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SmilER 101: Oral Exam and Regional Anesthesia in Dental Care

Posted by Richard Ngo, DMD on

The purpose of the SmilER series on dental trauma and infection management is to teach fundamental principles, pearls, and pitfalls in the care for dental patients in the emergency department. As many as 1.5% of ED visits are dental-related¹ and many emergency physicians have expressed the need for more comprehensive training in the oral cavity. This series was created as an introductory guide on the management of patients who report to the ED with dental-related conditions. The first module teaches the oral examination and demonstrates how to provide anesthesia in the oral cavity.

Author: Richard Ngo, DMD
 Editors: Cameron Lee, DMD, MD; Andrew Eyre, MD, MS-HPEd
Series Editor: Chris Nash, MD

Learning Objectives

  1. Review basic anatomy of the oral cavity.
  2. Understand how to perform a basic oral examination.
  3. Learn to perform basic regional anesthesia to each region of the oral cavity.

How well did you learn the material? Go to ALiEMU to take the multiple-choice quizzes to receive your badges and certificates.

Basic Oral Anatomy

Adult

The typical adult oral cavity contains 32 teeth split into 4 sections, with each quadrant containing 2 incisors, 1 canine, 1 premolars, and 3 molars. The universal numbering system labels dentition with numbers from 1 through 32 starting with the right maxillary third molar. When assessing the oral cavity for avulsed or damaged dentition, it is essential to note some individuals may have congenitally missing teeth or may have had dentition extracted in the past due to various reasons. Premolars can be found anterior to the molars, and they are smaller in width.

Permanent dentition named and numbered (modified from Shutterstock)

Pediatric

Whereas adults have 32 teeth, pediatric patients have 20 primary teeth, labeled A through T. Pre-adolescents have mixed dentition, consisting of both deciduous (“baby” or “primary”) dentition and succedaneous (“permanent”) dentition. Most pediatric patients will have lost all of their primary teeth by 12 years of age.

Tooth Anatomy

Each tooth follows the same overall anatomical structure, as seen in the diagram below. However, the shape, number of roots, function, and other attributes vary from tooth to tooth. When referencing dentition, coronal is the portion of the tooth towards the crown. On the other hand, apical (as in apex) is the portion of the tooth towards the root.

The Oral Examination

A thorough oral examination is essential in the ED assessment of patients with dental complaints. When assessing the oral cavity for avulsed or damaged dentition, it is essential to note that some individuals may have congenitally missing teeth or may have had dentition extracted in the past. Obtaining a thorough dental history and oral examination may help to alleviate any potential confusion regarding special anatomical considerations. Note findings such as absence of teeth, poor/damaged dentition, supernumerary teeth, extracted teeth, and tori.

This diagram reveals the eight regions of the oral cavity that the provider should examine carefully. Manual manipulation of the tongue is easier when gauze is used to obtain a steadier grip. A tongue depressor is recommended for examination of the posterior oropharynx.

Oral Tori

Oral tori are uncommon but normal variants of bone found along the palate or lingual aspect of the mandible. They are bony structures in the hard palate or the mandible, as shown below. It is important to know that these structures exist so as to avoid being unnecessarily alarmed.

Torus seen on the hard palate [exam, CT image]

Maxillary tori [exam, CT image]
Notably, tori differentiate themselves from cancers and abscesses in a few ways.
  1. Tori are typically bony to the touch as they arise from bone. In contrast, abscesses and soft tissue cancers are more fluctuant and/or softer than bone.
  2. Tori are typically symmetrical from side to side.
  3. Tori are typically asymptomatic.

Indications and Contraindications for Local Anesthesia

Local anesthesia is necessary before splint placement, incision and drainage, or any other procedure which involves significant and painful dental manipulation. It may also be used for temporary relief of substantial pain. Note that this is not a long-term solution but simply a temporary measure to bridge a patient to an outpatient dental appointment. In these cases, bupivacaine is recommended due to its longer half-life. The maximum dosage of local anesthetics should be calculated prior to administration (MDcalc).

With appropriate dosing and administration, you shouldn’t have to worry about toxicity, but you can read more about local anesthetic systemic toxicity (LAST) to be extra prepared.

Anesthesia of the Maxillary Teeth: Supraperiosteal Block

Supraperiosteal Block

Anesthesia of the maxillary dentition is achieved through supraperiosteal (“local”) infiltration of lidocaine. tThe maxilla is more porous than the mandible, allowing easier penetration of the bone and anesthesia of the dentition.

