Anatomy of the Temporomandibular(TMJ) joint

TMJ is a synovial joint between condyle of the mandible an mandibular fossa on the undersurface of the squamous part of the temporal bone.

The mandible is the single bone with the horizontal horse shoe shaped body, which is continuous at its posterior ends with a pair of vertical rami, each ramus is surmounted by a head or condyle.

The temporomandibular joint allows opening and closing the mouth and complex chewing or side to side movements of the lower jaw.

  

The cranium with which the mandible articulates, is also mechanically, a single componenet, with a mandibular fossa on each side. This complex is in effective functioning joint, as movement cannot take place at one temporomandibular joint, as movement cannot take place at one TMJ without a concomitant movement occurring at the joint on the opposite side.

The temporomandbular joints are thus the bilateral components of a craniomandibular articulation.

The joint is separated into upper and lower joint cavities by a fibrocartilagenous disc within it. Both bone surfaces are covered with a layer of fibrocartilage identical with that of the disc. There is no hyaline cartilage in the joint, so it is an atypical synovial joint.

The capsule is attached high p on the neck of the mandible anteriorly, near the articular margin of the head, but lower down the neck posteriorly. Above, it is attached anteriorly just in front of the articluar eminence of the temporal bone,posteriorly to the squamotympanic fissure,and medially and laterally to the margins of the mandibular fossa. It is lax above the disc, but taut below. The synovial membrane lines the inside of the capsule and the intracapsular posterior aspect of the neck of the mandible.

The articular disc attached around its periphery to the inside of the capsule and to the medial and lateral poles of the head of the mandible. Its upper surface is anteroposteriorly concavoconvex in the sagittal plane to fit the articular eminence and fossa. The inferior surface is concave in adaptation to the condyle. Anteriorly disc is continuous through its capsular attachment with the tendon of lateral pterygoid. 

Posteriorly disc divided into two laminae. The upper fibroelastic lamina is attached to the margin of the mandibular fossa. The lower non elastic fibrous lamina is attached to the neck of the mandible. Between the two laminae is a pad of loosely textured tissue continuing many blood vessels and sensory nerve endings. The disc has two transverse thickened bands it is thinnest and relatively avascular.

Temporal ligament and sphenomandibular ligament reinforce the capsule making it more strong.

Mandibular movements Video

TMJ Disc interferece disorders Videos

The temporomandibular system consists of three basic components; the temporomandibular joint or TMJ, the teeth,and the neuromuscular system.

Temporomandibular disorders come in many forms and varying degrees of severity. Basically TMD is a problem when you either experience pain and/or a loss of jaw function. The pain can range from a mild ache in the morning to a chronic debilitating pain. Loss of function can be mild jaw stiffness to being unable to open the jaw barely at all.

Disc interference disorders are one Category of TMDs.

 

Normal TMJ

 

Anterior disk displacement with reduction

 

Anterior disk displacement without reduction

 

How to Brush Your Teeth Properly

How to Brush your Teeth Properly Video

Pharmacological management of pain and anxiety-Paediatric Dentistry

Introduction

Effective pain management of a child, especially an anxious one, is a challenge to every dentist. The need for good management of anxiety and pain in paediatric dentistry is paramount. A common cause of complaint from parents and their children is that a dentist 'hurt' unnecessarily. Such a complaint can jeopardize access to life-long dental care.

Children are anatomically and physiologically different from adults. The anatomy of the airway means that breathing is through a narrower, more fixed 'wind pipe'. Physiologically, a child is less capable of taking in a bigger volume of air even when urgently required. Coupled with this, both the demand for oxygen (consumption) and the incidence of periodic breathing and apnoeas are higher compared to adults. These differences mean that a child can become hypoxic more easily.

Children's perception of pain

A child's perception of pain is purely subjective and varies widely, particularly with age. Infants up to about 2 years of age are unable to distinguish between pressure and pain. After the age of approximately 2 and up to the age of 10, children begin to have some understanding of 'hurt' and begin to distinguish it from pressure or 'a heavy push'. The problem is that it is not always possible to identify which children are amenable to explanation and who will respond by being co-operative when challenged with local anaesthesia and dental treatment in the form of drilling or extractions. Children over the age of 10 are much more likely to be able to think abstractly and participate more actively in the decision to use local anaesthesia, sedation, or general anaesthesia. Indeed, as children enter their teenage years they are rapidly becoming more and more like adults and are able to determine more directly, sometimes aggressively, whether or not a particular method of pain control will be used. The response is further determined by the child's coping ability influenced by family values, level of general anxiety (trait), and intelligence.

Key Points
Children are anatomically and physiologically different from adults this results in them becoming hypoxic more easily.
Children's response to pain is influenced by age, memory of previous negative dental experience, and coping ability.

