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Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars Associated With No Gross Pathology
J Oral Maxillofac Surg 67:856-861, 2009
Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars Associated With No Gross Pathology Fouad A. Al-Belasy, BDS, MSc, PhD,* Sinan Tozoglu, PhD, DDS,† and Umit Ertas, PhD, DDS‡ Purpose: This study was undertaken with the null hypothesis that in patients, fully denate or with 1 or
2 teeth missing and older than 25 years, mastication does not affect late mandibular fracture after surgical removal of impacted third molars (M3s) associated with no gross pathology. Materials and Methods: Five hundred sixty patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who had no gross pathology associated with their impacted lower M3s, were recruited in this study. They were operated on under local anesthesia using a standard technique and randomly assigned into 2 groups for nonroutine (NR group) and routine (R group) postoperative instructions. In the NR group, patients were postoperatively educated in the possibility of mandibular fracture and were given an emphasis on the necessity of limiting mastication to a soft diet for 4 weeks. In the R group, patients were given no such education or emphasis. Patients were followed up for 2 months, and data concerning patients’ age and gender; tooth position, angulation, and depth; date and site of surgery; and occurrence of late mandibular fracture were recorded and statistically analyzed. A value of P less than .05 was considered statistically significant. Results: In no patient group was there a late mandibular fracture recorded. All patients completed the follow-up period, and most of the R group patients had normal eating habits 10 to 14 days after surgery. In no patient group was there a statistically significant difference in relation to gender (P ⫽ .735), site of surgery (P ⫽ .552), class horizontal space available (P ⫽ .427), class highest portion of the M3 crown (P ⫽ .424), angulations of the teeth (P ⫽ .925), and severity of impaction (P ⫽ .445). Conclusions: In patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who have no jawbone atrophy and no systemic problems that may impair bone strength, mastication seems not to affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology. The remote possible risk of the late fracture shown in our patients indicates the need for no special precautions. © 2009 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 67:856-861, 2009 cases. The reason for this severe complication is believed to be multifactorial, and include: patient’s compliance, age, gender, state of dentition, degree of impaction, depth and relative volume of the tooth in bone, associated pathology, operation site, and the surgical technique.1,3-7 Noncompliant, fully dentate patients, particularly those who are older than 25 years and presenting with teeth deeply seated in bone, are at greater risk.1,3-7 Mastication seems to be the main precipitating factor where patients having full dentition are able to produce peak levels of biting forces that can place considerable stress on bone weakened by surgery and not yet fully restored or calcified.1,3-7 The greatest risk period seems to be during postoperative weeks 2 and 3,1,3 during which granulation tissue is being replaced by connective tissue in the extraction site.8 Therefore, it was emphasized that patients
The incidence of late mandibular fracture after surgical removal of impacted third molars (M3s) has been reported as 0.0013%,1 0.0042%,2 and 0.0046%.3 A recent literature search by Wagner et al4 resulted in 94 documented cases, and they added another 17 *Professor of Oral and Maxillofacial Surgery, Dean, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. †Assistant Professor, Department of Oral and Maxillofacial Surgery, Ataturk University Dentistry Faculty, Erzurum, Turkey. ‡Associate Professor, Department of Oral and Maxillofacial Surgery, Ataturk University Dentistry Faculty, Erzurum, Turkey. Address correspondence and reprint requests to Dr Al-Belasy: Department of Oral Surgery, Mansoura University, Mansoura, Dkahlia, Egypt; e-mail: [email protected] © 2009 American Association of Oral and Maxillofacial Surgeons
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should be informed of the desirability of masticatory limiting force for 2 months1 or a soft diet for up to 4 weeks.4,7 This study was undertaken with the null hypothesis that in patients, fully dentate or with 1 or 2 teeth missing and older than 25 years, mastication does not affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology.
Materials and Methods Five hundred sixty patients referred for surgical removal of impacted lower M3s were recruited in this study. Patients, fully dentate or with 1 or 2 teeth missing, were 262 females and 298 males ranging in age from 25 to 53 years with a mean age of 31.23 ⫾ 5.63 years and 32.46 ⫾ 6.11 years, respectively. For all patients a formal case history and clinical and radiographic examinations were performed. No history of medical problems including osteoporosis or metabolic bone disorders was identified in those patients, and their impacted M3s were associated with no gross pathology (eg, an odontogenic cyst or tumor). All patients were asked if they clenched or bruxed their teeth. Masseter muscle hypertrophy, if present, was noted. For all patients, explanations and warnings of the procedure were given and recorded in the case notes, and every patient was requested to sign a consent stating that he or she had been informed of and understood the nature and likely consequences of the procedure. Using panoramic radiographs, M3s positions were analyzed according to the Pell and Gregory9 system. The horizontal space available for M3 was grouped based on the amount of space as measured between the anterior border of the ascending ramus and the posterior border of the second molar as follows: Class I, adequate space available; Class II, inadequate space available; Class III, M3 located all or mostly within the ascending ramus. The vertical space was classified based on the highest portion of the M3 crown as follows: Class A, level at or above the occlusal plane; Class B, between the cementoenamel junction of the adjacent second molar and the occlusal plane; Class C, below the cementoenamel junction. The angulation of the M3, defined as angle of intersection between the long axis of the tooth and the mandibular occlusal plane,10 was classified according to Ma’aita and Alwrikat,11 and Iida et al12 as follows: horizontal: (less than 20°), mesioangular: (20°-80°), vertical: (80°100°), or distoangular: (more than 100°). In addition, the severity of impaction of the M3 was classified as either partial soft tissue, complete soft tissue, partial bony, or complete bony.13 However, only patients included were those with Class II or III, Class B or C,
partial, or complete bony impactions in any of the specified angulations. All patients were operated on under local anesthesia using a standardized surgical bur technique for tooth sectioning and necessary conservative bone removal after effecting an envelope flap extending from the mesial papilla of the lower first molar, around the necks of the teeth to the mid-distal of the lower second molar, and then posteriorly to and laterally up the anterior border of the mandible. To see whether counseling patients or limiting their diet has any value in the possible risk of late mandibular fracture, patients were randomly assigned into 2 groups for nonroutine (NR group) and routine (R group) postoperative instructions. Both NR and R were alternating, beginning with the first entered patient as the NR group. Patients in the NR group were postoperatively educated in the potentiality of mandibular fracture, and were given an unambiguous emphasis on the necessity of limiting mastication to a soft diet for 4 weeks.4,7 The quality of the soft diet was also emphasized.3 Patients in the R group were given no such education or emphasis. Patients were followed up for 2 months. The patients’ age and gender, date and site of surgery, and occurrence of late mandibular fracture were recorded. Then the 2 patient groups were compared for significant differences in age using the Student t test, and for significant differences in gender, site of surgery, tooth position, and angulation as well as severity of impaction using the 2 test. A value of P less than .05 was considered statistically significant.
