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Results of a new in vivo method of measuring occlusal wear in bruxists
Journal of Dentistry, 13, No. 2, 1985,
pp. 123-l
31 Prinfed in Great Britain
Results of a new in vivo method of measuring occlusal wear in bruxists” M. D. Russell, Department
MSc, BDS, FDS
of Restorative
Dentistry,
Birmingham
Dental Hospital
ABSTRACT Factors contributing to, and the role of parafunction in, the aetiology of occlusal wear are mentioned. A method of monitoring occlusal wear by recording dimensional changes in the thickness of silicone impressions under an acrylic onlay constructed directly in the mouth is described and the results presented. There was no statistically significant change in dimension of the impressions of faceted teeth when compared with those of non-faceted teeth over a six-month or one-year period. The need for a reliable method of monitoring occlusal wear is emphasized.
INTRODUCTION The difficulty of restoring severely worn dentitions is coupled with an uncertainty of the rate at which such wear occurs. It is also difficult to identify those individuals in whom it is likely to progress to a level which would require restoration. Whilst there may be more than one factor contributing to wear ( Table I), it is the opinion of the author that there is always a parafunctional overlay, an activity which varies in its recorded incidence ranging from 56 per cent (Shepherd, 197 1) in a group of patients attending the temporomandibular joint clinic, 8 1 per cent (Leof, 1944) of those suffering from periodontal disease to universal (Nadler, 1968) incidence in the population taken as a whole. Of the many signs indicative of parafunction (Table II), attrition patterns that do not conform to masticatory wear patterns have been said to be the most significant dental sign (Ramjford, 1970). The distinction between wear patterns which are due to normal function and those due to parafunction is not clear and presupposes, in the absence of an abrasive diet, that the teeth make contact during mastication, a contention disputed by some authors (Jankelson et al., 195 3; Thomson, 1975). It has been suggested that shiny facets with well-defined outlines are produced ‘almost exclusively’ during parafunction (Graf, 1969). In the present study, shiny wear facets have been taken as evidence of parafunction. The object of the study has been to compare the wear, if any, of a tooth exhibiting a shiny wear facet with a control tooth in the same mouth not exhibiting any faceting in a group of dental students over a period of one year.
MATERIALS
AND METHOD
The method devised is similar in principle to one described by Van Groeningen (198 1). An acrylic (Duralay Resin; Associated Dental Products, Swindon, UK) overlay was constructed *Presented at the Annual Conference of the British Society for the Study of Prosthetic Dentistry, Cardiff, 1984.
124
Journal of Dentistry,
Fig. 1. Construction of acrylic overlayoverwax-strip spacers using brush technique.
Vol. 1 ~/NO. 2 (1985)
Fig. 2. Injection of silicone impression reccssses in overlay.
material into
Table 1. Causes of tooth wear Disorders of tooth structures:
a inherited, e.g. amelogenesis imperfecta b, acquired, e.g. dental fluorosis
Diet:
a abrasive b, erosive Lack of posterior support Parafunction
Tab/e //. Signs of parafunction Occlusal or incisal wear facets Mobility of the teeth Migration of the teeth Fractures of the teeth Pain in and around the teeth Ridging of the buccal mucosa Scalloping of the lateral margins of the tongue Hypertrophy of the masseters Signs of mandibular dysfunction
over two selected teeth using the brush technique. One tooth was faceted, the other not. The overlay was spaced in the region of the tooth surface under investigation by an arbitrary thickness of wax (Kerrs Occlusal Indicator Wax; Cotterell’s & Co., London, UK) trimmed to form a narrow strip, folded at one end and draped over the buccal surface of the teeth (Fig. 1). The wax strips were removed when polymerization was complete and the recesses so formed were exposed fully by cutting back the buccal facing of the overlay before replacing it on the teeth. A silicone impression material (Xatlex; Wright Dental Sales (Birmingham) Ltd, UK)
125
Russell: Occlusal wear in bruxists
fig. 3. Orientation of impression out in paraffin wax.
prior to blocking
Fig. 4. Exposure of the impression after sectioning
cross-section of the on the microtome.
