Joiniuil
of Oral Rduihilitalioii.
1992. V o l u m e 19, pages 1 0 1 - 1 1 0
Dentine hypersensitivity — the effect of toothbrushing and dietary compounds on dentine in vitro: an SEM study E . G . A B S I , M. A D D Y ' " and D . A D A M S t Depwlmcnl of Examimmon and Emergency. *Deparlim'iil of I'eriodoiUology and jDeparimeni of Basic Denial Science. Dental School. University of Wales College of Medicine. Cardiff. Wales. U. K.
Summary Dentine hypersensitivity occuis when tientinal tubules are open on the dentine surface and patent to a vital pulp. There has been limited interest in the aetiology of dentine hypersensitivity. In particular, little is known about agents that remove the dentine smear layer to expose tubules. Tootlibrushing certainly may expose dentine, but •whether a toothbrusli per se has the effect of opening tubules has not been established. The aim of this study in vitro was to determine whether a toothbrush could remove or create a smear layer. In adtlilion, the combined effects of toothbrushing with dietary fluids on dentine was assessed. Toothbrushing was observed, by scanning eleetron microscopy, both to remove and to recreate a smear layer on dentine specimens. However, the proeesses took a considerable time, and under conditions of normal toothbiushing it is unlikely thai the latter plays a direet aetiological role in opening tubules. Indeed, together with toothpaste it is more likely that brushing has a therapeutic action by mechanically forming a smear layer. Conversely, and importantly, toothbrushing in the presence of dietary acitis enhaneed smear layer removal. This finding raises the question of whether the dental profession should be advising that teeth be brushed before meals rather than after, as is often the case. Introduction Dentine hypersensitivity is a relatively common (Graf & Galasse, 1977) and painful condition of the permanent dentition. Most attention has been directed towards treatment, and the literature contains reports of numerous clinical trials (see review by Addy & Dowell, 1983), some of which have been deseribed as 'belonging in the realms of testimonials' (Everett, Hall & Phatak, 1966). Unfortunately, little emphasis has been placed on understanding the aetiology of the condition (for review see Addy, 1990). Perhapsbeeauseof this lack of knowledge, recurrences of sensitivity, aneedotally, appear to be frequent. The hydrodynamic theory has been proposed to explain stimulus transmission across dentine (Gysi, 1900; Bramistrom, 1962). In support of this theory, sensitive dentine was shown to possess much larger numbers of wider tubules open at the surface than non-sensitive dentine (Absi, Addy & Adams, 1987). Exposed cervieal dentine is commonly seen in adults, although not all such lesions are sensitive. The factors that expose dentine and ojien tubules are still relatively Corrcspontlence: Professor M. Addy, Dcparlnicnl of Periodoiilology, Denial School, Cardiff CF4 4XY, Wales, U.K. 101
102
E.G. Absi et al.
uncertain. Aeid erosion from dietary and environmental faetors is definitely assoeiated with dentine hypersensitivity (Tonyz, 1983), and acids in vitro readily remove the dentine smear layer to expose the tubules (Addy, Absi & Adams, 1987). Moreover, eircumstantial evidence has implicated toothbrushing, at least, with the loealization of cervieal dentine exposure and dentine hypersensitivity (Addy, Mostafa & Neweombe, 1987). Whether a toothbrush alone actually opens dentinal tubules has not been confirmed. Certainly, erosive and abrasive agents together markedly enhanee hard tissue loss (Davis & Winter 1980), but their combined role in opening tubules requires further study. The aim of this investigation in vitro was to observe the effects of toothbrushing on dentine alone and in combination with dietary compounds. Materials and Method The teeth used in the experiments were recently extracted caries-free human incisors, canines and premolars. After thorough cleaning, the buccal root surfaces were root planed with curettes from the cemento-enamel junction to the apex, until dentine was clearly apparent. The apieal and cervical thirds were covered with masking tape, leaving Ihe middle third exposed. The exposed dentine of some specimens was then etched with 50% phosphoric acid for 1 min. Specimens so treated were termed 'etehed', and the untreated speeimens were termed 'unetehed'. Toothbrushing was simulated using an electric-motor-driven reciprocal action machine. The brush heads