J. Dent. 1’991;
19: 33-38
33
Fissure sealant wear at 30 months: new evaluation criteria M. R. Pintado, J. P. Conry* and W. H. Douglas Biomaterials Research Center, Department of Oral Science and *Department Minnesota School of Dentistry, Minneapolis, USA
of Preventive Sciences, University
of
ABSTRACT The volume, depth and area of fissure sealant wear at 30 months is reported. Eighteen premolar teeth were included in the study. The teeth were sealed (Concise, White Sealant, 3M Dental Products Div., St Paul, MN, USA) and an impression taken, yielding a baseline record. Subsequent impressions were taken at 6 mont_hs and 30 months. Epoxy replicas were made from all impressions and the occlusal surface of each replica was digitized using a displacement stylus and programmable retrieval system. A goodness-of-tit routine was used to compare the digitized replicas and quantify wear. At 30 months, there was a mean sealant volume loss of 0.43 + 0.24 mm3 (mean of the maximum depth loss = 221.8 + 115.1 pm; mean area loss = 0.62 f 0.15 mm2) for all teeth. A new parameter, the Occlusal Stability Ratio (OSR), is discussed which describes the relationship between sealant area and sealant volume. KEY WORDS: J. Dent. 1991;
Pit and fissure sealants, Clinical evaluation, Wear 19: 33-38
(Received 23 March 1990;
reviewed 20 June 1990;
accepted 14 August 1990)
Correspondence should be addressed to: MS Maria R. Pintado, Biomaterials Research Center, 16-2 12 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
INTRODUCTION The effectiveness of pit and fissure sealants in preventing occlusal caries is well documented (Cueto and Buonocore, 1965; Ripa, 1985; Simonsen, 1987). However, in many countries fissure sealants have not been established as an integral part of dental health care delivery (Horowitz and Frazier, 1982; Jerrell and Bennett, 1984; Gonzales et al., 1988). Poor retention and excessive wear are frequently cited reasons limiting the use of this preventive technique. Accurate quantitative clinical measurement of residual fissure sealant material has, until recently, proven difficult. The present authors have previously reported on a comprehensive method for quantitatively measuring fissure sealants (Pintado et al., 1988; Conry et al., 1990). Using computer-guided profilometry, the volume, depth and area of sealant applied to premolars have been measured clinically. Most recently Conryetal. (1989) have clinically measured the mean volume, depth and area of fissure sealant wear for premolar teeth at 6 months. The clinical wear findings at 6 months suggested that there was a disproportionate change in the volume, area and depth of sealant when one examined individual tooth groups @1991 Butterworth-Heinemann 0300-5712/91/010033-06
Ltd.
(maxillary first premolars, mandibular second premolars, etc.). The service life of a clinically applied fissure sealant may be marked by catastrophic failure due to debonding, microleakage, fracture, or massive relative loss of the sealant. Hopefully this is a rare event. However, the study preliminary to this report (Conry et al., 1989) showed that all fissure sealants undergo a progressive wear process, which exposes previously covered areas of the occlusal surface. The wear of resin-based materials has been extensively studied as intracoronal posterior composites (Braem etal., 1987; Wilson et al., 1988). However, a fissure sealant is essentially an extracoronal addition to the occlusal surface, and the relationship of its wear characteristics to the occlusal anatomy may be expected to be quite different from a restorative material. The present paper, which is a continuation of the previous study, reports on the fissure sealant wear of teeth at 30 months in tivo. The relationship between volume, depth and surface area of clinical wear is explored as a function of premolar anatomy.
34
J. Dent. 1991;19:
No. 1
METHODS AND MATERIALS The study was approved by the Committee for the Use of Human Subjects in Research at the University of Minnesota. A patient pool (n = 6) presented 22 maxillary and mandibular caries-free teeth for fissure sealing. The teeth were cleaned with a pumice slurry, washed and air dried, and a preliminary alginate scavenger impression was taken of each tooth, followed by a polyvinylsiloxane impression (Express, 3M Dental Products Div., St Paul, MN, USA). This impression was designated ‘before’. The teeth were sealed (Concise White Sealant, 3M Dental Products Div., St Paul, MN, USA) by a single operator. The method of sealant application has been described in detail in earlier reports (Pintado et al., 1988; Conry et al., 1990).The sealed surface was rubbed with a cotton pledget and carefully examined for occlusal interference, then adjusted where necessary. Impressions were taken, yielding the baseline record. Subsequent impressions were taken at 6 months and at 30 months. Twenty-one teeth were available for study at 6 months while 18 teeth were available at 30 months. All impressions were treated in the following manner: washed with a mild soap solution and rinsed with tapwater, then boxed with polyvinylsiloxane putty. Epoxy (Epoxy-Die, Ivoclar, Schann, Liechtenstein) replicas were made from the relevant impressions. The epoxy replicas were cured according to the manufacturer’s instructions. The replicas were removed from the impressions and visually examined for voids, bubbles or cracks under a binocular microscope. Any discrepancy noted was recorded. The sealant replicas were mounted in a nylon ring using stone (Die Keen, Columbus Dental, St Louis, MO, USA). An index jig was constructed for each replica, thus allowing the replicas of all sealed teeth at baseline, 6 months and 30 months to be located in approximately the same positions in the mounting ring. The occlusal surface of each epoxy replica was digitized, using a precise displacement stylus and programmable data retrieval system (DeLong et al., 1985). The system is currently capable of measuring changes of 0.0006 mm3 in anatomical contour. The X, Y and Z coordinates of approximately 25000 points were collected for each occlusal surface and stored in a microcomputer. The digitized images of the unsealed occlusal surface, baseline sealant, and the sealed tooth at 6 months and 30 months were superimposed in the computer memory using AnSur, a three-dimensional fitting program, and displayed by computer graphics. Thus, it was possible to compare all the stages of a sealed tooth in multiple pair combinations. Comparison of the baseline sealant surface and the 30 month surface allowed changes over that time period to be identified. These changes could be quantitatively expressed as volume, area or depth changes or qualitatively expressed by anatomical colour graphic representations in one, two or three dimensions. Thus, regions of wear could be related directly to the tooth anatomy.
