Australian Dental Journal, April, 1976 165

Volume 21, No. 2

Dentine hypersensitivity

Robert Harris AND

J. H. Curtin

AssTRAcr-Reports received from 32 dentists on the effect of a complex mixture of calcium sucrose phosphate and calcium orthophosphate used as a gel, toothpaste, or slurry in relieving pain in hypersensitive dentine show, in 137 patients, complete relief in 112. It was found that in 54 patients the prior use of stannous fluoride prophylactic paste was beneficial.

Introduction All dentists would confirm that hypersensitive

dentine is annoying to the patient and trouble- some to treat satisfactorily. Some patients report that pain is so severe as to constitute both a physical and emotional problem. Mastication of all but the very softest food produces a sharp pain response in some patients and others cannot enjoy hot or cold liquids and foods, or sweet carbohydrate foods, or acid foods because of the pain they evoke.

In assessing response to a stimulus some con- sideration must be given to the subject of pain. Two aspects should be mentioned. One is the pain threshold, which is fairly stable in the same individual, and this is the lowest intensity of pain just perceived under constant conditions; the other is the reaction threshold which is very variable and depends mainly upon psychological factors. Furthermore pain tolerance is also important. For example pain perception in two individuals may be the same but the tolerance of intensified pain may be. different. Meares1 believes that “we have latent within us a psychological mechanism which can be used to modify the perception of pain” and all clinicians are aware of this difference in the capacity between individuals to tolerate pain.

1 Meares, A.-Psychological control of organically Z:tcr- mined pain. Ann. Roy. Aust. Coll. Surg., 1: 42-46 (Dec.) 1967.

The variable success which has followed different treatments gives rise to speculation as to possible mechanisms whereby any one of different stimuli produce painful responses in the tooth.

It is generally accepted that enamel is devoid of nerves. The innervation of dentine although not rich has been establisheda. Nerve fibres enter the inner layer of dentine, there being more in the crown than in the root3 and the number of nerve fibres to dentinal tubules ranges from 1:200 to 1:20004 but the presence of intra-dentinal receptors has not been establisheds.

It has been suggested that the odontoblast and its process has some part in the mediation of pain in dentine; this is based on histological, embryological, and electrophysiological evidences.

All clinicians can report patients who have complained of pain produced unexpectedly by

2 Fernhead, R. W.-The histological demonstration of nerve fibres in human dentine. In, Sensory mechanisms in dentine. Edit. Anderson, D . J., Oxford, Pergamon Press 1963 (pp. 15-26).

3 Lavelle. C. P.-Zn. Applied physiology of the mouth. Edit. Lavelle. C. P., Bristol, John Wright and Sons Ltd.. 1975 (p. 288).

4 Fernhead, R. W.-The neurohistology of human dentine. Proc. Roy. SOC. Med., 54:10, 877-884 (Oct.) 1961.

5 Frank, R. M.-Ultrastructural relationship between the odontoblast, i t5 process and the nerve fibre. In, Dentine and pulp. Edit. Symons, N. B. B., London Livingstone 1968 (pp. 115-145).

6 Anderson, D . J., Matthews, B., and Shelton. L. E.- Variations in the sensitivity to osmotic stimulation of human teeth. Arch. Oral Biol.. 121. 43-47 (Jan.) 1967.

166 Australian Dental Journal, April, 197b

chewing on a hard object or where a restoration impinges heavily on an opposing tooth during mastication. In such instances, apart from a response in periodontal receptors, the pain may be caused by pressure through a thin layer of dentine to the pulp, or by the transmission of force to receptors in the dentine, or by the split- ting effect of the restoration acting as a wedge between the wall of enamel and dentine. The main theory relating to dentine sensitivity implies that there are receptors in the pulp and these are sensitive to mechanical disturbances that result from the displacement of the contents of the dentinal tubules79 8.9, 10.

Although there are no nerves in enamel the small percentage of water it contains is partly mobile and this is possibly associated with pain (due to osmotic pressure)3. When enamel is damaged the possibility of pain occurring is increased; for example in very early enamel caries there may be pulpal inflammatory changes11 and cracks in enamel may expose the dentine to the oral environment.

