The manipulation of the maxillomandibular complex (MMC) in orthognathic surgery has been used widely in the treatment of dentofacial deformities so as to optimize aesthetic and functional results, making these more stable in the long term. The aim of the present study was to perform a systematic literature review of the aesthetic and functional implications following rotation of the occlusal plane in orthognathic surgery, by evaluating skeletal stability, facial harmony, respiratory function, and temporomandibular joint (TMJ) function after clockwise or counterclockwise rotation of the MMC. A survey of Scopus, PubMed, and Cochrane databases was performed through which 10 papers were selected for the final review. From this review, it could be concluded that facial aesthetics, TMJ function, and skeletal and occlusal stability in the orthosurgical treatment of dentofacial deformities may be influenced by the surgical manipulation of the MMC (clockwise or counterclockwise rotation). However, although this treatment technique is used widely today, the results of the present study do not provide sufficient scientific evidence with regard to the choice of this approach.
Orthosurgical treatment is recommended for the correction of dentofacial deformities and often involves bimaxillary surgery. This procedure can be performed by altering the patient’s maxillomandibular complex (MMC) in order to optimize final functional (dental occlusion, respiration, temporomandibular joint (TMJ) and long-term stability) and aesthetic results.
Orthognathic surgery may be performed by means of ‘conventional’ treatment, or be complemented with clockwise or counterclockwise MMC rotation. ‘Conventional’ treatment is understood to be that where the cephalometric prediction tracing is able to correct antero-posterior maxillomandibular discrepancies through the pre-existing occlusal plane, and the final occlusal plane is determined by the mandibular occlusal plane after its autorotation, which occurs both clockwise and counterclockwise at a superior–posterior point to the condyle, depending, respectively, on the inferior or superior repositioning of the maxilla. Surgical planning that includes MMC occurs independently of a pre-existing mandibular occlusal plane.
In bimaxillary surgery cases, the vertical position of the upper incisors, the antero-posterior position of the maxilla, and the angulation of the occlusal plane are taken into account. These factors dictate the position of the mandible and affect both functional and aesthetic results. The impacts of these alterations have major implications for surgical planning, and long-term aesthetic stability and function of the stomatognathic system are of the utmost importance.
A specific treatment proposal is established according to the type of dentofacial deformity, by evaluating the surgical movements to be performed as well as aesthetic and functional effects on clinical and cephalometric variables that occur after orthognathic surgery.
The possibility of occlusal plane management in bimaxillary surgery was first described in the literature in 1985. Nevertheless, Wolford and Hilliard had already performed an occlusal plane alteration through MMC counterclockwise rotation as a differentiated surgical approach applied to a Class II patient in 1979, but this procedure was only publicized several years later.
There must be a correlation between clinical evaluation data (facial analysis) and cephalometric analysis so as to aid in the establishment of a surgical treatment plan. However, these data do not always correlate due to the abnormal orientation of the Frankfort plane, which must be corrected. The normal occlusal plane angular relation must be 8 ± 4° in relation to the Frankfort plane.
Autorotation of the mandible – following either the superior or inferior repositioning of the maxilla where the mandible can be repositioned without surgical manipulation – is one of the most stable long-term procedures in orthognathic surgery. This treatment is recommended for patients with excessive exposure of anterior and superior teeth at rest or smiling, or in large inter-labial distance cases, generating labial incompetence. These patients usually present anterior open bite and Angle’s Class II or I, where the superior and anterior repositioning of the maxilla with autorotation of the mandible will keep a Class I occlusion, only interfering in aesthetic improvement.
In situations where there is a decrease in the occlusal plane angulation (<4°), the gonial angle is very prominent, the chin very pronounced in relation to the alveolar process, and in cases where there is Angle’s Class II division 2 malocclusion (Class I or III may also occur) and deep overbite, the most acceptable treatment proposed is clockwise MMC rotation, i.e., an increase in the occlusal plane inclination.
For patients with an increase in occlusal plane angulation (>12°), mandibular deficiency, anterior vertical maxillary excess, and decreased chin projection, counterclockwise rotation is the most appropriate procedure, resulting in a decreased inclination of the occlusal plane angle. This technique limits the correction of Class III patients and is largely used in the treatment of patients suffering from obstructive sleep apnoea/hypopnoea syndrome (OSAHS).
Complementary genioplasty to MMC rotation allows optimization of the aesthetic results in both movements, and the shape of the chin plays an important role in the surgery decision-making process, provided that this is more important than its antero-posterior positioning (horizontal pogonion position).
Based on these concepts, the aim of the current study was to perform a systematic literature review of the functional and aesthetic implications of MMC clockwise or counterclockwise rotation in orthognathic surgery, including evaluation of skeletal stability, aesthetics, and respiratory and TMJ function.
Materials and methods
Study selection criteria
Article titles and/or abstracts were analyzed, delimiting for inclusion in this study the following: (1) specific studies focusing on the alteration and/or manipulation of the occlusal plane by means of clockwise, counterclockwise, or autorotation of the MMC; (2) studies in human beings; (3) studies published in the English language; (4) no time limit; (5) type of study: case report, case series, retrospective and/or prospective clinical study.
Inclusion criteria were adopted so as to obtain more general results in the review, without specifying cephalometric tracing type, surgical techniques used for articular disc repositioning, postoperative neurosensory evaluation, or surgical treatment of temporomandibular dysfunction (TMD).
An initial survey of PubMed, Scopus, and Cochrane databases was done using the following three search lines after a brief reading of the topics of interest: (1) ‘occlusal’, ‘plane’, ‘alteration’, ‘orthognathic’, ‘surgery’; (2) ‘occlusal’, ‘plane’, ‘rotation’, ‘orthognathic’, ‘surgery’; (3) ‘occlusal’, ‘plane’, ‘autorotation’, ‘orthognathic’, ‘surgery’.
