J. Periodontal Res. 13: 199-206, 1978
Oxytalan fibre response to tooth intrusion and extrusion in normal and lathyritic mice A statistical analysis MILTON R. SIMS
Department of Dental Health, University of Adelaide, South Australia Springs were applied to the mandibles of normal mice to produce intrusion of one first molar and extrusion of the opposite first molar. Treatments were randomly allocated to the right and left sides of the jaw. The experiment was repeated in lathyritic mice. Histologic sections demonstrated that major oxytalan fibres underwent marked changes in their angle of attachment to the cementum when comparing an intruded tooth with its extruded counterpart in cither normal or lathyritic animals. A sample of 10 angular readings was taken from each tooth. A mixed model analysis of variance showed a significant difference at the 1 % level in the angle attributed to the type of treatment applied. The data lend support to the hypothesis that oxytalan fibres are capable of independent function within the normal and also the pathologically affected periodontal ligament of mice. (Accepted jor ptihiication December 20, 1976)
ever, the precise function of the oxytalan fibre system has not been proven. In recent years the participation of various The present investigation was undertaken tissue compotients in the functional role of to examine the hypothesis (Sims 1973) that the periodontal ligament (Bien 1966, Piclon the oxytalan fibre system can function in1969) has reeeived increasing recognition. dependently of the collagen fibre system. The identification of oxytalan fibres in the Oxytalan fibre response to experimental inperiodontal ligaments of tnian and animals trusion and extrusion in norinal mice was (Fullmer 1958, Fullmer & Lillie 1958) has statistically analysed. These experiments added a further constituent to be evaluated were duplicated in lathyritic animals where for its contribution to the structure and vis- the tensile strength of collagen is reduced coelastic function of this connective tissue. (Berkowitz, Migdalski & Solomon 1972) reOn the basis of static histological studies, sulting in increased tooth mobility although different investigators (Rannie 1963, Loe & the oxytalan fibre systetn remains intact Nuki 1964, Simpson 1967, Canniehael 1968, (Sims 1976b). The intrusion and extrusion Edwards 197.1, Sims 1973, Campbell, Moore effects in lathyritic tnice were also examined & Matthews 1975, Beertsen, Everts & van using an analysis of variance. Experimental den Hoof 1974) have attributed various lathyrism provided the means to evaluate physiological roles to this fibre system. How- the response of the oxytalan meshwotk in Introduction
SIMS
200
the p;Uhologic;illy altered pcriodonlal ligament. Materials and Methods One luiiidred and sixty 2S day old inale al~ biiio miee I'rom Ihe Waitc AgricuUural Research Institute of the Uiiivei'sity of Adelaide were selected at ratuloiii aiul divided iiito two equal gi'oups. The expei'iiiieiital group was led, (td lihiltttit, a lathyritic diet cotnprising equal parts of grouiid sweel pea seeds (Ldlliyrtts odoratus) and a proprietary bruiid ol iiiousc cubes (Dasler & Milliser 1957, McCallufiT 1958). Cotilrol aiiiinals weic led gi'OLiiul iiiouse cubes ttd lihitiint. l^athyiism is known to produce maiked niicroscopie clianges in the molar periodontal ligament of yoiing rnice after seven days (Sliiis 1976b). 'Ihei'elore, alter one week on their tespective diets the lathyritic and normal animals were anaesthetized by the intraperioloneal injection ol veterinary neinbutal (Abbot l.aboi'atories. Sydney, New South Wales) diluted 1:19 iii physiological saliiie. Dosage was 0.3 mg of pentobarbitoiie sotliuni per 3.0 g body weight. The left and right sides of each mandible were sui'gically exposed. -Small springs Ibimcd from 0.035 mm diameter staiiiless steel orthodontic wire (A. J. Wileock, Whittlcsca, Victoria) were inserted into the inaiidibic on one side to pi-oduce extriision of the fii'st iinolar. On the opposite side of the jaw contriietion springs wei'e used to intrude the first molar. The contraction springs were different in design to the cxpaiision springs having a iiuidified arin which was inserted iiito the pi-edri!led mandible. This arm enhanced the stability
