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ORIGINAL ARTICLE

Morphologic and hemodynamic analysis ofdental pulp in dogs after molar intrusion withthe skeletal anchorage systemYuichi Konno,a Takayoshi Daimaruya,b Masahiro Iikubo,c Reiko Kanzaki,b Ichiro Takahashi,b

Junji Sugawara,d and Takashi Sasanoe

Sendai, Japan

Introduction: We have successfully treated skeletal open bite by intruding posterior teeth with the skeletalanchorage system. Our aim in this study was to morphologically and hemodynamically evaluate the changesin pulp tissues when molars are radically intruded. Methods: The mandibular fourth premolars of 9 adultbeagle dogs were divided into 3 groups: a sham operated group (n � 6, 3 dogs), 4-month intrusion group(n � 6, 3 dogs), and a further 4-month retention group (n � 6, 3 dogs). We evaluated the morphologicalchanges of the pulp and dentin—the amount of vacuolar degeneration in the odontoblast layer, the predentinwidth and nervous continuity in the pulp tissue, and the pulpal blood-flow response evoked by electricalstimulation in the dental pulp. Results: Extreme molar intrusion with the skeletal anchorage system causedslight degenerative changes in the pulp tissue, followed by recovery after the orthodontic force was released.Circulatory system and nervous functions were basically maintained during the intrusion, although a certainlevel of downregulation was observed. These morphologic and functional regressive changes in the pulptissue after molar intrusion improved during the retention period. Conclusions: Histologic changes andchanges in pulpal blood flow and function are reversible, even during radical intrusion of molars. (Am J
Orthod Dentofacial Orthop 2007;132:199-207)
Intrusive force application is thought to cause sev-eral pulpal tissue changes due in part to thecompression force on periapical blood vessels

created by the apical displacement of the tooth. Histo-logic studies showed that the application of continuousintrusive force causes pulp tissue changes such asdisruption of the odontoblastic layer,1 vacuolization,and circulatory disturbances.2 Previous information isavailable on the effect of brief intrusive forces onpulpal blood flow. Orthodontic intrusion of teethevoked a temporary reduction in pulpal blood flow

From the Graduate School of Dentistry, Tohoku University, Sendai, Japan.aResearch fellow, Division of Orthodontics and Dentofacial Orthopedics,Department of Oral Health and Development Sciences.bResearch associate, Division of Orthodontics and Dentofacial Orthopedics,Department of Oral Health and Development Sciences.cResearch associate, Division of Oral Diagnosis, Department of Oral Medicineand Surgery.dAssociate professor, Division of Orthodontics and Dentofacial Orthopedics,Department of Oral Health and Development Sciences.eProfessor and chairman, Division of Oral Diagnosis, Department of OralMedicine and Surgery.Reprint requests to: Yuichi Konno, Division of Orthodontics and DentofacialOrthopedics, Department of Oral Health and Development Sciences, TohokuUniversity, Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai980-8575, Japan; e-mail, [email protected], April 2005; revised and accepted, July 2005.0889-5406/$32.00Copyright © 2007 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2005.07.029
during the first minute after force application. Thenpulpal blood flow gradually increased toward preload-ing flow values for the next 4 minutes and returned tothe prestimulus level 3 minutes after unloading.3,4

These previous studies simply evaluated the short-termchanges in the blood flow of an incisor when intrusiveforce was applied and did not confirm histologicchanges in tooth movement accompanied by boneremodeling.

It was difficult to provide absolute anchorage formolar intrusion by using traditional orthodontic mech-anotherapy. We developed a skeletal anchorage system(SAS) to provide intraoral absolute anchorage fororthodontic tooth movement.5,6 We demonstrated mo-lar intrusion to achieve counterclockwise rotation of themandibular and occlusal planes to improve open biteswithout orthognathic surgery.7,8 Clinically, we ob-served no signs of iatrogenic problems in the dentalpulp of molars intruded using the SAS. In a previousstudy, we demonstrated remarkable mandibular fourthpremolar intrusion using the SAS in beagle dogs andreported that neither nerves nor blood vessels of theinferior alveolar neurovascular bundles were dam-aged.9 Few studies have investigated pulp responses fornoxious stimulation to evaluate the vitality and reactiv-
ity of the dental pulp during and after molar intrusion.
199

American Journal of Orthodontics and Dentofacial OrthopedicsAugust 2007

200 Konno et al

The antidromic activation of sensory nerves wasevoked by stimulation in the peripheral direction, and itfollowed that blood flow increased in the tissues theyinnervate.10,11 Moreover, vasodilatation in the pulp ofcats can also be elicited by electrical stimulation of themental nerve or the pulp of an adjacent tooth.12 Theseresults suggested that axon reflex vasodilatation in thedental pulp might be mediated by stimulation.

