June 1, 2014
by Brian Rittenberg, DDS, MSc, FRCD(C); Kris Lee, BSc, DDS, MD, FRCD(C)
Elective removal of impacted third molar teeth continues to be a controversial topic in dentistry. This is in part due to the difficulties in designing prospective studies examining the issue. There are those who advocate early removal of impacted third molars and others who feel that these teeth should only be removed if and when they have “caused a problem”. Early removal of impacted third molars is suggested in order to prevent the risks inherent in maintaining these impacted teeth as well as to limit future surgical risk. A more conservative approach to impacted third molars is based on the philosophy that the risks associated with the surgical procedure are too high and that the majority of these teeth may never create issues requiring intervention.
A recent editorial in this journal highlighted the controversy by suggesting that the current evidence-based literature supports a conservative approach to asymptomatic un-erupted third molar teeth.1 While the authors of this article welcome and advocate for evidence-based treatment, it should be made clear that the four sources referenced in that editorial were written by one author and amounted to that author’s opinion and not strong evidence.
This article will review several clinical situations, which illustrate some of the problems that can occur when impacted third molar teeth are not removed early in their development. Current evidenced based literature regarding impacted third molar teeth will also be reviewed in order to provide the information necessary to make sound treatment recommendations.
A healthy 70-year-old male patient presented to our clinic with an acute infection associated with impacted tooth 48. Clinical examination revealed a partially erupted tooth 48, with localized gingival swelling and purulent discharge. A panoramic radiograph was taken which demonstrated a mesio-angularly impacted tooth 48, with roots extending close to the inferior border of the mandible, and what appears to be either caries or external resorption affecting the crown of the tooth (Fig. 1). The patient was prescribed Amoxicillin 500mg TID for seven days, and .12 percent chlorhexidene mouth rinse. A recommendation was made to remove tooth 48 under sedative anesthetic once the acute phase of the infection had resolved.
The patient returned five days later for the removal of impacted tooth 48. Under sedative anesthetic, a full thickness flap was elevated to expose tooth 48, which was then sectioned to facilitate its removal. An elevator was then used to extract the tooth. With gentle force application, a mandible fracture propagated through the 48 site. The fracture was severely displaced and necessitated treatment including open reduction and internal fixation (Figs. 2 & 3). The fracture healed uneventfully however the damage to the inferior alveolar nerve, as a result of the fracture, was irreversible resulting in persistent anesthesia to the right inferior alveolar nerve distribution.
A 43-year-old female patient presented to our office on an urgent basis, with a two-day history of severe left sided facial pain and hot and cold sensitivity to tooth 37. Clinical exam revealed severe pain to percussion and cold sensitivity to tooth 37. The panoramic radiograph (Fig. 4) demonstrated a mesio-angularly impacted tooth 38, and deep caries associated with the distal aspect of tooth 37. After surgical consultation, tooth 38 was removed without complication and the patient was referred back to her dentist for treatment of tooth 37, which had an acute pulpitis secondary to the deep caries. Due to the depth of the caries, tooth 37 was subsequently deemed unrestorable and was eventually extracted. The patient is now considering replacement of tooth 37 with a dental implant.
A 27-year-old male patient presented with severe right facial pain and swelling that had progressively developed over the previous two days. He was otherwise healthy. On examination, the swelling on the right face involved the buccal and submandibular spaces, and was firm to palpation. There was significant trismus that made it difficult to perform a thorough intra-oral examination, however it was clear that the patient was in distress. The patient was transferred to hospital for further management, and upon arrival was started on intravenous Clindamycin and a CT scan and panoramic radiograph were obtained. The panoramic radiograph demonstrated impacted third molar teeth and specifically a cystic lesion associated with tooth 48, which had displaced the tooth to the posterior border of the right mandibular ramus (Fig. 5). The CT scan demonstrated deep space abscesses involving the right buccal, submandibular and lateral pharyngeal spaces resulting in severe constriction of the airway (Fig. 6).
