Teeth arrangement

Selection and Arrangement of Teethfor Complete Dentures

By: Dr. Rohan Bhoil

Contents

• Introduction• Review of literature• Selection of anterior teeth• Selection of Posterior teeth• Arrangement of teeth• Conclusion

Introduction• After casts are mounted & occlusal scheme

determined.• Maintenance of vertical dimension.• Anterior teeth – primarily aesthetics.• Posterior teeth – for mastication.• Harmony.

Why selection and arrangement deserve special attention ?

• Absence of periodontium.• Single unit on an unyielding base.• Necessity of bilateral balance.• Consequences of malocclusion.• Bearing of non vertical forces.• First molar & second premolar area.• Proprioception.• Incising with natural teeth.

Review of Literature

• Berry’s Biometric Ratio Method [1906]– Inverted CI resembles face form– Tooth size 1/16 face width & 1/20 face length

• Clap’s Tabular Dimension Table Method [1910]– Tooth size based on six anterior teeth– Enabled to specify mold

• Cigrande [1913]– Outline form of fingernail - Outline form of Central

incisor.

• Pound E. (1951) - dentures should be designed according to the principle of nature.

• French A. (1951) - teeth should be arranged according to the face form, arch form, width of mouth and ridge relation.

• Frush & Fisher (1955 – 59) - Sex, Personality and Age of the patient.

• Martone A. L. (1964) - loss of the teeth & their supporting structures produce radical changes in facial appearances.

• Curtis T. & Shaw E. (1987) - the esthetic results require more than the size, color, position and arrangement of complete denture teeth.

• Golden proportion - by Levin

• Preston (1993)

• Ward (2000) - Recurring Esthetic Dental (RED) proportion based on the different heights of the maxillary anterior teeth.

• However in a study: To evaluate the validity of Recurring Esthetic Dental proportion in natural dentition, J Conserv Dent. 2011 Jul-Sep; 14(3): 314–317., authors Shetty etal, found that RED proportion was not seen in natural dentition.

Methods Used to Select Artificial Anterior Teeth for the Edentulous Patient: A Historical Overview – Selten etal, Int J Prosthodont 1999:12:51

Concluded that to date, no universally reliable method of determining tooth form has

been found. The Williams classification (1914) is the most universally accepted method of determining anterior tooth form.

Assessment of Dental Appearance Following Changes in Incisor Angulation

Wolfart etal, Int J Prosthodont 2004;17:150–154.

• They evaluated the assessment of attractiveness of standardized changes in incisor angulation of different tooth arrangements and found that tooth arrangements showing central incisors with ideal axes are more attractive, than angulation of one or

both central incisors. And slight changes in the angulation of one or both

lateral incisors do not influence attractiveness negatively.

• Varjao etal, in their study on Intercommissural width as a guide for selection of anterior maxillary teeth ( Int J Prosthodont, 2005; 18;513-515)– Found that a weak correlation exists between the

corners of mouth and distal of canines and hence use of corners of mouth for selection of artificial teeth is generally inaccurate.

• Jaffar Abduo, in a systematic review (Int J Prosthodont 2013;26;26-33) on occlusal schemes for complete dentures has concluded that primarily as per patient acceptance, posterior tooth arrangement in conventional bilateral balanced occlusion and lingualized bilaterally balanced occlusion, are preferable to flat teeth arranged in monoplane occlusion.

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Anterior tooth selection

• Size • Form• Shade• Material

Size of Anterior Teeth• Size of Face & Head– Bizygomatic width / 3.3 – maxillary anteriors– Bizygomatic width / 16 - maxillary central– Length of face / 16 – maxillary central– 10:1 ratio of cranial circumference to upper

anterior teeth.

Anatomical Landmarks• Mark corners of mouth on wax occlusal rims.• Extension of parallel lines from lateral surface

of ala of nose onto maxillary occlusal rim.• A line perpendicular to midline of palate

through distal border of incisive papilla.

Maxillomandibular Relations -Mandibular anteriors : class II & III arches.

Contour of residual ridges - teeth placed to follow contour and size selected according to this position.

Vertical distance between ridges.

Lips – selection of length of maxillary anteriors.

High Lip Line

• Highest point of upper lip when smiling

• Cervical necks lie at or above this line

• If shorter teeth are selected, esthetics compromised

• Nose– Distance between tips of canine is same as width

of base of nose• Philtrum– Width of upper centrals, approximates the width

of philtrum

Pre – Extraction Records

• Facial Photographs• Diagnostic Casts• Radiographs• Teeth of Close Relatives• Extracted teeth.

