Partial Denture Failures Short Question And Answers

Partial Denture Failures Short Question And Answers

Failures

Multiple Choice Questions

Question 1. The commonest cause of failure in the minimum preparation bridges is:

1. Inadequate taper.
2. Loss of retention.
3. Failure of connector.
4. Perforation.
5. Occlusal wear.

Answer. 2. Loss of retention

Read And Learn More: Fixed Partial Denture Short Essay Question And Answers

Question 2. Which one of these is a mechanical failure in relation to crowns and bridges?

1. Distortion.
2. Porcelain fracture.
3. Fracture of connectors.
4. Fracture of acrylic facings.
5. All of the above.

Answer. 5. All of the above

Question 3. Which one of the following is a design failure in relation to crowns and bridges?

1. Over-prescribed bridges.
2. Inadequate abutment preparation.
3. Under-prescribed bridges.
4. All of the above.

Answer. 4. All of the above

Question 4. Which one of these is a clinical or laboratory failure in relation to crowns and bridges?

1. Overhang on the margins.
2. Poor shape or color.
3. Marginal defect.
4. All of the above.

Answer. 4. All of the above

Question 5. In metal-ceramic restorations, failures usually occur:

1. In the porcelain.
2. At the porcelain–metal interface.
3. In the metal.
4. At the metal–tooth interface.
5. In the tooth.

Answer. 1. In the porcelain

Extended Matching Questions

Theme: Crown and bridge failures

A. Periodontal disease.

B. Distortion of the bridge/crown.

C. Inadequate type of retainer.

D. Poor shape or color.

E. Occlusal problems.

F. Pericoronitis.

For each of the following failures, choose the most appropriate type from the list above. You may use each option once or not at all.

1. Mechanical failure.
2. Design failure.
3. Inadequate clinical technique.
4. Abutment failure.
5. Inadequate laboratory technique.

Partial Denture Failures Short Question And Answers

Question 1. A 40-year-old patient presents complaining of movement of his three-unit fixed-fixed bridge in which teeth FDI 15 and 17 are abutments and tooth FDI 16 is replaced by a pontic.

How can you clinically identify the failed retainer?

• Pressing the bridge and look for small bubbles in the saliva at the margins of the retainers.

List any two causes for this failure.

• Cementation failure
• Nonretentive preparations
• Secondary caries
• Poor design.

List any three solutions to manage this failure.

• Recommendation with chemically adhesive cement
• Cut off one retainer and convert it to a cantilever
• Preparations are redone and the retainer(s) are remade
• If needed, add additional abutments
• Change the design.

Question 2. A 40-year-old patient reports to your dental office with a complaint that his anterior metal-ceramic crown is fractured. On examination, it is found that the fracture surface is ceramic.

Explain whether the fracture is cohesive or adhesive failure.

• Cohesive failure.

How do you manage the fractured ceramic if the other features of the crown are satisfactory?

• Repair with composite and follow-up – temporary management
• Redo – permanent management.

How to prevent this type of fracture?

• Proper crown/bridge design
• Adequate preparation to have enough thickness for metal-ceramic or all ceramic to avoid distortion
• Extension of porcelain to the lingual side of the pontic.

Question 3. A 40-year-old patient reports to your dental office with a complaint that his anterior metal-ceramic crown is fractured. On examination, it is found that the fracture surface is between metal and ceramic.

Explain whether the fracture is cohesive or adhesive failure.

• Adhesive failure.

Explain how ceramic is bonded to the underlying metal.

• Through metal oxide layer.

How can you prevent this type of failure?

• Proper crown/bridge design
• Adequate preparation to have enough thickness for metal–ceramic or all ceramic to avoid distortion
• Extension of porcelain to the lingual side of the pontic.

Laminate Veneers

Veneer Definitions

Veneer

Veneer is a protective or ornamental facing – (GPT 7).

Laminate Veneer

It is a thin veneer facing which is laminated (adhesive bonded) to etched tooth structure by using resin cements.

Laminate Veneer Introduction

Laminate Veneer  1928 Dr Charles Pincus used veneers for movie stars. He used porcelain onto platinum foils and fixed them for actors with denture adhesives.

