Restorative dentistry Flashcards
(191 cards)
1
Q
2.1 a) What compounds are used for bleaching teeth?
A
i) Carbamide peroxide
ii) Hydrogen peroxide
iii) Sodium perborate
2
Q
2.1 b) How do bleaches work to removed discolouration from teeth?
A
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.
3
Q
2.1 c) What are the potential side effects of bleaching a tooth?
A
i) Sensitivity
ii) Shade regression
iii) Cervical resorption
iv) Irritation of the gingivae
4
Q
2.1 d) What non-vital bleaching techniques are there? Please describe the key features of each.
A
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.
5
Q
2.2 a) What is the difference between a craze, a crack and a fracture in a tooth?
A
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.
6
Q
2.2 b) Describe the symptoms a patient may complain of if they have a cracked cusp/tooth.
A
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
7
Q
2.2 c) What is the mechanism that causes the pain in cracked cusp/tooth?
A
i) Movement of the cracked pieces of tooth cause movement of fluid in the dentinal tubules, which stimulates A delta pain fibres.
8
Q
2.2 d) What special test could you use to aid diagnosis of a cracked cusp/tooth and what would the test show?
A
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.
9
Q
e) How would you treat a tooth with a cracked cusp?
A
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.
10
Q
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?
A
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.
11
Q
2.3 b) What requirements should be met prior to obturating a root canal?
A
i) The root canal must be completely prepared and be dry and asymptomatic
12
Q
2.3 c) If there is evidence of serous fluid seeping into the canal what does this suggest?
A
i) It suggests inflammation of the periapical tissues is present.
13
Q
2.3 d) What features would an ideal root canal filling material have?
A
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.
14
Q
2.3 f) How would you assess whether a root canal filing that you have done has been successful?
A
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.
15
Q
2.4 a) What is the difference between reattachment and new attachment?
A
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.
16
Q
2.4 b) What is meant by the term guided tissue regeneration (GTR) and why is it desirable in periodontal healing?
A
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.
17
Q
2.4 c) What factors would be considered desirable when designing a material for guided tissue regeneration (GTR)?
A
i) Biocompatibility
ii) Easy of clinical use
iii) Impermeable to cells
iv) Able to maintain the space created
v) Tissue integration
18
Q
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)
A
i) Collagen + Polylactic acid = resorbable
ii) Teflon (ePTFE) = non-resorbable.
19
Q
2.5 a) What information can be determined from periodontal probing?
A
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.
20
Q
2.5 b) What measurement gives the most accurate assessment with regards to periodontal destruction and why?
A
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.
21
Q
2.5 c) How must pressure should be applied on the probe when carrying out periodontal probing?
A
i) 0.25N
22
Q
2.5 d) What factors may influence the results of periodontal probing?
A
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.
23
Q
2.5 e) Where on a tooth should you assess pocket depths?
A
i) Probe in six places – mesial, mid and distal on both the buccal and lingual aspects.
24
Q
2.5 f) How would you assess the furcation area of a tooth with a periodontal probe?
A
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.
25
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.
26
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.
27
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.
28
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.
29
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.
30
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.
31
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
32
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
33
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.
34
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.
35
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.
36
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).
37
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.
38
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.
39
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
40
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
41
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.
42
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.
43
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.
44
2.12 c) What are the possible consequences of fluoride overdose?
i) Dental effects – enamel fluorosis, mottling, pitting.
ii) Toxic effects – gastrointestinal
45
2.12 d) What is the recommended fluoride concentration in the water supply for optimal caries prevention?
i) 1ppm (in UK)
46
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.
47
2.13 a) What is pulpitis?
i) Inflammation of the pulp.
48
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.
49
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.
50
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.
51
e) What treatment is available for a tooth with irreversible pulpitis?
i) Root canal treatment
ii) Extraction
52
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.
53
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.
54
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.
55
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)
56
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.
57
2.14 f) What are the consequences of microleakage?
i) Marginal discolouration of restorations.
ii) Secondary caries.
iii) Pulpal pathology.
58
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.
59
2.15 b) What is this treatment called for treating a small exposure of the pulp of caries removal?
i) Direct pulp capping
60
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.
61
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.
62
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.
63
2.16 a) What restorative material is capable of adhesion to the tooth tissue without surface pretreatment?
i) Glass ionomer
64
2.16 b) How may adhesion be improved for GIC?
i) Using a polyalkenoic acid conditioner.
65
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.
66
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.
67
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.
68
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.
69
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.
70
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.
71
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.
72
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.
73
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.
74
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.
75
2.18 c) Name two cause of extra-radicular failures of a root canal treatment.
i) Root fracture
ii) Radicular cysts.
76
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.
77
2.19 a) What is acid etching of enamel?
i) Application of a mild acid to the surface of enamel results in dissolution of about 10um of the surface of organic component, leaving a microporous surface layer up to 50um deep. The surface is thus pitted, and he unfilled resin of the restorative material is able to flow into the irregularities to form resin tags that provide micromechanical retention.
78
2.19 b) What acid is commonly used in etch and at what strength?
i) 30-40% phosphoric acid is commonly used.
ii) Etchants come as gel or liquid, however, in the newer systems the etchant is combined with dentine conditioner.