of the spring and facilitated the application of an axial force to the inolar erowns. In.. ti'usion and exti'usion springs were i'andomized between left aiid right sides of the jaw. Foi'ces applied were approximately 30 g as estiinated by activating the springs with a Correx Tension Ciauge (Haag-Strei(, A.G., Beriie, SwitzeiUuid) piior to insertion and following removal of the springs lor tissue processing. After positioning bolh tleviccs the aniinals were immediately sacrificed atid their heads fixed in aqueous neutral calciimi acetate formalin for 4H hoiirs. The mandibles were thcii dissected out, cleaiTed, and those jaws with tlislodged or imprecisely positioiied spiiiigs were discarded. After dividing Ihc mandibles al the symphy.sis paired specimens from each animal were decalcified iii 30 per ceiit lorinic acid and piocessed by the eelloidin-paiaffin double eiiTbedding techiiique. Seiial sections were eiit at cS nm thi'ough (he first molar in the tnesiodistal axial plane. When histological sections from either side of the mandible proved to be iiicoi i'cctly angled to the vertieal axis of the molar the aiiimal was eliiniiiated. Sections fiilfilling the required experimental criteria were oxidized in inonopersiilpliate (Ranaic 1963) and stained with a niodilieation of the aldehyde fuehsiii stain described by l^'ulhiiei'. Sheet/, & Narkates (1974). Normal and lathyritic aniinals were histologically processed initil 20 iiiaiidibles satisfying all experimental eriteria were obtained in each group. Data for a .s(alistica) analysis were obtained by treasuring the angle of attachinent ol major oxytalan fibres to the cemciitiim on the distal side of the intruded or extrud-
Fig. 1. The angle ol oxylalan fibre attachment resulting from intrusion of a first moiar. Lathyritic mouse. C: cementum; OX: oxytalan fibre. Oxone, aldehyde fuchsin. x 1000. Fig. 2. Attachment angie of a fibre of the oxytaian meshwork after molar extrusion in a iathyritic mouse. C: cementum; OX: oxyialan fibre. Oxone, aldehyde fuchsin. X 1000. Fig. 3. Oxytalan fibre angles to the root surface of an extruded molar. Apex ol distal rool. AB: alveolar bone; D. dentine; OX: oxytalan fibres. Oxone. aldehyde fuchsin. x 250. Fig. 4. Oxytalan fibre relationship to the root surface of an intruded moiar. Apex of distal root. AB: alveolar bone; D: dentine; OX: oxytalan fibres. Oxone, aidehyde fuchsin. x 250.
A N A L Y S i S
OF
O X Y T A L A N
F I B R E
R E S P O N S E
201
202
SIMS
ed first molars. Only those fibres which extended into the periodontal ligament for more than 30 ftm were assessed. The seleeted fibres were those located between the cementoenamel junction and a position 500 /{tn apically which approximated the coronal third of the ligament. Fibres passing transversely across the intersepta! alveolar crest (Sims 1973) were not measured. An independent observer measured and recorded the fibres using a research microscope with a XI00 oil immersion objective and a XIO eyepiece containing an engraved scale. Although the observer was blind to the source of the tissue sections, he came to recognize the particular drill hole patterns associated with the different types of experimental treatment. Incident fibre angles were measured by aligning the scale to the estimated direction of fibre attachment at the cementum and then revolving the eyepiece until the scale was parallel to the cementum surfaee (Figs. 1, 2). Where fibres attached as doublets or triplets all three angles were measured. A sample of ten angular readings was taken for each molar tooth. The experimental situation required a mixed-model analysis of variance, with fixed treatment effects and random mice and mice X treatment effects (Snedcor & Cochran 1967). Calculations were performed using the appropriate computer routine from the IMSL FORTRAN collection of functions and subroutines (International Mathematical and Statistical Libraries Inc., Houston, Texas).
tooth in the same animal. In the apical region a pronounced difference was also observed in the incidence angle of the prominent oxytalan fibres inserting into the cementum of extruded or intruded molars (Figs. 3, 4). Angular variations were not detected in those portions of the oxytalan fibre meshwork which linked the vessels to each other occluso-apically (Sims 1975, 1976a). Tangential sections through the buccal or lingual periodontal ligament of extruded molars showed that the longer oxytalan fibres were relatively straight as if stretched and under tension (Fig. 5). However, where fibres were cut obliquely to their principal orientation the resultant short lengths appeared very wavy as if they had rebounded after being stretched and divided while under tension. As a contrast, similar sections of intruded molars showed that the majority of oxytalan fibres were relatively wavy as if they had been able to relax along their course between the cementum and the blood vessels (Fig. 6). Experiments in lathyritic mice also showed a marked difference between the magnitude of the oxytalan fibre angles in the intruded and extruded molars Data of the 10 oxytalan fibre angular readings from each molar tooth are summarized by averages in Tables l(a) and l(b). Differences in fibre angulation resulting from extrusion and intrusion varied from approximately 16 to 66 degrees in normal mice and from 11 to 79 degrees in lathyritic mice. The analysis of variance for each group are shown in Tables 2(a) and 2(b). In both cases treatment effects are significant at the 1 % level.
