৪৮তম স্পেশাল বিসিএস ডেন্টাল ⎯ মডেল টেস্ট [Archived]

Indirect retainer :

1.Helps direct retainer by preventing displacement of denture.
2.Resist rotational movement around the fulcrum line.


Ref: Deepak

Function of guiding  plane :

1.Minimizes the wedging stresses 
2 Makes insertion & removal easier 
3.Stabilises the prosthesis against horizontal stress 
4  Stabilizes individual tooth
5.Improves oral hygiene 
6. Contributes indirect retention & frictional retention.

Ref: Deepak.

Parts of RPD :

1.Major connector: largest & most important. 
Connect all other component of the Prosthesis. Provides indirect retention 
2.Minor connector- Act as connecting link. Connect other part with Minar connector

3.Rest: Transmit occlusal forces on the denture along the long axis of the abutment tooth

4.Direct retainer: Prevent displacement of the denture 

5.Indirect retainer: Retain the denture component in place during displacement. 

6.Denture base : Distribute the force acting on the denture.

7. Artificial tooth replacement : Produce  contour & functions of missing teeth.

ref: Deepak.

Survey line: height of contour of the abutment teeth marked by carbon marker during surveying.

Type: 4types
1.High survey line- found in inclined teeth. Wrought wise clasp is used.

2. Medium Survey line. Suitable for Maker's clasp or roach clasp. Usually Aker's clasp is preferable.
 
3.Low survey line - Modified T clasp is used.
Found in marked inclination of teeth.

4.Diagonal survey line: Reverse circlet casp is used.Common in canine & premolar teeth.


ref: Deepak

Objective of Surveying :
1. Designing the RPD
2.Determining the path of insertion
3.marking the height of the contour above the undercut
4.Marking survey line 
5 Marking undesirable undercut

ref: Deepak 

Parts of FPD:

In denture :
1.Retainer
2.Connector
3.pontic

ref: Deepak

Abutment & saddle found in the mouth. 

Fracture of All ceramic FPD  depends on size,shape position of  the connector.

In Zirconia based ceramic FPD, minimal thickness of connector is 3mm to avoid the fracture.
In case of metal-ceramix FPD, it is 2.5 mm.

ref: Rangarajan

Over extended impression leads loss of retention & displacement of denture during tissue movement. 

Hence, Functional impression is taken by green stick compound  to record the tissue movement in sulcus. 

ref: Deepak 

Clinical maintenance of implant surgery :

Radiographic assessment : Most important tool in detecting osseointegration of the implant.

CBCT is not routinely done 
Subtraction radiograph is usually done to determine  the change in crestal bone level.

Ref: Deepak

Coronoid process is recorded to the distal portion of maxillary buccal sulcus to prevent interference between denture flange & mandibular movement which lead to severe pain in that area. 

ref: Deepak

Rochette bridge :

1.Developed by Rochette in 1973
2.First resin-bonded FPD in dentistry 
3 Attach to the tooth by mechanical retention having wing like retainer with multiple perforation.
4.Limitation - a)Limited retention b) Perforation weaken the metal retainer c) Causes wear & microleakage by exposed resin through the perforation.

Ref: Rangarajan

Beading & boxing is done before jaw relation in the master cast. 
Purpose:
Beading - preserving  the height & width of sulcus.
Boxing- obtaining uniform,smooth,well-shaped base.

Ref: Deepak

Methods to select the size of anterior tooth:

1.Using pre extraction records 
2.Using anthrophogolgical measurement
3.Using anatomical land mark.
4.Using  theoretical concepts
5. Other factors


A.Using pre extraction record :
1.Diagnostic casts.
2.Pre extraction photographs 
3.Pre extraction radiographs
4 Teeth of close relatives
5.Preserved extracted teeth- Best method to determine the size of the anterior tooth

Ref: Deepak

Choice of occlusion in different type of Prosthesis :

A.Implant supported full arched Prosthesis:
 1) Opposing natural tooth- occlusion with shallow anterior guidelines 
2)Opposing Complete denture- a)Bilateral balanced occlusion, b) Group function/mutually protected occlusion

B. In overdenture- 1)Bilateral balanced occlusion 2)Monoplane occlusion in resorbed ridge

C Posterior fixed Prosthesis - Mutually protected occlusion is preferred

D. Anterior fixed Prosthesis - 1) Mutually protected occlusion is preferred. 
2) Flat incisal platform in case of Class Div.1
3)Raised VD followed with full arch restoration 

E. Single implant Prosthesis :Light contact during heavy occlusion & no contact at MIP


ref: Deepak

Artificial teeth of CD:

1.Anatomic teeth- most commonly used, 33° angulation. Highly esthetic.
 30° cuspal angulation in anatomic teeth is called Pilkington-Turner teeth

2.Semi-Anatomic/low cusp teeth-  have 20° angulation. Used in mild discrepancies in jaw relation.

