Besides caries, various destructive processes of the dental hard tissues are rather common in the form of erosions and abrasions. Two cases and treatment of a specific type of pernicious process ascribed to the abusive use of citric acid are described. A discussion of the action of citric acid and its effect on dental tissues is presented. The question is raised as to the possible contribution of citric acid to the origin of other erosive processes.
Citric acid consumption and the human dentition
James L. Fuller,
DDS, MS
Wallace W. Johnson,
DDS, MS, Iow a City
A frequent and perplexing problem to most den tal practitioners is the diagnosis, probable origin, treatm ent, and prognosis of various processes (exclusive of caries) that are destructive to the dental hard tissues. This paper was prompted by a clinical result of an enamel destructive pro cess specific to the abusive intake of citric acid. However, a penetrating question, which is not totally answered at present, pertains to the pos sible role of citric acid as a contributing factor in other erosive processes of enamel, dentin, and cementum.
R ev iew of th e literatu re
As long ago as 1907, M iller 1 expounded on the “ wasting” of tooth tissue and classified a list of causative agents, including acids, dentrifices, and frictional forces. Since that time, there has seemingly been no concise agreement as to the process of various types of “ erosions” and “ abrasions,” nor have the etiologic and contrib utory factors been firmly established. When gen erally accepted definitions are compared, both abrasion and erosion seem to involve the loss of tooth structure. However, the abrasion process is considered to have a mechanical origin, where as erosion is generally considered to be the re 80 ■ JAD A, V o l. 95, J u ly 1977
sult of chemical or mechanicochemical factors. Mention is further made of idiopathic erosion, to which no concrete causative agents have been delineated .2 However, Rost and Brodie 3 de scribed erosionlike patterns on acrylic denture teeth, as well as the denture bases, suggesting the hyperactivity of adjacent soft oral tissues as the causative agent. It was further noted that these patients exhibited erosion of their natural teeth as well. Other findings have substantiated this original assumption .4-7 Sognnaes and co-workers 4 reported the inci dence of erosion to be about 18% in a large sam ple ( 10,000 ) of extracted teeth, and that cervical areas of incisors were the most common site of occurrence. This study further suggested intraorally operating frictional forces as contributing to the erosion pattern. Miller 1 originally listed abrasion from denti frices and toothbrushing as contributing to ero sion, and that assumption has been documented by more recent studies .8,9 O ther investigators have linked salivary factors to the erosion pro cess . 10,11 One study suggested that its finding of a greater incidence of erosions in patients with hyperthyroidism might be attributable to elevat ed thyroid hormone levels or the resulting meta bolic effect . 12 Externally introduced acids also have been
termed erosion-producing agents. The British Dental Association 13 described characteristic tooth erosions in factory workers and associat ed personnel, attributed to industrial acids of which they compiled a comprehensive list. It also has been generally known that the presence of gastric acids in the mouth as a result of fre quent vomiting may also cause insult to the en amel of teeth. Finally, the ingestion of various highly acidic foodstuffs has been cited as a factor in certain types of dental erosions. Most always, these foodstuffs are some sort of fresh citrus fruit, juice, extract, or confection containing high concen trations (low pH levels) of citric acid. Several clinical case studies 14' 21 suggest the sucking of fresh lemon halves and the sipping or drinking of pure lemon juice to be the etiologic factor in volved. Other cases have cited excessive intake of oranges ,21,22 and grapefruit and limes also have been suggested as contributory to enamel and dentin erosion. One review 21 reported a four fold increase in the consumption of commercial fruit juice preparations in Great Britain during the 16-year period, 1956-1972. Elsbury 23 suggested some basis for the de structiveness of citric acid. In an in vitro study, he indicated that citric acid erodes tooth struc ture at a rate more than double that of hydro chloric or nitric acids of the same concentration. He concluded that this type of dental erosion is related to the pH level, but that the attack rate differs because of specific properties of certain acids. He further described the unique process
Fig 1 ■ Case no. 1. Appearance of a nterior teeth at initial appoint m ent.
