References

1. Huffman RW. Part six, occlusal morphology. In: Guichet NF. Procedures for Occlusal Treatment—A Teaching Atlas. Anaheim: Denar, 1968:98.

2. Lundeen HC. Introduction to Occlusal Anatomy. Lexington, 1969.

3. Thomas PK. Syllabus on Full Mouth Waxing Technique for Rehabilitation. San Diego: Instant Printing Service, 1967.

4. Zeisz RC, Nuckolls J. Dental Anatomy. St. Louis: Mosby, 1949.

5. Linek HA. Tooth Carving Manual. Pasadena: Wood and Jones, 1949.

6. Burch JG. Introduction to Coronal Tooth Contour. Worthington, Ohio, 1975.

7. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE. Fundamentals of Fixed Prosthodontics, ed 3. Chicago: Quintessence, 1997.

Mandibular Teeth

Mandibular Left Central Incisor

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Mandibular Right Central Incisor

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Mandibular Left Lateral Incisor

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Mandibular Right Lateral Incisor

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Mandibular Left Canine

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Mandibular Right Canine

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Mandibular Left First Premolar

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Mandibular Right First Premolar

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Mandibular Left Second Premolar, H Form

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Mandibular Right Second Premolar, H Form

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Mandibular Left Second Premolar, Y Form

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Mandibular Right Second Premolar, YForm

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Mandibular Left First Molar

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Mandibular Right First Molar

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Mandibular Left Second Molar

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Mandibular Right Second Molar

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Maxillary Teeth

Maxillary Left Central Incisor

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Maxillary Right Central Incisor

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Maxillary Left Lateral Incisor

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Maxillary Right Lateral Incisor

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Maxillary Left Canine

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Maxillary Right Canine

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Maxillary Left First Premolar

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Maxillary Right First Premolar

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Maxillary Left Second Premolar

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Maxillary Right Second Premolar

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Maxillary Left First Molar

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Maxillary Right First Molar

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Maxillary Left Second Molar

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Maxillary Right Second Molar

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Coronal Form and Function

In the following section, an individual page is devoted to each of the teeth, both right and left, with the exception of the third molars. There are six views of the crown of each posterior tooth: occlusal view with proximal contacts, occlusal contacts, geometric inclined planes of the occlusal surface, the pathways of the opposing cusp tips during excursive movements, a facial view with proximal contacts, and a proximal silhouette.

Pages dealing with maxillary canines and incisors include an incisal view with proximal contacts, a lingual view, the excursive pathways of opposing incisal tables, a facial view with proximal contacts, and a proximal silhouette. Four of the same views are shown for the mandibular anterior teeth, with the deletion of the opposing incisal table excursions which do not occur on mandibular incisors and canines.

The centric contacts and the cusp locations shown are for the cusp-marginal ridge occlusal arrangement, since it is the type most commonly encountered. Primary contacts are shown in red, and secondary contacts are in yellow. Primary contacts are those which are most easily obtained, or those which are most desirable. With the exception of the maxillary first premolar, the primary contacts are cusp-fossa sets. Ideally, every occlusal surface waxed would demonstrate all of the contacts, primary and secondary, which should be found on that particular type of tooth. The fact is that this occurs very rarely in the fabrication of single restorations.

The practical solution is to obtain as many contacts as possible, with wide distribution over the occlusal surface to provide maximum stability. Cusps should have tripod contacts when possible, and single contacts on sloping surfaces should be avoided, since they may cause deflections. Marginal ridges sometimes will not provide good sites for contacts. The opposing cusps may be too short, necessitating a heightened marginal ridge that might be an obstruction in excursions. There should be at least one set of contacts on molar clinical wax patterns. When only the minimum number of contacts can be obtained, every effort should be made to utilize at least one cusp-fossa contact set.

The locations of opposing cusps are represented in the illustrations of posterior teeth by spheres, with arrows depicting the pathways traveled by the cusps in excursions. The course followed in a working excursion is blue, with protrusive shown in yellow, and nonworking in red.