Results In the NR group, patients were 129 females and 151 males, ranging in age from 25 to 53 years with a mean age of 31.36 ⫾ 5.66 years (females: 31.29 ⫾ 5.84 years; males: 31.42 ⫾ 5.51 years). In the R group, patients were 133 females and 147 males, ranging in age from 25 to 52 years with a mean age of 32.41 ⫾ 6.14 years (females: 31.18 ⫾ 5.45 years; males: 33.53 ⫾ 6.52 years). Concerning age, the R group showed a statistically significant difference (P ⫽ .035) (Table 1). Seven patients in the R group had masseter muscle hypertrophy and 11 had clenching or/and bruxism. No such findings, however, were noted in the NR group of patients. Patients treated in the NR group had 176 impacted M3s classified as Class II, 104 as Class III, 179 classified as Class B, and 101 as Class C. The angulations of these impacted M3s were mesioangular in 110 cases, distoangular in 29 cases, vertical in 88 cases, and horizontal in 53 cases. Surgery with bone removal was done for extraction of these M3s in both the right side (130 M3s) and the left side (150 M3s). Patients
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Table 1. AGE AND GENDER DISTRIBUTION OF PATIENTS
All Patients Age (yr) Minimum Maximum Mean SD Significance t df P
NR Group
R Group
F (n ⫽ 262)
M (n ⫽ 298)
F (n ⫽ 129)
M (n ⫽ 151)
Total (n ⫽ 280)
F (n ⫽ 133)
M (n ⫽ 147)
Total (n ⫽ 280)
25 50 31.23 5.63
25 53 32.46 6.11
25 50 31.29 5.84
25 53 31.42 5.51
25 53 31.36 5.66
25 50 31.18 5.45
25 52 33.53 6.52
25 52 32.41 6.14
0.153 260 .879
⫺3.007 296 .003
⫺2.112 558 .035
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; F, female; M, male. Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
or R group, and most patients in the R group had normal eating habits 10 to 14 days after surgery.
treated in the R group had 185 impacted M3s classified as Class II, 95 as Class III, 188 classified as Class B, and 92 as Class C. The angulations of these impacted M3s were mesioangular in 104 cases, distoangular in 31 cases, vertical in 94 cases, and horizontal in 51 cases. Surgery with bone removal was done for extraction of these M3s in both the right side (123 M3s) and the left side (157 M3s) (Table 2). In no patient group was there a statistically significant difference in relation to gender (P ⫽ .735), site of surgery (P ⫽ .552), class horizontal space available (P ⫽ .427), class highest portion of the M3 crown (P ⫽ .424), angulations of the teeth (P ⫽ .925), and severity of impaction (P ⫽ .445) (Table 2). The distributions of severity of impaction by gender, site of surgery, and tooth position and angulation showed no significant difference in the 2 patient groups (Table 3). All patients completed the follow-up period with no late mandibular fracture recorded in either the NR
Discussion The removal of M3s is 1 of the most common dentoalveolar surgical procedures.14 In consideration of extraction difficulties, it has been recommended that extractions be done before the age of 25 years.15 A univariate analysis based on removal of 354 mandibular M3s identified increased age as a factor that predicted the surgical difficulty of M3 extractions.16 Other factors ascribed to increased surgical difficulty included bony impaction, depth of tooth within bone, horizontal angulation, proximity to the inferior dental canal, male gender, and obesity.16 A study by Kaminishi et al17 noted an increase in patients over the age of 40 requiring M3 removal. The number increased from 10.5% in 1997 to 17.3% in
Table 2. SUMMARY OF RESULTS AND STATISTICAL ANALYSIS
Gender Group NR group (n ⫽ 280) No. % R group (n ⫽ 280) No. % Significance 2 df P
F
M
Site of Surgery RT
L
Class Horizontal Space Available II
III
Class Highest Portion of M3 Crown B
C
Severity of Impaction
Angulation M*
D
V
H
PB
CB
129 151 130 150 176 104 179 101 110 29 88 53 149 131 46.1 53.9 46.4 53.6 62.9 37.1 63.9 36.1 39.3 10.4 31.4 18.9 53.2 46.8 133 147 123 157 185 47.5 52.5 43.9 56.1 66.1 0.115 1 .735
0.353 1 .552
95 188 33.9 67.1
0.631 1 .427
92 104 31 94 51 158 122 32.9 37.1 11.1 33.6 18.2 56.4 43.6
0.640 1 .424
0.471 3 .925
0.584 1 .445
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; F, female; M, male; RT, right; L, left; M*, mesioangular; D, distoangular; V, vertical; H, horizontal; PB, partial bony; CB, complete bony. Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
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Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; PB, partial bony; CB, complete bony; F, female; M, male; RT, right; L, left; M*, mesioangular; D, distoangular; V, vertical; H, horizontal.
