Are bioresorbable polylactate devices comparable to titanium devices for stabilizing Le Fort I advancement?

The purpose of this study was to evaluate whether skeletal and dental outcomes following Le Fort I surgery differed when stabilization was performed with polylactate bioresorbable devices or titanium devices. Fifty-seven patients with preoperative records and at least 1 year postoperative records were identified and grouped according to the stabilization method. All cephalometric X-rays were traced and digitized by a single operator. Analysis of covariance was used to compare the postsurgical change between the two stabilization methods. Twenty-seven patients received bioresorbable devices (group R), while 30 received titanium devices (group M). There were no statistically significant differences between the two groups with respect to gender, race/ethnicity, age, or dental and skeletal movements during surgery. Subtle postsurgical differences were noted, but were not statistically significant. Stabilization of Le Fort I advancement with polylactate bioresorbable and titanium devices produced similar clinical outcomes at 1 year following surgery.

Soft tissue response to mandibular advancement using 3D CBCT scanning.

This prospective longitudinal study assessed the 3D soft tissue changes following mandibular advancement surgery. Cranial base registration was performed for superimposition of virtual models built from cone beam computed tomography (CBCT) volumes. Displacements at the soft and hard tissue chin (n = 20), lower incisors and lower lip (n = 21) were computed for presurgery to splint removal (4-6-week surgical outcome), presurgery to 1 year postsurgery (1-year surgical outcome), and splint removal to 1 year postsurgery (postsurgical adaptation). Qualitative evaluations of color maps illustrated the surgical changes and postsurgical adaptations, but only the lower lip showed statistically significant postsurgical adaptations. Soft and hard tissue chin changes were significantly correlated for each of the intervals evaluated: presurgery to splint removal (r = 0.92), presurgery to 1 year postsurgery (r = 0.86), and splint removal to 1 year postsurgery (r = 0.77). A statistically significant correlation between lower incisor and lower lip was found only between presurgery and 1 year postsurgery (r = 0.55). At 1 year after surgery, 31% of the lower lip changes were explained by changes in the lower incisor position while 73% of the soft tissue chin changes were explained by the hard chin. This study suggests that 3D soft tissue response to mandibular advancement surgery is markedly variable.

Long-term stability of adolescent versus adult surgery for treatment of mandibular deficiency.

In mandibular deficient patients, mandibular growth is not expected after the adolescent growth spurt, so mandibular advancement surgery is often carried out at 13 years. To test if the long-term stability for younger patients is similar to that for adult patients, the authors compared cephalometric changes from 1-year postsurgery (when changes due to the surgery should be completed) to 5-year follow up. 32 patients who had early mandibular advancement with or without simultaneous maxillary surgery (aged up to 16 for girls and 18 for boys), and 52 patients with similar surgery at older ages were studied. Beyond 1-year postsurgery, the younger patients showed significantly greater change in the horizontal and vertical position of points B and pogonion, the horizontal (but not vertical) position of gonion, and mandibular plane angle. 50% of younger patients had 2-4mm backward movement of Pg and another 25% had >4mm. 15% of older patients had 2-4mm change and none had >4mm. Long-term changes in younger patients who had two-jaw surgery were greater than for mandibular advancement only. Changes in younger groups were greater than for adult groups. Satisfaction with treatment and perception of problems were similar for both groups.

Mechanism and control of tooth eruption: overview and clinical implications.

OBJECTIVES: To review pre- and post-emergent eruption, with particular emphasis on distinguishing isolated molar ankylosis from primary failure of eruption (PFE) and genetic considerations in eruption problems. MATERIAL AND METHODS: Radiographic review of eruption failure patients; animal and human experiments; high precision observations of movements of erupting teeth. RESULTS: In pre-emergent tooth eruption, the controlling element is the rate of resorption of overlying structures. A path is cleared, and then the erupting tooth moves along it. This has clinical importance in recognizing the cause of eruption problems, particularly PFE, in which all teeth distal to the most mesial involved tooth do not erupt or respond to orthodontics. In our study of by far the largest sample of PFE cases yet reported, familial cases of PFE accounted for approximately (1/4) of all cases examined. Candidate genes now are being evaluated. In post-emergent eruption, control seems to be light forces of long duration that oppose eruption, rather than heavy forces of short duration such as those during mastication. Studies of human premolars in their passage from gingival emergence to the occlusal plane show that in this phase eruption occurs only during a few hours in the early evening. The critical hours for eruption parallel the time that growth hormone levels are highest in a growing child. In this stage intermittent force does not affect the rate of eruption, but changes in periodontal blood flow do affect it.

