Local anaesthesia- composition and dosage in dentistry

L.A techniques

1. Local Anaesthesia-Composition and dosage;Maxillary techniques

2. Definition: Local anaesthesia is defined as a loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves.

3. Desirable properties of LA Should not be irritating to the tissues to which it is applied Should not cause any permanent alteration of nerve structure Systemic toxicity should be low Time of onset of anaesthesia should be as short as possible The duration of action must be long enough to permit completion of the procedure yet not so long to require and extended recovery Should be free from producing allergic reactions Should be stable in solution and readily undergo biotransformation in the body

4. Composition of local anaesthetics Local anaesthetic agent:Lignocaine Hydrochloride-2%(20mg/ml) Reducing agent:Sodium meta-bisulphite-(0.5mg) Preservative:Methylparaben-0.1%(1mg) Diluting agent:Distilled water Fungicide:Thymol Isotonic solution:Sodium chloride or Ringer’s Solution-6mg Vasoconstrictor:adrenaline-1:80,000(0.012mg) To adjust pH-Sodium hydroxide Nitrogen bubble-1-2mm in diameter and is present to prevent oxygen from being trapped in the cartridge and potentially destroying the Vasopressor .

5. Actions of : Vasoconstrictor:Decreased blood flow to the site of injection,absorption of L.A by cardiovascular system is solved,decrease the risk of local toxicity,higher volume of local anaesthetic agent remain in and around the nerve for longer period,thereby increasing the duration of action,vasoconstrictor decreases bleeding at the site of their administration. Preservative:Stability of modern L.A is maintained by adding caprylhydro-cuprienotoxin which includes xylotox and methyl paraben .

6. Reducing agent:These act as preservatives for the vasoconstictor agents.Vasoconstrictors are unstable in solution and may oxidize,especially on exposure to prolonged sunlight.Sodium metabisulphite which competes for the available oxygen is added in the concentration between 0.05% and 0.1% Vehicle:The isotonic vehicle reduces discomfort during injection.

7. B.R.I.T: Bi-Rotational Insertion Technique: T he operator rotates the needle in a back-and-forth rotational movement while advancing the needle through the tissues; results in less deflection, less force is needed for needle penetration.

8. Dosages: To calculate the recommended dose,the following must be known: Concentration of the L.A Dilution percentages of vasoconstrictors Standard cartridge volume Maximum recommended dose Patients weight and general health status,including medications.

9. Maximum recommended doses: Lignocaine hydrochloride with epinephrine:7mg/kg Articaine:6.4mg/kg Bupivicaine:6.66 mg/kg

10. A 100% solution has 1000mg of L.A per ml.Therefore a 2% solution has.... 20mg/ml A cartridge of 2ml,therefore has 40mg of L.A. M.L.D for lignocaine hydrochloride is 7mg/kg . For a 70kg man,the maximum dosage of L.A he can recieve is-7*70kg =490mg. In 1 cartridge there is 2ml of L.A which contains 40mg of L.A,therefore the number of cartridges needed to achieve maximum lethal dose is 12.25 cartridges.(490*1/40)

11. Anatomical considerations Branches of maxillary nerve:

12. Injections used to anaesthetize the maxillary teeth,soft and hard tissues: Infiltration( supraperiosteal injection) Posterior superior alveolar nerve block(PSA) Middle superior alveolar n.b (MSA) Anterior superior alveolar n.b (ASA)( Infraorbital nb ) Greater palatine nb Nasopalatine nb 2 nd division nb (maxillary nb ) Anterior middle superior alveolar nb (AMSA) Palatal-(PASA)

13. Infiltration: Infiltration is a technique used to achieve pulpal anaesthesia for one or two maxillary teeth at a time. The area anaesthetised are the pulp,bucal soft and hard tissues of the anaesthetised teeth. Recommended needle-27 gauge short

14. Technique: Site of insertion-Height of the mucobuccal fold,at the apex of the tooth. The needle is inserted parallel to the maxillary bone and inserted till the needle tip is at or above the apex of the root. After two negative aspirations,1/3 rd of a cartridge of L.A is injected.

15. Posterior superior alveolar nerve block(PSA Provides pulpal anaesthesia to the three maxillary molars and supporting buccal soft tissue and bone. In 28% of patients,the mesiobuccal root of the maxillary first molar is not anaesthetised by this technique. Recommended needle-27 gauge short.

