Improvement of chin profile after mandibular setback and reduction genioplasty for correction of prognathism and long chin

Long-term hard and soft tissue response following isolated genioplasty: a systematic review

PURPOSE

Genioplasty facilitates alteration of the chin position and contour which contributes to aesthetics and function. The response of the hard and soft tissues following genioplasty has not been assessed after a year or more of the surgery being performed. Hence, the aim of this systematic review was to assess the response of the hard and soft tissues occurring at least 1 year after the procedure.

MATERIAL AND METHODS

A literature search was conducted in the following electronic databases: PubMed, Ovid, LILACS, and Cochrane Library. Potential articles were identified wherein only studies with genioplasty performed as an isolated procedure and with data at least 12 months after the procedure were included.

RESULTS

Five studies were included in this systematic review. Two of the articles included were considered to be of good quality while three were considered to be of moderate quality using a modified Downs and Black tool. The ROBINS-I tool showed a moderate risk of bias for most domains. The study characteristics revealed varying degrees of relapse for the hard and soft tissues.

CONCLUSIONS

In the anteroposterior plane, the soft tissue relapsed more than the hard tissues 3 years post genioplasty. However, relapse in the vertical plane showed a wide variation for both the hard and soft tissues. In the anteroposterior plane, the hard tissue to soft tissue response 2 years or more following genioplasty ranged from 1:0.77 to 1:0.91 while in the vertical plane the hard tissue to soft tissue response ranged from 1:0.67 to 1:1.16.

Orofacial Cleft and Mandibular Prognathism-Human Genetics and Animal Models

Many complex molecular interactions are involved in the process of craniofacial development. Consequently, the network is sensitive to genetic mutations that may result in congenital malformations of varying severity. The most common birth anomalies within the head and neck are orofacial clefts (OFCs) and prognathism. Orofacial clefts are disorders with a range of phenotypes such as the cleft of the lip with or without cleft palate and isolated form of cleft palate with unilateral and bilateral variations. They may occur as an isolated abnormality (nonsyndromic-NSCLP) or coexist with syndromic disorders. Another cause of malformations, prognathism or skeletal class III malocclusion, is characterized by the disproportionate overgrowth of the mandible with or without the hypoplasia of maxilla. Both syndromes may be caused by the presence of environmental factors, but the majority of them are hereditary. Several mutations are linked to those phenotypes. In this review, we summarize the current knowledge regarding the genetics of those phenotypes and describe genotype-phenotype correlations. We then present the animal models used to study these defects.

Effects of different surgical techniques and displacement distances on the soft tissue profile via orthodontic-orthognathic treatment of class II and class III malocclusions

Background

Orthognathic surgery can be carried out using isolated mandibular or maxillary movement and bimaxillary procedures. In cases of moderate skeletal malocclusion, camouflage treatment by premolar extraction is another treatment option. All these surgical procedures can have a different impact on the soft tissue profile.

Methods

The changes in the soft tissue profile of 187 patients (Class II: 53, Class III: 134) were investigated. The treatment approaches were differentiated as follows: Class II: mandible advancement (MnA), bimaxillary surgery (MxS/MnA), upper extraction (UpEX), or Class III: maxillary advancement (MxA), mandible setback (MnS), bimaxillary surgery (MxA/MnS), and lower extraction (LowEX) as well as the extent of skeletal deviation (moderate Wits appraisal: − 7 mm to 7 mm, pronounced: Wits <− 7 mm, > 7 mm, respectively). This resulted in five groups for Class II treatment and seven groups for Class III treatment.

Results

In the Class II patients, a statistically significant difference (p ≤ 0.05) between UpEX and moderate MnA was found for facial profile (N′-Prn-Pog’), soft tissue profile (N′-Sn-Pog’), and mentolabial angle (Pog’-B′-Li). In the Class III patients, a statistically significant differences (p ≤ 0.05) occurred between LowEX and moderate MxA for facial profile (N′-Prn-Pog’), soft tissue profile (N′-Sn-Pog’), upper and lower lip distacne to esthetic line (Ls/Li-E-line), and lower lip length (Sto-Gn’). Only isolated significant differences (p < 0.05) were recognized between the moderate surgical Class II and III treatments as well between the pronounced Class III surgeries. No statistical differences were noticed between moderate and pronounced orthognathic surgery.

Conclusions

When surgery is required, the influence of orthognathic surgical techniques on the profile seems to be less significant. However, it must be carefully considered if orthognathic or camouflage treatment should be done in moderate malocclusions as a moderate mandibular advancement in Class II therapy will straighten the soft tissue profile much more by increasing the facial and soft tissue profile angle and reducing the mentolabial angle than camouflage treatment. In contrast, moderate maxillary advancement in Class III therapy led to a significantly more convex facial and soft tissue profile by decreasing distances of the lips to the E-Line as well as the lower lip length.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13005-021-00264-4.

