Needle breakage

BREAKAGE and retention of dental needles within tissues has become an extremely rare occurrence with the introduction of single-use, disposable needles made of modern, stainless steel alloys. Nevertheless, occasional reports still appear and these are stressful and upsetting events for both patient and clinician alike. They are also very likely to lead to claims of clinical negligence.

Common factors

Needles tend to break at the hub which is the most rigid portion of the needle. In most injections this is not a significant problem as any fragment of needle sticking out of the gum can be straightforwardly retrieved with a haemostat. Difficulties arise when the needle has been inserted to the hub and it breaks. Here the elasticity of the soft tissues produces a rebound and the needle can become buried. In routine dental practice, such a scenario would be most likely when giving inferior dental nerve blocks (IDBs).

Needle breakage is more likely to occur when short needles are used (as they are more likely to be inserted to the hub) and also with narrower needles (30 gauge instead of 27 or 25). It can be associated with sudden movement of the patient or changing direction of the needle when inserted into the tissues. It invariably occurs with bending the needle prior to insertion, and inserting the needle into soft tissues for its entire length.

It is worth noting that the needle is a continuous strand of metal that starts at the tip and continues into the hub to exit on the opposite side into the cartridge. They do not “separate” as often described by clinicians.

Needles that break off entirely within soft tissue cannot be readily retrieved. Usually they do not move more than a few millimetres and become encased in scar tissue. Choosing to leave a needle fragment in the tissue instead of attempting its removal has been favoured in the past as it was thought to lead to fewer problems than having an extensive surgical procedure which is reliant upon plain radiographs to identify the position of the fragment.

The use of CT scans can now provide more accurate images and the availability of helical CT scanners has made this the investigation of choice. This technology, together with legal considerations and the concerns of both patients and clinicians about the fear of needle migration, has more recently tended to favour removal of the broken fragment. The procedure is usually done under general anaesthetic and must be carried out by an experienced oral surgeon or oral and maxillofacial surgeon.

Managing the situation

When a needle breakage occurs during a procedure it is important to remain calm. Tell the patient not to move and to keep their mouth open. Keep your hand that has been retracting the soft tissues in place. If the fragment is visible, retrieve it with a haemostat.

If the fragment it is not visible DO NOT attempt any incision or probing. Tell the patient what has happened and try to reassure them. Ask the patient to avoid excessive jaw movements and arrange immediate referral to your local oral and maxillofacial surgery unit for consultation.

Make a full and contemporaneous record of what has happened and how the situation has been or will be remedied. If you manage to retrieve the needle fragment retain it for your records. Inform your defence union of the incident.

At the oral and maxillofacial surgery department, an assessment will be made of the patient and the position of the retained needle fragment. Treatment options will be discussed and arrangements made for monitoring or surgery.

No local anaesthetic injection technique used in dentistry requires the needle to be bent for the injection to be successful, and the occurrence of truly “defective” needles is considered to be so low as to not be a factor.

Top tips for prevention of needle breakage

• Use larger gauge needles if significant depths of soft tissue are involved (25 gauge needles are appropriate for IDBs).
• Use long needles for injections requiring penetration of significant depths of soft tissues (>18mm).
• Do not insert the needle to its hub (unless it is absolutely essential for the success of the technique).
• Do not bend the needle.
• Do not redirect a needle once inserted into the tissues.
• Needles should not be forced against resistance.
• Consider changing needles if multiple injections are required.

Mr Mike Williams is a dental adviser with MDDUS