The aim of this study was to analyze the very long-term results after Herbst treatment with respect to changes in the mandibular incisor segment: incisor inclination, incisor alignment, and gingival status.
Fourteen patients were derived from a sample of 22 consecutive patients with Class II Division 1 malocclusions treated with the banded Herbst appliance. Intraoral photographs, mandibular dental casts, and lateral head films were analyzed from before (T1, age 12.5 years) and after (T2, age 14 years) treatment, and at 6 years (T3, age 20 years) and 32 years (T4, age 46 years) after treatment.
At T1, incisor inclination in the 14 subjects was, on average, 100.1°. From T1 to T2, the incisors were proclined in 11 (79%) of the 14 patients, with an average value of 5.2°. Maximum proclinations of 10° were found in 2 subjects. From T2 to T4, tooth inclination recovered completely in 7 (63%) of the 11 patients. Incisor irregularity values were, on average, 3.4 mm at T1 and 3.0 mm at T2. These increased from T2 to T4 by 40% and had an average value of 5.0 mm at T4. Clinically insignificant labial gingival recessions on single front teeth were registered in 1 subject at T2 and in 8 subjects at T4. Gingival recessions were seen especially on bodily displaced incisors.
In Herbst patients followed for 32 years after therapy, proclined mandibular incisors generally rebounded. The increase in posttreatment incisor tooth irregularity was not thought to be related to incisor tooth inclination changes but more likely resulted from physiologic processes occurring throughout life. Minor gingival recessions (especially on bodily displaced and crowded canines and incisors) seen in a few patients, 32 years after treatment, seemed not to be related to the posttreatment tooth inclination changes.
Proclined mandibular incisors rebounded in Herbst patients 32 years after therapy.
Incisor irregularity increased, probably because of the physiologic processes occurring throughout life.
Minor gingival recessions 32 years after treatment seemed unrelated to tooth inclination changes.
Proclination of the mandibular incisors is a frequent and unwanted side effect of Herbst therapy and is difficult to control irrespective of the anchorage system used. It has been suggested that orthodontic proclination of mandibular incisors could result in harmful effects to the bone-supporting tissues of the teeth and induce gingival recessions.
With respect to the Herbst appliance, incisor proclination has not been found to cause either labial gingival recessions or posttreatment crowding. However, in previous Herbst publications, the follow-up periods after treatment were relatively short (1-5 years) and usually ended in late adolescence or early adulthood when growth-related tooth-position changes still could occur. To date, there have been no long-term follow-up studies after Herbst therapy in which the follow-up period ends in the middle life of the patients, when growth-dependent changes in tooth position must be considered to be at an end.
Therefore, the aim of this investigation was to reexamine adolescent Herbst patients (ages, 12-14 years) at least 30 years posttreatment to assess the very long-term findings after Herbst therapy with respect to changes in the mandibular incisor segment: incisor inclination and irregularity and the occurrence of gingival recessions.
Material and methods
The patients in this study were derived from a well-defined sample of 22 consecutive patients with Class II Division 1 malocclusion treated with the Herbst appliance at the University of Malmö in Sweden in 1977 and 1978. The subjects were originally presented in 2 articles from 1982.
This study was approved by the ethical committee of the University of Malmö in Sweden (number 2012/44).
In 2011 and 2012, 30 to 33 years after Herbst therapy, these 22 subjects were recalled to the orthodontic department in Malmö for a follow-up investigation. At this time, the subjects were 42 to 48 years of age. Two persons were deceased, and 6 did not return, for several reasons. Thus, the final follow-up sample comprising 14 subjects (12 men, 2 women) is presented in detail in Table I .
|Patient||Sex||Treatment||Age (y)||Follow-up periods (y)||Retention (y)||Class II correction||Mandibular third molars|
|Herbst/Extr.||T1||T2||T3||T4||T2 -T3||T3-T4||T2-T4||Fixed/removable †||Stable/relapse||Yes/no ‡|
|1X||m||Herbst/extraction||13||17 ∗||21||48||4||27||31||F/R (2 y)||S||Yes|
|4||m||Herbst||13||14.5||20.5||47.5||6||27||33||R (4 y)||S||Yes|
|5||m||Herbst||13.5||15||19||46.5||4||27.5||31.5||R (3 y)||R (partial)||No|
|6||m||Herbst||13||14.5||20.5||47.5||6||27||33||No retention||R (total)||Yes|
|7||f||Herbst||13||14.5||20.5||48||6||27.5||33.5||R (2 y)||S||Yes (1 side)|
|8X||m||Herbst/extraction||13||15||22||48||7||26||33||F/R (4 y)||S||Yes|
|9||m||Herbst||12.5||14||20||45||6||25||31||R (2 y)||S||Yes (1 side)|
|10||m||Herbst||12||14||20||44||6||24||30||No retention||S||Yes (1 side)|
|11||f||Herbst||11||12.5||18.5||42.5||6||24||30||R (2 y)||S||No|
|12||m||Herbst||12.5||14||21||46||7||25||32||F/R (3 y)||R (1 side)||Yes|
|13||m||Herbst||12.5||14||21||45||7||24||31||R (2 y)||R (partial)||Yes|
|14||m||Herbst||12.5||14||22||45||8||23||31||R (2 y)||R (one side)||Yes|
|Summary||12 males||12 Herbst||12.5||14.3||20.4||46.1||6.1||25.7||31.8||4 No retention||9 Stable||12 Yes|
|Mean||2 females||2 Herbst/extraction||10 Retention||5 Relapse||2 No|
† F implies fixed retention with a mandibular lingual canine-to-canine retainer; R implies removable retention with an activator or a maxillary Hawley plate; F/R implies a fixed mandibular canine retainer in combination with a removable maxillary Hawley plate.