Fig 2 ■ Case no. 1. Radiograph of m axillary left central incisor at initial appointm ent.
of attack found with citric acid. Regardless of the reason for the consumption, all the case observations indicated that exces sive intakes of citric acid are capable of destroy ing tooth structure .14' 22 R ep o rt of cases
FULLER
JOHNSO N
THE AUTHO RS Dr. Fuller is associate professor of operative dentistry and Dr. Johnson is professor and chairm an
of operative dentistry, College of
Dentistry, University of Iowa, Iowa City, 52242. Address requests fo r reprints to Dr. Fuller.
■ Case no. 1: The past medical history of the 26-year-old woman was normal; the dental exam ination revealed normal soft tissues and 28 perm anent teeth with no caries or existing restora tions. The patient’s initial complaint centered on her desire for improvement in the appearance of her maxillary anterior teeth (Fig 1). It was noted that most of the enamel on the labial surfaces of the maxillary central incisors, plus a smaller portion of the enamel of the left lateral incisor, had been affected by some sort of process destructive to the tooth’s external hard tissue. The enamel in the affected areas was quite F u lle r— J o h n s o n : C ITRIC A C ID C O N S U M P T IO N A N D TEETH ■ 81
rough, with rather evenly distributed pitting. The individual pits seemed to remain in enamel, and none was more than a millimeter in diameter (usually less) at the opening. The color of the af fected teeth did not differ from that of the other anterior teeth. The pitted areas were not stained, and there was no evidence of caries. There was also a ledge near the gingival line, in the enamel of the cervical third of the labial surface of both central incisors, and there was no pitting cervical to this ledge. Periapical radiographs of the cen tral incisors revealed radiolucent areas of the crowns, which were especially well circum scribed at the cervical region (Fig 2). The patient had not noticed any pain or sensitivity associ ated with the teeth, but because of their appear ance, they were a source of concern to her. The history of the lesions, as related by the patient, was interesting. She was positive that they appeared during a “ tequila party” when she was a college student, about six years pre viously. As is the custom at this type of party, the drinking of tequila was followed by the suck ing of fresh lime or lemon halves. The patient stated (and demonstrated) that when sucking on the citrus fruit, the maxillary incisors were em bedded in the section of fruit, and this sequence of drinking and sucking fruit was almost continu ous during the party’s duration. The patient’s first indication of the condition occurred some time during the evening, when the labial sur faces of her “ upper front teeth felt rough.” Al though the patient regularly included citrus fruits in her diet, she claimed she had not before, nor since, consumed them in this manner. If the history, as recalled by the patient, is re liable it would appear that enamel destruction by high concentrations of citric acid occurred with in a relatively short period of time, actually a m atter of hours. ■ Case no. 2: A sophomore dental student re quested a dental consultation for his 23-year-old
Fig 3 ■ Case no. 2. A ppearance of anterior teeth at initial ap pointm ent. 82 ■ JADA, V o l. 95, J u ly 1977
Fig
4 ■ Patient
in
case 2 dem onstrates sucking of lemon.
wife. The medical history was normal, and the patient’s soft and hard oral tissues were healthy. The student’s reason for consultation was to learn if something could be done to improve the appearance of his wife’s maxillary central inci sors (Fig 3). Clinically, the enamel on the labial surfaces of both maxillary central incisors was very similar to that of the patient in case no. 1, except the de gree and coverage of the pitted area was less, and neither lateral incisor was noticeably in volved. Furthermore, there was no evidence of a ledge on the cervical third of the teeth; rather, the pitting simply faded out in that area. Radiographically, there was little difference between the two cases. The history in this case revealed a more insid ious onset. This patient could not pinpoint when the condition was first apparent, but it had been a concern to her for several years. She had sucked lemons since she was a young girl, al though she claimed the habit was sporadic, and that she only sucked one or two lemon halves in any one day (Fig 4). She also indicated that she had completely ceased the habit in the past year or two. ■ Treatment: Both patients were treated in the same manner. The affected teeth were isolated with a rubber dam, pumiced, cleansed, and dried. The affected areas were then acid conditioned (etched) with the acid provided in a commercial ly available acid-etch system. After water clean sing and air drying, an unfilled composite resin glaze from the same manufacturer was painted over the etched area and allowed to polymerize. The appearances of both patients were greatly improved by the use of the resin, which filled in the pits and covered the roughness. After three months (Fig 5, 6), the patients were recalled for examination, and the clinical appearance and condition of the coating were still acceptable.
