Structure and mineral content of human exposed cementum

Jpn. J. Oral Biol., 32 180-189, 1990.

ORIGINAL

Structure and mineral content of human exposed

cementum and changes following

phosphoric acid etching

Mie Kuroiwa, Tetsuo Kodaka, Kazuhiro Debari*,

Fumikazu Nakajima and Shohei Higashi

The Second and* First Department of Oral Anatomy,School of Dentistry, Showa University, 1-5-8

Hatanodai, Shinagawa-ku, Tokyo 142, Japan

〔Accepted for publication: December 8, 1989•l

Key words: exposed cementum / Ca and P content / acid etching / amount of dissolved Ca / fine

structure

Abstract: The structural and mineral content of human cervical cementum exposed in the oral cavi-

ty and changes following a 30% phosphoric acid etching were investigated with scanning electron

microscopy, electron-probe microanalysis, and atomic absorption spectrometry. Ca and P concentra-

tions, and the Ca/P molar ratio of the exposed cementum were significantly higher than in the unexpos-

ed cervical cementum. However, there was no significant difference in the amounts of Ca dissolved

from the exposed and the unexposed cementum by acid etching. These results indicate that the amounts

of dissolved Ca may be affected by the amounts of organic fibrous material in the cementum.

The acid etching strongly marked the ends of the extrinsic Sharpey's fibers in the exposed cementum,

whereas in the unexposed cementum these structures were more or less difficult to differentiate from

the intrinsic matrix following polishing and acid etching. The acid-influenced surface layers were di-

vided into two zones; a completely demineralized surfaces zone showing organic fibrous structures and

a partially demineralized subsurface zone, although the surface zone of the exposed cementum was cov-

ered with an organic felt-like sheath.

Introduction

Human fibrillar cementum, containing an

intrinsic matrix and extrinsic Sharpey's fi-

bers, is usually classified into acellular and cel-

lular cementum1-4).

In the cervical region, the acellular ce-

mentum, the gingiva, and the alveolar bundle

bone are normally closely connected with

the periodontal ligament; however, under

conditions of periodontal disease,the cementum

may become partly exposed to the environ-

ment of a periodontal pocket and subsequen-

tly to the oral cavity3,5). It has been suggest-

ed that the surface layer of the exposed

cementum undergoes hypermineralization6-8).

Also exposed cementum is apt to develop

wedge-shaped defects5,9) and/or dental car-ies10-12).

Acid-etch bonding methods have been usedfor sealing enamel fissures13-15). In this meth-

od, resins tightly adhere by resin-tags follow-ing acid etching of the enamel8,15-17). Recent-

ly, this approach has been widely used forthe restoration of Class V cavities which ofteninvolve cementum and dentin as well as en-

amel. In dentin adherence, the resins pene-trate into the dentinal tubules expanded by

acid etching, resulting in adherence by longresin-tags8,18-20).

The pathologically altered cervical region

more or less showing wedged-shaped defectsand/or dental caries may contain attrited en-

amel, dentin, and cementum, which are sur-

M. Kuroiwa et al.: Acid etching of exposed cementum 181

rounded by normal dental hard tissues. Naka-

jima8) has stated that wedge-shaped defectsare needed in the formation of bevels of thecervical enamel because resin strongly adher-ing to the enamel with a removed 'prismless'surface layer is reliable with resin-tags21,22).Based on the structures of the extrinsic Shar-

pey's fibers after acid etching, Nakajima8)has also suggested that attrited cementum sur-rounding wedge-shaped defects with the cer-vical enamel adheres to the resin-tags. Inaddition, he reported that a groove could beformed on the margin of the floor of attriteddentin for promoting the adherence, becausevital dental pulp existing under the floor issealed by the reparative dentin. On the otherhand, Staninec et al.23) have claimed thatcementum and the outermost surface of thedentin might not be suitable for obtainingadequate resin penetration.