Treatment in all subjects was performed by an author (H.P.) using a banded type of Herbst appliance with a simple anchorage system that did not include brackets on any teeth. Since treatment of the original 22-subject sample was designed as a clinical experimental study, no further fixed appliance treatment after the Herbst phase was planned. However, due to major tooth irregularities after the Herbst therapy, 4 premolars were extracted in 2 subjects (patients 1X and 8X), and maxillary and mandibular multibracket appliances were placed for about 1 year. Furthermore, for tooth alignment in a nonextraction patient (patient 12), a maxillary multibracket appliance treatment phase was instituted for 6 months after the Herbst phase. In these 3 patients, multibracket treatment after the Herbst phase aimed to align the teeth after the Class I dental arch and overjet corrections were achieved by the Herbst appliance.
Retention after Herbst treatment, performed in 10 of the 14 patients, was inconsistent and of short duration (2-4 years). No retainers were used in 4 subjects ( Table I ).
Intraoral photographs of the dentition, mandibular dental casts, and lateral head films were analyzed at 4 occasions: T1, before Herbst treatment; T2, after treatment (12 months after the Herbst appliance was removed and the occlusion had settled); for the 2 extraction patients (1X and 8X), T2 implied that all analyses were done after removal of the multibracket appliance; T3, 6 years after treatment at an average age of 20 years when the radius epiphysis/diaphysis plate was closed (hand-wrist stage R-J, according to Hägg and Taranger ); and T4, 32 years after treatment at an average age of 46 years.
The treatment and posttreatment changes of different variables were analyzed during the following observation periods: T1-T2, treatment changes; T2-T3, early posttreatment changes; T3-T4, late posttreatment changes; and T2-T4, total posttreatment changes.
The following intraoral Kodachrome color slides (Eastman Kodak, Rochester, NY) from T1, T2, and T3 and digital color pictures from T4 were analyzed: frontal view photographs of the teeth in centric occlusion, and occlusal view photographs of the mandibular teeth.
The photographs were used for the assessment of the existence of gingival recessions and for the detection of bodily displaced incisors and canines. By visual inspection, a recession on any of the 4 mandibular incisors was diagnosed if the level of the labial gingival margin was not in line on all teeth or the gingival margin had moved more apically when comparing photographs from the different times of examination. Normally, the labial gingival margin of the mandibular canines is positioned a little more apically than that of the incisors; therefore, a gingival recession on the canines was diagnosed if the level of the gingival margin had moved apically when comparing photographs from consecutive times of examination.
Two experienced orthodontists (H.P. and an orthodontist working in an orthodontic practice) separately analyzed all the photographs. On disagreement, consensus was reached after a joint reassessment of the pictures.
The biometric mandibular dental cast analysis of the 14 subjects was performed according to the method used in a recently published article. The mandibular dental casts from T1, T2, T3, and T4 were digitally photographed using a standard setup. The pictures were then evaluated with measurement analysis software (FACAD; Illexis AB, Linköping, Sweden). A millimeter ruler was included in the photographic setup and used for calibrating the photographic illustrations of the casts.
The linear difference of the anatomic contact points of the mandibular incisors mesial to the canines was assessed by the mandibular incisor irregularity index of Little with the FACAD analysis software.
For the assessment of the incisor inclination changes during the different examination periods, mandibular incisor inclination in relation to the mandibular plane was measured.
Because of the small sample size, the data of all 14 patients were presented individually at T1, T2, T3, and T4. No statistical tests were performed.
With a 2-week interval, the precision of the method in registering changes in mandibular incisor inclination and tooth irregularity was assessed by double evaluations of 10 randomly selected head films and dental casts. The errors of the method, determined according to Dahlberg’s formula, were 1.0° (incisor inclination) and 0.8 mm (incisor irregularity).
Individual changes are shown in Table II .
|Patient||Incisor inclination (°)||Irregularity index (mm)||Gingival recessions (teeth), yes/no||Bodily displaced teeth, yes/no|
|2||95.0||99.5||96.5||95.0||6.7||10.3||16.1||16.9||No||43||31, 43||31, 43||No||43||31, 43||31, 43|
|10||99.0||104.5||98.0||97.0||1.4||1.1||7.0||7.6||No||No||32, 42||32, 42||No||No||32, 42||32, 42|
|11||91.5||93.5||91.0||92.0||3.2||4.3||7.4||5.3||No||No||32, 42||32, 42||No||No||No||32|
|14||104.0||105.0||104.0||104.0||2.9||2.3||3.8||6.4||No||No||33,43||33, 43||No||No||No||31, 41|
|Mean/summary||100.1||104.2||101.1||101.7||3.4||3.0||4.1||5.1||14 No||13 No 1 Yes||7 No 11 Yes||6 No 14 Yes||14 No||13 No 1 Yes||11 No 5 Yes||7 No 9 Yes|