Fig 5 ■ Case no. 1. A ppearance three m onths after treatm ent.
Fig 6 ■ Case no . 2. A ppearance three m onths after treatm ent.
curred in two ways; that hydroxy apatite and fluorapatite dissolution can be the result of or caused by a liquid unsaturated with respect to either apatite. Larsen further found a significant difference in the way the two apatites reacted to the process of dissolution. The dissolution effects of citric acid on the teeth are apparently limited to the time of eating or drinking acid-containing foods. During a study of salivary citrate content after capsules of pure citric acid were ingested, Ericsson 26 found that the salivary content was less than that present after the chewing or drinking of foods and juices containing citric acid. H e concluded that there was no prolonged solubilizing effect of citric acid in the saliva after digestion and absorption of citrate-rich foods and beverages in the gastro intestinal tract .26 Several factors, then, seem to be at work in the cases described. Where there is habitual and abusive use of citrus fruits, particularly the le mon, the consumption rate is usually high. At the time of use, there may be prolonged contact of the fresh acidic juice and fruit pulp with the teeth. The result may be a rapid neutralization of the buffering capabilities of the saliva, fol
D iscussion
The ability of citric acid to erode tooth enamel could be attributable to one or more of three fac tors: the affinity this substance has for calcium; its high hydrogen ion concentration, owing to the presence of three carboxyl groups in each molecule; and the type of reaction that takes place when it is in contact with tooth enamel. Elsbury 23 said that the erosion of enamel by the mineral acids was self-limiting because of the formation of insoluble end products. However, he stated that the reaction between citric acid and enamel was not self-limiting in the same man ner and suggested that two different processes were at work. The first of these processes was the dissolution of the enamel to form a calcium citrate salt in inverse proportion to the pH of the solution; and the second was the withdrawal of the calcium from the solution to form a complex calcium citrate ion independent of the pH of the solution .23 Elsbury’s conclusions were similar to those of M cClure and Ruzicka 24 who earlier had suggested that calcium in tooth structure and the citrate ion formed a soluble calcium citrate com plex. The conclusions of Larsen 25 in 1973 were similar to those of Elsbury, and McClure and Ruzicka. He said that enamel dissolution oc
Fig 7 ■ Typical idiopathic cervical erosions.
lowed by a lowering of the pH level of the mouth contents, and an increase in the hydrogen ion concentration around the teeth. The areas of outer enamel that are in contact with the least buffered fruit acid for the longest period of time would be dissolved at a faster rate than other areas where the pH is not as low. This could be the cause of the typical but unusual erosive pat terns. Once the outer layers of enamel are re moved, the process may continue with greater ease as it contacts the less resistant inner layers. However, the simple fact that citric acid can have this effect on tooth enamel should also serve to alert the dentist to what might be occur ring in the mouths of many patients to whom the F u lle r— J o h n s o n : C ITR IC AC ID C O N S U M P TIO N AND TEETH ■ 83
consumption of acid foods and fruits is consid ered “ normal.” The areas of erosion that com monly occur around the gingiva or cervical areas of the teeth (often referred to as toothbrush or idiopathic erosion) could well be affected by acid dissolution of the enamel and dentinal surfaces. The regions of teeth near the gingiva, being less self-cleansing than other areas of the teeth, could harbor unbuffered acid contents of foods, fruits, and drinks in close proximity to cervical tooth surfaces for a considerable period of time before the acid contents are neutralized or washed away. The result could be the areas of gingival erosion (Fig 7) that are clean and noncarious, and that slowly enlarge in size and depth. The cases of citric acid dissolution of tooth enamel as described in this paper are unusual, somewhat rare, and of academic interest. It is hoped that their description will remind the den tal profession to suspect a high or abusive intake of food products containing citric acid whenever excessive or unusual erosive patterns of the en amel of teeth are observed.
