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Dynamic opening device for mandibular trismus
Temporomandibular joint
Dynamic Kenneth University
opening
device
E. Brown, Commander of Texas Dental
for mandibular
trismus
(DC) USN*
Branch, Houston,
Texas
conditions of u omp 1’icating sequelae arising from infections and infiammatory the oral cavity and adjacent structures can cause trismus, muscular rigidity, and partial ankylosis. Such physical limitations of mandibular ospening can prevent even initial treatment procedures from being performed. Eventual access to the oral cavity is imperative if such situations are to be satisfactorily resolved. The employment of “forced-opening” corrective procedures on the mandible could have serious and painful consequences. The pain created by a forced-opening technique usually requires a general anesthesia, in itself a hazardous task to perform as the immobile mandible makes a blind nasal intubation necessary. A gradual and less discomforting resolution of the problem can be obtained by use of a dynamic opening device. This device affords a firm and constant pressure over a protracted period to give marked impr0vement.l Limitation of mandibular opening sometimes impairs making impressions with conventional trays. The dentist must use a flat thin plate as a tray and must register only 2 to 3 mm. of the occlusal surfaces of the teeth with a thin layer of impression material. Casts made in such impressions afford sufficient occlusal contour to fabricate an acrylic resin stent which will he stable on the teetb and be sufficiently thin for insertion into the limited opening (Fig. I )
CONSTRUCTION OF THE OPENING DEVICE The pressure by the dynamic opening device is applied through two occlusal stents attached to the maxillary and mandibular dental arches. The stents consist of two perforated metal plates attached with two 10 gauge, 16” steel rods and an acrylic resin wafer which fits on the occlusal surfaces of the teeth. The acrylic resin matrix is placed on the same surface as the attached steel rods and retained on the plate by the resin that extrudes through the perforations (Fig. 2). The stents are The opinions or assertions contained herein are the private ones of the author and are not to be construed as official or reflecting the views of the Navy Department or the Naval Service at large. *Fellow, Prosthodontics, Maxillofacial Area, University M. D. Anderson Hospital and Tumor Institute. 438
of Texas Dental Branch and the
Volume 20 Number 5
Opening
device for
mandibular
trismus
Fig. 1. The limited degree of jaw opening restricts the dimension of the impression impression is often limited to a registration of the occlusal surfaces of the teeth.
439
tray. The
Fig. 2. The rods and acrylic resin indices are attached to the perforated metal plates. The fulcrum axes for both a completely dentulous arch and a partially edentulous dental arch are indicated by the solid line.
440
J. Pros. Dent. November, 1968
Brown
Fig. 3. Frontal elastic-generated
and lateral views of the dynamic opening forces.
opening
device indicate
the direction
of the
reduced to a thickness that will permit them to be placed in the mouth. Often the degree of opening impairs the initial placement of both stents, and tongue blades serve as wedges to obtain sufficient clearance in the posterior region. APPLICATION
OF FORCE
To establish stability, the application of force must be upon a fulcrum which passes through the middle supporting segment of the stent. The force generated by an opening device should be applied through a fulcrum axis in the bicuspid region when a full complement of natural teeth is present. When only a few natural teeth are remaining (e.g., incisors and one bicuspid), the anteroposterior dimension of the segment is reduced. The stability of a stent on a reduced supporting surface is dependent on the critical alignment of the fulcrum axis. The axis may be established by applying all loading forces along a line drawn parallel with the chord of the dental arch and passing through the midpoint of a bisecting perpendicular of the chord (Fig. 2) . CONTOUR
OF THE RODS
The rods of the opening device should possess narrow dimensions as they pass through the lips so they will not stretch the commissures of the mouth. The mandib-
Opening
device for mandibular
trismus
441
Fig. 4. The alignment of the vertical elastic forces to the fulcrum axes of the arch plates produces a resultant opening force as indicated by the arrows.
ular rod is positioned along a line one half inch exterior to the lateral surface of the cheeks and parallel to the occlusal plane. The maxillary rods are contoured in a similar alignment but extend one half inch farther buccally than the mandibular rods. The mandibular rod is crimped into a notch which is vertically aligned with the fulcrum axis of the dental arch to afford attachment of elastic bands. The position of the notch is critical in directing the tension generated by the device. The maxillary rod is formed with an acute angle which positions its notch directly below the notches of the mandibular rod. An additional posterior notch is placed on the mandibular rod to create an added downward and forward application of force on the mandibular stent (Fig. 3). The applied force may be altered by the number and sizes of elastics or by increasing the angle of the maxillary rod. An increase in the angle gives a greater distance and, in turn, greater tension to the elastics. However, the notches in the maxillary and mandibular rods should always be maintained in vertical alignment (Fig. 4). USE OF THE OPENING
DEVICE
The opening device should be worn with intermittent periods of rest to avoid excessive irritation by prolonged tension. Overzealous application of force should be avoided, A full explanation of the function of the device is provided for the patient, and he is encouraged to use the assembly as often as can be tolerated.
