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Tongue position in relation to edentulous mandibular impressions
REMOVABLE PROSTHODONTICS SECTIO~N EDI1‘ORS LOUIS
BLATTERFEIN
S. HOWARD
PAYNE
Tongue position in relation mandibular impressions H. Kotkin, University
B.D.S., M.Sc.(Dent),* of the Witwatersrand,
to edentulous
and J. C. G. Slabbert,
School of Dentistry,
Johannesburg,
B.D.S., H. Dip. Dent., M. Dent.** South Africa
T
ongue position has an important bearing on impression-making and the subsequent ability of a patient to manage with a mandibular denture. A tongue that is habitually postured in a retracted position has been equated with poor mandibular denture stability.le3 Retraction of the tip of the tongue has also been related to overall change in the shape and position of the tongue, which has been shown to occur in response to loss of oral bulk-occupying structures.4a5 The dimension of change was found to be commensurate with the degree of resorption that had taken place. The question arises as to whether control of tongue position during impression-making will produce a mandibular denture base with a form more acceptable to the patient with advanced resorption of the mandibular residual ridge. The purpose of this study is to describe an impression technique that provides a mandibular denture base with contours that encourage anterior positioning of the tongue for effective harnessing of the stabilizing and retentive forces exerted in this forward position.
Fig. 1. Trimmed impression tray.
METHOD The technique is essentially aimed at sublingual border molding. An impression tray that is 2 to 3 mm short of the depth of sulcus is constructed from a primary impression (Fig. 1). The tray handle, which can be called the localizing handle, serves as a device for positioning the tongue during impression-making. It can be fashioned from thick but flexible wire bent into a flattened arch with an attachment arm at either end. The key furnished with many impression material tubes is a useful source of wire. The height of the arch is approximately 15 mm and it spans the estimated intercanine distance of the proposed denture (Fig. 2). The tray is checked in the mouth for overextension and corrected where necessary before attaching the localizing handle. The attachment arms of the localizing handle are embedded into mounds of softened red impression compound placed on the outer surface of the tray (Fig. 3). While the compound is still soft, the tray is *I,e~turer, Depmrrnent of Prosthetic Dentistry. “*Flead, Ikpartment of Prosthetic Dentistry. 458
Fig. 2. Wire bent into shape of a flattened arch to form localizing handle.
positioned in the mouth and the patient is instructed to protrude the tip of the tongue through the arch of the localizing handle and to place it firmly against the vermillion zone of the lower lip. The tongue will thereby assume what can be called the lingual impression position. In this position, the tongue will also push the localizing handle, which at this stage is attached to the impression tray with softened compound, to the required vertical position relative to the tray (Fig. 4). Although the tray is usually kept in position by the patient’s APRIL
1987
VOLUME
57
NUMBER
4
TONGUE
POSITION
AND
MANDIBULAR
Fig. 3. Localizing
Fig. 4. Tongue related impression position.
IMPRESSIONS
handle attached to tray.
to localizing
handle
it is advisable for the dentist to assist in maintaining its stability. A generous amount of tempered and softened black impression compound (Sybron/Kerr, Romulus, Mich.) is then loaded into the inner intercanine section of the tray and the tray is seated in the mouth. The patient is instructed to place the tongue in the lingual impression position and to thrust it forcefully against the strongly resisting lower lip. The anterior lingual region is thus border-molded to establish a mechanism for tongue control in the form of a lingual guiding ramp (Figs. 5 and 6). Labial borders are simultaneously molded by finger manipulation. Overextension is corrected by repeating these procedures until the labial and anterolingual borders are judged to be correct (Fig. 7). The posterior sections of the tray are loaded separately. Progressive lingual border-molding is effected through muscular forces generated by the tongue as it repeatedly and forcefully assumes the lingual impression position. The posterior origin of the lingual guiding ramp will also be formed by this procedure. Buccal OF PROSTHETIC
DENTISTRY
ramp
fash-
in lingual Fig. 6. Superior
tongue,
THE JOURNAL
Fig. 5. Posterolingual aspect of guiding ioned f&m black compound.
aspect of lingual
guiding
ramp.
