1、Occlusion,Occlusion 牙合 is defined as the static relationship of teeth Articulation 咬合 is defined as the dynamic relationship of teeth Tooth alignment and occlusion is important in masticatory function Tooth positioning is not a random process A number of controlling factors are involved,Esthetic smi
2、le BMC 59.1,Concepts of Occlusion,Concepts of Occlusion Balanced Occlusion,Bilateral and balancing contacts through all excursive movements Protrusive 前伸 Laterotrusive 侧方 Developed for complete dentures Rationale was thought to provide stability to dentures through all excursive movements,Esthetic s
3、mile BMC 59.1,Concepts of Occlusion,Optimal OcclusionDynamic Individual Occlusion Concept is based on function and health rather than any ideal occlusal arrangement In the absence of pathology, no treatment to change a patients occlusion would be necessary Developed in the late 1970s,Esthetic smile
4、BMC 59.1,Morphological classificationmalocclusionnormal occlusion individual normal occlusion; ideal normal occlusion Functional classificationphysiological occlusionpathological occlusion Clinical classificationadaptable occlusionunadaptable occlusion,Classification of Occlusion,Tooth Alignment and
5、 Occlusion,Factors determining tooth position Normal intra-arch relationships Normal interarch relationships,Sagittal view of human skull BMC 62.6,Tooth Alignment and Occlusion Factors determining tooth position,Forces from many directions act to position the tooth in a position of equilibrium Lips
6、Cheeks Tongue Forces are light and constant Have the ability to move teeth over time Tooth stability is achieved in the neutral position,Anterior (top) and posterior (bottom) teeth in neutral position Okeson Fig. 3-1,Tooth Alignment and Occlusion Factors determining tooth position,When a tooth erupt
7、s out of alignment, forces from the tongue and lip can move the tooth to the neutral position Must be adequate space for the tooth If there is crowding, the muscular forces are insufficient to produce the necessary movement Orthodontic treatment would then be required,Anterior (top) and posterior (b
8、ottom) teeth in neutral position Okeson Fig. 3-1,Tooth Alignment and Occlusion Factors determining tooth position,Erupted teeth will be moved until an equilibrium is established Large tongue Tongue thrust Oral habits Thumb sucking Finger sucking Pencil sucking Chewing on a pipe Musical instruments,A
9、nterior open bite due to a large tongue (tongue at rest) Okeson Fig. 3-2a,Tooth Alignment and Occlusion Factors determining tooth position,Erupted teeth will be moved until an equilibrium is established Tongue thrust An anterior open bite has resulted from excessive labially directed forces from the
10、 tongue,Very active tongue producing an open bite Okeson Fig. 3-2c,Tooth Alignment and Occlusion Factors determining tooth position,Forces on proximal tooth surfaces Contacts with adjacent teeth maintain normal alignment There is a normal mesial migration of teeth towards the midline Normal function
11、 produces proximal surface wear Mesial migration tends to maintain contacts,Consequences of loss of a single molar Okeson Fig. 3-2d,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Plane of occlusion (PO) A line through the mandibular incisal ridges and the DB cusps of the second molars
12、 Actually a planar mean of the curvature of the surfaces Not flat Generated by a line drawn through all buccal cusp tips and incisal ridges connecting the lingual cusps and producing a plane Curved plane to allow multiple areas of contact during mandibular movement A result of inclination of teeth w
13、ithin the arches,Orientation lines and planes AE angle of eminentia FH Frankfort horizontal CS Curve of Spee PO Plane of occlusion IG Incisal guidance Ash Fig. 2-16,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Plane of occlusion (PO) A line through the mandibular incisal ridges and
14、the DB cusps of the second molars Actually a planar mean of the curvature of the surfaces Not flat Generated by a line drawn through all buccal cusp tips and incisal ridges connecting the lingual cusps and producing a plane Curved plane to allow multiple areas of contact during mandibular movement A
15、 result of inclination of teeth within the arches,Sagittal view of the angulation of mandibular teeth Okeson Fig. 3-5,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Plane of occlusion (PO) A line through the mandibular incisal ridges and the DB cusps of the second molars Actually a pl
16、anar mean of the curvature of the surfaces Not flat Generated by a line drawn through all buccal cusp tips and incisal ridges connecting the lingual cusps and producing a plane Curved plane to allow multiple areas of contact during mandibular movement A result of inclination of teeth within the arch
17、es,Sagittal view of the angulation of maxillary teeth Okeson Fig. 3-6,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Plane of occlusion (PO) A line through the mandibular incisal ridges and the DB cusps of the second molars Actually a planar mean of the curvature of the surfaces Not f