Findings
Histological sections demonstrated marked changes in the angle of attachment of major oxytalan fibres to the cementum surface in the coronal region. Molar extrusion in normal animals resulted in a generally acute fibre angle compared with the less acute fibre angles to the cementum of the intruded
Discussion
Histological assessment of experimental axial tooth movement in the mouse resulted in microscopically evident and statistically significant changes in the angle of attachment ol oxytalan fibres to the cementum surface
A N A L Y S I S
O F O X Y T A L A N
F I B R E
R E S P O N S E
203
Fig. 5. Tensioned oxytalan fibres in the cervical region of an extruded first mclar of a normal mouse. Buccal tangential section. D: dentine; OX: oxytalan fibres; V: vessel. Oxone, aldehyde fuchsin. X 450. Fig 6. Reiaxed oxytalan fibres in the cervical region of an intruded moiar of a normal mouse. Buccal tangential section. D; dentine; OX; oxytalan fibres; V; vessel.Oxone, aldehyde fuchsin. x 460.
in the coronal third of the periodontal ligament. Spatial changes in the relationship oi' the oxytalan fibre meshwork were also discerned in the apical region of the periodontal ligament although changes in this region were not analysed statistically. Since experimentally induced changes were evident at both the cervical and apical extremes of the root it is reasonable to infer that alterations also occur throughout the oxytalan fibre meshwork at its attachment to the cementum. It is recognized that the experimental loads applied to the molars were of different functional and physiological significance to those normally derived from vascular pulsation (Korber 1970) and the momentary
forces of mastication (Bien 1966). Nevertheless, under the experimental conditions employed, which amplified the range of normal tooth oscillation, the findings suggested that different regions of the oxytalan fibre meshwork were capable of some degree of independent functional variation from the collagen fibre system, cells, the extracellular substance, vessels and nerves. Whereas the collagen fibre system relates the tooth to the alveolar wall, the oxytalan fibre meshwork associates the tooth with the vascular system of the periodontal ligament (Sims 1973). The waviness of short portions of major oxytalan fibres in the extrusion experiments indicated that these fibres had recoiled be-
SIMS
204 Table 1(a)
Table 1(b)
Normal mice: average of 10 angular readings for each mouse-treatment combination
Lathyritic mice: average of 10 angular readings for each mouse-treatment combination
Intrusion
Extrusion
1 2
64.8 62.0
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
59.4 61.6 65.7 56.3 66.1 61.1 59.1 57.3 56.3 46.7 49.1 49.7 50.7 57.8 47.3 56.9 47.4 53.9
18.0 31.5 21.8 33.2 18.2 18.6 16.0 18.9 20.9 27.5 23.1 22.2 19.6 18.2 16.5 19.0 30.4 20.2 24.8 21.9
56.5
22.0
Mouse
18 19 20
Average over mice
Intrusion
Extrusion
1
60.4
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
52.0 44.9 53.2 50.2 71.0 67.0 64.4 62.3 64.3 59.4 58.0 76.8 76.0 72.4 79.3 76.4 67.7 60.4 72.2
33.7 30.0 25.7 30.3 23.1 18.3 26.8 25.9 19.5 35.4 22.8 19.8 21.2 11.2 26.8 26.5 16.2 17.0 37.2 19.2
64.4
24.3
Mouse
Average over
mice
Table 2(a) Analysis of variance for normal mice SS Mice Treatments Mice X Treatments Error Total
5486.33 118576.92 6742.13 42486.10 173291.48
DF 19 1 19 360 399
MS 288.75 118576.92 354.85 118.02
= 334.16*** 3.01
Table 2(b) Analysis of variance for lathyritic mice
Mice Treatments Mice X Treatments Error Total
SS 8167.65 160680.72 18645.03 67526.10 255019.50
DF 19 1 19 360 399
MS 429.88 160680.72 981.32 187.57
=
163.74*** 5.23
ANALYSIS
OF OXYTALAN
cause of loss of support along their length from anastotnoses with other major oxytalan fibres and the fine intercommunicating oxytalan fibres (Sims 1975). Other histological evidence also supports the view that oxytalan fibres exhibit elastomeric properties (Rannie 1963, Sims 1976a). Fullmer et al. (1974) state that the oxytalan fibre appears to possess unique properties yet shows similarities with elastic fibres. Preparation of tissues for routine histologic examination and evaluation results in a certain amount of shrinkage and some distortional changes (Smith 1962). While recognizitig the influence of such factors in the present study it is considered that the statistically significant differences demonstrated in the magnitude of the oxytalan fibre angles between extrusion and intrusion represented real effects produced in vivo and were not the consequences of tissue alterations associated with processing techniques. On the basis of the data presented, this investigation provides additional information on the response of the periodontal ligament to tooth loading and lends support to the hypothesis (Sims 1973, 1976a) that the oxytalati fibre system is capable of sonne degree of independent function within both the normal and pathologically affeeted periodontal ligament. A comparison of oxytalan fibre attachment angles between normal and lathyritic mice will be the subject of a further paper now in preparation. As Melcher & Walker (1976) have pointed out in their recent review, our knowledge of the behaviour of the constituents of the periodontal ligament following loading is meagre. Acknowledgement
The assistance of Mr. P. I. Leppard, Statistical Consultant, Department of Statistics, The University of Adelaide, is gratefully recorded.