Indications for Veneers

• Cosmetic – for stained teeth that cannot be bleached and for shaping anterior teeth
• Restorative – fractured, worn, or traumatized anterior teeth and for avoiding composite fillings
• Functional – to correct diastema, malaligned and malformed teeth. To reconstruct anterior canine-guided occlusion.

Contraindications of Laminate Veneers

• Large diastemas
• Bruxism
• Poor oral hygiene
• Severe malocclusions
• Severe fracture of the tooth
• Severe tooth rotations.

Types of Laminate Veneers

• Hollow ground denture teeth
• Preformed stock acrylic laminates
• Custom-made veneers – composite or porcelain.

Hollow ground denture teeth

Hollow ground denture teeth Advantages – Easy to prepare, less expensive.

Hollow ground denture teeth Disadvantages – They are opaque and only minimal color corrections are possible.

Preformed stock acrylic laminates (E.g. Componeer by Coltene)

Preformed stock acrylic laminates  Advantages – Readymade veneers.

Preformed stock acrylic laminates  Disadvantages – May not be available in all shapes and shades, expensive.

Custom-made Veneers (Types)

Composite resin

• Composite resin Advantage – Direct clinical technique – simple and less time consumption.
• Composite resin Disadvantage – May acquire stains and be difficult to polish.

Porcelain laminate veneers

Advantage – Highly esthetic, least plaque retention and characterization is possible.

Disadvantages – Indirect technique, requires lab support, expensive, and technique sensitive.

Porcelain Laminate Veneers

Indications

Same as general indications, such as discolored tooth, fractured tooth, diastema closure, malformed teeth, defective restorations, adolescent teeth (have large pulps), worn teeth (erosion/abrasion/attrition), root exposures, stained restorations, lengthened short crowns and smile designing.

Porcelain materials used

Pressable ceramic, lithium disilicate [E.g. Emax (Ivoclar Vivadent)] is the most favored core material 340MPa.

Alumina (690Mpa) or zirconia (1200–1400Mpa) may also be used as the core for the laminate veneer. But they are opaque, cannot be etched and hence, are not frequently used as the core.

Procedure

• Ceramic blocks (ingots) of lithium disilicate are heated at 1150 °C
• The softened ceramic is slowly injected under pressure into the mold at a high temperature under a vacuum
• The core is retrieved and layered with feldspathic porcelain and is stained and characterized
• This core is etchable with hydrofluoric acid and may be used in crowns, veneers, inlays, and onlays.

Selection of veneer cases

• At least 50% enamel should be present on the tooth surface to be bonded (for effective bonding of the veneer)
• 1mm circumferential principle’ – At least one millimeter of the peripheral margins of the prepared tooth should have enamel, this ensures a proper marginal seal3
• Shade selection is done before the preparation
• Selecting a lighter than the desired shade is desirable.

Mouth preparation before laminate preparation

If there are other carious surfaces, defective restorations, isolated discolored tooth areas, or any, class 3 cavities present restore them with composite before the veneer preparation.

Steps in preparation of a veneer

• Facial preparation/Finish line
• Proximal preparation
• Incisal preparation
• Finishing of preparation
• Gingival retraction
• Impression making
• Provisional restoration—generally not required
• Try-In
• Preparation of porcelain veneer for bonding – (HF acid etching and silane coupling application)
• Preparation of tooth for bonding – 37% phosphoric acid etch followed by bonding agent application
• Application of resin on veneer
• Seating and setting of veneer
• Check occlusion.

Facial preparation

• Gingival half of labial surface = 0.3mm reduction
• Labioincisal half = 0.5mm reduction
• Finish line = Chamfer
• Finish line termination : At crest of gingiva (equigingival)/slightly subgingival
• No sharp internal line angles—helps to avoid stress concentration on the porcelain
• Respect the facial convexity during tooth preparation.

Why chamfer finish line?

• Chamfer provides a definitive seat for accurate laminate positioning
• Chamfer is easily distinguishable in impressions and by the lab
• Provides adequately thick porcelain at margins
• Exposes enamel prisms near the cervical region at correct angle thereby increasing the surface area of enamel for better etching
• Chamfer make no internal line angles—less stress on porcelain
• Less destructive of tooth structure than shoulder preparation
• Chamfer provides gradual transition from tooth to veneer.

Proximal preparation

• Is the extension of facial reduction
• Should just end facial to contact area
• Should not break contact area
• Change to a smaller diameter bur (to prevent damage to adjacent tooth, if required).