4. Sognnaes, R.F.; W olcott, R.B.; and X ho nga, F.A. Dental erosion I. Erosion-like patterns occurring in association with other dental conditions. JADA 84:571 M arch 1972. 5. X ho nga, F.A.; W olcott, R.B.; and S ognnaes, R.F. D ental ero sion II. C linical m easurem ents of dental erosion progress. JADA 8 4:577 M arch 1972. 6. X ho nga, F.A., and Sognnaes, R.F. Dental erosion: Progress of erosion m easured clinically after various flu oride applica tions. JADA 87:1223 Nov 1973. 7. B rodie, A.G., and Sognnaes, R.F. Erosion-like dentu re m ark ings possibly related to hyperactivity o f oral soft tissues. JADA 88:1012 M ay 1974. 8. H arrington, J.H., and Terry, I.A. A utom atic and hand too thbrushing abrasion studies. JADA 68:343 M arch 1964. 9. M anly, R.S., and others. A m ethod for m easurem ent of abra sion o f dentin by toothbrush and dentifrice. J Dent Res 44:533 M ay-June 1965. 10. R app, G.W .; Prapuolenis, A.; and M adonia, J. Pyrophos phate: a fa c to r in tooth erosion. J D ent Res 39:372 M arch-April 1970. 11. Zipkin, I., and M cClure, F.J. Salivary citrate and dental erosion. J D ent Res 28:613 Dec 1949. 12. X ho nga, F.A., and Van Herle, A. T h e influence of hyper thyroidism on dental erosions. Oral Surg 36:349 S ept 1973. 13. British Dental Association m em orandum on the erosion of teeth . B r Dent J 106:239 April 7, 1959. 14. H ollow ay, P.J.; Mellanby, M.; and Stew art, R.J.C. Fruit drinks and tooth erosion. Br Dent J 104:305 M ay 6, 1958. 15. Stafne, E.C., and Lovestedt, S.A. Dissolution of tooth sub stance by lem on juice, acid beverages, and acids from other sources. JADA 34:586 May 1947. 16. A llan, D.N. Enam el erosion with lemon juice. Br D ent J 1 22:300 April 4, 1972.
Summary The habitual and abusive use of fruits and foods containing citric acid can cause serious dissolu tion effects on human tooth enamel. Because these effects can occur so easily, this paper sug gests that foods and fruits containing citric acid, as well as other acids, could be definite contribu tors to the many other forms of idiopathic ero sion so often observed by the dentist. There is a need for continued research and study in this area. 1. M iller, W .D. Experim ents and observations on the wasting of tooth tissue, etc. Dent Cosmos 49:1 Jan 1907. 2. Boucher, C.O. C urrent clinical dental term inology, ed 2. St. Louis, C. V. M osby C o., 1974. 3. Rost, T., and Brodie, A.G. Possible etiologic factors in de n tal erosion. J D ent Res 4 0:385 M arch-April 1961.
84 ■ JADA, V o l. 95, J u ly 1977
17. Hicks, H. Excessive citrus ju ice consum ption. C linical ob servations o f its effect on superficial and deep tissues of the oral cavity. JADA 41:38 July 1950. 18. Finch, L.D. Erosion associated with diabetes insipidus. Br D ent J 103:280 Oct 15, 1957. 19. M cLachan, W. Tooth dam age from use of citrus fruits. Br D ent J 131:385 Nov 2, 1971. 20. S panauf, A.J. Erosion arising from a nutritional facto r with concom itant bruxism. A clinical case report. Aust Dent J 18:233 Aug 1973. 21. Levine, R.S. Fruit ju ice erosion— an increasing danger? J D ent 2:85 No. 2, 1973-74. 22. Eccles, J.D., and Jenkins, W .G. Dental erosion and diet. J D ent 2:153 No. 4, 1973-74. 23. Elsbury, W .B. H ydrogen-ion concentration and the acid erosion of teeth. Br D ent J 93:177 O ct 7, 1952. 24. M cC lure, F.J., and R uzicka, S.J. T h e destructive effect of citrate vs. lactate ions on rats m olar tooth surface in vivo. J Dent Res 25:1 Feb 1946. 25. Larsen, M . Dissolution of enam el. Scand J D ent Res 82:518 D ec 1973. 26. Ericsson, Y. Investigations on th e occurrence and signif icance o f citric acid in the saliva. J Dent Res 32:850 Dec 1953.
