Enamel Hypoplasia

The cell responsible for enamel formation is the ameloblast. If the ameloblast is exposed to a stress when it is in its secretory phase it will stop secreting enamel matrix properly and the result will be an enamel hypoplasia. This enamel hypoplasia will then be a feature of the tooth for long after the person it was attached to is dead and buried, unless it is worn away. The permanency of enamel hypoplasias coupled with the fact that teeth are so durable over time makes hypoplasias a very useful indicator of physiological stress.

Enamel hypoplasias can be seen as: no enamel at all, grooves, horizontal lines and pits. Ameloblasts lay down enamel matrix in increments. These increments are separated by striae of Retzius, which under light microscope are seen as perikymata at the crown’s lateral surfaces. Each increment indicates a constant period of growth in an individual of between 6-12 days. This period of growth in an individual can be determined by counting the number of daily growth striations (seen as cross striations) within each increment.

Linear enamel hypoplasias (LEH) are seen as enlargements of the width of the striae. This enlargement is the result of enamel matrix not being secreted by the ameloblast during periods of stress. An LEH is seen as a groove; one side of the groove is called the occlusal wall (closer to the occlusal surface of the tooth) and represents the period of disrupted enamel formation and the other side of the groove is called the cervical wall (closer to the cervical part of the tooth) and represents the period of return to normal enamel formation. The duration of the disruption of enamel formation can be found by multiplying the number of perikymata in the occlusal wall by the daily growth striations within those perikymata. For example if three perikymata are seen in the occlusal wall and each perikymata consists of 8 daily growth increments, then the duration of disruption is approximately 24 days.

Anterior Interproximal Caries

Anterior interproximal caries is detected by transilluminating the teeth from the palatal side of the teeth, usually with the reflected light of the dental mirror. Further evidence of caries can be gained by using a DIAGNOdent or similar device I suppose.

Once the diagnosis of caries is confirmed, a tooth-coloured composite should be used to restore the tooth.

Begin by anaesthetising the tooth, then using a high-speed drill, access the anaesthetised carious tooth by cutting through the enamel. Access the tooth from the palatal side if possible so that the appearance of the tooth is affected as little as possible. A small round bur is usually used for palatal access in the high speed. Now remove the carious enamel and dentine with a low speed drill. Stained dentine that isn't soft should be left alone. However, if there is so much healthy but stained dentine that the tooth is visibly darkened when looking at the patient, then some healthy tissue may need to be sacrificed to improve aesthetics. A bevelled margin is important, especially on incisal margins and larger two-surface restorations. Prepare some glass ionomer cement (GIC) and line the cavity with it. Next construct the composite restoration.

The composite restoration is constructed in four steps:

1. First, apply mylar matrix strip and wedge the tooth to be restored, then acid etch the GIC-lined cavity to remove the microscopically small smear layer that blocks the dentinal tubules and to create porosities in the outer layer of enamel which allows micromechanical bonding between composite/adhesive and enamel.
   
2. Second, apply the primer - the primer lowers the contact angle of the adhesive liquid, thus helping it spread over the cavity.
   
3. Third, apply the adhesive (adhesive is the composite less the filler) to bridge the composite to the tooth and light cure it.
   
4. Fourth, apply the composite in steps, light-curing between and after the final step. The mylar matrix strip is wrapped around the tooth to shape and merge the composite to the tooth correctly.

Now that the restoration has been constructed, finish by polishing with Sof-Lex discs or other suitable polishing instruments. The fine-finishing bur in the high speed creates an excellent finish on the composite.

Syndromes Relevant to Dentistry

The word syndrome is derived from greek and means 'runs together'. Syndromes refer to medical conditions that have signs and symptoms that often occur together. A syndrome has no known cause, but may still be referred to as a syndrome even after the cause has been discovered, e.g. AIDS. If a dentist is alerted to one or more signs and/or symptoms of a suspected syndrome, they should look out for the other common signs and symptoms of the syndrome.

Neural Crest Syndromes

• DiGeorge Syndrome - remember the description of this syndrome with the mnemonic CATCH 22 - Cleft palate, Abnormal facies, Thymic aplasia, Cardiac defects, Hypocalcaemia, 22q11.2 deletion. May be caused by migration defects of neural crest derived tissues.
  
