Border moulding is defined as ‘the shaping of the border areas of an
impression material by functional or manual manipulation of the soft
tissue adjacent to the borders to duplicate the contour and size of the
Secondary or final impression can be defined as ‘the impression that
represents the completion of the registration of the surface or object’.
Border moulding can be done by using the following two
(i) Multistep or incremental or sectional border moulding
(ii) Single step or simultaneous border moulding
Multistep or incremental or sectional border
Refining of maxillary impression trays
• Green stick compound is added in sections to the shortened borders
of the custom tray. The compound is then heated with the flame
from an alcohol torch, tempered and moulded in the mouth.
• The tray is carefully removed from the mouth, and the modelling
compound is chilled in ice water.
• The border moulding is accomplished in the anterior region when
the upper lip is elevated and extended outwards, downwards and
• In the region of the buccal frenum, the cheek is elevated and then
pulled outwards, downwards and inwards and moved backwards and
forwards to simulate movement of the buccal frenum.
• Posteriorly, the buccal flange is border moulded when the cheek is
extended outwards, downwards and inwards.
• The PPS is formed through both hamular (pterygomandibular)
notches and across the palate over the vibrating line.
• Should the tray be underextended, the length is corrected by the
addition of modelling compound.
• A strip of low-fusing modelling compound is placed over the
vibrating line and through the hamular notches.
• After the border moulding procedure is completed, the spacer wax
is removed from the inside of the final impression tray.
• Holes are placed in the palate of the impression tray with a No. 6
round bur to provide escape ways for the final impression material.
Refining the tissue-bearing areas of the final
• The final impression material is mixed according to the
manufacturer’s instructions and uniformly distributed within the
• All the borders must be covered.
• The tray is positioned in the patient’s mouth.
• The border moulding procedures are performed first in the
posterior regions on both sides and then in the anterior region.
• When the impression material is completely set, the dentist removes
the impression from the mouth by grasping the handle of the tray
downwards and forwards in the direction of the labial inclination of
• The impression is inspected for acceptability.
Refining of mandibular impression trays
• Green stick compound is added to the borders of the resin tray in
sections, beginning with the labial flange, then the buccal flanges
and finally the lingual flanges.
• Each section of the modelling compound is heated and border
moulded before the next section is added.
• For the border moulding of the labial flange, the lower lip is lifted
outwards, upwards and inwards.
• In the buccal frenum region, the cheek is lifted outwards, inwards,
backwards and forwards to simulate the movement of the lower
• Posteriorly, the buccal flange is moulded when the cheek is moved
outwards, upwards, and inwards.
• The distobuccal sulcus is recorded by asking the patient to close the
mouth against resistance. The masseter muscle acting on the
buccinator muscle forms a notch in the impression called the
Border moulding of the lingual flanges
• The tray is placed in the patient’s mouth and the patient is
instructed to protrude the tongue.
• This movement creates the functional activity of the anterior part of
the floor of the mouth, including the lingual frenum and determines
the length of the lingual flange of the tray in this region.
• The tray is placed in the mouth and the patient is asked to push the
tongue forcefully against the front part of the palate.
• This action causes the base of the tongue to spread out and develops
the thickness of the anterior part of the lingual flange.
• The compound is then added to the area of the tray between the
premylohyoid and the postmylohyoid eminences on both the sides.
• The heated and tempered compound is placed in the patient’s
mouth and the patient is asked to protrude the tongue.
• This develops the slope of the lingual flange in the molar region to
allow for the action of the mylohyoid muscle.
• The action of the mylohyoid muscle, which raises the floor of the
mouth during this movement, determines the length of the flange in
• The distal end of lingual flange should extend about 1 cm distal to
• The flange should be shaped so as it turns laterally towards the
ramus below the level of retromolar pad and mylohyoid ridge.
• Compound on the distal end of flange is heated and the tray is
• The patient is instructed to protrude his/her tongue to activate the
• With the lower final impression tray in place in the mouth, the
patient should be able to wipe the tip of his/her tongue across the
vermillion border of the upper lip without noticeable displacement
• The compound forming posterior part of the retromolar fossa is
heated, the tray is placed in the mouth and the patient is asked to
• If the tray is too long, a notch will be formed at the posteromedial
border of the retromolar fossa, indicating tray encroachment on the
• The tray is adjusted accordingly.