Proximal reduction—when to break contact?

Contact is broken when existing proximal restoration are at the contact region in malpositioned teeth and diastemas.

Incisal preparation

The design varies in regard to the incisal preparation. The different types of incisal preparation are

• Window design preparation
• Feather edge preparation
• Incisal bevel preparation
• Incisal overlap/Incisal wrap/Lingual wrap design.

Incisal preparation—Different designs

• Window design
• Feather edge
• Incisal bevel
• Incisal wrap/lingual wrap.

Window design preparation – Preparation is close but not up to the incisal edge Limitations – Difficult to hide joint between the veneer and the tooth and hence, not a preferred design.

Feather edge preparation—Tooth prepared up to the incisal edge without incisal edge reduction.

Indications – When the existing crown length is acceptable.

Advantages – Maintains guidance on natural tooth.

Incisal bevel preparation – Buccopalatal bevel given and hence, more control over incisal esthetics. Not commonly done.

Incisal over lap/Incisal wrap/Lingual wrap design

Indications

• When crown lengthening is needed
• When the faciolingual thickness of tooth is too thin
• Fractured incisal edges.

Advantages

• Provides vertical stop
• Less stress concentration at incisal edge
• Increases the surface area for bonding
• Lingual reduction for incisal overlap—keeps porcelain under compression (in mandibular tooth)
• Chamfer 0.5 mm deep
• Bur is held parallel to lingual surface and the two proximal finish lines is connected to produce a mesial and distal notch
• Lingual finish line should be 1 mm away from centric contacts.

Finishing the preparation

• Remove all sharp line angles
• No sharp corners/angles.

Stump shade selection done — communicated to the lab (supported by a good photograph).

Gingival displacement – Gingival retraction done to expose finish line so that impression flows into sulcus – To record the tooth profile beyond finish line.

Impression material – Addition silicone (polyvinyl siloxane)—good dimensional stability.

Provisional restoration – Not usually required since the preparation is mostly in enamel there is less chances of postoperative sensitivity. In case temporary restoration is given eugenol-based preparations should not be used as eugenol remnant can hamper the polymerization of the resin cement.

Try- in – Try in pastes have the same optical properties as luting composite. So it is helpful to determine how the shade of the porcelain laminate veneer will be beforehand.

Adhesive Bonding of Veneer

The monoblock effect – Tooth + resin cement + ceramic restoration— is the key to the success towards the longevity of the restoration.

Preparation of the porcelain laminate veneer for bonding

• Hydrofluoric acid etching (2.5–10% for 1minute) – Hydrofluoric acid (HF) is a porcelain etchant. It selectively dissolves the glassy matrix from the applied surface which when washed away exposes the rough crystals thereby increasing the surface area for bonding
• Silane coupling agent application — is a major factor for resin cement bonding on to silica-based ceramics. Silanes are bifunctional molecules that bonds silicon dioxide with the OH groups on the ceramic surface. They also have a degradable functional group that copolymerizes with the organic matrix of the resin

Preparation of the tooth for bonding porcelain laminate veneer

• Etching the tooth with total etch (37% phosphoric acid) and or self etch philosophies
• Then the bonding agent is applied on the tooth and not cured (it is cured through the laminate veneers which are thin restorations).

Other steps for bonding laminate veneers

• The veneer is uniformly loaded with low viscosity resin
• Ensure complete seating of the veneer
• Laminate veneers are very thin restorations and need gentle handling as they are brittle before bonding
• They are carried to the tooth for bonding using special sticks with glue (e.g. Optrastick by Ivoclar) which could be removed after the veneer is cured
• Remove gross excess resin
• The margins where resin cement is exposed to air is applied with glycerin/vaseline to prevent oxygen from coming into contact with resin as contact of resin cement with oxygen in the air could inhibit the polymerization of the resin cement. This may lead to marginal leakage, discoloration and disintegration)
• Adjust occlusion—Check all excursion movements
• Eliminate interferences especially in lengthened crowns
• Ensure that there is no centric contact at enamel—porcelain margins.

Other Types of Veneers: Lumineers

• Lumineers are ‘no prep veneers’. They are marketed by Dent-Mat corporation, California as Cerinate Lumineers
• No local anesthetic administration nor tooth preparation is recommended here.

