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Anatomic limitations in intraoral roentgenography of the upper molar region
Oral Roentgenology ANATOMIC IJM.ITATIONS IN INTRAORAL ROENTGENOGRAPHY OF THE UPPER MOLAR REGION RUSSELL
G. STEPHENS, D.D.S., AND JOHN H. BARR, D.D.S., B.Sc., BOSTON, iKms.
I
T HAS been claimed correctly that a true roentgenographic orientation of teeth with their supporting structures will require placement of the film parallel to the long axes of the teeth. It also has been implied that this requirement can be satisfied almost routinely in intraoral periapical roentgenography, with particular advantage in upper molar regions.69 ~14 However, in order to retain a reasonable periapical view, numerous exponents of the parallel film technique have readily admitted the frequent need for departure from truly parallel film placement. Since this has raised doubt as to the validity of the implied claims for the technique, a study was undertaken to evaluate the effectiveness of routine parallel film placement in the upper molar region. Anatomic limitations are usually the determining factors in devising any intraoral technique designed to reproduce the entire tooth together with correctly oriented supporting bone. In the upper molar region, these determining factors will be (1) the length of the tooth, (2) the axial inclination of the tooth, (3) the height of the palate vault, and (4) the level of the inferoexternal border7 of the malar bone. Illustrations used in support of the parallel film, or “long-cone” technique have presupposed a generous height for the palat,e vault and an equally favorable level for the lower border of the malar bone63* (Fig. 1). Measurements have been obtained from 100 young white adults (90 of whom were males) in order to ascertain the anatomic limitations in this region. The only criteria used in t,he selection of subjects for measurement were as follows : (a) (b) (c) (d)
Minimum age 19 years to insure completed facial growth. Bilateral presence of upper first and second molar teeth free from extensive caries or gross abnormality of form. Normal occlusal level of molar teeth. Absence of torus palatinus.
From the Division of Oral Diagnosis, Tufts College Dental School. Presented before the International Association for Dental Research, Chicago, March 18, 1956. 1272
IKTRAORAL
ROESTGENOGRAPHY
OF UPPER
Fig.
1.,-Reproductions
of illustrations shown in support of technique for upper molar teeth, lateral
Fig.
2.-Instrument
used
to measure palate vault height, tance from midiine to malar
9IOIAR
presentations projection.%
malar bone.
height,
1273
REGIOS
8
of
arch
the
parallel
width,
and
fllrn
dis.
1274
RUSSELL
G. STEPHENS TABLE
AND JOHN
13. BARR
I -__MEDIAN
Ml%AN ;t$
MEASUREMENT
of palate
vault
/
gIi2~
plane
19 urn = 0.20
39
border of malar bone above the bp palpation and marked on skin)
25 om = 0.27
25
1.
Height
above occlusal
2.
Height of inferoexternal occlusal plane (located
3.
Arch width (between molar teeth)
4.
Distance from midline to external surface a point immediately over t,he inferoexternal malar bone
mesial
triangular
fossae
of
first
48
of the face at border of the
60
Using the instrument illustrated in Fig. 2, four measurements were recorded for each individual in the vertical plane through the two upper first molar teeth. These findings are summarized in Table I, while the distribution of individual measurements of height of the palate vault and height of the malar bone are presented in the form of a scatter diagram (Fig. 3).
Pig.
3.-Scatter
diagram
showing
data obtained on height of ferior border of malar bone.
paiate
vault
and
height
of
in-
On statistical analysis of the measurements, all distributions proved normal using the chi-square test for goodness of fit. Pearson product-moment coefficient of correlation was computed for the height of the palate vault and the height of the malar bone, and showed no correlation of any predictive vaIue (plus 0.18). Further confirmation of the measurements has been obtained by reference to a number of dried skulls. To illustrate the clinical significance of these findings, Fig. 4 was prepared to scale, using (1) the median or mean values from Table I, (2) Black’s2
Fig.
Fig. Fig. 4.-Section through orientation of malar co1 .rect Fig. L-Superimposition niq [ue (see Fig. 1).
4.
6.
upper first molar teeth based on mean values obtained, shon bone, flrst molar tooth, and palate vault height. on Fig. 4 of the projection of radiation for parallel iJIm tl
1276
RUSSELL
G. STEPHENS
AND
JOHN
II.
BARR
figure of 21 mm. for the average length of the upper first molar tooth, (3) an assumed tooth inclinationz* I3 of 10 degrees, and (3) iln allowance of 3 mm. soft tissue covering the lateral surface of the malar bone. It now bccoirm evident (Fig. 5) that the illustrations reproduced in Fig. I have grossly ovcrsimplified the technical problem with which WC are confronted. Jt, is ilklmediately apparent that in the u.aemge cast, with a lateral projection, it is impossible to reproduce an unobscured view of any pcriapical bone, irrespective of the technical approach. + 15. t 10. + 5.
