Flashcards in Year 3 (Clinical) Deck (340)
Define Kennedy Class II
Unilateral free end saddle
Define Kennedy Class I
Bilateral free end saddles
Define Kennedy Class III
Define Kennedy Class IV
Bounded saddle that crosses the mid line
What are the components of a partial denture
4. Reciprocating component
5. Major connector
What are the two types of clasp for partial denture and where are they used?
1. Occlusally approaching clasp: molars
2. Gingivally approaching clasp: premolars and canines
How much gutta percha should be left apically for a post prep?
How much dentine should remain surrounding the post?
1mm dentine lateral to the post
Why are grooves incorporated into post preparation?
1. To provide resistance (to the lateral forces subjected on the tooth daily)
2. NOT mainly for retention
Where should post preparation be avoided?
1. Upper first premolars (canine fossa leads to perforation)
2. Oval shaped root of lower premolars causes circular para post to have low retention inside the canal (use custom post instead)
3. Mesial root of lower molars
What are the uses of a facebow transfer?
1. Allows suitable orientation of the occlusal plane
2. Allows the maxillary cast to be mounted on the articulator in the correct anatomical position
3. Transfers relationship of the maxilla and mandibular rotation points to the articulator
*Facebow has nothing to do with ICP or OVD
What are the different methods of recording impression for crowns and bridges?
1. One stage impression (putty and wash recorded together)*
2. Two staged unspaced (putty is recorded first and then relined with wash)
3. Two staged spaced (putty is recorded with space allocated for wash)
a) Using polythene spacer
b) Recording putty impression before tooth preparation
c) Gouging away putty and providing escape channels for wash
*recommended as it is more accurate
Define combination syndrome
Dental condition seen in patients with completely edentulous maxilla and partially edentulous mandible with preserved anterior teeth
List features of combination syndrome
1. Mandibular ridge resorption
2. Flabby maxillary ridge
3. Enlarged tuberosities
4. Over erupted lower incisors
*try to avoid anterior guidance in combination syndrome
What are features of the Every denture?
1. All connector borders are at least 3mm from gingival margins
2. Open design of the saddle/tooth junction is employed
3. Point contacts between artificial teeth and abutment teeth to reduce lateral stresses to a minimum
4. Posterior wire stops are included to prevent distal drift of the posterior teeth (also contribute to bracing action posteriorly)
5. Flanges are included to assist bracing of denture
6. Lateral stresses are reduced by relying on guidance from remaining natural teeth to disclude the denture teeth on excursion
What is the act that governs the licensing, sale, supply, labelling and packaging of medicinal product?
The Medical Act of 1968
Under The Medical Act of 1968, what can a GDP prescribe under the NHS?
1. General sales list medicines
2. Pharmacy medicines
3. Prescription only medicine
Under The Medical Act of 1968, what can't a GDP prescribe under the NHS?
1. Unlicensed medicine
2. Medical device
What are features of general sales list medicines?
1. Sold or supplied other than the direction of a pharmacist
2. Can be purchased at retail outlet
b) Chlorhexidane mouthwash
c) Fluoride toothpaste <1500ppm
What are the features of pharmacy medicines?
1. Only from a pharmacy
2. Under the direction of a pharmacist
3. Can be sold over the counter without a prescription
4. Can be prescribed by a dentist, doctor or recognised non-medical practitioner
a) Corsodyl dental gel
b) Flouride tablets
c) Miconazole oral gel
What are examples of prescription only medicines?
1. All oral antibiotics
2. Duraphat toothpaste or any toothpaste >1500ppm
3. Aciclovir tablets
4. Topical and systemic anti fungal
What is the act that regulates what dentist and doctors can sell to patient?
The NHS Act 1977
What are two basic features that a prescription form should have?
1. Be signed by the prescriber
2. Be issued separately to each patient whom the clinic/contractor is providing services
What is the form used by a dentist to prescribe medicines?
What are the medications that can be prescribed on a FP10D form?
Medicines listed in the Dental Practitioners Formulary
What is the act that governs the misuse of drugs?
The Misuse of Drugs Regulations 2001
Under The Misuse of Drugs Regulations 2001, which schedules of drugs can a dentist administer?
Schedule 2, 3, 4 or 5*
*any person may administer to another any drug under schedule 5
What is the significance of taking a drug history?
1. Patient safety
2. Diagnostic significance
3. Effective and appropriate treatment
4. Hidden medical history
What are the barriers of taking a patient drug history?
1. Perceived relevance by patient
2. Non prescription drugs
3. Supplements, herbal remedies
In which circumstance is ICP used to record horizontal relationship?
When there is definite centric occlusion
In which circumstance is RCP used to record horizontal relationship?
When there is insufficient number of teeth present in the dentition
In which circumstance do you get a wax registration before taking a master impression?
When there is ICP present but not enough teeth to place the cast together by hand in ICP
How do you record ICP?
1. Hand articulate the cast and check it with patients mouth
If not possible
2. Use a wax wafer and get patient to bite together
If not possible
3. Use wax occlusal rims + bite registration paste
Why do we survey a cast?
1. Presence of undercuts
2. Type of support
3. Depth of undercut
4. The contour of the undercut relative to gingival margin
5. The path of insertion of the denture
What does a survey line indicate?
Marks the position of maximum convexity thus separating undercut from non undercut areas
What is the purpose of an undercut gauge?
Measures the extent of horizontal undercut
What are the sizes of undercut gauge available and what materials are associated with each size?
1. 0.25mm: cobalt chromium
2. 0.50mm: gold
3. 0.75mm: stainless steel
How deep is a rest seat?
1mm in depth
What is the length needed for an occlusally approaching clasp to be effective?
At least 15mm
What are equipments commonly used in dental extraction?
1. Coupland's elevators
4. Warwick James
What is the function of Coupland's elevators?
To sever the periodontal membrane thus dilating the bony socket surrounding the tooth
How are Coupland's elevators used?
1. Used sequentially from 1 > 2 > 3
2. Uses rotational force directed perpendicular to the tooth
How do you use luxators?
1. Used in the long axis of the tooth where it is pushed as far apically as possible
2. Finger rest is applied on the shank (of the dominant hand)
3. Finger and thumb support is applied on the alveolus
What variety of luxators are available?
When are cryers and Warwick James usually used?
1. Upper third molar
2. Retained roots
3. Removing inter septal bone
How do cryers differ from Warwick James?
Cryers have triangular pointed working end where as Warwick James have curved working end
For which tooth are forceps not recommend for?
Mandibular third molars
Describe the primary/preliminary movement of tooth extraction
1. Sever periodontal membrane
2. Generally dilate the socket
1. Force directed along long axis of the tooth
2. Blade of forceps towards root apex
Describe the secondary movement of tooth extraction
1. Complete dilation
2. Withdrawal of tooth
1. Depends on tooth root and morphology (usually buccal
a) Incisors, canines & lower premolars (single rooted): rotational movement
b) Upper premolars: buccal movement
c) Molars: buccal or figure of 8
Where should the operator stand for extraction of lower right tooth?
Behind the patient (on the right)
Where should the operator stand for extraction of lower left tooth?
In front of the patient (on the left)
Where should the operator stand for extraction of upper tooth?
In front of the patient with the patients head at shoulder height (when standing straight) and arms straight with forceps
What are the pink consent forms used for?
What are the yellow consent form used for?
What are five aspects of clinical record that must be present before you can proceed with an extraction?
1. Written diagnosis and treatment plan stating which tooth is to be extracted
2. Periapical radiograph of the tooth
3. A completed consent form
4. A contemporaneous medical history
5. A correct site surgery form
List 12 items that must be written in the clinical notes for the extraction appointment.
1. The procedure that was carried out
2. If medical history was checked at the beginning of the appointment
3. If any glucose drink was given or medications taken
4. The local anaesthetic administered (LA agent, batch number, expiry date, amount give, type of injection)
5. How the treatment was carried out
6. If any complications occurred
7. If closure was required
8. If haemostasis was achieved
9. Post operative instructions were give
10. Any antibiotics/analgesics given
11. Signed and dated by student and tutor
12. Completed correct site surgery form
What does minor oral surgery comprise of?
1. Removal of teeth/roots surgically
2. Treatment of bony pathology
3. Exposure of ectopic teeth
4. Soft tissue surgery (biopsy)
5. Closure of defects
When do we consider surgical approach?
