Anterior_Guidance_Canine_guidance_and_group_function

SWJTTON

EDITOR

Anterior literature

guidance: review

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function/canine

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Linda J. Thornton, D.D.S.* U.S. Army Dental Activity, Fort Sam Houston, Texas Anterior guidance, which can be categorized as group function or canine guidance, is essential for esthetics, phonetics, and mastication.

This article reviews the historical development and philosophies of both occlusal schemes. There is no scientific evidence that supports one occlusal scheme over the other. Where anterior guidance must be reestablished or where it changes, there currently appear to be more authorities who favor canine guidance over group function.

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nterior guidance is essential to a harmonious functional relationship in the natural dentition and is critical to a functional occlusion. Schuyler’* 2 emphasized the importance of anterior guidance over condylar guidance.

He observed that anterior guidance was controlled by an unyielding consistent tooth-to-tooth contact, whereas condylar guidance varied due to the flexibility of the joint.

Anterior guidance can be categorized into two occlusal schemes. These are group function and canine guidance.

Canine guidance is also known as canine-protected occlusion, mutually protected occlusion, canine disclusion, canine-lift, and canine rise. This article reviews the history and current relevance of the theoretical background for anterior guidance.

HISTORY Although these occlusal guidance systems are clearly divergent in both philosophy and technique, they both appear to have evolved from the common roots of bilateral balanced occlusion. Group function appears to have been the direct descendent of the balanced occlusion theory.3 This theory was conceived from Von Spee’s observations of the condylar path, which stated that “the course of movements which serve to grind food is determined not only by the mechanical configuration of the temporomandibular joint but is also very substantially affected by the occlusal anatomy of the teeth. Accordingly both are fitted to each other in a harmonious manner.“4 Advocates of balanced occlusion refer to this observation as the doctrine from which the theory germinated.3 The balanced occlusion

Presented before the National Capital Area Section of the American College of Prosthodontists, Washington, D.C. *Lieutenant Colonel, U.S. Army, DC; Fixed Prosthodontic Service.

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theory was based on Von Spee’s observations and on early research pioneered by such investigators as Christensen,5 Gysi,6 Monson,’ and Hal1.8 In the 1950’s Stuart,g-12 Stallard,g* l1 and McCollumlo originally advocated the use of balanced occlusion as the key to obtaining a harmonious relationship between condylar guidance and the occlusal surfaces of the teeth during all functional excursions. These clinicians later abandoned balanced occlusion in the natural dentition due to clinical failures.13-l5 Grangerr6* l7 defended the use of this theory in the natural dentition as well as in complete dentures. He observed that a true balanced occlusion maintained the entire dentition in a state of functional equilibrium.

GROUP FUNCTION The literature credits Schuyler18-20 with enlightening clinicians as to the destructive forces associated with balanced contacts. He observed that even though these contacts were essential for stability of complete dentures, they were traumatic to the natural dentition, causing temporomandibular joint (TMJ) dysfunction, periodontal involvement, or excessive wear. As a result of research conducted

by Schuyler and other investigators,21-2” balanced occlusion was replaced with unilateral balanced occlusion or group function.

The group function philosophy appears to be one of physiologic wear. Schuylerz4 and other advocates of group function25-27 viewed occlusal wear as a compensatory adaptive change that distributed stress to create a normal functional relationship.

Several authors28”’ have suggested that occlusal wear was natural and beneficial. Moser332deduced “it was nature’s plan for the cusps to wear in a particular and beneficial manner which is related to the vigorous function that primitive man was believed to have exhibited. This wear was an inevitable accompaniment of well-developed and well-sustained dentitions.“32 Beyron33 conducted a serial investigation of the progressive occlusal

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changes in the natural dentition. He demonstrated that group function was conducive to occlusal wear, and was capable of allowing an even distribution of stress. As the natural dentition matured, normal occlusal wear progressed, which maintained the teeth in a balanced state. It is indeed ironic that the findings of canine guidance advocates, for example, Scaife and Holt, 34 demonstrating that the percentage of patients with wear facets increased in direct proportion to the degree of group function, actually provided evidence to reinforce the theory of group function.

