Sir, socket medicaments may be utilised following exodontia to promote haemostasis or to prevent or manage post-extraction complications; however, there are potential disadvantages to their use. Surgicel (Ethicon, Neuchâtel, Switzerland), for example, has been demonstrated to cause temporary anaesthesia or paraesthesia when placed close to peripheral nerves1 such as in mandibular third molar sockets. It has been proposed that this nerve injury may be due to the potent acidity of the medicament or expansion of the material resulting in direct compression of the nerve.2 In our experience, most secondary care oral surgeons avoid the use of Surgicel in lower third molar sockets with a known or suspected intimate relationship with the inferior dental canal.

Alveogyl (Septodont, Saint-Maur-des-Fossés, France) is another socket medicament and is commonly used in the treatment for alveolar osteitis. It self-eliminates from the socket, and its retention can lead to foreign body reactions.3 As with many medicaments, the acidity or alkalinity of Alveogyl is not known,4 and the potential risk of nerve injury resulting from its placement has not been researched. Curiously, the manufacturer's safety data sheet for Alveogyl does not state the material's pH.5

We therefore undertook a benchtop experiment to investigate the pH of Alveogyl, mixing 1 g of the medicament in 10 ml normal saline, and measuring the pH using indicator paper (Johnson Test Papers, UK) according to the manufacturer's instructions. For comparison, pH testing was also undertaken on Surgicel mixed in 10 ml normal saline, and normal saline with no medicament.

Our results are shown in Figure 1. The Surgicel mixture was clearly acidic, with a pH of around 3. The Alveogyl mixture had a pH in the region of around 7-8, which is not significantly different to saline (pH 6-7 in our experiment), blood or tissue fluid.

Fig. 1
figure 1

pH testing strip results. A - Surgicel in normal saline; B - Normal saline; C - Alveogyl in normal saline

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We therefore suggest that Alveogyl is unlikely to cause a nerve injury following its placement into third molar sockets by virtue of its pH alone. However, the potential for a compressive injury to the nerve resulting from overzealous packing of the material deep into the socket still remains. We would advocate for more robust laboratory-based research to better understand the risks of using socket medicaments following lower third molar surgery. If practitioners do wish to use Alveogyl, then our recommendation would be that it is placed sparingly and superficially to prevent compressive nerve injury, and to encourage self-elimination of the material in order to prevent foreign body reaction from its retention.