was then injected by means of a ‘jiffy tube’ into the recess until it overflowed onto the buccal surface, while light digital pressure was applied to the overlay where necessary to stabilise it (Fig. 2). The silicone was removed, the flash trimmed with a scalpel leaving a tail (produced by the buccal outflow) by which the impression could be handled. The impressions were subsequently blocked out in paraffin wax with the long axis perpendicular to the envisaged plane of section on a microtome (Fig. 3). Twenty-five millimetre cuts to a depth of O-5 mm were made into the specimen, revealing the cross-sectional area at that depth (Fig. 4). The width of the crosssection at the mid point of its length was measured using a Travelling microscope in combination with a specially constructed stage which could be advanced by measured distances perpendicular to each other (Fig. 5). The procedure was repeated using the same overlay six months and one year later. In a pilot study, tive such impressions were taken of one tooth in live students. Three cuts of 0.5 mm, 1.0 mm and 1.5 mm depths were made and width measurements taken after each cut for statistical analysis to test the reproducibility of the experimental method. The main study was conducted on 18 dental students and 2 dental surgery assistants who fulfilled the necessary criteria of having a faceted tooth and a control tooth which was not faceted. Of the 20 subjects, 8 were females and 12 were males, with ages ranging between 19 and 33 years.
126
Journal of Dentistry,
Vol. 1 ~/NO. 2 (1985)
\
\
PLA&C Fig. 5. General view of travelling stage.
microscope
and
\
IMPRESSION MATERIAL
PARAFFIN WAX \ \
CASSETTE
Fig. 6. Effect of ‘dragging’ of impression material during sectioning on microtome. The upper pat-t of the diagram represents a plan view of the end elevation in the lower part of the diagram.
RESULTS Pilot study The results of the pilot study are shown in Table III. The rows represent the individuals on whose teeth impressions were taken, the columns represent the five impressions taken and the figures within each cell represent the measurement taken after each of the three cuts. Following a twoway analysis of variance, it was found there was no statistically significant difference between values within the cells or between the columns. However, there was, a statistically significant difference between rows (P = OW24). This was due to the arbitrary thickness of the spacer varying by a small but apparently significant amount. Pairs of rows with reducing differences between the mean values for these thicknesses were then compared using a Student’s t test to determine the smallest difference which could be detected statistically. This was found to be between O-047 (for Dav and Fair P = O-0668) and 0.07 1 (Dav and Dar P= 0). Hence it was concluded that the experimental method was capable of detecting changes in the silicone rubber impressions of the order of 0.05 mm. By substituting into the formula
where X, -X2 = 0.05 and s = standard deviation, the smallest number, n, of the measurements required to detect changes of dimension of 0.05 was found to be 18.
127
Russell:Occlusalwear in bruxists
Tab/e ///. Data from pilotstudy
Measurement
1 2
1
3
1.22 Dar
2 2
1
1.12
1.28 1.56 1.53
Tab/e IV
1.29 1.43
1.32
1.51
1.35 1.22
1.29
1.52 1.18
1.39
1.19
1.44 1.02
1.21 0.92
1.39 1.75
1.26 1.21
1.35 Fea
1.34
1.57
1.42 1.32
1.30 1.20
1.59
1.43 1.31
1.37
1.46
1.19
1.48 Fai
1.11
1.24
1.35
1.51 1.49
1.30
3
1.25 1.14
1.36
1.40 1.36
5 2
1
1.27
1.14
1.36 1.20
3
1.23
1.21 1.25
1.37
4 2
1.28
1.37 1.39
1.30
1
1.16
1.35 1.33
3
1.21 1.13
1.37
no.
1.25 1.24
1.08
Eng
3
1.27 1.26
Dav
Specimen 3 1 2
1.30 1.49
1.44
Width measurements of siliconeimpressions during durationof study Commencement
Name J.B.D. G.E. P.M.G. J.C.H. A.R.H. U.K. X.L. A.D.L. AJ.L. P.J.M. T.L.M. RAM. S.R. J.S. H.S. M.S. G.S. N.D.T. Lw.
