Clinical applications of concepts of functional anatomy and speech science to complete denture prosthodontics

Clinical applications of concepts of functional anatomy and speech science to complete denture prosthodontics

THE PHENOMENON COMPLETE DENTURE OF FUNCTION IN PROSTHODONTICS CLINICAL APPLICATIONS OF CONCEPTS OF FUNCTIONAL ANATOMY AND SPEECH SCIENCE COMPLETE DE...

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THE PHENOMENON COMPLETE DENTURE

OF FUNCTION IN PROSTHODONTICS

CLINICAL APPLICATIONS OF CONCEPTS OF FUNCTIONAL ANATOMY AND SPEECH SCIENCE COMPLETE DENTURE PROSTHODONTICS Part

VII.

Recording

TO

Phases*

ALEXANDER L. MARTONE, D.D.S., M.Sc.** Norfolk,

Vu.

HE PURPOSE of this article is to suggest clinical applications of functional anatomy and speech science to the development of impressions and the registration of maxillomandibular relations for complete dentures. Although these recording phases are a part of the construction of dentures, they are also a continuation of the diagnostic phase since they permit the dentist to learn more about the patient as the procedures are performed. They furnish opportunities to observe the patient’s willingness and ability to carry out instructions, his reflex responses, his healing capabilities, and his adaptability possibilities.

T

MOUTH

PREPARATION

The term “mouth preparation” is regularly used in treatment plans for patients with natural teeth. The principles and procedures of this preparation are designed to get the mouth in a healthy condition prior to starting restorative work. Edentulous mouths, also, need to be brought into as healthy a condition as possible before new dentures are constructed. Failure on the part of the dentist to recognize this need and to incorporate the necessary procedures in the treatment plan to meet the need precludes a successful prognosis. There is no justification for complicating the construction of complete dentures by beginning that construction on an unfavorable foundational support which can be improved by the proper preliminary treatment. During the clinical diagnostic examination, the dentist has had an opportunity to observe evidences of damage to the reflective tissues, the ridges, and the palate ; *Part I, J. PROS. DEN. 11:1009-1018, 1961; Part II, J. PROS. DEN. 12:4-27, 1962; Part III, J. PROS. DEN. 12:206-219, 1962; Part IV, J. PROS. DEN. 12:409-419, 1962; Part V, J. PROS. DEN. 12:629-636, 1962; Part VI, J. PROS. DEN. 12:817-834, 1962. **Associate, Departments of Prosthodontics and Anatomy, Medical College of Virginia. 4

$*;tr,er :”

PHENOMENON

OF FUNCTION

IN COMPLETE

DENTURE

PROSTHODONTICS

5

Fig. I.-A correlation of the anatomic landmarks. A, As seen in the mandibular arch of a patient. B, With the corresponding denture landmarks indicated on the mandibular preliminary impression (note that gray modeling compound was used for all illustrations for better definition). C, With the underlying anatomic structures reflected in a superior view of a dissection of the mandibular arch. A, An intraoral view of a patient’s mandibular arch showing: (I) labial frenum; (2) labial vestibule; (3) buccal frenum; (4) buccal vestibule; (5) alveolar ridge; (6) retrOmolar pad; (9) lingual tubercle; (10) alveololingual sulcus; (11) alveololingual fold; (13) salivary caruncle; (I 4) tongue; (17) lingual frenum. B, The mandibular preliminary compound impression showing the denture landmarks: (1) labial notch; (2) labial flange; (3) buccal notch; (4) buccal flange, (4~) masseter groove; (5) alveolar groove; (6) retromolar fossa; (7) pterygomandibular notch; (8) retromylohyoid eminence; (9) lingual tubercular fossa; (12) mylohyoid groove; (14) inclined plane for tongue: (IS) mylohyoid flange; (16) genial spine fossa; (17) lingual notch. C, A dissection of the mandibular arch showing: (2) cortical bone; (3) triangularis muscle; (4) buccinator muscle; (4~) buccal shelf, (4b) external oblique ridge, (4~) masseter muscle; (5) fibrous connective tissue, (5~) alveolar bone; (6) retromolar glands, (6b) temporal tendon; (7) pterygomandibular raphe; (8) medial pterygoid muscle, (8~) superior pharyngeal constrictor muscle, (Sb) retromylohyoid curtain; (9) lingual tuberosity; (11) sublingual gland, (11 a) mylohyoid muscle, (II b) lingual nerve; (12) mylohyoid muscle attachment and mylohyoid ridge; (15) alveololingual Sukus; (17) salivary caruncle. (Illustration for Fig. 1, C courtesy of Linden E. Edwards and Carl 0. Boucher.)

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MARTONE

J. Pros. Jan..Feb.,

Den. 1963

strained maxillomandibular relationships ; loss of tonicity in muscles and skin in and about the mouth, and impairment of functions which has resulted from these conditions. His preliminary treatment must be based on an evaluation of these findings in relation to their cause, the possibilities and prognosis for their treatment, and their significance in the determination of a treatment plan. In restoring a mutilated mouth to a healthy condition, the dentist has several treatment possibilities to consider. These include: (1) tissue rest, which tllay require the patient to go without dentures for a certain period of time, or which may be accomplished by altering the old dentures in indicated areas or modifying them by the use of soft, stimulating reline materials to permit periodic wearing of the dentures ; (2) conditioning exercises, such as have been described by Boos,l to be performed by the patient ; (3) nutritional therapy, particularly in relation to vitamin supplements; and (4) surgery. Frequently a mouth will require a combination of these treatments if it is to be put in a healthy condition. Although it is the dentist’s responsibility to select the preliminary treatment program, it is frequently the patient’s responsibility to see that it is carried out. This means that the patient must be educated as to what must be done and why it must be done. If the patient is unwilling to cooperate in this phase of treatment, the dentist should consider seriously whether to accept or reject the patient. BASIC

PRINCIPLES

OF

DENTURE

CONSTRUCTION

If the ultimate aim in the construction of complete dentures is to have them in harmonious relationship with the functions that occur in the mouth regions, the basic principles for their construction must reflect an application of functional anatomy. Edwards and Bouche9 have correlated the anatomy of the mouth with complete denture prosthodontics. The principles, which apply to the construction of all dentures, include (1) the utilization of the facial, tongue, and mandibular musculature to develop maximum tissue coverage within the limits of health and function; (2) the application of pressures on structures that can tolerate stress loads and give favorable leverage, e.g., the buccal shelf; (3) uniform bearing in relation to soft tissue thickness, i.e., light pressure on thin tissues and heavier pressure on thicker tissues; (4) maintenance of blood and nerve supply in a healthy, normal condition, and (5) control of tissues rather than displacement of them. Closed mouth impressions and functional impressions made under pressure by the patient displace tissues and structures. The impression procedure to be described is in accord with these principles. It is modified from a technique described by Boucher.3 It can be modified to meet the requirements for individual variations which may ‘exist in different patients. Some of these modifications will be suggested as the procedure is outlined. This procedure employs an open mouth technique and utilizes regional functional anatomy to record the shape of the oral mucous membrane in relation to the underlying structures in order that functional stress loads may be evaluated and dispersed to structures that can best carry them. This procedure is dependent upon the development of an accurate tray which is designed to resemble the completed denture. Such a tray is developed sectionally and perfected so that it carries the impression material to the desired regions.