Superimposition of 3D cone-beam CT models of orthognathic surgery patients.

OBJECTIVES: To evaluate the registration of 3D models from cone-beam CT (CBCT) images taken before and after orthognathic surgery for the assessment of mandibular anatomy and position. METHODS: CBCT scans were taken before and after orthognathic surgery for ten patients with various malocclusions undergoing maxillary surgery only. 3D models were constructed from the CBCT images utilizing semi-automatic segmentation and manual editing. The cranial base was used to register 3D models of pre- and post-surgery scans (1 week). After registration, a novel tool allowed the visual and quantitative assessment of post-operative changes via 2D overlays of superimposed models and 3D coloured displacement maps. RESULTS: 3D changes in mandibular rami position after surgical procedures were clearly illustrated by the 3D colour-coded maps. The average displacement of all surfaces was 0.77 mm (SD=0.17 mm), at the posterior border 0.78 mm (SD=0.25 mm), and at the condyle 0.70 mm (SD=0.07 mm). These displacements were close to the image spatial resolution of 0.60 mm. The average interobserver differences were negligible. The range of the interobserver errors for the average of all mandibular rami surface distances was 0.02 mm (SD=0.01 mm). CONCLUSION: Our results suggest this method provides a valid and reproducible assessment of craniofacial structures for patients undergoing orthognathic surgery. This technique may be used to identify different patterns of ramus and condylar remodelling following orthognathic surgery.

The effect of growth hormone on craniofacial growth and dental maturation in Turner syndrome.

Serial cephalometric and panoramic radiographs from a mixed longitudinal group of 28 subjects with Turner syndrome (TS), age 4.4-19.0 years, were evaluated for annualized growth increments of the craniofacial complex and dental development and were compared with a longitudinal control group from the Burlington growth study. The short and retrognathic face characteristic of the syndrome was due largely to the increased cranial base angle, decreased posterior face height, and decreased mandibular length, all of which were significantly different from the controls. Although increases in statural height occurred in the TS children who were treated with human growth hormone (GH), there was little or no effect on growth of the jaws, particularly in the older subjects, and the characteristic facies of the syndrome persisted. Dental development was advanced in all TS subjects, and GH administration had no effect on the rate of dental development.

Design and effectiveness of a computer-based continuing education program for orthodontists.

The design of computer-based continuing education for health professionals is an important consideration for Internet delivery because the size of graphic files greatly affects the speed with which information is delivered. Orthodontists who had indicated an interest in computer-based continuing education were shown via CD-ROM either a dynamic version of a computer continuing education program (with transitions and animations to liven up the content) or a plain version (identical content except that the transitions and animations were omitted). The program provided new information about superelastic arch wires for the initial stage of orthodontic treatment. For both versions, over 90% of the viewers thought the program was well done and provided useful information. Six of the orthodontists who received the dynamic version felt that the animations were distracting rather than helpful; only one who received the plain version felt that it was lifeless. A follow-up questionnaire showed that two-thirds of those who viewed the program had subsequently reviewed the performance data for the initial wire they were using and 20% had changed it, so the computer program was effective in changing clinical behavior. Those who saw the plain version also were more likely to have changed their clinical procedures. For Internet delivery of information to highly motivated professionals, it appears that transitions and animations are not necessary and may be more likely to decrease than increase the effectiveness of the teaching material.

Who seeks surgical-orthodontic treatment: a current review.