were from multitufted nylon filament toothbrushes*. Brushing was perpendieular to the long axis of the tooth to simulate a horizontal action. The machine operated at a fixed speed of 52 strokes min^' and under a head load of 100 g. Two specimens could be brushed simultaneously. In order to evaluate the effects of toothbrushing alone on dentine, duplicate etched and unetehed specimens were immersed in a water/saliva mixture and brushed for time periods of 1, 3, 30 min and 2, 4, 6 and 24 h. In order to evaluate the effects of dietary fluids and brushing on the dentine smear layer, duplieate unetehed specimens were immersed in dietary fluid/saliva mixtures for 3 min, or immersed in the dietary fluid/saliva mixture and brushed for 3 min. All fluid/saliva mixtures were obtained from volunteers who rinsed for 30s with 15-ml volumes of the fluids. Expectorates weie pooled for the respective lluid. All specimens were prepared for scanning electron microscopy and representative photomierographs were taken at x300 and xlOOO magnification. Two photomicrographs were randomly selected for each specimen, coded and scored blind for tubule numbers, using a previously deseribed grid method (Absi et at., 1987). During counting, every fifth tubule was marked, and the narrower diameter was subsequently measured with an eyepiece graticule. On a separate occasion the same photomicrographs were subjectively graded for the number of tubules present as follows: 0 = no tubules visible; ( + ) = a few tubules visible; ( + + ) = moderate numbers of tubules visible; (+ + +) = many tubules visible. The reproducibility of the scorer and correlation of the subjectively and objeetively determined numbers was assessed by duplicate recordings from 15 randomly selected photomicrographs. Repeat recordings were separated by 7 days. Although nol relevant to this particular study, the inter-examiner reprodueibility of the method was determined by having a second examiner score the photomicrographs. The degree of agreement between grading and counting was determined by the overlap coefficient (Mann* Oral B, Aylesbury, U.K.
•
Toothbrushing, diet and dentine
103
Whitney statistie free of sample size). Intta- and inter-examiner reprodueibility for counts was determined by correlation eoefficients, together with mean and standard deviations of paired differenees. Bias was tested by paired /-tests. Intra- and interexaminer agreement for grading was determined by Kappa statistics, both unweighted and weighted (Fleiss-Cohen weights), to take into accout the intrinsic ordering of
the -\-l ++I-\- + + grades. R e s u l t s
-
.•
••
'
.-'.- • •
'
•
'
'
• • . . ' • , ,
•..
Effects of brushing alone on unetehed specimens A summary of the visual changes on the unetehed dentine surfaces (Fig. 1) with time of brushing are shown in Table 1. After 30 min some loss of the smear layer was apparent, with tubules exposed. The graded and counted tubule numbers increased up to 4 and 6h (Fig. 2). By 24 h all measurement parameters were reduced toward the 30-min brushing time. Effects of brushing alone on etched specimens A summary of the visual changes on the etehed dentine surfaces with time of brushing are shown in Table 1. At the start of brushing large numbers of widely opened tubules were apparent. It is significant that the tubule numbers and diameters at this time were greater than at any time of brushing unetehed specimens. The tubule numbers graded and counted by observation decreased to 6h, and the tubule diameters decreased to 4h (Fig. 3). Tubule numbers and diameters had increased again at 24h, but not to baseline measurements.
Table 1. Effect of toothbrnsliing on imelched and etched dentine specimens Dentinal lubnles Time
Grade
Unetehed lmin
3min 30 min 2h 4h 611 24h
Counl '
0
.
''
Mean diameter ± SD (nm)
.
.; •
. 0
'
0 , 0 ,+ . , 40 + '': 39 + + .... • 44 . . + + • '• ' 54 + . .30
.: . ' . '
30min
+++
2h 4h 6h 24 h
+++ ++ + +/ + +
. . .' •'. •'-
•
.
67 ,59 .
•
65'•
;,•
79; 41 39 50
,, . ' , ' . ^
• '-•
+++ +++
. 0 0-5 ±0-3 0-4 ±0-2 2-0±0-7 1-2 ±0-3 0-7±0-t
••
'
•
. Q
.. •
Etched
_ lmin 3min
'
•
_ " ^
2-5±0-4 2-0±0-4 2-5±0-6
'
l-9±0-3 0-4 ±0-1 l-l±O-l 1-6 ±0-8
104
£.G. Absi et al.
Fig. 1. Scanning electron micrograph of root-plancti dentine surface (unetehed). Parallel-running striations in the smear layer are typical of the efleets produced by instrumentation. This smear layer remained intact when exposeil to tooth brushing with water and lilgh-pl I dietary lluids. Mag[ii(ication x540.