Citric acid consumption and the human dentition
James L. Fuller,
DDS, MS
Wallace W. Johnson,
DDS, MS, Iow a City
A frequent and perplexing problem to most den tal practitioners is the diagnosis, probable origin, treatm ent, and prognosis of various processes (exclusive of caries) that are destructive to the dental hard tissues. This paper was prompted by a clinical result of an enamel destructive pro cess specific to the abusive intake of citric acid. However, a penetrating question, which is not totally answered at present, pertains to the pos sible role of citric acid as a contributing factor in other erosive processes of enamel, dentin, and cementum.
R ev iew of th e literatu re
As long ago as 1907, M iller 1 expounded on the “ wasting” of tooth tissue and classified a list of causative agents, including acids, dentrifices, and frictional forces. Since that time, there has seemingly been no concise agreement as to the process of various types of “ erosions” and “ abrasions,” nor have the etiologic and contrib utory factors been firmly established. When gen erally accepted definitions are compared, both abrasion and erosion seem to involve the loss of tooth structure. However, the abrasion process is considered to have a mechanical origin, where as erosion is generally considered to be the re 80 ■ JAD A, V o l. 95, J u ly 1977
sult of chemical or mechanicochemical factors. Mention is further made of idiopathic erosion, to which no concrete causative agents have been delineated .2 However, Rost and Brodie 3 de scribed erosionlike patterns on acrylic denture teeth, as well as the denture bases, suggesting the hyperactivity of adjacent soft oral tissues as the causative agent. It was further noted that these patients exhibited erosion of their natural teeth as well. Other findings have substantiated this original assumption .4-7 Sognnaes and co-workers 4 reported the inci dence of erosion to be about 18% in a large sam ple ( 10,000 ) of extracted teeth, and that cervical areas of incisors were the most common site of occurrence. This study further suggested intraorally operating frictional forces as contributing to the erosion pattern. Miller 1 originally listed abrasion from denti frices and toothbrushing as contributing to ero sion, and that assumption has been documented by more recent studies .8,9 O ther investigators have linked salivary factors to the erosion pro cess . 10,11 One study suggested that its finding of a greater incidence of erosions in patients with hyperthyroidism might be attributable to elevat ed thyroid hormone levels or the resulting meta bolic effect . 12 Externally introduced acids also have been
termed erosion-producing agents. The British Dental Association 13 described characteristic tooth erosions in factory workers and associat ed personnel, attributed to industrial acids of which they compiled a comprehensive list. It also has been generally known that the presence of gastric acids in the mouth as a result of fre quent vomiting may also cause insult to the en amel of teeth. Finally, the ingestion of various highly acidic foodstuffs has been cited as a factor in certain types of dental erosions. Most always, these foodstuffs are some sort of fresh citrus fruit, juice, extract, or confection containing high concen trations (low pH levels) of citric acid. Several clinical case studies 14' 21 suggest the sucking of fresh lemon halves and the sipping or drinking of pure lemon juice to be the etiologic factor in volved. Other cases have cited excessive intake of oranges ,21,22 and grapefruit and limes also have been suggested as contributory to enamel and dentin erosion. One review 21 reported a four fold increase in the consumption of commercial fruit juice preparations in Great Britain during the 16-year period, 1956-1972. Elsbury 23 suggested some basis for the de structiveness of citric acid. In an in vitro study, he indicated that citric acid erodes tooth struc ture at a rate more than double that of hydro chloric or nitric acids of the same concentration. He concluded that this type of dental erosion is related to the pH level, but that the attack rate differs because of specific properties of certain acids. He further described the unique process
Fig 1 ■ Case no. 1. Appearance of a nterior teeth at initial appoint m ent.
