J. Dent. 1992; 20: 287-293
287
A comparison of four in vitro marginal leakage tests applied to root surface restorations M. F. W-Y. Ghan* and J. C. Glyn Jones Department
of Restorative
Dentistry,
University
of Leeds School of Dentistry,
Leeds, UK
ABSTRACT Marginal leakage associated with a variety of restorative materials, placed in root surface cavities of extracted teeth, was assessed by immersing the teeth in either acidified gelatin, eosin dye, silver nitrate or a solution of radiocalcium. The allocation of a score, dependent on the depth of tracer penetration at the interface, allowed comparisons to be made between the leakage tests employed. The rank order of the four leakage tests was generally consistent. Eosin resulted in the most severe leakage, followed by silver nitrate and radiocalcium, whilst acidified gelatin was the least sensitive method for demonstrating marginal leakage. Differences in leakage scores were not, however, always statistically significant. None of the four tests investigated was ideal, although eosin dye was considered to be the most appropriate method of demonstrating marginal leakage associated with root restorations. KEY WORDS: J. Dent. 1992; 1992)
Marginal
leakage, Root restorations
20: 287-293
(Received
16 December
1991;
reviewed
3 March 1992;
Correspondence should be addressed to: Mr M. F. W-Y. Chan, Department
of Restorative
accepted 27 April
Dentistry,
Leeds
Dental School, Clarendon Way, Leeds LS2 SLU, UK.
INTRODUCTION as the passage of bacteria, between a cavity wall and the restorative material applied to it (Kidd, 1976). It has been implicated in a variety of conditions, including marginal discolouration, hypersensitivity, marginal percolation, recurrent caries (Triadan, 1987) and pulpal pathology (Brannstrom and Nyborg, 1973). Many leakage tests have been used to investigate the cavity sealing ability of restorations both in titro and in tivo and these have been reviewed by Kidd (1976). Although much has been published about the marginal leakage associated with various restorative materials, little attention has been directed to an evaluation and comparison of the tests themselves. Different studies often yield conflicting results and this may be attributed to variations in experimental technique. Some form of Microleakage fluids,
may be defined
molecules,
or ions
*Presented in part fultilment of the requirements MDSc. University of Leeds, 1991. @ 1992 Butterworth-Heinemann 0300-5712/92/050287-07
Ltd.
for the degree of
standardization of microleakage testing would seem advisable in order to allow comparison of different studies (Shortall, 1982). Many in vitro investigations of marginal leakage seem remote from the clinical situation, and their value in predicting in tivo behaviour of new restorative materials remains open to question. Marginal leakage associated with restorations placed in enamel may be largely eliminated by the use of adhesive techniques (Hembree, 1986). However, many extensive Class II cavities have their cervical margin placed at or below the cemento-enamel junction where enamel is of poor quality or, more usually, absent. In addition, root caries and cervical erosion/abrasion lesions will continue to be a significant clinical problem as teeth are retained later in life. In all these instances satisfactory bonding with the elimination of marginal leakage remains elusive. It would seem appropriate, therefore, if a study of the more commonly used in vitro marginal leakage tests were to involve restorations placed in the root surface.
288
J. Dent. 1992; 20: No. 5
Tab/e 1. Materials used Materials
Manufacturer
ANA 2000 amalgam, non-gamma 2, extra high copper dental alloy
Nordiska Dental AB, Helsingborg, Sweden
904
Ketac-Fil, poly maleinate glass ionomer dental restorative material
ESPE Fabrik, Pharmazeutischer Praparate GMBH, Seefeld/Oberay, Germany
Ch-B MOO7
Tripton enamel/ dentine adhesive and Opalux hybrid, lightcured, dental composite
ICI Pharmaceuticals, Macclesfield, Cheshire, UK
Dentine primer: Lot NM 10 Bonding agent: Lot MM02 Opalux: Lot MN21 1
Gluma dentine bonding agent and Pekalux microfilled, light-cured dental composite resin
Bayer Dental, Leverkusen, Germany
4015s
The aim of the present study was to compare commonly used marginal leakage tests and evaluate suitability for use with root surface restorations.
MATERIALS
Barth no.
four their
AND METHODS
Sound premolar teeth extracted for orthodontic purposes were immediately placed in screw-top bottles containing isotonic saline and thymol crystals. Forty teeth with single or fused roots of more than three-quarters development were selected after being examined under an illuminated magnifier to exclude those with gross enamel fractures. Root surfaces were thoroughly cleaned of soft tissues with a scalpel blade and polished with flour of pumice and water using a bristle brush in a conventional speed, contra-angled handpiece. At all times the teeth were kept moist. Using a tungsten carbide pear-shaped bur (ASH Pear P.C.l, 330,7/008, Claudius Ash, Potters Bar, Herts, UK), in a high-speed handpiece with copious water coolant, a single operator prepared standardized Class V type cavities with 90” cavosurface margins on the buccal, lingual, mesial and distal root surfaces of each sample tooth, just below the cemento-enamel junction, The dimensions of each cavity were approximately 2 mm in width, 1 mm in depth and 4 mm long (occluso-cervically). The bur was changed after preparation of every five teeth. The four cavities in each sample tooth were restored by a different restorative technique (Table I). A computergenerated table of random numbers was used to allocate a particular technique to each tooth surface.
Technique 1 Amalgam was placed incrementally and hand condensed into the cavity. After the initial set the amalgam was
7-l 463
carved level with the cavity allowed to set fully without finishing was undertaken.
margins, burnished and disturbance. No further
Technique 2 The cavity was pretreated with 40% polyacrylic acid (Durelon, ESPE) on a cottonwool pellet agitated for 30 s. The cavity was subsequently washed with water for 15 s and dried with oil-free air for a further 15 s. Glass ionomer cement (Ketac-Fil) was placed in bulk and a mylar matrix strip applied for 3 min until the initial set had occurred. Excess material was trimmed with a scalpel blade and the restoration covered with a layer of varnish (ESPE) before being left to set fully.
Technique 3 A dentine bonding system (Tripton) employing materials which did not aim to remove the smear layer was used in accordance with the manufacturer’s instructions. The bonding agent was polymerized with a visible light source (Luxor light curing unit, ICI Cheshire, UK) for 30 s, prior to the bulk placement of composite resin (Opalux) and light curing for a further 30 s against a mylar matrix strip.
Technique 4 A dentine bonding system (GLUMA) employing a cleanser which is claimed to remove the smear layer was applied in accordance with the manufacturer’s instructions. The resin was applied to the dentine, air thinned, left uncured prior to bulk placement of composite resin (Pekalux). A mylar strip was applied against which the restoration was light cured for 30 s.