Naylor examined the effect of silver nitrate and the uncooled high speed bur on dentine sensitivity and found that the former failed to cause any change in sensitivity to cold or electrical stimula- tion and the latter decreased the sensitivity to cold and in one case produced desensitization. At histological examination in this latter case the underlying connection between the pulp and dentine was found to have been destroyed'z.

Certain dentifrices and toothbrushing techniques in combination may be the cause of buccal or labial abrasion and like erosion in an active stage both are often accompanied by hypersensitivity. The abrasive quality of a dentifrice is probably an important factor in prolonging hypersensitivity as layers of dentine become worn away. Stookey and Muhler'3 have shown the wide range in abrasive and polishing properties of powders and toothpastes as well as variability in these proper-

I Brannstrom, M. , and Astrom. A.-A study of the mec- hanism of pain elicited from dentine. J . Dent. Res., 43:4, 619-625 (July-Aug.) 1964.

8 Brannstrom. M.-Phvsio-Datholoeical asuects of dentinal and pulpal respons; to 'irritants. In, Dentine and pulp. Edit. Symons, N. B. B., London, Livingstone, 1968 (pp. 231-246).

9 Brannstrom. M.. and Astrom. A.-The hvdrodvnzmics of the dentine; its possible relationship to dentinal pain. Int. Dent. J., 22:2, 219-227 (June) 1972.

10 Beveridge, E. E., and Brown, A. C.-The measurement of human dental intradental pressure and its response to clinical variables. Oral Surg., Oral Med., Orel Path., ! 9 : 5 , 655-668 (May) 1965.

11 Brannstrorn, M., and Lind, P. 0.-Pulpal response to early dental caries. J . Dent. Res., 4 4 3 , 1M5-1050 (Sep1.-Oct.) 1965.

12 Naylor, M. N.-The effect of silver nitrate and the un- cooled high speed bur on dentine sensitivity I n , Dentine and pulp. Edit. Symons, N. B. B., London, Livingstone, 1968 (p. 252).

ties in some products. Powders generally were more abrasive than toothpastes. Ware and ChongI4 graded the abrasiveness of 17 dentifrices available in Australia and classed two as excessively abrasive and nine as slightly.

Since the content, in part, of the dentinal tubules is fluid applications of solutions of differ- ing osmotic pressures are sufficient to produce fluid flow so that deformation of nerve fibrils in the dentine and of odontoblasts can occur. Such variations occur quite frequently in the mouth and the pulp tissue, lying immediately beneath the exposed area of dentine, undergoes some inflammatory changes. It is possible, if changes in osmotic pressure could be blocked in the exposed dentine, that stimuli to the dentine could not reach the odontoblasts and hence the normal reparative processes of the pulp would occur and the deposition of dentine would be followed by a reduction and ultimately by the disappear- ance of the sensitivity.

The rationale in the use of caustics in treating hypersensitive dentine is that, as they are protein precipitants, transduction of stimuli to the pulpal nerve tissue is blocked by destruction of the odontoblastic processes and any nerve fibrils present in the dentine. To be effective, therefore, the caustics must penetrate the dentine and since dentine is not homogenous the degree of penetra- tion is variable.

Remineralization such as by the use of sodium fluoride15 or sodium silico-fluoride16 has been suggested. Strontium chloride is another agent first suggested by Pawlowska in 1956 and cited by Ross17 which has the ability to combine with colloids of enamel and dentine through adsorp- tion and it has also been found useful in remineralization of bone's.

Caustic agents most commonly used are zinc chloride, silver nitrate, formaldehyde solution and phenol. Their use is often accompanied by pain and silver nitrate produces an objectionable

13 Stookey. G. K.. and Muhler, J. C.-Laboratory studies concerning the enamel and dentine abrasion properties of common dentifrice polishing agents. J. Dent. Res , 47:4, 524-532 (July-Aug.) 1968.

14 Ware, A. L., and Chong, Joan K.-A review of denti- frices as therapeutic agents. Austral. Dent. J . 9:3, 203-208 (June) 1964.

15 Hoyt, W. J , and Ribby, R . G.-Use of sodium fluoride for desensitizing dentine. J.A.D.A., 30:17, 1372-1376 (Sept.) 1943.

16 Massler, M.-Desensitization of cervical cementum and dentine by sodium silicofluoride. J. Dent. Res., 34:5, 761-762 (Oct.) 1955.