• The final tray should be so formed that it can support the cheeks
and lips in the same manner as the finished denture would do.
• Holes are cut in the centre of the alveolar groove of the tray.
Refining of the tissue-bearing areas of the final
• The final impression material is mixed in proper quantities and
evenly distributed over within the tray, covering all the borders.
• The tray is positioned in the patient’s mouth and the borders are
• Once the material is set, the impression is removed from the mouth
and inspected for acceptability.
Single step or simultaneous border moulding
• A material that will allow simultaneous moulding of all borders has
• The number of insertions of the trays for maxillary
and mandibular border moulding is reduced to
• Development of all borders simultaneously avoids
propagation of errors caused by a mistake in one
section affecting the border contours in another
• The procedure followed is a technique that utilizes polyether
impression materials for border moulding.
• It significantly reduces the time required for making impressions.
• This is a clinical procedure in complete denture fabrication done to
• This is done after the upper and lower border moulding are
• Its primary objective is to record the denture-bearing area in great
detail and it also records the muscular peripheral tissues in
• This method makes use of a custom tray or special tray, prepared
• The borders of the tray should be 2 mm short from the peripheral
• The tray can be prepared from autopolymerizing resin or shellac
• Once the tray is ready, the peripheral structures are recorded by a
procedure called border moulding or peripheral tracing.
• Tracing compound or elastomers can be used.
• The impression material chosen for the secondary impression
should be of low viscosity to record the structures accurately.
• The materials of choice for the secondary impression are zinc oxide
eugenol impression paste and medium-bodied elastomeric
• The final impression material is mixed according to the
manufacturer’s instructions and uniformly loaded over the tray.
• All borders should be covered before placing the tray in the
• This impression is called wash impression because between the
properly moulded borders and the peripheral tissues, only a thin
• Once the material is set, the tray is removed from the mouth of the
patient and inspected for acceptability.
The choice of impression material depends on the following:
• Character and position of the tissues to be reproduced
• Technique used for making the impression
• Type of submucosa and the relationship of the supporting bone to
• Dimensional stability of the material after setting
Various materials commonly used for impression making in complete
• Modelling plastic or impression compound
• Rubber base impression material
• Certain modifiers are added to the impression plaster to regulate the
setting time and control the setting expansion.
• These plasters are not commonly used.
• Absorption of palatal secretions during setting
• Accurate record of tissue detail
• Easy manipulation and handling
• Subject to breakage due to brittleness
• Messy to use; separation of cast from the impression is tedious
• Pores in impression should be filled before pouring cast
• Undercuts cannot be recorded
• Impression compound is a reversible thermoplastic material, which
is used for making preliminary impressions.
• It is softened in a water bath at 64°C and kneaded until a uniform
• The impression is made using a stock tray.
• It has a good dimensional stability but excessive water
incorporation can cause dimensional change.
• Impression can be reinserted for evaluation of fit.
• Surface does not have to be treated before pouring the stone cast.
• Material can be beaded and boxed for pouring of cast.
• Due to its viscosity, it can displace the tissue surface and also it does
not record the surface details very accurately.
• Thermal conductivity of modelling compound is low, outer surface
of the impression softens first, whereas the inside sets the last.
• It is subjected to distortion during and after removal from the
• Higher is the temperature of compound during impression, more
are the chances of linear thermal expansion.
• Its basic composition is zinc oxide and eugenol.
• Plasticizers, fillers and other additives are added to alter certain
properties such as smoothness of the mix, adhesiveness and
• Tissue details are accurately recorded as a result of fluidity.
• The paste shows minimal distortion, if it is allowed to flow under
• It has a good flow and ease of handling.
• It is easy to bead and box for pouring of the cast.
• It is dimensionally stable on setting.
• Setting time is not easily controlled.
• Temperature and humidity influence the setting time.
• It is difficult to control at the borders.
• It may distort when removed from the undercuts.
• This impression makes use of agar (a reversible hydrocolloid) as the
• Hydrocolloid sols change property to gels under certain conditions.
• The agar is taken from the tempering section, which is at 46°C and
loaded on to a water-cooled rim lock tray.
• It requires heat for sol–gel transformation.
• It is an elastic material and, therefore, can be used to record
• It shows an excellent surface detail reproduction (up to 25 microns).
• It has a poor dimensional stability due to syneresis and imbibition.
• It is capable of displacing soft tissues.