In addition to the anatomical visualization of the occlusal disposition of the sealed surface, the methodology also yielded extensive numerate data, as already mentioned, which were analysed by a one-way ANOVA.
RESULTS The mean time between placement of the sealant and the ‘30 month’ evaluation was 30.8 months. Of the original 22 teeth sealed, 18 were available for study at 30 months. Four teeth were excluded from this population and are dealt with separately. On clinical examination, one maxillary second premolar had developed interproximal caries and was restored with a two surface amalgam restoration. One maxillary second premolar was found to have lost the sealant completely and the tooth had been resealed. In two other instances the patient was not available. The digital anatomical surfaces of two representative teeth are shown in Figs 1-4. The graphic display of an upper right first premolar is reproduced in Fig. 1. In this figure, green represents the fissure sealant coverage and red indicates wear within the fissure sealant. A profile ‘section’through the same tooth is illustrated inFig. 2. The green line represents the baseline condition and the red the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand comer of Fig. 2, showing the exact disposition of the profile. Similar graphic assemblies are shown in Figs 3 and 4, which refer to a lower left second premolar, where the colour lines and surfaces have the same interpretation. Software associated with this technology allowed for the integration of the depth, volume and area of sealant, and contributed significantly to the anatomical interpretation of the results. The numerate values for the loss of volume, mean maximum depth and area of fissure sealant wear at 30 months are reported in Tables Z and ZZ.The ratio of the area loss to the volume loss, which is termed the Occlusal Stability Ratio (OSR) in this report, is set out in Table ZZZ. The Occlusal Stability Ratio was calculated for each individual tooth and the means of these values are presented. This was done on statistical advice, and the values are slightly different from a ratio of the mean of areas to the mean of the volume. The mean volume loss and mean maximum depth loss of fissure sealant from premolars at 30 months was 0.43 f 0.24 mm3 and 221.8 + 115.1 urn, respectively, The mean surface area loss of material was 0.62 +_0.15 mm* for all premolars. One-way analysis of variance showed no significant overall differences between tooth groups by loss ofvolume (F = 1.34, P > 0.30), depth (F = 1.08, P > 0.39) and area (F = 1.72, P > 0.20) at 30 months. There was no need therefore to use a multirange test. However, grouping the data by time period, which offered a paired study (6 and 30 months), made a Student’s f test appropriate and showed a significant difference between all teeth for loss of volume (P < 0.01) and for depth (P < 0.05). The difference
Pintado et al.:
Fissure sealant wear
35
Fig. 7. The graphic reassembly of an upper right first premolar, where green represents the fissure sealant coverage and red indicates wear of the fissure sealant.
fig. 2. Profile ‘section’ through the same tooth in fig. 1, where the green line represents the baseline condition and the red line the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand corner that shows the exact disposition of the profile.
Fig. 3. The graphic reassembly of a lower left second premolar, where green represents the fissure sealant coverage and red indicates wear of the fissure sealant.
Fig. 4. Profile ‘section’ through the same tooth in Fig. 3, where the green line represents the baseline condition and the red line the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand corner that shows the exact disposition of the profile.
between area loss at 6 months and 30 months was not significant (P = 0.37). The trends in loss of sealant by volume, mean maximum depth and area are also displayed graphically in Figs 5-8, which are grouped by the occlusal anatomy of the premolars.
DISCUSSION This study demonstrates the progressive clinical loss of fissure sealant over time. The findings are consistent with the earlier sealant studies which report the greatest amount of material loss occurs shortly after sealant placement with lesser amounts of sealant loss over time (Jensen et aI., 1985). Studies on the wear of posterior
composites show that the wear is generally greatest in the first 6 months of clinical service (Leinfelder, 1985). In the 6 month report of the present study it was also noted that the occlusal wear of the maxillary premolars differed in extent and profile from the mandibular premolars. There were grounds for believing that the extent of occlusal loss was therefore related to tooth anatomy and the position of the tooth in the arch. Reference to Table I shows that this suggestion would appear to be true as it relates to the mandibular first premolar, which still showed substantially reduced loss of sealant both in depth and volume. However, it will be noted that the loss of sealant from the lower second premolar has caught up with that from the maxillary premolars after 30 months has elapsed in the mouth.
