Received 4 December 2014; accepted 7 May 2015; published 12 May 2015

ABSTRACT

The continuously growing esthetic awareness for the facial appearance and the spreading of information about the possibilities of adult treatment by public media result in an increase of adult patients which seek orthodontic treatment to improve their facial esthetics. In general, these patients show such a severe skeletal deformity that it is detectable even by non-experts because of its extraoral manifestation, which is the main motivation for treatment. Because of the nature of these deformities and because of the lacking growth usable for therapy the only promising treatment for these patients is the combined orthodontic-surgical approach. Besides a stable and functional occlusion with physiologic position of the condyle, the goals of treatment are the improvement of the dental and, above all, facial esthetics since the patient judges the success of treatment mostly by the extraoral appearance. The dentofacial appearance must be defined prior to treatment to plan the individual right approach in knowledge of the different treatment possibilities for Angle Class II deformities and thus be able to reach for both sides―patient and orthodontist― satisfying result. With this article, a systematic therapy concept to treat patients with Class II deformities and skeletal deep bite with a short lower face (short face syndrome) under consideration of the soft tissue analysis is presented.

Keywords:

Cephalometrics, Facial Proportions, Lower Face Height, Skeletal Deep Bite, Short Face Syndrome, Lengthening of the Lower Face, Bilateral Sagittal Split Osteotomy, Mandibular Advancement, Splint Therapy, Lateral Open Bite

1. Introduction

Dentoalveolar compensations can mask or correct a great number of minor deformities, but extensive sagittal corrections require more aggressive measures. Depending upon the extent of the problem and the timing, treatment modalities for Class II correction could be:

1) A causative approach in the form of influencing the growth components. Functional appliances for the ventral development of the mandible and simultaneous growth inhibition of the maxilla in the sagittal and vertical direction can be used [1] -[7] .

2) Manipulation of the dentoalveolar complex to gain space. The overjet can be reduced by distalisation of first molars into Class I followed by retraction of anterior teeth [8] -[10] .

3) Space gaining by extraction. Either all four premolars or just two maxillary premolars can be extracted in order to achieve a functional occlusion with Class I canine relationship [11] .

4) Orthognathic surgery to address the skeletal deformity if the treatment goals cannot be reached with first three possibilities listed above [12] -[14] .

In order to employ any of these above alternatives the correct diagnosis must be made followed by case-spe- cific treatment goals. Individualized treatment plan is based on studies of records such as facial photographs, panoramic radiographs, cephalograms, functional analysis, casts along with the assessment of patient’s motivation for treatment.

2. Patients’ Motivation for Orthodontic or Sugical Treatment

Numerous reports of patient motivation for orthodontic treatment can be found in the literature. Many of these studies investigate the impact of variables such as age, gender or social status on patients’ decision to seek treatment. It appears that the motivation and satisfaction factors vary among the individuals. For example, studies of Flanary [15] , Jacobson [16] and Kiyak [17] with respect to motivation, expectation and satisfaction show that 79% to 89% of the patients [18] [19] who were treated with orthognathic surgery received this form of treatment for esthetic reasons rather than functional. Moreover, their motivation for treatment was driven by the extent of the facial deformity. Kiyak also found that more women than men articulated their wish to improve their facial esthetics. It is noteworthy that patients after orthognathic surgery value esthetic motivations much higher than before, in contrast to functional factors [20] . The orthodontist must formulate a set of treatment goals to fulfill the optimal functional and esthetic demands of the individual. A purely occlusion oriented therapy may not be necessarily conducive to a facially esthetic satisfying result. A comprehensive analysis of the facial soft tissue relationships therefore, is key to optimal treatment. Patients judge the treatment result primarily by the improved extraoral appearance [5] [15] -[19] [21] -[26] .

3. Harmonic Relations of the Face

In the esthetic face the three vertical elements are distributed harmoniously. The total facial height (Trichion or hairline to soft tissue Menton; T-Me') is composed of 1/3 upper―(Trichion-Glabella; T-G'), 1/3 mid―(Glabella- Subnasal; G'-Sn) and 1/3 lower face (Subnasal-soft tissue Menton, Sn-Me') [12] [13] [27] -[34] (Figure 1(a), Figure 1(b), Figure 2(a), Table 1). Some authors describe the proportions as follows: The mid-face accounts for 47% (soft tissue Nasion-Subnasale) and the lower face (Subnasale-soft tissue Menton) for 53% of the face height [35] . In the harmonic lower face (Subnasal-soft tissue Menton; Sn-Me') there is a ratio of 1:2 between the distances from Subnasale-Stomion (Sn-Stm) to Stomion-soft tissue Menton (Stm-Me') (Figure 2(b), Table 1).

