Inferior subapical osteotomy for dentoalveolar decompensation of class III malocclusion in ‘surgery-first’ and ‘surgery-early’ orthognathic treatment

Abstract

Increasing experience with alternative timing protocols in orthognathic surgery has given way to new surgical and orthodontic techniques to shorten treatment times, reduce biological costs, and improve the final outcome. A prospective evaluation of class III patients who received an inferior segmental osteotomy (ISO) for decompensation of significantly retroclined lower incisors in the context of ‘surgery-first’ (SF) or ‘surgery-early’ (SE) timing protocols was performed. Treatment was planned virtually. A thorough periodontal assessment was performed at baseline and periodically until debonding. A minimally invasive surgical technique including selective interdental corticotomies and elective bone augmentation was used. Patient and orthodontist satisfaction with the treatment was evaluated. Eight patients (mean age 26.3 years) underwent surgery. One had isolated maxillary surgery and seven had bimaxillary surgery in combination or not with additional cosmetic procedures. The periodontal status of all patients remained stable throughout the observation period. The mean duration of orthodontic treatment was 8.7 months in the SF group and 10.5 months in the SE group. Satisfaction with treatment was extremely high. The ISO is a safe, reliable technique for dentoalveolar decompensation in timing protocols with a short or no orthodontic preparatory phase. This methodology may represent a reasonable approach in selected class III patients.

While the correction of a dysfunctional occlusion used to be the main therapeutic goal for orthognathic surgery patients, the wish to improve facial aesthetics or correct sleep-disordered breathing has become the motivation for treatment in many cases. Moreover, supported by the perception of surgery as safe and predictable, the number of adult patients who become engaged in orthodontic or combined orthodontic–surgical therapy is increasing steadily. Often, these patients present periodontal problems and job-time limitations for conventional preoperative orthodontic schemes and are good candidates for alternative timing approaches such as ‘surgery-first’ (SF) or ‘surgery-early’ (SE).

Besides immediate correction of the patient’s aesthetic concern and/or compromised airway, the main advantage of these timing schemes, in which surgery is performed before any orthodontic treatment (SF) or after a short preparatory phase (SE), is that subsequent orthodontic treatment and hence the total treatment time are significantly shorter. Improved orthodontic efficiency is probably related to the increased metabolic turnover of the regional acceleratory phenomenon (RAP) and a more favourable soft tissue tone after skeletal base correction.

Clinical experience has shown that routine preoperative dental alignment, full arch coordination, and incisor decompensation often tend to prolong the treatment time, with little or no clinically significant benefit for the patient. Besides, dental compensation can be resolved – totally or partially – with surgical osteotomies. This may be particularly relevant in periodontally compromised patients or cases with a narrow anterior alveolar ridge, where conventional incisor decompensation may lead to gingival recession or bone dehiscence and fenestration.

The so-called ‘subapical osteotomy’, ‘front-block’, or ‘anterior segmental osteotomy’ was described by Cohn-Stock in 1921. Almost a century of clinical experience later, the effectiveness of this osteotomy, and its subsequent technical modifications, for the treatment of mono and bimaxillary protrusion is widely acknowledged.

Details of the treatment concept and experience in SF and other alternative timing protocols of the present study authors is available in the scientific literature. Progressive understanding of the possibilities and limitations of these protocols has led to the development of new surgical and orthodontic techniques to further shorten treatment times, refine selection criteria, reduce biological costs, and ultimately improve the final outcome. In this context, the aim of the present study was to illustrate the value of the inferior subapical osteotomy – with proclination of the osteotomized segment – for accelerated decompensation of class III malocclusion. To this effect, a prospective evaluation of cases in which an inferior subapical osteotomy was indicated to surgically decompensate the antero-inferior region was performed. The focus was set on the analysis of selection criteria, feasibility of the procedure, complications, and final outcome.

Materials and methods

A prospective evaluation of all patients who received an inferior subapical osteotomy for dentoalveolar decompensation during a 5-year time period (June 2010 to June 2015) was performed. The guidelines of the Declaration of Helsinki on medical protocol and ethics were followed at all treatment stages. The performance of this study did not in any way alter the systematized protocol used at the study centre for the diagnosis, treatment, and follow-up of orthognathic surgery patients. Hence, additional approval from the local committee on ethical medical practice was not required.

