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23/09/2013
1
Minimally invasive dentistry:
A series of lectures
Everyday practice should be built on this
foundation
AKA
Does size matter? University of Birmingham Masters in AGDP
Part 1
…first, a few principles for the
lectures
Eastbourne, The Dental Practice Board
Board of Dental Practice Board, 1988
23/09/2013
2
The database
Over 500,000 restorations at the Dental
Practice Board, Eastbourne, Sussex,
11 years’ duration
Modified version of Kaplan-Meier
methodology used to plot survival curves
for different sub-groups
Dr.Steve Lucarotti
Direct placement
restorations Influence of patient factors
Influence of patient age
Influence of dentist factors
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3
Do young dentists make better fillings
than old dentists?
Influence of dentist age
Influence of dentist’s sex
Single pontic bridges • A total of 2,162 single pontic bridges
(excluding resin-retained bridges) were
identified in the data over a period of
eleven years.
• 2,035 porcelain bonded to gold
• Mostly on upper jaw, except 1st molars
Survival of bridge retainers:overall
Overall survival at 10 years:72%
0.5
0.6
0.7
0.8
0.9
1.0
0 1 2 3 4 5 6 7 8 9 10
Time in years from placement to re-intervention
Pro
po
rtio
n w
ith
ou
t re
-in
terv
en
tio
n
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…and last…
Influence of cavity design
Eleven Year Survival - by Treatment Code
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000
Time in days from placement to reintervention
Pro
po
rtio
n w
ith
ou
t re
-in
terv
en
tio
n
Overall
Single surface amalgam
Two surface amalgam, not MO or DO
MO or DO amalgam
MOD amalgam
Resin composite
Tunnel amalgam
Glass ionomer
Root filling + indirect restoration
Large cavities have poorer survival than small
Take home message Nothing lasts forever:
Size matters – big fillings last less
well than small
Take home message Keeping cavities as small as possible
is therefore important
nothing lasts forever
2 Humans by era Average lifespan at birth
Upper paleolithic 33
Neolithic 20
Bronze age &Iron age 35+
Classical Greek 28
Classical Roman 28
Pre-Columbian N American 25-30
Medieval Islamic Caliphate 35+
Medieval Britain 30
Early modern Britain 40+
Early 20th Century 30-45
Current world average 67.2
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Humans by era Average lifespan at birth
Upper paleolithic 33
Neolithic 20
Bronze age &Iron age 35+
Classical Greek 28
Classical Roman 28
Pre-Columbian N American 25-30
Medieval Islamic Caliphate 35+
Medieval Britain 30
Early modern Britain 40+
Early 20th Century 30-45
Current world average 67.2
Life expectancy at birth, 2008, (years)
over 80
over 75
over 70
67 to 70
60 to 67
50 to 60
45 to 50
40 to 45
under 40
Source:
Wikipedia
Life expectancy in industrialised
countries now 80 years
Therefore mean restoration longevity
must be 73 years!
Walter Breuning, age 113 years
All restorations are temporary,
except for the last one!
Message:
Start the restoration cycle as late as
possible (primary prevention)
Keep as much sound tooth structure as
possible (adhesion)
Increase the longevity of every
restoration as much as possible
(perfect seal and maintenance of
restoration)
Longevity of hip joint prosthesis = 15 years
nothing lasts forever
2
More important now than ever!!`
“The day is surely coming when
we will be practising
preventive rather than
reparative dentistry,
GV Black, 1896
3
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“The day is surely coming when
we will be practising
preventive rather than
reparative dentistry,
when we will so understand
the etiology and pathology
of dental caries that we will be
able to combat its
destructive effects by
systemic medication”
Does size matter? Minimally invasive dentistry
….aka
A definition
“Minimal intervention dentistry is a
philosophy of professional care
concerned with the first occurrence,
earliest detection and earliest
possible cure of disease, followed by
minimally-invasive and patient-
friendly treatment to repair
irreversible damage caused by such
disease” Tyas MJ, Anusavice KJ, Frencken JE, Mount GJ. Minimal intervention
dentistry – a review. FDI Commission Project 1-97. Int.Dent.J.2000:50:1-
12.