79
2.19 c) How long should the acid etch be applied for?
i) Usually 15 seconds.
80
2.19 d) What do you do after applying the etchant for the above length of time?
i) Wash away the etchant with water for at least 15 seconds.
81
2.19 e) What is likely to damage the etched enamel surface and reduce the efficacy of bonding?
i) Blood and saliva, and mechanical damage may occur by probing the area, rubbing cotton wool over it to dry it or by scraping across the surface with the suction tip or an instrument.
82
2.19 f) What do you understand by the term ‘total etch technique’ (or etch and rinse) and which acid would you use for it?
i) Using an acid to etch the enamel and condition the dentine at the same time. Commonly used acids include phosphoric acid (10-40%), nitric acid, oxalic acid and citric acid.
83
2.21 a) Name three agents that are used for chemical plaque control and state how they are thought to work?
i) 0.12% chlorhexidine digluconate
(1) Bacteriostatic at low doses and bacteriocidal at high concentrations.
(2) Bacterial cell walls are negatively charged due to the phosphate and carboxyl groups, but chlorhexidine is positively charged. Electrostatic charges cause the chlorhexidine to bind to the bacterial cell wall affecting the osmotic barrier and interfering with transport across the membrane.
(3) Unwanted affects are staining of teeth and altered taste.
ii) Quaternary ammonium compounds
(1) Cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride.
(2) Net positive charge reacts with the negatively charged bacterial cell walls, causing disruption of the cell wall, increase in permeability and loss of cell contents.
iii) Pyrimidine derivatives
(1) Hexetidine.
(2) Antibacterial and antifungal activity, affecting the rate of ATP synthesis in bacterial mitochondria.
iv) Phenols
(1) Antibacterial agents that penetrate the lipid components of bacterial cell walls.
(2) Anti-inflammatory action as they inhibit neutrophil chemotaxis.
(3) Examples are thymol (Listerine), bisphenol (triclosan)
v) Sanguinarine
(1) Benzophenathridine alkaloid and has antibacterial properties as it causes suppression of intracellular enzymes.
84
2.21 b) Some antimicrobials (antibiotics) have been formulated in such a way that they are suitable for use within a periodontal pocket. Give four advantages of administering a drug in this manner and name one such antimicrobial.
i) Drug is actually delivered to where it is needed, not through the whole body.
ii) High local drug concentrations can be achieved
iii) Fewer systemic side effects
iv) Overall lower doses of the drug need to be administered
v) Drug delivery is not dependent on patient compliance
vi) Prolonged drug release
vii) Examples: antimicrobials, tetracycline, metronidazole.
85
2.23 a) What are the risk factors for developing root caries?
i) Exposure of the root surface (pocketing, gingival recession or attachment loss)
ii) Cariogenic diet
iii) Decreased salivary flow (medications, previous radiotherapy, drugs, diabetes, aging)
iv) Poor oral hygiene – inaccessible areas (e.g. periodontal pockets); decreased manual dexterity; lack of access to dental healthcare or dental health is a low priority; removable prosthesis; restorations.
86
2.23 b) How would you manage a patient with multiple root caries?
i) Elimination of active infection (remove caries and place restorations, and preventive measures:
(1) Identify any risk factors that can be corrected.
(2) Oral hygiene advice
(3) Dietary analysis and advise
(4) Periodontal treatment as necessary
(5) Fluoride treatment in the surgery (e.g. Duraphat application) or home application (e.g. rinses)
(6) Recall
87
2.23 c) What restorative materials are commonly used for Class V lesions?
i) Glass ionomer, resin modified glass ionomer, composite, and amalgam.
88
2.24 a) Nowadays it is possible to bond amalgam to tooth structure. Give 4 potential advantages of this over non-bonded restorations of amalgam.
i) Decrease in microleakage – less destructive of tooth tissue as traditional methods of creating retention for restorations involve removing tooth tissue to create dovetails, undercuts and grooves, etc.
ii) May limit the need for dentine pins
iii) May increase fracture resistance of restored teeth
iv) Transmits and distributes forces better
v) There may be less postoperative sensitivity due to better sealing of the margins.
89
2.24 b) What other restorative materials can be bonded to tooth tissue?
i) Glass ionomers
ii) Composites
iii) Hybrid restorative materials, e.g. resin-modified glass ionomers, composers
iv) Ceramics – using special cements.
90
c) If you wanted to bond materials that are commonly used for anterior crowns how would they be pre-treated?
i) Conventional ceramics that are silica based are treated with hydrofluoric acid and ammonium bifluoride. They may also be sandblasted or air abraded. They are often treated with silane coupling agents.
ii) Alumina and zirconium oxide ceramics are surface roughened with air abrasion and then the surface is coated with a silicate.
91
2.25 a) What materials are commonly used for primary impressions for complete dentures?
i) Alginate
ii) Compound - thermoplastic
iii) Impression putty
92
2.25 b) What broad groups can hydrocolloid impression materials and synthetic elastomeric impression materials be divided into?
i) Hydrocolloids can be divided into: reversible (agar) and irreversible (alginate).
ii) Synthetic elastomeric impression materials can be divided into: Elastomers, Polysulfides, Polyethers and Silicone (addition cured/condensation cured).
