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Maxilla
Maxilla
Maxilla
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Maxilla
Position of the maxilla
Animation of the maxilla
Details
PrecursorFirst branchial arch[1]
Identifiers
Latinmaxilla
MeSHD008437
TA98A02.1.12.001
TA2756
FMA9711
Anatomical terms of bone

In vertebrates, the maxilla (pl.: maxillae /mækˈsɪliː/)[2] is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth.[3][4] The two maxillary bones are fused at the intermaxillary suture, forming the anterior nasal spine. This is similar to the mandible (lower jaw), which is also a fusion of two mandibular bones at the mandibular symphysis. The mandible is the movable part of the jaw.

Anatomy

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Structure

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The maxilla is a paired bone - the two maxillae unite with each other at the intermaxillary suture. The maxilla consists of:[5]

Inferior surface of maxilla

It has three surfaces:[5]

  • the anterior, posterior, medial

Features of the maxilla include:[5]

Articulations

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Each maxilla articulates with nine bones: frontal, ethmoid, nasal, zygomatic, lacrimal, and palatine bones, the vomer, the inferior nasal concha, as well as the maxilla of the other side.[5]

Sometimes it articulates with the orbital surface, and sometimes with the lateral pterygoid plate of the sphenoid.

Development

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Anterior surface of maxilla at birth
Inferior surface of maxilla at birth

The maxilla is ossified in membrane. Mall and Fawcett maintain that it is ossified from two centers only, one for the maxilla proper and one for the premaxilla.[6][7]

These centers appear during the sixth week of prenatal development and unite in the beginning of the third month, but the suture between the two portions persists on the palate until nearly middle life. Mall states that the frontal process is developed from both centers.

The maxillary sinus appears as a shallow groove on the nasal surface of the bone about the fourth month of development, but does not reach its full size until after the second dentition.

The maxilla was formerly described as ossifying from six centers, viz.:

  • One, the orbitonasal, forms that portion of the body of the bone which lies medial to the infraorbital canal, including the medial part of the floor of the orbit and the lateral wall of the nasal cavity.
  • A second, the zygomatic, gives origin to the portion which lies lateral to the infraorbital canal, including the zygomatic process.
  • From a third, the palatine, is developed the palatine process posterior to the incisive canal together with the adjoining part of the nasal wall.
  • A fourth, the premaxillary, forms the incisive bone which carries the incisor teeth and corresponds to the premaxilla of the lower vertebrates.
  • A fifth, the nasal, gives rise to the frontal process and the portion above the canine tooth.
  • And a sixth, the infravomerine, lies between the palatine and premaxillary centers and beneath the vomer; this center, together with the corresponding center of the opposite bone, separates the incisive canals from each other.

Changes by age

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At birth the transverse and antero-posterior diameters of the bone are each greater than the vertical.

The frontal process is well-marked and the body of the bone consists of little more than the alveolar process, the teeth sockets reaching almost to the floor of the orbit.

The maxillary sinus presents the appearance of a furrow on the lateral wall of the nose. In the adult the vertical diameter is the greatest, owing to the development of the alveolar process and the increase in size of the sinus.

Function

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Fracture of the left lacrimal / maxillary bone

The alveolar process of the maxillae holds the upper teeth, and is referred to as the maxillary arch. Each maxilla attaches laterally to the zygomatic bones (cheek bones).

Each maxilla assists in forming the boundaries of three cavities:

Each maxilla also enters into the formation of two fossae: the infratemporal and pterygopalatine, and two fissures, the inferior orbital and pterygomaxillary. -When the tender bones of the upper jaw and lower nostril are severely or repetitively damaged, at any age the surrounding cartilage can begin to deteriorate just as it does after death.[citation needed]

Clinical significance

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A maxilla fracture is a form of facial fracture. A maxilla fracture is often the result of facial trauma such as violence, falls or automobile accidents. Maxilla fractures are classified according to the Le Fort classification.

In other animals

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Sometimes (e.g. in bony fish), the maxilla is called "upper maxilla", with the mandible being the "lower maxilla". Conversely, in birds the upper jaw is often called "upper mandible".

