Indications and Management Protocol for the Use of Splints with the "Surgery First" Approach

The potential for skeletal and occlusal instability is a major drawback of the “surgery first” approach. A systematic review indicated that mandibular relapse in Class III patients is more conspicuous with the “surgery first” approach than with conventional surgical-orthodontic treatment.²² The difference was attributed to a marked tendency of mandibular counterclockwise rotation to compromise vertical stability, inevitably causing sagittal relapse. The authors therefore suggested more careful selection of patients for the “surgery first” approach, as well as a planned overcorrection in the surgical position of the jaws. In our opinion, however, the term “relapse” is inappropriate because the changes in the vertical dimension and the sagittal projection of the mandible are related to the conversion of an unstable occlusal relationship with cusp-to-cusp contacts to a maximum physiological intercuspation. These changes are predictable and should not be considered true relapse.²³ In our experience, the counterclockwise rotation of the mandible is caused by the vertical reduction and mandibular advancement between the planned transitional malocclusion and the final occlusion. This movement should be anticipated during presurgical planning by simulating the final occlusion.

Regarding postoperative occlusal stability, many authors have identified orthodontic extractions as one of the main contraindications to the “surgery first” approach.^8,9,18 Uribe and colleagues described a Class III extraction case utilizing a “surgery early” or “surgery first modified” approach, with the surgery following a brief initial orthodontic alignment.²⁴ Depending on the timing of orthognathic surgery, various approaches have been categorized as “surgery first,” “surgery early,” “surgery late,” ”surgery last,” “surgery only,” or “surgery never.”⁴ In extraction cases, orthognathic surgery should not be performed until the overcrowding has been resolved and most of the extraction space has been closed (“surgery early”), even if there are premature occlusal contacts that could create occlusal instability after surgery.⁴

Splint Management

The role of the occlusal splint (or wafer) is well established in both elective orthognathic surgery and in the “surgery first” approach. During the analytic model surgery, the planned 3D movements are transferred to the patient through specific measurements and reference points and a custom-made surgical splint. For a one-jaw maxillary or mandibular procedure, a single final splint is required after reproduction of the osteotomized jaw movement. For a double-jaw procedure, an intermediate splint is recommended to relate the osteotomized maxilla (or mandible) to the stable mandible (or maxilla), in addition to a final splint that relates the osteotomized mandible (or maxilla) to the fixated maxilla (or mandible).

In the “surgery first” approach, it is essential to reproduce and maintain the planned postoperative malocclusion, which can be unstable because of the lack of presurgical orthodontic treatment. The surgical splint helps to provide occlusal stability, to stabilize jaw osteotomies (often segmental), and sometimes to stabilize and control the malocclusion during the postsurgical period and the subsequent orthodontic treatment. If postoperative occlusal instability is not properly managed by the orthodontist, it could lead to unsatisfactory esthetic and occlusal results.

Despite the importance of splints in the “surgery first” approach, few studies have been reported. We published an article about the use of an occlusal splint to reposition the condyles before orthognathic surgery.³⁹ Nine studies have described the use of intermediate splints^{10,13,19,20,34,37,39-41}; six of these involved computer-aided design and manufacturing (CAD/CAM).^{13,19,34,37,39,40}

Of 24 articles describing the management of final splints in the “surgery first” approach, two indicated their use only for surgery,^30,34 18 reported their use for specific periods after surgery,^{13-16,19,20,25-29,31-33,35-38} and four did not report the duration of splint wear after surgery.^10,39-41 Four case reports described modifications of the final splints during the postsurgical period.^15,26,29,33

Only four authors indicated that the duration of splint wear after surgery was dependent on the type of surgery performed; in these cases, the final splints were used only after maxillary transverse expansion or segmental osteotomies.^13,19,37,38 Overall, the duration of final splint wear ranged from one week to three months. For one-jaw surgeries, the average duration of splint wear after surgery was 3.8 weeks (Table 1).

For two-jaw surgeries, the average was three weeks if the one study that enrolled TMD patients36 was included, and 2.7 weeks if that study was excluded (Table 2).

