Ken Hansen

TMD in relation to malocclusion and orthodontic treatment

OBJECTIVE The aim of this systematic literature review was to evaluate associations between different malocclusions, orthodontic treatment, and signs and symptoms of temporomandibular disorders (TMD). MATERIALS AND METHODS This review was part of a project at the Swedish Council on Technology Assessment in Health Care focusing on malocclusion and orthodontic treatment from a health perspective. As a first step, the literature was searched in the Medline and Cochrane Library databases from 1966 to May 2003. A later update was made in January 2005. Human studies in English or in Scandinavian languages were included. RESULTS Associations between certain malocclusions and TMD were found in some studies, whereas the majority of the reviewed articles failed to identify significant and clinically important associations. TMD could not be correlated to any specific type of malocclusion, and there was no support for the belief that orthodontic treatment may cause TMD. Obvious individual variations in signs and symptoms of TMD over time according to some longitudinal studies further emphasized the difficulty in establishing malocclusion as a significant risk factor for TMD. A considerable reduction in signs and symptoms of TMD between the teenage period and young adulthood has been shown in some recent longitudinal studies. CONCLUSIONS Associations between specific types of malocclusions and development of significant signs and symptoms of TMD could not be verified. There is still a need for longitudinal studies.

Does orthodontic proclination of lower incisors in children and adolescents cause gingival recession

In this investigation we sought to assess the effect of orthodontic proclination of lower incisors in children and adolescents with respect to the possible development of gingival recession. Ninety-eight children with a mean +/- SD start-of-treatment age of 12.8 +/- 1.4 years, treated with the Herbst appliance, were surveyed, for a total of 392 lower incisors. Lateral head films, dental casts and intraoral photographs were analyzed with respect to the degree of orthodontic proclination, crown height, and gingival recession. In all subjects, Herbst treatment resulted in varying degrees of lower-incisor proclination (mean = 8.9 degrees, range = 0.5 degrees to 19.5 degrees). In 380 of the surveyed teeth (97%), either no recession developed or preexisting recession remained unchanged during Herbst therapy. In only 12 teeth (3%) did recession develop or preexisting recession deteriorate during treatment. No interrelation was found between the amount of incisor proclination and the development of gingival recession. In conclusion, orthodontic proclination of lower incisors in children and adolescents seems not to result in gingival recession.

Long-term stability of orthodontic treatment and patient satisfaction. A systematic review.

OBJECTIVE To evaluate morphologic stability and patient satisfaction at least 5 years after orthodontic treatment. MATERIALS AND METHODS Published literature was searched through the PubMed and Cochrane Library electronic databases from 1966 to January 2005. The search was performed by an information specialist at the Swedish Council on Technology Assessment in Health Care. The inclusion criteria consisted of a follow-up period of at least 5 years postretention; randomized clinical trials, prospective or retrospective clinical controlled studies, and cohort studies; and orthodontic treatment including fixed or removable appliances, selective grinding, or extractions. Two reviewers extracted the data independently and also assessed the quality of the studies. RESULTS The search strategy resulted in 1004 abstracts or full-text articles, of which 38 met the inclusion criteria. Treatment of crowding resulted in successful dental alignment. However, the mandibular arch length and width gradually decreased, and crowding of the lower anterior teeth reoccurred postretention. This condition was unpredictable at the individual level (limited evidence). Treatment of Angle Class II division 1 malocclusion with Herbst appliance normalized the occlusion. Relapse occurred but could not be predicted at the individual level (limited evidence). The scientific evidence was insufficient for conclusions on treatment of cross-bite, Angle Class III, open bite, and various other malocclusions as well as on patient satisfaction in a long-term perspective. CONCLUSIONS This review has exposed the difficulties in drawing meaningful evidence-based conclusions often because of the inherent problems of retrospective and uncontrolled study design.

The mechanism of Class II correction in late Herbst treatment

The aim of this study was to analyze quantitatively the sagittal skeletal and dental changes contributing to Class II correction in patients treated with the Herbst appliance after the pubertal growth peak. The sample consisted of 21 subjects with a Class II, Division 1 malocclusion treated during the skeletal maturity stages MP3-H and -1, corresponding to a period after the maximum of pubertal growth (late treatment). A comparison was made with 22 Herbst subjects treated during the skeletal maturity stages MP3-E and -F, corresponding to a period before the maximum of pubertal growth (early treatment). Lateral head films from before and after Herbst therapy were analyzed, according to the method of Pancherz. As a result of the Herbst therapy, all patients attained a Class I or overcorrected Class I occlusal relationship. Class II molar correction averaging 6.1 mm was due to 37% skeletal and 63% dental changes. Overjet correction averaging 8.4 mm was due to 27% skeletal and 73% dental changes. Differences between the late and the early treated patients were only found for the dental changes. The upper anterior teeth were retroclined and the lower anterior teeth were proclined more in the late cases. The conclusion of the study was that the Herbst appliance is equally efficient in patients treated before and after the pubertal peak of growth. However, proclination of the lower incisors (anchorage loss) in late treated subjects is larger than in early treated subjects. This should be considered in treatment planning.

