The superior alveolar nerves are branches of the maxillary nerve (V2), which is part of the trigeminal nerve (cranial nerve V). These nerves are responsible for providing sensory innervation to the upper teeth, gums, and maxillary sinus. The superior alveolar nerves consist of three main branches: the posterior superior alveolar nerve, the middle superior alveolar nerve, and the anterior superior alveolar nerve.
Location
The superior alveolar nerves originate from the maxillary nerve (V2) in the pterygopalatine fossa. The posterior superior alveolar nerve arises from the maxillary nerve and enters the maxilla through small foramina on its posterior surface, innervating the upper molars. The middle and anterior superior alveolar nerves branch from the infra-orbital nerve (a continuation of the maxillary nerve) and run along the infra-orbital groove and canal within the maxilla, innervating the premolars, canines, and incisors, as well as the maxillary sinus.
Structure and Anatomy
The superior alveolar nerves consist of three main branches: the posterior superior alveolar nerve, middle superior alveolar nerve, and anterior superior alveolar nerve. These nerves provide sensory innervation to the upper teeth, gums, and maxillary sinus, and are branches of the maxillary division of the trigeminal nerve (V2). Below is a detailed description of the anatomy of these nerves.
Posterior Superior Alveolar Nerve (PSAN)
Origin
The posterior superior alveolar nerve arises from the maxillary nerve (V2) within the pterygopalatine fossa, shortly after the maxillary nerve exits the skull through the foramen rotundum.
Course
The posterior superior alveolar nerve travels laterally and slightly downward from the pterygopalatine fossa. It runs posterior to the maxilla and enters the bone through small alveolar foramina on the posterior surface of the maxilla, located near the tuberosity of the maxilla.
Branching
Once inside the maxilla, the posterior superior alveolar nerve gives off branches that run within the bone to reach the molar teeth. These branches form part of the superior dental plexus, which innervates the posterior upper teeth, particularly the molars.
Distribution
The posterior superior alveolar nerve provides sensory innervation to the upper molars, the adjacent gums, and a portion of the maxillary sinus. The branches interconnect with the other superior alveolar nerves within the bone.
Middle Superior Alveolar Nerve (MSAN)
Origin
The middle superior alveolar nerve is a branch of the infra-orbital nerve, which is itself a continuation of the maxillary nerve (V2). The infra-orbital nerve passes through the infra-orbital groove and canal in the floor of the orbit, and the middle superior alveolar nerve branches off within this canal.
Course
After branching from the infra-orbital nerve, the middle superior alveolar nerve runs inferiorly, within the maxilla, toward the premolar region. It travels through the bone to reach the upper premolars, where it contributes to the superior dental plexus.
Branching
The middle superior alveolar nerve forms connections with both the anterior and posterior superior alveolar nerves, creating an intricate network (the superior dental plexus) that innervates the upper teeth.
Distribution
The middle superior alveolar nerve supplies sensory innervation to the upper premolars, the adjacent gums, and part of the maxillary sinus. In some individuals, this nerve may be absent, in which case the premolars are innervated by the posterior or anterior superior alveolar nerves.
Anterior Superior Alveolar Nerve (ASAN)
Origin
The anterior superior alveolar nerve is another branch of the infra-orbital nerve, originating within the infra-orbital canal. It typically branches off the infra-orbital nerve just before the nerve exits through the infra-orbital foramen.
Course
After branching from the infra-orbital nerve, the anterior superior alveolar nerve travels inferiorly and anteriorly within the maxilla. It runs through a bony canal to reach the upper incisors and canines. Along its course, it contributes to the superior dental plexus, connecting with the other superior alveolar nerves.
Branching
The anterior superior alveolar nerve forms part of the superior dental plexus, providing sensory branches that innervate the anterior upper teeth. It also sends small branches to the maxillary sinus.
Distribution
The anterior superior alveolar nerve provides sensory innervation to the upper incisors, canines, the adjacent gums, and the anterior portion of the maxillary sinus. It plays an essential role in providing sensory input from the front part of the maxilla.
Superior Dental Plexus
The superior alveolar nerves (posterior, middle, and anterior) interconnect within the maxilla to form the superior dental plexus. This network of nerve fibers supplies sensory innervation to the maxillary teeth and the surrounding tissues. The plexus allows for a thorough distribution of sensory input from the teeth, gums, and maxillary sinus, ensuring that all areas receive adequate nerve supply.
Relations with Surrounding Structures
- Maxillary Sinus: All branches of the superior alveolar nerves provide some sensory innervation to the maxillary sinus. This relationship is important because dental infections or issues in the upper teeth can sometimes affect the sinus or vice versa.
- Maxillary Bone: The superior alveolar nerves run through canals within the maxilla, which houses the upper teeth. Their location within the bone makes them susceptible to injury or compression during dental procedures or trauma.
- Infra-orbital Nerve: The middle and anterior superior alveolar nerves branch from the infra-orbital nerve, which travels through the infra-orbital groove and canal on the floor of the orbit. This proximity to the orbit and the face is important for surgical considerations in the region.
Function
The superior alveolar nerves are responsible for providing sensory innervation to the upper teeth, gums, and maxillary sinus. These nerves, which include the posterior, middle, and anterior branches, play a vital role in transmitting sensory information such as pain, touch, pressure, and temperature from these areas to the brain. Below is a detailed explanation of the functions of the superior alveolar nerves.