Lumineers Advantages

• Patients are more comfortable with the idea of no preparation
• Temporaries are often unnecessary, lowering the cost of treatment
• Restorations bond strongly to enamel, so these stay
• Procedures are reversible if the results are not satisfactory
• There is minimal damage to the dental pulp.

Lumineers Disadvantages

• Esthetic changes are limited
• Limited potential for color change
• Difficulties manufacturing, inserting and bonding the restorations
• Patient complaints about excessive bulk
• Flat esthetics due lack of room to create deep embrasures.

Fixed Partial Dentures Introduction

Scientific advancements in the treatment of fixed partial denture prosthesis has taken place at all levels starting with diagnosis and treatment planning to options in types of restoration, to recent advances in equipments, soft tissue management, impression making, articulators, shade selection and newer materials for provisional prosthesis, luting and the definitive prosthesis.

Literature search was carried out using PubMed and Google scholar from 1993 to 2013 on review articles and evidence-based studies related to all the above mentioned aspects of the fixed prosthesis denture and has been projected as a summary in this article.

Fixed Partial Dentures Advancements in Diagnosis

Latest advancements have been in form of caries detection systems, such as1

DIAGNODent Laser Device (KaVo, Lake Zurich,Ill.) uses laser fluorescence to detect incipient caries. The device measures the fluorescence of bacterial products within carious lesions..

DIAGNODent Laser Device Advantages: A valuable device when combined with a visual examination to detect demineralization. It is capable to ascertain demineralization under sealants also.

DIAGNODent Laser Device Limitations: The readings can be recorded in the patient’s chart but cannot be used for comparison or large scale studies.

Digital Imaging Fiber – Optic Transillumination Device (DIFOTI)

• It allows images from all tooth surfaces to be digitally captured and stored
• The principle behind transilluminating teeth is that demineralized areas of enamel or dentine scatter light more than sound areas
• Incipient caries appear as darker areas in the resultant images.

Advantages – Simple to use and the instantly available images are easily interpreted. It can also be used as a patient education tool.

Limitations – Image interpretation is difficult, because the results are not directly quantified.

Quantitative Light-induced Fluorescence (1995)

• QLF is a more versatile system than either DIAGNODent or DIFOTI and can measure absolute mineral loss along with a number of other applications
• Good reproducibility of QLF methods clinically with reliability greater than 0.95 was reported after training
• Bacterial products appear as red fluorescence, determine the activity of lesions
• QLF can be used as a diagnostic system, rather than a detection device.

Advantages: Ability to detect root caries and early orthodontic demineralization. Other caries detection methods include electronic caries monitor, fiberoptic transillumination, bite wing radiographs.

Advancements in Restorative Options

Shortened Dental Arch Concept

The shortened dental arch (SDA) may be defined as having an intact anterior region but a reduced number of occluding pairs of posterior teeth.

In 1992, the World Health Organization stated that the retention, throughout life, of a functional, esthetic, natural dentition of not less than 20 teeth and not requiring recourse to prostheses should be the treatment goal for oral health.

The above concept adopts the fact that if the patient is having an intact anterior region but a reduced number of occluding pairs of posterior teeth with good occlusal stability and correct vertical dimension there is no need to restore the posterior edentulous spaces.

SDA protocol terminates the occlusal platform at the second premolar region. But the remaining teeth should be closely monitored and oral hygiene is to be well maintained with periodic recalls.

Minimally Invasive Prosthodontics/Microdentistry

This concept highlights maximum preservation of remaining sound teeth.4

Types

• Partial veneer crowns
• Resin-bonded bridges
• Laminate veneers
• Inlay/Onlay
• Anchor systems.

Advantages

• Less destructive
• Good esthetics
• Fixed restoration
• More comfort for the patient
• Less time
• Easy marginal finishing and cleaning.

Disadvantages

• Only can restore short span
• Commonly used materials are IPS E max, Zirpress (Zirconium oxide).

Anchor systems (CBW—Crown less bridge work)

In anchor system titanium anchors are adhesively bonded to the proximal sides of the abutment tooth and pontic is attached to this anchor.

Systems are – UDA and Delta bridge systems

Advantages

Minimal preparation, esthetic, less interference with existing occlusion and it is a reversible and repairable process.

