a clinical audit into the success rate of inferior alveolar nerve block analgesia in general dental...
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7/29/2019 A Clinical Audit Into the Success Rate of Inferior Alveolar Nerve Block Analgesia in General Dental Practice
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Introduction
The purpose of this study was to produce some
observational evidence of the success rate of inferior
alveolar nerve block (IDB) analgesia that is achieved
in general dental practice.
A recent article in the British Dental Journal1
referred to IDB analgesia and described how failures
could be minimised. Heasman and Beynon2 also
described failure of IDB analgesia citing the following
as some of the reasons for failure:
Intravascular injection.
Unusual local anatomy.
Idiosyncratic local analgesic resistant patients.
Accessory innervation to the teeth.
A study by Simon et al3 concluded that administration
of anaesthetic injections is a rarely discussed but sig-
nificant contributor to the overall professional stress for
many dentists. However the quoted success rates for
dental local analgesic administrations are enormously
variable with the range beginning as low as 80%.4-6
Until more evidence of the expected norms of failure
are quantified it will be difficult for dentists to assess
their own standards of technique in this important area
of pain control.
There are a number of potential neurological com-
plications of local anaesthetics used in dentistry.
These include facial nerve palsy, transient amaurosis,
transient paraesthesia and, rarely, transient unilateral
deafness.7 The continuous review of technique by
practitioners will help to minimise the risks involved.
With the advent of clinical governance in the UK it is
now essential that practitioners audit some of theirclinical procedures. Publication of results is clearly
needed to give some idea of the standards to be
expected.
LOCAL ANALGESIA AND PRIMARY DENTAL CARE
A Clinical Audit into the Success Rate ofInferior Alveolar Nerve Block Analgesia
in General Dental PracticeAndrew Keetley and David R Moles
KEY WORDS: CLINICAL AUDIT, INFERIORALVEOLAR NERVE BLOCKANALGESIA, FACIAL NERVE PALSY, GENERAL DENTAL PRACTICE PRIMARY DENTALCARE 2001;8(4):139-142
Aims and objectives:The aim of this
study was to produce some observa-
tional evidence of the success rate of
inferior alveolar nerve block (IDB)
analgesia that is achieved in general
dental practice. The objective was
to help provide some measure ofexpected failure rates and help dental
practitioners in their self-appraisal of
this crucial basic skill.
Method: Up to 100 consecutive IDB
analgesia procedures for four dentists
were recorded. In a subdivision of this
study 200 consecutive IDBs for a fifth
dentist were recorded.This dentist had
the greatest experience of giving IDB
analgesia of the dentists in this study.
In this part of the study the dentist
made a note if he anticipated that the
procedure would fail. The reason for
this was that it was felt that ex-
perienced dental practitioners could
predict when failure was about to
occur. The level of facial nerve palsy
was also recorded.
Results: Overall, 533 of 580 (91.9%)local anaesthetic administrations were
deemed to be successful. The only
factor that significantly affected the
likelihood of success was the practi-
tioner administering the local anaes-
thetic, and this was only borderline
statistically significant. In order to be
certain that the other factors did not
affect the outcome, the data were
re-analysed using the technique of
Poisson regression. This technique in-
vestigated the effects of each of the
factors in turn while controlling for
the differences in success that can be
attributed to the different practition-
ers. The regression analyses also did
not detect any differences in success
that could be attributed to any of the
other recorded factors. The incidenceof facial palsy was 0.3%.
Conclusion: This paper gives an
insight into the possible success rates
to be encountered by general dental
practitioners when they administer
IDB analgesia. The only recorded fac-
tor that could be shown to affect the
chance of a successful local analgesic
was the operator. The incidence of
facial nerve palsy at 0.3% may be
more common than has previously
been considered.
PRIMARY DENTAL CARE OCTOBER 2001 139
DA Keetley BDS, DGDP(UK), DPDS.
General Dental Practitioner, KirkhallamDental Practice,
Ilkeston, Derbyshire.
DR Moles MSc, BDS, DDPH.
Clinical Lecturer and MRC Special Fellow in Health Services
Research, Oral Pathology Unit, Eastman Dental Institute for
Oral Health Care Science,London.