Consent

Before you can do anything to a patient, even a simple examination, consent must be obtained. Consent may be implied, verbal, or written. The main purpose of written consent is to demonstrate post hoc, in the event of a dispute, that informed consent was obtained. It has the considerable advantage of making clinicians and patients pause to consider the implications of what is planned and to weigh the advantages and disadvantages so that a reasoned and informed choice can be made. The responsibility for informed consent is often shared between the referring primary care dentist and the secondary care service provider, especially where sedation and general anaesthesia are involved. Many health trusts and other employing authorities are increasingly demanding that written consent is obtained for all procedures. This is especially difficult now as the lower age of consent is no longer specifically limited. The sole criterion is whether or not the patient is 'able to understand' the procedures and their implications. If so, the patient is considered 'competent' and the child may give (or refuse) consent. It is usual to arrive at a consensus view among parents, child, and dental surgeon. A sufficiently informative entry should be placed in the patient's case records. As a pragmatic rule the age of 16 years still acts as a guide. But if a procedure is proposed and a child under 16 years says 'no' then consent has been refused. Fortunately, in paediatric dentistry the prospect of a life-saving operation is rare so a refusal of consent can be managed by a change in the procedure or by establishing a temporal respite. The current advice from the protection societies is that written consent must be obtained for a course of treatment. The plan of treatment proposed must indicate the nature and extent of the treatment and the approximate number of times that local anaesthesia and/or sedation is to be used. There is no need to obtain written consent for each separate time that sedation is used. If the plan of treatment changes and along with it the frequency or nature of sedation, then it is prudent to obtain written consent for the change. The greater risks associated with general anaesthesia require specific written consent for each and every occasion that treatment is carried out under general anaesthesia. Examples of suitably worded forms are available from the Medical Defence Societies.

Key Points
A conference that involves both the parent and child helps to gain informed consent:
    -discuss the dental problems;
    -discuss the treatment options/alternatives;
    -agree the treatment plan.
Write-up in the case record.
Obtain written (signed) consent

Systemic pain control

Children may need pain control for 'toothache' for a day or two before the removal of carious teeth. Often, the teeth are also abscessed so that it is necessary to combine antibiotic therapy with analgesia to obtain optimum pain relief. Additionally, analgesia is required postoperatively usually after dento-alveolar surgery.

The most common method of administration is by mouth. Small children, and some recalcitrant adolescents, refuse to take tablets so liquid preparations are needed. If other methods of administration, such as intramuscular or intravenous, are required then these injections should be administered by clinical staff experienced with these special techniques. Rectal administration is increasingly common as absorption from the rectal mucosa is rapid. If such a route of administration is to be used, specific consent must be obtained. It should be remembered that the dose for children of different ages needs to be carefully estimated to avoid the risk of an overdose (dangerous) or of an underdose (ineffective). The parents must be advised that all drugs must be stored in a safe place, in a child-proof container. Bathroom cabinets or kitchen cabinets are the safest places as they are out of reach and out of sight of small children. Specific advice on prescribing for children can be obtained from a local pharmacist or the British National Formulary (BNF).

The dosages for children can be calculated on the basis of a percentage chart. Often 'average' doses are used but the prescriber has the absolute responsibility to confirm that the dosages recommended are correct.

The common drugs used for pain control in children are paracetamol BNF and ibuprofen BNF. The potential side-effects and the dosages should be checked with the formulary before prescribing. Aspirin should not be used on children because of the risk of Reye's syndrome. The increase in asthma among children requires that this be considered before ibuprofen is prescribed. Narcotic analgesics such as codeine or morphine can be used on children but only after less powerful analgesics have been shown to be ineffective. As above, the dosage should be checked with the BNF.

Methods of pain control

The different methods of pain control vary from simple behaviour management to full intubational general anaesthesia in a hospital operating theatre. There is a strong relationship between the perception of pain experienced and the degree of anxiety perceived by the patient. Painful procedures cause fear and anxiety; fear and anxiety intensify pain. This circle of cause and effect is central to the management of all patients. Good behaviour management reduces anxiety, which in turn reduces the perceived intensity of pain, which further reduces the experience of anxiety.

Behaviour management have been covered in detail in and local anaesthetic techniques in. The majority of dental procedures on children can be carried out using a combination of these two techniques. This chapter will deal with the methods of sedation and general anaesthesia that are applicable to dental treatment in children.

Medical status

The wide variety of medical problems makes it difficult to be precise about the management strategy appropriate for each patient. Detailed descriptions of management of a variety of medical problems appear in a comprehensive book by Scully and Cawson (1998). With regard to sedation, the American Society of Anesthesiologists' (ASA) classification provides an excellent guide to the type of sedation or anaesthesia appropriate to an individual patient's medical and behavioural problems.

The decision as to whether a patient should be treated under general anaesthesia or local anaesthesia, or local anaesthesia with sedation depends on a combination of factors, the most important of which are:

(1) the age of the child;
(2) the degree of surgical trauma involved;
(3) the perceived anxiety and how the patient may (or has) responded to similar levels of surgical trauma;
(4) the complexity of the operative procedure;
(5) the medical status of the child.

