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Errors in
Prosthetic Dentistry: |
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After |
Before |
After |
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Errors in Prosthetic Dentistry |
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Prosthetic dentistry is an independent
scientific and applied branch in medicine with long history. |
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High
needs for prosthetic help are still caused frequent
complications after therapeutic interferences, high, sometimes
unwarrantable, activity of exodontists extracting teeth and
fangs, which could be saved by correct integrated approach to
treatment of the dental diseases.
Dental
mechanics producing dental apparatus, prostheses and dentures
not always accurately follow the instructions and keep the
technological process, inasmuch as they are not well informed
about the consequences of influence of breaking these
processes on the dental maxillary system and patient’s
organism. There are no elaborations and legislative acts for
rating the quality of dentures and dental apparatus in dental
prosthetic laboratories, and at clinic as well. |
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Diagnostics
- is a subject about the methods of research, disease
recognition, and patient’s status for the propose of the
treatment prescription and/or prophylactic means. The
diagnostics is also understood as a process of examining a
patient for the propose of disease recognition.
Diagnostics
- is a complex cognitive process in a doctor’s activity, whose
necessary elements are analytic and synthetic work of mind,
based on the data of examining the patient as well as the
knowledge and preceding experience of the doctor, and his/her
predecessor and/or colleagues, described in manuals,
monographs, and practical instructions.
Patient complaints about the acute pain in a region of the
particular tooth can be caused by acute pulpitis or
periodontitis. The etiological features of acute periodontitis
can be caries complications, complications after treating
pulpitis, wrong tooth filling or tooth crowning, stating over
the central occlusion, or as a result of overpressure (chronic
trauma) caused by partial adentia or acute mechanical injury.
In conclusion acute pereodontitis can develop with the wrong
made dental bridge or clasp producing overpressure upon the
tooth.
Acute pulpitis occurs as a result of not only complicated
treated or untreated caries, but also the wrong tooth
preparation for crowning and necrosis of the tooth hard tissue
under the decemented artificial crown. In the severe
periodontitis stage so called retrograde pulpitis can be
observed. One should remember, in some cases of pulpitis a
radiating pain can occur, and a patient can point at another
tooth and even at a tooth of the other jaw. The pain of the
pulpitis type is sometimes noted at papillitis, it can develop
from chronic trauma caused by a wrong tooth filling or
artificial crown and approximate contacts, which also can be a
result of a chronic trauma of the gingival papilla caused by a
food lump. Papillitis also occurs on a wrong made clasp
prosthesis (injury caused by a part of the prosthesis base or
clasp).
Patient complaints about the pain of local type in the mucous
tunic can be caused by its trauma at deep occlusion or
secondary adentia complicated by deep incisor occlusion,
distant shift of the lower jaw and lowering of occlusive
height, and also supraocclusive shift of one group of teeth.
Pain can be caused by trauma of the mucous tunic with a
low-quality denture or clasp prosthesis, and has local nature.
Pains, burning, pricking, tingle of various types at using a
clasp prosthesis can be caused by mechanical injury, allergic
reaction to the base material, diseases of the blood or
gastrointestinal tract, at using the denture by allergic
reaction to the alloys with high content of nickel, and also
beryllium.
In some cases interviewing patients it is possible to find out
that deterioration of the dental maxillary system status has
begun in the period or immediately after the systematic
disease. Extracting teeth from patients having such
concomitant diseases like diabetes, stomach ulcer, rheumatism,
atherosclerosis, liver diseases etc results in quick
development or complication of weight of the existing disease
of the dental maxillary system.
Bronchial asthma when applying for prosthetic help is a
contraindication for using the molding materials with scent
(repin, tiodent). For these patients it is not allowed to
relocate clasp prostheses directly in the oral cavity. Tooth
preparation must be made with constant wetting of the prepared
tooth and tooling. Scents and dust at preparing a tooth can
cause asthma attack.
Objective checkup is carried with clinical and special
laboratory methods, and includes examination, anthropomorphic
measurement, palpation, percussion, auscultation, and
laboratory analyses (blood, urine, saliva, biopsy materials
and smears, allergic tests), X-ray examination, myography and
rheography.
Clinical investigations are carried as questioning a patient,
because earlier taken data about subjective sensations are
required verification. |
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Determining an Occlusion Type and
Saving of Occlusive Correlations and Surface of Dentitions |
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Occlusion
type determination allows to construct correctly a prosthesis,
set up medical tactics as it changes, and surely to judge
correctly on pathogenesis of disturbance in the dental
maxillary system, diagnose and forecast.