FIGURE 6. Axial view of a CT scan demonstrating a right submandibular space abscess, extending into the lateral pharyngeal space resulting in a severely constricted airway (The top two arrows point to the abscess and gas produced by bacteria involved in the infection and the bottom arrow points to the extremely narrow and displaced airway).
The patient was immediately brought to the operating room, where an awake fibre-optic intubation took place to secure his airway. Following intubation, incision and drainage of the deep space abscesses took place, tooth 48 was removed and the associated cyst was enucleated. Following the procedure, the patient remained intubated in the Intensive Care Unit for 72 hours, and was extubated once the airway swelling had resolved. The histopathology was consistent with a dentigerous cyst and therefore no further management was required. Teeth 18, 28 and 38 were subsequently removed as an elective procedure without complication.
A 74-year-old man presented to the emergency department with left sided swelling and pain of 60-day duration. His medical history was significant for hypertension, coronary artery disease, angina, a mechanical aortic valve and Type II Diabetes. His medications consisted of antihypertensives, nitroglycerin, simvastatin, metformin and coumadin with a biweekly INR range of three to four (high). On examination there was mild trismus, swelling and erythema over the left cheek. Intra-orally he presented with a heavily restored dentition, no active periodontal disease, good hygiene but pus exudate from both the right and left third molar sites. Tooth #38 was lingually malpositioned and partially exposing a crown that was restored by his new GP three months ago (this restoration replaced an older failed restoration). He reports that his previous dentist who passed away recommended observing his wisdom teeth because of their unusual and “risky” position. He reports that they have been bothering him “on and off” since he was 18 (1958). The panoramic radiograph demonstrated impacted teeth 38 and 48. Tooth 48 appeared to have an enlarged follicle associated with it, while tooth 38 had significant recurrent decay (Fig. 7).
He was admitted to hospital, placed on IV antibiotics and consulted by medicine and anesthesia. His coumadin was reversed and switched to heparin therapy to enable a short window of opportunity to remove the tooth without a large bleeding risk. He consented only to the removal of the tooth on the left since “it was the only one bothering (him)”. Under general anesthesia tooth #38 was removed without complications. He stayed in hospital two more days with reinstitution of coumadin and without bleeding.
The patient presented back to clinic four days later with profuse bleeding from his mouth. Hemostatic measures were instituted with human tissue fibrinogen, collagen pressure packs and re-suturing. He was given a prescription of tranexamic acid (4.8 percent) mouth rinse and the bleeding was stopped.
Five days after this episode he presented again to the clinic with uncontrolled bleeding from the left side and he was hypotensive, diaphoretic and pale. He was readmitted to hospital with hemoglobin of 60 [normal >130] and transfused two units of blood. The patient was brought back to the operating room with a coumadin/heparin switch and repacking was performed with complete hemostasis being obtained. He was discharge one week later in good condition.
Ten days after his release from hospital the patient experienced another bleeding episode and returned to clinic where a new pressure pack was applied and sutured and more tranexamic acid mouth-rinse prescribed with good effect. There were no more bleeding episodes after this but his latest clinic check revealed a worsening of the condition of tooth #48 and the patient is now considering having it removed.
In this article, 4 cases have been presented to illustrate some of the potential problems that can arise if impacted third molar teeth are retained. These cases provide an opportunity to review the current literature related to the prophylactic removal of third molar teeth.
As with any surgical procedure, the recommendation to extract impacted third molar teeth should only be made after the risks and benefits of the procedure are critically evaluated. The risks are well described, as third molar extraction is one of the most commonly performed procedures in dentistry. In addition to the normal post-operative sequelae of surgery including pain, bleeding, swelling, and bruising, some patients can experience paresthesia to the distribution of the Inferior Alveolar Nerve (0.5-5 percent)2,3 and to a lesser degree lingual nerve injury, postoperative infection (4-6 percent),4 oral-antral communication, or mandibular fracture (0.00049 percent).5
While it is easy to identify the potential risks inherent in removing impacted third molar teeth, it is considerably more difficult to predict the potential benefits of this procedure. If a patient presents with pain, infection, pathology, or decay, the decision is an easy one, but it is much more difficult when these teeth are “asymptomatic”. White and Profitt cautioned about using the term “asymptomatic” as some confuse “asymptomatic” with “pathology free”.6 It is obvious that “asymptomatic” does not always equate with “pathology free”. For example, an impacted third molar associated with an enlarged follicle consistent with a dentigerous cyst can often be asymptomatic but clearly not free of pathology.