Records for more than 2,000 individuals seen in the Dentofacial Clinic of the University of North Carolina were examined to evaluate trends in referral patterns for orthognathic surgery and acceptance of surgical treatment The vast majority of patients have been white and female from the beginning, and the female-male ratio remained constant at 2:1 throughout the 1990s. The proportion of nonwhite patients increased significantly after 1995, with the change resulting almost totally from more Hispanic and Asian patients. The proportion of African Americans, who represent 22% of the general population, remained almost constant at 10%. Class III and long-face individuals were more likely to seek evaluation than those with Class II problems, but of those who were offered orthognathic surgery, relatively more of the Class II group accepted it. This may reflect greater severity of a Class II problem before a patient seeks treatment. More than 1 of the Clinic population had some sort of facial asymmetry, but the presence of asymmetry did not seem to influence the decision to have surgical treatment. The dental and skeletal characteristics of those who had surgery were similar to those of patients who did not have surgery, suggesting that the decision to elect a surgical treatment plan was influenced by factors other than clinical characteristics.

Long-term stability of surgical open-bite correction by Le Fort I osteotomy.

Skeletal changes greater than those observed in untreated adults have been noted beyond 1 year post-surgery in adult patients who had surgical correction of a long face deformity. The stability of skeletal landmarks and dental relationships from 1 to >3 years post-surgery was examined in 28 patients who had undergone surgery of the maxilla only, and in 26 patients who had undergone 2-jaw surgery to correct >2 mm anterior open bite. Although the average changes in almost all landmark positions and skeletal dimensions were less than 1 mm, point B moved down >2 mm and face height increased >2 mm in one-third of the maxilla-only group and in 40% of the 2-jaw group (>4 mm in 10% and 22% respectively). Overbite decreased 2-4 mm in only 7% of the maxilla-only and 12% of the 2 groups, with no changes >4 mm, because in three-fourths of the patients with an increase in anterior face height, further eruption of the incisors maintained the overbite relationship. In the maxilla-only group, mandibular length (Co-Pg) showed >2 mm long-term change in 45% of the patients, two-thirds of whom showed an increase rather than a decrease in length. In the 2-jaw group, no patients showed a decrease in Co-Pg length and one-third had an increase. For both groups, changes in overjet were smaller and less frequent than changes in mandibular length.

Cephalometric characteristics of Korean Class III surgical patients and their relationship to plans for surgical treatment.

In comparison to gender-matched normal Koreans, Korean patients selected for surgical correction of skeletal Class III problems have, on average, a shorter anterior and posterior cranial base, a shorter maxilla, a longer mandible, increased lower facial height, and a retrusive upper lip. In both males and females, about 40% of a group of Class III patients scheduled for surgery had a maxilla within one standard deviation of the normal position and a prognathic mandible, as compared with a group of normal Korean adults. Almost as many males (37%) in the surgical group had both a retrognathic maxilla and a prognathic mandible, while 18% had a retrognathic maxilla and normal mandible. In females, 25% had only a retrognathic maxilla and 25% had both jaws outside the normal range. The percentage of the Korean patients whose Class III relationship was primarily a result of mandibular prognathism (48%) is more than twice as high as the corresponding number for American Class III surgical patients (19%), somewhat higher than in Chinese patients (39%), and similar to the percentage of Japanese (50%). Maxillary surgery, alone or in conjunction with mandibular setback, is currently used in the treatment of most Class III patients. Both the esthetic consideration of widening the already broad Asian nose and the relative proportions of maxillary versus mandibular abnormalities suggest that mandibular setback alone can be considered for a higher number of Asian than Caucasian Class III patients.

An international comparison of early treatment of angle Class-II/1 cases. Skeletal effects of the first phase of a prospective clinical trial.