FIBRE
RESPONSE
205
References Beerlsen, W., Everts, V. & van den Hoof, A. 1974. Fine structure of fibroblasts in the periodontal ligament of the rat incisor and their possible role in tooth eruption. Arch. Oral Biol. 19: 1087-1098. Berkovitz, B. K. B., Migdalski, A. & Solomon, M. 1972. The effect of the lathyn'tic agent amino-acetonitvile on the unimpeded eruption rate in normal and root-resected rat lower incisors. Arch. Oral Biol. 17: 1755-1764. Bien, S. M. 1966. Fluid dynamic mechanisms which regulate tooth movement. In Advances in Oral Biology, Edited by Staple, P. H. Vol. 2, pp. 173-201, New York: Academic Press. Campbell, P. M., Moore, J. W. & Matthews, J. L. 1975. Orthodontically corrected midline diastemas; a histologic study and surgical procedure. Am. J. Orthod. 67: 139-158. Carniichael, G. G. 1968. Observations with the light microscope on the distribution and connexions of the oxytalan fibre of the lower jaw of the mouse. Arch. Oral Biol. 13: 765772. Dasler, W, & Milliser, R. V. 1957. Experimental lathyrism in mice fed diets containing sweet peas or /S-aminopropionitrile. Proc. Soc. Exp. Biol. Med. 96; 171-174. Edwards, jr. G. 1971. The prevention of relapse in extraction cases. Atn. J. Orthod. 60: 128141. Fullmer, H. M. 1958. Differential staining of connective tissue fibers in areas of stress. Science 127: 1240. Fullmer, H. M. & Lillie, R. D. 1958. The oxytalan fiber: A previously undescribed connective tissue fiber. J. Histochem. Cytochetn. 6: 425-430. Fullmer, H. M., Sheetz, J. H. & Narkates, A. J. 1974. Oxytalan connective tissue fibers: A review. J. Oral Path. 3: 291-316. Korber, K. H. 1970. Periodontal pulsation. J. Periodontol. 41: 382-390. Loe, H. & Nuki, K. 1964. Observations on the peracetic acid aldehyde fuchsin (oxytalan) positive tissue elements in the periodontium. Acta. Odotit. Scand. 22: 579-588. McCallum, H. M. 1958. Lathyrism in mice. Nature. (London). 182: 1169-1170. Melcher, A. H. & Walker, T. W. 1976. The periodontal ligament in attachment and as a shock absorber. In The Ertiption atid Occlusion of Teeth. Edited by Poole, D. F. G. & Stack, M. V. pp. 183-192. London, Butterworths.
206
SIMS
Picton, D. C. A. 1969. The effect of external forces on the periodontium. In Biology of the Periodontiutn. Edited by Melcher, A. H. & Bowen, W. H. Chapt. 8, pp. 363-419. London, Academic Press. Rannie, 1. 1963. Observations on the oxytalan fibre of the periodontal membrane. Trans. Eiirop. Orthod. Soc. pp. 127-137. Simpson, H. E. 1967. A three-dimensional approach to the microscopy of the periodontal membrane. Proc. R. Soc. Med. 60: 537-542. Sims, M. R. 1973. Oxytalan fiber system of molars in the mouse mandible. J. Dent. Re.t. 52: 797-803. Sims, M.R. 1975. Oxytalan-vascular relationships observed in histologic examination of the periodontal ligaments of man and mouse. Arch. Oral Biol. 20: 713-716. Sims, M. R. 1976a. Reconstitution of the human
oxytalan system during orthodontic tooth movement. Am. J. Orthod. 70: 38-58. Sims, M.R. 1976b. The oxytalan fibre system in the mandibular periodontal ligament of the lathyritic mouse. Joiirtuil of Oral Pail,, ology. In Press. Smith, A. 1962. The use of frozen sections in oral histology. Part 1, J. Med. Lab. Technol 19: 26-38. Snedcor, G. W. & Cochran, W. G. 1967. Factorial experiments. In Statistical Methods, 6th edition, Chapt. 12, pp. 339-380, Ames, Iowa State University Press. Address: Departtnent of Dental Health, University of Adelaide, Adelaide, South Australia, Australia, 5001
Oxytalan fibre response to tooth intrusion and extrusion in normal and lathyritic mice A statistical analysis MILTON R. SIMS
Department of Dental Health, University of Adelaide, South Australia Springs were applied to the mandibles of normal mice to produce intrusion of one first molar and extrusion of the opposite first molar. Treatments were randomly allocated to the right and left sides of the jaw. The experiment was repeated in lathyritic mice. Histologic sections demonstrated that major oxytalan fibres underwent marked changes in their angle of attachment to the cementum when comparing an intruded tooth with its extruded counterpart in cither normal or lathyritic animals. A sample of 10 angular readings was taken from each tooth. A mixed model analysis of variance showed a significant difference at the 1 % level in the angle attributed to the type of treatment applied. The data lend support to the hypothesis that oxytalan fibres are capable of independent function within the normal and also the pathologically affected periodontal ligament of mice. (Accepted jor ptihiication December 20, 1976)
