Biomedical subjects

H Pancherz

Publications and source records attributed to H Pancherz.

At least 37 records · Page 2Linked to original sources

PubMed1998

Temporomandibular joint growth adaptation in Herbst treatment: a prospective magnetic resonance imaging and cephalometric roentgenographic study.

The aim of this investigation was to analyze three possible adaptive TMJ growth processes contributing to the increase in mandibular prognathism accomplished by Herbst appliance therapy: (1) condylar remodeling; (2) glenoid fossa remodeling; and (3) condyle-fossa relationship changes. The subjects were 15 consecutive Class II malocclusions (11 males and four females, aged 11.5-17.5 years) treated with the Herbst appliance for an average period of 7 months. Condylar remodelling, glenoid fossa remodelling, and condyle-fossa relationship changes were analyzed by means of magnetic resonance imaging (MRI). From each subject, four MR images were evaluated: before treatment, start of treatment (when the Herbst appliance was placed), during treatment (6-12 weeks after appliance placement), and after treatment (when the appliance was removed). 'Effective condylar growth' (= the sum of condylar remodelling, fossa remodelling, and condyle-fossa relationship changes) was analyzed with the aid of pre- and post-treatment lateral cephalometric roentgenograms. In all 15 subjects, Herbst therapy resulted in an increase in mandibular prognathism. After 6-12 weeks of treatment MRI-signs of condylar remodelling were seen at the posterior-superior border in 29 of the 30 condyles. MRI-signs of glenoid fossa remodelling at the anterior surface of the postglenoid spine were noted in 22 of the joints. Condylar remodelling seemed to precede fossa remodelling. The condyle-fossa relationship was, on average unaffected by Herbst therapy. 'Effective condylar growth' during treatment was, on average, approximately five times larger in the Herbst group than in an untreated group with ideal occlusion (Bolton Standards) and the direction of the growth changes was relatively more horizontal in the treated cases. The results indicate that condylar as well as glenoid fossa remodelling seem to contribute significantly to the increase in mandibular prognathism resulting from Herbst treatment, while condyle-fossa relationship changes are of less importance. MRI renders an excellent opportunity to visualize temporomandibular remodelling growth processes.

Adaptation, Physiological↗

PubMed1997

Herbst appliance treatment of Class II, division 2 malocclusions.

The purpose of this investigation was to analyze quantitatively the sagittal skeletal and dental changes that contribute to occlusal correction in Herbst treatment of 14 Class II, Division 2 malocclusions. Forty Class II, Division 1 Herbst subjects were used for comparison. Lateral head films from before and after Herbst treatment were analyzed, according to the method of Pancherz. The results revealed that all patients were treated to Class I or overcorrected Class I molar and edge-to-edge incisor relationships. The maxillary and mandibular skeletal changes were similar in both examination groups. In the Class II, Division 2 subjects, sagittal molar and overjet corrections amounted to an average of 5.9 mm and 3.1 mm, respectively. When comparing the Class II, Division 2 with the Class II, Division 1 subjects, overjet correction was, for natural reasons, significantly larger (p < 0.001) in the Class II, Division 1 subjects. In the subjects with Class II, Division 2 malocclusions, the upper incisors were proclined (mean = 3.0 mm), whereas in the subjects with Class II, Division 1 malocclusions, the incisors were retroclined (mean = 2.3 mm). The lower incisors were on the average proclined more (p < 0.05) in the Class II, Division 2 subjects (mean = 3.4 mm) than in the Class II, Division 1 subjects (mean = 2.4 mm). For sagittal molar correction, no differences in tooth movements were seen between the two malocclusions groups. In conclusion, it was found that the Herbst appliance is most effective in the therapy of Class II, Division 2 malocclusions. Proclination of the lower incisors during treatment (anchorage loss) is advantageous in this type of malocclusion.

Adolescent↗

PubMed1997

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.

Adolescent↗

PubMed1997

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.

Adolescent↗

PubMed1997

The effects, limitations, and long-term dentofacial adaptations to treatment with the Herbst appliance.

