Occlusal Schemes for Complete Dentures PDF

314 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures bone may have been lost from the maxillae than from the mandible, and the occlusal plane should not be placed an equal distance between the two ridges. It also should not be at a level that would favor the we...

314 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures bone may have been lost from the maxillae than from the mandible, and the occlusal plane should not be placed an equal distance between the two ridges. It also should not be at a level that would favor the weaker of the two ridges (basal seats). The most reliable guides are esthetics or anterior tooth placement and the retromolar pads. The buccolingual position of the posterior teeth and the posterior arch form are determined anteriorly by the position of the canine and posteriorly by the shape of the basal seat and the location of the retromolar pads. The curvature of the arch of anterior teeth should flow pleasingly toward the posterior teeth. The posterior teeth are positioned in such a way that they are properly related to the bone that supports them and to the soft tissues that contact their facial and lingual surfaces. In the final tooth arrangement, the posterior form of the arch will be determined largely by the “neutral zone” between the cheeks and tongue. This is the space resulting from the removal of the posterior teeth and the loss of bone from the residual ridges. The pressure of the cheeks and tongue against the facial and lingual surfaces of the erupting natural teeth was strong enough to influence their alignment in the dental arch. These forces also are applied against dentures. Therefore the final arrangement of the arch must be developed with respect for the tongue and cheek (see Figure 17-15). The solution to the problem is to position the teeth along a line extending from the tip of the canine to the middle of the retromolar pad. This arbitrary line should pass through the central fossa of the mandibular premolars and molars (Figure 17-16). The basic principle for the buccolingual positioning of posterior teeth is that they should be positioned over the residual ridge. The canine and retromolar pad should provide guides for this arrangement. A B OCCLUSAL SCHEMES FOR COMPLETE DENTURE OCCLUSION The occlusal scheme or the tooth molds selected for occlusal rehabilitation will depend on the concept of occlusion that has been selected to satisfy the needs of the patient. The posterior teeth, arranged according to the occlusal concept selected, should fulfill the dentist’s philosophy of occlusion as well appear esthetically pleasing. Posterior tooth forms have aroused a great deal of controversy among clinicians and researchers. Chewing efficiency tests have shown a slight advantage to cusped teeth. Cuspal anatomy has not been shown to have any significant effect on the supporting tissues. Patient preference surveys have been inconclusive. Prosthetic tooth anatomy seems to be more important to dentists than to the patients who use the teeth. In the absence of clear evidence of the benefits of one tooth anatomy compared with others, dentists should use the least complicated procedures and tooth forms that will satisfy their con- Figure 17-15 A, Mandibular teeth positioned too far toward the buccal of the ridge (r) and too far toward the lingual (l). B, Positions of the mandibular teeth corrected from those shown in A. Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient 315 A B Figure 17-16 A, The mean residual ridge, as well as selected anatomical landmarks, provides the guidances used in the buccolingual and anteroposterior positioning of the mandibular posterior teeth. B, Centering the wax occlusal rim on the mandibular record base with the anatomical guides is essential to the appropriate placement of the artificial teeth. The basal seat, or mean residual ridge, and the retromolar pads bilaterally are used to develop the positioning and height of the wax occlusal rim. cepts of occlusion and articulation of a mucosal supported dentition. There are several schools of thought on the choice of occlusal forms of posterior teeth for the three concepts of occlusion most often selected, namely, (1) bilateral balance, (2) monoplane or nonanatomical, and (3) lingualized articulations. Anatomical molds usually are selected for bilateral balanced articulation; however, nonanatomical teeth can be used in a balanced concept with the use of compensating curves. Nonanatomical or cuspless teeth are generally the choice for monoplane 316 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures articulation, although teeth with cusps also can be used. For the lingualized occlusal concept, a combination of upper anatomical and lower nonanatomical molds has been introduced by several tooth manufacturers. Arranging Anatomical Teeth to a Balanced Articulation The anterior teeth are set with a minimal vertical overlap of 0.5 to 1 mm and 1 to 2 mm of horizontal overlap to establish a low incisal guidance (see Figure 17-14). After these requirements are satisfied, the teeth may be rotated, tipped, overlapped, or spaced to achieve naturalness. In the arrangement of the posterior teeth, most clinicians set the mandibular teeth before the maxillary because this provides better control of the orientation of the plane of occlusion both mediolaterally and superoinferiorly. Number of Posterior Teeth Set The decision on the number of teeth to use will depend on the available space for posterior teeth from the distal of the canine to the retromolar pad. Placing teeth on the residual ridge incline