Fig 2 ■ Case no. 1. Radiograph of m axillary left central incisor at initial appointm ent.
of attack found with citric acid. Regardless of the reason for the consumption, all the case observations indicated that exces sive intakes of citric acid are capable of destroy ing tooth structure .14' 22 R ep o rt of cases
FULLER
JOHNSO N
THE AUTHO RS Dr. Fuller is associate professor of operative dentistry and Dr. Johnson is professor and chairm an
of operative dentistry, College of
Dentistry, University of Iowa, Iowa City, 52242. Address requests fo r reprints to Dr. Fuller.
■ Case no. 1: The past medical history of the 26-year-old woman was normal; the dental exam ination revealed normal soft tissues and 28 perm anent teeth with no caries or existing restora tions. The patient’s initial complaint centered on her desire for improvement in the appearance of her maxillary anterior teeth (Fig 1). It was noted that most of the enamel on the labial surfaces of the maxillary central incisors, plus a smaller portion of the enamel of the left lateral incisor, had been affected by some sort of process destructive to the tooth’s external hard tissue. The enamel in the affected areas was quite F u lle r— J o h n s o n : C ITRIC A C ID C O N S U M P T IO N A N D TEETH ■ 81
rough, with rather evenly distributed pitting. The individual pits seemed to remain in enamel, and none was more than a millimeter in diameter (usually less) at the opening. The color of the af fected teeth did not differ from that of the other anterior teeth. The pitted areas were not stained, and there was no evidence of caries. There was also a ledge near the gingival line, in the enamel of the cervical third of the labial surface of both central incisors, and there was no pitting cervical to this ledge. Periapical radiographs of the cen tral incisors revealed radiolucent areas of the crowns, which were especially well circum scribed at the cervical region (Fig 2). The patient had not noticed any pain or sensitivity associ ated with the teeth, but because of their appear ance, they were a source of concern to her. The history of the lesions, as related by the patient, was interesting. She was positive that they appeared during a “ tequila party” when she was a college student, about six years pre viously. As is the custom at this type of party, the drinking of tequila was followed by the suck ing of fresh lime or lemon halves. The patient stated (and demonstrated) that when sucking on the citrus fruit, the maxillary incisors were em bedded in the section of fruit, and this sequence of drinking and sucking fruit was almost continu ous during the party’s duration. The patient’s first indication of the condition occurred some time during the evening, when the labial sur faces of her “ upper front teeth felt rough.” Al though the patient regularly included citrus fruits in her diet, she claimed she had not before, nor since, consumed them in this manner. If the history, as recalled by the patient, is re liable it would appear that enamel destruction by high concentrations of citric acid occurred with in a relatively short period of time, actually a m atter of hours. ■ Case no. 2: A sophomore dental student re quested a dental consultation for his 23-year-old
Fig 3 ■ Case no. 2. A ppearance of anterior teeth at initial ap pointm ent. 82 ■ JADA, V o l. 95, J u ly 1977
Fig
4 ■ Patient
in
case 2 dem onstrates sucking of lemon.
wife. The medical history was normal, and the patient’s soft and hard oral tissues were healthy. The student’s reason for consultation was to learn if something could be done to improve the appearance of his wife’s maxillary central inci sors (Fig 3). Clinically, the enamel on the labial surfaces of both maxillary central incisors was very similar to that of the patient in case no. 1, except the de gree and coverage of the pitted area was less, and neither lateral incisor was noticeably in volved. Furthermore, there was no evidence of a ledge on the cervical third of the teeth; rather, the pitting simply faded out in that area. Radiographically, there was little difference between the two cases. The history in this case revealed a more insid ious onset. This patient could not pinpoint when the condition was first apparent, but it had been a concern to her for several years. She had sucked lemons since she was a young girl, al though she claimed the habit was sporadic, and that she only sucked one or two lemon halves in any one day (Fig 4). She also indicated that she had completely ceased the habit in the past year or two. ■ Treatment: Both patients were treated in the same manner. The affected teeth were isolated with a rubber dam, pumiced, cleansed, and dried. The affected areas were then acid conditioned (etched) with the acid provided in a commercial ly available acid-etch system. After water clean sing and air drying, an unfilled composite resin glaze from the same manufacturer was painted over the etched area and allowed to polymerize. The appearances of both patients were greatly improved by the use of the resin, which filled in the pits and covered the roughness. After three months (Fig 5, 6), the patients were recalled for examination, and the clinical appearance and condition of the coating were still acceptable.
