19: 317-318
J. Dent. 1991;
317
Short Communication
Penetration of chlorhexidine amalgam restorations
around
E. A. M. Kidd and S. Joyston-Bechal* United Medical
and Dental Schools, London and *The London
Hospital
Medical
College, London,
UK
ABSTRACT A laboratory experiment, carried out on a restorative system known to leak, showed that chlorhexidine solutions and gels can pass around freshly packed amalgam restorations. KEY WORDS:
Restorations, Amalgam, Microleakage, Chlorhexidine
J. Dent. 1991;
19: 317-318
(Received 18 April 1991;
accepted 26April
1991)
Correspondence should be addressed to: Dr E. A. M. Kidd, Floor 26, Guy’s Tower, United Medical and Dental Schools of Guy’s and St Thomas’s Hospitals, Guy’s Hospital, London SE1 9RT. UK.
INTRODUCTION Secondary or recurrent caries is the most common cause of failure of amalgam restorations (Mj8r, 1989). Histologically, the early lesion may be considered in two parts: an ‘outer lesion’ formed on the surface of the tooth as a result of primary attack and a ‘cavity wall lesion’ which will only be seen if there is leakage between the restoration and the cavity wall (Hals et al., 1974). Chemical plaque control. with chlorhexidine solution or gel, has already been successfully applied to the problem of primary caries (Kidd, 1991), but no attention has been paid to its use in the management of recurrent disease. For this suggestion to be a viable proposition, research would be needed to determine: whether chlorhexidine can enter the microspace between the filling and the cavity wall; which organisms are responsible for recurrent disease; whether these organisms are sensitive to chlorhexidine. The present laboratory experiments address the first of these questions by trying to determine whether chlorhexidine can pass along the walls of a leaking filling. Since the freshly packed amalgam restoration is well known to leak(Kidd, 1976), this restoration was selected for the present work.
MATERIALS
AND METHODS
Six laboratory experiments have been carried out and in each the method was similar and as follows. Occlusal cavities were prepared in 20 caries-free extracted teeth. These cavities were restored with a high copper content, spherical amalgam alloy (Valient, L. D. Caulk Dentsply @ 1991 Buttenvorth-Heinemann 0300-5712/91/050317-02
Ltd.
Int., Milford, DE, USA). The roots of all teeth were covered with nail varnish. Ten teeth were designated test and exposed to a chlorhexidine solution or gel (Corsodyl, ICI Dental, Macclesfield, UK), while 10 were controls and remained in water. At the end of the experimental period (10 days) all restorations were carefully removed from the cavities with a small bur and the teeth were suspended in Azocarmine dye for 5 min. This dye is known to produce a water-resistant, violet-coloured, precipitate on tooth surfaces exposed to chlorhexidine and is made by dissolving 0.5 g of Azocarmine B in 100 ml of distilled water plus 1 ml of glacial acetic acid (Heyden and Rolla, 1970). All specimens were then washed in water. After 10 min of washing, specimens were examined for dye stain on the cavity walls, the examiner being unaware of whether the specimen was from the test or the control group. A different chlorhexidine regimen was used in each experiment. In Group 1 all 20 specimens were placed in water at 55 “C for 2 min. Test specimens were then placed in 0.2 per cent chlorhexidine solution (Corsodyl, ICI), surrounded by ice for 24 h. This extreme regimen was repeated daily for 10 days to encourage leakage around the fillings. In Group 2 test specimens remained for 10 days in 0.2 per cent chlorhexidine solution at 37 “C while controls remained in water at 37 “C. In Groups 3,4,5 and 6 all specimens were stored in water at 37°C for 10 days. The test specimens in Group 3 were exposed for 5 min to a 0.2 per cent chlorhexidine solution twice daily. Group 4 was identical except that 1 per cent gel (Chlorhexidine, ICI) was used instead of a solution. In Group 5 the test specimens were exposed for 5 min to a 1 per cent
318
J. Dent. 1991; 19: No. 5
chlorhexidine gel once daily. In Group 6 the test group was exposed for 1 min to a 0.2 per cent chlorhexidine solution twice daily.
