume that genetic factors are of major significance to the development of malocclusion. Studies of twin similarities have lent support to this concept. Use of the twin model to estimate genetic variance, however, involves the assumptions that there are no mean or total variance inequalities between monozygotic and dizygotic twins. The environmental (including biologic) differences between monozygotic and dizygotic twin development may therefore constitute a source of bias. Genetic variance and heritability were estimated for a series of arch and occlusal traits in sixty twins using recently developed methods that are unbiased by variance heterogeneity between zygosities. Heterogeneity was demonstrated for twenty of the forty traits, suggesting considerable amounts of hidden environmental determinance. Tooth-displacement means differed between monozygotes and dizygotes, indicating bias in that trait's genetic variance analysis. Significant heritability could not be demonstrated for overbite, overjet, buccal segment relation, total tooth displacement, and occlusal discrepancies in arch shape. Arch size, individual tooth displacement scores, and cross-bite show significant genetic variance, averaging only about 36 percent of the total variance of these traits.

Adolescent↗

A study of occlusion and arch widths in families.

It is often claimed that occlusal variation ("malocclusion") is under strong genetic control. This study of a large age-standardized series of families (parents and offspring) shows that the genetic contribution to occlusal variation is quite low. On average, only about 10 percent of the variation in overjet, overbite, crowding, tooth rotations, and molar relationships results from nonenvironmental causes. In contrast, about 60 percent of the variation in measurements of arch size and shape is attributable to heredity.

Cephalometry↗

A comparative analysis of intrusion of incisor teeth achieved in adults and children according to facial type.

A comparison was made of incisor intrusion achieved in adults and children with deep bite. Facial type was also examined for effect upon intrusion achieved. Fifty-five cases treated with bioprogressive mechanics were studied cephalometrically; subjects included twenty-four adults and thirty-one children. Neither age nor facial type was found to be statistically related to the amount of incisor intrusion achieved in this sample. A method of measuring intrusion at the root apices was devised and was thought to give a more accurate indication of actual bodily intrusion. More external root changes during treatment were observed for adults than for growing children. There was a wide latitude in the amount of intrusion observed in both groups and in all three facial types. Considerable overbite reduction was noted for the sample, and intrusion was found to be but one factor in this.

Adult↗

Dimensional changes in the dental arches of orthodontically treated cases.

Integrated data from lateral cephalometric radiographs and study models of fifty-three patients were studied to assess the interactions between dimensional changes occurring during orthodontic treatment and the postretention stability of these changes. A new technique was developed to study distal movement of canines. Distal movement of canines did not ensure a stable increase in intercanine width. There was no significant relationship between mesiodistal position of the first molars and changes in intermolar width. Eruption of the first molar in the postretention period was associated with greater stability in overbite. There was no great degree of correlation between depth of the curve of Spee and inclination of the occlusal plane or between changes in arch length and changes in inclinations of the incisors.

Cephalometry↗

Hypoglossia: case report and discussion.

A case of hypoglossia was observed between the ages of 3 and 15 years in a patient with micrognathia, congenital absence of three lower incisors, and a telescopic occlusion accompanied by an extremely narrow lower arch and severe overbite. Orthodontic intervention was begun when the patient was 8 years old. Craniofacial growth changes that occurred before and after orthodontic treatment are discussed. Cephalometric study of this case suggests the distinctive features of the postnatal growth pattern similar to other cases with the syndrome.

Adolescent↗

Influence of musical instruments on tooth positions.

A 2-year longitudinal investigation was conducted at five New York City junior high schools on 11- to 13-year-old children starting instrumental music education to determine what tooth movement, if any, resulted from the playing of certain musical instruments. Questionnaires, interviews, oral examinations, and dental casts were used at the start of instrumental study, after one year, and then after a second year. Statistically significant anterior tooth movements occurred in an overwhelming majority of the instrumentalists, while negligible movements were recorded for the controls over this period. As a result of this study, certain recommendations can be made by dentists when they are asked to suggest instruments which are dentally suited for children. In most cases they can suggest more than one instrument which would be of benefit dentally to the individual child, especially in the increase or reduction of overjet and overbite. The playing of the correct musical instrument can serve as an adjunct to the dentist or orthodontist in trying to accomplish certain tooth movements.

Adolescent↗

Orthodontic force systems: individualized treatment with open-minded "Begg" technique.

Conventional Begg technique is efficacious for alignment, overbite reduction, and anchorage conservation, but it has a number of deficiencies. Biomechanical systems should be determined by the characteristics of each individual malocclusion, not by habitual application of the same recipe to every patient. Check elastics can increase the bite-opening potency of the appliance, thus permitting control of root movement at any stage. Ribbon arch wires can provide torque control for either bolstering or expending anchorage. Extraoral traction can provide anchorage, control of orientation of the dentition within the face, and simplify and/or shorten treatment in some cases.