Chan and Glyn Jones:
The restored teeth were placed in isotonic saline at room temperature for 24 h and then the restorations, with the exception of amalgam, were polished with graded abrasive discs (Sof-lex, 3M, St Pauls, MN, USA) and petroleum jelly. The teeth were arbitrarily assigned to four groups, each consisting of 10 experimental teeth, as outlined below. All the teeth were subjected to thermal cycling for 24 h (approximately 150 cycles) in a machine designed and adjusted to allow the following cycling regimen: 45°C (1 min), 37°C (4 min), 15°C (1 min), 37°C (4 min). The choice of temperatures was considered to be clinically realistic based upon the work of Peterson et al. (1966) and Plant ef al. (1974). The teeth were subsequently aged in isotonic saline at room temperature for 1 week. To prevent unwanted ingress of tracer, the apices were sealed, with wax or glass ionomer cement, before coating the teeth with two layers of nail varnish to within 1 mm of the toothrestoration interface. The teeth were exposed at room temperature to one of four marginal leakage tests. The details of immersion times and concentrations were determined following a series of pilot studies to refine the experimental techniques (Chan, 1991): -
Group 1 was immersed for 1 h in 5% eosin dye buffered to pH 7.4 (modified from Glyn Jones et al., 1988). -Group 2 was immersed in a 50% (by weight) silver nitrate solution for 2 h in a light-proof container. The teeth were then rinsed with deionized water, placed in photodeveloping solution and exposed to natural and fluorescent light for 3 h (Shortall ef al., 1989). -Group 3 was immersed in 14% gelatin adjusted to pH 4.5 by the addition of 0.02 M lactic acid/sodium hydroxide buffer for 8 weeks (modified from Grieve, 1973). -Group 4 was immersed in a solution of radioactive calcium chloride with an activity ofO.1 mCi ml-l for 2 h. The pH was adjusted to 7.0 to avoid unwanted demineralization of cementum (modified from Phillips et al., 1961). Upon removal from the leakage agents the teeth from Groups 1, 2 and 3 were sectioned transversely at approximately the midpoint of the restorations, with a water-cooled diamond-impregnated wire saw, to allow evaluation. The eosin (Group 1) and silver nitrate (Group 2) specimens were scored directly with the aid of a stereo zoom microscope (X 2 magnification). Ground sections of approximately 80 pm were produced from specimens exposed to acidified gelatin (Group 3). These were examined with the aid of polarized light microscopy (X 25 magnification), after imbibition in water and subsequently quinoline. The specimens exposed to radiocalcium (Group 4) were sectioned using a diamond cutting disc, which proved most convenient for use in the radioactive tracer laboratory. Sections of approximately 2 mm thick were placed directly on Ultra-speed dental film (Eastman Kodak
Comparison
of in vitro marginal
0
Root
canal
leakage tests
289
4-i
Root
Fig. 1. Scoring leakage.
system
used for assessment
of marginal
Company, Rochester, NY, USA) for 18 h, in darkness, to produce autoradiographs. An automatic developer was used to process all the films following the manufacturer’s instructions. In order to help delineate the tooth section and cavity outlines a further set of autoradiographs was similarly prepared but, in addition, the samples were exposed for 0.07 s to X-ray irradiation by placing them at the tip of a long cone Intrex 70 kVp, 10 mA, dental X-ray machine (SS White, Kingston-Upon-Thames, Surrey, UK). Both sets of autoradiographs were examined with the aid of magnification (X 2) and used to score the restorations. The scoring system employed was as follows (Fig. 1):
o=
no marginal penetration or penetration just into cementum. 1 = penetration up to half the length of the cavity wall. 2= penetration of greater length than 1, but not including the floor of the cavity. 3= penetration involving the floor of the cavity. 4= diffusion into dentine. Assessment was performed by one operator on three occasions, the highest score for each restoration being used in later analyses. Where inconsistencies occurred the most frequent, or where there was wide disparity the median score was used.
OBSERVATIONS
AND RESULTS
In general eosin and silver nitrate demonstrated marginal leakage quite clearly (Figs 2, 3) although the assessment was not without some difficulty. The small area of cementum around the restorations, left uncoated by nail varnish, was readily stained by both eosin and silver. Occasionally this stain penetrated cementum into the root
290
J. Dent. 1992;
20: No. 5
Fig. 2. Examples of marginal leakage scores demonstrated by eosin dye. (Original magnification, X 2.)
Fig. 3. Examples of marginal leakage scores demonstrated by silver nitrate. (Original magnification, X 2.)
Fig. 4. Photomicrograph of artificial caries-like ‘outer’ and minimal ‘wall’ lesions imbibed in water. (Original magnification, X 25.)
Fig. 5. Autoradiograph demonstrating marginal leakage of samples immersed in radiocalcium and exposed to X-rays. (Original magnification, X 2.)
dentine masking leakage at the tooth-restoration interface. With care, however, it was possible to differentiate between the two patterns, the latter tending to have a more defined linear path and a higher colour density. It was noted that exposure to silver nitrate often resulted in glass ionomer restorations being stained by silver both from their external surface and/or via the tooth-restoration interface. There was also an adherent gross metallic deposit on the surface of all the amalgam restorations which was also present on the adjacent root surface. Examination of the acidified gelatin sections with polarized light microscopy confirmed the presence of artificial caries-like lesions in the outer cementum and dentine of all the root surfaces. These ‘outer’ lesions were of limited depth, had an intact surface layer, and showed the characteristic banding pattern running parallel to the surface (Phankosol et al., 1985). Examination of the cavity wall sometimes revealed an area of positive birefringence spreading a small distance along the cavity wall (Fig. 4). These ‘wall’ lesions were not found to progress very deeply and none received a score greater than 1. Some difficulty and subjectivity was experienced in the scoring, as the ‘wall’ lesions were little
deeper than the primary outer lesions and instead of being discrete and separate they tended to merge into the ‘outer’ lesions. Artificial caries-like lesions were most easily observed by polarized light microscopy after imbibition in water. In quinoline, similar, but less distinct features were apparent. The radiocalcium method of detecting marginal leakage was the most difficult to score objectively. The autoradiographs produced had a large grain size and consequently poor image definition. At times there was difficulty in defining the tooth-restoration interface, despite exposing the samples to X-rays. This was due to the similarity and radiopacity of dentine and some of the restorative materials used (Fig. 5). On examination of the autoradiographs the small area of cementum uncoated with nail varnish, surrounding the restorations, appeared to be the centre of a dense area of exposure. This spread both away and towards the centre of the tooth section and tended to mask leakage at the tooth-restoration interface. The greatest difficulty was differentiating between scores 0 and 1. A series of control teeth confirmed that the methods of sealing the teeth apically and coronally were completely
Chan and Glyn Jones:
Comparison
of in vitro
marginal
leakage
tests
291
Table II. Distribution of scores for the marginal leakage tests GLUMA and Pekalux ESCI
Score
ANA amalgam ESCl
Ketac-fil glass ionomer ESCl
0
1940
2084
3053
4192
1
21
2424
3957
0518
2
0004
2502
0100
0200
3
0001
0000
2000
3
100
4
7000
4100
2000
3
100
65
Tripton and Opalux ESCI
E, eosin; S, silver nitrate; C, artificial caries; I, radiocalcium.
effective in preventing unwanted leakage of the various tracers used in the study. An occasional unintentional overfill of some cavities was noted but did not result in any samples being rejected. The highest score for each restoration was used in the results rather than scores for each wall of the cavity, and it was considered that this would minimize the effects of an occasional cavity overfill. The distribution of leakage scores associated with the four leakage tests is shown in Table II. The MannWhitney U (two tailed) test was performed to compare differences between marginal leakage scores and determine the rank order of leakage tests for each of the four restorative materials examined (Fig. 6).
