Which Nerve Feels That Tooth?

Three superior alveolar nerves carry the upper teeth, and the palate has its own wiring. Front teeth are ASA. Stop drifting to the molar nerve.

Board Vignette: A 10-year-old boy is brought to the office after he fell on the playground and chipped a front tooth one hour ago. On examination the maxillary right central incisor has a fractured crown with a pinpoint pink pulp exposure that is exquisitely sensitive to cold air. There is no palatal laceration and the gum on the roof of the mouth is normal. Which nerve is carrying the pain from this tooth?

A. Posterior superior alveolar nerve (PSA)

B. Anterior superior alveolar nerve (ASA)

C. Nasopalatine nerve

D. Greater palatine nerve

The anterior superior alveolar nerve (ASA) carries pulp sensation from the maxillary incisors and canine. A fractured front tooth with an exposed pulp drives pain straight up the ASA. The trap is the posterior superior alveolar nerve (PSA), the superior alveolar nerve most students name first, but the PSA serves the molars at the back of the arch. The nasopalatine and greater palatine nerves carry the soft tissue of the palate, not the pulp inside the tooth. Front maxillary tooth equals ASA. Every time.

The Tooth Map

Tap a tooth. Watch which superior alveolar nerve lights up and trace the signal up to the maxillary nerve and the trigeminal ganglion. Then flip to palate mode to separate pulp from the gum on the roof of the mouth.

Tap any tooth

StartFront teeth are green (ASA), premolars are blue (MSA), molars are gold (PSA). Tap one and follow the signal up to the trigeminal ganglion.

ASA: incisors and canine

MSA: premolars

PSA: molars

Permanent teeth of the upper dental arch seen from below — The real maxillary arch from below: incisors and canine in front (ASA), premolars in the middle (MSA), molars at the back (PSA). Tap to expand.

From the Attending

Three superior alveolar nerves, front to back. ASA for the incisors and canine. MSA for the premolars and the mesiobuccal root of the first molar. PSA for the molars. ASA and MSA branch off the infraorbital nerve inside the canal. PSA splits off V2 earlier, back in the pterygopalatine fossa. All of it is the maxillary nerve, V2. When a front tooth breaks, the pain is ASA. Do not drift to the molar nerve because it sounds familiar. Know your clues.

The Four Nerves

Three for the teeth, two for the palate, one for the face. Tap a tab.

ASA

MSA

PSA

PALATE

Anterior Superior Alveolar (ASA)

The front-tooth nerve, the one students forget

TeethMaxillary incisors and canine (pulp)

Comes offInfraorbital nerve, inside the infraorbital canal

ParentInfraorbital nerve → maxillary nerve (V2)

AnesthesiaASA or infraorbital block, or local infiltration over the incisor

Board trapDrifting to PSA because it is the superior alveolar nerve you remember first

Middle Superior Alveolar (MSA)

The premolar nerve, and it is often missing

TeethMaxillary premolars plus the mesiobuccal root of the first molar (pulp)

Comes offInfraorbital nerve, inside the canal

VariabilityAbsent in many people; then ASA or PSA covers the premolars

AnesthesiaMSA or infraorbital block

Board trapThe first molar is split: mesiobuccal root is MSA, the rest is PSA

Posterior Superior Alveolar (PSA)

The molar nerve, the one everyone names first

TeethMaxillary molars (pulp), except the mesiobuccal root of the first molar

Comes offMaxillary nerve (V2) in the pterygopalatine fossa

RouteEnters the posterior maxilla through the PSA foramina

AnesthesiaPSA block high behind the maxillary tuberosity

Board trapA PSA block can fail on the first molar mesiobuccal root, which is MSA

The Palate Nerves

Soft tissue on the roof of the mouth, not the pulp

NasopalatineAnterior hard palate mucosa and gingiva, lingual to the incisors

ExitIncisive foramen, behind the central incisors

Greater palatinePosterior hard palate mucosa and gingiva

ExitGreater palatine foramen, near the second or third molar

Board trapThese are gum, not pulp: a numb incisor is ASA, a numb palate behind it is nasopalatine

Alveolar branches of the superior maxillary nerve and the sphenopalatine ganglion — The anterior, middle, and posterior superior alveolar branches of V2 dropping into the maxilla to reach the tooth roots. Tap to expand.