A longer average duration, four weeks, was reported after segmental osteotomies (Table 3).

The duration of splint wear would understandably increase in cases of occlusal instability or following segmental osteotomies, as would be true with conventional surgical-orthodontic treatment.

In the Maxillofacial Surgery Unit of the Fondazione Policlinico Universitario Agostino Gemelli IRCCS, we distinguish among four types of splints for use with the “surgery first” approach.

Repositioning splint.³⁹ This splint is helpful in a patient who exhibits TMD before surgery and undergoes a gnathological therapy to determine the analgesic and functional position of the condyles and their proper relationship to the other joint structures. The purpose of the repositioning splint is to record the positions of the condyles as defined by the gnathological therapy and to maintain them after the surgical osteotomies and repositioning of the dental arches.

Intermediate splint. An osteotomy wafer is routinely used in orthognathic surgery as an intermediate guide for repositioning the mobilized jaw relative to the intact jaw. An intermediate splint is used in bimaxillary surgery to guide the movement of one jaw relative to the other. There is some margin of error because the mandible is not a fixed bone, and therefore the condyle may not maintain its exact position within the glenoid fossa. An intermediate splint is mandatory in “mandible first” procedures and in “maxilla first” procedures when complex 3D movements of the maxilla are planned.

Final splint. Conventional orthognathic surgical planning requires precise movement of the jawbone segments. An interocclusal final wafer records and stabilizes the final occlusal relationship between the osteotomized maxilla and mandible. With the “surgery first” approach, however, the final splint establishes the objectives of a postsurgical transitional malocclusion.

In our initial experience with the “surgery first” approach, the final splint was maintained for 20 days and eventually used with elastics for occlusal stability. In most cases today, we use a final splint only as an occlusal check during the surgical procedure. For surgery involving segmental osteotomies or transverse maxillary expansion or in patients with occlusal instability due to deflecting precontacts, we maintain the final splint for at least two weeks after surgery.

Dynamic splint. We have recently developed a modification of the final splint to be worn during the initial phase of postsurgical orthodontic therapy, until the removal of occlusal interferences. Postsurgical occlusal instability seems to be the most critical disadvantage of the “surgery first” approach, because it can lead to skeletal instability.^8,9,21 Some authors recommend the presence of at least three occlusal stops during the postsurgical transitional malocclusion.¹⁶ Alternatively, with a “surgery early” approach, a short period of presurgical orthodontic treatment could eliminate the source of postoperative occlusal instability.⁴

The dynamic splint allows orthodontic treatment to be started as soon as possible after surgery, taking full advantage of the regional acceleratory phenomenon (RAP), which begins immediately after surgery and lasts for about three months. Even with a segmental osteotomy, when splint stabilization is needed for several days after surgery, the dynamic splint can promote the RAP during the stabilization phase, thus reducing the overall treatment time. The dynamic splint can also be used as an occlusal build-up to permit orthodontic movements that would otherwise be impeded by the opposing teeth, as with the proclination of upper anterior teeth in a Class II, division 2 malocclusion.

Two consecutive clinical cases are presented in this article to illustrate our protocol for the management of orthognathic occlusal splints, which allows us to treat even complex malocclusions.

Case 1

A 22-year-old female presented for treatment (Fig. 1). Facial esthetic analysis^42-48 noted a symmetrical face with good proportions, although the nasolabial fold, the angular area of the labial rim, and the cheekbone contour at Mx point indicated middle-third retrusion. The patient exhibited a complex smile with a smile index^49,50 of 62; the lip line was extremely low, with the upper lip almost totally concealing the incisors (−6mm) and the premolars (−6mm). The upper lip was festooned in a commissural smile. Black corridors were noticeable, owing to the retrusion and hypoplasia of the middle facial third. The profile was flat, with a facial angle of 179°. The nasolabial angle (103°), upper (29°) and lower (−74°) side angles, and chin-throat distance were normal.