In most vertebrates, the foremost part of the upper jaw, to which the incisors are attached in mammals consists of a separate pair of bones, the premaxillae. These fuse with the maxilla proper to form the bone found in humans, and some other mammals. In bony fish, amphibians, and reptiles, both maxilla and premaxilla are relatively plate-like bones, forming only the sides of the upper jaw, and part of the face, with the premaxilla also forming the lower boundary of the nostrils. However, in mammals, the bones have curved inward, creating the palatine process and thereby also forming part of the roof of the mouth.[8]

Birds do not have a maxilla in the strict sense; the corresponding part of their beaks (mainly consisting of the premaxilla) is called "upper mandible".

Cartilaginous fish, such as sharks, also lack a true maxilla. Their upper jaw is instead formed from a cartilaginous bar that is not homologous with the bone found in other vertebrates.[8]

Additional images

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  • Skull. Maxilla shown in green.
    Skull. Maxilla shown in green.
  • Skull. Maxilla shown in white.
    Skull. Maxilla shown in white.

See also

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Wikimedia Commons has media related to Maxilla.
This article uses anatomical terminology.

References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Maxilla

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from Grokipedia
The maxilla is a paired, irregularly shaped that forms the central portion of the midface, constituting the and contributing to the structure of the orbits, , and . It consists of a central body and four projecting processes—alveolar, frontal, zygomatic, and —that articulate with multiple cranial bones to support facial architecture and facilitate essential functions. Structurally, the body of the maxilla is pyramidal, with four surfaces: an anterior facial surface featuring the for neurovascular passage, a posterolateral infratemporal surface adjacent to the , a superomedial orbital surface forming the of the , and a medial nasal surface that houses the , the largest paranasal sinus with an adult volume of approximately 15 mL. The extends inferiorly to form the , anchoring the upper teeth via sockets, while the palatine process projects medially to form the anterior two-thirds of the in articulation with its counterpart from the opposite maxilla. The extends laterally to join the , reinforcing the cheek's prominence, and the frontal process ascends to articulate with the , contributing to the medial orbital rim and . Functionally, the maxilla serves as a critical load-bearing element in the , transmitting masticatory forces from the teeth to the cranium while providing attachment sites for muscles of , mastication, and the levator veli palatini. It also plays a role in vocalization and respiration by delineating the boundaries of the oral and nasal cavities, and its sinus aids in air humidification and lightening the skull's weight. Clinically, the maxilla's prominence makes it susceptible to trauma, notably in Le Fort fractures: type I involves horizontal separation of the , type II a pyramidal through the , and type III a craniofacial dysjunction detaching the entire midface. Its proximity to the complicates dental procedures like implants, often requiring augmentation due to , and congenital anomalies such as cleft palate frequently involve maxillary defects, impacting speech and feeding.

Anatomy

Structure

The maxilla is a paired, irregular bone that forms the upper jaw, with the right and left maxillae fusing at the intermaxillary suture along the midline in adults. It exhibits a pyramidal shape, comprising a central body and four main processes that contribute to the midfacial skeleton. The body of the maxilla is the central, pyramidal portion housing the maxillary sinus, also known as the antrum of Highmore, a pyramidal cavity that spans from the premolar region to the third molar area and averages approximately 15 mL in volume in adults. This body features four surfaces: the anterior (or facial) surface, which is convex and marked by the canine fossa—a shallow depression above the canine tooth—and the infraorbital foramen located about 1 cm inferior to the orbital rim; the posterior (or infratemporal) surface, which is concave and forms part of the infratemporal fossa; the medial (or nasal) surface, which contributes to the lateral nasal wall; and the superior (or orbital) surface, which forms the majority of the orbital floor. Extending from the body are the frontal process, a triangular projection that ascends medially to form part of the nasal bridge; the zygomatic process, a short lateral extension that articulates with the zygomatic bone and forms the superolateral border of the maxillary sinus; the alveolar process, a curved, inferior extension bearing the sockets for the upper teeth and terminating posteriorly at the maxillary tuberosity, a bulbous enlargement; and the palatine process, a horizontal plate projecting medially to form about two-thirds of the hard palate, with the greater and lesser palatine foramina located on its posterior border for passage of vessels and nerves. In adults, the maxilla measures approximately 52 mm in complex length (from the anterior nasal spine to the ) and 66 mm in maximum inter-maxillary width, though these dimensions exhibit with males showing greater robusticity and average lengths of 53.8 mm and widths of 67.7 mm, compared to 50.3 mm and 64.0 mm in females. Variations in maxillary structure include extensions of the sinus into the or tuberosity, occasional , and antral septations, which can influence overall robusticity.