0.584 1 .445 0.001 1 .979 0.231 1 .631 0.087 1 .768 2.528 1 .112 0.584 1 .445 0.763 1 .382 0.989 1 .320 0.584 1 .445 0.090 1 .764 0.075 1 .785 0.584 1 .445 0.075 1 .784
49 45 94 14 17 31 66 38 104 158 122 280 13 79 92 145 43 188 158 122 280 18 77 95 140 45 185 158 122 280 82 75 157 76 47 123 158 122 280
0.829 1 .363
29 22 51
30 23 53 49 39 88 12 17 29 58 52 110 149 131 280 19 82 101 130 49 179 149 131 280 18 86 104 131 45 176 149 131 280 76 74 150 73 57 130 149 131 280
NR group PB 60 89 CB 69 62 Total 129 151 R group PB 73 85 CB 60 62 Total 133 147 Significance 2 1.838 0.038 df 1 1 P .175 .845
0.584 1 .445
158 122 280
149 131 280
Total H V
Angulation
D Mⴱ Total C B Total III F
M
Total
RT
L
Total
II
Class Highest Portion of M3 Crown Class Horizontal Space Available Site of Surgery Gender
Severity of Impaction
Table 3. DISTRIBUTION OF SEVERITY OF IMPACTION BY GENDER, SITE OF SURGERY, AND LOWER THIRD MOLARS’ POSITIONS, AND ANGULATIONS IN THE 2 PATIENT GROUPS (N ⴝ 280 FOR EACH GROUP)
AL-BELASY ET AL
2002. The recent American Association of Oral and Maxillofacial Surgeons (AAOMS) outcome study on age-related M3 treatment supports the fact that oral and maxillofacial surgeons are now able to treat older patients with a low incidence of adverse outcomes.18 However, a consensus of the literature supports the concept that postoperative risks from M3 removal increase with age.19 All risks associated with M3 removal were noted to increase from age under 25, to 25 to 35, to over 35.20 Although rare,3 the risk of postoperative mandibular fractures after M3 impaction surgery may be age related, and 1 study shows a mean age at fracture to be 45 years.6 Concerning depth of impaction, it is not always recommended, unless pathologic conditions such as infection are present, to remove all the deeply impacted M3s and periodic radiographic check up will be good enough.21 Of conventional M3 removals 2% to 4% result in iatrogenic mandibular fracture, but these figures include the lingual plate or alveolus.20 However, conventional surgical removal of a deeply impacted M3 would require massive bone removal to get access to the tooth.21,22 The extensive bone removal required in this case might weaken the mandible and predispose to fracture.5 Late mandibular fractures reported in the literature were related to surgical removal of either partially or fully impacted M3s.1-7 However, it has been reported after removal of fully erupted M3s.23 It occurs usually in the second week after surgery and during chewing with a typical crackling sound.1,3-7,23 This type of fracture was arbitrarily defined by Perry and Goldberg3 as the one occurring any time after the patient has been dismissed from the office or operating room. Therefore, these fractures were considered to be indirectly the result of surgery rather than a direct intraoperative complication. Moreover, this complication was not explained on the basis of improper surgical force, as all events happened postsurgically at home during normal life.6 However, one may argue that segregating a late complication as an indirect result of surgery based on time of occurrence is not always the case. For example, “burning” of the bone as a result of increased frictional heat generated during site preparation is one of the most widely recognized reasons for implant failure.24,25 Interestingly, an unbalanced distribution of late mandibular fracture in the left over the right side was explained by better visualization of an operation site on the right from the normal position of the surgeon during treatment, resulting in less extensive osteotomy.4 Although mastication was the most commonly reported causative factor, late mandibular fracture after M3 removal was also reported after yawning,3 a cry of fear and postextraction osteitis,1 after tooth removal without bone removal,4 and after maxillofacial injury.26
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MASTICATION AND LATE MANDIBULAR FRACTURE AFTER SURGERY OF IMPACTED THIRD MOLARS
Although the enhanced biting force in fully dentate patients may cause enhanced stress to the mandible,4,7 the risk of late mandibular fracture after M3 surgery becomes very great in nonfully calcified mandibles1 or extensively weakened mandibles to the extent that a smaller or weaker strut or cortical shell of bone remains.3 Both yawning and yelling have been reported to cause dislocation of the temporomandibular joint,27-29 and fracture of the styloid process has also been reported after a fit or a yawn.30,31 Although the jaw tightens, the mouth stretches open wide, and the neck muscles clench during a 6-second stint of a yawn,32 and although fear, which is an unpleasant visceral feeling of anxiety, apprehension, or dread may show in a tightened muscle tension, tense mouth, and screaming,33 the trauma inflicted to the mandible by such experiences are so trivial that only the extensively weakened bone might fracture. Fracture of a jawbone associated with no gross pathology without bone removal or the application of force is difficult to understand. Also, postextraction osteitis, unless it has progressed to extensive osteomyelitis, is highly unlikely to lead to fracture at the extraction site of the M3. Postextraction osteitis, even precipitated by the inexperienced surgeon,34 has never been reported to cause late mandibular fracture, and its symptoms, if untreated, will last for about 7 to 14 days35 and may require 4 or more postoperative appointments before resolution.36 Therefore, a probable explanation for the occurrence of such late mandibular fracture is the direct intraoperative risk factors associated with excessive osteotomy and/or excessive force made by improper instrumentation and vigorous elevation of the tooth. In the present study, all impacted M3s were symptomatic and indicated for removal, and in no patient was there jawbone atrophy, tooth ankylosis, or any systemic problem that would impair bone strength. A careful surgical approach was adopted with conservative necessary bone removal and tooth sectioning. In no patient was late mandibular fracture recorded, and those in the R group were leading normal eating habits after pain relief. Although it is expected that clenching, bruxism, and masseter muscle hypertrophy may contribute to the late mandibular fracture after M3 surgery, because these problems may positively affect the bite force,37 7 patients in the R group who had masseter muscle hypertrophy and 11 who had clenching or/and bruxism did not show this. The results of this study seem to support the null hypothesis and indicate that in our set of patients with and without postoperative instructions there was no value in counseling patients or limiting their diet because of the possible risk of late mandibular fracture. These results also show that the risk of late
mandibular fracture was very remote in such patients indicating the need for no special precautions. In conclusion, in patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who have no jawbone atrophy and no systemic problems that may impair bone strength, mastication seems not to affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology. However, adequate surgical expertise is mandatory to ensure careful assessment and technique with good visualization, proper instrumentation, guided force application, and adoption of conservative necessary bone removal and tooth sectioning. The remote possible risk of late mandibular fracture showed in our set of patients with and without instructions indicates the need for no special precautions.