\‘&I~~~ Kumber

‘3 1

PHEI’JOMENON

PRELIMINARY

MANDIBULAR

OF

FUiXCTION

ITi

C03IPLETE

DESTURE

PROSTHODOKTICS

;

IMPRESSIOX

There are three advantages to making the preliminary mandibular impression first: (1) A special acrylic resin or vulcanite tray must be constructed for the final mandibular impression. (2) If a metal base is to be constructed for the mandibular denture, the time required for this will furnish an additional healing period for maxillary tissues. (3) As a rule, a patient experiences less discomfort during the making of a mandibular impression than during the making of a maxillary impression. By making the mandibular impressions first, the dentist may provide a psychologic benefit for apprehensive patients. Prior to the start of the impression procedure, a further study of the mandibular arch and its related structures enables the dentist to visualize the finished impression and the completed denture. This study is further supplemented by roentgenographic findings. A stock metal tray, approximately 5 mm. larger than the arch, is selected in order to carry sufficient bulk of black modeling compound necessary to obtain an overextended preliminary impression which reflects the anatomic landmarks. This impression is chilled in ice water, removed from the tray, and reinforced with 10 gauge wire. Observations are made of the anatomic landmarks and of the distance from the crest of the ridge to the reflective border tissues while the mouth is relaxed and about half open and the tongue is elevated slightly. This distance is outlined on the preliminary tray (Fig. 1). The labial, buccal, and lingual flanges are knife trimmed about 2 mm. short of this outline. The labial flange should be approximately 3 mm. thick. The buccal flange should be about 1 mm. thicker and should reflect the external oblique and masseter grooves. The lingual flange should be about 3 mm. thick in the anterior region, slightly thicker and sloping lingually in the region of the mylohyoid ridge. Distal to the distal end of the mylohyoid ridge, the flange should be about 4 mm. thick, turn laterally toward the ramus, and extend to the retromylohyoid curtain at

knife

Fig. 2.-The trimmed

various sections of the to the desired thicknesses.

mandibular

preliminary

compound

impression

tray

are

8

MARTONE

J. Pros. Jan.-Feb.,

Den. 1963

the back end of the alveololingual sulcus. This length and thickness of the distal extension of the lingual flanges of the modeling compound tray will restrain the movements of the tongue that are to be used in forming the anterior part of the lingual flange (Fig. 2). The lingual surface of the lingual flange in the mylohyoid region is thickened with red modeling compound in order that the tray may conform to the shape of the soft tissues which are affected by mylohyoid muscle when the tongue is elevated (Fig. 3). All the undercuts below the mylohyoid groove are removed. The impression surface of the lingual flange in this region is knife-trimmed to make the inside (buccal surface of the lingual flange) slope toward the tongue at about a 45 degree angle. An atrophied residual ridge will require additional knife trimming of the tray in direct proportion to the degree of relationship of the mylohyoid muscle attachment to the crest of the ridge. The accommodation thus afforded for this muscle and its attachment contraindicates surgical intervention to eliminate these structures as a dislodging force to the denture. The buccal flange should extend as far as possible within the anatomic limitations of the mouth and completely fill the buccal pouch because this flange will serve as one of the main stabilizers of the mandibular denture. The broad coverage design, within the health and tolerance of the tissues and structures, utilizes the buccal shelf to carry the heavy occlusal forces. Care must be taken not to overextend the buccal flanges laterally beyond the external oblique line. The underlying structures of cortical bone and horizontal fibers of the buccinator muscles are capable of supporting occlusal stress loads. The buccal surface of the flange should face upward and outward so that the middle fibers of the buccinator muscle and the suctorial pad can rest on it, thus perfecting the border seal and aiding in the stabilizing of the denture. The buccal molar flange is developed by heating the outer surface of the chilled tray from the buccal notch to the buccal surface opposite the retromolar pad and having the patient suck on the dentist’s index and middle fingers which are seating the tray in the premolar regions and his other index finger which is placed in the anterior region to complete the seal. The buccal notch region is developed by the activity of the buccal frenum which overlies the triangularis muscle. This muscle has its origin from a broad base on the mandible just below this frenum. Allowances should be made in the reflective borders for the broad movements of the triangularis muscle and the buccal frenum (Fig. 4). The buccal notch region is perfected, after heating, by elevating the cheek and lips with the index finger inward, outward, forward, and backward while the tray is held in position with the index finger of the other hand spanning the arch from one premolar region to the other. The procedure is repeated for the opposite side. The labial flanges, separated by the labial notch, are developed with three objectives in mind : ( 1) to provide proper thickness for esthetic considerations, (2) to establish a guide for seating the tray for the final impression, and (3) to perfect the labial border seal. A clear understanding of the functioning anatomy will help to accomplish these objectives. Dissections of the labial frenum do not reveal muscle fibers. However, the amount of vestibular space that is available for the labial flanges

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PHENOMENON

OF FUXCTION

IN COMPLETE

DENTURE

PROSTHODOXTICS

9

Fig. 3.-Three illustrations showing the functional anatomy, the related structures, and their effects on the compound impression in the mylohyoid region. A, An intraoral view of a patient with the tongue raised. Note the elevation of the sublingual tissues and structures above the residual ridge when this action occurs. B, The mandibular preliminary compound impression, knife trimmed, with the undercuts removed and red modeling compound added to the lingual surfaces of the mylohyoid regions of the lingual flanges. C, A superior view of a dissection of the right posterior alveolar region with the tongue elevated and the modeling compound impression in place: (AJ red modeling compound over the Iingual Aange: (BJ sublingual fold; (CJ buccinator muscle; (0) pterygomandibular raphe; (E) superior pharyngeal constrictor muscle; (F) tongue; (G) ramus of mandible.

J. Pros. Den. Jan..Feb., 1963

MARTONE

c.

Fig. 4.-The buccal shelf region is illustrated to show the possibilities and limitations of developing a broad coverage effect on the buccal flange of the modeling compound tray, and the stabilizing effect the adjacent structures have on the completed denture. A, An intraoral view of a patient showing the broad buccal shelf (BS) and its boundaries: (A) residual alveolar ridge; (B) retromolar pad; (C) masseter bulge; (II) external oblique line; (E) buccal frenum. B, The broad base buccal flange (BP) developed within the possibilities and limitations of the buccal shelf region affords support in a region capable of carrying the occlusal loads placed on the mandibular denture: (A) alveolar groove; (B) retromolar fossa; (C) masseter groove; (0) external oblique groove; (E) buccal notch. C, The mandibular denture base on the anatomic specimen is stabilized by the adjacent structures resting on the broad buccal and lingual flanges.