• It has a tendency to get easily distorted during the gelation period.
• It requires special water-cooled trays and equipment.
• It is not easy to manipulate.
• The tray should be held rapidly during gelation.
• It should be poured immediately.
• Alginate is the hydrocolloid used for this type of impression.
• Sol–gel transformation occurs by chemical reaction.
• Better peripheral seal than other impressions
• Accurate reproduction of undercut areas
• It has poor dimensional stability due to syneresis and imbibition.
• It should be poured immediately.
• It deteriorates rapidly at elevated temperatures.
Rubber base impression material
• It has an accurate reproduction of detail.
• It does not affect hardness of the stone surface.
• It is easy to manipulate and handle.
• It can record undercuts accurately.
• If the mass is not homogenous, distortion occurs.
• Ratio of material is critical.
• Low-fusing impression waxes are not accurate for impression
• These are only used as a corrective material to refine the borders.
• Sublingual crescent is the crescent-shaped area on the anterior floor
of the mouth formed by the lingual wall of the mandible and the
adjacent sublingual fold. It is the area of the anterior alveololingual
• Retromolar pad consists of glandular tissues and the fibres of
temporalis posteriorly, buccinator laterally and pterygomandibular
raphe and superior constrictor medially. It should be covered in the
denture to aid in posterior seal of the lower denture.
• Peripheral seal is the contact of the denture border with the limiting
structures to prevent the passage of air or food.
• Distobuccal border of the maxillary denture is limited by the
coronoid process, ramus of the mandible and the masseter muscle.
• The purpose of boxing the impression is to give definite shape to
the base of the cast and preserve the width of the border after
• Aesthetics of the denture begins during the impression stage itself.
• Mucostatic impression is the negative replica of the oral tissues on
• Recording jaw relation is difficult in denture construction of patient
• In the upper denture, the accurate adaptation of the labial flange
and the positioning of the teeth influence the aesthetics.
• Neutral zone concept was first proposed by Wilfred Fish.
Influence of Opposing Tooth Contacts, 78
Anatomy and Physiology of TMJ, 78
Axis around which the Mandible Rotates, 78
Actions of Muscles and Ligaments, 78
Envelope of Motion of the Mandible, 79
Envelope of Motion in the Sagittal Plane, 79
Envelope of Motion in the Frontal Plane, 81
Envelope of Motion in the Horizontal Plane, 81
Importance of Anterior and Posterior Reference Point, 85
Schools of Thought Regarding the Transverse
Advantages of Articulators, 88
Classification of Articulators, 90
Fully Adjustable Articulators, 94
Split Cast Method and Its Importance, 94
The mouth of the patient is considered as the best articulator, but it is
not possible to arrange prosthetic teeth in the patient’s mouth or to do
any intraoral procedure which is needed for construction of dentures.
Therefore, it is necessary to use a mechanical device which can
simulate jaw movements and transfer the relationship of the jaws to
this device. These devices are called articulator and facebow which are
Mandibular movements occur primarily around the
temporomandibular joint (TMJ) which is capable of making complex
movements. Condyles articulate with the temporal bone which is
along the posterior slope of the articular eminence and extends as far
forward as its crest. Movement of the mandible is related to three
planes of the skull, namely, the horizontal, frontal and sagittal planes.
(i) Rotational movement can occur around three reference planes:
• Rotation around the horizontal axis
• Rotation around the vertical axis
• Rotation around the sagittal axis
Based on the types of movement
(iv) Lateral excursive movement
Based on the extent of the movement
• Border movements around the horizontal plane
• Border movements around the sagittal plane
• Border movements around the frontal plane
Four movements of prime importance to complete denture service
(i) Hinge-like movement is used in opening and closing the mouth.
(ii) Protrusive movement is used in grasping and incising the food.
(iii) Right or left lateral movements are used in reduction of food.
(iv) Bennett movement is the bodily shift of the mandible which is
recorded in the region of rotating condyle on the working side.
Factors regulating movements of the mandible are as follows:
• Anatomy and physiology of the TMJ
• Axis, around which the mandible rotates
• Actions of muscles and ligaments
Influence of opposing tooth contacts
• One of the many factors which influence the jaw movements is
occlusion of the opposing teeth.
• Relationship of the occlusal surfaces is not only confined to teeth but
also to the muscles, TMJ and neurophysiological components.