Lacefield et al.24) have investigated the ten-sile bond strength of a glass-ionomer cementattached to enamel, dentin, and cementum,and reported that adhesion to acid-etched ce-mentum tended to be stronger than the non-etched cementum, although both enamel anddentin non-etched samples showed good re-sults.

As described above, there are various studi-es on the cementum exposed to the oralcavity3,5-12,23,24), however, basic histologicalstudies have scarcely been done. The presentstudy aims at investigating the structure andmineral content of the surface layer of humanexposed cementum, and their changes fol-lowing phosphoric acid etching. These obser-vations will be useful in discussing whetheracid-etch bonding methods are appropriate ornot for the restoration of cervical lesions in-volving cementum.

Materials and Methods

Labial or buccal cervical root surfaces ofhuman permanent teeth were used in thisstudy. The cementum was clinically, macro-scopically, and microscopically distinguishedinto three groups; exposed-old, unexposed-old, and unexposed-young cementum.

Twenty-five teeth extracted from patientsaged 43 to 54 years with advanced periodontaldisease, which were cariesfree and glossy on

the surfaces of the cervical cementum, were

used as specimens providing exposed-old ce-

mentum. Of the specimens used as unexposed-

old cementum, thirteen teeth were from pa-

tients aged 38 to 49 years with fissure enamel

caries, and fourteen third molars were from

patients aged 33 to 45 years, which had macro-

scopically a few remnants of periodontal liga-

ment on the cervical root surface. As speci-

mens of unexposed-young cementum, twenty-

seven premolars extracted from orthodontic

patients aged 9 to 12 years were used.

The teeth were fixed in 10% formalin at

pH 6.5, rinsed in running water, and then

distilled water. The crowns and apices were

cut off with a diamond wheel. Many of the

roots were polished on the surface using a

polishing brush with 0.3 ƒÊm alumina in order

to remove organic materials such as plaque

and other debris or remnants of periodontal

ligament; however, a few specimens in each

group were left intact.

Atomic absorption spectrometry (AAS)

A window 4 (2•~2)mmmm2 in area was made

on each cervical cementum surface of seven

exposed-old, eight unexposed-old (four third

molars), and thirteen unexposed-yound ce-

mentum of the specimens, and each tooth ex-

cept for the window area was covered with nail

varnish. The window area was etched with

10 ƒÊl of 30% phosphoric acid (H3PO4) at pH

1.4 for 60 seconds. The etching solution on

the surface was removed by washing with dis-

tilled water. The resulting solution was col-

lected and EDTA-4Na was added for a final

concentration of 0.25M and a volume of 10

ml. The amounts of dissolved Ca in this sam-

ple was measured using a Nichiden Varian

1100 atomic absorption spectrophotometer

with a calcium hollow-cathode lamp; the Ca

μg/mmmm2 was then calculated. The determina-

tion of Ca was carried out under the follow-ing experimental conditions; wave-length422.7 nm, slit width 5 nm, air-flow 7.5 l/min.,acetylene-flow 1.0 l/min25).

Electron probe microanalysis (SEM-EDXand SEM-WDX)

Five specimens treated with acid in each

group and six exposed-old, six unexposed-old(three third molars), and seven unexposed-young cementum of the non-etched specimens

182 Jpn. J. Oral Biol., 32: 180-189, 1990.

were embedded in styrol. They were longi-

tudinally cut with a diamond wheel and polish-

ed with 0.3 ƒÊm alumina on a polishing cloth.