Effects of dielarv products on dentine Without brushing. The dillerent dietary compounds produced a range of effects (Table 2), ranging from none (Fig. 1) to the opening of many dentinal tubules ( + + +) of wide diameter. The effects were not directly pH dependent, although it should be noted that the high-pH solutions, coffee, milk and tea produced no consistent changes on the dentine surface. All the other solutions of pH < 4 removed the smear layer to a variable extent after 3 min of exposure. Yoghurt and coke exposed a few tubules.
rig. 2. Scanning electron micrograph of a root-planed dentine surfaee (unetehed), brushed with water/ saliva Ior4h. Mueh of the smear layer has been removed to reveal dentinal lubules. Magnilieation x540.
Toolhhrushing. diet and dentine
105
Tahk' 2. Effecl of dietary proiUicis with and without brushing on licntine specimens
Product"^ Lctiiotiade (2-2) Coke (2-3) I3l;ickcurtanl jtiice (2-4) While wine (2-6) Grapefruit juice (2-7) Apple juice (3-t)) Red wine (3-2) OraJige juice (3-3) Yoghurt (4-1)
Grade
Count
No brush
brush
Meati diatiieter ± SD (Mill)
Grade
Mean diameter ± Sfl (inn)
+++
75
-I- +
43
59
2-3 ± 0-5 1-4 ±0-3 2-0 ± 0-6
+++ + ++
52
l - 0 ± t)-7
92
l-S±0-3 2-2 ± 0-6 2-5 ± 0-5 2-1 ± 0 - 3 0-9±tl-2 tl-l±tl-l (I-l ± tl-1 0-2 ± tl-1 (1
++
83
2-1 ±0-4
-1-
37
t)-4±0-l
.SI -1- + +
65
2-3 ±0-6 1-2 ±0-3
42
+ ++
101
4--I-
52 56 26
-f + +
M i l k (5-7)
Tea/milk (6-6) Coffee/mi Ik (6-6) Water (7-t))
-t-
0
0 0 0
0 12
tl
t)
l-t)±0-4 0-9 ± tl-4 I-l ±t)-7
3-t) ±0-2 t l - 4 ± t)-2 0 0 t)-4±t)-l tl
+ + -I-I--I- + -t--l- +
+ -(t) tl 0 tl
Count
66 45 79 43 >S 7 9 tl
* pM is shown in parentheses.
whereas lemonaile (Fig. 4), while wine, apple juice atul oratige juice exposed matty tubules. The other products were inteiniediate in their action on dentine. Tubule diameters after exposure varied, although most high-acidity soliiliotis exposed tubules of mean diameter innging from I—2|_t. Foi' yogluitt and coke, which exposed few tubules, the diametets were also narrow by eoniparison.
Fig. 3 . Seanning electron micrograph of an e t c h e d d e n t i n e surface brushed with wnter/saliva lor 4 h . Most tubule openitigs a t e n a i r o w e d e o m p a r e d to a d e n t i n e surfaee etclied with a ilietary lluid (cl. I"ig. 4). Magnilieation x,S40.
106
E.G. Absi et al.
Fig. 4. Scanning electron tnicrograpli of toot-planed dentine surface exposed to letiiotuide/saiiva lof 3 min. Most of the smear layer and surface tietails produced by instrumentation have been lost in Older to expose tubules. Magtiitteation x540.
With brushing. After 3 min, brushing with the dietary fluids was seen to etihatice the opening of tubules lor most products, as assessed by observation and by cotmting (Table 2). Thus most low-pH solutions were graded as ptoducing tnany and widely open tubules on the dentine surfaee (Fig. 5). Tubule diameters during this time period ranged fiom I—2-5|i. For the near-neutral pH lluids, brushing was noted to expose few if any tubules on the surface.
Fig. 5. Scanning eleetroti niierograph of a root-planed dentine surfaee. The lower half shows the conttol portioti wliieli was eovej-ed wilh tnasking tape atid reveals a stiiear layer. The upper portioti was brushed with blaekeurrant juiee/saliva. Nunietous tubule openitigs ate apparent. Magnifieation x540.
