Postoperative Complications: Do Antibiotics Help After Third Molar Surgery?

Monday, May 15, 2017

R.L. Wynn

Two recent studies took a closer look at the question of whether antibiotics prevent postoperative complications after third molar surgery. Both found that there are fewer postoperative complications after using antibiotics.

Community Practice Study

The first study was performed at University of Washington School of Dentistry in Seattle and can be accessed at: Lang MS, et al. “Do antibiotics decrease the risk of inflammatory complications after third molar removal in community practices?” J Oral Maxillofac Surg 2017; 75: 249-255.


This was a prospective cohort study which enrolled a sample of patients who had at least one third molar removed between June 2011 and May 2012 in a private practice setting by oral surgeons participating in a practice-based research collaborative. The measure was antibiotic use of any type, categorized as yes or no. The primary outcome variable was the presence or absence of an inflammatory complication defined as surgical site infection (SSI) or alveolar osteitis (AO) after third molar removal.

  • SSI diagnosis:
    • Visible frank purulence of the traction site at any point postoperatively
    • Unanticipated pain or edema warranting operative intervention or antibiotic use
  • AO diagnosis:
    • New-onset or increasing pain more than 36 hours after the operation
    • Clinical examination showing loss of blood clot with exposed bone, irrigation of the site, or gentle probing reproducing the pain
    • Marked pain relief with application of an anodyne dressing

The authors then created and computed a patient-level operative difficulty score (ODS). A score ranging from 0 to 6 was assigned for each third molar removed:

  • 0 = No extraction
  • 1 = Nonsurgical erupted
  • 2 = Surgical erupted
  • 3 = Soft tissue impacted
  • 4 = Partial bony impacted
  • 5 = Full bony impacted
  • 6 = Complicated or difficult full bony impacted

The score for each third molar removed was summed for a total ODS. For each patient, the ODS could range from 1 (nonsurgical extraction of 1 erupted third molar) to 24 (extraction of 4 difficult full bony impacted third molars).

A patient-level preoperative disease score (PDS) for severity was computed by summing the total number of preoperative disease conditions, such as caries, periodontal disease, cyst, infection, resorption, and fracture. A PDS score of 0 was interpreted as meaning that all third molars present were disease-free.


  1. Sample analysis was derived from 105 oral maxillofacial surgeons who contributed data for 2,954 patients having 9,123 third molars removed. Of the 2,954 patients who had at least one third molar removed, the mean age was 26.4 years and 48% were male.
  2. 75% of the sample received antibiotics in some form.
  3. Antibiotic group: The overall inflammatory complication frequencies (i.e., alveolar osteitis or surgical site infection) was 5%.
  4. Non-antibiotic group: The overall inflammatory complication frequencies (i.e., AO or SSI) was 7.5%.
  5. The difference in the inflammatory complication frequencies between the antibiotic group and non-antibiotic group was statistically significant and not by chance.
  6. The mean preoperative disease score was 2.2 (few disease conditions were present) and the mean operative difficulty score was 12 (out of a maximum 24)

The authors used the frequency of inflammation data to extrapolate “numbers needed to treat” values. The following were listed:

  1. 40 patients would need to be treated with antibiotics to prevent 1 postoperative inflammatory complication (SSI or AO).
  2. 143 patients would need to be treated with antibiotics to prevent 1 surgical site infection (SSI).
  3. 40 patients would need to be treated with antibiotics to prevent one case of alveolar osteitis (AO).

The patterns of antibiotic use were diverse, with variations among the type, dose, timing, and route of administration:

  • The specific antibiotics were penicillin, amoxicillin, clindamycin, erythromycin, tetracycline, or other.
  • Timing of use included preoperative, intraoperative, postoperative, or a combination of exposure times.
  • Delivery routes included oral, parenteral, intra-socket, or a combination.

An optimum antibiotic use strategy could not be identified.


This was a prospective study involving community office-based ambulatory oral and maxillofacial surgery practice settings, and the authors hypothesized that perioperative antibiotics would not have a statistically relevant effect on post-operative inflammatory complications after third molar surgery. The results, however, refuted that null hypothesis with the data showing significant decrease in inflammatory complications in the antibiotic group.

Study results suggest that antibiotic therapy, regardless of type, dose, frequency, or route of administration, is associated with a decreased risk of inflammatory complications after third molar removal.

The authors cited similar findings from a Cochrane review published in 2013, which is summarized below.

Cochrane Review Report

The second study can be accessed at: Lodi G, et al. “Antibiotics to prevent complications following tooth extractions.” Cochrane Database Syst Rev, 2012 Nov 14; DOI: 10.1002/14651858.CD003811.pub2.

The objective of the Cochrane study was to determine the effect of antibiotic prophylaxis following tooth extractions. The study searched five databases, most going back to 1980, including MEDLINE and the Cochrane Central Register of Controlled Trials. The selection of trials included randomized, double-blind, placebo-controlled trials of antibiotic prophylaxis in patients undergoing tooth extractions for any indication.


The review included 18 double-blind, placebo-controlled trials with a total of 2,456 participants. Compared to placebo, antibiotics probably reduce the risk of infection in patients undergoing third molar extractions by approximately 70% (rated as moderate-quality evidence). This was interpreted as needing 12 people (range 10-17) to be treated with antibiotics to prevent one infection following extraction of impacted wisdom teeth.

There was evidence that antibiotics may reduce the risk of dry socket by 38%, meaning that 38 people would need to take antibiotics to prevent one case of dry socket following extraction of impacted wisdom teeth.

There was some evidence, of moderate quality, that patients who have prophylactic antibiotics may have less pain overall 7 days after the extraction compared with those receiving placebo. That may be a direct result of the lower risk of infection.

There was no evidence of any difference between antibiotics and placebo in outcomes of fever, swelling, or trismus in the 7 days after tooth extraction.

There was evidence that antibiotics were associated with an increase in mild, transient adverse effects compared with placebo, meaning that for every 21 people who received antibiotics, an adverse effect is likely.


All the trials included in the review included healthy patients undergoing extraction of impacted third molars. It is unclear whether the evidence from this review is applicable to those with concomitant illnesses or immunodeficiency, or those undergoing the extraction of teeth due to severe caries or periodontitis.

Patients at a higher risk of infection are more likely to benefit from prophylactic antibiotics since infections in this group are likely to be more frequent, associated with complications, and be more difficult to treat.

One interesting closing message by the authors was the following: “Due to increasing prevalence of bacteria which are resistant to treatment to currently available antibiotics, clinicians should consider carefully whether treating 12 healthy patients with antibiotics to prevent one infection is likely to do more harm than good.”

Richard L. Wynn, BS Pharm, PhD, is professor of pharmacology at the Baltimore College of Dental Surgery, Dental School, University of Maryland Baltimore.

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