The University of North Carolina at Chapel Hill has established an extensive randomized trial to evaluate early treatment of Class-II/1 cases. As presented in this part of the study, a German treatment group was selected in parallel, based on identical prospective criteria, in the context of international cooperation with the Westfälische Wilhelms-Universität, Münster. One essential aspect of this study is the degree to which initially comparable groups can be established by careful alignment of selection criteria and of compilation and analysis of diagnostic records. Nine skeletal analysis parameters initially indicated that it is possible to select very similar though not absolutely identical groups in the context of international cooperation. The further results of the initial 15-month phase comprising functional orthodontic treatment in severe Class-II/1 cases showed significant mandibular effects in both treatment groups (USA UNC, Chapel Hill: modified Balters appliance; Germany WWU Münster: U-bow activator Type I). The groups were compared to a randomized control group with similar untreated malocclusions, established at Chapel Hill (USA, UNC, Chapel Hill). The results of this cooperative study reveal opportunities for critical evaluation of different treatment methods through international cooperation, utilizing existing prospective randomized studies.

The emerging soft tissue paradigm in orthodontic diagnosis and treatment planning.

Until now, orthodontic diagnosis and treatment planning has been based on hard tissue relationships and on the Angle paradigm that considers ideal dental occlusion 'nature's intended ideal form'. In this view, the clinician and nature are partners in seeking the ideal. In the modern biological model, variation is accepted as the natural form; ideal occlusion is the exception rather than the rule, and the orthodontist and nature are often adversaries. The orthodontist's task is to achieve the occlusal and facial outcomes that would most benefit that individual patient, whose esthetic concerns are often paramount. Because the soft tissues largely determine the limitations of orthodontic treatment, from the perspectives of function and stability, as well as esthetics, the orthodontist must plan treatment within the patient's limits of soft tissue adaptation and soft tissue contours. This emerging soft tissue paradigm in diagnosis and treatment planning places greater emphasis on clinical examination of soft tissue function and esthetics than has previously been the case, and new information in these areas is required.

Response of erupting human premolars to force application.

To test the hypothesis that human tooth eruption requires a critical time period during which no force is applied to the erupting tooth, the eruption of a maxillary second premolar in the prefunctional stage was recorded during the afternoon or evening hours in eight children, using an optical device based on the principle of Moiré magnification, while intermittent loads of 300-400 mN were applied to the teeth. When a tooth was erupting actively, light force applications either had no discernible effect or decreased the eruption rate for 2 min or less. When a tooth was intruding spontaneously rather than erupting, a varied response was observed, but the rate of intrusion never increased after force application. Often intrusion showed or halted, and especially during the evening, eruption was likely to occur after a force application during an initial period of intrusion. The conclusion is that, although light force applications significantly displace an erupting premolar, they have little or no effect on net eruption, and that a critical time period without force application is not necessary for eruption to occur.

Referring adult patients for orthodontic treatment.

BACKGROUND: An increasing number of adults are undergoing orthodontic treatment, but they still make up only a small proportion of all adults who could benefit from such therapy. The purpose of this article is to illustrate the appropriateness and value of orthodontic treatment in adults. METHODS: The authors review and summarize previous studies regarding adult orthodontic treatment. Data from these studies are compared to determine the prevalence of orthodontic treatment in adults, the reasons why many adults do not seek treatment and the outcomes of orthodontic treatment in adults. In addition, the authors describe a case to demonstrate how a combination of orthodontic therapy and orthognathic surgery can facilitate and complement prosthetic rehabilitation. RESULTS: Numerous studies indicate that two-thirds to three-fourths of adults possess some form of malocclusion, yet adults make up only 15 percent of all orthodontic patients. Reasons given by adults for not seeking treatment include a lack of awareness that orthodontic treatment can be performed in adults, apprehension about possible pain or discomfort and concern about social acceptance. However, most patients who underwent orthodontic treatment reported only mild discomfort of one to two days' duration, and only 20 percent of patients felt that the appliances had an adverse social effect. Overall, patients reported high levels of satisfaction with treatment. Orthognathic surgery in addition to orthodontics may be required for the most severe problems, and is compatible with subsequent fixed and removable prosthetic treatment. CONCLUSIONS: Adjunctive and comprehensive orthodontic treatment is feasible for adults of all ages. Correction of malocclusion makes it possible to improve the quality of periodontal and restorative treatment outcomes, in addition to providing psychosocial benefits. CLINICAL IMPLICATIONS: General dentists are often the first dental professionals to suggest orthodontic treatment and to refer patients to orthodontic specialists. Moreover, with the growing emphasis on cosmetic dentistry, more adults are likely to seek information regarding orthodontic surgery. This article provides general dentists with the information needed to communicate with patients about treatment.

