Archsoral
Bml. Vol.
20. pp. 291 to 296. Pergamon Press 1975 Pnnted in Great Breain
HISTOLOGY OF NATURAL SECONDARY CARIES ASSOCIATED WITH SILICATE CEMENT RESTORATIONS IN HUMAN TEETH E. HALS Department
of Cariology,
University
of Bergen. 5000 Bergen, Norway
Summary--Sections from 70 human permanent teeth with silicate restorations were studied by polarized light microscopy and microradiography. Both frequency and degree of secondary caries appeared low compared with previous findings in respect of amalgam. Both the tooth surface, surrounding the fillings and the cavity walls had acquired a high degree of caries resistance caused by fluorides released from the silicate material. The lesions observed displayed the same pattern as in corresponding previous experimental studies. Increased radiopacity of cavity walls in enamel and dentine relative to normal tissue was relatively frequent, as was retrograde secondary caries.
INTRODUCTION
This study is part of a comprehensive investigation of lesions associated with various filling materials both irl vitro (Hals and Nernaes, 1969, 1971 ; Hals, 1974; Hals and Kvinnsland, unpublished), and in z,ivo (Hals and Leth Simonsen, 1971!; Hals and Norderval, 1973; Hals and Kvinnsland, unpublished), and natural secondary caries (Hals, 1971; Hals, Hoyer Andreassen and Bie, 1974). In all these studies the lesions displayed the same basic pattern: (1) an outer lesion, which showed the features of a primary attack developing on the outer surface of the tooth; (2) a cavity wall lesion, appearing as a rim of altered enamel or enamel and dentine caused by acid penetrating the interface between filling material and cavity wall.
For brevity. the term “positive zone in quinoline” was used to indicate the positively birefringent zone of carious lesions of the enamel visible in quinoline and examined by polarized light. Every complete section was regarded as an occlusal and cervical “secondary caries risk” (Hals IX ul.. 1974). This registration unit was preferred to the unit “cavity”, partly because in many sections one of the cavity walls broke during processing or was not deemed satisfactory for examination. For the statistical evaluation of the data in Tables 3-4. a test concerning the difference of two proportions (Hayslett. 1971; formula 8.9, page 123) was used.
RESULTS
The secondary caries lesions were categorized outer lesions and cavity wall lesions.
MATERIAL AND METHODS
The material consisted of extracted permanent human teeth, which, except for 1 premolar, were all incisors and canines. The teeth contained class V silicate fillings which in most cases were more or less eroded. In other cases, the surface of the filling material seemed to be intact except for a discoloured furrow at the border related to the cavity margin. On macroscopic examination, the margin of the tooth cavity around the filling generally revea.led very slight signs of secondary caries or no changes. The teeth, which had been stored in neutralized formalin or alcohol solutions, were cleaned, and one to two buccolingual sections were cut in the longitudinal axis. Only sections satisfying conditions specified by Hal s and Leth Simonsen (1972) were accepted. The details of section preparation, polarized light microscopy and microradiography are given in Hals and Nernaes (1971). In all, 105 sections from 70 teeth were examined.