Review of Waxing Technique

There are two wax-added techniques for waxing the occlusal surface of a restoration and two basic occlusal schemes that can be formed. The first wax-added technique was developed by E. V. Payne.1 This same method, using a wax of a different color for each of the features, has been widely promulgated by H. C. Lundeen to teach functional waxing.2 Buccal cusps are developed first, progressing from cones to buccal ridges, mesial and distal cusp ridges (axial contours), and then triangular ridges, before starting the same sequence on the lingual cusps. Marginal ridges are finally added to connect the two, and supplemental anatomy is refined.

This technique is usually associated with the cusp-marginal ridge occlusion scheme in which the functional cusp contacts the opposing occlusal surfaces on the marginal ridges of the opposing pair of teeth, or in a fossa (Fig 9). It is basically a one-tooth-to-two-teeth arrangement. Because the majority of natural dentitions have this type of occlusion, it is commonly used for the single restorations and limited occlusal restorations most frequently seen in daily practice.

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Fig 9a

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Fig 9b

The other wax-added technique is the invention of P. K. Thomas.3 All cusp cones are positioned initially, starting with the functional cusps (maxillary lingual and mandibular buccal). Marginal ridges and cusp ridges are added next, followed by axial ridges. The full axial contours are finished, providing a border around the entire occlusal table called the “fish’s mouth.” Triangular ridges are then added, and any voids are filled in to complete the occlusal surface.

This method is most often associated with the cusp-fossa relation in which each functional cusp is nestled into the occlusal fossa of the opposing tooth (Fig 10). It is a tooth-to-tooth arrangement that gives excellent distribution of occlusal forces and stability to the teeth. Because it varies from the scheme usually found in a natural occlusion, it can be used only when restoring several contiguous teeth and the teeth opposing them.

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Fig 10a

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Fig 10b

The Payne/Lundeen technique is commonly associated with the cusp-marginal ridge occlusion; the Thomas technique, with the cusp-fossa occlusion. It should be borne in mind, however, that the method and the occlusal arrangement are not inseparable. Although the Thomas technique was meant for the cusp-fossa scheme, it can be used for developing a cusp-marginal ridge occlusal relationship simply by altering cusp placement.

A brief review of waxing is presented here to expedite student progress through a wax pattern. A more detailed presentation of all aspects of fabricating wax patterns can be found elsewhere.7

The functional cusps (lingual of the maxillary and buccal of the mandibular) are located first, using a PKT No. 1. They should be positioned so they will contact the appropriate fossa or marginal ridge of the opposing tooth. Next, the nonfunctional cusps are placed (Fig 11). On the maxillary teeth, the nonfunctional cusps should be short enough to miss contacting the buccal cusps of the mandibular teeth during excursions. On the mandibular teeth, the lingual cusps should be slightly shorter than the buccal. The lingual cusps of mandibular molars should also be placed as far to the lingual and as far from each other as possible.

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Fig 11 Cones (yellow) are placed for all cusps with a PKT No. 1. Functional cusps are located first.

The marginal ridges and cups ridges (both mesial and distal) are added next, using a PKT No. 1 (Fig 12). The highest points on the occlusal surfaces are the tips of the cusp cones. The marginal ridges should never be higher than the cusps. The cusp tips and the edges of the marginal ridge should be as sharp as possible. The buccolingual dimension of each occlusal table formed by the ridges should be approximately 55% of the overall buccolingual dimension of the respective tooth. The occlusal surface is dusted with zinc stearate and the articulated casts are moved through the various excursions. The pathways which would normally be followed by the cusps of the respective opposing teeth are shown in the illustrations of the individual teeth (pages 28 to 57).

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Fig 12 Form the marginal ridges and cusp ridges (blue) with a PKT No. 1.

The maxillary lingual ridges or mandibular buccal ridges are then waxed in to provide the silhouette of the final contour of the respective axial surface (Fig 13). Next, use the PKT No. 1 to fill in any voids or discrepancies between the crests of the cusp ridges and the facial or lingual axial contours. Smooth the axial surfaces with a PKT No. 4 to complete the “fish’s mouth,” so named because of the appearance of the cusp and marginal ridges at this point (Fig 14).

