Bimaxillary protrusion is a unique dentofacial deformity trait that can exist in an individual as an isolated problem or in combination with other skeletal and dental-related issues. Orthodontist and oral and maxillofacial surgeons are often the main primary team involved in the management of bimaxillary protrusion. Clinical dilemma often exists as cases can either be treated orthodontically or may require a combination of orthodontic and skeletal segmental orthognathic surgery. This article aims to help clinicians improve their approach to management of bimaxillary protrusion by creating a classification based on the severity that can guide treatment selection.
Key points
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All cases of bimaxillary protrusion should be analyzed in holistic manner which includes a subjective and objective assessment.
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Bimaxillary protrusion patients with an underlying Class II skeletal pattern and a hypoplastic chin should receive a full airway assessment to ensure that there is no increased risk to develop obstructive sleep apnea with the orthodontic only approach.
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Treatment planning must be individualized based on each patient’s facial type to ensure favorable posttreatment changes in the vertical direction.
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Clinicians should be able to predict the long-term esthetic and functional outcomes and provide a good informed consent especially in patients who receive orthodontics with extractions before skeletal maturity.
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All moderate to severe bimaxillary protrusion cases would benefit from a combined discussion between the oral and maxillofacial surgeon and orthodontist before coming up with a final treatment plan.
Introduction
Bimaxillary protrusion is a dentofacial deformity trait that can present in all different skeletal patterns. Clinically, the trait is associated with the presence of a protrusive anterior dentoalveolar segment of the maxilla and mandible. This produces an appearance of unsightly protruding anterior teeth, increased procumbence of the lips and a convex lateral facial profile. These clinical features are often perceived negatively with regard to facial attractiveness. It can occurs in almost every ethnic group but relatively more common in the Asian and African populations , ,
Patients with this trait often seek esthetic improvements. This is because the clinical features have been shown to lead to negative psychosocial effects translating from poor self-esteem. , , , , The key factor in ensuring good treatment outcome is often focused on ensuring esthetic satisfaction. It is therefore important that the selected treatment modality is able to address the patient’s esthetic concern in short term as well as long term. ,
However, very often clinicians find themselves in a dilemma in selecting the right treatment modality. This is due to the heterogeneity of clinical presentation in every patient with bimaxillary protrusion. Bimaxillary protrusion can be treated orthodontically or by a combination of orthodontics with segmental orthognathic surgery. The traditional orthodontic approach to this skeletal trait is often via extractions of all four first premolars to reduce the anterior proclination. Advancements related to the usage of skeletal anchorage devices (SADs) in orthodontics have introduced approaches that distalize the anterior segment using a non-extraction protocol. Last, management can include a combined orthodontic and surgical approach which would involve segmental orthognathic surgery.
Treatment planning that focuses on only the biomechanics to correct the anterior proclination without proper clinical analysis can lead to a satisfactory occlusion from a clinical point of view but an unhappy patient from an esthetic point of view. Fig. 1 is an example of an end point of a case with bimaxillary protrusion. She was treated orthodontically by retraction of the anterior segment with extraction of all four first premolars. The patient however was dissatisfied at the end of the treatment with the esthetic outcome. It is therefore fundamental to have a good approach in reaching a diagnosis that then guides an individualized patient-specific treatment modality.
Approach to diagnosis
Clinical diagnosis before deciding on the treatment modality of choice depends on the following:
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Subjective assessment
- B.
Objective clinical assessment ( Fig. 2 )
Fig. 2 Objective Clinical Assessment Checkpoints. - C.
Radiographic Assessment
Subjective Assessment
Patient factor
Every patient comes with a certain perception of their problem and an expectation on the treatment outcome. They also have an expected timeline for treatment completion. This must be clearly identified at the pretreatment consultation stage. Clinicians must ensure that each patient is aware of the limitations and risks for each treatment approach. An important factor is the age of the patient at the consultation. Identifying growing patients that should postpone definitive treatment until skeletal maturity is fundamental especially when segmental orthognathic surgery is indicated. Fig. 1 shows a patient whom received orthodontic treatment at the age of 15 with all four first premolar extractions. She is now 30 years old and dissatisfied with the current aesthetic outcome. Corrective surgery at this point is more complicated because of the previous treatment that included extractions. This highlights the importance of age at the point of consultation. The clinician must be able to ensure a treatment modality that has a good functional and esthetic outcome on skeletal maturity. This is especially important if the treatment involves irreversible interventions such as extractions. The decision of not considering a combined surgical orthodontic approach in an indicated case may lead to compromised outcomes and possible medicolegal implications. Clinicians need to balance patient expectations together with objective clinical findings when coming up with their final treatment plan.
Objective Clinical Assessment
Facial esthetics assessment
Pretreatment facial esthetic assessment guides the initial consultation. It improves patient understanding with regards to the expected posttreatment changes based on the treatment offered. This is especially important in the skeletal immature patients. This assessment can prevent unnecessary extractions that may compromise long-term management of the esthetic component as seen in the case shown in Fig. 1 .
Facial esthetic assessment involves a frontal and lateral facial analysis. The frontal facial analysis classifies the facial types into mesofacial, brachyfacial, or dolichofacial. This is to ensure posttreatment facial harmony. The pretreatment amount of incisor show at rest is the next important assessment. Retractions of the anterior segment to correct the protrusion can lead to changes to the incisal show and upper lip length. These changes should meet the patient’s expectations as it has implications to the patient’s smile. Underlying concomitant skeletal asymmetries need to be diagnosed to ensure that the patient understands the limitations of each treatment modality in addressing the skeletal asymmetry.