In this study, the pulpal nerves of the experimentalteeth were electrically stimulated at the threshold level,and blood flow was assessed with a laser Dopplerflow meter. We carried out experiments to determinewhether detectable changes in the pulpal blood flowcould be evoked by electrical stimulation as a pain-producing stimulus of the pulpal nerve before and aftermolar intrusion, and after mechanical retention. Addi-tionally, we evaluated the pulpal nerve continuity afterextreme molar intrusion using wheat-germ agglutininconjugated with horseradish peroxidase (WGA-HRP,type IV, Sigma, St Louis, Mo) as an anterograde andretrograde axonal tracer. If the pulpal nerve is notdamaged and normally continuous, it will be trans-ported to the pulpal nerve through the mental nerve.

Our aim in this study was to evaluate the morpho-logic and functional changes in pulp tissuee whenmolars are intruded and after they have been mechan-ically retained, using morphologic and hemodynamicanalyses.

MATERIAL AND METHODS

Nine adult female beagles (age, 12 months) wereused in this investigation. The bilateral mandibularfourth premolars were divided into 3 groups: a shamoperated group (C group, n � 6, 3 dogs), a 4-monthintrusion group (I group, n � 6, 3 dogs), and a 4-monthretention group after 4 months of intrusion (R group,n � 6, 3 dogs). In the dogs in the C group, the anchorplate was implanted, and no orthodontic force wasapplied; they served as controls. In the I group and theR group, the premolars were intruded by using theanchor plate for 4 months, and an additional 4 monthsof retention was carried out for the intruded molars inthe R group.

The anchor plates (ORTHOANCHOR plate, T-S-Land T-S-R, 18.85 mm long; pure titanium) and bonescrews (ORTHOANCHOR screw, 0.2 mm � 5 mm,pure titanium) (Dentsply Sankin, Tokyo, Japan) used foranchorage of tooth movement were specifically designedfor orthodontic treatment, as shown in Figure 1, a.

The surgical procedures for the implantation ofanchor plates were described previously.9 Briefly, theanimals were anesthetized with sodium pentobarbital
(Wako Chemicals, Tokyo, Japan) at a dose of 25 mg
per kilogram of body weight. Local anesthesia (2%lidocanine, Fujisawa Yakuhin, Tokyo, Japan) was ap-plied at the implantation sites of the anchor plates. A2-cm mucosal incision was made in the buccal mandi-ble, and the mucoperiosteal flap was reflected inferiorlyto the lower border of the mandible. The anchor plateswere fixed on the buccal side of the mandible with 3titanium bone screws, and the hook was placed in themiddle area of the mandibular third and fourth premo-lars (Fig 1, c). Another bone screw was fixed on thelingual alveolar bone between the fourth premolar andthe first molar (Fig 1, d). The mucoperiosteal flap wasrepositioned, and the surgical wound was sutured withthe long arm of the anchor plate intraorally exposed.Additionally, bone markers were inserted into thebuccal cortical bone around the anchor plate as refer-ence points to measure tooth movement by superim-posing the tracings of radiographs. After a 3-weekhealing period, an intrusive force (100-150 g) wasapplied to each mandibular premolar for 4 months.During the experimental period, the tooth and thetransmucosal portions of the anchor plates were cleanedby brushing and irrigation with 0.2% aqueous chlo-rhexidine.

To evaluate the amount of molar intrusion, stan-dardized dental radiographs were taken by using a filmholder attached to the titanium miniplates and the thirdpremolar. Standardized radiographs, with 200-mmfocus-to-object distance and 2 mm object-to-film dis-tance, were taken every 4 weeks. The radiographs weremagnified 5 times with a mounted slide projector. Thetitanium miniplate and screws, teeth, lower border ofthe mandible, inferior alveolar neurovascular bundle,and bone markers were traced.