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;”

PIIE~OMENON

OF F~h‘CTIOi$

IX

c’OXI’LETE

DENTURE

I’ROSTIIODONTICS

11

varies greatly. This is due in part to the action of the mentalis muscles in elevating the mandibular lip and thus reducing the vestibular space.“*” The labial flange of the chilled tray is perfected, after heating, by lightly elevating the mandibular lip and moving it slightly from side to side with the index finger and thumb and then releasing it. The outer surface of the tray is uniformly heated and tempered. It is seated in the mouth and held in place I)y the index and middle fingers applying light, equal pressures on each side and by the thumb acting as a stabilizer under the mandible. The buccal and labial surfaces of the buccal and labial flanges are molded by elevating the cheeks and lips outward, backward, then slightly inuard and forward with the index finger and thumb of the left hand. An elevation of the mandibular lip and a slight movement of it from side to side border molds the labial flange and makes allowance for the labial frenum (Fig. 5 j . The lingual surfaces of the mandibular flanges are developed by starting in the anterior regions and border molding each region in a sequence of steps, working toward the distal extent of the mandibular modeling compound impression. This sequence of border molding provides an extension and bulk of modeling compound in regions which restrict the unnatural tongue movements that are to be used in subsequent steps of developing the impression. The extension of the lingual flange of the tray at the lingual notch and in the premylohyoid regions is border molded l)y heating the lingual flange from one premolar region to the opposite premolar region and having the patient thrust the tongue outward and upward. These tongue movements elevate the genioglossus muscle which has its origin in the superior genial spine and its insertion in the tongue. This muscle, in turn, elevates the lingual frenum, thus forming the lingual notch in the flange (if the lingual frenum attaches high enough on the ridge). At the same time the sublingual fold, composed mostly of sublingual gland and submaxillary gland duct, is elevated. Because these glandular substructures are delicate and soft, overextension of the lingual flanges in these premylohyoid regions is likely to occur. In order to avoid this, it is necessarv to repeat the procedures which have been described. The thickness of the anterior part of the lingual flange is determined by reheating it from tlze 2i~g~nl side and having the patient thrust the tongue hard against the palate (Fig. 6). Then with the impression chilled, the buccal surfaces of both lingual flanges are heated at the same time and the tongue is thrust out hard. This action will eliminate any undercut under the mylohyoid ritlge and determine the angle of the slope of the buccal surface of the lingual flange in the molar region, i.c., in the region of the prominent mylohyoid ridge. The impression is chilled again, ant1 the inferior edges of both lingual flanges and retromylohyoid eminences are heated separately, and the patient is instructed to thrust the tongue out hard and then into the opposite cheek. These tongue movements aid in determining the extension of the lingual flanges downward into the alveololingual S&US. They add retention to the mandibular denture by perfecting the border seal in the inferior and posterior I’art of the al~~eololingd sulcus (Fig. 7), and by developing a plane at the distal end of the lingual surface of the lingual flange which will guide the tongue on top of the lingual flange in the molar region.

12

J. Pros. Dell. Jan.-Feb., 1963

MARTONE

A.

B.

c.

Fig.

B.-For

legend see oppostte page.

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IL3 PHEFOkfENON

OF FUKCTIOK

IN

COMPLETE

DENTURE

PROSTHODONTICS

13

The distal extension (the retromylohyoid eminence) of the lingual flange should fill the retromylohyoid space when the impression is in place and the tongue is thrust out (Fig. 8). This space lies at the distal end of the alveololingual sulcus. The posterior boundary of the retromylohyoid space is the retromylohyoid curtain. which is formed by the mucous membrane covering the superior pharyngeal conis the anstrictor muscle and extending downward from it. Its medial boundary terior tonsillar pillar (glossopalatine arch‘). In order to limit the distal extension of the, lingual flange, the impression is chilled, the distal border is heated, and the patient is instructed to protrude the tongue as far as possible. The retromylohyoid curtain and the glossopalatine arch are brought forlvartl by this movement. The inside (impression j surfaces oi the retromolar fossae and retromyloh~oid enlinences of the tray are border molded by slightly heating these surfaces on both the right and left sides of the chilled tray. The trap is seated in the mouth and held firmly in place by the two index fingers which are placed on the top of the posterior parts of the tray. The patient is instructed to open the mouth wide (to cause the pterygomandibular raphe to be brought forward), thrust the tongue out, and then close the mouth. The downward pressure on the mandible causes the elevator muscles to contract ; thus, the masseter muscles bulge forward against the buccinator muscles to form the masseter grooves at the distobuccal angles of the buccal flanges lateral to the retromolar pads (Fig. 9 ). At the same time, the internal (medial j pterygoitl muscles distal to the retromylohyoid curtains bulge forward against the curtains and push them against the distal ends of the lingual flanges of the impression. It is of extreme importance that the modeling compound should not be overheated and not be dislodged during these movements. The procedure should be repeated several times to perfect the border molding in this region. The impression is removed from the mouth (Fig. 10) ; a cast is poured, and an outline is made on it for an acrylic resin tray. ACRYLIC

RESIN

TRAY

The construction of an uccunzte tony is the key to developing an accuvatc hpression. The choice of the corrective impression material is of secondary importance if the tray is functionally accurate. Such a tray must he designed and shaped to resemble the outline of the completed denture. It must be modified with relief areas to provide sufficient space for the impression material so that it may control and record the shape of all of the anatomic structures during function and without displacing them. The retromolar pad regions, soft tissues, and structures at the reflective borders are examples of this. _--. ~ .-____. ___..Fig. B.-The available space for the development of the labial flanges and the relations and variability of the underlying structures are shown. A, An intraoral view of the alveolar ridge and labial vestibule. B, A hemisection view of an edentulous mouth, with residual alveolar ridge resorption, showing the space available for a denture base when the tongue is elevated. Note the attachments of the mentalis and genioglossus muscles and their relation to the crest of the ridge: (A) genioglossus mUSCle; (B) mandible; (C) mentalis muscle; (D) hard palate; (I3) residual alveolar bone. C, A hemisection view of an edentulous mouth with extreme residual alveolar ridge resorption showing the obliteration of the space available for the labial flange and the mandibular lip resting on the crest of the ridge. Note the small amount of residual alveolar bone and the migration of the top of the mandible which would be supporting a denture base toward the attachments of the mentalis muscles: (A) genioglossus muscle; (B) mandible; (C) mentalis muscle; (D) hard palate.

MARTONE

J. Pros. Jan.-Feb.,

Den. 1963

A.

B.

Fig. B.-The premylohyoid regions of the modeling compound impression are border molded by the action of the tongue thrust into the anterior palatal region. A, An intraoral view of the patient’s tongue thrust hard into the palatal region, elevating the sublingual fold above the residual ridge in the premylohyoid and genial regions. B, The modeling compound impression tray is held in place by the index and middle fmgers while the patient is border molding the soft, heattreated modeling compound in the premylohyoid region by elevating the tongue. C, The impression surface of the mandibular modeling compound impression showing the borders in the premylohyoid and genial regions perfected as a result of this activity.

