SPACE ANALYSIS Flashcards
- What does space analysis entail ?
Comparison of amount of space available and amount of space required to align teeth.
Done directly on SM’s OR by computer algorithem after digitising.
- How do you calculate the space available ?
Measure the ARCH PERIMETER ( M of 6-6)
Over contact points on the posterior teeth and on the incisal edges anteriorly.
Can divided the archinto segments- straight line approx.
Contour a piece of brass wire to the line of occlusion and then straighten it out for measurements.- This method has been found to underestimate the extent of crowding ( Jphal et al 1997 EJO).
How do calculate the space required ?
Measure the widths of each erupted tooth from contact point to contact point.
Estimate the size of UE teeth.
Sum of wisths od individual teeth
if > amount of space available= space deficiency.
if < amount of space available= space xs
- What are the assumptions of such a space analysis ( ie when you measure the width of teeth and the amount of actual space available) ?
- AP position of incisors is correct
- ( becasue retroclined incr cx)
- (because proclined reduced cxing)
- All teeth are present and are of a normal size ( anomalies have significant space implications).
- Space available wont change sue to growth ( which it can)
- Well proportioned face, litle tendency for dentition to be displaced during growth, but in those with jaw discrepancy the teeth shift ant/post.
- Space analysis is less accurate for those with skeletal problems.
- What three methods can be used to estimate the size of UE teeth ?
- Measurement of teeth on xrays.
- Estimation from proportionality tables
- Combo of xrays and prediction table method.
- Measurement of teeth on xrays ?
- UNDISTORTED X-ray
- We then compensate for magnification ( which would have occured ) by doing the folloiwng calculation:
- True width of Primary Molar X true width UE T
Apparent width on xray apparent width
- Accuracy: fair/good
- Can be used U L Arches
- All ethnic groups
- Estimation of UE tooth from proportionality table ?
- ~ good correlation bw size of erupted incisors and UE CANINES + PM’s.
- Moyers prediction table
White Americans
MD width of LOWER INCISORS measured
Predict size of U +L UE’d 3,4,5
NB: U2’s width very unreliable and so not used.
Accuracy ~ good for N .Europeans
Tendency to OVERESTIMATE size od UE’d tooth.
Can be used for UL Arches
No need for XRAYS.
- Tanaka +Johnston 1974 Method of predicting width of UE’d tooth ?
- Good for the prediction of UE’d Canines and PM’s
- Conducted a study onn 506orthodontuc patients
- They believed that Moyers analysis hadnt been validated on a sample other then that reported by Moyers
- Y= A+B (X)
- Y= sum of MD width of UE Canines and PM’s.
- X= Sum of MD width of LINC’s
- A and B= Constants
- MAXILLARY ARCH: Y= 11+0.5 (X)
- MANDIBULAR ARCH: Y= 10.5 +0.5 (X)
Good accuracy for European population
No xrays/ reference tables needed
Overestimated space required for caucasian females in UL Arches.
Underestimates space in African- american males in L Arches.
- Combination method for estimating size of UE teeth
- ( Staley and Kerber 1980)
- Read canine width directly from the sum of incisor widths ( from SMs).
- PM widths from xrays
- Can ONLY BE USED IN L ARCH
- ~ accurate for those of European ancestry
- From the SM’s on ONE SIDE measure MD widths of L 1 &2
- From the LCPA measure the MD width of the UE 4&5
- Total MD widths of the 4 teeth compare the measurement value to estimate tooth size from the Hixon Oldfather chart (graph developed from the lower growth data).
REPEAT STEP 1-3 for the other side of the arch.
- Bolton Analysis 1958
- Evaluated 55 vases with EXCELLENT Occlusions
- He developed 2 ratios for Estimating TSD
- By measuring MD widths of MD teeth MX teeth.
OVERALL RATIO = Sum MD teeth width 12 teeth x100
- Sum MX teeth width 12 teeth
ANTERIOR RATIO = Sum MD 6 ANT Teeth X 100
Sum MX 6 ANT teeth
Boltons SD are used to determine if tooth reduction or enlargements are necessary.