Sensory Innervation to the Upper Teeth
The primary function of the superior alveolar nerves is to provide sensory innervation to the maxillary teeth, ensuring the brain receives detailed information about any sensations from these teeth.
Posterior Superior Alveolar Nerve
- Molars: The posterior superior alveolar nerve innervates the maxillary molars, providing sensory input related to pain, pressure, and temperature. This includes sensations from the tooth pulp, periodontal ligaments, and surrounding tissues.
- Pain Detection: It plays a critical role in detecting dental pain, such as tooth decay, trauma, or periodontal infections affecting the molar teeth.
Middle Superior Alveolar Nerve
- Premolars: The middle superior alveolar nerve innervates the maxillary premolars. It provides sensory input from the premolar teeth, which is essential for detecting pain caused by issues such as cavities, root infections, or trauma to the premolar teeth.
- Pressure and Temperature: It also helps detect pressure and temperature changes, particularly during chewing or when consuming hot or cold food and beverages.
Anterior Superior Alveolar Nerve
Incisors and Canines: The anterior superior alveolar nerve innervates the maxillary incisors and canines, providing sensory feedback about pain and pressure from these anterior teeth. This nerve is crucial for detecting problems like dental infections, fractures, or enamel erosion in the front teeth.
Sensory Innervation to the Gums
The superior alveolar nerves supply the maxillary gingiva (gums) that surround the upper teeth. This innervation is crucial for detecting sensations related to pressure, pain, and irritation, particularly from trauma or inflammation.
Posterior Superior Alveolar Nerve
Posterior Gingiva: This nerve supplies the gingiva surrounding the maxillary molars, allowing for detection of irritation or pain from gum disease, periodontal infections, or trauma in the posterior part of the mouth.
Middle Superior Alveolar Nerve
Premolar Gingiva: The middle superior alveolar nerve provides sensation to the gums surrounding the maxillary premolars. Sensory feedback from this area is important in monitoring gum health and detecting conditions like gingivitis or periodontitis.
Anterior Superior Alveolar Nerve
Anterior Gingiva: The anterior superior alveolar nerve supplies sensation to the gingiva surrounding the maxillary incisors and canines. This nerve plays a key role in detecting gum inflammation or irritation in the front part of the mouth.
Sensory Innervation to the Maxillary Sinus
All three branches of the superior alveolar nerves—posterior, middle, and anterior—contribute sensory fibers to the maxillary sinus. This sensory innervation plays a role in detecting pain or pressure from the sinus mucosa, particularly during conditions like sinusitis.
Posterior Superior Alveolar Nerve
Posterior Maxillary Sinus: The posterior superior alveolar nerve provides sensory feedback from the posterior part of the maxillary sinus. This is crucial for detecting inflammation, infection, or increased pressure in the sinus cavity, which may cause discomfort or pain.
Middle Superior Alveolar Nerve
Middle Maxillary Sinus: The middle superior alveolar nerve supplies the middle portion of the maxillary sinus. It transmits pain and pressure sensations from this area, particularly during sinus infections or allergic reactions that result in sinus congestion.
Anterior Superior Alveolar Nerve
Anterior Maxillary Sinus: The anterior superior alveolar nerve innervates the anterior portion of the maxillary sinus. It helps detect sensations from the sinus mucosa, particularly during sinus pressure buildup or infections affecting the front part of the sinus.
Detection of Dental Pain and Discomfort
The superior alveolar nerves are crucial for detecting various forms of dental pain and discomfort, including:
- Dental Caries (Cavities): Pain from tooth decay is transmitted through these nerves, allowing for early detection of caries.
- Tooth Sensitivity: The superior alveolar nerves play a key role in detecting tooth sensitivity, such as reactions to cold or hot stimuli or pressure changes during chewing.
- Periodontal Disease: The nerves help detect pain and discomfort associated with infections or inflammation of the gums and supporting structures around the teeth.
Detection of Trauma and Damage to Teeth and Gums
The superior alveolar nerves are responsible for detecting trauma or injury to the teeth and gums, such as:
- Fractured Teeth: Pain from cracked or fractured teeth is transmitted via these nerves, prompting protective responses like avoiding certain foods or seeking dental care.
- Gum Irritation or Injury: Irritation or injury to the gums from factors like sharp food particles, aggressive brushing, or dental tools is sensed by these nerves.
Clinical Significance
The superior alveolar nerves are clinically significant due to their role in providing sensory innervation to the upper teeth, gums, and maxillary sinus. Damage or irritation to these nerves can occur during dental procedures, such as extractions, root canals, or maxillary surgeries, leading to numbness, pain, or altered sensation in the upper teeth and gums. These nerves are also closely associated with the maxillary sinus, so conditions like sinusitis or maxillary sinus surgery can result in referred pain or altered sensations in the upper teeth and jaw.
The superior alveolar nerves are frequently targeted during local anesthesia for dental procedures. Inadequate anesthetic block of these nerves can lead to persistent pain during treatments, while over-blocking can cause temporary sensory loss. Damage or irritation to these nerves can also result in referred pain, such as toothache-like symptoms from sinus issues. Proper understanding of their anatomy is essential to avoid complications in dental and surgical interventions.