ever, the precise function of the oxytalan fibre system has not been proven. In recent years the participation of various The present investigation was undertaken tissue compotients in the functional role of to examine the hypothesis (Sims 1973) that the periodontal ligament (Bien 1966, Piclon the oxytalan fibre system can function in1969) has reeeived increasing recognition. dependently of the collagen fibre system. The identification of oxytalan fibres in the Oxytalan fibre response to experimental inperiodontal ligaments of tnian and animals trusion and extrusion in norinal mice was (Fullmer 1958, Fullmer & Lillie 1958) has statistically analysed. These experiments added a further constituent to be evaluated were duplicated in lathyritic animals where for its contribution to the structure and vis- the tensile strength of collagen is reduced coelastic function of this connective tissue. (Berkowitz, Migdalski & Solomon 1972) reOn the basis of static histological studies, sulting in increased tooth mobility although different investigators (Rannie 1963, Loe & the oxytalan fibre systetn remains intact Nuki 1964, Simpson 1967, Canniehael 1968, (Sims 1976b). The intrusion and extrusion Edwards 197.1, Sims 1973, Campbell, Moore effects in lathyritic tnice were also examined & Matthews 1975, Beertsen, Everts & van using an analysis of variance. Experimental den Hoof 1974) have attributed various lathyrism provided the means to evaluate physiological roles to this fibre system. How- the response of the oxytalan meshwotk in Introduction
SIMS
200
the p;Uhologic;illy altered pcriodonlal ligament. Materials and Methods One luiiidred and sixty 2S day old inale al~ biiio miee I'rom Ihe Waitc AgricuUural Research Institute of the Uiiivei'sity of Adelaide were selected at ratuloiii aiul divided iiito two equal gi'oups. The expei'iiiieiital group was led, (td lihiltttit, a lathyritic diet cotnprising equal parts of grouiid sweel pea seeds (Ldlliyrtts odoratus) and a proprietary bruiid ol iiiousc cubes (Dasler & Milliser 1957, McCallufiT 1958). Cotilrol aiiiinals weic led gi'OLiiul iiiouse cubes ttd lihitiint. l^athyiism is known to produce maiked niicroscopie clianges in the molar periodontal ligament of yoiing rnice after seven days (Sliiis 1976b). 'Ihei'elore, alter one week on their tespective diets the lathyritic and normal animals were anaesthetized by the intraperioloneal injection ol veterinary neinbutal (Abbot l.aboi'atories. Sydney, New South Wales) diluted 1:19 iii physiological saliiie. Dosage was 0.3 mg of pentobarbitoiie sotliuni per 3.0 g body weight. The left and right sides of each mandible were sui'gically exposed. -Small springs Ibimcd from 0.035 mm diameter staiiiless steel orthodontic wire (A. J. Wileock, Whittlcsca, Victoria) were inserted into the inaiidibic on one side to pi-oduce extriision of the fii'st iinolar. On the opposite side of the jaw contriietion springs wei'e used to intrude the first molar. The contraction springs were different in design to the cxpaiision springs having a iiuidified arin which was inserted iiito the pi-edri!led mandible. This arm enhanced the stability
of the spring and facilitated the application of an axial force to the inolar erowns. In.. ti'usion and exti'usion springs were i'andomized between left aiid right sides of the jaw. Foi'ces applied were approximately 30 g as estiinated by activating the springs with a Correx Tension Ciauge (Haag-Strei(, A.G., Beriie, SwitzeiUuid) piior to insertion and following removal of the springs lor tissue processing. After positioning bolh tleviccs the aniinals were immediately sacrificed atid their heads fixed in aqueous neutral calciimi acetate formalin for 4H hoiirs. The mandibles were thcii dissected out, cleaiTed, and those jaws with tlislodged or imprecisely positioiied spiiiigs were discarded. After dividing Ihc mandibles al the symphy.sis paired specimens from each animal were decalcified iii 30 per ceiit lorinic acid and piocessed by the eelloidin-paiaffin double eiiTbedding techiiique. Seiial sections were eiit at cS nm thi'ough (he first molar in the tnesiodistal axial plane. When histological sections from either side of the mandible proved to be iiicoi i'cctly angled to the vertieal axis of the molar the aiiimal was eliiniiiated. Sections fiilfilling the required experimental criteria were oxidized in inonopersiilpliate (Ranaic 1963) and stained with a niodilieation of the aldehyde fuehsiii stain described by l^'ulhiiei'. Sheet/, & Narkates (1974). Normal and lathyritic aniinals were histologically processed initil 20 iiiaiidibles satisfying all experimental eriteria were obtained in each group. Data for a .s(alistica) analysis were obtained by treasuring the angle of attachinent ol major oxytalan fibres to the cemciitiim on the distal side of the intruded or extrud-