as it ascends to the pad should be avoided. If only three teeth are to be arranged, it is more convenient to drop the first premolar and place the second premolar and the first and second molars into the available space. Eliminating the first premolar is a logical choice because this tooth has less occlusal surface for the mastication of food. Setting the Mandibular Teeth First The primary consideration in positioning the premolars is that they follow the form of the residual ridge. The facial surface of the premolars should be perpendicular to the occlusal rim, and yet slightly facial to the canine, but never farther facially than the buccal flange. In the ideal situation, the mandibular first and second premolars, with their central grooves, are positioned on a line from the canine tip to 1 to 2 mm below the top of the retromolar pad (Figure 1717). Before the first premolar is positioned, a small section of the mandibular wax occlusal rim is removed to accommodate the first and second premolars. A small cone of soft pink baseplate wax is attached to the neck of the first premolar tooth, and it is positioned in the arch in contact with the canine and with its central grooves on the reference line from the tip of the canine to the retromolar pad. The long axis of the tooth is positioned so that the cusp tips are level with the remaining mandibular wax occlusal rim. The second premolar is set in a similar manner. When these lower teeth have been arranged, a segment of the maxillary occlusal rim is removed to accommodate the first maxillary premolar, which is set into maximum intercuspation with the two lower premolars. If a space develops between the maxillary canine and first premolar, the maxillary first premolar is aligned with the canine, and the maxillary second premolar is positioned in the upper arch. Then the two mandibular premolars are repositioned to achieve maximum intercuspation with the maxillary premolars. The mandibular first premolar may need to be adjusted mesiodistally to fit into the available space. Reshaping of the tooth by grinding usually will satisfy the space requirements. Maintenance of the occlusal plane by positioning the mandibular teeth at the appropriate height is of paramount importance as is the placement of their central grooves on the reference line from the tip of the canine to the retromolar pad. The first three premolars set (two mandibular and one maxillary) are the key to the relative anteroposterior intercuspation of all the remaining posterior teeth. Once the premolars are set and properly related to each other, positioning of the remaining mandibular posterior teeth is easily accomplished. In the positioning of the mandibular first molar, the central groove is placed on the canine to retromolar pad reference line. The vertical height of the tooth is adjusted by positioning the cusp tips on the occlusal plane. After these adjustments are completed, the maxillary first molar is articulated with the mandibular first molar. A small segment of the wax occlusal rim is removed, and the tooth is attached to the record base with a small cone of soft baseplate wax. After the tooth is positioned, it is sealed to the record base with molten wax and the hot no. 7 spatula. After the maxillary first molar is positioned, the articulator is closed so that the mandibular tooth will assist in seating the maxillary tooth into maximum intercuspation. The index finger is used to hold the cervical neck of the maxillary tooth in place while the articulator is closed. Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient 317 1-2 mm A B Figure 17-17 A, A point 1 to 2 mm below the top of the retromolar pad and the tip of the positioned mandibular cuspid are guides used in the placement of the mandibular posterior teeth. B, The central grooves of the posterior teeth are positioned on a line between the cuspid tip and the middle of the retromolar pad. When only three posterior teeth are arranged, it is essential that the central grooves of the molars be positioned slightly to the buccal to avoid crowding the tongue. This will develop the desired lingual cusp contact of the maxillary molar in the central fossa of the mandibular antagonist. The same procedure is used for setting the remaining maxillary teeth. The teeth on the opposite side of the dental arches are arranged in a similar manner. Setting the Maxillary Teeth First In arranging the maxillary posterior teeth first, start with the maxillary first premolar and continue the arrangement of the teeth through to the second molar. During the positioning of these teeth, the maxillary lingual cusps are aligned with the reference line that has been scribed on the mandibular wax occlusal rim from the mandibular canine tip to the middle of the retromolar pad. Positioning the maxillary teeth with a slight opening of the contact points between these teeth allows the mandibular teeth to better assume their correct mesiodistal position as they are interdigitated with the maxillary posterior teeth. Because this intercuspation is very exacting, it is best done by placing the mandibular first molar in position first. For the first molar to be placed and still preserve the reference line on the wax occlusal rim, a block of wax approximately the size of the mandibular molar tooth is all that is removed from 318 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures the mandibular wax occlusal rim. When the mandibular first molar is placed in position without adjoining teeth, it is possible to determine its correct anteroposterior position more easily. If the mandibular first premolar is positioned