The Armamentarium

Lecture 5

The basic equipment's required for the use of local anesthetics in dentistry include:
Dental cartridge syringe Anesthetic cartridge Disposable dental needle Additional (Topical antiseptic, Topical anesthetic, Applicator sticks, Cotton gauze and Hemostat ).

Loading the conventional dental syringe

Step one : Retract the syringe piston

Step two : insert anesthetic cartridge

Insert harpoon or claw into rubber plungerengage the rubber plunger



Step three : needle attachment

Step five : Check free flow of solution

Basic injection technique

Basic principles of an injection technique

Patient management Proper preparation of injection site. Correct injection technique.

Patient management

No approach is available to eliminate all fears but they can be minimized : Patient position. Proper technique. Keep the syringe out of site of patient. Use of premedication to reduce anxiety (N2O and oxygen sedation, diazepam )

The patient should be seated in a comfortable reclining position

The dentist either stands or seats himself beside the patient (8 – 10 o'clock position based on the site to be injected)


Position yourself correctly and adjust the patients position for optimal access and vision (e.g. raise or lower the dental chair )

Use a new sharp dental needle.

Load the dental syringe with the cartridge first followed by the needle.

Check the free flow of solution

The syringe should be ready for use before injection

Keep the dental syringe out of site of patient

Grasp the syringe in a palms up position

A palms down position is not desirable and does not offer good support

Retract the lip with your index finger and thumb of non-operating hand with the use of a piece of gauze.


For cheek retraction you can either use a dental mirror or your index finger and thumb of non-operating hand.

Apply topical anesthesia

Dry the site of injection with gauze or cotton


The bevel of needle should face the bone. This is applicable in the maxillary anterior teeth ,premolar region and lower anterior teeth.
Slowly insert needle to intended position. Try avoid touching bone. For infiltration its only 3-4mm.


Adjust your self correctly and use finger rests for good stabilization during the injection


After reaching the target area gently aspirate ,if positive reposition needle and if negative slowly inject solution .This is mandatory in block techniques.
Rate of solution flow is about 1ml/ min for infiltration and 2 ml/ min for block technique

Place the dental syringe at a safe site and recap needle.

The dental syringe
The dental syringe should have certain criteria: Durable and withstands sterilization Accepts a variety of cartridges and needles Provide effective aspiration Inexpensive , lightweight and simple to use.

Classification of dental syringes

Material constructed: metalic Stainless steel (non-disposable) Chrome plated brass (non-disposable) Plastic (disposable and non-disposable) Aspirating , non-aspirating , self aspirating Special designs : Jet injectors , periodontal ligament injection syringes and computerized local anesthetic delivery systems (wand).

Barrel

Thumb ring
Piston
Finger grip
Needle head adapter
Claws or harpoon

Aspirating and non- aspirating types

Breech or side loading

Top loading

Self aspirating dental syringe

Jet injectors
This is a new method of injecting local anesthetic solution without using a dental needle ( needless injection). Using this device, the release of a mechanically activated spring forces 0.05 -0.2 ml of solution under high pressure through a very small orifice into the mucosa. This syringe is used for mucosal injections to reduce pain before the injection of local anesthetic solution using the conventional dental syringe.

Jet injector

The periodontal ligament injection syringe

Computer controlled L.A. Delivery System (CCLAD system)

Care and handling
Wash, clean and sterilize. Dismantle after 5 autoclaving's and lubricate. Clean harpoon or tip every time. Replace harpoons or claws after prolonged use.

Problems

Leakage during injection Broken cartridge. Bent harpoon. Disengagement of the harpoon or claw from plunger. Surface deposits.

The anesthetic cartridge

Barrel
Aluminum cap
Neck
Rubber plunger
Volume of cartridge 1.7 ml 1.8 ml 2 ml 2.2 ml

Label on the cartridge

Name of anesthetic agent and v.c. Concentration of anesthetic agent and v.c. Name of preservative. Volume of solution. Supplier. Expiry date. Advantages of the label????

Care and handling

Usually come in vacum sealed tin containers or boxes containing blister packs. Sterilization after opening is not warranted. No autoclaving.

The cartridges are packed in tin containers of 50 cartridge or blister packs of (5-10) cartridges each.



1- Breakage (or cracks) of dental cartridge due to : Transportation or storage. Excessive force on injection. Harpoon or claw damaging glass.
Problems


2- Bubbles in the dental cartridge: Single small sized bubble are normal (nitrogen gas). large sized bubbles are due to freezing. 3-Extruded plungers: Extruded plunger with accompanying air bubble is due to freezing. Extruded plunger with no air bubble is the result of solutions diffusing into the cartridge (storage for a long period in alcohol).


4-Altered appearance of solution: Solution should be crystal clear. Solutions in the cartridge have a shelf life of 18 months. Any evidence of color changes such as yellowing, cloudiness or sedimentation may indicate a breakdown of solution. This is mostly due to breakdown of vasoconstrictor due to excess heat or light. Storage should be in a cool dark place (20-22 c). Do not use solutions beyond expiry dates.


5- Corrosion of aluminum cap Identified by a white powdery deposit when the cartridge is immersed in disinfecting solutions containing ammonium salts. Disinfect cartridges with isopropyl or ethyl alcohol (70%). Or it may indicates fracture of one of cartridge in the container 6- Leakage of solution: Eccentric needle perforation of rubber diaphragm. This produces an ovoid hole around the needle that is prone to leakage Cracks in the glass of cartridge.

7-Sticky plunger: In the past paraffin was used as a sealant around the rubber stopper but when it hardened the plunger was difficult to advance. Nowadays silicone coating is used Plastic cartridge also may cause this problem 8-Disinfection: Most appropriate is to instantly wipe the cartridge with a gauze soaked in 70% ethyl alcohol or isopropyl. Avoid long term disinfection.


Important note : under no circumstances should any needle or cartridge be used on more than one patient.

Dental needle

Tip with bevel
Shaft or shank
Hub
Syringe adapter
Cartridge penetrating end



Currently used dental needles are strong, flexible, sharp ended, sterile and to be used on a single patient only. Reduced pain and ease of needle insertion into the tissue is owned to the sharpness of needle tip and cutting bevel. Designs of needle bevel include short, long, multibeveled. Dental needles are also treated with an antifriction substance to enhance insertion.

Sharpness of needle may be lost from: The manufacture Multiple injections Forcible bone contact on needle insertion. Passing the needle shaft along a piece of sterile gauze helps to identify any barb at the end of needle tip. Never insert the needle to the hub: Most weakest point of needle is at the junction of shaft and plastic hub If it fractures it will then be difficult to retrieve.

Types of dental needle

Length Short(10-25mm) Long(25-40mm)
Gauge This refers to the diameter of needle lumen (internal diameter) 25,27,30.

Gauge of dental needle

Number 25 27 30
Outside diameter (mm) 0.5 0.4 0.3
Internal diameter (mm) 0.25 0.20 0.15


Infiltration techniques Short Gauge 30 Block injection techniques Long Gauge 27 Reduce fracture incidence provides good aspiration less deflection on needle insertion
Needle selection

Care and handling

Always use only on one patient. Discard after 3-4 penetrations. Cover when not used. Always be ware of position of needle. Properly dispose of.


Problems
Pain on needle insertion. Breakage. Pain on needle withdraw from tissue. Injury to patient or dentist.