Articulations

The maxilla forms articulations with nine bones, including the superiorly via the frontomaxillary suture, the posteriorly through the ethmomaxillary suture, the along the medial orbital wall, the anteriorly on the , the laterally by means of the zygomaticomaxillary suture, the posteriorly at the palatomaxillary suture, the at the spheno-maxillary fissure, the medially within the , and the opposite maxilla medially via the intermaxillary (median ) suture. These articulations are predominantly suture joints, classified as synarthroses or immovable fibrous joints that interlock the irregular bone margins with , ensuring structural integrity of the . Examples include the frontomaxillary suture, which connects the frontal process of the maxilla to the , and the zygomaticomaxillary suture, linking the of the maxilla to the maxillary process of the . The maxilla is also indirectly involved in the (TMJ), a between the and , through its , which anchors the upper teeth that occlude with the mandibular teeth to facilitate movement. Ligamentous supports contribute to the stability of maxillary-related functions, particularly the temporomandibular ligament (lateral ligament of the TMJ), a thickening of the that extends from the articular of the —part of the formed by the of the maxilla—to the neck of the , thereby reinforcing the lateral aspect of the and limiting excessive mandibular protrusion or depression. This ligament indirectly bolsters maxillary stability by securing the masticatory apparatus involving the upper . The suture joints of the maxilla provide essential rigidity to withstand and transmit masticatory forces from the teeth to the cranium during , with the zygomaticomaxillary suture experiencing significant stress under bite loading to maintain framework . This biomechanical role ensures efficient force distribution without compromising the bone's position relative to adjacent cranial structures.

Vascular and Neural Supply

The arterial supply to the maxilla is derived primarily from the , the larger terminal branch of the , which courses through the before dividing into three parts and giving off key branches that perfuse the maxillary bone and associated structures. Specific branches include the posterior superior alveolar artery, which arises from the third part of the and supplies the , posterior teeth, and adjacent bone; the , a continuation of the that enters the via the and provides blood to the anterior maxilla, including the and floor; and the , originating from the (a branch of the ), which emerges through the to vascularize the and palatal gingiva. These arteries ensure robust to support the bone's role in and sinus function. Venous drainage of the maxilla occurs primarily through the maxillary vein, which accompanies the maxillary artery and collects blood from the pterygoid venous plexus, a network of interconnected veins in the infratemporal fossa that receives tributaries from the maxillary sinus, nasal cavity, and infraorbital region. The pterygoid plexus communicates with the cavernous sinus via emissary veins and drains inferiorly into the maxillary vein, which then merges with the superficial temporal vein to form the retromandibular vein; from there, blood flows into the facial vein and ultimately the internal jugular vein. This pathway facilitates efficient return of deoxygenated blood from the maxillary region. However, the valveless nature of the plexus (valvular incompetence) increases the risk of retrograde spread of infections to the cavernous sinus. Sensory innervation of the maxilla is provided by the maxillary nerve (CN V2), the second division of the trigeminal nerve (CN V), which exits the skull via the foramen rotundum and enters the pterygopalatine fossa to distribute branches throughout the midface. Key branches include the posterior superior alveolar nerves, which arise proximal to the infraorbital fissure and innervate the maxillary molars, premolars, and buccal gingiva; the infraorbital nerve, the terminal continuation of V2 that emerges through the infraorbital foramen to supply the anterior maxilla, including the incisors, canines, upper lip, and cheek; the greater and lesser palatine nerves, which descend through the palatine canal to provide sensation to the hard and soft palate, respectively; and the superior alveolar nerves collectively forming a plexus for the maxillary teeth and periodontium. Motor innervation to the maxilla is indirect, primarily through branches of the mandibular nerve (CN V3) to the medial and lateral pterygoid muscles, which influence mandibular movement relative to the fixed maxilla during mastication. Lymphatic drainage from the maxilla, including the gingiva, sinus mucosa, and palatal tissues, follows pathways to the submandibular lymph nodes (level I) via buccal and inferior collecting trunks, with additional routes to the retropharyngeal nodes for midline and posterior structures. These nodes serve as the primary first-station filters before efferents proceed to deeper cervical chains, aiding in immune surveillance of the upper oral cavity. Understanding these vascular and neural pathways is clinically significant for maxillary procedures, as they guide targeted anesthesia techniques such as maxillary nerve blocks via the greater palatine canal or infraorbital approach, which interrupt sensory transmission from V2 branches to achieve profound hemi-maxillary analgesia for dental extractions or sinus surgeries.