Patients were selected for an inferior subapical osteotomy (isolated or combined with another facial osteotomy) on the basis of the following inclusion criteria: (1) non-growing status; (2) dentofacial deformity with significant retroclination of the lower incisors; (3) SF or SE timing protocol; (4) sufficient interdental space at the selected segmentation sites to guarantee a periodontally safe osteotomy; (5) stable periodontal situation; and (6) informed consent.

In all cases, the routine protocol for diagnostic work-up and three-dimensional (3D) surgical planning of the study centre was followed. This method has been validated and described in detail elsewhere. In brief, it consists of the following steps: (1) detailed interview and thorough clinical assessment of the patient by the combined surgical–orthodontic team. (2) Radiological evaluation with cone-beam computed tomography (CBCT) (i-CAT version 17–19; Imaging Sciences International, Hatfield, PA, USA). (3) Dental arch anatomy registration by digital scanning (Lava Scan ST Scanner; 3M ESPE, Ann Arbor, MI, USA). (4) Generation of an augmented virtual skull model with accurate representation of the bony and dental tissues by .stl file fusion (CBCT plus intraoral scan). (5) 3D virtual orthodontic setup, in which the orthodontist predicts the final (at the end of orthodontic treatment) position and axial inclination of each individual tooth. This is a crucial step prior to the surgeon’s skeletal base correction simulation in complex SF and SE cases, where the patient’s baseline occlusion cannot serve as a reliable guide for skeletal repositioning. (6) Virtual simulation of the orthognathic osteotomies, including the inferior subapical osteotomy, with Dolphin Imaging (version 11.0; Chatsworth, CA, USA) ( Figs 1 and 2 ). The ideal interdental site for segmentation (between the lateral incisor and canine, or between the canine and first premolar) is chosen based on arch shape correction objectives and the amount of interdental space for a safe osteotomy. The amount of proclination given to the front-block segment in the software is corroborated on the dental casts. (7) CAD/CAM (computer-aided design and computer-aided manufacturing) production of the intermediate and final splints.

Fig. 1
Virtual simulation of the orthognathic osteotomies (frontal view).

Fig. 2
Virtual simulation of the orthognathic osteotomies (profile view).

The preoperative periodontal evaluation consisted of a complete periodontal charting. The following parameters were recorded at baseline: plaque index, probing pocket depth (PPD), gingival recession, bleeding on probing, and clinical attachment level (CAL). All measurements were taken by the same calibrated examiner. PPD was measured from the gingival margin with a CP-11 periodontal probe. Gingival recession was measured from the cemento-enamel junction to the gingival margin (gingival recession was equal to 0 whenever the cemento-enamel junction was covered). CAL was calculated by adding the values of gingival recession and PPD. All measurements were made at six sites per tooth: mesiovestibular (mv), central-vestibular (cv), distovestibular (dv), mesiolingual (ml), central-lingual (cl), and distolingual (dl). Two weeks prior to treatment, all patients were scheduled for oral hygiene instructions as well as for professional supragingival debridement according to individual needs, and the patient’s ability to maintain optimal oral hygiene standards was checked.

In cases managed with SF, no preoperative orthodontic preparation apart from bracket bonding 2–7 days before surgery was implemented. In this group of patients, the first soft archwire was not placed until 24 h before surgery in order to avoid dental movements that could render the CAD/CAM splint inaccurate.

All patients were operated on under general anesthesia by the same surgeon (FHA). Monomaxillary cases (mandibular bilateral sagittal split osteotomy and or inferior subapical osteotomy) were treated in an outpatient context. Bimaxillary cases were discharged after 24 h.