Adolescent↗

Morphologic changes in the transverse dimension using the Fränkel appliance.

Anthropologic studies have shown that the incidence of malocclusion increases as societies become urbanized. Crowding seems to be one of the most common findings. Possible explanations for this have been heredity, dietary changes, poor eruption patterns, and mouth breathing, among others. Many clinicians begin treatment early in order to minimize this maldevelopment. Various early-treatment approaches have included serial extraction, lingual holding arches, palatal expansion, functional appliances, partial fixed appliances, and headgear. Expansion with the functional regulator offers one solution to crowding. If this expansion can be shown to be significant in amount and stable, then the Fränkel appliance merits consideration regardless of the clinician's choice of fixed appliances. Fifty patients treated with the Fränkel appliance from the private practice of the author were analyzed to evaluate changes in the transverse dimension. The ages ranged from 5.9 to 13.8 years, with the average age 9.6 years (+/- 1.54). Twenty-nine patients were girls and twenty-one were boys. The Angle molar relationships were distributed as follows: Class I-21 patients; Class II-27 patients; and Class III-2 patients. All patients were Caucasians and were selected for treatment on the basis of the presence of crowding, excessive overjet or overbite, or excessive open-bite. The presence of crowding was determined by a study model and Panorex analysis. All patients reported in this study were considered cooperative and wore their appliances for approximately 20 hours per day. Five cephalometric measurements were taken: nasal cavity width, maxillary width, mandibular width, intercanine width, and intermolar width. All cephalograms were originally traced by the same technician at Rocky Mountain Data Systems, Inc. When there was a discrepancy between the RMDS tracing and the author's tracing, the author's tracing was used. Data to serve as controls were provided by Rocky Mountain Data Systems, Inc. The sample is based on forty children measured over a 5-year period between the ages of 8 and 13 years. Twenty patients had an Angle Class I molar relationship, and twenty patients had an Angle Class II molar relationship. Two Student's t statistics were used to evaluate these measurements. Means, standard deviations, and standard errors are shown. The Bonferroni inequality method is used to determine if these five measurements are significant, and all five measurements were simultaneously significant at the 0.05 level. From the statistical results as well as the cephalometric descriptive analyses, it appears that the Fränkel appliance precipitates a limited but potentially significant increase in arch length which will benefit the patient if the results are stable.

Activator Appliances↗

An American Board of Orthodontics case report.

A case report of a Class II, Division 2 malocclusion with a deep anterior overbite, mandibular first premolars lingual to the maxillary first premolars in centric occlusion, and a functional shift on closure, accompanied by moderate facial convexity with a deficient mandible anteriorly and vertically, treated to the standards of the American Board of Orthodontics, is presented.

Adolescent↗

Effect of maxillary osteotomy on subsequent craniofacial growth in adolescent monkeys.

LeFort I osteotomy was performed on seven adolescent Macaca fascicularis monkeys to study its effect on the subsequent dentocraniofacial growth. Eight adolescent monkeys were used as controls. Tantalum implants were inserted at predetermined areas in certain craniofacial bones of all monkeys. For stereometric cephalometry, implants were placed in both the left and right sides of the facial bones. Lateral cephalometric radiographs of all monkeys were taken prior to and immediately after metallic implant placement, immediately after maxillary osteotomy, and thereafter every 4 weeks during the postsurgical period. At least two cephalograms were taken on each occasion, one with the teeth in occlusion and the other with mouth wide open. The latter was used to view the mandibular condyle adequately. These findings suggest that the maxillary osteotomy did disturb the vertical growth of the maxilla at the PNS and retarded the horizontal growth at the premaxilla. The anterior growth of the maxilla and mandible and the vertical growth of the face were substantially reduced. The most interesting finding was also a reduction of the mandibular growth in all of its dimensions. The rate and the amount of reduced anterior mandibular growth were found to be coordinated with the anterior maxillary growth which resulted in all animals showing a normal overjet, overbite, and occlusion throughout the postsurgical observation period.

Animals↗

Investigation of chewing patterns in deep-bite malocclusions before and after orthodontic treatment.