Differences in soft-tissue thickness changes after bimaxillary surgery between patients with vertically high angle and normal angle

INTRODUCTION

We evaluated soft-tissue thickness changes after bimaxillary surgery according to vertical facial patterns in patients with skeletal Class III malocclusion with mandibular prognathism.

METHODS

Forty-three Korean patients (16 men and 27 women; mean age, 22.6 ± 4.1 years) with skeletal Class III malocclusion who underwent bimaxillary surgery were divided into 2 groups: normal-angle group (N group) and high-angle group (H group), on the basis of the presurgical angle of the mandibular plane relative to the sella-nasion plane (SN-MP). Changes in hard-tissue landmarks and soft-tissue thickness before and after surgery were analyzed from reconstructed 3-dimensional cone-beam computed tomography images. Postoperative soft-tissue thickness in both groups was compared with that in 40 patients with normal skeletal Class I malocclusion in the reference group.

RESULTS

Group N (27°-37°) and group H (>37°) did not differ significantly in terms of sex and age before surgery. Preoperative pogonion (Pog) thickness was significantly less in group H (9.7 ± 1.6 mm) than in group N (10.8 ± 1.9 mm) (P = 0.042). Adjusted multiple linear regression analysis showed a weak positive linear relationship between the SN-MP before surgery and soft-tissue Pog thickness change (R² of 0.361; P = 0.001) after surgery, but the area below the lower lips was not completely normalized despite surgery.

CONCLUSIONS

The thickness of the soft-tissue Pog may increase slightly after surgery in patients with skeletal Class III malocclusion with a higher preoperative mandibular plane angle, but normalization in the area cannot be completely achieved despite surgery.

Design and manufacture of dental-supported surgical guide for genioplasty

Background/purpose

Genioplasty were used widely to correct chin deformities. The purpose of this study was to design and manufacture a dental-supported surgical guide for genioplasty surgery and assess for surgical accuracy.

Materials and methods

eleven patients with chin deformities were treated in this study. The computed tomography (CT) data of the patient's skull and the digital dental models of stone dental models were acquired preoperatively. For each patient, a virtual three-dimensional (3D) model of the skull was constructed and enhanced with digital dental models. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on clinical examination and 3D cephalometry. The surgery was simulated preoperatively which allowed the design of a cutting guide and a dental-supported repositioning guide for genioplasty, which was then 3D-printed and used during operation after disinfection. After surgery, the outcome was evaluated by superimposing the postoperative CT model onto the preoperative model, recording the linear and angular deviation of landmarks and plane, then measuring the differences between the planned and actual outcomes.

Results

The osteotomy and repositioning were successfully performed as planned using surgical guides. No inferior alveolar nerve damage was seen in this study. The dental-supported surgical guide showed excellent accuracy, with the largest differences between the planned and the postoperative chin segment being 0.9 mm and 3.2°.

Conclusion

The dental-supported surgical guide designed preoperatively provided a reliable method of transfer genioplasty planning. This can assist surgeons in accurately performing osteotomy and repositioning bone segments during a genioplasty.

Reduction genioplasty for mandibular prognathism and long chin

BACKGROUND

When evaluating patients' profile, surgeons usually note the lack of the chin projection and may suggest chin augmentation, but they rarely discuss reduction of an over-projecting chin. This is unfortunate, since there are quite many individuals who have macrogenia and would aesthetically benefit from corrective surgery, but the chin reduction is seldom offered. The reason for this is the lack of experience, lack of the technical equipment necessary, or sometimes lack of knowledge. The present study conveys 25 years of experience with the reduction genioplasty.

METHODS

From 1994 to 2019, 47 patients (39 females, 6 males, and 2 male to female transsexuals) underwent 49 chin reduction procedures. All patients were operated and followed up by the author. The transoral approach was used in 23 patients, and in 24 patients the procedure was done through the straight 4- to 6-cm-long submental incision. The air-driven pneumatic chisel was employed for reduction of the mandibular bone (MicroAire, Charlottesville, VA, USA). Forty-eight operations were carried out under dissociative and local anaesthesia on an outpatient basis, and one procedure was done under general endotracheal anaesthesia.

RESULTS

Both mandibular bone and the soft tissues of the chin were reduced, or modulated according to the needs of each patient. Operations were technically easier when executed by the submental approach because of better exposure of the mandibular rim and the higher precision in the remodelling of the soft tissues. Thirty-six patients (77%) could be followed up for a mean of 2.5 years (range 9 months to 12 years). Twenty-eight of evaluated patients (78%) described the outcome as very good or good. Four patients described the result as acceptable and another 4 as bad. In the majority of cases the evaluation by the surgeon correlated well with the opinion of patients, but in five cases surgeon estimated result with the higher score than the patient. Overall good results were illustrated by the photographs of the clinical examples. Complications were few and manageable. Transient neuropathies were common and more frequent with the transoral approach. Five patients required minor intervention for skin indentations at the jaw line developed during the healing phase.