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Aims and ObjectivesThe aim of this study is to help provide some measure of
expected failure rates and help dental practitioners in
their self-appraisal of this crucial basic skill. It has to beemphasised that if a skill cannot be measured it cannot
be managed. However, armed with some information
regarding expected failure rates, general dental practi-
tioners will be more able to audit their own results.
MethodologyOne hundred consecutive IDB analgesia procedures for
four dentists were recorded. In a subdivision of this
study 200 consecutive IDBs for a fifth dentist were
recorded. This dentist had the greatest experience of giv-
ing IDB analgesia of the dentists in this study. In this partof the study the dentist made a note if he anticipated that
the procedure would fail. The reason for this was that it
was felt that experienced dental practitioners could pre-
dict when failure was about to occur. The incidence of
any facial nerve palsy was recorded.
Anaesthetic technique
A 27 gauge long needle was used. The anaesthetic in all
cases was lignocaine 2%/adrenaline 1:80,000. Self-aspi-
rating syringes were used in all cases. Although there is
evidence to suggest that accidental intra-arterial injection
can be avoided with traditional local anaesthetic car-tridges8 the practice involved in the study had used the
Astra self-aspirating system for many years. The classic
IDB technique was used. This involves injecting into the
pterygomandibular space while the barrel of the syringe
is parallel with the occlusal surfaces of the mandibular
teeth. Figure 1 describes the anatomy of the region. The
aim is detect bone with tactile skill close to the lingula.
No attempt was made to influence dentists as to whether
they used the indirect or direct method of IDB. The alter-
native IDB techniques described by Gow-Gates9 and
Akinosi10
were not employed in this study. It is felt thatthese techniques are not commonly used by general
practitioners.
The criteria for recording a successful IDB procedure
was that the labial attached mucosa between the lower
second incisor and the lower canine tooth, on the
affected side, should be sufficiently anaesthetised to
allow firm probing with a sharp explorer. Only one car-
tridge of anaesthetic was allowed and no buccal infiltra-
tion analgesia used until the test for success had been
made. A further category for failure was that when,
despite this first test showing success, the patient
showed signs of discomfort during dental procedure.The data collected for each local anaesthetic adminis-
tration are listed in Table 1. These data were analysed
using chi-squared and Poisson regression techniques to
determine whether any of the recorded factors influ-
enced the likelihood of obtaining successful analgesia.
ResultsFor up to 100 consecutive IDB analgesia procedures (200
for one dentist) the following information was recorded
for each patient: date of birth, sex, quadrant anaes-
thetised, dental procedure performed. The number ofpatients (458) is fewer that the number of IDBs (580)
because some patients returned on several visits during
their treatment.
The results are displayed in Tables 2, 3 and 4. Five
hundred and eighty inferior alveolar nerve blocks were
administered by the five participating practitioners dur-
ing the course of the audit. The recipient patients varied
in age from 6 to 93 years old, with a mean age of 38.4
years (standard deviation 16.8 years). There were slightly
more female (298, 51.4%) than male patients in the sam-
ple. Half (292, 50.3%) of the patients received the local
anaesthetic as part of conservation treatment. The nextmost common procedure requiring inferior alveolar
nerve block was extraction (138, 23.6%).
Overall, 533 (91.9%) of local anaesthetic administra-
SUCCESS RATE OF IDBS
140 PRIMARY DENTAL CARE OCTOBER 2001
Factor Possible values for factor
Practitioner administering 1-5
the anaesthetic
Sex of patient Male/female
Age of patient 6-93 years
Quadrant Lower left/lower right
Reason for local anaesthetic Conservation, periodontal
(procedure) therapy, endodontics, extraction
Outcome of anaesthetic Success/f ailure
Table 1: Information collected for each local
anaesthetic administration
A
B
E
F
C
D
Figure 1 Diagrammatic description of the inferior alveolar nerve block.
A: Mandibular ramus. B: Masseter. C: Medial pterygoid. D: Buccal fat
pad. E: Superior constrictor of the pharynx F: Buccinator.