References 1. Libersa P, Roze D, Cachart T, et al: Immediate and late mandibular fractures after third molar removal. J Oral Maxillofac Surg 60:163, 2002 2. Alling CC, Alling RD: Indications for management of impacted teeth, in Alling CC, Helfrick JF, Alling RD (eds): Impacted Teeth. Philadelphia, Saunders, 1993, p 46 3. Perry PA, Goldberg MH: Late mandibular fracture after third molar surgery: A survey of Connecticut oral and maxillofacial surgeons. J Oral Maxillofac Surg 58:858, 2000 4. Wagner KW, Otten JE, Schoen R, et al: Pathological mandibular fractures following third molar removal. Int J Oral Maxillofac Surg 34:722, 2005 5. Iizuka T, Tanner S, Berthold H: Mandibular fractures following third molar extraction. A retrospective clinical and radiological study. Int J Oral Maxillofac Surg 26:338, 1997 6. Krimmel M, Reinert S: Mandibular fracture after third molar removal. J Oral Maxillofac Surg 58:1110, 2000 7. Woldenberg Y, Gatot I, Bodner L: Iatrogenic mandibular fracture associated with third molar removal. Can it be prevented? Med Oral Patol Oral Cir Bucal 12:E70, 2007 8. Amler MH, Johnson PL, Salman I: Histological and histochemical investigation of human alveolar socket healing in undisturbed extraction wounds. J Am Dent Assoc 61:32, 1960 9. Pell GJ, Gregory T: Report on a ten-year study of a tooth division technique for the removal of impacted teeth. Am J Orthod 28:660, 1942 10. Tevepaugh DB, Dodson TB: Are mandibular third molars a risk factor for angle fractures? A retrospective cohort study. J Oral Maxillofac Surg 53:646, 1995 11. Ma’aita J, Alwrikat A: Is the mandibular third molar a risk factor for mandibular angle fracture? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 89:143, 2000 12. Iida S, Hassfeld S, Reuther T, et al: Relationship between the risk of mandibular angle fractures and the status of incompletely erupted mandibular third molar. J Cranio-Maxillofac Surg 33:158, 2005 13. Meisami T, Sojat A, Sandor GK, et al: Impacted third molars and risk of angle fracture. Int J Oral Maxillofac Surg 31:140, 2002 14. Kunkel M, Morbach T, Kleis W, et al: Third molar complications requiring hospitalization. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 102:300, 2006 15. Obiechina AE, Oji C, Fasola AO: Impacted mandibular third molars: Depth of impaction and surgical methods of extraction among Nigerians. Odonto-Stomatologie Tropicale 94:33, 2001 16. Renton T, Smeeton N, McGurk M: Factors predictive of difficulty of mandibular third molar surgery. Br Dent J 190:607, 2001 17. Kaminishi RM, Lam PS, Kaminishi KS, et al: A 10-year comparative study of the incidence of third molar removal in the aging population. J Oral Maxillofac Surg 64:173, 2006
AL-BELASY ET AL 18. Haug RH, Perrot DH, Gonzalez ML, et al: The American Association of Oral and Maxillofacial Surgeons Age-Related Third Molar Study. J Oral Maxillofac Surg 63:1106, 2005 19. The American Association of Oral and Maxillofacial Surgeons. White paper on third molar data: A task force in March 2007. Available at: http://www.aaoms.org/docs/third_molar_white_paper.pdf 20. Bruce RA, Frederickson GC, Small GS: Age of patients and morbidity associated with mandibular third molar surgery. J Am Dent Assoc 101:240, 1980 21. Kwon YD, Ryu DM, Lee B, et al: Separation of the buccal cortical plate for removal of the deeply impacted mandibular molars. Int J Oral Maxillofac Surg 35:180, 2006 22. Jones T, Garg T, Monaghan A: Removal of a deeply impacted mandibular third molar through a sagittal split ramus osteotomy approach. Br J Oral Maxillofac Surg 42:365, 2004 23. Komerik N, Karaduman AI: Mandibular fracture 2 weeks after third molar extraction. Dent Traumatol 22:53, 2006 24. Eriksson AR, Albrektsson T: The effect of heat on bone regeneration: An experimental study in the rabbit using the bone growth chamber. J Oral Maxillofac Surg 42:705, 1984 25. Johns RB, Jemt T, Heath MR, et al: A multicenter study of overdentures supported by Branemark implants. Int J Oral Maxillofac Implants 7:513, 1992 26. Dunstan SP, Sugar AW: Fractures after removal of wisdom teeth. Br J Oral Maxillofac Surg 35:396, 1997 27. Shorey CW, Campbell JH: Dislocation of the temporomandibular joint. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 89:662, 2000
861 28. Tesfaye Y, Lal S: Hazard of yawning. Can Med Assoc J 142:15, 1990 29. Tesfaye Y, Skorzewska A, Lal S: Hazard of yawning. Can Med Assoc J 145:1560, 1991 30. McCorkell SJ: Fracture of an ossified stylohyoid bone. J Trauma 25:1010, 1985 31. McGinnis JM: Fracture of an ossified stylohyoid bone. Arch Otolaryngol 107:460, 1981 32. New Scientist Archive. The big yawn. New Sci Magazine 160: 72, 1998 Available at: http://home.earthlink.net/⬃adamsamy/ PDFs/BigYawn.pdf 33. Givens DB: Center for Nonverbal Studies: Fear. Copyright 1998-2005. Available at: http://members.aol.com/nonverbal2/ fear.htm 34. Sisk AL, Hammer WB, Shelton DW, et al: Complications following removal of impacted third molars: The role of the experience of the surgeon. J Oral Maxillofac Surg 44:855, 1986 35. Laskin DM: Extraction of teeth—Exodontia, in Laskin DM (ed): Oral and Maxillofacial Surgery. St. Louis, Mosby, 1985, p 42 36. Osborn TP, Frederickson G, Small IA, et al: A prospective study of complications related to mandibular third molar surgery. J Oral Maxillofac Surg 43:767, 1985 37. Koole R, Steenks MH, Zonneveld FW, et al: Botulinum toxin type A treatment of cosmetically disturbing masseteric hypertrophy. Ned Tijdschr Geneeskd 142:529, 1998
Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars Associated With No Gross Pathology Fouad A. Al-Belasy, BDS, MSc, PhD,* Sinan Tozoglu, PhD, DDS,† and Umit Ertas, PhD, DDS‡ Purpose: This study was undertaken with the null hypothesis that in patients, fully denate or with 1 or
2 teeth missing and older than 25 years, mastication does not affect late mandibular fracture after surgical removal of impacted third molars (M3s) associated with no gross pathology. Materials and Methods: Five hundred sixty patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who had no gross pathology associated with their impacted lower M3s, were recruited in this study. They were operated on under local anesthesia using a standard technique and randomly assigned into 2 groups for nonroutine (NR group) and routine (R group) postoperative instructions. In the NR group, patients were postoperatively educated in the possibility of mandibular fracture and were given an emphasis on the necessity of limiting mastication to a soft diet for 4 weeks. In the R group, patients were given no such education or emphasis. Patients were followed up for 2 months, and data concerning patients’ age and gender; tooth position, angulation, and depth; date and site of surgery; and occurrence of late mandibular fracture were recorded and statistically analyzed. A value of P less than .05 was considered statistically significant. Results: In no patient