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Fig 13 Axial ridges (red) are placed over the cusps with a PKT No. 1.

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Fig 14 Finish filling in the axial contours (green) and smooth them with a PKT No. 4.

Build up the triangular ridge for each of the cusps with the PKT No. 1 (Fig 15). The line along which the bases of these ridges meet will be the central groove of the occlusal surface. Remember! The bases must be broader than the apex at the cusp tip. The ridges should be convex both buccolingually and mesiodistally to provide point contacts with the opposing cusps. Check the occlusion in the intercuspal position, and in excursions as well.

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Fig 15 Use a PKT No. 1 to make the triangular ridges (red).

All voids remaining on the occlusal surface are eliminated with a PKT No. 2. Supplemental anatomy is formed by the junction between the triangular ridge and the adjacent cusp or marginal ridges. The PKT No. 5 is used to refine the ridges (Fig 16). Developmental and supplemental grooves are smoothed with a PKT No. 3 (Fig 17). Dust the wax patterns with zinc stearate and check the occlusal contacts in the intercuspal and excursive positions.

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Fig 16 The ridges are rounded and finished with a PKT No.5.

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Fig 17 Smooth the grooves and fossae with a PKT No. 3.

Rationale for Occlusal Waxing

Students frequently ask the question, “Why put all those grooves on the occlusal surface? Why not put simple inclined planes on a flat table?” To answer the question, it is necessary first to analyze the features of the occlusal surface of the tooth. This surface is comprised of positive and negative features: the cusp tips and ridges make up the positive features, while the grooves and fossae are the negative. The ridges, when properly formed, are convex in all directions, and contacts with opposing teeth are numerous (Fig 1).

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Fig 1 There are numerous occlusal contacts (arrows) on an occlusal surface that is correctly waxed. The lingual surface of the mandibular first molar has been cut away to show the occlusion with the maxillary first molar.

The convex surfaces of ridges produce a distributed contact pattern with small contacts. In this way, occlusal forces are distributed over a wide area of the occlusal surface, minimizing stress and wear. Contact areas that are small and bordered by marked depressions (ie, grooves) allow for complete and rapid disclusion in excursive movements (Fig 2).

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Fig 2 Properly formed occlusal morphology allows for small centric contacts (A) and complete disclusion in excursions (B).

On the other hand, occluding surfaces that are flat are more likely to produce large contact areas (Fig 3). Broad, flat contacting areas are more likely to remain in apposition without disclusion when mandibular excursions occur. The friction resulting from teeth continuing to touch during excursions will often cause greater wear.

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Fig 3 Occlusal morphology made with only inclined planes produces large contacts in centric occlusion (A) with a likelihood that there will be continued contact in excursions (B).

Because of the reduced contact surface area resulting from an occlusal surface comprised of convex ridges bordered by grooves, the restoration is more efficient. Ridge against ridge produces a shearing action that is more effective than the pounding or crushing action produced by flat surface against flat surface. The difference is real: patients who have restorations with flat surfaces replaced by those with ridges and grooves will often comment on the reduced effort required for chewing food.

Triangular Ridges

The most important features on an occlusal surface are the ridges. The seams along which the ridges meet form the grooves and the fossae of the occlusal surface. Many novice waxers attempt to create occlusal morphology by cutting V-shaped furrows into flat inclined planes on the occlusal surface of a wax pattern (Fig 4). The results are rarely, if ever, satisfactory.

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Fig 4 Well-formed ridges and grooves will be more convex and functional (A) than will the occlusal surface in which grooves have been carved into a flat plane (B).

The triangular ridge is the major ridge or lobe of every cusp. It extends from the cusp tip to the central groove (Fig 5A). It is essentially triangular: narrow at the cusp tip and wide at its base in the central groove. The grooves to the mesial and distal of it converge toward the cusp tip (Fig 5B).6

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Fig 5 The triangular ridge is triangular (A) and is bounded by converging grooves (B) (after Burch6).

When viewed in either a faciolingual section or a mesiodistal section, the triangular ridge is convex (Fig 6). If the triangular ridges are placed correctly, the correct groove pattern will occur as a natural by-product.