Toothbrushing, diet and dentine
107
Scoring evaluation Grading and counting. The degree of consistency between grading and scoring is summarized in Fig. 6. The overlap coefficient is 0-1 (a value of 0 would indicate perfect separation, and a value of 0-5 would indicate complete lack of separation), suggesting that theie is only a small degree of overlap, particularly for +/-f- + , and therefore close agreement between grading and counting. Inter- and intra-examiner reproducibility for counts. Inter- and intra-examiner reproducibility is sutntnarized in Table 3. In each case the correlation coefficient is high, btit this otily indicates a strong association. A /-test based on differences revealed no significant evidence of bias of one observer compared with the other. The ititraexaminer differences reached significance (P a. O
20
-I- -t-i- +++ Examiner 1 Overlap coefficient
0-025, 0-1
J
-I-
L
-t-f -t-i-t-
Examiner 2 1st time
Examiner 2 2nd time
0-0,0-0
0-0,0-071 Overall 0-008, 0-058
Fig. 6. Intet- atid intt-a-exaniiner variatioti of open tubule cottiit sliowitig degree of consistency between gtade atid scot-e assigned.
108
E.G. Absi et al.
Table 3. Ititer- and intra-exatniner variation and agteenient for coutititig and gratling detitinal tubules
Tubule counts Correlation SD of diffeicEiee (-test Tubule grading Unweighted Observed Expected Kappa Weighted Obsetved Kxpectcd Kappa
ltiter-cxamitier
Intra-exatniner
0-89 3-t)7 1-49 (NS)
0-99 -1-60 -2-16*
0-8tl 0-34 0-70
0-80
0-34 0-70
t)-95
0-95
tl-69
0-69
0-84
0-84
NS = tiot sigtiilicatit. * Signilieanl at /'-Y. M. & At:)AMS. D. (1987) Dentine hypersensitivity: a study of the patency of detititial lubules iji sensitive and non-sensitive cervical dejitine. .lournid of Clinical I'criodonlologv. 14. 280. AtM)Y, M. (1990) Etiology aiid clinical iniplicatiotis of iletititie hypersetisitivity. Denial Clinics of Norlh America. 34. 503. At)t)i', M. & Dowtn.t.. P. (1983) Dentitie liypetsensitivity — a review. Clinical and in-vitro evahiatioti of treattiienl agetits. .loiirnal of Clinical Periodonlology. 10. 356. At)tDY, M. & MostAi-A. P. (1989) Detititie hypetsetisitivity. 11. Etfeets ptxnlueeil by the uptake in vitro of toothpastes oti to detiliiie. Journal of Oral Rehahililation. 16. .35.
110
E.G. Absi c\.i\\.
At)DY. M., Atist. E.G. & AtJAMS, D. (1987) Detititie hypetsetisitivity: effects //; vitro of aeids and dietary substances on root planed antl burred denti[ie. Jotirnat of Clinical I'eriodontologv, 14, 28t). Anm. M., Gtfttnnttis, G., DtJMMtiK, P., KtNGtjoN, A. & SttAW, W.C. (1987) The distribution of plaque and gingivitis and the inlluence of brushitig hatui in a group of 11 — 12 year old schoolehildten. .loiirncil of Clinical I'eriodonlology. 14, 564. AtMJY, M., Mo.stAt-A, P. & NiiWcOMtiii, R. (1987) Dentine hypeisetisitivity; the distribulioti of reeession, sensitivity and plaque. Jonrnal of Dentistry. 15, 242. At.t-XANt3t;t(, A.Ci. (1971) A study of the distribution of supra and subgingival calculus, bacterial plaque ajid gingival inliamtiiation in the mouths of 400 individuals. Journal of Feriodonlologv, 42, 21. BtiANNSTROM, M. (f962) A hydrodynatnic tneehanism in the transmission of pain-ptodueing stimuli tht-ough the dentine. Iti: Sensory Mechanisms in Dentine (ed. D..I. Andersoti), pp 73-80. Petganioti Press, London. DAVts. W.B. & WtNtHt(, P..1. (1980) The effect of abrasion on enatiiel atid detititie after exposute to dietary acid, /iritish Dental Jotirnat, 148. 253. Evtitit'Tt\ F.G., l-lAtJ., W.B. & PttATAK, N.M. (1966) Ttcaltiietil of hypersensitive dentitie. Jotirttal of Oral Therapeutics atid I'liartnacology. 2, 300. Fi.YNN, .)., GAt.LOWAY, R. & Ot(ct 1 At
of Oral Rduihilitalioii.
