Restorative dentistry Flashcards
2.1 a) What compounds are used for bleaching teeth?
i) Carbamide peroxide
ii) Hydrogen peroxide
iii) Sodium perborate
2.1 b) How do bleaches work to removed discolouration from teeth?
i) All bleaches form hydrogen peroxide, which is a powerful oxidising agent that breaks down into oxygen and free radicals. The molecules that discolour the teeth are broken down by the free radicals and oxygen and the resulting small molecules are lost from the tooth by diffusion.
2.1 c) What are the potential side effects of bleaching a tooth?
i) Sensitivity
ii) Shade regression
iii) Cervical resorption
iv) Irritation of the gingivae
2.1 d) What non-vital bleaching techniques are there? Please describe the key features of each.
1) Walking bleaching technique
2) Inside-outside technique
3) In-surgery technique
4) Individual tooth bleaching using trays
i) Walking bleaching technique:
(1) Gutta percha (GP) is removed from a satisfactorily root canal treated tooth to a level of 2-3mm below the epithelial attachment.
(2) The cut face of the root canal GP is seal with about 2-3mm of GIC. It is important to get the barrier at the correct level to ensure that the whole of the crown is bleached but to prevent material seeping through dentine below the epithelial attachment as cervical resorption could occur.
(3) The bleaching material is sealed in the cavity with a pledget of cotton wool and a temporary restoration placed. (some people etch cavity to open dentine tubules prior to bleaching, although this is not universally accepted.)
(4) The original technique used sodium perborate, although it is possible to use carbamide or hydrogen peroxide.
(5) The patient is review after 2-3 days and the procedure repeated until the desired colour is achieved.
ii) Inside-outside technique
(1) The first part of the technique is similar to the first two steps in the walking bleaching technique. (remove 2-3mm GP below epithelial attachment and place 2-3mm GIC as barrier)
(2) The access cavity is left open
(3) The patient applied bleaching solution into the access cavity and into a bleaching tray every 2 hours during the day time and also wear the bleaching tray overnight.
(4) The bleaching solution used is usually 10% carbamide peroxide.
(5) The advantages of this technique are that it allows the tooth to be bleached from both the internal and external aspects, but does require a very compliant and dextrous patient.
iii) In-surgery technique
(1) The tooth in question is isolated with rubber dam.
(2) The access cavity is opened.
(3) Hydrogen peroxide (up to 35%) is placed in the access cavity.
(4) Activated with light or laser to speed up the activation of free radicals.
iv) Individual tooth bleaching using trays.
(1) Bleaching agent is applied to a single tooth by using a tray which only has a space for the agent to cover the discoloured tooth.
(2) This may be combined with the walking bleach technique n order to speed up the bleaching process.
2.2 a) What is the difference between a craze, a crack and a fracture in a tooth?
i) Craze = an area of weakness in tooth structure where further propagation will result in a crack. They can be identified using fibre-optic illumination.
ii) Crack = definitive break in the continuity of tooth structure which begins in the enamel of the cementum, but no separation is evident. They can be seen with fibre-optic illumination, or in good clinical light.
iii) A fracture is when the tooth structure has separated into two or more distinct pieces and is visible clinically and often radiographically.
2.2 b) Describe the symptoms a patient may complain of if they have a cracked cusp/tooth.
i) Symptoms depend on the health of the pulp.
ii) Initially it will be sharp pain, usually from a posterior tooth, which occurs on biting, but the patient may notice that is worse when the bit is released (rebound pain). The pain is usually a short duration, and it may also be triggered by changes in temperature, e.g. cold.
iii) If it progresses to irreversible pulpitis the patient will have symptoms of irreversible pulpitis, i.e. continuous throbbing pain that is worse on lying down. Often poorly localised and may radiate along the jaw
2.2 c) What is the mechanism that causes the pain in cracked cusp/tooth?
i) Movement of the cracked pieces of tooth cause movement of fluid in the dentinal tubules, which stimulates A delta pain fibres.
