regional anatomy for local anesthesia in dentistry

Regional Anatomy for Local Anesthesia in Dentistry

Local infiltration:A type of injection that anaesthetize a small area of

(one or two teeth and associated structures) by depositing local anaesthetic agent near terminal

nerve endings.-Used for maxillary and anterior mandibular teeth anaesthesia. Nerve block:

a type of injection that anaesthetize a larger area than a local infiltration by depositing of local anaesthetic agent near large nerve trunks.

-Used for maxillary and mandibular teeth anaesthesia.

Posterior Superior Alveolar Block

Nerves anaesthetized:

PSA nerve

Areas Anaesthetized -Pulps of all maxillary molars with possible exception

of mesiobuccal root of maxillary first molar (which may be supplied by Middle Superior Alveolar Nerve)-Buccal Mucoperiosteum (Gingiva / alveolar bone /periodontal ligament) of maxillary molars

Target area: PSA nerve just before it enters the maxilla through posterior superior alveolar nerve foramina in the Infratemporal Fossa Surface distal to the zygomatic process of maxilla, superior to the apex of 2nd molar. Point of insertion:At mucco-buccal fold above maxillary 2nd molar Needle Direction:Posteriorly 45 degrees angle to the long axis of 2nd molarSuperiorly 45 degrees angle to the occlusal plane Medially 45 degrees angle to the occlusal plane Syringe Barrel should be extended from the ipsilateral side of labial comissure.Depth of penetration: 15mm Amount Administered:0.9-1.2 ml

Complications -Pterygoid Plexus penetration and causing a bluish-reddish extraoral swelling in case of needle insertion too far distally causing hematoma, thereby aspiration is always important -Inadvertent anaesthesia of mandibular nerve. Contraindicated in patients with Hemophilia due to inability to control bleeding and apply pressure.

Middle Superior Alveolar Nerve

Present in 28-30 % of peopleNerves anaesthetized Middle Superior Alveolar nerve

Areas Anaesthetized Pulps of premolars and possibly mesiobuccal root of 1st molar.Buccal mucoperiosteum of premolars

Target area:MSA nerve at the apex of 2nd premolar Point of insertion:Muccobuccal fold above 2nd premolar until tip is above the apex of 2nd premolar Amount administered:0.9-1.2 ml

Anterior Superior Alveolar Nerve Nerves anaesthetized:Anterior Superior Alveolar nerve Area anaesthetized: Pulp of Anterior Teeth Labial mucoperiosteum

Target area:Anterior Superior Alveolar Nerve at the apex of canine in the canine fossa Point of insertion:At the muccobuccal fold anterior and parallel to the canine eminence (posterior to the canine fossa) Direction of needle:10 Degrees angle parallel to the long axis of upper canine Amount Administered:0.9-1.2 ml

Infraorbital Nerve Block

Nerves anaesthetized:Infra orbital nerve :-superior labial n.-lateral nasal nerve-inferior palpebral nerveASA nerveMSA nerve Areas anaesthetized:Pulps and Buccal mucoperiosteum of the maxillary central incisors till the maxillary premolars Skin of upper lip, lower eyelid, and side of the nose

Target Area: Anterior and Middle Superior Alveolar Nerve as they move superiorly to join Infraorbitral nerve after entering infraorbital foramen. For location of infraorbital Nerve, Palpation of the infraorbital notch moving downwards 10 mm until localization of a depression is felt.The infraorbital foramen is about 1-4 mm medial to the eye pupil when the patient looks straight forward. A line drawn linear from the pupil to the infraorbital foramen till the ipsilateral labial comissure. Point of insertion:At the height the muccobuccal fold at the apex of the 1st premolar Depth of insertion:-pre-injection estimation of the distance extraorally usually at the depth 16mm.

The needle is inserted while keeping the finger of the other hand on the infra-orbital foramen Direction of the needle:The needle must be parallel to the long access of the 1st premolar to avoid premature contact with the maxilla. The point of contact should be at the upper rim of Infraorbital foramen maintaining a contact with the bone of the roof of infraorbital foramen prevents overinsertion and puncture of the orbit. Amount of Administration:0.9-1.2mm

Greater palatine nerve block

(Pressure Anaesethesia due to painful administration) Nerve Anaesthetized:Greater palatine nerve Areas anaesthetized:Palatal mucoperiosteum of maxillary teeth from the premolar till the molar to the midline.