DISCUSSION The rank order of the four leakage tests was, in the main, consistent. Eosin dye resulted in the most severe leakage, followed by silver nitrate and radiocalcium. Acidified gelatin was the least effective in demonstrating marginal leakage. These differences were not, however, always significant and the ranking of silver nitrate when used with amalgam was at variance with the other restorative materials employed. Previous comparisons of leakage tests have been performed using restorations placed in enamel and have often yielded conflicting results. An early comparison of radioiodine and crystal violet dye tests found that the isotope penetrated around the margins of amalgam to a greater extent than the dye (Going et al., 1960b), although there was no apparent statistical analysis of the results. However, with composites, when radiocalcium and basic Amalgam
Ketac
r
r
E
C
C
s
E
C
Tripton rE
t
GLUMA rE
I
C
L , C
t I i
Decreasing severity of leakage
1
Fig. 6. Rank order of leakage tests for each of the four restorative materials. (Note: the brackets denote that there was no significant difference at the P < 0.05 level.) E, Eosin; S, silver nitrate; C, artificial caries; I, radiocalcium.
fuchsin dye tests were compared (Crim et al., 1985), it was reported that both methods were equally effective and penetrated the tooth-restoration interface to a similar degree. Several workers have suggested that the ability of tracer elements to demonstrate leakage is related to the molecular size of the particles employed. Going (1964) considered that radioisotopes would demonstrate greater marginal leakage than a dye, the particle size of which was of molecular proportion compared to the much smaller ionic proportion of the isotope tracer. Similar opinions were expressed by Douglas et al. (1989) who regarded silver nitrate as a severe test of marginal leakage due to the small size of the silver ion. Hals and Nernaes (1971) considered the acidified gelatin technique to be a severe test as the wall lesions were thought to be caused by diffusion of hydrogen ions along the cavity-restoration interface. In a histological context, Horobin (1982) stated that the rate of dye diffusion into or out of the tissue depended on its molecular size, which was often indicated by molecular or ionic weight. The finding that eosin dye exhibited the greatest marginal leakage in the present study suggests that the size of the tracer molecule is not the only important factor in demonstrating marginal leakage. Going et al. (1960a) stated, in relation to different radioisotopes, that the ionic charge and chemical reactivity of a tracer, as well as the physical and chemical nature of the restorative material, may influence the depth of marginal penetration. The immersion time in the leakage agent might also be expected to affect the extent of marginal leakage. Whilst the four tests investigated employed differing immersion times, that using the sh0rtest;i.e. eosin, demonstrated the greatest degree of leakage. The pilot study showed that immersion of samples in eosin dye for extended periods resulted in such gross leakage that the sections became flooded and could not be scored. It was impossible to relate areas of leakage to individual restorations and to determine whether cross-leakage had occurred. The results of the present study support the findings of Wu et al. (1983) who compared radiocalcium and silver nitrate techniques. They claimed that the latter had several advantages including greater marginal penetration
292
J. Dent. 1992;
20: No. 5
around composite restorations. Passive ion exchange occurs between calcium ions present in the dental hard tissues and those of the isotope solution (Going et al., 1968), which may reduce the extent of marginal leakage demonstrated by radiocalcium. Trowbridge (1987) has stated that isotopes may have an affinity for both tooth structure and restorative materials resulting in a misleading distribution of the isotospe. Radioisotope tests are relatively expensive and involve an elaborate experimental technique to deal with the potential hazards of handling radioactive substances and to satisfy accompanying statutory regulations. Glass ionomer restorations were often observed to be stained by silver. This is consistent with the &dings of Shortall et al. (1989) who reported that glass ionomer luting cement failed to prevent microleakage and that the cement actually seemed to take up the silver stain itself. These workers suggested that this phenomenon was either due to diffusion of silver ions through the cement or the formation of a new cement. The uptake of silver by the restorative material could, in theory, decrease that available for penetration into dentine and contribute to an underestimation ofthe amount of marginal leakage that occurred. Previous workers have reported difficulty in obtaining consistent results when silver nitrate was used with amalgam restorations (Wu et al., 1983). In the present study silver nitrate consistently failed to reveal marginal leakage of amalgam restorations. It is possible that the silver ions in solution may react with constituents of amalgam and thus be unavailable to diffuse along any marginal gaps. In addition the formation of a gross metallic deposit on the surface of the amalgam may seal the margins of the restoration, again preventing diffusion of silver ions into marginal gaps. In the acidified gelatin technique the immersion of samples in water-based gelatin for 8 weeks may result in significant water absorption and hygroscopic expansion of resin-based materials. One could speculate that this may result in the closure of any initial marginal gaps that formed on polymerization (Hansen and Asmussen, 1989) and a decrease in marginal leakage. Alternatively, early finishing of restorations, as undertaken in this study, may force debris into the open marginal gaps and prevent subsequent closure by hygroscopic expansion (Asmussen, 1985). This aspect warrants further investigation in the future. Glass ionomer materials release significant amounts of fluoride which tends to offer protection against acid demineralization (Pm-ton and Rodda, 1988). There seems no apparent explanation, however, for the finding that there were relatively few wall lesions around amalgam restorations. The diffusion of hydrogen ions along a marginal gap is not a visible occurrence. The effects may only be determined if demineralization of dentine occurs of sufficient magnitude to be detected by polarized light microscopy. In contrast, the diffusion of dye molecules along a marginal gap allows direct visualization.
It must be recognized that the present study does not attempt to take into account the effects of functional occlusal stresses, pulpal pressure and dentinal fluid outflow or prolonged ageing of restorative materials. Despite the limitations of this in vitro study, such investigations in clinical simulation models are considered to be an important form of evaluation. They provide a relatively rapid means of discriminating between the clinically important behaviour of different materials (Wilson, 1990).
CONCLUSIONS 1. None of the tests evaluated appear to be ideal for demonstrating marginal leakage associated with root restorations although eosin dye was judged to be the most appropriate method for use with the materials selected. 2. The radiocalcium test was associated with several problems and its continued use is difficult to justify. 3. It would appear that the use of the silver nitrate test with amalgam restorations is inappropriate and in addition the results of this test with glass ionomer restorations should be treated with caution. 4. The acidified gelatin test failed to demonstrate marginal leakage as effectively as the other tests employed in this study. 5. The results of in vitro studies should be compared with long-term clinical trials to ascertain their accuracy and reliability in predicting the behaviour of restorative materials in tivo.
Acknowledgements The authors would like to thank their colleagues at Leeds School of Dentistry: Dr J. JSirkham of the Department of Oral Biology who helped with the radioisotope technique employed in this study; Mr G. Fairpo of the Biometrics Department for his assistance with the statistical analysis; Mr I. S. Smith for his technical advice and assistance; Mr D. Hawkridge for his advice and preparation of the photographic records, and Mrs A. Durbin for preparation of the illustrations.