A harmonious soft tissue relationships is a reflection of the harmony of the underlying skeletal structures. This was described by Burstone in 1958 [27] and later modified by Legan and Burstone [33] . The skeletal mid face (N-Ans) is made of 45% and the lower face (Ans-Me) of 55% (Figure 2(c), Table 2).

4. Problem

The above-described harmonic division of the face can be disturbed by a variety of factors. A disharmony of the skeletal structures can, but not necessarily, influence the soft tissue profile. Understanding this fact is critical to analysis, diagnosis and treatment planning. The harmony of facial relations is disturbed in the Class II short-face syndrome patient. The skeletal lower face, thus the vertical soft tissue profile, shows a deficiency in the midface [12] [13] [28] [33] [36] -[38] (Figures 3(a)-(c), Table 3). The short lower face is caused by an anterior rotation of the mandible and a reduced interbase angle (skeletal deep bite). The anterior rotation of the mandible is often combined with a small Gonial angle. The characteristic consequence of the short lower face is an increased ratio of posterior to anterior face height. (Figure 4, Table 4). The short lower face is the primary esthetic concern to the patient [25] , and is the main reason why they opt for a combined orthodontic surgical treatment.

Possible symptoms of the short-face-syndrome are:

1) Short lower face, dominant chin and an increased mentolabial sulcus (Figures 3(a)-(c), Figure 4).

2) The cephalometric parameters show a small mandibular plane-interbase angle, the ratio of posterior to anterior face height (PFH/AFH) is increased. There is a discrepancy of the soft tissue harmony of upper to lower face. (Figure 4, Table 3, Table 4).

3) Intraorally one can detect a distal occlusion, deep bite, supraocclusion of the lower anteriors and a deepened curve of Spee (Figures 5(a)-(d)).

Thus in general, the goals of orthodontic treatment are:

1) Esrablishment of a Class I, stable and functional occlusion with physiologic position of the condyles.

2) Improvement of the facial esthetics.

3) Improvement of the dental esthetics within the framework of the periodontal health.

4) Stability of the result.

5) Fulfill the expectations and satisfy the patient.

Special attention must be paid to some critical aspects of treatment in the short-face syndrome patient. The improvement of the facial esthetics is not only related to the sagittal but also to the vertical dimension. This means that in the short-face syndrome patients, a lengthening of the lower face should be reached without increasing the chin prominence. A lengthening of the lower face as causal therapy with corresponding effects on the facial esthetics can only be accomplished with a combined orthodontic-orthognathic surgery procedure where the Gonial angle and thus the interbase angle is increased [38] -[40] . Surgical enlargement of the mandibular plane angle harmonizes the ratio of posterior to anterior face height.

5. Solution and Concept of Therapy

These above-established treatment goals are reached decisively with surgery. The necessary lengthening of the lower face is achieved by the translation or rotation of the tooth-bearing segment of the mandible during surgery. The orthodontist plans and controls the extent of these movements [39] [40] . Prerequisite for the stability of the enlarged gonial angle by this move, is a three-point support at the incisors and molars at the time of the surgery. Mandible can be rotated posteriorly only when the lower front teeth are in contact with the palatal surfaces of the maxillary incisors. Once the incisors are occluded, the skeletal correction is accomplished by a clockwise rotation of the mandible. This maneuver increases the lower face height and enlarges the gonial angle (Figures 6(a)-(c), Figure 7, Figure 8). Although the mandible is displaced anteriorly, the chin prominence is accentuated only a little because the posterior rotation compensates for the ventral movement, which in these patients is an advantage. The flattening of the sublabial sulcus can also be observed (Figures 6(a)-(c), Figure 8).