• In complete dentures, the occlusal surfaces on teeth should contact
bilaterally and simultaneously to enhance the stability (balanced
• The inclined planes of the denture teeth should be positioned in
such a way that they are in harmony with the other factors that
• TMJ is divided into two compartments by the articular disc.
• Movement in the upper compartment is primarily translatory, whereas
movement in the lower compartment is primarily rotational.
• Mandibular movements can be translatory or rotational or
Axes around which the mandible rotate
• Mandible can rotate around three reference axes, namely,
horizontal, sagittal and vertical.
• Horizontal axis of rotation: Mandibular movement around this axis is
a hinge movement, i.e. opening and closing movement (Fig. 5-1).
• This axis is used to properly orient the maxillary cast on the
• In lateral movements, the mandible rotates around the vertical axis
passing through the condyle on the working side because the
condyle on the balancing side moves forward and medially (Fig. 5-
• Mandibular movement around the sagittal axis occurs during lateral
movement, as the balancing side condyle moves not only forwards
and medially but also downwards because of the slope of the
articular eminence (Fig. 5-3).
FIGURE 5-1 Mandibular movements around horizontal axis.
FIGURE 5-2 Mandibular movement around vertical axis.
FIGURE 5-3 Mandibular movement around sagittal axis.
Actions of muscles and ligaments
• Muscles responsible for mandibular movements show increased
activity during any jaw movement.
• The activity and interaction of various muscles for series of jaw
movements can be determined using electromyography.
• Temporal and inframandibular muscles retrude the mandible and
maintain it in this most posterior position.
• Lateral pterygoid muscle moves the mandible and the condyle
forward during uncontrolled opening movements.
• It is also responsible for making lateral and protrusive movement of
the mandible which is necessary to make eccentric interocclusal
records or pantographic tracings.
• Muscular control of all the movement of the mandible is governed
by impulses from the central nervous system.
• Loss of teeth eliminates the source of receptors that are located in
the periodontium. These receptors help in controlling the position
• Such a loss is compensated by construction of dentures with centric
relation (CR) coinciding with the centric position.
Envelope of motion of the mandible
Envelope of motion is defined as ‘the three-dimensional space
circumscribed by the mandibular border movements within which all
unstrained mandibular movement occurs’. (GPT 8th Ed)
Envelope of motion or maximum border movements can occur
around three planes, namely, the sagittal, horizontal and frontal plane.
Envelope of motion in the sagittal plane (fig. 5-4)
• Tracing is made when a pathway of the bead attached to the lower
• The tracing starts at point P, which represents the most protruded
position of the mandible with both upper and lower anterior teeth
• As the patient moves the mandible posteriorly, it reaches the centric
occlusion (CO) position which is the position of maximum
intercuspation of the posterior teeth.
• When the mandible is further retruded, it attains the most posterior
relation to the maxilla which is represented by the point CR.
• Single restorations are usually constructed at the CO position.
• Multiple restorations and complete dentures are fabricated with
their occlusion in harmony with CR.
• As a patient opens the jaws, there is a separation of the teeth and the
mandible moves in its most retruded position to the position of
• Till the position of MHO, the condyles rotate without translation
• Opening of the jaws beyond MHO will force the condyles to translate,
i.e. to move forward and downward from their most posterior
• Translatory movement of the condyles continue till the maximum
• At the point MO, the condyles are in their most anterior position in
relation to the mandibular fossa.
• The line joining CR–MHO represents the posterior terminal hinge
• This movement is clinically used to locate the transverse hinge axis
(THA) for mounting the cast on the articulators.
• The line joining MO–point P represents the pathway of the
mandible, as it moves from its most open position to the most
• The masticatory cycle can be viewed in the sagittal plane and can be
superimposed on the envelope of motion.
• The masticatory cycle begins from CO and then extends downwards
and then upwards to end again at this point.
• In complete dentures, the CR and CO positions should coincide
with each other and, therefore, the masticatory cycle terminates at
• The mandibular rest position occurs somewhere downwards and
slightly forwards from the point CR as indicated by REST(R).
• This rest position is the habitual postural position of the mandible
when the patient is at ease in the upright position.
• The rest position is one of the most important reference positions to
record the vertical jaw relations.
FIGURE 5-4 Envelope of motion in the sagittal plane.
Envelope of motion in the frontal plane (fig. 5-5)
• The envelope of motion seen in the frontal plane resembles a shield.
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