first, the inconstant vertical overlap might crowd the tooth into difficult intercuspation with the maxillary teeth, and this would be continued throughout all the mandibular posterior teeth. Therefore placement of the mandibular first premolar is left until last to take up all the variation in vertical and horizontal overlap of the anterior teeth. The first premolar is then ground to fit the remaining space. The second mandibular molar is placed after the positioning of the first molar, thereby assuring its anteroposterior correctness. The mandibular second premolar is next placed, after another block of wax has been cut away from the occlusal rim. The mandibular first premolar is the last tooth to be placed. It frequently needs to be ground because of the minimal space remaining between the second premolar and the canine after these teeth have been arranged in maximum intercuspation. For this reason, the tooth must be ground and shaped to fit the space available. The teeth on both sides of the dental arches are arranged in a similar manner. Evaluating Bilateral Balanced Articulation The presence of a balanced articulation can be inspected after all the maxillary and mandibular teeth have been arranged. However, it must be remembered that unless the teeth are positioned in exactly the same location in the articulator as they were when their primordial forms were carved in the cutting instrument, they will not balance. Furthermore, if the end-controlling factors recorded from the patient and transferred to the instrument are also not the same as those used in developing the tooth molds, one should not expect a perfect bilateral balance to be present. With luck, what one will see during this exercise is that some minor deflections are observed and that some tooth material is available for selective reshaping after processing to achieve the required balanced articulation during the various movements. The amount of movement of the articulator in a lateral direction during this evaluation process should be minimal, usually bringing the maxillary and mandibular canines into an end-to-end relation to each other will suffice. Arranging Nonanatomical Mandibular Posterior Teeth to Balanced Articulation The arrangement of nonanatomical posterior teeth with both anteroposterior and mediolateral compensating curves permits the establishment of a balanced articulation. In such arrangements, the mandibular teeth usually are arranged first followed by the maxillary teeth. The contours established in the wax occlusal rim and the use of the several reference lines and guides developed for the anatomical arrangement also are used with the nonanatomical teeth. The major difference is in the positioning of the mandibular posterior teeth to develop the compensating curves. Number of Posterior Teeth Set Most often, the number of posterior teeth used in balanced articulation with nonanatomical teeth will be limited to three. It is more convenient to drop the first premolar and place the second premolar and the first and second molars into the available space. Eliminating the first premolar is a logical choice because this tooth has less occlusal surface for the mastication of food. With the elimination of the first premolar and with the use of only three posterior teeth, it often is necessary to position the two molars slightly to the facial. Anteroposterior Compensating Curve The anteroposterior compensating curve begins at the distal marginal ridge of the first posterior replacement tooth (which is usually the second premolar) and continues through the second molar (Figure 17-18). The amount of curvature developed is dependent on the steepness of the condylar guidance, but it rarely requires more than a combined 20-degree elevation of the occlusal surfaces of the posterior teeth from the horizontal plane of orientation established by the anterior and posterior reference points. The anteroposterior curve is developed to provide the needed tooth structure for balancing contacts in the protrusive movement. Mediolateral Compensating Curve A mediolateral compensating curve also is needed to provide the needed tooth structure to achieve balanced articulation during lateral movements. This curve also is initiated with the first replacement tooth and Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient continues through the second molar. The degree to which the facial cusps are elevated in relation to the lingual cusps to establish this curve will vary with the condylar and incisal guidances. The curve usually does not exceed 5 to 10 degrees from the horizontal plane of orientation when viewed in the frontal plane (Figure 17-19). 319 First Premolar The position of the first mandibular replacement tooth (second premolar) will be dictated by the position of the lower anterior teeth. The second premolar should be positioned immediately next to the canine, with no space allowed to detract from pleasing esthetics. The central fossa of the mandibular premolar tooth is aligned with the Figure 17-18 The anteroposterior compensating curve involves the cuspid tips and the retromolar pads as the anatomical guides. The curve begins with the mesial of the molar positioned level with the plane of occlusion and the distal surface slightly elevated. The curve continues with the placement of the second molar with the distal surface located at or above the top of the retromolar pad. The extent of the curve rarely exceeds 20 degrees. Figure 17-19 The mediolateral curve is formed by slightly elevating the buccal cusps of the posterior teeth above the lingual cusps. The curve usually does not exceed 10 degrees from the horizontal plane. 