1. When conventional approach is unsuccessful
2. Decoronated tooth
3. Impacted teeth
Why do we raise a flap?
1. For visualisation purposes
2. Protects vital structures
3. To allow a clean closure
State the principles of flap design
1. The flap is broader at the base to prevent loss of perfusion
2. Include the papilla
3. Ensure that margins are on sound bone
4. Avoid tearing the flap
5. Ensure flap is broad enough to give adequate access to what you are doing
6. Avoid important anatomical structure
What are the important anatomical structures to avoid when designing a flap?
1. Mental nerve
2. Lingual nerve
3. Nasopalatine & greater palatine nerves/vessels
What are the factors that makes accessing a tooth for extraction difficult?
1. Orientation of the tooth
2. Existing caries/restorations: weakens the tooth
3. Root canal treatment: weakens the tooth
4. Patients age: younger bone has more elasticity
5. Bone quality: the denser the bone the harder the extraction
6. Root anatomy: curved roots are hard to extract
7. Proximity to structures
What is the instrument used to raise a flap?
Howarth's elevator is used to raise flap and protect vital structure
What is the use of a Mitchell's osteo trimmer?
Remove granulation tissue in tooth socket
What are the uses of bitewing radiography?
1. The detection of dental carries in the upper and lower premolars and molars
2. Monitoring the progression of dental caries
3. The assessment of existing restoration
4. The assessment of periodontal condition (secondary use)
What are the teeth included in a bitewing?
Premolars, molars and distal of canine
How does a bitewing change when a patient has erupted third molars (long dental arch)?
Two bitewings per side are taken:
1. Premolars bitewings
2. Molar bitewings
When are vertical bitewings indicated?
1. BPE score of 4 or *
2. Other BPE score with significant gingival recession
Why is radiography useful for caries diagnosis?
1. Reveals more lesion than clinical examination alone
2. Allows us to see areas inaccessible to direct vision
3. Allows us to estimate depth and extent of caries
4. Allows us to monitor progression/regression of caries over time
List types of caries
3. Smooth surface
State the classification of proximal caries
D1: outer enamel
D2: inner enamel
D3: outer dentine
D4: inner dentine
D5: pulpal involvement
What is the best way to detect occlusal caries?
Direct vision of a dry tooth
When do you restore a tooth with caries?
When the lesion has causes a cavitation. Temporary tooth separation could be used to help check cavitation
What is the earliest stage of occlusal caries detected on a radiograph?
D3 (D1 and D2 occlusal caries will never be detected on a radiograph)
What is a Mach Band effect?
Edge enhancement effect produced in the brain which leads to false positives
What is the earliest stage of root caries?
D3 as there are no enamel on the root surface
Where should the crestal bone be in relation to the cemento-enamel junction?
How do you measure bone loss on a radiograph?
Bone loss: (Distance from CEJ to bone level) - (2mm)
What are early signs on bone loss on a radiograph?
1. Loss of cortical density
2. Rounding off of junction between alveolar crest and lamina dura
3. Blunting of crest
How do you classify bone loss?
What are the 3 things that should be noted in a radiographic report?
1. Periodontal bone and calculus
2. Proximal surface caries
3. Occlusal caries
4. Other findings (cyst, torus, retained roots, Turner's hypoplasia)
List the essential image characteristics of a bitewing radiograph
1. No evidence of bending of the image of the teeth
2. No foreshortening or elongation of the teeth
3. Ideally no horizontal overlap (if present should not obscure more than half of enamel thickness)
4. Should cover distal surface of the canine and mesial surface of the most posterior erupted teeth
5. The periodontal bone level should be visible and equally imaged in the maxilla/mandible
6. There should be good density and contrast between enamel and dentine
How often should bitewings be taken for permanent dentition?
High risk: 6 months
Moderate risk: 12 months
Low risk: 24 months
How often should bitewings be taken for primary dentition?
Low risk: 6 months
Moderate risk: 12 months
High risk: 12-18 months
List treatment options for free end saddles
1. Shortened dental arch
2. Distal cantilever bridges
3. Removable partial denture
4. Implant supported/retained prosthesis
When is an acrylic free end saddle usually indicated?
As a transitional denture
What is the negative consequence of acrylic denture?
As they rely on mucosal support to retain the denture, they act as gum strippers and thus damage the gingival tissues
How do you stop adverse loading of the free end saddles on the ridge?
To cover as much of the denture bearing area as possible:
1. Cover the retro molar pad area
2. Extend into the lingual sulcus
How is support provided in CoCr free end saddle denture?
Combination of tooth support and mucosa support:
1. Tooth support from anterior aspect of saddle
2. Mucosal support posteriorly
What is the general rule of rest seat specific to free end saddles?
The rest seat MUST always be placed on the mesial aspect of the abutment teeth to ensure even distribution of load
What are the two approach to prevent denture rotation in displaceable mandibular tissues?
1. Rigid connector between mucosa and tooth supported parts of the denture (most favoured approach)
2. Flexible major connected that allows mucosal supported parts to move independently of the tooth supported parts
What is the technique used when designing a rigid connection?
Altered cast technique
Describe the altered cast technique
1. CoCr framework carries an acrylic special tray that covers the saddles
2. A mucodisplacive impression of the saddle is taken using ZnOE
3. The free end saddle part of the old cast is cut off
4. A new cast is made incorporating the old cast and the mucodisplacive impression of the free end saddle
5. A new denture is fabricated based on the altered cast
6. The resulting lower denture should resist tissue displacement when load is applied to the denture
Give example of a stress breaker design
Split lingual plate
State the essential factors when designing a free end saddle
1. Denture teeth should lie on the ridge
2. Ensure maximum denture extension: halfway up the retro molar pad
3. Ensure even occlusal contact in retruded contact position
4. Reduce size of occlusal table (Eg: not including 7s)
5. Keep clasps flexible (wrought stainless steel wire)
What are the advantages of using a rigid connector instead of flexible connectors?
1. Simplicity of the design
2. Simplified technical procedures
3. Gives more control over applied load
4. Flexible connectors (stress breakers) give poorer lateral stability
5. Flexible connectors are more likely to cause soft tissue entrapment and lead to fracture of the denture
Which component of the free end saddle provides indirect support?
Clasps that resists denture rotation that occurs at the rests (after the rests have resist rotation of the clasp)
Which component of the free end saddle provides indirect retention?
1. Anterior rests
2. Continuous clasp
3. Anterior palatal bars
4. Lingual plates
How is indirect retention provided in a free end saddle?
1. When a patient bites into a toffee and separate their teeth, the denture will rotate away from the saddle areas
2. Thus the denture will rotate around the clasp as the clasp tries to resists displacement of the denture
3. That rotation is that resisted by any rests or connector anterior to the clasp (anterior to that axis of rotation)
4. This causes the denture to move downwards toward the tissue again
What are the two other options for treating a free end saddle?
1. Bridges (but can lead to overloading on abutment teeth)
2. Implants (consider available bone, surgical morbidity and cost)
What makes the Every denture hygienic?
1. Mucosa-borne only
2. Has no clasp or rest
3. Retained by frictional contact of the Every denture with natural teeth
How does the Every denture prevent gingival trauma?
Lack of marginal coverage
Are distal stabilisers in an Every denture clasps?
No. They are there to improve bracing action of the denture
When do we use an Every denture?
To restore multiple bounded edentulous area in the maxillary jaw
What are other design of acrylic denture?
1. Spoon denture
2. T shape denture
*although provided minimum gingival coverage there is a potential hazard of inhalation or ingestion
What are indications of providing an acrylic denture?
1. Interim denture before a definitive treatment plan can be formulated
2. The remaining teeth have poor prognosis and their extraction and subsequent addition to the denture is anticipated
3. An immediate denture replacing anterior teeth
*it is never a permanent solution in the lower arch
What are the disadvantages of acrylic denture?
1. No rests so they rely on tissue support
2. Limited support provided by tissue as teeth can resist vertical loading much better than mucosa
3. Acrylic denture requires maintenance
What are limitations to the Every denture?
1. Prone to fracture
2. Maximal coverage of palatal tissues
3. Excessive adjustment on denture insertion leads to loss of retention
What is the function of the RPI system?
To avoid damaging the distal abutment tooth in a free end saddle
What are features of a cast cobalt chromium clasp?