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:”

PHENOMENON

OF FUNCTIOP~

IN COMPLETE DENTURE

PR~STH~DONTICS

15

The tray should be further modified in order that occlusal stress loads may be placed and directed on the supporting anatomic structures that can best tolerate them. The primary stress-bearing regions are the buccal shelf regions. Provisions should be made for relief in the regions that cannot tolerate occlusal pressures and stresses. A sharp ridge crest and certain ridge slopes are examples of such regions. A planned design of the recording surfaces of an accurate tray to accomplish these objectives may be made in two ways : ( 1) by grinding from the inside surface of the tray, or (2) by providing for relief (space) inside the tray before its fabrication. The latter method has the advantage of allowing the dentist to observe

A.

B.

Fig. 7.-The action of the tongue trust in the cheek on the opposite side is shown in relation to the underlying structures, and in the effects it produces in border molding the buccal and inferior surfaces in the mylohyoid and retromylohyoid regions of the lingual flanges of the mandibular modeling compound impressions. A, An intraoral view of the patient’s tongue thrust in the opposite cheek. Observe the dominance of the tongue and the elevation of the sublingual fold in relation to the residual ridge. B, The mandibular modeling compound impression is in place in the anatomic specimen with the tongue pulled over to the opposite side. Note the relation of the sublingual structures to the mylohyoid part of the lingual flange. (Red modeling compound has been added to form the nearly horizontal incline). C, The same specimen with the mucous membrane removed and a transparent acrylic resin denture base in place. Observe the underlying structures and their relationships to the denture base, particularly the mylobyoid muscle and its relation to the flange. D, A posterior view of a modeling compound impression, Green stick modeling compound has been added to the retromylohyoid eminences in order to create slight pressure in the retromylohyoid fossae. Inclined planes (A) facing in and down have been developed on the lingual surfaces of the distal extensions (retromylohyoid eminences) of the lingual flanges.

J. Pros. Den. Jan.-Feb., 1963

B.

C

Fig. R-Three illustrations showing the anatomy in action related to the static anatomy of a specimen and their effects on border molding the distal extension of the lingual flange of a mandibular modeling compound impression. A, The patient’s tongue is thrust out hard. Note the relation of the tongue to the residual ridge and the forward movement of the retromylohyoid curtain, resulting in a reduction in the retromylohyoid space. B, Superior aspect of an anatomic specimen with the modeling compound impression in place and the tongue pulled forward. Ob serve the forward movement of the retromylohyoid curtain border molding the distal end of the lingual flange. The tongue glides over the inclined plane of the lingual flange and is resting on the lingual flange in the mylohyoid (molar) region. C, A modeling compound impression showing the development of (A) the distal end of the lingual flange; (B) the retromylohyoid emlnence (note the green stick compound added to the eminence); (Cj the masseter groove: (D) the retromolar fossa, and IE) the buccal flange.

“N$$‘;r ‘1” PHENOMENON

OF FUNCTION

Ii\i COMPLETE

DENTURE

PROSTIIODONTICS

17

A.

B.

c.

Fig. R.-The development of the retrOmOlar fossae, the distal extensions, and masseter grooves in the modeling compound tray is illustrated in relation to the retromolar pad of the anatomic specimen and the underlying structures. A, The retromolar fossae: (A) the distal end of the impression (retromylohyoid eminences), and 03) the masseter grooves are developed by slightly heating the impression and holding it firmly in place with the two index fingers. The patient’s tongue is thrust out, and the mandible is elevated against the downward pressure of the Angers. B, A closeup Superior View Of an anatomic specimen showing the retromolar pad and the dissection of the related structures: (A) retromolar pad; (B) buccinator muscle; (C) pterygomandibular raphe; (0) superior pharyngeal constrictor muscle: (E) mandible; (F) temporal tendon. C, A closeup superior view Of the same specimen after the removal of the mucous membrane, and the dissection of the retromolar pad and related underlying structures: [A) retromolar pad; {& buccinator muscle; (C) pterygomandibular raphe; CL?} superior pharyngeal constrictor muscle; (E) glands; (F) temporal tendon.

18

J. Pros. Den. Jan:Feb., 1963

MARTONE

Fig. lO.-The

completed mandibular

modeling

compound impression.

the amount of relief provided for the individual foundational support in his mouth. MODIFICATION

patient in relation to the type of

OF THE TRAY FOR A ZINC OXIDE AND EUGENOL

WASH IMPRESSION

The final impression may be controlled by the dentist by outlining in pencil on the cast made from the preliminary impression the extent and thickness of the space needed for the final impression (Fig. 11) . The relief areas are outlined on the cast for the secondary stress-bearing areas, namely, the crest of the ridge and the ridge slopes, the alveololingual sulcus between the premylohyoid eminences, the buccal frenum regions, and the retromolar pads. One layer of pink baseplate wax, 1 mm. thick, is warmed and molded to the cast in the designated relief areas. One thickness of 28 gauge green casting wax, 0.5 mm., is added to the wax over the retromolar pad areas (Fig. 12). These regions are easily displaceable because of the many components of mucous membrane, fibers of the buccinator and superior pharyngeal constrictor muscles, pterygomandibular raphe, glandular tissue, blood

cast: (A) crest and Fig. ll.- The design of the relief areas is outlined on the mandibular slopes of ridge; (B) retromolar pads; (Cj buccal frenum regions; (0) anterior part of the alveololingual sulcus (between the premylohyoid eminences).

Vo’ume l3 Number 1

PHENOMENON

Fig. 12.-Wax,

OF FUNCTION

in the desired thicknesses,

IN COMPLETE DENTURE

PROSTHODONTICS

is placed on the design of the relief

19

areas on the

cast.

Fig. 13.-The shaded areas are the labial flange; spacer wax (Fig.

impression surface of the completed and relieved acrylic resin tray. The lighter not relieved: (A) buccal flanges; (B) labial surface of the inferior border of (C) retromylohyoid eminences. All other surfaces have been formed over the 12).

vessels, and nerves that make up their architectural pattern. The activity of the buccinator and superior pharyngeal constrictor muscles, which join to form the pterygomandibular raphe, necessarily limits the amount of pressure to be applied, if these muscles are not to become dislodging forces for the denture. For this reason, additional space for relief must be provided inside the parts of the tray that cover the retromolar pads. The amount of relief space should be modified to accommodate different anatomic foundational conditions. For example, a spiny, knife-edge residual alveolar ridge may require an additional 0.5 mm. of relief space ; soft, pendulous hyperplastic tissue, unsupported by bone, may require an increase of 0.5 mm. of relief space. The primary stress-bearing areas (the buccal shelves) between the buccal frenula and the retromolar pads, the labial vestibule between the buccal frenula, and the retromylohyoid fossae are not relieved in order that the stress loads can be directed to the structures supported by cortical bone that can best carry the pressures and serve as contact areas for the impression tray (Fig. 13).

J. Pros. Den. Jan.-Feb., 1963

MARTONE

F

F

16.

