Interruption of the Arterial Inferior Alveolar Flow and Its Effects on Mandibular Collateral Circulation and Dental Tissues W. A. CASTELLI, C. E. NASJLETI, and R. DIAZ-PitREZ University of Michigan Medical and Dental School, Department of Anatomy, Veterans Administration Hospital, Ann Arbor, Michigan 48104, USA and Annapolis Hospital, Detroit, Michigan The interruption of circulation through the good nutrition to the bone and in accelera- inferior alveolar artery was followed by the ting the healing process.2-4 On certain oc- establishment of a fast retrograde blood flow casions, however, because of the nature and through the vessel. The mental artery and extent of the pathological process, the re- the mandibular branch of the sublingual section of the artery is an imminent fact.5.6 artery were the main vessels to contribute to Thus, preserving the main collateral circu- that flow. No histopathologic changes were lation to the mandibular segments remain- found in the experimental hemimandibles; ing after surgery is important for a success- however, temporary regressive changes were ful mandibular reconstruction. found in the dental pulps of molars. This investigation involves the study of the retrograde circulation established in the mandibular body after the inferior alveolar As has been stated by Skopakof,' the mental artery has been cauterized, the relative branch of the inferior alveolar artery and participation of the mental artery and the the mandibular branch of the sublingual mandibular branch of the sublingual artery artery are the main collateral vessels that in originating and maintaining a retrograde supply the mandibular body when circula- blood flow, and the histopathologic changes tion through the inferior alveolar artery has that might occur in the mandibular body as been interrupted. These vessels must ex- a result of the interruption of circulation perience a compensatory process of growth through the inferior alveolar artery. to meet the nutrient demands of the man- dibular body. However, the kinetics and Materials and Methods physiologic mechanisms involved in the The rhesus monkey (Macaca mulatta) was growth of the vessels as a consequence of the the animal chosen for this investigation be- inferior alveolar artery obliteration have not cause the morphology of the mandible, been discussed in detail. It is also probable teeth, dental supporting tissues, and related that the tissues located too distally to be vascular supply are similar to those of supplied by the newly established retrograde man.7-9 circulation might have suffered some patho- ANGIOGRAM STUDY.-Nine young adult physiologic changes as a result of distur- monkeys of both sexes and with permanent bances in the hemodynamics of the local dentitions were used. General anesthesia blood flow. was induced with pentobarbital sodium During surgical interventions on the man- (Nembutala), 30 mg/kg of body weight. dible, the preservation of the inferior alveo- The skin over the parotideomasseteric lar artery in the inferior alveolar canal has area was prepared routinely for surgery with been considered important in providing adequate drapes to circumscribe the sur- Received for publication August 15, 1974. a Nembutal Sodium R, 50 mg/ml, Abbott Labora- Accepted for publication January 9, 1975. tories, Chicago, Ill. 708 Vol 54 No. 4 MANDIBULAR COLLATERAL CIRCULATION 709 FIG 1.-Schematic representation of newly established retrograde circulation in mandible after inferior alveolar artery was cauterized. gical field. A vertical cutaneous incision was tersection of two imaginary lines linking made anterior to the auLricle and inferior to the coronoid process-mandibular angle, and the zygomatic archi to expose the parotid the mandibular condyle-facial groove on the gland and masseter muscle covered by the basilar border of the mandible. A careful parotideomasseteric fascia. After preparing drilling of the ramus followed until the in- suitable skin flaps, the fascia was dissected ferior alveolar artery was identified. In most loose, the parotid gland packed posteriorly, instances, dLuring the arterial cauterization, and the masseter muscle incised vertically to th-e inferior alveolar nerve was damaged be- reach the lateral surface of the ramus. The cause of its close proximity to the artery in detachment of some masseter fibers from thd the inferior alveolar canal. Closing of the suirface of tlhe ramus was necessary to create wound ended the surgical stage. space for working with the suirgical bur. A daily intramuscular injection of peni- TFhe area of the mandibular ramus to be cillin-streptomycin (Combioticb) was given drilled to locate the inferior alveolar canal opening was determined by the point of in- b Combiotic, Pfizer, Inc., New York, NY. FIG 2.