© 1991 European Orthodontic Society

European Journal of Orthodontics 13 (1991) 471-481

Long-term effects of the Herbst appliance in relation to the treatment growth period: a cephalometric study Ken Hansen,* Hans Pancherz,** and Urban Hagg*** 'Department of Orthodontics, University of Lund, Malmo, Sweden, "Department of Orthodontics, University of Giessen, Germany, and "'Department of Children's Dentistry and Orthodontics, University otHong Kong, JHong Kong _

SUMMARY The aim of this study was to analyse the long-term effects of Herbst treatment on the dentofacial complex with special reference to the growth period in which the patients were treated. The sample consisted of 40 male subjects with a Class II, division 1 malocclusion treated successfully with the Herbst appliance for an average period of 7 months. The patients were reinvestigated at the end of the growth period, on average 6.6 years (SD = 1.0 years) after therapy. Nineteen patients were treated before the maximum of pubertal growth (prepeak), 15 at the maximum (peak) and 6 after the pubertal growth maximum (post-peak). Sagittal skeletal and dental changes occurring during and after Herbst treatment were evaluated on lateral radiographs in centric occlusion. At the time of follow-up examination no group differences were seen in sagittal dental arch relationships. During the follow-up period after Herbst treatment maxillary and mandibular growth development were favourable and comparable in all three groups: mandibular growth exceeding maxillary growth by an average of 4.3 mm (SD = 2.4mm). For natural reasons, however, the amount of jaw growth during the follow-up period was larger in the subjects treated before the maximum of pubertal growth than in the subjects treated at the later stages. The conclusion of this study was that the growth period in which Herbst treatment was performed did not seem to have any conclusive efffect on the long-term results. However, in order to favour occlusal stability after treatment and to reduce the time of post-treatment retention, Herbst therapy in the permanent dentition at or just after peak height velocity of growth is recommended.

Introduction

In consecutively treated Class II, division 1 malocclusion cases the immediate as well as the short-term follow-up effects of the Herbst appli-ance-(Herbst, 1934)-have-been thoroughly-analysed in several investigations (Pancherz, 1979, 1981, 1982, 1985; Pancherz and Hagg, 1985; Pancherz and Hansen, 1986, 1988; Pancherz and Littmann, 1988, 1989; Pancherz and Stickel, 1988). At the end of treatment an overcorrected Class I dental arch relationship with incomplete cuspal interdigitation is a common finding (Pancherz 1979, 1981, 1982, 1985; Pancherz and Hansen, 1986). During the first 6 months after treatment, however, the occlusion generally settles into Class I due to recovering tooth movements (Pancherz and Hansen, 1986). When relating the appliance effects to the patient's level of somatic maturation at therapy,

a larger increase in sagittal condylar growth was found when treatment was performed at peak height velocity of growth than when treatment was performed before or after that period (Pancherz and Hagg, 1985; Hagg and Pancherz, " 1988;"Panchefz andXiftmahn, 1988): The"infln-" ence of the treatment growth period on the long-term results has to this date not been considered. Thus, the aim of this study was to analyse the long-term effects of Herbst treatment on the dentofacial complex with special reference to the growth period at which the patients were treated. Subjects In 1990 the original sample of consecutively patients treated with the Herbst appliance at the Orthodontic Department, Faculty of Odontology, Malmo, comprised 170 ..subjects with

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Class II, division 1 malocclusions. The first 40 male subjects treated that fulfilled the following criteria were selected for this study.

Table 2. The design of the Herbst appliance, used in treating the patients had been described elsewhere (Pancherz, 1985).

1. No extractions of permanent teeth. 2. A follow-up of at least 5 years after treatment the patients at the end of the growth period at the time of follow-up. In this study, the end of the growth period was defined as: (i) a complete fusion of the epiphysis of the radius (stage Ru; Bjork, 1972) as seen on handwrist radiograph; (ii) an annual increment of height not exceeding 5 mm (Taranger and Hagg, 1980) during the final year of examination.

Analysis of the profile radiographs

An outline of the patient details is given in Table 1.

Lateral head films in centric occlusion were analysed at three stages: before treatment, 6 months post-treatment when the occlusion had settled (Pancherz and Hansen, 1986) and at the time of follow-up, an average of 6.6 years (SD 1.0 years) post-treatment. The cephalometric changes occurring during three observation periods were analysed. Observation period I. Changes during the period from before treatment to 6 months posttreatment (treatment/settling).