93
2.25 c) What do you understand by the following terms. Give one disadvantage of each. A) Mucostatic impression B) Mucocompressive impression
i) Mucostatic = an impression taken with the mucosa in its resting state. It provides a good fit at rest and therefore good retention, i.e. most of the time but when the patient chews the denture will tend to rock around the most incompressible area, e.g. palatine torus.
ii) Mucocompressive = an impression taken when the denture-bearing area is subjected to compressive force. This results in a denture that is maximally stable during function but not at rest.
94
2.25 d) What do you understand by the term selective mucocompressive impression?
i) This is an impression taken with only certain areas of the denture-bearing area being subjected to the compressive force.
95
2.26 a) What is meant by the term RVD and OVD and what is their significance?
i) RVD is resting vertical dimension. It is a measure of the vertical height of the patient’s lower face and is measured as the distance between two arbitrary points – one related the maxilla and the other to the mandible with the patients at rest.
ii) OVD is the occlusal vertical dimension. It is a similar measure to that mentioned above, but is taken with the patient’s teeth in occlusion. The difference between the two measurements gives the freeway space, which is the vertical gap between the patient’s teeth at rest.
96
2.26 b) Name one way of measuring the RVD or the OVD.
i) Willis gauge to measure between two points on the face (e.g. nose and chin)
ii) Swallowing is thought to show the rest vertical dimension. MMM. Slowly blow out.
97
2.26 c) In which patients is it important to measure the OVD?
i) Those patients with partial dentures and no natural teeth occluding, and in patients with complete dentures when changing the OVD of a worn dentition.
98
2.26 d) What factors may affect the jaw position at rest?
i) Stress
ii) Head posture
iii) Pain
iv) Age
v) Neuromuscular disorders
vi) Bruxism
99
2.27 a) What do you understand by the following terms: A) Group function B) Canine guidance C) Balanced occlusion?
i) Group function = during lateral excursions there is contact between several upper and lower teeth on the working side and no contacts on the non-working side.
ii) Canine guidance = during lateral excursions there is contact between upper and lower canine teeth on the working side only and no contact on the non-working side.
iii) Balance occlusion = simultaneous contacts between opposing artificial teeth on both sides of the dental arch.
100
2.27 b) Which would you try to create in a complete denture case?
i) Balanced occlusion
101
2.27 c) What is the difference between balanced occlusion and balanced articulation?
i) Balanced articulation is simultaneous contact of opposing teeth in central and eccentric positions as the mandible moves, i.e. it is a dynamic relationship whereas balanced occlusion is a static situation.
102
2.27 d) When trying to achieve the correct occlusion in a complete denture case what factors will affect the occlusion in protrusive movements?
i) Incisor guidance angle
ii) Cusp angles of the posterior teeth
iii) Condylar guidance angles
iv) Orientation of the occlusal plane
v) Prominence of the compensating curve
103
2.27 e) What do you understand by the term lateral compensating curve and how does it affect the set up of complete denture teeth?
i) During lateral excursions the mandible does not move in a horizontal plane only. There are vertical components to the movement due to the condylar guidance angle and the incisor guidance angle. To achieve occlusion in lateral excursions when the mandible and lower denture carry out these tipping movements the upper teeth need to be inclined buccally so that the occlusal plane of the teeth lie on a curve (viewed in the coronal plane). This is analogous to the Monson curve in the natural dentition.
104
2.28 a) Give three advantages and three disadvantage of an immediate denture.
i) Advantages:
(1) Patient is never without teeth and so there are psychological advantages.
(2) Aesthetics – patient is never without teeth.
(3) Artificial teeth can be set in the same position as the natural ones.
(4) Soft tissue support.
(5) Easier to register jaw relations as they are taken when the patient had teeth.
(6) Bleeding easier to control after extractions.
ii) Disadvantages:
(1) Denture may not fit after extraction.
(2) Will need relining/copying or remaking.
(3) Will not fit when the alveolus remodels.
(4) Unable to try-in
(5) May need many visits for adjustment.
105
2.28 b) What do the terms flanged and open face mean with respect to an immediate upper complete denture? Give an advantage and disadvantage of each.
i) Flanged means that the denture has a flanged periphery, like normal complete denture.
(1) Advantage is that retention is good and will make future adjustments easier.
(2) Disadvantage is that the lip may be over supported/appear too bulbous.
ii) Open faced means that there is no buccal flange and the denture teeth sit at the edge of the extraction sockets of the natural teeth.
(1) Advantage is that it can be used when there are large undercuts, it often has good aesthetics initially.
(2) Disadvantages are retention is poor and when resorption occurs a gap appears between the gingival margin of the denture teeth and the mucosa.
106
2.28 c) If you wanted to adjust the fit of an immediate denture in the future, what methods can you use?
i) Relining
ii) Rebasing
iii) Copy dentures
iv) Total remake
107
2.30 a) What is a dental surveyor and what is the objective of surveying the diagnostic cast?
i) A dental surveyor is an instrument that is used to determine the relative parallelism of two or more surfaces of the teeth or other parts of the cast of a dental arch. The objectives of surveying the diagnostic cast are to identify:
(1) The most desirable path of insertion that will eliminate or minimise interference to placement and removal.