RESULTS In this study Azocarmine
dye stain indicated the presence of chlorhexidine. In all control groups dye stain was lost after 10 min washing with water, indicating the absence of chlorhexidine. In test Group 1, all 10 samples exposed continuously to chlorhexidine but temperature cycled showed dye stain after 10 min of washing. In Group 2, all 10 specimens exposed continuously to chlorhexidine solution at 37°C showed dye stain. In Group 3, eight out of 10 specimens exposed to chlorhexidine solution for 5 min twice per day showed dye stain. In Group 4, nine out of 10 specimens exposed to chlorhexidine gel for 5 min twice per day showed dye stain. In Group 5, live out of 10 specimens exposed to chlorhexidine gel for 5 min once per day showed dye stain. In Group 6, six out of 10 specimens exposed to chlorhexidine solution for 1 min twice per day showed dye stain.
DISCUSSION Groups 5 and 6 represent current clinical practice in the control of primary caries but chlorhexidine penetration was not as effective as with other groups. While it is impractical to rinse for 5 min twice per day, as in Group 3,
a twice-daily application of gel, as in Group 4, might be a clinical possibility. Freshly packed amalgam restorations were chosen for these experiments because this system is well known to leak and is thus comparable to the clinical situation of a defective leaking filling. Old amalgam restorations were not suitable because the investigators would have no way of knowing whether these restorations were defective or whether corrosion products had blocked any leakage pathways (Hals et al., 1974). The results of the present study show that chlorhexidine can pass along the space between filling and cavity wall. If it can also be shown that the organisms responsible for the disease are sensitive to chlorhexidine at these concentrations, a clinically realistic regimen might be devised for the management of recurrent caries.
References Hals E., Andreassen B. H. and Bie T. (1974) Histopathology of natural caries around silver amalgam fillings. Caries Res. 8, 343-358. Heyden G. and R811a G. (1970) A histochemical staining method for chlorhexidine. Arch. Oral Biol. 15, 1387-1388. Kidd E. A. M. (1976) Microleakage in relation to amalgam and composite restorations. Br. Dent. J. 141, 305-310. Kidd E. A. M. (1991) The role of chlorhexidine in the management of dental caries. Znt Dent J. (in press). Mjcjr I. A. (1989) Amalgam and composite resin restorations: longevity and reasons for replacement. In: Anusavice K. J. (ed.), Quality Evaluation of Dental Restorations. Chicago, Quintessence, pp. 61-68.
J. Dent. 1991;
317
Short Communication
Penetration of chlorhexidine amalgam restorations
around
E. A. M. Kidd and S. Joyston-Bechal* United Medical
and Dental Schools, London and *The London
Hospital
Medical
College, London,
UK
ABSTRACT A laboratory experiment, carried out on a restorative system known to leak, showed that chlorhexidine solutions and gels can pass around freshly packed amalgam restorations. KEY WORDS:
Restorations, Amalgam, Microleakage, Chlorhexidine
J. Dent. 1991;
19: 317-318
(Received 18 April 1991;
accepted 26April
1991)
Correspondence should be addressed to: Dr E. A. M. Kidd, Floor 26, Guy’s Tower, United Medical and Dental Schools of Guy’s and St Thomas’s Hospitals, Guy’s Hospital, London SE1 9RT. UK.
INTRODUCTION Secondary or recurrent caries is the most common cause of failure of amalgam restorations (Mj8r, 1989). Histologically, the early lesion may be considered in two parts: an ‘outer lesion’ formed on the surface of the tooth as a result of primary attack and a ‘cavity wall lesion’ which will only be seen if there is leakage between the restoration and the cavity wall (Hals et al., 1974). Chemical plaque control. with chlorhexidine solution or gel, has already been successfully applied to the problem of primary caries (Kidd, 1991), but no attention has been paid to its use in the management of recurrent disease. For this suggestion to be a viable proposition, research would be needed to determine: whether chlorhexidine can enter the microspace between the filling and the cavity wall; which organisms are responsible for recurrent disease; whether these organisms are sensitive to chlorhexidine. The present laboratory experiments address the first of these questions by trying to determine whether chlorhexidine can pass along the walls of a leaking filling. Since the freshly packed amalgam restoration is well known to leak(Kidd, 1976), this restoration was selected for the present work.
MATERIALS
AND METHODS
Six laboratory experiments have been carried out and in each the method was similar and as follows. Occlusal cavities were prepared in 20 caries-free extracted teeth. These cavities were restored with a high copper content, spherical amalgam alloy (Valient, L. D. Caulk Dentsply @ 1991 Buttenvorth-Heinemann 0300-5712/91/050317-02
Ltd.