The lateral facial analysis helps to group patients with bimaxillary protrusion to the skeletal Classes I–III. It also identifies a hypoplastic chin. Several soft tissue angles and characteristics play an important role in facial esthetics. These include the nasolabial angle, labiomental fold, and the presence of an incompetent lip. Clinicians must be familiar with the expected changes that will happen to these parameters with each suggested treatment modality.
Functional assessment
The presence of functional issues also plays a part in deciding the treatment of choice. Functional assessment includes an airway and dental examination. Airway assessment is important as orthodontic correction of the anterior dentoalveolar proclination by extractions of all four first premolars in the presence of an underlying skeletal Class II, and hypoplastic chin will increase the risk of developing obstructive sleep apnea (OSA) in a susceptible patient. The airway assessment should include tonsil grading, the body mass index, and the presence of transverse discrepancies of the maxilla or a V-shaped maxilla. These are all independent risk factors for OSA. If these factors are present in a patient whom receives extractions for distalization of the anterior segment, the risk for OSA will be potentiated. This group of patients stands to benefit skeletal segmental orthognathic surgery to correct the bimaxillary protrusion as well as to improve their airway parameters.
Next is the dental assessment. This includes identifying space restrictions/crowding, presence of a favorable overjet and overbite, and the angle’s classification. These findings lead to the possible need for extractions as well as if SADs or segmental orthognathic should be considered.
Radiographic assessment
Lateral Cephalometry
Lateral cephalometry acts as an adjunct to clinical assessment ( Fig. 3 ). It provides angular measurements to supplement the diagnosis with regards to skeletal analysis, baseline dental deviations, and esthetic prediction. This enhances the ability of clinicians to give valid information to their patients based on the suggested treatment modality and manage expectations with regards to treatment time and esthetic outcomes. Lateral cephalometry analysis can be systematically divided to :
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Skeletal Analysis
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Dental Angular Measurements
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Esthetic Predictions
Skeletal Analysis
Skeletal angular measurements help to predict the feasibility of an orthodontic only approach. It gives a prediction on the amount of dental movement that will be needed to correct the bimaxillary protrusion and diagnose any underlying skeletal deformities. It also allows analysis of the posterior pharyngeal space to identify patients at risk of developing OSA posttreatment. The important baselines angles include:
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Sella to Nasion and A-point (SNA): Assessment of the anterior posterior position of the maxilla to indicate if the maxilla is normal, prognathic, or retrognathic.
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Sella to Nasion and B-point (SNB): Assessment of the anterior posterior position of the mandible to determine if the mandible is normal, prognathic, or retrognathic.
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A-point to Nasion and B-point (ANB): This angle will determine if the patient is a skeletal Class I, II, or III.
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Frankfurt-mandibular plane angle (FMPA): This angle will determine the facial proportion and vertical growth pattern of the patient. This helps support the earlier clinical assessment of facial type. This component has an important correlation to the types of biomechanics that need to be considered when correcting the anterior proclination which has an impact to the vertical height of the face. This change must be in favorable to the baseline facial type of the patient.
• Dental angular measurements
This measurement indicates the amount of retraction needed at the level of the anterior incisors to correct the convex lateral facial appearance. This amount indirectly translates to the distal space needed to retract the anterior segment and if this can be achieved by premolar extractions or by the use of skeletal anchorage devices (SADs). In the presence of severe skeletal deformities and discrepancy, the retraction of the anterior segment will require segmental orthognathic surgery.
The important parameters that will need measurement include:
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Upper incisor to palatal plane (U1-PP): This documents the degree of proclination of the anterior upper incisors.
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Lower incisor mandibular plane angle (IMPA): This documents the degree of proclination of the lower incisors.
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Interincisal angle (IIA): This angle determines the severity of bimaxillary protrusion leading to the procumbence of the incisors.
• Esthetic predictions
Functional esthetic occlusal plane
The functional esthetic occlusal plane (FAOP) provides important information concerning the (i) vertical relationship of the incisors with the lips at rest and (ii) the position of molars in contact. This facilitates understanding with regards to the limitation of a selected treatment modality to the esthetic and functional demands (occlusion) of the patient. It also provides valuable esthetic information as it analyzes the relationship of the incisor with the lips. This will then indicate if the exposure is within the acceptable limits according to age. At the same time, it also indicates the reference position of molars and their respective vertical dimension. This assessment is important as it takes into consideration the posttreatment outcome in patients with different skeletal patterns. Bimaxillary protrusion patients stand to benefit significantly from this assessment as it incorporates esthetic outcomes instead of focusing purely on the biomechanics required to correct the angular measurements.
Esthetic plane
The esthetic plane (E-plane) is a simple linear line drawn from the tip of the nose to the tip of the chin. It allows for an assessment of the position of the upper lip and lower lip in relation to this line. It has been documented that a pleasant smile is produced if the lower lip is 2 mm behind this line and the upper lip is 4 mm behind this line. This assessment helps the clinician to decide if an extraction protocol or a non-extraction protocol would produce a good smile at the end of the treatment. This line can also determine the degree of concavity or convexity from an underlying skeletal problem that may indirectly indicate the need for segmental orthognathic surgery.
Therapeutic options
This review article attempts to group bimaxillary protrusion patients into mild, moderate, and severe. This will improve the ability to screen patients holistically. The grouping suggested is based on the specific clinical and radiographic criteria as shown in Tables 1 , 2 and 3 . The management suggested for each group is based on the treatment approaches reported in the literature. It can either be via orthodontics only or orthodontics with segmental orthognathic surgery.
| Treatment Approach: Orthodontics | |
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| Non-Extraction Orthodontics | Extraction Orthodontics |
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| Lateral Cephalometry | |
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