320 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures reference line from the tip of the canine to the middle of the retromolar pad. The long axis of the tooth is perpendicular to the occlusal plane, and the facial cusp is slightly elevated above the lingual cusp. First Molar Position the mandibular first molar next to the premolar with the mesial marginal ridge at the same level as the distal marginal ridge of the premolar and its distal marginal ridge slightly elevated. This will position the tooth with its long axis directed anteriorly. The anteroposterior compensating curve begins with this tooth. The distal of the first molar should be elevated approximately 1 mm above the occlusal plane that was established by the anterior and posterior reference points. The amount of elevation may need to be increased or decreased, depending on the mechanical equivalent recorded for the horizontal condylar guidance. A high, condylar guidance will require a greater compensating curve. The central fossa of the first molar should be slightly to the facial in relation to the reference line from the canine to the retromolar pad. This will avoid possible crowding of the tongue. When viewed in the frontal plane, the mediolateral compensating curve, initiated with the setting of the premolar, should be maintained by a slight elevation of the facial cusp above the lingual cusp. The tooth is sealed with the hot no. 7 spatula and pink wax when its arrangement has been achieved. Second Molar The mandibular second molar is positioned with the mesial marginal ridge at the same level as the distal marginal ridge of the first molar. The anteroposterior compensating curve is continued posteriorly by elevating the distal of this second molar tooth approximately 2 mm above the occlusal plane established by the reference points. The long axis of this tooth also will be anteriorly directed. The central fossa of the second molar also will be positioned slightly to the facial of the reference line. The facial cusps of both the first and second molars should be in a straight line when viewed from the occlusal surface. The teeth should not be positioned “around” the remaining residual ridge. The mediolateral compensating curve should be continued as viewed in the frontal plane. When the arrangement is completed, the tooth is sealed to the record base with the hot no. 7 spatula. Remaining Mandibular Posterior Teeth The mandibular posterior teeth are arranged for the other side of the arch with the same criteria and procedures as just outlined. As the remaining teeth are positioned, they should be evaluated in relation to the teeth on the opposite side of the arch. This is extremely important, especially in trying to maintain (1) the appropriate level of the occlusal plane and (2) the same degree of anteroposterior and mediolateral compensating curves for both sides of the mandibular arch. When all teeth have been properly positioned, they are sealed to the record base with pink baseplate wax. Arranging Nonanatomical Maxillary Posterior Teeth to Balanced Articulation First Premolar For most patients, only three maxillary posterior teeth will be used. In such instances, only one premolar and two molars are the customary teeth selected. The premolar selected is usually the maxillary first premolar because of its longer occlusal cervical height, which provides a more esthetic arrangement. After some of the wax occlusal rim distal to the canine is removed, the first premolar is set. Place a small portion of soft, pink wax on the neck of the maxillary premolar and attach the tooth to the record base. Carefully close the articulator and establish contact between the occlusal surface of the maxillary tooth and the central fossa or marginal ridges of the mandibular antagonist. There should be approximately 1 to 2 mm of horizontal overlap of the maxillary facial cusp in relation to the mandibular facial cusp. This relationship will help prevent cheek biting and also will contribute to the attainment of a balanced articulation. First Molar Position the maxillary first molar tooth alongside the premolar, aligning their marginal ridges and facial surfaces. Carefully close the articulator and establish contact between the maxillary occlusal surface and the central fossa or marginal ridges of the mandibular antagonist. Maintain maximum contact between the maxillary occlusal surface with the central fossa of the lower tooth and the 1 to 2 mm of horizontal overlap of the maxillary facial cusp in relation to the mandibular facial cusps. View the tooth-to-tooth relationships from Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient the lingual by turning the instrument around and looking through the tongue space. Seal the tooth with pink wax. Second Molar Position the maxillary second molar tooth with a small cone of pink wax. Again, carefully close the articulator and establish the tooth contacts as you did with the first molar. Seal the tooth to the record base. Remaining Maxillary Posterior Teeth The maxillary posterior teeth are arranged for the other side of the arch with the same criteria and procedures as previously outlined for maxillary posterior teeth. As the remaining teeth are positioned, they should be evaluated for the required contacts between the maxillary occlusal surfaces and the central fossae and marginal ridges of the mandibular antagonists. When all teeth have been properly positioned, they are sealed to the record base with pink wax and evaluated. Bilateral balanced articulation between the maxillary and mandibular teeth will be developed and