There are no hard and fast rules, and every procedure in every child must be assessed individually and the different elements considered in collaboration with the parent and, where appropriate, with the child. For example, the younger the child the greater the likelihood of a need for general anaesthesia. At the other end of the age range it is unlikely that a 15-year old will need general anaesthesia for simple orthodontic extractions, although this might be required for moderately complex surgery, such as exposing and bonding an impacted canine. The degree of trauma involved is also another factor; a single extraction is most likely to be carried out under local anaesthesia, removal of the four first permanent molars is most likely to be carried out under general anaesthesia. Anxiety perceived as excessive, especially after an attempt at treatment under local anaesthesia and sedation, would lead to simple treatment such as conservative dentistry being carried out under a general anaesthetic usually involving endotracheal intubation. Serious medical problems, for example, cystic fibrosis with the associated respiratory problems would justify using sedation instead of general anaesthesia even for more traumatic surgery, such as removal of impacted canines, but it would be appropriate to carry out this sedation in a hospital environment. The degree of intellectual and/or physical impairment in handicapped children would also be a factor to be considered.

General anaesthesia carries with it a finite risk of serious morbidity such as psychological trauma and even death (3 to 4 per million). No child should be submitted to a general anaesthetic without consideration of this potentially devastating outcome. Intermediate between the minimally intrusive techniques of local anaesthesia and the major intrusion of general anaesthesia are the techniques of conscious sedation.

Key Points
Each child should be assessed on their merits and an appropriate method of pain control used.
The vast majority of children are amenable to satisfactory treatment using behaviour management and local anaesthesia alone.
No child should be submitted to a general anaesthetic without consideration of potential risk.

Conscious sedation techniques

Introduction

Conscious sedation is defined as:

A technique in which the use of a drug or drugs produces a state of depression of the central nervous system enabling treatment to be carried out, but during which verbal contact with the patient is maintained throughout the period of sedation. The drugs and techniques used to provide conscious sedation for dental treatment should carry a margin of safety wide enough to render unintended loss of consciousness unlikely. The level of sedation must be such that the patient remains conscious, retains protective reflexes, and is able to understand and respond to verbal commands.

The routes of administration of sedative drugs used in clinical paediatric dentistry are oral, inhalational, intravenous, and transmucosal (e.g. Nasal, rectal, sublingual). However, the transmucosal routes are little used in the United Kingdom and currently, intravenous sedation is considered unsuitable for the operator/sedationist when working on children. Current developments in intravenous techniques, especially the use of target-controlled infusion pumps and patient-controlled sedation (PCS) may prove to be sufficiently effective and safe for use by the operator/sedationist, but further research is required.

Key Point
The goal of conscious sedation is to use a pharmacological agent to augment behavioural management to decrease anxiety levels while maintaining a responsive patient.

General facilities

The use of sedative drugs carries the risk of inadvertent loss of consciousness. Although the techniques are designed to reduce this risk to a minimum it should always be borne in mind that every time a sedative is given to a patient there is a risk of an idiosyncratic reaction to the drug, which may result in hypoxia or unexpected loss of consciousness. The clinician must arrange the clinical session so that sedation, irrespective of complications, can proceed smoothly and safely. This includes the need for all patients who are having sedation to be accompanied. This can be any adult, who understands the implications and potential problems of caring for a child during the later stages of recovery. In addition, the clinical facilities need to include suitable resuscitation equipment coupled with the knowledge and skills to use them.

Key Points
The main complications related to paediatric conscious sedation are:
    -hypoxia,
    -nausea,
    -vomiting,
    -inadvertent loss of consciousness (general anaesthesia/over sedation).
Morbidity and mortality increase with:
    -young age,
    -worsening ASA classification.

Emergency equipment

Suitable emergency equipment must be available easily to hand since time is of the utmost importance. For this reason emergency equipment and drugs should be within arms reach of the operator and ready for immediate use. Training of the dental team is a requirement, irrespective of whether conscious sedation is practised. Training should be updated at regular intervals of not more than 1 year. It is essential that each member of the dental team knows exactly what is required of them in an emergency. The dental surgeon has the responsibility of ensuring the easy availability of drugs, particularly oxygen, and to see that the drugs in the emergency kit are not past their 'use by' date.

Emergency equipment for the dental surgeon

The following are items of equipment that a dental surgeon should be prepared to use in an emergency.

1. High volume suction for clearing the airways of saliva, debris, and blood. This must be capable of reaching the floor as a patient may be removed from the dental chair to lie on the floor to enable resuscitation.
2. An emergency supply of oxygen. A regular working supply of oxygen from an inhalation sedation unit is an alternative.
3. Positive pressure ventilation apparatus with a self-inflating bag.
4. Face masks to fit children and adolescents.
5. Three sizes of oral airways.