Fig. 14.-The superior surface of the completed acrylic resin tray with three positioning handles placed in the neutral zone which is the area that will be occupied by the teeth on the finished denture. Fig. 15.-The first corrective impression made in a zinc oxide and eugenol impression material in the functional acrylic resin tray. Note the pressure areas that are to be corrected where the tray shows through the sine oxide and eugenol wash. Fig. 16.-The final corrected mandibular impression. Note that no part of the tray shows through the impression wash and that the “S” curve has been perfected in the lingual flanges.

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PHENOMENON

OF FUNCTION

IN

COMPLETE

DENTURE

PROSTHODONTICS

21

The acrylic resin tray is constructed to resemble the completed denture. It has an over-all thickness of 3 mm. extending to the reflections as recorded on the cast. The lingual flanges over the mylohyoid regions should be 5 to 6 mm. thick. Three handles, approximately 2 by 8 by 8 mm., are built in a vertical position on the tray to serve as positioning posts. The anterior handle is placed slightly labial to the crest of the ridge in the position of the incisor teeth, and the two posterior handles are located directly over the crests of the ridge at the lowest points of the ridge, as viewed from the side, to avoid pressures on the inclines which would cause the tray to tend to slide forward or backward. The location of these handles is in the neutral zone between the cheeks and the tongue. Thus, the handles of the tray occupy the position of the teeth on the finished denture (Fig. 13). All undercuts are removed from the impression surface of the tray and 3 mm. of tray material is removed from the bz~cab surface of the lingual flange. This provides space for the tissues above the mylohyoid muscle when the tongue is elevated or thrust to the opposite side, simulating the function of removing food from the buccal vestibule. The basic outline of the border of the lingual flange resembles that of an “S,” and it should slope toward the tongue in the molar region, The buccal surface of the buccal flange should slope toward the cheek so it faces up and out. ZINC

OXIDE

AND

EUGENOL

IMPRESSION

The tray, loaded with a zinc oxide and eugenol impression material, is carried into the dry, half-opened mouth. With a rotating movement, the retromylohyoid eminences are seated into place. The anterior part of the tray is seated by placing the index and middle fingers of one hand on the posterior positioning handles. After 15 seconds, the index finger of the other hand is placed on the anterior handle, and the patient is directed to swallow for 1.5 seconds, then suck for the same amount of time. After 15 seconds, the index finger is removed from the anterior handle, light pressure is maintained on the posterior handles, and the patient is instructed to open the mouth wide and hold this position for 15 seconds, then touch the maxillary lip with the tongue and maintain this position for 15 seconds. There is a critical time factor involved in recording these functional movements and positions within the setting period of the impression material. The patient’s ability to perform the correct movement at the right time can determine the success of the impression. A rehearsal of these movements by the patient before the impression is made is beneficial for all patients, but essential for those who have a slow reflex response or who customarily perform only delicate, limited movements. CORRECTIVE

IMPRESSION

PROCEDURE

Even though extreme care has been taken to construct an accurate tray designed to control the soft impression material, and to meet the requirements of a functionally adequate final impression, the first zinc oxide and eugenol impression is seldom clinically acceptable (Fig. 15). H owever, it does serve as a means for evaluating the accuracy of the modified tray. Zinc oxide and eugenol impression material lends itself readily to corrective procedures which are necessary in perfecting the impression.

22

MARTONE

J. Pros. Den. Jan.-Feb., 1963

A final impression may be considered adequate when no areas of the tray show through the impression wash. Such areas indicate pressure spots and require further reduction with a sharp vulcanite scraper. After the pressure areas have been relieved in the tray, the remaining zinc oxide and eugenol impression paste is removed from the tray except that over the retromylohyoid eminences, the buccal flanges, and the labial side of the labial flanges. A new mix of zinc oxide and eugeno1 paste is applied to the corrected tray, the impression procedure is repeated, and the impression is removed and re-evaluated. This corrective procedure is repeated until all of the pressure areas have been eliminated (Fig. 16). PRELIMINARY

MAXILLARY

IMPRESSION

Before the preliminary maxillary impression is started, a visual and tactile study of the anatomy of the maxillary arch and its related structures enables the dentist to form a mental impression of the requirements of the finished denture. During the building of the impression, his ability to observe the anatomy and knife trim the impression to conform it to the anatomy will save repeated insertions of the impression in the mouth. Observations are made, with the patient’s mouth half open, of : the thickness of the soft tissue covering the median palatine suture ; the size and shape of the torus palatinus, if any ; the rugae ; the incisive papilla ; the labial vestibule (the area between the right and left buccal frenula and the distance from the crest of the ridge to the labial reflective tissues) ; the buccal vestibule (the space between the ridge and the cheeks extending from the buccal frenula to the hamular [pterygomaxillary] notches and the space to be filled by the buccal flanges of the denture) ; and the posterior palatal seal region, which lies between the right and left hamular notches. At the midline of this region are two small indentations (foveae palatinae) which are used as a midway landmark in determining the location of the distal extent of the denture. The vibrating line, an imaginary line where movement begins in the soft palate when the patient says “ah,” is usually located about 2 mm. anterior to the foveae palatinae (Fig. 17). Initial procedures for making the preliminary maxillary impression are similar to those used for the mandibular arch. The chilled modeling compound impresFig. 17.-A correlation of the anatomic landmarks: A, as seen in the maxillary arch of the patient; B, with the corresponding denture landmarks indicated on the maxillary preliminary impression; and C, with the underlying anatomic structures reflected in a superior view of a dissection of the maxillary arch. A, An intraoral view of the patient’s maxillary arch showing: (1) labial frenum; (2) labial vestibule; (3) buccal frenum; (4) buccal vestibule; (5) coronoid bulge; (6) residual alveolar ridge; (7) maxillary tuberosity; (8) hamular notch: (9) posterior palatal seal region; (IO) foveae palatinae; (II) median palatine raphe; (12) incisive papilla; (13) rugae region. B, The maxillary preliminary impression showing the denture landmarks: (2) labial notch: (2) labial flange; (3) buccal notch; (4) buccal flange; (5) coronoid contour; (6) alveolar groove; (7) maxillary tubercular fossa; (8) pterygomaxillary seal; (9) posterior palatal seal; (10) foveae palatinae eminences; (11) median palatine groove; (12) incisive fossa: (13) rugae grooves. C, A dissection of the maxillary arch showing: (1) mucous membrane (no muscles present); (2) superficial muscles of facial expression (the depressor septi nasi muscle is shown in this dissection); (3) caninus muscle; (4) buccinator muscle; (5) ramus of mandible, (so) masseter muscle; (6) Abrous connective tissue covering the residual ridge, (6~) alveolar bone; (7) fibrous connective tissue, (7s) maxillary tuberosity; (8) hamular notch, (8~) pterygoid hamulus, (8b) tendon of tensor veli palatini muscle; (9) palatal glands, (9a) median palatal raphe of the soft palate: (10) foveae palatinae ducts and glands; (11) median palatine suture; (12) nasopalatine foramen, (I2a) nasopalatine blood vessels and nerves; (23) fibrous connective tissue. (Illustration for Fig. 17, C courtesy of Linden F. Edwards and Carl 0. Boucher.)

gt;;e;

\”

PHENOMENON

OF

FUNCTION

IN

COMPLETE

DENTURE

PROSTHODONTICS

23

sion is removed from the oversized stock metal tray and is developed into a modeling compound tray in which the final impression will be made. MAXILLARY

MODELING

COMPOUND

TRAY

The compound tray is knife trimmed to resemble the approximate size of the finished denture. Following the contours of the anatomic structures, a pencil out-

Fig.