refined after the dentures are processed with the selective occlusal reshaping procedures. Arranging Nonanatomical Teeth to Monoplane Articulation The technique for arranging cuspless teeth in a flat plane or monoplane occlusal concept is a distinct departure from what has been previously described. With this concept of occlusion, there is no attempt to eliminate deflective occlusal contacts in lateral or protrusive excursions. The dentist’s desire to achieve an optimal esthetic result will require some vertical overlap of the anterior teeth. However, this can generally be accommodated for with sufficient horizontal overlap to permit a range of anterior and lateral movements without anterior tooth contacts. Basically, the patient can clench and grind in and around maximum intercuspation during both functional and nonfunctional activities. However, some deflective occlusal contacts of the posterior teeth will be experienced. When the nonanatomical teeth are arranged to satisfy the monoplane occlusal concept, the condylar inclinations on the articulator are set at 0 degrees. The articulator is reduced to a simple hinge articulator. With the mandibular wax occlu- 321 sion rim positioned on its cast on the articulator, a small segment of the rim is removed from the posterior tooth area. The maxillary posterior teeth are positioned one at a time with the mandibular wax occlusal rim and its references and guides for tooth placement. The maxillary teeth are positioned to occlude with the flat surface of the mandibular wax occlusion rim and to approximate the position of the maxillary occlusion rim contour that was previously determined. There should be approximately 1 to 2 mm of horizontal overlap of the maxillary facial cusp in relation to the mandibular wax occlusal rim. When completed, the occlusal surfaces of the maxillary posterior teeth should be flat against the mandibular wax occlusal rim. The mandibular teeth are arranged so they will maximally contact the upper teeth. A segment of the mandibular wax occlusal rim is removed to accommodate each tooth. Each tooth, in turn, is placed with a small cone of wax, and the articulator is closed while the wax is still warm. The tooth is arranged in maximum contact with the flat lingual cusp of the maxillary tooth contacting the central groove area of the flat mandibular posterior tooth. The anteroposterior relation of the upper and lower teeth is not critical because of the absence of cusps. Any combination of premolars or molars can be used to fill the available space. The posterior limit of the extent of these teeth is the point at which the mandibular ridge begins to curve upward toward the retromolar pad. Arranging Mandibular Posterior Teeth to Lingualized Articulation Lingualized articulation has been advocated by many practitioners over the past 70 years, and in most instances these clinicians have done so with a variety of tooth molds. However, what has been lacking for the practitioner are tooth molds designed specifically for this concept. Myerson Lingualized Integration (MLI) molds represent an occlusal scheme designed for this concept. It has been suggested that these molds will provide maximum intercuspation, an absence of deflective occlusal contacts, adequate cusp height for selective occlusal reshaping, and a natural and pleasing appearance. The MLI teeth are available in two posterior tooth molds: (1) controlled contact (CC) and 322 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures (2) maximum contact (MC) molds. The primary difference in the two molds is the maxillary posterior teeth. The mandibular teeth are the same for both molds. The mandibular teeth were designed with lower cusp heights and multiple occlusal spillways to assist in mastication. The selection of one or the other mold (CC or MC) is dependent on the patient’s ability to consistently reproduce their centric jaw relation position. Judgments regarding this capability are generally made during several appointments before and after the maxillomandibular record appointment. For those patients in whom uncertainty exists in the registration and reproducibility of the centric jaw relation position, the CC mold is suggested because it provides for greater freedom of movement around maximum intercuspation. For those patients in whom muscle control is not a problem and jaw relation records are easily repeated, the MC mold may be the tooth selection of choice. In the MC mold, the maxillary teeth are more anatomical in appearance with greater cusp heights. This form demands some minor reshaping and refinement of the occlusal fossae and marginal ridges of the mandibular teeth during the arrangement of the teeth to accept the lingual cusps of the maxillary teeth. With the MC mold, a more exacting occlusion can be attained in maximum intercuspation, and bilateral balanced articulation can be developed over a greater range of movement both anteroposteriorly and mediolaterally. Lingualized integration is based on the maxillary lingual cusp functioning as the main supporting cusp in harmony with the occlusal surfaces of the lower teeth. From the position of maximum intercuspation, the maxillary lingual cusps glide over the opposing teeth with an absence of deflection during nonrestrictive lateral and protrusive movements. The maxillary cusp heights in the CC mold are lower and permit greater flexibility around maximum intercuspation. The tooth contacts in eccentric positions remain as bilateral balanced articulation, even though the range of contact is less because of the reduced height to the maxillary lingual cusps. However, a greater range