The amount of tooth movement of the 18 fourthpremolars, defined as the distance between the 2 linesconnecting the mesial and distal root apices, wasmeasured by superimposing those tracings on the tita-nium bone markers and the anchor plate. Actual toothmovement was calculated by dividing the measuredvalues by 5. As described in our previous study,9 theintraobserver difference was about 0.015 mm, and thestandard deviation of the mean differences between 2observers was 0.03 mm.

To prevent damage on the nerve by WGA-HRPinjection, pulpal blood flow was measured 2 daysbefore the experimental period of each group. Theanimals were anesthetized with sodium pentobarbital atan initial dose of 30 mg per kilogram intravenously,supplemented, when necessary, with additional dosesof 20 to 30 mg per kilogram. Because our previousstudy indicated that pulpal blood flow strongly de-
pended on systemic blood pressure,13 we continuously

od flow

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 132, Number 2

Konno et al 201

monitored blood pressure in the femoral artery with apressure transducer and recorded it on a polygraph(Polygraph 360 system, NEC, Tokyo, Japan). Thus, weverified that there was no influence from the center.

The animals were intubated and paralyzed by intra-venous injection of pancuronium bromide (Mioblock,Sankyo, Tokyo, Japan; 0.4 mg per kilogram initially,then constant infusion of approximately 0.2 mg perkilogram per hour), and artificial ventilation was main-tained with a respirator (model SN-480-3, Shimano,

Fig 1. SAS components, surgical proceduressystemic blood pressure. a, Orthodontic ancplacement of anchor plate on cortical bonemechanics using orthodontic anchor plate andtation of and monitoring system for pulpal blo

Tokyo, Japan) with a mixture of 25% pure oxygen and

75% room air at a frequency of 20 to 24 times perminute. Each animal lay on a warmer table, with thetemperature thermostatically maintained at 42°C. Thehead was fixed to a steel table with a magnetic clamp(MB-B, Kanetue, Tokyo, Japan) with a bar attached tothe frontal sinus. The jaws were held open with siliconeputty.

The pulpal blood flow of the fourth mandibularpremolar was recorded noninvasively with a modifiedconventional laser Doppler flow meter (ALF 21D;

monitoring system for pulpal blood flow andlates and monocortical bone screws and b,r mucoperiosteal flap. c and d, Orthodontical bone screw. e and f, Schematic represen-

and systemic blood pressure.

, andhor pundelingu

Advance, Tokyo, Japan), which emits a 5 mW intensity


202 Konno et al

beam of monochromatic light from a laser diode. Theflow meter’s probe (outer diameter: 1.5 mm) is com-posed of 2 glass graded-index optical fibers, 1 trans-mitting and the other receiving, each with a corediameter of 100 �m. With transmitted laser light, weused 2 probes, 1 fiber of which served as the transmitteron the labial side of the tooth, and the other (havingbeen placed to the lingual side) served as the receiver.The method used to monitor pulpal blood flow wassimilar to that reported previously.14 This equipmentgives no absolute values but permits relative changes inblood flow to be assessed.

To enable a reliable interpretation of the measure-ments, the 2 probes of the flow meter were stabilized byinserting them into a stainless-steel tube (inner diame-ter; 1.5 mm) attached to the buccolingual sides of theacrylic stent, with its center positioned at the centrallong axis and 4 mm below the premolar cusp (Fig 1, f).

To verify the reliability of the transmitted laser lightat a laser power of 5 mW, a pilot study was conductedin the bilateral fourth premolars in 4 dogs. Beforetreatment of the pulp to induce necrosis, pulpal bloodflow and systemic blood pressure were measured in 4subjects. After monitoring in each experimental sub-ject, the pulp of the left premolar was exposed with ahigh-speed water-cooled diamond bar, and Periodonwas applied (Neo Dental Chemical Products, Tokyo,Japan) to cause necrotic changes of the pulp tissue. Aweek later, the pulpal blood flow of the bilateral fourthpremolar was monitored again.

The output signals measured with transmittedlaser light registered 0 aubitory units (a.u.) in allnonvital teeth. On the other hand, vital teeth beforePeriodon treatment showed 3.21 a.u. on average. Thetransmitted laser with the laser power increased to 5mW monitored pulpal blood flow and assessed toothpulp vitality. Blood flow signals from outside thepulp were not detectable.

