What is Bolton analysis in orthodontics?

Bolton analysis (Bolton 1958) compares the sum of mesiodistal crown widths of mandibular teeth to maxillary teeth to detect tooth size discrepancies that would prevent ideal occlusion and contact after orthodontic treatment. Two ratios are calculated: the anterior ratio (6 anterior teeth) with an ideal of 77.2%, and the overall ratio (all 12 teeth) with an ideal of 91.3%.

What is the ideal Bolton anterior ratio?

The ideal Bolton anterior ratio is 77.2% (SD ±1.65%), based on Bolton's original 1958 study of 55 subjects with ideal occlusion. This means the sum of the mesiodistal widths of the 6 lower anterior teeth (canine to canine) should be 77.2% of the sum of the 6 upper anterior teeth.

What is the ideal Bolton overall ratio?

The ideal Bolton overall ratio is 91.3% (SD ±1.91%). This is calculated from all 12 teeth in each arch (first molar to first molar). It is less commonly used clinically than the anterior ratio as posterior teeth are more amenable to occlusal adjustment.

What does mandibular excess mean in Bolton analysis?

Mandibular excess means the lower teeth are collectively too wide relative to the upper arch. The actual Bolton ratio exceeds the ideal (>77.2% anterior, >91.3% overall). Clinically this may require interproximal reduction (IPR) of lower teeth, accepting residual upper spacing, or incorporating the discrepancy into treatment planning.

What does maxillary excess mean in Bolton analysis?

Maxillary excess means the upper teeth are collectively too wide for the lower arch. The Bolton ratio falls below the ideal (<77.2% anterior, <91.3% overall). Clinically this may require IPR of upper teeth, accepting residual lower spacing after alignment, or adjusting treatment mechanics accordingly.

When is Bolton discrepancy clinically significant?

A discrepancy exceeding ±2 standard deviations is generally considered clinically significant: >2.3 mm for the anterior ratio and >4.4 mm for the overall ratio (based on Bolton's SDs of 1.65% and 1.91% applied to average arch sums). Discrepancies of 1–2 mm may still affect final occlusion and should be accounted for in treatment mechanics.

Bolton Analysis Calculator

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Anterior (77.2%) & Overall (91.3%) tooth size discrepancy — Bolton 1958. Enter mesiodistal crown widths in mm for real-time analysis.

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Anterior teeth — used in both ratios

Posterior teeth — Overall ratio only

FDI tooth notation

Maxillary Arch (Upper)

Mesiodistal widths in mm · right → left (patient view)

📄 Bolton 1958

Anterior sum: — mm Total sum: — mm

Mandibular Arch (Lower)

Mesiodistal widths in mm · right → left (patient view)

📄 Bolton 1962

Anterior sum: — mm Total sum: — mm

Measurement guide: Record the maximum mesiodistal crown diameter at the widest contact point using digital callipers or a digital study model. Measure on the buccal surface for premolars and molars, and on the labial surface for anterior teeth. Use the same magnification consistently across all teeth. 📄 Othman & Harradine 2006

Anterior Ratio

Ideal: 77.2%

— % Enter anterior teeth

Overall Ratio

Ideal: 91.3%

— % Enter all 12 teeth

Evidence Sources

1. Bolton WA (1958). Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod. 28(3):113–134. — Original study establishing ideal ratios (77.2% anterior, 91.3% overall) from 55 subjects with excellent occlusion. DOI

2. Bolton WA (1962). The clinical application of a tooth-size analysis. Am J Orthod. 48(7):504–529. — Clinical application and calculation method for the two ratios. DOI

3. Othman SA, Harradine NW (2006). Tooth-size discrepancy and Bolton's ratios: a literature review. J Orthod. 33(1):45–51. — Confirms clinical significance thresholds and measurement methodology. DOI

4. Santoro M, et al. (2000). Mesiodistal crown dimensions and tooth size discrepancy of the permanent dentition. Am J Orthod Dentofacial Orthop. 117(2):169–174. — Normative crown width data used in reference table. DOI

Average Mesiodistal Crown Widths — Reference Values Santoro et al. 2000

Tooth	Upper (mm)	Lower (mm)
Central incisor (1)	8.7	5.3
Lateral incisor (2)	6.9	5.9
Canine (3)	7.8	6.8
1st premolar (4)	7.1	7.1
2nd premolar (5)	6.6	7.0
1st molar (6)	10.1	11.2

Values are means from Santoro et al. 2000 (mixed US sample). Significant variation exists across ethnic groups — individual measurement is always preferred over reference values for clinical decisions.

Frequently Asked Questions

What is Bolton analysis?

Bolton analysis compares summed mesiodistal crown widths of lower to upper teeth to identify tooth size discrepancies that prevent ideal occlusion after orthodontic treatment. Two ratios are calculated: anterior (6 teeth, ideal 77.2%) and overall (12 teeth, ideal 91.3%).

When is a discrepancy clinically significant?

A discrepancy >2 standard deviations is generally significant: anterior excess >2.3 mm or overall excess >4.4 mm. However, even 1–2 mm discrepancies in the anterior segment can affect canine and incisor contacts and must be incorporated into treatment mechanics.

How do you correct a Bolton discrepancy?

Options include: interproximal reduction (IPR) of teeth in the excess arch, accepting residual spacing in the deficient arch, implant-supported crown to build up a small tooth, or combination approach. Anterior mandibular excess most often requires lower IPR.

Does Bolton analysis apply to primary teeth?

Bolton's original ratios were established for permanent dentition only. Modified analyses exist for mixed dentition prediction using Moyers tables combined with Bolton ratios for erupted permanent teeth.

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