J Oral Maxillofac Surg 62:689-692, 2004
The Presurgical Workup Before Third Molar Surgery: How Much Is Enough? Hadar Better, MD, DMD, MSc,* Itzhak Abramovitz, DMD, † Biniamin Shlomi, DMD,‡ Adrian Kahn, DMD,§ Yaakov Levy, DMD, Amit Shaham, DMD,¶ and Gavriel Chaushu, DMD, MSc** Purpose:
We sought to assess the indications for patient referral for computed tomography (CT) scan before third molar extraction. The influence of the data obtained from the CT scans on the surgical outcome and morbidity was also evaluated. Patients and Methods: There were 189 patients in the study (120 females and 69 males). Sixty-five patients were referred to receive CT and formed the study group. The remaining patients were included in the control group. Results: There were no statistically significant differences between the groups with regard to demographic data and tooth and root angulations. Indications for tooth extraction such as pain, swelling, pericoronitis, caries, endodontic problems, pathology, and prosthetic considerations were similar. The proximity of the tooth root to the inferior alveolar canal was the only statistically significant difference between the 2 groups (P ⬍ .001). The treatment plan outcomes for extraction, surgical extraction, and follow-up were comparable. The surgeon changed the initial decision from “surgical extraction” to “follow-up” in only 1 case after CT scan. Conclusions: Within the limits of the present study, it can be concluded that the main reason for CT scan referral is the proximity of the third molar root to the inferior alveolar canal (⬍1 mm). The data obtained from the CT scan had minimal effect on the final surgical outcome. The routine use of CT scan in cases of third molar extractions cannot be recommended. © 2004 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 62:689-692, 2004 A recent editorial stressed the importance of presurgical evaluation to discover systemic or local and
general or specific perioperative risk. Every surgeon attempts to rule out any condition that can be discovered preoperatively and might seriously complicate the outcomes of the surgical procedure.1 Altered sensation is the most frequent severe complication encountered after third molar surgery. Predisposing factors include direct or indirect trauma during the use of surgical rotating instruments or root elevators.2-8 Former investigations found the incidence of sensory loss after third molar surgery to range from 0.4% to 5.5% for the inferior alveolar nerve3,8-12 and from 0.06% to 11.5% for the lingual nerve.2,4,8-10,12,13 The anatomic relationship between the inferior alveolar nerve and the third molar therefore is one of the most important data elements to be obtained during the presurgical evaluation to enable the most appropriate decision-making.14,15 Presurgical 3-dimensional radiographic evaluation of the topographic relationship may be a major contribution in preventing loss of sensation after third molar surgery. Such information can be obtained by the use of a computed tomography (CT) scan. In the past decade, CT emerged as the most useful imaging modality to outline the relationship between bone and adjacent anatomic struc-
*Attending, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. †Clinical Instructor, Department of Endodontics, Hebrew University-Hadassa Faculty of Dental Medicine, Jerusalem, Israel. ‡Attending, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. §Attending, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. 㛳Attending, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. ¶Chief Resident, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. **Head, Oral and Maxillofacial Surgery Unit, Tel Aviv Sourasky Medical Center, and Senior Lecturer, School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. Address correspondence and reprint requests to Dr Chaushu: Oral and Maxillofacial Surgery Unit, The Tel Aviv Sourasky Medical Center, Tel Aviv, Israel; e-mail:
[email protected] © 2004 American Association of Oral and Maxillofacial Surgeons
0278-2391/04/6206-0009$30.00/0 doi:10.1016/j.joms.2003.12.009
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CT SCAN BEFORE THIRD MOLAR EXTRACTION
Table 1. DEMOGRAPHIC DATA
Gender Female
Male
Age (yr)
Computed Tomography Scan
43 (66%) 77 (62%)
22 (34%) 47 (38%)
31 29
Yes No
NOTE. P ⫽ NS.
tures.16 As a result, one might infer that CT allows the surgeon to achieve a realistic presurgical notion of the anatomic relationship, thereby minimizing the risk of nerve injuries. However, the biological and financial cost-effectiveness of CT must be evaluated before its routine application. A recent study compared conventional panoramic radiography with volumetric CT images for presurgical assessment of impacted third molars. The authors stressed the “increased diagnostic usefulness” of CT in delineating the topographic relationship between the mandibular nerve and the apices of impacted third molars over conventional panoramic radiographs.17 The main question of the previously cited editorial in regard to this article was, “What are we to do with such information?” Search of the English literature did not yield any guidelines for whether to perform a CT scan as part of the presurgical evaluation. The aim of the present prospective study was to evaluate the indications for patient referral for CT scan before third molar extraction. The influence of the data obtained from the CT scans on decision-making and on the surgical outcome was also evaluated.
