Na visão clássica do crescimento sutural, a proliferação de células activas nas margens suturais, pensava-se causar a expansão intrínseca com a separação dos ossos adjacentes (126). Um papel activo na expansão nas margens suturais foi igualmente atribuído aos fibroblastos contractivos (miofibroblastos) (4) e à orientação oblíqua das fibras suturais (48). No entanto, foi demonstrado que o crescimento ósseo nas margens suturais, é secundário e passivo relativamente a forças separativas externas. Existem evidências, através de vários estudos utilizando métodos experimentais tais como a dissecação (82,105,113,125), autotransplantação (83,124), e o cultivo invivo (65,97). Vários estudos incluem os de Kokich (54) e Persson (91).
Os efeitos da compressão e tracção ao longo das suturas faciais têm sido documentados, nos humanos, nos primatas não humanos e outros animais (121). As suturas comprimidas caracterizam-se histologicamente pela absorção de osso ao longo das margens suturais, quando são aplicadas forças por forma a alterar as relações espaciais dos ossos envolventes. Quando as forças são interrompidas, as suturas normalizam-se histologicamente (10,80,106,114,118). As tracções ao longo das suturas faciais, produzem a separação dos ossos, com o consequente alargamento das suturas e aumento do rácio da deposição óssea nas margens suturais. Quando as forças de tracção são interrompidas, as suturas de igual forma, normalizam-se histologicamente (35,49,106).
Alguns estudos, recorrendo a técnicas altamente especializadas têm avaliado os efeitos quantitativos das forças mecânicas nas suturas. De particular importância, são os textos de Meikle et al. (74-77), Green et al. (34), Miyawaki e Forbes (79), e Yen et al. (129,131). Alguns estudos encontram-se resumidos na tabela 4.
Tabela 4 – Estudos específicos que avaliam quantitativamente os efeitos das forças mecânicas nas suturas. De Cohen (16)
Muitos outros estudos experimentais têm-se focado na perturbação do ambiente sutural. Por razões de conveniência, esses estudos podem-se dividir segundo os seus efeitos na (1) alteração muscular das suturas* (58,86,122,123); (2) na alteração do sistema nervoso das suturas (29); (3) danos cranianos segundo padrões suturais (31,85,86); (4) reposição óssea contendo suturas (30,110); e (5) transplante ósseo contendo suturas (22,23,68,70,71,83,88-90,124). Os resultados destes estudos indicam que as suturas são altamente adaptativas durante o crescimento e desenvolvimento.
* - Person (93) embriões de frango paralisados através dum agente neuromuscular bloqueador para avaliação do papel da actividade muscular no desenvolvimento das suturas. Apesar das articulações sinoviais não se formarem, a limitação de movimento não interferiu com o normal desenvolvimento sutural.
0 - M. Michael Cohen, Ruth E. MacLean (2000): Craniosynostosis: Diagnosis, Evaluation, and Management, 2nd ed. USA: Oxford University Press.
4 - Azuma M, Enlow DH, Frederickson RG, Gaston LG (1975): A myofibroblastic basis for the physical forces that produce tooth drift and eruption, skeletal displacement at sutures, and periosteal migration. In: McNamara JA, ed., Determinants of Mandibular Form and Growth. Center For Human Growth and Development, Monograph No. 4, Craniofacial Growth Series, Ann Arbor: University of Michigan Press, pp. 179-207.
6 - Behrents RG, Carlson DS, Abdelnour T: (1978): In vivo analysis of bone strain about the sagittal suture in Macaca mulatta during masticatory movements. J Dent Res 57:904-908.
10 - Brandt HC, Shapiro PA, Kokich VG (1979): Experimental and postexperimental effects of posteriorly directed extraoral traction in adult Macaca fascicularis. Am J Orthod 75:301-317.
16 - Cohen MM Jr (1993): Sutural biology and the correlates of craniosynostosis. Am J Med Genet 47:581-616.
22 - Engdahl E, Ritsilä V, Uddströmer L (1978): Growth potential of cranial suture bone autografts. I. An experimental macroscopic investigation in young rabits. Scand J Plast Reconstr Surg Hand Surg 12:119-123.
23 - Engdahl E, Ritsilä V, Uddströmer L (1978): Growth potential of cranial suture bone autografts. II. An experimental macroscopic investigation in young rabits. Scand J Plast Reconstr Surg Hand Surg 12:125-129.