3. Cusp less teeth- no cuspal. anglation.set in balanced occlusion.used in Bruxism.

4 Cross bite teeth
5.Metal insert teeth

Ref: Deepak

Natural dentition has 3types of curve:

A.Anteroposterior curves/ Curve of Spee-  failure to arrange the teeth according to this curve leads to Christensen's phenomenon 

B.Lateral curves- a)Wilson's curve- Premolars are arranged according to this curve to avoid interference during lateral movement 

b) Monsoon's curve - Arrangement of teeth according to this curve results lateral balance of occlusion. 


Ref: Deepak

After final closure in lab procedure of CD fabrication,  flasks are kept at room temperature for 30-60min commonly called bench curing. 

Purpose:
1.Equalize the pressure throughout the mould space
2.Offers longer exposure for better bonding  the teeth with the base material 
3.Allows time for uniform dispersion of monomer throughout the mass.


Ref: Deepak 

Seaqulae of wearing CD:

A.Direct:

1.Denture stomatitis 
2.Flabby Ridge
3.Traumatic ulcer
4  Epulis fissuratum
5.Burning Mouth Syndrome(BMS)
6.Gagging.
7.Residual Ridge Resorption(RRR) - Most common & important sequelae of wearing denture.


ref: Deepak

Microbial flora around the stable implants is

Gram- positive facultative anaerobic cocci & nonmotile bacilli(rods)

1.S.sanguinis
2.S.mitis

ref: Deepak

Short term temporary crown :
1.Used for maximum of 2 weeks.
2.Indicated after tooth preparation in FPD
3 Polycarbonates or Aluminum are the most commonly used short term temporary crown 


ref: Deepak

Based on biodynamic activity or biological response   implants are 3 types:

1.Biotolerant-Gold,Cobalt-chomium alloys,Zirconium, Stainless steel [metal]

Buccal flange is the Only part of the denture flange that is  to be relieved because it has active muscle fibres[ Levator anguli oris, Orbicularis oris, Buccinator.]
ref: Deepak

Mid palatine raphe :

Relief structure of upper jaw. Has thin submucous covering. Most sensitive to pressure. Hence must be relieved during CD fabrication.

ref: Deepak

Absolute contraindications of implant :

1.Active growth period(below 17yrs)
2. Smokers received radiotherapy 
3.undergo radiation over 70GY
4. Leukemic pt with positive ZAP-70 markers
5.osteoradionecrosis


red: Deepak

Limiting structure of lower jaw:

1.Labial frenum
2.Labial vestibule 
3.Buccal frenum
4.Buccal vestibule 
5.Lingual frenum
6.Retro molar pads
7.pterygomandibular raphe
8.Alveololingual sulcus.

Relief area of lower jaw: 
Mental Foramen
Genial tubercle
Torus mandibularis
Crest of alveolar Ridge 

Ref: deepak

Role of saliva in retention of CD:

1.Thick mucous saliva- loss of retention
2 Thin watery saliva- Compromised retention
3 Thin serous salive- provides good cohesion & retention.

ref: Deepak

DC improves the appearance of face by.
1 Restoring natural display of teeth & gum
2.Restoring lower facial height 
3.Restores lip &  cheek fullness
4.Fills out of wrinkle& creases caused by loss of teeth.

ref: Manappallil 

Patient self care in implant surgery :
A. Brushing 
B.Auxiliary aids & antimicrobial rinses:
1)Inter proximal brushes 
2)Dental floss
3)Oral irrigation 
4)Antiseptic &antibiotic rinses: Commonly prescribed antibacterial agent is Chlorhexidine.
Effect: a)Forms acquired pellicle that act as a chemical reservoir & relased antibacterial action over a prolonged duration of time.
b)Aids in fibroblast attachment to implant surfaces


ref: Deepak

Occlusal rim:
Has 3 form of arch that generally follow natural form of arch:
1.Square
2 Tapering
3 Ovoid 