2.2 d) What special test could you use to aid diagnosis of a cracked cusp/tooth and what would the test show?
i) Clinical examination of a dry tooth with a good light from different angles, and if necessary, using transillumination and magnification, will often show a crack.
ii) Place something (tooth sleuth, cotton wool, rubber dam, etc.) between each tooth and over individual cusps and get the patient to bit, which will cause the crack to open and elicit pain.
iii) The second test can also be carried out after placing methylene blue dye on the tooth, which will highlight the crack.
iv) Vitality tests show the tooth to be vital (provided the pulpitis is reversible).
v) Radiographs often do not show up small cracks.
e) How would you treat a tooth with a cracked cusp?
i) If the tooth had symptoms of irreversible pulpitis, a root canal treatment would be indicated, or extraction if the patient declines root canal treatment.
ii) Removal of the restoration and further investigation of the size of the crack; if it is extending into the pulp, root canal treatment will be required.
iii) A temporary measure may be required to allow the pulp to settle and the tooth to be reassessed. This may involve placement of an adhesive restoration such as composite resin, glass ionomer or a bonded amalgam. As a very temporary measure an orthodontic band around the tooth, or a copper ring, may be placed around the tooth.
iv) Long-term restoration will involve a full-coverage crown or partial coverage onlay or adhesive restoration to splint the remaining tooth structure.
2.3 a) When preparing a root canal both files and reamers may be used. What is the difference between these two types so instrument?
i) A file has much tighter spirals along its length and produces a cutting action when it is withdrawn from the root canal whereas a reamer has a looser spiral and is used by rotating and withdrawing.
2.3 b) What requirements should be met prior to obturating a root canal?
i) The root canal must be completely prepared and be dry and asymptomatic
2.3 c) If there is evidence of serous fluid seeping into the canal what does this suggest?
i) It suggests inflammation of the periapical tissues is present.
2.3 d) What features would an ideal root canal filling material have?
i) Non irritant to periapical/periradicular tissues.
ii) Easy to handle, insider into the root canal and remove if the root canal filling fails.
iii) Radiopaque, but should not stain the tooth tissue, or be visible through the coronal tooth tissue.
iv) Sterile
v) Bacteriostatic
vi) Provide a good seal to the root canal and be stable and not shrink, and be impervious to water or liquids.
2.3 f) How would you assess whether a root canal filing that you have done has been successful?
i) Patient history – absence of any reports of pain, swelling, discharge, mobility of the tooth.
ii) Clinical examination – functional tooth, integrity of the restoration in/on the tooth, absence of swelling, mobility, a sinus, tenderness to percussion, tenderness to palpation.
iii) Radiographic findings – good quality obturation to the appropriate length.
iv) Depending on the time since obturation there may still be a radiolucency that is present. However, if sufficient time has elapsed since the last appointment, then shrinkage or disappearance of the radiolucency.
2.4 a) What is the difference between reattachment and new attachment?
i) Reattachment = the reunion of the connective tissue to a root surface that has been separated by either incision or an injury.
ii) New attachment = union of connective tissue with a root surface that was previously pathogenically altered.
2.4 b) What is meant by the term guided tissue regeneration (GTR) and why is it desirable in periodontal healing?
i) Following periodontal treatment, it is hoped that a functional attachment with periodontal fibres embedded in bone at one end and cementum at the other will occur. However, the junctional epithelium has a large regenerative capacity and will grow down and cover exposed connective tissue creating a long epithelial attachment with the root if not excluded from the wound.
ii) Using a membrane, it is possible guide the tissue regeneration to prevent epithelial cells from gaining access to the root surface and also preventing gingival connective tissue from contacting the root surface. It also creates small space to allow stem cells from the periodontal ligament and alveolar bone to migrate, differentiate and hopefully repopulate the exposed root surface to form a new attachment.