of contact is probably not necessary for most edentulous patients, and the bilateral balanced articulation achieved with the CC mold is very acceptable. A natural appearance to the “buccal corridor” is provided by both MLI molds. The facial surfaces and cusps for the maxillary tooth forms provide the illusion of naturalness because of their anatomical form. In the arrangement of the teeth for lingualized articulation, the mandibular teeth are set first to establish the occlusal plane. The MLI tooth scheme calls for anteroposterior and mediolateral compensating curves arranged in the mandibular arch, thereby permitting balanced articulation between the maxillary lingual cusps and the mandibular teeth during various jaw movements. The superoinferior position of the mandibular teeth in relation to the tongue and the medial roll of the buccinator muscle is again an important consideration during the arrangement of the teeth. The mediolateral positioning of the mandibular teeth in relation to the tongue and cheek interactions also is considered. Number of Posterior Teeth Set The decision on the number of teeth to use with lingualized articulation will depend on the available space for posterior teeth. Most often, the number of posterior teeth will be limited to three. The second premolar, with its wider occlusal surface, and the first and second molars are the teeth most often selected for the arrangement. Anterior and Posterior Reference Points The anterior references that assist in tooth positioning are the same as those described earlier. A line drawn between the anterior and posterior reference points will establish the plane of occlusion and serve as the starting point for the setting of the teeth. Buccolingual Positioning of the Teeth A line that extends from the tip of the canine to the middle of the retromolar pad will help in determining the buccolingual positioning of the teeth. Eliminating a premolar in the tooth arrangement places the first molar in a more anterior position. The wider first molar in the anterior position will crowd the tongue if it is not positioned properly. Both the first and second molars should be positioned slightly to the facial of the reference line to increase the space available to the tongue. Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient Anteroposterior Compensating Curve The anteroposterior compensating curve begins with the distal marginal ridge of the first premolar tooth and continues through the last replacement tooth or the second molar. The amount of curvature is dependent on the condylar guidance mechanical equivalent established by the protrusive interocclusal record. Only rarely will the condylar guidance be more than 30 degrees if the maxillary cast has been mounted with a face bow. Obviously, the third point of reference used with the face bow will influence the mounting. It is recommended that the bite fork, positioned parallel to the mean residual ridge of the maxillary arch, be used as the third point of reference. The anteroposterior curve is established to permit a balanced articulation along the protrusive pathway. Mediolateral Compensating Curve A mediolateral compensating curve is established to provide balanced articulation during lateral movements. The curve is initiated with the first replacement tooth (second premolar) in the mandibular arch and continues through the second molar. This curve is created by positioning the facial cusp slightly above the lingual cusp. A mediolateral compensating curve usually will not exceed 5 to 10 degrees from the horizontal plane of occlusion as viewed in the frontal plane. Premolar The first premolar tooth is positioned in contact with the canine and with its long axis perpendicular to the occlusal plane. The occlusal surface is positioned on the occlusal plane; however, the facial cusp is elevated slightly above the lingual cusp to establish the mediolateral compensating curve. The second premolar is eliminated from the arrangement. First Molar The mesial marginal ridge of the first molar is placed in contact with the distal margin of the premolar. The distal marginal ridge of this tooth is elevated slightly above the mesial marginal ridge to create the anteroposterior compensating curve. The mediolateral compensating curve is maintained by elevating the facial cusp of the molar slightly above the lingual cusp. The central fossa of the first molar is positioned slightly to the facial of 323 the reference line connecting the canine with the middle of the retromolar pad. Second Molar The mesial marginal ridge of the second molar is placed level with the distal of the first molar, and the anteroposterior compensating curve is continued by elevating the distal marginal ridge of this tooth. In general, the distal of the second molar will be at the height of the top of the retromolar pad. The central fossa of the second molar is positioned to the facial of the buccolingual reference line and in a straight line with the first molar. The mediolateral compensating curve is continued by elevating the facial cusps above the lingual cusps. Remaining Mandibular Posterior Teeth The mandibular posterior teeth are arranged for the other side of the arch with the same criteria and procedures, as previously outlined. As the remaining teeth are positioned, it is extremely important to maintain (1) the appropriate level of the occlusal plane and (2) the same degree of anteroposterior and mediolateral compensating curves for both sides of the mandibular arch. Arranging Maxillary Posterior Teeth to Lingualized Articulation Premolar The first tooth arranged in the maxillary arch