Assessment of patients for orthognathic surgery.

Rapid advances in orthognathic surgery now allow the clinician to treat severe dentofacial deformities that were once only manageable by orthodontic camouflage. These cases were often compromised with unacceptable facial esthetics and unstable occlusal results. Over the past 25 years, there have been numerous improvements in technology and the surgical management of dentofacial deformities. These progressions now allow more predictable surgical outcomes, which ensure patient satisfaction. Not all patients are candidates for surgical treatment; therefore, patient assessment and selection remains paramount in the process of diagnosing and treatment planning for this type of irreversible treatment. The inclusion of patients in the decision-making process increases their awareness and acceptance of the final result. The past three decades indicate an increased usage of orthodontic treatment by both children and adults. Patient demographic profiles for severe occlusal and facial characteristics are presented in an effort to understand the epidemiological factors of malocclusion and predict the population's need for this service.

Long-term cephalometric changes in untreated adults compared to those treated with orthognathic surgery.

A surprisingly large amount of long-term remodeling of facial structures has been noted in the period between 1 and 5 years post-orthognathic surgery. To evaluate whether these changes are greater than in patients with similar morphology who did not have surgery, long-term changes in hard tissue landmarks were examined in 33 untreated adults and compared to long-term changes in skeletal Class II surgery patients who underwent maxillary impaction, mandibular advancement, or both. Although the changes were small in both groups, mean changes were greater in the surgical patients; the surgical patients also showed a higher percentage of significant changes. Horizontal changes were in a forward direction in the untreated group and a backward direction in the surgical groups. We conclude that normal adult growth cannot account for the long-term changes observed following jaw surgery. In some instances, postsurgical changes leading to relapse continue much longer than would have been expected.

Effect of ion implantation of TMA archwires on the rate of orthodontic sliding space closure.

A split-mouth randomized clinical trial was used to determine whether ion implantation of beta-titanium archwire would facilitate sliding space closure. After bilateral maxillary first premolar extractions, 0.19 x 0.025-inch beta-titanium arch wires, ion-implanted on one half only, were placed in 30 subjects aged 10 to 42 years wearing unimplanted 0.022 inch slot appliances. Nickel-titanium springs (150 g) were placed bilaterally to close the extraction spaces. Space closure was measured intraorally at monthly intervals until either the space on one side closed or 6 months had elapsed. The median rates of space closure were not significantly different between the ion-implanted and the unimplanted sides. The average rate of space closure on these beta-titanium wires, with or without ion implantation, was similar to the rate reported on stainless steel arch wires.

Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey.

Data from the third National Health and Nutrition Examination Survey (NHANES III) provide a clear picture of malocclusion in the US population. Noticeable incisor irregularity occurs in the majority of all racial/ethnic groups, with only 35% of adults having well-aligned mandibular incisors. Irregularity is severe enough in 15% that both social acceptability and function could be affected, and major arch expansion or extraction of some teeth would be required for correction. About 20% of the population have deviations from the ideal bite relationship; in 2% these are severe enough to be disfiguring and are at the limit for orthodontic correction. In Mexican-Americans compared to the rest of the population, incisor irregularity and both severe Class II and Class III malocclusions are more prevalent, but deep bite and open bite are less prevalent. Application of the Index of Treatment Need to the survey data reveals that 57% to 59% of each racial/ethnic group has at least some degree of orthodontic treatment need. Over 30% of white youths, 11% of Mexican-Americans, and 8% of blacks report receiving treatment. Severe malocclusion is observed more frequently among blacks, which may reflect their lower level of treatment. Treatment is much more frequent in higher income groups, but approximately 5% of those in the lowest income group and 10% to 15% of those in intermediate income groups report being treated.