1. Needs to be 15mm in length to avoid permanent deformation in an undercut of 0.25mm
2. Use only with molar teeth
3. If undercut does not exist it should be created with composite resin
4. Only the terminal third engages the undercut
What are features of wrought stainless steel clasp?
1. Should engage an undercut of 0.75mm
2. Should be 7mm or more
3. Occlusally approaching clasp could be used in premolars or canine region
What are two of the most common cast cobalt chrome lingual connector?
1. Lingual bar
2. Lingual plate
Which situation contraindicates a gingival approaching clasp?
A large tissue undercut because it must be spaced well away from the ridge and inevitably rubs against the cheeks
When do you record BPE?
1. For all new patients
2. For patient with codes 0, 1 or 2 BPE should be recorded annually
What is the subsequent step when a BPE code 3 is obtained?
1. DPC for that sextant
2. BPE for all other sextants with 0,1 and 2
What is the subsequent step when a BPE code 4 is obtained?
1. DPC through out the entire dentition
Can BPE be used to assess response to periodontal therapy? Justify.
2. It does not provide information about how sites within a sextant change after treatment
3. Instead probing depth should be recorded at 6 sites per tooth
How often should patients with BPE code 3 and 4 (pre treatment) have their pocket depths measured (post treatment)?
At least annually
Which BPE codes are radiographs (to assess alveolar bone level) indicated for?
Codes 3 and 4
What are the 3 factors to consider in your periodontal patient before arriving at the diagnosis?
1. Medical condition/diseases of the patient
a) History and exam
b) Special test or lab test
c) Medical consultation
2. How severe is the bone loss
a) Mild: 1-2mm
b) Moderate: 3-4mm
c) Severe: >5mm
3. Localised or generalised
a) Localised: 30%
List the main clinical features of chronic periodontitis
1. Most prevalent in adults but can occur in children and adolescents
2. Amount of destruction is consistent with presence of local factors
3. Subgingival calculus is frequent finding
4. Associated with variable microbial pattern
5. Slow to moderate rate of progression but may have period of rapid progression
6. Can be associated with local predisposing factor (tooth related or iatrogenic)
7. May be modified and/or associated with systemic diseases
8. Can be modified by other factors other than systemic disease (smoking and emotional stress)
List the primary and secondary clinical feature of aggressive periodontitis
1. Except for periodontitis, patients are otherwise clinically healthy
2. Rapid attachment loss and bone destruction
3. Familial aggregation
1. Amounts of microbial are inconsistent with severity of periodontal tissue destruction
2. Elevated proportions of
a) Actinobacillus actinomycetemcomitans
b) Porphyromonas gingivalis (in some populations)
3. Phagocyte abnormality
4. Hyperesponsive macrophage phenotype (prostaglandin E2 and interleukin 1Beta)
What are specific features of localised aggressive periodontitis?
1. Circumpubertal onset
2. Robust serum antibody to infecting agent
3. Localised first molar/incisor presentation
What are specific features of generalised aggressive periodontitis?
1. Usually affecting person under the age of 30 but patients may be older
2. Poor serum antibody response to infecting agent
3. Pronounced episodic nature of destruction of attachment and alveolar bone
4. Generalised attachment loss affecting at least 3 permanent teeth other than first molars and incisors
What are the aims of non surgical periodontal therapy?
1. Removal of attached biofilm and non attached microflora in the gingival sulcus and periodontal pocket
2. Removal of plaque retentive factors (calculus, overhanging restoration and areas of cementum hypoplasia and resorption)
3. Rendering the root surface as smooth as possible
How is recurrent infection of the periodontal pocket prevented?
1. Meticulous gingival plaque control via
a) Daily oral hygiene
b) Professional mechanical tooth cleaning
2. Address local risk factors
3. Minimise the effect of systemic risk factors
4. Alteration or elimination of putative periodontal pathogen
What are some of the reason patients fail to comply with oral hygiene advice?
1. Unwillingness to perform self oral care
2. Poor understanding of the recommendation
3. Lack of motivation
4. Poor dental health beliefs
5. Stressful life events
6. Low socio economic status
List ideal feature of a toothbrush
1. Handle size appropriate to age and dexterity
2. Head size appropriate to the size of patients mouth
3. Round ended nylon or polyester filaments not larger than 0.009" in diameter
4. Soft bristle configuration as defined by ISO
5. Bristle pattern that enhances plaque removal approximally and at the gingival margin
List the active ingredients of toothpaste
2. Antibacterial agent (triclosan)
3. Desensitising agent (potassium nitrate, strontium)
4. Anti tartar agent (pyrophosphates)
5. Sodium bicarbonate
6. Enzymes (increases antibacterial properties of saliva)
7. Xylitol (reduces level of cariogenic bacteria in the mouth)
List the inactive ingredients in toothpaste
3. Binding agents
4. Humectants (to retain moisture)
7. Abrasives (silica or powdered calcium salts)
What are interproximal cleaning aids available?
2. Wooden sticks
4. Bottle brushes
What are indications of root surface debridement?
1. Highly motivated patient who has achieved a high standard of supra and subgingival plaque control but still has evidence of active disease
2. Pockets with active disease (pocket >5mm which bleeds on probing)
3. The presence of detectable sub gingival deposits in a risk patient (aggressive cases) despite an a science of overt clinical signs of inflammation
What are contraindications of root surface debridement?
1. Poorly motivated patient who does not demonstrate high standard of supra and subgingival plaque control
2. Patients with high INR
3. The absence of BOP from a deep but stable pocket
List root surface debridement protocols
1. Confirm sites requiring root surface debridement
2. Administer LA
3. Patients rinse with 0.2% chlorhexidane mouthwash for 60s
4. Carefully probe sites to identify deposits
5. Use ultrasonic hand piece
6. Use site specific curettes
7. Recheck with complete removal of deposits with probe
8. Re-instrument and irrigate using ultrasonic scaler
9. Post operative instructions
List Gracey protocols
1. Select correct instrument to site
2. Identify working end
3. Insert passively and parallel to long axis of root
4. Ensure good finger rest
5. Ensure correct operator/patient position
6. Turn toe to engage root surface
7. Excuse the following strokes:
a) Vertical strokes
b) Oblique strokes
c) Horizontal strokes
How long should the revaluation be after a non surgical periodontal treatment?
3 to 6 months
What are the expected outcomes of sites that have been successfully treated? (periodontal treatment)
1. Absence of plaque
2. Absence of gingival bleeding
3. Reduction in pocket depth
What are the expected outcomes of sites that have been unsuccessfully treated? (periodontal treatment)
1. Persisting inflammation
2. Persisting pocketing
What are reasons for periodontal treatment failure?
1. Inadequate plaque control
2. Inadequate debridement
3. Persisting smoking
What should be done when periodontal treatments fails?
1. Improve plaque control
2. Smoking cessation
3. Repeat debridement
4. Consider surgical debridement
5. Anti microbials
What does a periodontal treatment require to be successful?
1. Proper diagnosis
2. Adequate plaque control
3. Subgingival debridement
4. Long term maintenance
Why is periodontal disease a classic chronic inflammatory condition?
Because it is characterised by persisting inflammation with concurrent attempts at repair
What are features of an untreated periodontal lesion?
1. Bleeding in probing: due to increased gingival blood flow and ulceration of the pocket epithelium
2. Redness and swelling: due to increased gingival blood flow and loss of gingival connective tissue
3. Increased pocket depth: due to gingival swelling, loss of attachment and loss of fibrous gingival cuff
4. Increased mobility: due to loss of attachment (including bone loss) and also slight effect of loss of fibrous gingival cuff
What are the effects of healing on periodontal pockets?
1. Reduction in swelling: due to resolution of inflammation
2. Reduction in redness: due to resolution of inflammation and increased collagen production
3. Reduction in BOP: due to decreased blood flow and healing of sulcular epithelium
4. Reduction of pocket depth: due to formation of fibrous gingival cuff, formation of long epithelial attachment and increased gingival recession
What are the cellular events that occur during a periodontal healing?
1. Reduction in gingival vasodilation and swelling
2. Migration of gingival fibroblast into area and formation of mature gingival collagen fibres
3. Healing of sulcular epithelium, ultimately resulting in formation of a long junctional epithelium
4. Limited bone remodelling but little or no regeneration of crestal bone height and new periodontal ligament
Describe the time scale of periodontal healing post treatment
1. Visible effects: 1-2 weeks
2. Most effects: 1-2 months
3. Final outcome: up to 9 months
When do we consider anti microbials for periodontal patients?