From the Attending

Two questions split this whole topic. Is the problem the tooth or the gum? Tooth pulp is the superior alveolar nerves: ASA, MSA, PSA. Palatal soft tissue is the palatine nerves: nasopalatine in front, greater palatine in back. Then, which tooth? Front equals ASA, middle equals MSA, back equals PSA. Pulp versus palate, then front versus back. Answer those two and you never miss one of these.

Pulp vs Palate

The single distinction that defeats these questions. Each row shows the structure; the nerve, tissue, and exit start blurred. Predict each row, then tap to reveal.

read the structure, call the nerve, then tap that one row to check it

Structure	Nerve	Tissue	Exit
Incisors and canine	Anterior superior alveolar (ASA)	Tooth pulp	Off infraorbital nerve in the canal
Premolars	Middle superior alveolar (MSA)	Tooth pulp	Off infraorbital nerve in the canal
Molars	Posterior superior alveolar (PSA)	Tooth pulp	Off V2 in the pterygopalatine fossa
Gum behind the incisors	Nasopalatine	Palatal soft tissue	Incisive foramen
Posterior palatal gum	Greater palatine	Palatal soft tissue	Greater palatine foramen
Lower eyelid, side of nose, upper lip	Infraorbital	Facial skin	Infraorbital foramen

Distribution of the maxillary and mandibular nerves on the face — The maxillary nerve (V2) fanning across the midface. Its terminal infraorbital branch becomes pure facial skin once it leaves the foramen. Tap to expand.

From the Attending

Look at the third column. Three rows of pulp, two rows of palatal gum, one row of facial skin. The superior alveolar nerves never touch the roof of the mouth, and the palatine nerves never feel a toothache. The infraorbital nerve is the parent trunk on the face, and after it leaves the foramen it is pure skin: lower eyelid, side of the nose, upper lip. Mix up the columns and you pick the wrong answer. Keep them straight and the question answers itself.

Name That Nerve

Commit to a branch before the answer drops.

A patient has pain or numbness in the mouth. First fork: is the problem inside a tooth, or in the soft tissue on the roof of the mouth?

Inside a tooth (the pulp)

Soft tissue of the hard palate (the gum)

Tooth pulp. So this is a superior alveolar nerve. Which tooth is involved?

A front tooth: incisor or canine

A premolar

A molar

Palatal soft tissue. So this is a palatine nerve, not an alveolar nerve. Which part of the palate?

Anterior hard palate, just behind the upper incisors

Posterior hard palate, back near the molars

From the Attending

Notice the funnel. One fork tells you pulp or palate. The second fork tells you which nerve. A question about a numb half of the hard palate behind the incisors is nasopalatine, even though the incisors above it are ASA. The tissue you are asked about, pulp or mucosa, decides the column before the tooth decides the row. Read what the question is touching.

Wrong Answer Autopsy

Every distractor has a reason it tempts you. Tap to flip and find it.

Posterior Superior Alveolar

Why it feels right: it is the superior alveolar nerve everyone learns first, so the brain reaches for it on any tooth question.

The Trap: a front tooth hurts, and you answer PSA because it is the famous one.

flip for the rule →

The Rule

The problem

The PSA serves the maxillary molars at the back of the arch. It cannot reach the incisors. A central incisor is the most anterior tooth there is.

Keep it straight

Front equals ASA, back equals PSA. If the stem names an incisor or canine, the answer is never the posterior nerve.

Infraorbital Nerve

Why it feels right: it is the parent trunk, and the ASA and MSA really do branch off it, so it sounds like the tooth answer.

The Trap: numbness of the cheek and lip, and you call it a tooth nerve.

flip for the rule →

The Rule

The problem

After it exits the infraorbital foramen, the infraorbital nerve is cutaneous: lower eyelid, side of the nose, cheek, and upper lip skin. The tooth branches have already left it inside the canal.

Keep it straight

Infraorbital on the face equals skin, not pulp. A pure cheek-and-lip numbness stem is infraorbital; an isolated toothache is the alveolar branch.