Development

The maxilla originates from the mesenchyme of the first pharyngeal arch during early embryogenesis, with intramembranous ossification initiating around the sixth to seventh week of gestation from two primary centers: one for the body of the maxilla and another for the premaxilla. These centers, located near the developing tooth germs and influenced by neural crest-derived cells, expand and fuse by the eighth week to form a single paired bone, establishing the foundational framework for the upper jaw. During prenatal growth, the maxilla undergoes progressive expansion, particularly in the , which elongates to accommodate emerging tooth buds as dental lamina forms around the seventh week. Concurrently, the begins as a small evagination from the middle at approximately 10 weeks of , gradually pneumatizing the bone and contributing to its lightweight structure by the third trimester. Postnatally, the maxilla experiences rapid growth in childhood through appositional bone deposition at key sutures, such as the fronto-maxillary and zygomatico-maxillary, displacing the bone downward and forward in coordination with cranial base expansion. During , remodeling intensifies with further enlargement of the , which approaches adult volume by ages 12-15, enhancing facial projection and airspace. In adulthood, particularly following edentulism, the undergoes progressive resorption, leading to vertical and horizontal that can reduce ridge height by up to 50% within the first year post-extraction, influenced by pneumatization and lack of functional stimuli. Hormonal factors significantly modulate maxillary advancement during , with stimulating overall sutural growth and bone apposition, while sex steroids—particularly and testosterone—amplify these effects by enhancing insulin-like growth factor-1 expression and accelerating remodeling rates. Developmental anomalies, such as cleft lip and palate, arise from failures in the fusion of the maxillary processes with the medial nasal prominences around the sixth to seventh week, resulting in incomplete separation of the oral and nasal cavities and associated .

Functions

In Mastication and Dentition

The maxillary forms the superior boundary of the oral cavity, housing 16 embedded within the alveolar processes of the maxilla. These teeth are secured in individual alveolar sockets, which are bony depressions lined by a thin layer of compact , providing structural support during . The periodontal ligament, a fibrous , anchors each root to the alveolar socket walls, allowing slight micromovements to absorb occlusal forces while maintaining stability. In mastication, the maxilla plays a critical biomechanical by distributing forces generated during occlusion across the . During and , occlusal loads are transmitted from the teeth through the alveolar to the basal maxilla, with the acting as a key posterior to absorb and dissipate impact, particularly from molar grinding. The of the maxilla provides leverage for the , enhancing the mechanical efficiency of closure and force application in the posterior region. The maxillary dentition aligns with the to achieve Class I occlusion, characterized by the mesiobuccal cusp of the fitting into the buccal groove of the mandibular first molar, ensuring even force distribution and efficient mastication. This alignment supports an average bite force of 500-700 N in adults, primarily generated at the molars, which influences overall occlusal harmony and prevents uneven wear. Functional shifts occur with age, as erupt progressively; for instance, the first permanent molars typically emerge around 6 years, establishing the posterior occlusion and guiding subsequent dental alignment. In later life, edentulism leads to progressive resorption of the , compromising maxillary stability and reducing the bone's capacity to support prosthetic restorations or residual .