as
Outer /rsion.s
Outer lesions in the enamel occurred in 61 per cent of sections (Table 1). Most of the lesions were relatively superficial, band-shaped areas (Figs. I- 3 and 8) whilst advanced lesions showed a trapezoidal shape (Fig. 4). Breach of surface continuity was observed in a few cases. In a high proportion (Table 3), the lesions showed radiolucency when examined by microradiography (Figs. 3a, 4a and 8a). Usually the radiolucency decreased in the deeper parts of the lesion (Fig. 4a) whilst in a few cases there was an intermingling of radiopaque and radiolucent areas (Fig. 8a). The occurrence of areas showmg increased radiopacity relative to Intact enamel was exceptional (Fig. 3a). In polarized light, after imbibition in quinoline, the body of the lesions displayed negative birefringence of 291
E. Hals
292 Table I. Natural
secondary
caries associated
with silicate fillings. Frequency lesions
Enamel Outer lesions Cavity wall lesions
Number of observed cases Number of secondary caries risks Dentine
58:Y5 (61”“) 77:94(X2”,,)
varying degree (Figs. 4b, 3b). Positive zones in quinoline. often conspicuous, were present in the majority (Table 3, Figs. 1, 2, 4b and 8b). Out of I5 outer lesions of the ccmentum. I I showed cavitation (Fig. 5). often extending into the dentinc, whilst 4 cases revealed more or less rddioluccncy of the cementum without breach of surface continuity (Fig. 6). CuritJ’ wu// lesior~ ad r~rtnxpulc ,secor~dctr_r caries Width of the cavity wall lesions, which to a varying degree encompassed the fillings, ranged 8-85 kun in the enamel and 8- 160 pm in the dentine. The frequency of wall lesions of the enamel was high (Table I). In sections imbibed in distilled water and examined by polarized light, these lesions showed a narrow surface zone displaying negative birefringcnce. In some cases, an increase of this birefringence relative to that of intact enamel was associated with a lack of structural detail in the surface zone. In sections imbibed in quinoline, the surface zone was in most cases delimited against the intact enamel by a narrow positive zone between pseudo-isotropic lines (Table 3) or only by a thin pseudo-isotropic zone (Fig. 7). All cavity wall lesions of the enamel could be observed by polarized light. In the microradiographs. 36 per cent showed a surface zone of increased radiopacity relative to intact enamel (Table 2). A subsurface radiolucent rim or line was present in 14 per cent but. in 3 of these I I cases, the surface zone revealed increased radiopacity relative to the intact enamel (Fig. #a) and a corresponding increase of negative bire-
Table 2. Natural
secondary
Cementum 15:21 (71?,)
55: 60 (92”,,)
fringence (Figs. 8b, c). A laminated wall lesion was observed in a single section (Fig. 9). In the dentinal walls of the cavities, the frequency of lesions was still higher than in the enamel walls (Table I). All the lesions showed radiolucency of varying distribution and intensity, whilst more than hdlf also included areas of increased rddiopacity relative to the intact dentine (Table 2). In some cases, a subsurface layer of increased radiopacity was covered by a narrow surface rim of radiolucent dentine (Fig. IO) whilst in other cases the increased radiopacity was restricted to a surface zone of varying width (Fig. I I). Changes in the cavity walls interpreted as retrograde secondary caries were frequently observed (Figs. 12- 14. Table 2). In Table 3, data from the present study and the experimental studies are compared. !n natural secondary caries, the frequency of outer lesions was significantly higher than in the experimental groups. Also. the frequency of outer lesions with a positive zone in quinoline was much higher than in the iti rirro group. The slightly higher frequency of radiolucent outer lesions in the “natural” group was not statistically significant. A comparison between the groups concerning frequency of cavity walls showed no significant difference. A positive zone in quinoline was present in all cavity wall lesions in the i&lGo group. The ditrerence in frequency relative to the “natural” and in citro groups was statistically significant. The frequency of wall lesions disclosing radiolucency or increased radiopacity was about equal in the “naturaf’ and “;,I rko” groups whilst these features were not observed in the irr vitrogroup.
caries associated with silicate fillings. Frequency of various features of cavity wall lesions including retrograde secondary caries
Enamel 77 wall lesions Only observable by polarized light ( S”,; spaces)* Displaying increased radiopacity Retrograde secondary caries Displaying both radiolucency and increased radiopacity * Darling (1958).
of outer lesions and cavity wall
Dentine 55 wall lesions
66 (86Y”) I1 (14”;,) 28 (37’;J 33 (43’:i) 3 (4?$
0 55 (1Oo’:,,) 35 (64’:);) 33 (60:J 35 (64”.)
Caries associated with silicate cement restorations
293
Table 3. Data perta.ining to natural secondary caries of the enamel associated with silicate fillings (present study) compared to previous in uitro* and in uimt studies Statistical difference natural Secondary Natural
caries In ritro
Secondary caries
in citw z
Statistical difference natural
P
irl ciao
ill r~iw
I
14:32 (44YJ 4: 14 (29X 9: 14
I.70
P
Outer lesions
Frequency Radiolucency
(> 5:/, spaces) Positive zone in quinoline
58:95 (61”;) 24: 58 (41’:;) 51:58 (88(z)
27:61 (44%) 3~27 (11:‘J 6~27 (22”;))
2.05
< 0.05
1.57
N.S.
77194 \W;
54:61 (89%) 0:54 W,) 40: 54 (74%) 0:54 (OU,,J
I.11
N.S.
