Although Emil Herbst was the first to use a FFA as early as 1905, its popularity in clinical applications has only been established in the last three decades. The FFA has gone through an evolutionary transition in design and uses from its first version of a rigid telescoping system (rigid FFA), that is, the Herbst’s appliance, followed by flexible versions (flexible FFA) to more recent appliances systems which are relatively flexible, yet rigid enough (hybrid type) to sustain forward mandibular position. The mesial ends of most FFAs receive anchorage from mandibular dentition. Hence, it is challenging to control unwanted dental effects ( Fig. 64.1.i ).

Herbst’s appliance.

(A) Components of type I Herbst’s appliance. (B) Banded Herbst’s appliance.

FFAs are integral components of orthodontic armamentarium, used in both compliant and non-compliant patients for their enhanced effectiveness in correcting malocclusion in a shorter duration. Most FFAs are variations of a telescopic mechanism. The FFA is attached bilaterally to the maxillary molars on their distal end and mesially to the mandibular arch to hold it in a forward posture. FFAs with numerous modifications are available in the market; however, they can be broadly grouped into three categories ( Table 64.1 ).

Current thinking on the use of the FFA is that its mesial end is connected to a temporary anchorage device (a bone plate) placed in the body of the mandible. This is called an implant-supported FFA. The implant or plate-supported FFA derives the anchorage from the mandible, so unwanted dental changes are minimised or eliminated altogether. Digital technology and metal 3D printing have recently been integrated into FFA, resulting in digital planning and metal-printed Herbst’s appliances becoming a clinical reality ( Fig. 64.1.ii ).

A metal-printed Herbst’s appliance.

(A–C) Steps in digital design. (D) Metal-printed Herbst’s appliance in the mouth.

Source: Reproduced with permission from Graf S, Tarraf NE, Kravitz ND. Three-dimensional metal printed orthodontic laboratory appliances. Semin Orthod. 2021;27(3):189–93. https://doi.org/10.1053/j.sodo.2021.09.005 .

The FFA has several advantages over a removable functional appliance.

• 1.

  FFAs have the advantage of generating continuous stimuli for mandibular growth without any interruption.

• 2.

  FFA is relatively smaller, allowing better adaptation to the oral cavity. Current understanding regarding the use of the FFA indicates that its mesial end is connected to a temporary anchorage device, specifically a bone plate positioned within the mandible. This arrangement is commonly referred to as an implant-supported FFA.

• 3.

  FFAs successfully treat class II malocclusion in a shorter period with less need for patient cooperation.

• 4.

  Their most significant advantage is for those patients who report for orthodontic treatment at the fag end of the facial growth. FFAs, being 24-h wear appliances, produce a rapid sagittal correction, taking maximum benefits from a short span of remaining skeletal growth. This seems to be the most appropriate indication of FFA besides the non-compliant patient.

The FFAs are generally contraindicated in patients with vertical growth patterns, anterior open bite and where lower incisors are proclined. Most appliances cause proclination of the mandibular incisors, which may not be desirable in subjects with large incisor mandibular plane angle (IMPA). Patients with susceptible root resorption are also not good candidates for extra loading of forces generated from FFA. Implantable devices now allow functional appliances to be attached directly to the mandible, eliminating dental malocclusion contradictions.

It is characterised by a fixing system to the crowns or bands ( Fig. 64.1.i ) or to the wire framework (splint design, Fig. 64.1.iii ) through the use of screws. This is the most commonly used design of the Herbst’s appliance. It is necessary to solder the axles to the molar bands or crowns and then fix the tubes and plungers with the screws. Herbst’s appliance does not permit lateral jaw movements. It is challenging to align the right and left axles, making them susceptible to breakages. Breakages are common in Herbst’s appliances.

(A) Splint design of Herbst’s appliance. (B) Components of Type IV Herbst’s appliance. The ball and socket joint are held together with a C clip.

It has a system that permits its fitting directly onto the arch wires using special screw locks. The rigid appliance, fixed on relatively less rigid arch wires, has several drawbacks. It causes difficulties in lateral movements of the jaw, and stress fracture of the arch wires is common.