References Rasmussen E. (1985) Clinical
relevance of physical, chemical, and bonding properties of composite resins. Oper. Dent. 10, 61-73. Brannstrom M. and Nyborg H. (1973) Cavity treatment with a microbicidal fluoride solution: growth of bacteria and the effect on the pulp. J. Pro&ret. Dent. 30, 303-310. Chan M. F. W-Y. (1991) An Evaluation and Comparison of Four In Vitro Marginal Leakage Tests. MDSc dissertation, University of Leeds. Crim G. A., Swartz M. L. and Phillips R. W. (1985) Comparison of four thermocycling techniques. .J. Prosthet Dent. 53, 50-53. Douglas W. H., Fields R. P. and Fundingsland J. (1989) Comparison between the microleakage of direct and indirect composite restorative systems. J. Dent. 17, 184-188.
Chan and Glyn Jones:
Glyn Jones J. C., Grieve A. R. and Youngson C. C. (1988) Marginal leakage associated with three posterior restorative materials. J. Dent. 16, 130-134. Going R. E. (1964) Cavity liners and dentin treatment. J. Am. Dent. Assoc. 69,415-422. Going R. E., Massler M. and Dute H. L. (1960a) Marginal penetration of dental restoratives by different radioactive isotopes. J. Dent. Res. 39, 273-284. Going R. E., Massler M. and Dute H. L. (1960b) Marginal penetration of dental restoratives as studied by crystal violet dye and ‘-“I. J. Am. Dent. Assoc. 61, 285-300. Going R. E., Myers H. M. and Prussin S. G. (1968) Quantitative method for studying microleakage in vivo and in vitro. J. Dent. Res. 47, 1128-1132. Grieve A. R. (1973) The occurrence of secondary caries-like lesions in vitro. Br. Dent. J. 134, 530-536. Hals E. and Nemaes A. (1971) Histopathology of in vitro caries developing around silver amalgam fillings. Caries Res. 5, 58-77. Hansen E. K. and Asmussen E. (1989) Marginal adaptation of posterior resins: effect of dentin-bonding agent and hygroscopic expansion. Dent. Mater. 5, 122-126. Hembree Jr J. H. (1986) In vitro microleakage of a new dental adhesive system. J. Prosthet. Dent. 55, 442-445. Horobin R. W. (1982) An outline of staining theory. In: Bancroft J. D. and Stevens A. (eds), Theory and Practice of Histological Techniques, 2nd edn. Edinburgh, Churchill Livingstone, Chap. 6, pp. 95-109. Kidd E. A. M. (1976) Microleakage: a review. J. Dent. 5, 199-206.
Comparison
of in vitro marginal
leakage
tests
293
Peterson E. A., Phillips R. W. and Swartz M. L. (1966) A comparison of the physical properties of 4 restorative resins. J. Am. Dent, Assoc. 73, 1324-1336. Phankosol P., Ettinger R. L., Hicks M. J. et al. (1985) Histopathology of the initial lesion of the root surface: an in vitro study. J. Dent. Res. 64, 804-809. Phillips R. W., Gilmore H. W., Swartz M. L. et al. (1961) Adaptation of restorations in vivo as assessed by 45Ca. J. Am. Dent. Assoc. 62,9-20. Plant C. G., Jones D. W. and Darvell B. W. (1974) The heat evolved and the temperatures attained during the setting of the restorative materials. Br. Dent. J. 137, 233-238. Purton D. G. and Rodda J. C. (1988) Artificial caries around restorations in roots. J. Dent. Res. 67, 817-821. Shortall A. C. (1982) Microleakage, marginal adaptation and composite resin restorations. Br. Dent. J. 153, 223-227. Shortall A. C., Fayyad M. A. and Williams J. D. (1989) Marginal seal of injection moulded ceramic crowns cemented with three adhesive systems. J. Prosthet. Dent. 61, 24-27. Triadan H. (1987) When is microleakage a real clinical problem? Oper. Dent. 12, 153-157. Trowbridge H. 0. (1987) Model systems for determining biologic effects of microleakage. Oper. Dent. 12, 162-172. Wilson N. H. F. (1990) The evaluation of materials: relationship between laboratory investigations and clinical studies. Oper. Dent. 15, 149-155. Wu W., Cobb E. and Dermann K. (1983) Detecting margin leakage of dental composite restorations. J. Biomed. Mater. Res. 17, 37-43.
Book Reviews Atlas of Dentition in Childhood. H. S. Duterloo. Pp. 227. 1991. London, Wolfe. Hardback, f 45.00. At the heart of this atlas is a detailed description of the development of the dentition as observed on panoramic radiographs. The author successfully uses dry skull panoramic images in conjunction with labelled line diagrams and photographs of the skeletal material. This is prepared with exemplary thoroughness. The atlas also includes a description of panoramic technique, how to interpret tooth position and evaluate growth and finally examples of more common pathological conditions. It was gratifying to see space devoted to the important aspects of positioning for panoramic radiography, an area often poorly understood. The author sensibly emphasizes the limitations of panoramic images and describes the various soft tissue shadows which occur, although the anatomical ‘ghost’ shadows are not covered in any detail. It would have been valuable to underline the importance of these by using examples of the common artefacts they produce and which lead to diagnostic errors. Some criticisms are justifiable. The diagram of soft tissue shadows incorrectly puts the ‘corner of the mouth’ shadow over the second molar. The stylohyoid ligament is erroneously described as the stylomandibular ligament. The quality of the clinical radiographs is patchy in the latter part of the atlas; for example the radiograph supposedly illustrating an abnormal condyle is useless because of a superimposed earring shadow. The text is sometimes awkward; what is an ‘outspoken angular process’? What is ‘juvenile deforming arthrosis’? The persistent use of the term ‘X-ray’ for radiograph and of ‘anamnesis’ are also irritating. Overall, the impression was of an excellent treatise on
dental development on panoramic radiographs, which should be useful as a reference for dental students and orthodontic trainees. However, it is ‘bulked out’ with a mediocre section on pathology which is far better covered in other textbooks. While the author is to be commended for his efforts, there remains room for revision in subsequent editions. K. Horner Laboratory Manual for General and Oral Pathology. S. Eda. Pp. 258. 1991. New Malden, Quintessence. Hardback, f 65.00. This is a manual which is intended to be used for practical histopathology teaching in conjunction with examination of histological sections. It has been prepared by the pathology departments of seven Japanese dental schools with the highly laudable aim of standardizing teaching. The format of book is approximately half text and half illustrations, mainly coloured photomicrographs. The topic coverage starts with six chapters, largely devoted to basic pathology, while the remaining 15 are on oral pathology. The writing throughout suffers from errors of English syntax and there are areas of curious terminology, some of which are wrong. The coverage of the basic pathology is somewhat more extensive than in UK dental schools. The quality of the illustrations ranges from excellent to very poor with considerable variation in the colour rendering of H 8 E stains. Overall, although the concept is interesting, the production of this volume both in terms of the text and the quality of the illustrations is such that it cannot be recommended for use in the UK. D. G. MacDonald
287
A comparison of four in vitro marginal leakage tests applied to root surface restorations M. F. W-Y. Ghan* and J. C. Glyn Jones Department
of Restorative
Dentistry,
University
of Leeds School of Dentistry,
Leeds, UK
ABSTRACT Marginal leakage associated with a variety of restorative materials, placed in root surface cavities of extracted teeth, was assessed by immersing the teeth in either acidified gelatin, eosin dye, silver nitrate or a solution of radiocalcium. The allocation of a score, dependent on the depth of tracer penetration at the interface, allowed comparisons to be made between the leakage tests employed. The rank order of the four leakage tests was generally consistent. Eosin resulted in the most severe leakage, followed by silver nitrate and radiocalcium, whilst acidified gelatin was the least sensitive method for demonstrating marginal leakage. Differences in leakage scores were not, however, always statistically significant. None of the four tests investigated was ideal, although eosin dye was considered to be the most appropriate method of demonstrating marginal leakage associated with root restorations. KEY WORDS: J. Dent. 1992; 1992)
Marginal
leakage, Root restorations
20: 287-293
(Received
16 December
1991;
reviewed
3 March 1992;
Correspondence should be addressed to: Mr M. F. W-Y. Chan, Department
of Restorative
accepted 27 April
Dentistry,
Leeds
Dental School, Clarendon Way, Leeds LS2 SLU, UK.