1992. V o l u m e 19, pages 1 0 1 - 1 1 0
Dentine hypersensitivity — the effect of toothbrushing and dietary compounds on dentine in vitro: an SEM study E . G . A B S I , M. A D D Y ' " and D . A D A M S t Depwlmcnl of Examimmon and Emergency. *Deparlim'iil of I'eriodoiUology and jDeparimeni of Basic Denial Science. Dental School. University of Wales College of Medicine. Cardiff. Wales. U. K.
Summary Dentine hypersensitivity occuis when tientinal tubules are open on the dentine surface and patent to a vital pulp. There has been limited interest in the aetiology of dentine hypersensitivity. In particular, little is known about agents that remove the dentine smear layer to expose tubules. Tootlibrushing certainly may expose dentine, but •whether a toothbrusli per se has the effect of opening tubules has not been established. The aim of this study in vitro was to determine whether a toothbrush could remove or create a smear layer. In adtlilion, the combined effects of toothbrushing with dietary fluids on dentine was assessed. Toothbrushing was observed, by scanning eleetron microscopy, both to remove and to recreate a smear layer on dentine specimens. However, the proeesses took a considerable time, and under conditions of normal toothbiushing it is unlikely thai the latter plays a direet aetiological role in opening tubules. Indeed, together with toothpaste it is more likely that brushing has a therapeutic action by mechanically forming a smear layer. Conversely, and importantly, toothbrushing in the presence of dietary acitis enhaneed smear layer removal. This finding raises the question of whether the dental profession should be advising that teeth be brushed before meals rather than after, as is often the case. Introduction Dentine hypersensitivity is a relatively common (Graf & Galasse, 1977) and painful condition of the permanent dentition. Most attention has been directed towards treatment, and the literature contains reports of numerous clinical trials (see review by Addy & Dowell, 1983), some of which have been deseribed as 'belonging in the realms of testimonials' (Everett, Hall & Phatak, 1966). Unfortunately, little emphasis has been placed on understanding the aetiology of the condition (for review see Addy, 1990). Perhapsbeeauseof this lack of knowledge, recurrences of sensitivity, aneedotally, appear to be frequent. The hydrodynamic theory has been proposed to explain stimulus transmission across dentine (Gysi, 1900; Bramistrom, 1962). In support of this theory, sensitive dentine was shown to possess much larger numbers of wider tubules open at the surface than non-sensitive dentine (Absi, Addy & Adams, 1987). Exposed cervieal dentine is commonly seen in adults, although not all such lesions are sensitive. The factors that expose dentine and ojien tubules are still relatively Corrcspontlence: Professor M. Addy, Dcparlnicnl of Periodoiilology, Denial School, Cardiff CF4 4XY, Wales, U.K. 101
102
E.G. Absi et al.
uncertain. Aeid erosion from dietary and environmental faetors is definitely assoeiated with dentine hypersensitivity (Tonyz, 1983), and acids in vitro readily remove the dentine smear layer to expose the tubules (Addy, Absi & Adams, 1987). Moreover, eircumstantial evidence has implicated toothbrushing, at least, with the loealization of cervieal dentine exposure and dentine hypersensitivity (Addy, Mostafa & Neweombe, 1987). Whether a toothbrush alone actually opens dentinal tubules has not been confirmed. Certainly, erosive and abrasive agents together markedly enhanee hard tissue loss (Davis & Winter 1980), but their combined role in opening tubules requires further study. The aim of this investigation in vitro was to observe the effects of toothbrushing on dentine alone and in combination with dietary compounds. Materials and Method The teeth used in the experiments were recently extracted caries-free human incisors, canines and premolars. After thorough cleaning, the buccal root surfaces were root planed with curettes from the cemento-enamel junction to the apex, until dentine was clearly apparent. The apieal and cervical thirds were covered with masking tape, leaving Ihe middle third exposed. The exposed dentine of some specimens was then etched with 50% phosphoric acid for 1 min. Specimens so treated were termed 'etehed', and the untreated speeimens were termed 'unetehed'. Toothbrushing was simulated using an electric-motor-driven reciprocal action machine. The brush heads were from multitufted