Nasopalatine Nerve

Why it feels right: it sits right behind the upper incisors, so it feels like the incisor nerve.

The Trap: an incisor problem, and you pick the nerve that lives next to it on the palate.

flip for the rule →

The Rule

The problem

The nasopalatine nerve carries the mucosa and gingiva of the anterior hard palate, the soft tissue lingual to the incisors. It does not enter the tooth and does not feel pulp pain.

Keep it straight

Nasopalatine is the gum behind the incisors, not the incisor pulp. Pulp is ASA; the palatal mucosa over it is nasopalatine.

Greater Palatine Nerve

Why it feels right: it is a palate nerve, so it gets picked whenever the roof of the mouth is mentioned.

The Trap: anterior palate procedure, and you grab the wrong palate nerve.

flip for the rule →

The Rule

The problem

The greater palatine nerve covers the posterior hard palate and exits the greater palatine foramen near the second molar. It does not reach the anterior palate behind the incisors.

Keep it straight

Greater palatine is the back of the palate; nasopalatine is the front. Anterior palatal anesthesia is the nasopalatine block at the incisive foramen.

Left maxilla outer surface showing the infraorbital foramen — The infraorbital foramen on the maxilla: where the infraorbital nerve reaches the face, after the ASA and MSA tooth branches have peeled off inside the canal. Tap to expand.

Memory Hooks

Predict first, then tap to unblur.

🦷

A, M, P run front to back

Anterior, Middle, Posterior, front to back.A = incisors and canineM = premolarsP = molarsThe names are a map: read them front to back and you have the order of the teeth.

tap to reveal

🪥

Front tooth equals ASA

Stem says incisor or canine → lock ASA.The single most missed point: a fractured or abscessed incisor drives pulp pain through the anterior superior alveolar nerve, not the posterior one. PSA is the famous name, but it lives at the back. Do not look back.

tap to reveal

🧊

Pulp vs Palate

Alveolar nerves feel the tooth.Palatine nerves feel the gum on the roof of the mouth.Toothache → ASA, MSA, PSA. Numbing or cutting palatal mucosa → nasopalatine or greater palatine. Different tissue, different nerve.

tap to reveal

👀

Infraorbital is the face

Infraorbital on the face = skin only.Once the maxillary nerve becomes the infraorbital nerve and exits the foramen, it carries the lower eyelid, side of the nose, cheek, and upper lip. The tooth branches (ASA and MSA) peeled off earlier, inside the canal. Cheek and lip numbness is infraorbital, not a toothache.

tap to reveal

🦷

The first molar is split

The first molar straddles the MSA / PSA border.Its mesiobuccal root is usually MSA, while the rest of the molars are PSA. That is why a PSA block can leave the first molar partly painful.

tap to reveal

🍽

Front palate vs back palate

Nasopalatine = incisive foramen → anterior hard palate.Greater palatine = greater palatine foramen → posterior hard palate.Front foramen, front palate. Back foramen, back palate.

tap to reveal

Bony palate and alveolar arch with the incisive and greater palatine foramina — The bony palate from below: the incisive foramen in front (nasopalatine, anterior palate) and the greater palatine foramen near the molars (greater palatine, posterior palate). Tap to expand.

Prove It

Original board-style vignettes. One at a time. Tap each teaching beat to reveal the chain.

From the Attending

These stems hide the answer behind a familiar name. Front tooth pulp is ASA. Premolar pulp is MSA. Molar pulp is PSA. Palatal gum is nasopalatine in front and greater palatine in back. Cheek and lip skin is infraorbital. Find the tissue first, then the location. The tooth that broke or the gum that is numb tells you the nerve. Right click or long press to cross out a choice, double tap to highlight one. Don't overthink it.

Which Nerve Feels That Tooth?

The Tooth Map

The Four Nerves

Anterior Superior Alveolar (ASA)

Middle Superior Alveolar (MSA)

Posterior Superior Alveolar (PSA)

The Palate Nerves

Pulp vs Palate

Name That Nerve

Wrong Answer Autopsy

Memory Hooks

Prove It

Keep Going