Fig. 1. The angle ol oxylalan fibre attachment resulting from intrusion of a first moiar. Lathyritic mouse. C: cementum; OX: oxytalan fibre. Oxone, aldehyde fuchsin. x 1000. Fig. 2. Attachment angie of a fibre of the oxytaian meshwork after molar extrusion in a iathyritic mouse. C: cementum; OX: oxyialan fibre. Oxone, aldehyde fuchsin. X 1000. Fig. 3. Oxytalan fibre angles to the root surface of an extruded molar. Apex ol distal rool. AB: alveolar bone; D. dentine; OX: oxytalan fibres. Oxone. aldehyde fuchsin. x 250. Fig. 4. Oxytalan fibre relationship to the root surface of an intruded moiar. Apex of distal root. AB: alveolar bone; D: dentine; OX: oxytalan fibres. Oxone, aidehyde fuchsin. x 250.
A N A L Y S i S
OF
O X Y T A L A N
F I B R E
R E S P O N S E
201
202
SIMS
ed first molars. Only those fibres which extended into the periodontal ligament for more than 30 ftm were assessed. The seleeted fibres were those located between the cementoenamel junction and a position 500 /{tn apically which approximated the coronal third of the ligament. Fibres passing transversely across the intersepta! alveolar crest (Sims 1973) were not measured. An independent observer measured and recorded the fibres using a research microscope with a XI00 oil immersion objective and a XIO eyepiece containing an engraved scale. Although the observer was blind to the source of the tissue sections, he came to recognize the particular drill hole patterns associated with the different types of experimental treatment. Incident fibre angles were measured by aligning the scale to the estimated direction of fibre attachment at the cementum and then revolving the eyepiece until the scale was parallel to the cementum surfaee (Figs. 1, 2). Where fibres attached as doublets or triplets all three angles were measured. A sample of ten angular readings was taken for each molar tooth. The experimental situation required a mixed-model analysis of variance, with fixed treatment effects and random mice and mice X treatment effects (Snedcor & Cochran 1967). Calculations were performed using the appropriate computer routine from the IMSL FORTRAN collection of functions and subroutines (International Mathematical and Statistical Libraries Inc., Houston, Texas).
tooth in the same animal. In the apical region a pronounced difference was also observed in the incidence angle of the prominent oxytalan fibres inserting into the cementum of extruded or intruded molars (Figs. 3, 4). Angular variations were not detected in those portions of the oxytalan fibre meshwork which linked the vessels to each other occluso-apically (Sims 1975, 1976a). Tangential sections through the buccal or lingual periodontal ligament of extruded molars showed that the longer oxytalan fibres were relatively straight as if stretched and under tension (Fig. 5). However, where fibres were cut obliquely to their principal orientation the resultant short lengths appeared very wavy as if they had rebounded after being stretched and divided while under tension. As a contrast, similar sections of intruded molars showed that the majority of oxytalan fibres were relatively wavy as if they had been able to relax along their course between the cementum and the blood vessels (Fig. 6). Experiments in lathyritic mice also showed a marked difference between the magnitude of the oxytalan fibre angles in the intruded and extruded molars Data of the 10 oxytalan fibre angular readings from each molar tooth are summarized by averages in Tables l(a) and l(b). Differences in fibre angulation resulting from extrusion and intrusion varied from approximately 16 to 66 degrees in normal mice and from 11 to 79 degrees in lathyritic mice. The analysis of variance for each group are shown in Tables 2(a) and 2(b). In both cases treatment effects are significant at the 1 % level.