CONCLUSIONS

Skilful chin reduction surgery is safe and the aesthetic improvement could be quite spectacular, which is also rewarding for the patients. Complications in this patient series were few and manageable. More surgeons should include chin reduction in their repertoire.

Advantages of performing mentoplasties with customized guides and plates generated with 3D planning and printing. Results from a series of 23 cases

PURPOSE

To evaluate the benefits of performing mentoplasty using custom guides and plates in a series of 23 patients.

PATIENTS AND METHODS

An 18-month observational study in 23 patients (16 women, 7 men) who underwent procedures for chin augmentation (n = 15), reduction and centering mentoplasty (n = 6), chin asymmetry correction (n = 1) and placement of a custom chin implant to correct esthetics (n = 1) was conducted in the Department of Oral and Maxillofacial Surgery of Hospital Universitario Dexeus (Barcelona, Spain).

RESULTS

A mentoplasty technique using customized surgical guides and plates, performed under local anesthesia and oral sedation, was performed in every case. Surgery times were approximately 45 min. Postoperative recovery was satisfactory in all patients. There were no intraoperative or serious postoperative complications, except for one self-limiting edema and some small hematomas of no clinical significance. Post-operative pain intensity measured by the Visual Analog Scale (VAS) was less than 3 (mild pain) in 80% and 4-7 (moderate pain) in 20% of patients.

CONCLUSION

The results obtained in this study show that using customized surgical guides and plates in performing mentoplasty is an advantage over conventional techniques as they provide greater accuracy and safety in the surgery and more predictable results. This simplifies the procedure.

Mandibular Body Resection and Setback for Severe Malocclusion in Lymphatic Malformations

Extensive lymphangiomas of the facial skeleton result in deforming forces leading to ongoing masticatory, speech, oral hygiene, and airway problems. This paper presents a small series of patients with severe mandibular overgrowth secondary to lymphatic malformations. Following debulking of the malformations and tongue reductions, the authors describe the results of their treatment with bilateral mandibular body resections and setback. The authors' results suggest that severe functional impairment from deforming malformations can be addressed in childhood with orthognathic surgery. Improved occlusion, oral closure, and airway opening can be achieved using this procedure.

A systematic review on soft-to-hard tissue ratios in orthognathic surgery part II: Chin procedures

PURPOSE

Precise soft-to-hard tissue ratios in orthofacial chin procedures are not well established. The aim of this study was to determine useful soft-to-hard tissue ratios for planning the magnitude of sliding genioplasty (chin osteotomy), osseous chin recontouring and alloplastic chin augmentation.

MATERIAL AND METHODS

A systematic review of English and non-English articles using PubMed central, ProQuest Dissertations and Theses, Science Citation Index, Elsevier Science Direct Complete, Highwire Press, Springer Standard Collection, SAGE premier 2011, DOAJ Directory of Open Access Journals, Sweetswise, Free E-Journals, Ovid Lippincott Williams & Wilkins total Access Collection, Wiley Online Library Journals, and Cochrane Plus databases from their onset until July 2014. Additional studies were identified by searching the references. Search terms included soft tissue, ratios, genioplasty, mentoplasty, chin, genial AND advancement, augmentation, setback, retrusion, impaction, reduction, vertical deficit, widening, narrowing, and expansion. Study selection criteria were as follows: only academic publications; human patients; no reviews; systematic reviews or meta-analyses; no cadavers; no syndromic patients; no pathology at the chin or mandible region; only articles of level of evidence from I to IV; number of patients must be cited in the articles; hard-to-soft tissue ratios must be cited in the articles or at least are able to be calculated with the quantitative data available in the article; if all patients of one article have had bilateral sagittal split osteotomy (BSSO) performed along with chin osteotomy, there should be an independent group evaluation of the data concerning to the chin; and no restriction regarding the size of the group. Independent extraction of articles by two authors using predefined data fields, including study quality indicators (level of evidence).

RESULTS

The search identified 22 articles. Eleven additional articles were found in their reference sections. Of these, two were evidence level IIIb, three were evidence level IIb, and the rest were evidence level IV. Three studies were prospective in nature. A high variability of soft-to-hard tissue ratios regarding genioplasty seemed to disappear if data were stratified according to confounding factors. With the available data, a soft-to-hard pogonion ratio of 0.9:1 and 0.55:1 could be used for chin advancement and chin setback surgery, respectively.