The purpose of this article is to summarize the existing scientific data with respect to the short- and long-term effects of the Herbst appliance on the occlusion and on the maxillo/mandibular complex. The article also discusses the treatment indications and possible treatment limitations. The Herbst method is most effective in the treatment of Class II malocclusions. Long-term stability seems to be dependent on a stable cuspal interdigitation. Marked mandibular morphological changes occur during therapy and sagittal condylar growth is increased. Posttreatment, most of the mandibular morphological changes revert and no long-term influence of Herbst treatment on mandibular growth can be verified. The appliance effect on the maxillary complex can be compared with that of a high-pull headgear. Without proper retention, however, this effect is of a temporary nature. Herbst treatment is especially indicated in the permanent dentition at or just after the pubertal peak of growth. Mixed dentition treatment is not recommended, as a stable cuspal interdigitation after therapy is difficult to achieve and relapses are prone to occur. In the nongrowing patient, the appliance should be used with great caution.

Adaptation, Physiological↗

PubMed1997

Cephalometric characteristics of Class II division 1 and Class II division 2 malocclusions: a comparative study in children.

A comparison of dentoskeletal morphology in 347 Class II division 1 and 156 Class II division 2 malocclusions was performed using lateral cephalometric radiographs. Children at the ages of 8-10 years and 11-13 years were evaluated. The results of the study revealed broad variations in the variables analyzed. Skeletal Class II and Class III as well as hypo- and hyperdivergent maxillary/mandibular jaw base relationships were seen in both malocclusion samples. Noteworthy was the high frequency of cases with mandibular retrusion (Class II division 1 sample: 48% of the younger and 29% of the older subjects; Class II division 2 sample: 48% of the younger and 49% of the older subjects) and a short lower face (97%-100%). In conclusion it can be said that, except for the position of the maxillary incisors, no basic difference in dentoskeletal morphology exists between Class II division 1 and Class II division 2 malocclusions.

Adolescent↗

PubMed1997

The mechanism of Class II correction during Herbst therapy in relation to the vertical jaw base relationship: a cephalometric roentgenographic study.

This retrospective Herbst study analyzes and compares the sagittal dental and skeletal effects contributing to Class II correction in subjects with small or large pretreatment mandibular plane angles. Lateral headfilms of 15 hypodivergent (ML/NSL < or = 26 degrees) and 16 hyperdivergent (ML/NSL > 39 degrees) Class II subjects treated to a Class I occlusal relationship with the Herbst appliance were analyzed. Radiographs were taken before and after an average treatment period of 7 months. Cephalograms were evaluated according to the method of Pancherz. In both groups, impprovements in sagittal incisor and molar relationships were achieved by greater dental than skeletal changes. The amount of skeletal changes contributing to overjet and molar correction was larger in the hyperdivergent group (37% and 44%, respectively) than in the hypodivergent group (25% and 25%, respectively). Dental and skeletal changes contributing to Class II correction were found to be independent of the vertical jaw base relationship. Thus, a hyperdivergent jaw base relationship did not affect the treatment response unfavorably.

Adolescent↗

PubMed1997

Long-term effects of Class II correction in Herbst and Bass therapy.

This study compared the initial and long-term skeletal and dental effects of Herbst and Bass appliance therapy for correction of Class II malocclusion. The sample comprised 18 pairs of boys matched for growth period at the time of therapy, with similar pre-treatment sagittal and vertical jaw base relationships. One boy in each pair was treated with the Herbst and the other with the Bass appliance. At follow-up, 15 boys of the Herbst group and 17 of the Bass group were available. Lateral cephalograms in centric occlusion taken before treatment, after 6 months of treatment and at the end of growth were analysed. After 6 months of treatment the Bass appliance seemed to have a greater effect on mandibular jaw base position. The correction of overjet and sagittal molar relationship was more complete in the Herbst patients due to dental changes. At follow-up varying effects both between and within pairs were observed. Overall, the skeletal and dental changes from start of treatment to end of growth were of the same magnitude. A restraining effect on the position of the maxilla was observed in both groups, somewhat more pronounced in the Bass sample. Both treatment methods are most useful in correction of severe Class II malocclusions. It was, however, difficult to find possible differences in treatment effects between the two methods due to great individual variations of growth.