Note: These items should form part of an armamentarium of any dentist when treating patients using local anaesthesia alone.

Emergency drugs

Suitable emergency drugs must be available and because of the need for speed, the drugs must be stored with the emergency equipment. Training of the dental surgeon and their staff in the use of drugs has the same requirements as for equipment. The nature and content of 'emergency drugs' kits are usually determined by a local resuscitation adviser.

Emergency drugs for the dental surgeon

The following are drugs that the dentist should be prepared to use in an emergency:

1. Oxygen.
2. Adrenaline hydrochloride 1 mg/ml (1000 mg/ml), that is, 1 : 1000 on a 1 ml ampoule for subcutaneous or intramuscular injection. The IMS Min-I-Jet system is particularly quick and easy to use.
3. Hydrocortisone sodium phosphate 100 mg per vial. To be made up to 1 ml with physiological saline immediately before use. For intravenous injection.
4. In addition to the above drugs suitable needles and syringes should be available to enable drugs to be drawn up and administered parenterally.
5. Flumazenil (benzodiazepine anatagonist) for reversing unexpected over-sedation from orally, intravenously, or rectally administered benzodiazepine.

Emergency equipment for medically qualified and those staff trained in advanced life support

1. A laryngoscope, endotracheal tubes, and forceps to manipulate the endotracheal tubes during intubation.
2. A cricothyrotomy kit.
3. An electrocardiograph.
4. A defibrillator.

Emergency drugs for medically qualified and/or specially trained staff

1. Adrenaline 1 : 10, 000 (10 ml vials).
2. Atropine 1 mg/10 ml (10 ml vials).
3. Calcium chloride 10% (10 ml vials).
4. Lignocaine 100 mg/10 ml (1%) (10 ml vials).
5. Isoprenaline 0.2 mg/ml (10 ml vials).
6. Frusemide 80 mg/8 ml (8 ml vials).
7. Sodium bicarbonate 8.4% (50 ml vials).
8. Glucose 50% (50 ml vials).
9. Naloxone 4 mg/ml (1 ml vials).
10. Aminophylline 250 mg/10 ml (10 ml vials).
11. Diazemuls 10 mg/2 ml (2 ml vials).
12. Flumazenil 500 ug/5 ml (5 ml vials).

Many of these drugs are available in prefilled syringes. It is the responsibility of the dentist to ensure the availability of the drugs required by the medical staff who may be called to deal with an emergency. Equally, it is the responsibility of the same medical staff to advise the dental surgeon of his or her precise requirements with regard to emergency drugs. This advice must be in writing. These can be reviewed by reading the following: European Resuscitation Council (1992). Guidelines for basic and advanced life support. Resuscitation, 24, 103-10.

Key Points
Dental surgeons and their staff should at least be capable of providing basic life support:
    -Airways;
    -Breathing;
    -Circulation;
    -ABC.
The dental team should have at least yearly basic life support training.
The dental surgeon is responsible for ensuring the readiness of emergency equipment and drugs.

Preparation for conscious sedation

Environment

There should be a suitable area where the child can sit quietly before the operation so that the sedative can be administered and the child monitored while it is taking effect. As a general rule it is not wise to let children have medication at home as quiet supervision of the child within the surgery premises is prudent. A journey to the surgery under the increasing influence of a mood-altering drug is not the most propitious way of preparing distressed children for treatment. These strictures do not apply to inhalation sedation or intravenous sedation. However, the facilities suitable for providing care apply equally to oral, inhalational, and intravenous sedation. During treatment there must be effective suction equipment and in the event of a power failure, a mechanically operated backup. Sedated patients often hallucinate or misinterpret words and actions and so, a chaperone to safeguard the operator-sedationist is also essential. Once treatment is complete the child should be able to sit (or lie) quietly until sufficiently recovered to be accompanied home.

A further important strategy is to have a checklist so that the dental surgeon can be sure that all important elements of sedation have been properly considered.

Preoperative instructions

These should be provided in writing and cover such points as ensuring that a suitable companion brings the child to and from the surgery, that only a light meal is eaten 2 h or more before an appointment for sedation. In this context, a light meal is a cup of tea and a slice of toast. Postoperatively, suitable arrangements need to be in place for travel and to ensure that the child plays quietly at home. In addition to these specific points 'local' rules are likely to apply.

Key Points

• To carry out conscious sedation:
• informed consent is mandatory;
• preoperative and postoperative instructions should be given prior to the sedation visit;
• patient assessment includes medical, dental, and anxiety history;
• appropriate facilities, child-friendly environment and sedation trained staff are essential;
• the operator-sedationist, irrespective of gender, must be chaperoned at all times;
• the child must be accompanied by an adult escort;
• a checklist is important to ensure all preparations are in place.