Disadvantages

Difficult to clean, only in short span, cannot be used in free end saddles and in parafunctional habit cases, requires good skill and experience.

Resin-bonded Fixed Partial Dentures (RBFPD)

First introduced in the 1970s by Rochette presently more advanced bonding and bridge materials such as fiber-reinforced composites and Zirconium has increased the longevity of resin-bonded restoration.

Good bonding with minimal abutment preparation increase the bond strength of the RBFPD.

Advantages

• Minimal tooth preparation
• Decreased pulpal trauma
• Minimal periodontal irritation
• Anesthesia is often not needed
• Easy margin placement and cleaning due to supragingival margin
• Improved esthetics
• Reduced cost with less chair time
• Provisional restoration not required
• Re bonding is possible.

Limitations

• Debonding is the commonest cause of failure
• Design is outside the dimensions of the natural tooth hence, bulky contours
• “Graying out” of teeth that are thin labiolingually at the incisal surfaces
• Good alignment of abutments is required
• No space correction
• Good lab precision required
• Restricted to single teeth replacements.

Advancement in materials includes coating of zirconia with a glass infiltration agent by heating above the glass transition temperature. This is called selective infiltration etching emerged in 2006. This technique creates sliding and splitting of the surface grains creating nano porosities where the adhesive resin can infiltrate and interlock. This technique increases the bond strength.

Advancements in Tooth Preparation/Equipments

Equipments: Recent advances in hand pieces.

Laser treatment for hard tissues

Goldman et al., in 1964 introduced laser into dentistry.

Amongst the type of lasers the Er: YAG laser was tested in 1988 on hard tissues

Advantages – Decreased vibrations and noise causing more comfort to the patient, low pulpal temperatures, reduces amount of bacteria in surgical field, good control of bleeding, improved visualization of the surgical field, and can be performed with less injectable anesthesia. Burkes etal reported that even without water-cooling the prepared cavities showed no cracks and low or no charring.

Gimbel observed that the Er: YAG laser is capable of removing cement, composite resin and glass ionomer which can be used in removal of crowns and bridges.8

Limitations – Although they are useful for caries removal and tooth preparation, the erbium lasers are unable to remove gold and porcelain, accessibility to the treatment area is limited, and apart from the line supply an additional air supply is required. It is presently used only as an adjunct to conventional technique.

DJP Evans et al. observed that though patients were comfortable with lasers, dentist preferred the conventional method because after using laser they had to use conventional handpieces to complete the cavity due to difficulty in access and slow speed of cutting.9

Dental Air Abrasion Handpiece (KaVo PROPHYflex 3)

Indications

• Cleaning of enamel before etching for subsequent fissure sealing
• Cleaning before using DiagnoDent caries detector
• Cleaning of implant surfaces
• Fast and pain-free removal of plaque and stains
• Preparation of cavities for improved bonding.

Advancements in Soft Tissue Management

Gingiva Pastes and Gels

Recent advances in soft tissue management include cordless gingival retraction methods using injectable materials such as Expasyl (Kerr Corporation)  and magic foam (ColteneWhaledent). These materials ensure hemostasis and open the sulcus.

Other cordless techniques are Traxodent Hemodent Paste Retraction System (Premier Products Company) and Gingitrac (Centrix).

Modified impression techniques, such as matrix system and modified shell system are also presently employed.

Advancements Impression Materials

More recently the three-dimensional (3D) digital scanners are being used to capture 3D virtual images of tooth preparations, from which restorations are fabricated directly (CAD/CAM systems) or indirectly (dedicated impression scanning systems for the creation of accurate master models).

The computer-aided design/computer-aided manufacture (CAD/CAM)

• They feed data obtained from accurate digital scans of teeth directly into milling systems
• The milling systems carve restorations out of ceramic or composite resin blocks without the need for a maxillary and mandibular model
• Another modified way is to scan the master models poured from elastic impressions digitally and to create stereolithic models on which the restorations are made.

Principles Behind 3d Surface Imaging

These devices contain a digital map of the surface of an object and collect data on its three dimensional size and shape which form a point cloud representing the 3D coordinates of the digitized surface.

Two types of 3D surface scanners are available:

Coordinated Measuring Machines (CMM) – in which a measuring probe moves over the surface to determine the coordinates of the points comprising the surface.