Several investigators35*38 questioned the efficacy of canine guidance. Schuyler,35 who was in the vanguard of the group function advocates, commented: “Why place all of the stress upon the cuspid? At all times when the prominence of cuspid teeth preclude contact of all the other teeth in eccentric positions, functional efficiency, comfort and the most desirable or favorable distribution of functional force to the periodontium is negated.“35 Lucia,36 an advocate of canine guidance, queried: “What happens to the proprioceptive protection if the cuspids are missing, badly broken down, or periodontally involved?“36 In order for canine-protected occlusion to function, the anterior teeth must be healthy; otherwise a balanced type of occlusion was necessary. Weinberg37 questioned whether the “strategic location” of the canines away from the fulcrum was effective in reducing the compression to the TMJ. He illustrated in canine guidance that the TMJ was capable of superior displacement and compression due to unsupported posterior muscle force. Alexander38 suggestedthere was no clinical, biologic, or histologic evidence supporting a “protective mechanism” associated with canine teeth. Tooth mobility would occur when the functional forces exceeded the physiologic limits of the periodontium of any tooth.

Whether physiologic tooth movement was greater during group function or canine guidance is still debatable. O’Leary et a1.,3gobserving the mean mobility of teeth, discovered that the canines approached a more physiologic function with group function vis-a-vis canine guidance. The reason for this phenomenon was discovered by DiPietro,40 who categorized canine guidance as being associated with a low-degree Frankfort mandibular angle (FMA) and an increased biting force, while group function was associated with a high-degree FMA and a decreased biting force.

The philosophy advocated by Schuyler was incorporated with those of Pankey and Mann to form a concept of treatment known as the Pankey-Mann-Schuyler philosophy for complete occlusal rehabilitation29 41 Since its conception, the objective of this philosophy has been to achieve the principles of occlusion developed by Schuyler, which include maximum contact of the teeth in centric relation; simultaneous contact of the anterior and posterior teeth on the working side during lateral excursions; anterior disclusion of posterior teeth in protrusion; and no contacts on the balancing side teeth during lateral excursions. These goals were sequentially accomplished by first emphasizing examination, diagnosis, and treatment planning; establishing 480

an anterior guidance that has the best possible esthetics, function, and comfort; selecting and restoring a lower posterior occlusion that was in harmony with anterior guidance and condylar guidance; and using the functionally generated path technique to restore the upper posterior occlusion in harmony with anterior guidance and condylar guidance. This philosophy of occlusal rehabilitation can be used to fulfill the goals of a theoretically ideal occlusion, which consists of no TMJ dysfunction, no periodontal involvement, and little or no occlusal wear.

CANINE

GUIDANCE

Canine guidance is disclusion by the canines of all other teeth in lateral excursions.42 D’Amico,3 and Scaife and Holt34 suggested that the concept of canine guidance had its genesis in Nagao’s43 refutation of Von Spee’s observations of the condylar path, in which he stated “the curve of Spee is not closely related either to the manner of movement of the lower jaw, or to the efficiency of mastication.“43 Von Spee may have planted the seeds of canine guidance when he made reference to the overbite of the upper canines, although he considered this observation insignificant.4 Fick,44 a German anatomist, questioned Von Spee’s findings. However, he was unable to sufficiently disprove them. Nagao43 undertook his comparative study on the curve of Von Spee in order to substantiate Fick’s objections. The significance of Nagao’s research was either overlooked or ignored because the preponderance of clinicians were advocates of balanced occlusion. In fact, balanced occlusion was considered essential to any organized dentition.‘j It was against such a background that Nagao’s study was introduced. Therefore to suggest that balanced occlusion could be considered destructive to the natural dentition was a charge that had to be issued with extreme caution. A significant contribution swaying clinical opinion away from balanced occlusion was made by Shaw.45 This anthropologist interpreted balanced occlusion appearing in the natural dentition as malocclusion.

Ironically, the clinical application of canine guidance was initiated by Stuart and Stallardg and by McCollum and Stuart,lO who were originally staunch advocates of balanced occlusion. While researching the balanced occlusion theory, these clinicians concluded that the theory was flawed and they were courageous enough to admit “the majority of their cases did not stand the rigid test of time and were failures.“17 They attributed this failure to the trauma caused by multitudinous, simultaneous contacts that resulted in occlusal wear, periodontal involvement, or TMJ dysfunction. Influenced by Shaw and by clinical experiences, Stuart and Stallardg concluded that occlusal wear was not a functional aim, which was their original hypothesis, but was one of nature’s unavoidable mistakes.

