Lecture 1: Malocclusion - PDF

LECTURE 1: MALOCCLUSION Both central and lateral incisors may be lingually ANGLE’S CLASSIFICATION OF MALOCCLUSION inclined Canines can also be labially inclined Subdivision – When distocclusion occurs in one s...

LECTURE 1: MALOCCLUSION Both central and lateral incisors may be lingually ANGLE’S CLASSIFICATION OF MALOCCLUSION inclined Canines can also be labially inclined Subdivision – When distocclusion occurs in one side of the dental arch only. Example: Class II Division I Subdivision C. CLASS III (DEWEY MESIOCLUSION) Mesial to normal in its relationship with maxillary 1st molar and interdigitation of remaining teeth reflects this: Lower incisors inclined excessively to lingual despite crossbite Individual tooth irregularities Space provided for tongue appears greater Class I – Easiest (65%) Tongue lies on the floor of the mouth Class II,1 – Difficult (28%) Maxillary arch constricted Class II,2 – More Difficult (4%) Arch length deficient Class III – Most Difficult Case (3%) Maxillary incisors more lingually inclined than class I or class II division I Class II division 1 SUBTYPES OF CLASS III Max incisors are protrusive, proclined Type I Excessive OJ, deepbite, accentuated curve of Spee EDGE TO EDGE bite If viewed separately, suggest a true occlusal Class II division 2 relation, teeth even, alignment both maxillary and Angles CL II Div 2 mandibular ○ 4% Dental arches of good shape ○ Maxillary central incisors retroclined Type II ○ Lateral incisor proclined Mandible crowded and lingual to maxillary incisors Facial profiles Maxillary teeth in good alignment Mandibular incisors lingual to maxillary incisors Landmark: but definitely crowded/bunched (mandible – Tip of the forehead lingual to the maxillary) Type III ○ Anterior bony protuberance on your Maxillary teeth are crowded/bunched forehead is called Nasion Mandibular teeth in good alignment Tip of the upper lip Mandibular incisors labial to maxillary incisors Tip of the chin 4  DENTAL MEDICINE - 4B ORTHODONTICS 2 - MIDTERMS Dr. Leonela Tan Transcribed by: Barrientos, R LECTURE 2: KEYS TO OCCLUSION Key 2: Crown Angulation 6 KEYS TO OCCLUSION Key 3: Crown Inclination Key 1: Molar Relationship (Interarch relationship) Key 4: Rotations Key 2: Crown Angulation Key 5: Tight Contacts Key 3: Crown Inclination Key 6: Curve of Spee Key 4: Rotations Key 5: Tight Contacts If one key is not met, the work is not yet done. Because there will Key 6: Curve of Spee be a deviation at any point and would affect the stability of the III. Lecturer: Dr. Ida Marie Manlangit treatment. IV. Reference: PPT LEGEND KEY 1: MOLAR RELATIONSHIP ⁈ 1. The mesiobuccal cusp of the upper first permanent from lecturer book/notes pls search molar falls within the groove between the mesial and middle cusp of the lower first permanent molar. Lawrence F. Andrews, DDS (1972) 2. Distal surface of the distal marginal ridge of the Lawrence Andrews was an orthodontist upper first permanent molar contacts and occludes One of the basis for an orthodontist for their within the mesial surface of the mesial marginal patient’s treatment ridge of the lower second molar. There are additional guidelines that the dentist 3. The mesiolingual cusp of the upper first molar doesn’t know. seats in the central fossa of the lower first molar. 4. The premolars have a cusp embrasure relationship Set of static (stationary when u bite) occlusal buccally, and a cusp-fossa relationship lingually. goals for tooth relationships in the intercuspal 5. Maxillary canine has a cusp-embrasure position relationship with mandibular canine & 1st premolar The cusp tip is slightly mesial to Ronald Roth embrasure "consistent with desirable functional occlusal goals, If it falls on the embrasure, it’s the best provided that the occlusal interdigitation occurs 1-1.5 mm is acceptable but if it goes more with the mandible in centric relationship” than that, it’s a class 2. Occlusal goals: centric occlusion & centric relation 6. The mesiobuccal cusp of the upper first permanent Provide stability molar falls on the buccal groove of the lower first permanent molar. Centric occlusion how the patient bites (occlusal interdigitation) Angle classification: CLASS 1 Centric relation: describing the position of the condyle and TMJ or treatment right on the embrasure jaw relationship between maxilla and mandible falls on interarch when the mandible is in a retruded position. Most anterior superior position of the condyle disc assembly within the glenoid fossa relationship of maxilla, mandible when the mandible is in most posterior (retruded) position KEY 2: CROWN ANGULATION