Monitoring the sedated child

Clinical status

Sedative drugs are also central nervous system and respiratory depressants and as such, cause a variety of effects from mild sedation, deep sedation, and general anaesthesia and, in excessive concentrations, even death. For this reason, the facilities outlined above are necessary in the unlikely event of unexpected loss of consciousness. It is important that dental surgeons working with children have a very clear idea of the clinical status of sedated patients. These are:

(1) the patient's eyes are open;
(2) the patient is able to respond verbally to questions;
(3) the patient is able to independently maintain an open mouth (this may preclude the use of a mouth-prop);
(4) the patient is able to independently maintain a patent airway;
(5) the ability to swallow;
(6) the child is a normal pink colour.

All these criteria are evidence of conscious sedation. For this reason it is important not to let a child go to sleep in the dental chair while receiving treatment with sedation as closed eyes may be a sign of sleep, over-sedation, loss of consciousness, or cardiovascular collapse.

Pulse oximetry

Pulse oximetry is a non-invasive method of measuring arterial oxygen saturation using a sensor probe placed on the patient's finger or ear lobe, which has a red light source to detect the relative difference in the absorption of light between saturated and desaturated haemoglobin during arterial pulsation. The probe is sensitive to patient movement, relative hypothermia, ambient light, and abnormal haemoglobinaemias, so false readings can occur. In room air, a child's normal oxygen saturation (sao₂) is 97% to 100%. Adequate oxygenation of the tissues occurs above 95% while oxygen saturations lower than this are considered hypoxaemic.

Key Points
Monitoring a sedated child involves:
alert clinical monitoringskin colour, response to stimulus, ability to keep mouth open, ability to both swallow and to maintain an independent airway, normal radial pulse;
the use of a pulse oximeter (except for nitrous oxide inhalation sedation).

Oral sedation

Introduction

The onset of the effect of oral sedatives is variable and is largely dependent on the individual's rate of absorption from the gastro-intestinal tract, which can be affected by the rate of gastric clearance, the amount of food in the stomach, and even the time of the day. In addition, the dosage is determined by the body weight. Therefore, a set of properly calibrated bathroom scales is needed to enable the correct dose of sedative to be estimated for each patient. Despite this, some children may spit out the drug, leaving the clinician uncertain about the exact dosage that was administered. To combat this, some sedationists administer the liquid sedative using a syringe placed in the buccal mucosa or mix the drug with a flavoured elixir. The patient may require up to an hour of supervised postoperative recovery.

Oral sedatives

Diazepam

The most familiar of the benzodiazepines is diazepam, usually administered at a dosage of 250 ug/kg. For a 6-year-old child this is approximately 5 mg but could be as low as 3.9 mg or as high as 6.6 mg. For a much older patient, for example, a 15-year old, the average dose would be 13.6 mg and may vary from 9.7 mg to 18.9 mg.

Midazolam

Midazolam is another benzodiazepine that is more commonly used as an intravenous agent. However, its use as an oral sedative is growing though, currently it does not have a product licence for this application. The intravenous liquid is bitter to taste and so the preparation is often mixed with a fruit flavoured drink. The oral dose is higher (0.3-0.7 mg/kg) than the intravenous dose because the oral midazolam reaches the systemic circulation via the portal circulation which decreases the drug's bioavailability, necessitating a higher oral dosage. Evidence is still relatively scant, especially in children under 8 years of age, and so the use of oral midazolam is still largely restricted to specialist hospital practice.

Chloral hydrate

Chloral hydrate is a chlorinated derivative of ethyl alcohol, the 'Micky Finn'. It is a weak analgesic and psychosedative with an elimination half-life of about 8 h. In small doses (40-60 mg/kg, but not exceeding 1 g), mild sedation occurs but it can be ineffective in the management of the more anxious child. Nausea and vomiting are common due to gastric irritation. The drug also depresses the blood pressure and the respiratory rate, myocardial depression and arrhythmia can also occur. Recently, there has been concern that there is a risk of carcinogenesis. Although it is still in widespread use around the world it is gradually becoming obsolete.

Other drugs

There are other oral sedative drugs that are commonly reported in the literature in relation to paediatric dental sedation. These include: hydroxyzine hydrochloride and promethazine hydrochloride (psychosedatives with an antihistaminic, antiemetic, and antispasmodic effect), and ketamine which is a powerful general anaesthetic agent which, in small dosages, can produce a state of dissociation while maintaining the protective reflexes. Common side-effects of hydroxyzine hydrochloride and promethazine hydrochloride are dry mouth, fever, and skin rash. Side-effects of ketamine include hypertension, vivid hallucinations, physical movement, increased salivation, and risk of laryngospasm, advanced airway proficiency training is, therefore, essential. Ketamine carries the additional risk of increase in blood pressure, heart rate, and a fall in oxygen saturation when used in combination with other sedatives.

Evidence to support the single use of either hydroxyzine hydrochloride, promethazine hydrochloride, or ketamine is poor.