A knowledge of chewing provides a better understanding of normal jaw movement and can help form a basis for assessing the effects of malocclusion on jaw function. This study was conducted to describe the effects of deep-bite malocclusion on masticatory function and to determine what changes may occur with orthodontic correction. Five subjects, each exhibiting deep overbite in the early permanent or adult dentition, were selected for this study. Two subjects had Class II, Division 1 malocclusions, and the other three had Class I malocclusions. By means of the "replicator system" jaw movements during border movements and unilateral chewing were recorded and analyzed by computer plots. The typical chewing pattern of all five subjects was characterized by midsagittal opening, wide lateral closing movements, tooth gliding, and a pause at the intercuspal position and during swallowing. Comparison of these findings with chewing data from normal children in previous studies indicated that the deep-bite malocclusion did not create a major disturbance in chewing. Some differences between the preoperative and postoperative condition were noted, however. Prior to treatment, three subjects showed a nearly vertical chewing cycle which avoided tooth contact at the border path. Following treatment, all subjects showed a greater coincidence between the closing chewing path and the lateral border movement. This indicated more gliding tooth contact after treatment. Following deep-bite correction, the border paths showed a refinement of the intercuspal position (IP) and an increased steepness in lateral tooth guidance near IP. The total vertical component of tooth guidance was reduced by treatment.

Adolescent↗

Maxillary traction splint: a cephalometric evaluation.

Orthodontists are particularly interested in knowing exactly what skeletal and dental changes are produced by headgear. With headgear and fixed appliances, part of the observed change is due to the headgear, part to the fixed appliances, and part to growth. Since the maxillary traction splint moves the teeth en masse, the dentoskeletal changes are due primarily to the headgear force. Selective mandibular dental changes can be produced by adjusting the mandibular occlusal contacts against the splint. In this study forty-seven patients with maxillary dentoalveolar protrusions and Class II, Division 1 malocclusions were treated with orthopedic headgear that attached to a full-coverage maxillary occlusal splint. Fifty-two patients were selected as a control for evaluation of growth changes versus treatment changes. Lateral cephalograms were taken before and after treatment, and the sagittal skeletal and dental changes were evaluated and quantified. The results of the investigation revealed (1) the establishment of a Class I posterior occlusion, (2) a significant overjet reduction, averaging 4.24 mm, (3) inhibition of vertical development of the maxilla and slight intrusion of the maxillary dentition, (4) overbite reduction by leveling of the mandibular dentition, (5) no indication that mandibular growth is accelerated, and (6) no significant increase in the mandibular plane angle. The maxillary traction splint is an effective means of correcting maxillary dentoalveolar protrusion in growing patients prior to fixed appliance therapy. The second phase of treatment with fixed appliances is necessary for individual tooth positioning and for detailing the occlusion.

Adolescent↗

Bilateral congenital absence of maxillary lateral incisors: a craniofacial and dental cast analysis.

The dental casts and cephalometric records of forty-three patients exhibiting bilateral congenital absence of maxillary lateral incisors were evaluated to determine the nature and extent of any concurrent craniofacial and dental anomalies. The effects of bilateral orthodontic space closure were evaluated on a subsample of twenty-two cases. The data revealed normal dental arch length, arch width, overjet, and overbite, while significant tooth size discrepancies were found in several anterior and posterior teeth. Craniofacial deviations from normal included smaller maxillary length, smaller mandibular length, smaller anterior cranial base, and nasal bone. Vertical facial dimensions, both anterior and posterior, were significantly less, as was the mandibular plane angle. Soft-tissue examination revealed a 10 degrees greater nasiolabial angle, which was increased a further 5 degrees as a result of a mean incisor retraction of 1.5 mm during space closure. The craniofacial anomalies noted in the present sample were similar to those seen in persons with clefts and may reflect a common etiology related to a developmental disturbance during fusion of the facial processes in utero. In the treatment of patients with bilateral congenital absence of maxillary incisors, mechanotherapy designed to open the mandibular plane, increase the vertical dimension, and move the maxillary posterior teeth forward is recommended in order to prevent worsening the Class III tendency and to minimize maxillary incisor and upper lip retraction. Most cases will require significant mesiodistal reduction in tooth size in order to achieve an optimal occlusion.

Adolescent↗

Activator headgear therapy.

A method of treatment is described using an activator and cervical headgear simultaneously to correct malocclusions of the Class II, Division 1 type. The case reports of ten treated patients are used to demonstrate the effects of the application of this technique. Changes in the dentition and facial skeleton were analyzed and the significance of the different responses to the application of the same appliances assessed. The hypothesis proposing that a simultaneous application of both appliances may result in a number of desirable effects greater than that induced by each individual appliance is examined. The hypothetical basis for the application of this technique is partially substantiated by the clinical observations. Within a period of about 1 year, correction of the Class II molar occlusion to a Class I molar occlusion is obtained, with a simultaneous reduction of overbite and overjet. Skeletal changes were found to be variable and related to facial type and the rate of facial growth. Brachyfacial and mesofacial types responded most favorably to treatment. The most favorable effects were observed when there was a large quantitative mandibular growth and brachyfacial or mesofacial growth pattern. In dolichofacial types with a slow mandibular growth rate, mandibular rotation was found to be clockwise; cervical traction appears contraindicated, and a combination of activator with occipital medium to high pull is considered more appropriate.