6 months
1 year
Con trot
Faceted
Control
Faceted
Control
Faceted
1.01 1.40 1.12 1.63 1.36 1.49 0.92 -
1.09 1.24 0.94 1.26 1.18 1.72 1.04 1.03 1.37 1.27 1.48 1.34 1.43 1.21 1.37 1.19 1.07 1.18 1.36
0.86 1.41 1.09 1.56 1.39 1.28 1.12 -
1.23 1.60 1.01 1.21 1.17 1.59 0.86 1.14 1.44 1.27 1.57 1.52 1.49 1.05 1.29 1.19 1.03 1.04 1.79
1.32 1.40 1.13 1.78 1.53 1.34 1.29 -
1.02 1.41 1.04 1.25 1.12 1.30 0.99 1.25 1.78 1.19 1.57 1.28 1.39 1.07 1.38 1.26 1.24 1.05 2.00
1.69 2.20 1.20 1.53 1.21 1.63 1.46 1.39 1.29 1.33 1.40
1.66 2.16 1.27 1.67 1.39 1.50 1.58 1.22 1.26 1.41 1.70
1.74 2.16 1.27 1.74 1.24 1.55 1.54 1.36 1.45 1.42 1.65
Main study The results are shown in Tables Wand Y the latter being the changes in dimension of silicone impressions over the one-year period: D, represents the change in dimension during the first six months, D, represents the change that occurred in the second six months and D, + D, the change which occurred over the whole of the one-year period. c andfrefer to the control and faceted teeth
128
Journal of Dentistry,
Table K Results of main study expressed D’C
D’f
-0.15 0.01 -0.03 a.07 0.03 -0.21 0.20 0.03 -0.03 -0.04 0.07 0.14 0.18 -0.13 0.12 -0.17 -0.03 0.08 0.30 x0.01
*
5
0.14 0.36 0.07 -0.05 -0.01 Xl.1 3 -0.18 0.1 1 0.07 0.00 0.09 0.18 0.06 -0.06 -0.08 0.00 -0.04 -0.14 0.43 0.043
D’c 0.46 0.01 0.04 0.22 0.14 0.06 0.17 0.08 0.08 0.00 0.00 0.07 -015 0.05 -0.04 0.14 0.19 0.01 -0.05 0.054
as dimensional
D’f
*
-0.21 -0.19 0.03 -0.04 -0.05 -0.29 0.13 0.1 1 0.34 -0.08 0.00 -0.24 -0.10 0.02 0.09 0.07 0.21 0.01 0.21 0.00 1
changes
D’c + D’c
of controlling
D’f+D’f
0.31 0.00 0.01 0.1 5 0.17 -0.15 0.37 0.11* 0.05 -0.04 0.07 0.21 0.03 -0.07 0.21 4.03 0.16 0.09 0.25
-0.07 0.17 0.13 -0.01 -0.06 -0.42 -0.05 0.22 0.41 -0.08 0.09 -0.06 -0.04 -0.04 0.01 0.07 0.17 -0.13 0.64
0.10
0.05
*Value calculated from average of other values. No non-faceted individual to serve as a control.
Tab/e VI. Methods
Vol. 1 ~/NO. 2 (1985)
tooth in this
bruxism
Autosuggestion (Boyens, 1940) Biofeedback (Dowdell er al, 1974) Automated relaxation training (Heller and Foargione, 1975) Massed Practice Therapy (Aver, 1976) Occlusal guards (Brayer and Erlich, 1976) Occlusal adjustment (Ramjford, 1961) Drug therapy (Chassins, 1959)
respectively. Individual A.D.L. had no teeth which were not faceted to serve as a control. An average value for D, was, therefore, calculated as indicated by the asterisk in Table I/ The difference between the mean changes in dimension of the silicone impressions of the faceted and control teeth during the second six-month period was 0.053 mm, which was the only value to approach statistical significance (P = O-068). However, the mean change in dimension of the impression of the non-faceted tooth was greater than that for the faceted tooth (0.054 mm and 0.001 mm, respectively).
DISCUSSION Several clinical approaches have been devised to control parafunction (Table VZ). The shortcoming in all these approaches is that there has been no satisfactory method of monitoring parafunction and, therefore, of testing the efficiency of the treatment designed to control it.
