GENERAL
The Hall Technique 10 years on: Questions and answers
N. P. T. Innes,*1 D. J. P. Evans,1 C. C. Bonifacio,2 M. Geneser,3 D. Hesse,2 M. Heimer,1 M. Kanellis,3 V. Machiulskiene,4
J. Narbutaité,4 I. C. Olegário,5 A. Owais,3 M. P. Araujo,5 D. P. Raggio,5 C. Splieth,6 E. van Amerongen,2
K. Weber-Gasparoni3 and R. M. Santamaria6
InInbrief
brief
Discusses the development and acceptance of the Provides information on where to find out more Reports an overview of high quality evidence from
Hall Technique. about the Hall Technique. randomised control trials supporting use of the Hall
Technique in day to day practice.
It is ten years since the first paper on the Hall Technique was published in the British Dental Journal and almost 20 years since
the technique first came to notice. Dr Norna Hall a (now retired) general dental practitioner from the north of Scotland had,
for many years, been managing carious primary molar teeth by cementing preformed metal crowns over them, with no local
anaesthesia, tooth preparation or carious tissue removal. This first report, a retrospective analysis of Dr Hall’s treatments, caused
controversy. How could simply sealing a carious lesion, with all the associated bacteria and decayed tissues, possibly be clinically
successful? Since then, growing understanding that caries is essentially a biofilm driven disease rather than an infectious
disease, explains why the Hall Technique, and other ‘sealing in’ carious lesion techniques, are successful. The intervening
ten years has seen robust evidence from several randomised control trials that are either completed or underway. These have
found the Hall Technique superior to comparator treatments, with success rates (no pain or infection) of 99% (UK study)
and 100% (Germany) at one year, 98% and 93% over two years (UK and Germany) and 97% over five years (UK). The Hall
Technique is now regarded as one of several biological management options for carious lesions in primary molars. This paper
covers commonly asked questions about the Hall Technique and speculates on what lies ahead.
Questions Although conventional preformed crowns are usage of crowns was reported in hypothetical
used to carry out the Hall Technique, and it is case treatment plans, even amongst paediatric
What is the Hall Technique? simply a different way of using these crowns, dentistry specialists. Tran stated that, ‘Mastery
The Hall Technique is a method for using crowns fitted this way are usually referred to of the crown continues to elude thousands of
preformed metal (also known as stainless steel) simply as Hall crowns. More information can graduating dentists every year who, as a result
crowns to manage carious primary molar teeth, be found on Wikipedia (https://en.wikipedia. of their discomfort, shy away from it and rely
by seating a correctly sized crown over the org/wiki/Hall_Technique, as of 6 March 2017), on huge amalgams to restore primary teeth.’2
tooth and sealing the carious lesion in, using a where there is also a downloadable illustrated During an audit of paediatric dental service
glass ionomer luting cement. Local anaesthesia PDF manual explaining when to, and how to, provision in the north east of Scotland in 1997,
is not required, tooth preparation is not carried carry out the technique from the correspond- one general dental practitioner, Dr Norna Hall
out, and no carious tissue is removed (Fig. 1). ing author. Table 1 lists the indications and (hence the name the Hall Technique) was
contraindications for the Hall Technique. found to be the only dentist, out of 150 in the
regional audit, regularly placing preformed
1
School of Dentistry, University of Dundee, Dundee, United
Kingdom; 2Department of Cariology, Pedodontology
How did the Hall Technique come crowns in children. During discussion, it
and Endodontology, Amsterdam, Netherlands; 3College about and when did it start being became apparent that Dr Hall was using the
of Dentistry, Iowa City, Iowa, United States; 4Faculty of
Odontology, Lithuanian University of Health Sciences,
used? crowns in an unconventional way – not placing
Eiveniu 2, Kaunas, Lithuania; 5Dental School, Sao Paolo, In the mid-1990s, it was generally accepted local anaesthesia, removing caries or preparing
Brazil; 6Zahnmedizin & Kinderzahnheilkunde, Greifswald,
Germany
that crowns were the most predictable res- the tooth. Dr Hall worked in an area with high
*Correspondence to: Professor Nicola Innes toration for primary molars, rarely failing. levels of caries and low treatment acceptance.
Email: n.p.innes@dundee.ac.uk
However, in 1996 in Scotland, a total of only She had gradually adapted conventional crown
Refereed Paper. Accepted 7 February 2017 164 crowns were fitted.1 There is some evidence placement to this technique in an attempt to
DOI: 10.1038/sj.bdj.2017.273 that this is not a dissimilar situation from other respond to the demand for treatment that was
©
British Dental Journal 2017; 222: 478-483
countries. In Australia in 2003, a relatively low quick, and did not involve local anaesthesia.