(2) Tooth and tissue undercuts.
(3) Tooth surfaces that are, or need to be parallel so that they act as guide places during insertion and removal.
(4) And measure areas of teeth that may be used for retention.
(5) Whether tooth and bony areas of interference need to be eliminated surgically by selecting different paths of insertion.
(6) Undesirable tooth undercut that needs to be avoided, blocked out or eliminated.
(7) Potential sites for occlusal rests and where they need to be prepared.
108
2.30 b) What is a dental articulator?
i) It is an instrument that is used to reproduce jaw relationships and movements of the lower jaw relative to the upper. Casts of both upper and lower jaws are mounted on the articulator.
109
2.30 c) How would you classify articulators?
i) Hinge articulator
ii) Average value articulator
iii) Adjustable articulator – simple adjustable; fully adjustable
110
2.30 d) What is a facebow and what is it used for?
i) A facebow is an instrument that measures the relationship of either the maxillary or mandibular arch to the intercondylar axis and is used to transfer these measurements to an articulator. This means that the articulated casts will have the same relationship to the hinge axis of the articulator as the teeth and the intercondylar axis.
111
2.31 a) Name five muscles whose movements may affect the peripheral flanges of a complete denture.
i) Geniohyoid
ii) Orbicularis oris
iii) Mentalis
iv) Mylohyoid
v) Buccinator
vi) Palatopharyngeus
vii) Palatoglossus
112
2.31 b) Where is the posterior margin of an upper complete denture usually situated? A) Anterior to the fovea palatine B) Posterior to the fovea palatine
i) Anterior to the fovea palatinae
113
2.31 c) What is a post-dam and what function does it perform?
i) A post-dam is a raised lip on the posterior border of the fit surface of an upper complete denture. It compresses the palatal soft tissue to form a border seal.
114
2.31 d) Where is the post dam usually positioned?
i) It usually lies at the junction of the non-moveable hard palate (anteriorly) and the moveable soft palate (posteriorly).
115
2.31 e) What do you understand by the term ‘neutral zone’?
i) The area between the tongue, lips and cheeks where the displacing forces of the muscles is minimal. It is the ideal area into which a prosthesis should be placed to minimise displacing forces.
116
2.32 a) What is the Kennedy classification for partially edentulous arches?
i) Class I = bilateral free end saddles
ii) Class II = unilateral free end saddle
iii) Class III = posterior bounded saddle
iv) Class IV = single anterior bounded saddle that crosses the midline (no mods)
v) Number of additional edentulous gap is indicated by a modification number.
117
2.32 b) What Kennedy classification does this charting fit into?
4321I123
54321I12347
i) Upper = Kennedy Class I
ii) Lower = Kennedy Class II modification 1
118
2.32 c) What are the stages in designing a partial dentures?
i) Saddles, support, direct retention, indirect retention, minor + major connector
(1) Outline saddle areas and decide which teeth to be replaced
(2) Place occlusal rest seats
(3) Place clasps for direct retention – remember reciprocating arms
(4) Place the indirect retainers
(5) Connect the denture
119
2.32 d) What is meant by the term direct retainer in a partial denture?
i) Any element of a partial denture that provides resistance to movement of denture away from supporting tissues.
120
2.32 e) Name the two broad classes of clasps.
i) Gingivally approaching clasps for premolars and anteriors.
ii) Occlusally approaching clasps for molars.
121
2.32 f) Clasps do not work in isolation, but are often termed as being a clasp unit. What else is incorporated into a clasp unit?
i) Clasp, rests, reciprocating arm, minor connector.
122
2.32 g) Why are these other features needed? (clasp unit)
i) Occlusal support/Rests will allow loads to be transferred along the long axis of the teeth. It will also enable to clasp arm to be accurately located in the undercut on the tooth and prevents movement of denture into soft tissues.
ii) Reciprocation is needed as all clasps on teeth must be balanced by something on the opposite surface to act as a balance. This will prevent inadvertent force being applied to a tooth in one direction only and acting like an orthodontic appliance. Reciprocating arm opposes the forces of the clasps to prevent orthodontic movement.
iii) Minor connector – connects all components to major connector.
123
2.33 a) Copy dentures are sometimes indicated for patients. In what situations would these be made?
i) Occlusal wear on a set of previously successful complete dentures.
ii) Need for replacement of the denture base material.
iii) Patient was initially given immediate dentures and they need to be replaced.
iv) Patient has a set of complete dentures that they have been happy with but are now unretentive/worn, especially elderly patients who may find it hard to adapt to a completely new set of dentures.
v) To make a spare set of dentures.
vi) If a patient has had problems with previous dentures it is advisable to copy the set that they like the most.
124
2.33 b) What are the advantages of making a set of copy dentures?
i) Simple clinical steps, quicker than starting from scratch.
ii) Reduced number of laboratory steps; no special trays needed; no record blocks needed.
iii) Patient is never without their denture
iv) Original dentures are not altered in any way
v) More predictable patient acceptance.
125
2.33 c) Briefly describe the stages in making a set of copy dentures.
i) Steps for making copy dentures (one method – others are available):
(1) Alginate impressions are taken of the dentures in boxes.
(2) The dentures are given back to the patient.