This was followed by ultrasonic cleaning in

distilled water and by dehydration with alco-

hol. The ground smooth surfaces were coated

with carbon and subjected to electron probe

microanalysis with a Hitachi X-560 scanning

electron microscope fitted with a Kevex 7000

Q energy dispersive detection system (SEM-

EDX). At each surface layer five points

were analyzed about 10 ƒÊm from the cementum

surface under 15 kV accelerating voltage

and 1•~10-10 A specimen current. The ana-

lysis data should be recognized as those of

the surface layer of the cementum, because

the SEM-EDX point analysis detects an area

of about 5-10 ƒÊm in diameter. The standard

sample was fluorapatite. After analysis by

the SEM-EDX, three acid-etched and non-

etched specimens in each group were analyz-

ed from the cementum surface towards the

cement-dentin junction by a Hitachi X-560

scanning electron microscope fitted with a

wave-length dispersive detection system

(SEM-WDX) at 25 kV accelerating voltage

and 0.5•~10-9 A specimen current. Each

surface layer was analyzed again at the five

points by the SEM-EDX under the same

conditions as described above.

Scanning electron microscopy (SEM)

In each group, some specimens containing

intact, polished, and acid-etched cementum

were longitudinally fractured. This was fol-

lowed by ultrasonic cleaning in distilled wa-

ter, dehydrating with alcohol, and drying

with a critical point CO2. These specimens

were observed with a Hitachi S-430 scanning

electron microscope (SEM) after coating with

a 10-15 nm thick layer of platinum.

Results

The cervical roots of the unexposed-young,

unexposed-old, and exposed-old cementum

used in this study were covered with acellu-

lar fibrillar cementum. The cementum was

clearly classified, when the roots were fractur-

ed and then observed by SEM (Figs. la-c).

In the unexposed-young cementum (Fig. 1

a), the extrinsic Sharpey's fibers, which are

made of periodontal ligament fibers penetrat-

ing into the cementum, were observed. The

intrinsic matrix fibers in the narrow spaces

between the extrinsic Sharpey's fibers were

loose, so that the natural surface of the young

cementum was not clearly observed. The

thickness of the young cementum was about

15-20 ƒÊm. On the other hand, in the un-

exposed-old cementum (Fig. 1b), the ligament

and extrinsic Sharpey's fibers were clearly

distinguished.

The unexposed-old and exposed-old ce-

mentum (Figs. 1b, c) were distinguished by

whether there were periodontal ligament fibers

attached on a cementum surface or not. The

extrinsic Sharpey's fibers in the exposed-old

cementum were more clearly distinguished

from the intrinsic matrix fibers than those of

the unexposed-old cementum.

The concentrations of Ca and P were ana-

lyzed in the surface layer of the cementum

by the SEM-EDX (Table 1). The Ca and P

concentrations, and Ca/P molar ratio of the

exposed-old cementum were significantly (p<

0.01) higher than those of the unexposed-

young and the unexposed-old cementum, which

had similar values.

The polished cementum surfaces and the

surfaces following 30% phosphoric acid etch-

ing were observed by the SEM (Figs. 2a-c

and 3a-c). The polishing made the unexpos-

ed-young cementum surface smooth and clear

(Fig. 2a). Following acid etching, the extrin-

sic Sharpey's fibers became loose and appear-

ed as villus-like structures (Fig. 3a). The

unexposed-old cementum surface also appear-

ed smooth following polishing (Fig. 2b),

though the acid etching made the ends of the

extrinsic Sharpey's fibers form faint reliefs

(Fig. 3b). In the exposed-old cementum, the

ends of the extrinsic Sharpey's fibers were

densely scattered as disk-like structures in

the matrix surface composed of the intrinsic

fibers (Fig. 2c). Following the acid etching,

the disk-like structures were slightly elevated

in the matrix surface (Fig. 3c).

The amounts of Ca dissolved from each

group of cementum was measured by the

AAS, and the Ca ƒÊg/mmmm2 was calculated

(Table 2). There was no significant dif-

ference between the exposed-old and the

unexposed-old cementum, although the expos-


Fig. 1 Fractured SEM images of the unexposed-young (a), unexposed-old (b), and exposed-old

cementum (c) in the cervical regions. PF: periodontal ligament fiber, SF: extrinsic

Sharpey's fiber, MF: intrinsic matrix fiber, CS: cementum surface, D: dentin. Bar=

5ƒÊm.