It was designed to permit greater flexibility of the mandibular movements through a ball and socket system at the maxillary end. The screw is replaced with a unique locking clasp. The main disadvantage was the loosening and breakage of the locking clasp ( Fig. 64.1.iv ).

Herbst’s appliance attached with crowns and transpalatal bar.

CBJ (Ormco, Glendora, USA) were installed with a horizontal advancement of 6 mm in this case.

Source: Cited and reproduced from Brito DBA, Henriques JFC, Fiedler CF, Janson G. Effects of Class II division 1 malocclusion treatment with three types of fixed functional appliances. Dental Press J Orthod. 2019 Sept–Oct;24(5):30–9. DOI: https://doi.org/10.1590/2177-6709.24.5.030-039.oar .

Variations on the Herbst’s appliance and similar systems, utilising ball attachments, have appeared to:

• 1.

  Improve patient comfort and acceptance.

• 2.

  Minimise clinical problems such as solder failure and breakages.

• 3.

  Reduce the frequency of emergency appointments.

• 4.

  Allow lateral mandibular movements.

• 5.

  Allow easy application in splints for correction in mixed dentition.

Other Herbst’s type appliances include:

• 1.

  The cantilevered bite Jumper (Ormco 1717 West Collins Avenue, Orange, CA 92867).

• 2.

  MALU Herbst’s appliance (SAGA Dental Supply A/S, post-box 216, Kongsviner, Norway).

• 3.

  Flip-Lock Herbst appliance (TP Orthodontics, Inc., 100 Center Plaza, LaPorte, IN 46350).

• 4.

  The Magnetic telescopic device ^, (Ritto, 1997, 1999).

Herbst’s appliance is supplied in a pack consisting of a pair of tube sleeves and a plunger that fits together. There are four axles and corresponding screws, one set for each quadrant. To distinguish the right side of the tube from the left side, place it in position buccal to crown on the maxillary first molar. The correct tube at its mesial end is directed slightly inwards ( Fig. 64.1.iii ). Pancherz used soldered axles on the maxillary first molars and mandibular first premolar bands, but that is always not possible, especially in mixed dentition.

Alternatively, a splint design with acrylic coverage over several teeth may be suggested. The acrylic cap over the lower incisors helps in limiting the amount of proclination of the incisors during treatment Fig. 64.1.iii .

After impressions and duplicate sets of dental casts, the bite is recorded in a class I molar relationship. There is no universal agreement on the ‘ideal’ amount of forward position of the mandible for bite recording. Most clinicians agree on end-to-end incisor bite registration in patients with an overjet of approximately 7 mm or less. Suppose the overjet is greater than 7 mm. In that case, a bite registration representing half of the overjet distance is obtained for initial appliance fabrication. Then, the Herbst’s appliance is reactivated every 2–3 months in increments of 2–3 mm until an end-to-end incisal relationship is achieved.

The wax bite is transferred to the working models which are articulated on semi-adjustable or a hinge articulator. The wire framework on upper and lower working models is done similar to the one shown by Howe and later described by McNamara. ^,

Herbst’s appliance in the mouth is not comfortable to experience. Once fitted, the patient is unable to bring the mandible back in centric occlusion. For the first few days, signs of muscle pain appear in and around over the jaw muscles and around temporomandibular joint (TMJ). There are also difficulties due to altered speech and mastication. Most patients adjust to the appliance within 1–2 weeks.

The appliance will produce rapid changes in occlusion within 3–6 months, showing correction of class II malocclusion to class I occlusion. Clinically, signs of maxillary molar distalisation, which is termed the ‘Headgear Effect’, can also be visualised. After 6–9 months, the appliance is removed, and the second phase of treatment is started with fixed appliance therapy. The purpose of the fixed appliance phase is to retain the buccal occlusion and detail the posterior occlusion.

Herbst’s appliance with fixed multibracket therapy can be successfully used as an alternate appliance combination for non-surgical, non-extraction treatment of class II division I subjects in early and late adulthood. Ruf and Pancherz, in subjects ranging from 15.7 to 44.4 years (mean 21.4 years), found successful outcomes in the short-term investigation. Both skeletal and dental changes contributed to class II correction. Overjet correction occurred mainly in dental changes (13% skeletal and 87% dental). Similarly, molar correction occurred with 22% skeletal and 78% dental changes.

