ID Theme 2

What is cephalometry?

Study and classification of the proportions of the head and face (during growth/development)

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What is Angle's skeletal classification?

Measures angle of the relationship between the mandible and maxilla (accounding for degrees between nose and chin). More focus on facial skeleton than dentition, infinite blending between categories.

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What defines Class I (Angle's skeletal classification)?

Mandible is 'normally' related to the maxilla (normal varying between populations)

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What defines Class II (Angle's skeletal classification)?

Mandible is retruded relative to the maxilla (hard to achieve an anterior seal)

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What defines Class III (Angle's skeletal classification)?

Mandible protruded relative to the maxilla (making posterior seal difficult)

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What constitutes a normal bite?

Maxilla just a little wider than mandible. Means maxillary palatal cusps contact mandibular central fossae/mandibular buccal cusps contact maxillary central fossae (so palatal maxillary and buccal mandibular are the functional cusps)

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What is a crossbite?

Mandible is slightly wider than the maxilla; maxillary buccal cusps contact mandibular central fossae, mandibular palatal cusps contact maxillary central fossae (functional cusps reversed)

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What is scissorsbite?

Maxilla significantly wider than the mandible so teeth dont contact (on one/both sides)

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What is intercuspal position (ICP)?

Maximum interdigitation between the teeth, mandible and maxilla contact. Stable and reproducible. Bolus broken up here during chewing.

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What do molar classifications measure?

Relationship between the mesio-buccal cusp of the 1st permanent maxillary molar and the buccal groove of the 1st permanent mandibular molar. Unlike incisal releationship not always determined by jaw relationship (as molars last to erupt).

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What defines a class I molar relationship?

Buccal cusp of upper 6 is on the buccal groove of the lower 6

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What defines a class II molar relationship?

Mesio-buccal cusp of the upper 6 is a full tooth width mesial to the buccal groove of the lower 6 (can be measured in 1/2 and 1/4 units)

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What defines a class III molar relationship?

Mesio-buccal cusp of the upper 6 is a full tooth width distal to the buccal groove of the lower 6 (can be measured in 1/2 and 1/4 units)

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What do incisal classifications measure?

Relationship between the mandibular incisal edge and the cingulum plateau on the palatal surface of the maxillary incisor. Determined by jaw relationship, subject to overjet and overbite.

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What are overjet and overbite?

Overjet = horizontal distance between the incisors in mm. Overbite = vertical distance between the incisors in mm/% coverage.

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What defines a class I incisal relationship?

Mandibular incisal edge occludes with/lies below the maxillary cingulum plateau

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What defines a class II division 1 incisal relationship?

Mandibular incisal edge posterior to the maxillary cingulum plateau (with the maxillary incisors of average inclination/proclined so the overjet is increased)

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What defines a class II division 2 incisal relationship?

Mandibular incisal edge lies posterior to the maxillary cingulum plateau, but the maxillary incisors are retroclined to reduce the overjet (so normal/slightly increased). Decreases risk of trauma but lateral incisors often pushed out of arch.

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What defines a class III incisal relationship?

Mandibular incisal edge lies anterior to the maxillary cingulum plateau

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What is occlusion?

The contacts between the teeth. Should be considered in ICP and at rest (when freeway space)/during function. Occurs 3 months (for incisors) to 6 months (for molars) after clinical emergence.

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What is disclusion?

When teeth aren't touching

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What is articulation?

The contact relationship between teeth during function

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What are lateral and protrusive tooth excursions?

These occur from the ICP to achieve articulation

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What defines the working side/non-working side?

Working = side mandible moves towards during function (left/right depends on individual), mandible rotates during function. Non-working = side mandible moves away from in function so teeth are in disclusion, mandible orbits during function

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What is canine guided occlusion?

In lateral excursions only the canines contact to achieve articulation

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What is group guidance?

In lateral excursions both the canines and at least one set of posterior teeth contact to achieve articulation

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What should be taken into account when treating guidance teeth?

Restorations should be avoided/made of hard-wearing material since they are likely to fracture or alter the guidance pattern (causing discomfort/damaging other teeth as masticatory muscles overwork to regain)

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How do eruption patterns differ in African populations?

May experience earlier 3rd molar eruption (though crown formation dates similar) and/or earlier anterior crown completion

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What occurs in the first phase of the permanent dentition?

1, 2 and 6 (occasionally ony 1 and 6 in the mandible) erupt from 6-8.5

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What occurs in the second phase of the permanent dentition?

3, 4, 5 and 7 erupt between 11-12

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What occurs in the third phase of the permanent dentition?

Third molars erupt between 17-21

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What do dental panoramic radiographs (DPR's) show?

Root surface (especially facing bone as more mineralised) and crown white, dentine darker and alveolar bone grey (as less mineralised). Soft tissues black.

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How does calcification present in DPR's?

Observed as white outline within lamina dura alongside shape of four/five cusps in molars

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How does crown completion present in DPR's?

White crown with only beginnings of root formation (dentine slightly extended below crown). In lower 6 at 3, in lower 7 at 6.5.

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How does root bifurcation present in DPR's?

In lower permanent molars, white mass below the incomplete crown roots to form pulp chambers. At 4.5 in lower 6, 8.5 in lower 7.

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How does root completion present in DPR's?