In Facial Structure and Speech

The maxilla serves as a foundational element of the midface , forming a paired structure that fuses at the midline to support the viscerocranium and overlying soft tissues. Its anterior surface projects forward, contributing to the inferior margin of the and articulating with the via the frontal to establish the central and inferior aspects of the . This projection also provides essential support for the upper , as the maxillary prominences develop into the lateral portions of the lip through fusion with the medial nasal processes during embryogenesis. Laterally, the of the maxilla extends to articulate with the , forming the malar eminence that defines the prominence of the cheeks and enhances the overall width of the face. In terms of aesthetic proportions, the maxilla plays a critical role in achieving facial harmony by influencing the midface profile and balance. Maxillary advancement procedures in reposition the bone anteriorly to correct deficiencies, thereby improving nasolabial angles and lip positioning relative to the E-line, which enhances overall facial esthetics. Such interventions, particularly in maxilla-only or bimaxillary approaches, refine midface proportions and reduce nasal-lip discrepancies, promoting a more balanced and symmetrical appearance without excessive prominence of the . The maxilla contributes to speech mechanics through its formation of the and alveolar ridge, which are vital for articulating specific sounds. The anterior , composed primarily of the maxillary process, and the alveolar ridge provide contact points for the in producing palatolingual such as /s/, /t/, /d/, /n/, and /l/, where elevation and grooving shape airflow for precise . Additionally, the maxilla indirectly supports velopharyngeal closure by anchoring the , which serves as the fixed anterior boundary for the soft palate's elevation during speech; this closure directs airflow orally, preventing hypernasality and ensuring clear production. Developmentally, maxillary growth significantly shapes convexity from infancy through adulthood, with the most pronounced anteroposterior changes occurring during early postnatal periods. Between 0.4 and 5 years, the maxilla exhibits rapid forward and vertical expansion, emphasizing anteroposterior maturation that establishes initial midface projection and convexity. As growth progresses into childhood and , the maxilla advances more slowly than the , leading to a relative posterior repositioning evidenced by decreases in the SNA angle (up to 2.2° in males) and an overall reduction in profile convexity. By adulthood, minimal further maxillary growth occurs, allowing mandibular dominance to further straighten the profile while changes, such as nasal protrusion, may subtly restore some convexity.

In Respiration and Sinuses

The palatine process of the maxilla forms the anterior two-thirds of the , which constitutes the floor of the , while the posterior third is contributed by the horizontal plate of the . This bony foundation supports the and facilitates the separation between the oral and nasal passages, ensuring efficient airflow during respiration. The medial surface of the maxilla, forming part of the lateral wall of the , includes contributions to the inferior , where the opens to drain tears into the nasal passage. The , the largest paranasal sinus located within the body of the maxilla, plays key roles in by conditioning inspired air through humidification, warming, and , thereby protecting the lower from dry or cold environmental conditions. It also contributes to voice by amplifying sound waves during and provides shock absorption to cushion impacts to the upper teeth and facial structures. In adults, the average volume of the maxillary sinus is approximately 15 mL, expanding from approximately 0.07 mL (70 mm³) at birth through biphasic growth: a rapid phase in (0-3 years) followed by steady enlargement until around age 18, after which it stabilizes or slightly increases with pneumatization. Mucociliary clearance in the maxillary sinus relies on its ciliated pseudostratified columnar epithelium, which propels mucus toward the sinus ostium—a small opening on the medial wall that drains into the middle meatus of the nasal cavity, allowing secretions to enter the nasopharynx for expulsion. This mechanism maintains sinus patency and prevents accumulation of debris or pathogens, with airflow directed through the ethmoidal infundibulum to support overall nasal ventilation. Physiologically, the maxillary sinus is susceptible to pressure imbalances, such as during air travel or , where rapid changes in cause mucosal engorgement or hemorrhage if the is obstructed, leading to in the maxillary region. Its adjacency to the enhances olfaction by modulating airflow toward the in the superior nasal region, improving odorant delivery and sensory perception.

