The purpose of this follow-up prospective longitudinal study was to determine what changes occurred in the condyle/fossa relationship after treatment. Orthodontic posttreatment records, including corrected tomograms of 106 white patients (58 Class I and 48 Class II Division 1), from a pretreatment sample of 232 patients, were analyzed. The average pretreatment age was 13.6 ± 3.0 years. The average length of treatment was 2.3 ± 0.6 years for the Class I group and 2.8 ± 0.9 years for the Class II Division 1 group. With orthodontic treatment, the condyle became more concentrically positioned, and a significant (P <.05) decrease in left and right anterior, posterior, and superior joint spaces was observed in most subjects. There was no statistically significant correlation between changes in the condyle/fossa relationship based on age, gender, skeletal or dental variables, signs or symptoms of temporomandibular disorder, headgear use, type of elastics, or nonextraction vs extraction treatment. (Am J Orthod Dentofacial Orthop 2002;122:486-90)
The wear resistance of tooth enamel that had undergone eight different treatments regarding the bonding procedure has been investigated. In comparison to sound enamel, the outer 3 microns of the etched-surface enamel show a decreased wear resistance against toothbrushing in vitro. Remineralization, either direct or preceded by acidified phosphated fluoride (APF) application, did not improve the wear resistance. The prophylactic effect of the APF treatment of etched enamel is considerable and is not lost after the soft, outer surface layer has worn off.
The aim of the present article was to identify morphologic characteristics in the craniofacial skeleton of the 11-year-old child that could indicate potential development of a Class III skeletal pattern. A radiographic material consisting of 24 children (13 girls, 11 boys) at an average age of 11 years 0 months, who in adulthood demonstrated a Class III skeletal pattern, was compared with a control group of 33 children (16 boys, 17 girls, average age 11 years 6 months) chosen retrospectively on the basis of Class I occlusion. The analysis was performed by means of both linear and angular variables and results are reported both as group means and individual analyses. No one morphologic trait indicative of potential Class III development could be isolated because the study clearly demonstrated the existence of different skeletal combinations. The development of the maxilla, both in size and position, was clearly demonstrated by the linear analysis to be an etiologic factor in Class III development. However, maxillary retrognathism was usually masked in the angular analysis because a reduction in length of the anterior base with subsequent effect on the position of point nasion was often seen in these cases. Mandibular prognathism was a frequent observation, although a true macrognathia was uncommon. In the majority of cases, mandibular prognathism was the result of an increase in the ratio between mandibular length and dorsal position of the glenoid fossa (articulare). The relative merits of angular and linear analyses are discussed in relation to the results presented.
In this exhaustive review, a number of parameters related to maxillary and mandibular second molar-extractions are discussed. The parameters reviewed include the timing of extractions and the effect of extractions on third molar eruption, posterior interdigitation, and incisor imbrication. The advantages and limitations of this procedure are outlined. The available information strongly suggests that the extraction of second molars relieves crowding in the posterior part of the arch, causes faster eruption of third molars, and diminishes the number of unerupted and/or impacted third molars. Consideration of the decrease in the number of impacted third molars after second molar extraction should be balanced with the fact that the extracted teeth are usually sound and are unimpacted. In addition, the third molars that do erupt frequently are poorly angulated and/or in poor contact with the first molars. This will necessitate an additional “late” period of fixed-appliance therapy to bring these teeth into good occlusion.
The purpose of this article was to simulate graphically the probable orthodontic-orthopedic results of different types of extraoral traction applied to the upper dentition. Forces and movements are vectors; apart from individual variation in the amount of reaction to forces, the reactive movement vector at any given site of an influenced hard-tissue unit depends mainly on the position of its center of resistance relative to the force vector and on the amount and time of force application. In growing patients the resulting movement can then be appraised by the addition of reactive movement and average growth-movement vectors. Standardized assumptions have been made to simulate and compare qualitatively the significance and implications of five different types of commonly used extraoral traction on the upper dentition. Biomechanical parameters (such as the system factor describing the reciprocal relation between the lever arm of a force and the corresponding distance between the centers of resistance and rotation) have been arbitrarily assessed. Where cervical gear on the upper dentition is used, the resulting simulations suggest that raising the outer arms of the face-bow means less posterior effect on the upper dentition, less vertical molar control, and an increased tendency to open the bite. Where high-pull traction is applied, graphic simulations using a constant angulation, but different position of the force vector, indicate that moving the force line from a backward to a more forward position would mean a change from posterior to anterior rotation, from pronounced to no vertical molar control, from excessive incisor elongation to complete vertical incisor control, and from considerable distal effects to nearly none on the upper dentition.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this paper was to compare retrospectively the effect on the soft tissues of two contrasting forms of treatment for Class II, Division 1 malocclusion. The first group of 30 persons exhibited uncrowded dentitions and were treated without extractions by means of the Andresen activator. No other appliance was used. The second group was also composed of 30 persons. These subjects were treated with the Begg appliance in its classical form. All of the Begg subjects showed varying amounts of crowding and were treated by extraction of four first premolars. It was believed that the Andresen appliance would maintain the incisors in the most labial position possible, while the Begg group with premolar extractions would involve the maximum lingual incisal movement. These groups were compared with a third group of 22 untreated persons who also exhibited Class II, Division 1 malocclusions. The overjets in the treated groups were successfully reduced in both cases by retraction of the upper incisors; in the Begg group only, retraction of lower incisors was also performed. The upper incisors were retracted substantially more in the Begg group than in the Andresen group, but there was only a slight difference within the two groups in the final position of the upper lip relative to a vertical reference line through sella. There was also a slight difference in the lengths of upper and lower lips within the two treated groups. The lower lip followed the lower incisors more closely in the Begg group. Both upper and lower lips “uncurled” in the treated groups and this probably allowed them to be held together with little strain. There was a wide variation in individual response in all three groups.
