the aim of this review is to evaluate the effectiveness of using Herbst Appliance in II class malocclusions caused by a backward mandibular position.

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Skeletal and dental effects of Herbst appliance in II class malocclusion: a systematic review

 

Abstract: the aim of this review is to evaluate the effectiveness of using Herbst Appliance in II class malocclusions caused by a backward mandibular position.

Materials and method: for this review scientific articles found in data base like PubMed, EMBASE, web of Science have been taken into account and the research has been done with the following keywords: II class, Herbst, effects, fixed functional appliance.

Discussion: Interesting result have been obtained by analyzing several studies. A significant decrese has been misured in SNA and ANB, and an increase of SNB,  Go-Gn, SNA-Gn as skeletal effects and a decrese of overjet as the result of dento-alveolar effects.

Conclusions: Herbst appliance is an efficient system to treat II class, both of skeletal and dental effects.

 

Introduction 

There are different type of II class: caused by a protrusion of the maxilla, a retrusion of the mandible,  or both. In the Caucasian population the 85% of II class are caused by a mandibular retrusion. Functional appliances are very used in the treatment of this type of II class and Herbst appliance represents a fixed functional one. Because of its fixed structure it is the only functional appliance that doesn’t need a collaboration, so its effects are more predictable. This is the reason of it hight success rate.

By the cephalometric analysis SNA, SNB, ANB angles and Witts index indicates a II class caused by a mandibular retrusion.

Herbst appliance was developed by Emily Herbst in the early 1900s and it was reintroduced by Pancherz in the late 1970 (1).

Usually the Herbst appliance is attached to bands  on upper molars and lower premolars or molars (banded Herbst design) or cast splints (cast splint Herbst design). The appliance can also be attached to stainless steel crowns (stainless steel crown Herbst design) and to acrylic splints (acrylic splint Herbst design) which, in addition to the banded an cast splint designs, form the four basic designs of the Herbst appliance . Other Herbst variation include space-closing Herbst designs, cantilevered Herbst designs, and expansion designs.

In all this structure the appliance has bilateral telescope anchored to lower and upper arch and so it keeps mandible in protrusion 24h/die.

Each telescopic mechanism consist of a tube and a plunger which fit togheter, two pivots, and two locking screws.

The appliance allow the mandible to perform not only opening movements but also small lateral movements, mainly because of the loose fit of the tube and plunger at their sites of attachement.

At the biginning of 2000s a new type of bands (Rollo bands) were introduced into the market (2), similar to a preformed crown with a hole in the chewing part that permits the correct cure of the cement so to reduce the countless fractures of the structure. In fact the main problem of the Herbst is this one. Moreover it coud lead to soft tissue injuries, pivot breakege, lower splint breakege, band or component debonding, demineralization (acrylic splint Herbst design) and proinclination of lower incisors.

On the other hand these complications are surmountable: the possible fracture with the use of Rollo band and vetroionomeric cement, decubitus of soft tissue with a reduction of lateral movements and composite on the pivots, the hypomineralization with an accurate hygiene and fluoride sessions, the proinclination of the lower incisors with the use of mini screw that can increase skeletal anchorage and reduce dental effects.

There are three types of thelescopic Herbst:

1. Herbst Miniscope
2. Herbst HTH
3. Herbst MTH

Herbst miniscope guarantees  6 degrees of lateral movement, Herbst HTH 20 degrees, and Herbst MTH 12 degrees. Herbst MTH was created to reduce the problem of decubitus ulcers and fractures of the structure that could occur with the other two models with their laterality.

It was created by Antonio Manni and it is caracterized by Rollo band and acrylic lower splint (3).

Because f its dental support, Herbst appliance caused not only skeletal effects but olso dental effects.

 

Materials and method

For this rewiev scientific articles found in data base like PubMed, EMBASE, web of Science have been taken into account and the research has been done with the following keywords: II class, Herbst, effects, fixed functional appliance.

Several studies have been published about the use of Herbst appliance; in this review are not considered case report concerning the standard Herbst stucture but only the modified one (with miniscrew). As the result of this analysis only 20 full articles have been selected from 50.

 

Review

Many studies demonstrate the effectiveness of the Herbst device (4,5,6,7).

According to Pancherz et al. (8,9) it determines dental effects like the distalization and intrusion of the upper molar, the retroinlination and extrusion of the upper incisor, the mesialization and extrusion of lower molars, proinclination and intrusion of the lower incisors.

The skeletal effects are the reduction of the maxillary growth (headgear effect), increasing in growth of mandible, the renew of the articular fossa, a clockwise rotation of the occlusal plane, a bit increase in ante-inferior vertical growht, that is reduced in the acrylic splint Herbst than in the bands one.

According to Xin Yang et al. (10) there is a decrease of  0.56 of SNA angle and 1,08 of ANB, an increase of 1.06 for SNB. The decrease of the overjet is about 4,8 mm, and for the overbite 1,69.

The  increse of Co-Go is 1,76 mm, Co-Gn  1,74 mm, the II class molar relationship decreas of 5,70 mm, Apoint- OLp of 0,52 mm and Pg-OLp increase of 1,45.

