The onset of delayed infection after lower third molar germectomy is influenced by the amount of distal space. This retrospective study aimed to determine whether the incidence of delayed onset infection is related to the space distal to the second molar. The ratio between the distal space and the crown width, measured according to the Ganss protocol on panoramic radiographs, was obtained for 218 surgical germectomies performed for orthodontic reasons in 134 patients. A delayed onset infection occurred following 20 germectomies at between 2 and 8 weeks after surgery; purulent exudates from the alveolus and swelling were present. In 16 of the 20 cases of infection, a Ganss ratio of <0.5 showed the almost complete absence of space distal to the second molar. This study found that the distal space was significantly and inversely correlated with delayed onset infection ( P = 0.004). From a clinical point of view, it is important for the surgeon to be aware that a higher Ganss ratio may indicate that a delayed onset infection is less likely to occur and that a lower Ganss ratio could indicate a greater likelihood of this type of infection, so that the patient can be properly informed.
Postoperative complications resulting from the surgical removal of third molars can be divided into immediate (early) and delayed types. Immediate complications have been investigated extensively and include factors related to the patient (age, sex, oral hygiene, consumption of alcoholic beverages ), the tooth (partial or complete impaction, impaction depth, previous pericoronitis, extractions needing bone removal, tooth sectioning, type of impaction ), drugs taken (therapy before and/or after extraction ), and the surgeon (experience or flap design, use of rotary or piezoelectric instruments ).
Delayed onset infections, with a lower reported incidence of 0.5% to 1.8%, have been less investigated, but they represent a true problem that the surgeon must face, because the late emergence of pain and swelling and the need for antibiotic therapy can lead the patient to be disappointed with the dentist and sometimes to neglect the problem and not mention it.
There is an increased likelihood of delayed onset infection following the extraction of mandibular third molars with total soft tissue retention, a lack of distal space, and a vertical or mesioangular inclination ; tooth sectioning, bone retention, and depth of inclusion are also considered risk factors for these infections. Impaction of the third molar in the ramus is associated with a reduction in the distal space and this situation can lead to food impaction and a greater difficulty in maintaining proper oral hygiene.
It was hypothesized that a lack of distal space – Pell and Gregory class III – would be the most important factor in the onset of delayed infection after the extraction of impacted mandibular third molars. The purpose of this retrospective study was to determine whether the incidence of delayed infection after lower third molar germectomy is related to the absence of space distal to the second molar.
Materials and methods
A retrospective analysis of the records of 134 patients (68 male and 66 female), who had one or two mandibular third molar germs extracted at least 6 months before the beginning of the study, was performed. Only incompletely formed third molars were evaluated, because in such cases it is possible to reduce the influence of root shape and type of impaction, and a highly standardized surgical procedure can be used. The germectomy was performed for orthodontic reasons, either before or after orthodontic treatment, because of a lack of distal space and/or the need for molar distalization.
Inclusion criteria encompassed the following: American Society of Anesthesiology (ASA) category 1 status, without any history of allergies; extracted tooth with root development less than one-third of the total root length. Bone surgery was performed with a cortical window of the same size (3 × 6 mm), positioned distobuccal to the second molar. All patients presented complete periodontal healing at 3 months after surgery (probing depth <4 mm distal to the second molar). All patients were followed for at least 1 year after extraction to evaluate any delayed complication.
Exclusion criteria were previous episodes of pain and swelling in the same area and the consumption of antibiotics or anti-inflammatory agents in the month preceding the surgery.
The initial record search identified 188 patients who had undergone 305 germectomies between 2010 and 2013 in a private practice in Bologna, Italy. Only patients who had completed all follow-up visits were evaluated in this study. Ethical approval was obtained from the necessary ethics committee.
A total of 218 germectomies in 134 patients who completed the follow-up were evaluated. The evaluation was based on the Ganss protocol ; the relationship between the space available in the retromolar region and the mesiodistal width of the third molar crown was analyzed on panoramic radiographs. When this ratio was <1, after the evaluation of germ development based on a previous panoramic radiograph, the third molar germ was scheduled for extraction. For each tooth germ, the numeric value of the space/width ratio was calculated according to the Ganss protocol ( Fig. 1 ).
All of the cases, when evaluated using the Pell and Gregory classification, were class IIC or IIIC; therefore, they had the same impaction depth. Regarding the lack of distal space, the crowns were half or fully covered by the anterior border of the ramus.