Findings
Histological sections demonstrated marked changes in the angle of attachment of major oxytalan fibres to the cementum surface in the coronal region. Molar extrusion in normal animals resulted in a generally acute fibre angle compared with the less acute fibre angles to the cementum of the intruded
Discussion
Histological assessment of experimental axial tooth movement in the mouse resulted in microscopically evident and statistically significant changes in the angle of attachment ol oxytalan fibres to the cementum surface
A N A L Y S I S
O F O X Y T A L A N
F I B R E
R E S P O N S E
203
Fig. 5. Tensioned oxytalan fibres in the cervical region of an extruded first mclar of a normal mouse. Buccal tangential section. D: dentine; OX: oxytalan fibres; V: vessel. Oxone, aldehyde fuchsin. X 450. Fig 6. Reiaxed oxytalan fibres in the cervical region of an intruded moiar of a normal mouse. Buccal tangential section. D; dentine; OX; oxytalan fibres; V; vessel.Oxone, aldehyde fuchsin. x 460.
in the coronal third of the periodontal ligament. Spatial changes in the relationship oi' the oxytalan fibre meshwork were also discerned in the apical region of the periodontal ligament although changes in this region were not analysed statistically. Since experimentally induced changes were evident at both the cervical and apical extremes of the root it is reasonable to infer that alterations also occur throughout the oxytalan fibre meshwork at its attachment to the cementum. It is recognized that the experimental loads applied to the molars were of different functional and physiological significance to those normally derived from vascular pulsation (Korber 1970) and the momentary
forces of mastication (Bien 1966). Nevertheless, under the experimental conditions employed, which amplified the range of normal tooth oscillation, the findings suggested that different regions of the oxytalan fibre meshwork were capable of some degree of independent functional variation from the collagen fibre system, cells, the extracellular substance, vessels and nerves. Whereas the collagen fibre system relates the tooth to the alveolar wall, the oxytalan fibre meshwork associates the tooth with the vascular system of the periodontal ligament (Sims 1973). The waviness of short portions of major oxytalan fibres in the extrusion experiments indicated that these fibres had recoiled be-
SIMS
204 Table 1(a)
Table 1(b)
Normal mice: average of 10 angular readings for each mouse-treatment combination
Lathyritic mice: average of 10 angular readings for each mouse-treatment combination
Intrusion
Extrusion
1 2
64.8 62.0
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
59.4 61.6 65.7 56.3 66.1 61.1 59.1 57.3 56.3 46.7 49.1 49.7 50.7 57.8 47.3 56.9 47.4 53.9
18.0 31.5 21.8 33.2 18.2 18.6 16.0 18.9 20.9 27.5 23.1 22.2 19.6 18.2 16.5 19.0 30.4 20.2 24.8 21.9
56.5
22.0
Mouse
18 19 20
Average over mice
Intrusion
Extrusion
1
60.4
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
52.0 44.9 53.2 50.2 71.0 67.0 64.4 62.3 64.3 59.4 58.0 76.8 76.0 72.4 79.3 76.4 67.7 60.4 72.2
33.7 30.0 25.7 30.3 23.1 18.3 26.8 25.9 19.5 35.4 22.8 19.8 21.2 11.2 26.8 26.5 16.2 17.0 37.2 19.2
64.4
24.3
Mouse
Average over
mice
Table 2(a) Analysis of variance for normal mice SS Mice Treatments Mice X Treatments Error Total
5486.33 118576.92 6742.13 42486.10 173291.48
DF 19 1 19 360 399
MS 288.75 118576.92 354.85 118.02
= 334.16*** 3.01
Table 2(b) Analysis of variance for lathyritic mice
Mice Treatments Mice X Treatments Error Total
SS 8167.65 160680.72 18645.03 67526.10 255019.50
DF 19 1 19 360 399
MS 429.88 160680.72 981.32 187.57
=
163.74*** 5.23
ANALYSIS
OF OXYTALAN
cause of loss of support along their length from anastotnoses with other major oxytalan fibres and the fine intercommunicating oxytalan fibres (Sims 1975). Other histological evidence also supports the view that oxytalan fibres exhibit elastomeric properties (Rannie 1963, Sims 1976a). Fullmer et al. (1974) state that the oxytalan fibre appears to possess unique properties yet shows similarities with elastic fibres. Preparation of tissues for routine histologic examination and evaluation results in a certain amount of shrinkage and some distortional changes (Smith 1962). While recognizitig the influence of such factors in the present study it is considered that the statistically significant differences demonstrated in the magnitude of the oxytalan fibre angles between extrusion and intrusion represented real effects produced in vivo and were not the consequences of tissue alterations associated with processing techniques. On the basis of the data presented, this investigation provides additional information on the response of the periodontal ligament to tooth loading and lends support to the hypothesis (Sims 1973, 1976a) that the oxytalati fibre system is capable of sonne degree of independent function within both the normal and pathologically affeeted periodontal ligament. A comparison of oxytalan fibre attachment angles between normal and lathyritic mice will be the subject of a further paper now in preparation. As Melcher & Walker (1976) have pointed out in their recent review, our knowledge of the behaviour of the constituents of the periodontal ligament following loading is meagre. Acknowledgement
The assistance of Mr. P. I. Leppard, Statistical Consultant, Department of Statistics, The University of Adelaide, is gratefully recorded.
