Local Anesthesia

Dental syringe
A dental syringe is a syringe for the injection of a local anesthetic.^[26] It consists of a breech-loading syringe fitted with a sealed cartridge containing an anesthetic solution.In 1928, Bayer Dental developed, coined and produced a sealed cartridge system under the registered trademark Carpule^®. The current trademark owner is Kulzer Dental GmbH.
The carpules have long been reserved for anesthetic products for dental use. It is practically a bottomless flask. The latter is replaced by an elastomer plug that can slide in the body of the cartridge. This plug will be pushed by the plunger of the syringe. The neck is closed with a rubber cap. The dentist places the cartridge directly into a stainless steel syringe, with a double-pointed (single-use) needle. The tip placed on the cartridge side punctures the capsule and the piston will push the product. There is therefore no contact between the product and the ambient air during use.In the UK and Ireland, manually operated hand syringes are used to inject lidocaine in to a patient's gums.
Other anesthetics used in dentistry

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  Topical anesthetics benzocaine, eugenol, and forms of xylocaine are used topically to numb various areas before injections or other minor procedures. Topical anaesthetics in dentistry act on the peripheral nerves on mucosal surfaces to reduce sensation. Topical anaesthetics will contain either lidocaine or benzocaine as their active ingredient and come in a variety of forms, including solutions, creams, gels, and sprays. Indications for topical anaesthesia in dentistry includes:
  
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    Needle insertion for infiltration anaesthesia
    
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    Root planning or scaling
    
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    Dry socket
    
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    Rubber dam placement
    
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    Reduction of pain in a wounded area
    

Topical anaesthesia can also be used to reduce dental phobia, especially in children, by reducing discomfort and pain.

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  Nitrous oxide (N₂O), also known as "laughing gas", easily crosses the alveoli of the lung and is dissolved into the passing blood, where it travels to the brain, leaving a dissociated and euphoric feeling in most cases. Nitrous oxide is used in combination with oxygen. Often (especially with children) a sweet-smelling fruity scent similar to an auto^{[clarification needed]} scent is used with the gas to inspire deep inhalation.
  
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  General anesthesia drugs such as midazolam, ketamine, propofol and fentanyl are used to put a person in a twilight state or render them completely unconscious and unaware of pain. Dentists who have completed a training program in anesthesiology may also administer general IV and inhalation anesthetic agents.
  
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  Midazolam (Versed), a drug that represses memories of the procedure, is usually given two hours prior to the procedure in combination with Tylenol in general anesthesia so the person will go home with no memories of being in surgery.
  
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  Sevoflurane gas in combination with nitrous oxide and oxygen is often used during general anesthesia followed by the use of isoflurane gas to maintain anesthesia during the procedure. In children sweet fruity scents are often used with the gases to inspire deep inhalation. Scents come in cherry, apple, bubblegum, watermelon, etc...
  
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  Propofol, a drug with similar effects to Sodium Pentathol, is often used through intravenous infusion through an IV during general anesthesia after gasses are initiated.
  
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  Morphine is often used to control pain during the dental surgery under general anesthesia. The morphine is usually administered through IV.
  
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  Ketorolac is often administered through IV to suppress both pain and inflammation while under general anesthesia.Drugs used in combination with general anesthesia
  

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  Decadron a steroid is often administered through IV to suppress inflammation and swelling resulting during the surgery while under general anesthesia.
  
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  Ondansetron brand named Zofran is often administered to prevent nausea during surgery which may result from blood draining into the stomach while under general anesthesia, or it is given afterwards for nausea which may result from the anesthesia.
  

Local anesthesia and the pregnant patient
Provided a dentist performs proper aspiration to avoid intravenous injections, local anesthetics containing epinephrine (adrenaline) are safe to use during pregnancy. lignocaine and prilocaine are assigned a category B ranking by the FDA and are therefore safe for use during pregnancy. Lignocaine and prilocaine are sold as 2% and 4% formulations, respectively. It is therefore safer to use the lignocaine so as to administer a lower concentration of the drug to the pregnant patient. Mepivicaine, articaine, bupivicaine are given an FDA category C ranking and so should be avoided. Benzocaine, the ingredient of most topical anesthetic formulations, is also ranked as category C and should be avoided. Lignocaine should be used as topical anesthetic instead.
Epinephrine in high doses is harmful to a pregnant woman in that it affects uterine blood flow. However its use in low dose with local anesthetic administration is warranted. The epinephrine causes vasoconstriction which in turn reduces systemic distribution of the anesthetic as well as prolongs its action in addition to decreasing bleeding at the operating site. Lidocaine 2% with 1:100,000 adrenaline is the local anesthetic of choice in the treatment of pregnant women.^[29]
Allergy to local anaesthetic
Allergic reactions from local anaesthesia have been reported in some patients. However, this occurrence is rare even in patients who had a past history of adverse reactions to LA.There are mainly 2 classes of local anaesthetic agents: Amide or Ester linkages, based on their chemical structure. E.g. of amide LA: lidocaine, prilocaine, articaine, mepivacaine

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  E.g. of ester LA: benzocaine, procaine
  

Genuine allergic reactions of an amide LA is very uncommon. An ester LA is more possible to result in an allergic reaction because the compound will be broken down to para-aminobenzoic acid (PABA) which is a trigger for allergic reactions.^[31] In general dentistry, only topical applications of LA contains esters (benzocaine) when applied onto area before LA is administered.If one is allergic to an ester LA, then the use of other types of ester LA should be avoided as the breakdown of all esters will produce PABA. However, patients allergic to ester LA will usually not be affected by amide LA because PABA is not produced upon breakdown of amide LA. Unlike ester LA, allergy to an amide LA will not eliminate the use of other types of amide LA. Some reactions are caused by administration of too much drug, usually because of the route of entry of drug (intravenously) or the quick uptake of drug into the system, or the aftereffect of the vasoconstrictor. Unfavourable reactions to LA can be classified into 3 different groups: psychogenic, allergic, toxic.