Activator Appliances↗

PubMed1997

Stress-induced changes in the functional electromyographic activity of the masticatory muscles.

The present study was undertaken to assess the effect of a non-experimental emotional stress situation on the functional electromyographic (EMG) activity of the masticatory muscles. The material comprised 15 dental students without signs and symptoms of disorders from the temporomandibular system. The activity of the masseter and anterior temporalis muscles was recorded bilaterally by means of surface EMG. The subjective degree of helplessness of the subjects was assessed and related to the EMG activity response, to assess a possible interrelation. The EMG activity during the stress situation was significantly greater than for the non-stress situation. This shift in EMG activity was seen for all the muscles and all the functions analyzed. No significant gender differences were found. When the subjective degree of helplessness is taken into consideration, women showed significantly higher ratings than male subjects. The Helplessness Scale ratings correlated with the changes in EMG activity.

Adult↗

PubMed1996

Frontal sinus development as an indicator for somatic maturity at puberty?

The possibility of predicting the stage of somatic maturity by analyzing frontal sinus growth was evaluated. The study was performed on 53 adolescent boys, and the frontal sinus size development was assessed on lateral head films. The accuracy of the prediction procedure was tested by comparing the prediction stage with the longitudinal growth data for body height of the subjects. The results revealed that: If the only prediction was whether the pubertal growth peak in height has been passed (group B), the precision of the method was rather high (approximately 90%). However, if the age of body height peak was to be predicted, the method accuracy was lower (approximately 55%). No significant difference existed between the 1- and 2-year prediction intervals. The study suggests that the somatic maturity stage may be predicted rather accurately by analyzing frontal sinus development on pre-existing lateral head films.

Adolescent↗

PubMed1996

The effect of Herbst appliance treatment on the mandibular plane angle: a cephalometric roentgenographic study.

The purpose of this investigation was to assess the individual reaction pattern and the long-term effect of Herbst appliance treatment on the vertical jaw base relationship, as expressed by the mandibular plane angle (ML/NSL). In the evaluation special reference was given to the pretreatment vertical jaw base relationship (hypodivergent, normodivergent or hyperdivergent). Lateral head films of 80 patients (47 males and 33 females) from before, at start (when the appliance was placed) and at the end of Herbst treatment (when the appliance was removed) as well as 6 months and 4.5 to 5 years posttreatment were analyzed. The ML/NSL angle was on the average unaffected by Herbst therapy. Posttreatment, a continuous decrease in the ML/NSL took place. Male subjects showed a larger angular decrease than female subjects. However, a large interindividual variation existed. No statistically significant differences were found between hypodivergent, normodivergent, and hyperdivergent subjects.

Adolescent↗

PubMed1996

The reliability of the Frankfort Horizontal in roentgenographic cephalometry.

This longitudinal investigation was undertaken to assess the reliability of the Frankfort Horizontal line (FH) when using either anatomical Porion (Po-a) or machine Porion (Po-m) as reference landmarks. Lateral head films (22 pairs) from subjects at the ages of 11 and 14 years were analysed twice. The results revealed that: (i) the registration error of Po-a was larger than of Po-m; (ii) for Po-a the registration error from the 11 year head films was approximately twice as large as from the 14 year head films; (iii) Po-m was, on average, located approximately 9 mm below and 2 mm anterior to Po-a; (iv) during the 3 years of observation, Po-m changed its position downward markedly more than Po-a; (v) due to the diverging location of machine Porion (Po-m) in relation to true Porion (Po-a) and the large change of Po-m with time, the FH was affected considerably. It was concluded that machine Porion was unsuitable for the construction of the FH. A misjudgement of the reference line may result in diagnostic misinterpretations and lead to false conclusions in longitudinal studies, e.g. when the outcome of a particular treatment procedure is evaluated.

Activator Appliances↗

PubMed1996

Development of the frontal sinus in relation to somatic and skeletal maturity. A cephalometric roentgenographic study at puberty.

