Biomechanical association of dental and temporomandibular pathology in a medieval Nubian population.код для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 85~201-205 (1991) Biomechanical Association of Dental and Temporomandibular Pathology in a Medieval Nubian Population SUSAN G. SHERIDAN, DIANE M. MITTLER, DENNIS P. VAN GERVEN, AND HERBERT H. COVERT Department of Anthropology, University of Colorado, Boulder, Colorado 80309 KEY WORDS Temporomandibular joint, Biomechanics, Tooth loss, Dental pathology ABSTRACT An analysis of the relationship between oral pathology and degenerative change at the temporomandibular joint (TMJ) was undertaken on an archaeological sample of 122 adult crania from the Medieval site of Kulubnarti in Sudanese Nubia. The crania were sorted into 2 groups: those demonstrating clearly visible bony changes at the joint (TMJ+1 and those without visible change (TMJ- 1. These groups were compared according to 1) age; 2) sex; 3) active dental pathologies (abscesses, caries, partial socket resorption); 4) tooth loss with complete socket resorption; and 5) dental attrition. No statistically significant association was evident between degenerative change at the TMJ and age, active dental pathologes, or dental attrition; however, sex differences and posterior tooth loss with complete socket resorption revealed a significant correspondence to degenerative TMJ changes. Both of these factors agree with the clinical literature and with biomechanical models (most notably that of Hylander) based upon modern populations. Furthermore, the results support the contention that paleopathological conditions can be analyzed from a clinical and functional biomechanical perspective. Interest in disorders of the temporomandibular joint (TMJ) has mainly focused on the clinical and biomechanical as ects of this joint. A rapid rise in these disor ers among modern populations has attracted much clinical attention, while biomechanical research has concentrated on the functional role of the mandible and associated musculature in mastication. It has been estimated that between 5080% of the American public suffers from some form of TMJ dysfunction (Gerschman and Reade, 1988; Lewis, 1988).This range in estimates reflects a continuin lack of systematic methodology for the de inition, diagnosis, and treatment of such conditions (Weinber 1987). Biomeckanical considerations have focused extensive1 on the relationship between the mandi le and temporal bone durin mastication, and have led to considerable de ate as to whether the mandible functions as a lever (Hylander, 1975; Picq et al., 19871, rt B 8 a link (Robinson, 1946;Taylor, 19861,or both (Gingerich, 1979). Hylander (1975) provided a detailed description of this debate and argued strongly in favor of the lever hypothesis. The lever-action model has important implications for clinical research due to its predictive value (Fig. 1).According to this model, TMJ reaction forces are ordinarily larger on the balancing side than on the workin side (where the bite force is exerted). f 3 ecause individuals with dental pathologies (such as abscesses and caries) on one side of the mouth preferentially chew on the o posite (healthy) side, the lever-action mode predicts that in these individuals the masticatory forces should ass mostly through the teeth on the heaghy side and through the condyle on the diseased side. The reverse should occur if there is unilat- P % @ 1991 WILEY-LISS. INC Received January 18,1990;accepted November 13,1990. 202 S.G. SHERIDAN ET AL Y While Hylander’s model has apparent utility in explaining morphological variation in archaeological PO ulations, its utility for the analysis of bony $MJ changes in such populations has yet to be determined. Indeed, althou h degenerative joint changes in the appenficular and axial skeleton have been of FORCE considerable interest to paleopathologists, the TMJ has received little attention in spite of the clinical interest and biomechanical modeling available. Reasons for this lack of attention no doubt include the fact that archaeological remains only provide a partial BITE FORCE / record of TMJ disease, and as Bell (1986) stated, “mastication involves many structures-bones, joints, muscles, teeth, glands, Fig. 1. Bite forces in Hylander’s lever-action model. nerves of different types, blood vessels . . .”