Apical root resorption during orthodontic treatment. A prospective study using cone beam CT.

OBJECTIVE To investigate the incidence and severity of root resorption during orthodontic treatment by means of cone beam computed tomography (CBCT) and to explore factors affecting orthodontically induced inflammatory root resorption (OIIRR). MATERIALS AND METHODS CBCT examinations were performed on 152 patients with Class I malocclusion. All roots from incisors to first molars were assessed on two or three occasions. RESULTS At treatment end, 94% of patients had ≥1 root with shortening >1 mm, and 6.6% had ≥1 tooth where it exceeded 4 mm. Among teeth, 56.3% of upper lateral incisors had root shortening >1 mm. Of upper incisors and the palatal root of upper premolars, 2.6% showed root shortenings >4 mm. Slanted surface resorptions of buccal and palatal surfaces were found in 15.1% of upper central and 11.5% of lateral incisors. Monthly root shortening was greater after 6-month control than before. Upper jaw teeth and anterior teeth were significantly associated with the degree of root shortening. Gender, root length at baseline, and treatment duration were not. CONCLUSION Practically all patients and up to 91% of all teeth showed some degree of root shortening, but few patients and teeth had root shortenings >4 mm. Slanted root resorption was found on root surfaces that could be evaluated only by a tomographic technique. A CBCT technique can provide more valid and accurate information about root resorption.

Long-term effects of Herbst treatment on the mandibular incisor segment: a cephalometric and biometric investigation.

The purpose of this study was to analyze mandibular incisor changes during and after Herbst treatment with respect to tooth inclination and anterior crowding. The sample consisted of 24 Class II, Division 1 subjects (15 boys and 9 girls) treated with Herbst appliance. Dental casts and lateral head films from before and after treatment, 6 months after treatment and at the end of the growth period (at least 5 years after treatment) were analyzed. During treatment, the lower incisors were proclined (ILi/ML) an average of 10.8 degrees and the incisal edge (li) moved anteriorly by 3.2 mm. The available space and the irregularity index in the lower anterior region were in general unaffected by therapy. During the first posttreatment period of 6 months, the lower incisor inclination (ILi/ML) recovered an average of 7.9 degrees and the incisal edge (li) moved posteriorly by 2.5 mm. However, the available space was almost unchanged. During the second posttreatment period, i.e., from 6 months after treatment to the end of growth, the lower incisor inclination remained on average unchanged in relation to the mandibular plane (ILi/ML) but the teeth retroclined in relation to the nasion-sella line (ILi/NSL). The available space decreased (mean 0.8 mm, p < 0.01) and the irregularity index increased (mean 2.0 mm, p < 0.01). The correlation between changes in the ILi/NSL and in the NSL/ML angles was moderate (r = -0.57, p < 0.01), indicating that the reduction in the ILi/NSL angle was partly a result of anterior mandibular growth rotational changes. In conclusion, it can be said that the proclination of the lower front teeth during Herbst treatment did not result in incisor crowding after treatment. In a long-term perspective, the development of incisor crowding was thought to be associated with normal craniofacial growth changes.

The nasion-sella reference line in cephalometry: A methodologic study

This investigation was undertaken to examine the effects of the registration error of the nasion-sella reference line (NSL) upon the values of angular and linear head film measurements. A comparison was made between two methods of constructing the NSL: (1) using the anatomically defined landmarks nasion and sella (L method) and (2) using the stable skull structures in the anterior cranial base (S method). Double registrations of sixteen pairs of lateral head films, from before and after 3 years of activator treatment, were performed by two observers. The results of the investigation revealed the following: (1) The registration error of the NSL affected angular and linear head film measures to a considerable degree. (2) The registration error was larger for the S method than for the L method. (3) The two observers differed in locating the NSL. The interobserver difference was especially apparent for the S method. The clinician should be aware of the NSL-registration error in the analysis of both single and serial radiographs. A misjudgment of the position of the reference line may result in diagnostic misinterpretations, thus affecting treatment planning or leading to false conclusions when the outcome of a particular treatment procedure is evaluated. In longitudinal studies covering a short period of growth, the L method would be the method of choice.

