Diagnosis and Treatment Planning in Surgery First Approach

Abstract

Surgery first approach is evolving as a better accepted treatment modality in contemporary orthognathic treatment. It has gained popularity gradually over the traditional orthognathic surgery as it involves performing of orthognathic surgery with minimal or no presurgical orthodontic phase. A correct diagnosis is the fundamentals of a precise treatment outcome. The present chapter discusses in detail about the diagnosis and treatment planning in surgery first approach as they lay the foundation for the best clinical outcome. This chapter is intended to provide an insight into the orthodontic and surgical consideration in surgery first approach. It entails the conventional as well as advanced diagnostic tools and treatment strategies in surgery first approach. It also encompasses the strategic planning of cases based on the specific requirements and objectives which further helps in execution of appropriate treatment plan. This chapter would thus be an essential guide for trainees and practicing clinicians in maxillofacial surgery and orthodontics.

1. Introduction

The primary indication for surgical orthodontic treatment is severe skeletal malocclusion with jaw discrepancy such that the camouflage orthodontic treatment alone is insufficient to obtain acceptable results.

The concept of envelop of discrepancy introduced by Ackerman and Proffit, delineates the limits of different types of orthodontic treatment and thus helps in deciding the preliminary line of treatment. The essence of this concept is as follows. When a moderate skeletal discrepancy exists and there is no potential for further growth, orthodontic camouflage should be considered as the treatment option. Extraction of some teeth will usually be required so that enough space in the arch can be created to allow required movement of other teeth. The treatment should result in reasonable occlusal stability and pleasing aesthetics. For a severe skeletal discrepancy, the final treatment option is orthognathic surgery and orthodontic treatment. Once growth has ceased, surgery becomes the only means of correcting a severe jaw discrepancy (Figure 1) [1].

Figure 1.

The envelopes of discrepancy, showing the amount of change in the antero-posterior and vertical planes of space. Inner envelope: change from orthodontics alone. Middle envelope: orthodontic tooth movement combined with growth modification. Outer envelope: orthognathic surgery [1].

The conventional approach to orthognathic surgery requires a variable length of preoperative orthodontic preparation, the surgery, and a relatively stable period of postoperative orthodontics. It involves progressive deterioration of facial esthetics and dental function, and causes significant patient discouragement and discomfort [2].

In the recent years, a drift towards revising the line of treatment that achieves immediate improvement in the facial esthetics has arisen. Hence, a different approach, the surgery-first approach, is to proceed with the orthognathic surgery in the beginning without presurgical orthodontic preparation, and most of the orthodontic treatment is performed postoperatively.

The concept of Surgery-first was introduced by Brachovogel in 1991, with the goal of reducing some of the disadvantages and inconveniences of pre-surgical orthodontics [3]. This concept of “surgery-first and orthodontics second” is called “SFOA” (Surgery-First-Orthognathic-Approach) or “SFA” (Surgery-First approach) no requirement of tooth movement or minimal decompensation of tooth for a short period of time in clinical scenarios with occlusal interference, usage of surgery to fasten the achievement of improvement of facial aesthetics which is patient’s primary concern.

It reduces total treatment time due to RAP (rapid acceleratory phenomenon) along with improvement in upper airway constriction [4]. These factors improve the quality of care and lead to high patient satisfaction rates from the early stages of treatment and improved cooperation during postsurgical orthodontics and thus has a positive psychosocial effect on patients [5]. The proposed benefits of surgery first have led to a growing acceptance in surgical and orthodontic communities toward these protocols. Surgery first approach is thus exhibiting a paradigm shift in the field of jaw surgery.

An illustration of computer assisted simulation of conventional orthognathic surgery and surgery first approach is shown here Figures 2–4.

Figure 2.

Conventional orthognathic surgery approach.

Figure 3.

Surgery first approach.

Figure 4.

Favorable and unfavorable case scenarios for SFOA (Liou et al. [6]).