Methods

Observation period 2. Changes during the period from 6 months post-treatment to the end of growth.

The patient sample was divided into three groups according to the growth period in which they were treated (Pancherz and Hagg, 1985). Nineteen patients were treated before the maximum of pubertal growth (prepeak), 15 at the maximum (peak) and 6 after the maximum (post-peak) (Fig. 1). Standard cephalometric measures of the three groups are shown in

Total observation period. Changes during the period from before treatment to the end of growth. In the analysis of the headfilms landmarks were marked on the radiograph with a wellsharpened All-stabilo pencil (Schwan-Stabilo, Germany). The radiographs were digitized with a Scriptel RDT digitizer (Scriptel Corporation,

Table 1 Distribution of 40 male Class II, division 1 malocclusion cases treated with the Herbst appliance. Nineteen subjects were treated before the maximum of pubertal growth (prepeak), 15 at maximum (peak) and 6 after maximum (post-peak).

Age at follow-up (years)

Treatment period (years)

Settling period (years)

Observation period 1 (treatment + settling) (years)

Prepeak (n= 119) Mean 12.24 SD 0.69 Range 10.7-13.3

19.82 1.01 17.3-21.2

0.56 0.16 0.5-1.0

0.50 0.03 0.4-0.6

1.06 0.17 0.9-1.5

6.52 0.61 5.5-8.0

7.58 0.56 6.5-8.6

Peak(«=15) Mean 12.90 SD 0.60 Range 11.7-13.8

19.70 0.96 18.4-21.4

0.59 0.16 0.5-1.1

0.50 0.05 0.4-0.6

1.09 0.19 0.9-1.7

5.71 1.08 4.5-7.7

6.81 1.11 5.5-8.7

Post-peak (/i = 6) Mean 14.16 SD 1.10 Range 13.1-16.3

20.78 1.67 18.6-23.3

0.65 0.12 0.5-0.8

0.51 0.01 0.5-0.5

1.15 0.13 1.0-1.3

5.46 1.70 4.5-8.3

6.62 1.68 5.5-9.5

Total (n = 40) Mean 12.77 SD 0.96 Range 10.7-16.3

19.92 1.13 17.3-23.3

0.58 0.15 0.5-1.1

0.50 0.04 0.4-0.6

1.09 0.17 0.9-1.7

6.06 1.07 4.5-8.3

7.15 1.05 5.5-9.5

Growth period

Age at start (years)

Observation period 2 (years)

Total observation period (years)

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LONG-TERM EFFECTS OF HERBST APPLIANCE

40

Peak

Post-peak

Figure 1 Distribution of 40 males Class II, division 1 malocclusions, treated with the Herbst appliance, in relation to the peak height velocity (PHV) during treatment. Division of the subjects into three growth-period groups: prepeak, peak and post-peak. The length of the treatment period (—) is shown.

1. ss-OLp—position of the maxillary jaw base. Columbus, USA) and the measurements and calculations were made by a computer. No 2. pg-OLp—position of the mandibular jaw corrections were made for linear radiographic base. enlargement (approximately 7 per cent in the 3. ss-pg—position of the maxilla in relation median plane). to the mandible (ss-OLp minus pg-OLp). The head-films from 6 months post-treatment _and_follow-upwere_superimposed o_n_the^ before _ _. _4. js-OLp—ppsjtion of Jhe maxillary central_ treatment film using stable skull structures in incisor. the anterior cranial base for orientation (Bjdrk 5. ii-OLp—position of the mandibular central and Skieller, 1983). incisor. The occlusal line (OL—a line through is and 6. is-ii—overjet (is-OLp minus ii-OLp). the distobuccal cusp of the maxillary permanent first molar) and the occlusal line perpendicular 7. is-ss—position of the central maxillary (OLp) through sella, from the first radiograph, incisor in relation to the maxillary base were used as a reference grid (Fig. 2). The grid (is-OLp minus ss-OLp). was transferred to the subsequent radiographs 8. ii-pg—position of the central mandibular after superimposition of the headfilms. An anaincisor in relation to the mandibular base lysis of sagittal skeletal and dental changes was (ii-OLp minus pg-OLp). performed according to the method of Pancherz (1982; Fig. 2). The analysis comprised the fol9. ms-OLp—position of the maxillary first lowing variables. molar.

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K. HANSEN ET AL.