Table 1 Ca and P concentrations, and Ca/P molar ratio of the surface

cementum layer analyzed by the SEM-EDX (mean•}S.D.)

Table 2 Amounts of Ca dissolved from the

cementum surface analyzed by the

AAS (mean•}S.D.)

ed-old cementum tended to dissolve less than

the unexposed-old cementum. Whereas, both

the unexposed-old and exposed-old cementum

released significantly (p<0.01) less Ca than

the unexposed-young cementum.

The acid-etched cementum was fractured and

then observed by the SEM (Figs. 4a-c). The

unexposed-young (Fig. 4a), unexposed-old (Fig.

4b), and exposed-old cementum (Fig. 4c) had

surface layers showing fibrous structures. These

layers measured approximately 10-12 ƒÊm, 5-

15ƒÊm, and 4-12ƒÊm in thickness, respectively.

In the acid-etched exposed-old cementum

(Fig. 4c), the cementum surface had struc

tures similar to a dense felt-like membrane,

and there was an intermediate zone showing

faint slits along the extrinsic Sharpey's fibers

between the surface layer showing a fibrous

structure and a deeper sound layer. The

thickness of this zone was about 5 ƒÊm.

After the changes of cementum constituents

following the acid etching were investigated,

the longitudinal ground plane in each group

of specimens was analyzed by the SEM-WDX.

Figures 5 and 6 show examples of the

exposed-old cementum. The ground plane

of the exposed-old cementum is distinguished

into the surface (I), subsurface (II), and

deeper (III) zones by the SEM images (Fig.

5). At the left Figure 6 is a control line-an-

alysis of the SEM-WDX, and at the right is

an example following the acid etching. In

Figure 6-left, the no-etched surface layer

184 Jpn. J. Oral Biol., 32: 180-189, 1990.

Fig. 2

Fig. 3

Fig. 4


Fig. 5 SEM image in the longi-tudinal ground plane of theexposed-old cementum. Thesurface (I), subsurface (II) ,and deeper (III) zones corre-spond with those of Figure6-right. An arrow shows thecementum surface. Arrow-head: boundary of II andIII.Bar=5μm.

showed a peak of hypermineralization. After

the acid etching, the higher mineralized layer

disappeared in the surface, and small amounts

of the Ca and P elements were detected in

the surface zone (Fig. 6-left). This zone mea-

sured about 5-10 ƒÊm in thickness (Fig. 5).

When this area was analyzed by the SEM-

EDX, the Ca and P concentrations were

0.28•}0.16 and 0.28•}0.10 weight %, respec-

tively. These results indicate that the surface

zone had been almost completely demineraliz-

ed by phosphoric acid.

Under the line analysis of the acid-etched

exposed-old cementum (Fig. 6-left), both the

Ca and P concentrations abruptly rose to about

5-10 ƒÊm from the surface. Subsequently,

these concentrations abruptly increased again

4-5 ƒÊm from the surface, and then maintain-

Fig. 6 SEM-WDX line analysis in the longitudinal ground plane

of the exposed-old cementum following phosphoric acid

etching. Left: control, Right: acid etching, the surface

(I), subsurface (II), and deeper (III) zones: see Figure5. Arrows show the cementum surfaces .

ed high concentrations towards the cement-dentin junction, so that the subsurface andthe deeper zone were formed. The subsur-face zone was, therefore, slightly influencedby the acid, and was classified as a partiallydemineralized zone. The deeper zone wasthe sound cementum.

The completely demineralized surface and

partially demineralized subsurface zones re-vealed by the SEM-WDX analysis (Figs. 5, 6)corresponded to the fibrous surface and inter-mediate zones (Fig. 4c), respectively.

Discussion

It is known that the cervical 1/3 root re-gion of a human tooth is usually covered withacellular fibrillar cementum1-4). In thisstudy, specimens of the unexposed-young, un-

Fig. 2 Surface SEM images of the unexposed-young (a), unexposed-old (b), and exposed-old cementum

(c) following brush polishing. SF: extrinsic Sharpey's fiber, MF: intrinsic matrix fiber. Bar=5ƒÊm.