Indications of SFOA

2. Diagnosis

Diagnosis is the definition of the problem. Treatment planning is based on diagnosis and is the process of planning needed to eliminate the problems. Diagnosis of a surgical case does not differ for conventional and surgery first approach. Diagnosis provides guidance to the surgeon and the orthodontist regarding the needs of the case. Study models, clinical examination, and soft tissue cephalometrics have all been used to guide facial treatment [6]. Though SFA can be considered as an advantageous procedure it also has certain disadvantages associated with it to overcome the problems. The occlusion cannot be used as a reference for determining the treatment goal hence the final occlusion interpretation is challenging. Post operative occlusion immediately achieved after SFA is mostly unstable. Due to such problems this concept requires an accurate diagnosis and meticulous treatment planning for beginners, cases with minimal dental discrepancies, in sagittal, vertical, and transverse planes, could be ideal cases to start with for SFOA.

2.1 Intended transitional malocclusion (ITM)

In the model surgery procedure, the crucial step is to predict the intended transitional malocclusion (ITM), to fabricate surgical splint and later facilitate the postsurgical movement of the teeth [7]. For predictable splint fabrication and skeletal movements ITM attained should have enough stability and 3-point contact between upper and lower models is a pre-requisite. In some cases, initiation of some orthodontic movement to resolve occlusal interferences and allow stable transitional malocclusion maybe required when such temporary occlusion cannot be established [8, 9].

2.2 Advantages of surgery first approach

Both conventional and 3D surgical planning is discussed in this chapter.

2.3 Methods for planning and predicting surgical outcome using cephalometrics

There are various methods available for planning and predicting surgical outcomes such as [10]:

1. Manual acetate tracing techniques.

2. Photo cephalometric method.

3. Computerized cephalometric prediction.

4. Videocephalometrics.

5. Three-dimensional cephalometric prediction.

2.4 Pre-surgical planning through manual cephalometric prediction

Model surgery and paper surgery furnishes a secure method of designing a treatment plan for a surgical patient, using the fundamental diagnostic tools such as photographs, study models and cephalograms.

After a detailed clinical and radiographic assessment, the data obtained is integrated in the paper surgery to set up a surgical plan. Further, the model surgery is reproduced on a face-bow transfer, transferred on articulator which facilitates surgical splint creation. The treatment plan, when using 2D data, is essentially a composite of clinical evaluation and cephalometric (both lateral and posteroanterior cephalograph) assessment using Schwarz’s ‘gnathic profile field (GPF)’ [9].

3. 2D planning

3.1 Clinical Evaluation

See Table 1

Table 1.

Clinical evaluation in surgical patients.

3.2 Occlusion and study cast evaluation

1. Occlusal functional evaluation [6]:

   The functional analysis is performed to analyze the centric occlusion and centric relation; any discrepancy between CR CO, bite of convenience or occlusal slide; and interocclusal rest space is noted.

2. Study cast analysis

3.3 Temporomandibular joint evaluation

An evaluation of temporomandibular joint before the orthognathic surgery is essential with regard to diagnostic and prognostic aspect. Mandibular movements along with maximum mouth opening, deviation and TMJ signs if any are recorded. Correct positioning of the condyle in the fossa is a critical part of the orthognathic surgical procedure and information obtained during the pre-treatment evaluation may be useful during the surgery [11].

3.4 Lateral cephalometric radiographic evaluation

The clinical examination along with cephalometric evaluation constitutes the important diagnostic criteria. The information from lateral and posteroanterior cephalometric radiographs forms a crucial part of the database for orthognathic surgical treatment planning. With the help of cephalometrics orthodontists can create a treatment plan through a visual and surgical treatment objective and it also helps to keep a track of the progress of the treatment. Soft tissue cephalometrics is a way of calibrating the facial deformity and identifying its underlying causes. The soft tissue parameters and profile at the end of treatment is greatly influenced by how the orthodontist and surgeon manage the dentoskeletal components (Figure 5) [6].

Figure 5.

Summary of 2D evaluation.