2.4 c) What factors would be considered desirable when designing a material for guided tissue regeneration (GTR)?
i) Biocompatibility
ii) Easy of clinical use
iii) Impermeable to cells
iv) Able to maintain the space created
v) Tissue integration
2.4 d) What of the following material used in guided tissue regeneration (GTR) are resorbable and which are non-resorbable? (A. Collagen. B. Polylactic acid. C. Teflon (ePTFE) (expanded poly tetrafluoroethylene)
i) Collagen + Polylactic acid = resorbable
ii) Teflon (ePTFE) = non-resorbable.
2.5 a) What information can be determined from periodontal probing?
i) Pocket depth, i.e. distance from gingival margin to base of the gingival pocket.
ii) Presence of bleeding after probing.
iii) Attachment loss, distance in mm from the cementoenamel junction (CEJ) to the base of the gingival pocket.
2.5 b) What measurement gives the most accurate assessment with regards to periodontal destruction and why?
i) The measurement of attachment loss from the CEJ to the base of the pocket, as it gives a true idea of how much connective tissue attachment loss form the root surface there has been; also it is not influenced by false pocketing.
2.5 c) How must pressure should be applied on the probe when carrying out periodontal probing?
i) 0.25N
2.5 d) What factors may influence the results of periodontal probing?
i) Pressure applied to the probe and the angle the probe is inserted.
ii) Thickness of the probe.
iii) The contour of the tooth.
iv) The presence of calculus.
v) Inflammation of the gingival tissues.
vi) Position of the gingival margin.
vii) Patient tolerance.
2.5 e) Where on a tooth should you assess pocket depths?
i) Probe in six places – mesial, mid and distal on both the buccal and lingual aspects.
2.5 f) How would you assess the furcation area of a tooth with a periodontal probe?
i) Pass the probe horizontally between the roots to measure loss of periodontal support. Various classification systems are available, e.g. Hamp et al. Use Nabers probe.
(1) Degree 1 = loss of support less than one-third the bucco-lingual width of the tooth.
(2) Degree 2 = loss of support more than one-third the bucco-lingual width of the tooth but not encompassing the total width of the furcation area.
(3) Degree 3 = through and through defect.
2.6 a) What do you understand by the following terms? A) Biological width B) Attached gingivae C) Free gingivae
i) A) Biological width = Combined width of the attachment to the tooth from the most coronal aspect of the junctional epithelium to the most apical attachment of the gingival fibres at the level of the alveolar bone crest.
ii) B) Attached gingivae = Apical to the free gingivae is the attached gingivae, which extends from the free gingival groove to the mucogingival junction.
iii) C) Free gingivae = extends from the most coronal aspect of the gingival contour (free gingival margin) to the free gingival groove.
2.6 b) What is the function of gingival crevicular fluid?
i) It is an inflammatory exudate from the gingival crevicular tissues and forms part of the defence mechanism of the dento-gingival junction as it carries antimicrobial factors into the crevice.
- It is thought to wash debris such as dead epithelial cells and bacteria out of the crevice.
- It also carries polymorphonuclear leukocytes, macrophages, lysozyme and immunoglobulins into the gingival crevice, which have an antimicrobial affect.
2.6 c) Why might clinicians wish to sample it and what techniques are used to get such a sample?
i) There is a move to find diagnostic test for periodontal disease activity, and it is possible that the crevicular fluid may contain components that could be used as reliable biomarkers. Tools used would be microcapillary tubes, absorbent paper and gingival washing.
2.7 a) What is the difference between scaling and root surface instrumentation?
i) Scaling is the removal of deposits of plaque & calculus from a tooth surface whereas root surface instrumentation is the removal of subgingival deposits of plaque, calculus and necrotic cementum. Disrupt the subgingival biofilm so that the environment is more likely to promote healing.
