Broadricks Flag Tech. imp

A study of the proximity of the Broadrick ideal occlusal curve

to the existing occlusal curve in dentate patients

H. L. CRADDOCK*, C. D. LYNCH†, P. FRANKLIN*, C. C. YOUNGSON‡ AND

M. MANOGUE* *Division of Restorative Dentistry, Leeds Dental Institute, Leeds, UK, †Cork University Dental School and Hospital,

Cork, Ireland and ‡Department of Restorative Dentistry, Liverpool Dental School, Liverpool, UK

SUMMARY Increasingly, clinicians are called upon to

restore dentitions, which have become mutilated

because of tooth loss, wear, trauma and disease. In

many cases, restoration of the occlusal plane may be

required. A simple tool, which provides the labor-

atory technician with an approximation of the

patient’s original occlusal curve may be useful. The

purpose of this study is to determine the accuracy of

the occlusal curve designed using the Broadrick flag.

A total of 100 patients with intact dental arches

were examined, and deviations from the Broad-

rick curve were measured on scanned study mod-

els using a software package. Simple descriptive

statistics were used to investigate the data, and

intra-examiner reliability was examined using a

Bland Altman plot. The results demonstrated little

deviation from the Broadrick curve in natural adult

dentitions, mean deviation 0Æ1262 mm, 95% confid-

ence interval )0Æ32 to 0Æ2844. Good intra-examiner

reliability was achieved. It can be concluded that the

Broadrick flag method may be of use in determining

an appropriate occlusal curve for dentate individu-

als with deranged occlusal planes.

KEYWORDS: Broadrick flag, occlusal curve, restoration

Accepted for publication March 7 2005

Introduction

It is becoming apparent that more patients will remain

at least partially dentate for their entire life. It is

important to understand the overall effects of loss of

teeth on patients and the rationale behind the main-

tenance and replacement of teeth. A Finnish study (1)

carried out in 1977–1978 and repeated in 1989, showed

that there were improvements in the number of

remaining teeth in the 30–39 age group, but the middle

aged and elderly patients still had a reduced dentition,

generating a need for some form of prosthetic replace-

ment for many years to come. In 2000, Steele et al. (2)

found that in the UK, the proportion of edentulous

adults had fallen to 13%. This paper also demonstrated

that most individuals will retain some natural teeth, but

this will only be of benefit if enough are retained to

maintain adequate function.

When investigating the numbers of antagonistic pairs

of teeth remaining, Battistuzzi et al. (3) found that the

most commonly missing posterior tooth was the first

permanent molar. Marcus et al. (4) had similar findings,

and Meskin and Brown (5), reported that mandibular

posterior teeth were more likely to be missing than

maxillary.

Both Craddock and Youngson (6) and Killiaridis

et al. (7), detected overeruption in a high proportion of

cases with unopposed posterior teeth. Drifting and

tipping of teeth adjacent to an extraction site is a

commonly reported phenomenon. Teeth commonly

drift or tip unless restrained by contact with adjacent

teeth or occlusal contacts in the opposing arch, and

the direction of tip or drift will also be under these

influences. Papandreas et al. (8), using cephalometric

analysis, measured space closure following extraction

of first premolars in the mandible of adolescent

subjects. The authors found that the crowns of the

lower first molars moved mesially more than the

apices resulting in tipping or a combination of tipping

and mesial drift.

ª 2005 Blackwell Publishing Ltd 895

Journal of Oral Rehabilitation 2005 32; 895–900

These movements play a part in the derangement of

the patients’ occlusal scheme following posterior tooth

loss, and may result in difficulties in redefining the

curve for occlusal reconstruction.

In classical descriptions of an intact normal natural

dentition (9), an anteroposterior curve exists, which

passes through the cusp tip of the mandibular canine

and the buccal cusp tips of the mandibular premolar

and molar teeth and extends posteriorally to pass

through the anterior point of the mandibular condyle.

(Fig. 1) The radius of this curve is 4 ins, and is best

viewed from the lateral aspect. It is referred to as the

‘Curve of Spee’ after the German anatomist who first

described it in 1890. Arrangement of the posterior teeth

to follow this curve permits posterior tooth disclusion

on mandibular protrusion given proper anterior tooth

guidance.