Drawbacks of 2D diagnostic aids in SFOA [12]

4. 3D planning

Three-dimensional computer-aided surgical planning techniques for craniofacial deformities were introduced by Xia et al and Swennen et al. For accurate diagnosis and meticulous virtual surgical treatment planning, obtaining precise data from the imaging of the orofacial region in 3 dimensions is absolutely necessary to complement the clinical examination particularly when treating complex malocclusions with maxillo-mandibular orthognathic surgery [12].

Cone-beam computed tomography (CBCT) for imaging the craniofacial region heralds a true paradigm shift from a 2-dimensional to a 3-dimensional (3D) approach which diagnoses the problem in all 3 spatial planes considering pitch, roll and yaw [13, 14].

CBCT permits a 3D display of the craniofacial structures with possibilities of image segmentation, thereby augmenting the role of imaging from diagnosis to simulation of the orthognathic surgical procedures and fabrication of the computer-manufactured surgical splints surgical splints for effective treatment outcome [12].

It is also possible to visualize the virtual patient by creating an integral fusion model combining the data from all 3 important tissue groups using a CBCT reconstructed bony volume, digital dental models, and a textured facial soft tissue image. The rapid prototyping technology combined with SFOA has aided in virtual setup, treatment simulations and surgical splint fabrication, leading to improved treatment accuracy by eliminating the error. The 3D techniques have profoundly improved the surgery first treatment outcomes, but have disadvantages of increased radiation dose, technique sensitive procedure and high cost.

However, the potential glitch in discrepancies between virtually planned orthodontic movements and actual ones cannot be eliminated totally with introduction of 3D virtual orthodontic set up technology (Figure 6) [15].

Figure 6.

Summary of 3D evaluation.

5. SFOA approaches

SFOA procedure incorporates the following steps which are meticulous treatment planning, accurate demonstration of the model surgery and definite post-surgical orthodontics. The 2 approaches are i) surgical driven and ii) orthodontic driven. First approach corrects jaw and dental problems via the surgical procedure and second approach corrects the jaw deformity through surgery and dentition through skeletal anchorage system (SAS) (Table 2) [16, 17].

Features	Orthodontic driven	Surgery driven
Background	Technique was given by Sugawara et al of Japan and termed it as ‘Sendai surgery first’ (SSF) for correction of skeletal and dental deformities using surgery followed by SAS	Skeletal and majority of dental deformities are corrected using surgical approach
Post-surgical orthodontics	Done using SAS which corrects multiple dental complexities	Done with routine orthodontic biomechanics as the complex dental problems are surgically corrected

Table 2.

Two types of SFOA approach.

6. Guidelines for surgery first approach

6.1 General guidelines

6.2 Specific guidelines

6.2.1 Antero-posterior and vertical decompensation in Class III cases

In Surgery first approach, the incisors can be positioned either orthodontically or surgically after the surgery, in contrast to positioning them orthodontically in a proper inclination in the supporting bone to show the true extent of skeletal discrepancy (decompensation) before surgery in conventional surgery [11].

1. For proclined maxillary incisors: the correction of inclination can be done by 2 methods.

   

   Lack of occlusal antagonist in the mandibular 2nd molar maybe a drawback of the first approach. Hence the second approach is recommended.

   

2. For retroclined and crowded lower incisors:

   

3. Class III case with moderate to steep curve of spee:

   For prevention of post operative forward and upward rotation of the mandible it is levelled pre operatively or by anterior segmental osteotomy surgical procedure. Through upward and forward rotation of the mandible there is improvement of chin projection in case of class II mandibular retrognathism, but it worsens in case of class III mandibular prognathism. Intrusion of lower incisors and extrusion of upper incisors can be done to prevent post operative upward and forward rotation on the mandible.

4. In order to prevent relapse of mandibular skeletal malocclusion a chin cup can be applied post operatively in initial 3 months.