Root changes from conical and open with a dark seperation (between it and the lamina dura) to become closed and pointed (closely surrounded by lamina dura). Occurs at 9 in lower 6 and 15 in lower 7.

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What is emergence? What are its sub-categories?

Tooth eruption process - at 6 in lower 6 and 12 in lower 7. First emergence through alveolar bone up to gingival line, then clinical emergence through the gingiva to reach partial eruption (be seen).

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When does root resorption occur?

In the primary dentition when the permanent try to erupt (occurs labially so roots at an angle) or later in life when permanent become infected. Distal roots resorb before mesial, and earlier in girls.

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What is exfoliation? When does it occur?

Shedding of primary teeth; 1 year (for anterior teeth) to 1.5 years (for posterior teeth) after onset of resoprtion

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How can it be determined if teeth are partially/fully erupted from a DPR?

Look at soft tissue line (appears as shadow below white of top of crown)

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How do you go about determining age from DPR's?

Determine status of lower 6 then lower 7 (checking with upper, except bifurcation). Look for calcification of 8 at 8-10 years (crypt from 6). Incisors considered (vary, lower central and lateral possibly same). Then canines/premolars (most variable).

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What can cause early loss of the primary teeth?

Due to caries or extraction. Affects distribution/symmetry, posterior teeth may move mesially.

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What can cause primary retention?

Failure of permanent to resorb primary roots through dilaceration or hypodontia. Recognised as asymmetry between contralateral eruption; underlying permanent should be checked.

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What is dilaceration?

Abnormal angle between the permanent tooth crown and the primary tooth root. Common in maxillary incsors (through trauma) - may cause their impaction (development in hard palate). Otherwise, permanent doesn't erupt.

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What can result from trauma to the primary dentition?

Dilaceration, cessation of root growth (so stunted roots can't support tooth) or growth of permanet root and crown at 90 degrees (preventing eruption/extraction)

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What are the most common missing teeth in hypodontia?

Third molars (in 20-30% population), lower 2nd premolars and upper lateral incisiors (upper premolars and lower central incisors next - canines, 1st/2nd molars rare)

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What is a common occurance of syndromic hypodontia in the European population?

Localised incisor-premolar hypodontia

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What is hypodontia associated with?

Reduced crown and root size, conical crown shape, enamel hypoplasia, molar taurodontism (elongation of pulp chamber), delayed eruption, primary retention and impaction of maxillary canines

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What is associated with supernumerary teeth (hyperdontia)?

Extra teeth smaller and prevent eruption of other teeth. Twice as common in males.

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What can you determine from an unerupted tooth in a DTP which appears to have had its roots resorbed?

It is at/close to its eruption date

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How are permanent incisors extracted?

Lower = bucco-lingual technique as roots compressed mesio-distally. Upper = rotation.

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What is the longest tooth with the longest root?

Upper permanent canine

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How can you determine the upper permanent canine from the lower?

Upper has lingual surface much wider than palatal. In lower only slightly wider and labial enamel extends more apically, root more compressed, lingual fossa not as deep.

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How are the permanent canines extracted?

Upper = rotation. Lower = combinational technique (bucco-lingual to loosen socket then rotational to extract)

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What is an abnormal feature of the upper 1st premolar?

Its distal slope is shorter than its mesial slope

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How can upper and lower premolars be distinguished?

Upper = wider labio-palatally so form heaxagon/hard to roll. Lower = circular so easily rolled,. Also larger palatal cusp in upper than lingual in lower.

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How are premolars extracted?

Lower = conical roots so extracted via rotation. Upper = root compressed mesio-distally so buccal lingual extraction technique used (and two root canals may cause fracture).

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Which premolars form a canine groove/fossa?

Upper 1st = groove and fossa. Lower 1st = groove but no fossa. Upper and lower 2nd = no canine groove or fossa.

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How do the roots of the permanent molars reduce differently?

Upper = retain triangular shape. Lower = square close to crown, becomes circular.

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How are all molars (permanent and primary) extracted?

Bucco-lingal technique to prevent fracture of multiple roots

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What is the hardest/easiest tooth to remove?

Hardest = upper 1st molar. Easiest = upper 3rd molar.

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How can the orientation of type II upper 2nd molars be determined?

Mesio-marginal ridge higher than disto-marginal ridge

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Why is it sometimes hard to determine between the upper and lower 3rd permanent molars?

Root number may be 3 or 2 (for either)

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What is a characteristic feature of the lower 2nd permanent molar?

Tips of buccal (functional) cusps closer to central fissure to aid occlusion with the central fossa of the upper

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What are features of the deciduous dentition?

Enamel thinner so caries more rapid/incisal wear more likely. Pulp chamber larger than in permanent so pulp horn extends to produce thinner dentine in these areas.

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How are the deciduous incisors extracted?

All via rotation (as conical root) except upper central (extraceted via bucco-lingual as compressed labio-palatally)

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What is a determining feature of the upper deciduous canine?

Usually symmetrical crown - if not distal cusp will be shorter (unlike in all other canines)

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Which deciduous molars form a molar tubercle (on their largest mesio-buccal cusp, from the buccal cingulum)?

Upper 1st and lower 1st (though still low buccal cingulum in in lower 2nd (more pronounced than in upper 2nd))

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