17 Ross, M. R.-Hypersensitive teeth: Effect of strontium chloride in a compatible dentifrice. J . Periodont., 32:1, 49-53 (Jan.) 1961.

18 Shorr, E., and Carter, A. C.-The usefulness of stron- tium as an adjunct to calcium in the remineralization of the skeleton in man. Bull. Hosp. Joint Dis , 1339 , 1952.

Australian Dental Journal, April, 1976 167

discolouration. Fluoride solutions, topically Following that initial work preparations con- applied and augmented by mouth rinses avoid to taining CSP* were made available to approxi- some extent these objections, but some patients mately 80 dental practitioners. Thirty-two of these find the fluorides distasteful. were prepared to record systematically observa-

Strontium chloride as a dentifrice has been tions on the efficacy of the preparations and this shown to have value but the hypersensitivity in paper presents the results of their observations. some cases returns. Experimental

Studies on sugar 20, 21 on the dissolution of hydroxapatite and on the hardening of human tooth enamelz2 demonstrated that a complex mixture of calcium sucrose phosphate and calcium orthophosphate not only reduced dissolution but could effectively remineralize enamel. Furthermore when this complex was incorporated in a toothpaste the rehardening, in vitro, was rapid. A later report23 showed that this calcium sucrose phosphate-calcium orthophos- phate complex (CSP) produces a surface effect on the tooth enamel.

The method of production of the complex has been described24 and is based on that of Neuberg and Pollak (1910). It is a complex mixture containing 85 per cent calcium sucrose phos- phates and 15 per cent calcium orthophosphate. It is a fine white powder with a bland neutral taste, is not hygroscopic, is stable, and is readily soluble in water producing a slightly alkaline solution which is slightly more viscous than a sucrose solution of equivalent concentration. The biological and chemical stability of CSP in aqueous solutions is similar to that of correspond- ing sucrose solutions and consequently they should not be stored for long periods; various enzymes will cause a breakdown of the product.

Craig25 studied the effect of CSP incorporated in a dentifrice and as a gel when applied to cervical areas of the teeth of 12 patients who had suffered from hypersensitivity in the cervical areas of teeth.

I9 Napper, D. H., and Smythe, B. M.--l’he dissolution kinetics of hydroxyapatite in the presence of kink poisons. J. Dent. Res., 4 5 5 , 1775-1783 (Nov.-Dec ) 1966.

20 Brady, B. H. G.. Napper, D. H. and Smythe, B. M.- Dissolution kinetics of hydroxyauatite. Nature, 2125057. . . . 77-78 (Oct.) 1966.

21 Brady, B. H. G., Napper, D. H., and Smythe, B. M.- Effect of additives on the rate of dissolution of hydroxy- apatite in unstirred acid buffers. J . Dent. Res., 47:4, 603-612 (July-Aug ) 1968.

22 Lilienthal. B.. NaDDer. D. H.. and Smvthe. B. M.-The hardening and -softening of human tooth enamel. Austral. Dent. J., 13:3, 219-230 (June) 1968.

23 Rogerson, M. J.-The role of a czlcium sucrose phos- phate-calciums orthophosphate complex in the reduc- tion of dental caries. Austral. Dent. J. . 18:3, 160-166 (June) 1973.

24 Curtin, J. H., and Gagolski, J.-Water-soluble phosphate compositions and process for preparing U S . Patent 3,375, 168 (March 26, 1968).

25 Craig, G. C.-Some observations on the use of a calcium sucrose phosphate-calcium orthophosphate complex as a desensitizing agent. Austral. Dent J., 1 8 5 6 , 328-330 (0ct.-Dec.) 1973.

Results From the records it was possible to obtain

acceptable data on 137 adult patients suffering from dentine sensitivity in one or more teeth arising from hot or cold applications, sweet or acid foods, toothbrushing or other tactile stimuli. The sensitivity had existed in most cases for between one and three years and the treatment consisted of topical application by the dentist supplemented by home care with either tooth- paste, gel or a slurry made up from the powder and water. The toothpaste contained approxi- mately 5 per cent and the gel 40 per cent of CSP respectively.

Four procedures were followed in the use of the CSP (Table 1).