Monitoring during oral sedation

This involves alert clinical monitoring and at least the use of a pulse oximeter.

Clinical technique

The following regimen, using the example of diazepam, was found to be effective in clinical practice:

(1) on arrival of the patient check whether, preoperative instructions have been followed;
(2) weigh the patient and estimate the dose of diazepam;
(3) have the dosage checked by a second person;
(4) administer diazepam ~1 h before the treatment;
(5) allow the patient to sit in a 'quiet' room;
(6) once ready, start and complete the treatment with (or without) local anaesthesia;
(7) once the treatment is complete, allow the patient to recover in the quiet room until ready to return home;
(8) reiterate the postoperative instructions to escort.

Inhalation sedation

Introduction

This is synonymous with inhalation of an oxygen-nitrous oxide gas mixture in relatively low concentrations, usually 20-50% nitrous oxide. The technique is unique as the operator is able to titrate the gas against each individual patient. That is to say, the operator increases the concentration to the patient, observes the effect, and as appropriate, increases (or sometimes decreases) the concentration to obtain optimum sedation in each individual patient.

Inhalation sedation consists of three elements.

1. The administration of low-to-moderate concentrations of nitrous oxide in oxygen to patients who remain conscious. The precise concentration of nitrous oxide is carefully titrated to the needs of each individual patient.

2. As the nitrous oxide begins to exert its pharmacological effects, the patient is subjected to a steady flow of reassuring and semi-hypnotic suggestion. This establishes and maintains rapport with the patient.

3. The use of equipment that exceeds the current BSI Standard for safety cut-out devices installed within inhalation sedation equipment. This means that it is not possible to administer 100% nitrous oxide either accidentally or deliberately (the cut-off point is usually 70%). This is an important and critical clinical safety feature that is essential for the operator/sedationist.

Equipment for inhalation sedation with oxygen-nitrous oxide gas mixture

The most widely used equipment for inhalation sedation is the Quantiflex MDM, which enables the operator to deliver carefully controlled volumes and concentrations of gases to the patient. In addition to the machine head that controls the delivery of gases, it is also necessary to have a suitable scavenging system, and an assembly for the gas cylinders, either a mobile stand or a pipeline system with cylinders stored remote from the machine head.

Clinical technique

Of the inhalation sedation techniques available, the following is the easiest, the most flexible, and the least likely to cause surgery pollution. The control unit for the Quantiflex MDM has a single control for the total flow of gases, and a central, vertically placed, dial is turned to regulate simultaneously the percentage flow of both gases. Either of these controls can be changed without altering the other. The actual percentage of gases being delivered is monitored by observing the flow meters for oxygen and nitrous oxide, respectively. There are 15 steps for the technique:

1. Check the machine.
2. Select the appropriate size of nasal mask and clean it with alcohol.
3. Connect up the scavenging pipe.
4. Set the mixture dial to 100% oxygen.
5. Settle the patient in the dental chair.
6. Turn the flow control to 3 l/min and allow the reservoir bag to fill with oxygen.
7. With the patient's help, position the nasal mask gently and comfortably to preclude any leaks. If necessary explain the way the mask is used.
8. Turn the flow control knob to the left until the flow rate of oxygen (l/min) matches the patient's tidal volume. This can be monitored by watching the reservoir bag, and should take 15-20 s. When the patient inspires, the reservoir bag gets smaller. When the patient breathes out the reservoir bag gets larger as it fills with the mixture of gases emanating from the machine.
9. Simultaneously, reassure the patient about the sensations that will be felt. Encourage the patient to concentrate on breathing gently through the nose. If the reservoir bag appears to be getting too empty then the flow of oxygen should be increased until the flow rate in l/min matches the patient's minute volume.
10. Turn the mixture dial vertically to 90% oxygen (10% nitrous oxide).Wait for 60 s.
11. Turn the mixture dial to 80% oxygen (20% nitrous oxide). Wait 60 s, above this level the operator should exercise more caution and consider whether further increments should be only 5%. With experience, operators will be able to judge whether further increments are needed.
12. At the appropriate level of sedation dental treatment can be started.
13. To bring about recovery turn the mixture dial to 100% oxygen and oxygenate the patient for 2 min before removing the nasal mask.
14. Turn the flow control to zero and switch off the machine.
15. The patient should breathe ambient air for a further 5 min before leaving the dental chair. The patient should be allowed to recover for a total period of 15 min before leaving.

At all times the patient must remain conscious. This is judged by the five clinically discernible signs described previously.

The above method of administration is the basic technique that is required in the early stages of clinical experience for any operator. This method ensures that the changes experienced by the patient do not occur so quickly that the patient is unable to cope. Once the operator has sufficient skill and confidence the stages can be 'concertinaed', for example, by starting at 20% nitrous oxide and reducing the time intervals between increments.