. (Adapted from Hylander, 1975). Studying one portion in isolation from the others can prove difficult. In addition, ancient populations fre uently ex erienced a magnitude of dental isease an associated tooth loss during life far in excess of that era1 disease in the TMJ rather than the anticipated by most biomechanical models teeth; that is, masticatory forces should pass (Armelagos, 1968; Bergman and Hansson, primarily through the teeth on the side with 1979; Brothwell, 1972). the diseased joint, but through the condyle Therefore, an examination of the cranial on the healthy side. Both these adaptations remains from a Medieval Nubian population serve to reduce pain during mastication; was undertaken to determine the presence however, they result in as mmetrical stress and extent of degenerative bony changes in on the TMJ, and may lea to eventual joint the TMJ, and to assess the relationshi between dental disease, tooth loss and MJ de eneration. fn addition to lefthight asymmetry, poste- degeneration in light of the lever-action rior (molar) tooth loss has been observed to model. Excellent preservation of complete contribute to TMJ degeneration in living crania and dentitions make this an ideal populations. With the loss of posterior teeth, population for study. High rates of dental the frequency of anterior (incisal) biting and wear during life resulted in rapid and early associated joint loading increases. Hylander antemortem tooth loss, particularly in the (1978) has demonstrated that the mandible posterior dentition. This population thereacts symmetrically as a lever during incisal fore, provides an excellent Sam le for a debiting and asymmetrical1 during molar bit- termination of the extent to w ich a wide ing. It is to be ex ected t at abnormal joint divergence from a healthy dental arcade conforces such as t ose produced by severe forms to Hylander’s predicted association asymmetric lefthight molar chewing or ex- between chewing patterns, joint forces and cessive anterior chewing may lead to tissue TMJ changes. remodeling and subsequent degeneration in MATERIALS AND METHODS the TMJ (Bell, 1986; Faulkner et al., 1985). The relationshi between TMJ mor holThe skeletal population used in this study ogy and anterior ite forces has also een was excavated by the third author in 1979 examined from an evolutionary pers ective. from the site of Kulubnarti in Northern Hinton and Carlson (1979) observe a sub- Sudan. Kulubnarti is located in a region stantial size reduction in the glenoid fossa called the Batn et Hajar (“belly of rock), an and mandibular condyle in ancient Nubian area described by Adams (1977, .26)as “the opulations excavated near Wadi Halfa. most barren and forbidding o all Nubian !his pattern of decreased joint size from environments.” Subsistence in this re ion Mesolithic through Christian times was in- was marginal, even with low population enter reted as a res onse to facial reduction, sities. The ancient inhabitants of this area, re uced anterior ite forces, and reduced like their modern counterparts, existed as reaction forces in the TMJ. sedentary agriculturalists practicing small 3 a B K !i R K \ \ 8 P cf g 5 RIOMECHANICAL ASSOCIATION OF DENTAL AND TEMPOROMANDIBULAR PATHOLOGY scale farming along the banks of the Nile (Carlson et al., 1974).The principal cultigens were cereal grains, including millet and sorghum. Milling, combined with the blowing sands of the Nubian Sahara, led to gritty contamination of foodstuffs. This resulted in a rapid rate of toothwear, a hi h fre uency of apical abscess, and tooth loss y mi life. Two cemeteries were excavated at Kulubnarti yielding a total of 418 individuals, representing both sexes and ages ranging from 5 months in utero to 51+ years. Preservation of the remains was remarkable. Many were naturally mummified due to the exceptionally dry climate; annual rainfall averages less than a millimeter