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Fig 6 The triangular ridge is convex in faciolingual section (A) or in mesiodistal section (B) (after Burch6).

The grooves themselves perform an important function in occlusal restoration. If they are adequate in width and depth, and if they transverse the occlusal surface in the proper directions, they will permit the unimpeded passage of opposing cusps in excursive movements. The grooves in a wax pattern are refined by moving the articulated casts through the various excursions in order to detect any interferences which should be removed from the walls of the grooves (ie, the sides of the ridges.

The Effect of Anterior Guidance

The incisors and canines are the most anterior teeth in the dental arches. They comprise the anterior determinant of mandibular movement and help to guide the mandible in its excursions forward (protrusive movements) and to the left and right (lateral movements). Dentists have direct control over this determinant through restoration, equilibration, or orthodontic movement. The other determinants of occlusion, the temporomandibular joints and the neuromuscular system, are not to be discounted in their effect on mandibular movement; however, they are not under the direct control of the dentist.

The contact of the anterior teeth in excursions affects the movements of the mandible. This in turn affects cusp placement and height, and groove direction and depth, which will be tolerable in the posterior restoration. Restoration of anterior teeth must be undertaken carefully, since changes in the morphological features of these teeth can change the anterior guidance, with possible deleterious effect on the posterior occlusion.

The greater the vertical overlap of the anterior teeth, the longer the posterior cusps may be (Fig 7). Conversely, the less the vertical overlap, the shorter the cusps of posterior teeth must be. The greater the horizontal overlap of the anterior teeth, the shorter the cusps of posterior teeth must be (Fig 8). The cusps may be longer when the horizontal overlap is small.

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Fig 7 An increased vertical overlap of anterior teeth allows longer posterior cusp length (A). Decreased vertical overlap requires a decrease in posterior cusp length (B).

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Fig 8 An increased horizontal overlap of anterior teeth requires a decrease in posterior cusp length (A). Decreased horizontal overlap allows longer posterior cusp length (B).

Preface

Morphology is the organized study of natural form and structure, with no regard for function. In the strictest sense, therefore, this manual is not a textbook on morphology. Instead, it is concerned with the function and configuration of the occluding surfaces of cast restorations and with their axial contours. Although the patterns are based on natural form, they are stylized human interpretations and not exact duplications of any specific natural teeth. Reproduction of the occlusal features and contours portrayed on the following pages will produce functional restorations which are in physiologic harmony with the soft tissues of the mouth.

In dental morphology courses, students of dentistry learn the form of dental structures, study distinguishing characteristics of the various classes of teeth, and, in most curricula, engage in some waxing exercises. It has been our experience, as teachers, that students in the more advanced stages of their dental training forget many of the details of occlusal form and function which they learned earlier.

Relatively complex ridge/groove patterns, cusp placement, and axial contours which were learned in years past may not spring instantly to the mind of the student when he or she is making a wax pattern. It is our objective to provide a ready reference for waxing in that situation. Included are groove and ridge patterns, location of occlusal contacts, paths traced by opposing incisal tables or cusp tips in excursions, the location and size of proximal contacts, and axial contours.

Mastery of the mental concept of the tooth’s appearance and perfection of the skills to translate that concept into three-dimensional reality require repetition and practice. This manual should aid the student while he or she acquires the experience to make the transition from novice to expert.

A brief review of the sequence for forming an occlusal surface by the “wax-added” or “drop wax” technique is included. However, the student should have previously developed some skills by doing exercises described in one of the manuals on waxing. The illustrations on the following pages are not the concept of any one individual, but rather a blend of many.

Those familiar with the study of occlusal morphology and waxing will recognize the influence of Payne, Lundeen, Thomas, Zeisz and Nuckolls, and Linek. The illustrations in this manual are by Dr. Jack Morrison, based on sketches by Dr. Herbert Shillingburg.

The authors would like to express their appreciation to Dr. Lowell D. Whitsett, Professor Emeritus and Former Chair of the Department of Occlusion at the University of Oklahoma College of Dentistry, for his helpful criticism and suggestions.