Occlusion
determination and saving of occlusive correlations are carried
with the closed dentitions and low jaw in physiological rest.
First of all the extent of incisor occlusion is measured.
Normally at orthognathic occlusion its value is 3.3±0.3. If it
grows it means the presence of another type of occlusion or
pathological changes in the dental maxillary system (lowering
of occlusive height and distant shift of the lower jaw), which
occur when the dentitions are affected (by pathological dental
abrasion or extraction of a part or entire dentition).
Simultaneously as the extent of incisor occlusion increases
because of distant shift of the lower jaw the character of
occlusive correlation changes (the teeth of the upper and
lower jaws contact with one antagonist only, e.g. canine with
canine. Inasmuch as shift of the lower jaw and lowering
occlusion can cause affect of the muscular system and/or
temporomandibular joint, it is obligatory to determine the
depth of the incisor occlusion with calculating size of the
lower part of the face at physiological rest of the lower jaw
and central occlusive correlation. The interocclusive space is
measured, i.e. interval between the dentitions at
physiological rest of the lower jaw. Normally it equals to 2-4
mm.
Checking
occlusive contacts one should simultaneously learn character
of the lower jaw motion by opening and closing the mouth.
Normally disconnection of the dentitions with maximal opening
of the mouth equals to 40-50 mm. Opening of the mouth can be
troubled by acute inflammations, neuralgia, myopathy, affected
joint. Shift character is determined on space shift of the
center line of the lower jaw dentition with relating to the
center line of the upper dentition on stages of slow opening
and closing the mouth.
Lack of
convergence of the center line, vertical line between the
central incisors of the upper and lower jaws can be symptoms
of various diseases: affection of the right or left
temporomandibular joint, fractures of the jaws, pathological
realignment in the dentitions caused by partial loss of teeth,
presence of the masticatory teeth on one side. For instance,
acute or chronic arthritis of the right temporomandibular
joint causes shift of the lower jaw to the left, decreasing
pressure on the intraarticular disk.
For estimating the occlusive plane the angles of the mouth of
a patient are stretched aside with forefingers in such a way
the central incisors to be seen out of the red border of the
upper lip not less than 0.5 cm, and the edge of the central
incisors are on focus (dentist’s eyes on level of patient’s
half-opened mouth). So the entire dentition of the upper jaw
is on the dentist’s focus. This method is applicable without
abrasion of the frontal teeth. |
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Complications by using
metal-ceramic dentures (MCD) can be a consequence of: |
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- side effects of dentures
-
side
effect of dental prosthetic materials
-
medical or technical errors.
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The first
group of the consequences is caused by needs of sizeable
abrasion of hard tissues of the bearing teeth prepared for
MCD, which should be considered inevitable.
Side
effect of materials is basically caused by intolerance or
allergic reaction of some patients to the components of the
metal alloys used in producing MCD. This side effect can be
reduced to minimum by individually selecting for every patient
a metal alloy existing in the assortment, that are base,
semiprecious and noble metals shown to him/her, taking into
consideration individual sensibility and allergic
predisposition. Ceramic coating is the most biologically
indifferent dental prosthetic material of all known.
The third
group of the consequences of complications occurs most
frequently, it is explained by multistage and technologically
complex producing of MCD, required both dentist’s and dental
mechanic’s high skill, and impeccable accuracy on all stages.
These errors are considered as medical, because finally a
dentist is an inspector of technical quality of producing an
article, and responsible for quality of treating. |
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Depending
upon a character of the consequences we distinguish:
-
errors without causing clinical complications
-
errors causing reversible clinical complications
-
errors causing irreversible clinical complications (loss of
bearing tooth or group of teeth, both bearing, and
antagonistic, affection of periodontium).
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From the
point of view of the consequences the first fundamental stage
is most important – drawing a plan of treating based on
accurate detailed examination of a patient and diagnosing. On
this stage it is possible:
-
wrong
collection of information for producing MCD
-
choosing a wrong construction of MCD
-
breaking the order of treating.
