Avoidance of milk and dairy products after oral surgery—is such a recommendation still valid? A cross-sectional study among German and international oral and maxillofacial surgeons and dental practitioners with review of the literature

Nearly 3.5 billion people worldwide are affected by oral diseases [1]. According to statistics, dolor post extractionem occurs in 3 to 4% of all tooth extractions [2]. In order to avoid serious complications, patients are routinely advised to abstain from nicotine, alcohol, and caffeine after dental surgery, among others.

In addition, patients in German speaking countries are traditionally advised to avoid milk and dairy products after dentoalveolar surgery. This recommendation can be found in postoperative recommendations for patients as issued by health insurance companies, on numerous internet pages of the German lay press and in internet forums [3]. A Google search for the German search terms “dairy products” and “tooth” (“Milchprodukte“ & ”Zahn“) returned 354,000 entries; a search for the German for “milk” and “implant” (“Milch“ & “Implantat“) as many as 820,000 entries, the great majority of which on the subject of abstention from milk and dairy products after oral surgery [4, 5]. However, no guidelines or evidence for a possible causal link with intraoral infections of wounds exist for the consumption of milk and dairy products following dentoalveolar surgery, neither in Germany, e.g., from the Association of Scientific Medical Societies in Germany (Wissenschaftliche Medizinische Fachgesellschaften, AWMF) nor worldwide, e.g., from the American Dental Association (ADA) or the National Institute for Health and Care Excellence (NICE). We investigated the recommendations as made by dentists and OMFS in Germany by way of a pilot study based on a representative collective of general dentists in private practice and specialized OMFS, with the result that not only more than half of German general therapists; also, over 40% of specialists for oral surgery and OMFS advised to abstain from consumption of milk and dairy products after dentoalveolar surgical procedures [6]. The study also revealed a major inhomogeneity of the reasons given for such a recommendation [6] (see Table 1).

We were wondering how relevant recommendations are in the rest of the world compared to the above. The study in hand aims for clarification of the following questions: (a) How do recommendations of German dentists and OMFS differ from recommendations worldwide? (b) Which pathophysiological reason supports the recommendation to abstain from dairy products? (c) Does a review find evidence for such a recommendation?

Contrary to the received opinion well established among German dentists and OMFS [6], no evidence can be found in the pertinent literature supporting adverse effects of consumption of milk and dairy products after dentoalveolar surgery.

According to the findings of our survey, in the majority of countries, avoidance of dairy products is not recommended after dentoalveolar surgery (see Table 6), while the majority of the international surveys adopt a neutral position. In countries such as Italy, India, Thailand, and the USA, surgeons actually make recommendation in favor of consumption of dairy products like milkshakes, ice cream, or yoghurt after dentoalveolar surgery, due to their satiating and cooling effects on the surgical site. A common practice is asking the patient to start having ice cream around 30 min to 1 h post any minor surgical procedure.

Diametrically opposed the situation in the German-speaking and related regions (e.g., Flanders in Belgium): in our German survey, a slight majority (56.1%) was reported to advise their patients against consumption of milk and dairy products [6], with a significant difference between dentists and OMFS in Germany (p = 0.027) (see Table 7), of which those with a focus on surgical procedures attributed at least a minor positive effect on wound healing to milk and dairy products [6]. Compared to the international collective, there was a striking difference regarding the sources of information given by OMFS and specialist dentists for oral surgery (Table 8). Oral surgeons stated lectures at university, specialist literature, personal experience, and recommendations from other dentists as sources of information significantly more frequently. We have been unable, however, to identify the exact specific original source of the recommendation to abstain from dairy products as traditionally made at many German universities. At the time of the First World War, the recommended diet [43] for patients who had sustained injuries to the jaw was liquids, specifically soup, milk in any form, dishes with eggs, and a variety of meat extracts [43]. Textbooks from the time of the Second World War still recommended a diet containing eggs, milk, and cocoa for same patients [44]. Therefore, the current recommendation was only propagated after the World War II.