nylon filament toothbrushes*. Brushing was perpendieular to the long axis of the tooth to simulate a horizontal action. The machine operated at a fixed speed of 52 strokes min^' and under a head load of 100 g. Two specimens could be brushed simultaneously. In order to evaluate the effects of toothbrushing alone on dentine, duplicate etched and unetehed specimens were immersed in a water/saliva mixture and brushed for time periods of 1, 3, 30 min and 2, 4, 6 and 24 h. In order to evaluate the effects of dietary fluids and brushing on the dentine smear layer, duplieate unetehed specimens were immersed in dietary fluid/saliva mixtures for 3 min, or immersed in the dietary fluid/saliva mixture and brushed for 3 min. All fluid/saliva mixtures were obtained from volunteers who rinsed for 30s with 15-ml volumes of the fluids. Expectorates weie pooled for the respective lluid. All specimens were prepared for scanning electron microscopy and representative photomierographs were taken at x300 and xlOOO magnification. Two photomicrographs were randomly selected for each specimen, coded and scored blind for tubule numbers, using a previously deseribed grid method (Absi et at., 1987). During counting, every fifth tubule was marked, and the narrower diameter was subsequently measured with an eyepiece graticule. On a separate occasion the same photomicrographs were subjectively graded for the number of tubules present as follows: 0 = no tubules visible; ( + ) = a few tubules visible; ( + + ) = moderate numbers of tubules visible; (+ + +) = many tubules visible. The reproducibility of the scorer and correlation of the subjectively and objeetively determined numbers was assessed by duplicate recordings from 15 randomly selected photomicrographs. Repeat recordings were separated by 7 days. Although nol relevant to this particular study, the inter-examiner reprodueibility of the method was determined by having a second examiner score the photomicrographs. The degree of agreement between grading and counting was determined by the overlap coefficient (Mann* Oral B, Aylesbury, U.K.
•
Toothbrushing, diet and dentine
103
Whitney statistie free of sample size). Intta- and inter-examiner reprodueibility for counts was determined by correlation eoefficients, together with mean and standard deviations of paired differenees. Bias was tested by paired /-tests. Intra- and interexaminer agreement for grading was determined by Kappa statistics, both unweighted and weighted (Fleiss-Cohen weights), to take into accout the intrinsic ordering of
the -\-l ++I-\- + + grades. R e s u l t s
-
.•
••
'
.-'.- • •
'
•
'
'
• • . . ' • , ,
•..
Effects of brushing alone on unetehed specimens A summary of the visual changes on the unetehed dentine surfaces (Fig. 1) with time of brushing are shown in Table 1. After 30 min some loss of the smear layer was apparent, with tubules exposed. The graded and counted tubule numbers increased up to 4 and 6h (Fig. 2). By 24 h all measurement parameters were reduced toward the 30-min brushing time. Effects of brushing alone on etched specimens A summary of the visual changes on the etehed dentine surfaces with time of brushing are shown in Table 1. At the start of brushing large numbers of widely opened tubules were apparent. It is significant that the tubule numbers and diameters at this time were greater than at any time of brushing unetehed specimens. The tubule numbers graded and counted by observation decreased to 6h, and the tubule diameters decreased to 4h (Fig. 3). Tubule numbers and diameters had increased again at 24h, but not to baseline measurements.
Table 1. Effect of toothbrnsliing on imelched and etched dentine specimens Dentinal lubnles Time
Grade
Unetehed lmin
3min 30 min 2h 4h 611 24h
Counl '
0
.
''
Mean diameter ± SD (nm)
.
.; •
. 0
'
0 , 0 ,+ . , 40 + '': 39 + + .... • 44 . . + + • '• ' 54 + . .30
.: . ' . '
30min
+++
2h 4h 6h 24 h
+++ ++ + +/ + +
. . .' •'. •'-
•
.
67 ,59 .
•
65'•
;,•
79; 41 39 50
,, . ' , ' . ^
• '-•
+++ +++
. 0 0-5 ±0-3 0-4 ±0-2 2-0±0-7 1-2 ±0-3 0-7±0-t
••
'
•
. Q
.. •
Etched
_ lmin 3min
'
•
_ " ^
2-5±0-4 2-0±0-4 2-5±0-6
'
l-9±0-3 0-4 ±0-1 l-l±O-l 1-6 ±0-8
104
£.G. Absi et al.
Fig. 1. Scanning electron micrograph of root-plancti dentine surface (unetehed). Parallel-running striations in the smear layer are typical of the efleets produced by instrumentation. This smear layer remained intact when exposeil to tooth brushing with water and lilgh-pl I dietary lluids. Mag[ii(ication x540.