borders are molded by hand manipulation. Because border-molding is accomplished through strong muscle forces and by firm manipulation of the cheeks, it is not necessary to reduce borders before making the secondary impression. However, impression regions related to the mylohyoid ridge and other bony prominences should be scraped to a depth of approximately 1 mm to avoid pressure on these potentially sensitive regions (Fig. 8). A thin impression is made with zinc oxide-eugenol impression material while the patient is instructed to exert a gentle tongue and lip pressure in assuming the lingual impression position. Gentle manipulation is sufficient to border mold the buccal and labial borders (Fig. 9). The impression is boxed and a cast is poured in artificial stone. The integrity of the established contours must be carefully maintained (Fig. 10) and reproduced in the trial denture (Fig. 11) and the completed mandibular denture (Fig. 12). At all appointments, the important role of the tongue in controlling the mandibular denture is explained and emphasized. This type of 459
KOTKIN
Fig. 7. Undersurface molded anterolingual
of impression tray shows borderand labial borders.
Fig. 8. Completed
compound
Fig. 9. Final zinc oxide-eugenol
impression.
paste impression.
reinforcement is integral to the psychophysiologic preparation of the patient for acceptance of the denture.
DISCUSSION RATIONALE
AND TREATMENT
The basis of this impression technique is the fabrication of a mandibular denture that will restore oral bulk 460
Fig. 10. Borders of sublingual poured cast.
guiding
AND
SLABBERT
ramp marked on
Fig. 11. Trial denture.
Fig. 12. Completed denture. rounded at marked borders ramp.
and provide
a stabilizing
Sharp contours were of sublingual guiding
lingual
guiding
ramp
(Fig.
12). The guiding ramp is formed under the influence of controlled muscular activity in the region of the mandibular anterior teeth. Such activity is mediated through the localizing handle, which is purposely located in the region previously occupied by the mandibular anterior APRIL
1987
VOLUME
57
NUMBER
4
TONGUE
POSITION
AND
MANDIBULAR
IMPRESSIONS
Sublin Salivary
Fig. 13. A representation of a sublingual guiding ramp in sagittal section illustrates relationship of soft and bony tissues to denture. Tongue is in a favorable anterior position as-depicted in Fig. 4..
teeth. Border-molding of the lingual guiding ramp depends to a large extent on the activity of the genioglossus muscle. Marked electromyographic activity has been recorded in this muscle when it acts against resistancc.D When the tongue is protruded in the absence of such resistance, surprisingly little electromyographic activity is produced. These findings imply that the bordermolding activity of the genioglossus muscle will be enhanced by the resistance offered by the lip, as the tongue, guided by the localizing handle, exerts pressure against it. Under the influence of the guiding ramp, the tongue is encouraged to assume a normal position as described by Wright et a1.2.’ In this particular position, the tip of the tongue is in contact with the mandibular incisors while its distal margins are related to the lingual surfaces of the posterior teeth. Brill et al.’ describe a comparable tongue position that would also be conducive to good muscular control of the mandibular denture. The tongue, with its inferior surface in apposition to the ramp, will also assume a high position relative to the resorbed mandibular residual ridge. Such a position is similar to the high tongue position that Heath’ recorded for piezographs molded in mouths with advanced resorption of the mandibular residual ridge. The posteroinferior border of the guiding ramp is related to the sublingual glands and the genioglossus muscle (Fig. 13). Forward positioning of an active or passive tongue will impart favorable stabilizing and retentive forces that will act through the ramp. In addition, and in accordance with the Jorgensen formula cited by Brill,” physical retentive forces will be enhanced by the wider sublingual borders. The highly resilient sublingual tissues have a valvular effect against such borders thereby enhancing the border seal. THE IOURNAL
OF PROSTHETIC
DENTISTRY
According to Fish,“, 5 the progressive loss of oral bulk in the edentulous patient is accompanied by a commensurate shortening and broadening of the tongue. He therefore infers that this behavior is a compensatory response, a functional demand on the tongue to form part of the anterior wall of the respiratory tract. This concept is supported by central nervous system connections and controls as evidenced by the so-called “tonguesafety” function of the genioglossus muscle.’ This muscle shows increased electromyographic activity on inspiration during sleeping and during waking hours thereby assisting in the maintenance of a patent airway. Another study by Richardson and Allen” confirms most of Fish’s findings but they were unable to demonstrate tongueshortening in their subjects. This discrepancy between the two studies can be explained on the basis of the considerable differences in the periods of edentulousness in the two groups of subjects. A corollary to Fish’s4, 5 findings suggests that the tongue would be encouraged to assume an anterior position should lost oral bulk be restored with a denture fabricated according to principles in the described impression technique. In the course of his piezographic studies, Heath’ observed that when the amounts of gel used to form shapes of the potential denture space were increased, the increased bulk was accommodated lingually by a subject with severe resorption and in the vestibule by a subject with a prominent ridge. These observations indicate that sublingual extensions that can be tolerated extremely well by patients with advanced resorption may not be that well tolerated by patients with prominent residual ridges. Numerous well-tried impression techniques already exist for patients with satisfactory ridges and sublingual extensions may exceed their tolerance for the additional denture bulk. 461
KOTKIN
SUMMARY
AND CONCLUSIONS
stability 4. 5. 6.