Regarding the reasons given as listed in Table 1, the theory of an interaction between milk and antibiotics may apply for some classes of agents, e.g., tetracycline and quinolone (neither an antibiotic of preferred choice in dentistry). Milk and dairy products may indeed reduce bioavailability of tetracyclines by up to 80% [45]. The most frequently used antibiotics in dentistry, however, such as amoxicillin, propicillin, phenoxlmethyl penicillin, and clindamycin, and less frequently used cefaclor, cefuroxime, cefpodoxime, erythromycin, roxithromycin, clarithromycin, azithromycin, nitroimidazole, and metronidazole [46], do not interact with milk and dairy products. It is well known that milk is a good culture medium for certain bacterial colonies. As it is rich in numerous amino acids and minerals and due to the lactose contained inside, it may promote growth of bacteria, including pathogenic bacteria in the oral cavity, with adverse effect on wounds. And while lactobacilli are indeed required for the production of dairy products, such as yoghurt and cheese, exclusively such thermophile lactic acid bacteria are utilized here which are not pathogenic.

It is further argued that clotting may be inhibited by consumption of dairy products, with a risk of resulting dry socket and dolor post extractionem. Fibrinolytic plasminogen, which is also been found in milk, is believed to be responsible for the inhibition of clotting. The determining factor for the evaluation of the effect of plasminogen on coagulum development is concentration in milk (0.3–2.5 μg/ml) compared to serum concentration (200 μg/ml) [47]. The plasmin concentration in blood is 100–1000 times higher than in milk. The conclusion may be that the effect of milk on blood coagulation is not relevant and negligible in comparison to the concentration of plasminogen in the coagulum itself.

Some practitioners argue that milk and dairy products will react with resorbable sutures. In many resorbable suture materials, the degradation process is of a hydrolytic nature. In order for, e.g., tensile strength of suture material to be affected by dairy products, pH would need to be affected for an extended period of time. Absorbable suture materials are relatively more sensitive to the pH value than non-resorbable materials. The degradation of synthetic resorbable sutures, however, is more pronounced in an alkaline milieu in general rather than at physiological or acidic pH range [48]. Some opponents believe in a historical basis of the recommendation to avoid dairy products after oral surgery in an empirically elevated risk of contracting tuberculosis after consumption of dairy products in the past—obsolete today. Tuberculosis is a bacterial infectious disease, caused by the obligate pathogenic Mycobacterium tuberculosis complex, M. tuberculosis, M. bovis, and M. caprae. The latter two are zoonoses, communicable from infected animals to humans. A tuberculosis infection in humans most frequently develops into pulmonary tuberculosis and is currently the most widespread lethal bacterial infectious disease, with 10 Million individuals developing tuberculosis annually. According to the World Health Organization (WHO), there were about 1.4 million deaths due to tuberculosis worldwide in 2019, with Bangladesh, China, India, Indonesia, Nigeria, Pakistan, the Philippines, and South Africa accounting for approx. half of all known cases of tuberculosis [49]. A variety of tuberculosis is M. bovis which is transmitted through consumption of unpasteurized milk. Those affected by cervical tuberculous lymphadenitis, also called scrofula (historically known as The King’s Evil) [50], will exhibit cervical gland tumors and abscesses and lesions of the skin in the area of the affected lymph nodes. According to the WHO, extrapulmonary tuberculosis was diagnosed in 15% of the 6.3 million cases in Europe in 2016. The majority of cases of tuberculous cervical lymphadenopathy, however, occur in developing countries. In Europe, infections with Mycobacteria mainly affect immigrants and immunocompromised individuals. Women are relatively more frequently affected by scrofulosis, men by pulmonary tuberculosis [51]. The disease may recur and develop into a chronic, progressive form, Lupus vulgaris (Tuberculosis luposa or ulcerative Lupus faciei). The belief that raw milk may incur the risk of infection with tuberculosis was still well founded at the beginning of the twentieth century; in 1901, as many as 80% of cattle in Germany tested positive for tuberculin [52]. However, since 1997, the cattle population in Germany has been officially declared free from tuberculosis, as 99.9% of cattle are not affected [53]. Currently, the majority of cases of bovine tuberculosis occur in countries such as Ethiopia, India, and China, which also frequently report cases of tuberculosis in humans [53‐57]. Why no recommendation is made in these countries to abstain from consumption of dairy products after dentoalveolar surgery yet needs to be established. In Germany, tuberculosis is a notifiable disease and affected cattle populations are required by law to be culled. Milk undergoes heat treatment (pasteurization/ultra-high temperature treatment), destroying all pathogenic germs, including Mycobacteria in the milk, and a danger of infection through consumption of milk after dentoalveolar surgery no longer exists [47, 58]. According to the Centers for Disease Control and Prevention (CDC), the risk of infection through contaminated raw milk is 150 times greater than by consuming pasteurized milk. Especially infants, pregnant women and people with weakened immune systems are in danger of illnesses and hospitalization. These pathogens are most often Brucella, Campylobacter, Cryptosporidium, E. coli, Listeria, Salmonella, and mastitic streptococci [59].