Non-contact scanners – A laser beam is incident on the surface to be scanned and a camera-like device, such as a charged coupled device or a position sensitive detector, records the location of the point at which the laser beam strikes the device.

Systems available

• CADENT iTero
• 3M ESPE Lava COS
• CEREC by Sirona
• E4D by D4D Technologies
• The Cadent and 3M ESPE machines produce models that are sent to the lab to produce the restoration of choice
• Sirona and D4D include milling units for immediate chair side fabrication of the final restoration.

CEREC AC can be used for fabrication of a model-only system by purchasing it without the milling center. It uses blue LED optical scanner and requires the use of powder.

E4D’s system includes the interoffice milling center to produce same-day single crowns using Culp’s database of dental anatomy. It uses a LASER scanner and does not require powder. Here scanning can be done intraorally, on the conventional impression or the poured model..

LAVA COS (chair side oral scanner) is a video format that uses the blue LED scanning system that requires powder. The downloaded scan information produces a model that allows for fabrication of any type of restoration.

iTero is an optically assisted laser scanner that does not require powder. This optics allows real time imaging, which produces a milled model allowing for fabrication of restorative needs.

Glidewell developed a scanning system that was introduced at the 2011 Chicago Midwinter Meeting. The system uses an optical scanning platform.

Comparison of digital impression and conventional impression

• Digital impression is more efficient than conventional impression.
• Overall treatment time is longer for conventional impression technique.
• Treatment comfort of the digital impression technique was higher.

Advancements in Articulators

• Virtual articulators by simulation of real patient data allows analyses with regard to static and dynamic occlusion as well as to jaw relation
• The virtual articulator requires digital 3D representations of the jaws and the specific data on jaw movements
• It then simulates jaw movements and provides a dynamic visualization of the occlusal contacts. They are of two types, completely adjustable and mathematically simulated.

Completely Adjustable Virtual Articulator

• Records/reproduces paths of the mandible using an electronic jaw registration system called jaw motion analyser
• The entire mandibular movements and their recorded paths can be viewed in the computer screen from different planes
• The software calculates and visualizes both static and kinematic occlusal collisions and is used in designing and correction of occlusal surfaces in computer-aided designing systems.

Eg. Kordass and Gartner virtual articulators.

Mathematically-simulated Virtual Articulator

• Records/reproduces movements of the articulator based on mathematical simulation of articulator movements
• These virtual articulators allow for additional settings, such as curved Bennett movement or other movements for adjustment in ideal settings.
• The main disadvantage is that it behaves as a mean value articulator and it is not possible to obtain individualized movement paths of each patient.

Eg. Stratos 200, Szentpetery’s virtual articulator.

Advantages of Digital Articulators over Mechanical Dental Articulator

• The main goal of the digital articulator is to improve the design of dental prosthesis, adding kinematic analysis to the design process
• Commonly used semiadjustable articulators, cannot represent the effects of resilience of the soft tissue or the time-dependent muscle-guided movement pattern of mastication
• Also they cannot represent the real dynamic condition of the occlusion in mouth.

Advancements in Shade Matching

The first shade guide was introduced in 1956 by Vita Zahnfabrik for the measurement of ceramic color systems.

The development from visual analysis to spectrophotometers was a milestone in shade matching.

Types of Spectrophotometeric Shade Guides

Easy shade standard

Easy shade compact

• The Vita easy shade is one of the latest spectrophotometers available for clinical use
• The instrument’s software gives absolute CIE lab* color values for natural teeth
• When assessing the color of a ceramic, the spectrophotometer provides the differences from color value presets in the instrument database (Figs 15 and 16)
• The easy shade compact introduced in 2009 was smaller, wireless and easier to handle
• The difference between the compact and standard was that the compact has a single spectrophotometer whereas standard has two
• The tip of the instrument is placed on the buccal surface of the tooth and the LCD screen at the base of the instrument displays the absolute CIElab* values of the tooth.

Advancements in Provisional Restoration Materials

A provisional prosthesis is prosthesis designed to enhance esthetics, provide stabilization and/or function for a limited period of time, and should be replaced by a definitive prosthesis after a period of time (G.P.T-8).

The materials commonly used are polymethylmethacrylate, polyethylmethacrylate, bisacryl composites, polyvinylmethyl methacrylate and visible light cured urethane dimethacrylate.