Clinical Significance

Fractures and Trauma

Maxillary fractures, often resulting from high-energy , represent a significant portion of injuries, accounting for 6-25% of all fractures. These injuries are commonly associated with accidents (MVAs), assaults, and falls, with MVAs being the leading cause in up to 50-73% of cases, particularly among males aged 20-30 years who exhibit a 3:1 to 12:1 predominance over females. The maxilla's central position in the midface makes it vulnerable to forces that disrupt its articulations with adjacent bones, leading to immediate functional and aesthetic impairments. The Le Fort classification system categorizes maxillary fractures based on the pattern of midfacial separation from the skull base, originally described through experimental studies on cadavers. Le Fort type I, or horizontal maxillary fracture, involves a transverse break through the lower maxilla, separating the alveolar process and hard palate from the upper face, typically caused by a low-force impact directed upward against the maxillary alveolar rim. Le Fort type II, known as the pyramidal fracture, extends from the nasal bridge through the maxilla and orbital floor to the pterygoid plates, resulting from a midfacial impact that creates a pyramidal detachment. Le Fort type III, or craniofacial dysjunction, represents a complete transverse separation of the midface from the cranium, often involving the zygomatic arches and naso-orbito-ethmoidal complex, and is triggered by high-energy blows to the upper maxilla or nasal bridge. These fractures frequently occur in combination due to the variable nature of trauma. Symptoms of maxillary fractures include facial swelling, ecchymosis (particularly periorbital in types II and III), with an anterior open bite, and midfacial mobility upon . More severe presentations may involve epistaxis, , along the , and () indicating dural violation in types II and III. Diagnosis begins with () protocols to assess airway, , and circulation, followed by a thorough for deformity and neurological deficits. Computed tomography (CT) scanning with fine cuts (≤3 mm) and 3D reconstructions serves as the gold standard for confirming fracture extent, associated injuries, and orbital involvement. Acute management prioritizes airway protection, as midfacial edema or posterior displacement can compromise ventilation, potentially necessitating intubation or tracheostomy. Hemorrhage control and cervical spine stabilization follow per ATLS guidelines. For displaced fractures, initial stabilization involves closed reduction with maxillomandibular wiring (MMF) to restore occlusion, while open reduction and internal fixation using titanium plates and screws provide definitive rigid stabilization, often delayed 3-5 days to allow edema resolution. Undisplaced fractures may be managed conservatively with analgesics, antibiotics, and a soft diet, but surgical intervention is indicated for those threatening vision, airway, or globe position.

Pathologies and Disorders

The maxilla is susceptible to various congenital anomalies, most notably . Cleft lip arises from the failure of fusion between the frontonasal (medial nasal) and maxillary processes during embryonic development between the 4th and 7th weeks of . Cleft palate results from the failure of the palatal shelves derived from the maxillary processes to fuse, typically occurring between the 6th and 12th weeks of . These conditions occur with an incidence of approximately 1 in 1,000 live births globally, though rates vary by ethnicity and region. In cases of cleft lip and palate, —a underdevelopment of the maxillary bone—manifests in 15% to 50% of affected individuals, leading to midfacial retrusion, , and functional impairments in feeding and speech. Infectious pathologies primarily involve maxillary sinusitis, an of the that can be acute or chronic and is triggered by viral, bacterial, allergic, or fungal agents. Odontogenic origins account for up to 10-40% of maxillary sinusitis cases, often stemming from dental abscesses, apical periodontitis, or periapical infections that extend through the thin bony floor of the sinus, causing symptoms such as pain, , and purulent discharge. Chronic forms may persist due to unresolved dental or anatomical predispositions like oroantral fistulas. Neoplastic disorders of the maxilla include odontogenic tumors such as , the second most common odontogenic after , which originates from remnants of dental lamina or and presents as a locally aggressive, radiolucent lesion often in the posterior maxilla. , particularly primary intraosseous variants, represents a rare malignant odontogenic tumor arising de novo from odontogenic , accounting for less than 1% of oral malignancies and exhibiting destructive with potential for regional . Maxillary , though uncommon due to the maxilla's rich vascular supply, occurs rarely as a complication of untreated odontogenic infections or , leading to and sequestration in fewer than 1% of head and neck cases. Degenerative conditions affecting the maxilla encompass osteoporosis-related , where systemic reduction in compromises the trabecular architecture of the maxillary , increasing susceptibility to fractures and failure. , a chronic disorder of accelerated , involves the jaws in approximately 17% of cases, with the maxilla affected more frequently than the at a ratio of 2.3:1, resulting in expanded, cotton-wool-like radiopacities, altered , and potential deformities such as maxillary enlargement. Diagnostic evaluation of maxillary pathologies relies on and histopathological techniques tailored to the suspected . (MRI) excels in assessing involvement, such as in or tumor extension, by differentiating mucosa, secretions, and masses with high contrast resolution. For neoplastic lesions, remains the gold standard for definitive , providing histological confirmation of tumor type and margins through incisional or excisional sampling.