36
3. Dent.
1991;
19:
No. 1
Tab/e 1. Volume and maximum death loss of fissure sealant at 6 and 30 months Depth change (pm)
Volume change {mm”) Premolar tooth group
6 months*
30 months
6 months*
30 months
Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1 st (n = 3) Mandibular 2nd (n = 4)
0.27 k 0.19
0.50 + 0.29
187.7
Ifr 78.5
252.7
+_ 136.6
0.27 + 0.14
0.46 + 0.24
131.6
+ 59.2
220.1
+ 121.7
0.06 k 0.02
0.17 +_0.04
88.0 f 33.9
148.5
+ 47.1
0.19+0.12
0.48 + 0.15
127.9
+ 77.5
224.7
+_ 1 17.4
All teeth (n = 18)
0.22 zk 0.16
0.43 -c 0.24
145.3
k 73.6
221.8+
115.1
*Conry et a/., 1989.
Tab/e II. Occlusal area of fissure sealant placed and area lost at 6 and 30 months Baseline * (mm’)
6 months f (mm’)
30 months Imm’l
7.37 +_ 1.02
0.63 + 0.30
0.63 + 0.10
9.36 + 1.38
0.69 + 0.17
0.64 + 0.08
6.60 + 0.20
0.28 + 0.17
0.40 zk 0.10
8.94 zk 1.88
0.56 f 0.29
0.74 f 0.13
8.03 +_1.60
0.57 + 0.27
0.62 * 0.15
Premolar tooth group Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1 st (n = 3) Mandibular 2nd (n = 4)
All teeth (n = 18) *Pintado et al., 1988. tConry et a/., 1989.
Tab/e 111.Occlusal stability ratio (area loss/volume sealant at 6 and 30 months Premolar tooth group
loss) of
6 months
30 months
Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1st (n = 3) Mandibular 2nd (n = 4)
2.90 2.81 4.67 3.15
1.56 1.56 2.39 1.62
Overall ratio for all teeth (n = 18)
3.23
1.71
Note: the ratio is the mean ratio derived from individualteeth.
Table II shows that the unique position of the mandibular first premolar is maintained at 30 months in that it displayed the least overall loss of occlusal coverage compared to the other premolars. However, the maxillary premolars showed no change in occlusal coverage between 6 months and 30 months (the slight decrease at 30 months is within the standard error of the measurement technique). This is true even though the same maxillary teeth continued to demonstrate volumetric loss over the same period. The mandibular teeth are different in behaviour in that the loss of area of coverage here is progressive in the period between 6 months and 30
months in the mouth. It is clear that no single parameter fully describes the character of fissure sealant wear observed here. It could be argued that the volume (or depth) of loss of sealant is not directly clinically relevant. What is important is the area of coverage needed to ensure that the anatomically critical areas remain safely obturated. Volume (or depth) of loss of sealant is extremely important indirectly in that it results in loss of area of coverage. We propose a new parameter in sealant studies which will quantitatively express these concepts-the Occlusal Stability Ratio (OSR): loss of occlusal area of sealant OSR =
= mm-1
loss of volume of sealant The OSR value expresses the ability of the fissure sealant coverage to remain stable and insensitive to volume loss due to occlusal force and function. In an ideal case this ratio would tend towards zero, given that volumetric loss of sealant will always be clinically present at some level. The OSR values for the present study are shown in Table III. The ratio is the mean ratio derived from individual
Pintado et al.: Fissure sealant wear
0.8
0.8
37
r
F 0.6-
10
15 20 Time (months)
25
30
Fig. 6. Change in wear parameters of the maxillary first and Time (months)
Fig. 5. Change in wear parameters of fissure sealants over time for all teeth. -El-,volume (mm3);-+, area (mm*); +, depth (mm).
I
second premolars over time. Solid lines, maxillary second premolar; broken lines, maxillary first premolar; +, volume (mm’); -4-, area (mm2); b, depth (mm).
I
40 Time (months)
Time (months)
Fig. 7. Change in wear parameters of the mandibular first
Fig. 8. Change in wear parameters of the mandibular second
premolar over time. U, volume (mmj); (mm2); +, depth (mm).
premolar over time. -C!-, (mm2); --C-, depth (mm).
-+--,
area
teeth. It will be noted that the maxillary premolars show the lowest OSR values and the mandibular first premolar the highest. These observations on the relationship between sealant loss by volume, depth and occlusal area coverage are shown graphically in Figs 5-8. Fig. 5 presents the data for all premolar teeth considered as a group. As expected, all three parameters rise sharply during the first 6 months in viva. However, it is in the period between 6 months and 30 months that the discriminating changes occur. The area remains relatively unchanged for the group. The loss of volume is progressive and the loss of depth of sealant shows a marked slowing down. These typical changes are also shown in Fig. 6, where the maxillary first and second premolars are considered together.