2.7 b) Give a brief description of the following periodontal instruments and when you would choose to use them?
i) Scaler: Working end of a scaler in cross-section is an inverted triangle shape with two cutting edges superiorly and a blunt inferior edge. The tip of the scaler ends in a point. They tend to be used for removal of supragingival deposits or removing calculus that is located just below gingival margin.
ii) Curettes: They may be universal or site-specific (Gracey curettes). The working part of the instrument has a spoon-shaped blade with two curved cutting edges if universal or a single cutting edge if site-specific. A universal curette may be used throughout the whole mouth for the removal of supra- and sub-gingiva calculus. A whole set of site-specific curettes would be needed to access the whole mouth but they may be used for removal of supra- and subgingival calculus.
iii) Hoes: They have one cutting edge bevelled at 45 degrees to the shank and which is designed in four different positions to create instruments that can be used on the mesial, distal, buccal and lingual surfaces of teeth. They can be used on all tooth surfaces but are particularly good for sub-gingival scaling and root surface instrumentation.
2.7 c) What are the types of mechanical instruments used for periodontal treatment?
i) Ultrasonic = converts electric energy into high-frequency vibrations.
ii) Magnetostrictive = in these the pattern of vibration of the tip is elliptical and so all sides of the tip are active.
iii) Piezoelectric units = in this the pattern of vibration is back and forth so the two sides of the itp are active.
iv) Sonic handpieces = uses air pressure to cause vibrations but vibrates at a slower rate than an ultrasonic instrument.
v) Air abrasive systems – these appear to be more useful in removing surface stains than removing deposits of calculus.
2.8 a) Name five causes of intrinsic discoloration of vital teeth.
i) Trauma resulting in pulpal death
ii) Fluorosis
iii) Tetracycline staining
iv) Amelogenesis imperfecta
v) Dentinogenesis imperfecta
2.8 b) The appearance of discoloured teeth can be improved by methods which require tooth preparation and those that do not. Please name two of each.
i) Methods requiring preparation:
(1) Veneer
(2) Crown
ii) Methods not requiring preparation:
(1) Bleaching
(2) Microabrasion
(3) Composite veneers
c) How would you remove extrinsic staining from tooth surfaces.
i) Polishing the surface with pumice slurry and water or prophylaxis paste.
ii) Ultrasonic cleaners
iii) Bleaching.
2.9 a) What do you understand by the terms primary dentine, secondary dentine and tertiary dentine?
i) Primary dentine = formed before eruption or within 2-3 years after eruption and consists of mainly circumpulpal dentine. It also includes mantle dentine in the crown and the hyaline layer and granular layer in the root.
ii) Secondary dentine = regular dentine that is formed during the life of the tooth and laid down in the floor and ceilings of the pup chamber. It is a physiological type of dentine after the full length of root has formed.
iii) Tertiary dentine = divided into reparative and reactionary dentine, both of which are laid down in response to noxious stimuli. Reactionary dentine is laid down in response to mild stimuli whereas reparative dentine is laid down directly beneath the path of injured dentinal tubules as a response to stronger stimuli and are irregular.
2.9 b) What is the difference between internal and external resorption?
i) Internal resorption starts within the pulp chamber of a tooth.
ii) External resorption starts on the surface of a tooth, most commonly the root surface.
2.9 c) Are teeth with internal resorption likely to be vital or non-vital?
i) Internal resorption can only occur in vital teeth (or partially vital teeth).
2.9 d) Are teeth with external resorption likely to be vital or non-vital?
i) External resorption may occur in vital or non-vital teeth.
2.9 e) Replacement resorption may result in ankylosis? What are the signs of ankylosis?
i) Different sound from a normal tooth when it is percussed. Metallic sound.
ii) Lacks PDL space on radiograph
iii) Has no physiological mobility.
iv) May become infraoccluded as the jaw grows around it.