• Hemifacial microsomnia - lower half of face affected (on one or both sides). Most commonly mouth, mandible and ears.
• Sturge-Weber Syndrome - most obvious feature is a port-wine stain on the face. Neurological abnormalities are also commonly seen as angiomas can develp on the brain (the same side as the port-wine stain). Glaucoma also commonly develops. Increased vascularity of the hard and soft tissue of the jaw on the same side as the port-wine stain may occur and this can cause dental problems such as swelling, premature tooth eruption and periodontal problems.
  
• Thalidomide malformations - phocomelia (very short or absent long bones). (S) enantiomer of thalidomide thought to be the neural crest toxin.
  
• Treacher-Collins - often present with underdeveloped facial bones, micrognathia, microtia, cleft palate. Half have hearing problems due to defects in middle ear bones.
  

Motivational Interviewing

The idea behind motivational interviewing is that giving people direct advice is not a good idea for a number of reasons:

• they may not have given you all the relevant information for whatever reason
• what would work for you may not work for them
• offering advice can seem condescending and judgemental
  

therefore motivational interviewers work from the premise that the person with the problem is actually in the best position to find the most ideal solution that would work for them and that the interviewer's role is to assist them to come up with their own solution.

Motivational interviewing has 4 principles: express empathy, develop patient's discrepancy, manage patient's resistance, and support patient's self-efficacy.

1. Express empathy - Listen to the patient and use your reflective listening skills so they feel listened to.
2. Develop patient's discrepancy - help the patient see the gap between what they want and how they're acting. For example, "you've told me you really want to stop smoking, but two months later you're still smoking a pack a day". The point here is to highlight the discrepancy between the patient's goals and their behaviour, not to tell them off or make them feel judged. Try to discover what it might be that is causing this discrepancy. For example, perhaps they have a partner who smokes around them? Once barriers are discovered, work with the patient to find ways around them.
   
3. Manage patient's resistance - the patient is in control. If they don't want to talk about something, don't insist - you will only piss them off.
   
4. Support patient's self-efficacy - encourage patient to come up with their own solutions. Praise any progress they make.
   

Reflective Listening

Reflective listening is where you put aside your own feelings and get really interested in what the other person has to say without giving in to the temptation of offering advice. It helps to pretend to be a reporter who is trying to get enough information from the other person, so they can write an accurate report.

There are two types of reflective listening. Simple reflective listening, where you simply repeat back what the person has said to you and complex reflective listening, where you repeat back what they said and how they feel in your own words.

Complex reflective listening builds rapport with the patient and is a good way to check that you have perceived what the patient said correctly. The patient also gets to hear what they have just said and consider if what they said is really what they meant or how they feel. This may lead to the patient questioning the beliefs that cause them to engage in unhealthy behaviour.

It is not always essential to reflect back both the content of the patient's message and their feelings. In fact, it is probably better to save this until after you have enough information to feel confident that you understand both the content and the feeling behind what they have told you. Sometimes it is better to just paraphrase the facts (content) of the patient's message and other times it may be better to focus entirely on how the patient must feel.

Examples

Paraphrase facts
"You would like to keep the tooth if possible because you can't afford an implant"
Reflect feelings
"You're upset because you've had to wait a long time to get an appointment"
Complex reflective listening
"You're frustrated because this is the second time you have had to come in to have your dentures fixed. You've already spent $500 and it's been over a month since you first came in"

Click here to read a good article on communication skills, including reflective listening.

Dental Definitions

This page will be updated regularly as I think of new terms that should go on it.

Ameloblast
A specialised epithelial cell responsible for laying down enamel during tooth development.

Armamentarium
Consists of the syringe, needle and cartridge.

Ectoderm
The embryonic tissue that gives rise to the nervous system and body surfaces including enamel and the epidermis. The neural crest is also derived from the ectoderm.

Ectomesenchyme
See Neural crest

Enamel
Hardest substance in the body made from ameloblasts during tooth development. Composed of calcium and potassium, mostly in the form of hydroxyapatite.

Endoderm
The embryonic tissue that gives rise to much of the gastrointestinal tract, respiratory tract and endocrine glands including the liver and pancreas.

Hydroxyapatite
The potassium and calcium mineral - Ca₁₀(PO₄)₆(OH)<sub>2 - found in enamel, dentine, cementum and bone. Highest concentration is found in enamel. The OH ion can be replaced with fluoride which makes the mineral harder.

Inferior Alveolar Nerve
Originates from the mandibular nerve, one of the branches of the trigeminal nerve. The inferior alveolar nerve carries sensory information from all the teeth,</sub> the bone and gum of _{the mandible. The inferior alveolar nerve gives rise to the mental nerve.}

Mesenchyme
Originates from the mesoderm and forms connective tissue - bone and cartilage - among other things.