* should place in neutral zone 
Width- Anteriorly 5 mm, posteriorly 8-10mm

Ref: Manappallil 

Type of face bow used in CD articulation :

A.Arbitrary face bow- most widely used[ Hanau face bow].
B. Kinematic face bow.

ref: Deepak & Manappallil 

General consideration during tray selection of CD fabrication :

1. At least 2-3mm clearance between ridge & tray
2.Handle tilts downward 
3.Should cover tuberosity & hamular notch
4.Materials should not react with the tray.
5.perforation is need for alginate impression 
6.Have over extended border

ref: Deepak

Retention:
Resist displacement against the denture's path of insertion /away from the basal seat in vertical direction 

Stability : Resist displacement  of denture in horizontal /lateral direction 

Support :Resist vertical movement of denture towards basal seat.

ref: Deepak & Manappallil 

Orientation jaw relation : recording of this relation gives auguration of the maxilla in relation  to the base of the skull & also affect the plane of occlusion of the denture.

For this reason this relation is recorded first. 

ref: Deepak

Types of obturator :

Based on phase of treatment :
1. Immediate surgical obturator - inserted at time of surgery.

2.Delayed surgical obturator - inserted 7-10days after surgery 

ref: deepak

Type of Pontics: Based on mucosal contact

A.With mucosal contact:
a) Saddle pontic.
b) Ridge lap pontic
c)Modified ridge lap pontic
d) Ovate pontic
e) Modified ovate pontic
f)Root form pontic 
g) Natural tooth pontic
h)Lancebergs pontic

B.Without mucosal contact:
a) Bullet pontic
b)Hygienic or sanitary pontic 
c)Fish belly pontic.
d) Perel pontic

Special pontic :
a)Quinns pontic
b)Schwartz pontics 
c)Pontic clasp
d)Articular.etc.

ref: Deepak 2nd edition

Indications of Sub gingival margin in FPD:

1.Short clinical crown 
2.Subgingival caries or lesion.
3.Contact area at or below the gingival crest
4 Gummy smile
5.Unmanageable tooth sensitivity 
6 Requires additional retention 

ref: Deepak

Occlusal reduction in different restoration :.
1.Gold Alloy : ~1-1.5mm
2. Metal ceramic : 1.5- 2/ ~2mm 
3. Complete cast/metal crown: 1- 1.5mm
4.All ceramic restoration : minimum 2mm

Ref: Deepak &  Live mcq 39 Q solution 

Type of retainers of FPD:

A.Based on tooth coverage :
a) Full veneer crown-Most retentive & ideal because can resist masticatory forces in all direction

b)Partial veneer crown- Less retentive but require less tooth reduction than full veneer crown.Need pins for additional  retention

c) Conservative retainers- Require minimal tooth preparation. Can not accept heavy occlusal load & primarily indicated for anterior teeth

Ref: Deepak

Tarnish: Discoloration of the surface of metallic appliance due to chemical action forming a thin surface film is known as Tarnish. 

Effect : 
1.Loss of surface gloss & luster 
2.Decrease finishing of the surface 
3 Loss of aesthetic quality

ref: Shama bhat

Corrosion:

Loss of material from the metal surface by chemical attack on the surface particle is called corrosion.

It is the continuation of tarnish with loss of surface material. 
As corrosion oxidizes the mercury, its prevent amalgamation &keeps the particle unmixed.

Dissimilar metal restoration in the mouth gives galvanic shock as a result of wet corrosion.
Usually coupon test is done to measures the amount of surface loss due to corrosion.

ref: Shama bhat

Auxiliary materials : Aid in the fabrication process but do not actually become part of restorative, appliance or prosthesis. 

Example- Gypsum product, impression materials, casting investment, waxes,etching gel,custom tray materials 

Restorative materials -used to repair or replace tooth structure. Example - Amalgam,composites,ceramics,cast metal structure & denture materials. 