The upper incisor’s retroinclination changes from 3,2° to 8,2° at the end of the treatment; the lower incisor’s proinclination changes from 5° to 10,8° (11).

This great proinclination isn’t connected with any lower iincisors recessions and can be reduced thanks to miniscrew.

According C. Luzi et al.(12,13), two miniscrew (6 mm long, 1.5 mm in diameter) inserted between lower first and second premolars on each side can increase skeletal anchorage and reduce lower incisors proinclination.

The TADs were tied tigthly to the customized hooks on the Herbst appliance with 0,12 stainless steel ligatures. This rigid connection provided indirect slkeletal anchorage to the mandibular basal bone, with the aim of avoiding any dentoalveolar compensations in the lower dentition during the bite-jumping period.

 

Conclusion

Compared to other removable functional appliances (14,15,16), the Herbst appliance is fixed to the teeth and thereby is able to work 24 hours a day. In addition, the duration of treatment is relatively short (7-9 months), while the removable functional appliances usually require 2-4 years, thus making the Herbst appliance suitable for postpuberal patients and young adults. The main advantages of the Herbst appliance include the short and standardized treatment duration, the lack of reliance on patient compliance to attain the desired treatment effects, the easy acceptance, and patient tollerance. In addition, the distalizing effects of the maxillary first molars contributes to the avoidance of extractions in class II malocclusions with maxillary crowding or maxillary surgery in patients at the end of their growth. Other advantages include the improvement in the patient’s profile immediately after placement, the absence of removable parts, the manteinance of good oral hygiene, the simultaneous use of fixed appliances, and the ability of modify the appliance for various clinical applications.

So with an appropriate use and indications and in right patients  it is considered a valid appliance in the treatment of II class.

 

References

1. ”L'ortodonzia e i suoi dispositivi”- Elsevier Masson ed., F. Montagna, N. Lambini,V. Piras, G.    Denotti.
2. A. Manni, M. Cozzani, L. Mazzotta, V. P. Fiore, S. Mutinelli. Acrylic splint Herbst and Hanks telescoping Herbst: A retrospective study of emergencies, retreatments, treatment times and failures. Elsevier Maisson, 2014.
3. A. Manni, M. Cozzani, S. Mutinelli, C. Cerruto, P. Giraudo, R. Romano. Comparison of complications in the conventional telescopic Herbst rod and tube and Manni telescopic Herbst
4. .Paulsen HU, Jarle A., Bakke M., Herskind A., C-T scanning and radiographic analysis of temporomandibular joint and cephalometric ananlysis in a case of Herbst tretment in late puberty Eur J Orthod 1995;17:167-175
5. Thiruvenkatachari B., Harrison J.E., Worthington H.V., O’Brien K.D. Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children. Cochrane Database Syst. Rev. 2013; (11):CD003452. [PubMed]
6. Pancherz H., Stickel A. Position changes of mandibular condyle in Herbst treatment, radiographic study. Inf. Orthod. Kieferorthop 1989;21:515-527.
7. M. Portelli, A. Militi, M. Cicciù e coll. No compliance correction of class II malocclusion in growing patients with Herbst appliance: a case report. Open dent. J. 2018, 12:605-613.
8. Pancherz H, Hansen K. Occlusal changes during and after Herbst treatment: a cephalometric investigation, Eur J Orthod. 1986; 8:215-228
9. Pancherz H, Hansen K., Mandibular anchorage in Herbst treatment. Eur. J. Orthod.1988;             10:149-164
10. Xin Yang, Y. Zhu, H. Long, Y. Zhou, F. Jian, N. Ye. The effectiveness of the Herbst appliance for patients with class II malocclusion: a meta-analysis. E. J. Of Orthod 2015 1-10.
11. . Hansen K, Koutsonas TG, Pancherz H. Longterm effects of Herbst treatment on the mandibular incisor segment: a cephalometric and biometric investigation. Am J Orthod Dentofacial Orthop 1997;112:92-103
12. C. Luzi, V. Luzi, B. Melsen. Mini implants and the efficiency of Herbst treatment :a preliminary study. Progress in Orthod 201314:21
13. C. Luzi, V. Luzi, B. Melsen, P. Carletti. Case report: the miniscrew-anchored  herbst. JCO, 2012. vol XLVI, n°7.
14. Schiavoni R, Grenga V., Non extraction treatment of a high angle class II case with a modify Herbst appliance, J Clin Orthod 1994;28:453-457
15. Andresen et al, Revisione sistematica della relazione tra eventi traumatici dentali ed entità dell'overjet, 1999 E. J. Of Orthod. 1989,21:503-518
16. Kevin O' Brien, PhD, Msc, J. Wright,A. Murray et al. Effectiveness of treatment for class II malocclusion with the Herbst or Twin Block appliance: a randomized, controlled trial. Am J Orthod Dentofacial Orthop 2003;124:128-37

 

 

 

 

 

 

 

 

 

 

 

Source(s) of Funding

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PubMed, EMBASE, Web of Science

Competing Interests

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orthodontic, medicine