Table 2 Cephalometric records describing dentofacial morphology in 40 male Class II malocclusion cases treated with the Herbst appliance. Nineteen patients were treated before the maximum of pubertal growth (prepeak), 15 at maximum (peak) and 6 after maximum (post-peak). Registrations before treatment (Before), 6 months after treatment (Six), and at the end of the growth period (Follow-up). Prepeak

Peak

Post-peak

Mean

SD

Mean

SD

Mean

SD

Before Six Follow-up

81.3 80.8 81.6

3.6 3.8 3.8

81.0 80.9 81.2

3.3 3.4 3.9

82.5 82.6 82.9

3.0 2.7 3.2

SNB

Before Six Follow-up

75.4 76.4 77.8

3.0 3.5 3.4

75.8 77.0 77.8

2.7 3.0 3.2

77.2 78.6 79.2

3.6 3.8 4.3

ANB

Before Six Follow-up

5.9 4.3 3.9

2.1 2.1 2.2

5.2 3.9 3.4

1.3 1.3 1.4

5.2 4.0 3.6

1.2 2.0 2.5

SNPg

Before Six Follow-up

76.2 77.1 78.9

3.1 3.5 3.4

77.1 78.1 79.4

2.8 3.0 3.3

78.9 80.4 81.1

3.4 3.6 4.3

SN/SBa

Before Six Follow-up

132.4 132.4 132.9

3.9 3.9 4.3

132.6 132.7 133.5

6.1 6.6 6.1

129.5 129.5 129.4

3.0 2.7 3.0

NSL/NL

Before Six Follow-up

7.6 8.4 7.9

2.1 2.1 3.0

7.2 8.0 7.5

3.4 3.3 4.2

7.2 6.8 6.3

2.9 2.8 3.4

NSL/ML

Before Six Follow-up

32.4 32.2 27.6

5.3 5.5 6.7

31.4 31.3 27.9

6.5 6.7 7.8

29.1 27.6 25.5

6.2 6.4 7.8

NL/ML

Before Six Follow-up

24.8 23.9 19.7

5.4 5.4 6.1

24.2 23.3 20.3

5.5 5.4 6.5

21.9 20.8 19.2

6.0 5.6 6.8

ML/RL

Before Six Follow-up

122.4 123.4 115.7

6.5 6.8 8.2

121.8 122.4 117.0

5.9 6.5 7.0

119.8 119.4 117.3

2.2 3.3 4.4

11,21/NL

Before Six Follow-up

113.0 110.1 109.7

6.0 4.8 5.3

113.5 106.9 106.6

7.0 7.6 7.9

112.1 106.1 105.6

8.9 6.8 5.9

31,41/ML

Before Six Follow-up

100.1 102.8 103.7

6.4 6.8 7.8

100.6 102.3 101.6

7.3 4.7 6.7

102.5 106.7 107.0

6.0 8.9 9.1

11,21/ 31,41

Before Six Follow-up

122.1 123.2 126.9

7.5 5.7 8.9

121.7 127.6 131.4

7.1 7.2 9.6

123.5 126.4 128.2

9.5 8.4 8.8

Variable

Period

SNA

10. mi-OLp—position of the mandibular first molar. 11. ms-ss—position of the first maxillary molar in relation to the maxillary base (ms-OLp minus ss-OLp). 12. mi-pg—position of the first mandibular molar in relation to the mandibular base (mi-OLp minus pg-OLp).

13. ms-mi— molar relation (ms-OLp minus mi-Olp). A computer calculated composite tracing of the three growth groups was performed at the different times of examination. Each tracing was composed of a continuous series of approximately 220 points. Computer-constructed templates were used for the skull base, the nasal

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Observation period 1 OLp

Figure 2 Measuring points used in the cephalometric analysis. The nasion-sella line (NSL) and the reference grid (OL and OLp) are shown. (Modified from Pancherz, 1982.)

bone, the maxilla, the upper and lower incisors, and the mesial contours of the first molars. Statistical methods The arithmetic mean (mean) and standard deviation (SD) for each variable were calculated. t-Tests for paired samples were performed to assess the statistical significance of changes occurring in the different observation periods. t-Tests for independent samples were used to assess group differences. The levels of significance used were />

Long-term effects of the Herbst appliance in relation to the treatment growth period: a cephalometric study.

The aim of this study was to analyse the long-term effects of Herbst treatment on the dentofacial complex with special reference to the growth period ...
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