17.-For

legend

see opposite

page.

J. Pros. Den.

Jan.-Feb.,

1963

Fig. l&-The various sections of the maxillary preliminary compound impression tray are knife trimmed to the desired thicknesses. The labial and buccal flanges are reduced to a thickness of 2 mm.: (A) buccal notches; (B) labial notch.

line is made along the borders 2 mm. below the edge of the impression. The borders are reduced 2 mm. in accordance with this outline. From about 5 mm. distal to the buccal notch to the corresponding point on the opposite side, the labial and buccal flanges are reduced to a thickness of 2 mm. If the borders do not reach the reflective tissues when the mouth is in a resting position, red modeling compound may be added and border molded to establish adequate length of the flange. Flanges of this thickness allow sufficient space for the final impression material which must record, with minimal distortion, the shape of the structures during functional movements (Fig. 18). They also provide a normal amount of support for the lips and cheeks. If additional lip support is required, however, the thickness should be increased. The amount of thickness is determined by the amount of residual bone lost, and varies with the length of time the natural teeth have been missing. The longer the teeth have been out, the thicker the flange must be. Esthetic considerations thus begin when the tray is made.

Fig. lg.-Low-fusing red modeling compound is added to the borders of the buccal flanges: (A) to All the buccal vestibules. The coronoid contours (0) are perfected. The transfer of the vibrating line (B) from the mouth extends through both hamular notches (C) and across the palate 2 mm. anterior to the foveae palatinae (E).

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;”

PHENOMENON

OF FUNCTION

IN COMPLETE

DENTURE

I’ROSTHODONTICS

25

The alveolar groove and palatal surfaces of the impression are perfected by repeated insertions of the impression into the mouth after its impression surface has been softened and minimal pressure used. The crest of the maxillary residual alveolar ridge serves as the primary stress-bearing area because the underlying soft tissues are made up of fibrous connective tissue, closely attached to bone and not easily displaceable under the masticatory loads. The rugae region serves as a secondary stress-bearing area because the tissues are of similar composition and are set at an angle to the occlusal surface of the residual ridge. Thus, because of its raised and irregular architectural outer surface, it aids in the stability of the denture against thrusts in an anterior direction. The buccal flanges are developed to fill the buccal vestibule completely without interfering with function. Red modeling compound is added to these borders, if necessary, and the patient is instructed to move the mandible from side to side, protrude it, and then open the mouth wide (Fig. 19). By increasing the surface area, the forces of adhesion, cohesion, and capillary attraction are increased propor-

Fig. 20.-Low-fusing green modeling compound is added to the posterior palatal seal region (C), extending approximately 2 mm. anterior to the vibrating line (B). The pterygomaxillary and posterior palatal seal regions are perfected.

tionally, thus improving the border seal and retention. However, if the flanges are overextended or made too thick, the tray will interfere with mandibular movements, and retention of the denture will be decreased. POSTERIOR PALATAL

SEAL

The distal end of the modeling compound tray must extend posteriorly 2 mm. beyond the vibrating line. This line is located by having the patient say “ah” several times and observing where the motion begins in the palate. An indelible pencil is used to mark the location of the line in the mouth. The tray is inserted in the mouth for the transfer of this marking. The tray is removed, chilled, and green modeling compound is placed over the region of the vibrating line (the area of the posterior palatal seal). This compound is 4 mm. in width and extends 2 mm. on either side of the vibrating line. It is placed through the hamular notches and onto the distal ends of the buccal flanges. The green compound is then chilled, heated,

26

MARTONE

tempered, and held in the mouth under steady pressure by the index finger placed on the center of the palate just anterior to the position of the posterior palatal seal. The thickness of the seal is determined by the displaceability of the underlying soft tissues in this region, but it should not exceed 1 mm. (Fig. 20). The maxillary modeling compound tray is modified by scraping compound from the impression surface with a sharp knife or vulcanite scraper (depending on the contour of the area) to provide sufficient space for the final impression material. This makes it possible to record the shape of the underlying tissues and structures without distortion. The posterior palatal seal is maintained as it was formed in green compound. No relief is made in the posterior palatal seal area of the tray because the corresponding anatomic region is capable of tolerating pressures since it is composed mostly of palatal glands which are displaceable. With the exception of the posterior palatal seal, the height of the entire border is reduced 1.5 mm. A

Fig. al.-The entire impression surface is scraped to the desired depths as shown, with the exception of the pterygomaxillary and posterior palatal seal regions, in order to provide space for the final impression wash material.

Fig. 22.-A wash flow lines from palatal Fig. 23.-Another salivary secretions had

impression made of zinc oxide and eugenol impression material showing glandular secretions in the posterior part of the palate. impression made in the same tray with zinc oxide and eugenol after the been lessened by administration of Pro-Banthine.

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PIIENOMENON

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DENTURE

PROSTHODONTICS

27

space of at least 0.5 mm. is provided over the impression surface, and the rugae and incisive papilla regions are provided with an additional 0.5 mm. of space (Fig. 21). CHOICE

OF

THE

FINAL

IMPRESSION

MATERIAL

Tf a functionally accurate tray has been constructed, various materials may be used for making the final impression. G The specific material selected, however, must be used in accordance with the directions supplied by the manufacturer if the desired results are to be obtained. Selection of the material may be governed by diagnostic findings or by the degree of success the dentist has with a specific material. The essential oils in the zinc oxide and eugenol impression paste materials stimulate the flow of palatal salivary secretions. A final impression in zinc oxide and eugenol paste, developed for a patient \vith copious heavy, ropy, palatal secretions may reflect the flow lines caused by these secretions (Fig. 22). Flow lines in a final impression are actually indications of an erosion of the wash material in a region where the tissues are readily compressible by this hydraulic action. Such an area of erosion in a final wash impression builds up hydraulic pressures because the posterior palatal seal prevents the material from escaping. Consequently, a denture made from such an impression will have an area which is not in contact with the underlying tissues in this region. The outline of this defective surface in an impression resembles an “&I” in shape. The administration of 15 mg. of Pro-Banthine* with phenobarbital (a drug which lessens salivary secretions) one-half hour before the impression is made will reduce the defects. The absence of flow lines from those secretions is apparent in the impression shown in Fig. 23. Premeditation of this nature may be considered if impression materials, such as polysulfide and silicone rubber which require a dry operating field, are to be used. Prior to the making of these impressions, the patient should rinse the mouth and swallow twice. ‘Dry gauze is then placed over the glandular region of the paiate until the impression procedure begins. The necessity for these procedures for a final impression in a patient with heavy, ropy, palatal secretions can be minimized by using a modified plaster’ as the corrective wash material. Such secretions are readily absorbed by this material, leaving the soft tissues in direct contact with the impression material. This material accurately records the tissues and underlying structures without distorting and displacing them. MAXILLARY

FINAL

IMPRESSION

The tray carrying the plaster wash is positioned and gently rotated to place. The tray is held in place with a light pressure from the index finger of the right hand in the center of the tray anterior to the posterior palatal seal. When the Plas*G. D. Sea-k tPlastogum.