volume (mm3); --+-,
area
of occlusal change. This is displayed graphically in Fig. 7. The loss of area is progressive between 6 months and 30 months, although slowed down, as already mentioned. The loss of volume is almost linear with time over the whole clinical period of 30 months. The loss of depth of sealant rises steeply over the first 6 months and then slows down to such an extent that the curves of depth and volume cross over in Fig, 7. These mandibular first premolar features are also somewhat reflected inFig. 8 for the mandibular second premolar, with the qualification that there was no volume and depth crossover. It is suggested in the present study that these results are interpretable in terms of premolar anatomy. The maxillary premolars present steep anatomy in the cuspal inclines The mandibular first premolar shows a unique pattern
38
J. Dent. 1991;19:
No. 1
which afford considerable protection for the sealant in lateral excursion. This presents a very stable occlusal coverage in the clinical period beyond the 6 month period. Conversely, the mandibular premolars, particularly the mandibular first premolar, present a more open anatomy. This results in a more progressive loss of sealant as measured by all three parameters. It is a general consideration that if the sealant can survive to 30 months, then there is less chance of further change and, therefore, the fissures remain protected. Sealant coverage is fundamentally an extracoronal addition of sealant onto the existing anatomy. In this respect it is uniquely different from an intracoronal restoration. The intracoronal restoration may wear, but the coverage is fixed and defined by the outline form of the cavity (Lugassy,A-985). The occlusal coverage for sealants is not a fixed value and is influenced by the volume loss in different ways. The present study shows that the maxillary premolars are likely to demonstrate more stability of occlusal coverage over the long term compared to the corresponding lower premolars. Acknowledgements The authors wish to express their appreciation to Dr Louise B. Messer for her assistance in the initial years of the study. This research was supported in part by NIH grant No. 2S07-RR-05322.
References Braem M., Lambrechts P., Vanherle G. et al. (1987) Three year quantitative in-viva wear results of four posterior composites. J. Dent. Rex 66, (Abstr. 477), 166.
Conry J. P., Pintado M. R. and Douglas W. H. (1989) Clinical volume loss of fissure sealant at 6 months. J. Dent. Res. 68, (Abstr. 452), 923. Conry J. P., Pintado M. R. and Douglas W. H. (1990) Measurement of fissure sealant surface area by computer. Quintessence lnt. 21, 27-33. Cueto E. I. and Buonocore M. G. (1965) Adhesive sealing of pits and fissures for caries prevention. lADR Program and Abstracts of Papers, 43rd General Meeting, (Abstr. 4OO), 137. DeLong R., Pintado M. and Douglas W. H. (1985) Measurement of change in surface contour by computer graphics. Dent. Mater. 1, 27-30. Gonzales C. D., Frazier P. J. and Messer L. B. (1988) Sealant knowledge and use by pediatric dentists: 1987 Minnesota survey. .T.Dent. Child. 55,434-440. Horowitz k M. and Frazier P. J. (1982) Issues in. the widespread adoption of pit-and-fissure sealants. .I. Public Health Dent. 42, 312-323. Jensen 0. E., Handelman S. L. and Perez-Diez F. (1985) Occlusal wear of four pit and fissure sealants over two years. Pediatr. Dent. 7, 23-29. Jerrell R. G. and Bennett C. G. (1984) Utilization of sealants by practicing pedodontists. J. Pedodont. 8, 378-386. Leinfelder K. F. (1985) Evaluation of clinical wear of posterior composite resins. In: Vanherle G. and Smith D. C. (eds), Posterior Composite Resin Dental Restorative Materials. The Netherlands, Peter Szulc, pp. 501-509. Lugassy A. A. (1985) Laboratory model for the quantification of clinical occlusal wear. J. Dent. Res. 64, (Abstr. 63), 181. Pintado M. R, Conry J. P. and Douglas W. H. (1988) Measurement of sealant volume in vivo using image processing technology. Quintessence ht. 19, 613-617. Ripa L. W. (1985) The current status of pit and fissure sealants: a review. Can. Dent. Assoc. J. 5, 367-379. Simonsen R. J. (1987) Retention and effectiveness of a single application of white sealant after 10 years. J. Am. Dent. Assoc. 115, 31-36. Wilson N. H. F., Wilson M. A. and Smith G. A. (1988) A clinical trial of a visible light cured posterior composite resin restorative material: four-year results. Quintessence ht. 19, 133-139.
Book Review The Dental Patient. Vol. I. Clinical Dentistry. Edited by C. Scully. Pp. 252. 1989. Oxford, Heinemann. Hardback, f 35.00.