Titles and abstracts of all identified articles were then analyzed by three independent reviewers (CLS, ANB, and OLCJr).
The database survey was updated on April 28, 2013, and resulted in 10 selected articles for the systematic review presented in ‘Results’ section.
The three reviewers (CLS, ANB, and OLCJr) collected the following data after a full reading of the articles included in the sample: analysis of the type of study, type of occlusal plane alteration (clockwise, counterclockwise, and/or autorotation), postoperative follow-up, as well as aesthetic and functional results obtained. Any disagreements between reviewers were resolved through additional discussions.
A flowchart of the selection and evaluation procedure is given in Fig. 1 .
Following the initial selection and amalgamation of the first two search topic lines (‘alteration’ × ‘rotation’) by the three reviewers, a total of 16 potentially relevant items were identified, among which six were duplicates, i.e., these papers were found in both the ‘alteration’ and ‘rotation’ groups; so a shortlist of 10 relevant articles was reached. Two further articles found through the ‘autorotation’ search item were added, thus reaching a sample of 12 relevant articles; two of these were duplicates, i.e., they were found in the ‘alteration’/’rotation’ and ‘autorotation’ groups. A final sample of 10 relevant articles was then accessed fully and analyzed.
An evaluation of methodological quality was done by combining PRISMA statement criteria in order to verify the strength of the scientific evidence available in the current literature for clinical decision-making purposes.
The classification of the potential risk of bias for each study followed the criteria listed here, used by Clementini et al. : (1) random selection in (of) the population (sample); (2) definition of inclusion/exclusion criteria; (3) follow-up loss reported; (4) validated measurements; (5) statistical analysis. If the study included all these criteria, it was classified as having a low risk of bias; if one of the above criteria was missing, it was classified as having a moderate risk of bias; if two or more criteria were missing, it was classified as having a high risk of bias.
The survey identified a total of 10 articles that met the study inclusion criteria; details of these studies are shown in Table 1 . Of the 10 articles, seven were case series reports, one was a retrospective study, one included a case report, and one was a clinical report.
|Author, year, Ref.||Type of study||Occlusal plane movement||Postoperative observation period||Results|
|Wolford et al. a 1993, 1994||Case series||Group 1: 14 patients submitted to MMC clockwise rotation||21–23 months||Good facial harmony, aesthetics, and facial balance; stable and functional occlusal relationship; asymptomatic postoperative TMJ without detectable long-term alterations|
|Chemello et al. a 1994||Group 2: 27 patients submitted to MMC counterclockwise rotation|
|Rosen 1993||Case series||Group of 11 patients submitted to MMC counterclockwise rotation||9–24 months||The author observed a few long-term clinically significant alterations of immediate postoperative values as compared to the final value; however, these variations did not alter the patients’ facial architecture as a whole|
|Reyneke et al. 2007||Retrospective study||Group 1: 22 patients without MMC manipulation||Group 1: 14.1 months||The long-term skeletal stability of the MMC clockwise and counterclockwise rotations could be compared favourably to the postoperative skeletal stability of conventional surgical treatment when MMC rotation was located around the condylar point|
|Group 2: 25 patients submitted to MMC clockwise rotation||Group 2: 13.3 months|
|Group 3: 41 patients submitted to MMC counterclockwise rotation||Group 3: 13.9 months|
|Yosano et al. 2009||Case series||Sample of 16 patients submitted to MMC clockwise rotation||12 months||Rigid fixation of the mandible is one of the most important factors to obtain good occlusal plane stability and preserve the aesthetic and functional benefits obtained by altering the MMC|
|Pinho and Figueiredo 2011||Case report||Patient submitted to MMC counterclockwise rotation||12 months||After 1 year the patient did not report TMJ symptoms and/or signs and presented stable occlusion without relapses in this period of time|
|Brevi et al. 2011||Case series||Sample of 33 patients with OSAHS submitted to MMC counterclockwise rotation||6 months||Excellent functional results, such as a significant improvement in respiratory function and absence of relapse at the 6-month postoperative follow-up|
|Bang et al. 2012||Case series||Sample of 31 Korean patients submitted to MMC clockwise rotation||6 months||The maxilla and the mandible had a clinically insignificant relapse during this period; for this reason, the MMC clockwise rotation can be considered a predictable technique and a relatively stable procedure that is without clinical alterations or relapse|
|Tsai et al. 2012||Clinical case||Patient submitted to MMC clockwise rotation||10 months||Facial–skeletal stable results during the 10-month postoperative period|
One retrospective case series study showed a low risk of bias, whereas four studies showed a moderate risk of bias, and five showed a high risk of bias, as shown in Table 2 .
|Author, year, Ref.||Random selection in population||Defined inclusion/exclusion criteria||Reported loss to follow-up||Validated measurements||Statistical analysis||Estimated potential risk of bias|
|Wolford et al. 1993||No||No||Yes||Yes||No||High|
|Wolford et al. 1994||No||No||Yes||Yes||No||High|
|Chemello et al. 1994||No||Yes||Yes||Yes||Yes||Moderate|
|Reyneke et al. 2007||Yes||Yes||Yes||Yes||Yes||Low|
|Yosano et al. 2009||No||Yes||Yes||Yes||Yes||Moderate|
|Pinho and Figueiredo 2011||No||No||Yes||Yes||No||High|
|Brevi et al. 2011||No||Yes||Yes||Yes||Yes||Moderate|
|Bang et al. 2012||No||Yes||Yes||Yes||Yes||Moderate|
|Tsai et al. 2012||No||No||Yes||Yes||No||High|