group was there a late mandibular fracture recorded. All patients completed the follow-up period, and most of the R group patients had normal eating habits 10 to 14 days after surgery. In no patient group was there a statistically significant difference in relation to gender (P ⫽ .735), site of surgery (P ⫽ .552), class horizontal space available (P ⫽ .427), class highest portion of the M3 crown (P ⫽ .424), angulations of the teeth (P ⫽ .925), and severity of impaction (P ⫽ .445). Conclusions: In patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who have no jawbone atrophy and no systemic problems that may impair bone strength, mastication seems not to affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology. The remote possible risk of the late fracture shown in our patients indicates the need for no special precautions. © 2009 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 67:856-861, 2009 cases. The reason for this severe complication is believed to be multifactorial, and include: patient’s compliance, age, gender, state of dentition, degree of impaction, depth and relative volume of the tooth in bone, associated pathology, operation site, and the surgical technique.1,3-7 Noncompliant, fully dentate patients, particularly those who are older than 25 years and presenting with teeth deeply seated in bone, are at greater risk.1,3-7 Mastication seems to be the main precipitating factor where patients having full dentition are able to produce peak levels of biting forces that can place considerable stress on bone weakened by surgery and not yet fully restored or calcified.1,3-7 The greatest risk period seems to be during postoperative weeks 2 and 3,1,3 during which granulation tissue is being replaced by connective tissue in the extraction site.8 Therefore, it was emphasized that patients
The incidence of late mandibular fracture after surgical removal of impacted third molars (M3s) has been reported as 0.0013%,1 0.0042%,2 and 0.0046%.3 A recent literature search by Wagner et al4 resulted in 94 documented cases, and they added another 17 *Professor of Oral and Maxillofacial Surgery, Dean, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. †Assistant Professor, Department of Oral and Maxillofacial Surgery, Ataturk University Dentistry Faculty, Erzurum, Turkey. ‡Associate Professor, Department of Oral and Maxillofacial Surgery, Ataturk University Dentistry Faculty, Erzurum, Turkey. Address correspondence and reprint requests to Dr Al-Belasy: Department of Oral Surgery, Mansoura University, Mansoura, Dkahlia, Egypt; e-mail: [email protected] © 2009 American Association of Oral and Maxillofacial Surgeons
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should be informed of the desirability of masticatory limiting force for 2 months1 or a soft diet for up to 4 weeks.4,7 This study was undertaken with the null hypothesis that in patients, fully dentate or with 1 or 2 teeth missing and older than 25 years, mastication does not affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology.
Materials and Methods Five hundred sixty patients referred for surgical removal of impacted lower M3s were recruited in this study. Patients, fully dentate or with 1 or 2 teeth missing, were 262 females and 298 males ranging in age from 25 to 53 years with a mean age of 31.23 ⫾ 5.63 years and 32.46 ⫾ 6.11 years, respectively. For all patients a formal case history and clinical and radiographic examinations were performed. No history of medical problems including osteoporosis or metabolic bone disorders was identified in those patients, and their impacted M3s were associated with no gross pathology (eg, an odontogenic cyst or tumor). All patients were asked if they clenched or bruxed their teeth. Masseter muscle hypertrophy, if present, was noted. For all patients, explanations and warnings of the procedure were given and recorded in the case notes, and every patient was requested to sign a consent stating that he or she had been informed of and understood the nature and likely consequences of the procedure. Using panoramic radiographs, M3s positions were analyzed according to the Pell and Gregory9 system. The horizontal space available for M3 was grouped based on the amount of space as measured between the anterior border of the ascending ramus and the posterior border of the second molar as follows: Class I, adequate space available; Class II, inadequate space available; Class III, M3 located all or mostly within the ascending ramus. The vertical space was classified based on the highest portion of the M3 crown as follows: Class A, level at or above the occlusal plane; Class B, between the cementoenamel junction of the adjacent second molar and the occlusal plane; Class C, below the cementoenamel junction. The angulation of the M3, defined as angle of intersection between the long axis of the tooth and the mandibular occlusal plane,10 was classified according to Ma’aita and Alwrikat,11 and Iida et al12 as follows: horizontal: (less than 20°), mesioangular: (20°-80°), vertical: (80°100°), or distoangular: (more than 100°). In addition, the severity of impaction of the M3 was classified as either partial soft tissue, complete soft tissue, partial bony, or complete bony.13 However, only patients included were those with Class II or III, Class B or C,
partial, or complete bony impactions in any of the specified angulations. All patients were operated on under local anesthesia using a standardized surgical bur technique for tooth sectioning and necessary conservative bone removal after effecting an envelope flap extending from the mesial papilla of the lower first molar, around the necks of the teeth to the mid-distal of the lower second molar, and then posteriorly to and laterally up the anterior border of the mandible. To see whether counseling patients or limiting their diet has any value in the possible risk of late mandibular fracture, patients were randomly assigned into 2 groups for nonroutine (NR group) and routine (R group) postoperative instructions. Both NR and R were alternating, beginning with the first entered patient as the NR group. Patients in the NR group were postoperatively educated in the potentiality of mandibular fracture, and were given an unambiguous emphasis on the necessity of limiting mastication to a soft diet for 4 weeks.4,7 The quality of the soft diet was also emphasized.3 Patients in the R group were given no such education or emphasis. Patients were followed up for 2 months. The patients’ age and gender, date and site of surgery, and occurrence of late mandibular fracture were recorded. Then the 2 patient groups were compared for significant differences in age using the Student t test, and for significant differences in gender, site of surgery, tooth position, and angulation as well as severity of impaction using the 2 test. A value of P less than .05 was considered statistically significant.