The initial time intervals of 60 s are used because clinical experience shows that shorter intervals between increments can lead to too rapid an induction and over-dosage.

The correct level of clinical sedation with nitrous oxide

One of the problems for the inexperienced clinician is to determine whether or not the patient is adequately sedated for treatment to start. By careful attention to signs and symptoms experienced by the patient the dentist will soon be able to decide whether the patient is ready for treatment.

The very rapid uptake and elimination of nitrous oxide requires the operator to be acutely vigilant so that the patient does not become sedated too rapidly.

Objective signs

The objective signs showing the patient is ready for treatment are:

(1) the patient is awake;
(2) the patient is relaxed and comfortable;
(3) the patient responds coherently to verbal instructions;
(4) pulse rate is normal;
(5) blood pressure is normal;
(6) respiration is normal;
(7) skin colour is normal;
(8) pupils are normal and contract normally if a light is shone into them;
(9) the laryngeal reflex is normal;
(10) the gag reflex is reduced;
(11) reaction to painful stimuli is lessened;
(12) there is a general reduction in spontaneous movements;
(13) the mouth is maintained open on request.

Subjective symptoms

Subjective symptoms experienced by the patient are :

(1) mental and physical relaxation;
(2) a tingling sensation (paraesthesia) singly or in any combination of lips, fingers, toes, or over the whole body;
(3) mild intoxication and euphoria;
(4) lethargy;
(5) a sense of detachment, sometimes interpreted as a floating or drifting sensation;
(6) a feeling of warmth;
(7) indifference to surroundings and the passage of time;
(8) dreaming;
(9) lessened awareness of pain.

If the patient tends to communicate less and less, and is allowing the mouth to close, then these are signs that the patient is becoming too deeply sedated. The concentration of nitrous oxide should be reduced by 10 or 15% to prevent the patient moving into a state of total analgesia.

Monitoring during nitrous oxide sedation

During inhalation sedation it is essential that the clinician monitors both the patient and the machinery. For healthy patients with ASA I or II, use of a radial pulse is sufficient. For patients with ASA III or IV, treatment within a hospital environment and pulse oximetry, blood pressure cuff, and/or electrocardiograph monitoring would be prudent. This applies to only a very small proportion of patients such as those with cystic fibrosis with marked lung scarring or children with severe congenital cardiac disease where there is high blood pressure or cyanosis.

The patient

The clinician should pay careful attention to the patient's level of anxiety. This is achieved by assessing the patient's responses to an operative stimulus such as the dental drill. The level of sedation is assessed by the patient's demeanour compared with his or her presedation behaviour. It is important to note that different patients exhibit similar levels of impairment at different concentrations of nitrous oxide. If the patient appears to be too heavily sedated then the concentration of nitrous oxide should be reduced. There is no need to use pulse oximetry or capnography (to measure exhaled carbon dioxide levels) as is currently recommended for patients being sedated with intravenously administered drugs.

The machinery

At all stages of inhalation sedation, it is necessary to monitor intermittently the oxygen and nitrous oxide flow meters to verify that the machine is delivering the gases as required. In addition, it is essential to look at the reservoir bag to confirm that the patient is continuing to breathe through the nose the nitrous oxide gas mixture. Little or no movement of the reservoir bag suggests that the patient is mouth breathing, or that there is a gross leak, for example, a poorly fitting nasal mask.

Key Points
For nitrous oxide inhalation sedation:
set the flow;
slowly titrate the dose;
monitor the patient's response;
monitor the equipment.

The planes of inhalation sedation

The administration of oxygen-nitrous oxide gas mixture for sedating child patients induces three levels or planes of analgesia and sedation.

Plane 1: moderate sedation and analgesia

This plane is usually obtained with concentrations of 5-25% nitrous oxide (95-75% oxygen). As the patient is being encouraged to inhale the mixture of gases through the nose, it is necessary to reassure him or her that the sensations described by the clinician may not always be experienced. The patient may feel tingling in the fingers, toes, cheeks, tongue, back, head, or chest. There is a marked sense of relaxation, the pain threshold is raised, and there is a diminution of fear and anxiety. The patient will be obviously relaxed and will respond clearly and sensibly to questions and commands.

Other senses, such as hearing, vision, touch, and proprioception, are impaired in addition to the sensation of pain being reduced. The pupils are normal in appearance and contract when a light is shone into them. The peri-oral musculature, so often tensed involuntarily by the patient during treatment, is more easily retracted when the dental surgeon attempts to obtain good access for operative work. The absence of any side-effects makes this an extremely useful plane when working on moderately anxious patients.

Plane 2: dissociation sedation and analgesia

This plane is usually obtained with concentrations of 20-55% nitrous oxide (80-45% oxygen). As with plane 1, patients do not always experience all the symptoms. This should be remembered when reassuring and encouraging them.