Fig. 3 Surface SEM images of the unexposed-young (a), unexposed-old (b), and exposed-old cementum (c)

following brush polishing and phosphoric acid etching. SF: extrinsic Sharpey's fiber, MF: intrin-

sic matrix fiber. Bar=5ƒÊm.

Fig. 4 Fractured SEM images following acid etching of the unexposed-young (a), unexposed-old (b)- and

exposed-old cementum (c). Arrows show the cementum surfaces . I: surface fibrous zone. Arrow-

heads indicate slits(S) in the subsurface zone(II). Bar=1ƒÊm.

186 Jpn. J. Oral Biol., 32: 180-189, 1990.

exposed-old, and exposed-old cementum wererecognized macroscopically and shown by theSEM (Figs. 1a-c).

The exposed-old cementum surface mightbe similar to the surface of inorganic acellu-lar cementum in the resting or very slowlymineralizing stage2,26) and to the surfacewith a majority of tightly packed spericaldomes4), although the ends of the extrinsicSharpey's fibers on the exposed-old cementumsurface were more or less flat owing to attri-tion (Fig. 1c). The ends were slightly ele-vated following brush-polishing (Fig. 2c).

Considering the significant difference inthe amounts of dissolved Ca between the un-exposed-young and unexpoed-old cementumfollowing 30% phosphoric acid etching(Table 2), the mineral contents should differfrom each other. However, there was noevidence in the SEM-EDX data with preacidetching (Table 1), and the fibrous structureswere clearly seen in the unexposed-youngcementum as compared with those of the un-exposed-old cementum (Figs. 1a, b). Theseresults, therefore, suggest that the apposition-al ratio of mineralized materials is more orless constant during cementum formation12,27),although the quantitative ratio of the intrinsicmatrix and extrinsic Sharpey's fibers acceler-ate (Figs. 3a, b). In other words, the differ-ence in the amounts of dissolved Ca betweenthe unexposed-young and the unexposed-oldcementum can be ascribed to the density ofboth the intrinsic matrix and the extrinsicSharpey's fibers.

Selvig27) has suggested in the maturationstage of cementum formation that additionalmineral is deposited within and on the intrin-sic matrix and extrinsic Sharpey's fibers aswell as in the rest of the matrix. The samedeposition occurs in cementum following ex-

posure to the oral cavity28). Thus, the intrin-sic matrix and extrinsic Sharpey's fibers ofthe exposed cementum will lose organic sub-stance in the surface layer, although the acid-etched cementum maintains organic fibrousmaterials (Figs. 3c, 4c, 5, 6). Judging fromthe significant elevations of Ca and P concen-trations, and of the Ca/P molar in the expos-ed-old cementum (Table 1), it is concludedthat secondary mineralization had occured in

the surface layer (Fig. 6-left)7,8). Presum-ably, appositional Ca and P deposited in theexposed surface layer did not derive frombody fluids, but from saliva.

Mechanical pressure such as tooth-brushingapplied to an exposed cementum will moreor less bring about condensation as well asattrition in the surface layer8), so that thehypermineralization in the surface layer ofthe exposed-old cementum (Fig. 6-left) maybe accelerated8) and the mineral content mightapproach to that of the enamel. It seemed,therefore, that the amounts of dissolved Cawould be less in the exposed-old than inthe unexposed-old cementum. However, thedepth of a fibrous demineralized surface zonecould not distinguish the exposed from theunexposed-old cementum (Figs. 4b, c). Cer-tainly, the amounts of dissolved Ca was notsignificantly different, although some tenden-cy in this direction was recognized (Table 2).On the other hand, the exposed-old cementum

possessing significntly higher Ca concentra-tion than the unexposed-young cementum(Table 1) showed significantly lower amountsof dissolved Ca than it (Table 2).