There are a number of undergraduate texts available on the market which cover that difficult transition to becoming a clinical student. Volume I of the present series (we are promised four volumes) has to have a unique style that will make it an attractive book to buy and, once bought, read. The Dental Patient manages this well, for it is very well illustrated, committed heavily to tabular summaries of information and has further reading lists for the diligent. The pages are wide and the typeface easy to read. Photographic manipulation of illustrations demands firm editorial work: mostly, this has been achieved, but inevitably there are exceptions. Some of the photographs have been perfectly judged so as to show the part in question with its identifying anatomical features; a few are less so, with unnecessary material
that distracts the reader. The quality of reproduction of the radiographs and CT scans is generally poor, due to loss of both contrast and detail. This volume is edited by Professor Scully of Bristol Dental School, who is also the largest contributor. Much of the material can be found in his other textbooks that describe the subject of general diagnosis and management in more detail, yet throughout there is an appealing freshness and selective exclusion of detail. Some of the 10 chapters have more than one author, resulting in changes both in style and in presentation of the line drawings. Certain chapters are especially well written, for example ‘The Principles of Prescribing’; it will be hard to find a better vignette for the new clinical student. Perioperative management covers both consent as well as the practical aspects of full operating theatre conditions. There is some cross-referencing but the index is satisfactory. In all, a worthy book but it does compete with others on the market, including more by the same author. H. Cannell
19: 33-38
33
Fissure sealant wear at 30 months: new evaluation criteria M. R. Pintado, J. P. Conry* and W. H. Douglas Biomaterials Research Center, Department of Oral Science and *Department Minnesota School of Dentistry, Minneapolis, USA
of Preventive Sciences, University
of
ABSTRACT The volume, depth and area of fissure sealant wear at 30 months is reported. Eighteen premolar teeth were included in the study. The teeth were sealed (Concise, White Sealant, 3M Dental Products Div., St Paul, MN, USA) and an impression taken, yielding a baseline record. Subsequent impressions were taken at 6 mont_hs and 30 months. Epoxy replicas were made from all impressions and the occlusal surface of each replica was digitized using a displacement stylus and programmable retrieval system. A goodness-of-tit routine was used to compare the digitized replicas and quantify wear. At 30 months, there was a mean sealant volume loss of 0.43 + 0.24 mm3 (mean of the maximum depth loss = 221.8 + 115.1 pm; mean area loss = 0.62 f 0.15 mm2) for all teeth. A new parameter, the Occlusal Stability Ratio (OSR), is discussed which describes the relationship between sealant area and sealant volume. KEY WORDS: J. Dent. 1991;
Pit and fissure sealants, Clinical evaluation, Wear 19: 33-38
(Received 23 March 1990;
reviewed 20 June 1990;
accepted 14 August 1990)
Correspondence should be addressed to: MS Maria R. Pintado, Biomaterials Research Center, 16-2 12 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA.
INTRODUCTION The effectiveness of pit and fissure sealants in preventing occlusal caries is well documented (Cueto and Buonocore, 1965; Ripa, 1985; Simonsen, 1987). However, in many countries fissure sealants have not been established as an integral part of dental health care delivery (Horowitz and Frazier, 1982; Jerrell and Bennett, 1984; Gonzales et al., 1988). Poor retention and excessive wear are frequently cited reasons limiting the use of this preventive technique. Accurate quantitative clinical measurement of residual fissure sealant material has, until recently, proven difficult. The present authors have previously reported on a comprehensive method for quantitatively measuring fissure sealants (Pintado et al., 1988; Conry et al., 1990). Using computer-guided profilometry, the volume, depth and area of sealant applied to premolars have been measured clinically. Most recently Conryetal. (1989) have clinically measured the mean volume, depth and area of fissure sealant wear for premolar teeth at 6 months. The clinical wear findings at 6 months suggested that there was a disproportionate change in the volume, area and depth of sealant when one examined individual tooth groups @1991 Butterworth-Heinemann 0300-5712/91/010033-06
Ltd.
(maxillary first premolars, mandibular second premolars, etc.). The service life of a clinically applied fissure sealant may be marked by catastrophic failure due to debonding, microleakage, fracture, or massive relative loss of the sealant. Hopefully this is a rare event. However, the study preliminary to this report (Conry et al., 1989) showed that all fissure sealants undergo a progressive wear process, which exposes previously covered areas of the occlusal surface. The wear of resin-based materials has been extensively studied as intracoronal posterior composites (Braem etal., 1987; Wilson et al., 1988). However, a fissure sealant is essentially an extracoronal addition to the occlusal surface, and the relationship of its wear characteristics to the occlusal anatomy may be expected to be quite different from a restorative material. The present paper, which is a continuation of the previous study, reports on the fissure sealant wear of teeth at 30 months in tivo. The relationship between volume, depth and surface area of clinical wear is explored as a function of premolar anatomy.
34
J. Dent. 1991;19:
No. 1
METHODS AND MATERIALS The study was approved by the Committee for the Use of Human Subjects in Research at the University of Minnesota. A patient pool (n = 6) presented 22 maxillary and mandibular caries-free teeth for fissure sealing. The teeth were cleaned with a pumice slurry, washed and air dried, and a preliminary alginate scavenger impression was taken of each tooth, followed by a polyvinylsiloxane impression (Express, 3M Dental Products Div., St Paul, MN, USA). This impression was designated ‘before’. The teeth were sealed (Concise White Sealant, 3M Dental Products Div., St Paul, MN, USA) by a single operator. The method of sealant application has been described in detail in earlier reports (Pintado et al., 1988; Conry et al., 1990).The sealed surface was rubbed with a cotton pledget and carefully examined for occlusal interference, then adjusted where necessary. Impressions were taken, yielding the baseline record. Subsequent impressions were taken at 6 months and at 30 months. Twenty-one teeth were available for study at 6 months while 18 teeth were available at 30 months. All impressions were treated in the following manner: washed with a mild soap solution and rinsed with tapwater, then boxed with polyvinylsiloxane putty. Epoxy (Epoxy-Die, Ivoclar, Schann, Liechtenstein) replicas were made from the relevant impressions. The epoxy replicas were cured according to the manufacturer’s instructions. The replicas were removed from the impressions and visually examined for voids, bubbles or cracks under a binocular microscope. Any discrepancy noted was recorded. The sealant replicas were mounted in a nylon ring using stone (Die Keen, Columbus Dental, St Louis, MO, USA). An index jig was constructed for each replica, thus allowing the replicas of all sealed teeth at baseline, 6 months and 30 months to be located in approximately the same positions in the mounting ring. The occlusal surface of each epoxy replica was digitized, using a precise displacement stylus and programmable data retrieval system (DeLong et al., 1985). The system is currently capable of measuring changes of 0.0006 mm3 in anatomical contour. The X, Y and Z coordinates of approximately 25000 points were collected for each occlusal surface and stored in a microcomputer. The digitized images of the unsealed occlusal surface, baseline sealant, and the sealed tooth at 6 months and 30 months were superimposed in the computer memory using AnSur, a three-dimensional fitting program, and displayed by computer graphics. Thus, it was possible to compare all the stages of a sealed tooth in multiple pair combinations. Comparison of the baseline sealant surface and the 30 month surface allowed changes over that time period to be identified. These changes could be quantitatively expressed as volume, area or depth changes or qualitatively expressed by anatomical colour graphic representations in one, two or three dimensions. Thus, regions of wear could be related directly to the tooth anatomy.