Stuart and StalIard clinically examined Shaw’s theories by making full coverage restorations on maxillary canines in patients showing evidence of occlusal wear to facilitate posterior disclusion during eccentric movements. They

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suggested that this procedure was not only acceptable to the patient but provided a canine lift that would halt the rate of wear.ll Stuart12 concluded that natural dentition, where teeth interdigitate in centric relation but have no cross-tooth or tooth-mouth balance, had the slowest rate of wear. It was his contention that the use of this technique was a preventive measure to future periodontal disease. Its primary purpose was to save the teeth and in turn the periodontium.12 Other investigators, such as Scott and Baum46 and Shooshan, viewed the lost canine function as primarily a mechanical problem and suggested during excursive movements a distance of at least 0.5 mm between the posterior opposing teeth. These investigators postulated that there was no apparent harm if the restoration created a greater separation.

Influenced by earlier investigators,sy 45,48 D’Amico,4s in his treatise on canine-protected occlusion, proselytized this theory to its popularity. He analyzed occlusal wear in light of its significance to man’s relatives, thus raising considerable skepticism as to whether the balanced occlusal relationship of man’s teeth or of the teeth of any other member of the primate family ever existed. D’Amico4g studied the function of the canines from the anthropoid apes to modern man. He theorized that the overlapping of the canines was originally displayed in the great apes due to their nonabrasive diet. As man’s diet and environment changed, so did the form and function of the canines. Occlusal wear caused a progressive reduction of vertical relation, edgeto-edge occlusion, and a wide range of lateral and protrusive movements. With the advent of a soft diet there was a gradual change back to the overlapping relationship of the canines. D’Amico deduced from this “the canines have been casualties of function rather than casualties of evolution.“4s Another tenet of D’Amico’s theoryso was that the canines acted as “nature’s stressbreakers” to protect the periodontium and supporting structures from lateral stress during eccentric movements. Upon functional contact by the canines, the periodontal proprioceptive impulses are transmitted to the mesencephalic root of the fifth cranial nerve, which altered the motor impulses to the musculature. The resultant involuntary reaction relaxed the muscles and thus decreased the adverse effects of the lateral force to the periodontium. D’Amico concluded, if all natural teeth had this “involuntary physiologic factor,” balanced occlusion could be applied without fear of periodontal or restorative failure. The literature is replete with investigators who substantiated D’Amico’s findings.

Stuar@i observed the canines had a higher minimal lateral pressure threshold. Corbin and Harrison52 reported the canines were the most sensitive intraoral structures to blunt stimulation. Another study by Kruger and Miche153 revealed that canines had a higher concentration of neurons than any other teeth. More recent research by Kawamura54 demonstrated that those teeth most sensitive to pressure were the incisors, canines, and premolars, followed by the molars, which were the least sensitive.

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Siebert55 upheld the view that the movement of the canines during canine guidance was well within its physiologic limits and that canine-protected occlusion was “the only one which could prevent disclusion or even traumatogenic occlusion. “55 Goldstein56 used periodontal disease index scores to substantiate these findings and showed that the canines and molars in canine guidance had a lower mean periodontal index than their counterparts in group function. D’Amico50 further expounded that if the canines were not allowed to have a horizontal overlap of approximately 1 mm to establish a slight freedom of movement during centric occlusion, the effectiveness of the proprioceptive impulses would be destroyed. If this occurred, it would cause “havoc to the periodontium and the TMJ articulation.“50 Di’Amico’s findings were not substantiated

by Scaife and Holt,s4 who discovered that out of 1200 patients, 91.5% exhibited canine contact in centric occlusion.

The research conducted by Shaw,45 by Stuart and Stallard,g and by D’Amico4s was incorporated into the present gnathologic concept. 57Proponents of this concept believed that each tooth had a specialized function. The incisors were used for biting, the posterior teeth were used for grinding and crushing, and the canines were used for grasping and tearing. In order for the stomatognathic system to function, teeth must work independently of each other. The canines, due to their crown-root ratio, strategic location away from the fulcrum, and stress-breaking capabilities, were the most likely candidates for this function.

