The handbook of preclinical dentistry
Introduction
The aim of this manual is to provide students with instructions for practical exercises on models and
simulators. It should serve students of Preclinical Dentistry I and II. Information contained herein can
replace neither lectures nor practical lessons in clinical dentistry.
Content:
I. CAVITY PREPARATION AND MAKING OF THE FILLING
Classification of carious cavities, their preparation and fillings according to Black
Principles of preparation
Examination, preparation and filling tools
Cavity preparation in individual classes
Techniques for cavity preparation and making of the filling
II. BASICS OF PRECLINICAL ENDODONTICS
Definition of endodontics
Morphology of the pulp chamber and root canals
Endodontic instruments
Basics of manual preparation
Basics of root canal filling
Classification of carious cavities and prepared cavities
The division of dental carries into five classes according to G. V. Black is of practical significance
for cavity preparation.
I. class: Caries in pits and fissures
These caries appear in fissures (on the occlusal surfaces of premolars and molars), caries in
foramen caecum are also ranged into this class. Foramen caeca are pits on buccal surfaces of the
lower molars, palatal surfaces of upper molars, and on palatal surfaces of upper incisors.
II. class: Caries on proximal surfaces of premolars and molars
They usually begin under the contact point or in its close proximity or in the gingival third
of proximal surface. They can be covered by a ridge of hard tissues or be opened in the
direction of occlusal surface.
III. class: Caries on proximal surfaces of incisors and canines with no damage of incisal
edge
They arise close to the contact point and may spread in the gingival, incisal or labiooral
direction.
IV. class: Caries on proximal surfaces of incisors and canines with damage of incisal edge
Incisal edge is weakened and lost (so-called loss of cusp). This class includes not only
defects caused by caries, but also by injuries. In case of injuries, the loss of dental tissue
is more extensive. Treatment of both carious and non-carious defects is similar.
V. class: Cervical caries
These are caries located in the gingival third of the crown. In this area we can find also
defects which are not caused by caries (erosion, abrasion, wedge defects). They are
treated similarly as caries.
VI. class: Caries on cusps or abraded incisal edge
These are small, isolated defects which do not exceed the cusp or the incisal edge (they
affect neither proximal space nor fissures). These defects were added later to the original
Black’s classification.
Principles of preparation
Caries result from repeated exposure to acids produced from sugar fermentation caused
by microbes in dental biofilm. At the beginning loss of minerals occurs without any
defect on the dental tissue, later dental tissues disintegrate and a cavity is created. The
cavity must be treated by preparation and filling. Greene Vardiman Black defined
preparation as follows: “By the phrases ‘Excavation of cavities’, ‘Preparation of cavities’
or ‘Cavity preparation’ is meant such a mechanical treatment of the injuries to the teeth
produced by dental caries as will best fit the remaining part of the tooth to receive a
filling restoring the original form, give it strength, and prevent recurrence of decay in the
same surface” (Black 1914: 105). This definition determines the basic principles of
preparation:
1. The principle of preventive extension
Preparation is performed in a way that maximally reduces the risk of secondary caries
formation (caries at the edge of the filling). It is vital to correctly determine the outline of the
cavity. The criteria which matter the most are the type of filling material and the level of oral
hygiene.
All carious dentin must also be removed so that recurring caries under the filling are
prevented.
2. The principle of retention
Preparation must be performed in such a way that the filling does not fall out of the cavity.
3. The principle of resistance
Preparation must be performed in such a way that the tooth treated with the filling
withstands the strains of its function (biting and chewing). This rule concerns both dental
tissues and filling.
Individual steps of preparation:
1. First we need to gain access to the carious lesion and open it.
Then the undermined enamel or ridge of dental tissues above the carious lesion must be
removed; it may also be necessary to remove the old filling, push away or remove any
ingrown gingival tissue or separate teeth most commonly with a wedge, less often with a
separator.
We can use carbide or diamond burs with standard grit (blue code) with ca 200,000
revolutions per minute on handpiece with red strip; alternatively, we can use an airturbine
handpiece mainly for removal of old fillings or for cutting through a thick ridge of
dental tissues.
2. Determining the outline of the cavity – preventive extension
The criteria that need to be taken into consideration are mainly the type of filling
material used and the level of oral hygiene.
3. Removal of carious dentin
Softened dentin is excavated with a rotary instrument – with a ball bur (small number of
revolutions, about 3,000 per minute) in a handpiece with a blue or green strip (blue or
green handpiece); or manually with an excavator.
4. Securing retention
Retention depends on the type of material used (undercuts, fissures and grooves for
amalgam, dental tissue etching for composite, treatment with conditioner for glass
ionomer cement).
5. Securing resistance
Resistance depends on the size and location of the caries and on the material used (the
filling must be thick enough, no sharp edges and no undermined cusps, and others).
6. Treating cavity edges
Again the type of material used, and location of carious lesion are decisive. In some cases
enamel is bevelled, in others smoothening is performed. A fine diamond bur with red
code is usually used.
7. Toilet and final examination of a cavity
Washing and drying, visual examination and examination with an explorer.
Preparation techniques
1. Preparation with a rotary instrument
It is vital that the instruments are sharp and centred (after being anchored no
instrument must be eccentric).
We hold the handpiece correctly.
2. We guide the preparatory instrument most commonly at a right angle to the surface
of the tooth and prepare the cavity with a slight pressure and with interruptions (1
period preparation, 2 periods break). In this way we protect dental tissues from
overheating.
3. We prepare smooth lines.
4. We interrupt preparation and check the result with direct and indirect look.
Preparation practice with plates from Novodur should serve for acquiring correct
instrument guiding and creating smooth lines. It is a good training before preparation
on models.