INTRODUCTION as the passage of bacteria, between a cavity wall and the restorative material applied to it (Kidd, 1976). It has been implicated in a variety of conditions, including marginal discolouration, hypersensitivity, marginal percolation, recurrent caries (Triadan, 1987) and pulpal pathology (Brannstrom and Nyborg, 1973). Many leakage tests have been used to investigate the cavity sealing ability of restorations both in titro and in tivo and these have been reviewed by Kidd (1976). Although much has been published about the marginal leakage associated with various restorative materials, little attention has been directed to an evaluation and comparison of the tests themselves. Different studies often yield conflicting results and this may be attributed to variations in experimental technique. Some form of Microleakage fluids,
may be defined
molecules,
or ions
*Presented in part fultilment of the requirements MDSc. University of Leeds, 1991. @ 1992 Butterworth-Heinemann 0300-5712/92/050287-07
Ltd.
for the degree of
standardization of microleakage testing would seem advisable in order to allow comparison of different studies (Shortall, 1982). Many in vitro investigations of marginal leakage seem remote from the clinical situation, and their value in predicting in tivo behaviour of new restorative materials remains open to question. Marginal leakage associated with restorations placed in enamel may be largely eliminated by the use of adhesive techniques (Hembree, 1986). However, many extensive Class II cavities have their cervical margin placed at or below the cemento-enamel junction where enamel is of poor quality or, more usually, absent. In addition, root caries and cervical erosion/abrasion lesions will continue to be a significant clinical problem as teeth are retained later in life. In all these instances satisfactory bonding with the elimination of marginal leakage remains elusive. It would seem appropriate, therefore, if a study of the more commonly used in vitro marginal leakage tests were to involve restorations placed in the root surface.
288
J. Dent. 1992; 20: No. 5
Tab/e 1. Materials used Materials
Manufacturer
ANA 2000 amalgam, non-gamma 2, extra high copper dental alloy
Nordiska Dental AB, Helsingborg, Sweden
904
Ketac-Fil, poly maleinate glass ionomer dental restorative material
ESPE Fabrik, Pharmazeutischer Praparate GMBH, Seefeld/Oberay, Germany
Ch-B MOO7
Tripton enamel/ dentine adhesive and Opalux hybrid, lightcured, dental composite
ICI Pharmaceuticals, Macclesfield, Cheshire, UK
Dentine primer: Lot NM 10 Bonding agent: Lot MM02 Opalux: Lot MN21 1
Gluma dentine bonding agent and Pekalux microfilled, light-cured dental composite resin
Bayer Dental, Leverkusen, Germany
4015s
The aim of the present study was to compare commonly used marginal leakage tests and evaluate suitability for use with root surface restorations.
MATERIALS
Barth no.
four their
AND METHODS
Sound premolar teeth extracted for orthodontic purposes were immediately placed in screw-top bottles containing isotonic saline and thymol crystals. Forty teeth with single or fused roots of more than three-quarters development were selected after being examined under an illuminated magnifier to exclude those with gross enamel fractures. Root surfaces were thoroughly cleaned of soft tissues with a scalpel blade and polished with flour of pumice and water using a bristle brush in a conventional speed, contra-angled handpiece. At all times the teeth were kept moist. Using a tungsten carbide pear-shaped bur (ASH Pear P.C.l, 330,7/008, Claudius Ash, Potters Bar, Herts, UK), in a high-speed handpiece with copious water coolant, a single operator prepared standardized Class V type cavities with 90” cavosurface margins on the buccal, lingual, mesial and distal root surfaces of each sample tooth, just below the cemento-enamel junction, The dimensions of each cavity were approximately 2 mm in width, 1 mm in depth and 4 mm long (occluso-cervically). The bur was changed after preparation of every five teeth. The four cavities in each sample tooth were restored by a different restorative technique (Table I). A computergenerated table of random numbers was used to allocate a particular technique to each tooth surface.
Technique 1 Amalgam was placed incrementally and hand condensed into the cavity. After the initial set the amalgam was
7-l 463
carved level with the cavity allowed to set fully without finishing was undertaken.
margins, burnished and disturbance. No further
Technique 2 The cavity was pretreated with 40% polyacrylic acid (Durelon, ESPE) on a cottonwool pellet agitated for 30 s. The cavity was subsequently washed with water for 15 s and dried with oil-free air for a further 15 s. Glass ionomer cement (Ketac-Fil) was placed in bulk and a mylar matrix strip applied for 3 min until the initial set had occurred. Excess material was trimmed with a scalpel blade and the restoration covered with a layer of varnish (ESPE) before being left to set fully.
Technique 3 A dentine bonding system (Tripton) employing materials which did not aim to remove the smear layer was used in accordance with the manufacturer’s instructions. The bonding agent was polymerized with a visible light source (Luxor light curing unit, ICI Cheshire, UK) for 30 s, prior to the bulk placement of composite resin (Opalux) and light curing for a further 30 s against a mylar matrix strip.
Technique 4 A dentine bonding system (GLUMA) employing a cleanser which is claimed to remove the smear layer was applied in accordance with the manufacturer’s instructions. The resin was applied to the dentine, air thinned, left uncured prior to bulk placement of composite resin (Pekalux). A mylar strip was applied against which the restoration was light cured for 30 s.