Some dentists advise against dairy products because of contained bacterial cultures. Live probiotic cultures are part of fermented dairy products and are intended to have health benefits when consumed. Those microorganisms also occur naturally in lactic acid products such as yogurt, kefir, or buttermilk. That is why we have made a literature review on probiotics to find out if there are any possible wound healing disorders or wound infections after use of probiotics. Our review also encompasses studies into the effect of probiotics and synbiotics on a variety of skin wounds including infected and non-infected wounds, diabetic wounds, and burn injury models. The studies, in vitro and in vivo, all arrived at the identical result and conclusion that probiotics and synbiotics are able to inhibit those wound pathogens which cause surgical site infections [60] and thus will sometimes be able to reduce required hospitalization and quantity of antibiotics [27, 29, 30, 34]. This may also help prevent development of multidrug resistant bacteria. Moreover, the use of probiotics helped to reduce inflammatory markers [15, 22, 61]. These results of our literature search agreed with the results of other systematic reviews into the influence of probiotics, prebiotics, and/or synbiotics [42, 62‐64]. As our research question focuses on the effect of dairy products in the oral cavity, the caveat would be that the available literature mainly deals with the effect of probiotics on skin wounds. In an additional in vitro study into the post-wound interactions between gingival epithelial cells and drinkable yogurt, the authors observed a positive effect on oral wound healing. This was explained by an increase in various keratins and in β-defensin-2 production [65]. These keratins are important for the development of epidermal structures [66]. β-defensin stimulates cell migration and angiogenesis at wound sites and promotes wound closure [38, 65].

There are several limitations to this study. While the German survey may well be considered representative, the international survey so far constitutes a mere random sample of individuals. Even though they are generally based at universities, the results are not representative or robust for worldwide validity. They may, however, well constitute evidence of a trend. Further national surveys may be able to offer evidence-based validity.

As our research question investigates the effect of dairy products in the oral cavity, our review of probiotics was included with the reservation that it mainly covers skin wounds. The majority of the in vivo studies reviewed were conducted in countries in Asia and Europe. They may therefore not generally applicable for other populations.

Available data indicate that the German-speaking areas differ significantly in their dietary recommendations after dentoalveolar surgery. The recommendation to abstain from milk and dairy products, as made by over 50% of dentists surveyed in the German pilot study, is neither evidence-based nor can its origin or scientific basis be established. Most plausible seems the empirical experience with historical background (scrofula), which today can safely be considered as no longer relevant due to pasteurization of milk. Taking on board the fact that the incidence of tuberculosis is on the rise again, and so are antibiotic-resistant strains, a possible transoral access of tuberculosis should not be taken lightly or disregarded.

The validity of the routine recommendation to abstain from consumption of milk and dairy products after dentoalveolar surgery, a widespread practice in Germany today, nevertheless should be challenged and re-examined.