Russell: Occlusal wear in bruxists
129
Kardachi (1979) highlighted the problem associated with using electromyography to monitor parafunctional activity: seven consecutive nocturnal records were required to establish the average e.m.g. activity and a baseline from which subsequent comparisons could be made. Forgione (1974) devised an occlusal splint consisting of differentially coloured, microdotted laminae which became progressively exposed during bruxing activity. The number of microdots of the appropriately coloured lamina represented the level of bruxing activity. Whether the claimed reduction in parafunctional activity associated with wearing the splint is maintained after cessation of treatment remains uncertain (Mejias and Mehta, 1982). If occlusal wear is a significant sign of parafunction as has been suggested (Ramjford and Ash, 1970) then a method of measurement of occlusal wear would be useful in monitoring parafunction and testing the efficiency of treatments designed to control it. Xonga (1977) method of measuring tooth wear on silicone models in devised an in vitro stereomicroscopic relation to reference points. He recorded average tooth wear of 0.23-O-24 mm in bruxists compared with 0.04-006 mm in non-bruxists. In the present study, the difference between the mean change in dimension of the silicone impressions of the control and faceted teeth was 0.053 mm (P = 0.068), but was not statistically significant (P = 0.068). However, the mean change in dimension for the control teeth exceeded that for the faceted teeth (0.054 mm and 0.01 mm, respectively). If the hypothesis were correct then this value should have been0. Individual readings for both control and faceted teeth far exceeded the expected change in dimension: in some cases the values were in tenths of a millimetre rather than hundredths of a millimetre; in other cases negative values were obtained which, if taken literally, represented an augmentation of the tooth surface. There can be no rational explanation of these anomalies which can only be due to experimental error. The results suggest greater wear having occurred on the control teeth than on the faceted teeth. The results of the pilot study are disappointing, particularly in view of the encouraging results of the pilot study. Three causes of experimental error may be advanced: 1. The silicone impression tended to drag during sectioning and become extruded from the wax block (Fig. 6). The effect was to produce two outlines to the section when viewed under the microscope. Although the outer outline was taken as the true dimension, some error would have been introduced. 2. The second source of error, but one which would have occurred in the pilot study, was incorrect orientation of the impression during the blocking-out procedure (Fig. 7). However, to produce the magnitude of error encountered in some of the readings in the present study, the angle at which the impression would have to have been placed in the wax and to the subsequent plane of section would be obvious on visual inspection. 3. Acrylic resin undergoes a polymerization contraction. No allowance was made for this, the impressions being taken immediately after the acrylic overlay was constructed. The contraction which would have occurred could have affected the accuracy of the second record taken after the first six months. Since further contraction would not have occurred, the third record taken after the second six months would not have been similarly affected. 4. Where the outline of the cut surface of the impressions was not regular (this was especially so with those of the non-faceted control teeth), the point at which the measurement of the width of the impression was made would be critical and adversely affected where opposite sides diverged markedly, in spite of adopting the rule of measuring at the midpoint of the length of the impression.
130
Journal of Dentistry, Vol. 1 ~/NO. 2 (1985)
f =dxcos0
Fig. 7. Effect of incorrection orientation of impressions during blocking out in paraffin wax. Assuming a true dimension dof 1.5 mm, for the’false’ dimension
f to be more than 1.55 mm, the angle ’ would have to be more than 18”.
While the results of this study have been inconclusive, the quest for a method of measuring occlusal wear remains a goal worth pursuing. Without an objective means of monitoring occlusal wear, there can be no rationale behind the many proposed treatment methods alleged to control it.
Acknowledgements The author wishes to thank Mr M. J. Shaw for his encouragement and inspiration, Professor R Browne for access to the oral pathology laboratory facilities and Mr F. Duncombe and Mr S. Bovis for technical assistance.
REFERENCES Ayer W. A (1976) Massed practice exercises for the elimination of tooth grinding habits. Behav. Res. Ther. 14, 163. Boyens P. J. ( 1940) Value of autosuggestion in therapy of bruxism and other biting habits. J. Am. Dent. Assoc. 27, 1773. Brayer L. and Erlich J. (1976) The night guard: its uses and dangers of abuse. J. Oral Rehabil. 3, 188. Chasins A. F. (1959) Methocarbamol as an adjunct in the treatment of bruxism. J. Dent. Med 14, 166. Dowdell L. R, Clark N. G. and Kardachi B. J. (1974) Biofeedback: control of masticatory muscle spasm. Med BioL Eng. 14,295. Forgione A. G. (1974) A simple but effective method of quantifying bruxism behaviour. J. Dent. Res. 53, (Special issue) Abstract 292, 127. Graf H. (1969) Bruxism. Dent. CZin. North Am. 13, 659. Heller R F. and Forgione A. G. (1975) An evaluation of bruxism control: massed positive proactive and automated relaxation training. J. Dent. Res. 54, 1120. Jankelson B., Hoffman G. M. and Hem-iron J. A. (1953) The physiology of the stomatognathic system. J. Am. Dent. Assoc. 46, 375. Kardachi B. J. R (1979) A comparison of biofeedback and occlusal adjustment in bruxism. J. Periodontal. 49, 367. Leaf M. (1944) Clamping and grinding habits: their relationship to periodontal disease. J. Am. Dent, Assoc. 31, 184.