Fig 5 ■ Case no. 1. A ppearance three m onths after treatm ent.
Fig 6 ■ Case no . 2. A ppearance three m onths after treatm ent.
curred in two ways; that hydroxy apatite and fluorapatite dissolution can be the result of or caused by a liquid unsaturated with respect to either apatite. Larsen further found a significant difference in the way the two apatites reacted to the process of dissolution. The dissolution effects of citric acid on the teeth are apparently limited to the time of eating or drinking acid-containing foods. During a study of salivary citrate content after capsules of pure citric acid were ingested, Ericsson 26 found that the salivary content was less than that present after the chewing or drinking of foods and juices containing citric acid. H e concluded that there was no prolonged solubilizing effect of citric acid in the saliva after digestion and absorption of citrate-rich foods and beverages in the gastro intestinal tract .26 Several factors, then, seem to be at work in the cases described. Where there is habitual and abusive use of citrus fruits, particularly the le mon, the consumption rate is usually high. At the time of use, there may be prolonged contact of the fresh acidic juice and fruit pulp with the teeth. The result may be a rapid neutralization of the buffering capabilities of the saliva, fol
D iscussion
The ability of citric acid to erode tooth enamel could be attributable to one or more of three fac tors: the affinity this substance has for calcium; its high hydrogen ion concentration, owing to the presence of three carboxyl groups in each molecule; and the type of reaction that takes place when it is in contact with tooth enamel. Elsbury 23 said that the erosion of enamel by the mineral acids was self-limiting because of the formation of insoluble end products. However, he stated that the reaction between citric acid and enamel was not self-limiting in the same man ner and suggested that two different processes were at work. The first of these processes was the dissolution of the enamel to form a calcium citrate salt in inverse proportion to the pH of the solution; and the second was the withdrawal of the calcium from the solution to form a complex calcium citrate ion independent of the pH of the solution .23 Elsbury’s conclusions were similar to those of M cClure and Ruzicka 24 who earlier had suggested that calcium in tooth structure and the citrate ion formed a soluble calcium citrate com plex. The conclusions of Larsen 25 in 1973 were similar to those of Elsbury, and McClure and Ruzicka. He said that enamel dissolution oc
Fig 7 ■ Typical idiopathic cervical erosions.
lowed by a lowering of the pH level of the mouth contents, and an increase in the hydrogen ion concentration around the teeth. The areas of outer enamel that are in contact with the least buffered fruit acid for the longest period of time would be dissolved at a faster rate than other areas where the pH is not as low. This could be the cause of the typical but unusual erosive pat terns. Once the outer layers of enamel are re moved, the process may continue with greater ease as it contacts the less resistant inner layers. However, the simple fact that citric acid can have this effect on tooth enamel should also serve to alert the dentist to what might be occur ring in the mouths of many patients to whom the F u lle r— J o h n s o n : C ITR IC AC ID C O N S U M P TIO N AND TEETH ■ 83
consumption of acid foods and fruits is consid ered “ normal.” The areas of erosion that com monly occur around the gingiva or cervical areas of the teeth (often referred to as toothbrush or idiopathic erosion) could well be affected by acid dissolution of the enamel and dentinal surfaces. The regions of teeth near the gingiva, being less self-cleansing than other areas of the teeth, could harbor unbuffered acid contents of foods, fruits, and drinks in close proximity to cervical tooth surfaces for a considerable period of time before the acid contents are neutralized or washed away. The result could be the areas of gingival erosion (Fig 7) that are clean and noncarious, and that slowly enlarge in size and depth. The cases of citric acid dissolution of tooth enamel as described in this paper are unusual, somewhat rare, and of academic interest. It is hoped that their description will remind the den tal profession to suspect a high or abusive intake of food products containing citric acid whenever excessive or unusual erosive patterns of the en amel of teeth are observed.