Implant- biomaterials that introduced into the body through bone & tissue graft


ref: Manappallil 

Different ways of fabricating a metallic restoration in dentistry :
1.Direct restoration 
2. Casting
3.Foil adaption & sintering
4.Electro forming
5.Machining
6.Three dimensional printing

Among them casting is the most commonly used method for fabrication of metal structure. 

ref: Manappallil 

Mucostatic materials -Produce minimal or least displacement of the tissue during impression. 

Example - Plaster, ZnO eugenol paste, low viscosity alginates,low viscosity elastomers 

Mucocompressive materials : Displace the tissue during impression. 

Example - Compound,high viscosity alginates, high viscosity elastomers. 


ref: Manappallil 

ref: Manappallil 
Impression compound :

Synonym -Modeling compound or modelling plastic
Oldest impression material. 
Rigid, reversible which set by physical change.
Mainly used for making impression of edentulous ridges.

Application :

GICs show sensitivity to moisture contamination and surface desiccation.

To prevent water exchange, restoration should be protected by
1.Resin bonding agent
2.cocoa butter
3.Petroleum jelly
4.Varnish

Among these, resin bonded agents provide best Surface protection as they fill the Microporosities of the surface & stay longer time in comparison to other agents. 

ref: Nisha Garg 

Type of GICs according to their use:

Type I- For luting cements
Type II- For restorations 
Type III- Liner & Bases
Type IV- Fissure sealants 
Type V- Orthodontic Cements
Type VI - Core build up
Type VII-Fluoride releasing cements 
Type VIII- For ART
Type IX- Pediatric GICs

ref: Nisha Garg 

After cementation of GICs,cement surface is protected From drying with 
1. A special varnish, or 2.Unfilled light cured resin bonding agent or 3. Cocoa butter or petroleum jelly. 

Failure to protect the cement surface results in a chalky or crazed Surface.

Causes : 
1 Inadequate protection of freshly set cement(from air)
2.Low power/liquid ratio
3 Improper manipulation 

ref: Manappallil 

During firing of the porcelain, a vacuum or negative pressure is created to reduce the porosity in the ceramic.

ref: Manappallil 

For fabricating complete denture base, heat cured acrylic resin is the most widely used resin.

Classification of denture base material :

ref: Manappallil

Classification of Amalgam :

Based on the presence of alloyed metals

1.Binary alloys- contain 2 metals 

2.Ternary alloys- contain 3 metals

3.Quaternary alloys- contain 4 metals

Out of these, Quaternary alloys are most acceptable 

ref: Nisha Garg 

Expansion that occurs due to reaction of mercury with alloy components is called mercuroscopic expansion or primary expansion.

It is seen only in low copper alloy

ref: Nisha Garg 

Aim of condensation in dental amalgam:

1. To increase the density of the restoration 
2.To reduce voids
3.To remove excess mercury
4.To adapt the amalgam to the preparation walls & margin.
5. To increase the strength
6.To decrease the creep

Ref: Manappallil

Failure are commonly seen in composite restoration:
1.Discoloration,specially at margin 
2.Fracture of margins.
3.Secondary caties
4.Postoperative sensitivity 
5.Gross fracture of restoration 
6.Loss of contact after a period of time
7.Accumulation of plaque around the restoration


ref: Nisha Garg 

Composition of Dental composite:
1.Resin matrix 
2.Filler or dispersed phase
3.Coupling agent
4Activator- initiator system
5.Inhibitiors
6.Coloring agent
7.Ultraviolet absorber -Added to prevent discoloration. Act like suncreen to composite.
Commonly used UV absorber is Benzophenone

ref :Nisha Garg 

Classification of elastomers:

Based on viscosity : 4types

Type 0- Putty consistency(very heavy)

Type 1- Heavy-bofied consistency(tray consistency) 

Type 2- Medium bodied consistency( regular bodied) 

Type 3- Light bodied(Syringe consistency)

ref: Manappallil 

In ordinary water, gypsum product dissolved leading to loss of surface Detail. 

To preserve the surface gypsum cast is soaked in water of saturated solution of calcium known as slurry water.

ref: Manappallil 

Inlay casting wax:

Oldest waxes in dentistry 
Used to make pattern for crown, inlay,FPDs.


ref: Manappallil 

In torch melting casting machine system,
Flame has 4 zone 
From inward to outward-

1.Mixing Zone : no heat, dark in color

2.Combustion zone: green in color,  partial combustion occurs  & has an oxidizing Nature.