Advancements in Luting Agents

Temporary Cement

Luting the temporary/provisional/treatment restoration is done with a class of eugenol and eugenol-free cements.

Eugenol-free luting agents are Ora TempNE, Kavitan®CEM, Centrix access, TempSpan® Transparent,

TempSpan® CMT, Embonte, GC Fuji TEMP LT™—GC America

Integrity® TempGrip™ —Dentsply Caulk, RelyX™ Temp—3M ESPE.

OraTempNE

• Radioopaque eugenol free, self curing cement based on zinc oxide
• Working time 1–2 mins
• Setting time 3–4 mins.

Kavitan CEM

Gel-based consistency and extraordinary adhesion to tooth structure. Its the ideal material for cementing crowns and bridges, inlays and onlays onto a metal base.

• Optimal film thickness
• Excellent fixation consistency
• High compressive strength
• Low solubility and disintegration
• Anti-caries effect due to long-time fluoride release
• Optimal biocompatibility.

Centrix access

• A softer, semi-elastic set allows for easier removal and minimal clean up
• Eugenol-free temporary cement with calcium hydroxide
• Does not influence the setting of resin-based filling and luting materials
• Working time ≥ 2 minutes
• Setting Time (37°C) = 4 – 10 minutes.

TempSpan® Transparent

• Transparent—ideal for the highly esthetic anterior zone
• Ideal retention—securely retains provisional restorations and facilitates easy removal
• Non-eugenol—ensures compatibility with resin-based permanent cements
• Auto-mix delivery—provides accurate placement into the provisional with minimal waste
• Dual-Cure—offers ideal working time with on command cure.

TempSpan® CMT

Apart from the above properties it contains three desensitizers (potassium nitrate, sodium fluoride and calcium phosphate).

Embonte

ZOE-based used for temporary crowns, splints and for trial cementation of permanent restorations. Has a 30-second mix time and working time of 4 minutes at 72°F.

GC Fuji TEMP LT™—GC America 

• The first glass ionomer provisional and implant cement
• Provides versatility, reliability, durability and ease of use
• Greater fluoride release
• Excellent seal and low patient sensitivity
• Two minutes working time and one minute set time in the mouth
• Paste–paste automix syringe delivery system
• Smooth consistency and low film thickness.

Integrity® TempGrip™ —Dentsply Caulk

• Smooth seating from optimal flow
• Fast procedure with short set time
• Easy removal with cement that stays in crown—not on the tooth
• Reliable mixing with automix syringe delivery
• Reliable strength from high compressive and flexural strength and low film thickness.

Contains 2–9 g syringes and 20 mixing tips.

RelyX™ Temp—3M ESPE

Advantages

• Extremely low film thickness for use with precision fitting restorations
• High retention to tooth yet easy removal.

Advancements in Definitive Restorative Materials

Duceram LFC (‘hydrothermal low fusing ceramic)

• Composed of an amorphous glass containing hydroxyl ions
• Greater density, higher flexural strength, greater fracture resistance and lower hardness than feldspathic porcelain
• Due to the absence of leucite crystals, the hardness of the material and its ability to abrade the opposing natural tooth structure is claimed to be reduced
• Duceram LFC has two layers. A base layer leucite containing porcelain which is placed on a refractory die and then baked at 930°C
• The second layer, is applied over the base layer using powder slurry technique and baked at 660°C. This material is available in a variety of shades and can be characterized with surface stains and modifiers.

Uses

Ceramic inlays, veneers and full contour crowns.

Injection moulded glass ceramic/Leucite-reinforced hot pressed glass ceramic (Optec OPC)

• This system was first described by Wohlwend et al. and became available commercially as IPS Empress and Optec OPC
• It is a precerammed glass reinforced with leucite that prevents crack propagation without diminishing its translucency
• The available ingots are heated and injected under pressure and temperature into a mold created by the lost wax technique to produce a restoration
• Less susceptible to fatigue failure than conventional feldspathic porcelain but shows a lower compressive strength than metal ceramics or In-ceram restorations.

Advantages

• Lack of metal or opaque ceramic core
• Moderate flexural strength
• Excellent fit
• Excellent esthetics.

Disadvantages

• Potential to fracture in posterior areas
• Need for special equipment (pressing oven and die material).

Uses

Indicated for single anterior crowns, inlays, onlays and veneers.