1. As an adjunct to mechanical therapy
2. After specificity testing has been carried out
3. Patients who are smokers
4. Specific infections:
d) Aggressive periodontitis
List the protocol for whole mouth disinfection
1. RSD of all pockets in 2 visits within 24 hours
2. Tongue brushing with 1% CHX gel for 1 minute
3. Mouth rinsing with 0.2% CHX rinse for 2 minutes
4. Subgingival irrigation of all pockets (x3 in 10 minutes) with 1% CHX gel
5. 2x daily rise with 0.2% CHX
6. 2x daily spray of tonsils with 0.2% CHX
This is done for 2 months
Define local anaesthetic
A drug which reversibly prevents transmission of a nerve impulse in the region it is applied, without affecting consciousness
Describe the structure of LA
1. Has two components
a) Lipid soluble, hydrophobic aromatic group
b) Charged hydrophilic group
2. The bond between them determines the class of drug
a) Amide bond: Lignocaine, Prilocaine
b) Ester bond: Procaine, Benzocaine
How does local anaesthetic work?
1. Unionised form of the LA crosses the cell membrane of the neurone
2. The LA gets ionised inside the neurone cells
3. Block sodium-specific ion channels of the neurone cell membrane
4. Inhibits sodium influx and reverse the rate of depolarisation of excitable membranes
5. Prevents pain transmission
How does an abscess reduces the efficacy of local anaesthetic?
1. An abscess creates an acidic environment which lowers the pH of the surrounding tissues
2. Because LA are weak bases, an low pH causes the weak base to dissociate into its ionised form
3. This reduces the fraction of unionised form of the LA thus reducing its efficacy
4. There is also increased blood supply around the area thus increases clearance of LA by blood from site of injection
How is the CNS affected by toxic levels of LA in the system?
It consists of two phase reaction
1. Excitatory (initially)
a) Numbness of tongue and circumoral area
c) Visual disturbances
2. Depressive (later)
How is the cardiovascular system affected by toxic levels of LA?
2. Circulatory collapse
What are the effects of toxic levels of LA in the circulation?
1. Tingling of lips
2. Slurred speech
3. Reduced level of consciousness
8. Prolonged paraesthesia
What happens in methemoglobinaemia?
1. Haemoglobin is converted to methemoglobin (ferric form) which has reduced ability to release oxygen
2. This leads to:
a) Shortness of breath
e) Loss of consciousness
3. Treatment includes oxygen and methylene blue
4. Prilocaine can cause cyanosis due to this
What is the maximum dose of 2% lignocaine with adrenaline for a five year old child?
1. A 5 year old weighs 20kg
2. Maximum dose of lignocaine is 4.4mg per kg of body weight
3. 20 x 4.4kg = 88mg is the maximum dose
4. 2% lignocaine has 20 mg per 1ml
5. 1 cartridge has 2.2ml (44mg)
6. Thus the 88mg max dose is achieved when 2 full cartridges are given
How do you estimate a child's average weight?
(Age + 4) x 2
What is the maximum dosage of commonly used anaesthetic agent in children?
One tenth of 2.2ml cartridge per kg of body weight
How does articaine differ from lignocaine?
1. Articaine is 95% protein bound where as lignocaine is 65% protein bound
2. Articaine up has a thiopene group (unique among amides) which increases its lipid solubility thus facilitates greater diffusion through soft tissues (better lipid solubility = better nerve penetration = better anaesthesia)
3. Articaine can diffuse through cortical bone where as lignocaine can't
What are advantages of articaine?
1. High intraneural concentration
2. More extensive longitudinal spreading
3. Better conduction blockade
What are the injection techniques often used in children?
3. Intra papillary
4. Indirect palatal
5. Direct palatal
6. Inferior dental block
What are the two types of local anaesthetic commonly used?
1. Benzocaine 20% (comes in flavours)
2. Xylonor gel (lidocaine)
What procedures indicate intra papillary injection?
To provide palatal anaesthesia for:
1. Matrix band
2. Rubber dam
3. Stainless steel crown
4. Removal of primary incisors and canines
Describe the steps for intra papillary injection
1. First administer buccal anaesthesia and wait until analgesia is achieved
2. Penetrate interdental papilla to depth of 1-2mm
3. Needle and syringe are parallel to the occlusal plane
4. Inject slowly
5. Slowly advance needle and keep injecting until blanching of palate is observed
6. Repeat on the other (mesial/distal) side of the tooth
What is an indirect palatal injection?
1. Similar to intra papillary but the needle is angle upwards
2. Suitable for removal of maxillary molars
3. Can be reinforced with direct palatal
How does the mandibular foramen of a child differ to than of an adult?
Mandibular foramen is lower and deeper on the internal surface of the ramus
Describe the steps of an inferior dental block for children
1. Get the patient to open widely
2. Palpate the external oblique ridge
3. Needle is inserted from the opposite side of the mouth
4. The barrel of the syringe is held over the first primary molar
5. Penetrate the mucosa and inject small amount of solution
6. Advance gently with slow injection and aspiration
7. On contact with bone, withdraw slightly and deposit remainder
8. In older children, the lingual nerve should be anaesthetised as well
What are the indication and contraindications of intraligamental injection?
1. Adjunct to failed infiltration/block
2. Alternative to block
3. Patients with bleeding disorder
1. Children at risk of bacteaemia (forcing bacteria from oral environment into their blood)
2. Patients with cardiac arrhythmias or hypertension (forcing LA at high pressure which could make their heart beat faster)
Describe the intraligamental technique
1. Give a buccal infiltration first
2. Introduce needle into periodontal sulcus of mesial surface
3. Advance until resistance is felt
4. Commence injection (where resistance will be encountered)
5. This is repeated for the distal surface
What is the name of the system that delivers computerised local anaesthetic?
What are the four aspects of children behaviour management?
1. Tell show do
2. Positive reinforcement
Which regulation required employers to start using safer sharps?
Health and Safety Regulation of 2013
What are special tests!
Investigations that provide the clinician with additional information to allow them to reach a definitive diagnosis/exclude differential diagnosis
What are examples of special tests?
a) Bitewing: vertical bitewing if you have deep periodontal pocket
b) Peri apical: crowned teeth (lose vitality asymptomatically) advanced bone loss, symptomatic (apical periodontitis)
c) DPT: multiple pathologies in most quadrant
2. Sensibility tests
a) Ethyl chloride
c) Electric pulp tester
d) Test cavity
3. Percussion test
4. Cone beam computer tomography
8. Cracked teeth using a tooth slooth
What are methods to record tooth wear?
1. Serial study models
2. Clinical photographs
3. Silicone indices
4. Tooth wear index (Smith and Knight)
5. Basic erosive wear examination (Bartlett)
What are indications for restorative treatment in tooth wear cases?
1. Aesthetic concern
2. Sensitivity (not managed by topical measures)
3. To restore function
4. Rapidly progressing wear
*most of the time prevention and monitoring is all that is required
List the uses of articulated study models
1. Allows you to create a treatment plan without the patient being present
2. Assess static and dynamic occlusal contact
3. Assess and measure inter occlusal space
4. Determines shapes and sizes of saddles
5. Helps to identify soft tissue defects
6. Assess contour, crown height and angulation of teeth
7. Enables you to survey the cast
When presenting treatment options what are the features it should contain?
List the 5 stages of treatment
1. Emergency/pain relief
What is included in an emergency treatment?
1. Urgent referral of suspicious lesion
2. Drainage of abscess
3. Pain relief
c) Gingival conditions such as necrotising ulcerative gingivitis
4. Desensitising treatment
What is included in a prevention phase?
1. Smoking cessation
2. Oral hygiene instruction and disclosing plaque
3. Dietary analysis and advice
a) Frequency of sugar
b) Erosive food and drinks
4. De sensitising toothpaste
a) Professionally applied
b) Prescribed toothpaste
What is a a stabilisation phase and what does it include?
Treatment required to eradicate any pathology
2. Caries removal
3. Root canal therapy
4. Extraction of teeth with hopeless prognosis
5. Re asses patient to ensure suitability to progress to next level
6. Re asses treatment plan and finalise design for any prosthesis
What is included in a provisionalisation phase?