Form of Anterior Teeth

• Pre-extraction records• Form and Contour of Face

Leon William’s Classification

• Square• Square – Tapering• Tapering • Ovoid

Dentogenic Concept• Frush & Fisher (1957), Dynesthetics

• Sex factor– Feminine : softness– Masculine : boldness & hardness

• Personality factor– Vigorous type, medium type & delicate type

• Age factor– Incisal edge, erosion, diastema, stippling of

interdental papilla.

Shade selection for Anterior Teeth

Shade Selection• Along side of nose – basic hue, value &

chroma.

• Under lips – only incisal edge exposed – effect of colour with mouth relaxed.

• Under lips – only cervical end covered – smile.

• Use of Squint test.

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Posterior tooth selection

• Size • Form• Shade

Size of Posterior Teeth• Buccolingual Width– Sufficient to act as a table to

hold food.– Less than width of natural

teeth.– Not to encroach on tongue

space and buccal corridor.– Limits forces directed to ridge.

• Mesiodistal Width– Edentulous space available.– Placed as far as possible posteriorly.– Not over beginning of ascending area of ramus

and retromolar pad.

• Occlusogingival Height– Determined by available inter ridge space, occlusal

plane and height of anterior teeth.– Teeth with largest possible vertical length that can

be used without grinding are preferred for aesthetics.

Form of Posterior Teeth• Anatomic Teeth– Cusp teeth.– Simulate occlusal surface.– Varying degrees of inclinations (10°, 20°, 30°, 40°)– Standard is 33°– Cusp incline < 33°, is termed semi-anatomic teeth.– Advantages.– Disadvantages.

10°

20°

30°

Non- Anatomic Teeth• Cuspless, Monoplane or Zero degree teeth.• Offer less resistance to horizontal forces– Bruxism– Poor residual ridges– Uncoordinated muscular movements– Mal relationship of jaws –class II & III

DisadvantagesShearing efficiencyPoor aestheticsLateral & protrusive balance not possible.

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Shade Of Posterior Teeth

• Harmonize with the shade of the anterior teeth.

• Bulk influences the shade of teeth– select a slightly lighter shade

for the premolars

Selection of Tooth Material

• Resin– Composite Resin– Acrylic Resin• Monolithic• Cross – linked• IPN linked

• Porcelain – When aesthetics are paramount– Adequate interarch space is available.

Resin & Porcelain Teeth• Wear potential• Grinding & adjusting• Bonding to denture base• Abrasion of opposing dentition• Colour stability• Impact sound• Rebasing• Impact resistance.

Posterior Tooth Forms – Historical Development

• Anatomic teeth– Trubyte teeth (1914) by

Gysi– Channel tooth (1927) by

Sears– Metal insert in resin

(1942) by Vincent– Crossblades (1961) by

Sosin

• Non-anatomic teeth– Inverted cusp tooth (1929) by Hall- sharp

concenteric ridges around cup like depressions.

– True-kusp (1929) by Meyerson – buccal lingual ridges with sluiceways between them.

– Chopping block (1934) by Nelson

– Non-lock (1939) by Swenson

– Vitallium Occlusal (1946) by Hardy

Teeth Arrangement

• Anatomical landmarks• Ridge relation• Balanced occlusion • Neutral zone

Anatomical landmarks

• Residual ridge– Position in relation to ridge due

to resorptive pattern.• Arch form– Square, tapering & ovoid arch

forms

• Retromolar pad– Too low a occlusal plane causes tongue biting and

too high a occlusal plane can cause instability and strain.

• Parotid Duct– Maxillary first molar

• Rugae – Labial surface of canine

10.5mm

• Incisive papilla– Midline– Central incisor– Perpendicular line

Teeth Arrangement for Class I Ridge Relation

• Wax rim contours aid selection and setting:– Occlusal vertical dimension– Angulation of facial rims affects lip support– Overjet

• Place reference marks on the occlusion rims to aid in tooth selection and placement.

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Orientation Of Occlusal Plane

Occlusal planeUpper rim • Anteriorly - parallel to inter pupillary line • Posteriorly - parallel to Camper's line

Lower rim • Anteriorly – lower lip• Posteriorly - Half to two/third retromolar pad.

Ideal Arrangement Of Teeth

• Anterior teeth

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Central Incisor

• Long axis – parallel to the long axis of the patient face.

• The midline of the dental arch – the centre of face

• Labial contour – blend with the contour of face.

• Rotation on long axis – varies depending on arch form

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Maxillary lateral incisor

• Set at angle of 50 to the perpendicular • Incisal edge is about 1 mm short of the

horizontal plane• Labial surface is inside at the cervical end • Distal half of rotated slight lingually

50

Canine• Cervical end is more prominent labially• Canine is the turning point of arch – mesial half is harmony with ant teeth – distal half harmony with post teeth (PM)

• Tip of cusp is in contact with the occlusal plane

The lower anterior teeth

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Central Incisor

• Long axis – Parallel to vertical viewed from front

• Slopes labially when viewed from side • Incisal edge 1-2mm above the horizontal plane

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Lateral Incisor

• Long axis – parallel to the vertical viewed from front.