& Co.

28

MARTONE

J. Pros. Den. Jan.-Feb., 1963

togum begins to lose its shiny appearance and assumes a dull, velvety sheen, the borders of the impression are molded. In order to perfect the borders near the buccal notches, the cheek is grasped below the buccal frenum with the index finger and thumb of the free hand and pulled downward, forward, and backward. This procedure is repeated for the opposite side. The form of the labial notch is developed by gently grasping the lip at the philtrum with the same two fingers and gently elevating the lip straight upward, forward, and downward. The lip is not moved laterally during this manipulation to maintain the border seal in this critical area. The distobuccal flange borders are molded by stroking the cheeks downward with the thumb and forefinger of the free hand. The patient is then instructed to open the mouth wide and move the lower jaw from side to side. When the mouth is opened wide, the space in the buccal vestibules is reduced. This is due to the facts that the mucous membrane of the cheek is pulled down by the mandible and the rami move forward into the spaces as the mouth is opened wide. When the mandible is moved from side to side, the distobuccal angles of the buccal flanges of the impressions are contoured, and their thicknesses are molded by the rami and the soft tissues overlying them and the coronoid processes of the mandible. The impression is removed from the mouth after the plaster has thoroughly set. A final impression that fulfills the anatomic objectives has no areas of the tray showing through the wash material except at the posterior palatal seal. The posterior palatal seal on the tray should show through the wash material because pressures have been purposely directed against this area (Fig. 24). Other areas of the tray which show through indicate pressure spots which must be relieved and subsequently perfected by removing the inadequate impression and making an entirely new wash impression. When the impression has been perfected, the cast is poured. STABILIZED

DENTURE

BASES

It is essential that comfortable, stabilized, and accurate denture bases be constructed before acceptable maxillomandibular records can be made. These bases can be made by sprinkling self-curing acrylic resin on the casts and allowing it to harden. However, for many patients it is desirable to construct a metal cast base for the mandibular denture because it has the advantages of (1) accuracy which is retained, (2) reduction in bulk which is possible because of the strength and rigidity of the casting, and (3) its compatibility with the underlying tissues. This metal casting serves as both the temporary and permanent base (Fig. 25). ANATOMICALLY

CONTOURED

OCCLUSION

RIMS

Occlusion rims serve as a means for making provisional vertical dimension registrations and for transferring these registrations to the articulator, and as bases and guides for the placement of teeth. It is logical, therefore, to use functional anatomy to determine the contours of these rims. When no other aids are available, this may be done by having the patient mold the wax or compound

pJi;tr

‘1” PHENOMENON

0F FUNCTION

IN COMPLETE

DENTURE

PROSTHODONTICS

29

Fig. 24,The perfected maxillary plaster wash impression. Note the anatomically formed posterior palatal seal in the modeling compound tray showing through the plaster wash, indicating that the desired pressure had been developed in this region.

Fig. 25.-The cast metal mandibular suggests its use whenever possible.

base. Note the broad coverage

design. The advantages

occlusion rims by functional movements of swallowing to contour the rim to resemble the space where the natural teeth and supporting structures were. When pre-extraction diagnostic casts, showing the dimensions and contours of the patient’s natural teeth and supporting structures, are available, I construct occlusion rims in accordance with these dimensions and cont0urs.r If the patient’s old dentures were made in accordance with the principles of good denture construction, those dentures may be modified to determine the potential denture space.5x8 MAXILLOMANDIBULAR

RELATIONS

Unfortunately, centric relation is probably the only maxillomandibular record in complete denture prosthodontics that can be precisely repeated and exactly verified. Vertical dimensions and other records are dependent upon the judgment of

30

J. Pros. Den. Jan.-Feb., 1963

MARTONE

the dentist in determining the necessary compromises between neuromuscular functions in the mouth region, bony contours of the residual ridges, and esthetic factors. Acceptable records begin with provisional registrations in which occlusion rims, made on stabilized bases, are the recording medium. More accurate records can be made and errors can be more readily observed later when the teeth, set in the occlusion rims, intercuspate in the interocclusal records. The methods which will be suggested for making these records have been selected because (1) they are clinically practical since they are comparatively simple procedures to perform ; (2) they require a minimal amount of apparatus which would interfere with the patient’s normal functional performances, and (3) they provide records which are sufficiently accurate for practical purposes. VERTICAL

RELATIONS

Vertical dimension has to do with the length of the face as it is maintained either by the balanced tonicity of the supramandibular and inframandibular muscles or by the occlusion of the teeth. Qualifying phrases must be used with the term vertical dimension to designate the one being considered. In recording maxillomandibular relations, the vertical dimension of rest position is the first position registered. This is a physiologic position and exists only in the patient’s mouth. It is the vertical separation of the two jaws which exist when the entire mandibular musculature is in a state of tonic contraction. This measurement is a provisional reference point from which the recording of the vertical dimension of occlusion may be related. Vertical dimension of occlusion is the vertical separation of the two jaws that occurs when the teeth are in occlusal contact. It is a relation that is established by the dentist and transferred to the articulator. The vertical dimension of occlusion is less than the vertical dimension of rest position. The difference between the two dimensions is the interocclusal distance. PROVISIONAL

VERTICAL

DIMENSION

OF

PHYSIOLOGIC

REST

POSITION

With the patient in a relaxed, restful position with the eyes closed, several functional methods may be used to obtain acceptable physiologic rest position records which should then be correlated. After each of the functional activities of swallowing, speaking, and breathing, the patient’s mandible assumes a resting position by being suspended by the equal tonicity of its musculature. When the lips are in slight contact with each other, facial measurements are recorded between two landmarks, the base of the nose and the mentolabial sulcus (Fig. 26). Swallowing.-The act of swallowing is used initially because it provides a more natural action to determine the height of the mandibular occlusion rim. The occlusa.l surface of the mandibular occlusion rim is uniformly softened in a warm water bath, and the occlusion rim is placed in the patient’s mouth. With the maxillary occlusion rim in place, the patient is asked to swallow several times. The space between the two facial reference points is determined and recorded. l

““‘ume I3 Number 1

PHENOMENON

OF FUNCTION

IN COMPLETE

DENTURE

PROSTHODONTICS

31

Fig. 26.-The mouth region. The black arrows indicate the measurable facial landmarks of physiologic rest position at 60 mm. The distance from the white arrow above the mentolabial sulcus to the black arrow at the base of the nose measures 57 mm. and represents the vertical dimension of occluion. The distance between the two registrations represents the interocclusal distance.