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tions were deemed to be successful. The success rates
for each of the potential explanatory factors are shown
inTable 3. The only factor that significantly affected the
likelihood of success was the practitioner administering
the local anaesthetic, and this was only borderline statis-
tically significant at the 5% level (chi-squared 4 df=9.56,
p=0.048). In order to be certain that the other factors did
not affect the outcome, the data were re-analysed using
the technique of Poisson regression. This technique
investigated the effects of each of the factors in turn
while controlling for the differences in success that can
be attributed to the different practitioners. The regression
analyses (results not shown) also did not detect any dif-
ferences in success that could be attributed to any of the
other recorded factors.
The percentage failure rates for each dentist are
shown inTable 4 with additional note of the number ofyears since qualification.
Dentist 5 felt that he could identify when failure was
about to occur immediately following the procedure. The
results show that in eight out of 10 failures the prediction
was accurate, unexpected failure occurring only in two
out of a total 179 consecutive IDBs. In only one case did
the dentist predict a failure and the IDB actually achieve
success. This raises the question that if failure is pre-
dictable should dental procedures be postponed at
that point and alternative methods of pain control be
considered?
An incidental finding in the study was that facialnerve palsy occurred in two patients. The dentist was
different in these two cases. This gives the complication
an incidence of 0.3% in this series. This is possibly higher
than some may have expected. Interestingly dentist 5
had wrongly predicted IDB failure in the case that
developed facial nerve palsy. It appears that the proce-
dure was identified as differing from the usual on that
patient at that time.
DiscussionIn this audit of inferior alveolar nerve blocks, the only
recorded factor that could be shown to affect the chance
of a successful local analgesic was the operator. This
reinforces the notion that successful analgesia is tech-
nique-sensitive. The implications of this are that training
should continue through a dentists vocational training
year and beyond. A regular audit of success rates would
help practitioners to determine whether their technique
was improving as they would expect or not.
The greater success rate of IDB by the most ex-
perienced dentist was not unex-
pected. However, it is accepted thatthis is a small study. There is also the
possibility that the greater success of
more experienced dentists is pro-
vided by other confounding vari-
ables. It is said that dentists get to
know their patients and this helps
in, for example, providing successful
IDB analgesia for their patients. This
may be true. An established practi-
tioner may have a large group of
patients who place increased trust in
their dentist, having built a relation-ship over a number of years. There
is potential at least for some degree
of placebo effect on success. How-
ever it is unlikely that this would extend to the patient
continuing with surgery or extractions if analgesia was
not successful.
Perhaps patients get to know their dentist, the point
being that if a dentist provides unsuccessful analgesia on
several occasions the patient is likely to seek treatment
elsewhere. This may lead to a certain amount of self-selec-
tion with more established practitioners treating a group
of patients on whom IDB is successful. If this were truethen there would also be a group of patients who sought
treatment with a new dentist. The least experienced
Number of % Failure
years since rate of IDB
qualification an analgesia
Dentist 1 Less than 1 10.1%
Dentist 2 Less than 1 9.0%
Dentist 3 4.5 years 11.2%
Dentist 4 14.5 years (8.5 years PT) 3.7%
Dentist 5 14.5 years 5.6%
Total 580 IDB procedures 8.1%
Factor Value of factor Administrations Successes (%) P-value
Practitioner 1 179 169 (94.4) 0.048
2 109 105 (96.3)
3 97 84 (86.6)
4 88 80 (90.9)
5 107 95 (88.8)
Sex of patient Male 282 258 (91.5) 0.727
Female 298 275 (92.3)
Quadrant Left 297 277 (93.3) 0.216
Right 283 256 (90.5)
Procedure Conservation 292 268 (91.8) 0.238
Periodontal 66 63 (95.5)Endodontics 85 74 (87.1)
Extraction 137 128 (93.4)
Procedure Frequency (%)
Conservative/restorative procedures 292 (50.3)
Endodontic procedures 85 (14.7)
Periodontal procedures 66 (11.4)
Extractions 137 (23.6)
Total 580 (100.0)
DA KEETLEY, DR MOLES
PRIMARY DENTAL CARE OCTOBER 2001 141
Table 2: Distribution of dental procedure type for
the total sample
Table 4: Percentage failure rates for each dentist
Table 3: Success rates for inferior alveolar nerve blocks by potential
explanatory factors
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dentists in this study were new to the practice and were
treating a higher proportion of patients who were new to
the practice. There is the possibility that some of these
patients were from a different self-selected group,
namely who had found IDB unsuccessful in the past.