Mesoderm
The embryonic tissue that gives rise to all the tissues of the teeth except enamel. Also gives rise to muscle and bone.

Methaemoglobinaemia
Higher than normal methaemogolobin in the blood. Signs and symptoms include shortness of breath, fatigue, cyanosis and loss of consciousness. Methaemoglobin is a form of haemoglobin that does not bind oxygen. Methaemoglobinaemia can be caused by the local anaesthetics prilocaine and articaine.

Neural crest
A transient component of the ectoderm that appears during the formation of the neural tube. The neural crest cells migrate after the neural tube has closed and give rise to the bones and muscles of the face. These cells are also referred to as 'ectomesenchyme' because they behave like mesenchyme, but unlike the mesenchyme, they are derived from the ectoderm.

Pericoronitis
Swelling and infection of the gums surrounding a tooth. Common in partially-erupted third molars.

_{Periodontium
The tissue that surrounds and supports the teeth. Periodontium consists of alveolar bone, cementum, gingiva, and periodontal ligament.}

Signs
Features of a medical condition seen by the dentist.

Symptoms
Features of a medical condition experienced by the patient

Syndrome
Literally means 'runs together'. A syndrome is a medical condition characterised by a collection of signs and symptoms that often occur together and which usually has no clear cause.

_{Trigeminal Nerve
The fifth cranial nerve. Three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves.}

Trismus
Inability to open mouth. Most commonly caused by a pericoronitis of the third molar or inflammation of the muscles of mastication.

Inferior Alveolar Block

There are 3 methods of achieving inferior alveolar block: Direct, Gow-Gates, and Akinosi. I will only cover the Direct method here.

Direct method
Your thumb should be positioned on the coronoid notch of the mandible as shown in the adjacent photo and your first finger should be positioned on the posterior border of the ramus on the patient's jaw.

We anaesthetise the inferior alveolar nerve by inserting the needle about 1 to 1.5 cm above the mandibular occlusal plane and about halfway between the coronoid notch and the pterygomandibular raphe. If the barrel of the syringe is over the contralateral premolars, then the angle will be about right.

Push the needle in until bone is felt (a depth of 2-3 cm usually), then withdraw the needle slightly away from the bone - the end of the needle should now be in the pterygomandibular space. Now aspirate to ensure the needle isn't in the inferior alveolar artery or vein before slowly injecting the local anaesthetic into the pterygomandibular space. We inject here because this is where the inferior alveolar and lingual nerves can be found.

Provided this was done correctly, after a few minutes the entire bone, periodontium, gum and teeth of the side injected will be anaesthetised. A bit of the tongue, the lip and the skin on the chin will also be anaesthetised on that side.

Complications
Never buy pink pills from turban headed indian liquor shop owners. That's the mnemonic to remember the complications of anterior alveolar nerve block.

• Never - Needle Breakage
  
• Buy - Bruising
  
• Pink - Pain
  
• Pills - Paraesthesia
  
• From - Facial paralysis
  
• Turban - Trismus
  
• Headed - Haematoma formation
  
• Indian - Infection
  
• Liquor - Lip biting
  
• Shop - Sloughing
  
• Owners - Oedema

Other complications are transmission of infections, fainting, and methaemoglobinaemia (prilocaine and benzocaine).

History and Examination

After looking at a few different examples on how to go about performing a thorough history and examination on dental patients, I feel most comfortable with this format (so far):

RFV (Reason For Visit)

In the patient’s own words. “Why did you come to see us today?”

HPC (History of Presenting Complaint)

If applicable

MH (Medical History) First go over medical questionnaire with client.

“Are you taking any medicines or drugs?” Look for prescribed, pharmacy, supplements, social drugs	Drug related questions (4)
“Have you ever smoked?
“Do you drink alcohol or take any social drugs?”
“Have you ever had any allergies?” Penicillin especially

“Have you ever been admitted to hospital for an operation?”	Operations and cardiorespiratory (4)
“Have you ever had any problems with your heart?” Blood pressure too.
“Have you ever had any problems with bleeding?”
“Have you ever had any problems with your chest or with breathing?” Asthma and infections.

“Are you pregnant?”	Miscellaneous (2)
“Are you fit and well?”

DH and SH (Dental History and Social History)

“How often do you go to the dentist?”	At the dentist (5)
“When was the last time you went to the dentist and what did the dentist do?”
“What types of dental treatment have you had previously?” Identifying problems with GA or LA and finding out what has been done before – orthodontics, periodontics, root canal…
“How do you feel about dental treatment?”
“What do you think about the appearance of your teeth?”