(3) In the lab the alginate moulds are poured up in self-curing acrylic bases.
(4) The copy dentures are now assessed and adjusted as necessary by the clinician and tried in the patient’s mouth and used to take an occlusal record.
(5) These are sent to the laboratory and articulated, and then denture teeth are set up.
(6) Copy dentures are used as special trays and impressions are taken of the fit surface.
(7) In the laboratory the copy dentures are converted into heat-cured acrylic dentures.
126
2.34 a) Fill in the blanks. ..A... is tooth surface loss from non-bacterial …B… attack. Smooth …C… surfaces are seen with restorations standing …D… . Tooth surface loss of the …E… surfaces of the …F… incisors is seen in cases of gastric reflux and vomiting. …G… is physical wear of a tooth by an external agent and may result in …H… cavities at the …I… . …J… is physical wear of a tooth by another tooth, and is commonly affects …K… and …L… surfaces. Abfraction lesions are thought to be due to a combination of …M… and occlusally-induced tooth …N… .
(a) Erosion
(b) Chemical
(c) Plaque-free
(d) Proud
(e) Palatal
(f) Upper
(g) Abrasion
(h) Class V
(i) Gingival margins
(j) Attrition
(k) Occlusal
(l) Interproximal
(m) Abrasion
(n) Flexure
127
2.34 b) What could be the cause of severe erosion in a 16-year-old girl?
i) Vomiting - Anorexia nervosa, bulimia nervosa
ii) GORD, gastric reflux
iii) Pregnancy
iv) Diet – excessive fizzy drink consumption.
128
2.34 c) What specialist treatment should she receive? (suspect bulimia nervosa)
i) If suspect bulimia nervosa then that is outside the scope of management for a dental practitioner. She needs to be referred to her general medical practitioner for further assessment and possible referral to a psychiatrist.
129
2.35 b) How can you determine the working length of a root canal?
i) Apex locator
ii) Working length radiograph with an instrument in the canal (at least K15)
130
3.35 c) What do you understand by the terms zip, elbow and transportation with respect to preparation of root canals?
i) Zip and elbow are phenomena that occur due to instruments trying to straighten out within a root canal. An hourglass shape is created with the narrowest part being called the elbow and the zip being the flared apical part. The problem with this type of canal shape is that it is difficult to fill the apical portion well.
ii) Transportation is the selective removal of dentine from one area of the root canal. This is done electively, for example when widening the coronal part of a root canal, or can be iatrogenic error.
131
2.36 a) What are the advantages of using a crown down method for preparation of a root canal?
i) Preparing the canal from the crown down gives better access.
ii) Flaring of the coronal part first removes restrictions and help prevent instruments binding short of the working length.
iii) The coronal part is usually where most of the infected material is present. If this is removed and cleaned first it limits the possibility of spreading the infected material to the apical and periapical tissues.
iv) If you estimate the working length and then change the coronal part of the preparation it may inadvertently alter the length.
v) Coronal preparation first allows irrigants to gain access to more of the root canal system.
132
2.36 b) Why are root canals irrigated during preparation for root canal fillings?
i) Physical removal of dentine by instruments does not get rid of all the bacteria in the root canal system. Irrigants reach the areas instruments cannot, and remove bacteria that would otherwise be inaccessible.
133
2.36 c) Name two commonly used irrigants.
i) Sodium hypochlorite
ii) EDTA (ethylene diamine tetra acetic acid)
iii) Local anaesthetic solution
iv) Chlorhexidine
v) Iodine-based irrigant
vi) Citric acid
134
2.36 d) Give five properties of an ideal root canal filling material.
i) It must be capable of sealing the canal apically, laterally and coronally.
ii) It should be radiopaque
iii) It should be bacteriostatic
iv) It should not irritate periradicular tissues
v) It should be easy to handle, insert and if needed remove
vi) It should be impervious to moisture
vii) It should be dimensionally stable.
135
2.37 a) What is an overdenture and how does it differ from an onlay denture?
i) An overdenture is a denture which derives its support from one or more abutment teeth by completely covering them beneath its fitting surface.
ii) An onlay denture is a partial denture that overlays the occlusal surface of all or some of the teeth. It is often used to increase the occlusal vertical dimension.
136
2.37 b) Give four advantages of an overdenture.
i) Preservation of the alveolar bone around the retained roots – preserve bony width, height and contour.
ii) Improved stability, retention and support.
iii) Preserved proprioception.
iv) Decreased crown-root ratio which reduces damaging lateral forces and reduces mobility in teeth with reduced periodontal support.
v) Increased masticatory force
vi) Psychological benefit of not losing all teeth.
137
2.37 c) In what groups of patients would overdentures be useful?
i) Severe tooth wear
ii) Patients with hypodontia
iii) Cleft lip and palate patients
iv) Motivated patients with good oral hygiene.
138
2.37 d) What factors need to be considered in choosing and preparing the abutment teeth? (overdentures)
i) The abutment should ideally be bilateral and symmetrical with a minimum of one tooth space between them.
ii) Order of preference: canine, molars, premolars, incisors.
iii) Healthy attached gingivae and periodontal support, minimal mobility.
iv) Dome root surface 2-4mm above gingival margin.
v) Root canal treatment may be required.