The prevalence of enamel decalcification beneath orthodontic bands has indicated the need for a fluoride-releasing, enamel-adhesive orthodontic luting cement. The purpose of this study was to compare the retentive bond strengths of orthodontic bands cemented with two new fluoride-releasing cements, a zinc polycarboxylate and a glass ionomer, with the retentive bond strength of bands cemented with the standard orthodontic cement zinc phosphate. The site of cement failure was also evaluated. One hundred eighty extracted human molar teeth were embedded in resin blocks and randomly assigned to three cement groups. Adapted bands were cemented by a clinically acceptable technique. The cemented teeth were then assigned to one of three time intervals--24 hours, 7 days, and 60 days--and thermocycled in synthetic saliva. The force required to initially fracture the cement bond was used as a measure of cement retention. By means of the Instron, a tensile load was applied to each cemented band. The maximum retentive strength (cement failure) was interpreted from the stress-strain curve at the point where linearity deviated. The failure site was judged subjectively: between cement and enamel, within the cement, or between cement and the band. Using stress at failure, an analysis of variance showed no significant differences among the retentive strengths of the three cements. The chi-square test revealed a significant difference (P less than 0.01) between failure sites of the zinc phosphate and glass ionomer cements. Significantly more bands cemented with the glass ionomer failed at the cement/band interface, leaving the cement adhered to the tooth.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this study was to determine if apical root resorption associated with orthodontic treatment continues after the termination of active treatment (that is, the removal of fixed appliances). A sample of 45 subjects who had experienced root resorption during treatment was selected from the orthodontic clinic at the State University of New York at Buffalo. The length of the maxillary central incisors was measured from lateral cephalometric radiograms taken before treatment, after active treatment, and after retention. From these data, the resorption occurring during and after active treatment was calculated. The mean amount of root resorption during active treatment was 2.93 mm. The mean amount of root resorption during the posttreatment period was 0.1 mm. There was a statistical difference between these two means using the Student's t test at the 0.05 level of significance. The reliability coefficient comparing the first tracings and measurements in the 19 cases that were retraced and remeasured was r = 0.993. The data from this radiographic study support the hypothesis that root resorption associated with orthodontic treatment ceases with the termination of active treatment. There was also evidence to suggest that when posttreatment root resorption does occur, it is not necessarily associated with large amounts of root resorption during the active treatment period. It is more likely associated with other factors, such as traumatic occlusion and active force-delivering retainers.
This article investigates the relationship of skeletal facial pattern and soft-tissue nasal form. The case sample comprises 123 white female subjects, aged 11.0 to 20.6 years, with no histories of pathology, trauma, surgical intervention, or orthodontic treatment. Measurements were made from cephalometric radiographs, posteroanterior radiographs, and the physioprint photographs. Skeletal classifications were based on the relationship of the maxilla to the mandible; the three classifications were straight profile, retrusive chin profile, and prognathic profile. Pearson product-moment correlation coefficients were used to test intercorrelations of all quantitative variables (including age) with each other. Correlations were highly significant for age, the three profile measurements, and two of the frontal measurements. Hence, noses and skeletal structures showed, as expected, increases with age. Also, profile measurements were highly significantly correlated; larger noses were larger in all profile dimensions. A stepwise discriminant analysis was used to study nonquantitative categories of nasal shape (straight, convex, and concave). This analysis indicated that more than 86% of patients in the sample of 123 demonstrated a correlation of nasal shapes with specific skeletal groupings. Patients with straight profiles tended to have straight noses; convex profiles accompanied convex nasal shapes; and concave profiles were found with concave nasal shapes. The clinical significance of this research is to emphasize the importance of total facial harmony (especially nasal shape) during orthodontic diagnosis and treatment planning.