1. Anterior Maxilla

Administration of local anesthesia to the anterior maxillary dentition can be particularly painful for patients given the extensive neural anatomy of the nose. Thus, it is essential to begin laterally and work in a stepwise fashion medially. Additionally, one can consider topical anesthesia with viscous lidocaine or benzocaine before using the needle.

2. Posterior Maxilla

For posterior maxillary teeth, use a short needle to minimize the risk for developing a hematoma. Taut retraction of the lip and the attached mucosa provides tension which makes needle penetration easier. Additionally, retraction activates proprioceptive fibers, which helps distract the patient from the pain of needle insertion.

Supraperiosteal Block: Site of local anesthetic deposition for infiltration technique to anesthetize regions of the maxilla. Source: NYSORA.COM

Technique

  1. Aim for the tooth apex and advance the needle while maintaining a needle position parallel to the long axis of the tooth.
  2. Penetrate the mucogingival junction with the bevel pointing towards the bone.
  3. Make contact with bone.
  4. Aspirate.
  5. Inject 1-2 cc of anesthetic.

Anesthesia of the Mandibular Teeth: Inferior Alveolar Nerve Block

Inferior Alveolar Nerve Block

The inferior alveolar nerve (IAN) is a branch of the mandibular nerve (V3 of the trigeminal nerve). Anesthesia of this nerve will result in anesthesia of the ipsilateral mandibular teeth to the midline, as well as the skin and mucous membranes of the lower lip, skin of the chin, and the labial gingiva of the anterior teeth. The goal is to inject local anesthetic in the region of the IAN before it enters the mandibular foramen at the medial aspect of the mandible.

Landmark Anatomy

The following figures help to clarify major anatomical landmarks for the IAN block:

Inferior Alveolar Nerve Block: Pay attention to the site of entrance of the alveolar nerve into the mandible, and note the coronoid notch as an important landmark.

Inferior Alveolar Nerve Block: The pterygomandibular raphe is a useful landmark to guide the intraoral injection point. When the patient’s mouth is held as wide as possible, the raphe tenses and becomes a visible reference line. The injection point (labeled with an X above) should be just lateral to the line so that the needle does not penetrate the raphe itself. An optional pre-step is to apply topical anesthesia with viscous lidocaine or benzocaine at the planned injection site prior injection.

Technique

  1. Place the thumb in the ipsilateral coronoid notch and visualize a line extending from the thumb back to the pterygomandibular raphe (roughly two-thirds up the finger nail).
  2. Keep the needle parallel to the occlusal plane with the bevel positioned away from the bone.
  3. Enter with the syringe oriented on the contralateral mandibular premolars.
  4. Insert the needle 1 cm above the occlusal plane and 3-5 mm lateral of the pterygomandibular raphe.
  5. Advance the needle 20-25 mm to sound bone.
  6. Retract 1-2 mm.
  7. Aspirate.
  8. Inject 75% of the total dose in this region.
  9. While removing the needle, inject the remaining 25% dose to anesthetize the lingual nerve. The total amount injected will be approximately 1-2 cc of anesthetic.
  10. Ensure adequate anesthesia by testing the patient for any acute pain upon manipulation. Keep in mind that it may take up to 5 minutes for the block to take effect following administration.

Of note, given its proximity to the IAN, the lingual nerve is also sometimes anesthetized during this block. This leads to anesthesia of the anterior two thirds of the tongue, the lingual gingiva, and the mucosa of the floor of the mouth.

Adjunctive Blocks

  1. Mandibular Incisors: The IAN block is typically sufficient to anesthetize the ipsilateral mandibular dentition and soft tissues. However it can somestimes under-anesthetize the mandibular incisors, If this occurs, we recommend adjunctive supraperiosteal blocks, as noted in the previous section. Note that supraperiosteal blocks, while useful in the maxilla, will not reliably attain complete anesthesia of the mandibular dentition as the mandible is less porous.
  2. Lips: The mental block is useful for the soft tissues of the lip anteriorly

Peer Reviewed

All information has been expert peer-reviewed by an oral and maxillofacial surgeon.

Reference

  1. Hupp J, Ellis E, Tucker M. Contemporary Oral and Maxillofacial Surgery. Elsevier; 2019.
  2. Kademani D, Tiwana P. Atlas of Oral and Maxillofacial Surgery. Saunders; 2015.

Author information

Richard Ngo, DMD

Oral and Maxillofacial Surgery Resident
Massachusetts General Hospital

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