The above-described results and discussionssuggest that the amounts of dissolved Cashould be directly proportional to the densityof the intrinsic matrix and extrinsic Sharpey'sfibers, whereas it should be inversely propor-tional to the degree of mineralization.

Human cervical root surface exposed tothe oral cavity3,5) may develop wedge-shapeddefects5,9) and dental caries10,11). Wedge-shaped defects should be mostly occupied withattrited and exposed dentin, but the dentinis enclosed by narrow zones of attrited enameland cementum, and exposed cementum8).Cervical caries area should include damagedenamel, dentin, and cementum surroundingthe exposed cementum. Therefore, the resin-restorations are concerned with enamel, den-tine, and cementum in the acid-etch bondingmethods.

In the acid-etch bonding methods, it is knownthat rough enamel planes based on prismstructures15-17) and rough dentin planes con-taining expanded dentinal tubules8,18-20induce

the formation of resin-tags, although vital

dental pulp often underlays the exposed den-


tin.In cementum adherence, Nakajima8) sug-

gested that the attrited cementum combinedwith the resin-tags based on the structures ofthe extrinsic Sharpey's fibers following acidetching, and that an exposed cementum sur-face revealed by acid etching showed deficientstructures. Staninec et al.23) reported that nostatistically significant benefit could be demon-strated from etching and bonding cementumand the outer layer of dentin.

In this study, the surface of the exposed-oldcementum, following brush polishing and sub-sequently phosphoric acid etching, showed atightly dense structure similar to the preacid-etched surface (Figs. 2c, 3c). The acid etch-ing, moreover, caused the ends of the extrin-sic Sharpey's fibers to become slightly elevat-ed from the intrinsic matrix surface, so thata moderately uneven surface was formed onthe exposed-old cementum (Fig. 3c).

Phankosol et al.29) reported that a radio-paque surface layer was found with 47% ofthe artificial caries lesions in human root sur-faces. Kaufman et al.30) also showed the layerin microbial caries of human cementum invitro. Heritier31) reported a 0.5 ƒÊm thick

layer of electron dense materials featuring acrust in the dentin surface exposed with around bar and etched with 50% phosphoricacid.

In our phosphoric acid etching, however,the hypermineralized surface layer was notfound in the cementum at all (Figs. 5, 6-right).The acid-etched surface of the exposedoldcementum showing tightly dense structuresis not a mineralized membranous sheath asreported by Heritier31) but an organic one(Figs. 3c, 4c, 5, 6-right). This thin surfacemembrane, which probably contains the intrin-sic matrix and extrinsic Sharpey's fiers withremnants of periodontal ligament, has been

pressed by several mechanical forces in the

oral cavity.

The moderately uneven structures in the

acid-etched exposed-old cementum (Fig. 3c)

suggest that resins may adhere the cementum

to resin-tags. This bonding may be compar-

ed to the case of acid etching in glass-ionom-

er cement24). However, there was a com-

pletely demineralized zone measuring about 5-

10 ƒÊm thick in the surface layer of the acid-

etched cementum, whereas the natural car-

ies10-12) and artificial caries of human ce-

mentum29,30) showed demineralized zones inthe subsurface cementum. It is, therefore, sug-

gested that resin adherence is not always-expected to last for a long time, owing to thecompletely demineralized surface zone whichis weak against mechanical forces. On the

other hand, the moderately uneven surfacebased on the ends of the Sharpey's fibers

will adhere to resins for a time (Fig. 4c).With the acid-etch bonding methods for

the cervical root region, if the thin organicmembrane of the exposed-old cementum follow-ing acid etching is taken off by grinding,

and then the resin is strongly pressed to thefreshened surface, the bonding resin will pen-etrate into the partially demineralized subsur-face zone through the completely demineraliz-

ed fibrous surface zone; the bonding resinmay form net-like resin-tags extending into

the two zones. Thus, the exposed-old ce-mentum will strongly adhere the resins to thetags. In this respect, however, additionalstudies will be required

Acknowledgments

We wish to acknowledge the careful technicalwork with an atomic absorption spectrometor byProf. Y. Kaneko and Assist. Prof. M. Tomita,Department of Hygiene and Oral Health, Schoolof Dentistry, Showa University.

