The pain and discomfort associated with dentistry is a primary reason many patients delay or avoid going to the dentist. This can lead to severe consequences for oral health. Providing a comfortable experience that is as pain-free as possible ultimately ensures patients continue to seek the oral care they need. One common complaint about visiting the dentist is the pain of the needle stick used to inject local anesthetic. Topical anesthetic is one proposed solution to this issue as it can effectively numb the patient prior to needle penetration.

Needle insertion vs. Infiltration

To administer local anesthetic for oral procedures, a needle is required. Fear of needles and the pain of a needle stick are one reason why patients have anxiety about visiting the dentist. Topical anesthetic is highly effective at reducing the pain of needle insertion. However it has not been shown to be as effective at reducing the pain of local anesthetic infiltration. These two sources of pain are different – one involves the penetration of the needle and the other is the effect of the anesthetic as it is administered. Buffering anesthetic and warming before administration can often help the second cause of pain. Slowing down the rate of injection can also help. However to ease the pain of the needle stick a topical anesthetic may be most effective.

VAS Score

Many studies of the efficacy of topical anesthetics use the visual analog scale (VAS). The VAS is a way to have participants in a study self-report pain in order to track pain progression and compare scores between patients. VAS has been used for many years and has been shown to be a reliable way to measure pain in studies. The score is self-reported by having the participant record a mark at one point along a 10cm line that represents a continuum between two ends of the scale from 0cm (no pain) to 10cm (worst pain).

In studies of topical anesthetics for dentistry, it has been shown that topical anesthetics result in lower VAS scores after application compared to placebo. The effects of using a topical anesthetic may be both pharmacological and psychological. There is a definitely a physical effect on numbing the oral mucosa prior to a needle stick. However the psychological effect is also present in which the patient may be more relaxed knowing they are receiving a topical anesthetic and will not feel the needle penetration.

Needle Gauge

Even though different gauge needles are sometimes used to reduce pain, the evidence shows that the needle gauge is not a significant factor in pain of the needle stick for oral local anesthetic administration. After a needle is used the first time, the needle blunts even if there is no contact with bone. For that reason, subsequent injections are rated as more painful than the first injection. The actual pain associated with the needle stick is the same for different gauge needles, meaning this should not be considered as a primary way of reducing pain for the patient.

A large study was conducted that included 930 injections administered to 810 adult patients using 25- and 27-gauge needles for mandibular inferior alveolar block injections and 25-, 27-, and 30-gauge needles for  maxillary buccal infiltration or palatal injections. The participants rated their pain using an eleven-point scale. The results showed there was no difference in the perception of pain between the different gauges of needles. The researchers concluded that since there is no difference in pain scores, wider gauge needles may be preferable due to their decreased risk of breakage and less pressure needed for aspiration.

Topical Application Time and Regions

Research has shown there is no benefit to leaving topical on longer than 2 minutes to improve efficacy. Leaving the topical on longer than approximately 2-3 minutes only increases the risk of tissue sloughing. The place where the needle is inserted also affects pain scores. For example, injections in the anterior of the hard palate are rated as being more painful than injections that are more posterior. Recent research has suggested that topical anesthetic is most effective when used to reduce the pain of needle puncture in the maxilla. This research is mostly conducted using lidocaine 5% and similar formulations however and not compounded topical anesthetic which has higher concentrations of anesthetic ingredients.

Needle Phobia

In some cases the fear of going to the dentist is not associated just with the actual pain but the anticipation of pain and needles. It may be just due to a fear of needles in general – not specifically those used in a dental office. As many as 1 out of 3 patients may have extreme anxiety about getting an injection at the dentist. The fear of the needle often far exceeds the actual pain of the needle stick. However since the fear is real enough to the patient to potentially make them avoid the dentist altogether, it is something that needs to be addressed. Topical anesthetic is one way to alleviate the pain of a needle stick to reduce a patient’s anxiety around needles.

Topical Anesthetic Formulations

Most studies on topical anesthetics in dentistry utilize commercially available products like 5% lidocaine. Not as many studies utilize compound topical anesthetics, which can be much more powerful. “The Baddest Topical in Town” (BTT) for example contains lidocaine 12.5%, tetracaine 12.5%, prilocaine 3%, and phenylephrine 3% in one gel or ointment. Pain relief for needle insertion has clearly been demonstrated for topical anesthetics but there are differing opinions as to where it is most effective.

In a study of the comparative efficacy of a compounded topical anesthetic vs. a benzocaine-only product for the placement of orthodontic temporary anchorage devices it was found that the compounded product was more effective. Temporary anchorage devices (TADs) are a kind of miniscrew placed to provide orthodontic anchorage, which are commonly used in orthodontics. While local injected anesthetic can be used, some providers use only topical or a combination of both anesthetic types.

Articles

• Validation of Digital Visual Analog Scale Pain Scoring With a Traditional Paper-based Visual Analog Scale in Adults – Journal AAOS
• Effect of Time on Clinical Efficacy of Topical Anesthesia – Anesthesia Progress
• A comparison of 2 topical anesthetics on the discomfort of intraligamentary injections: a double-blind, split-mouth volunteer clinical trial – Oral Surgery
• Comparison of Inferior Dental Nerve Block Injections in Child Patients Using 30-Gauge and 25-Gauge Short Needles – Anesthesia Progress
• Factors Influencing the Discomfort of Intraoral Needle Penetration – Anesthesia Progress
• Comparative Efficacy of 2 Topical Anesthetics for the Placement of Orthodontic Temporary Anchorage Devices – Anesthesia Progress
• Size doesn’t matter: Needle gauge and injection pain – Anesthesia and Pain Control