A straightforward advancement of the mandible when the curve of Spee is leveled, might correct the sagittal discrepancy, but not the vertical; chin will become prominent, and the face concave. It will then be necessary to perform genioplasty (Figure 7, Figure 8). Another important aspect in mandibular advancement is the stretching of the suprahyoid muscles. they have been (especially digastric) suggested to cause relapse; the greater the translation the larger the stretching or strain on these muscles (Figure 9). Rotation minimizes this effect (Figure 10). Carlson [41] and Reynolds [42] showed in the primates that mandibular advancement produces stretching and strain on the soft tissue of the suprahyoid complex. Concurrently, forces are produced to pull the mandibular segment dorsally. Ellis too reported on the posterior positioning of the condyle following the surgical advancement of the mandible [43] . The postsurgery posterior position is supposed to be a result of these muscle forces in the dorsal direction. In all these studies the advancement of the mandible was performed without taking the strain on the muscles into account. Our approach to treatment of short-face syndrome patients at the University of Würzburg [39] [40] avoids stretching of these muscle fibers. Typically, we take the following steps in treatment:

1) Pre-surgery measures and orthodontic setup:

・ Splint therapy to establish the centric relation for final treatment planning.

・ Orthodontics to adjust the dental arches to each other and to decompensate the skeletal deformity.

・ Splint therapy to establish the centric relation 4 - 6 weeks prior to surgery.

2) Surgery to correct the skeletal deformity.

3) Orthodontics for finishing the occlusion.

4) Retention to stabilize the result.

5.1. Pre-Surgery Measures and Orthodontic Setup

5.1.1. Splint Therapy to Establish the Centric Relation for Final Treatment Planning

It is often necessary to insert an initial splint in these patients either for the treatment of temporomandibular joint

problems or for diagnostics [44] -[49] . Celenza [50] -[52] and Calagna et al. [53] have showed that by tiring the muscles with a splint, the mandible could be retruded more than the hinge-axis position. In Class II div.1 patients a ventral positioning of the mandible is normally observed. Habitually, these patients protrude the mandible to make lip-closure possible. If there is a discrepancy of centric occlusion and centric position of the condyles (centric relation) after splint therapy, all diagnostic records (cephalograms, facial photographs, study casts and articulated casts) need to be re-taken in centric relation to be able to set up the final treatment plan [38] -[40] (Figures 11(a)-(c)).

5.1.2. Orthodontic Preparation

The aim of the orthodontic preparation is to align the dental arches, harmonize in three dimensions of space and to eliminate the dental compensations. Special care must be taken for the transversal dimension at the canines to prevent premature contacts during surgery―it forces the mandible distally. The upper dental arch in Class II deformities usually shows a deficit in the transversal dimension relative to the lower arch. The correction of this discrepancy by widening the upper arch can be impeded or even made impossible when there is a stable occlusion (Figure 12(a), Figure 12(b)). Splint therapy deprograms the occlusion. In the short-face syndrome patients the lower arch is not leveled prior to surgery so that the curve of Spee and the deep bite is left uncorrected. For this purpose arch wires with corresponding bends are inserted (Figures 13(a)-(d)). Leveling of the lower arch by

incisor intrusion increases the overjet. In turn, mandible requires greater advancement at the expense of rotational movement. In the event teeth have compensated for the skeletal deformity, and the curve of Spee nonexistent, extrusion of the lower anteriors might be necessary [39] [40] .

5.1.3. A Second Splint Therapy to Establish the Centric Relation 4 - 6 Weeks Prior to Surgery

The aim of this procedure is to register a physiologic position of the condyle (centric relation) [44] -[47] . An inaccurate position of the mandible results in an incorrect planning of the amount of advancement and with that in an inevitable relapse.

5.2. Surgery to Correct the Skeletal Deformity

The surgical advancement is performed via a sagittal split osteotomy [54] -[58] . The centric positioning of the condyle during orthognathic surgery is a standardized procedure to keep the correct position of the condyles [14] [59] -[62] (Figure 14).

5.3. Post-Surgial Orthodontics

As a consequence of the posterior rotation of the segment with 3-point contact, a lateral open bite forms, and requires early correction (Figure 15(a), Figure 15(b)). Thus, early application of orthodontic forces after surgery is crucial. Generally on the 4^th postoperative day, post surgical orthodontics is instigated to close the lateral open bite without losing skeletal height, and at the same time to put the finishing touches and to stabilize and occlusion.

According to our concept, the open bite should be corrected by extrusion of the upper posterior teeth only and not by intrusion of the anteriors. The closure of the lateral open bite is done in two phases:

1) The maxillary steel archwire is replaced by 0.018 × 0.025 NiTi. Extrusive bends for the premolars and the first molar are incorporated in this archwire and vertical elastics are used to augment the extrusive effect while minimizing the intrusive reaction to the remaining teeth. The elastics are placed in such a manner that one tooth in the upper jaw and two teeth in the lower jaw are loaded. Some days later, the extrusive step in the open bite area―mostly the first or second premolar―is increased, and the elastic use continued (Figures 16(a)-(c)).