Hence the term “canine disclusion” was formulated.

SUMMARY The historical development and philosophies of both anterior occlusal schemes have been discussed. To suggest that one occlusal scheme is superior to the other is not scientifically defensible. When the anterior guidance system must be reestablished or changed, current wisdom appears to number more proponents of canine guidance than of group function techniques.

REFERENCES 1. Schuyler storative 2. Schuyler

CH. An evaluation of incisal guidance and its influence in redentistry.

J PROSTHET DENT 1959;9:374-8.

CH. Factors of occlusion applicable to restorative dentistry.

J

PROSTHET DENT 1953;3:772-82.

3. D’Amico A. Origin and development of the balanced occlusion theory.

J South Calif Dent Assoc 1960;28:317-8.

4. Von Spee FG. The condylar path of the mandible in the glenoid fossa.

Read at Kiel, Germany, March 1890.

5. Christensen C. The problem of the bite. Dent Cosmos 1905;47:1184. of articulation.

Dent Cosmos 1910;52:1.

6. Gysi A. The problem 7. Monson GS. Applied mechanics to the theor,y of mandibular movements. Dent Cosmos 1932;74:1039-53.

8. Hall RE. Relations and movements of the mandible.

J Am Dent Assoc 1929;16:1643.

9. Stuart CE, Stallard H. Diagnosis and tratmenb of occlusal relations of the teeth. In: Stuart CE, Stallard H, eds. A syllabus on oral rehabilitation and occlusion.

San Francisco: University Iof California, 1959.

10. McCollum BB, Stuart CE. A research report.

South Pasadena, Calif: Scientific Press. 1955.

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11. Stuart CE, Stallard H. Diagnosis and treatment of occlusal relations of the teeth. Texas Dent J 1957;75:430-5.

12. Stuart CE. Is an early cuspid rise essential to periodontal health? J West Sot Periodontol 1958;6:76.

13. Lucia VO. The gnathological concept of articulation.

Dent Clin North Am 1962;March:183-97.

14. Schweitzer JM. Concepts of occlusion. A discussion. Dent Clin North Am 1963;Nov:649-71.

15. Schweitzer JM. Dental occlusion: a pragmatic approach. Dent Clin North Am 1969;13:687-724.

16. Granger ER. Bio-mechanics of periodontal disease. J Periodontol 1950;21:98-105.

17. Granger ER. Functional relations of the stomatognathic system. J Am Dent Assoc 1954;48:638-47.

18. Schuyler CH. Correction of occlusal disharmony of the natural dentition. NY State Dent J 1947;13:445.

19. Schuyler CH. Considerations of occlusion in fixed partial dentures. Dent Clin North Am 1959;March:175-85.

20. Schuyler CH. Fundamental principles in the correction of occlusal disharmony, natural and artificial. J Am Dent Assoc 1935;22:1193-1202.

21. Muhleman HR, Savdir S, Rateitschak KH. Tooth mobility-its causes and significance. J Periodontol 1965;36:148-53.

22. Glickman I. Inflammation and trauma from occlusion, co-destructive factors in chronic periodontal disease. J Periodontol 1963;34:5-10.

23. Hillam DG. Stresses in the periodontal ligament. J Periodont Res 1973;8:51-6.

24. Schuyler CH. The function and importance of incisal guidance in oral rehabilitation.

J PROSTHET DENT 1963;13:1011-29.

25. Weinberg LA. Force distribution in mastication, clenching, and bruxism. Parts 1 & 2. Dent Digest 1957;63:58-61; 116-20.

26. Alexander PC. Analysis of cuspid protective occlusion. J PROSTHET DENT 1963;13:309-17.

27. Beyron HL. Characteristics of functionally optimal occlusion and principles of occlusal rehabilitation.

J Am Dent Assoc 1954;48:648-56.

28. Linghorne WJ. A new theory of nature’s plan for human dentition. Oral Health 1938;28:525-9.

29. Forde TH. Oral dynamics. Dent Digest 1951;57:10-6.

30. Gregory WK, Broadbent BH, Hellman M. Development of occlusion.

1st ed. Philadelphia: University of Pennsylvania Press, 1941:57.