Chan and Glyn Jones:
The restored teeth were placed in isotonic saline at room temperature for 24 h and then the restorations, with the exception of amalgam, were polished with graded abrasive discs (Sof-lex, 3M, St Pauls, MN, USA) and petroleum jelly. The teeth were arbitrarily assigned to four groups, each consisting of 10 experimental teeth, as outlined below. All the teeth were subjected to thermal cycling for 24 h (approximately 150 cycles) in a machine designed and adjusted to allow the following cycling regimen: 45°C (1 min), 37°C (4 min), 15°C (1 min), 37°C (4 min). The choice of temperatures was considered to be clinically realistic based upon the work of Peterson et al. (1966) and Plant ef al. (1974). The teeth were subsequently aged in isotonic saline at room temperature for 1 week. To prevent unwanted ingress of tracer, the apices were sealed, with wax or glass ionomer cement, before coating the teeth with two layers of nail varnish to within 1 mm of the toothrestoration interface. The teeth were exposed at room temperature to one of four marginal leakage tests. The details of immersion times and concentrations were determined following a series of pilot studies to refine the experimental techniques (Chan, 1991): -
Group 1 was immersed for 1 h in 5% eosin dye buffered to pH 7.4 (modified from Glyn Jones et al., 1988). -Group 2 was immersed in a 50% (by weight) silver nitrate solution for 2 h in a light-proof container. The teeth were then rinsed with deionized water, placed in photodeveloping solution and exposed to natural and fluorescent light for 3 h (Shortall ef al., 1989). -Group 3 was immersed in 14% gelatin adjusted to pH 4.5 by the addition of 0.02 M lactic acid/sodium hydroxide buffer for 8 weeks (modified from Grieve, 1973). -Group 4 was immersed in a solution of radioactive calcium chloride with an activity ofO.1 mCi ml-l for 2 h. The pH was adjusted to 7.0 to avoid unwanted demineralization of cementum (modified from Phillips et al., 1961). Upon removal from the leakage agents the teeth from Groups 1, 2 and 3 were sectioned transversely at approximately the midpoint of the restorations, with a water-cooled diamond-impregnated wire saw, to allow evaluation. The eosin (Group 1) and silver nitrate (Group 2) specimens were scored directly with the aid of a stereo zoom microscope (X 2 magnification). Ground sections of approximately 80 pm were produced from specimens exposed to acidified gelatin (Group 3). These were examined with the aid of polarized light microscopy (X 25 magnification), after imbibition in water and subsequently quinoline. The specimens exposed to radiocalcium (Group 4) were sectioned using a diamond cutting disc, which proved most convenient for use in the radioactive tracer laboratory. Sections of approximately 2 mm thick were placed directly on Ultra-speed dental film (Eastman Kodak
Comparison
of in vitro marginal
0
Root
canal
leakage tests
289
4-i
Root
Fig. 1. Scoring leakage.
system
used for assessment
of marginal
Company, Rochester, NY, USA) for 18 h, in darkness, to produce autoradiographs. An automatic developer was used to process all the films following the manufacturer’s instructions. In order to help delineate the tooth section and cavity outlines a further set of autoradiographs was similarly prepared but, in addition, the samples were exposed for 0.07 s to X-ray irradiation by placing them at the tip of a long cone Intrex 70 kVp, 10 mA, dental X-ray machine (SS White, Kingston-Upon-Thames, Surrey, UK). Both sets of autoradiographs were examined with the aid of magnification (X 2) and used to score the restorations. The scoring system employed was as follows (Fig. 1):
o=
no marginal penetration or penetration just into cementum. 1 = penetration up to half the length of the cavity wall. 2= penetration of greater length than 1, but not including the floor of the cavity. 3= penetration involving the floor of the cavity. 4= diffusion into dentine. Assessment was performed by one operator on three occasions, the highest score for each restoration being used in later analyses. Where inconsistencies occurred the most frequent, or where there was wide disparity the median score was used.
OBSERVATIONS
AND RESULTS
In general eosin and silver nitrate demonstrated marginal leakage quite clearly (Figs 2, 3) although the assessment was not without some difficulty. The small area of cementum around the restorations, left uncoated by nail varnish, was readily stained by both eosin and silver. Occasionally this stain penetrated cementum into the root
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Fig. 2. Examples of marginal leakage scores demonstrated by eosin dye. (Original magnification, X 2.)
Fig. 3. Examples of marginal leakage scores demonstrated by silver nitrate. (Original magnification, X 2.)
Fig. 4. Photomicrograph of artificial caries-like ‘outer’ and minimal ‘wall’ lesions imbibed in water. (Original magnification, X 25.)
Fig. 5. Autoradiograph demonstrating marginal leakage of samples immersed in radiocalcium and exposed to X-rays. (Original magnification, X 2.)
dentine masking leakage at the tooth-restoration interface. With care, however, it was possible to differentiate between the two patterns, the latter tending to have a more defined linear path and a higher colour density. It was noted that exposure to silver nitrate often resulted in glass ionomer restorations being stained by silver both from their external surface and/or via the tooth-restoration interface. There was also an adherent gross metallic deposit on the surface of all the amalgam restorations which was also present on the adjacent root surface. Examination of the acidified gelatin sections with polarized light microscopy confirmed the presence of artificial caries-like lesions in the outer cementum and dentine of all the root surfaces. These ‘outer’ lesions were of limited depth, had an intact surface layer, and showed the characteristic banding pattern running parallel to the surface (Phankosol et al., 1985). Examination of the cavity wall sometimes revealed an area of positive birefringence spreading a small distance along the cavity wall (Fig. 4). These ‘wall’ lesions were not found to progress very deeply and none received a score greater than 1. Some difficulty and subjectivity was experienced in the scoring, as the ‘wall’ lesions were little
deeper than the primary outer lesions and instead of being discrete and separate they tended to merge into the ‘outer’ lesions. Artificial caries-like lesions were most easily observed by polarized light microscopy after imbibition in water. In quinoline, similar, but less distinct features were apparent. The radiocalcium method of detecting marginal leakage was the most difficult to score objectively. The autoradiographs produced had a large grain size and consequently poor image definition. At times there was difficulty in defining the tooth-restoration interface, despite exposing the samples to X-rays. This was due to the similarity and radiopacity of dentine and some of the restorative materials used (Fig. 5). On examination of the autoradiographs the small area of cementum uncoated with nail varnish, surrounding the restorations, appeared to be the centre of a dense area of exposure. This spread both away and towards the centre of the tooth section and tended to mask leakage at the tooth-restoration interface. The greatest difficulty was differentiating between scores 0 and 1. A series of control teeth confirmed that the methods of sealing the teeth apically and coronally were completely
Chan and Glyn Jones:
Comparison
of in vitro
marginal
leakage
tests
291
Table II. Distribution of scores for the marginal leakage tests GLUMA and Pekalux ESCI
Score
ANA amalgam ESCl
Ketac-fil glass ionomer ESCl
0
1940
2084
3053
4192
1
21
2424
3957
0518
2
0004
2502
0100
0200
3
0001
0000
2000
3
100
4
7000
4100
2000
3
100
65
Tripton and Opalux ESCI
E, eosin; S, silver nitrate; C, artificial caries; I, radiocalcium.
effective in preventing unwanted leakage of the various tracers used in the study. An occasional unintentional overfill of some cavities was noted but did not result in any samples being rejected. The highest score for each restoration was used in the results rather than scores for each wall of the cavity, and it was considered that this would minimize the effects of an occasional cavity overfill. The distribution of leakage scores associated with the four leakage tests is shown in Table II. The MannWhitney U (two tailed) test was performed to compare differences between marginal leakage scores and determine the rank order of leakage tests for each of the four restorative materials examined (Fig. 6).