Target area:Anterior to where the Greater palatine nerve enters the foramina between the mucoperiosteum till the horizontal plate of palatine bone (between the junction of the maxillary alveolar process and the posterior hard palate at the apex of the 2nd molar. A cotton swab will be used to apply pressure and locate the foramen by moving it from 1st molar posterior until it falls slightly in a depression and notice blanching of the tissues.-Insertion and injection will occur under pressure causing bowing of the needle Direction of the needle:90 degrees angle to the palate Point of insertion:Slightly anterior to the depression of Greater Palatine Foramen Amount of Administration:0.45ml

Nasopalatine Nerve block

(Most painful) Nerves Anaesthetized:Nasopalatine nerve Areas anaesthetized:Palatal Mucoperiosteum of anterior teeth bilaterally

Target Area:Nasopalatine nerve as it exits from incisive foramen (beneath incisive papilla) Point of insertion:Apply Pressure anaesthesia by a cotton swab (on the other side of the papilla) at the palatal mucosa lateral to the incisive papilla (10 mm palatal to the center)Advance the needle in 45 degrees angle to the palate until it reaches the palatal bone followed by withdrawal slightly and slow injection.-Never insert directly into the papilla (extremely painful) Amount administered:0.45 ml

Maxillary Nerve: Nerves Anaesthetized:Maxillary Nerve:-Posterior superior alveolar nerve -Middle superior alveolar nerve -Anterior Superior Alveolar nerve -Infraorbital nerve -Greater Palatine nerve-Nasopalatine nerve Areas Anaesthetized:Pulps , Buccal and Palatal mucoperiosteum of all Maxillary teeth on the same side of injection Lateral aspect of nose, lower eyelid and upper lip.

Target Area:Maxillary Nerve as it passes through the pterygopalatine fossa

Point of insertion:After the localization of the greater palatine Nerve using (pressure Anaesthesia using cotton swab) the needle should be inserted into the palatal mucosa with a small amount of local anaesthetic agent injection to lessen the patients discomfort. Blanching should be noted Advancing of the needle further and localization of the Greater Palatine foramen with the needle .Advancing the needle further until it reaches 30mm approximatelyNo forcing of the needle should be attempted.

Amount administered:1.8ml

Inferior Alveolar Nerve Block

(The least success rate due anatomical variations and great depth of soft tissue penetration) Nerves anaesthetized:Inferior Alveolar Nerve Incisive and Mental terminal branches of inferior alveolar nerve Lingual nerve Areas Anaesthetized:Pulps of all mandibular teeth of the side of injectionAnterior 2/3rd of the tongue Buccal and lingual mucoperiosteum of the side of injection except buccal mucoperiosteum of mandibular molars.Skin of the lower lip

Target Area:In the Pterygomandibular Space at the entry point of the inferior alveolar nerve to the mandibular foramen accompanied by lingual nerve. Point of Insertion: At the 3/4th the distance from the deepest portion of the coronoid notch (vertical height) and the pterygomandibular fold (found 10 mm superior to the occlusal plane of the mandibular molars) Direction of needle:The syringe Barrel of the contralateral premolars Advancing the needle along the occlusal plane of the mandible, the needle should enter 20-25 mm until the mandible is contacted. Amount of administration:1.5 ml

Lingual Nerve block

After deposition of solution at the inferior alveolar nerve , the needle is withdrawn to half its length and injected while withdrawed and ceasing injection before the needle exit the

tissues.

Amount administered: 0.3 ml

Troubleshoots:-Early Bone Contact (too far anteriorly on the ramus), is corrected by withdrawal of the needle partially or completely and bringing the syringe barrel more medially (towards the anterior teeth). -If no bone contact (too far posteriorly on the ramus), is corrected by the withdrawal partially or completely and bringing the syringe barrel more laterally (towards molar teeth) Failures:1-Failures related to the accessory innervations of lower 1st molars by Nerve to Mylohyoid and, lower premolars by cutaneous coli (cervical plexus c2/c3) and cross innervations of mandibular incisors. 2-Bifid Inferior Alveolar nerve with two mandibular foramina -correction is done administering local anaesthetic more inferior to the usual landmarks. Complications: Transient facial paralysis if facial nerve (represented as drooping of the eye and labial comissure ) is mistakenly anaesthetized due to incorrect administration of local anaesthetic into the parotid salivary gland because there is no bone contact (too far posteriorly ) Hematoma Paraesthesia due to trauma of lingual nerve.

Long buccal Nerve

Nerves Anaesthetized:Long buccal nerve Areas Anaesthetized:Buccal mucoperiosteum of Mandibular molars

Target Area:Buccal nerve as it passes anteriorly to the anterior border of the ramus and through the buccinator muscle before entering the buccal region.

Point of insertion:Mucosa distal and buccal to the most distal mandibular molar. (On the anterior border of the ramus).

Depth of insertion:2mm Amount of administration:0.3 ml

Mental Nerve Block

Nerves Anaesthetized:Mental division of the Inferior alveolar nerve Areas Anaesthetized:Buccal mucoperiosteum from premolar to centrals of the mandibular teeth Skin of the lower lip

Target Area:A point anterior to where the mental nerve exits the mandible through the mental foramen. Point of insertion:At the muccobuccal fold anterior to the foramen usually found between the 1st and 2nd premolars.Localization of the mental foramen is by palpating and feeling a depression and sore pain upon pressure. Also surrounded by smooth bone. Depth of penetration:6mm

Amount of administration:0.6 ml

Incisive Nerve Block

Nerves Anaesthetized: Incisive and mental divisions of the inferior alveolar nerve Areas Anaesthetized:Pulps and Buccal Mucoperiosteum of teeth found anterior to the mental foramen

Target Area:A point anterior to where the mental nerve exits the mental foramen.(No insertion of the needle through the foramen to prevent injury and due to difficult insertion.)L.A agent could be directed into the foramen under pressure. Point of insertion: Anterior to the depression created by the mental foramen at the mucco-buccal fold in a horizontal angulation. -Finger Pressure is applied extraorally after injection to force L.A agent into the mental foramen to prevent mental block which is not needed.