Results In the NR group, patients were 129 females and 151 males, ranging in age from 25 to 53 years with a mean age of 31.36 ⫾ 5.66 years (females: 31.29 ⫾ 5.84 years; males: 31.42 ⫾ 5.51 years). In the R group, patients were 133 females and 147 males, ranging in age from 25 to 52 years with a mean age of 32.41 ⫾ 6.14 years (females: 31.18 ⫾ 5.45 years; males: 33.53 ⫾ 6.52 years). Concerning age, the R group showed a statistically significant difference (P ⫽ .035) (Table 1). Seven patients in the R group had masseter muscle hypertrophy and 11 had clenching or/and bruxism. No such findings, however, were noted in the NR group of patients. Patients treated in the NR group had 176 impacted M3s classified as Class II, 104 as Class III, 179 classified as Class B, and 101 as Class C. The angulations of these impacted M3s were mesioangular in 110 cases, distoangular in 29 cases, vertical in 88 cases, and horizontal in 53 cases. Surgery with bone removal was done for extraction of these M3s in both the right side (130 M3s) and the left side (150 M3s). Patients
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MASTICATION AND LATE MANDIBULAR FRACTURE AFTER SURGERY OF IMPACTED THIRD MOLARS
Table 1. AGE AND GENDER DISTRIBUTION OF PATIENTS
All Patients Age (yr) Minimum Maximum Mean SD Significance t df P
NR Group
R Group
F (n ⫽ 262)
M (n ⫽ 298)
F (n ⫽ 129)
M (n ⫽ 151)
Total (n ⫽ 280)
F (n ⫽ 133)
M (n ⫽ 147)
Total (n ⫽ 280)
25 50 31.23 5.63
25 53 32.46 6.11
25 50 31.29 5.84
25 53 31.42 5.51
25 53 31.36 5.66
25 50 31.18 5.45
25 52 33.53 6.52
25 52 32.41 6.14
0.153 260 .879
⫺3.007 296 .003
⫺2.112 558 .035
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; F, female; M, male. Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
or R group, and most patients in the R group had normal eating habits 10 to 14 days after surgery.
treated in the R group had 185 impacted M3s classified as Class II, 95 as Class III, 188 classified as Class B, and 92 as Class C. The angulations of these impacted M3s were mesioangular in 104 cases, distoangular in 31 cases, vertical in 94 cases, and horizontal in 51 cases. Surgery with bone removal was done for extraction of these M3s in both the right side (123 M3s) and the left side (157 M3s) (Table 2). In no patient group was there a statistically significant difference in relation to gender (P ⫽ .735), site of surgery (P ⫽ .552), class horizontal space available (P ⫽ .427), class highest portion of the M3 crown (P ⫽ .424), angulations of the teeth (P ⫽ .925), and severity of impaction (P ⫽ .445) (Table 2). The distributions of severity of impaction by gender, site of surgery, and tooth position and angulation showed no significant difference in the 2 patient groups (Table 3). All patients completed the follow-up period with no late mandibular fracture recorded in either the NR
Discussion The removal of M3s is 1 of the most common dentoalveolar surgical procedures.14 In consideration of extraction difficulties, it has been recommended that extractions be done before the age of 25 years.15 A univariate analysis based on removal of 354 mandibular M3s identified increased age as a factor that predicted the surgical difficulty of M3 extractions.16 Other factors ascribed to increased surgical difficulty included bony impaction, depth of tooth within bone, horizontal angulation, proximity to the inferior dental canal, male gender, and obesity.16 A study by Kaminishi et al17 noted an increase in patients over the age of 40 requiring M3 removal. The number increased from 10.5% in 1997 to 17.3% in
Table 2. SUMMARY OF RESULTS AND STATISTICAL ANALYSIS
Gender Group NR group (n ⫽ 280) No. % R group (n ⫽ 280) No. % Significance 2 df P
F
M
Site of Surgery RT
L
Class Horizontal Space Available II
III
Class Highest Portion of M3 Crown B
C
Severity of Impaction
Angulation M*
D
V
H
PB
CB
129 151 130 150 176 104 179 101 110 29 88 53 149 131 46.1 53.9 46.4 53.6 62.9 37.1 63.9 36.1 39.3 10.4 31.4 18.9 53.2 46.8 133 147 123 157 185 47.5 52.5 43.9 56.1 66.1 0.115 1 .735
0.353 1 .552
95 188 33.9 67.1
0.631 1 .427
92 104 31 94 51 158 122 32.9 37.1 11.1 33.6 18.2 56.4 43.6
0.640 1 .424
0.471 3 .925
0.584 1 .445
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; F, female; M, male; RT, right; L, left; M*, mesioangular; D, distoangular; V, vertical; H, horizontal; PB, partial bony; CB, complete bony. Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
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Al-Belasy et al. Mastication and Late Mandibular Fracture After Surgery of Impacted Third Molars. J Oral Maxillofac Surg 2009.
Abbreviations: NR, nonroutine postoperative instructions; R, routine postoperative instructions; PB, partial bony; CB, complete bony; F, female; M, male; RT, right; L, left; M*, mesioangular; D, distoangular; V, vertical; H, horizontal.
