Occlusion and form and function

Exam 4

1. Occlusion Form and Function Chapter 15-16

2. General Information Occlusion occurs when maxillary and mandibular teeth contact each other in any functional relationship Study of occlusion is concerned with all factors involved in development, stability, and function of masticatory system Occlusion first occurs after the eruption of the primary dentition

3. Ideal Occlusion Ideal occlusion implies complete, harmonious relationship of teeth, as well as all other mouth structures Teeth would conform to specific pattern that includes 138 occlusal contacts on all 32 permanent teeth This ideal relationship rarely exists

4. Ideal Occlusion Maxillary teeth facially overlap mandibular by ⅓ and is distally positioned by ½ tooth length from the mandibular Referred to as Interdigitation Also noted by the positioning of the permanent first molars and canines

5. Normal Occlusion Normal occlusion is similar to ideal occlusion with added common variations Variations are considered acceptable if there is functional comfort and stability of alignment Necessary for each tooth to be able to withstand the biting force The biting force for posterior teeth is about 100-170lbs The first permanent molars are considered key and is the same as in an ideal occlusion

6. Malocclusion Any deviation from ideal positioning of teeth Can be minor in one tooth, severe in several teeth or the jaws Based on the relationship of the maxillary and mandibular first molars and canines Any variation in this relationship constitutes malocclusion

7. Occlusal Deviations Involving Several Teeth Openbite is existing space between mandibular and maxillary teeth Can be anterior or posterior, unilateral or bilateral Overbite is a d eep or vertical overlap of maxillary teeth onto mandibular teeth E xceeds normal or 1 /3rd depth of mandibular incisors

8. Occlusal Deviations Involving Several Teeth Overjet is a horizontal overlap creating a protrusion or space Between the labial surface of the mandibular incisors and the lingual surface of the maxillary incisors Crossbite is facially positioned mandibular tooth, or teeth Can be: anterior or posterior buccal or lingual

9. Occlusal Deviations Involving Several Teeth Edge-to-edge or end-to-end is contacting incisal edges or cusp tips of opposite arch, rather than interlinking of cusp and fossae Actually a crossbite or precrossbite Underjet is a horizontal relationship where maxillary anteriors are lingual to mandibular anteriors

10. Occlusal Deviations Involving Individual Teeth Labioversion / buccoversion T ooth positioned more facially than normal Linguoversion Tooth positioned more lingually than normal Infraversion Tooth positioned below plane of occlusion

11. Occlusal Deviations Involving Individual Teeth Supraversion Tooth positioned above plane of occlusion Torsoversion Rotated tooth

12. Angle’s Classification of Occlusion Dr. Angle was first to develop a system to classify malocclusion Because mandible is movable, Angle’s classification relates to anterior–posterior or mesiodistal deviations in relation to first molar The first permanent molars are considered the key to occlusion. Three classifications

13. Class I: Neutrocclusion (Normal) Both permanent first molar and canine relationship are in ideal position Mesiobuccal cusp of maxillary first molar rests in mesiobuccal groove of mandibular first molar Maxillary canine occludes with distal inclined plane of mandibular canine and first premolar Can be deviations of the anterior teeth but the molars will have ideal positioning

14. Class II: Distocclusion The mandibular first permanent molar and canine are more posterior By at the least width of a premolar more than ideal position Even when molars are in a more distal position, other deviations can occur Creating two divisions Class II, Division I Class II, Division II

15. Class II: Distocclusion Division I Protrusion of incisors or overjet ; overbite, crowding, or labial inclination of maxillary incisors Division II Protrusion of maxillary lateral incisors Retrusion of maxillary central incisors

16. Class III: Mesiocclusion Permanent mandibular first molar and canine are more anterior By at least the width of a premolar more than normal position When molars are more mesially located, other conditions can also occur Anterior crossbite Edge-to-edge contact

17. Related Terms Profiles Mesognathic : normal profile Prognathic : when mandible protrudes Retrognathic : when mandible retrudes Centric Occlusion : the most Retruded position of the condyle in the mandibular fossa Functional Malocclusion : occlusal deviation created by habits or muscular dysfunctions. Certain habits such as thumb sucking or revise or deviant swallowing may cause malocclusion depending on the intensity, duration, and/or age at which they occur

18. Primary Teeth Occlusion Spacing of primary teeth plays important part of occlusion of permanent teeth The position of the primary second molar is important determinant of permanent tooth alignment If second molars are in Class I position, permanent teeth will usually be guided into Class I position The positioning is then referred to as Class I mesial step

19. Primary Teeth Occlusion Primary molars often show cusp to cusp relationship called terminal plane Also considered Class I Extra space is provided in the area of the molars allowing for the mesial shift of the permanent mandibular first molar

20. Primary Teeth Occlusion B: Mesial Step The distal surface of the mandibular molar is mesial to that of the maxillary molar, thereby forming a mesial step. Most children have this relationship. A: straight (flush) terminal plane. T he distal surfaces of the second primary molars are on the same vertical plane. A moderate number of children have this relationship. C: Distal Step The distal surface of the mandibular molar is distal to that of the maxillary molar, thereby forming a distal step. Few children have this relationship.

21. Summary Occlusion occurs when maxillary and mandibular teeth are in contact in any functional relationship Ideal occlusion occurs when teeth conform to specific pattern of contacts Angle’s classification used to describe relationship of first molars and canines

22. General Information For teeth to masticate food, appropriate position in arch must be maintained Correct positioning also necessary to assist protection of supporting structures which sustain tooth function Form and function are concerned with how position and shape of teeth enable use

23. Proximal Contact Areas A small spot on mesial and distal surface of each tooth that contacts proximal tooth Every tooth, except last molars in arch, has both distal and mesial contact area These areas are generally widest point on the crown of tooth Contact areas of the anterior teeth are located more incisally than the posterior

24. Function of Contact Areas Proper contact between teeth prevents food from packing between them Protects gingiva from food lodged between the teeth Stabilize teeth in arch by providing mutual support

25. Interproximal Spaces The area between each tooth normally filled with interdental papilla Boundaries form triangle with sides of proximal surfaces of teeth The base in alveolar crest and apex is contact area The apex of the interproximal space boundary Widest point of the crown of the tooth

26. Function of the Interproximal Space Appropriate width between each tooth (base of the triangle) is important to Provide enough space for periodontal structures Allow ample bone between each tooth for adequate support Maintain level of gingival tissue

27. Embrasures Any curvature, either toward or away from contact area Located on incisal, occlusal, lingual, or facial surface Often referred to as spillways because they assist food in “spilling” away from tooth

28. Function of the Embrasures Embrasures or spillways act as an escapement Keeps food from clinging to teeth or forced into interproximal spaces Assists in cleaning tooth and protects gingival tissue from being irritated by keeping food away from it

29. Compensating Curvatures Compensating curvatures of the arches account for the strength, efficiency and stability of teeth Have no special use other than assist in define occlusion Main use is construction of dentures or balancing of arches

30. Compensating Curvatures Curve of Spee When viewed from a point opposite the first molars and the teeth are in normal alignment, a curve forms on the line of the occlusal plane Extends from the incisal edge of the central incisors to the distal buccal cusp of the second molar The curve is concave toward the mandible

31. Compensating Curvatures Curve of Wilson A curvature visable when the arches are viewed from a frontal position Concave curvature that extends from the cusp tip of the right molar to the cusp tip of the left molar

32. Summary Proper proximal contact areas prevent food from packing between teeth Embrasures act as spillway so that food does not cling to teeth Interproximal spacing allows adequate space for periodontal structures to support teeth