We carried out experiments to determine whetherdetectable changes in pulpal blood flow could beevoked by electrical stimulation of a pulpal nerve. Theelectrical stimulation was applied to the pulp in theexperimental teeth in each of the 3 groups by using anoninvasive tooth pulp stimulation test; in a stepwisemanner, we increased the electrical stimuli deliveredwith an electric pulp tester (Analytic Technologies,Redmond, Wash). Before stimulation, each tooth wascarefully cleaned with alcohol, dried with a stream ofair, and isolated with cotton wool. The cathode of thestimulator was attached so that it made firm contactwith the buccal surface of the tooth at least 3.5 mm
from the gingival margin. Pulpal blood flow and sys-
temic blood pressure were recorded before, during, andafter the stimulation.

Data analysis

Pulpal blood-flow signals were analyzed by usingMacLab (ADInstruments, Castle Hill, NSW, Austra-lia). The peak values of the pulpal blood-flow changeswere expressed as percentages of the baseline bloodflow (baseline, mean of the prestimulation flow for 3minutes; peak, mean of the maximum flow for 30seconds during or after stimulation in the sameanimal) and given as mean � standard deviaiton.15

The calculated peak values after electrical stimulationin the I group were compared with those in the C andthe R groups. Statistical analysis was undertaken withSPSS for Windows (SPSS, Chicago, Ill). Differenceswere evaluated with the Mann-Whitney U test, and Pvalues less than .05 were considered significant.

To evaluate nerve continuity, WGA-HRP in phys-iologic saline solution was injected into the mentalnerve as an antidromic and anterograde neural tracer.After recording the pulpal blood flow and axon reflexvasodilatation, topical injection of WGA-HRP (Toyobo,Osaka, Japan) into the mental nerve was carried out asdescribed by Marfurt and Turner.16 The bilateral mentalforamen and nerve were exposed by removing the sur-rounding tissues, and 1 �L of 5% WGA-HRP in salinesolution was injected through a glass micropipette(diameter, 50 to 70 �m) connected to micro syringe.Total injection (1 �L � 5 times) required at least 10minutes, and the micropipette was left in place for anadditional 5 minutes before being withdrawn. Thisinjection was carefully performed to prevent any dif-fusion of the tracer.

All animals were killed 48 hours after the end of theexperiment. Each animal was anesthetized with sodiumpentobarbital and perfused with paraformaldehydethrough both common carotid arteries. The middle partof the mandibular bodies including the fourth premolarswas dissected. The specimens were decalcified in eth-ylene diamine tetra-acetic acid for 16 weeks. Then theywere divided into the mesial area (including mesialroot) for histologic evaluation of the pulp with sur-rounding tissues and the distal area (including distalroot) for evaluation of the pulpal nervous tissue. Themesial area of each specimen was embedded in paraffinafter decalcification. Five-micrometer thick serial sec-tions through the pulp in an axio-buccolingual directionwere prepared. The sections were stained with hema-toxylin and eosin for histologic observation of the pulptissue. Additionally, the distal root of the experimentalpremolar was dissected out and stored overnight in 20%
sucrose solution. The distal root was cryoembedded in

point


Konno et al 203

OCT compound (Sakura seiki Products, Osaka, Japan)and then sectioned at 20 �m with a cryostat. Thesections were reacted according to a tungstate modifi-cation of the tetramethylbenzidine technique for thevisualization of horseradish peroxidase.17 After com-pleting the reaction, all sections were air-dried andcounterstained with 0.1% neutral red. The sectionswere then observed with a phase contrast microscope.

RESULTS

The results of the radiographic analysis are summa-rized in Figure 2. The amount of tooth movementduring the experimental period was 2.9 � 0.5 mm onaverage in the I group and 3.0 � 0.5 mm in the Rgroup. There was no statistically significant differencebetween the 2 groups. The fourth premolars wereintruded in 4 months without lingobuccal and mesio-

Fig 2. Radiographic images of fourth premolaretention. d, Amount and time course of toothMean and SD bars are indicated at each time

distal tipping, and the root apices had penetrated into

the alveolar bone wall (Fig 2, b). The intruded fourthpremolars of the R group were stable through the4-month retention period as shown in Figure 2, c.

Typical recordings of the 3 experimental groups areshown in Figure 3, a-c. No changes in systemic arterialblood pressure were induced by the electrical stimulationthroughout the experiment (upper traces, Fig 3, a-c).