Patients and Methods
guidelines for CT referral were given to the surgeons to enable evaluation of the indications for routine patient referral to CT scan before third molar extraction. In 65 cases, the surgeon considered it valuable to complement the panoramic radiographs with CT before performing surgery. All patients were informed about the need for further CT radiologic assessment to reveal the exact position of the third molar apices in relation to the mandibular canal. VARIABLES AND DATA COLLECTION
All clinicians were simultaneously asked to complete a structured form that included: 1) demographic data, age, gender; 2) indications for extraction, prosthetic, pathology, endodontics, caries, pericoronitis, pain, swelling; and 3) data obtained from the panoramic radiographs, tooth angulation (mesioangular, distoangular, vertical), root angulation (the differences between the angle formed by the long axis drawn perpendicular to the occlusal plane of the crown of the mandibular third molar and the central line of the lower third of the root through the root apex),18 and mandibular canal proximity. The surgical outcome (extraction, surgical extraction, and follow-up), changes in surgical decisionmaking, and loss of sensation were also recorded. The surgeons were also asked to mention their reason for CT referral. DATA ANALYSIS
The database was constructed from the structured form. Sixty-five patients were referred to CT and composed the study group. The remaining patients were included in the control group. Statistical analysis between the 2 groups was performed with 2 test.
DESIGN AND SAMPLE
This prospective study was composed of 189 patients aged 16 to 76 years (average age, 30 ⫾ 11 years; 69 men and 120 women) who were referred to the Oral and Maxillofacial Surgery Unit between January 2001 and December 2001 for treatment of their impacted lower third molars. All patients had been routinely examined using conventional panoramic radiographs. Deliberately, no clinical or radiographic
Results There were no statistically significant differences between the groups with regard to demographic data (Table 1). Indications for tooth extraction such as pain, swelling, pericoronitis, caries, endodontic problems, pathology, and prosthetic considerations were similar (Table 2). Data obtained from the panoramic
Table 2. TOOTH POSITION AND ROOT MORPHOLOGY
Mandibular Canal Proximity (mm) ⫹1
0 to 1
2 (3%) 63 (97%) 49 (39%) 75 (61%) P ⬍ .001
Root Angulation (°) ⫹90
2 (4%) 0
90 to 45
45 to 0
10 (15%) 22 (33%) 11 (9%) 43 (35%) P ⫽ NS
V
Computed Tomography Scan
27 (42%) 75 (60%)
Yes No
Angulation 0
H
31 (48%) 70 (56%)
15 (23%) 14 (11%)
Abbreviations: H, horizontal; DA, distoangular; MA, mesioangular; V, vertical.
DA
MA
4 (6%) 19 (29%) 7 (6%) 28 (23%) P ⫽ NS
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BETTER ET AL
Table 3. INDICATIONS FOR TOOTH EXTRACTION
Prosthetic
Pathology
Endodontic Problems
4 (6%) 4 (3%)
5 (8%) 5 (4%)
0 2 (2%)
Caries
Pericoronitis
Pain
Swelling
Computed Tomography Scan
19 (29%) 47 (38%)
44 (67%) 55 (45%)
49 (74%) 93 (76%)
20 (30%) 27 (22%)
Yes No
Signs and Symptoms
NOTE. P ⫽ NS.
radiographs were similar with regard to tooth and root angulations, whereas the proximity of the tooth root to the inferior alveolar canal was the only statistically significant difference between the 2 groups (P ⬍ .001) (Table 3). The treatment plan outcomes for extraction, surgical extraction, and follow-up were comparable (Table 4). The surgeon changed the initial decision from “surgical extraction” to “followup” in only 1 case after CT scan. In this specific case, the transaxial CT reconstructions showed a close anatomic relationship between the mandibular nerve and the apex of the impacted third molar. The risks were explained to the patient, who preferred follow-up over surgery. None of the patients reported an incidence of loss of sensation after injury to the inferior alveolar nerve.