抄録:口腔内へ露出したヒト歯頸部セメント質の構造と組成,および酸腐蝕後の変化をSEM, EDX,

WDX,原子吸光を用いて検索した。露出セメント質のCa,P濃度およびCa/P比は,非露出セメント質よ

り有意に高い値を示した。しかし,酸腐出によって溶出するCaの量は,露出セメント質の方が少ない傾向

がみられたが,有意性はみられなかった。その結果,溶出するCaの量は,石灰化量よりもセメント質の基

質線維の量に影響されることが推察された。酸で腐蝕した露出セメント質の表面は,非露出セメント質と比

べ,明瞭なセメント質シャーピー線維の断端が観察された。しかし,その表面はフエルト状の有機性薄膜か

らなり,内部は完全に脱灰された表層下の2層に区別された。近年おこなわれている酸腐蝕ボンディンダ法

188 Jpn. J. Oral Biol., 32: 180-189, 1990.

において,酸腐蝕後,引き続き露出セメント質の脱灰層を機械的に除去すれば,レジンは部分的に脱灰され

た層に浸透し,タグが形成される可能性がある。

References

1) Freeman, E.: Periodontium in Oral Histo-logy: Development, Structure, and Function(Ten Cate, A.T. ed.) 2nd edn., pp.234-263,The C.V. Mosby Company, St. Louis, 1985.

2) Armitage, G.C.: Cementum in Orban'sOral Histology and Embryology (Bhasker,S.N. ed.) 10th edn., pp.175-197, The C.V.Mosby Company, St. Louis, 1986.

3) Furseth, R., Selvig, K.A. and Mjor, I.A.:The Periodontium in Human Oral Embryo-logy and Histology (Mjor, I.A. and Fejersk-ov, O. eds.), pp.131-176, Munksgaard, Co-penhagen, 1986.

4) Schroeder, H.E.: Cementum in the Peri-odontium (Okshe, A. and Vollrath, L. eds.)pp.23-128, Springer-Verlag, Berlin, 1986.

5) Boyle, P.E.: Regressive changes in deninand pulp; The structure and function of toothsupporting tissues in Kronfeld's Histologyof The Teeth and Their Surrounding Struc-ture (Boyle, P.E. ed.) 4th edn., pp.75-108;297-319, Lea & Febiger, Philadelphia, 1955.

6) Selvig, K.A. and Zander, H.A.: Chemicalanalysis and microradiography of cementumand dentin from periodontally diseasedhuman teeth. J. Periodontol. 33: 303-310,1962.

7) Miyashita, H., Kotaku, Y., Kuriyama, M.,Suzuki, K., Hasegawa, K. and Takiguchi,R.: Studies on the exposed cementum (in

Japanese). J. Showa Univ. Dent. Soc. 2:23-31, 1982.

8) Nakajima, F.: A morphological study onthe restration of tooth wedge-shaped defectswith composite resin (in Japanese). Jpn. J.Conserv. Dent. 27: 295-313, 1984.

9) Spoug, J.D.: Diseases of the teeth, Ac-

quired (noncarious) lesions of teeth in OralPathology, pp.171-188, The C.V. MosbyCompany, St. Louis, 1973.

10) Furseth, R. and Johansen, E.: A micro-radiographic comparison of sound and carioushuman dental cementum. Arch. Oral Biol.13:1197-1206, 1968.

11) Westbrook, J.L. Miller, A.S., Chilton, N.W., Williams, F. L. and Mumma, R.D.:Root surface caries; a clinical, histopatho-logic and microradiographic investigation.Caries Res. 8: 249-255, 1974.