2.11 a) Name four general risk factors for periodontal disease (14)
i) Modifiable systemic:
(1) Smoking
(2) Diabetes
(3) Poor diet
(4) Certain medications
(5) Stress
(6) Nutrition
(7) Alcohol
(8) Obesity/overweight
ii) Non-modifiable factors:
(1) Genetics
(2) Age
(3) Socio-economic status
(4) Pregnancy
(5) Adolescence
(6) Leukaemia
2.11 b) Name two localised risk factors for periodontal disease. (8)
i) Acquired:
(1) Plaque & calculus
(2) Partial dentures
(3) Open contacts
(4) Overhanging & poorly contoured restorations
ii) Anatomical:
(1) Malpositioned teeth
(2) Furcations
(3) Root grooves & concavities
(4) Enamel pearls
2.11 c) Give two risk factors for gingival recession
i) Trauma – excessive toothbrushing, digging fingernails into gingivae, biting pencils.
ii) Traumatic incisor relationship
iii) Thin tissues
iv) Prominent roots.
a) How does fluoride affect teeth prior to eruption?
i) Teeth have more rounded cusps and shallower fissures.
ii) The crystal structure of the enamel is more regular and less acid soluble.
2.12 b) How does fluoride affect teeth after eruption?
i) Decreases acid production by plaque bacteria
ii) Prevents demineralisation and encourages remineralisation of early caries.
iii) Remineralised enamel is more resistant to further acid attacks.
iv) Thought to affect plaque and pellicle formation.
2.12 c) What are the possible consequences of fluoride overdose?
i) Dental effects – enamel fluorosis, mottling, pitting.
ii) Toxic effects – gastrointestinal
2.12 d) What is the recommended fluoride concentration in the water supply for optimal caries prevention?
i) 1ppm (in UK)
2.12 e) What do the following terms mean and at what dose do they occur for fluoride? I) safely tolerated dose II) potentially lethal dose III) certainly lethal dose
i) Safely tolerated dose – 1mg/kg body weight. This is the level below which symptoms of toxicity are unlikely to occur.
ii) Potentially lethal dose – 5mg/kg body weight. This is the lowest dose that has been associated with fatality.
iii) Certainly lethal dose – 32-64mg/kg body weight. At this dose survival of the individual is unlikely.
2.13 a) What is pulpitis?
i) Inflammation of the pulp.
2.13 b) What is reversible vs irreversible pulpitis?
i) Reversible pulpitis is a sharp pain, set off by hot/cold things and sweet things. It is poorly localised and lasts for several seconds. Irreversible pulpitis is a throbbing pain, set off by biting or spontaneously. It is well localised and lasts for hours.
2.13 c) What types of nerve fibres are there in the pulp?
i) A Beta fibres are large, fast conducting proprioceptive fibres.
ii) A Delta fibres are small sensory fibres.
iii) C fibres are small unmyelinated sensory fibres.
(1) Thermal changes in the oral environment cause rapid displacement of dentinal tubular contents, resulting in pain. This effect, known as the hydrodynamic effect, is the regulator of pain sensation in thermal-pulp testing. Hundreds of axons enter the tooth from the apical foramen to provide it with its sensory supply
(2) The A fibres are mainly stimulated by an application of cold, producing sharp pain, whereas stimulation of the C fibres produces a dull aching pain. Because of their location and arrangement, the C fibres are responsible for referred pain.
(3) Ninety percent of the A fibres are A-delta fibres, which are mainly located at the pulp– dentin border in the coronal portion of the pulp and concentrated in the pulp horns. The C fibres are located in the core of the pulp, or the pulp proper, and extend into the cell-free zone underneath the odontoblastic layer.
(4) The A-delta fibres have a small diameter and therefore a slower conduction velocity than other types of A fibres, but are faster than C fibres. The A fibres transmit pain directly to the thalamus, generating a fast, sharp pain that is easily localized. The C fibres are influenced by many modulating interneurons before reaching the thalamus, resulting in a slow pain, which is characterized as dull and aching.
(5) The A fibres respond to various stimuli such as probing, drilling and hypertonic solutions through the hydrodynamic effect. This effect depends on the movement of the dentinal fluid in the dentinal tubules in response to a stimulus.