Russell: Occlusal wear in bruxists
131
Mejias J. E. and Mehta N. R (1982) Subjective and objective evaluation of bruxing patients undergoing short term splint therapy. J. Oral Rehabil. 9, 279. Nadler S. C. (1968) The importance of bruxism. .I. Oral Med 23, 142. Ramjford S. P. ( 196 1) Bruxism: a clinical and electromyographic study. J. Am. Dent. Assoc. 62, 21.
Ramjford S. and Ash M. (1970) Occlusion. Philadelphia, Saunders, p. 23 1. Shepherd R W. (197 1) Bruxism: the changing situation. Aust. Dent. J. 16, 243. Thomson H. (1975) Occlusion. Bristol, Wright, chap. 6, pp. 89-90. Van Groeningen G. (1981) Zn vivo abrasion of composites: a quantitative Quintessence In& 12, 1101. Xonga F. A. (1977) Bruxism and its effect on the teeth. J. Oral Rehabil. 4, 65.
investigation.
pp. 123-l
31 Prinfed in Great Britain
Results of a new in vivo method of measuring occlusal wear in bruxists” M. D. Russell, Department
MSc, BDS, FDS
of Restorative
Dentistry,
Birmingham
Dental Hospital
ABSTRACT Factors contributing to, and the role of parafunction in, the aetiology of occlusal wear are mentioned. A method of monitoring occlusal wear by recording dimensional changes in the thickness of silicone impressions under an acrylic onlay constructed directly in the mouth is described and the results presented. There was no statistically significant change in dimension of the impressions of faceted teeth when compared with those of non-faceted teeth over a six-month or one-year period. The need for a reliable method of monitoring occlusal wear is emphasized.
INTRODUCTION The difficulty of restoring severely worn dentitions is coupled with an uncertainty of the rate at which such wear occurs. It is also difficult to identify those individuals in whom it is likely to progress to a level which would require restoration. Whilst there may be more than one factor contributing to wear ( Table I), it is the opinion of the author that there is always a parafunctional overlay, an activity which varies in its recorded incidence ranging from 56 per cent (Shepherd, 197 1) in a group of patients attending the temporomandibular joint clinic, 8 1 per cent (Leof, 1944) of those suffering from periodontal disease to universal (Nadler, 1968) incidence in the population taken as a whole. Of the many signs indicative of parafunction (Table II), attrition patterns that do not conform to masticatory wear patterns have been said to be the most significant dental sign (Ramjford, 1970). The distinction between wear patterns which are due to normal function and those due to parafunction is not clear and presupposes, in the absence of an abrasive diet, that the teeth make contact during mastication, a contention disputed by some authors (Jankelson et al., 195 3; Thomson, 1975). It has been suggested that shiny facets with well-defined outlines are produced ‘almost exclusively’ during parafunction (Graf, 1969). In the present study, shiny wear facets have been taken as evidence of parafunction. The object of the study has been to compare the wear, if any, of a tooth exhibiting a shiny wear facet with a control tooth in the same mouth not exhibiting any faceting in a group of dental students over a period of one year.
MATERIALS
AND METHOD
The method devised is similar in principle to one described by Van Groeningen (198 1). An acrylic (Duralay Resin; Associated Dental Products, Swindon, UK) overlay was constructed *Presented at the Annual Conference of the British Society for the Study of Prosthetic Dentistry, Cardiff, 1984.
124
Journal of Dentistry,
Fig. 1. Construction of acrylic overlayoverwax-strip spacers using brush technique.