8. 9. IO.
2.
3.
Are anterior D. Ray McArthur, University
of North
replacement
kNT
1966;
Fish F. The functional anatomy of the rest position of the mandible. Dent Pratt 1961;11:178-88. Fish SF. The respiratory associations of the rest position of the mandible. Br Dent J 1964;116:149-59. Basmajian JV. Muscles alive: their functions revealed by electromyography. 4th ed. Baltimore: Williams & Wilkins Co, 1978; Brill N, Tryde G, Cantor R. The dynamic nature of the lower denture space. J PROSTHET DENT 1965;15:401-18. Heath R. A study of the morphology of the denture space. Dent Pratt Dent Ret 1970;21:109-17. Brill N. Factors in the mechanism of full denture retention: a discussion of selected papers. Dent Pratt 1967;18:9-19. Richardson A, Allen R. Mandibular posture following tooth extraction. J Dent 1980;8:315-20.
Re,hnnl reque\1c 10: DR. H. KOTKIN UNIVERSITY OF THE WITWATERSRAND Scrmo~ OF DENTISTRY 1 JAN SMUTS AVE. JOHANNESBURG 2001 SoLlTFr AFRICA
teeth too small?
D.D.S., M.S.* Carolina,
School of Dentistry,
Chapel
W
Hill,
oodhead’ expressed concern that anterior artificial teeth may be slightly smaller than their natural counterparts. McArthur* observed that patient complaints generally relate to the maxillary central incisor being perceived as too large rather than too small. Actually, the mesiodistal, rather than the incisogingival measurement, is probably the more critical dimension for an anterior replacement tooth. In a previous study, measurements on orthodontic casts determined the mean mesiodistal width for the permanent maxillary right central incisor to be 8.86 mm.’ This value is similar to that reported by others.3-9 The mean, sex-specific incisor diameters were found to be 8.96 mm for men and 8.79 for women.’ Other studies also showed men to have larger incisor teeth than women’0-‘4 and black persons to have larger incisors than Caucasians.“-“’ The purpose of this study was to determine the
*Associate Professor. Department of Removable Prosthodontics 462
PRO5TflET
359-362. 7.
REFERENCES hlarmor I?. Hebertson JE. The use of swallowing in making complete kwer impressions. J PROSTHET DENT 1968;19:20818. Wright CR, Muyskens JH, Strong LH, Westerman KN, Kingery RH. Williams ST. A study of the tongue and its relation to denture stability. J Am Dent Assoc 1949;39:269-75. Wright CR Evaluation of the factors necessary to develop
dentures. J
SLABBERT
16:414-30.
An adjustable easily located impression tray handle was used as a device to control tongue position and muscular forces for mandibular complete denture impression-making. This technique is indicated where advanced residual ridge resorption is present. A denture made with a lingual guiding ramp conforming to such an impression is not a panacea for all mandibular denture problems, which have many complex causes. However, the lingual guiding ramp technique gains support from established physiological findings and can yield gratifying clinical results.
I.
in mandibular
AND
N.C.