Effects of dielarv products on dentine Without brushing. The dillerent dietary compounds produced a range of effects (Table 2), ranging from none (Fig. 1) to the opening of many dentinal tubules ( + + +) of wide diameter. The effects were not directly pH dependent, although it should be noted that the high-pH solutions, coffee, milk and tea produced no consistent changes on the dentine surface. All the other solutions of pH < 4 removed the smear layer to a variable extent after 3 min of exposure. Yoghurt and coke exposed a few tubules.
rig. 2. Scanning electron micrograph of a root-planed dentine surfaee (unetehed), brushed with water/ saliva Ior4h. Mueh of the smear layer has been removed to reveal dentinal lubules. Magnilieation x540.
Toolhhrushing. diet and dentine
105
Tahk' 2. Effecl of dietary proiUicis with and without brushing on licntine specimens
Product"^ Lctiiotiade (2-2) Coke (2-3) I3l;ickcurtanl jtiice (2-4) While wine (2-6) Grapefruit juice (2-7) Apple juice (3-t)) Red wine (3-2) OraJige juice (3-3) Yoghurt (4-1)
Grade
Count
No brush
brush
Meati diatiieter ± SD (Mill)
Grade
Mean diameter ± Sfl (inn)
+++
75
-I- +
43
59
2-3 ± 0-5 1-4 ±0-3 2-0 ± 0-6
+++ + ++
52
l - 0 ± t)-7
92
l-S±0-3 2-2 ± 0-6 2-5 ± 0-5 2-1 ± 0 - 3 0-9±tl-2 tl-l±tl-l (I-l ± tl-1 0-2 ± tl-1 (1
++
83
2-1 ±0-4
-1-
37
t)-4±0-l
.SI -1- + +
65
2-3 ±0-6 1-2 ±0-3
42
+ ++
101
4--I-
52 56 26
-f + +
M i l k (5-7)
Tea/milk (6-6) Coffee/mi Ik (6-6) Water (7-t))
-t-
0
0 0 0
0 12
tl
t)
l-t)±0-4 0-9 ± tl-4 I-l ±t)-7
3-t) ±0-2 t l - 4 ± t)-2 0 0 t)-4±t)-l tl
+ + -I-I--I- + -t--l- +
+ -(t) tl 0 tl
Count
66 45 79 43 >S 7 9 tl
* pM is shown in parentheses.
whereas lemonaile (Fig. 4), while wine, apple juice atul oratige juice exposed matty tubules. The other products were inteiniediate in their action on dentine. Tubule diameters after exposure varied, although most high-acidity soliiliotis exposed tubules of mean diameter innging from I—2|_t. Foi' yogluitt and coke, which exposed few tubules, the diametets were also narrow by eoniparison.
Fig. 3 . Seanning electron micrograph of an e t c h e d d e n t i n e surface brushed with wnter/saliva lor 4 h . Most tubule openitigs a t e n a i r o w e d e o m p a r e d to a d e n t i n e surfaee etclied with a ilietary lluid (cl. I"ig. 4). Magnilieation x,S40.
106
E.G. Absi et al.
Fig. 4. Scanning electron tnicrograpli of toot-planed dentine surface exposed to letiiotuide/saiiva lof 3 min. Most of the smear layer and surface tietails produced by instrumentation have been lost in Older to expose tubules. Magtiitteation x540.
With brushing. After 3 min, brushing with the dietary fluids was seen to etihatice the opening of tubules lor most products, as assessed by observation and by cotmting (Table 2). Thus most low-pH solutions were graded as ptoducing tnany and widely open tubules on the dentine surfaee (Fig. 5). Tubule diameters during this time period ranged fiom I—2-5|i. For the near-neutral pH lluids, brushing was noted to expose few if any tubules on the surface.
Fig. 5. Scanning eleetroti niierograph of a root-planed dentine surfaee. The lower half shows the conttol portioti wliieli was eovej-ed wilh tnasking tape atid reveals a stiiear layer. The upper portioti was brushed with blaekeurrant juiee/saliva. Nunietous tubule openitigs ate apparent. Magnifieation x540.