6.2.2 Antero-posterior and vertical decompensation in Class II cases

In class II mandibular retrognathism with a moderate to steep curve of spee and proclined mandibular incisors:

In Class II division 2 cases, a short-term period of minimal orthodontics to upright the incisors or to overcorrect the jaw deformity to Class III relations is indicated to provide sufficient overjet for surgical correction.

6.2.3 Transverse arch coordination

In surgery-first approach, the intercanine and intermolar widths of the upper and lower dentitions are coordinated by either surgery or postoperative orthodontic tooth movement in contrast to conventional surgery where the transverse arch coordination is managed either during pre-surgical orthodontics or during the surgery.

The excessive buccal overjet would be solved postoperatively by the occlusal force or vertical chin cap or orthodontically by a 0.032-inch Beta-titanium constricting transpalatal arch in a short period of time because of the RAP. The transverse dimension often poses a special challenge when performing model surgery in surgery first cases. Depending on the degree of discrepancy between the two arches, the orthodontist can resolve this issue by planning for segmental osteotomies in more severe cases or possibly plan on resolving the issue post-surgically by arch coordination and elastics.

6.3 Surgery first approach with SAS

Recent innovative developments and the relevance of temporary anchorage devices (TADs) or skeletal anchorage system (SAS) in the orthodontics have made postsurgical orthodontic treatment more predictable and scalable.

The outcome of post orthodontic results is based on the orthodontist’s expertise towards the conduct of the model surgery [18].

The use of temporary anchorage devices in the post-surgical phase that includes extractions or segmented osteotomies can correct the disparities which are encountered during the challenging surgical phase [8]. In addition, SAS mechanics with SFA can be used to compensate for any surgical errors or skeletal relapse (Figure 7).

Figure 7.

Orthodontic mechanics used to distalize entire mandibular dentition with miniplate anchorage.

Diagnosis and treatment planning for surgical orthodontic treatment of patients with skeletal class II relationship with a deep bite pattern and short anterior face is quite challenging. Traditionally the treatment would include pre surgical orthodontics, incisor decompensation, tooth alignment as well as arch coordination. In patients who have short face with deep bite often have heavy occlusal forces due to strong muscles, which may make all these processes more complex.

When surgery is performed first in such cases, the facial height is increased, but the Class II malocclusion worsens to Class III, with an edge-to-edge incisor relationship immediately after surgery. This situation therefore requires the use of Class III orthodontic mechanics. Because it can predictably distalize the mandibular molars in nongrowing patients, the SAS makes it possible to correct a Class III malocclusion and lower incisor proclination without premolar extractions. At the same time mandibular arch can be leveled by extruding the premolars [19].

The TAD permits a wider range of orthodontic vectors and avoids premature bracket loading with secondary troublesome dental extrusion. Interdental corticotomies can augment the tooth movement through RAP and further enhance the orthodontic treatment outcome [20].

7. Conclusion

SFOA has biological, psychological and functional advantages over the conventional orthognathic surgical treatment. SFOA is commonly performed for Class III patients but with precise diagnosis and meticulous treatment planning, it can be adapted for treating Class II patients with retrognathic mandible, one advanced way being the use of SAS along with SFOA.

The future of SFOA technique lies in using augmented skull models, virtual orthodontic set-up to replace the mounted study model set-up and the computer-aided design and computer-aided manufacturing fabrication of surgical splints [19].

3D planning technologies are a clinical reality today. Interpretation of patient’s expectations and co relation of this with proper diagnosis and preparation and execution of accurate treatment plan forms the basis for successful orthognathic surgery. Though virtual 3D planning is an additional aid in diagnosis and surgical planning, it is the responsibility of the orthodontist to continue to be experts in traditional approaches of cephalometry as well [11].

According to Pelo et. al Initial therapeutic process as well as Greater part of the responsibility regarding the final result must also be undertaken by the surgeon. Hence the orthodontist does not condition the surgeons work any longer which is contrary to the traditional approach.

Acronyms and abbreviations

SFOA

surgery first orthognathic approach

SFA

surgery first approach

SAS

skeletal anchorage system

ITM

intended transitional malocclusion