139
2.38 a) What is the definition of osseointegration?
i) A direct structural and functional union between ordered living bone and the surface of a load-carrying implant (Alberktsson et al 1981)
140
2.38 b) Give three situations when implants may be used in the head and neck.
i) Single tooth replacement
ii) Bridge abutment
iii) Support for overdentures
iv) To support facial prosthesis and hearing aids
v) Orthodontic anchorage
141
2.38 c) Give three patient-related factors that may affect the success of implant placement
i) Oral hygiene
ii) Periodontal assessment
iii) Previous radiotherapy
iv) Smoking
v) Bisphosphonate medication usage
142
2.38 d) What anatomical factors need to be considered with regard to implant placement?
i) Bone height
ii) Bone width
iii) Bone density or quality
iv) Proximity to inferior dental nerve
v) Proximity to maxillary sinus
vi) Tooth position
143
2.38 e) What would you see clinically if an implant failed?
(1) Mobility
(2) Pain
(3) Ongoing marginal bone loss
(4) Soft tissue infection
(5) Peri-implantitis
144
2.38 f) Success rate for single implants are …A… than in edentulous patients. Success rate for implants in partially dentate patients are …B… than in edentulous patients.
i) A) better
ii) B) better
145
2.39 a) What are the constituents of dental amalgam?
i) Silver
ii) Tin
iii) Copper
iv) Zinc
v) Mercury
146
2.39 b) What are the gamma, gamma 1 and gamma 2 phases, and what is the importance of these different phases?
i) Gamma (y) phase is Ag3Sn
ii) Gamma 1 phase is Ag2Hg3
iii) Gamma 2 phase is Sn7Hg
iv) Gamma 2 is the weakest part of amalgam – it has the lowest tensile strength and is the softest of the phases. If amount of gamma 2 phase can be limited in the final dental amalgam the resulting amalgam will be stronger.
147
2.39 c) What is the setting reaction of dental amalgam?
i) Ag3Sn + Hg -> Ag3Sn + Ag2Hg3 + Sn7Hg
==> (y + mercury -> y + y1 + y2)
iii) This is followed by y2 + AgCu -> Cu6Sn5 + y1: leaving little or no y2
148
2.39 d) What do you understand by the terms lathe cut particles and spherical particles? What is the significance of the different types?
i) Lathe cut alloy is made by chipping of pieces form a solid ingot of the alloy. This results in particles of different shapes and sizes.
ii) Spherical particles are made by melting the ingredients of the alloy together and spraying them into an inert atmosphere. The droplets then solidify into spherical pellets that are regular in shape and can be more closely packed together. This results in amalgam that requires less condensation force and results in increased strength of amalgam.
149
2.39 e) Why is it more common practice to overfill a cavity and then carve it down?
i) When amalgam is condensed the mercury rises to the surface of the restoration. To try and minimise the residual mercury left in the restoration it is usually to overfill the preparation and the excess mercury-rich amalgam can be carved away leaving the lower mercury containing amalgam which has a greater strength and better longevity.
150
2.39 f) How should you store waste amalgam?
i) In a sealed container under liquid, usually x-ray fixative, solution.
151
2.40 a) What are dental ceramics made out of?
i) Feldspar, silica (quartz) and kaolin
152
2.40 b) What are the three technical stages in producing a porcelain jacket crown?
i) First stage is compaction. The powder is missed with water and applied the die so as to remove as much water as possible and compact the material such that there is a high dentistry of particles, which minimises firing shrinkage.
ii) Next stage is firing. Crown in heated in a furnace to allow the molten glass to flow between the powder particles and fill the voids.
iii) Last stage is glazing: which is done to produce a smooth and impervious outer layer.
153
2.40 c) Give one advantage and disadvantage of porcelain jacket crowns.
i) Advantages:
(1) Excellent aesthetics
(2) Low thermal conductivity
(3) High resistance to wear
(4) Glazed surface resists plaque accumulation
ii) Disadvantages:
(1) Poor strength and very brittle, so often fracture
(2) Firing shrinkage so must be overbuilt
154
2.40 d) How has the main disadvantage of porcelain jacket crowns been overcome?
i) By fusing the porcelain to medal to produce a metal ceramic restoration; by making reinforced ceramic core systems; and by creating resin-bonded ceramics.
155
2.40 e) What does CAD-CAM mean in connection with ceramic restorations?
i) Computer assisted/aided design/manufacture.
156
2.40 f) Give three requirements of a metal-ceramic alloy.
i) High bone strength to the ceramic
ii) No adverse reaction with the ceramic
iii) Melting temperature must be greater than the firing temperature of the ceramic
iv) Accurate fit
v) Biocompatible
vi) No corrosion
vii) Easy to use and cast
viii) High elastic modulus
ix) Low cost
157
2.41 a) What are the uses of dental cements? (3)
i) Luting agents.
ii) Cavity lining and bases.
iii) Temporary restorations.
158
2.41 b) Give two examples of the types of material used for each purpose.
i) Luting agents – modified zinc phosphate, zinc oxide and eugenol, zinc polycarboxylate, glass ionomer, resin modified glass ionomer, compomers, resin cements.
ii) Cavity lining and bases – calcium hydroxide, zinc oxide and eugenol
iii) Temporary fillings – zinc oxide and eugenol (kalzinol), glass ionomer (chem-fil, ketac), polycarboxylate (poly F), self-setting zinc oxide cements (cavit).