In today's orthodontic practice, disease control must undergo major reevaluation and restructuring. The knowledge of the natural history and treatment of many highly transmissible diseases to which orthodontic personnel are at high risk is changing rapidly. Among these diseases are acquired immune deficiency syndrome (AIDS), hepatitis B virus, and the herpesvirus complex (currently five types). If barrier techniques are not in place, it is possible to cross-infect orthodontic personnel and patients alike. Clinical orthodontics, with its higher volume of patients (on a daily basis) than other dental practices, requires a custom-made sterilization schema tailored to each office. Proper organization of instruments to permit orderly processing, storing, and use is even more important than before. Turnaround time of processing instruments, corrosion control, and minimizing of dulling of cutting edges are critical. Treatment of surfaces and chair/unit facilities with improved disinfection techniques is a necessity. Protection of hands and eyes by appropriate means is discussed with practical guidelines for the use of gloves by chairside personnel. Many fomites (inanimate disease transmitters) lurk in the orthodontic office and must be eliminated. Finally, the most important ingredient to any change--the orthodontic office staff--must be enlightened, trained, and supervised by the orthodontist to effectively and efficiently switch from the old to the new.
In this study eight macerated, human child skulls (dental age approximately 9.5 years) were subjected to a standardized high-pull headgear traction system. Tensile forces from 0.5 to 3.5 N (1 N = 0.1 kgf) per side were produced to the maxillae. Displacements of skeletal components were determined at 22 indicator points per skull by means of laser holography. Coordinated displacements and variations in amount and direction were established in all skulls. The overall amount of displacements was primarily a characteristic of an individual skull, not of a particular displacement. On the average, the maxillae were displaced in a slightly downward and posterior direction almost parallel to the occlusal plane. No deformations of skeletal components were seen. Results indicated that initial displacements of the maxillae and other skeletal components are not in the same direction as the direction of applied forces.
Intrusion has been regarded as a very controversial topic in the orthodontic literature. Although it seems a logical way to handle deep overbite in adult patients who have elongated teeth, reports on iatrogenic damage have led to the suggestion of alternative methods. Considering the disadvantages of these alternatives, it seems reasonable, however, to improve our knowledge of tissue reaction as related to intrusion. Three Macaca fascicularis monkeys were used for the experiment. By means of a segmented arch approach, the upper incisors and the four first premolars were submitted to forced eruption for 8 weeks followed by 12 weeks of intrusion. A split-mouth technique was used to study the influence of oral hygiene on the tissue reaction. On the right side of the mouth, the teeth were brushed with chlorhexidine three times per week. On the left side, no oral hygiene was performed. After intrusion of the teeth, a 1-to-14 day retention period with passive appliance preceded the killing of the monkeys. A buccolingual hematoxylin- and eosin-stained serial section was produced, and soft- and hard-tissue reactions described. It appeared that the hygiene program could limit but not prevent gingival inflammation. There was, however, a marked difference in the histologic picture of the marginal bone on the two sides. On the hygiene side, clear signs of bone deposited during forced eruption were still present. This was not the case on the nonhygiene side. The extension of bone resorption was also different on the two sides.(ABSTRACT TRUNCATED AT 250 WORDS)
The aim of this study was to clarify whether orthodontic movement of autotransplanted premolars will affect the final root length of the transplants. A group of 29 autotransplanted premolars that had been orthodontically treated was compared with a group of 30 autotransplanted premolars that had not been orthodontically treated. Contralateral teeth in both groups served as controls. The root lengths of the transplants as well as the controls were measured on the radiographs immediately after transplantation and also after orthodontic treatment and complete root formation. The results demonstrated that there was no statistically significant difference between the original and final root lengths of the transplants in the two samples or between the contralateral teeth. The autotransplantation of the premolars resulted in an average shortening of 1 to 2 mm compared to the contralateral control teeth. Furthermore, orthodontic movement of the transplants appeared to have a tendency to shorten the final root length.
The role of nasal respiratory function in oral and facial development remains unclear in spite of the long-standing interest of clinicians. Much of the current controversy stems from our inability to define mouth breathing in objective terms and evaluate nasal airway impairment quantitatively. Recent advances in respiratory monitoring technology provide new opportunities to assess upper airway breathing more objectively. The purpose of this study was to describe a new approach for measuring oral and nasal respiration and to test its reliability. The technique involves inductive plethysmography and the data provide an assessment of respiratory mode without the need to enclose the subject's head in an airtight box. The data were compared to pneumotachography and the results demonstrate the reliability of the technique.