In approaches where the duration of Herbst’s appliance use was doubled, followed by fixed appliance therapy using a control group data, Tomblyn et al., in a mixed sample, reported that a majority of changes measured on lateral cephalogram were dentoalveolar in nature (62%). The changes attained during Herbst’s therapy were maintained during the fixed appliance phase of treatment.

Yang X et al., based on meta-analysis of 12 studies, concluded that Herbst’s appliance is effective in the management of class II div 1 treatment and significant improvements do occur in in dental relations and skeletal changes on Co-Gn, which represents an increase in the length of the mandible.

Maxillary growth: Herbst’s appliances have been found to have a minimal or insignificant restraining effect on maxillary growth. However, it significantly affects the maxillary molar, causing it to drive and tilt distally. The distalising effect on the maxillary molars is a by-product of the FFA anchored to the molars and is often called the headgear effect.

Mandibular growth: The main therapeutic effect of Herbst’s appliance is an enhancement of the sagittal mandibular growth, while vertical growth is unaffected by this treatment. Pancherz reported that with the banded Herbst’s appliance, the sagittal molar correction was contributed by skeletal and dental changes. The contribution of skeletal changes was 41%, and the remaining 59% was due to dentoalveolar changes in young adolescent group.

Overjet: The overjet correction was 56% due to skeletal changes and 44% due to dentoalveolar changes. Dentoalveolar changes include lower incisor proclination, maxillary molar distalisation and intrusion. These changes are similar to those produced by high-pull headgear.

Bite opening: Vertically, the overbite is reduced. This occurs by an intrusion of lower incisors and an enhanced eruption of lower molars.

Effects on the craniofacial skeleton: Short-term cephalometric changes produced by splint design Herbst’s appliance in growing subjects have shown that correction of molar relation was mainly due to forward mandible positioning, some forward shift of lower molar and distal drive of upper molars. Appliance therapy results in an increase in mandibular length, reduction in ANB angle and increase in anterior facial height. Studies have documented significant increases in mandibular length compared to untreated controls that ranged an average of 2.0 mm for a 6-month period for the banded appliance and 3.0 mm for a year treatment period for the acrylic splint Herbst’s appliance.

During the post-treatment period, most of the mandibular morphological changes revert to normal, and no long-term influence of Herbst’s treatment on mandibular growth can be verified. Its effects on the maxilla are similar to that of a high pull headgear.

Herbst’s treatment is especially indicated in the permanent dentition at or just after the pubertal peak of growth so that good occlusion and inter-digitation can be achieved. Long-term effects of Herbst’s treatment on TMJ have been investigated in clinical and MRI studies without any adverse findings. On the contrary, Herbst’s appliance could prove useful in patients with anterior disc displacement. ^,

A systematic review reported that a splint type of Herbst’s appliance in treating adolescents significantly improves class II division I malocclusion and changes in the facial skeleton. The use of the splint type Herbst’s appliance in treating adolescents with class II division 1 malocclusion resulted in increased anteroposterior length of the mandible, increased vertical height of the ramus, increase in lower facial height, mandibular incisor proclination, mesial movement of lower molars and distal movement of upper molars. The appliance caused a significant decrease in the inter-maxillary discrepancy improvements of overjet and overbite. The appliance does not produce significant changes on the upper incisors. The upper molars are significantly more retruded (1.5–5.4 mm), slightly intruded and retroclined 5.6 degrees after treatment.

The long-term stability and effects of Herbst’s appliance:

The long-term stability and effects of Herbst’s appliance have been investigated. Based on a systematic review and meta-analysis of 20 of the 76 identified appliances, including Herbst and Twin Force Bite Corrector, Bock NC et al. concluded that little information is available on the stability of the results after FFA therapy except for Herbst’s appliance. Results achieved through Herbst’s appliance therapy show good stability. Good stability of dentoskeletal is reported though evidence is low. Except for the Herbst’s appliance, evidence for other FFAs is not available on long-term stability.

Herbst’s treatment showed good occlusal stability 2.5 years after treatment in adults with class II division 1 malocclusions.