is the first premolar. This tooth is selected because of its cusp tip to cervical margin height. A longer tooth will provide a more esthetic expression of naturalness along the buccal corridor. The tooth is positioned in contact with the canine and with its long axis perpendicular to the occlusal plane. The lingual cusp is positioned to contact the marginal ridge or occlusal fossa of its mandibular antagonist. No attempt is made at this time to balance the facial or lingual cusps in lateral or protrusive movements. Maximum interdigitation of the lingual cusp against the occlusal surface of the mandibular tooth is the primary consideration. First Molar The mesial marginal ridge of the first molar is placed in contact with the distal margin of the premolar. The lingual cusp is positioned in the central fossa of the mandibular tooth, and 324 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures maximum interdigitation is assured. Often, a Class I molar relationship will not be present. Such a relationship is not necessary, and positioning of the teeth to establish such a relationship is discouraged. Integration of the lingual cusps with the marginal ridge or fossa of the mandibular antagonist is the primary consideration. Position of the tooth emphasizing maximum intercuspation will continue the mediolateral compensating curve established in the arrangement of the mandibular teeth. Second Molar The mesial marginal ridge of the second molar is placed level with the distal of the first molar. The anteroposterior compensating curve is continued when the tooth is closed into contact with the mandibular tooth. Again, maximum intercuspation is essential, as is the maintenance of the mediolateral compensating curve. Arranging the Maximum Contact Mold In the arrangement of the MC mold, the maxillary teeth are positioned with the incisal pin slightly open when the lingual cusps are in contact with their mandibular antagonists. The prominence of the maxillary lingual cusps will require some occlusal reshaping of the central fossae and marginal ridges of the lower teeth to establish maximum intercuspation. After each maxillary tooth is positioned, a thin sheet of articulating paper is interposed between the tooth and its mandibular antagonist. The articulator is closed, marking the first contact point. The contact point on the occlusal surface of the mandibular tooth is enlarged by grinding with a round bur to permit the lingual cusp to obtain positive seating with the lower tooth. This process is continued until maximum interdigitation is achieved and the incisal pin is in contact with the incisal table. Remaining Maxillary Posterior Teeth The remaining maxillary posterior teeth are arranged for the other side of the arch with the same criteria and procedures, as previously outlined. OCCLUSAL MODIFICATIONS AND THE SELECTIVE RESHAPING PROCESS Processing changes, coupled with the lack of occlusal balance before processing, requires a remount procedure to correct occlusal discrepancies and to obtain a balanced articulation. The occlusal reshaping procedures usually are performed at the denture delivery appointment. Establishing Maximum Intercuspation It is much easier to develop maximum intercuspation at the centric jaw relation position when the prostheses are on the articulator. Once maximum intercuspation is achieved, balanced articulation in the several eccentric movements may be attained in the mouth. After the clinical remount of the maxillary and mandibular complete dentures, small strips of articulating paper are placed on the occlusal surfaces of the mandibular teeth. With the articulator locked in the hinged position, all occlusal prematurities are marked. Using a Brasseler carbide trimming and finishing bur no. 7010, remove tooth structure in all areas of contact except the maxillary lingual cusps. Premature contacts most often are at the central fossae or marginal ridges of the lower teeth and on the lingual inclines of the maxillary facial cusps. Continue marking the contacts and reshaping the teeth until all lingual cusps in the maxillary posterior teeth demonstrate maximum intercuspation with their mandibular antagonists (Figure 17-20). Remember this procedure is one that establishes the maxillary lingual cusp as the main supporting cusp in the occlusal contact pattern. The dentures are returned to the oral environment after the occlusal reshaping procedures to verify that maximum intercuspation has been achieved at centric jaw relation position (Figure 17-21). Adjusting the Working and Balancing Contacts Working side interferences will result from contact between the lingual inclines of the maxillary facial cusps and the facial inclines of the facial cusp of the mandibular tooth in lateral excursions. Balancing side interferences will occur between the lingual cusps of the maxillary teeth as they move across the lingual inclines of the facial cusps of the mandibular teeth in lateral excursions. Balancing contacts are the direct result of the compensating curves Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient 325 Figure 17-20 The lingual cusps of the maxillary posterior teeth are the main supporting cusps that interdigitate with the central fossae and marginal ridges of the mandibular posterior teeth. Figure 17-21 Maximum intercuspation as viewed from the buccal. being out of harmony with the lingual cusps, and the refinement of the occlusal contacts between the maxillary lingual cusp and the occlusal surface of the mandibular teeth is required. The development of a harmonious working and balancing occlusion will require the judicious reduction