Biometric methods of analysis Flashcards
(55 cards)
Three planes for biometric analysis of plaster models
- Transverse
- Sagittal
- Horizontal
- For anteroposterior discrepancies
- Projection on maxilllary tuberosity
Transverse plane
- Assessment of transverse discrepancies
- Projection on midsagittal plane
- Perpendicular to transverse plane
- Sagittal plane
- Assessment of vertical discrepancies
- Projection onto occlusal surfaces
- Perpendicular to other planes
Horizontal plane
- Distal to maxillary tuberosity
- Between second premolar and first molar
Identification of transverse plane on study model
- Anterior part= intersection of palatine raphe and second palatine ruga
- Posterior part- 1) most posterior point of palatine raphe before bisection 2) Intersection of diagonols connecting palatine fovea
Identification of Sagittal plane on study model in maxillary arch
- Anterior part- projection of mental spine under lingual frenulum
- Posterior part- Midline from upper model base to lower model base
Identification of Sagittal plane on study model in mandibular arch
Identification of horizontal plane on study model
Parallel to occlusal plane
Tooth size discrepancies can be
- Intra-arch
- Inter-arch
-Correlation in MD and BL dimensions of mandibular incisors
-MD mandibular incisor width/BL mandibular incisor width* 100
-MD mandibular lateral incisor width/BL mandibular lateral incisor width*100
-MD value greater than mean and BL value=proximal reduction required
Peck and peck index
Peck and peck Index measured with
Divider and boleys gauge
-Correlation between sum of incisor widths of maxillary and mandibular teeth
-Harmony between arches assessed
-Sum of maxillary MD widths—sum of mandibular incisor widths (si:SI)=3.4/0.7 coefficient
-Range from 0.72-0.77
Tonn index
Tonn index reversed
-SI:si=4:3
-coefficient of 1.35
-range from 1.22-1.42
Tonn index value for edge to edge bite
1.22
Tonn index for Deep overbite
1.42
-Determines discrepancies between MD widths of maxillary and mandibular teeth
-MD widths 12 maxillary and mandibular teeth measured
-Sum of MD width of 12 mandibular/Sum of MD widths of 12 maxillary teeth*100=91.3%
-Increased ratio= mandibular tooth material excess
-Decreased ratio= maxillary tooth material excess
Boltons ratio
-Assesses discrepancies in frontal area of arch
-Sum of MD width 6 mandibular teeth/sum of MD width of 6 maxillary
-Ratio<72.2% = maxillary anterior tooth material excess
-Ratio > 77.2% = mandibular Tooth material excess
Boltons anterior ratio
Rational for boltons ratio and boltons anterior ratio
-comparison between overall and anterior ratio allows evaluation of problematic arch
-correlation between lateral segments length and MD widths of anterior teeth
-Upper and lower arch divided into one anterior and two lateral segments
-Lateral segments measured with cord from M surface of canines to D surface of first molars
-Maxillary anterior segment= sum of maxillary incisors (SI)
-Mandibular anterior segment=sum of width of mandibular incisors*1.35(tonns index)
-Ideally maxillary and mandibular anterior segments =< lateral segments
Gerlach
-comparison of space available and required for correct alignment of permanent teeth
-allows prediction of dental arch growth
-measured from D of last posteriors to distal surface of opposite side
-Sum of MD of permanent teeth measured and compared with arch perimeter
-Difference in space available and required is sufficient/ deficient or excess
Aim of arch perimeter analysis
-evaluation of width of dental arch in permanent dentition
-Sum of MD widths of Maxillary right central incisor and maxillary right first molar
-rarely have abnormalities in shape, size or agenesis
-MD sum widths of right maxillary central and first molar determines posterior width of arch
-Right maxillary premolar added to sum after eruption
Evaluation according to chateau
According to chateau, 8 yr d dental arch growth increment in maxillary tuberosity=
16mm(8mm) each side
According to chateau, 12 yr d dental arch growth increment in maxillary tuberosity=
8mm(4mm each side)
According to chateau, 16 yr d dental arch growth increment in maxillary tuberosity=
4mm (2mm each side)