Treatment with a Herbst’s appliance seems to offer stable correction of the sagittal occlusal relationships in Class II patients with retrognathic or prognathic facial types, with the vertical changes being more pronounced in the prognathic cases.

The skeletal maturation and growth changes in the craniofacial region continue during adulthood and beyond. The classical study by Pancherz on 32-year follow-up dentoskeletal structures is the most interesting. The sample of 22 consecutively Herbst-treated children in the 12–14 age group was followed 6 years and 32 years after treatment. Six years after treatment, growth of the craniofacial skeleton continued, which is represented by a significant increase of the angles SNB and a decrease of the ANB. In the analysis of the sagittal, changes in the occlusion (linear measurements) showed significant forward growth of the mandible (6.1 mm; P<0.001) and the maxilla (3.0 mm; P<0.01). While angular changes did not occur during the following 24 years, significant sagittal growth occurred in the mandible (2.8 mm; P<0.01) and the maxilla (3.1 mm; P<0.01). In a total of 32 years of post-treatment, continuous forward growth of the mandible (8.9 mm; P<0.001) and the maxilla (6.1 mm; P<0.001) occurred. These changes in skeletal growth of the craniofacial region point out that clinicians should be watchful of the growth adversely affecting occlusion stability ( Figs 64.2 and 64.3 ).

Pre-treatment records:

Extraoral and intraoral photographs and lateral cephalogram.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI: 10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID: PMC6018450.

Intraoral right photograph showing Herbst’s appliance placement.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2): 87–109. DOI: 10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID: PMC6018450.

Intraoral right photograph showing fixed appliance.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Post-treatment records:

Extraoral and intraoral photographs and lateral cephalogram.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Followup records at 10 years.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

(i) Cephalometric tracings superimposition on the cranial base (black = initial; blue = after Herbst’s appliance; red = treatment completion; green = 10 years after treatment completion). (ii) Maxillary superimposition (ANS-PNS registered at ANS). (iii) Mandibular superimposition (Xi-Pm registered at Pm).

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Pre-treatment records:

Extraoral and intraoral photographs and lateral cephalogram.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Intraoral right photograph after Herbst’s appliance placement.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2): 87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Intraoral right photograph showing fixed appliance.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Post-treatment records: Extraoral and intraoral photographs and lateral cephalogram.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

Followup records at 5.5 years

(i) Cephalometric tracings superimposition on the cranial base (black = initial; blue = after Herbst’s appliance; red = treatment completion). (ii) Maxillary superimposition (ANS-PNS registered at ANS). (iii) Mandibular superimposition (Xi-Pm registered at Pm). (iv) Extraoral and intraoral photographs.

Source: Moro A, Borges SW, Spada PP, Morais ND, Correr GM, Chaves CM Jr, Cevidanes LHS. Twenty-year clinical experience with fixed functional appliances. Dental Press J Orthod 2018;23(2):87–109. DOI:10.1590/2177-6709.23.2.087-109.sar. PMID: 29898162; PMCID:PMC6018450.

In a study on samples of actively growing patients treated with MPA IV for a period of 6 months, a significant reduction in overjet overbite and a considerable improvement in the facial skeletal profile was noted. Class II correction is contributed by a combination of skeletal changes (57.24%) and dental changes (42.76%). Mandibular length is increased to an average of 2.0 mm. Overjet correction is primarily due to proclination of the lower incisors, lingual tipping of upper incisors and skeletal changes in the mandible. An uprighting and distalisation of the upper molars also contributed to the molar correction. The most unwanted effect is the flaring of lower incisors, which may be detrimental to periodontal health, more so if there is a proclination of incisors/pre-existing large IMPA.

The introduction of JJ, a spring-loaded device covered with vinyl-coated tubing and provision of attachments to the upper molar tube and to the lower arch wire in the canine premolar region, was a significant change from traditional rigid Herbst’s appliance. The main advantage of FFFA JJ is its flexibility, which allows the patient to close in centric relation and efficiently perform lateral movements. JJ is used in combination with fixed appliance therapy. It is known to cause a rapid correction of class II relations, with a major contribution from dental changes. It causes a significant increase in IMPA, which is not desired ( Fig. 64.6 ).

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