478 BRITISH DENTAL JOURNAL | VOLUME 222 NO. 6 | MARCH 24 2017
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, GENERAL
Fig. 1 Series of three photographs showing a crown being fitted to tooth 84 (lower right 1st primary molar). a) Different crowns are tried
over the tooth until the correct size is found (covering the cusps and giving a feeling of ‘spring back’. Note that gauze is being used for
airway protection. b) The crown is filled with glass ionomer cement. c) The crown is seated over the tooth (there is no local anaesthetic,
tooth preparation or caries removal) and, in this case, the child has used their bite force to seat the crown with cotton wool to help
distribute the force. The gingiva is blanching as the crown is sitting slightly subgingivally, further improving the seal and preventing the
lesion progressing. Same child as Fig. 3
She also found that both crown placement
techniques (conventional and Hall Technique) Table 1 Indications and contra-indications for (teeth) using the Hall Technique for
managing primary molars with caries lesions assessed as at risk of progressing and
gave similar outcomes and her population
causing pain/sepsis before exfoliation
found it comfortable and acceptable.3 From her
meticulously kept and detailed notes, we were Indications include Proximal lesions, cavitated or non-cavitated
teeth with: Occlusal lesions, non-cavitated if the child is unable to accept a fissure sealant
able to collect data and publish a retrospective Occlusal lesions, cavitated if the child is unable to accept selective caries removal
analysis on the survival of the teeth she had
Contra-indications Where no ‘clear band of dentine’ can be seen on a radiograph
been treating that way (now ten years ago) in include teeth with: Signs or symptoms of irreversible pulpitis, or dental infection (sepsis)
the British Dental Journal.4 Clinical or radiographic signs of pulpal exposure, or periradicular pathology
Crowns/teeth so broken down they would be unrestorable with conventional techniques
Children where the airway cannot be managed safely
How can sealing caries into a tooth
be successful?
A Hall Crown is a predictably successful growing understanding that dental caries is a does not have to involve surgical eradication of
restoration. When a carious lesion is sealed biofilm-driven disease resulting from a change the biofilm, carious tooth tissue and all plaque
into a tooth, the biofilm (the community of in the relationship between our bacterial guests bacteria to stop the progress of the disease.
microbes, their products and extracellular (who generally prevent pathogens from colo- Instead, maintaining a non-cariogenic biofilm,
polymeric matrix) is physically prevented from nising us) and ourselves, when our intake of continually removing the biofilm through
accessing nutrition from its main substrate, refined carbohydrate becomes excessive. This toothbrushing with fluoridated toothpaste and
dietary carbohydrate. This means that the excessive intake, when it occurs, forces a allowing tissue to remineralise, or moving a
actively carious/cariogenic lesion becomes a change from a healthy, symbiotic coexistance, cariogenic biofilm to a non-cariogenic state
non-cariogenic lesion. Like other treatments to a dysbiotic, imbalanced association.6,7 When will all be successful in preventing the ongoing
aimed at managing carious lesions by sealing environmental conditions change to reduce demineralisation of tooth tissue.
them in, a Hall crown works by depriving the microbial diversity and stability (for example Preformed metal crowns (regardless of method
lesion of fuel and making the environment with an increase in dietary sugar, favouring of placement) have consistently been shown to
unfavourable for its progression. The dental the proliferation of aciduric and acidogenic perform better than restorations for the man-
pulp lays down reparative dentine, effectively species), an imbalance occurs; increased acid agement of dental caries in primary teeth, and
retreating in response to the advancing carious production overwhelms the local reminer- this is because of the high quality seal that can
lesion. By sealing in the carious lesion, we are alisation systems, causing demineralisation predictably be achieved.9,10 The Hall Technique
essentially tipping the balance in this race in of tooth tissue, and a carious lesion forms. can essentially be thought of as an extension of
favour of the pulp, with the aim of arresting the There are many ways of controlling the the indirect pulp cap (where the pulp has carious
lesion before it advances far enough to cause demineralisation process, including (but not tissue left over it but is sealed in). This approach
irreversible inflammation of the dental pulp. It limited to): removing the biofilm; increasing relies on obtaining a good seal, and a crown
is worth exploring this change in our under- saliva (quantity and mineralisation potential); placed using the Hall Technique allows that
standing of dental caries as this underpins the adding fluoride; reducing sugar frequency good seal to be achieved, with a high degree of
Hall Technique and is at the heart of changes through diet change; and, of course, physically predictability. Whilst it is equally possible to seal
in our management strategies. blocking cariogenic biofilm from its substrate.8 a carious lesion into a tooth using a restorative
The oral biofilm is one of the most complex This is how fissure sealants and crowns placed material such as composites or glass ionomers,
biofilms of our human microbiome communi- using the Hall Technique work. it is more difficult, especially in a young child, to
ties, and in health, has biodiversity, balance and The clinical relevance of this is that once the achieve the same high quality of seal, especially
stability in its community members.5 There is a disease has become established, managing it in occluso-proximal cavities.
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