Vol. 1 ~/NO. 2 (1985)
Fig. 2. Injection of silicone impression reccssses in overlay.
material into
Table 1. Causes of tooth wear Disorders of tooth structures:
a inherited, e.g. amelogenesis imperfecta b, acquired, e.g. dental fluorosis
Diet:
a abrasive b, erosive Lack of posterior support Parafunction
Tab/e //. Signs of parafunction Occlusal or incisal wear facets Mobility of the teeth Migration of the teeth Fractures of the teeth Pain in and around the teeth Ridging of the buccal mucosa Scalloping of the lateral margins of the tongue Hypertrophy of the masseters Signs of mandibular dysfunction
over two selected teeth using the brush technique. One tooth was faceted, the other not. The overlay was spaced in the region of the tooth surface under investigation by an arbitrary thickness of wax (Kerrs Occlusal Indicator Wax; Cotterell’s & Co., London, UK) trimmed to form a narrow strip, folded at one end and draped over the buccal surface of the teeth (Fig. 1). The wax strips were removed when polymerization was complete and the recesses so formed were exposed fully by cutting back the buccal facing of the overlay before replacing it on the teeth. A silicone impression material (Xatlex; Wright Dental Sales (Birmingham) Ltd, UK)
125
Russell: Occlusal wear in bruxists
fig. 3. Orientation of impression out in paraffin wax.
prior to blocking
Fig. 4. Exposure of the impression after sectioning
cross-section of the on the microtome.
was then injected by means of a ‘jiffy tube’ into the recess until it overflowed onto the buccal surface, while light digital pressure was applied to the overlay where necessary to stabilise it (Fig. 2). The silicone was removed, the flash trimmed with a scalpel leaving a tail (produced by the buccal outflow) by which the impression could be handled. The impressions were subsequently blocked out in paraffin wax with the long axis perpendicular to the envisaged plane of section on a microtome (Fig. 3). Twenty-five millimetre cuts to a depth of O-5 mm were made into the specimen, revealing the cross-sectional area at that depth (Fig. 4). The width of the crosssection at the mid point of its length was measured using a Travelling microscope in combination with a specially constructed stage which could be advanced by measured distances perpendicular to each other (Fig. 5). The procedure was repeated using the same overlay six months and one year later. In a pilot study, tive such impressions were taken of one tooth in live students. Three cuts of 0.5 mm, 1.0 mm and 1.5 mm depths were made and width measurements taken after each cut for statistical analysis to test the reproducibility of the experimental method. The main study was conducted on 18 dental students and 2 dental surgery assistants who fulfilled the necessary criteria of having a faceted tooth and a control tooth which was not faceted. Of the 20 subjects, 8 were females and 12 were males, with ages ranging between 19 and 33 years.
126
Journal of Dentistry,
Vol. 1 ~/NO. 2 (1985)
\
\
PLA&C Fig. 5. General view of travelling stage.
microscope
and
\
IMPRESSION MATERIAL
PARAFFIN WAX \ \
CASSETTE
Fig. 6. Effect of ‘dragging’ of impression material during sectioning on microtome. The upper pat-t of the diagram represents a plan view of the end elevation in the lower part of the diagram.
RESULTS Pilot study The results of the pilot study are shown in Table III. The rows represent the individuals on whose teeth impressions were taken, the columns represent the five impressions taken and the figures within each cell represent the measurement taken after each of the three cuts. Following a twoway analysis of variance, it was found there was no statistically significant difference between values within the cells or between the columns. However, there was, a statistically significant difference between rows (P = OW24). This was due to the arbitrary thickness of the spacer varying by a small but apparently significant amount. Pairs of rows with reducing differences between the mean values for these thicknesses were then compared using a Student’s t test to determine the smallest difference which could be detected statistically. This was found to be between O-047 (for Dav and Fair P = O-0668) and 0.07 1 (Dav and Dar P= 0). Hence it was concluded that the experimental method was capable of detecting changes in the silicone rubber impressions of the order of 0.05 mm. By substituting into the formula
where X, -X2 = 0.05 and s = standard deviation, the smallest number, n, of the measurements required to detect changes of dimension of 0.05 was found to be 18.
127
Russell:Occlusalwear in bruxists
Tab/e ///. Data from pilotstudy
Measurement
1 2
1
3
1.22 Dar
2 2
1
1.12
1.28 1.56 1.53
Tab/e IV
1.29 1.43
1.32
1.51
1.35 1.22
1.29
1.52 1.18
1.39
1.19
1.44 1.02
1.21 0.92
1.39 1.75
1.26 1.21
1.35 Fea
1.34
1.57
1.42 1.32
1.30 1.20
1.59
1.43 1.31
1.37
1.46
1.19
1.48 Fai
1.11
1.24
1.35
1.51 1.49
1.30
3
1.25 1.14
1.36
1.40 1.36
5 2
1
1.27
1.14
1.36 1.20
3
1.23
1.21 1.25
1.37
4 2
1.28
1.37 1.39
1.30
1
1.16
1.35 1.33
3
1.21 1.13
1.37
no.