*comes between stabilisation and restorative
1. A phase where any trial changes are made
2. Provisional crowns
3. Acrylic denture
4. Allow resolution for periodontal treatment
5. Create space for restoration (Dahl appliance)
What is included in a restorative phase?
1. Definitive restoration
2. Indirect restoration
3. Tooth replacements
What is included in the maintenance phase?
1. Recall interval
2. Re motivate patient
3. Periodontal care
4. Repeat radiographs
5. Follow up on root canal therapy or trauma
6. Monitoring: study models, photos, silicone index
Define tooth surface loss
Non carious loss of tooth tissue as a result of normal physiological process that occurs through out life
What does tooth surface loss become pathological?
1. When the rate of loss prejudice the tooth survival
2. When it concerns the patient
List the four classes of tooth surface loss
Irreversible loss of dental hard tissue due to a chemical process of acid dissolution but not involving bacterial plaque acid
Loss by wear of tooth substance or a restoration caused by factors other than tooth contact
Loss by wear of tooth substance or a restoration caused by mastication or contact between occluding or approximal surfaces
Pathological loss of tooth enamel and dentine caused by biomechanical loading of forces
What is the key step in management of tooth surface loss?
The aetiology of the TSL should be identified prior to patient management
What are the two sources of acid?
What are the causes of intrinsic acid?
1. Gastro oesophageal reflux disorder
a) Most common cause of intrinsic acid
b) 7% of individuals have daily acid reflux
c) Monitored with Spechler (7 day diary of acid reflux: occurrence, severity of discomfort, difficulty swallowing, coughing/wheezing)
2. Cyclic vomiting syndrome
3. Irritable bowel syndrome
4. Motion sickness
7. Self induced vomiting
a) Bulimia nervosa
c) Anorexia nervosa
8. Rumination (ability to relax the lower oesophageal sphincter and reflux gastric content into the mouth and re-swallow)
What are key features of anorexia?
1. Aversion of food resulting from a complex interaction between biological, social, individual and family factors leading to severe weight loss
2. BMI less than 17.5
3. Average age of 16 years old
What are key features of bulimia?
1. Over eating followed by inappropriate compensatory behaviour
2. Average age of 25 years old
3. BMI more than 17.5
4. Key signs include:
a) Callus at the back of the hand (Russell's sign)
b) Asymptomatic palatal haematoma
What causes bilateral episodic parotid enlargement?
Any condition whereby the individual is frequently vomiting. This is because the parotid has to put a lot of effort to produce saliva and flush it out after an episode of vomiting
State 5 drinks with erosive potential
1. Carbonated flavoured drinks (sparkling water is not)
2. Flavoured water
3. Red wine
4. Fruit juice
5. Cider (beer is not)
State 5 food with erosive potential
1. Fresh fruit
5. Brown sauce
How does medication have an effect on erosion?
Direct effect: the medication itself is erosive
1. Vitamin c
3. Some iron preparation
Indirect effect: the medication causes
1. Nausea and vomiting
2. Dry mouth
How does the plaque biofilm provide a protective mechanism against erosion?
1. Physical protection from the acid
2. Provides a closed system hence mineralisation (prevents the wash out effect of demineralisation products)
Distinguish function, parafunctional and dysfunction
1. Function: normal movement
2. Dysfunction: abnormal movement
3. Parafunction: normal movement but abnormal frequency
What are key features of parafunction?
1. Controlled by the central nervous system
2. Emotionally driven (relates to stress and emotional distress)
3. Beyond the conscious control of the patient
4. Intermittent (may be historic or active)
5. Difficult to diagnose
What are some of the clinical findings of parafunctional activity?
1. Masseteric hypertrophy
2. Cheek ridging
3. Scalloped tongue
1. Matching wear facets
2. Fractured cusp
3. Broken restorations
4. Missing porcelain
What are features of TSL that is attrition dominant?
1. Flattened incisal and occlusal surface
2. Equal degree of wear in both arches
3. Teeth closely fit together
What are features of TSL that is combination of attrition and erosion?
Cupping of restorations can be seen
What are features of TSL that is erosion dominant?
1. Palatal and labial surfaces of upper incisors are most severely affected
2. Generalised loss of anatomy
3. Proud restorations
What are the clinical problems with TSL
a) Increase in tooth translucency
b) Fracture of enamel
c) Short teeth (due to grinding away of incisal surface)
d) Yellow teeth (due to dentine layer showing)
2. Sensitivity and pain
a) Exposure of dentinal tubules
b) Pulpal inflammation
c) Pulpal exposure
Does attrition lead to a decrease in OVD?
2. This is due to dento alveolar compensation (the alveolus erupts to bring the teeth together).
3. However, dento alveolar compensation is:
b) Not uniform
What is the commonly used tooth wear index?
Smith and Knight
0: no wear
1: loss of enamel
2: loss of dentine LESS than 1mm
3: loss of dentine 1-2mm
4. Pulpal exposure or MORE than 2mm loss of dentine
*good for screening but not for monitoring patient
What is another tooth wear index (other than Smith and Knight)?
Khan and Young Index
B: bowl shaped erosion
C: cervical lesion
E: near exposure
F: frank exposure
Besides using tooth wear index what are other ways to monitor tooth surface loss?
2. Silicone index and casts of the patients dentition
3. Micro CT scan
How does fluoride help with erosion?
Fluoride goes into the hydroxyapatite and makes the crystal more resistant to acid
Simple compounds of metallic and non metallic elements
A material that has cooled to a rigid solid condition without crystallising
Distinguish between crystalline and amorphous in terms of its atomic order
Crystalline exhibits long range and periodic atomic order where as amorphous (glasses) lacks the long range atomic order (possess some crystallinity)
Which part of the cooling curve tells you the thermal expansion coefficient of the substance?
Slope of the cooling curve for solid and liquid
What is the most common biological complication of crowning an abutment for bridges?
1. Loss of pulp vitality of the abutment teeth
2. Caries of abutment teeth
What is the most common technical complication of crowning a tooth?
1. Loss of retention
2. Fracture of material
What are the requirements of a resin bonded bridge?
1. Maximum palatal coverage
3. Sound enamel (with no previous restoration)
4. Protected occlusion from static and dynamic occlusion
5. Moisture isolation can be achieved during cementation
State ante's law
The total periodontal membrane area of the abutment teeth must equal or exceed that of the teeth to be replaced
What are important features to consider when designing a bridge?
1. Crown margins of the abutment tooth in supra gingival locations
2. The width of the improximal areas contoured to allow optimal interdental cleansing
3. Excellent plaque control by patient
What are the mechanical factors to consider in tooth preparation for a bridge?
1. Removal of sufficient tooth structure to avoid occlusal interference and correct emergence profile
2. Maximum retention and resistance form
3. Maximum strength of connector
What are the biological requirements to consider in tooth preparation for a bridge?
1. Preservation of as much dentine as possible over the pulp
2. Avoidance of placing gingival margin at/beyond the junctional epithelium
3. Provide open embrasures to allow interproximal cleaning
How does the biological width affects placement of crown margins?
1. The margin of the crown should not be placed at/beyond the junctional epithelium. Failure to do so will causes gingivitis and gingival recession as the tissues try to recreate its biological width.
2. Biological width = 1mm of junctional epithelium + 1mm of connective tissues attachment (it is essentially the distance between the CEJ and crestal bone level)
What could be done to a crown with a very short clinical height?
1. Crown lengthening surgery
2. Impression for crown prep can only be taken 6 months after (to allow gingival tissues to heal)
Under which circumstance are subgingival margin indicated?
1. To gain retention
2. For aesthetic reason
3. Due to caries and trauma which leaves very little sound enamel
What are indications of providing a crown?
1. Extensively restored tooth at risk of fracture
3. Tooth wear
4. To alter occlusion
5. To support weakened teeth due to RCT
What are the basic principles for a crown preparation?
1. Even and adequate reduction
2. Maintain natural tooth planes
3. Margins must end on natural tooth
4. Minimal taper but avoid undercuts
5. Gentle curves and no sharp edges
What are the two functions of retraction cord?
1. To stop bleeding of the gingival tissues
2. To expand the gingival sulcus thus allowing impression material to flow in
Describe the Dahl appliance
1. Composite is placed on the palatal aspect of upper anterior teeth
2. This causes the intrusion of the anterior and eruption of the posterior teeth
3. This provides space anteriorly for bridgework
4. After 6 months the incisors intrude by 1mm and molars erupt by 1.5mm into occlusion
When is an onlay indicated instead of a crown?