mesiodistal width of a maxillary right central incisor for natural and replacement dentitions. The natural dentitions were represented by samples of subjects from varying age groups. It was assumed that there would be a decrease in the mesiodistal incisor width in the older age groups. For the most part, the reduction in width represents proximal wear. However, significant incisal wear of tapering tooth forms will also contribute to a reduced mesiodistal width. Tooth wear is normal and is only considered pathologic when the survival of the tooth is in jeopardy.20-22 METHODS In a previous study, a sharpened Boley gauge was used to measure the maximum width of the permanent maxillary right central incisor to the nearest 0.1 mm on casts from orthodontic patients whose treatment had been completed.’ The original sample consisted of 56 women and 44 men. This method was repeated and the sample size was increased by 400 casts with 281 women and 219 men in the expanded sample. APRIL
1987
VOLUME
57
NUMBER
4
BLATTERFEIN
S. HOWARD
PAYNE
Tongue position in relation mandibular impressions H. Kotkin, University
B.D.S., M.Sc.(Dent),* of the Witwatersrand,
to edentulous
and J. C. G. Slabbert,
School of Dentistry,
Johannesburg,
B.D.S., H. Dip. Dent., M. Dent.** South Africa
T
ongue position has an important bearing on impression-making and the subsequent ability of a patient to manage with a mandibular denture. A tongue that is habitually postured in a retracted position has been equated with poor mandibular denture stability.le3 Retraction of the tip of the tongue has also been related to overall change in the shape and position of the tongue, which has been shown to occur in response to loss of oral bulk-occupying structures.4a5 The dimension of change was found to be commensurate with the degree of resorption that had taken place. The question arises as to whether control of tongue position during impression-making will produce a mandibular denture base with a form more acceptable to the patient with advanced resorption of the mandibular residual ridge. The purpose of this study is to describe an impression technique that provides a mandibular denture base with contours that encourage anterior positioning of the tongue for effective harnessing of the stabilizing and retentive forces exerted in this forward position.
Fig. 1. Trimmed impression tray.
METHOD The technique is essentially aimed at sublingual border molding. An impression tray that is 2 to 3 mm short of the depth of sulcus is constructed from a primary impression (Fig. 1). The tray handle, which can be called the localizing handle, serves as a device for positioning the tongue during impression-making. It can be fashioned from thick but flexible wire bent into a flattened arch with an attachment arm at either end. The key furnished with many impression material tubes is a useful source of wire. The height of the arch is approximately 15 mm and it spans the estimated intercanine distance of the proposed denture (Fig. 2). The tray is checked in the mouth for overextension and corrected where necessary before attaching the localizing handle. The attachment arms of the localizing handle are embedded into mounds of softened red impression compound placed on the outer surface of the tray (Fig. 3). While the compound is still soft, the tray is *I,e~turer, Depmrrnent of Prosthetic Dentistry. “*Flead, Ikpartment of Prosthetic Dentistry. 458
Fig. 2. Wire bent into shape of a flattened arch to form localizing handle.
positioned in the mouth and the patient is instructed to protrude the tip of the tongue through the arch of the localizing handle and to place it firmly against the vermillion zone of the lower lip. The tongue will thereby assume what can be called the lingual impression position. In this position, the tongue will also push the localizing handle, which at this stage is attached to the impression tray with softened compound, to the required vertical position relative to the tray (Fig. 4). Although the tray is usually kept in position by the patient’s APRIL
1987
VOLUME
57
NUMBER
4
TONGUE
POSITION
AND
MANDIBULAR
Fig. 3. Localizing
Fig. 4. Tongue related impression position.
IMPRESSIONS
handle attached to tray.
to localizing
handle
it is advisable for the dentist to assist in maintaining its stability. A generous amount of tempered and softened black impression compound (Sybron/Kerr, Romulus, Mich.) is then loaded into the inner intercanine section of the tray and the tray is seated in the mouth. The patient is instructed to place the tongue in the lingual impression position and to thrust it forcefully against the strongly resisting lower lip. The anterior lingual region is thus border-molded to establish a mechanism for tongue control in the form of a lingual guiding ramp (Figs. 5 and 6). Labial borders are simultaneously molded by finger manipulation. Overextension is corrected by repeating these procedures until the labial and anterolingual borders are judged to be correct (Fig. 7). The posterior sections of the tray are loaded separately. Progressive lingual border-molding is effected through muscular forces generated by the tongue as it repeatedly and forcefully assumes the lingual impression position. The posterior origin of the lingual guiding ramp will also be formed by this procedure. Buccal OF PROSTHETIC
DENTISTRY
ramp
fash-
in lingual Fig. 6. Superior
tongue,
THE JOURNAL
Fig. 5. Posterolingual aspect of guiding ioned f&m black compound.
aspect of lingual
guiding
ramp.
borders are molded by hand manipulation. Because border-molding is accomplished through strong muscle forces and by firm manipulation of the cheeks, it is not necessary to reduce borders before making the secondary impression. However, impression regions related to the mylohyoid ridge and other bony prominences should be scraped to a depth of approximately 1 mm to avoid pressure on these potentially sensitive regions (Fig. 8). A thin impression is made with zinc oxide-eugenol impression material while the patient is instructed to exert a gentle tongue and lip pressure in assuming the lingual impression position. Gentle manipulation is sufficient to border mold the buccal and labial borders (Fig. 9). The impression is boxed and a cast is poured in artificial stone. The integrity of the established contours must be carefully maintained (Fig. 10) and reproduced in the trial denture (Fig. 11) and the completed mandibular denture (Fig. 12). At all appointments, the important role of the tongue in controlling the mandibular denture is explained and emphasized. This type of 459
KOTKIN
Fig. 7. Undersurface molded anterolingual
of impression tray shows borderand labial borders.