31. Williams CH. Correction of abnormalities of occlusion. J Am Dent Assot 1952;44:748-56.

32. Moses CH. The significance of stress in the practice of preventive and restorative dentistry. J Dent Med 1952;7:101-3.

33. Beyron HL. Occlusal changes in adult dentition. J Am Dent Assoc 1954;48:674-86.

34. Scaife RR, Holt RE. Natural occurence of cuspid guidance. J PROSTHET DENT 1969;22:225-9.

35. Schuyler CH. Factors contributing to traumatic occlusion. J PROSTHET DENT 1961;11:708-15.

36. Lucia VA. Modern gnathological concepts. 1st ed. St Louis: CV Mosby Co, 1961:293.

37. Weinberg LH. Temporomandibular joint function and its effect on concepts of occlusion. J PROSTHET DENT 1976;35:553-66.

38. Alexander PC. The periodontium and the canine function theory. J PROSTHET DENT 1967;18:571-8.

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39. O’Leary TJ, Shanley BDS, Drake RB. Tooth mobility in cuspidprotected and group function occlusions. J PROSTHET DENT 1972;27: 21-5.

40. DiPietro GJ. A study of occlusion as related to the Frankfort-msndibular plane angle. J PROSTHET DENT 1977;38:452-8.

41. Mann AW, Pankey LD. Concepts of occlusion. The P. M. philosophy of occlusal rehabilitation.

Dent Clin North Am 1963;Nov:621-36.

42. Dawson PE. Evaluation, diagnosis and treatment of occlusal problems.

1st ed. St Louis: CV Mosby Co, 1974213.

43. Nagao M. Comparative studies on the curve of Spee in mammals, with a discussion of its relation to the form of the fossa mandibularis.

J Dent Res 1919;1:159-202.

44. Fick R. Handbuch der Anatomic und mechanik der gelenk. Dritter teil.

1911:l.

45. Shaw DM. Form and function in teeth-a relational unifying principle applied to interpretation.

Int J Orthod 1924;10:703.

46. Scott ME, Baum L. Procedure and technics for restoring “canine function” for abraded teeth. J South Calif Dent Assoc 1964;32:23-8.

47. Shooshsn ED. A pin-ledge casting technique-its application in periodontal splinting. Dent Clin North Am 1960;March:189-206.

48. Jones H. Australian aborigines. Am J Physical Anthropol 1947;5:142-.

49. D’Amico A. The canine teeth-normal functional relation of the natural teeth of man. J South Calif Dent Assoc 1958,26:6-23; 49-60; 127-42; 175-82; 194-208; 239-41.

50. D’Amico A. Functional occlusion of the natural teeth of man. J PROSTHFZ DENT 1961;11:899-915.

51. Stuart D. Some aspects of the innervation of teeth. Proc R Sot Med 1927;20:1625.

52. Corbin KB, Harrison F. Function of mesencephalic root of fifth cranial nerves. J Neurophysiol 1940;3:423.

53. Kruger L, Michel F. A single neurol analysis of buccal cavity representation in the sensory trigeminal complex of the cat. Arch Oral Biol 1962;7:491-503.

54. Kawamura Y. Neurophysiologic background of occlusion. Periodontics 1967;5:175-83.

55. Siebert G. Recent results concerning physiological tooth movement and anterior guidance. J Oral Rehabil 1981;8:479-93.

56. Goldstein GR. The relationship of canine-protected occlusion to a periodontal index. J PROSTHET DENT 1979;41:277-83.

57. Htiman R, Regenos J, Taylor R. Principles of occlusion. Columbus, Ohio: HR Press, 19691-B-3.

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DR. LINDA J. THORNTON 2422 LEDGE HOLLOW SAN ANTONIO, TX 78232

Contributing authors Furmon M. Gardner, D.D.S., Colonel, U.S. Army, DC, 102nd Med DET (DS), USA Dentac-Vincenza, APO New York.

Vincent A. Petrucci, D.D.S., Colonel, U.S. Army, DC, Fort Jackson, S.C.

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