18、lat Generated by a line drawn through all buccal cusp tips and incisal ridges connecting the lingual cusps and producing a plane Curved plane to allow multiple areas of contact during mandibular movement A result of inclination of teeth within the arches,Frontal view of the angulation of maxillary t
19、eeth Okeson Fig. 3-7,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Plane of occlusion (PO) A line through the mandibular incisal ridges and the DB cusps of the second molars Actually a planar mean of the curvature of the surfaces Not flat Generated by a line drawn through all buccal
20、cusp tips and incisal ridges connecting the lingual cusps and producing a plane Curved plane to allow multiple areas of contact during mandibular movement A result of inclination of teeth within the arches,Frontal view of the angulation of mandibular teeth Okeson Fig. 3-8,Tooth Alignment and Occlusi
21、on Normal Intra-arch Relationships,Curve of Spee Anteroposterior curvature of the arch Formed by a line joining the mandibular incisal ridges to the buccal cusps of the mandibular posterior teeth,Curve of Spee- the anteroposterior curvature of the arch Mohl Fig. 4-4,Tooth Alignment and Occlusion Nor
22、mal Intra-arch Relationships,Curve of Wilson Mediolateral curvature of the arch Formed by drawing a line through the buccal and lingual cusps of the molars Usually concave in an unworn dentition Can be convex when the dentition is worn (resulting in shorter buccal cusps of the mandibular molars; cal
23、led a reverse Curve of Wilson.,Curve of Wilson- the mediolateral curvature of the arch (posterior view Mohl Fig. 4-5a,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Curve of Wilson Mediolateral curvature of the arch Formed by drawing a line through the buccal and lingual cusps of the
24、molars Usually concave in an unworn dentition Can be convex when the dentition is worn (resulting in shorter buccal cusps of the mandibular molars,Curve of Wilson- the mediolateral curvature of the arch (posterior view Mohl Fig. 4-5b,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Stan
25、dardized formulae were sought to describe intra-arch relationships Bonwill, WGA 1889 Described a 4 inch equilateral triangle from condylar centres to mesial of the mandibular incisors Monson, GS 1932 Described a sphere (“Sphere of Monson”) with a radius of 4 inches that was equidistant from the cond
26、ylar centres and the occlusal surfaces of the posterior teeth Both are oversimplifications and generalizations that apply to some people but not all Represent a geometrical ideal,Bonwills triangle and Monsons sphere Mohl Fig. 12-3,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Occlusa
27、l surfaces of the teeth Cusps Cusp ridges Grooves Sulci Function in breaking up food into smaller piecesOcclusal table 50-60% of the total buccolingual dimension of the tooth Masticatory forces are applied to this area Positioned within the confines of the root,Occlusal table (top) Okeson Fig. 3-9 O
28、uter and inner inclines of the crown (bottom) Okeson Fig. 3-10,Tooth Alignment and Occlusion Normal Intra-arch Relationships,Occlusal surfaces of the teeth Cusps Cusp ridges Grooves Sulci Function in breaking up food into smaller piecesOcclusal table 50-60% of the total buccolingual dimension of the
29、 tooth Masticatory forces are applied to this area Positioned within the confines of the root,Mesial and distal inclines of teeth Okeson Fig. 3-11,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal buccolingual relationship of the molars Okeson Fig. 3-12,An interarch relationship re
30、lates the teeth in one arch to the teeth in the other arch As the mandible closes, the occlusal relationship of the teeth is determined Arch length Distance from the distal surface of one third molar to the other in the same arch 128mm Max arch 126mm Mand arch Arch width Distance across the arch Man
31、dibular width is slightly less than maxillary width,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal buccolingual relationship of the molars Modified after Okeson Fig. 3-12,Normal buccolingual relationship allows for efficient use of musculature in chewing Minimizing trauma from c
32、heek or tongue-biting Supporting cusps buccal cusps of Mandibular posterior teethlingual cusps of Maxillary posterior teeth Centric cusps Centric holding cusps Stamp cusps Maintain vertical dimension or distance between the maxilla and mandible,Tooth Alignment and Occlusion Normal Interarch Relation
33、ships,Centric holding cusp position (mandibular first molar) BLUE centric cusps YELLOW non-centric cusps Okeson Fig. 3-14,Centric holding cusps are important in mastication Contact occurs on outer and inner inclines of the cusp Centric holding cusp position is approximately 1/3 into the total buccol
34、ingual dimensionWhat is the significance of the position of the centric cusps in this buccolingual direction?,Forces are directed over the long axis of the tooth and are dissipated through the root.,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal buccolingual relationship of the