159
2.41 c) What zinc-based cement bonds to tooth substance?
i) Zinc polycarboxylate
160
2.41 d) How should this material be mixed and why?
i) On a glass slab as it must not be mixed on anything that absorbs water, also a glass slab can be cooled and this will increase the working time.
161
2.41 e) Which cement should not be used under composite restorations and why?
i) Zinc oxide and eugenol as the eugenol is thought to interfere with the proper setting of the composite material.
162
2.41 f) Which material is used for pulp capping and why?
i) Calcium hydroxide as it is extremely alkaline (pH 11), which helps with formation of reparative dentine. It is also antibacterial and has a long duration of action
163
2.41 g) Which cement is thought to reduce sensitivity of a deep restoration?
i) Zinc oxide and eugenol is thought to reduce sensitivity due to the obtundent and analgesic properties of the eugenol.
164
2.42 a) What are the indications for anterior veneers? (5)
i) Discoloration of teeth
ii) For closure of spaces/median diastema
iii) Hypoplastic teeth
iv) Fracture of teeth
v) Modifying the shape of a tooth
165
2.42 b) What materials are used for veneers?
i) Porcelain
ii) Composite (direct/indirect)
166
2.42 c) What would you need to check prior to advising placement of veneers?
i) Is the discoloration enough to warrant treatment of is it so severe that is will not be masked?
ii) The patient’s smile line – this helps determine which teeth need treatment if for aesthetic reasons only, placement of cervical margin.
iii) Is there enough crown present to support a veneer?
iv) Any occlusal restrictions e.g. edge to edge occlusion, imbrication?
v) Any parafunctional habits?
vi) Is there an alternative option, bleaching?
vii) Stability – caries, perio. Good OH
167
2.42 d) What is the long term prognosis of veneers and what would you warn the patient about?
i) May require replacement in the long term (e.g. approximately 4 years for composite veneers) as a result of:
ii) Risk of chipping of incisal edge
iii) Debonding
iv) Need to keep good gingival health
168
2.42 e) What is the thickness of the veneers?
i) Usually 0.5-0.7mm
169
2.42 f) What are the key points during tooth preparation?
i) Tooth reduction labially – depth cuts are helpful
ii) Chamfer finish line is helpful for the technician
iii) Margin – slightly supragingival unless discoloration, then margin can be subgingival
iv) Extended into embrasure but short of contact point.
v) Incisally either chamfer or wrap over onto palatal surface.
170
2.43 a) What is the function of a post and core?
i) Provides support and retention for the restoration and distributes stresses along the root.
171
2.43 b) What is important to check prior to placement of a post and why?
i) The condition of the orthograde root filling and the apical condition as placement of the post will make it difficult to redo the root canal filling so if necessary repeat orthodgrade root treatment.
ii) Radiographs to assess for apical pathology bone levels, quality of obturation, if root fracture, width, length, angulation and curvature of the root. Assess for coronal pathology radiographically and clinically. Assess mobility, pocketing, periodontal health. Check good oral hygiene. Enough occlusal clearance.
172
2.43 c) What is the ideal length of the post?
i) Ideal length is at least the length of the crown; approximately two-thirds of the canal length; and the apical seal must not be disturbed so at least 4mm of the well-condensed gutta percha should be left.
173
2.43 d) Give a classification of a post and core system.
i) Prefabricated or custom made
ii) Parallel sided or tapered
iii) Threaded, smooth or serrated.
174
2.43 e) What are the ideal characteristics of a post?
i) Have adequate length
ii) Be as parallel as possible
iii) Have a roughened or serrated surface
iv) Not rotate in the root canal
175
2.43 f) What measures can be taken to avoid post perforation?
i) Avoid large diameter post in small tapered roots, instead use tapered post and cement passively.
ii) Avoid long post in curved roots
iii) Avoid threaded post which will increase internal stress within root canal.
iv) Assess angulation and curvatures of root radiographically.
176
2.43 g) How would you manage a post perforation?
i) Depends on the location of the perforation.
ii) If in coronal third, try to incorporate into the design of the post crown, e.g. diaphragm post and core preparation.
iii) For a minimal perforation in the middle third seal the perforation (e.g. lateral condensation) and reposition the post.
iv) For a perforation in the apical two-thirds, use a surgical approach to try to reduce the exposed post and seal the perforation. If attempting repair of perforations, the use of MTA – mineral trioxide aggregate – would be preferable. Due to the poor long-term prognosis, extraction and implant placement may be favoured.
177
2.44 a) When are posterior crowns used?
i) Bridge abutments
ii) Restoring endodontically treated teeth.
iii) Repairing tooth substance lost due to extensive caries/remaining tooth substance requires protection.
iv) Fracture teeth.
v) Situations in which it is difficult to produce a reasonable occlusal form in a plastic material.
178
2.44 b) What are the principles of tooth preparation for a posterior crown?
i) Remove enough tooth substance to allow adequate thickness of the material.
ii) Develop adequate retention and resistance form.
iii) Marginal integrity, supragingival and onto sound tooth where possible.