per year. The earliest of the cemeteries is dated from early Christian times (c. 550-750 A.D.), the other from the remainder of the Christian era (c. 7501500 A.D.). The sample selected for the present study consisted of 122 adult (18 to 51-t years) crania from the combined Kulubnarti cemeteries. Subadults were excluded from the present analysis due to a lack of observable TMJ change and in order to avoid the complicatin factor of dental eruption. Fol owing sample selection, a systematic macroscopic examination of the crania was undertaken to determine those individuals with clearly visible de enerative changes in the temporomandibu ar region (Fig. 2). Those demonstrating significant porosity of the articular eminence and/or bony exostoses in the TMJ were labeled as TMJ+. Due to the multicausality of such disorders, no attempt was made to determine the etiology of the problems in this category (Gerschman and Reade, 1988). Those displaying no evidence of joint change were classified as the TMJ- group. Dental pathology, degree of socket resorption, and dental attrition were also examined. Dental athologies (caries, abscesses) were recorde per tooth for each individual. Socket resorption was classified as either partial or com lete and recorded for each tooth. Degree o tooth wear was scored using rocedures described by Smith (1984). mith’s method was selected because it allowed inclusion of the anterior dentition and provided an eight-step method of seriation. Subjects were categorized according to 1) age; 2) sex; 3) active dental pathologies at time of death including caries, abscesses, and partially resorbed sockets; 4) complete socket resorption; and 5)tooth wear. Age and sex for all individuals were previously estab- 203 $3. f P B f! E Fig. 2. Example of degenerative bony changes in the TMJ+ group. lished by Van Gerven et al. (1981) using multiple criteria. Mean number of cavities, abscesses, and partially and completely resorbed sockets per individual were calculated for those in the TMJ+ and TMJ- groups. Mean stage of tooth wear was also calculated and compared for these two groups. RightAeft wear asymmetry was determined by taking the absolute difference between the wear scores for left and right tooth antimeres. Variance was also computed for each group. RESULTS AND DISCUSSION As indicated in Table 1, of the 122 adult crania examined, 17 were classified as TMJ+, 105 as TMJ-. Comparison of the two groups by age using Student’s t revealed no statistically significant differences (Table 2). Mean age at death for the TMJ+ (34 yrs) and TMJ- (35 yrs) individuals differed by less than a year. However, small sample size may have contributed to this lack of association. Indeed, when grouped by decade, 50% of the TMJ+ individuals fell in the 40-51+ age group, suggesting a possible age effect. There was no significant difference in the roportion of females to males in the !MJ- group. However, in the T M J t grou the ancient Nubians conformed to the mo,: ern clinical pattern. As with moderns, Nubian females outnumbered males (x’ = 2.88; one tailed, P < 0.05). Indeed, the near 3:l Nubian ratio approximates the modern clinical female-to-male ratio of 4:l (Gerschman and Reade, 1988). Analysis of active dental pathologies revealed that members of the TMJ+ group 204 S.G. SHERIDAN ET AL. TABLE 1. Association of sex and condition of TMJ TMJ+ = subjects with TMJ degeneration and TMJ- indicates those without bonv degeneration Sex TMJ- TMJ+ Male n 50 47.6 55 29.4* 12 70.6* 55 52.4 67 5 sil Female n w1 Total in) Total (n) 17 105 *Significant using the chi-square test at P 122 < 0.05 demonstrated fewer abscesses (0.241 individual) and carious lesions (0.71/ individual) compared to their TMJ- counter arts (0.79 and 1.39 respectively), the dif erences were not statistically significant. Mean number of partially resorbed sockets was highest in the TMJ+ group (2.88 compared to 2.27). However, overall, the number of active pathologies remained highest with the TMJ- individuals (4.45 vs. 3.82).This is not sur rising given the expected delay between isruption in mastication and resultant bony