Intraoral examination found agenesis of the four second premolars, previous extraction of the lower right first molar, and a retained deciduous upper right canine and second molar. The upper right canine and lateral incisor were transposed, the upper right lateral incisor was palatally positioned, and the upper right central incisor was rotated 90°. The lower left first and second molars and lower right second molar were mesially inclined; the molar relationship was Class III. The upper arch was narrow, with severe crowding in the anterior segment, but the lower anterior teeth exhibited spacing. The Bolton Index was affected by the presence of hypoplastic lateral incisors.

Cephalometric analysis confirmed a meso­facial pattern (FMA = 24°, LFH = 47°), a skeletal Class III malocclusion (convexity = −7.3mm), and a retrusive maxilla (maxillary depth = 82°). The upper incisors were proclined (U1-OP = 47°), and the lower incisors were retroclined (L1-OP = 81°). The anterior maxillary height was deficient (Sn′-U1 = 17.5), but the anterior mandibular height (L1-M′) was almost normal. Projections to the true vertical line (TVL) appeared normal except for soft-tissue B-point (4mm) and soft-tissue pogonion (7mm), which were protrusive.

Some of these shifts were copied from the 2D visual tracings. The mandible was then positioned in the final occlusion, based on the prediction tracings. Finally, the surgical expansion of the maxilla required to achieve a stable occlusion was added. The virtual image of the final splint was obtained from the stereolithographic (STL) files of the postsurgical occlusion (Fig. 6).

In a second step, all surgical movements of the lower jaw were eliminated, and the STL file of the intermediate splint occlusion was obtained from this position (Fig. 7).

The STL files were sent to the technician, who processed the images using Exocad^‡‡‡ software. The surgical splints were designed to include holes for metal ligatures in the interproximal spaces. The software determines the thickness of resin needed to avoid fractures during surgery; if this minimum thickness is not achieved, the splint planning must be reevaluated. In the present case, the thickness was appropriate. The STL files with 3D images of the surgical splints were transferred to a DWS 020D^§ prototyping machine, which printed the splints in Dental SG^§§ surgical resin. The final splint was cut away in the area of the upper right permanent canine and retained deciduous canine to allow the programmed distalization of the permanent canine.

A few days before surgery, .018" MBT^§§§ preadjusted appliances were bonded, and passive sectional .017" × .025" stainless steel wires were inserted in both arches. During surgery, a Le Fort I osteotomy was performed to advance the maxilla 6mm and expand it 3mm, a BSSO was performed with a slight setback of the mandible, and the deciduous upper right canine was extracted.

Leveling of the lower arch was initiated with .012" nickel titanium sectional wires and an .016" × .016" Elgiloy^**** Blue overlay wire between the central and lateral incisors. One month later, the lower incisor proclination and molar uprighting were begun using an .016" × .022" Elgiloy Blue utility arch and then an .016" × .022" Elgiloy Blue continuous archwire with steps at the edentulous spaces (Fig. 9), along with .014" and .016" nickel titanium piggyback wires.

After 11 months of treatment, the lower anterior spaces were closed by mesializing the lower canines and premolars. Finishing archwires were .016" × .022" and .017" × .025" nickel titanium in the upper arch and .016" × .022" Elgiloy and .017" × .025" stainless steel in the lower arch.

Total treatment time was 15 months (Fig. 10). 

Intraoral examination found a narrow upper arch and a slightly retroclined upper left first molar. The lower arch was ovoid-shaped. Agenesis of all four permanent second premolars was noted, with retained deciduous second premolars. Perio­dontal defects at the level of the upper and lower incisors, hypoplastic upper lateral incisors, and triangular tooth shapes were also observed. The lower midline was shifted 2mm to the left, and the upper midline was shifted 1.5mm to the right. The molar relationship was Class III. No signs or symptoms of TMD were present.

Cephalometric analysis confirmed a skeletal Class III malocclusion (ANB = −2.6°) with a retrusive maxilla (SNA = 79°), a protrusive mandible (81°), and a hyperdivergent facial type (facial axis = 85°). The upper incisors were slightly retroclined (U1-OP = 62°); the lower incisors were retroclined (L1-OP = 80.5°). An overjet of −1.4mm and an overbite of −.2mm were measured. Projections to the TVL were normal except for soft-tissue pogonion (3.5mm), which was protrusive.

