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The removal of a mandibular third molar typically provokes pain, inflammation and trismus, as well as other complications of varying frequency.1,2,3,4

Numerous studies have indicated that the incidence of complications after molar extraction is higher among women taking oral contraceptives,5,6,7,8,9,10,11,12 although some authors have not detected any association.13,14

The aim of the present study was to investigate the influence of oral contraceptive use on pain, trismus and dry socket (localized alveolar osteitis) after removal of a mandibular third molar.

Materials and Methods

A total of 267 women aged 17 to 45 years, all of whom underwent removal of a mandibular third molar at the University Hospital Complex of Santiago de Compostela (Spain), were included in the study. Patients aged more than 45 years were excluded from the study because of the much lower incidence of oral contraceptive use in this age group. Of the 267 patients, 87 were taking oral contraceptives, the mean age in this group was 25 years (SD 6 years). The remaining 180 patients were not taking contraceptives, the mean age in this group was 26 years (SD 7 years).

All extractions were performed by the same surgeon, under local anaesthesia (2% lidocaine with 1:80,000 epinephrine) and using the same surgical technique, with preliminary closure of the wound using absorbable suture.

After extraction, patients received prophylactic antibiotics (500 mg of amoxicillin every 8 h for 7 days) and anti-inflammatories (20 mg of piroxicam every 12 h for 3 days). Patients were told that in case of pain they could use analgesics, in accordance with its severity.

Maximum interincisal distance (MID) was determined before extraction, and 24 h and 5 days after extraction. At both follow-ups, we questioned the patient about analgesic use, and evaluated dry socket on the basis of clinical findings and reported symptoms (loss or necrosis of the wound clot, exposed alveolar bone, unpleasant odour, persistent severe postoperative pain). All follow-ups were performed by the same observer (PMG), who did not know whether the patient was taking contraceptives.

In the data analysis, a number of factors with potential effects on the risk of postoperative complications were considered, namely age, prior consumption of antibiotics, pre-operative state of the molar (asymptomatic, pain, pericoronitis), and difficulty of extraction (classified as I — extraction with forceps, II — ostectomy, III — ostectomy and coronal section, or IV — complex extraction).

Continuous variables are expressed in the text as means. Means were compared between groups by Student's t tests. For categorical variables, frequencies were compared by Fisher's exact tests. Statistical significance was taken to be indicated by p values of less than 0.05.

Results

Neither age nor any of the clinical factors considered differed significantly between the contraceptives and no-contraceptives groups (Table 1).

Table 1 Demographic and clinical characteristics of the two patient groups.
Full size table

The incidence of postoperative trismus did not differ significantly between the two groups: on day 1, mean MID was 31 mm (SD 12 mm) in the contraceptives group and 33 mm (SD 13 mm) in the no-contraceptives group (p = 0.114).

Dry socket developed in 17 (6.4%) of the 267 patients: 10 patients (11.5%) in the contraceptives group and 7 patients (3.9%) in the no-contraceptives group. This difference is statistically significant (p = 0.017), and suggests that the risk of dry socket was three times higher in the contraceptives group. In all cases the dry socket was observed on day 5, as expected, given that processes of this type start 3 – 4 days after extraction. Complications were observed in only two cases, in which a lesion involving the dental nerve was detected.

Postoperative pain was significantly more frequent in the contraceptives group, both on day 1 (26 (29.9%) of patients in the contraceptives group reported use of analgesics, versus 19 (10.6%) in the no-contraceptives group; p < 0.001) and on day 5 (12 (13.8%) versus 9 (5.0%); p = 0.024).

Discussion

The most common postoperative complication of surgical removal of the impacted mandibular third molars is dry socket, due to fibrinolysis of the clot, typically as a result of invasion by oral-cavity bacteria.5

The incidence of post-extraction dry socket among women began to show a marked increase with respect to the incidence among men from the 1960s onwards, when oral contraceptives came into widespread use. In 1974, Schow9 observed post-extraction dry socket in 45% of women taking oral contraceptives, versus 17% of women not taking contraceptives, leading him to suggest that the incidence of dry socket is increased by oral contraceptive use. Similarly, in 1977, Sweet15 observed post-extraction dry socket in 19% of women taking oral contraceptives, versus 17% of women not taking contraceptives.

The higher incidence of dry socket among women taking oral contraceptives has been attributed to the pharmacological activity of the drug, since oral contraceptives induce increased fibrinolysis,16 and since dry socket has been attributed to increased fibrinolytic activity.17,18 Birn19 has suggested that trauma of the alveolar bone may induce transformation of plasminogen into plasmin, favouring fibrinolysis of the clot. Muhonen11 observed that fibrinolytic activity is increased during menstruation, favouring dry socket during this period.

The great majority of more recent studies have supported these hypotheses,3,4,5,6,7,8,9,10,11,12 and have considered oral contraceptive use to be a risk factor for dry socket after third molar removal. Some authors, including Larsen,13 have not detected any association between contraceptive use and dry socket, though it should be noted that this study was based on a relatively small sample.

The results of the present study support the view that oral contraceptive use increases the risk of dry socket: specifically, the incidence of dry socket was about 2 – 3 times higher in the women taking oral contraceptives than in the women not taking oral contraceptives. Our values for the incidence of dry socket (in both the contraceptives group and the no-contraceptives group) are similar to those reported in previous studies that have evaluated the incidence of complications after removal of mandibular third molars.1,2,3,4 By contrast, the studies of Hermesch,5 Catellani8 and Larsen13 obtained much higher control-group values (ranging from 17% – 30%), possibly reflecting methodological problems.

There have been no previous studies of the effects of oral contraceptive use on trismus after removal of mandibular third molars. In the present study, we did not detect any significant between-group difference in mean trismus (as revealed by maximum interincisal distance).

A previous study did not detect any significant effect of oral contraceptive use on the incidence of pain after removal of mandibular third molars.5 However, we found that the incidence of postoperative analgesic use was significantly higher in the contraceptives group than in the no-contraceptives group, particularly on day 1, raising the possibility that oral contraceptive use may affect the pain threshold, for physiological reasons as yet unknown.