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The
contra-indications for using dentures are:
-
teeth
with pathology of periodontitis
-
defects of dentition of long extension
-
teeth
with short crown part
-
hard
dental convergence
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Producing
MCD in the enumerated above cases is possible after:
-
efficiency of treating pathology of periodontitis
-
leveling the power domination of the dentitions of the upper
and lower jaws and choosing enough number of bearing teeth
and a harder (firmer) metal alloy for MCD
-
restoring the crown part of sharply shorted teeth with
insertion of stump pins, and necessarily after the
corresponding orthopedic reconstruction of myotatic reflex
of the temporomandibular joint, connected with increasing
the height of the lower part of the face at physiological
rest
-
carefully analyzing the X-rays of the converging teeth for
solving a problem of allowing to abrade necessary amount of
hard tissues on the vital teeth, necessarily to provide
removal of tooth pulp, abrading and, according the data,
restoration necessary shape of the tooth with a pin
insertion.
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Choosing
a shape of MCD one should take into consideration that for
prophylaxis of chipping the ceramic coating the metal skeleton
of MCD must not have constant internal exertion, that is
inevitable when producing console type of MCD or prostheses of
long extension, including 5-7 units or more. Accurate choice
of MCD model is important from the point of view of
prophylaxis of diseases (overpressure) of periodontium of the
bearing and antagonistic teeth.
Features
of producing MCD are a kind of preparing the bearing teeth:
abrasion of a large amount of the hard tissues of teeth,
necessary metal coating (about 0.4 mm) and ceramic coating
(1.2-1.5 mm), creating parallels or necessary obliquity of the
bearing teeth. Errors made on this stage can be subdivided
into errors at preparing intact teeth and teeth with removed
pulp.
As
preparing a tooth MCD, shaping a stump of prosthesis-applied
teeth is important. Errors can occur in creating the shape and
size of stump of the bearing teeth. |
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At overarasion of a prepared
tooth as a complication decementation of MCD and bad fixation
of the denture can occur. Chipping the ceramic coating is
possible, that happens when on a short stump its height is
restored due to thickening of the coating, but not the metal
skeleton.
At
deficient shortening of a tooth stump lack of occlusive space
occurs, and therefore local overpressure of the
prosthesis-applied tooth or the ceramic coating is too thin.
In this condition chipping the ceramic coating and generation
of periodontal overpressure of a bearing or antagonistic tooth
(direct traumatic node), abrasion of an antagonist or breaking
of a bearing tooth can be expected. |
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Producing MCD obliquity of the
bearing tooth stump after preparing is most important. At low
obliquity can occur complications in putting on the denture or
for putting on the denture efforts will be required, that
causes internal overpressure in the skeleton of MCD, and as a
result chipping the ceramic coating. Low obliquity of the
prepared tooth stump can cause deficient putting of the
denture when it is fixed, and as a result the cement surplus
gets out with a difficulty. According to the data given by the
most of specialists obliquity of a prepared tooth is
considered to be equal to 5 degree. At high obliquity because
of abrasion of the retention areas of fixation of the tooth
stump it gets wedge-shaped, it greatly weakens denture
fixation and can cause frequent decementing.
Besides preparation of a teeth with high obliquity formation
can cause such a technical error as modeling a metal skeleton
of the cone-shaped base crown, an as a result chipping the
ceramic coating in a long term after the denture fixation
because of absence of a metal base for the ceramic coating at
vertical direction of power masticatory pressure.
According to the opinion of the most of specialists preparing
the base, especially frontal, teeth for MCD the vestibular
cervical ledge has to be formed, otherwise the following
complications can develop:
-
chipping the
ceramic coating in the cervical area because of deformation
of metal (very thin) skeleton
-
cosmetic
defect of MCD in the cervical area of the base tooth –
transparency of the opaque (ground) coating of ceramics
through the very thin coating of dentine, the crown color
can change
-
trauma of
the side periodontium (cervical gum area) caused by the
expanded side of the crown.
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Poor molding of outlines of a
prepared tooth can occur in using low-quality molding material
(obligatory to check expiry date), and also wrong mixing
molding paste. The most frequent reasons of producing
low-quality MCD are poor molding and reflection in the mold of
the cervical area of the prepared tooth. It can be a result of
taking the mold directly after preparing. We do believe,
according to the large clinic data, taking a mold of prepared
teeth for MCD should be provided in the next visit after
preparing, because in this case of preparing the cervical area
of the tooth a trauma of the gum side is inevitable, causing
reflective inflammatory reaction of the gum that disfigures
the relief of the cervical gum area. Poor molding of the
cervical area is also possible without prior retraction of the
gum. Excellent results of taking molds can be received before
taking a mold with the first (base) coat without preparing a
tooth and the more exact mold in the next visit after
preparing. |
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V. Kopeykin |
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Good luck! |
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Dental Laboratory
"DENTA" |
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