If dentine thickness will be less than 1mm after crown prep
What are two most common lattices for metal?
1. Face centered cubic cell
2. Body centered cubic cell
State the properties of metal
1. Strong bonds: high melting and boiling points
2. Good stiffness: high modulus of elasticity
3. Ductile: can be pulled into wires
4. Malleable: can be beaten into sheets
5. Good conductor of heat and electricity
6. Opaque (non aesthetics)
Define an alloy
Two or more metals that are mutually soluble in each other in the molten state
How does the grain size of alloy affect its yield stress?
1. Finer grain structures = higher yield stress values (better tensile strength)
2. Finer grain structures is achieved by rapid cooling (more nuclei formed)
Define precious metal
Contains metals of high economic value: gold, platinum, palladium, silver, rhodium, iridium, ruthenium and osmium
Define noble metal
A precious metal that is tarnish to resistant (thus silver is not a noble metal)
Define gold substitute alloys
Precious metal alloys NOT containing gold
Define base metal alloys
Alloys not containing precious metal to impart their corrosion resistance
Distinguish type I and type IV high-noble alloys
1. Type I:
b) High ductility
c) High corrosion resistance
d) 85% gold
2. Type IV:
a) Extra hard
b) High tensile strength
c) High modulus of elasticity
d) Has 65% gold
What is the composition of high-noble alloys?
40% gold or 60% other noble metals
What are the uses of each type of high-noble alloys in dentistry?
1. Type I: inlay (single surface)
2. Type II: inlay or onlay (not to be used in thin sections)
3. Type III: onlay or crown (potential for fracture)
4. Type IV: crown or bridge
What are the components in a high-noble alloy and their effects respectively?
1. Gold: corrosion resistance
2. Copper: hardness
3. Silver: to counteract the reddish colour of copper
4. Palladium: increase melting point and hardness
5. Platinum: increase melting point
6. Zinc: prevent oxidation during melting (oxygen getter)
What are two types of corrosion metal undergoes?
1. Chemical corrosion
2. Electrochemical corrosion
What are the categories of electrochemical corrosion?
1. Galvanic corrosion
2. Local galvanic corrosion
3. Concentration corrosion
4. Stress corrosion
What changes in the composition of noble alloys (from high-noble alloys)?
Increases copper, silver, and palladium to substitute gold
What are other alloys that can be substituted for type III and IV high-noble alloys?
1. Very strong (25% stiffer than any high-noble alloys)
2. Can be used for long span and implant supported prosthesis
3. Palladium resists corrosion
What are the use of silver-palladium alloy?
Suitable for low stress bearing inlays due to low strength and high ductility
Give an example of base metal alloys and its use
1. Cobalt chromium: removable partial denture
2. Nickel chromium
What are the composition of base metal alloys?
1. Cobalt: 35-65% (hardness)
2. Chromium: 11-26% (corrosion resistance unless subjected to high concentration of chlorine)
3. Nickel: 0-30% (hardness and ductility)
4. Molybdenum: little amount (strength and hardness)
What are the advantages of cobalt/nickel chromium?
1. High modulus of elasticity (can be used in thinner sections)
3. High strength
4. Low density (feels light in patient's mouth)
Compare noble metal alloys and base metal alloys in terms of their physical properties
1. Nickel chromium (base metal alloy) is more rigid than gold
2. Noble metal alloy resist oxidation and acid attack where as base metal alloys oxidise readily and are susceptible to acid attack
3. Gold offers better accuracy/fitting since it gives less casting shrinkage
What the uses of the 4 types of base metal alloys in dentistry?
1. Type I: inlays
2. Type II: large inlays, onlays and crowns
3. Type III: bridge pontics
4. Type IV: long span bridges and implant superstructures
What are some biocompatibility concerns with alloys?
1. Palladium at low doses can cause allergic reaction
2. Nickel allergy causes contact dermatitis
3. Beryllium is known carcinogen
4. Gold and amalgam can cause lichenoid reaction
What are dental implants made of?
2. Titanium alloy (Ti6Al4V is the most common one)
What are the function of aluminium and vanadium in Ti6Al4V alloy?
Ti6Al4V consists of two lattice structure
1. Aluminium: stabilises the alpha hexagonal close packed structure
2. Vanadium: stabilises the beta body centered cubic structure
What are the advantages of using titanium?
3. Corrosion resistance (has a dynamic inert oxide layer)
4. Strong and low priced
What are the advantages and disadvantages of zirconia dental implants?
2. No allergies
3. More holistic
4. Biofilm (no plaque accumulation)
2. Chipping of crown
Define lost wax casting
A technique where a wax pattern is heated, vaporised and subsequently replaced by a metal
What are the 7 steps to lost wax casting?
Stage 1: impression
Stage 2: die production
Stage 3: wax on die
Stage 4: wax investment with a sprue
Stage 5: Investing
Stage 6: Wax burnout
Stage 7: Casting
What are the requirement of alloys in a porcelain fused to metal crown?
1. Must have potential to bond to dental porcelain (need oxide forming elements thus small amount of base metals)
2. Has a coefficient of thermal expansion similar to dental porcelain
3. Sufficiently high solidus temperature to permit the firing of porcelain on the metal framework
What are the causes of porcelain-to-metal fracture?
Fracture originating from metal surface
1. Surface metal contamination
2. Incomplete degassing
3. Under fired opaque porcelain
4. Improper metal thickness
5. Incorrect metal conditioner
6. Reused metal alloy
Fracture at opaque layer and entering the bulk porcelain
1. Porosity at opaque layer
2. Cracks at opaque layer
3. Incomplete opaque bonding from firing at a too low temperature
What are the causes of porcelain fracture?
1. Design or procedural error
a) Too little bulk of metal
b) Sharp angles in porcelain
c) Improper margin design
2. Malocclusion or impact stresses
3. Thermal contraction incompatibility
a) Built in stresses generate cracks at pores
b) Thermal fatigue propagates cracks
Which all ceramics system has the highest flexural strength and fracture toughness?
Polycrystalline oxide ceramics
What are the uses of glass ceramics? And state example of brand names.
1. Inlay and onlay
3. Anterior single crown
1. Empress I
2. Empress II
3. Empress Esthetic
*provides high aesthetics but weak
What are the uses of glass infiltrated ceramics? And state example of brand names.
1. Substructure for anterior and posterior single crowns
1. In ceram Alumina
2. In ceram Spinell
3. In ceram Zirconia
*less porosity thus provides better strength but loses aesthetics
What are the uses of polycrystalline oxide ceramics? And state example of brand names.
1. Anterior and posterior single crowns (alumina/zirconia)
2. Anterior and posterior bridge framework (zirconia)
*uses CAD/CAM technology
What are the disadvantages of traditional feldspathic porcelain?
1. Low fracture resistance
2. Construction technique sensitive
a) Shrinkage due to fusing when fired
b) High skills required to achieve good aesthetic
3. Low flexural strength
Why do porcelains fracture (especially feldspathic porcelain)?
1. Inability to dissipate stress due to lack of shared free electrons
2. Flaws are created during manufacturing which leads to stress concentration (act as initiating sites for crack formation)
3. Cracks in porcelain are more likely to propagate (when subjected to tensile forces as they have low flexural strength)
4. Once a crack starts to propagate, less stress is required to continue crack propagation and the crack quickly accelerates
What are the methods to increase the fracture resistance of porcelain?
1. Provide support using a stronger substrate: laminate to metal to decrease influence of internal flaws
a) Cast substructure (porcelain fused to metal)
b) Adapted substructure (swagged foil)
c) Requires alteration to porcelain to avoid great mismatch in coefficient of thermal expansion between the two material (this is achieved by adding leucite which increases the CTE value closer to metal)
2. Produce ceramics that are tougher and stronger
a) High strength crystalline ceramics as a core: milled from prefabricated high strength block (Procera)
b) High leucite ceramics as core: high leucite (crystalline fillers) glass ceramics (IPS Empress)
What are the grades of chipping and how are they treated?
1. Grade 1: fracture surfaces were polished
2. Grade 2: fracture surfaces were repaired with resin based composite
3. Grade 3: severe chipping requiring replacement of affected prosthesis
What is leucite-reinforced ceramics?