In addition to the anatomical visualization of the occlusal disposition of the sealed surface, the methodology also yielded extensive numerate data, as already mentioned, which were analysed by a one-way ANOVA.
RESULTS The mean time between placement of the sealant and the ‘30 month’ evaluation was 30.8 months. Of the original 22 teeth sealed, 18 were available for study at 30 months. Four teeth were excluded from this population and are dealt with separately. On clinical examination, one maxillary second premolar had developed interproximal caries and was restored with a two surface amalgam restoration. One maxillary second premolar was found to have lost the sealant completely and the tooth had been resealed. In two other instances the patient was not available. The digital anatomical surfaces of two representative teeth are shown in Figs 1-4. The graphic display of an upper right first premolar is reproduced in Fig. 1. In this figure, green represents the fissure sealant coverage and red indicates wear within the fissure sealant. A profile ‘section’through the same tooth is illustrated inFig. 2. The green line represents the baseline condition and the red the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand comer of Fig. 2, showing the exact disposition of the profile. Similar graphic assemblies are shown in Figs 3 and 4, which refer to a lower left second premolar, where the colour lines and surfaces have the same interpretation. Software associated with this technology allowed for the integration of the depth, volume and area of sealant, and contributed significantly to the anatomical interpretation of the results. The numerate values for the loss of volume, mean maximum depth and area of fissure sealant wear at 30 months are reported in Tables Z and ZZ.The ratio of the area loss to the volume loss, which is termed the Occlusal Stability Ratio (OSR) in this report, is set out in Table ZZZ. The Occlusal Stability Ratio was calculated for each individual tooth and the means of these values are presented. This was done on statistical advice, and the values are slightly different from a ratio of the mean of areas to the mean of the volume. The mean volume loss and mean maximum depth loss of fissure sealant from premolars at 30 months was 0.43 f 0.24 mm3 and 221.8 + 115.1 urn, respectively, The mean surface area loss of material was 0.62 +_0.15 mm* for all premolars. One-way analysis of variance showed no significant overall differences between tooth groups by loss ofvolume (F = 1.34, P > 0.30), depth (F = 1.08, P > 0.39) and area (F = 1.72, P > 0.20) at 30 months. There was no need therefore to use a multirange test. However, grouping the data by time period, which offered a paired study (6 and 30 months), made a Student’s f test appropriate and showed a significant difference between all teeth for loss of volume (P < 0.01) and for depth (P < 0.05). The difference
Pintado et al.:
Fissure sealant wear
35
Fig. 7. The graphic reassembly of an upper right first premolar, where green represents the fissure sealant coverage and red indicates wear of the fissure sealant.
fig. 2. Profile ‘section’ through the same tooth in fig. 1, where the green line represents the baseline condition and the red line the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand corner that shows the exact disposition of the profile.
Fig. 3. The graphic reassembly of a lower left second premolar, where green represents the fissure sealant coverage and red indicates wear of the fissure sealant.
Fig. 4. Profile ‘section’ through the same tooth in Fig. 3, where the green line represents the baseline condition and the red line the change in contour at 30 months in the mouth. An orientation contour is given in the top left hand corner that shows the exact disposition of the profile.
between area loss at 6 months and 30 months was not significant (P = 0.37). The trends in loss of sealant by volume, mean maximum depth and area are also displayed graphically in Figs 5-8, which are grouped by the occlusal anatomy of the premolars.
DISCUSSION This study demonstrates the progressive clinical loss of fissure sealant over time. The findings are consistent with the earlier sealant studies which report the greatest amount of material loss occurs shortly after sealant placement with lesser amounts of sealant loss over time (Jensen et aI., 1985). Studies on the wear of posterior
composites show that the wear is generally greatest in the first 6 months of clinical service (Leinfelder, 1985). In the 6 month report of the present study it was also noted that the occlusal wear of the maxillary premolars differed in extent and profile from the mandibular premolars. There were grounds for believing that the extent of occlusal loss was therefore related to tooth anatomy and the position of the tooth in the arch. Reference to Table I shows that this suggestion would appear to be true as it relates to the mandibular first premolar, which still showed substantially reduced loss of sealant both in depth and volume. However, it will be noted that the loss of sealant from the lower second premolar has caught up with that from the maxillary premolars after 30 months has elapsed in the mouth.