The natural arrangement of the posterior occlusal

scheme may be disturbed by rotation, tipping and

overeruption of posterior teeth, most commonly occur-

ring following posterior tooth loss. Provision of a

restoration within such a ‘disturbed’ posterior occlusal

scheme, may result in the introduction of a posterior

protrusive interference (10). The challenge to the

restorative dentist when restoring posterior dentitions

is to design an occlusal scheme in harmony with the

patient’s incisal and condylar guidance, and permitting

total posterior disclusion on mandibular protrusion.

In 1963, Dr Lawson Broadrick developed an instru-

ment to provide a guide to the most suitable position

and orientation of the posterior occlusal scheme where

the natural Curve of Spee has been deranged (Brown

and Lewis, Pers. comm., June 2004 ). This instrument is

commercially marketed as the ‘Broadrick Occlusal

Plane Analyser’*, often referred to as the ‘Broadrick

flag’. This instrument includes a laminated piece of

cardboard that is attached to the superior aspect of the

upper member of a semi-adjustable articulator. Its

purpose is to permit reconstruction of the Curve of

Spee in harmony with anterior and condylar guidance

(10). It requires that articulated casts of the patient’s

dentition be mounted in the articulator following face-

bow transfer. As the Curve of Spee is an arc of circle

that passes through the cusp tip of the mandibular teeth

and mandibular condyle, it is possible to locate the

centre of the Curve on the Broadrick flag using a

compass. Lynch and McConnell (11) described the use

of teeth for both the anterior and posterior survey

points for determination of the occlusal curve. In their

study, the mandibular canine was selected as the

‘Anterior Survey Point’ from which an arc of 4 ins

was drawn using the compass on the Broadrick flag

(Fig. 2). The distal incline of the disto-buccal cusp of the

most distal molar was selected as the ‘Posterior Survey

Point’ (PSP) from which a corresponding arc of 4 ins

was drawn onto the laminated plastic card. Should the

position of the distal molar be unsuitable, then the most

anterior point of the condylar element on the articu-

lator may be selected, as originally described by Broad-

rick. The point of the compass should then be placed at

Fig. 1. Determination of the curve of Spee.

Fig. 2. Broadrick anterior survey point.

*Teledyne Water Pik, Fort Collins, CO, USA.

H . L . C R A D D O C K et al.896

ª 2005 Blackwell Publishing Ltd, Journal of Oral Rehabilitation 32; 895–900

the intersection of arcs on the flag. A curve can then be

drawn through the lower teeth to demonstrate the ideal

position of the mandibular cusp tips (Fig. 3). Teeth (or

portions of teeth) that are overerupted, infra-occluded,

rotated or tipped can then be identified (11). The

position of these teeth can then be modified when

restoring the posterior dentition.

While the Broadrick flag has been commercially

available for over 40 years, there is no published work

to support the contention that the curve it produces

exists in the natural dentition.

Aim of the study

The aim of this study is to investigate whether the

Broadrick flag method of determining the appropriate

occlusal curve for individual patients has any basis in

natural dentitions.

Method

A total of 100 dentate individuals with no missing

posterior teeth were recruited. Consecutive patients in

the Undergraduate Restorative Clinic, with intact upper

and lower arches (all teeth present with the exception

of third molars), were invited to participate in the

study. All patients were over 18 years of age.

The sample consisted of 50 female and 50 male

patients. The age range of the sample was 20–79 years.

The mean age was 50Æ26 years, with a standard devi-

ation of 13Æ05. The 50% of the subjects had the curve

assessed on the right side of the arch and 50% on the

left. Allocation to each group was random.

Alginate impressions were taken of the upper and

lower dentition. Following disinfection, these were cast

immediately. A ‘snap’ removal of the impression was

performed to minimize distortion of the material on

removal from the mouth. The models were then

trimmed in a seven-sided configuration, so that the

buccal plane would lie parallel to the scanner surface

when the models were placed on it. Each pair of study

models was placed on the scanning bed of a Black

widow 9636 USB three dimensional scanner†. They

were scanned with a millimetre scale rule included in

each image at a resolution of 1401 DPI at 50% scale in

full colour. The images were stored in Microsoft ‘Picture

it’ format to retain the three dimensional quality of the

image.

Using the Broadrick flag method described by Lynch

and McConnell (11), the ideal occlusal plane was

created using the scanned images. The software used

was QuickCAD Millennium edition. This method of

estimating an ideal occlusal curve uses anterior and

posterior points in order to determine its radius, and

thereby allow the curve to be scribed on study models.