3.Reducing zone: Hottest part of the flame,Blue in color, fusion of casting alloy is occurred here.

4.Oxidizing zone: Outermost Zone.

ref: Manappallil 

Shrink spot porosity - caused by incorrect cooling sequence & freezing the sprue before the rest of the cast.

Suck back porosity:- Inadequate sequence of solidification leads to suck back porosity. 

Pin hole porosity-  expelling dissolved gas during solidification leaving tiny void in the cast. 

Back pressure porosity : Caused by inadequate venting of the mould.


ref: Manappallil 

Biological properties of dental materials :
Should be

1.Non toxic
2.Non irritant 
3.Non allergic 
4.Not be mutagenic

ref: Manappallil 

Viscosity: property of a fluid that resists the force which is causing the fluid to flow.

Adhesion : Force of attraction between unlike molecules. 
Cohesion : Force of attraction between same kind of molecules.

Plasticity: capability of being moulded to receive ant form by any external forces but do not under go any expansion or contraction.

Ref: A H S Rahman sir, Manappallil 

Soldering :Joining of two metal by other matel having lower melting point than parent metal to be joined 

Welding : Joining of two metal without using other metal/solder.
 Casting : Procedure to force molten metal or alloy into a burnt out mould by  centrifugal force

Brazing /soldering investment : Assembling the parts of a restoration by soldering.

Ref: A H S Rahman sir, Manappallil 

Hydrocolloid elastics impression material [alginate,agar agar] shows characteristic dimensional change syneresis & Imbibition.



As hydro colloid use water as the dispersion medium, They are prone for dimensional change either loss or gain of water.

 Swelling of the gel by absorbing water from humid environment /emmersed in water,is known as imbibition.

Exuding the water from the gel is known an syneresis.

This dimensional change can alter the cast, hence, hydrocolloid impression should be poured immediately after taking the impression / covered by a dump cloth witb rubber bowl for 1hour.




ref: Manappallil 

Commonly used elements that incorporate into the materials to make radiopaque are

1.Heavy metal glass [Strontium or barium glasses

2. Compounds[Barium sulphate]

3.Metal oxides[Zirconium dioxide, Ytterbium oxide]
Radiopacity helps told detect problems within the restorations,teeth,bone etc. 

ref: Manappallil 

In resin restoration, material of choice as base is Ca(OH)2 as ZnO eugenol cement interfere with its polymerization. 

ref:Manappallil 

Film thickness is an important property of dental cement specially for  Luting cement. 
Because -
It improves the seating of the restoration 
Improvees bonding Between teeth & restoration surface 
Minimizes the air spaces & structural defect present in the bulk of the cement. 

Maximum film thickness for luting cement is 25micrometer

ref: Manappallil 

Outstanding characteristics of Zinc polycarboxylate cement is to bond chemically with tooth structure.  Carboxyl group chelated with calcium in the tooth structure. 


Composite resin-Micromechanical bonding with bonding agent

GICs- chemical bonding 

Amalgam- Mechanical Locking achieved by proper cavity design.

Zinc phosphate- micromechanical bond to the tooth structure. 



ref: Manappallil 

Composite resin may contain a variety of fillers

1.Ground quartz 
2.Glasses or ceramic containing heavy metals.
3.Boron silicates
4.Lithium aluminum silicates
5.Ytterbium tri fluoride
6.Colloidal silica

In Conventional composite resign, most commonly used filler is Ground quartz. 


ref: Manappallil 

Chief disadvantage of Zno eugenol paste is burning sensation caused by eugenol.

Other disadvantages are-

1.Requires special tray for impression 
2.Sticky in nature & adhere to tissues
3.Eugenol cause tissue irrigation 
4 Can not used for making impression of teeth & undercut area.

ref: Manappallil 

In construction of cast RPD, master cast is duplicated in investment materials which is known as Refractory cast &used in the fabrication of the cast partial denture framework. 

ref: Manappallil 

Because of poor adhesion of alginate, impression can be retained by Mechanical interlocking feature.  

A rim lock (a beading around the edge of the tray)
& perforation (hole or slit) in the tray  elevate the adhesion property of the alginate. 

ref: Manappallil