• Slope labially

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Canine

• Long axis- slightly lean towards midline

when viewed from front – slightly lingually when viewed

from side • Cusp is slightly above 0.2 mm

above the horizontal plane

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• Canine key of occlusion– The distal incline of the lower canine should align

with the mesial incline of the upper canine.

Limits To Placing Anterior Teeth

• The medio lateral and antero posterior position of maxillary ant teeth – limited by phonetics and esthetics

Phonetics

• Long teeth F sounds like V• S sounds – two tongue positions– Palate– Lower anterior teeth

Upper posterior teeth arrangement

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First Premolar

• long axis – parallel to vertical axis when

view from labial side.• Palatal cusp is 0.2 mm sort of

its buccal cusp from horizontal plane.

Due consideration is given in esthetics in female

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2nd Premolar

• Both buccal and palatal cusps touches the occlusal plane

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The First Molar

• Long axis– Long axis slopes bucally

when viewed distally from side.

• Mesiolingual cusp

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• Molar key of occlusion– The mesiobuccal cusp of the maxillary permanent

molars should coincide with the mesiobuccal groove of the mandibular permanent molar

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2nd molar

• More inclined than 1st molar• Cusps above horizontal plane

Maxillary teeth set, checked on a flat plane

Lower Posterior Teeth

69

First Premolar

Long axis – parallel to the vertical axis

• lingual cusp is below the horizontal plane • buccal cusp about 02 mm above occlusal

plane

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Second Premolar

• Long axis–parallel to vertical axis

• Both cusp are about 02 mm above the horizontal plane

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The First Molar

• Long axis– leans lingually when viewed from the front – mesially when viewed from the side

• All the cusps are at higher level above the horizontal plane than those of second premolar

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2nd molar • More inclined than 1st molar• Cusps above horizontal plane

Teeth arrangement checked in patients mouth

Setup for class II & III cases

Set up in class II jaw relations• In this setting, the flattened lingual cusp of upper

premolars occludes with the flattened buccal cusp of lower premolars and a large buccal horizontal overlap occurs in the bicuspid area.

• Upper molars are set with their lingual cusp in the modified central cusp of the lower teeth.

• Posteriors should have a centric occlusion with stable non-deflective stops.

Setup in Class III relation• If ridges are edge to edge, then anterior teeth are

also placed edge to edge.

• In cases of extreme protrusion, – negative or reverse horizontal overlap is used,– a larger lower tooth mold can be used,– Interchange of upper and lower teeth– First premolar may be eliminated from upper arch– Transverse ridges of upper posteriors are grinded away

to eliminate mesiodistal interlocking.

Balanced Occlusion • After centric balance is achieved, teeth

arrangement is modified to achieve eccentric balance.

• At least a semi-adjustable articulator is required.

• For lateral balance, buccal cusps of posterior teeth should contact on working side and on non-working side, contact should occur between mandibular buccal & maxillary palatal cusps.

• To develop balanced occlusion in Protrusion– With the anterior teeth edge to edge, contacts

should simultaneously be established in the posterior teeth.

– Factors affecting balance• Condylar inclination cannot be altered.• Incisal guidance can be manipulated limitedly.• Cuspal inclination is determined by selection of teeth.• So mainly, the anterio-posterior Curve of Spee

influences protrusive balance.• Thus, steeper the condylar inclination, steeper should

be the compensating curve with low cuspal inclination, to achieve protrusive balance, while maintaining the centric contact.

Setup in neutral zone technique

• Neutral zone is recorded.• Impression is indexed.• Teeth arrangement is guided by index.• Posterior teeth may require to be trimmed

lingually so that they fit into index space.• Polished surfaces of denture are also

contoured to replicate record.

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Characterization

• Subtle chips ,stains make teeth look more natural

• Highest quality of art is to conceal art

Conclusion

• Selection and Arrangement of teeth is an art based upon biomechanical factors, governing the ultimate success of dentures.

References• Zarb - Bolender : Prosthodontic treatment for edentulous

patients. Twelfth edition, 2004.

• Sharry J.J. : Complete denture prosthodontics, 1968.

• Rahn and Heartwell : Textbook of complete denture, 4th edition, 1993.

• Boucher. C.O: Prosthodontic treatment for edentulous patients. Tenth edition

• Dental Clinics of North America : Esthetic Dentistry, April 1989

Thank you !!!