The Anterior Survey Point was taken as half way down

the distal facing slope of the lower canine tip, and

the PSP was the mid point of the posterior slope of the

disto-buccal cusp of the mandibular second molar. The

intercept of these arcs was used to determine the survey

centre, which was drawn to pass through the points on

the lower canine and second molar already described

(Fig. 4). The maximum deviation was measured in the

long axis of the tooth with the greatest deviation form

the ‘Broadrick’ curve. The distance from the most

deviated cusp tip to the scribed curve was measured.

For class 2 incisal relationships, the initial arc radius

was 3Æ75 in and class 3 relationships a 5-in arc was

used. When the deviation was outside the existing

curve, a positive notation was given to the value of the

deviation. If the deviation was inside the curve, a

negative notation was given. When no deviation was

detected, a value of zero was given.

The incisal relationship was determined by the

overjet measurement and classified as follows:

1–3 mm overjet – class l (48% of subjects); >3 mm

Fig. 3. Drawing occlusal curve.

†Devcom Ltd, Sterling, UK.

B R O A D R I C K I D E A L O C C L U S A L C U R V E I N D E N T A T E P A T I E N T S 897


overjet – class ll (45% of subjects); <1 mm or reverse

overjet – class lll (7% of subjects).

Ten of the subjects already examined, approximately

10% of the total sample, were re-examined to deter-

mine intra-examiner reliability. The re-examination

group were chosen at random, and were examined at

an existing scheduled dental appointment between

three and six months after their initial examination.

The intra-examination reliability was therefore calcu-

lated.

Results

The mean deviation from the Broadrick generated

occlusal curve was 0Æ1262 mm, standard deviation

0Æ797, 95% confidence interval )0Æ32 to 0Æ2844.

(Table 1). The extent of the deviation ranged from

)1Æ69 mm to 2Æ5 mm.

55% of the subjects investigated had no teeth

deviating from the generated curve. Of those with a

measurable deviation, three subjects had a maximum

deviation between 0Æ01 and 0Æ5 mm, 15 had a

maximum deviation between 0Æ51 and 1 mm, 18

had a maximum deviation between 1Æ01 and 1Æ5 mm,

and nine had a measurable deviation >1Æ5 mm

(Table 2, Fig. 5).

When a single examiner is used, it is important to

determine intra-examiner reliability. The Bland Altman

plot, showing all plots lying within two standard

deviations of the mean, demonstrates good intra-

examiner reliability. (Chart 2).

Correlation coefficients showed no statistically signi-

ficant correlation between the deviation from the

Broadrick curve and age, sex and overjet. (Table 3).

Discussion

The sample contained a wide age range of adult patients

of both sexes, mean age 50Æ26, standard deviation

13Æ05. As the patients were chosen from a combined

care Clinic of Leeds Dental Institute, it is believed that

they are representative of a population of similar age

likely to be encountered in General Dental Practice, and

may be of a comparable age range to patients having

Fig. 4. Broadrick occlusal plane drawn on image of scanned study

models.

Distribution of deviation from Broadrick curve

0

10

20

30

40

50

60

70

1·51–2·5 0·51–1·5 0·5 to–0·5 0·51–1·5 1·51–2·5

Deviation from Broadrick curve

Nu

mb

er o

f su

bje

cts

Fig. 5. Chart 1: normal distribution

of deviations from the Broadrick

Occlusal Curve.



lost posterior teeth (5) and suffered derangement of the

occlusal curve.

This method of model measurement has previously

been described by Craddock and Youngson (6), and has

been found to be reliable. The use of widely available

equipment and ‘user friendly’ software for model

measurement mean this method could have a wide

range of applications.

When assessing the accuracy of the Broadrick flag

method of determining the orientation of an individ-

ual’s occlusal curve, it is important to appreciate exactly

what is being measured in this investigation. The only

measurement recorded for each individual was the

maximum deviation from the Broadrick Curve for an

individual tooth, and that therefore it is likely that the

majority of teeth along the curve are likely to be a

closer fit. Deviation for an individual tooth may be due

to several factors, including tooth fracture, tooth wear,

poorly contoured restorations, tooth tipping and drift-

ing and failure of complete eruption, and may not be

representative of the fit of the curve for the remainder

of the quadrant.