Gow-Gates (Mandibular nerve block)

Nerves Anaesthetized:Mandibular division of trigeminal Nerve Areas Anaesthetized Pulps, buccal and lingual mucoperiosteum of mandibular teeth on the side of injectionThe anterior 2/3rd of the tongue The Skin of the lower lip Skin of the Temple anterior to the ear

Target AreaAnteromedial border of the neck of the condoyle while mouth opening is as wide as possible Point of insertion:Height:At the mucosal tissue above the occlussal height.Needle insertion is occlusal to the level of 2nd mandibular molar just distal to the mesiopalatal cusp of 2nd molar . Direction of the needle :The imaginary line from the labial commissure till the intertragal point of the ear. With syringe barrel at the Canine Area of the contralateral side Depth of insertion:25mm Amount of administration :1.8ml After L.A administration and needle withdrawal the mouth should be kept opened to allow complete diffusion of L.A and allow it to bath the whole nerve trunk by placing the nerve closer to the injection site at the neck of the condyle .

Vazirani Akinosi Nerve Block

(Used in cases of trismus ) Nerves Anaesthetized :Inferior Alveolar Nerve Nerve to mylohyoid Lingual Nerve Areas Anaesthetized :All pulps and Lingual mucoperiosteum of mandibular teeth Buccal mucoperiosteum of mandibular teeth except molars Skin of lower lip Anterior 2/3rd of the tongue

Target Area:Medial aspect of ramus in the region of Inferior Alveolar Nerve , Lingual and Nerve to mylohyoid from foramen ovale toward the mandibular foramen . Point of Insertion :Medial surface of the ramus adjacent to maxillary tuberosity at the height of the muccobuccal fold . Instruct the patient to close his /her mouth .Insertion is between the medial border of the ramus and the maxillary tuberosity at the level of cervical margins of maxillary molars . Direction of the needle :Parallel to the occlusal plane Depth of Insertion:23-25 mm Bevel away from the bone Amount of Administration :1.5 ml

Supplemental Anaesthesia

Supplemental Injection Techniques :

1-Intraligamentary (Periodontal ligament )2-Intaosseous An.3-Intrapulpal An.

1-Intraligamentary Anaesthesia

Point of insertionInsertion of the needle at 30 degrees angle to the long axis of the tooth and the mesiobuccal aspect of the root The needle is forced via periodontal ligament to maximum penetration until it is wedged between the tooth and the crestal bone The bevel of the needle should face toward the root to permit easy advancement It may be necessary to bend the needle to achieve proper angle especially on the distal aspects of 2nd and 3rd molars . The solution is injected under strong pressure at each root in a minimum of 20 seconds . The needle should remain in position for at least 5 seconds following injection to prevent the loss of solution via the needle tract in the mouth . Amount administered 0.2 ml

2-Intraosseous Anaesthesia (Alternative regional block Anaesthesia ) Areas Anaesthetized Bone Soft Tissue Root structure in the area of injection Target area Cancellous bone of the jaws Point of Insertion Lateral perforation at a point 0.2 mm apical to the intersection of lines drawn horizontally along the gingival margins of the teeth and a vertical line through the interdental papilla . Vertical perforation at a point on the alveolar crest either mesial or distal to the treatment area.An infiltration injection of 0.2 ml solution is given in the buccal sulcus or attached gingival , site of subsequent cortical penetration . The cortex is breached using a perforator in the inter-radicular region . The matched needle is attached to syringe and located at the opening of the cortex and solution is injected directly in cancellous space 1 ml solution . Complications :1-Palpitaion2-Post- injection- pains 3-Fistula formation due to application of constant pressure against the bone leads to the buildup of heat fistula formation4-seperation of perforator which is corrected by removal with a hemostat,5-Perforation of lingual plate

3-Intrapulpal Anaesthesia Anaesthesia is achieved by pharmacological action of the L.A and pressure causing ischemia which is achieved by fitting the needle snugly into the canal Bending the needle may be necessary to gain access to the canal and injected slowly and resistance should be felt Amount administered 0.2 ml

References

-Handbook of Local Anaesthesia . Stanley F. Malamed. Fourth edithion

-Illustrated Anatomy of the Head and Neck .Margaret J. Fehrenbach, Susan W. Herring. Elsevier, 4th edition 2012.

-Netter’s Head and Neck Anatomy for Dentistry. Neil S.Norton, Elsevier ,2nd edition 2012.