0.584 1 .445 0.001 1 .979 0.231 1 .631 0.087 1 .768 2.528 1 .112 0.584 1 .445 0.763 1 .382 0.989 1 .320 0.584 1 .445 0.090 1 .764 0.075 1 .785 0.584 1 .445 0.075 1 .784
49 45 94 14 17 31 66 38 104 158 122 280 13 79 92 145 43 188 158 122 280 18 77 95 140 45 185 158 122 280 82 75 157 76 47 123 158 122 280
0.829 1 .363
29 22 51
30 23 53 49 39 88 12 17 29 58 52 110 149 131 280 19 82 101 130 49 179 149 131 280 18 86 104 131 45 176 149 131 280 76 74 150 73 57 130 149 131 280
NR group PB 60 89 CB 69 62 Total 129 151 R group PB 73 85 CB 60 62 Total 133 147 Significance 2 1.838 0.038 df 1 1 P .175 .845
0.584 1 .445
158 122 280
149 131 280
Total H V
Angulation
D Mⴱ Total C B Total III F
M
Total
RT
L
Total
II
Class Highest Portion of M3 Crown Class Horizontal Space Available Site of Surgery Gender
Severity of Impaction
Table 3. DISTRIBUTION OF SEVERITY OF IMPACTION BY GENDER, SITE OF SURGERY, AND LOWER THIRD MOLARS’ POSITIONS, AND ANGULATIONS IN THE 2 PATIENT GROUPS (N ⴝ 280 FOR EACH GROUP)
AL-BELASY ET AL
2002. The recent American Association of Oral and Maxillofacial Surgeons (AAOMS) outcome study on age-related M3 treatment supports the fact that oral and maxillofacial surgeons are now able to treat older patients with a low incidence of adverse outcomes.18 However, a consensus of the literature supports the concept that postoperative risks from M3 removal increase with age.19 All risks associated with M3 removal were noted to increase from age under 25, to 25 to 35, to over 35.20 Although rare,3 the risk of postoperative mandibular fractures after M3 impaction surgery may be age related, and 1 study shows a mean age at fracture to be 45 years.6 Concerning depth of impaction, it is not always recommended, unless pathologic conditions such as infection are present, to remove all the deeply impacted M3s and periodic radiographic check up will be good enough.21 Of conventional M3 removals 2% to 4% result in iatrogenic mandibular fracture, but these figures include the lingual plate or alveolus.20 However, conventional surgical removal of a deeply impacted M3 would require massive bone removal to get access to the tooth.21,22 The extensive bone removal required in this case might weaken the mandible and predispose to fracture.5 Late mandibular fractures reported in the literature were related to surgical removal of either partially or fully impacted M3s.1-7 However, it has been reported after removal of fully erupted M3s.23 It occurs usually in the second week after surgery and during chewing with a typical crackling sound.1,3-7,23 This type of fracture was arbitrarily defined by Perry and Goldberg3 as the one occurring any time after the patient has been dismissed from the office or operating room. Therefore, these fractures were considered to be indirectly the result of surgery rather than a direct intraoperative complication. Moreover, this complication was not explained on the basis of improper surgical force, as all events happened postsurgically at home during normal life.6 However, one may argue that segregating a late complication as an indirect result of surgery based on time of occurrence is not always the case. For example, “burning” of the bone as a result of increased frictional heat generated during site preparation is one of the most widely recognized reasons for implant failure.24,25 Interestingly, an unbalanced distribution of late mandibular fracture in the left over the right side was explained by better visualization of an operation site on the right from the normal position of the surgeon during treatment, resulting in less extensive osteotomy.4 Although mastication was the most commonly reported causative factor, late mandibular fracture after M3 removal was also reported after yawning,3 a cry of fear and postextraction osteitis,1 after tooth removal without bone removal,4 and after maxillofacial injury.26
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MASTICATION AND LATE MANDIBULAR FRACTURE AFTER SURGERY OF IMPACTED THIRD MOLARS
Although the enhanced biting force in fully dentate patients may cause enhanced stress to the mandible,4,7 the risk of late mandibular fracture after M3 surgery becomes very great in nonfully calcified mandibles1 or extensively weakened mandibles to the extent that a smaller or weaker strut or cortical shell of bone remains.3 Both yawning and yelling have been reported to cause dislocation of the temporomandibular joint,27-29 and fracture of the styloid process has also been reported after a fit or a yawn.30,31 Although the jaw tightens, the mouth stretches open wide, and the neck muscles clench during a 6-second stint of a yawn,32 and although fear, which is an unpleasant visceral feeling of anxiety, apprehension, or dread may show in a tightened muscle tension, tense mouth, and screaming,33 the trauma inflicted to the mandible by such experiences are so trivial that only the extensively weakened bone might fracture. Fracture of a jawbone associated with no gross pathology without bone removal or the application of force is difficult to understand. Also, postextraction osteitis, unless it has progressed to extensive osteomyelitis, is highly unlikely to lead to fracture at the extraction site of the M3. Postextraction osteitis, even precipitated by the inexperienced surgeon,34 has never been reported to cause late mandibular fracture, and its symptoms, if untreated, will last for about 7 to 14 days35 and may require 4 or more postoperative appointments before resolution.36 Therefore, a probable explanation for the occurrence of such late mandibular fracture is the direct intraoperative risk factors associated with excessive osteotomy and/or excessive force made by improper instrumentation and vigorous elevation of the tooth. In the present study, all impacted M3s were symptomatic and indicated for removal, and in no patient was there jawbone atrophy, tooth ankylosis, or any systemic problem that would impair bone strength. A careful surgical approach was adopted with conservative necessary bone removal and tooth sectioning. In no patient was late mandibular fracture recorded, and those in the R group were leading normal eating habits after pain relief. Although it is expected that clenching, bruxism, and masseter muscle hypertrophy may contribute to the late mandibular fracture after M3 surgery, because these problems may positively affect the bite force,37 7 patients in the R group who had masseter muscle hypertrophy and 11 who had clenching or/and bruxism did not show this. The results of this study seem to support the null hypothesis and indicate that in our set of patients with and without postoperative instructions there was no value in counseling patients or limiting their diet because of the possible risk of late mandibular fracture. These results also show that the risk of late
mandibular fracture was very remote in such patients indicating the need for no special precautions. In conclusion, in patients, fully dentate or with 1 or 2 teeth missing and older than 25 years who have no jawbone atrophy and no systemic problems that may impair bone strength, mastication seems not to affect late mandibular fracture after surgical removal of impacted M3s associated with no gross pathology. However, adequate surgical expertise is mandatory to ensure careful assessment and technique with good visualization, proper instrumentation, guided force application, and adoption of conservative necessary bone removal and tooth sectioning. The remote possible risk of late mandibular fracture showed in our set of patients with and without instructions indicates the need for no special precautions.
