Dentistry – Method or material for testing – treating – restoring – or... – Endodontic
Reexamination Certificate
2000-01-27
2001-04-17
Lucchesi, Nicholas D. (Department: 3732)
Dentistry
Method or material for testing, treating, restoring, or...
Endodontic
C433S102000, C433S081000
Reexamination Certificate
active
06217335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention is related to the field of endodontistry. More particularly, the invention is related to systems and operating methods for the preparation of root canals for obturation. The systems and methods involve the use of at least instruments which are dedicated for specific purposes in the inventive methods and systems and are designed for minimal intrusion into the apical portion.
2. The Relevant Technology
To preserve a tooth with a pulp that is diseased or is potentially diseased, it is generally necessary to remove as much of the pulp material as is possible from the pulp canal of the tooth, to shape the root canal(s) without excessively weakening the root canal walls, to prevent or minimize the presence of bacteria through the use of irrigants and dressings, and lastly, to clean the walls of the root canal(s) by removing the smear layer created during instrumentation of the root canal(s). These steps are all done to prepare the root cavity for sealing or obturation which involves filling the root canal with biocompatible materials, such as gutta percha, before the pulp cavity is sealed, thereby promoting the healing and functional recovery of the tooth. This procedure is referred to as root canal therapy.
As indicated hereinabove, root canal preparation involves pulp removal, cleaning of the root canal walls and shaping of the canal walls. This is typically achieved through a guided procedure with the use of instruments which are moved either manually, mechanically or by combinations thereof. These instruments are files or bits that are configured to bore and/or cut. Mechanical instrumentation can be achieved through the use of endodontic handpieces coupled to instruments such as files. The endodontic handpieces can impart rotational motion to a file, reciprocal motion by alternately rotating a file clockwise and counterclockwise, sonic movements or ultrasonic movements.
Before endodontic therapy is begun, a preoperative x-ray image is obtained to assess the health and the pathological status of the tooth and to determine the approximate initial length of the root canal(s). Once the approximate length of the root canal(s) has been determined, an instrument can be selected for use in the root canal which has an appropriate working length.
The schematic representations shown in
FIGS. 1A and 1B
are similar to a typical x-ray image. As shown in
FIGS. 1A and 1B
, an x-ray image of teeth generally show teeth
10
with sufficient clarity to view some of the properties of roots
12
and the root canals
14
located therein, particularly the location of the radiographic apex
17
. The location of the radiographic apex often does not coincide with the true apical terminus of the canal just beyond the apical foramen
16
. The distance between radiographic apex
17
and a fixed reference position on the occlusal surface of a tooth is used to determine the working length of the instruments.
FIG. 1B
, which is an enlarged view of root
12
a
shown in
FIG. 1A
, shows the relative position of the radiographic apex designated at line
17
in relation to that of the endodontic apex and the anatomical apex designated respectively by lines
18
and
19
. This condition is typical of an apex in living teeth. whereas a pathological apex can appear in a partially autolyzed state, as shown in FIG.
34
C.
Preoperative or intraoperative x-ray images of a tooth requiring endodontic treatment, such as the x-ray image depicted in
FIG. 1A
, are obtained by lingual placement of film packets as shown in
FIG. 2
at
22
which is supported by an x-ray film packet holder (not shown) and a long cone x-ray head (not shown) located outside of the cheek. Although, x-ray images obtained as shown in
FIG. 2
from a buccal-lingual x-ray projection are generally useful for determining the overall characteristics of a tooth, the approximate initial length of the root canal(s), and the working length for a file, such images provide only limited information regarding the overall anatomy of the root canal.
The information is limited because only one dimension of the overall anatomy of the pulp cavity can be viewed in vivo. In the standard buccal-lingual projection such images show only a linear profile of the root canal and cannot show a tridimensional view of a tooth and its root canal(s). Although, it would be very helpful to view a tooth from a position between the teeth or from the interproximal space such a mesial-distal view cannot be clearly produced when the tooth is still positioned in a patient's mouth. Since information is needed of all three dimensions in order to correctly understand the overall anatomy of the root canal and yet only two-dimensional images of a tooth can be obtained, x-ray images are sometimes relied on to reach incorrect conclusions regarding the anatomy of the root canal. More particularly, if not properly evaluated, x-ray images can be misleading as to the actual length of the root canal and the position of the foramen or foramina.
The difficulties encountered by an endodontist in assessing the overall anatomy of teeth from just the x-ray images obtained from buccal-lingual x-ray projections can be clearly identified with reference to
FIGS. 3-6
.
FIGS. 3A-6A
are longitudinal cross-sectional schematic views of extracted teeth taken from the front or back of the respective tooth which correspond with typical images obtained from buccal-lingual x-ray projections
FIGS. 3B-6B
are longitudinal cross-sectional schematic views of the same extracted teeth shown respectively in
FIGS. 3A-6A
taken from the mesial-distal or side view that cannot be obtained or seen while the teeth are still positioned in a patient's mouth.
Note that by varying the angle of incidence of the x-ray beam mesiodistally and distomesially additional x-ray images can be made which provide some additional information about the anatomy of the tooth. However, we can never obtain a three-dimensional image!
FIGS. 3-4
illustrate that in order to properly prepare a root canal it is necessary for practitioners to rely heavily on their experience, knowledge acquired through a study of typical anatomical structures, and on their visually acquired experience with longitudinal and transverse dental cross-sections at various heights.
FIG. 3A
depicts a lower premolar
30
from the buccal-lingual view of the tooth which shows root
32
and a root canal
34
therein that appears to be rather narrow and to have a relatively uniform perimeter along its length.
FIG. 3B
, however, shows that when seen from the mesial-distal view, the root canal is initially fairly wide over more than half its length, and then tapers significantly before eaching the apical foramen
36
. Comparing
FIG. 3A
with
FIG. 3B
clearly shows that when limited to knowledge derived from an x-ray corresponding to the image shown in
FIG. 3A
, the practitioner may not be able to accurately assess the anatomical structure of the root anatomy. Additionally,
FIG. 3C
shows that instead of an apical foramen there may be double, triple or quadruple foramina as indicated in research performed by the applicant and by others. The triple foramina
36
a
,
36
b
and
36
c
shown in
FIG. 3C
may not be detectable when viewed only from the buccal-lingual view shown in FIG.
3
A.
FIG. 4B
depicts an upper premolar
40
with roots
42
a
and
42
b
and root canals
44
a
and
44
b
located therein. Comparing FIG.
4
A and
FIG. 4B
reveals a problem which is similar to the problem revealed by comparing
FIG. 3A
with FIG.
3
B. More particularly, by comparing
FIG. 3A
with
FIG. 3B
or
FIG. 4A
with
FIG. 4B
, it is easily understood that the practitioner may not be able to accurately assess the anatomical structure of the root anatomy when limited to knowledge derived from an x-ray image. Since the configuration of pulp chamber
48
may be difficult to accurately and fully ascertain from only an x-ray image, a practitioners also relies, as indicated hereinabove, on accumulate
Fischer Dan E.
Riitano Francesco
Lucchesi Nicholas D.
Ultradent Products Inc.
Workman & Nydegger & Seeley
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