(6) Although the normally slow capillary outward movement does not stimulate the nerve endings and cause pain, rapid fluid flow, as in the case of desiccating or drying dentin, is more intense and is likely to activate the pulpal nociceptors.
(7) Heat or cold stimuli cause fluid movement through the dentinal tubules, resulting in a painful sensation in a tooth with a viable sensory. This response is due to the rapid temperature change that causes a sudden fluid flow within the tubules and deforms the cell membranes of the free nerve endings. A gradual change in temperature, however, does not cause an immediate pain response because rapid fluid movement excites the A-delta fibres. The C fibres elicit a response to a gradual temperature change.
2.13 d) What special tests could you use to help diagnose reversible/irreversible pulpitis?
i) Percussion
ii) Vitality tests
iii) Radiographs
(1) Thermal pulp testing depends on the outward and inward movement of the dentinal fluid, whereas electric pulp testing depends on ionic movement.
(2) Because of their distribution, larger diameter than that of C fibres, their conduction speed and their myelin sheath, A-delta fibres are those stimulated in electric pulp testing.
(3) C fibres do not respond to electric pulp testing. Because of their high threshold, a stronger electric current is needed to stimulate them
(4) Based on the hydrodynamic effect, outward movement of dentinal fluid caused by the application of cold (contraction of fluid) produces a stronger response in A-delta fibres than inward movement of the fluid caused by the application of heat.
e) What treatment is available for a tooth with irreversible pulpitis?
i) Root canal treatment
ii) Extraction
2.14 a) Patients may have thermal sensitivity following the placement of a restoration. One theory for this is the thermal shock theory. However, another theory for the cause of thermal sensitivity is now more widely accepted – what is it called and what is it based on?
i) Theory of pulpal hydrodynamics
(1) Fluid can move along dentinal tubules and when there is a gap between the restoration and the dentine, fluid will slowly flow outwards. A decrease in temperature leads to sudden contraction in the is fluid, and consequently increased flow, which the patient will feel as pain.
2.14 b) How can restorative techniques limit thermal sensitivity?
i) When the thermal shock theory was widely accepted, insulating the cavity with a base material was used to prevent pain. Now that the hydrodynamic theory is more widely accepted the aim is to seal the dentine and increase the integrity of the interface between the dentine and the restorative material.
2.14 c) What are cavity sealers used for?
i) To prevent leakage at the interface of the restorative material and the cavity walls, and to provide a protective coating to the cavity walls.
2.14 d) Give the types of cavity sealers?
i) Varnishes (e.g. a synthetic resin-based material or a natural resin or gum)
ii) Adhesive sealers which also bond at the interface between the restorative material and cavity walls (e.g. glass ionomer luting cement)
2.14 e) What is meant by the term microleakage?
i) Microleakage is the passage of bacteria, fluids, molecules or ions along the interface of a dental restoration and the walls of the cavity preparation.
2.14 f) What are the consequences of microleakage?
i) Marginal discolouration of restorations.
ii) Secondary caries.
iii) Pulpal pathology.
2.15 a) You are cutting a cavity in a vital upper first permanent molar. You have removed all the caries but then you create a small exposure of the pulp. How would you proceed?
(1) If the tooth is not isolated already – isolate the tooth with a rubber dam.
(2) Dry the cavity
(3) Place calcium hydroxide over the exposure.
(4) Cover with cement/liner, e.g. glass ionomer
(5) Restore as normal.
(6) Inform the patient
(7) Arrange review.
2.15 b) What is this treatment called for treating a small exposure of the pulp of caries removal?
i) Direct pulp capping
2.15 c) What are you hoping will happen to the tooth by carrying out direct pulp capping?
i) A dentine bridge will form – tertiary dentine laid down.
ii) The pulp will remain vital.
2.15 d) When would direct pulp capping not be appropriate?
i) Non-vital tooth
ii) History of spontaneous pain – irreversible pulpitis
iii) Evidence of periapical pathology
iv) Large exposure
v) Contamination of the exposure with saliva, oral flora or bacteria from the caries.