3.12
Bml. Vol.
20. pp. 291 to 296. Pergamon Press 1975 Pnnted in Great Breain
HISTOLOGY OF NATURAL SECONDARY CARIES ASSOCIATED WITH SILICATE CEMENT RESTORATIONS IN HUMAN TEETH E. HALS Department
of Cariology,
University
of Bergen. 5000 Bergen, Norway
Summary--Sections from 70 human permanent teeth with silicate restorations were studied by polarized light microscopy and microradiography. Both frequency and degree of secondary caries appeared low compared with previous findings in respect of amalgam. Both the tooth surface, surrounding the fillings and the cavity walls had acquired a high degree of caries resistance caused by fluorides released from the silicate material. The lesions observed displayed the same pattern as in corresponding previous experimental studies. Increased radiopacity of cavity walls in enamel and dentine relative to normal tissue was relatively frequent, as was retrograde secondary caries.
INTRODUCTION
This study is part of a comprehensive investigation of lesions associated with various filling materials both irl vitro (Hals and Nernaes, 1969, 1971 ; Hals, 1974; Hals and Kvinnsland, unpublished), and in z,ivo (Hals and Leth Simonsen, 1971!; Hals and Norderval, 1973; Hals and Kvinnsland, unpublished), and natural secondary caries (Hals, 1971; Hals, Hoyer Andreassen and Bie, 1974). In all these studies the lesions displayed the same basic pattern: (1) an outer lesion, which showed the features of a primary attack developing on the outer surface of the tooth; (2) a cavity wall lesion, appearing as a rim of altered enamel or enamel and dentine caused by acid penetrating the interface between filling material and cavity wall.
For brevity. the term “positive zone in quinoline” was used to indicate the positively birefringent zone of carious lesions of the enamel visible in quinoline and examined by polarized light. Every complete section was regarded as an occlusal and cervical “secondary caries risk” (Hals IX ul.. 1974). This registration unit was preferred to the unit “cavity”, partly because in many sections one of the cavity walls broke during processing or was not deemed satisfactory for examination. For the statistical evaluation of the data in Tables 3-4. a test concerning the difference of two proportions (Hayslett. 1971; formula 8.9, page 123) was used.
RESULTS
The secondary caries lesions were categorized outer lesions and cavity wall lesions.
MATERIAL AND METHODS
The material consisted of extracted permanent human teeth, which, except for 1 premolar, were all incisors and canines. The teeth contained class V silicate fillings which in most cases were more or less eroded. In other cases, the surface of the filling material seemed to be intact except for a discoloured furrow at the border related to the cavity margin. On macroscopic examination, the margin of the tooth cavity around the filling generally revea.led very slight signs of secondary caries or no changes. The teeth, which had been stored in neutralized formalin or alcohol solutions, were cleaned, and one to two buccolingual sections were cut in the longitudinal axis. Only sections satisfying conditions specified by Hal s and Leth Simonsen (1972) were accepted. The details of section preparation, polarized light microscopy and microradiography are given in Hals and Nernaes (1971). In all, 105 sections from 70 teeth were examined.