CONCLUSION

Advancement and extrusion movements of the chin segment show respectively a 0.9:1 of sPg:Pg horizontally and 0.95:1 of sMe:Me vertically. Setback and impaction movements show respectively a -0.52:1 of sPg:Pg horizontally and -0.43:1 of sMe:Me vertically. Prospective studies are needed that stratify by confounding factors such as type of osteotomy technique, magnitude of the movement, age, sex, race/ethnicity, and quantity and quality of the soft tissues. More specifically, studies are needed regarding soft-to-hard tissue changes after chin extrusion ("downgrafting"), intrusion ("impaction"), and widening and narrowing surgery.

Effect of maxillary advancement on the change in the soft tissues after treatment of patients with class III malocclusion

The aesthetic outcome of treatment has become increasingly important to patients having orthognathic surgery. The aim of this observational cohort study based on clinical records was to evaluate the effect of maxillary advancement on changes to the soft tissues. We studied 53 patients with class III malocclusion (29 women and 24 men, mean (SD) age 28 (11) years). We identified all patients treated between 1 January 2002 and 30 December 2013 who could be monitored postoperatively for 6 months. To study the effect of maxillary advancement on changes to the soft tissue we distinguished between patients who had had less than 6mm, and those with 6mm advancement or more. In those who had had less than 6mm, we found no significant changes in the soft tissue in the region of the nasolabial angle. However, the lip-chin- throat angle (p=0.016), cervical length (p=0.002), lower lip (p=0.007) and upper lip distance (p=0.0001) from the aesthetic line changed significantly. On the other hand, the changes to the soft tissue in the submental and nasolabial regions were significant in patients with 6mm advancement or more, and indicated a clear improvement in the aesthetic outcome of this region. This aesthetic change for the good in the submental and nasolabial regions after maxillary advancement of 6mm or more should be considered when planning treatment, and reduction in the mandibular setback will reduce the risk of development of a double chin.

Consideration of effect of the amount of mandibular setback on the submental region in the planning of orthodontic-orthognathic treatment

Aesthetic outcome has gained in importance in the treatment of patients with orthognathic problems. Historically, Class III malocclusions have historically been treated by isolated mandibular setback and maxillary advancement, whereas bimaxillary procedures have recently become the more common option. Functional outcome and stability have been discussed previously. The aim of this observational study was to evaluate the effect of mandibular setback (BSSO) on the cervical region. We studied 38 Class III patients (20 women and 18 men, mean (SD) age 25 (0.8) years) who we identified from our clinical records and who were treated between 1 January 2002 and 30 December 2012 with mandibular setback procedures and followed up for 6 months. To study the effect of the amount of mandibular setback on the aesthetic outcome we have distinguished between patients with less than 5mm setback and those with 5mm or more. In patients whose mandibular setback was less than 5mm there was no significant change in cervical length. However, it decreased significantly in patients in whom the movement was 5mm or more. Postoperatively the lip-chin-throat angle (p=0.02), the length of the lower lip (p=0.002), and the length of the upper lip (p=0.003) from the aesthetic line also differed significantly between the 2 groups. Our observations strongly suggest that all these relations should be considered when treatment is being planned to avoid an unpleasant aesthetic impact on the chin region.

The extent of chin ptosis and lower incisor exposure changes following the osseous genioplasties

The incision and dissection of the mentalis muscles are inevitable to access the osteotomy line during genial surgery. As the mentalis muscles elevate the central lower lip and support the lip vertically, inadvertent scarring or lengthening of these muscles may lead to lip incompetence and may increase the lower incisor exposure (LIE) that will cause an unaesthetic result. The aim of this study was to evaluate the extent of lip ptosis, LIE, and other soft-tissue changes following different types of osseous genioplasty procedures.Twenty-nine patients (18 females, 11 males) were included in this study. Patients were classified into 3 groups with respect to their genial movement type as genial setback (n = 10), genial advancement (n = 10), and vertical reduction (n = 9). Preoperative and postoperative lateral cephalograms were analyzed to evaluate the horizontal and vertical soft-tissue changes of the lower lip and chin in the 3 genioplasty groups. The statistical evaluations were performed with regression analysis. The mean increase in the LIE was 1.88 mm. Lower incisor exposure and soft-tissue thickness at pogonion were increased significantly in all patients (P < 0.05). Statistically significant differences for lower lip length and vertical position of soft-tissue supramentale values were detected in patients who underwent vertical reduction genioplasty (P < 0.05). Genioplasty procedures requiring the mentalis muscle release cause a 1.88-mm increase in LIE. Vertical positional alterations of the lower lip were especially observed following the vertical reduction genioplasty. Clinician should be aware of this consequence in the course of treatment planning.