The development of the frontal sinus in relation to somatic and skeletal maturity was analysed in 26 male subjects aged 9-22 years by means of longitudinal data obtained from lateral head films, handwrist radiographs and body height growth curves. These were grouped together and analysed in a cross-sectional manner. The results revealed that the final size of the frontal sinus varied considerably. Analogous to body height growth at puberty, the enlargement of the frontal sinus exhibited a similar pattern with a well-defined peak, which on average occurred 1.4 years after the body height peak. In comparison with skeletal maturity, 65 per cent of the subjects reached the sinus peak during the hand radiographic stages MP3-G or MP3-H, while the body height peak coincided with an earlier maturity stage (MP3-FG).

Adolescent↗

PubMed1996

Can frontal sinus development be used for the prediction of skeletal maturity at puberty?

The precision of a new procedure predicting skeletal maturity on the basis of frontal sinus development was tested in 59 boys with an Angle class-II division-1 malocclusion. Lateral head films were used for the analysis of frontal sinus development, and handwrist radiographs were used for the assessment of skeletal maturity. The results showed that skeletal maturity could be predicted with a certainty of about 85% when using a 1-year prediction interval and with a certainty of about 75% when using a 2-year prediction interval. In conclusion, the study showed that skeletal maturity can be predicted with rather high accuracy by means of the analysis of frontal sinus development as imaged on lateral headfilms.

Adolescent↗

PubMed1996

Is quantitative electromyography reliable?

The reliability of quantitative electromyography (EMG) of the masticatory muscles was investigated in 14 subjects without any signs or symptoms of temporomandibular disorders. Integrated EMG activity from the anterior temporalis and masseter muscles was recorded bilaterally by means of bipolar surface electrodes during chewing and biting activities. In the first experiment, the influence of electrode relocation was investigated. No influence of electrode relocation on the recorded EMG signal could be detected. In a second experiment, three sessions of EMG recordings during five different chewing and biting activities were performed in the morning (I); 1 hour later without intermediate removal of the electrodes (II); and in the afternoon, using new electrodes (III). The method errors for different time intervals (I-II and I-III errors) for each muscle and each function were calculated. Depending on the time interval between the EMG recordings, the muscles considered, and the function performed, the individual errors ranged from 5% to 63%. The method error increased significantly (P < .05 to P < .01) with the time interval between recordings. The error for the masseter (mean 27.2%) was higher than for the temporalis (mean 20.0%). The largest function error was found during maximal biting in intercuspal position (mean 23.1%). Based on the findings, quantitative electromyography of the masticatory muscles seems to have a limited value in diagnostics and in the evaluation of individual treatment results.

Adolescent↗

PubMed1995

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 (molar 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 had 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.

Adolescent↗

PubMed1995

Is orthopantomography reliable for TMJ diagnosis? An experimental study on a dry skull.

The accuracy of orthopantomography in reproducing the temporomandibular joint area was analyzed on a dry skull. The results based on this study of a single skull revealed that the radiographic image of the temporomandibular joint did not correspond to the anatomic condylar and fossa components or to their actual relationship. To a large extent, changes in skull position affected the radiographic temporomandibular joint image, simulating anterior condylar flattening, osteophytes, narrowing of joint space, and left/right condylar asymmetry. Orthopantomography may have questionable reliability for temporomandibular joint diagnostic purposes.

Humans↗

PubMed1994

[Facial morphology and the size and activity of the masseter muscle].

The study presented here was conducted for the purpose of investigating the possible relationship of masseter muscle size and activity to facial morphology. The study examined 50 adults, 25 males and 25 females, by means of electromyography, ultrasonography, and facial photography. The following results were obtained. There was considerable variation in masseter muscle activity and size both between the 2 groups and among individuals in each group. Partly there were strong differentiation's between the males and the females. The interrelationships between masseter muscle activity and size and facial morphology in both groups were generally weak, however, the links were more discernible in the women than in the men. Female subjects with thin faces and large mandibular planes had reduced masseter thickness, whereas women with a small anterior facial height index displayed when relaxed less masseter muscle activity and a smaller masseter width.

Adult↗