First mention: Mount GJ. Minimal treatment of
the carious lesion. Int.Dent.J.1991:41:55-59
…another mention! Extension for prevention was
taught as recently as 1983
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Three principles for MID
Early caries detection
& caries risk assessment
Remineralisation of demineralised
enamel & dentine
Optimal caries preventive measures
Only when these have failed and a cavity
has developed should a minimally invasive
operative intervention be undertaken
Does size matter?:Objectives
Which bonding agents work best in which
situation?
How to minimise stress in posterior
composite restorations and suggest a
minimal cavity design
How to repair worn anterior teeth using
resin composite
Preparation depth matters for veneers
Does size matter?:Aims
To illustrate the potential for injury
to the pulp during operative intervention
To demonstrate that large restorations
provide poorer longevity than small
To suggest some minimal intervention
methods of treatment
Does size matter?:Aims
To demonstrate that large restorations
provide poorer longevity than small
Does size
matter?
Does drilling and
filling affect teeth?
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8
Dentine/pulp reactions to full crown procedures Dahl BJ, J.Oral Rehabil.1977:4:247-254
Severe acute pulp reactions were observed
subjacent to the dentinal tubules cut in full
crown preparation
Tooth preparation and pulp degeneration Christensen GJ. JADA 1997:128:353-354
Factors associated with pulp
degeneration include:
•Use of worn out diamonds and burs
•Improper cutting techniques (heavy
cutting loads)
•Excessive preparation depths
•Inadequate water coolant
•Over-drying tooth preparation
•Exothermic chemical reactions
of provisional materials
Tooth preparation and pulp degeneration Christensen GJ. JADA 1997:128:353-354
CONCLUSION
Patients should be warned that pulpal death
and endodontic therapy can result
from crown placement
Long term effects of crown preparation on pulp vitality Felton D. et al. J.Dent.Res. Abstract 1139 High incidence of pulpal necrosis with full
coverage restorations (13.3%)
Placement of foundations resulted in
a significant increase in pulp morbidity
(18% vs 8%)
Correlation between length of temporisation
and pulp necrosis
Clinical complications in fixed prosthodontics Goodacre GJ et al. J.Prosthet.Dent.2003:90:31-41. Literature review of past 50yrs
Of 823 crowns studied, 27 needed
endodontic treatment, mean incidence
of 3%, range 0 to 6%
Pulpal evaluation of teeth
restored with fixed prostheses Jackson CR, Skidmore AE, Rice RT
J.Prosthet.Dent.1992:67:323-325
130 patients with a crown or bridge
fitted 1984-1988
603 teeth assessed in 1990
166 had already received RCT,
leaving 437 crowned while vital
5.7% required RCT during the
observation period
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Prevalence of periradicular periodontitis associated with crowned teeth in an adult Scottish subpopulation Saunders WP, Saunders EM. Brit Dent.J.1998:185:137-140
802 crowns assessed radiographically
458 vital at preparation
87 (19%) had radiographic signs of
peri-radicular disease
344 crowned teeth had previous root filling,
51% of these had peri-radicular radiolucency
Prevalence of periradicular periodontitis associated with crowned teeth in an adult Scottish subpopulation Saunders WP, Saunders EM. Brit Dent.J.1998:185:137-140.
CONCLUSION:
Pulpal damage may occur during
procedures to provide a crown
Iatrogenic injury to the pulp in dental procedures. Bergenholtz G. Int.Dent.J.1991:41:99-110.
LITERATURE REVIEW: CONCLUSIONS
Iatrogenic (“dentistogenic”) injury to the
dental pulp is not an insignificant problem
in clinical dentistry
Pulpal necrosis occurs with a frequency of
10-15% over a period of 5-10 years
Take home message
Drilling isn’t great!