Fig. 8. Completed
compound
Fig. 9. Final zinc oxide-eugenol
impression.
paste impression.
reinforcement is integral to the psychophysiologic preparation of the patient for acceptance of the denture.
DISCUSSION RATIONALE
AND TREATMENT
The basis of this impression technique is the fabrication of a mandibular denture that will restore oral bulk 460
Fig. 10. Borders of sublingual poured cast.
guiding
AND
SLABBERT
ramp marked on
Fig. 11. Trial denture.
Fig. 12. Completed denture. rounded at marked borders ramp.
and provide
a stabilizing
Sharp contours were of sublingual guiding
lingual
guiding
ramp
(Fig.
12). The guiding ramp is formed under the influence of controlled muscular activity in the region of the mandibular anterior teeth. Such activity is mediated through the localizing handle, which is purposely located in the region previously occupied by the mandibular anterior APRIL
1987
VOLUME
57
NUMBER
4
TONGUE
POSITION
AND
MANDIBULAR
IMPRESSIONS
Sublin Salivary
Fig. 13. A representation of a sublingual guiding ramp in sagittal section illustrates relationship of soft and bony tissues to denture. Tongue is in a favorable anterior position as-depicted in Fig. 4..
teeth. Border-molding of the lingual guiding ramp depends to a large extent on the activity of the genioglossus muscle. Marked electromyographic activity has been recorded in this muscle when it acts against resistancc.D When the tongue is protruded in the absence of such resistance, surprisingly little electromyographic activity is produced. These findings imply that the bordermolding activity of the genioglossus muscle will be enhanced by the resistance offered by the lip, as the tongue, guided by the localizing handle, exerts pressure against it. Under the influence of the guiding ramp, the tongue is encouraged to assume a normal position as described by Wright et a1.2.’ In this particular position, the tip of the tongue is in contact with the mandibular incisors while its distal margins are related to the lingual surfaces of the posterior teeth. Brill et al.’ describe a comparable tongue position that would also be conducive to good muscular control of the mandibular denture. The tongue, with its inferior surface in apposition to the ramp, will also assume a high position relative to the resorbed mandibular residual ridge. Such a position is similar to the high tongue position that Heath’ recorded for piezographs molded in mouths with advanced resorption of the mandibular residual ridge. The posteroinferior border of the guiding ramp is related to the sublingual glands and the genioglossus muscle (Fig. 13). Forward positioning of an active or passive tongue will impart favorable stabilizing and retentive forces that will act through the ramp. In addition, and in accordance with the Jorgensen formula cited by Brill,” physical retentive forces will be enhanced by the wider sublingual borders. The highly resilient sublingual tissues have a valvular effect against such borders thereby enhancing the border seal. THE IOURNAL
OF PROSTHETIC
DENTISTRY
According to Fish,“, 5 the progressive loss of oral bulk in the edentulous patient is accompanied by a commensurate shortening and broadening of the tongue. He therefore infers that this behavior is a compensatory response, a functional demand on the tongue to form part of the anterior wall of the respiratory tract. This concept is supported by central nervous system connections and controls as evidenced by the so-called “tonguesafety” function of the genioglossus muscle.’ This muscle shows increased electromyographic activity on inspiration during sleeping and during waking hours thereby assisting in the maintenance of a patent airway. Another study by Richardson and Allen” confirms most of Fish’s findings but they were unable to demonstrate tongueshortening in their subjects. This discrepancy between the two studies can be explained on the basis of the considerable differences in the periods of edentulousness in the two groups of subjects. A corollary to Fish’s4, 5 findings suggests that the tongue would be encouraged to assume an anterior position should lost oral bulk be restored with a denture fabricated according to principles in the described impression technique. In the course of his piezographic studies, Heath’ observed that when the amounts of gel used to form shapes of the potential denture space were increased, the increased bulk was accommodated lingually by a subject with severe resorption and in the vestibule by a subject with a prominent ridge. These observations indicate that sublingual extensions that can be tolerated extremely well by patients with advanced resorption may not be that well tolerated by patients with prominent residual ridges. Numerous well-tried impression techniques already exist for patients with satisfactory ridges and sublingual extensions may exceed their tolerance for the additional denture bulk. 461
KOTKIN
SUMMARY
AND CONCLUSIONS
stability 4. 5. 6.