Toothbrushing, diet and dentine
107
Scoring evaluation Grading and counting. The degree of consistency between grading and scoring is summarized in Fig. 6. The overlap coefficient is 0-1 (a value of 0 would indicate perfect separation, and a value of 0-5 would indicate complete lack of separation), suggesting that theie is only a small degree of overlap, particularly for +/-f- + , and therefore close agreement between grading and counting. Inter- and intra-examiner reproducibility for counts. Inter- and intra-examiner reproducibility is sutntnarized in Table 3. In each case the correlation coefficient is high, btit this otily indicates a strong association. A /-test based on differences revealed no significant evidence of bias of one observer compared with the other. The ititraexaminer differences reached significance (P a. O
20
-I- -t-i- +++ Examiner 1 Overlap coefficient
0-025, 0-1
J
-I-
L
-t-f -t-i-t-
Examiner 2 1st time
Examiner 2 2nd time
0-0,0-0
0-0,0-071 Overall 0-008, 0-058
Fig. 6. Intet- atid intt-a-exaniiner variatioti of open tubule cottiit sliowitig degree of consistency between gtade atid scot-e assigned.
108
E.G. Absi et al.
Table 3. Ititer- and intra-exatniner variation and agteenient for coutititig and gratling detitinal tubules
Tubule counts Correlation SD of diffeicEiee (-test Tubule grading Unweighted Observed Expected Kappa Weighted Obsetved Kxpectcd Kappa
ltiter-cxamitier
Intra-exatniner
0-89 3-t)7 1-49 (NS)
0-99 -1-60 -2-16*
0-8tl 0-34 0-70
0-80
0-34 0-70
t)-95
0-95
tl-69
0-69
0-84
0-84
NS = tiot sigtiilicatit. * Signilieanl at /'-Y. M. & At:)AMS. D. (1987) Dentine hypersensitivity: a study of the patency of detititial lubules iji sensitive and non-sensitive cervical dejitine. .lournid of Clinical I'criodonlologv. 14. 280. AtM)Y, M. (1990) Etiology aiid clinical iniplicatiotis of iletititie hypersetisitivity. Denial Clinics of Norlh America. 34. 503. At)t)i', M. & Dowtn.t.. P. (1983) Dentitie liypetsensitivity — a review. Clinical and in-vitro evahiatioti of treattiienl agetits. .loiirnal of Clinical Periodonlology. 10. 356. At)tDY, M. & MostAi-A. P. (1989) Detititie hypetsetisitivity. 11. Etfeets ptxnlueeil by the uptake in vitro of toothpastes oti to detiliiie. Journal of Oral Rehahililation. 16. .35.
110
E.G. Absi c\.i\\.
At)DY. M., Atist. E.G. & AtJAMS, D. (1987) Detititie hypetsetisitivity: effects //; vitro of aeids and dietary substances on root planed antl burred denti[ie. Jotirnat of Clinical I'eriodontologv, 14, 28t). Anm. M., Gtfttnnttis, G., DtJMMtiK, P., KtNGtjoN, A. & SttAW, W.C. (1987) The distribution of plaque and gingivitis and the inlluence of brushitig hatui in a group of 11 — 12 year old schoolehildten. .loiirncil of Clinical I'eriodonlology. 14, 564. AtMJY, M., Mo.stAt-A, P. & NiiWcOMtiii, R. (1987) Dentine hypeisetisitivity; the distribulioti of reeession, sensitivity and plaque. Jonrnal of Dentistry. 15, 242. At.t-XANt3t;t(, A.Ci. (1971) A study of the distribution of supra and subgingival calculus, bacterial plaque ajid gingival inliamtiiation in the mouths of 400 individuals. Journal of Feriodonlologv, 42, 21. BtiANNSTROM, M. (f962) A hydrodynatnic tneehanism in the transmission of pain-ptodueing stimuli tht-ough the dentine. Iti: Sensory Mechanisms in Dentine (ed. D..I. Andersoti), pp 73-80. Petganioti Press, London. DAVts. W.B. & WtNtHt(, P..1. (1980) The effect of abrasion on enatiiel atid detititie after exposute to dietary acid, /iritish Dental Jotirnat, 148. 253. Evtitit'Tt\ F.G., l-lAtJ., W.B. & PttATAK, N.M. (1966) Ttcaltiietil of hypersensitive dentitie. Jotirttal of Oral Therapeutics atid I'liartnacology. 2, 300. Fi.YNN, .)., GAt.LOWAY, R. & Ot(ct 1 At
