0099-2399/90/1611-0528/$02.00/0 JOURNAL OF ENDODONTICS Copyright 9 1990 by The American Association of Endodontists
Printed in U.S.A. VOL. 16, NO. 11, NOVEMBER1990
Comparison of the Radiographic Appearance of Root Canal Size to Its Actual Diameter John K. Kuyk, DDS, and Richard E. Walton, DMD, MS
Clinically, the apparent radiographic diameter size does not always seem to correspond to the true canal size. The objective of this study was to compare canal size on periapical radiographs with the actual canal diameter as determined histologically. Periapical radiographs were exposed on 36 teeth on 5 human cadavers. Mesial-to-distal boundaries of canals were measured in the cervical, middle, and apical thirds. The teeth were extracted, the roots histologically processed, and cross-sections made in the cervical, middle, and apical thirds. Measured values of diameter from radiographs were compared with true canal widths as measured from the corresponding level of histological sections by using a correlated t test. All sections of all roots demonstrated a canal histologically, although some regions had no canal visible radiographically. In general, there was statistically no difference (p < 0.001) between the histological and radiographic measurements even when pulpal calcifications were present. However, in some roots there were marked discrepancies between radiographs and histological sections as to canal diameter.
pared with measurements of the actual object dimension. These studies were on dentin models, natural extracted teeth, and in situ in teeth in alveoli of preserved mandibles. Hedin found good correlation between the true breadth of the canal and that projected on the film. However, his studies did not necessarily reflect the clinical situation in which the interpretation would be from periapical radiographs. To date, no studies have been published in which visual (naked eye) assessment of root canal width and appearance on standard periapical radiographs in humans have been measured and compared with the true widths. The objective of this investigation was to determine whether the radiographic appearance of canal size corresponds to actual diameter of the canal.
M A T E R I A L S AND M E T H O D S
Determination of Radiographic Canal Width On five human cadavers, intraoral dental periapical radiographs were taken prior to removal of the teeth. Cone orientation was a straight facial projection using a paralleling technique (Rinn XCP instruments). Exposures were at 65 kVp, 15 mA at appropriate exposure time to give maximal quality films. A consistent source-to-film distance was used. The radiographs were examined on a view box with the peripheral light blocked out with the use of a magnifier-viewer (10). In those root areas that were clearly visible, the mesial and distal boundaries of the canal were carefully marked on the radiographs with a fine-pointed instrument (dissecting needle) in the mid-cervical, middle, and mid-apical thirds of each root (Fig. 1); these measurements were to be compared with measurements on corresponding histological sections (Fig. 2). For making measurements on the radiographs, they were viewed at x5 power under a stereomicroscope with an eyepiece-measuring grid. The canal widths, as determined from the earlier marked reference points, were determined and measured in 0.01-mm increments by the same operator at two different time periods. A reliability test (11) was performed to test the reliability of intraoperator measurements.
The radiograph is a valuable aid in root canal treatment. It is not only used in diagnosis, but is also a means to evaluate the curvature, size, number, shape, and degree of calcification of pulp canals. Clinically, the apparent width of a canal on a periapical radiograph does not always seem to depict the true size of the canal. For example, a canal that is readily visible on a radiograph may be difficult to locate a n d / o r negotiate with endodontic instruments. On the other hand, a canal may appear to be calcified (obliterated) radiographically, but is readily negotiable clinically. Investigators have reported on the microscopic diameter of root canals (1-5) and the overall volume o f the pulp space (6). However, little has been published comparing the perceived radiographic diameter of root canals to their true diameter. In order to determine general radiographic sizes, Hedin and colleagues (7-9) analyzed densitometrically the radiographic images of canals; these images were then corn-
Localization and Preparation of Histological Specimens After extraction, the teeth were stored in alcohol. Prior to dividing the roots into thirds, the teeth were aligned precisely
528
Vol. 16, No. 11, November 1990
FIG 1. Periapical radiograph from cadaver. A r r o w h e a d s show levels of canal width measurements in the cervical, middle, and apical one third of the canine.