as
Outer /rsion.s
Outer lesions in the enamel occurred in 61 per cent of sections (Table 1). Most of the lesions were relatively superficial, band-shaped areas (Figs. I- 3 and 8) whilst advanced lesions showed a trapezoidal shape (Fig. 4). Breach of surface continuity was observed in a few cases. In a high proportion (Table 3), the lesions showed radiolucency when examined by microradiography (Figs. 3a, 4a and 8a). Usually the radiolucency decreased in the deeper parts of the lesion (Fig. 4a) whilst in a few cases there was an intermingling of radiopaque and radiolucent areas (Fig. 8a). The occurrence of areas showmg increased radiopacity relative to Intact enamel was exceptional (Fig. 3a). In polarized light, after imbibition in quinoline, the body of the lesions displayed negative birefringence of 291
E. Hals
292 Table I. Natural
secondary
caries associated
with silicate fillings. Frequency lesions
Enamel Outer lesions Cavity wall lesions
Number of observed cases Number of secondary caries risks Dentine
58:Y5 (61”“) 77:94(X2”,,)
varying degree (Figs. 4b, 3b). Positive zones in quinoline. often conspicuous, were present in the majority (Table 3, Figs. 1, 2, 4b and 8b). Out of I5 outer lesions of the ccmentum. I I showed cavitation (Fig. 5). often extending into the dentinc, whilst 4 cases revealed more or less rddioluccncy of the cementum without breach of surface continuity (Fig. 6). CuritJ’ wu// lesior~ ad r~rtnxpulc ,secor~dctr_r caries Width of the cavity wall lesions, which to a varying degree encompassed the fillings, ranged 8-85 kun in the enamel and 8- 160 pm in the dentine. The frequency of wall lesions of the enamel was high (Table I). In sections imbibed in distilled water and examined by polarized light, these lesions showed a narrow surface zone displaying negative birefringcnce. In some cases, an increase of this birefringence relative to that of intact enamel was associated with a lack of structural detail in the surface zone. In sections imbibed in quinoline, the surface zone was in most cases delimited against the intact enamel by a narrow positive zone between pseudo-isotropic lines (Table 3) or only by a thin pseudo-isotropic zone (Fig. 7). All cavity wall lesions of the enamel could be observed by polarized light. In the microradiographs. 36 per cent showed a surface zone of increased radiopacity relative to intact enamel (Table 2). A subsurface radiolucent rim or line was present in 14 per cent but. in 3 of these I I cases, the surface zone revealed increased radiopacity relative to the intact enamel (Fig. #a) and a corresponding increase of negative bire-
Table 2. Natural
secondary
Cementum 15:21 (71?,)
55: 60 (92”,,)
fringence (Figs. 8b, c). A laminated wall lesion was observed in a single section (Fig. 9). In the dentinal walls of the cavities, the frequency of lesions was still higher than in the enamel walls (Table I). All the lesions showed radiolucency of varying distribution and intensity, whilst more than hdlf also included areas of increased rddiopacity relative to the intact dentine (Table 2). In some cases, a subsurface layer of increased radiopacity was covered by a narrow surface rim of radiolucent dentine (Fig. IO) whilst in other cases the increased radiopacity was restricted to a surface zone of varying width (Fig. I I). Changes in the cavity walls interpreted as retrograde secondary caries were frequently observed (Figs. 12- 14. Table 2). In Table 3, data from the present study and the experimental studies are compared. !n natural secondary caries, the frequency of outer lesions was significantly higher than in the experimental groups. Also. the frequency of outer lesions with a positive zone in quinoline was much higher than in the iti rirro group. The slightly higher frequency of radiolucent outer lesions in the “natural” group was not statistically significant. A comparison between the groups concerning frequency of cavity walls showed no significant difference. A positive zone in quinoline was present in all cavity wall lesions in the i&lGo group. The ditrerence in frequency relative to the “natural” and in citro groups was statistically significant. The frequency of wall lesions disclosing radiolucency or increased radiopacity was about equal in the “naturaf’ and “;,I rko” groups whilst these features were not observed in the irr vitrogroup.
caries associated with silicate fillings. Frequency of various features of cavity wall lesions including retrograde secondary caries
Enamel 77 wall lesions Only observable by polarized light ( S”,; spaces)* Displaying increased radiopacity Retrograde secondary caries Displaying both radiolucency and increased radiopacity * Darling (1958).
of outer lesions and cavity wall
Dentine 55 wall lesions
66 (86Y”) I1 (14”;,) 28 (37’;J 33 (43’:i) 3 (4?$
0 55 (1Oo’:,,) 35 (64’:);) 33 (60:J 35 (64”.)
Caries associated with silicate cement restorations
293
Table 3. Data perta.ining to natural secondary caries of the enamel associated with silicate fillings (present study) compared to previous in uitro* and in uimt studies Statistical difference natural Secondary Natural
caries In ritro
Secondary caries
in citw z
Statistical difference natural
P
irl ciao
ill r~iw
I
14:32 (44YJ 4: 14 (29X 9: 14
I.70
P
Outer lesions
Frequency Radiolucency
(> 5:/, spaces) Positive zone in quinoline
58:95 (61”;) 24: 58 (41’:;) 51:58 (88(z)
27:61 (44%) 3~27 (11:‘J 6~27 (22”;))
2.05
< 0.05
1.57
N.S.
77194 \W;
54:61 (89%) 0:54 W,) 40: 54 (74%) 0:54 (OU,,J
I.11
N.S.
3.12