8. 9. IO.
2.
3.
Are anterior D. Ray McArthur, University
of North
replacement
kNT
1966;
Fish F. The functional anatomy of the rest position of the mandible. Dent Pratt 1961;11:178-88. Fish SF. The respiratory associations of the rest position of the mandible. Br Dent J 1964;116:149-59. Basmajian JV. Muscles alive: their functions revealed by electromyography. 4th ed. Baltimore: Williams & Wilkins Co, 1978; Brill N, Tryde G, Cantor R. The dynamic nature of the lower denture space. J PROSTHET DENT 1965;15:401-18. Heath R. A study of the morphology of the denture space. Dent Pratt Dent Ret 1970;21:109-17. Brill N. Factors in the mechanism of full denture retention: a discussion of selected papers. Dent Pratt 1967;18:9-19. Richardson A, Allen R. Mandibular posture following tooth extraction. J Dent 1980;8:315-20.
Re,hnnl reque\1c 10: DR. H. KOTKIN UNIVERSITY OF THE WITWATERSRAND Scrmo~ OF DENTISTRY 1 JAN SMUTS AVE. JOHANNESBURG 2001 SoLlTFr AFRICA
teeth too small?
D.D.S., M.S.* Carolina,
School of Dentistry,
Chapel
W
Hill,
oodhead’ expressed concern that anterior artificial teeth may be slightly smaller than their natural counterparts. McArthur* observed that patient complaints generally relate to the maxillary central incisor being perceived as too large rather than too small. Actually, the mesiodistal, rather than the incisogingival measurement, is probably the more critical dimension for an anterior replacement tooth. In a previous study, measurements on orthodontic casts determined the mean mesiodistal width for the permanent maxillary right central incisor to be 8.86 mm.’ This value is similar to that reported by others.3-9 The mean, sex-specific incisor diameters were found to be 8.96 mm for men and 8.79 for women.’ Other studies also showed men to have larger incisor teeth than women’0-‘4 and black persons to have larger incisors than Caucasians.“-“’ The purpose of this study was to determine the
*Associate Professor. Department of Removable Prosthodontics 462
PRO5TflET
359-362. 7.
REFERENCES hlarmor I?. Hebertson JE. The use of swallowing in making complete kwer impressions. J PROSTHET DENT 1968;19:20818. Wright CR, Muyskens JH, Strong LH, Westerman KN, Kingery RH. Williams ST. A study of the tongue and its relation to denture stability. J Am Dent Assoc 1949;39:269-75. Wright CR Evaluation of the factors necessary to develop
dentures. J
SLABBERT
16:414-30.
An adjustable easily located impression tray handle was used as a device to control tongue position and muscular forces for mandibular complete denture impression-making. This technique is indicated where advanced residual ridge resorption is present. A denture made with a lingual guiding ramp conforming to such an impression is not a panacea for all mandibular denture problems, which have many complex causes. However, the lingual guiding ramp technique gains support from established physiological findings and can yield gratifying clinical results.
I.
in mandibular
AND
N.C.
mesiodistal width of a maxillary right central incisor for natural and replacement dentitions. The natural dentitions were represented by samples of subjects from varying age groups. It was assumed that there would be a decrease in the mesiodistal incisor width in the older age groups. For the most part, the reduction in width represents proximal wear. However, significant incisal wear of tapering tooth forms will also contribute to a reduced mesiodistal width. Tooth wear is normal and is only considered pathologic when the survival of the tooth is in jeopardy.20-22 METHODS In a previous study, a sharpened Boley gauge was used to measure the maximum width of the permanent maxillary right central incisor to the nearest 0.1 mm on casts from orthodontic patients whose treatment had been completed.’ The original sample consisted of 56 women and 44 men. This method was repeated and the sample size was increased by 400 casts with 281 women and 219 men in the expanded sample. APRIL
1987
VOLUME
57
NUMBER
4