6.6. General comments and clinical implications

Despite the abundant research on orthognathic surgery, there still seem to exist many open questions. Etiology, epidemiology, TMJ function, indications for and outcome of orthognathic surgery and economic aspects involve uncertainty and controversy or have not been much studied. Cost-benefits and cost-effectiveness have hardly been discussed at all. When we are dealing with elective surgery, the benefits shoud clearly outweigh the possible adverse effects. The competition for economic resources obliges the health care service producers to justify the treatment practices with more accurate results.

Human biophysiological phenomena are basically the same throughout the world, but psychosocial backgrounds may differ considerably between cultures. Dentofacial deformities, when serious enough to warrant surgical-orthodontic therapy, involve both psychosocial and biological considerations. Little is known about these from the Finnish point of view, although orthognathic surgery services are available routinely in almost all parts of Finland. The aim of this study was to introduce a comprehensive view to clarify some of the open questions.

The majority of patients in this study reported pain-related or functional problems as the reasons for seeking orthognathic surgery. This impression was confirmed by the clinical findings of a high prevalence of TMD. Nevertheless, esthetic concerns cannot be ignored, as facial disfigurement due to dentofacial deformities may represent a psychological handicap (Belfer et al. 1982, Tobiasen et al. 1987). The high level of patient satisfaction with the treatment without any evident psychological adverse effects and with a low official complaint rate shows good cost-effectiveness in the psychosocial respect.

The effects of orthognathic surgery on TMD turned out to be favourable in this study, although some of the signs and symptoms failed to disappear. It seems, however, that the positive treatment outcome mainly occurred in patients with skeletal Class II, non-open-bite deformities (or mandibular hypoplasia/retrognathia), who have TMD of mainly muscular pain origin or muscle contraction headache. To increase the degree of certainty in the diagnostic phase of this category, temporary occlusal splint therapy can be recommended (Tucker & Thomas 1986) as well as repeated measurements of TMD before treatment due to the fluctuation of the symptoms. Those with TMD of internal derangement type may or may not benefit from orthognathic surgery, similarly to other dentofacial deformities. The patients with skeletal Class II, non-open bite deformity can most often be treated with orthodontics and BSSO, which was found to be overall the cheapest treatment compared to the others. The complication rate is also extremely low, the only complication being neurosensory disturbance of IAN, which is pretty much avoidable with careful patient selection and a good, gentle surgical technique. When these prerequisites are taken into account, orthognathic surgery can be regarded as cost-effective and probably also increases the quality of life as shown by Hatch et al. (1998), Fig.7.

However, dentofacial deformities with skeletal open bite constitute a more controversial category. Although some improvement in TMD would be gained with orthognathic surgery, the risk for relapse is considerably high, varying within 3–35% of cases, as reported in numerous studies (Haymond et al. 1991, Denison et al. 1989, Fischer et al. 2000, Hoppenreijs et al. 1996, Lopez-Gavito et al. 1985). Recently, Aghabeigi et al. (2001) examined TMD in an open-bite deformity group and found preoperatively 32% to suffer from TMJ pain, 40% from dysfunction and 7% from limited opening. The overall prevalence of TMD was not significantly different after orthognathic surgery. Since the correction of these deformities often also requires bimaxillary surgery, the expenses of their treatment may be high. Kerstens et al. (1989) found asymptomatic patients with a high mandibular plane angle (skeletal open bite) operated on by means of bimaxillary surgery to show a higher incidence of postoperative TMD compared to the other dentofacial deformities. An explanation for this has suggested to lie in the potential joint pathology due to a different morphology of the TMJs in patients with mandibular hypoplasia with a high mandibular plane angle (O´Ryan & Epker 1984). Open-bite deformities are also prone to condylar resorption, especially if the subject is a young female with posteriorly inclined condyles (Hoppenreijs et al. 1998). Therefore, cost-effectiveness in these deformities may be low.

Although, at an individual level, it may be difficult to predict the treatment outcome exactly, on the basis of the earlier literature and the present study, some clinical recommendations for orthognathic surgery can be suggested:

• if mandibular surgery is needed, it is preferable to have orthognathic surgery performed before the age of 30, in order to minimize risk for neurosensory IAN disturbances. If the patient is over 50 years of age, only heavy indications for sagittal ramus osteotomy outweigh the potential risk for IAN damage.

• patients with skeletal Class II non-open bite deformity, who have TMD of mainly muscular origin with or without headache, seem to benefit most from orthognathic surgery. Before definitive decisions, measurement tools, such as Helkimo´s Dysfunction Index (1974) or TMD Treatment Need Classification (Kuttila et al. 1998) for pretreatment assessments, are recommended due to the fluctuation of TMD. Temporary occlusal splint therapy could be tried as a pretreatment test.

• patients with handicapping, unesthetic dentofacial discrepancy should evidently be offered treatment even without any pre-existing functional or pain-related problems. Measurement tools, such as the Index of Treatment Need (IOTN) (Brook & Shaw 1989), can be used in evaluations of these subjects.

• patients with skeletal open-bite deformity must be assessed with special care before the decision to perform orthognathic surgery due to the lower cost-effectiveness of the treatment. If treatment is highly indicated, consider LeFort I osteotomy instead of bimaxillary procedures due to the lesser risk for condylar resorption (Hoppenreijs et al. 1998) and the lower costs.

• because no direct association between the magnitude of malocclusion and TMD has been proven, prophylactic treatment of asymptomatic dentofacial deformities does not seem to be indicated.