Raffaele Schiavoni*, Vittorio Grenga*
* Private Practice in Orthodontics, Rome
The Herbst appliance has proved to be effective in the treatment of Class II malocclusions1-22. Different methods of stabilization of the telescope mechanism have been described by different authors. The first design proposed by Pancherz in 1979 proved to be difficult both in terms of construction and clinical management because of frequent breakage23-29. One of the easiest systems of stabilization was proposed by McNamara and it consisted of upper and lower acrylic splints (Figs. 1 a-c)30-33.
Diagnosis and treatment plan
A 12-years old female presented with the chief complaint of protrusive upper incisors and difficulty in closing her lips. Clinical examination revealed a convex, retrognathic profile, lip incompetence at rest and protrusion of the upper lip. The patient had a Class II, division 1 malocclusion with an overjet of 11 mm and an overbite of 3 mm. She was in the permanent dentition with an accentuated curve of Spee and a narrow upper arch (Figs. 2 a-f). Cephalometric analysis (Fig. 3) revealed retrusion of the mandible (SNPg 70,5Â°) with a skeletal Class II (ANPg 5,1Â°). Vertical parameters showed a hyperdivergent pattern of growth (SN/Go-Gn 38,9Â°, Ans-Pns/Go-Gn 29,3Â°). The upper and lower incisors were mildly protruded (1/Ans-Pns 117,7Â°, 1/Go-Gn 101,7Â°).
1. Obtain a symmetrical Class I occlusion without extractions;
2. Improve facial appearance by stimulating mandibular growth;
3. Avoid any extrusion of the posterior teeth of the mandible and reposition the upper incisors to allow for-nent dentition. Moreover the apward rotation of the mandible. pliance was well tolerated during meals and was never found any Treatment progress compliance problem. The appliance The first phase of treatment (9 was removed only for oral hygiene. months) involved the use of an acry-The construction bite was made with lic splint Herbst appliance. The the lower jaw protruded until the in-splints were not cemented due to cisors were edge to edge and then the possibility of maintaining good lowered to obtain a molar clearanoral hygiene and to perfect retention ce of 4-5 mm. The acrylic splints of the appliance due to the perma-were designed and built for even distribution of occlusal contacts (Figs 4 a-c). After nine months the sagittal correction was achieved and the patient presented with a posterior open bite of 3-4 mm (Figs 5 a-c). The anchorage of the Herbst appliance inhibits the dental eruption and spontaneous interocclusal setting that would normally occur. Therefore, a posterior open bite is usually present when the acrylic splints are removed. The Herbst appliance was removed and upper arch was fully bonded (.022 slot MBT prescription) and a .016 NiTi archwire was applied. The patient was instructed to wear the lower splint full time included during the meals in order to avoid the posterior shifting of the lower jaw reaching the maximum intercuspation (Figs 6 a-c). Archwire sequence of the upper arch was .016 NiTi - .019 x .025 NiTi - .019 x .025 SS. After six months the posterior open bite was closed by counterclockwise rotation of the lower jaw and the lo-wer splint was discontinued (Figs 7 a-c). At this time the lower arch was fully bonded for final alignment and coordination with the upper arch. After 22 months of treatment the patient was debonded. Two essix full coverage retainer were fitted to be worn nighttime.
Figs 6 a-c Upper arch bonded and lower splint still in place.
Figs 7 a-c Posterior open bite closed by counterclockwise rotation of the mandible.
The patient?s facial appearance improved even though lip incompetence at rest was still present. Patient and her parents were totally satisfied with the result. A full Class I cuspid and molar relationship were achieved (Figs 8 a-f). Cephalometric nalysis (Fig. 9) revealed a normalization of the sagittal discrepancy (ANPg 2,8Â°) with control of clockwise mandibular rotation (SN/Go-Gn 38,9Â°, Ans-Pns/Go-Gn 26,4Â°). The inclination of the palatal plane increased (SN/Ans-Pns from 9,6Â° lower incisors were mildly proclined (1/Go-Gn from 101,7Â° to 109,5Â°) as expected in all the kinds of Herbst stabilization11,51,52.
Diagnosis and treatment plan
A 12 years old female presented with the chief complaint of crowding of upper front teeth with upper malocclusion with an overjet of 6,3 mm and an overbite of 4,6 mm. She was in permanent dentition with no crowding in the lower arch and an accentuated curve of Spee due to the infraocclusion of the posterior teeth of the lower arch (Figs 10 a-f).