DISCUSSION The rank order of the four leakage tests was, in the main, consistent. Eosin dye resulted in the most severe leakage, followed by silver nitrate and radiocalcium. Acidified gelatin was the least effective in demonstrating marginal leakage. These differences were not, however, always significant and the ranking of silver nitrate when used with amalgam was at variance with the other restorative materials employed. Previous comparisons of leakage tests have been performed using restorations placed in enamel and have often yielded conflicting results. An early comparison of radioiodine and crystal violet dye tests found that the isotope penetrated around the margins of amalgam to a greater extent than the dye (Going et al., 1960b), although there was no apparent statistical analysis of the results. However, with composites, when radiocalcium and basic Amalgam
Ketac
r
r
E
C
C
s
E
C
Tripton rE
t
GLUMA rE
I
C
L , C
t I i
Decreasing severity of leakage
1
Fig. 6. Rank order of leakage tests for each of the four restorative materials. (Note: the brackets denote that there was no significant difference at the P < 0.05 level.) E, Eosin; S, silver nitrate; C, artificial caries; I, radiocalcium.
fuchsin dye tests were compared (Crim et al., 1985), it was reported that both methods were equally effective and penetrated the tooth-restoration interface to a similar degree. Several workers have suggested that the ability of tracer elements to demonstrate leakage is related to the molecular size of the particles employed. Going (1964) considered that radioisotopes would demonstrate greater marginal leakage than a dye, the particle size of which was of molecular proportion compared to the much smaller ionic proportion of the isotope tracer. Similar opinions were expressed by Douglas et al. (1989) who regarded silver nitrate as a severe test of marginal leakage due to the small size of the silver ion. Hals and Nernaes (1971) considered the acidified gelatin technique to be a severe test as the wall lesions were thought to be caused by diffusion of hydrogen ions along the cavity-restoration interface. In a histological context, Horobin (1982) stated that the rate of dye diffusion into or out of the tissue depended on its molecular size, which was often indicated by molecular or ionic weight. The finding that eosin dye exhibited the greatest marginal leakage in the present study suggests that the size of the tracer molecule is not the only important factor in demonstrating marginal leakage. Going et al. (1960a) stated, in relation to different radioisotopes, that the ionic charge and chemical reactivity of a tracer, as well as the physical and chemical nature of the restorative material, may influence the depth of marginal penetration. The immersion time in the leakage agent might also be expected to affect the extent of marginal leakage. Whilst the four tests investigated employed differing immersion times, that using the sh0rtest;i.e. eosin, demonstrated the greatest degree of leakage. The pilot study showed that immersion of samples in eosin dye for extended periods resulted in such gross leakage that the sections became flooded and could not be scored. It was impossible to relate areas of leakage to individual restorations and to determine whether cross-leakage had occurred. The results of the present study support the findings of Wu et al. (1983) who compared radiocalcium and silver nitrate techniques. They claimed that the latter had several advantages including greater marginal penetration
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around composite restorations. Passive ion exchange occurs between calcium ions present in the dental hard tissues and those of the isotope solution (Going et al., 1968), which may reduce the extent of marginal leakage demonstrated by radiocalcium. Trowbridge (1987) has stated that isotopes may have an affinity for both tooth structure and restorative materials resulting in a misleading distribution of the isotospe. Radioisotope tests are relatively expensive and involve an elaborate experimental technique to deal with the potential hazards of handling radioactive substances and to satisfy accompanying statutory regulations. Glass ionomer restorations were often observed to be stained by silver. This is consistent with the &dings of Shortall et al. (1989) who reported that glass ionomer luting cement failed to prevent microleakage and that the cement actually seemed to take up the silver stain itself. These workers suggested that this phenomenon was either due to diffusion of silver ions through the cement or the formation of a new cement. The uptake of silver by the restorative material could, in theory, decrease that available for penetration into dentine and contribute to an underestimation ofthe amount of marginal leakage that occurred. Previous workers have reported difficulty in obtaining consistent results when silver nitrate was used with amalgam restorations (Wu et al., 1983). In the present study silver nitrate consistently failed to reveal marginal leakage of amalgam restorations. It is possible that the silver ions in solution may react with constituents of amalgam and thus be unavailable to diffuse along any marginal gaps. In addition the formation of a gross metallic deposit on the surface of the amalgam may seal the margins of the restoration, again preventing diffusion of silver ions into marginal gaps. In the acidified gelatin technique the immersion of samples in water-based gelatin for 8 weeks may result in significant water absorption and hygroscopic expansion of resin-based materials. One could speculate that this may result in the closure of any initial marginal gaps that formed on polymerization (Hansen and Asmussen, 1989) and a decrease in marginal leakage. Alternatively, early finishing of restorations, as undertaken in this study, may force debris into the open marginal gaps and prevent subsequent closure by hygroscopic expansion (Asmussen, 1985). This aspect warrants further investigation in the future. Glass ionomer materials release significant amounts of fluoride which tends to offer protection against acid demineralization (Pm-ton and Rodda, 1988). There seems no apparent explanation, however, for the finding that there were relatively few wall lesions around amalgam restorations. The diffusion of hydrogen ions along a marginal gap is not a visible occurrence. The effects may only be determined if demineralization of dentine occurs of sufficient magnitude to be detected by polarized light microscopy. In contrast, the diffusion of dye molecules along a marginal gap allows direct visualization.
It must be recognized that the present study does not attempt to take into account the effects of functional occlusal stresses, pulpal pressure and dentinal fluid outflow or prolonged ageing of restorative materials. Despite the limitations of this in vitro study, such investigations in clinical simulation models are considered to be an important form of evaluation. They provide a relatively rapid means of discriminating between the clinically important behaviour of different materials (Wilson, 1990).
CONCLUSIONS 1. None of the tests evaluated appear to be ideal for demonstrating marginal leakage associated with root restorations although eosin dye was judged to be the most appropriate method for use with the materials selected. 2. The radiocalcium test was associated with several problems and its continued use is difficult to justify. 3. It would appear that the use of the silver nitrate test with amalgam restorations is inappropriate and in addition the results of this test with glass ionomer restorations should be treated with caution. 4. The acidified gelatin test failed to demonstrate marginal leakage as effectively as the other tests employed in this study. 5. The results of in vitro studies should be compared with long-term clinical trials to ascertain their accuracy and reliability in predicting the behaviour of restorative materials in tivo.
Acknowledgements The authors would like to thank their colleagues at Leeds School of Dentistry: Dr J. JSirkham of the Department of Oral Biology who helped with the radioisotope technique employed in this study; Mr G. Fairpo of the Biometrics Department for his assistance with the statistical analysis; Mr I. S. Smith for his technical advice and assistance; Mr D. Hawkridge for his advice and preparation of the photographic records, and Mrs A. Durbin for preparation of the illustrations.