of heavy working side contacts. These heavy working contacts are created during the adjustment of maximum intercuspation when the premature contacts were eliminated. After the working and balancing contacts are marked, careful selective grinding procedures are performed. Adjusting 326 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures the working and balancing contacts is a clinical procedure to be completed after the complete dentures are positioned over their residual ridges. With articulating paper positioned between the posterior teeth bilaterally, carefully guide the patient into a lateral movement. The extent of the movement will be approximately 2 to 3 mm in the molar region. Working interferences will appear as markings on the lingual inclines of the facial cusps of the maxillary teeth as they pass over the facial inclines of the mandibular facial cusps. Occlusal reshaping procedures with the use of the Brasseler carbide trimming and finishing bur no. 7010 are completed by gently grinding the lingual inclines of the maxillary facial cusp that demonstrate interferences. Balancing interferences and maximum intercuspation contacts may occur very near to each other on the occlusal surfaces of the mandibular teeth. The maximum intercuspation stop is generally in the central portion of the tooth, whereas balancing contacts begin in the same area and move in a distal facial direction onto the lingual inclines of the mandibular facial cusps. The width of the balancing contact markings may be very small, and care must be used in reducing balancing interferences. If the balancing contact must be reduced, it will be only the facial portion of the mandibular marking that is altered. Selective grinding of the entire contact area will result in the loss of maximum intercuspation. The selective occlusal reshaping procedures should be continued until a smooth, free-gliding movement is observed (Figures 17-22 and 17-23). Adjusting the Protrusive Contacts Protrusive contacts result from the maxillary lingual cusps gliding over the distal lingual “cusp” of the mandibular tooth in a straight protrusive movement (Figure 17-24). Should deflective protrusive contacts be observed, as evidenced by heavy occlusal markings, their refinement will be necessary. Position articulating paper between the posterior teeth bilaterally and guide the mandible into a protrusive movement from maximum intercuspation. Premature protrusive contacts also may appear between the lingual inclines of the maxillary facial cusps and the facial inclines of the mandibular facial cusps during this movement. Such contacts may be eliminated by grinding on the mandibular facial cusp with the Brasseler bur. When heavy maxillary facial cusp contacts occur, their removal or the modification of the opposing deflective contacts on the mandibular teeth must be Figure 17-22 Right working movement demonstrates the occlusal contacts between the maxillary buccal cusps and the mandibular posterior teeth during this lateral movement. Chapter 17 Selecting and Arranging Prosthetic Teeth and Occlusion for the Edentulous Patient 327 Figure 17-23 During the right lateral movement, the maxillary lingual cusps contact the lingual inclines of the mandibular buccal cusps to create a balanced articulation. Figure 17-24 During the protrusive movement, a balanced articulation is achieved by contact between the maxillary buccal cusps of the posterior teeth and the buccal cusps of their mandibular antagonists. accomplished without disturbing any of the contacts required in the other movements. When the anterior teeth are brought into contact in a protrusive movement, it is desirable to have the posterior teeth contact bilaterally to prevent tilting and dislodgment of the dentures. If the anterior teeth contact prematurely in the protrusive movement, the anterior mandibular teeth are the teeth usually modified, keeping the esthetics of the dentures in mind. 328 Part Three Rehabilitation of the Edentulous Patient: Fabrication of Complete Dentures With the occlusal reshaping procedures accomplished for maximum intercuspation and working, balancing, and protrusive movements, the occlusion is examined for holding contacts in centric jaw relation position. The occlusion also is examined for an absence of deflective occlusal contacts during all of these mandibular movements. SUMMARY OF TOOTH SELECTION AND ARRANGEMENT Treatment of edentulous patients is enjoyable when one has empathy, listening skills, and an appreciation of dental esthetics. Impressions and recordings of healthy tissues need to be made and accurately transferred to an articulator. Teeth should be positioned in harmony with intraoral and circumoral muscle activity and adjusted so that they occlude and articulate evenly. Several different prosthetic tooth molds have been produced, and each has some purported advantages. In the absence of a clear advantage, dentists should use tooth molds that are esthetically pleasing and have a simple procedure for setup. Bibliography Academy of Prosthodontics: Glossary of prosthodontic terms, ed 6, J Prosthet Dent 71:41-112, 1994. Beck HO: Occlusion as related to complete removable prosthodontics, J Prosthet Dent 27:246-256, 1972. 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Pound E: Utilizing speech to simplify a personalized denture service, J Prosthet Dent 24:586-600, 1971. Sproull RC: Color matching in dentistry. I. The three dimensional nature of color, J Prosthet Dent 29:416-424, 1973. Sproull RC: Color matching in dentistry. II. Practical applications of the organization of color, J Prosthet Dent 29: 556-567, 1973.