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1991;
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Tab/e 1. Volume and maximum death loss of fissure sealant at 6 and 30 months Depth change (pm)
Volume change {mm”) Premolar tooth group
6 months*
30 months
6 months*
30 months
Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1 st (n = 3) Mandibular 2nd (n = 4)
0.27 k 0.19
0.50 + 0.29
187.7
Ifr 78.5
252.7
+_ 136.6
0.27 + 0.14
0.46 + 0.24
131.6
+ 59.2
220.1
+ 121.7
0.06 k 0.02
0.17 +_0.04
88.0 f 33.9
148.5
+ 47.1
0.19+0.12
0.48 + 0.15
127.9
+ 77.5
224.7
+_ 1 17.4
All teeth (n = 18)
0.22 zk 0.16
0.43 -c 0.24
145.3
k 73.6
221.8+
115.1
*Conry et a/., 1989.
Tab/e II. Occlusal area of fissure sealant placed and area lost at 6 and 30 months Baseline * (mm’)
6 months f (mm’)
30 months Imm’l
7.37 +_ 1.02
0.63 + 0.30
0.63 + 0.10
9.36 + 1.38
0.69 + 0.17
0.64 + 0.08
6.60 + 0.20
0.28 + 0.17
0.40 zk 0.10
8.94 zk 1.88
0.56 f 0.29
0.74 f 0.13
8.03 +_1.60
0.57 + 0.27
0.62 * 0.15
Premolar tooth group Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1 st (n = 3) Mandibular 2nd (n = 4)
All teeth (n = 18) *Pintado et al., 1988. tConry et a/., 1989.
Tab/e 111.Occlusal stability ratio (area loss/volume sealant at 6 and 30 months Premolar tooth group
loss) of
6 months
30 months
Maxillary 2nd (n = 7) Maxillary 1 st (n = 4) Mandibular 1st (n = 3) Mandibular 2nd (n = 4)
2.90 2.81 4.67 3.15
1.56 1.56 2.39 1.62
Overall ratio for all teeth (n = 18)
3.23
1.71
Note: the ratio is the mean ratio derived from individualteeth.
Table II shows that the unique position of the mandibular first premolar is maintained at 30 months in that it displayed the least overall loss of occlusal coverage compared to the other premolars. However, the maxillary premolars showed no change in occlusal coverage between 6 months and 30 months (the slight decrease at 30 months is within the standard error of the measurement technique). This is true even though the same maxillary teeth continued to demonstrate volumetric loss over the same period. The mandibular teeth are different in behaviour in that the loss of area of coverage here is progressive in the period between 6 months and 30
months in the mouth. It is clear that no single parameter fully describes the character of fissure sealant wear observed here. It could be argued that the volume (or depth) of loss of sealant is not directly clinically relevant. What is important is the area of coverage needed to ensure that the anatomically critical areas remain safely obturated. Volume (or depth) of loss of sealant is extremely important indirectly in that it results in loss of area of coverage. We propose a new parameter in sealant studies which will quantitatively express these concepts-the Occlusal Stability Ratio (OSR): loss of occlusal area of sealant OSR =
= mm-1
loss of volume of sealant The OSR value expresses the ability of the fissure sealant coverage to remain stable and insensitive to volume loss due to occlusal force and function. In an ideal case this ratio would tend towards zero, given that volumetric loss of sealant will always be clinically present at some level. The OSR values for the present study are shown in Table III. The ratio is the mean ratio derived from individual
Pintado et al.: Fissure sealant wear
0.8
0.8
37
r
F 0.6-
10
15 20 Time (months)
25
30
Fig. 6. Change in wear parameters of the maxillary first and Time (months)
Fig. 5. Change in wear parameters of fissure sealants over time for all teeth. -El-,volume (mm3);-+, area (mm*); +, depth (mm).
I
second premolars over time. Solid lines, maxillary second premolar; broken lines, maxillary first premolar; +, volume (mm’); -4-, area (mm2); b, depth (mm).
I
40 Time (months)
Time (months)
Fig. 7. Change in wear parameters of the mandibular first
Fig. 8. Change in wear parameters of the mandibular second
premolar over time. U, volume (mmj); (mm2); +, depth (mm).
premolar over time. -C!-, (mm2); --C-, depth (mm).
-+--,
area
teeth. It will be noted that the maxillary premolars show the lowest OSR values and the mandibular first premolar the highest. These observations on the relationship between sealant loss by volume, depth and occlusal area coverage are shown graphically in Figs 5-8. Fig. 5 presents the data for all premolar teeth considered as a group. As expected, all three parameters rise sharply during the first 6 months in viva. However, it is in the period between 6 months and 30 months that the discriminating changes occur. The area remains relatively unchanged for the group. The loss of volume is progressive and the loss of depth of sealant shows a marked slowing down. These typical changes are also shown in Fig. 6, where the maxillary first and second premolars are considered together.