Meecham1 put forward the case for using a blunder-
buss approach for patients who had experienced failed
anaesthesia in the past. The rationale is that it is moredifficult to gain patients trust if they have been hurt in
the past. The blunderbuss approach is to use IDB and
buccal infiltration from the onset with the possible addi-
tion of a second IDB higher up the mandibular ramus.
Dentists in this study achieved successful IDB analge-
sia at the second attempt after failure had occurred. This
may be because it is easier to move the needle painlessly
in tissue and palpate the bony landmarks. Also a higher
needle position was employed on all repeat injections.
Factors identified by dentist 5 that helped predict an
unsuccessful IDB were:
Unable to locate anatomical landmarksespeciallythe pterygomandibular raphe.
Unable to find a bony landmark with the needle.
Unable to direct the needle satisfactorily due to tough
tissue in the pterygomandibular space.
Awkward tongue. Either excessively large or due to
lifting posteriorly. Some patients seem unable to allow
the tongue to rest passively.
Difficult anatomy where posterior teeth have been lost
and alveolar resorption has been excessive.
Needle curved when withdrawn. This is usually a sign
that the dentist has struggled to manipulate the needle
within the tissues.It is interesting that some practitioners seem reticent to
provide IDB analgesia using other techniques whenever
they can. Although dentists cite infiltration analgesia as
more comfortable than IDB analgesia, there is evidence
to show that patients do not perceive any difference.11
Conclusion
Inferior alveolar nerve block analgesia (IDB) is an
important feature of general dental practice. This paper
gives an insight into the possible success rates to be
encountered by general dental practitioners when they
administer IDB analgesia. The only recorded factor that
could be shown to affect the chance of a successful localanalgesic was the operator. The incidence of facial nerve
palsy may be more common than has previously been
considered.
References1. Meechan JG. How to overcome failed local anaesthesia. Br Dent J 1999;186:15-20.
2. Heasman PA, Beynon ADG. Clinical anatomy of regional analgesia: an approach
to failure. Dent Update 1986;Nov/Dec:469-76.
3. Simon JF, Peltier B, Chambers D, Downer J. Dentists troubled by the administra-
tion of anaestheic injections: Long term stresses and effects. Quintessence Int
1994;25:641-6.
4. Evers H, editor. Handbook of Dental Local Anaesthesia. Copenhagen: Schultz
Medical Information, 1981.
5. Rood J.P. Some anatomical and physiological causes of failure to achievemandibular anaesthesia. Br J Oral Surg 1977:15:75-82.
6. Cowan A. Minimum dosage technique in the clinical comparison of representa-
tive modern local anaesthetic agents. J Dent Res 1964:43:1228-9.
7. Crean S, Powis A. Neurological complications of local anaesthetics in dentistry.
Dent Update 1999;Oct:344-9.
8. Meechan JG, Czachur KJ, Blair GS, McCabe JF. The ability of traditional and
self aspirating dental local anaesthetic cartridges to aspirate blood under
simulated arterial conditions Br Dent J 1986;160:239-41.
9. Gow-Gates GAE. Mandibular conduction anesthesia: a new technique using
extra-oral landmarks. Oral Surg 1973;36:321-8.
10. Akinosi JO. A new approach to the mandibular nerve block. Br J Oral Surg
1977;15:83-7.
11. Matthews R, Ball R, Goodley A, Lenton J, Riley C, Sanderson S, et al. The
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Acknowledgement: Miss G Taylor for help with illustration.
SUCCESS RATE OF IDBS
142 PRIMARY DENTAL CARE OCTOBER 2001
Correspondence: DA Keetley,
The Manor House, Bramcote, Nottingham NG9 3DR.
E-mail: [email protected]