16. Technique: Site of insertion-Height of the buccal fold,adjacent to the maxillary second molar,with the syringe held in an upwards,inwards and backwards direction,and inserted to a depth of 16mm After two negative aspirations,1/2 a cartridge of L.A is injected,over 30 seconds.

17. Middle superior alveolar n.b (MSA) Provides pulpal anaesthesia to the maxillary premolars and the mesiobuccal root of the maxillary first molar,and supporting buccal soft and hard tissues. Recommended needle-27 gauge short.

18. Technique: Site of insertion-Height of the buccal fold,adjacent to the maxillary second premolar.Needle is inserted till its tip is located way above the apex of the second premolar. After 2 negative aspirations,1/2 a cartridge of local anaesthetic is slowly injected.

19. Anterior superior alveolar n.b (ASA)( Infraorbital nb ) Provides pulpal anaesthesia to five maxillary anterior teeth-The incisors,canine and two premolars,and also anaesthetises the buccal supporting soft tissue and bone,the skin of the lower eyelid,the lateral side of the nose,upper lip. Recommended needle-25 gauge long.

20. Technique: The infraorbital foramen is palpated,lip retracted,the needle is inserted at the height of the buccal fold,adjacent to the maxillary first premolar. The needle is held parallel to the maxillary bone and inserted till bone is contacted at the roof of the infraorbital foramen. After 2 negative aspirations,1/2-1/3 rd of a cartridge is deposited over 30-40 seconds.

21. Greater palatine nb (Anterior palatine nb ) Provides anaesthesia to the posterior portion of the hard palate and its overlying soft tissues extending anteriorly as far as the first premolar and medially to the midline. Recommended needle-27 gauge short

22. Technique: The greater palatine foramen is palpated(cotton swab may be used for this),the needle is inserted into the soft tissue,just anterior to the greater palatine foramen. As the needle is advance,L.A is deposited slowly,upon contacting bone,1/4 th -1/3 rd a cartridge of L.A is deposited,over 15-20 seconds.

23. Nasopalatine nb Provides anaesthesia to the anterior portion of the hard palate,affecting both soft and hard tissues,from the mesial of the right first premolar to the mesial of the left first premolar.

24. Technique: Traditional-The needle is inserted,just lateral to the incisive papilla,advanced till bone is contacted,after 2 negative aspirations,0.3 ml of L.A is deposited. Multipl injection technique-1 st injection is an infiltration of 0.3ml to the labial soft tissues between the central incisors.2 nd injection is an infiltration to the now limp papilla between the two central incisors.L.A is administered as the needle is advanced,until blanching is noted on the palatal soft tissues.3 rd injection is a traditional Nasopalatine nb .

25. 2 nd division nb (maxillary nb ) Provides anaesthesia to the pulp of the teeth of that side of the maxilla, supporting hard and soft buccal tissues, the soft tissues and bone of the hard palate and some of the soft palate medially till the midline, the skin of the lower eyelid, lateral side of the nose, cheek,upper lip. Recommended needle-25 gauge long.

26. Technique: The needle is inserted into the greater palatine foramen,and advanced to a depth of 30mm.After 2 negative aspirations,1.8ml of L.A is deposited slowly over at least 60seconds.

27. Anterior middle superior alveolar nb (AMSA) Provides pulpal anaesthesia to the incisors,canine and premolars of that side,buccal soft tissue and bone,palatal soft tissue and bone. Recommended needle-27 gauge short

28. Technique: The needle is inserted at a point halfway along the line between the premolars and the midline of the palate. 1.4-1.8ml of L.A is slowly deposited.

29. Palatal-(PASA) Provides pulpal anaesthesia to both central incisors,both lateral incisors and to a lesser degree,both canines,as well as the labial and palatal soft and hard tissues of these teeth. Recommended needle-27 gauge short

30. Technique: The needle is inserted lateral to the incisive papilla,slowly to a depth of 6-10mm into the incisive canal.Following negative aspiration,1.4-1.8ml of local anaesthetic is administered slowly.

31. Contraindication to local anaesthetics

32. Local complication of LA Needle breakage Paraesthesia Facial nerve paralysis Trismus Soft tissue injury Haematoma Pain on injection Burning on injection Infection Edema Sloughing of tissues Post anaesthetic intra oral lesions

33. Systemic complications Overdose Allergy idiosyncrasy

34. References: Malamed , Stanley. Handbook of Local Anesthesia. 5 th Edition. Mosby. 2004

35. Thankyou Dr.Vikram Perakath B.D.S