29 - Gardner DE, Luschei ES, Joondeph DR (1980): Alterations in the facial skeleton of the guinea pig following a lesion of the trigeminal motor nucleus. Am J Orthod 78:66-80.
30 - Giblin N, Alley A (1944): Studies in skull growth. Coronal suture fixation. Anat Rec 88:143-153.
31 - Girgis FG, Pritchard JJ (1958): Effects of skull damage on the development of sutural patterns in the rat. J Anat 92:39.
34 - Green DD, Hembry RM, Atkinson SJ, Reynolds JJ, Meikle MC (1990): Immunolocalization of collagenase and tissue inhibitor of metalloproteinases (TIMP) in mechanically deformed fibrous joints. Am J Orthod Dentofacial Orthop 97:281-288.
35 - Guyman G, Kokich VG, Oswald R (1980): Ankylosed teeth as abutments for palatal expansion in the rhesus monkey. Am J Orthod 77:486-499.
47 - Hickory WB, Nanda R (1987): Effect of tensile force magnitude on release of cranial suture cells into S phase. Am J Orthod Dentofacial Orthop 91:328-334.
48 - Hinton DR, Becker LE, Muakkassa KF, Hoffman HJ (1984): Lambdoid synostosis. Part1: The lambdoid suture: Normal development and pathology of "synostosis." J Neurosurg 61:333-339.
49 - Jackson G, Kokich VG, Shapiro PA (1979): Experimental and postexperimental response to anterioly directed extraoral force in young Macaca nemestrina. Am J Orthod 75:318-333.
54 - Kokich VG (1986): Biology of sutures. In: Cohen MM Jr (ed), Craniosynostosis: Diagnosis, Evaluation, end Management. New York: Raven Press, pp. 81-103.
58 - Koskinen L (1977): Adaptive sutures: Changes after unilateral mastigatory muscle resection in rats. A microscopic study. Proc Finnish Dent Soc, Vol 73, Suppl X, pp. 1-79.
65 - Lewis EA, Irving JT (1970): An autoradiographic investigation of bone remodelling in the rat calvarium grown in organ culture. Arch Oral Biol 15:769-776.
68 - Markens IS (1975): Transplantation of the future coronal suture to the dura mater of 3- to 4-month-old rats. Acta Anat (Basel) 93:29-44.
70 - Markens IS, Oudhof HAJ (1980): Morphological changes in the coronal suture after replantation. Acta Anat (Basel) 107:289-296.
71 - Markens IS, Taverne AAR (1978): Development of cartilage in transplanted future coronal sutures. Acta Anat (Basel) 100:428-434.
74 - Meikle MC, Heath JK, Atkinson SJ, Hembry RM, Reynolds JJ (1989): Molecular biology of stressed connective tissues at sutures and hard tissues in vitro. In: The Biology of Tooth Movement, ed. by L.A. Norton and C.J. Burstone, Boca Raton: CRC Press, Inc, pp. 72-86.
75 - Meikle MC, Heath JK, Hembry RM, Reynolds JJ (1982): Rabbit cranial suture fibroblasts under tension express a different collagen phenotype. Arch Oral Biol 27:609-13.
76 - Meikle MC, Heath JK, Reynolds JJ (1984): The use of in vitro models for investigating the response of fibrous joints to tensile mechanical stress. Am J Orthodont 85:141-53.
77 - Meikle MC, Sellers A, Reynolds JJ (1979): Rabbit cranial sutures in vitro: a new experimental model for studying the response of fibrous joints to mechanical stress. Calcif Tissue Int 28:137-44.
79 - Miyawaki S, Forbes DP (1987): The morphologic and biochemical effects of tensile force application to the interparietal suture of the Sprague-Dawley rat. Am J Orthod Dentofacial Orthop 92:123-133.
80 - Moffett BC (1971): Remodeling of the craniofacial articulations by various orthodontic appliances in Rhesus monkeys. Eur Orthod Soc Trans, pp 207-216.
81 - Mörndal O (1986): DNA-synthesis in mechanically stimulated osteogenic tissue: An autoradiographic study using tritiated thymidine. Eur J Orthod 8:30-34.
82 - Moss ML (1954): Growth of the calvaria in the rat. Am J Anat 94:333-362.