“How do you take care of your teeth?”	Brushing and flossing (3)
“How often do you brush your teeth and how long for?”
“How often do you floss?”

“Have you ever had any pain or clicking from your jaw joints?”	Bruxing (2)
“Do you grind your teeth or bite your nails?”

“Can you tell me what you’d typically have for breakfast…lunch…dinner?	Diet (3)
“What are your favourite foods?”
“What are your favourite drinks?”

“What do you do?” SES	Miscellaneous (2)
“Where do you live?” Fluoride and traveling distance/time

EO (Extra Oral Examination)

Head and face appearance – symmetry, colour, swellings.

Eyes – colour

TMJ – feel for clicking, locking or crepitus. Also feel muscles of mastication for tenderness.

Neck – palpate from behind starting under chin.

IO (Intra Oral Examination)

Oropharynx and tonsils.

Inspect entire oral mucosa.

Examine teeth for caries and quality of any restorations. Chart teeth present.

Occlusion – relationship between arches. Prematurities and displacements seen during closure?

CPITN.

Oral hygiene.

The Armamentarium and Basic Injection Technique

The Armamentarium

The armamentarium is composed of:

1. The syringe
2. The needle
3. The local anaesthetic cartridge

The syringe - The syringe has three parts - a screw thread to attach the needle, the plunger to push the contents out of the cartridge, and the ring to allow the dentist control over administering the local anaesthetic. Syringes can be reusable metal or disposable plastic. Most metal syringes allow the dentist to aspirate. Aspiration is useful so that the local anaesthetic isn't inadvertently injected into a vein. This is particularly important if there is adrenaline in the cartridge as adrenaline injected into the vein may cause the patient's heart rate to skyrocket. The plastic syringe has the advantage of being disposable which is desirable from a cross-infection point of view.


The needle - The needle has one end that penetrates the diaphragm of the cartridge and the other end penetrates the person. Needles come in different lengths and diameters. Common lengths are long (41mm), short (25mm) and ultra-short (10mm). The diameters are expressed by the term "gauge". The gauge of a needle is indicating the internal diameter of the needle. Something that confuses me is that the thinner the needle is the larger its gauge is. For example, a 30 gauge is thinner than a 25 gauge! Theoretically the greater the gauge the less painful an injection will be, but in practice patients usually experience the same sensation from 30 gauge to 23 gauge.


The cartridge - The cartridge contains the local anaesthetic and usually a vasoconstrictor like adrenaline. The vasoconstrictor causes the blood vessels adjacent to the injection site to constrict which means that less local anaesthetic gets into the systemic, so less is needed to achieve anaesthesia where needed.

Basic Injection Technique

Commonly used local injection techniques are infiltration, nerve block, intrapulpal, supraperiosteal, intraligamental, and intraosseous.

If the cartridge is below room temperature - as it will be if stored in the refrigerator, it must first be warmed to room temperature. This will make the experience much more comfortable for the patient.

Put personal protective equipment on - gloves, mask, eye wear, etc.

Now load the cartridge followed by the needle into the syringe. Check the flow out of view from the patient and don't spray into the air like you see on the movies. That sort of thing scares patients.

Now that the armamentarium is ready, prepare the patient by tilting them back 45 degrees and adjusting the height of the chair so that the patient's head is at your elbow level.

Dry the area you will be injecting into with some cotton gauze.

Next you may apply topical anaesthetic to the area. Supposedly this will cause anaesthesia 2-3mm into the mucosa if allowed to penetrate for 2 minutes. This topical anaesthetic should make the initial penetration of the needle painless.

While waiting the 2 minutes for the topical to kick in, run through the procedure with the patient.

Now bring the syringe to the patient - keeping it out of their view. Stretch the mucosa you will be injecting into to minimise the pain and tissue damage. Then, making sure you have a good finger/hand rest, insert the needle the length of its bevel into the mucosa. Inject a drop of local anaesthetic - wait a moment - then push the needle into the tissue a little deeper and inject another drop. Continue this process until the target is reached.

Now that the target is reached, aspirate to ensure you're not injecting into a blood vessel, and then slowly deposit the rest of the local anaesthetic (a 2.2mL cartridge should take no less than 2 minutes to inject). While doing this communicate with the patient and observe them for signs of discomfort or reaction to the contents of the cartridge.

If the patient faints (vasodepressor syncope), lie him flat with feet at or slightly above chest level.