Discussion The clinical potential of new technology is one of the most challenging tasks in clinical research, yet the biological and financial cost-effectiveness of such new technology requires an evidence-based approach with regard to its routine application. Such an approach can guide patient-informed consent, third-party reimbursement, and medical-legal risk management in practice.1 The use of CT reconstructed paraxial images allows an improved notion of the topographic relationship between the third molar and the adjacent anatomy.17 However, the exact anatomic course of the apices in relation to the mandibular canal could be shown with only 70% accuracy, despite the use of CT paraxial images. The effect of such accuracy on decision-making is thus questionable. The first issue tested in the present study was the rationale of sur-
Table 4. OUTCOME OF THE SURGICAL PROCEDURE
Follow-Up
Surgical Extraction
Extraction
Computed Tomography Scan
1 (1%) —
61 (94%) 111 (90%)
3 (5%) 13 (10%)
Yes No
NOTE. P ⫽ NS.
geons for referring their patients to CT as part of the presurgical evaluation of third molar extraction. The radiographic assessment is required to determine the position of the tooth, the number and morphology of the roots, bone coverage and density, and the relationship between the roots and the mandibular canal. The results of the present study show that neither the indication for third molar extraction nor tooth and root angulations could be considered sufficiently important for the surgeons to justify the patient’s referral to CT. The only justification for CT referral was a close proximity of the apices to the mandibular canal. The second purpose of the study was to evaluate whether the data obtained from the CT influenced the decision-making or morbidity regarding extraction of third molars. The results of the present study show that the surgeons changed their decision in only 1 case and that there were no cases of altered sensation. The rationale for the routine use of a new preoperative imaging modality includes a direct effect on decision-making, on surgical outcome, or operative comorbidity.1 The results of the present study therefore cannot promote the routine use of dental CT before third molar extraction at this time. In addition, the relatively high level of radiation doses, as well as the time and labor required, with resulting costs, are not justified.19 The issues of third-party reimbursement, medicallegal considerations, and curiosity are inadequate reasons for the routine use of a new preoperative imaging modality.1 At the end of the present study, the results were shown to the participating surgeons, and they then were asked if 1 of the above 3 reasons could be considered part of their motivation for CT referral. The unanimous response was medical-legal considerations. Within the limits of the present study, it can be concluded that the main reason for CT scan referral is the proximity of the third molar root to the inferior alveolar canal (⬍1 mm). The data obtained from the CT scan have minimal effect on the final surgical outcome or morbidity. The routine use of CT scan in cases of third molar extractions cannot be recommended.
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CT SCAN BEFORE THIRD MOLAR EXTRACTION 11. Rood JP, Nooraldeen BAA: The radiological prediction of inferior alveolar nerve injury during third molar surgery. Br J Oral Maxillofac Surg 28:20, 1990 12. Wofford DT, Miller RI: Prospective study of dysesthesia following odontectomy of impacted mandibular third molars. J Oral Maxillofac Surg 45:15, 1987 13. Fielding AF, Rachiele DP, Frazier G: Lingual nerve paresthesia following third molar surgery. A retrospective clinical study. Oral Surg Oral Med Oral Pathol Oral Radiol Oral Endod 84:345, 1997 14. Smith AC, Barry SE, Chiong AY: Inferior alveolar nerve damage following removal of mandibular third molar teeth: A prospective study using panoramic radiography. Aust Dent J 42:149, 1997 15. Chandler LP, Laskin DM: Accuracy of radiographs in classification of impacted third molar teeth. J Oral Maxillofac Surg 46:656, 1998 16. Abrahams JJ, Berger SB: Inflammatory disease of the jaw: Appearance on reformatted CT scans. AJR Am J Roentgenol 170: 1085, 1998 17. Pawelzik J, Cohnen M, Willers R, et al: Comparison of conventional panoramic radiographs with volumetric computed tomography images in the preoperative assessment of impacted mandibular third molars. J Oral Maxillofac Surg 60:979, 2002 18. Yamaoka M, Furusawa K, Hayama H, et al: Relationship between third molar development and root angulation. J Oral Rehabil 28:198, 2001 19. Schmuth GP, Freisfeld OK, Schu ¨ ller H: The application of computerized tomography (CT) in case of impacted maxillary canine. Eur J Orthod 14:296, 1992