over the radiograph to achieve the same orientation and were notched on the direct facial surface in the mid-cervical, middle, and mid-apical thirds to correspond with the exact level of the measured regions on the radiograph. The roots were mounted on a Gillings-Hamco bone-sectioning machine: cross-sectional culs were made at each level to correspond to the exact location of radiographic measurement. These root specimens were decalcified and routinely processed for histological preparation and paraffin embedded. A 5- to 7-urn cross-section was cut at the specimen surface: this corresponded to the precise level of radiographic measurement. The sections were stained with H & E. By using these techniques, 89 specimens were taken from 41 roots of 36 teeth.
Root Canal Dimensions
529
FiG 2. Cross-section of the same level as the a r r o w s in the apical one third of the canine shown in Fig. 1. The notch (N) was made by a bur to show the direct facial surface. Measurements were made of the canal width between the a r r o w s . This measurement (0.52 mm) was then compared with the apical one third measurement (0.48 mm) on the radiograph of Fig 1. In this region of the root, the measurements were close (hematoxylin and eosin); original magnification x40).
Identification of Intraeanal Calcifications and Irregular Secondary Dentin At the measured levels, the presence of calcifications (pulp stones, etc.) in the canals was noted as well as the presence and the width of the irregular secondary dentin surrounding the canals.
Evaluation Determination of True (Histological) Canal Width The actual mesiodistal widths of the canals were determined from the histological slides under the same stereomicroscope at x5 power with the use of a grid in the eyepiece. Measurements in 0.01-ram increments were made of the maximum diameter perpendicular to the orientation notch on the facial aspect (Fig. 2). All measurements were made by one operator. A subset of 20 randomly chosen histological sections were later measured by the same operator with a subsequent reliability test (11). This subset of measurements was taken approximately 3 months after the first reading to prevent operator memory from biasing the measurements.
Because of the duplicate orientation and the identical levels between radiograph and root sections, exact comparisons of radiographic and histological width could be made (Figs. 1 and 2). For an overall comparison of diameters, a Pearson correlations was derived using the t statistic value. This t test was performed on the first set of values as measured from the radiographs and from the true root canal widths as measured from the histological sections. A correlated t test was also run on a subset of 24 sections in which calcifications were identified. This was to determine if the presence of a pupal calcification modified the relationship of perceived radiographic diameter to the true (histological) diameter.
530
Kuyk and Walton
Journal of Endodontics
Also compared were those histological and radiographic specimens which varied more than 0.2 mm in their respective measurements to attempt to identify those factors that may have been responsible for the altered radiographic size and/ or appearance of those same canals. RESULTS
Intraoperator Reliability Measurement comparisons taken at two time intervals were very high for both the radiographic and histological values. The reliability value for the radiographic measurements was 0.9447 and for the histological measurements, 0.9859.
Histological Radiographic Size Variations All sections of all roots demonstrated the presence of a canal which was visible histologically, although there were seven (8%) sections from four roots which had no canal visible radiographically (Figs. 3 and 4). In 37 samples (41%) the radiographic measurement was larger than the histological measurement. It was identical in 4 samples (5%) and smaller in 48 samples (54%). However, visually detectable, or major, diameter differences (>0.2 mm) were present in several sections (24 of 89 or 27%). In the majority of these (21 of 24 or 87%), the actual size (histological) was greater than the visual size (radiographic). There was no obvious, consistent finding (calcifications, etc.) to logically explain these differences.
FrG 4. The exact level of the region indicated by the a r r o w in Fig. 3. A small canal of 0.24 mm in width is present, although there is radiographic "obliteration" (hematoxylin and eosin; original magnification x40).