Surgical and Orthodontic Relevance

Orthodontic interventions targeting the maxilla often address transverse deficiencies through appliances such as the rapid maxillary expander (RME), which separates the midpalatal suture to widen the upper arch in growing patients with maxillary constriction. This technique is particularly effective in adolescents with permanent , promoting skeletal expansion while minimizing dental tipping when applied early. For anteroposterior discrepancies, LeFort I enables precise maxillary advancement, typically by 5-8 mm, to correct Class III malocclusions and improve facial harmony. Stability is generally high, with advancements of 1 cm or more showing no increased risk of ischemia or . Surgical approaches to the maxilla include the Caldwell-Luc procedure, a traditional sublabial method providing direct access to the for removal of diseased mucosa or foreign bodies. This technique involves an antrostomy through the , allowing irrigation and drainage, though it has largely been supplanted by less invasive options. Endoscopic sinus surgery (ESS) represents a modern alternative, using nasal endoscopes to widen ostia and restore ventilation in the with minimal external incisions. For patients with cleft palate-related defects, prosthetic obturators seal palatal openings to facilitate speech and mastication, often customized with acrylic bases and clasps for interim or definitive use. Recent advances since 2020 have integrated for patient-specific maxillary implants, enhancing precision in reconstruction after trauma or tumor resection through computer-assisted design and or bioresorbable materials. These custom implants improve fit and reduce operative time in maxillofacial procedures. Minimally invasive fixation of maxillary fractures now employs resorbable plates, such as 1.5-2 mm poly-L/DL-lactic acid systems, which degrade over time without requiring removal and provide adequate stability in pediatric and moderate-displacement cases. Complications in maxillary surgery include neurosensory deficits from infraorbital or alveolar nerve injury, occurring in up to 75% of LeFort I cases temporarily, with most resolving within 1-3 months. Relapse in orthognathic procedures like LeFort I advancement affects 10-20% of patients, often exceeding 2 mm horizontally due to soft tissue tension or skeletal drift. Multidisciplinary care in maxillary interventions coordinates orthodontists, surgeons, prosthodontists, and speech therapists to optimize outcomes, such as integrating obturators with surgical advancements for cleft patients to restore function and articulation. This team approach ensures comprehensive rehabilitation, addressing occlusal, aesthetic, and phonetic needs post-procedure.

In Mammals

In mammals, the maxilla consists of paired bones that form the central portion of the upper , featuring prominent alveolar processes that house the roots of teeth in the characteristic diphyodont , where two successive sets of teeth develop over the lifespan. This pattern supports diverse feeding strategies, with the alveolar margins varying in height and contour to accommodate different tooth morphologies. In some , such as , a distinct remains separate from the maxilla, bearing the incisors and contributing to the rostral extension of the . Anatomical variations in the maxilla reflect adaptations to diet and locomotion across mammalian orders. Carnivores exhibit an elongated maxilla that accommodates enlarged canines for seizing and tearing prey. Herbivores, by contrast, possess broad palatine processes of the maxilla that form an expansive , facilitating the lateral grinding motions essential for processing fibrous plant material, as exemplified in equids where the wide palatal shelf supports cheek teeth. In , the maxilla is notably shortened relative to other mammals, reducing the overall rostrum length to align with forward-facing orbits and enhanced ; this trend culminates in hominids, where the maxilla resembles the compact form adapted for varied omnivorous diets. Functional adaptations further diversify maxillary morphology. For instance, equids have extensive maxillary sinuses that occupy much of the bone's volume, balancing the demands of a heavy, herbivorous . Representative examples highlight these specializations. feature a prominent —a toothless gap in the maxillary dental arcade between the robust incisors and molars—that enables the cheeks to fold inward, preventing interference during gnawing on hard materials. In cetaceans, the maxillae are disproportionately large relative to body size; odontocetes retain teeth embedded in the for grasping prey, while mysticetes have evolved toothless maxillae that anchor plates for filter-feeding on and . These adaptations underscore the maxilla's role in enabling the ecological diversity of mammals.