volume (mm3); --+-,
area
of occlusal change. This is displayed graphically in Fig. 7. The loss of area is progressive between 6 months and 30 months, although slowed down, as already mentioned. The loss of volume is almost linear with time over the whole clinical period of 30 months. The loss of depth of sealant rises steeply over the first 6 months and then slows down to such an extent that the curves of depth and volume cross over in Fig, 7. These mandibular first premolar features are also somewhat reflected inFig. 8 for the mandibular second premolar, with the qualification that there was no volume and depth crossover. It is suggested in the present study that these results are interpretable in terms of premolar anatomy. The maxillary premolars present steep anatomy in the cuspal inclines The mandibular first premolar shows a unique pattern
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J. Dent. 1991;19:
No. 1
which afford considerable protection for the sealant in lateral excursion. This presents a very stable occlusal coverage in the clinical period beyond the 6 month period. Conversely, the mandibular premolars, particularly the mandibular first premolar, present a more open anatomy. This results in a more progressive loss of sealant as measured by all three parameters. It is a general consideration that if the sealant can survive to 30 months, then there is less chance of further change and, therefore, the fissures remain protected. Sealant coverage is fundamentally an extracoronal addition of sealant onto the existing anatomy. In this respect it is uniquely different from an intracoronal restoration. The intracoronal restoration may wear, but the coverage is fixed and defined by the outline form of the cavity (Lugassy,A-985). The occlusal coverage for sealants is not a fixed value and is influenced by the volume loss in different ways. The present study shows that the maxillary premolars are likely to demonstrate more stability of occlusal coverage over the long term compared to the corresponding lower premolars. Acknowledgements The authors wish to express their appreciation to Dr Louise B. Messer for her assistance in the initial years of the study. This research was supported in part by NIH grant No. 2S07-RR-05322.
References Braem M., Lambrechts P., Vanherle G. et al. (1987) Three year quantitative in-viva wear results of four posterior composites. J. Dent. Rex 66, (Abstr. 477), 166.
Conry J. P., Pintado M. R. and Douglas W. H. (1989) Clinical volume loss of fissure sealant at 6 months. J. Dent. Res. 68, (Abstr. 452), 923. Conry J. P., Pintado M. R. and Douglas W. H. (1990) Measurement of fissure sealant surface area by computer. Quintessence lnt. 21, 27-33. Cueto E. I. and Buonocore M. G. (1965) Adhesive sealing of pits and fissures for caries prevention. lADR Program and Abstracts of Papers, 43rd General Meeting, (Abstr. 4OO), 137. DeLong R., Pintado M. and Douglas W. H. (1985) Measurement of change in surface contour by computer graphics. Dent. Mater. 1, 27-30. Gonzales C. D., Frazier P. J. and Messer L. B. (1988) Sealant knowledge and use by pediatric dentists: 1987 Minnesota survey. .T.Dent. Child. 55,434-440. Horowitz k M. and Frazier P. J. (1982) Issues in. the widespread adoption of pit-and-fissure sealants. .I. Public Health Dent. 42, 312-323. Jensen 0. E., Handelman S. L. and Perez-Diez F. (1985) Occlusal wear of four pit and fissure sealants over two years. Pediatr. Dent. 7, 23-29. Jerrell R. G. and Bennett C. G. (1984) Utilization of sealants by practicing pedodontists. J. Pedodont. 8, 378-386. Leinfelder K. F. (1985) Evaluation of clinical wear of posterior composite resins. In: Vanherle G. and Smith D. C. (eds), Posterior Composite Resin Dental Restorative Materials. The Netherlands, Peter Szulc, pp. 501-509. Lugassy A. A. (1985) Laboratory model for the quantification of clinical occlusal wear. J. Dent. Res. 64, (Abstr. 63), 181. Pintado M. R, Conry J. P. and Douglas W. H. (1988) Measurement of sealant volume in vivo using image processing technology. Quintessence ht. 19, 613-617. Ripa L. W. (1985) The current status of pit and fissure sealants: a review. Can. Dent. Assoc. J. 5, 367-379. Simonsen R. J. (1987) Retention and effectiveness of a single application of white sealant after 10 years. J. Am. Dent. Assoc. 115, 31-36. Wilson N. H. F., Wilson M. A. and Smith G. A. (1988) A clinical trial of a visible light cured posterior composite resin restorative material: four-year results. Quintessence ht. 19, 133-139.
Book Review The Dental Patient. Vol. I. Clinical Dentistry. Edited by C. Scully. Pp. 252. 1989. Oxford, Heinemann. Hardback, f 35.00.
There are a number of undergraduate texts available on the market which cover that difficult transition to becoming a clinical student. Volume I of the present series (we are promised four volumes) has to have a unique style that will make it an attractive book to buy and, once bought, read. The Dental Patient manages this well, for it is very well illustrated, committed heavily to tabular summaries of information and has further reading lists for the diligent. The pages are wide and the typeface easy to read. Photographic manipulation of illustrations demands firm editorial work: mostly, this has been achieved, but inevitably there are exceptions. Some of the photographs have been perfectly judged so as to show the part in question with its identifying anatomical features; a few are less so, with unnecessary material
that distracts the reader. The quality of reproduction of the radiographs and CT scans is generally poor, due to loss of both contrast and detail. This volume is edited by Professor Scully of Bristol Dental School, who is also the largest contributor. Much of the material can be found in his other textbooks that describe the subject of general diagnosis and management in more detail, yet throughout there is an appealing freshness and selective exclusion of detail. Some of the 10 chapters have more than one author, resulting in changes both in style and in presentation of the line drawings. Certain chapters are especially well written, for example ‘The Principles of Prescribing’; it will be hard to find a better vignette for the new clinical student. Perioperative management covers both consent as well as the practical aspects of full operating theatre conditions. There is some cross-referencing but the index is satisfactory. In all, a worthy book but it does compete with others on the market, including more by the same author. H. Cannell