References Rasmussen E. (1985) Clinical
relevance of physical, chemical, and bonding properties of composite resins. Oper. Dent. 10, 61-73. Brannstrom M. and Nyborg H. (1973) Cavity treatment with a microbicidal fluoride solution: growth of bacteria and the effect on the pulp. J. Pro&ret. Dent. 30, 303-310. Chan M. F. W-Y. (1991) An Evaluation and Comparison of Four In Vitro Marginal Leakage Tests. MDSc dissertation, University of Leeds. Crim G. A., Swartz M. L. and Phillips R. W. (1985) Comparison of four thermocycling techniques. .J. Prosthet Dent. 53, 50-53. Douglas W. H., Fields R. P. and Fundingsland J. (1989) Comparison between the microleakage of direct and indirect composite restorative systems. J. Dent. 17, 184-188.
Chan and Glyn Jones:
Glyn Jones J. C., Grieve A. R. and Youngson C. C. (1988) Marginal leakage associated with three posterior restorative materials. J. Dent. 16, 130-134. Going R. E. (1964) Cavity liners and dentin treatment. J. Am. Dent. Assoc. 69,415-422. Going R. E., Massler M. and Dute H. L. (1960a) Marginal penetration of dental restoratives by different radioactive isotopes. J. Dent. Res. 39, 273-284. Going R. E., Massler M. and Dute H. L. (1960b) Marginal penetration of dental restoratives as studied by crystal violet dye and ‘-“I. J. Am. Dent. Assoc. 61, 285-300. Going R. E., Myers H. M. and Prussin S. G. (1968) Quantitative method for studying microleakage in vivo and in vitro. J. Dent. Res. 47, 1128-1132. Grieve A. R. (1973) The occurrence of secondary caries-like lesions in vitro. Br. Dent. J. 134, 530-536. Hals E. and Nemaes A. (1971) Histopathology of in vitro caries developing around silver amalgam fillings. Caries Res. 5, 58-77. Hansen E. K. and Asmussen E. (1989) Marginal adaptation of posterior resins: effect of dentin-bonding agent and hygroscopic expansion. Dent. Mater. 5, 122-126. Hembree Jr J. H. (1986) In vitro microleakage of a new dental adhesive system. J. Prosthet. Dent. 55, 442-445. Horobin R. W. (1982) An outline of staining theory. In: Bancroft J. D. and Stevens A. (eds), Theory and Practice of Histological Techniques, 2nd edn. Edinburgh, Churchill Livingstone, Chap. 6, pp. 95-109. Kidd E. A. M. (1976) Microleakage: a review. J. Dent. 5, 199-206.
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Peterson E. A., Phillips R. W. and Swartz M. L. (1966) A comparison of the physical properties of 4 restorative resins. J. Am. Dent, Assoc. 73, 1324-1336. Phankosol P., Ettinger R. L., Hicks M. J. et al. (1985) Histopathology of the initial lesion of the root surface: an in vitro study. J. Dent. Res. 64, 804-809. Phillips R. W., Gilmore H. W., Swartz M. L. et al. (1961) Adaptation of restorations in vivo as assessed by 45Ca. J. Am. Dent. Assoc. 62,9-20. Plant C. G., Jones D. W. and Darvell B. W. (1974) The heat evolved and the temperatures attained during the setting of the restorative materials. Br. Dent. J. 137, 233-238. Purton D. G. and Rodda J. C. (1988) Artificial caries around restorations in roots. J. Dent. Res. 67, 817-821. Shortall A. C. (1982) Microleakage, marginal adaptation and composite resin restorations. Br. Dent. J. 153, 223-227. Shortall A. C., Fayyad M. A. and Williams J. D. (1989) Marginal seal of injection moulded ceramic crowns cemented with three adhesive systems. J. Prosthet. Dent. 61, 24-27. Triadan H. (1987) When is microleakage a real clinical problem? Oper. Dent. 12, 153-157. Trowbridge H. 0. (1987) Model systems for determining biologic effects of microleakage. Oper. Dent. 12, 162-172. Wilson N. H. F. (1990) The evaluation of materials: relationship between laboratory investigations and clinical studies. Oper. Dent. 15, 149-155. Wu W., Cobb E. and Dermann K. (1983) Detecting margin leakage of dental composite restorations. J. Biomed. Mater. Res. 17, 37-43.
Book Reviews Atlas of Dentition in Childhood. H. S. Duterloo. Pp. 227. 1991. London, Wolfe. Hardback, f 45.00. At the heart of this atlas is a detailed description of the development of the dentition as observed on panoramic radiographs. The author successfully uses dry skull panoramic images in conjunction with labelled line diagrams and photographs of the skeletal material. This is prepared with exemplary thoroughness. The atlas also includes a description of panoramic technique, how to interpret tooth position and evaluate growth and finally examples of more common pathological conditions. It was gratifying to see space devoted to the important aspects of positioning for panoramic radiography, an area often poorly understood. The author sensibly emphasizes the limitations of panoramic images and describes the various soft tissue shadows which occur, although the anatomical ‘ghost’ shadows are not covered in any detail. It would have been valuable to underline the importance of these by using examples of the common artefacts they produce and which lead to diagnostic errors. Some criticisms are justifiable. The diagram of soft tissue shadows incorrectly puts the ‘corner of the mouth’ shadow over the second molar. The stylohyoid ligament is erroneously described as the stylomandibular ligament. The quality of the clinical radiographs is patchy in the latter part of the atlas; for example the radiograph supposedly illustrating an abnormal condyle is useless because of a superimposed earring shadow. The text is sometimes awkward; what is an ‘outspoken angular process’? What is ‘juvenile deforming arthrosis’? The persistent use of the term ‘X-ray’ for radiograph and of ‘anamnesis’ are also irritating. Overall, the impression was of an excellent treatise on
dental development on panoramic radiographs, which should be useful as a reference for dental students and orthodontic trainees. However, it is ‘bulked out’ with a mediocre section on pathology which is far better covered in other textbooks. While the author is to be commended for his efforts, there remains room for revision in subsequent editions. K. Horner Laboratory Manual for General and Oral Pathology. S. Eda. Pp. 258. 1991. New Malden, Quintessence. Hardback, f 65.00. This is a manual which is intended to be used for practical histopathology teaching in conjunction with examination of histological sections. It has been prepared by the pathology departments of seven Japanese dental schools with the highly laudable aim of standardizing teaching. The format of book is approximately half text and half illustrations, mainly coloured photomicrographs. The topic coverage starts with six chapters, largely devoted to basic pathology, while the remaining 15 are on oral pathology. The writing throughout suffers from errors of English syntax and there are areas of curious terminology, some of which are wrong. The coverage of the basic pathology is somewhat more extensive than in UK dental schools. The quality of the illustrations ranges from excellent to very poor with considerable variation in the colour rendering of H 8 E stains. Overall, although the concept is interesting, the production of this volume both in terms of the text and the quality of the illustrations is such that it cannot be recommended for use in the UK. D. G. MacDonald