In Other Vertebrates

In fish, the maxilla forms a key component of the upper suspension, articulating with the and other cranial elements to enable significant mobility during feeding. This mobility allows the maxilla and to slide forward and protrude, facilitating prey capture by expanding the gape and directing flow over sensory structures. In species like those in the order , the maxilla's ligamentous connections to the palatoquadrate further enhance this protrusible mechanism, optimizing feeding in aquatic environments. In amphibians, the maxilla is a distinct, often tooth-bearing that contributes to the upper , remaining separate from adjacent elements like the and nasal throughout development. For instance, in anurans such as , the maxilla supports pedicellate teeth adapted for grasping prey, with its posterior process articulating flexibly with the quadratojugal. Reptiles exhibit a similar configuration, where the maxilla is typically a separate, robust bearing conical or acrodont teeth for piercing and holding ; in squamates like , it integrates into the kinetic apparatus. Crocodilians represent a specialized case among reptiles, with the maxilla housing robust maxillary sinuses that extend into the antorbital region, aiding in structural reinforcement and potentially respiratory functions. These sinuses, present in taxa like rhombifer, form part of a complex paranasal system that invades the maxilla anterior to the antorbital sinus. Birds lack a traditional toothed maxilla, instead featuring a reduced maxilla fused with the and bones to form the lightweight upper , or rhamphotheca-covered . The maxillopalatine process contributes to this structure, providing a thin, pneumatic framework that minimizes weight for flight while supporting the beak's keratinous sheath. Unlike mammals, birds possess a single primary paranasal sinus, the infraorbital sinus, located within the maxilla and lacrimal bones, though it differs structurally from mammalian maxillary sinuses and some species exhibit additional pneumatic diverticula for or vocalization. Beak adaptations vary phylogenetically and ecologically; raptors like possess a sharply hooked maxilla for tearing flesh, whereas granivores such as finches have a conical, crushing form suited to seed processing. Key differences from mammalian maxillae include the absence of complex dentition in birds and the prevalence of kinetic mechanisms in reptiles like lizards, where the maxilla participates in amphikinesis via loose articulations with the braincase and palate. This streptostylic movement of the quadrate allows independent maxillary excursion, enhancing gape for diverse prey without the rigid fusion seen in mammals.

Evolutionary Aspects

The maxilla originated as one of the dermal bones forming the upper in early gnathostomes, which first appeared approximately 420 million years ago during the Silurian-Devonian transition. These bones evolved from derivatives of the mandibular , a homologous to the gill arches of ancestral jawless vertebrates, enabling the formation of a functional jaw apparatus in stem gnathostomes like placoderms. In these early forms, the maxilla served as a primary dermal element supporting the oral lining and teeth, contributing to the predatory capabilities that defined gnathostome diversification. Key evolutionary transitions in the maxilla occurred within synapsid lineages leading to mammals, including the complete loss of the distinct in therian mammals around 200 million years ago during the . This fusion and reduction streamlined the therian facial skeleton, enhancing structural efficiency without a separate premaxillary element, a shift absent in non-therian mammals like monotremes. are present in some non-mammalian therapsids and cynodonts, with their further development in early mammals lightening the by pneumatizing the maxillary , reducing overall mass while maintaining rigidity for mastication. These changes reflect adaptations for endothermy and increased metabolic demands in mammalian ancestors. Across clades, the maxilla adapted to diverse ecological pressures, such as dietary shifts in carnivorous dinosaurs where elongation of the maxillary facilitated prey capture and in theropods like abelisaurids. In birds, the of flight around 150 million years ago drove reductions in maxillary mass through fusion and loss of , resulting in a lightweight, kinetic structure that minimized weight while preserving mobility. These adaptations highlight the maxilla's role in functional trade-offs, from robust elongation for predation to streamlined reduction for aerial locomotion. The genetic underpinnings of maxillary evolution involve Hox genes, which pattern the pharyngeal arches and inhibit jaw formation in anterior regions, establishing the default mandibular identity that the maxilla inherits. Fossil evidence from Australopithecus species, such as A. afarensis dated to about 3.9-2.9 million years ago, reveals a progressive shortening of the maxilla compared to earlier hominins, reflecting reduced facial prognathism and adaptations to terrestrial foraging in early human evolution. Pre-20th-century anatomical views erroneously regarded the human maxilla as solely an "intermaxillary bone," overlooking its broader dermal origins until Goethe's 1784 identification of the premaxilla challenged this distinction between human and animal skulls.

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