83 - Moss ML (1957): Experimental alteration of sutural area morphology. Acta Anat (Basel) 127:569-590.
85 - Moss ML (1960): Inhibition and stimulation of sutural fusion in the rat calvaria. Anat Rec 136:457-468.
86 - Moss ML (1961): Extrinsic determination of sutural area morphology in the rat calvaria. Acta Anat (Basel) 44:263.
88 - Nash SB, Kokich VG (1985): Evaluation of cranial bone suture autotransplants in the growing rabbit. Acta Anat (Basel) 123:39-44.
89 - Oudhof HAJ (1982): Sutural growth. Acta Anat (Basel) 112:58-68.
90 - Oudhof HAJ, Markens IS (1982): Transplantation of the interfrontal suture in the Wistar rat. Acta Anat (Basel) 113:39-46.
91 - Persson KM (1989): Regulating factors in suture development, growth, and closure. In: Scientific Foundations and Surgical Treatment of Craniosynostosis, edited by J.A. Persing, M.T. Edgerton, J.A. Jane, Baltimore: Williams and Wilkins, Ch. 6, pp. 45-49.
93 - Persson M (1983): The role of movements in the development of sutural and diarthrodial joints tested by long-term paralysis of chick embryous. J Anat 137:591-599.
97 - Petrovic A, Charlier JP, Hermann J (1968): Les mechanismes de croissance de crâne. Bull Assoc Anat (Nancy) 143:1376-1392.
105 - Selman AJ, Sarnat BG (1957): Growth of the rabbit snout after extirpation of the frontonasal suture. A gross and serial roentgenographic study by means of metallic implants. Am J Anat 101:273-293.
106 - Shapiro PA (1976): Responses of the nonhuman primate amxillary complex to mechanical forces. In: Factors Affecting the Growth of the Midface, edited by J.A. McNamara, Jr., Center for Human Growth and Development, Ann Arbor, MI, pp. 327-348.
110 - Smith HG, McKeown M (1974): Experimental alteration of the coronal sutural area: A histological and quantitative microscopic assessment. J Anat 118:543-539.
111 - Southard KA, Forbes DP (1989): The effects of force magnitude on a sutural model: A quantitative approach. Am J Orthod Dentofacial Ortgop 93:460-466.
112 - Steenvoorden GP, van de Velde JP, Prahl-Andersen B (1990): The effect of duration and magnitude of tensile mechanical forces on sutural tissue in vivo. Eur J Orthod 12:330-339.
113 - Stenström SJ, Thilander BL (1967): Facial skeleton growth after bone grafting to surgically created premaxillo-maxillary defects: An experimental study in the guinea pig. Plast Reconstr Surg 40:1-12.
114 - Thörs O (1964): Compression of facial sutures by external pressure (Milwaukee Brace) demonstrated by the implant method. Trans Eur Orthod Soc, pp 221-232.
118 - Tuenge RH, Elder JR (1974): Posttreatment changes following extraoral high-pull traction to the maxilla of Macaca mulatta. Am J Orthod 66:618-644.
121 - Wagemans PAHM, van de Velde J-P, Kuijpers-Jagtman (1988): Sutures and forces: A review. Am J Orthod Dentofacial Orthop 94:129-141.
122 - Washburn SL (1946): The effect of facial paralysis on the growth of the skull of rat and rabbit. Anat Rec 94:163-168.
123 - Washburn SL (1947): The relation of the temporal muscle to the form of the skull. Anat Rec 99:239-248.
124 - Watanabe M, Laskin DM, Brodie AG (1957): The effect of autotransplantation on growth of the zygomatico-maxillary suture. Am J Anat 100:319-336.
125 - Watzek G, Grundschober F, Plenk H Jr, Eschberger J (1982): Experimental investigation into the clinical significance of bone growth at viscerocranial sutures. J Max-Fac Surg 10:61-79.
126 - Weinmann JP, Sicher H (1955): Bone and Bones, 2nd ed. St. Louis: C.V. Mosby Company, pp. 88-91.
129 - Yen EHK, Pollit DJ, Whyte WA, Suga DM (1990): Continuous stressing of mouse interparietal suture fibroblasts in vitro. J Dent Res 69:26-30.
131 - Yen EHK, Yue CS, Suga DM (1989): Effect of force level of synthesis of Type III and Type I collagen in mouse interparietal suture. J Dent Res 68:1746-1751.
