# Growth Prediction and Treatment Timing

> Growth prediction and timing for NEET-MDS Orthodontics: pubertal spurt ages, CVM and Fishman SMI, Bjork growth rotation, Jarabak ratio and VTO limitations.

- Canonical URL: https://prepelephant.com/topics/neet-mds/orthodontics/growth-prediction-timing
- Exam / course: NEET-MDS · Subject: Orthodontics
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Growth Prediction and Treatment Timing", PrepElephant, https://prepelephant.com/topics/neet-mds/orthodontics/growth-prediction-timing

## Direct answer

Timing, not mechanics, decides whether growth can be modulated at all. The pubertal spurt — on average 10–12 years in girls and 12–14 in boys — is the window in which mandibular functional advancement earns its skeletal component; transverse expansion and Class III maxillary protraction respond best earlier still, in the mixed dentition, while the sutures are compliant. Once the spurt passes (roughly CVM CS4–CS5, or two to three years after menarche in girls), growth modification is closed and the options narrow to camouflage or surgery. Maturation is assessed, never assumed: hand-wrist films read against Fishman's eleven skeletal maturity indicators, cervical vertebral maturation stages on the cephalogram already taken, or dental calcification as a rough proxy; direction is forecast from the Jarabak ratio and Björk's growth rotation concept, with visual treatment objectives (VTOs) sketching the forecast honestly, within limits.

## What you must remember

- **Scammon's curves and the spurt:** neural tissue matures early, genital tissue late; the adolescent spurt in general and mandibular growth peaks at about 10–12 years in girls and 12–14 in boys, with peak height velocity roughly coinciding with peak mandibular velocity.
- **Sex differences:** girls start earlier, finish earlier (growth essentially complete two to three years post-menarche); boys start later, grow longer and larger — a 13-year-old boy is often still pre-peak where a 13-year-old girl is finished.
- **Fishman's SMI system:** eleven skeletal maturity indicators at six sites on the hand-wrist film; ossification of the adductor sesamoid of the thumb heralds the imminent spurt, and fusion of the distal radial epiphysis (SMI 11) marks its end.
- **CVM stages:** CS1–CS6 from vertebral concavities and body shapes, with the mandibular peak falling in the year after CS3 — the functional appliance trigger.
- **Björk's implant studies:** metallic implants proved rotational growth of the jaws — forward (anterior) rotation deepening the bite in short faces, backward rotation opening it in long faces; surface remodeling partially masks the rotation.
- **Jarabak ratio:** posterior to anterior facial height 62–65 per cent suggests balanced or forward rotation; below 62 per cent flags vertical, backward-rotating growth with open bite tendency.
- **VTO:** Ricketts' and Johnston's visual treatment objectives extrapolate growth and planned movement; they forecast direction better than millimetres and must never be sold to patients as promises.
- **Appliance-to-window mapping:** functional appliances CS2–CS3; RME and facemask in the early mixed dentition; headgear orthopaedics during active growth; serial extraction beginning 8–9 years.

## Sequencing one patient through her window

An 11-year-old girl with a Class II division 1, narrow maxilla and CS2 vertebrae sits on the front edge of her spurt. Sequence matters: rapid maxillary expansion first, because the transverse correction wants a compliant suture and six months of retention; the twin block follows immediately, timed so its active phase straddles CS3 and the peak mandibular growth it rides. By CS4 the functional phase is weaned and fixed appliances detail the occlusion while the deceleration curve still contributes. Her brother, two years older but skeletally younger (CS1 on his film — a common androgynous surprise in boys), is told to wait; starting his functional phase now would exhaust the appliance's cooperation budget before his growth arrives. Their cousin, three years past menarche and at CS5, has no growth forecast left to offer: her identical malocclusion is now a choice between camouflage and surgery. The same three-plan fork in one family demonstrates the entire subject: the diagnosis of maturity, not the malocclusion, wrote the plans.

## Where viva examiners probe

The first probe is method equivalence — CVM against hand-wrist maturation — where the credited answer is that both predict the timing of the spurt comparably, with CVM requiring no additional radiation. The second distinguishes chronological, dental and skeletal age, noting that dental eruption is the least reliable proxy and Demirjian's calcification stages only moderate correlates. The rotation question separates memorisers from understanders: forward rotation produces a deep bite tendency with a strong chin and is associated with a Jarabak ratio at or above the mid-60s; backward rotation produces the long-face, open-bite pattern with the ratio below 62. Finally, examiners punish overclaiming for the VTO — the honest position is that prediction of growth direction is useful while prediction of growth magnitude remains imprecise.

## Frequently asked questions

### When does the pubertal growth spurt occur in boys and girls?

On average 10–12 years in girls and 12–14 in boys, with girls entering earlier and finishing earlier; boys' growth continues longer.

### Which skeletal maturity indicator marks the end of adolescent growth?

Fusion of the distal radial epiphysis, Fishman's eleventh SMI; sesamoid ossification of the thumb, by contrast, heralds the imminent spurt.

### What did Bjork's implant studies demonstrate?

That the jaws grow by rotation — forward rotation with deep bite tendency in short faces, backward rotation with open bite tendency in long faces — with surface remodeling partially concealing the rotation.

### How is the Jarabak ratio used in growth prediction?

A posterior-to-anterior facial height ratio of 62–65 per cent suggests balanced or forward growth, while values below 62 per cent predict vertical, backward-rotating development.

### What are the honest limits of a VTO?

It forecasts the direction of growth and treatment change better than their magnitude, so it guides planning rather than guaranteeing outcomes.