Overjet reduction and molar correction in fixed appliance treatment of Class II, Division 1, malocclusions: Sagittal and vertical components

The purpose of this study was to quantitatively evaluate skeletal and dental changes contributing to Class II correction in patients treated with the Begg technique. The sample consisted of 18 male subjects with Class II, division 1, malocclusions treated with fixed appliances (Begg technique, nonextraction) for an average period of 1.3 years (standard deviation, 0.24 years). Lateral radiographs in habitual occlusion taken at 6 months before the start of treatment, at the start of treatment, and 6, 12, and 18 months after the start of treatment were analyzed. During the control period, normal sagittal and vertical growth changes occurred. In the initial treatment period (0 to 6 months), the overjet reduction (6.6 mm; P <. 001) and the molar correction (2.2 mm; P <.001) were obtained mainly by dental movements. The overbite was reduced by 4.1 mm (P <.001). The NSL/ML and NL/ML angles increased by 1.5 degrees (P <.05) and 1. 4 degrees (P <.01), respectively, and the anterior lower facial height increased by 3.1 mm (P <.001). During the second period of treatment (6 to 12 months), the molar correction continued to improve, and the anterior lower facial height continued to increase. During the third period (12 to 18 months), a small relapse in overjet and overbite was noted, but the anterior lower facial height continued to increase. During the total treatment period (0 to 18 months), the overjet reduction and molar correction were 5.8 mm (P <. 001) and 3.0 mm (P <.001), respectively. Mandibular growth exceeded maxillary growth by 1.1 mm (P <.01). The overbite correction and the increase in anterior lower facial height were 3.0 mm (P <.001) and 5. 0 mm (P <.001), respectively. The NSL/ML angle increased 1.0 degrees (P <.05). The conclusions were that the changes contributing to the Class II correction were mostly dental. Vertically, the net effects of treatment were an increase in the mandibular plane angle and in lower anterior facial height.

Long-term Effects of the Herbst Appliance on the Dental Arches and Arch Relationships: A Biometric Study

The purpose of this study was to evaluate biometrically the treatment and post-treatment effects of the Herbst appliance on the dental arches and arch relationships. The sample consisted of 53 Class II, division 1 malocclusion patients (33 boys and 20 girls) treated with the Herbst appliance. The mean age of the patients before treatment was 12·5 years (SD = 1·2 years). Dental casts were analysed before treatment, after treatment, 6 months post-treatment and at the end of the growth period (5–10 years post-treatment). The following variables were assessed: sagittal molar and canine relationships, overjet, overbite, maxillary and mandibular arch perimeters, and inter-molar and inter-canine dental arch widths. During treatment, the overjet, overbite, and sagittal molar relationship were overcorrected in most of the cases, while the sagittal canine relationship was normalized. The maxillary and mandibular arch perimeters increased during treatment, as did dental arch widths (moral and canine). In the long-term (mean = 6·7 years after treatment), Herbst appliance treatment resulted in a normal or over-corrected sagittal molar relationship in 79 per cent and a normal canine relationship in 68 per cent of the cases. Eighty-three per cent of the subjects has an overjet of 4·5 mm or less. In the long-term, the arch perimeters seemed to follow a normal dental development pattern. The increase of the upper molar and canine dental arch widths during treatment remained virtually stable whilst the lower intermolar arch widths seemed unaffected by treatment.

Root resorption diagnosed with cone beam computed tomography after 6 months of orthodontic treatment with fixed appliance and the relation to risk factors

OBJECTIVES To investigate root resorption after 6 months of active orthodontic treatment and its relation to possible risk factors. MATERIALS AND METHODS Ninety-seven patients (10-18 years) with a Class I malocclusion and crowding treated with fixed appliance and premolar extractions were examined with cone beam computed tomography before and after 6 months of active treatment. The exposure covered all teeth from first molar to first molar in both jaws. The Malmgren index was used to evaluate the degree of root resorption. Irregular root contour (score 1) was seen in most teeth already before active treatment, and therefore resorptions were registered only as score 2 (<2 mm, minor resorption) or higher. RESULTS Minor root resorption was noted in 10% of the patients and severe root resorption, >2 mm (score 3) was found in four patients. Root resorption was more frequently seen in the upper jaw, especially the incisors. There was no statistically significant correlation of root resorption with any of the selected risk factors. CONCLUSIONS After 6 months of treatment, clinically significant resorption was diagnosed in 4% of the patients, ie, in 96% of the patients the radiographic examination did not reveal any significant information. The selected risk factors did not have any impact on the amount of resorption after 6 months of active treatment.