chan es at the TMJ. f in mastication was Long-term C isruption assessed using complete socket resorption as a measure of protracted tooth loss prior to death. The analysis proved highly significant at P < 0.01 using Student’s t. TMJ+ individuals displa ed nearly two times as many resorbed soc ets (10.24/individual) as the TMJ- group (5.46hndividual). Of the 10.24totally resorbed sockets per individual, 80% were associated with the posterior dentition. This highly significant association between posterior tooth loss and disorders of the TMJ conformed to predictions based upon current clinical literature which lists such tooth loss as a major contributor to TMJ disorders (Bergman and Hansson, 1979; Christensen and Ziebert, 1986; Faulkner et al., 1987; Furstman, 1965; Granados, 1979; Hatjigiorgis et al., 1987; Weinberg, 1987). Anal sis of tooth loss produced patterns of sex dif erence and anteriorJposterior loading consistent with the clinical and biomechanical literature (most notabl Hylander 1975, 1978);however, analysis o tooth wear as an indicator of lefthight asymmetry, was less successful. Based on Hylander’s model one would expect to find evidence of preferential chewing in the TMJ+ group on the same side as the disorder. No such trend was evident. TABLES. Betweengroupcomparisons of agp,sex, active dental pathologies, complete socket resorption, and tooth wear for subjects with TMJ degeneration ( T M J I ) and those without (TMJ-I Variables x Age i w 9 x Total active pathologies U Number of partially resorbed sockets i Number of apical abscesses Number of carious lesions % Number of completely resorbed sockets X Dental attrition F L/R differences (average of all antimeres) Variance of L/R difference scores Samole size *Significant using the t-test a t P TMJt 34 TMJ- 2.88 35 4.45 2.27 0.24 0.71 0.79 1.39 3.82 10.24% 5.16 0.87 0.72 17 5.46% 4.97 0.73 0.46 105 < 0.01 f B i P F Analysis of 1eftJright differences in wear using Smiths 8-stage system produced no corres ondence between wear asymmetry and T& degeneration. Mean stage of wear for the TMJ+ group was 5.16,4.97for the TMJindividuals. The avera e difference between wear on the left and rig t sides was less than one stage in Smith‘s system for the TMJ+ group (0.87), as well as the TMJ- group 10.73).Asymmetry was also assessed by computing variance values from the TMJ+ and TMJ- groups. While the TMJ+ variance was larger (0.72 vs. 0.46), the values were not significant at the 95% confidence level. In summary, while the present analysis failed to demonstrate a significant association between degenerative changes in the TMJ and active dental pathology or 1eftJright chewing asymmetry, sex differences, and posterior tooth loss revealed a significant correspondence to bon TMJ degeneration. Age differences also s owed a strongly related trend, although not significant at the 95% confidence level. These associations were highly consistent with the clinical literature, as well as Hylander’s lever hypothesis. Furthermore, the results support the contention that aleopathological conditions can be analyze from a clinical and functional, biomechanical perspective. a i 1 CONCLUSIONS 1. Of the 122 Nubian crania examined, 13.9% demonstrated degenerative changes in the temporomandibular joint. 2. A trend toward increased degeneration with increased age was evident, with 50% of BIOMECHANICAL ASSOCIATION OF DENTAL AND TEMPOROMANDIBULAR PATHOLOGY the TMJ+ individuals aged 40 to 51-t. The results were, however, insignificant at P > 0.05. 3. Sex differences related to TMJ degeneration corresponded to the modern pattern. There were more Nubian female sufferers than males; this agrees with current clinical of a greater female-to-rnale ratio (Gerschrnan and Reade, 1988; et al., 1987). 4.Active dental pathologies, as indicators of more recent disease events, showed no significant relationship to degenerative changes in the TMJ. 5. Total resorption of the alveolar bone was much more prevalent in the TMJ+ individusocket Such tooth loss with resorption illdicated a longer history of oral disease. 6. In the TMJ+ group, 80% of the cornpletely resorbed sockets occurred in the pasterior dentition. 