The amounts of increase in pulpal blood flowevoked by the electrical stimulation, expressed as apercentage of resting, were 347.8% � 59.8% (n � 6) inthe C group, 157.8% � 23.3% (n � 6) in the I group,and 330.3% � 54.6% (n � 6) in the R group (Mann-Whitney U test, Fig 3, d). Because this response wasnot associated with increased systemic arterial bloodpressure, it was assumed to be due to pulpal vasodila-tion. The pulpal blood-flow responses were signifi-cantly lower in the I and C groups (P �.05), and the

efore intrusion; b, after intrusion; and c, afterment. Broken line, I group; solid line, R group.(n � 9).

rs: a, bmove

signal reaction, reduced during intrusion, was restored


204 Konno et al

to near the control value by the end of the retentionperiod. There was a significantly greater increase in theR group compared with the I group (P �.05).

The pulp tissues in the C group exhibited normalhistologic appearance (Fig 4, a). Odontoblasts had thecharacteristically columnar shape in the coronal por-tion. Most teeth in the I group showed marked changesin the pulp and dentin (Fig 4, b). Higher vacuolizationof the odontoblast layer than that of controls andreduction in the width of predentin layer were seen inthe I group. Inflammatory responses were not generallyseen, and a slight cellular infiltration was discerned.

Fig 3. Systemic blood pressure and responses in pul-pal blood flow in electrically stimulated control andexperimental fourth premolars: a, C group; b, I group; c,R group. d, Pulpal blood-flow response in each groupwas quantitated. Pulpal blood response in I group wassignificantly lower than in other groups (P �.05). BP,blood pressure; PBF, pulpal blood flow. Arrows indicateelectrical stimulation in time course.

Reductions in the number of capillary blood vessels in

the periodontal ligament below the apical foramen andin the size and number of odontoblast and fibroblastscompared with the C group were found immediatelyafter intrusion (Fig 4, b and h). At the end of theretention period, the amount of vacuolization in theodontoblast layer was reduced in the R group comparedwith that in the I group. Moreover, the predentin widthwas slightly larger in the R group than in the I group(Fig 4, c). There was a noticeable increase in theconcentration of capillary blood vessels in the peri-odontal ligament below the apical foramen region in theR group compared with the I group (Fig 4, i).

The intensity of WGA-HRP labeling varied amongdogs, but no great difference in distribution was ob-served. The WGA-HRP reaction products indicatedrich innervations in dental pulp. The labeled nervebundle entered the root pulp through the apical dentalforamen with the blood vessel parallel to the long axisof the tooth. The nervous continuity was maintained inthe 3 groups (Fig 4, d-f).

DISCUSSION

The laser Doppler flow meter, developed in the1970s as a noninvasive electro-optical technique tomeasure the velocity of red cells in skin capillaries, hasbeen used for the diagnosis of pulp vitality in humanteeth.18 It was originally developed to measure bloodflow in the skin, in which capillaries are much closer tothe surface than in the dental pulp. Hence, the widelyused laser power (2 mW) is insufficient for detectingpulpal blood flow with transmitted laser light (at leastwith the current type of apparatus). We developed atransmitted laser light flow meter apparatus and dem-onstrated that high-powered (5 mW) transmitted laserlight could be a better tool for both monitoring thepulpal blood flow of the teeth and assessing tooth-pulpvitality than the conventional back-scattered light flowmeter apparatus.19,20 Therefore, the transmitted laserlight was found to be useful for the assessment of toothpulp vitality both because blood-flow signals did notinclude flow of nonpulpal origin, and also because theoutput signals and responses to blood-flow changeswere clear and could easily be monitored.

In previous studies, researchers reported that degen-erative changes, vacuolization of the odontoblast layer,circulatory disturbances,2 and transient reduction of theamount of pulpal blood flow21 were induced in pulptissues after short-term tooth intrusion. Based on ourhistologic findings, the pressure generated by the intru-sive force reduced the number of capillary bloodvessels below the apical foramen. In addition, wedemonstrated that it was possible to record the increase
and decrease in pulpal blood flow caused by electrical


Konno et al 205

Fig 4. Photmicrographs of sections from pulp tissue from fourth premolars: a and d, C group; b and e,I group; c and f, R group. Vacuolization in odontoblast layer in I group was outstanding in hematoxylinand eosin staining (a-c). Nervous continuity in all experimental groups indicated by WGA-HRP labeling(white arrows). Photomicrographs from apical tissue: g, C group; h, I group; i, R group. Arrowheadsindicate capillary vessels. Original magnification � 400 (a-c), � 400 (d-f), and � 200 (g-i). Black arrows,
Vacuolization in odontoblast layer; D, Dentin; P, pulp tissue; ob, odontoblasts.