Infilterable ceramic/High alumina ceramic (in Ceram)

• The fine grained alumina powder particles are mixed with water to form a suspension or slurry referred to as a ‘slip’ and painted onto an absorbent refractory die
• The die draws excess water from the slurry and forms a layer of solid alumina on the surface which is sintered at 1120°C for 10 hours to produce an opaque porous core
• In the second phase, glass infiltration material of appropriate shade is applied onto the core and fired at 1100°C for 3–5 hours
• This molten glass infiltrates into the residual pores by capillary action, and results in a dense composite structure which has 20 times the strength of the core material
• Its flexural strength is 450 MPa when compared to any other dental ceramic
• The core is then veneered with conventional dentin and enamel feldspathic porcelains
• A compositional analysis has revealed alumina to be 99.56 wt% and the infiltration glass to be lanthanum aluminosilicate with small amounts of sodium and calcium
• Lanthanum decreases the viscosity of the glass to assist infiltration and increases its index of refraction to improve the translucency of ceramic
• Disadvantage with high alumina ceramics is their high opacity, which limits their use to the construction of high strength substructures

Inceram spinel

Spinel is used instead of alumina which contains aluminum and magnesium oxide (MgAlP4) Because of the lower refractive index of spinel compared to alumina, the translucency of ceramic is improved but has low flexural strength. The fabrication process is similar to In-ceram.

Advancements in Permanent Luting Cement

The most recent development in the field of dental cements was the introduction of resin cements, they are Bis-GMA based resins which bond with micromechanical type of adhesion. Later systems bonded chemically to tooth structure, e.g. META.

Resin Cements

• Resin cements in combination with a dentin bonding agent, give superior bonding but due to concerns for postoperative sensitivity a total etch is still a concern as many bonding agents need a total etch
• A combination bonding agent that bonds to tooth structure and resin cement that adheres to the bonding agent and to silane-treated porcelain is also observed to give superior bonding properties.

Resin-modified Glass Ionomer (RMGI) cements

Uses – luting of crowns and bridges, inlay and onlay restorations. They are hybrid formulations of resin and glass ionomer components.

Disadvantages – Excess water sorption, ceramic fracture. E.g. RelyX Luting, RelyX Luting Plus (3M/ESPE), Fuji Plus (GC) and UltraCem RRGI Luting Cement.

Adhesive Resin Cements

They are self-adhesive giving good bonding. E.g: MaxCem (Kerr), RelyX Unicem (3M/ESPE).

Hybrid Acid-based CaAl/Glass Ionomer

• Is based on calcium aluminate/glass ionomer. E.g: Ceramir C and B (Doxa Dental AB, Uppsala, Sweden)
• Uses—is a new dental luting agent intended for permanent cementation of crowns and bridges, gold inlays and onlays, prefabricated metal, cast post and cores, all-zirconia or all alumina crowns
• The cement is a water-based hybrid composition comprising of calcium aluminate and glass ionomer and after setting (3–4 hours) it reaches a basic pH of ~8.5
• This basic PH makes it bioactive and it has unique properties, such as apatite formation and remineralization which develop quickly and continue to be active.

References

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• Kayser AF. Shortened dental arches and oral function.
• World Health Organization. Recent advances in oral health.Murdoch-Kinch CA, McLean ME. “Minimally invasive dentistry” JADA.
• Aboushelib MN, Kleverloan CJ, Feilzer AJ. Selective infiltration etching for a strong and a durable bonding with Zirconia based restorations.
• Goldman L, Hornby P, Meyer R, Goldman B. Impact of the laser on dental caries.
• Burkes EJ, Hoke J, Gomes E, Wolbarsht M. Wet versus dry enamel ablation by Er: YAG laser.
• Gimbel CB. Hard tissue laser procedures.
• DJP Evans “A clinical evaluation of an Erbium: Yag Laser for dental cavity preparation”.
• Livadits GJ. The matrix impression system for fixed prorthodontics.
• Conrad HJ, Wook-Jin Seong, et al. Current ceramic materials and systems with clinical recommendations: A systemic review.
• Lööf J, Svahn F, Jarmar T, Engqvist H, Pameijer CH. A comparative study of the bioactivity of three materials for dental applications, Dental Materials, vol. 24, no. 5. 2008; pp. 653-9.