Overjet measurement is useful for determining the

incisal classification, however, in order to determine the

relative anterior projection of the dental bases for

determination of the skeletal classification, cephalo-

metric analysis for each individual would have been

necessary. Bearing in mind the radiation dosage for this

type of radiograph, it would not have been ethically

appropriate to expose patients for the purpose of our

research, and incisal classification was used in this

study, whilst appreciating the limitations of this method.

The Broadrick flag was designed as an instrument to

provide a guide to the location of the centre of the

Curve of Spee. The results from this study support its

use as a scientific instrument. However, there are

certain aesthetic and functional scenarios that require

the centre of the curve located to be modified slightly.

In patients with a class II skeletal pattern, the use of a 4-

in curve would result in mandibular posterior teeth that

are ‘too low’. These modifications were incorporated

into this study. If this had not been the case, a situation

could arise, which could introduce posterior interfer-

ences and overeruption of the opposing maxillary teeth.

Conversely, in a patient with a prognathic mandible, a

4-in radius would result in a curve that is too steep,

again leading to posterior occlusal interferences (11).

The number of class lll patients was relatively low

and further study of this subgroup may be appropriate.

However, for the remaining two incisal classification

groups, there was no correlation between overjet and

deviation from the occlusal curve, somewhat reinfor-

cing the use of a different arc radius for class ll incisal

relationships.

Extension of the occlusal curve through the mandib-

ular condyle is considered essential when designing

proper posterior disclusion (12). The anterior point of

Table 1. Mean, range and standard deviation of deviation from

Broadrick curve

Minimum Maximum Mean SD

Deviation from Broadrick

curve in millimetres

)1Æ69 2Æ5 0Æ126 0Æ797

Table 2. Extent of deviation from the Broadrick Curve

No deviation Deviation within �0Æ5 mm Deviation 0Æ51 mm 1 mm Deviation 0Æ11 mm 1Æ5 mm Deviation >1Æ5 mm

No. of subjects 55 3 15 18 9

Bland altman plot of deviation from ideal curve

Mean of measurement2·01·51·00·50·0–0·5–1·0–1·5

Diff

eren

ce in

mea

sure

men

ts

0·18

0·16

0·14

0·12

0·10

0·08

0·06

0·04

0·02

0·00

–0·02

–0·04

–0·06

–0·08

Fig. 6. Chart 2: Bland Altman plot of intra-examiner reliability.

Table 3. Correlation of deviation with sex, age and overjet

Correlation of deviation with: Correlation coefficient

Sex 0Æ036

Age )0Æ064

Overjet (mm) 0Æ056

B R O A D R I C K I D E A L O C C L U S A L C U R V E I N D E N T A T E P A T I E N T S 899


the condylar element is a useful choice for the PSP

when the position of the distal mandibular molar is

unsuitable.

It will be appreciated that the bucco-lingual position

of the posterior teeth should also be considered when

providing posterior restorations. When viewed from the

anterior aspect, the mandibular molars have a slight

lingual inclination and the buccal cusps of these teeth

are higher than the lingual. This arrangement is

referred to as the ‘Curve of Wilson’, the purpose of

which is to permit lateral mandibular excursions free

from posterior interferences (13). The Curves of Spee

and Wilson were combined by George Monson, who in

1920 (14, 15) proposed that the mandibular teeth

should be arranged to close around a sphere of 4-in

radius, with the mandibular incisal edges and cusp tips

touching the sphere. It will be appreciated that when

posterior restorations are being designed, these should

permit posterior disclusion in an anteroposterior and

lateral direction.

The aims of restorative treatment are usually: to

prevent and treat dental and periodontal disease, to

restore form, to restore function and to maintain and

restore aesthetics.

Many of these aims are interrelated, and the restor-

ation of occlusal form may have effects on all the other

aims. To have a tool, which accurately predicts occlusal

form for an individual, which had been validated on

non-restored patients, allows the clinician to make

evidence based decisions when restoring occlusal

schemes.

The results of this study indicate that the use of the

Broadrick flag method provides a good approximation

of the natural occlusal curve for a wide range of

patients, with no correlation between deviation for this

curve and age or sex of the patients, or the incisal

classification.

Conclusion

The use of the Broadrick flag can determine an accept-

able occlusal curve for individual dentate patients.

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Correspondence: H. L. Craddock, Room 6129, Leeds Dental Institute,

Clarendon Way, Leeds LS2 9LU, UK.

E-mail: [email protected]



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Broadricks Flag Tech. imp