What to do when the zebra walks in the door H.J. Lapointe
A. introduction: With the exception of relatively unusual geographic circumstances,
the usual assumption that one may make about hoofbeats outside your window is
that they are being made by a horse and not a zebra. In other words: common things
happen commonly. This is true in dentistry where the majority (but not all!) of practice
is dedicated to the detection, prevention and treatment of relatively few diseases.
Dental caries, periodontal disease and trauma claim the lion’s share of problems that
we are asked to deal with. Never the less, less common problems, ZEBRAS,
occasionally come into the picture and impact on management. These zebras are the
many and various diseases, tumours, hyperplasias, cysts and assorted lumps and
bumps that make up the world of oral pathology. It is this world that I hope to explore,
in small part, today.
B. Rationale: the reasons for occasionally revisiting this subject are straight forward.
These are uncommon lesions that are easy to forget when we see them so
infrequently. Despite this, we need some review and preparation for the day the zebra
walks in, unannounced. Preparation for this unexpected event requires thinking
ahead, organization and work in order to be of use. It requires:
1. prior knowledge of the look and feel of normal tissues
2. prior knowledge of the various diseases
3. a systematic approach for finding pathology
4. a systematic approach for identifying pathology
5. clinical tools or procedures for sampling or removing pathology
6. practice …
C. Objectives: our objectives for today’s discussion are the following:
1. To better understand how clinical behavior reflects the underlying disease process
and how this impacts on the otherwise normal appearance and function of tissues.
2. To reveal the patterns of presentation of the various types of pathological lesions.
3. To review some common (and-not-so-common) lesions of the oral mucosa and
jaws.
4. To use the process of data Interpretation and differential diagnosis to help
definitively diagnose lesions of the mucosa and jaws.
5. To Illustrate and explain clinical techniques of incisional and excisional biopsy and
removal of lesions such as mucoceles. epulis fissuratum, papilloma, fibroma, etc.
6. To allow participants to exercise their skills and participate In the formation of
differential diagnoses for various oral lesions.
D. Biological Behaviour:
1.Normal: While initially somewhat obvious, the concept of what constitutes
“NORMAL”, requires a little clarification. Normal must be understood as a spectrum
of “normal variation”. Many factors impact on this variation and these include:
Age: infant, toddler, child, teen, adult, mature and elderly
race: African, Asian, European or American aboriginal
previous disease: caries, periodontal disease, cancer, trauma, infection
habits: oral hygiene, tooth brushing, bruxism, etc
These issues include such concepts as “normal healing”, “normal development”,
“normal sequelae”, etc. Despite this variation and the factor that impact on it, the
implication is clear...”normal” is what we commonly expect to see and per se does
NOT require further investigation or further management.
2. Abnormal: In contrast, abnormal implies th
different about the situation. Initially we see o
and, most importantly, the implication is that
this abnormal behavior of pathoses that troub
swelling, nerve invasion, causation of pain, m
this “BAD” behavior that we want to either sto
of “bad” behavior is the underlying structure
How does underlying biology drive clinical be
3. Clinical presentation: In order to explore th
the examples of cancer and Infection. In the c
metastatic potential of the tumour are a funct
cell division and adhesion that allow uncontro
the cells on normal tissue. In the case of infec
result of the multiplication of micro-organism
and very importantly, the host’s response to b
In both of these cases, the knowledge of the u
progression of disease allow us to detect, cla
management of such a case begins with the p
Interpretation of the “facts” we gather about t
within a biological context and begin working
a. History: We start with the story told by the
lesion differs from that of an infection and thi
the two diseases. The tumour is usually relati
and is often noticed when it interferes with fu
problems with denture fit (for example). In co
painful and associated with a clear cut etiolog
or impacted tooth.
b. Examination findings: Following through w
findings also differ but are consistent with the
lesions. Tumours often present as lumps with
Contrast, infection may be much less discrete
(inflammation) indicates a different process o
The use of these two examples illustrates the
that allows us to categorize and manage clini
story or history of chief complaint and we the
information gathered by clinical examination.
us a sense of the disease process, whether it
inflammatory, traumatic, neoplastic, cong
4. Differential diagnosis: Having listened to th
now in a position to start thinking about diagn
that may prove to be one of many things. The
differential diagnosis.
The differential diagnosis is a list of the p
Once established, the differential diagnosis is
investigation in order to rule in or rule out item
include further imaging, blood tests, biopsy a
5. Review of pathology: Rather than review d
classifications, I have elected to look at them