-Angiogram, one day after surgery. Tenuous alveolodental branches (ADB) were notice- able in premolar area (E). Control hemimandible (C). 710 CASTELLI, NASJLETI, AND DIAZ-PkREZ J Dent Re5 JUIY-August 1975 FIG 3.-Angiogram, two days after surgery. Full retrograde blood flow has been established on experimental side (E). Arterial anastomotic bridges (AAB) are also distinct structures. Man- dibular branch (MB). for four days postoperatively to prevent the mandibular branclh of the sublingual secondary infections of the surgical wound, artery were measured on the specimens and and the monkeys were given a soft diet for radiograph1s using a dissecting microscope a week. The animals were killed at 1, 2, with1 a micrometer scale attached to it. 4, 5, and 12 days, and tlhree, four, six, and HISTOLOGICAL S&1UDY.-As a result of the nine weeks after suLrgery. Immediately after angiogram evaliation, a hiistological study the monikeys were killed, both external ca- of the premolars and molars, periodontal rotid arteries were cannullated and a modi- membranes, and related alveolar bone was fied Sclhlessinger's radiopaqlue mass1o was Ineeded for better evaluation of the probable perftused into the facial area for angiogram changes in those tissues as a result of altera- study. Pressure, averaging about 105 mm tions in local circulation. The same sur of mercLury, was used for injecting the radio- gical operation was performed On six addi- paque material in botlh arteries, and this tional monkeys. The monkeys were killed pressure was comparable to the systolic pres- at 1, 5, and 12 days, and three, four, and sure in rhiesus monkeys.1' five weeks after surgery. Some heads were All heads were removed and fixed in 10% perfused with an aqueous solution of India buffered Formalin solution. The mandibles ink to help in vascular studies. Proper man- were extracted and cleaned and the perio- dibular blocks were cut out and histolog- steum was detached. Later, they were in- ically processed. Final serial sections were dividually radiographed. The external treated with hematoxylin and eosin and diameter of the mental artery and that of Mallory stains. FIG 4.-Angiogram, five days after surgery. Mandibular branch (MB) traversing mandibular symphysis. AAB, arterial anastomotic bridges; E, experimental side; C, control side. MICRONS 800olP 700- 600- \s Mandibular Branch (Sublingual artery) 5001 400- 9,___ _~~~~~~~~~~~~~~~~~-* 300- 200- .4 Mental Branch ( Inferior alveolar artery) 100- 0 I i I 2 3 4 5 6 7 8 9 W E E K S Fic 5.-Relative growth of mental branch as compared with mandibular branch after circulation through inferior alveolar artery was interrupted. Measurementsy-taken x -from -specimens - -and --angiograms. q - -pm, -micrometers. - - - A~ ~ ~~~~A wv I-A \a F/*W ,< s w : 4N6 tfi te > e* ; M* FIG 6.-One day after surgery. On experimental side (E), shrinkage of fibrocytes as well as shrinkage and grouping of odontoblasts occurred in dental pulp of second molar. C, control side (mag X 125) . 711 712 CASTELLI, NASJIETI, AND DIAZ-PE2REZ J Dent Res July-August 1975 Results imens from monkeys killed up to the ninth ANGIOGRAM FINDINGS.-Angiograms of spec- month postoperatively, there was radio- imens obtained one, two, tlhree, and five days graphlic evidence of the existence of a well- after surgery revealed that a retrograde established retrograde blood flow as well as blood flow tlhroughl the inferior alveolar definite, functioning arterial anastomotic artery had been established. However, the bridges. degree of repletion of the artery and its The degree of participation of tlhe man- branches, judgecd by the intensity of their dibular branch of the sublingual artery and radiolucent images, was variable and not the mental branch in originating and main- lhomogenous. A sclhematic drawing of the tain-ing the retrograde blood flow throuLghi newly established retrogradle circulation is the inferior alveolar atrtery is explained in presented in Figure 1. In the specimen ob- Figure 5. During the first five days of the tained one day after surgery, very tenuous experiment there was a consistent increase, alveolodental branches were noticeable only from 300 to 700 micrometers (rm), in the at the premolar area of tlhe mandibular external diameter of the mandibular branch. body. At the molar area, lhowever, these In all othler specimens studied up to the branches were unremarkable (Fig 2). Two ninth week, little increase occurred. Th-e ex- days after surgery, a full retrograde blood ternal diameter of the mental branch flow liad been establislhed anid distinct ar- slhowed a slower but progressive increase terial anastomotic bridges were demonstra- throughiout thlle experimental period. Twen- ble on the angiograms. Anastomotic bridges ty-four lhours