After considering the advantages and disadvantages of conventional surgical-orthodontic treatment and the “surgery first” approach, the patient elected “surgery first” treatment. The surgery would include a Le Fort I osteotomy for a 4.8mm advancement, 1.5mm anterior impaction, 3.5mm posterior impaction, 1.5mm left rotation, and 3mm transverse expansion of the maxilla. A BSSO would be performed to achieve a 2.6mm pogonion setback, 5mm elevation, and midline correction of the mandible.

Orthodontic treatment objectives were to normalize the overjet and overbite, align and procline the upper incisors, and achieve a Class I canine relationship and a Class II molar relationship (because of the missing upper second premolars). We also planned to align the lower incisors and perform interproximal reduction (IPR) of .3mm at each contact to avoid excessive proclination and to reduce the excessive Bolton Index.

As in Case 1, two visual treatment simulations were drawn using Dolphin software (Fig. 13). Dental casts were mounted on a SAM 2 articulator, and model surgery was performed (Fig. 14). Analysis of the model surgery indicated occlusal instability in the transitional malocclusion,²¹ due to interferences between the right canines and left molars. The occlusal interference on the right side was created by a 45° rotation of the upper canine; on the left side, the interference was caused by retroclination of the upper first molar.

The transverse expansion of the maxilla from the median osteotomy would require about 40 days of postsurgical stabilization with an occlusal splint. We decided to utilize segmental mechanics to move the upper right canine and left first molar into proper positions during the early postoperative stage, thus eliminating the occlusal interferences while the patient wore the final splint. The prescription for the upper arch therefore involved 1.5mm expansion of the left molar and 15% rotation of the right canine.

About three weeks before surgery, SmartClip^§§§ .018" MBT-prescription appliances were bonded in both arches, and an intraoral TRIOS scan was taken. The 3D files of the bracketed arches were combined with the patient’s CBCT images using SureSmile^** software. After the planned surgical movements were reproduced on the virtual 3D model (Fig. 15), a virtual orthodontic setup was performed. The prescription of five robotized custom arches began with .017" × .025" copper nickel titanium archwires to be placed the day before surgery; these wires would be passive on all teeth except the upper right canine and left first molar (Fig. 16).

Once the mandible was repositioned, the required surgical expansion of the maxilla was added to ensure a stable occlusion. This position was then used to obtain the STL file for the virtual final splint (Fig. 18).

Planning of the final splint in this case showed premature contacts of the upper right canine and left first molar, requiring an occlusal correction by means of a 2° rotation of the jaw on its hinge axis. Therefore, the planned postsurgical occlusion appeared to be Class II with an increased overjet. Once the interference of the upper right canine and left first molar were removed during the postsurgical stage, the mandible would rotate counterclockwise, correcting the apparent Class II relationship.

All movements relative to the lower jaw were eliminated to obtain the STL file for the intermediate splint (Fig. 19).

The STL files were sent to the technician, who processed the images using Exocad software, as in Case 1 (Fig. 20).

The programmed SureSmile sequence of archwires continued with .016", .016" × .016", and .016" × .022" copper nickel titanium and .017" × .025" stainless steel for alignment. Triangle elastics (³⁄16", 3.5oz) were worn between the upper and lower canines and lower first premolars to maintain the correct occlusion, and vertical elastics were worn for about two months before debonding to improve intercuspation. Thermoformed retainers were delivered for both arches.

Total treatment time was 15 months (Fig. 23). All treatment objectives were achieved, including an optimal occlusion with good intercuspation, normal overjet and overbite, and Class I canine and Class II molar relationships. Facial esthetics showed a marked improvement resulting from the reduced vertical dimension, the sagittal increase in the middle facial third, and the setback of pogonion with its “anti-aging” effect. This result was enhanced by the correction of maxillary hypoplasia, with consequent esthetic improvement of the nasolabial folds and labial commissures. The lip line was refined, and the gummy smile at the premolars was eliminated. Cephalometric tracings confirmed the skeletal and occlusal improvements.