FIBRE
RESPONSE
205
References Beerlsen, W., Everts, V. & van den Hoof, A. 1974. Fine structure of fibroblasts in the periodontal ligament of the rat incisor and their possible role in tooth eruption. Arch. Oral Biol. 19: 1087-1098. Berkovitz, B. K. B., Migdalski, A. & Solomon, M. 1972. The effect of the lathyn'tic agent amino-acetonitvile on the unimpeded eruption rate in normal and root-resected rat lower incisors. Arch. Oral Biol. 17: 1755-1764. Bien, S. M. 1966. Fluid dynamic mechanisms which regulate tooth movement. In Advances in Oral Biology, Edited by Staple, P. H. Vol. 2, pp. 173-201, New York: Academic Press. Campbell, P. M., Moore, J. W. & Matthews, J. L. 1975. Orthodontically corrected midline diastemas; a histologic study and surgical procedure. Am. J. Orthod. 67: 139-158. Carniichael, G. G. 1968. Observations with the light microscope on the distribution and connexions of the oxytalan fibre of the lower jaw of the mouse. Arch. Oral Biol. 13: 765772. Dasler, W, & Milliser, R. V. 1957. Experimental lathyrism in mice fed diets containing sweet peas or /S-aminopropionitrile. Proc. Soc. Exp. Biol. Med. 96; 171-174. Edwards, jr. G. 1971. The prevention of relapse in extraction cases. Atn. J. Orthod. 60: 128141. Fullmer, H. M. 1958. Differential staining of connective tissue fibers in areas of stress. Science 127: 1240. Fullmer, H. M. & Lillie, R. D. 1958. The oxytalan fiber: A previously undescribed connective tissue fiber. J. Histochem. Cytochetn. 6: 425-430. Fullmer, H. M., Sheetz, J. H. & Narkates, A. J. 1974. Oxytalan connective tissue fibers: A review. J. Oral Path. 3: 291-316. Korber, K. H. 1970. Periodontal pulsation. J. Periodontol. 41: 382-390. Loe, H. & Nuki, K. 1964. Observations on the peracetic acid aldehyde fuchsin (oxytalan) positive tissue elements in the periodontium. Acta. Odotit. Scand. 22: 579-588. McCallum, H. M. 1958. Lathyrism in mice. Nature. (London). 182: 1169-1170. Melcher, A. H. & Walker, T. W. 1976. The periodontal ligament in attachment and as a shock absorber. In The Ertiption atid Occlusion of Teeth. Edited by Poole, D. F. G. & Stack, M. V. pp. 183-192. London, Butterworths.
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Picton, D. C. A. 1969. The effect of external forces on the periodontium. In Biology of the Periodontiutn. Edited by Melcher, A. H. & Bowen, W. H. Chapt. 8, pp. 363-419. London, Academic Press. Rannie, 1. 1963. Observations on the oxytalan fibre of the periodontal membrane. Trans. Eiirop. Orthod. Soc. pp. 127-137. Simpson, H. E. 1967. A three-dimensional approach to the microscopy of the periodontal membrane. Proc. R. Soc. Med. 60: 537-542. Sims, M. R. 1973. Oxytalan fiber system of molars in the mouse mandible. J. Dent. Re.t. 52: 797-803. Sims, M.R. 1975. Oxytalan-vascular relationships observed in histologic examination of the periodontal ligaments of man and mouse. Arch. Oral Biol. 20: 713-716. Sims, M. R. 1976a. Reconstitution of the human
oxytalan system during orthodontic tooth movement. Am. J. Orthod. 70: 38-58. Sims, M.R. 1976b. The oxytalan fibre system in the mandibular periodontal ligament of the lathyritic mouse. Joiirtuil of Oral Pail,, ology. In Press. Smith, A. 1962. The use of frozen sections in oral histology. Part 1, J. Med. Lab. Technol 19: 26-38. Snedcor, G. W. & Cochran, W. G. 1967. Factorial experiments. In Statistical Methods, 6th edition, Chapt. 12, pp. 339-380, Ames, Iowa State University Press. Address: Departtnent of Dental Health, University of Adelaide, Adelaide, South Australia, Australia, 5001