Correlation of Radiographic (Perceived) with Histological (True) Measurements Generally, the 89 sections showed comparative histological and radiographic measurements to be significantly similar as shown by the correlated t test (Table I). The t statistic was -1.0905, with a probability value (two tailed) of
Printed in U.S.A. VOL. 16, NO. 11, NOVEMBER1990
Comparison of the Radiographic Appearance of Root Canal Size to Its Actual Diameter John K. Kuyk, DDS, and Richard E. Walton, DMD, MS
Clinically, the apparent radiographic diameter size does not always seem to correspond to the true canal size. The objective of this study was to compare canal size on periapical radiographs with the actual canal diameter as determined histologically. Periapical radiographs were exposed on 36 teeth on 5 human cadavers. Mesial-to-distal boundaries of canals were measured in the cervical, middle, and apical thirds. The teeth were extracted, the roots histologically processed, and cross-sections made in the cervical, middle, and apical thirds. Measured values of diameter from radiographs were compared with true canal widths as measured from the corresponding level of histological sections by using a correlated t test. All sections of all roots demonstrated a canal histologically, although some regions had no canal visible radiographically. In general, there was statistically no difference (p < 0.001) between the histological and radiographic measurements even when pulpal calcifications were present. However, in some roots there were marked discrepancies between radiographs and histological sections as to canal diameter.
pared with measurements of the actual object dimension. These studies were on dentin models, natural extracted teeth, and in situ in teeth in alveoli of preserved mandibles. Hedin found good correlation between the true breadth of the canal and that projected on the film. However, his studies did not necessarily reflect the clinical situation in which the interpretation would be from periapical radiographs. To date, no studies have been published in which visual (naked eye) assessment of root canal width and appearance on standard periapical radiographs in humans have been measured and compared with the true widths. The objective of this investigation was to determine whether the radiographic appearance of canal size corresponds to actual diameter of the canal.
M A T E R I A L S AND M E T H O D S
Determination of Radiographic Canal Width On five human cadavers, intraoral dental periapical radiographs were taken prior to removal of the teeth. Cone orientation was a straight facial projection using a paralleling technique (Rinn XCP instruments). Exposures were at 65 kVp, 15 mA at appropriate exposure time to give maximal quality films. A consistent source-to-film distance was used. The radiographs were examined on a view box with the peripheral light blocked out with the use of a magnifier-viewer (10). In those root areas that were clearly visible, the mesial and distal boundaries of the canal were carefully marked on the radiographs with a fine-pointed instrument (dissecting needle) in the mid-cervical, middle, and mid-apical thirds of each root (Fig. 1); these measurements were to be compared with measurements on corresponding histological sections (Fig. 2). For making measurements on the radiographs, they were viewed at x5 power under a stereomicroscope with an eyepiece-measuring grid. The canal widths, as determined from the earlier marked reference points, were determined and measured in 0.01-mm increments by the same operator at two different time periods. A reliability test (11) was performed to test the reliability of intraoperator measurements.
The radiograph is a valuable aid in root canal treatment. It is not only used in diagnosis, but is also a means to evaluate the curvature, size, number, shape, and degree of calcification of pulp canals. Clinically, the apparent width of a canal on a periapical radiograph does not always seem to depict the true size of the canal. For example, a canal that is readily visible on a radiograph may be difficult to locate a n d / o r negotiate with endodontic instruments. On the other hand, a canal may appear to be calcified (obliterated) radiographically, but is readily negotiable clinically. Investigators have reported on the microscopic diameter of root canals (1-5) and the overall volume o f the pulp space (6). However, little has been published comparing the perceived radiographic diameter of root canals to their true diameter. In order to determine general radiographic sizes, Hedin and colleagues (7-9) analyzed densitometrically the radiographic images of canals; these images were then corn-
Localization and Preparation of Histological Specimens After extraction, the teeth were stored in alcohol. Prior to dividing the roots into thirds, the teeth were aligned precisely
528
Vol. 16, No. 11, November 1990
FIG 1. Periapical radiograph from cadaver. A r r o w h e a d s show levels of canal width measurements in the cervical, middle, and apical one third of the canine.