Fig. 6.-Correctly represented projections of radiation for Darallel film placement accordWith 5 degree tooth inclination, palate height mast be not ing to varying tooth inclinations. With 10 degree tooth inclinaless than 21 mm., and malar height must be 2S mm. or more. tion, palate height must be not less than 19 mm., and maJar height must be 29 mm. or more. With 15 degree tooth inclination, palate height must be not less than 17 mm., minimal malal height is 32 mm.
Correctly represented parallel film placement. would call for the projections of radiation illustrated in Fig, 6, accordin, u to any tooth inclinations which maa be considered appropriate, and allowing the unlikely assumpt’ion that the film could be placed in contact with the palate vault throughout its length. Reference to the data in the scatter diagram (Fig. 3) discloses that with parallel film pIacement and 2 mm. of pcriapical bone regarded as a minimum aeccptable view, molar tooth inclinations of 5 degrees or 10 degrees permit these requirernents to be satisfied in no more than 15 per cent of the cases studied. With axial inclinations of 15 degrees or greater, the requirements could not be met in any instance. In an additional 35 per cent of persons, however, the ent,ire length of the tooth could be reproduced together with less than the 2 mm. of [Jeriapkd bone. These percentages increase if parallel film placement is disregarded, that is, by utilizing all possible combinations of film placement and vertical angu-
INTRAORAL
ROESTGENOGRAPHY
OF UPPER
MOLAR
REGION
1277
Again referring to the scatter diagram (Fig. 31, lation of the radiation. analysis of the data reveals that films with 2 mm. of unobscured periapical bone can be expected under these conditions in 25 per cent of cases if tooth inclination is 5, 10, or 15 degrees, but often at the sacrifice of correct orientaIn an additional 50 per cent of instances, the entire lengt~h tion of structures. of the tooth can be reproduced, but with less than the suggested 2 mm. of periapical bone. Our study supports the frequent need for compromise conceded by exponents of the parallel film technique. Modification of the technique inevitably entails distortion of the relationships of teeth and supporting bone as depicted on the roentgenographic film. Only a useful correlation between malar heights and palate vault heights, or between palate vault heights and tooth lengths, would simplify the technical problems of a lateral projection of the first molar tooth. We have shown that there is virtually no correlation between the former measurements ; investigation already has been undertaken into the possibility of a useful correlation between tooth length and palate vault height in individuals. The superior attributes of the parallel film have not been questioned, but routinely successful use of the necessary projection does not appear feasible in the face of anatomic limitat,ions in the upper molar region. References 1. Barr, 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
John H.: An Effective and Practical Roentgenographic Technic, J. Canad. D. A. 21: 30, 1955. Black, G. V.: Descriptive Anatomy of the Human Teeth, Philadelphia, 1902, S. S. White Manufacturing Company. Diamond, Moses : Dental Anatomy, New York, 1952, The Macmillan Company. Fitzgerald, G. M.: in Adumbration, or Dental Roentgenography I : An Investigation the Factors that Control Geometric Unsharpness, J. Am. Dent. A. 34: 1, 1947. Fitzgerald, G. M.: Vertical Angulation, Film Placement Dental Roentgenography II: and Increased Object-Film Distance, J. Am. Dent. A. 35: 160, 1947. Fitzgerald, G. M.: Dental Roentgenography. III : The Roentgenographic Periapieal Survey of the Upper Molar Region, J. Am. Dent. A. 38: 293, 1949. Gray, Henry : Anatomy, Descriptive and Surgical, London, 1897, Longmans, Green & Co. McCormack, Donald W. : Dental Roentgenology, A Technical Procedure for Furthering the Advancement Toward Anatomical Accuracy, Calif. S. Dent. A. .J. 13: 89, 1937. Richards, A. G.: Roentgenographic Technics Made to Order, J. Am. Dent. A. 39: 396, 1949. Salzmann, J. A.: Principles of Orthodontics, Philadelphia, 1943, J. B. T,ippineott Company. Updegrave, W. J.: Paralleling Extension-Cone Technique of Intraoral Dental Radiography, ORAL SURG., ORAL &kD:, AND ORAL PATH. 4: 1250, 1951. Waggener, D. T.: Newer Concepts m Dental Roentgenology, J. Canad. D. A. 17: 363, 1951. Wheeler, R. C.: Textbook of Dental Anatomy and Physiology, Philadelphia, 1946, W. B. Saunders Company. Williams, S. W.: The Paralleling Technic for Intraoral Roentgenology, J. Am. Dent. A. 43: 419, 1951.