12) Hals, E. and Selvig, K.A.: Correlated

electron probe microanalysis and microradio-

graphy of carious and normal dental ce-mentum. Caries Res. 11: 62-75, 1977.

13) Gwinnett, A.J. and Buonocore, M.G.:Adhesives and caries prevention; a prelimi-nary report. Brit. Dent. J. 119: 77-80, 1965.

14) Gwinnett, A.J.: Morphology of the inter-face between adhesive resins and treated hu-man enamel fissures as seen by scanning elec-tron microscopy. Arch. Oral Biol. 16: 237-238, 1971.

15) Silverstone, L.M.: Fissure sealants; labo-ratory studies. Caries Res. 8: 2-26, 1974.

16) Gwinnett, A.J. and Matsui, A.: A studyof enamel adhesives; the physical relation-ship between enamel and adhesive. Arch.Oral Biol. 12: 1615-1620, 1967.

17) Buonocore, M.G., Matsui, A. and Gwinnett,A.J.: Penetration of resin dental mate-rials into enamel surfaces with reference tobonding. Arch. Oral Biol. 13: 61-70,1968.

18) Bowen, R.L.: Adhesive bonding of vari-ous materials to hard tooth tissues. XXII. Theeffects of a cleanser, mordant, and polySACon adhesion between a composite resin anddentin. J. Dent. Res. 59: 809-814, 1980.

19) Suizu, S.: Tags penetrating dentin in twotypes of composite resin (in Japanese). Jpn.

J. Consev. Dent. 24: 88-92, 1981.20) Jedrychowski, J.R., Caupto, A.A. and Prola,

J.: Influence of a ferric chloride mor-dant solution on resin-dentin retention. J.Dent. Res. 60: 134-138, 1981.

21) Ripa, L.W., Gwinnett, A.J. and Buonocore,M.G.: The prismless' outer layer ofdeciduous and permanent enamel. Arch. OralBiol. 11: 41-48, 1966.

22) Kodaka, T., Nakaima, F. and Kuroiwa, M.:Distribution patterns of the surface "prism-less" enamel in human decisuous incisors.Bull. Tokyo Dent. Coll. 30: 9-19, 1989.

23) Staninec, M., Mochizuki, A., Tanizaki, K.,Fukuda, K. and Tsuchitani, Y.: Effect ofetching and bonding on recurrent cariesin teeth restored with composite resin. J.Prosthet. Dent. 53: 521-525, 1985.

24) Lacefield, W.R., Reindl, M.C. and Retief,D.H.: Tensile bond strength of a glass-ionomer cement. J. Prosthet. Dent. 53: 194-198, 1985.

25) Kuroiwa, M, Nakajima, F. and Kodaka, T.:Acid-etched effects after some preparations of


enamel surfaces in human deciduous teeth (inJapanese). J. Showa Univ. Dent. Soc. 3:221-226, 1984.

26) Jones, S.J.: The root surface; an illustrat-ed review of some scanning electron micro-scope studies. Scanning Microsc. 1: 2003-2018, 1987.

27) Selvig, K.A.: An ultrastructural study ofcementum formation. Acta Odont. Scand.22: 105-120, 1964.

28) Selvig, K.A.: Biological changes at thetooth-saliva interface in periodontal disease.

J. Dent. Res. 48: 846-855, 1969.

29) Phankosol, P. Ettinger, R.L., Hicks, M.J.and Wefel, J.S.: Histopathology of theinitial lesion of the root surface; an in vitrostudy. J. Dent. Res. 64: 804-809, 1985.

30) Kaufman, H.W., Pollock, J.J. and Gwinnett,A.J.: Microbial caries induction in the rootsof human teeth in vitro. Arch. Oral Biol.33: 499-503, 1988.

31) Heritier, M: Effects of phosphoric acid onroot dentin surface. A scanning and trans-mission electron microscopic study. J. Perio-dont. Res. 19: 168-176, 1984.

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Structure and mineral content of human exposed cementum