1.25 1.24
1.08
Eng
3
1.27 1.26
Dav
Specimen 3 1 2
1.30 1.49
1.44
Width measurements of siliconeimpressions during durationof study Commencement
Name J.B.D. G.E. P.M.G. J.C.H. A.R.H. U.K. X.L. A.D.L. AJ.L. P.J.M. T.L.M. RAM. S.R. J.S. H.S. M.S. G.S. N.D.T. Lw.
6 months
1 year
Con trot
Faceted
Control
Faceted
Control
Faceted
1.01 1.40 1.12 1.63 1.36 1.49 0.92 -
1.09 1.24 0.94 1.26 1.18 1.72 1.04 1.03 1.37 1.27 1.48 1.34 1.43 1.21 1.37 1.19 1.07 1.18 1.36
0.86 1.41 1.09 1.56 1.39 1.28 1.12 -
1.23 1.60 1.01 1.21 1.17 1.59 0.86 1.14 1.44 1.27 1.57 1.52 1.49 1.05 1.29 1.19 1.03 1.04 1.79
1.32 1.40 1.13 1.78 1.53 1.34 1.29 -
1.02 1.41 1.04 1.25 1.12 1.30 0.99 1.25 1.78 1.19 1.57 1.28 1.39 1.07 1.38 1.26 1.24 1.05 2.00
1.69 2.20 1.20 1.53 1.21 1.63 1.46 1.39 1.29 1.33 1.40
1.66 2.16 1.27 1.67 1.39 1.50 1.58 1.22 1.26 1.41 1.70
1.74 2.16 1.27 1.74 1.24 1.55 1.54 1.36 1.45 1.42 1.65
Main study The results are shown in Tables Wand Y the latter being the changes in dimension of silicone impressions over the one-year period: D, represents the change in dimension during the first six months, D, represents the change that occurred in the second six months and D, + D, the change which occurred over the whole of the one-year period. c andfrefer to the control and faceted teeth
128
Journal of Dentistry,
Table K Results of main study expressed D’C
D’f
-0.15 0.01 -0.03 a.07 0.03 -0.21 0.20 0.03 -0.03 -0.04 0.07 0.14 0.18 -0.13 0.12 -0.17 -0.03 0.08 0.30 x0.01
*
5
0.14 0.36 0.07 -0.05 -0.01 Xl.1 3 -0.18 0.1 1 0.07 0.00 0.09 0.18 0.06 -0.06 -0.08 0.00 -0.04 -0.14 0.43 0.043
D’c 0.46 0.01 0.04 0.22 0.14 0.06 0.17 0.08 0.08 0.00 0.00 0.07 -015 0.05 -0.04 0.14 0.19 0.01 -0.05 0.054
as dimensional
D’f
*
-0.21 -0.19 0.03 -0.04 -0.05 -0.29 0.13 0.1 1 0.34 -0.08 0.00 -0.24 -0.10 0.02 0.09 0.07 0.21 0.01 0.21 0.00 1
changes
D’c + D’c
of controlling
D’f+D’f
0.31 0.00 0.01 0.1 5 0.17 -0.15 0.37 0.11* 0.05 -0.04 0.07 0.21 0.03 -0.07 0.21 4.03 0.16 0.09 0.25
-0.07 0.17 0.13 -0.01 -0.06 -0.42 -0.05 0.22 0.41 -0.08 0.09 -0.06 -0.04 -0.04 0.01 0.07 0.17 -0.13 0.64
0.10
0.05
*Value calculated from average of other values. No non-faceted individual to serve as a control.
Tab/e VI. Methods
Vol. 1 ~/NO. 2 (1985)
tooth in this
bruxism
Autosuggestion (Boyens, 1940) Biofeedback (Dowdell er al, 1974) Automated relaxation training (Heller and Foargione, 1975) Massed Practice Therapy (Aver, 1976) Occlusal guards (Brayer and Erlich, 1976) Occlusal adjustment (Ramjford, 1961) Drug therapy (Chassins, 1959)
respectively. Individual A.D.L. had no teeth which were not faceted to serve as a control. An average value for D, was, therefore, calculated as indicated by the asterisk in Table I/ The difference between the mean changes in dimension of the silicone impressions of the faceted and control teeth during the second six-month period was 0.053 mm, which was the only value to approach statistical significance (P = O-068). However, the mean change in dimension of the impression of the non-faceted tooth was greater than that for the faceted tooth (0.054 mm and 0.001 mm, respectively).