The swallowing procedure should be repeated if necessary. The occlusion rims are removed from the patient’s mouth, and separated. Phonetics.-Certain speech sounds may serve as an aid in recording physiologic rest position. Speech containing VL sounds brings the lips together and positions the mandible in physiologic rest. The patient is instructed to say a series of ‘yy1sounds until he experiences fatigue sensations at which time a measurement is made. Breathing.---Facial measurements obtained immediately after the patient has inhaled and exhaled several times serve as additional aids in recording physiologic rest position. Pre-extraction records, photographs, and observations of facial contours and of the old dentures may also be utilized in determining physiologic rest position. A correlation of these various findings serves as a reference position for the first provisional step in obtaining the vertical maxillomandibular relation records. The occlusion rims are finished and contoured to dimensions and shapes similar to those of the artificial teeth and supporting bases that will occupy the space the natural teeth and supporting structures occupied. VERTICAL

DIMENSION

OF OCCLUSION

A permanent record of the vertical dimension of occlusion has been a matter of concern in prosthodontics because of the foundational changes which occur continuously as a result of degenerative processes. Such a record, made while the natural teeth are present or at the time dentures are constructed, can be of great value in the future prosthodontic treatment of the patient. PROVISIONAL

VERTICAL

DIMENSION

OF OCCLUSION

Speech activities, similar to those used in recording the physiologic rest position, are employed in determining the provisional vertical dimension of occlusion. Phonetics.-The patient is asked to count rapidly from 45 to 70. Observations

32

J. Pros. Den. Jan.-Feb., 1963

MARTONE

should be made by standing slightly to the side of the patient. During the speech performance, the two occlusion rims should not contact each other, Probably the most critical closures to observe for any interference will occur during the utterance of the s sounds as in 46, 56, and 60 through 69. If interference is noted, the occlusion rims should be reduced in height until there is a slight clearance when the patient makes the s sounds. PROVISIONAL

CENTRIC

RELATION

Centric relation is a bone-to-bone relation in the patient’s mouth. It is recorded provisionally, and this recording is used as a starting horizontal reference relation in developing an occlusal scheme. It can be verified for accuracy because it can be duplicated and reproduced. This position becomes of extreme importance because centric relation will be observed and checked continually at every available opportunity from the construction phase through the postoperative phase. Every appointment begins and ends with the rehearsal of centric relation closures in order that the patient and the dentist can recognize this positional relationship. The maxillary occlusion rim is scored by cutting two nonparallel grooves, 4 mm. in depth, on each side in the premolar and molar regions. The height of the occlusal surfaces of the mandibular occlusion rim is cut down about 3 mm. A roll of soft beeswax 5 mm. in diameter is placed on the occlusion rim, replacing the wax previously removed. The beeswax is made uniformly soft by heating it in a warm water bath in order that equalized pressures can be recorded. ORIENTATION

OF THE

MAXILLARY

CAST

ON

THE

ARTICULATOR

The use of the arbitrary face-bow transfer to relate the maxillary cast to the articulator is a simple and practical procedure which requires approximately five minutes of the dentist’s time. Its accuracy is sufficiently close to that of the more complicated and more time-consuming kinematic transfer procedure for practical purposes, since the recording bases are supported by displaceable, movable structures and tissues. The fact that the face-bow transfer is frequently omitted may be because it is an additional step. However, the procedure can be combined with the provisional registrations of vertical dimension of occlusion and centric relation, and the facebow assembly, supported by and fastened to the occlusion rims, may be removed from the mouth and related to the articulator in one step. PROVISIONAL

CENTRIC

RELATION

AND

FACE-BOW

RECORDS

The mandibular denture base is placed in the patient’s mouth. With the facebow fork fastened to the maxillary occlusion rim, the maxillary base is also stabilized in the mouth with the thumb and forefinger of the left hand. The patient is instructed to pull the jaw back. Simultaneously the mandible is gently guided to its retruded horizontal position by the dentist’s index finger of the right hand pushing on the chin. The patient is then asked to swallow and hold. The act of swallowing elevates the mandible near to the vertical level of the established vertical relation when the patient had natural teeth.O

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PHENOMENON

OF FUNCTION

IN

COMPLETE

DENTURE

PROSTHODONTICS

33

The face-bow is attached to the fork and related to the predetermined positions on the patient’s face. The entire combined record assembly is removed as a single unit and related to the articulator. The face-bow serves to support both casts in position while they are attached with plaster to the articulator. SUMMARY

In the first article of this series, the significance of the vitality factor of a patient was suggested, and the problems associated with attempts to “measure” functional anatomy were recognized. In the recording phases of denture construction, we are confronted with such problems. Necessarily, then, the development of impressions and the registrations of maxillomandibular relations involve a series of provisional steps which must be thoroughly tested and verified before acceptable final results are attained. Just as the preliminary modeling compound impression was the initial step in developing an accurate, functional, final impression, so the provisional maxillomandibular registrations, made with the occlusion rims, are the first approach to establishing the final registrations. With the selection of teeth and the placement of them in the occlusion rims, we continue our verifications of measurements of functional anatomy. This phase will be considered in the next article which will consider esthetic factors and carry the construction phases to their completion. REFERENCES

1. Boos, R. H.: Complete Denture Technique, Including Preparation and Conditioning, D. Clin. N. America, pp. 215-230, March, 1957. 2. Edwards, L. F., and Boucher, C. 0. : Anatomy of the Mouth in Relation to Complete Dentures, J.A.D.A. 29:331-345, 1942. 3. Boucher, C. 0. : Impressions for Complete Dentures, J.A.D.A. 30:14-25: 1943. 4. Martone, A. L., and Edwards, L. F.: The Phenomenon of Function m Complete Denture Prosthodontics. Anatomy of the Mouth and Related Structures. III. Functional Ana-

tomic Considerations,J. PROS.

DEN.

12:206-219,1962.

5. Martone, A. L. : The Phenomenon of Function in Complete Denture Prosthodontics. Clinical Applications of Concepts of Functional Anatomy and Speech Science to Complete Denture Prosthodontics. VI. The Diagnostic Phase, J. PROS. DEN. 12:817-834, 1962. 6. Woelfel, J. B. : Contour Variations in Impressions of One Edentulous Patient, J. PROS. DEN.

12~229-254,1962.

7. Roberts, A. L. : The Effects of Outline and Form Upon Denture Stability and Retention, D. Clin. N. America, pp. 293-303, July, 1960. 8. Sears, V. H.: Comprehensive Denture Service, J.A.D.A. 64:538, 1962. 9. Shanahan, T. E. J.: Physiologic Vertical Dimension and Centric Relation, J. PROS. DEN.

6:741-747,1956. 909 NORFOLK MEDICAL TOWER NORFOLK 7. VA.