Cephalometric analysis (Fig. 11) revealed a dental Class II malocclusion with no skeletal discrepancies in the sagittal plane (SNA to 12,5Â°) probably due to the intrusion forces produced by the telescope mechanism on the posterior segment of the upper dentition. The ramus height also increased (from 39,1 mm to 40,2 mm) in agreement with the theories of condylar displacement and growth, left cuspid out of the arch. Clinical examination revealed a convex, mild retrognathic profile with a well pronounced labiomental fold. The angle between submandibular plane and prethyroid plane (cervical angle) was accentuated.
The patient had a Class II, division 1 82,2Â°, SNPg 77,4Â°). Vertical parameters showed a brachyfacial pattern of growth (SN/Go-Gn 26Â°, Ans-Pns/Go-Gn 17Â°). Lower incisors were mildly proclined (1/Go-Gn 110Â°).
1. Obtain a symmetrical Class I occlusion without extractions;
2. Improve facial appearance unrolling lower lip and creating a more pleasant cervical angle;
3. Allow the extrusion of the posterior lower teeth to correct the curve of Spee and to improve the overbite increasing the posterior vertical dimension.
The first phase of treatment involved the use of an acrylic Herbst appliance similar to case one both for the construction and the clinical ma-nagement (Figs 12 a-c). After nine months the sagittal correction was achieved and the patient showed a posterior open bite of 3-4 mm. The Herbst appliance was removed and upper arch was fully bonded (.022 slot MBT prescription) and a .016 Ni-Ti archwire was applied (Figs 13 a-c). Contacts were present between left and right second molars, so in the next appointment it was possible bond all the lower arch to enhance the eruption of the lower posterior teeth increasing posterior vertical dimension (Figs 14 a-c). Archwire sequence of the upper and lower arches was .016 NiTi -.019 x .025 NiTi - .019 x .025 SS. The final phase of treatment involved the use of upper and lower SS .016 arch-wires and intermaxillary elastics from upper second bicuspid to lower second molar to obtain optimal intercuspation between upper second bicuspid and the embrasure between lower second bicuspid and lower first molar (Figs 15 a-c).Total treatment time was 24 months. Two essix full coverage retainer was applied to be worn nighttime.
The patient ?s facial appearance improved not only for the normalization of the labio-mental fold but also for the reduction of the cervical angle. A full Class I cuspid and molar relationship was achieved (Figs 16 a-f). Cephalometric analysis (Fig. 17) revealed no significant variations in the sagittal parameters. Also in this case the palatal plane tilted backward and upward (SN/Pns-Ans from 9,1Â° to 10,8Â°) and the ramus height increased from 43,3 mm to 46 mm.
The Herbst appliance, stabilized with acrylic splints according to the McNamara design, is easy to construct, not expensive and well tolerated by the patients. The frequency of complications and the breakages of this kind of appliance are very rare when not absolutely absent. Laboratory and chair time are reduced.
For all these reasons in an orthodontic practice the management of this kind of appliance is never critical.
Moreover if the appliance is not cemented the oral hygiene is well maintained. At this stage an important key point is to induce in the patient a strong motivation to wear the appliance 24 hours per day meals included. The patient can remove the appliance only for oral hygiene. If the clinician is not sure of the patient cooperation, the appliance must be cemented. The use of the Herbst appliance stabilized with acrylic splints in different growth pattern Class II patients, induce always the same occlusal aspect at the end of Herbst phase: a posterior open bite. The next phase of treatment (posterior open bite management) can be modulated by the clinician in order to obtain better aesthetic and clinical results. In the hyperdivergent growth pattern the main goals are to reduce or better to control the vertical dimension and to induce a counterclockwise rotation of the mandible with an increase in the projection of the chin on the sagittal plane. In these cases the proclination of the upper incisors and/or the intrusion of the lower incisors together with transversal coordination of the arches allow this kind of rotation inducing the closure of the posterior open bite and minimizing the extrusion of the posterior teeth. With a normal growth pattern the main goal is to increase vertical dimension to get a lower anterior third of the face esthetically more pleasant. In these cases this can be achieved by inducing dentoalveolar vertical growth of the posterior segment and for that closing the posterior open bite and give a vertical support to the new condyledisk-ramus situation.
The Herbst appliance is useful in the correction of both skeletal and dental Class II malocclusions. The splint type of stabilization permits a vertical distraction of the condyle with a consequent increase of the mandible ramus length and the creation of a posterior open bite that the clinician can manage to obtain optimal results in patients with different types of growth. Unfortunately it appears to be impossible to avoid the proclination of the lower incisors confirming the difficulty to manage the incisors inclination with all types of Herbst stabilization11,51,52.
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