Int., Milford, DE, USA). The roots of all teeth were covered with nail varnish. Ten teeth were designated test and exposed to a chlorhexidine solution or gel (Corsodyl, ICI Dental, Macclesfield, UK), while 10 were controls and remained in water. At the end of the experimental period (10 days) all restorations were carefully removed from the cavities with a small bur and the teeth were suspended in Azocarmine dye for 5 min. This dye is known to produce a water-resistant, violet-coloured, precipitate on tooth surfaces exposed to chlorhexidine and is made by dissolving 0.5 g of Azocarmine B in 100 ml of distilled water plus 1 ml of glacial acetic acid (Heyden and Rolla, 1970). All specimens were then washed in water. After 10 min of washing, specimens were examined for dye stain on the cavity walls, the examiner being unaware of whether the specimen was from the test or the control group. A different chlorhexidine regimen was used in each experiment. In Group 1 all 20 specimens were placed in water at 55 “C for 2 min. Test specimens were then placed in 0.2 per cent chlorhexidine solution (Corsodyl, ICI), surrounded by ice for 24 h. This extreme regimen was repeated daily for 10 days to encourage leakage around the fillings. In Group 2 test specimens remained for 10 days in 0.2 per cent chlorhexidine solution at 37 “C while controls remained in water at 37 “C. In Groups 3,4,5 and 6 all specimens were stored in water at 37°C for 10 days. The test specimens in Group 3 were exposed for 5 min to a 0.2 per cent chlorhexidine solution twice daily. Group 4 was identical except that 1 per cent gel (Chlorhexidine, ICI) was used instead of a solution. In Group 5 the test specimens were exposed for 5 min to a 1 per cent
318
J. Dent. 1991; 19: No. 5
chlorhexidine gel once daily. In Group 6 the test group was exposed for 1 min to a 0.2 per cent chlorhexidine solution twice daily.
RESULTS In this study Azocarmine
dye stain indicated the presence of chlorhexidine. In all control groups dye stain was lost after 10 min washing with water, indicating the absence of chlorhexidine. In test Group 1, all 10 samples exposed continuously to chlorhexidine but temperature cycled showed dye stain after 10 min of washing. In Group 2, all 10 specimens exposed continuously to chlorhexidine solution at 37°C showed dye stain. In Group 3, eight out of 10 specimens exposed to chlorhexidine solution for 5 min twice per day showed dye stain. In Group 4, nine out of 10 specimens exposed to chlorhexidine gel for 5 min twice per day showed dye stain. In Group 5, live out of 10 specimens exposed to chlorhexidine gel for 5 min once per day showed dye stain. In Group 6, six out of 10 specimens exposed to chlorhexidine solution for 1 min twice per day showed dye stain.
DISCUSSION Groups 5 and 6 represent current clinical practice in the control of primary caries but chlorhexidine penetration was not as effective as with other groups. While it is impractical to rinse for 5 min twice per day, as in Group 3,
a twice-daily application of gel, as in Group 4, might be a clinical possibility. Freshly packed amalgam restorations were chosen for these experiments because this system is well known to leak and is thus comparable to the clinical situation of a defective leaking filling. Old amalgam restorations were not suitable because the investigators would have no way of knowing whether these restorations were defective or whether corrosion products had blocked any leakage pathways (Hals et al., 1974). The results of the present study show that chlorhexidine can pass along the space between filling and cavity wall. If it can also be shown that the organisms responsible for the disease are sensitive to chlorhexidine at these concentrations, a clinically realistic regimen might be devised for the management of recurrent caries.
References Hals E., Andreassen B. H. and Bie T. (1974) Histopathology of natural caries around silver amalgam fillings. Caries Res. 8, 343-358. Heyden G. and R811a G. (1970) A histochemical staining method for chlorhexidine. Arch. Oral Biol. 15, 1387-1388. Kidd E. A. M. (1976) Microleakage in relation to amalgam and composite restorations. Br. Dent. J. 141, 305-310. Kidd E. A. M. (1991) The role of chlorhexidine in the management of dental caries. Znt Dent J. (in press). Mjcjr I. A. (1989) Amalgam and composite resin restorations: longevity and reasons for replacement. In: Anusavice K. J. (ed.), Quality Evaluation of Dental Restorations. Chicago, Quintessence, pp. 61-68.