G. STEPHENS, D.D.S., AND JOHN H. BARR, D.D.S., B.Sc., BOSTON, iKms.
I
T HAS been claimed correctly that a true roentgenographic orientation of teeth with their supporting structures will require placement of the film parallel to the long axes of the teeth. It also has been implied that this requirement can be satisfied almost routinely in intraoral periapical roentgenography, with particular advantage in upper molar regions.69 ~14 However, in order to retain a reasonable periapical view, numerous exponents of the parallel film technique have readily admitted the frequent need for departure from truly parallel film placement. Since this has raised doubt as to the validity of the implied claims for the technique, a study was undertaken to evaluate the effectiveness of routine parallel film placement in the upper molar region. Anatomic limitations are usually the determining factors in devising any intraoral technique designed to reproduce the entire tooth together with correctly oriented supporting bone. In the upper molar region, these determining factors will be (1) the length of the tooth, (2) the axial inclination of the tooth, (3) the height of the palate vault, and (4) the level of the inferoexternal border7 of the malar bone. Illustrations used in support of the parallel film, or “long-cone” technique have presupposed a generous height for the palat,e vault and an equally favorable level for the lower border of the malar bone63* (Fig. 1). Measurements have been obtained from 100 young white adults (90 of whom were males) in order to ascertain the anatomic limitations in this region. The only criteria used in t,he selection of subjects for measurement were as follows : (a) (b) (c) (d)
Minimum age 19 years to insure completed facial growth. Bilateral presence of upper first and second molar teeth free from extensive caries or gross abnormality of form. Normal occlusal level of molar teeth. Absence of torus palatinus.
From the Division of Oral Diagnosis, Tufts College Dental School. Presented before the International Association for Dental Research, Chicago, March 18, 1956. 1272
IKTRAORAL
ROESTGENOGRAPHY
OF UPPER
Fig.
1.,-Reproductions
of illustrations shown in support of technique for upper molar teeth, lateral
Fig.
2.-Instrument
used
to measure palate vault height, tance from midiine to malar
9IOIAR
presentations projection.%
malar bone.
height,
1273
REGIOS
8
of
arch
the
parallel
width,
and
fllrn
dis.
1274
RUSSELL
G. STEPHENS TABLE
AND JOHN
13. BARR
I -__MEDIAN
Ml%AN ;t$
MEASUREMENT
of palate
vault
/
gIi2~
plane
19 urn = 0.20
39
border of malar bone above the bp palpation and marked on skin)
25 om = 0.27
25
1.
Height
above occlusal
2.
Height of inferoexternal occlusal plane (located
3.
Arch width (between molar teeth)
4.
Distance from midline to external surface a point immediately over t,he inferoexternal malar bone
mesial
triangular
fossae
of
first
48
of the face at border of the
60
Using the instrument illustrated in Fig. 2, four measurements were recorded for each individual in the vertical plane through the two upper first molar teeth. These findings are summarized in Table I, while the distribution of individual measurements of height of the palate vault and height of the malar bone are presented in the form of a scatter diagram (Fig. 3).
Pig.
3.-Scatter
diagram
showing
data obtained on height of ferior border of malar bone.
paiate
vault
and
height
of
in-
On statistical analysis of the measurements, all distributions proved normal using the chi-square test for goodness of fit. Pearson product-moment coefficient of correlation was computed for the height of the palate vault and the height of the malar bone, and showed no correlation of any predictive vaIue (plus 0.18). Further confirmation of the measurements has been obtained by reference to a number of dried skulls. To illustrate the clinical significance of these findings, Fig. 4 was prepared to scale, using (1) the median or mean values from Table I, (2) Black’s2
Fig.
Fig. Fig. 4.-Section through orientation of malar co1 .rect Fig. L-Superimposition niq [ue (see Fig. 1).
4.
6.
upper first molar teeth based on mean values obtained, shon bone, flrst molar tooth, and palate vault height. on Fig. 4 of the projection of radiation for parallel iJIm tl
1276
RUSSELL
G. STEPHENS
AND
JOHN
II.
BARR
figure of 21 mm. for the average length of the upper first molar tooth, (3) an assumed tooth inclinationz* I3 of 10 degrees, and (3) iln allowance of 3 mm. soft tissue covering the lateral surface of the malar bone. It now bccoirm evident (Fig. 5) that the illustrations reproduced in Fig. I have grossly ovcrsimplified the technical problem with which WC are confronted. Jt, is ilklmediately apparent that in the u.aemge cast, with a lateral projection, it is impossible to reproduce an unobscured view of any pcriapical bone, irrespective of the technical approach. + 15. t 10. + 5.