442
J. 1’10s.Dent. November, 1968
Brown
SUM MARY Where pathollogic conditions restrict mandibular opening, an elastic-loaded, dynamic opening device can often aid in improving limited jaw opening. The application of pressure is derived by elastic tension on rods that are attached to occlusal stents. The positioning of the elastic tension is critical to the direction of the opening force and to the stabilization of the stents. The dynamic opening device can provide improvement to impaired jaw opening and has definite clinical value for some patients. Reference 1. Dar&sac,
M.: Correction
U. S. NAVAL HOSPITAL DENTAL SERVICE GREAT LAKES, ILL. 60088
of Ankylosis
of Jaws, J. A. M. A. 10: 1-b-l 8, 1922
Dynamic Kenneth University
opening
device
E. Brown, Commander of Texas Dental
for mandibular
trismus
(DC) USN*
Branch, Houston,
Texas
conditions of u omp 1’icating sequelae arising from infections and infiammatory the oral cavity and adjacent structures can cause trismus, muscular rigidity, and partial ankylosis. Such physical limitations of mandibular ospening can prevent even initial treatment procedures from being performed. Eventual access to the oral cavity is imperative if such situations are to be satisfactorily resolved. The employment of “forced-opening” corrective procedures on the mandible could have serious and painful consequences. The pain created by a forced-opening technique usually requires a general anesthesia, in itself a hazardous task to perform as the immobile mandible makes a blind nasal intubation necessary. A gradual and less discomforting resolution of the problem can be obtained by use of a dynamic opening device. This device affords a firm and constant pressure over a protracted period to give marked impr0vement.l Limitation of mandibular opening sometimes impairs making impressions with conventional trays. The dentist must use a flat thin plate as a tray and must register only 2 to 3 mm. of the occlusal surfaces of the teeth with a thin layer of impression material. Casts made in such impressions afford sufficient occlusal contour to fabricate an acrylic resin stent which will he stable on the teetb and be sufficiently thin for insertion into the limited opening (Fig. I )
CONSTRUCTION OF THE OPENING DEVICE The pressure by the dynamic opening device is applied through two occlusal stents attached to the maxillary and mandibular dental arches. The stents consist of two perforated metal plates attached with two 10 gauge, 16” steel rods and an acrylic resin wafer which fits on the occlusal surfaces of the teeth. The acrylic resin matrix is placed on the same surface as the attached steel rods and retained on the plate by the resin that extrudes through the perforations (Fig. 2). The stents are The opinions or assertions contained herein are the private ones of the author and are not to be construed as official or reflecting the views of the Navy Department or the Naval Service at large. *Fellow, Prosthodontics, Maxillofacial Area, University M. D. Anderson Hospital and Tumor Institute. 438
of Texas Dental Branch and the
Volume 20 Number 5
Opening
device for
mandibular
trismus
Fig. 1. The limited degree of jaw opening restricts the dimension of the impression impression is often limited to a registration of the occlusal surfaces of the teeth.
439
tray. The
Fig. 2. The rods and acrylic resin indices are attached to the perforated metal plates. The fulcrum axes for both a completely dentulous arch and a partially edentulous dental arch are indicated by the solid line.
440
J. Pros. Dent. November, 1968
Brown
Fig. 3. Frontal elastic-generated
and lateral views of the dynamic opening forces.
opening
device indicate
the direction
of the
reduced to a thickness that will permit them to be placed in the mouth. Often the degree of opening impairs the initial placement of both stents, and tongue blades serve as wedges to obtain sufficient clearance in the posterior region. APPLICATION
OF FORCE
To establish stability, the application of force must be upon a fulcrum which passes through the middle supporting segment of the stent. The force generated by an opening device should be applied through a fulcrum axis in the bicuspid region when a full complement of natural teeth is present. When only a few natural teeth are remaining (e.g., incisors and one bicuspid), the anteroposterior dimension of the segment is reduced. The stability of a stent on a reduced supporting surface is dependent on the critical alignment of the fulcrum axis. The axis may be established by applying all loading forces along a line drawn parallel with the chord of the dental arch and passing through the midpoint of a bisecting perpendicular of the chord (Fig. 2) . CONTOUR
OF THE RODS
The rods of the opening device should possess narrow dimensions as they pass through the lips so they will not stretch the commissures of the mouth. The mandib-
Opening
device for mandibular
trismus
441
Fig. 4. The alignment of the vertical elastic forces to the fulcrum axes of the arch plates produces a resultant opening force as indicated by the arrows.
ular rod is positioned along a line one half inch exterior to the lateral surface of the cheeks and parallel to the occlusal plane. The maxillary rods are contoured in a similar alignment but extend one half inch farther buccally than the mandibular rods. The mandibular rod is crimped into a notch which is vertically aligned with the fulcrum axis of the dental arch to afford attachment of elastic bands. The position of the notch is critical in directing the tension generated by the device. The maxillary rod is formed with an acute angle which positions its notch directly below the notches of the mandibular rod. An additional posterior notch is placed on the mandibular rod to create an added downward and forward application of force on the mandibular stent (Fig. 3). The applied force may be altered by the number and sizes of elastics or by increasing the angle of the maxillary rod. An increase in the angle gives a greater distance and, in turn, greater tension to the elastics. However, the notches in the maxillary and mandibular rods should always be maintained in vertical alignment (Fig. 4). USE OF THE OPENING
DEVICE
The opening device should be worn with intermittent periods of rest to avoid excessive irritation by prolonged tension. Overzealous application of force should be avoided, A full explanation of the function of the device is provided for the patient, and he is encouraged to use the assembly as often as can be tolerated.
442
J. 1’10s.Dent. November, 1968
Brown
SUM MARY Where pathollogic conditions restrict mandibular opening, an elastic-loaded, dynamic opening device can often aid in improving limited jaw opening. The application of pressure is derived by elastic tension on rods that are attached to occlusal stents. The positioning of the elastic tension is critical to the direction of the opening force and to the stabilization of the stents. The dynamic opening device can provide improvement to impaired jaw opening and has definite clinical value for some patients. Reference 1. Dar&sac,
M.: Correction
U. S. NAVAL HOSPITAL DENTAL SERVICE GREAT LAKES, ILL. 60088
of Ankylosis
of Jaws, J. A. M. A. 10: 1-b-l 8, 1922