7. ~ ~of dental~attrition l provided ~ no evidence for preferential left/right chewing among TMJ sufferers. These results indicate a highly significant association between long term tooth loss and disoders of the TMJ. This agrees with the current clinical literature which lists loss of occlusion as a major contributor to such disorders (Bergman and Hansoon, 1979. Christensen and ziebert, 1986; Fau]kne; et 1987; Granados, 1979; Hatjigiorgis et a]., 1987; Weinberg, 1987). It ap ears that within this population extensive oss of posterjor teeth and subsequent anterior chewing was the principal factorin degeneration of the TMJ. Posterior loss led to increased loading at the TMJ, resulting in degenerative changes in the joint. The clear associatjon between a shift in bite force from the molars to the incisorsin the TMJ+ group is if the is as a lever (Chrktensen viewed as P ACKNOWLEDGMENTS This research was partially funded by NSF grant N ~ 9077-5-535~. . we wish to thank Drs. Matt Cartmill and William Hylander, as well as the anonymous reviewers, for their extremely useful comments and suggestions. LITERATURE CITED Adams WY (1977) Nubia: Corridor to Africa, London: Allen Lane. 205 ArmelagosGJ (1968)Paleopathology of three Archeological Populations From Sudanese Nubia. (Ph.D.Thesis, University of Colorado, Boulder). Bell WE (1986)Temporomandibular Disorders: Classification, Diagnosis, Management. 2nd Edition. Chicago: Yearbook Medical Pub. Bergman L-E, and Hansson T 11979) Hard tissue chan es of the temporomandibular joint in an archeoosteofogical material from the 11th century. Swed. Dent. J. 3:149-155. Brothwell DRl1972) Digging Up Bones: The Excavation, Treatment, and Study of Human Skeletal Remains. 2nd Edition. London: British Museum of Natural History. Carlson DS, Armelagos GJ, and Van Gerven DP (1974) Factors influencing the etiology of cribra orbitalia in prehistoric Nubia. J. Human Evol. 3:405-410. Christensen LV, and Ziebert GJ (1986)Effects of experimental loss of teeth on the temporomandibular joint. J. Oral Rehabil. 13:587-598. Faulkner MG, Hatcher DC, and Hay A (1987) A 3D investigation of TMJ loading, J. Biomech. 20:9971002. FurstmanLl1965)Theeffectoflossofocclusionuponthe mandibular joint. Am. J. Orthodontics. 51245-261, Gerschman JA, and Reade PC (19881 Disorders of the related structures. Aus~ temporomandibular i ~joint and tralian Family Physician. 17:239-244. Gingerich PD (1979)The human mandible: lever, link, or both?Am. J. Phys. Anthrop. 51:135-138. Granados J I (1979)The influence of the loss of teeth and attrition on the articular eminence. J. Prosthet. Dent. 42: 78-84. Hatjigiorgis CG, Grisius RJ, Fenster RK, and Neff PA (1987)Atomographic study ofthe temporomandibular joint ofedentulous patients. J. Prosthet. Dent. 57:354358. Hinton RJ, and Carlson DS (1979)Temporal changes in human temporomandibular joint size and shape. Am. J. Phys. Anthrop. 50:325-334. Hylander WL (1975)Thehuman mandible: lever or link? Am, J. Phys. Anthrop. 43:227-242. Hylander WL (1978)Incisal bite force direction in humans and the functional significance of mammalian mandibular translation. Am. J. Phys. Anthrop. 48:l8. Lewis T (1988)Temporomandibular joint disorders. Radiologic Technology, 59:351-352. Meng HP, Dibbets JMH, Van Der WeeleLT, and Boering G (1987) Symptoms of temporomandibular joint dysfunction and predisposing factors. J. Prosthet. Dent. 57:215-222. Picq PG, Plavcan JM, and Hylander W (1987)Nonlever action of the mandible: the return of the hydra. Am. J. Phys. Anthrop. 74:305-307. Robinson AB (1946)The temporomandibular joint: Theory of reflex controlled nonlever action of the mandible. J. of the Am. Dent. Assoc. 33:1260-1271. Smith BH (1984) Patterns of molar wear in huntergatherers and agriculturalists. Am. J. Phys. Anthrop. 63:39-56, Taylor RMS (1986)Nonlever action ofthe mandible. Am. J. Phys. Anthrop. 70:417-421. Van Gerven DP, Sanford MK, and Hummert J R 11981) Mortality and culture “change” in Nubia’s Batn el Hajar. J. Human Evol. 10:395-408. Weinberg LA (1987)Aconceptual overview of TMJ pain. NYS Dent. J. 53:18-24.