……for teeth
A basic principle:
Minimally invasive methods
of treatment should be
employed where possible
…therefore
% of teeth damaged by dentists
0
23/09/2013
10
% of teeth damaged by dentists
!
Root perforations
Following hemisection in which the unreparable
mesial half of the root was removed, iatrogenic
damage can be seen on the distal surface of LL5
Does cutting Class II cavities cause
damage to adjacent teeth?
YES!!!
Cardwell JE, Roberts BJ. Damage to adjacent
teeth during cavity preparation?
J.Dent.Res.1972::51:1269-1270.
Long TD.
J.Dent.Res.1980:59(Spec.Issue):1799.
Elderton RJ. Positive dental prevention.
London, Heinemann Medical Books, 1987:57-95.
Progression of approximal caries in relation
to iatrogenic preparation damage
Qvist V, Johannessen L, Bruun M
J.Dent.Res.1992:71:1370-1373
77 dentists from Public Dental Health Service
in Denmark
Die-stone models of 187 new Class II cavities
Examined with stereomicroscope
Damage found on 66% of adjacent surfaces
Teeth followed for 7 years
Progression of approximal caries in relation
to iatrogenic preparation damage
Qvist V, Johannessen L, Bruun M
J.Dent.Res.1992:71:1370-1373
RESULTS
Operative treatment needed on 10% of
undamaged surfaces
Operative treatment needed on 35% of
damaged surfaces (p<0.05)
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11
Progression of approximal caries in relation
to iatrogenic preparation damage
Qvist V, Johannessen L, Bruun M
J.Dent.Res.1992:71:1370-1373
CONCLUSION
Iatrogenic preparation damage is a frequent
side-effect of operative intervention with
approximal caries lesions…the damage
increases caries progression and need for
restorative treatment of the adjacent teeth.
Progression of approximal caries in relation
to iatrogenic preparation damage
Qvist V, Johannessen L, Bruun M
J.Dent.Res.1992:71:1370-1373
CONCLUSION
Danish dentists damage teeth!!!
Does size matter? ….regarding crowns
Tooth structure removal for various
preparation designs for anterior teeth Edelhoff D, Sorensen JA. J.Prosthet.Dent.2002:47:502-509
Tooth structure removal for various
preparation designs for anterior teeth Edelhoff D, Sorensen JA. J.Prosthet.Dent.2002:47:502-509
Typodont teeth
Prepared for porcelain veneers (4 variations), all-ceramic crowns (2 variations), resin-retainer, metal-ceramic crown
10 preparations per group, by one clinician
Removed tooth structure measured by “gravimetric analysis”
Tooth structure removal for various
preparation designs for anterior teeth Edelhoff D, Sorensen JA. J.Prosthet.Dent.2002:47:502-509
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Tooth structure removal for various
preparation designs for anterior teeth Edelhoff D, Sorensen JA. J.Prosthet.Dent.2002:47:502-509
Tooth structure removal for various
preparation designs for anterior teeth Edelhoff D, Sorensen JA. J.Prosthet.Dent.2002:47:502-509
CONCLUSIONS:
All-ceramic and metal-ceramic
crown preparations required the
removal of 63% to 72% of the
total crown weight
Preparations for veneers and
resin-bonded prostheses removed
3% to 30% of crown weight
Tooth substance removed for a
metal-ceramic crown was 4.3 times
greater than for a ceramic veneer
Preparation for all-ceramic crowns
was 11% less invasive than for
metal-ceramic
Quantification of residual dentine
thickness Davis GJ.J.Dent.2012:40:571-576
Micro CT scans taken of extracted teeth before and
after crown preparation for metal-ceramic crown
16 extracted upper central incisor teeth
Residual dentine thickness measured
Quantification of residual dentine
thickness Davis GJ.J.Dent.2012:40:571-576
RESULTS
All but one of the prepared teeth had regions with
residual dentine thickness of 1.5mm, in 6 teeth it was
less than 1mm and in 3 it was less than 0.5mm
Is this a problem?