35、molars Modified after Okeson Fig. 3-12,Guiding cusps lingual cusps of Mandibular posterior teethbuccal cusps of Maxillary posterior teeth Non-centric cusps Non-centric holding cusps Shear cusps Non-centric holding cusp position is approximately 1/6 into the total buccolingual dimension Cusps tend to
36、 be sharper with defined cusp ridges and tips,Tooth Alignment and Occlusion Normal Interarch Relationships,FUNCTIONAL OUTER ASPECT Outer aspect of centric cusp contacts about 1mm,Functional Outer Aspect Modified after Okeson Fig. 3-15,Tooth Alignment and Occlusion Normal Interarch Relationships,Cros
37、sbite relationship of the molars Okeson Fig. 3-13,Identify the centric holding cusps when there is a posterior crossbite relationship.LINGUAL CUSPS of Mandibular posterior teeth BUCCAL CUSPS of Maxillary posterior teeth,Tooth Alignment and Occlusion Normal Interarch Relationships,Mandibular bucco-oc
38、clusal line Okeson Fig. 3-16,Contact Relationships- Buccolingual A line drawn through the buccal cusps of mandibular teeth illustrates the Bucco-occlusal line Line follows arch form and is smooth and continuous Line divides the outer and inner aspects of the mandibular centric cusps,Tooth Alignment
39、and Occlusion Normal Interarch Relationships,Maxillary bucco-occlusal line Okeson Fig. 3-17,Contact Relationships- Buccolingual A line drawn through the lingual cusps of maxillary teeth illustrates the Linguo-occlusal line Line follows arch form and is smooth and continuous Line divides the outer an
40、d inner aspects of the mandibular centric cusps,Tooth Alignment and Occlusion Normal Interarch Relationships,Central fossa line Okeson Fig. 3-18,Contact Relationships- Buccolingual A continuous line drawn through the central developmental grooves of maxillary and mandibular posterior teeth illustrat
41、es the Central fossa (CF) line Line follows arch form and is smooth and continuous,Tooth Alignment and Occlusion Normal Interarch Relationships,Central fossa line, contacts and embrasures Modified after Okeson Fig. 3-18,The contacts are usually slightly buccal to the central fossa line.,Tooth Alignm
42、ent and Occlusion Normal Interarch Relationships,Central fossa line, contacts and embrasures Modified after Okeson Fig. 3-18,The buccal embrasure is smaller and shaped like a wide V. The lingual embrasure area is larger and is shaped like a long narrow V.,Tooth Alignment and Occlusion Normal Interar
43、ch Relationships,Central fossa line, contacts and embrasures Modified after Okeson Fig. 3-18,What is the clinical significance of the contact position and embrasure shape?,The lingual embrasure acts as a spillway. Food is directed towards the tongue during mastication. The tongue then directs the fo
44、od back towards the occlusal table. This is more efficient than having the perioral and buccinator muscles direct food towards the occlusal table in the other direction.,Tooth Alignment and Occlusion Normal Interarch Relationships,Central fossa line and bucco-occlusal line Okeson Fig. 3-20,In a norm
45、al occlusion, the MANDIBULAR BUCCAL CUSPS (CHC) will occlude in the central fossa and on marginal ridges of the maxillary posterior teeth.,Tooth Alignment and Occlusion Normal Interarch Relationships,Central fossa line and bucco-occlusal line Okeson Fig. 3-20,In a normal occlusion, the MAXILLARY LIN
46、GUAL CUSPS (CHC) will occlude in the central fossa and on marginal ridges of the mandibular posterior teeth.,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal contacts in a Class I occlusion Okeson Fig. 3-23,Contact Relationships- MesiodistalOcclusal contacts result from centric cu
47、sps contacting the opposing CF line Contacts will occur in or on Central fossaeAND Marginal ridges and embrasures,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal contacts in a Class I occlusion Modified after Okeson Fig. 3-23,Contact Relationships- Mesiodistal Occlusal contacts r
48、esult from centric cusps contacting the opposing CF line Contacts will occur in Central fossae Comparable to a mortar and pestle（臼杵） Two dissimilar shaped surfaces meet result in a spillway being produced and masticatory efficiencySUMMARY STATEMENTSMesiolingual cusp of each maxillary molar occludes
49、in the central fossa of the opposing mandibular molarMesiobuccal cusp of each mandibular molar occludes on the mesial marginal ridge of the opposing maxillary molar,Tooth Alignment and Occlusion Normal Interarch Relationships,Normal contacts in a Class I occlusion Modified after Okeson Fig. 3-23,Con
50、tact Relationships- Mesiodistal Occlusal contacts result from centric cusps contacting the opposing CF line Contacts will occur in Central fossae Comparable to a mortar and pestle Two dissimilar shaped surfaces meet result in a spillway being produced and masticatory efficiency Marginal ridges and embrasures Cusp tip is very convex Marginal ridge is slightly convex (flat by comparison) Actual contact is not cusp tip but 0.5mm area around it,