Fig. 6.-Correctly represented projections of radiation for Darallel film placement accordWith 5 degree tooth inclination, palate height mast be not ing to varying tooth inclinations. With 10 degree tooth inclinaless than 21 mm., and malar height must be 2S mm. or more. tion, palate height must be not less than 19 mm., and maJar height must be 29 mm. or more. With 15 degree tooth inclination, palate height must be not less than 17 mm., minimal malal height is 32 mm.
Correctly represented parallel film placement. would call for the projections of radiation illustrated in Fig, 6, accordin, u to any tooth inclinations which maa be considered appropriate, and allowing the unlikely assumpt’ion that the film could be placed in contact with the palate vault throughout its length. Reference to the data in the scatter diagram (Fig. 3) discloses that with parallel film pIacement and 2 mm. of pcriapical bone regarded as a minimum aeccptable view, molar tooth inclinations of 5 degrees or 10 degrees permit these requirernents to be satisfied in no more than 15 per cent of the cases studied. With axial inclinations of 15 degrees or greater, the requirements could not be met in any instance. In an additional 35 per cent of persons, however, the ent,ire length of the tooth could be reproduced together with less than the 2 mm. of [Jeriapkd bone. These percentages increase if parallel film placement is disregarded, that is, by utilizing all possible combinations of film placement and vertical angu-
INTRAORAL
ROESTGENOGRAPHY
OF UPPER
MOLAR
REGION
1277
Again referring to the scatter diagram (Fig. 31, lation of the radiation. analysis of the data reveals that films with 2 mm. of unobscured periapical bone can be expected under these conditions in 25 per cent of cases if tooth inclination is 5, 10, or 15 degrees, but often at the sacrifice of correct orientaIn an additional 50 per cent of instances, the entire lengt~h tion of structures. of the tooth can be reproduced, but with less than the suggested 2 mm. of periapical bone. Our study supports the frequent need for compromise conceded by exponents of the parallel film technique. Modification of the technique inevitably entails distortion of the relationships of teeth and supporting bone as depicted on the roentgenographic film. Only a useful correlation between malar heights and palate vault heights, or between palate vault heights and tooth lengths, would simplify the technical problems of a lateral projection of the first molar tooth. We have shown that there is virtually no correlation between the former measurements ; investigation already has been undertaken into the possibility of a useful correlation between tooth length and palate vault height in individuals. The superior attributes of the parallel film have not been questioned, but routinely successful use of the necessary projection does not appear feasible in the face of anatomic limitat,ions in the upper molar region. References 1. Barr, 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.
John H.: An Effective and Practical Roentgenographic Technic, J. Canad. D. A. 21: 30, 1955. Black, G. V.: Descriptive Anatomy of the Human Teeth, Philadelphia, 1902, S. S. White Manufacturing Company. Diamond, Moses : Dental Anatomy, New York, 1952, The Macmillan Company. Fitzgerald, G. M.: in Adumbration, or Dental Roentgenography I : An Investigation the Factors that Control Geometric Unsharpness, J. Am. Dent. A. 34: 1, 1947. Fitzgerald, G. M.: Vertical Angulation, Film Placement Dental Roentgenography II: and Increased Object-Film Distance, J. Am. Dent. A. 35: 160, 1947. Fitzgerald, G. M.: Dental Roentgenography. III : The Roentgenographic Periapieal Survey of the Upper Molar Region, J. Am. Dent. A. 38: 293, 1949. Gray, Henry : Anatomy, Descriptive and Surgical, London, 1897, Longmans, Green & Co. McCormack, Donald W. : Dental Roentgenology, A Technical Procedure for Furthering the Advancement Toward Anatomical Accuracy, Calif. S. Dent. A. .J. 13: 89, 1937. Richards, A. G.: Roentgenographic Technics Made to Order, J. Am. Dent. A. 39: 396, 1949. Salzmann, J. A.: Principles of Orthodontics, Philadelphia, 1943, J. B. T,ippineott Company. Updegrave, W. J.: Paralleling Extension-Cone Technique of Intraoral Dental Radiography, ORAL SURG., ORAL &kD:, AND ORAL PATH. 4: 1250, 1951. Waggener, D. T.: Newer Concepts m Dental Roentgenology, J. Canad. D. A. 17: 363, 1951. Wheeler, R. C.: Textbook of Dental Anatomy and Physiology, Philadelphia, 1946, W. B. Saunders Company. Williams, S. W.: The Paralleling Technic for Intraoral Roentgenology, J. Am. Dent. A. 43: 419, 1951.