206 Konno et al

stimulation of the pulpal nerve. Because the innervationwas maintained in the 3 groups and there was noassociated change in femoral blood pressure, it can beassumed that these effects were due to pulpal vasodi-latation and vasoconstriction. Previous research sug-gested that a parasympathetic vasodilator mechanism isnot present in feline dental pulp.20 Therefore, it can beconsidered that the sensory and sympathetic nerves inthe pulp were not damaged, and the peripheral circula-tory mechanism was maintained, whereas the apparentreduction in blood flow in response to electrical stim-ulation suggested actual suppression of the blood sup-ply to the pulp tissue. Taking these into consideration,pulpal tissues might have been exposed to a reductionin nutrients or oxygen when the intrusive force wasapplied to the teeth.

The greatly reduced width of the predentin layerobserved in the pulp of the teeth in the I group, in whichthe vacuolization was the most marked of the 3 groups,suggested that the matrix formation was retarded orinhibited by the low blood supply. Because morecapillaries in the apical area and reduction of thevacuolization in the pulp were found in the R group,repair of the odontoblast layer might have occurredbecause of the improved circulatory pattern that re-sulted from angiogenesis in the apical area after themechanical retention. Additionally, no significant dif-ferences in the extent of vasodilation evoked by elec-trical stimulation were found between the C and Rgroups. It is suggested that alteration in the circulatorypattern and reparative changes occurred in the pulp asa result of the retention. Therefore, it can be consideredthat the encapsulated pulp tissue was severely disruptedduring the application of intrusive force, although it didnot undergo necrotic changes, and that recovery fromthe degenerative changes can occur after the releasefrom compression.

The activation of sensory nerves in the pulp bydirect electrical stimulation induces a long-lastingblood-flow increase in the pulp in normal conditions asshown in this and previous studies.22,23 Upon activationof these nerves, vasoactive neurokinins, such as sub-stance P (SP) and calcitonin gene-related peptide(CGRP), might be released from sensory nerve termi-nals. The initial component of axon reflex-mediatedvasodilation is mediated by SP, whereas the continuinglong-lasting rise in blood flow depends on CGRP.24,25

SP might lead to endogenous activation of inflamma-tory mediators released in the pulp. This aspect becameobvious when it was found that pulpal vasodilation inresponse to the local application of bradykinin oc-curred, to a great extent, via the activation of sensory
nerves.26 On the other hand, sympathetic vasoconstric-
tion is counteracted by the local activation of sensorynerves and the release of vasodilator neuropeptides.Reflex activation of sympathetic nerves and localrelease of noradrenaline attenuates the release ofCGRP and SP. Overall, the process is regarded as anappropriate defense response that enhances the trans-portation of nutrients and metabolites to the pulptissue. Taken together, the blood-flow response to theelectrical stimulation to the pulp could be regulatedby SP or CGRP.

In this study, we demonstrated the effects of long-term, radical molar intrusion using SAS on morpho-logic and hemodynamic changes in pulp tissues. Al-though radical molar intrusion caused slight regressivechanges in the pulp tissue in the short term, blood flowand innervation were maintained in the pulp chamber,and the axon reflex vasodilatation could be detected.Therefore, we concluded that the histologic changesand the changes in pulpal blood flow and function arereversible even during radical intrusion of molars.However, in humans, it is still unclear whether theapplication of intrusive forces for longer than 4 monthsaffects pulp viability. Further experiments are neededto clarify the biologic effects of intrusion of molarswith SAS.

CONCLUSIONS

Although remarkable molar intrusion with SAScaused slight regressive changes in pulp tissues, theblood flow and the nervous system were kept in thedental pulp, and the axon reflex vasodilatation wasdetected, indicating that functions of the blood vesselsand the nerves were maintained. Furthermore, thesemorphologic and functional regressive changes in pulptissue after molar intrusion improved during the reten-tion period. These results indicated that changes indental pulp after radical intrusion with SAS are less andreversible.

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