The surgical approach for the inferior subapical osteotomy consisted of a horizontal incision between the two lateral incisors at a level below the attached gingiva and above the buccal sulcus. The mucoperiosteal flap was elevated carefully to expose the prospective box-shaped osteotomy line. A piezoelectric microsaw (Implant Center 2; Satelec-Acteon Group, Tuttlingen, Germany) was used to design the osteotomy and to perform additional interdental corticotomies at selected sites, with the aim of further enhancing the RAP and facilitating orthodontic decrowding. While corticotomies were interrupted when the superficial spongiosa was reached, and hence light bleeding was detected, the boundaries of the inferior subapical osteotomy were deepened towards the lingual cortex ( Fig. 3 ). At the vertical interdental segmentation sites, the attached gingiva of the papilla was only slightly elevated and the piezoelectric abutment was tunnelled upwards towards, but not reaching, the inter-alveolar crest. The osteotomy was completed with gentle rotation manoeuvres of a 6-mm straight osteotome (Epker DO-181; Bontempi, Tuttlingen, Germany). Once repositioned, no rigid fixation system, besides the adapted archwire itself, was used to fix the segment in its final position. Additionally, interdental gaps greater than 3 mm were grafted (Apatos, OsteoBiol; Tecnoss, Giaveno, Italy). Likewise, horizontal osteotomy gaps greater than 3 mm were grafted in order to smooth the transition between the chin and the repositioned front-block segment.

Fig. 3
Inferior subapical osteotomy and interdental corticotomies to facilitate orthodontic decrowding.

Postoperative orthodontic treatment was started no later than 2 weeks postoperatively in order to benefit from the RAP. At this point, the composite bridges were removed and the archwire was substituted with expanding coils. If necessary, the inclination of the intermediate mandibular fragment was further modified with elastic mechanics.

Postoperative CBCT imaging was performed 1 month and 1 year after surgery. Periodontal checkups were scheduled on a monthly basis during the first two postoperative months and then every 3 months. A final check-up was performed after orthodontic debonding. The following parameters were evaluated: plaque index, PPD, gingival recession, bleeding on probing, and CAL.

Patient satisfaction with treatment was evaluated on a 0–10 visual analogue scale (VAS) at the 6-month follow-up appointment.

Results

During the 5-year study period, a total of eight patients (three female, five male) underwent an inferior subapical osteotomy for dentoalveolar decompensation purposes at the study centre ( Table 1 ). Their mean age at the time of surgery was 26.3 years (range 14–49 years). For all patients, the preoperative malocclusion was skeletal class III with combined sagittal-transverse maxillary hypoplasia and severely compensated mandibular incisors.

Table 1
Demographic characteristics, surgical procedure, timing protocol, total treatment time, and satisfaction with treatment for the study sample.
Case Sex Age at time of surgery, years Orthognathic surgery procedure Ancillary cosmetic procedure(s) Timing protocol Total treatment time, months Satisfaction with treatment (VAS)
Patient Orthodontist
1 F 17 Bimaxillary surgery:
Four-piece LFI + BSSO
Inferior subapical osteotomy
Rhinoplasty SF 8 10 10
2 M 38 Bimaxillary surgery:
One-piece LFI + BSSO
Inferior subapical osteotomy
Genioplasty
Malar augmentation (PBFP technique)
Cervical liposuction
SF 10 10 10
3 F 14 Bimaxillary surgery:
One-piece LFI + BSSO
Inferior subapical osteotomy
Recontouring of the mandibular lower border SE 12 10 10
4 F 27 Bimaxillary surgery:
Four-piece LFI + BSSO
Inferior subapical osteotomy
Genioplasty
Malar augmentation (PBFP technique)
SF 12 10 9
5 M 25 Bimaxillary surgery:
Four-piece LFI + BSSO
Inferior subapical osteotomy
SF 8 8 9
6 M 49 Bimaxillary surgery:
Four-piece LFI + BSSO
Inferior subapical osteotomy
SF 7 10 9
7 M 18 Bimaxillary surgery:
One-piece LFI + BSSO
Inferior subapical osteotomy
Genioplasty SF 7 9 9
8 M 23 Monomaxillary surgery:
One-piece LFI
Inferior subapical osteotomy
SE 9 9 10
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Dec 14, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Inferior subapical osteotomy for dentoalveolar decompensation of class III malocclusion in ‘surgery-first’ and ‘surgery-early’ orthognathic treatment
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