**8. Complications**

**8. Intraoral lidocaine patch (dentipatch):** This patch contains 10-20% lidocaine which is placed on dry mucosa for 15 minutes and provides suitable anesthesia for the mandible

**9. Jet–injection:** In this technique, a small amount of anesthetic drug driven into the submucosa without a needle. The air pressure is used for the infiltration of the drug into the mucosa through tiny pores. This method is particularly useful for topical anesthesia

**10. Vibrajet:** It is a device that provides high frequency vibrations in the dental injection

**11. Accupal:** This is a tool to create pressure and vibration at the injection site. These men‐ tioned irritate the larger nerve fibers and cause the lack of sensitivity during the penetra‐

**12. TENS (transcutaneous electronic nerve stimulation):** The result of this method in patient comfort and it provides less pain during the injection. This has been demonstrated especially for IAN nerve block techniques, while topical anesthesia does not cause significant changes to reduce pain during the injection. This technique stimulates the nervous system and it starts before injecting and the pulse rate increases to make a good shake to the patient. The needle is inserted at an area between the electrodes of TENS while generated impulses are continuing at the same level. After withdrawing the injection and removing the needle, pulses are slowly reduced and stopped (Figure 11). [38]

syringe which causes a relative decrease in pain during the injection [37].

and maxilla [36].

for palatal injection [36].

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tion of the needle [37].

**Figure 11.** Transcutaneous electronic nerve stimulation

The complications of the injection of local anesthetic drugs can be divided into two parts namely systemic and local complications, explained below.

### **8.1. Local complications**


clude not using a 30 gauge needle for IAN block injection, not bending the needles¸ preventing full penetration of the needle into the tissues and precision during injection for young patients or children that can make sudden moves resulting in needle breakage [1].When the needle breakage occurs during the inferior alveolar nerve block injection, it can often be found in the pterygomandibular space, but can migrate to adjacent vital structures and cause damage to them (Figure 12). An unusual case of broken needle displacement during the IAN block injection into the external audito‐ ry canal is reported for a 25-year-old woman [40].

**Figure 12.** Broken needle shown in the panoramic radiograph


the IAN block injection can cause this complication. Prevention is the best cure. When it occurs, inform the patient of the incident, removal of eye lenses and eye protection should be carried out. It must be explained that nerve function will return to normal within a few hours [2].

clude not using a 30 gauge needle for IAN block injection, not bending the needles¸ preventing full penetration of the needle into the tissues and precision during injection for young patients or children that can make sudden moves resulting in needle breakage [1].When the needle breakage occurs during the inferior alveolar nerve block injection, it can often be found in the pterygomandibular space, but can migrate to adjacent vital structures and cause damage to them (Figure 12). An unusual case of broken needle displacement during the IAN block injection into the external audito‐

**6. Long-term sensory changes:** This can be due to direct damage to nerves and the contam‐ ination of local anesthetic drugs with alcohol that has a neurolytic effect. The most common sensory change is paresthesia. Direct damage is the most common cause of longterm sensory changes, which happens through three mechanisms. Firstly, injury to the nerve fibers. Secondly, the destruction of small vessels in epineurium and the creation of interneural hemorrhage. Finally, the destruction of connective tissue and creation of edema sets in. The dose and concentration of the local anesthetic drugs are contributing factors in this process. According to studies, high concentration drugs such as 4% articaine and prilocaine can cause long-term sensory changes more than other drugs. During injection, the lingual nerve is affected more than other nerves by direct damage. Sensory changes usually resolve within 8 weeks during which the patient should be informed and

**7. Facial nerve paralysis:** Temporary damage to the facial nerve can occur as a result of the spread of local anesthetic drugs to the parotid capsule. Great penetration of the needle in the Akinosi-Vazirani technique or the inappropriate posterior direction of the needle in

re-injection of the drug in the affected area should be avoided [2].

ry canal is reported for a 25-year-old woman [40].

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**Figure 12.** Broken needle shown in the panoramic radiograph

**8. Soft tissue damage:** After injection, children often bite their lips and cheeks, followed by numbness in these areas (Figure 13). Avoidance of anesthetics with long-term effects, placement of cotton rolls between the teeth and lips, informing the patient to not use warm materials and not bite the oral tissues are effective ways of preventing soft tissue damage. If this happens we need to check for the appropriate use of antibiotics, analgesics and overlying creams on the injury site [1]. In cases of soft tissue injury following numbness, correct diagnosis is very important. Sometimes misdiagnosis causes incorrect treatment such as hospitalization, unnecessary surgical interventions and administration of sys‐ temic antibiotics due to improperly suspected bacterial infections. Effective communica‐ tion between dentists and other medical staffs can help prevent these events [41].

**Figure 13.** After injection, children often bite their lips and cheeks, because of numbness in these areas.


**Figure 14.** Osteonecrosis following the intraosseous injection

### **8.2. Systemic complications**

**11. Intraoral lesion occurrences after injection:** Recurrent aphthous stomatitis and herpetic lesions originate from this type of lesion that can occur two days after the injection due to the trauma of the needle at the injection site. Treatment will be palliative and the lesions

**12. Eye complications:** Eye complications can occur following the injection of anesthetic drugs in the maxilla and mandible. A permanent loss of vision is reported following a prilocaine injection for tooth extraction in a 73-year-old man prior to surgery for the mitral valve. Visual injury following the injection of anesthetic in dentistry is extremely rare and its mechanism is unknown. A possible etiology is retinal and choroid artery occlusion following the intra-arterial injection which strongly emphasizes the need for aspiration prior to the injection [42]. The next case is a report of paralysis of the right lateral rectus muscle and blurred vision after IAN block and infiltration injections were done in the right maxilla to extract the number 8 tooth in the right mandible and maxilla in a 22-yearold woman who had been normal in terms of systemic health. In this patient, blurred vision and diplopia resolved 6 hours after the injection. The mechanism of this condition is deep anesthetic injections in the retromaxilla, drug diffusion through the greater palatine channel and the lack of the bony barrier between the orbit and this area [43]. In general, the most common ocular complications due to anesthetic injection include: diplopia, mydriasis, eyelids ptosis and abduction disorder and damaged eye. These complications can occur several minutes after the injection and can resolve spontaneously without causing permanent injury and a known mechanism for them is anesthetic drug

**13. Rare complications:** There are reports of osteonecrosis following the intraosseous injection probably due to the heat of bone drilling done to make a perforation hole for the injection (Figure 14). In addition, systemic disease, such as diabetes and HIV can also have

will resolve spontaneously within 7 to 10 days [1].

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diffusion to the orbital area [44].

an effect in creating this phenomenon [45].

**Figure 14.** Osteonecrosis following the intraosseous injection


oxygen and leads to cyanotic conditions in patients 1 to 3 hours after the injection of anesthesia. The symptoms of cyanosis are created when levels of methemoglobin reach 10 to 20 percent. Increase of methemoglobin levels causes various symptoms such as dyspnea and tachycardia. Children, with methemoglobin reductase and G6PD enzyme deficiency are at a higher risk than other people to methemoglobinemia. The treatment of methemoglobinemia is the intravenous injection of 1-2 mg/kg methylene blue [1].