All of the extractions were performed under local anaesthesia (mepivacaine with epinephrine 1:100,000). Patients were treated with 2 g amoxicillin or amoxicillin–clavulanic acid tablets 1 h before surgery and a chlorhexidine (0.2%) mouth rinse for 1 min immediately before surgery.
The germs of the lower third molars were surgically extracted by the same surgeon, who has more than 20 years of experience in oral surgery. The surgical technique used was similar to that described in a previous study : a triangular flap was raised with a releasing incision placed mesial to the second molar; the osteotomy necessary to expose the tooth was performed using a rounded carbide bur on a high-speed hand-piece without air spray under copious water irrigation. A cortical window of the same size (3 × 6 mm) was performed distobuccal to the second molar. To minimize the quantity of bone removal, the tooth was sectioned into four parts with a high-speed fissure bur and the pieces were then removed individually. The socket was then rinsed with physiological saline solution and sutured, in all of the cases with No. 4 4–0 silk sutures. The duration of surgery, determined by the interval between the initial incision and final suturing, was noted in the patient’s records.
Postoperative care and procedures
Antibiotic therapy was continued in the postoperative period (tablets every 8 h for 4 days). The dose administered was 0.5 g or 1 g, depending on the patient’s weight. Starting on the day after surgery, the patients rinsed twice daily with 0.20% chlorhexidine solution for 15 days. After 7 days, the surgeon removed the sutures and performed an assessment of the surgical site.
In all cases, the patient was followed up after 4 weeks to confirm the maintenance of good oral hygiene and the absence of a socket infection (purulent discharge). The patients were instructed to contact the dental office in the case of any further problems with pain or infection; in such cases, they were followed up within a few hours. Three months after the extraction, periodontal probing distal to the second molar was performed to verify complete periodontal healing.
Age, sex, panoramic radiographs, length of surgery (min), and the space/width ratio according to the Ganss protocol were recorded on an Excel spreadsheet by the same researcher (S.C.) independent of the surgeon; this researcher also noted the occurrence of delayed infection.
The Ganss ratio, age at germectomy, and duration of the surgery were considered predictor variables of the outcome variable ‘delayed infection’, which was diagnosed in the presence of swelling and/or purulent drainage from the alveolus arising 15 days to 2 months post extraction. In the early stages of infection, swelling (intraoral and/or extraoral) could present without the purulent drainage. Infection was sometimes associated with fever. Pain, when present, was moderate.
The predictor variables did not follow a Gaussian distribution (Shapiro–Wilk test, P = 0.02), thus comparisons of these parameters between the groups with and without infection were performed using the Mann–Whitney U -test.
Stepwise discriminant analysis was used to determine the best combination of predictor variables (discriminant function). A new dataset of 62 germectomies, different from those from which the discriminant functions were derived, was collected to ‘try out’ (cross-validate) in a predictive manner the utility of the discriminant functions. The effectiveness of the Ganss ratio in classifying infection cases was evaluated by means of the receiver operating characteristic (ROC) curve using the probability values derived from the discriminant analysis. The α level was set at 0.05.
The study patients had a mean age of 15 years (range 12–20 years); the age range was due to individual variations in tooth development.
Eighteen of the 134 patients (13.4%) presented a delayed infection between 2 and 8 weeks after germectomy ( Table 1 ), with purulent exudates from the alveolus and swelling. Two of these patients, both 15 years old, presented an infection at 4 weeks after surgery on both the left and right side, with an almost complete absence of space distal to the second molar, as shown by the values of the Ganss ratio. In total, 20 (9.2%) cases of infection were observed in the whole sample of germectomies ( n = 218).
|Patient number||Case of delayed onset infection||Sex||Ganss ratio||Age (years)||Length of surgery (min)||Onset of infection (weeks)|
Furthermore, two of the subjects presented an infection with drainage of purulent exudates from the alveolus at suture removal after 1 week (0.9%); one reported fever and the other dehiscence with healing by secondary intention.
No statistically significant difference was observed between patients with and without infection regarding sex or age, although the incidence of delayed infection was higher in females (16.7%) than in males (10.3%) and in younger patients (15 ± 1 years) than in older patients (16 ± 2 years). However, the male to female ratio was a significant predictor ( P = 0.0001): the ratio was 0.64 in the presence of infection and 1.11 in its absence. The length of surgery was similar in the two groups ( Table 2 ).