DISCUSSION Several clinical approaches have been devised to control parafunction (Table VZ). The shortcoming in all these approaches is that there has been no satisfactory method of monitoring parafunction and, therefore, of testing the efficiency of the treatment designed to control it.
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Kardachi (1979) highlighted the problem associated with using electromyography to monitor parafunctional activity: seven consecutive nocturnal records were required to establish the average e.m.g. activity and a baseline from which subsequent comparisons could be made. Forgione (1974) devised an occlusal splint consisting of differentially coloured, microdotted laminae which became progressively exposed during bruxing activity. The number of microdots of the appropriately coloured lamina represented the level of bruxing activity. Whether the claimed reduction in parafunctional activity associated with wearing the splint is maintained after cessation of treatment remains uncertain (Mejias and Mehta, 1982). If occlusal wear is a significant sign of parafunction as has been suggested (Ramjford and Ash, 1970) then a method of measurement of occlusal wear would be useful in monitoring parafunction and testing the efficiency of treatments designed to control it. Xonga (1977) method of measuring tooth wear on silicone models in devised an in vitro stereomicroscopic relation to reference points. He recorded average tooth wear of 0.23-O-24 mm in bruxists compared with 0.04-006 mm in non-bruxists. In the present study, the difference between the mean change in dimension of the silicone impressions of the control and faceted teeth was 0.053 mm (P = 0.068), but was not statistically significant (P = 0.068). However, the mean change in dimension for the control teeth exceeded that for the faceted teeth (0.054 mm and 0.01 mm, respectively). If the hypothesis were correct then this value should have been0. Individual readings for both control and faceted teeth far exceeded the expected change in dimension: in some cases the values were in tenths of a millimetre rather than hundredths of a millimetre; in other cases negative values were obtained which, if taken literally, represented an augmentation of the tooth surface. There can be no rational explanation of these anomalies which can only be due to experimental error. The results suggest greater wear having occurred on the control teeth than on the faceted teeth. The results of the pilot study are disappointing, particularly in view of the encouraging results of the pilot study. Three causes of experimental error may be advanced: 1. The silicone impression tended to drag during sectioning and become extruded from the wax block (Fig. 6). The effect was to produce two outlines to the section when viewed under the microscope. Although the outer outline was taken as the true dimension, some error would have been introduced. 2. The second source of error, but one which would have occurred in the pilot study, was incorrect orientation of the impression during the blocking-out procedure (Fig. 7). However, to produce the magnitude of error encountered in some of the readings in the present study, the angle at which the impression would have to have been placed in the wax and to the subsequent plane of section would be obvious on visual inspection. 3. Acrylic resin undergoes a polymerization contraction. No allowance was made for this, the impressions being taken immediately after the acrylic overlay was constructed. The contraction which would have occurred could have affected the accuracy of the second record taken after the first six months. Since further contraction would not have occurred, the third record taken after the second six months would not have been similarly affected. 4. Where the outline of the cut surface of the impressions was not regular (this was especially so with those of the non-faceted control teeth), the point at which the measurement of the width of the impression was made would be critical and adversely affected where opposite sides diverged markedly, in spite of adopting the rule of measuring at the midpoint of the length of the impression.
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Journal of Dentistry, Vol. 1 ~/NO. 2 (1985)
f =dxcos0
Fig. 7. Effect of incorrection orientation of impressions during blocking out in paraffin wax. Assuming a true dimension dof 1.5 mm, for the’false’ dimension
f to be more than 1.55 mm, the angle ’ would have to be more than 18”.
While the results of this study have been inconclusive, the quest for a method of measuring occlusal wear remains a goal worth pursuing. Without an objective means of monitoring occlusal wear, there can be no rationale behind the many proposed treatment methods alleged to control it.
Acknowledgements The author wishes to thank Mr M. J. Shaw for his encouragement and inspiration, Professor R Browne for access to the oral pathology laboratory facilities and Mr F. Duncombe and Mr S. Bovis for technical assistance.
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investigation.