Even more difficult are impacted third molar teeth that are both asymptomatic and pathology free. It is in this situation that we must rely on the evidence-based literature available to help guide our treatment recommendations. The literature classifies the potential problems associated with the retention of impacted third molar teeth into the following categories: periodontal problems, caries, crowding of anterior teeth and pathology.
A recent study published in the Journal of Oral and Maxillofacial Surgery in 2012 looked at periodontal condition related to impacted third molar teeth in 409 healthy young adults with a mean age of 25. The study found that 65 percent of these subjects had at least 1 probing site of >4mm associated with the third molar and 20 percent associated with the distal aspect of the second molar.7 Four pockets of >4mm associated with the third molars were found in 23 percent of subjects. More interestingly, of the 106 subjects that did not have a pocket at the initial exam, 38 percent developed at least 1 pocket of >4mm at the third molar site during follow-up examination (median 4.1 years). A previous study found similar results in that the presence of third molars were associated with pocket depth >=5 mm on the distal of the second molar or around the third molar in 25 percent of subjects.8
Based on these studies, it seems that the presence of third molars may have a detrimental effect on the periodontal health of second and third molar teeth. Whether this leads to more serious and generalized periodontal problems in the oral cavity is unclear. If the patient decides or the dentist recommends leaving the third molars in place, special attention must be paid at these sites with long-term observation. Moreover, the
patient needs to understand the ramification of having active periodontal pockets in the oral cavity. Studies have linked chronic inflammatory processes such as periodontal disease with newborn low birth weight and prematurity, atherosclerosis, coronary artery disease, and renal insufficiency.9-12
Caries is a common occurrence in an erupted or partially erupted third molar. A recent study examined the prevalence of caries and found that 24 percent of the subjects had caries or a restored surface on a third molar. This study also found that 50 percent of the patients, despite not having decay on their third molars, had caries on either the first or second molar.7 In another study, Shugars found that 29 percent of subjects aged 22 to 32 (N=211) had occlusal caries on a third molar. The prevalence increased to 33 percent at follow-up (median 2.9 years).13
Anterior teeth crowding
Dental crowding associated with the anterior mandibular teeth is likely multifactorial. Physiologic mesial drift, occlusal forces on mesially inclined teeth, mesial vectors of muscle contraction, developing third molars, mandibular and complex facial growth patterns, soft tissue maturation, occlusal factors, and connective tissue changes all play a role.14 To date, it has not been possible to design a study that only tests the effect of third molars on anterior dental crowding. The most comprehensive study thus far is a randomized controlled trial looking at the effect of early third molar extraction on late anterior mandibular crowding.15 The study found no statistical difference between the extraction and non-extraction groups and hence wisdom teeth should not be removed for the sole purpose of preventing late anterior mandibular crowding.15
The follicle of impacted third molars can undergo cystic and neoplastic changes. A study found cystic changes on histologic sections in as high as 50 percent of their subjects with asymptomatic third molars.16 Another study found a 51 percent incidence of dentigerous cysts, a 1.9 percent incidence of keratocystic odontogenic tumors (formerly odontogenic keratocysts), and a 0.96 percent incidence of ameloblastomas associated with impacted third molar teeth in their subjects.17 Although these all represent benign pathology, the destructive capability of these lesions is significant, and the subsequent surgical management is considerably more complex than the removal of an impacted third molar without such pathology.