The residual dentine thickness following tooth
preparation has a critical influence on
subsequent pulp degeneration. Murray PE et al.
Hierarchy of pulp capping and repair activities.
Am.J.Dent.2002:15:236-243.
2mm or more of residual dentine is critical in
preventing pulp damage. Stanley HR. Dental
iatrogenesis. Int.Dent.J.1994:44:3-18.
1mm of dentine might protect the pulp from the
cytotoxic effects of zinc phosphate cement. Pameijer CH et al., Biocompatability of a glass ionomer luting
agent.. Am.J.Dent.1991:4:134-141
23/09/2013
13
Poorly
fitting
crowns
aren’t
great
either!
…while on the subject of crowns… Take home message Because of the potential for pulpal
damage or damage to adjacent teeth,
minimal or non-intervention should
always be considered
However!!!
Some patients
choose
intervention!
The effect of cavity size on tooth fracture
Literature review
tooth fracture
A common clinical problem (Braly&
Maxwell, 1981, Cavel et al., 1985)
Problem is increasing as more patients
keep their teeth longer (Liebow, 1976)
Number of cracked cusps associated
with LARGE restorations is increasing
(Fisher, 1982)
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tooth fracture: effect of cavity
dimension
Minimal cavity preparation advocated 70 years ago (Bronner, 1930, Markley, 1951)
Vale (1956) showed a decrease in the strength of a prepared tooth when cavity width increased from one quarter to one third of the isthmus width
Least susceptibility to fracture was in teeth with narrow/shallow restorations (Re et al., 1982)
tooth fracture: effect of cavity
dimension
Breaking the continuity of enamel
weakens teeth (Hood, 1990)
Narrow isthmus/deep pulpal floor
weakens teeth more than wide/shallow
preparation (Blaser et al., 1983)
A survey of cusp fractures in a
population of dental practices Fennis et al., 2002
28 clinicians in Nijmegen participated
Recorded information on cusp # for 3
months, including patient age, tooth,
size of cavity, restorative material,
cause of # etc. on a special form
A survey of cusp fractures in a
population of dental practices Fennis et al., 2002
238 cases of cusp # recorded
Mean age of patients = 44yrs (range 21 to 79)
No difference between mandible & maxilla
More women than men involved
Molars (79%), premolars (21%)
Maxillary molars had more buccal cusp #s
No difference in cusp # in premolars
A survey of cusp fractures in a
population of dental practices Fennis et al., 2002
Mastication reported as most frequent
cause of #
77% of # teeth had MOD restoration
88% had an amalgam restoration
Root filled teeth significantly more
susceptible to subgingival fracture
23/09/2013
15
Take home message Teeth with smaller fillings are more
resistant to fracture.
…in other words, size matters
Which material might be best
at preventing cusp fracture?
Another literature review!
tooth fracture: effect of
restorative material
Cusps are reinforced when a bonded composite technique is used (Morin et al., 1984, Eakle, 1985, 1986)
Composite restores strength of teeth with class I cavities to similar levels as sound teeth (Watts, et al., 1987)
Fissure sealants do not improve strength of teeth (Schultz et al., 1986)
Strength of composite-restored premolars was half of intact teeth (Reel & Mitchell, 1989)
tooth fracture: effect of
restorative material
MOD gold inlays sandblasted, tin-plated and
cemented with adhesive resin showed better
laboratory fracture resistance than MOD gold
inlays cemented with phosphate cement
(Eakle & Staninec, 1992)
Composite restorations using Superbond
DBA in wide MOD cavities improved the
fracture strength of maxillary premolars
(Sheth et al., 1988)
Take home message: Literature review indicates
that
a composite restoration
may prevent tooth fracture