179
c) How much tooth reduction is required for different materials used for posterior crowns?
i) Full veneer gold crown = 1.5mm functional cusp, 1mm elsewhere.
ii) Porcelain fused to metal crown = same tooth reduction as for gold crown except where porcelain coverage is required, more tooth substance must be removed. Chamfer finish.
iii) Occlusal reduction – metal occlusal surface requires same tooth reduction as for gold crown.
iv) All porcelain – occlusal surface 2mm supporting cusps and 1.5mm non-supporting cusps; buccal reduction 1.2-1.5mm; margins 1.2-1.5mm; shoulder: if porcelain to tooth margin, otherwise chamfer finish as for gold crown.
180
2.44 d) What features affect retention and resistance form of the crown preparation? Give 3 for each form.
i) Retention relies on the height, diameter and taper of the preparation. If will also be increased by the placement of boxes, grooves, pins and surface texture.
ii) Resistance relies on taper of preparation, height to diameter ratio, correctly aligned and positioned grooves and boxes.
181
2.44 e) What are the advantages of partial coverage crown over full coverage crown?
i) Preservation of tooth structure.
ii) Less pulpal damage
iii) Margins more likely to be supragingival
iv) Remaining tooth substance can act as a guide for the technician
182
2.45 a) 21-year-old women present with gingival recession affecting the lower incisors. How will you manage this?
i) Take a thorough history:
(1) Present concerns, sensitivity
(2) History of presenting complaint
(3) Dental history
(4) Toothbrushing history, frequency and duration
(5) Any previous orthodontic treatment.
ii) Then examination should include assessment of presence of plaque, recession, probing depth, bleeding, amount of attached gingivae, presence of functional gingivae, tooth mobility, vitality testing, occlusion, oral hygiene technique and instructions.
183
2.45 b) If the recession is mild on all except the lower left lateral incisor how would you proceed?
i) Target traumatic tooth brushing and improve plaque control; monitor the progression with clinical measurements, photographs, and treat sensitivity. Take impression for study models.
184
2.45 c) What are the possible causes of gingival recession?
i) Traumatic toothbrushing
ii) Incorrect toothbrushing technique
iii) Abrasive toothpaste
iv) Traumatic occlusion/incisor relationship
v) Tooth out of arch
vi) Orthodontic movement of tooth labially
vii) Habits such as rubbing of gingivae with fingernail, pen, etc.
185
2.45 d) If the gingival recession continues on the lower left lateral incisor what other options may you consider?
i) Mucogingival surgery to correct recession by a:
(1) Lateral pedicle graft
(2) Double papilla flap
(3) Coronally repositioned flap (these can be sewn with a interpositional graft)
(4) Free gingival graft to provide a wider and functional zone of attached gingivae.
(5) Thin acrylic gingival veneer stent (rarely used)
186
e) Where is the free graft often taken from? (mucogingival surgery)
i) Palate
187
2.46 a) Give six clinical feature of necrotising ulcerative gingivitis?
i) Rapid onset
ii) Erythema
iii) Painful, punched out ulceration
iv) Grey pseudomembrane
v) Necrosis of inter-dental papillae/blunted interdental papilla.
vi) Lower anterior region
vii) Submandibular/regional lymphadenopathy
viii) Halitosis
ix) Metallic taste
x) Gingival bleeding
xi) Sloughing of gingiva tissue/grey residue
xii) Pyrexia
xiii) Malaise
xiv) Poor oral hygiene
188
2.46 b) What organisms are implicated?
i) Fuso-spirochaetal organisms (Borrelia vincentii, Fusobacterium fusiformis) and Gram-negative anaerobes including, Porphyromonas, Treponema species, Selenomonas species and Prevotella species.
189
2.46 c) What are the risk factors for necrotising ulcerative gingivitis?
i) Poor oral hygiene
ii) Pre-existing gingivitis
iii) Smoking
iv) Stress
v) Malnourishment and rehabilitation. Poor diet/vitamine deficiencies.
vi) HIV/compromised immune system
vii) Age less than 35
190
2.46 d) How would you treat it?
i) Advise on factors which can predispose to the disease
ii) Dietary advise
iii) Smoking cessation counselling
iv) Oral hygiene instructions
v) Analgesic advise + high fluid intact and adequate nutrition.
vi) Scaling/RSD
vii) Metronidazole 400mg TDS 3/7 or amoxicillin 500mg TDS 3/7
viii) Mouthwash – chlorhexidine 0.12% or 0.2% TDS MW or hydrogen peroxide 6% MW TDS 7/7.
ix) Onward referral to GMP in cases that warrant further investigation
x) Review. Should improve in 24-48 hours.
191
2.47 a) Give 4 indications for periodontal surgery?
i) There are no strict indications of periodontal surgery but in certain clinical situations it is more likely to be indicated:
(1) Pockets greater than 6mm
(2) Pockets associated with thick fibrous gingivae
(3) Furcation involvement
(4) Mucogingival deformities or extensive periodontitis lesion requiring reconstruction or regenerative treatment
(5) Short clinical crown height requiring increase in clinical crown height
(6) Gingival hyperplasia