Activator Appliances↗

Begg-edgewise diagnosis-determined totally individualized orthodontic technique: foundations, description, and rationale.

This article presents an appliance system designed to facilitate efficient treatment by the use of the biomechanical approach considered most suitable by the orthodontist for the individual patient. The system described uses narrow, single brackets with 0.022 X 0.028 inch edgewise arch wire slots and 0.020 X 0.020 inch vertical slots for various auxiliaries. There are five brackets that differ only in the torque of the arch wire slot-0 degree, 5 degrees, 10 degrees, 15 degrees, and 20 degrees. Thus, an appropriate bracket can be selected for any tooth in any situation. The brackets and bonding pads are small in all dimensions to ensure optimal appearance and interbracket arch wire spans and minimal lip and cheek irritation. This also lessens occlusal interference, enamel surface involved in bonding, and problems with gingival proximity and oral hygiene. The basic buccal tubes are conventional 4.5 mm long, 0.022 X 0.028 inch torqued edgewise tubes. A buccal tube assembly with a similar additional rectangular tube carried diagonally at a 15 degree angle across the buccal surface of the basic tube (its mesial end pointing gingivally) is used in extraction cases with deep overbites or moderate-to-severe anchorage requirements. The angulated outer tube carries the main (working) arch wire during the bite-opening and retraction phases of treatment. A rectangular sectional wire in the inner tube and second premolar bracket locks the molar and premolar teeth together so that neither can tip independently. As a unit they provide anchorage for bite opening and retraction. The gingivally positioned and angulated outer tube directs the arch wire out of danger of distortion from mastication and provides a built-in biteopening effect. The molar and premolar teeth, in effect, become a single large tooth with its center of resistance (CR) further mesial than the CR of the molar. Sectional wires result in a more favorable system of moments created by arch wires and elastics. This delivers more intrusive force to the incisors with less tendency to tip the anchor units. The appliance provides the orthodontist with an extensive range of options in treatment mechanics--from anchorage conservation and rapid movement of limited tipping by light forces to translation or stabilization with precise three-dimensional control.

Adolescent↗

Posttreatment changes of skeletal morphology following treatment aimed at restriction of maxillary growth.

In the evaluation of the success of orthodontic treatment, an analysis of posttreatment changes was essential. Twenty-eight patients with increased overjet and overbite, a high mandibular plane angle, and perioral dysfunction had been treated by means of normal maximal restriction of maxillary development. The posttreatment changes of the skeletal morphology was analyzed and related to both pretreatment morphology and treatment-produced changes. The correlation analysis demonstrated that less than 25% of the variation in posttreatment changes could be accounted for by pretreatment morphology. However, the dependency of posttreatment changes on treatment-produced changes was stronger with regard to both linear and angular measurements. Upon analyzing the changes in mandibular prognathism during and after treatment, all combinations of downward and forward growth were presented. In some cases the increase in prognathism during treatment would continue after treatment; in others the reverse was true. Opening of the Y axis would in some cases be constant, leading to a decrease in mandibular prognathism. In others a pronounced anterior rotation moved the pogonion forward following treatment. A dental relapse as a consequence of skeletal relapse was seen only in cases in which normal perioral function, including normal lip closure and absence of tongue-thrust swallowing, had not been established.

Adolescent↗

Dentoskeletal and tongue soft-tissue correlates: a cephalometric analysis of rest position.

The relationship between dentoskeletal and tongue soft-tissue variables has been quantified in a sample of 60 adult females with normal and anterior open-bite malocclusions. Three lateral rest-position head films were obtained for each subject. A principal component analysis reduced the data base and six significant canonical correlations were identified. The first canonical correlation (r1 = 0.962) represented a size-related correlation factor between the two groups of variables. Subjects with characteristics of a short face syndrome and some evidence of overbite had tongue tips positioned below the lower occlusal plane (r2 = 0.929). In contrast, skeletal open-bite subjects (r4 = 0.759) revealed tongue tips ahead of and above the lower incisor teeth with the mandible in the rest position. Undererupted mandibular teeth (r5 = 0.666) were associated with a reduced tongue height and an inferior epiglottis; short tongue length (r6 = 0.563) correlated with a linear combination of upright central incisors, a small overjet, a low ANB angle, unerupted maxillary and mandibular teeth, and a steep occlusal plane. The multivariate statistical analysis extracted clinically significant associations between tongue soft-tissue and dentoskeletal variables. Tongue posture at rest in skeletal open-bite subjects appeared to be related to incisor position.

Adolescent↗