Prophylactic third molar extraction implies that the teeth are removed before problems arise. Typically this is done when patients are between 16-25 years of age or when the roots have completed two-thirds of their development. Third molars at this age seem to be easier to remove as the surrounding bone is softer, more pliable, and there is less curvature in the roots with wider periodontal ligaments. Younger patients also tend to be healthier and take fewer medications and therefore have less perioperative risk with respect to anaesthesia, intraoperative and post-operative sequelae. This practice is supported by a large cohort study that found complication rates being 1.5 times more likely if the patient is greater than 25 years of age.22
Randomized, prospective controlled studies are considered the benchmark by which clinicians should make decisions regarding treatment. Although these studies provide us with the most meaningful data, they are difficult to design and implement. While most of the studies included in this brief review were carried out at major teaching institutions and were published in peer-reviewed journals, they are considered low level evidence.
When the Cochrane database of systematic reviews investigated the topic of “Surgical removal versus retention for the management of asymptomatic impacted wisdom teeth” in 2012,23 only one study was found that met their inclusion criteria, and that study was considered to be at “high risk for bias”.15 The outcome measure of the study was anterior dental crowding and a statistical difference was not identified between the extraction and the non-extraction group.15 Based on this study, the Cochrane review concluded that “watchful monitoring” of asymptomatic third molars may be the most prudent strategy. This statement is often mis-quoted as the most evidence based approach for the management of wisdom teeth, when in fact it merely illustrates that there is no evidence linking third molars to anterior dental crowding. Interpreting this as the reason to maintain impacted third molars is simply wrong.
The most comprehensive review of the subject can be found in the “White Paper” published by the American Association of Oral and Maxillofacial Surgery in 2007 and updated in 2013.24 The White Paper is the most thorough review of the literature as it pertains to third molars. The databases included in the review were Ovid Medline, PubMed, Google Scholar, and the Cochrane Database. Case reports, which are the weakest form of evidence, were excluded. The intention of this paper was not to impart a biased opinion on the subject, but rather to critically evaluate the potential effects of maintaining impacted third molar teeth as well as the risks associated with their extraction. In general, the White Paper found that when all factors were considered, the evidence based literature supports early removal of impacted third molar teeth, and demonstrates that maintenance of impacted third molar teeth is associated with a variety of adverse effects.
Dentistry and medicine have evolved through the years to provide patients with extremely high levels of care. This evolution resulted in the birth of dental and medical specialties, allowing for more focused development is specific areas of treatment. These specialties have spearheaded the advancement of knowledge in specific areas through focused research both at the basic science and clinical levels. This has allowed for both general dentists and specialists in various areas to provide ideal evidence-based treatment to their patients. It therefore seems prudent to avoid one specialty from commenting on the evidence-based practices of another either through editorials or non-peer reviewed articles thus recklessly influencing reader’s clinical decision-making process. It should be made clear, the intention of this article is not to promote recommending early removal of impacted third molars without an appropriate risk/benefit analysis. Instead, we have attempted to provide sufficient information by way of case studies and a review of the literature, to help with that decision-making process.
Based on this review, it seems that the most reasonable approach that dentists can take when approaching the subject of prophylactic removal of impacted third molars is to inform the patient of the potential risks and benefits of treatment versus observation and allow them to make a well educated and informed decision. OH
Dr. Brian Rittenberg is an Oral and Maxillofacial Surgeon with Crescent Oral Surgery, and is an attending surgeon at Mount Sinai Hospital in Toronto, Ontario. He attended dental school and completed his surgical residency at the University of Toronto. Brian is a Fellow of the Royal College of Dentists of Canada and is the current president of the Ontario Society of Oral and Maxillofacial Surgeons (OSOMS).
Dr. Kris Lee is an Oral and Maxillofacial Surgeon with Crescent Oral Surgery in Toronto, Ontario. He is an attending surgeon at Mount Sinai Hospital. Kris received his Bachelor of Science degree in 1999 and his Dental Degree in 2003 from the University of Toronto. He the
n completed 1 year of training in Periodontics at the University of Pittsburgh. Kris continued his education at the University of Michigan where he received his Medical Degree and Oral and Maxillofacial Surgery Certificate. He is a Fellow of the Royal College of Dentists of Canada and a Diplomate of the American Board of Oral and Maxillofacial Surgery.
The authors would like to thank Dr. Eddie Reinish and Dr. Marco Caminiti for their assistance in preparation of this article.
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