A. When one method of application of the agent was used (76 patients).

B. When a combination of two or more methods used (7 patients).

C. Gel applied to the tooth after prophylaxis with stannous fluoride paste (17 patients).

D. Gel applied after prophylaxis with stannous fluoride and held in place with Orabase (37 patients).

From Table 1 it will be seen that 112 patients claimed complete relief, twenty-one obtained some reduction in sensitivity and four reported failures of the method.

It should be noted that methods C and D were claimed to be the most successful. In the case of method D the use of Orabase ensured that the CSP paste or gel was not rapidly washed away by saliva. All patients obtained relief for at least six months.

Seven types of pain producing stimuli were recorded for 100 patients (Table 2) and failure to gain total relief occurred in those patients in which three or more factors operated. Hot, cold, sweet and touch being the stimuli which were present in the four complete failures.

Of the 145 reactions recorded 16 only were attributed to tactile stimuli (probing, or touching the dentine with a clasp). Temperature changes were the most frequent recorded stimuli (77) and these were distributed almost evenly between hot and cold since the majority claimed that both temperature changes caused reaction. Reactions to - * Supplied by courtesy of CSR Limited and Washington

H. Soul Pattinson Co. Ltd.

168 Australian Dental Journal, April, 1976

TABLE 1

The effect of CSP in reducing hypersensitive dentine in adults ~ ~~~

Group Method of application Some relief No. of Results

patients complete relief or failure

A CSP powder applied directly to affected area CSP applied as slurry +SO% with water CSP gel (40% CSP) Toothpaste (5y0 CSP)

8 30 22 16

Sub-total

B Affected area treated with gel, patient given toothpaste for home use 2 Affected area treated with gel, patient given toothpaste for home use 3 Atfected area treated at later date with CSP slurry, due to recurrence of pain or non-relief Affected area treated with slurry, patient

Affected area treated with CSP powder, given toothpaste for home use

patient given toothpaste for home use

1

1

Sub-total (7)

C Gel applied to affected area in conjunction with Sn F, prophylaxis 17

D Prophylaxis with rubber cup and prophy- laxis paste contains fluoride, followed by treatment with CSP slurry or gel, then cov- ered with a commercial oral gel product* to hold CSP in place

Sub-total

TOTAL

- 2

3 -

17

* Orabase

tactile stimuli (brushing or chewing) were recorded rABLE 2

for 34 patients and of the chemical stimuli most were induced by sweet foods or drink. However the reaction to the sweet stimulus was always Stimulus No. associated with temperature changes and tooth- brushing. Cold 42

Type of stimulus producing a painful response in exposed hypersensitive dentine in 100 adults

Temperature Hot 35

In 43 cases relief was immediate on direct application of the gel or slurry but in the remain- ing cases several applications were required. In all cases home use of toothpaste or gel was used to reinforce the treatment. A majority of those dentists who did not return detailed reports indicated that they had used CSP and found it to be the most effective of any method of desensitizing hypersensitive dentine.

Tactile Toothbrush 20* Chewing 14** Probing 16

Chemical Sweet 15 Sour 3

Total 145 - -

*Three with dentine exposed by erosion ** All with dentine exposed by attrition

Discussion been curetted or exposed in the course of periodontal therapy or operative procedures the

adults at some time. Some patients suffer patient frequently develops hypersensitivity which extremely severe pain induced by changes in may be transitory or of a more permanent nature. temperature, tactile or chemical stimuli and any Where only partial or transitory relief by treat. one of these may be encountered several times ment occurs the patient becomes discouraged and each day. Where the root or coronal dentine has poor methods of oral hygiene develop. Such a

Dentine hypersensitivity probably affects most

Australian Dental Journal, April, 1976 169

situation becomes self perpetuating and increases the risk that dental caries will develop in the exposed cervical dentine.

In assessing the results reported here it should be emphasized that we are dealing with a series of case reports submitted by 32 dentists. From the data it is possible to make a clinical assess- ment of the value of CSP as a desensitizing agent. The hypersensitivity had existed for periods between 1 and 3 years except in the case of a small number of patients (17) with dentine exposed as the result of accidental trauma. These latter patients were treated with stannous fluoride solution followed by CSP.