1. Feldspathic glass infiltrated by leucite crystal
2. Leucite has good optical properties
3. It also has a large coefficient of thermal expansion (when compared to other feldspar glasses) which made it easier to fit the veneer over metal sub structure (PFM crowns and bridges)
4. Leucite is a potassium-aluminium-silicate mineral
5. Brand name: IPS Empress
What is ceramic optimised polymer?
1. A material that combines the aesthetics of ceramics, the handling of veneering resins and unmatched abrasion of natural enamel
2. Also known as ceromer (ceramics + polymer)
3. Features a high particle content of inorganic filler (fine ceramic particles) and an organic matrix that fills the spaces between the particles
4. Brand name: Targis
How does zirconia help prevent crack propagation?
1. Zirconia exists in 3 different states:
2. From transforming from a) to c) the material expands
3. Force is applied to the material > creates stress > meta stable tetragonal phase > stable monoclinic phase > expansion closes the gap > prevents crack propagation
How do traditional cements retain crowns and bridges?
By frictional fit
What are some of the uses of dental cements?
1. Luting, fixation, cementation: used for luting inlays, crown, veneers etc on prepared tooth (Eg: glass ionomer)
2. To protect pulp from heat and chemical irritation: used as liners and bases (Eg: calcium hydroxide and zinc oxide eugenol)
3. To stimulate secondary dentine formation
4. As a temporary filling material (Eg: glass ionomer or resin modified GI)
Define luting agent
A material that acts as an adhesive to hold together an indirect restoration to the tooth structure. They are designed to be either permanent or temporary
What are permanent cements used for?
1. Long term cementation of cast restoration
2. Eg: inlay, crowns, bridges, laminate veneers and orthodontic fixed appliance
What are temporary cements used for?
1. When the restoration has to be removed eventually
2. Eg: temporary/provisional restoration
What are the variables affecting the cement?
1. Mixing time: ensure manufacturer's instructions are followed for mixing time, working time and delivery time
2. Humidity: premature exposure of cements to humid/warm environment can create a loss of water from liquid or add moisture to powder (which affects the delivery time)
3. Powder to liquid ratio: consistency is altered with too much or too little powder
4. Temperature: some cements have an exothermic reaction (should be mixed on a cool slab)
5. Thickness: there should be sufficient cement to fill the space but not too thick that it causes occlusal interference
What is the general setting reaction of cements?
Powder (basic) + liquid (acidic) = salt (cement) + water
*it is an acid base reaction
What are ideal properties of cements?
1. Low viscosity and film thickness (good flow characteristics)
2. Low solubility (to maintain marginal seal)
3. Translucency (for aesthetics purposes)
4. Radiopacity (to help distinguish between recurrent caries)
6. High compressive and tensile strength
7. Adequate working time and ease of use
What are two categories of cements?
1. Adhesive: chemical and mechanical interlocking
2. Non adhesive (conventional): micromechanical only (as it is filling space)
State the chemical reaction of zinc oxide eugenol cement
Zinc oxide + eugenol = zinc eugenolate (chelated structure) + water
What are features of zinc oxide eugenol cement?
1. Powder: zinc oxide + zinc acetate
2. Liquid: eugenol + olive oil
3. Sets very slowly unless moist
4. Mechanically weak
5. Can be used as lining in deep cavities without causing harm to the pulp
6. Has a desensitising effect on dentine (due to oil of cloves)
7. Main uses:
b) Temporary cement
8. Trade names:
a) Temp E
What are features of resin modified zinc oxide eugenol cement?
1. Powder: zinc oxide
2. Liquid: eugenol + resin
3. Very low irritancy to pulp
4. Due to presence of resin it has better mechanical properties than ZnOE
5. Main uses: linings
6. Trade name: Kalzinol
What are features of EBA cements?
1. Also another modified ZnOE
2. Powder: zinc oxide + zinc acetate + resin + silica
3. Liquid: eugenol + resin + EBA
4. EBA encourages the formation of crystalline structure which produces a stronger matrix to hold the particles together
5. Main uses:
a) Temporary cements
b) Temporary fillings
6. Trade name:
What are the features of zinc phosphate cement?
1. Powder: zinc oxide + 10% magnesium oxide
2. Liquid: phosphoric acid + water + aluminium phosphate
3. Fast reaction that results in formation of zinc phosphate
4. When powder is mixed with liquid, phosphoric acid attacks the surface of the particles and release zinc ions into the liquid
5. Water is critical to the reaction
6. A cool slab should be used for mixing to prolong setting times
7. The liquid should not be dispensed until mixing is to be initiated (to prevent water from evaporating)
8. Has two types:
a) Type I: used for luting casting. Smaller particles that enables the cement to flow out into thin layer (less than 25 micrometer) between a casting and tooth
b) Type II: all other application. Contains larger particles and can routinely achieve a film thickness of 40 micrometers
9. Main uses:
a) Luting agent
b) Temporary restoration
10. Trade name: De Trey Zinc
What are features of copper cement?
1. Powder: zinc oxide + black copper oxide
2. Liquid: phosphoric acid
3. Copper oxide is bactericidal but also gives a black appearance
4. Main uses:
a) Filling in deciduous teeth
b) Cementing splints and orthodontic devices (limited use nowadays)
What are features of silicate cements?
1. Powder: powdered glass containing alumina, silica and flourides
2. Liquid: phosphoric acid
3. First directly placed aesthetic filling material
4. Now rarely used
What are features of silicophosphate cement?
1. Powder: zinc oxide + aluminisilicate glass
2. Liquid: phosphoric acid + buffer
3. A hybrid of silicate and phosphate cement
4. Main uses:
a) Filling in primary teeth
b) Cementing porcelain crown/orthodontic bands
5. Trade name:
What are features of polycarboxylate cements?
1. Powder: zinc oxide + 10% magnesium oxide
2. Liquid: polyacrylic acid solution
3. Reaction forms zinc polycarboxylate
4. Rapid setting reaction of 30-40s
5. Psudoplastic thus care should be taken not to produce thinner mixes
6. Trade name:
a) Poly F plus
7. Stronger than zinc oxide eugenol but weaker than zinc phosphate
8. Reaches a neutral pH within 5-30 minutes
9. Appears viscous but flows under pressure
10. Sets within 6-9 minutes
11. Adhesive and fairly biocompatible
12. However it is soluble
What are features of calcium hydroxide cement?
1. Main constituent: calcium hydroxide paste
2. Simplest version is suspension of calcium hydroxide in water (which dries out to give a layer of calcium hydroxide)
3. Anti bacterial and may promote remineralisation of dentine
4. Main uses:
b) Pulp capping
c) Pulp protection
5. Trade names:
How do modern cements differ from traditional cements and what are examples of modern cements?
1. Modern cements are adhesive (do not rely on frictional fit)
a) Resin modified glass ionomer cement
b) Resin cement
c) Compomer cement
What are features of resin cements?
1. Composition: bis GMA or urethane dimethacrylate with fillers of barium glass or silica
2. Set by chemical reaction (self curing) or dual cured (chemical and light curing)
3. Adhesive (increases retention)
4. Very hard and low solubility (reduces leakage)
5. Good tensile and compressive strength (x10 more than zinc phosphate)
6. Good aesthetics
7. But difficult to remove and requires separate adhesive agents to be applied
8. Adhesive system:
a) Micromechanical bond to tooth
b) Chemical bond to porcelain and metal
9. Trade names:
b) Rely X
What are features of one step resin cement?
1. Flows under pressure
2. No prior preparation of enamel or dentine is used (self adhesive)
3. Releases fluoride
4. Bonds all ceramics, resin composites and metals
5. Moisture tolerant
6. Compressive strength of about 200 MPa
7. Dual cured: acid base reaction of inorganic fillers with phosphoric acid methacrylates
What are the different conditioning required for different ceramics?
1. Glass ceramics: etching with 95% hydrofluoric acid and silanization
2. Glass infiltrated ceramics: sandblasting 100mm with alumina oxide
3. Oxide ceramics (Al): sandblasting 100mm with alumina oxide and silanization with MDP
4. Oxide ceramics (Zr): sandblasting 50mm with alumina oxide and silanization with MDP
Why do we finish/polish restoration?