2.15 e) What are the advantages of using rubber dam for dental treatment?
i) Isolation and moisture control – especially important for moisture sensitive techniques, e.g. acid etching before composite restoration
ii) Prevention of inhalation of small instruments e.g. during endodontic treatment.
iii) Improved access to the tooth/teeth – no soft tissues, e.g. tongue in the way
iv) Patients do not swallow water and other irrigants.
v) Soft tissues protected from potentially noxious materials, e.g. etchant.
2.16 a) What restorative material is capable of adhesion to the tooth tissue without surface pretreatment?
i) Glass ionomer
2.16 b) How may adhesion be improved for GIC?
i) Using a polyalkenoic acid conditioner.
2.16 c) How does GIC bond to tooth tissue?
i) Micromechanical interlocking – hybridisation of the hydroxyapatite-coated collagen fibril network.
ii) Chemical bonding – ionic bonds form between the carboxyl groups of the polyalkenoic acid and the calcium in the hydroxyapatite.
2.16 d) Besides the obvious advantage of being adherent, what other advantages are there of using GIC?
i) It releases fluoride.
ii) Quick to use as limited pretreatment of the tooth surface is needed.
2.16 e) In what clinical situations is GIC used?
i) As a permanent direct restorative material, suitable for deciduous and permanent teeth.
ii) As a temporary restoration.
iii) As a luting cement
iv) As a cavity lining or base.
v) As a core build-up material
vi) As a retrograde root filling material
vii) As a pit and fissure sealant.
2.17 a) What do you understand by the term ‘the smear layer’?
i) When tooth tissue is cut, the debris is smeared over the tooth surface. This is called the smear layer and it contains any debris produced by production of instrumentation of dentine, enamel or cementum. It is calcific in nature or a contaminant that precludes interaction of restorative materials with the underlying pure tooth tissue.
2.17 b) Dentine can be treated with acid (or conditioned). What does this achieve?
i) Within dentine, acid treatment removes most of the hydroxyapatite and exposes a microporous network of collagen. The smear layer is altered or dissolved. The bonding that results is diffusion based and relies on the exposed collagen fibril scaffold being infiltrated by the resin.
2.17 c) Why are primers needed during the process of creating an adhesive restoration?
i) The dentine surface after conditioning is difficult to wet with bonding agents. The primer increases the wettability of the surface which allows the resin to spread and penetrate the tubular dentine. This improves the bonding of the subsequently applied adhesive resin.
2.17 d) What do you understand by the term hybrid layer and where would you find it?
i) The hybrid layer is the area in which the resin of the adhesive system has interlocked with the collagen of the dentine, providing micromechanical retention.
2.17 e) What do dentine bonding agents do?
i) Form resin tags in the dentine tubules.
ii) Stabilises the hybrid layer.
iii) Form a link between the resin primer and the restorative material.
2.18 a) What are the aims of obturating a root canal?
i) To prevent reinfection of the cleaned canal.
ii) To prevent periradicular exudate from entering the root canal.
iii) To seal any remaining bacterial in the root canal.
2.18 b) Name three causes of intra-radicular failure of a root canal treatment.
i) Necrotic material left in the canal.
ii) Bacteria left in the root canal system (lateral or accessory canals).
iii) Contamination of the canal during treatment.
iv) Loss/lack of coronal seal.
v) Persistent infection after treatment.
2.18 c) Name two cause of extra-radicular failures of a root canal treatment.
i) Root fracture
ii) Radicular cysts.
2.18 d) What are the indications for an apicectomy (surgical endodontics)?
i) Infection due to a lesion that requires a biopsy, eg. Radicular cyst.
ii) Instrument stuck in canal with residual infection.
iii) Impossible to fill apical third of root due to anatomy or pulp calcification.
iv) Perforation of the root.
v) Post crown with excellent margins but persistent apical pathology.
vi) Infected, fractured apical third of root.