and the condyle in the glenoid fossa most antero posterior part The red line signifies the long axis. The tip is called Dynamic functional the crown angulation. The blue line is the move jaw left and right angulation of the tooth. MESIODISTAL CROWN TIP 6 KEYS TO NORMAL OCCLUSION BY ○ angle between the long axis of the crown LAWRENCE F. ANDREWS and a line 90 degrees from the occlusal plane Expressed in degrees, plus or minus Key 1: Molar Relationship (Interarch relationship) Positive angulation 5  LECTURE 2: KEYS TO OCCLUSION ○ The gingival portion of the long axis of each crown is distal to the occlusal/incisal portion of that long axis Determines the amount of Mesio-distal space occupied Affects occlusion and esthetics ➔ Angulation- think of tip (mesial or distal) ➔ gingival portion is slightly distal (positive tip) ➔ negative angulation if it doesn’t follow it ➔ amount of mesiodistal space occupied KEY 4: ROTATIONS Teeth should be free of undesirable rotations Rotated molar occupy more space in the dental arch Rotated incisor occupy less space than those correctly aligned There’s crowding KEY 3: CROWN INCLINATION Rotated canine Labio-lingual or bucco-lingual torque affects esthetics and Angle formed by a line which is 90 degrees to the may lead to occlusal occlusal plane as viewed from the mesial or distal interferences Drawn or shown in a proximal view Check the canine Expressed in degrees (- or +) guidance Upper maxillary anteriors have positive torque Affect occlusal while the rest have negative torque. relationship CROWN INCLINATION 1. The crowns of the maxillary incisors are placed so that the incisal portion of the labial surface is labial KEY 5: CONTACT POINTS to the gingival portion of the clinical crown. 2. In all other crowns, the occlusal portion of the labial In the absence of abnormalities like tooth-size or buccal surface is lingual to the gingival portion; discrepancies, contact point should be tight (to be 3. From the max canines to the premolars, the lingual steady and not move) crown inclination is constant and more pronounced Not always visible in a cast, use or increases in the molars floss to check and there should 4. For the lower crowns (canines to molars), the be a resistance. If there’s no lingual inclination progressively increases resistance upon flossing, the contact points are not yet tight. PROPER INCLINATION Contact points prevent relapse. affects normal overbite and posterior occlusion KEY 6: CURVE OF SPEE Insufficient (negative)anterior crown inclination A flat occlusal plane should be the treatment goal TORQUE INCLINATION OR not be deeper than 1.5 mm Needs to be flat curve of spee (cusp will be (include the crown or the root torque) touching the line w/ slight concavity) Curve of spee naturally deepens and the bite ➔ Root (buccal root torque) deepens and patient has overbite or overjet ➔ Lingual root torque (crown torque) How to determine the curve of spee? ➔ Only the maxillary incisor (central and lateral) has a Draw a line from the incisal edges of the central positive crown inclination, and all the rest are incisors to the distal cusp tip of the most posterior lingually inclined teeth. ➔ Starting from the canine are buccally Good curve of spee = parallel root ➔ Canine when set is lingual crown torque ➔ Class 2 div 2- lingual crown torque ➔ Increase in crown torque is greater in the mandibular 6  LECTURE 2: KEYS TO OCCLUSION DEEP CURVE OF SPEE The deeper the curve of spee, the more space is required (CLASS 2) Presence of a more contained area for the upper teeth Flat curve of spee REVERSE CURVE OF SPEE Excessive space for each tooth (CLASS 3) (Right and left canine guidance) KEY 7: CORRECT TOOTH SIZE (Bennett and McLaughlin, 1993) – additional key Tooth size discrepancy would have resulted in either spacing or crowding in either of arches Discrepancy may exist prior to treatment but frequently not noticed until the finishing stage Interproximal reduction to tooth size in one arch or restorative procedure to tooth size in opposite arch should be discussed with patient/parents before treatment Roth (1981) Added more characteristics of normal occlusion: CR=CO Exclusion of posterior teeth during protrusion Inclusion of canine teeth solely during lateral excursions of the mandible Even bilateral contacts in buccal segments during centric excursion of teeth. Consider the functional occlusion Summary: Success (getting patient a good occlusion) of orthodontic treatments can be achieved when all static and functional objectives of occlusion exist and achieving stable centric relation with all teeth in maximum intercuspal position 7