References 1. Libersa P, Roze D, Cachart T, et al: Immediate and late mandibular fractures after third molar removal. J Oral Maxillofac Surg 60:163, 2002 2. Alling CC, Alling RD: Indications for management of impacted teeth, in Alling CC, Helfrick JF, Alling RD (eds): Impacted Teeth. Philadelphia, Saunders, 1993, p 46 3. Perry PA, Goldberg MH: Late mandibular fracture after third molar surgery: A survey of Connecticut oral and maxillofacial surgeons. J Oral Maxillofac Surg 58:858, 2000 4. Wagner KW, Otten JE, Schoen R, et al: Pathological mandibular fractures following third molar removal. Int J Oral Maxillofac Surg 34:722, 2005 5. Iizuka T, Tanner S, Berthold H: Mandibular fractures following third molar extraction. A retrospective clinical and radiological study. Int J Oral Maxillofac Surg 26:338, 1997 6. Krimmel M, Reinert S: Mandibular fracture after third molar removal. J Oral Maxillofac Surg 58:1110, 2000 7. Woldenberg Y, Gatot I, Bodner L: Iatrogenic mandibular fracture associated with third molar removal. Can it be prevented? Med Oral Patol Oral Cir Bucal 12:E70, 2007 8. Amler MH, Johnson PL, Salman I: Histological and histochemical investigation of human alveolar socket healing in undisturbed extraction wounds. J Am Dent Assoc 61:32, 1960 9. Pell GJ, Gregory T: Report on a ten-year study of a tooth division technique for the removal of impacted teeth. Am J Orthod 28:660, 1942 10. Tevepaugh DB, Dodson TB: Are mandibular third molars a risk factor for angle fractures? A retrospective cohort study. J Oral Maxillofac Surg 53:646, 1995 11. Ma’aita J, Alwrikat A: Is the mandibular third molar a risk factor for mandibular angle fracture? Oral Surg Oral Med Oral Pathol Oral Radiol Endod 89:143, 2000 12. Iida S, Hassfeld S, Reuther T, et al: Relationship between the risk of mandibular angle fractures and the status of incompletely erupted mandibular third molar. J Cranio-Maxillofac Surg 33:158, 2005 13. Meisami T, Sojat A, Sandor GK, et al: Impacted third molars and risk of angle fracture. Int J Oral Maxillofac Surg 31:140, 2002 14. Kunkel M, Morbach T, Kleis W, et al: Third molar complications requiring hospitalization. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 102:300, 2006 15. Obiechina AE, Oji C, Fasola AO: Impacted mandibular third molars: Depth of impaction and surgical methods of extraction among Nigerians. Odonto-Stomatologie Tropicale 94:33, 2001 16. Renton T, Smeeton N, McGurk M: Factors predictive of difficulty of mandibular third molar surgery. Br Dent J 190:607, 2001 17. Kaminishi RM, Lam PS, Kaminishi KS, et al: A 10-year comparative study of the incidence of third molar removal in the aging population. J Oral Maxillofac Surg 64:173, 2006
AL-BELASY ET AL 18. Haug RH, Perrot DH, Gonzalez ML, et al: The American Association of Oral and Maxillofacial Surgeons Age-Related Third Molar Study. J Oral Maxillofac Surg 63:1106, 2005 19. The American Association of Oral and Maxillofacial Surgeons. White paper on third molar data: A task force in March 2007. Available at: http://www.aaoms.org/docs/third_molar_white_paper.pdf 20. Bruce RA, Frederickson GC, Small GS: Age of patients and morbidity associated with mandibular third molar surgery. J Am Dent Assoc 101:240, 1980 21. Kwon YD, Ryu DM, Lee B, et al: Separation of the buccal cortical plate for removal of the deeply impacted mandibular molars. Int J Oral Maxillofac Surg 35:180, 2006 22. Jones T, Garg T, Monaghan A: Removal of a deeply impacted mandibular third molar through a sagittal split ramus osteotomy approach. Br J Oral Maxillofac Surg 42:365, 2004 23. Komerik N, Karaduman AI: Mandibular fracture 2 weeks after third molar extraction. Dent Traumatol 22:53, 2006 24. Eriksson AR, Albrektsson T: The effect of heat on bone regeneration: An experimental study in the rabbit using the bone growth chamber. J Oral Maxillofac Surg 42:705, 1984 25. Johns RB, Jemt T, Heath MR, et al: A multicenter study of overdentures supported by Branemark implants. Int J Oral Maxillofac Implants 7:513, 1992 26. Dunstan SP, Sugar AW: Fractures after removal of wisdom teeth. Br J Oral Maxillofac Surg 35:396, 1997 27. Shorey CW, Campbell JH: Dislocation of the temporomandibular joint. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 89:662, 2000
861 28. Tesfaye Y, Lal S: Hazard of yawning. Can Med Assoc J 142:15, 1990 29. Tesfaye Y, Skorzewska A, Lal S: Hazard of yawning. Can Med Assoc J 145:1560, 1991 30. McCorkell SJ: Fracture of an ossified stylohyoid bone. J Trauma 25:1010, 1985 31. McGinnis JM: Fracture of an ossified stylohyoid bone. Arch Otolaryngol 107:460, 1981 32. New Scientist Archive. The big yawn. New Sci Magazine 160: 72, 1998 Available at: http://home.earthlink.net/⬃adamsamy/ PDFs/BigYawn.pdf 33. Givens DB: Center for Nonverbal Studies: Fear. Copyright 1998-2005. Available at: http://members.aol.com/nonverbal2/ fear.htm 34. Sisk AL, Hammer WB, Shelton DW, et al: Complications following removal of impacted third molars: The role of the experience of the surgeon. J Oral Maxillofac Surg 44:855, 1986 35. Laskin DM: Extraction of teeth—Exodontia, in Laskin DM (ed): Oral and Maxillofacial Surgery. St. Louis, Mosby, 1985, p 42 36. Osborn TP, Frederickson G, Small IA, et al: A prospective study of complications related to mandibular third molar surgery. J Oral Maxillofac Surg 43:767, 1985 37. Koole R, Steenks MH, Zonneveld FW, et al: Botulinum toxin type A treatment of cosmetically disturbing masseteric hypertrophy. Ned Tijdschr Geneeskd 142:529, 1998