1. To remove excess material so that the restoration fits
2. To produce a smooth surface
3. Maintain correct occlusal relationship
4. Reduce intraoral corrosion of metal restoration
5. Enhance aesthetics and longevity of restored teeth
Describe the sequential use of finishing instruments?
1. Gross reduction, contouring and marination:
a) Coarse treatment with abrasive particle 100 micrometers or larger
b) Efficiently remove restoration materials with minimal removal of adjacent sound tooth structure
2. Intermediate abrasive finishing:
a) Medium treatment with abrasive particles less than 100 micrometers but greater than 15 micrometers.
b) Removes severe scratches and surface defects created by initial procedure
3. Final polishing:
a) Fine treatment with abrasive particles ranging from less than 20 micrometers to 0.3 micrometers
b) Results in an enamel like lustre to surface of restored teeth
What are the two types of abrasive in dentistry?
1. Bonded: sandpaper, cut-off discs
2. Loose: toothpaste, polishing paste
What are the factors affecting abrasion?
1. Velocity of the abrasive (directly proportional)
2. The force applied to the abrasive (directly proportional)
3. The hardness of the material being abraded (inversely proportional)
4. Particle size of both the abrasive and composite (also type of particles in the composite)
5. Shape of the abrasive (the sharper the more effective)
6. Lubrication (water is the most common lubricant)
What is the side effects of abrasion?
1. Material from the scratch is displaced
2. Distortion in region adjacent to the scratch
What are instruments for gross reduction?
1. Diamond burr
2. Fluted finishing burr
3. Abrasive finishing disc
What are instruments for intermediate reduction?
1. Coated abrasive disc
2. Bonded abrasive devices
3. Fine diamond and multi fluted finishing burr
What are instruments for final finishing and polishing?
1. Extrafine coated abrasives
2. Loose abrasive polishing paste
What are the porcelain to metal bonding mechanism?
1. Mechanical bonding (extensive)
a) Sandblasting provides surface roughness which leads to mechanical inter-digitation
- Surface energy determines wetting
- Surface roughness determines degree of mechanical inter-digitation
2. Chemical bonding (extensive)
a) Occurs by oxide mixing
- Thin metal oxide alloys with porcelain oxide
- Transition zones of oxide from metal to porcelain
b) Oxidation of metal alloys
- Tin, indium, iron or zinc may be added to alloy
- Pre oxidising treatment may be painted on surface
- Metalizing bonding agents may be painted on
*there is no physical bonding
What is the most common oral malignant neoplasm?
Squamous cell carcinoma
What are some other uncommon oral malignant neoplasm?
1. Malignant salivary gland tumours
2. Malignant melanoma
4. Neoplasm of bone and connective tissue
5. Metastatic neoplasm (from breast, lung, kidneys etc)
What are the 3 aetiology factors of squamous cell carcinoma ?
What are the lifestyle factors associated with SCC?
1. Tobacco use
2. Alcohol consumption
3. Sexual lifestyle
4. Poor oral hygiene
5. Dietary factors
What are the environment factors associated with SCC?
1. Socioeconomic factors
2. Exposure to other carcinogens (irradiation, HPV)
What are 3 factors in a competent immune system?
1. Infection control
3. Clearance of altered autologous cells
What are the genetic factors associated with SCC?
1. Chronic inflammatory mucosal disease
2. Defects in DNA repair
3. Defects in immune system
What is a carcinogen?
Any substance, radionuclide or radiation that is an agent involved in causing cancer. They either damage the genome or disrupt the cellular metabolic process
1. Genotoxin: causes irreversible genetic damage or mutation by binding to DNA (Eg: NMU, UV light)
2. Nongenotoxin: do not directly affect DNA but act in other ways to promote growth (Eg: hormones)
What are the various categories of carcinogens?
Group 1: definitely carcinogenic to humans
Group 2A: probably carcinogenic to humans
Group 2B: possibly carcinogenic to humans
Group 3: not classifiable as carcinogenic to humans
Group 4: probably not carcinogenic to humans
Describe the multiple steps to cancer?
1. Mutagenic agent acts on DNA in basal cells
2. DNA mutation
3. DNA mutation escapes DNA repair
4. DNA mutation is not lethal to cell
5. DNA mutation escapes apoptosis
6. Mutated viable cell escapes immune system
List some of the premalignant chronic mucosal inflammatory lesion
1. Lichen planus
4. Lichenoid lesion
What are the clinical signs of SCC?
1. Swelling, thickening or roughness on the tongue, cheek or floor of mouth
2. White/red patches along the side of the tongue or on the lip
3. Persistent sores in the lips, tongue, palate or throat
4. Erosive lesion with hard borders
6. Unexplained bleeding in the mouth or throat
7. Soreness in the back of mouth or in the throat
8. Hoarseness, chronic sore throat or changes in the voice
State the dose of radiotherapy for oral cancer?
1. Total dose: 50-70 Gy
2. 1.8-2 Gy per day 5 days a week over 6-8 weeks
3. Among the complications are:
b) Salivary gland damage > xerostomia > candidosis
c) Osteoradionecrosis (if total dose is more than 50 Gy it will never be safe to extract teeth)
Describe the TNM staging system
1. T: describes size and degree of invasion of tumour
T0: no sign on primary tumour
Tis: carcinoma in situ
T1: less than 20mm
T3: more than 40m
T4: tumour extends into bone, skin and neck
2. N: describes the involvement of regional lymph nodes
N0: no tumour cells in regional lymph nodes
N1: single regional lymph node metastasis on the same side less than 30mm
N2: single regional lymph node metastasis on the same side 30-60mm
N3: tumour spread to contra lateral side and to numerous lymph nodes
3. M: describes distant metastasis
M0: no distant metastasis
M1: metastasis to distant organs (beyond regional lymph nodes)
What is the treatment of oral candidosis?
1. Control of predisposing factor
2. Clearance of infection foci
3. Anti fungals
a) Primarily topical (Nystatin and Chlorhexidane)
b) If patient is immunocompromised combine with systemic anti fungal for a week
What are the two common strains that causes candidosis in cancer patients?
1. Candida Glabrata
2. Candida Krusei
*also the strain that gets resistance to Azoles
How does alcohol cause oral cancer?
1. The first metabolite of alcohol is acetaldehyde which is mutagenic
2. This can occur either
a) In the liver: liver cancer
b) In the mouth via oral microbes (they possess alcohol dehydrogenase enzyme): mouth cancer
What are aerobic microorganisms in the mouth?
1. Gram positive cocci
a) Staph (aurius, epidermidis)
b) Strep (milleri, mutans, pyogenes, sanguis)
2. Gram negative cocci
3. Gram positive rods
4. Gram negative rods
What are anaerobic microorganisms in the mouth?
1. Gram positive cocci
2. Gram negative cocci
3. Gram positive rods
4. Gram negative rods
a) Bacteroides (gingivalis, intermedius, oralis)
What are the common culprits in oral infection?
1. Gram negative rods
2. Gram positive cocci
What are the different types of antibiotics based on their mode of action?
1. Action on cell wall/membrane
2. Inhibition of protein synthesis
3. Inhibition of nucleus acid synthesis
List the non resistant and resistant penicillins with beta-lactamase
1. Non resistant
c) Co amoxiclav
List three broad spectrum penicillin
3. Co-amoxiclav (amoxicillin and clavulanic acid)
How does tetracycline inhibit bacteria protein synthesis?
1. By blocking tRNA binding
2. Examples of antibiotics from this class are
How does aminoglycosides inhibit bacterial protein synthesis?
1. By blocking mRNA recognition
2. Examples of antibiotic using this mechanism are
3. By translocation
4. Example of antibiotic using this mechanism is
List examples of parenteral and broad spectrum cephalosporins
2. Broad spectrum
List examples of Quinolones
2. Naladixic acid
What are adult doses for some common antibiotics?
1. Penicillin V: 500mg-1000mg QDS
2. Amoxycillin: 250-500mg TDS
3. Flucloxacillin: 250-500mg QDS
4. Metronidazole: 200-400mg TDS
5. Erythromycin: 250-500mg QDS
6. Cefalexin: 250-500mg QDS
7. Cefradine: 250-1000mg QDS
What are signs of anaphylaxis?
1. Itching, flushing, hives
5. Laryngeal oedema
6. Loss of consciousness
7. Cardiac arrest
8. Weak pulse (syncope)
What antibiotics are indicated and contraindicated in a pregnant woman?