The observations show that, of the 137 patients, 112 had complete relief from pain. Those who reported only some relief (211, such as a reduced reaction, have been grouped together with those who reported only a transitory relief (4) and with this loading complete success was reported in 81.7 per cent of patients. The result is comparable with the success rate reported by Ross17 and Skurnik26 and better than that reported by Meffert and HoskinsZ7 and Cohena who used a dentifrice containing strontium chloride.

Ross'? noted that most patients complained of hypersensitivity to thermal changes and fewer to sweets or tactile stimuli. Similar observations were made by Meffert and Hoskins27.

Although much has been written on the subject of pain from the dentine and pulp in which the role of nerve tissue, osmotic pressure changes, and chemical stimuli have all been explored, a recent review by Anderson29 has shown that the mechan- ism is not really known. Experimental evidence from studies on animals cannot be extrapolated to mechanisms in man.

It will be confirmed by all practitioners that dentine is not nearly as sensitive immediately after trauma as it is a week later. Anderson29 also confirmed that sensitivity is circumscribed by cutting two cavities in the same tooth in a patient. One cavity was cut and tested on the first visit

26 Skurnik, H.-Control of dental hvnersensitivity. J. Periodont., 342 , 183-185 (March) 1963.

27 Meffert, R. M., and Hoskins, S. W.-Effect of a stron- tium chloride dentifrice in relieving dental hypersensi- tivity. J. Periodont., 35:3, 232-235 (May-June) 1964.

28 Cohen, A.-Preliminary study of the effects of a stron- tium chloride dentifrice for the control of hypersensitive teeth. Oral Surg., Oral Med.. Oral Path., 14:9, 1046- 1052 (Sept.) 1961.

29 Anderson, D. J.-Pain from dentine and pulp. Brit. Med. Bull., 3 1 2 , 111-114 (May) 1975.

30Hiatt, W. H., and Johansen, E.-Root preparation I. Obturation of dentinal tubules in treatment of root hypersensitivity. J. Period., 43:6, 373-380 (June) 1972.

31 Levin M. P., Yearwood L. L., and Carpenter W. ti.- The' desensitizing effe'ct of calcium hydrdxide and magnesium hydroxide on hypersensitive dentine. Oral Surg., Oral Med.. Oral Path.. 35:5, 741-746 (May) 1973.

and then filled with gutta percha for a week. Before testing it again the other cavity was cut and both were tested. The first showed character- istic increased sensitivity whilst the second freshly cut was less sensitive. From this it may be deduced that an inflammatory reaction had developed in the adjacent pulp and this was the cause of the sensitivity.

Hiatt and Johansen30 noted that roots, sensitive after periodontal therapy, were desensitized in most cases by rubbing a CaHPO4 paste over the exposed root surface and calcium hydroxide31 has been used in a similar way.

In assesing a desensitizing agent it may be ideal to set up and conduct a double blind controlled clinical trial but in practice this is difficult to implement. The patient is suffering acute pain at frequent intervals during the day and seeks relief from this pain when eating and drinking or using the toothbrush. His statement that the pain has been alleviated by the applica- tion of the desensitizing agent in one or other form enables a clinical assessment to be made. Further- more the agent should not be distasteful to use otherwise patient co-operation is fleeting and failure is assured.

Currently CSP is available as a gel (40 per cent) or toothpaste (1 0 per cent) designed to ensure satisfactory shelf life and the powder form can be obtained from the manufacturers. Solutions and slurries should be freshly prepared. The toothpaste and gel have a pleasant taste and the abrasive quality of the former is at a minimal and acceptable level. When used in combination with stannous fluoride the patients reported com- plete relief in all cases.

Summary 1. Reports from 37 dentists on the use of a

calcium sucrose phosphate calcium orthophos- phate complex (CSP) in the control of hyper- sensitive dentine have been collated.

2. One hundred and thirty seven patients were treated and 112 claimed complete control of sensitivity for at least six months.

3. When the complex was used in conjunction with stannous fluoride success was reported in all cases. 4. The complex is available as a toothpaste and

a gel. Acknowledgement

The support and co-operation of the dentists who submitted data on patient reactions is grate- fully acknowledged.

CSR Research Laboratories, Box 39, P.O.,

Roseville, N.S.W., 2069