4. Sognnaes, R.F.; W olcott, R.B.; and X ho nga, F.A. Dental erosion I. Erosion-like patterns occurring in association with other dental conditions. JADA 84:571 M arch 1972. 5. X ho nga, F.A.; W olcott, R.B.; and S ognnaes, R.F. D ental ero sion II. C linical m easurem ents of dental erosion progress. JADA 8 4:577 M arch 1972. 6. X ho nga, F.A., and Sognnaes, R.F. Dental erosion: Progress of erosion m easured clinically after various flu oride applica tions. JADA 87:1223 Nov 1973. 7. B rodie, A.G., and Sognnaes, R.F. Erosion-like dentu re m ark ings possibly related to hyperactivity o f oral soft tissues. JADA 88:1012 M ay 1974. 8. H arrington, J.H., and Terry, I.A. A utom atic and hand too thbrushing abrasion studies. JADA 68:343 M arch 1964. 9. M anly, R.S., and others. A m ethod for m easurem ent of abra sion o f dentin by toothbrush and dentifrice. J Dent Res 44:533 M ay-June 1965. 10. R app, G.W .; Prapuolenis, A.; and M adonia, J. Pyrophos phate: a fa c to r in tooth erosion. J D ent Res 39:372 M arch-April 1970. 11. Zipkin, I., and M cClure, F.J. Salivary citrate and dental erosion. J D ent Res 28:613 Dec 1949. 12. X ho nga, F.A., and Van Herle, A. T h e influence of hyper thyroidism on dental erosions. Oral Surg 36:349 S ept 1973. 13. British Dental Association m em orandum on the erosion of teeth . B r Dent J 106:239 April 7, 1959. 14. H ollow ay, P.J.; Mellanby, M.; and Stew art, R.J.C. Fruit drinks and tooth erosion. Br Dent J 104:305 M ay 6, 1958. 15. Stafne, E.C., and Lovestedt, S.A. Dissolution of tooth sub stance by lem on juice, acid beverages, and acids from other sources. JADA 34:586 May 1947. 16. A llan, D.N. Enam el erosion with lemon juice. Br D ent J 1 22:300 April 4, 1972.
Summary The habitual and abusive use of fruits and foods containing citric acid can cause serious dissolu tion effects on human tooth enamel. Because these effects can occur so easily, this paper sug gests that foods and fruits containing citric acid, as well as other acids, could be definite contribu tors to the many other forms of idiopathic ero sion so often observed by the dentist. There is a need for continued research and study in this area. 1. M iller, W .D. Experim ents and observations on the wasting of tooth tissue, etc. Dent Cosmos 49:1 Jan 1907. 2. Boucher, C.O. C urrent clinical dental term inology, ed 2. St. Louis, C. V. M osby C o., 1974. 3. Rost, T., and Brodie, A.G. Possible etiologic factors in de n tal erosion. J D ent Res 4 0:385 M arch-April 1961.
84 ■ JADA, V o l. 95, J u ly 1977
17. Hicks, H. Excessive citrus ju ice consum ption. C linical ob servations o f its effect on superficial and deep tissues of the oral cavity. JADA 41:38 July 1950. 18. Finch, L.D. Erosion associated with diabetes insipidus. Br D ent J 103:280 Oct 15, 1957. 19. M cLachan, W. Tooth dam age from use of citrus fruits. Br D ent J 131:385 Nov 2, 1971. 20. S panauf, A.J. Erosion arising from a nutritional facto r with concom itant bruxism. A clinical case report. Aust Dent J 18:233 Aug 1973. 21. Levine, R.S. Fruit ju ice erosion— an increasing danger? J D ent 2:85 No. 2, 1973-74. 22. Eccles, J.D., and Jenkins, W .G. Dental erosion and diet. J D ent 2:153 No. 4, 1973-74. 23. Elsbury, W .B. H ydrogen-ion concentration and the acid erosion of teeth. Br D ent J 93:177 O ct 7, 1952. 24. M cC lure, F.J., and R uzicka, S.J. T h e destructive effect of citrate vs. lactate ions on rats m olar tooth surface in vivo. J Dent Res 25:1 Feb 1946. 25. Larsen, M . Dissolution of enam el. Scand J D ent Res 82:518 D ec 1973. 26. Ericsson, Y. Investigations on th e occurrence and signif icance o f citric acid in the saliva. J Dent Res 32:850 Dec 1953.