2) After the NiTi-wire is passive in the upper jaw a NiTi wire replaces the lower steel archwire. Again, up-and-down elastics are used to close the residual open bite by extrusion of the premolars, and as little as possible by intrusion of the anterior teeth. Now one tooth in the lower is loaded against two teeth in the upper jaw (Figure 17).

5.4. Retention

Following surgery reorientation of skeletal parts by the muscle pull could be a significant problem for the soft tissues balance. This strain on the muscles is reduced significantly by rotation of the mandible as described above. To allow the muscles to adapt to the new situation, we suggest a bimaxillary appliance for retention e.g., a bionator. The construction bite must be taken with teeth only slightly disoccluded. If the mandibular advancement was significant, especially in patients with tense or short muscles of the suprahyoid complex, a physiotherapeutic treatment is prescribed to rehabilitate and reorient the muscles to their new positions. Furthermore, a bonded canine to canine retainer might be recommended, especially in patients with severely malposed teeth prior to treatment.

6. Treatment Results

Treatment results are assessed as follows:

Cephalometrics:

Posterior rotation increased the Gonion angle by 7˚, which resulted in an increased interbase angle (ML-NL). Consequently, the upper and lower face were harmonized (N-Ans: Ans-Me or UFH:LFH = 45%:55%). The lengthening of the lower face increased the total face height and harmonized the posterior to anterior face

(PFH/AFH = 69%). Pogonion (Pg) was advanced only a little with the correction of the skeletal deformity which is reflected in the relatively small increase of the angle SN-Pg (Figure 18, Table 3, Table 4).

Extraoral:

The effects of skeletal correction on the soft tissue profile are depicted in Figures 19(a)-(d). The sagittal discrepancies are corrected without making the chin more prominent. The mentolabial sulcus was also reduced with the posterior rotation of the mandible.

Intraoral:

The intraoral pictures show a stable Class I occlusion (Figures 20(a)-(c)). The closure of the lateral open bite with the described extrusion mechanics supported by up-and-down elastics was achieved primarily by extrusion of the premolars and molars. The extrusive step is largest at the first premolar where the lateral open bite was broadest (Figure 21).

7. Discussion

Diagnostic records taken in a centric position of the condyle are of key importance in planning treatment for the orthognathic surgery patient. To ensure this position, deprogramming of the occlusion for a period (4 - 5 weeks) is necessary. This step is particularly important in Class II deformities with increased overjet as these patients

are known to habitually protrude for lip seal. Treatments planned without consideration of the condylar location in the fossa run the risk of inadequate advancement and post surgical setback of condyles in the fossa; oftentimes labeled as relapse [14] [42] [43] [59] .

We demonstrate in this report that patients with the short-face-syndrome are best treated by posterior rotation of the mandible. The clinician is cautioned that leveling of the lower dental arch prior to surgery reduces the effectiveness of the surgical move. The leveled dental arch will force a straightforward advancement. As discussed earlier, without the rotational component, the chin becomes undesirably prominent. It may even stretch the suprahyoid muscles beyond their natural tolerance and elicit relapse.

From a dental perspective it is important to realize that labial tipping of the lower anteriors promotes posterior rotation of the mandibular segment during surgery. Naturally, the surgical rotation as described gives rise to a lateral open bite. The three-point-contact (molars and anteriors) could potentially overload the anterior teeth and can harm (root resorption) teeth. Thus, we advocate closure of the created lateral open bite as soon as possible following surgery. This can be done by extrusion of the buccal teeth and as little as possible by intrusion of the anterior teeth. A strategic plan for treatment based on the concepts outlined in this report, in our experience, ensures satisfactory facial esthetics and stability.

8. Conclusion

By means of the systematic treatment approach presented, class II deformities with a skeletal deep bite and short lower face can be treated with predictable success and without esthetic compromises. The treatment result shows that it is necessary to leave or to create a certain curve of Spee depending on the extent of the deformity to end with a satisfactory result with respect to function, esthetics and stability. The posterior rotation of the dental segment of the lower arch during surgery is essential to obtain the desired effect. It can be concluded that it is only possible to reach the preset treatment goals with an exact diagnosis and knowledge of the necessary orthodontic preparation in combination with the surgical procedure.

References

NOTES

^*Corresponding author.