over the radiograph to achieve the same orientation and were notched on the direct facial surface in the mid-cervical, middle, and mid-apical thirds to correspond with the exact level of the measured regions on the radiograph. The roots were mounted on a Gillings-Hamco bone-sectioning machine: cross-sectional culs were made at each level to correspond to the exact location of radiographic measurement. These root specimens were decalcified and routinely processed for histological preparation and paraffin embedded. A 5- to 7-urn cross-section was cut at the specimen surface: this corresponded to the precise level of radiographic measurement. The sections were stained with H & E. By using these techniques, 89 specimens were taken from 41 roots of 36 teeth.
Root Canal Dimensions
529
FiG 2. Cross-section of the same level as the a r r o w s in the apical one third of the canine shown in Fig. 1. The notch (N) was made by a bur to show the direct facial surface. Measurements were made of the canal width between the a r r o w s . This measurement (0.52 mm) was then compared with the apical one third measurement (0.48 mm) on the radiograph of Fig 1. In this region of the root, the measurements were close (hematoxylin and eosin); original magnification x40).
Identification of Intraeanal Calcifications and Irregular Secondary Dentin At the measured levels, the presence of calcifications (pulp stones, etc.) in the canals was noted as well as the presence and the width of the irregular secondary dentin surrounding the canals.
Evaluation Determination of True (Histological) Canal Width The actual mesiodistal widths of the canals were determined from the histological slides under the same stereomicroscope at x5 power with the use of a grid in the eyepiece. Measurements in 0.01-ram increments were made of the maximum diameter perpendicular to the orientation notch on the facial aspect (Fig. 2). All measurements were made by one operator. A subset of 20 randomly chosen histological sections were later measured by the same operator with a subsequent reliability test (11). This subset of measurements was taken approximately 3 months after the first reading to prevent operator memory from biasing the measurements.
Because of the duplicate orientation and the identical levels between radiograph and root sections, exact comparisons of radiographic and histological width could be made (Figs. 1 and 2). For an overall comparison of diameters, a Pearson correlations was derived using the t statistic value. This t test was performed on the first set of values as measured from the radiographs and from the true root canal widths as measured from the histological sections. A correlated t test was also run on a subset of 24 sections in which calcifications were identified. This was to determine if the presence of a pupal calcification modified the relationship of perceived radiographic diameter to the true (histological) diameter.
530
Kuyk and Walton
Journal of Endodontics
Also compared were those histological and radiographic specimens which varied more than 0.2 mm in their respective measurements to attempt to identify those factors that may have been responsible for the altered radiographic size and/ or appearance of those same canals. RESULTS
Intraoperator Reliability Measurement comparisons taken at two time intervals were very high for both the radiographic and histological values. The reliability value for the radiographic measurements was 0.9447 and for the histological measurements, 0.9859.
Histological Radiographic Size Variations All sections of all roots demonstrated the presence of a canal which was visible histologically, although there were seven (8%) sections from four roots which had no canal visible radiographically (Figs. 3 and 4). In 37 samples (41%) the radiographic measurement was larger than the histological measurement. It was identical in 4 samples (5%) and smaller in 48 samples (54%). However, visually detectable, or major, diameter differences (>0.2 mm) were present in several sections (24 of 89 or 27%). In the majority of these (21 of 24 or 87%), the actual size (histological) was greater than the visual size (radiographic). There was no obvious, consistent finding (calcifications, etc.) to logically explain these differences.
FrG 4. The exact level of the region indicated by the a r r o w in Fig. 3. A small canal of 0.24 mm in width is present, although there is radiographic "obliteration" (hematoxylin and eosin; original magnification x40).
Correlation of Radiographic (Perceived) with Histological (True) Measurements Generally, the 89 sections showed comparative histological and radiographic measurements to be significantly similar as shown by the correlated t test (Table I). The t statistic was -1.0905, with a probability value (two tailed) of