As the patient enters this plane, psychological symptoms, described as dissociation or detachment from the environment, are experienced. Sometimes this dissociation is minimal, at other times it is profound. It may also take the form of a euphoria similar to alcoholic intoxication (witness the laughing gas parties of the mid-nineteenth century). The patient may feel suffused by a warm wave, and may experience a slight humming or buzzing in the ears, and a drowsiness or light-headedness sometimes described by the patient as a 'floaty' or 'woozy' feeling.

The overall demeanour of the patient will be relaxed and acquiescent. Apart from the overall appearance of relaxation, one of the few tangible physical signs is a reduction in the blink rate. At the deeper level of this plane of sedation the psychological effects become more pronounced. Occasionally, a patient will repeat words or phrases several times in succession. The words repeated may or may not make sense.

There is a noticeable tendency for the patient to dream, the dreams usually being of a pleasant nature. It is believed by many operators that the dreams experienced by the patient are to some extent conditioned by the ideas and thoughts introduced by the dental surgeon during the induction phase of sedation. The sedative effect is considerably pronounced, with both psychosedation and somatic sedation being present.

The psychosedation takes the form of a relaxed demeanour, and a willingness on the part of the previously unwilling patient to allow treatment regarded as frightening or especially traumatic. The somatic sedation takes the form of physical relaxation, unresisting peri-oral musculature, and occasionally an arm or leg sliding off the side of the dental chair indicating profound relaxation. The analgesic effect is probably accentuated by the sedation and sense of detachment. The patient is still able to respond to questions and commands, although there may be a considerable mental effort involved in thinking out the answer. The response is usually delayed and sluggish. Paraesthesia may be more pronounced and cover a greater area of the body than in plane 1. The patient is nevertheless obviously conscious and can demonstrate this by keeping the mouth wide open to assist the dental surgeon during operative treatment. On recovery, the patient may exhibit total amnesia. Nausea is a rare side-effect and very occasionally (in less than 0.003% of administrations) a patient may vomit.

Plane 3: total analgesia

This plane is usually obtained with concentrations of 50-70% nitrous oxide (50-30% oxygen). It has been claimed, that analgesia is so complete that extraction of teeth may be carried out in this plane. This has not been our experience. In this plane there is an increased tendency to dream. It is important to recognize that in a small number of patients as little as 50% nitrous oxide may bring about loss of consciousness. It is for this reason that dentists must exercise considerable caution if the concentration of gas coming from the machine rises above 40% nitrous oxide.

If the patient does become too deeply sedated and enters this third plane of total analgesia, he or she begins to lose the ability to independently maintain an open mouth and will be unable to co-operate or respond to the dentist's requests. If this 'open mouth' sign is lost, the operator can be sure that the patient is too deep in the plane of total analgesia and within a few minutes is likely to enter the plane of light anaesthesia. It is for this reason that a mouth prop must never be used, for if a prop is used the open mouth sign would not function.

If sedation is too deep and the patient shows signs of failing to co-operate, then the dentist should reduce the concentration of nitrous oxide by 10 or 15% for a couple of minutes. If it is considered necessary to lighten the sedation even more rapidly, the nasal hood should be removed and the patient allowed to breathe ambient air. The patient will return to a lighter plane within 15-20 s.

This plane of total analgesia is regarded as a buffer zone between the clinically useful planes of moderate and dissociation sedation and analgesia, and the potentially hazardous plane of light anaesthesia.

Clinical application

The technique of nitrous oxide sedation can be used for a wide range of procedures involving the cutting of hard or soft tissue where local anaesthesia will usually be needed to supplement the general analgesia from the nitrous oxide. The major disadvantage (or minor if handled properly) is the inconvenience of the nasal hood restricting access to the upper incisor area if an apicectomy is required. This problem can be overcome by careful retraction of the upper lip and counterpressure from the thumb held on the bridge of the nose.

Scavenging

Repeated exposure to environmental pollution with nitrous oxide can cause megaloblastic anaemia and problems with both conception and pregnancy. The Control of Substances Hazardous to Health (COSHH) advises that over a time-weighted average (TWA) of 8 h, the exposure should not exceed 100 p.p.m. This is five times lower than the safest dose found in animal studies.

Surgery contamination is affected by the modus operandi of the dental surgeon. Considerable care needs to be taken to discourage the patients from mouth breathing, to use rubber dam whenever possible, and ensure that full recovery is carried out with the nasal hood in place. Effective scavenging equipment is extremely simple in design. This design of scavenger can be used on a normal relative analgesia machine without any specific modifications to the machine itself. All that is required is a change in the design of the nasal hood and the tubing leading from the machine to the hood. First, the expiratory and/or air entrainment valve on the nasal hood itself is removed and replaced with a simple blank because the use of this valve is obsolete. The efferent tube that leads away from the nasal mask is doubled in diameter to reduce resistance and connects to a specially devised exhaust pipe built into the wall or floor of the surgery. If considered essential, negative pressure can be applied at this connection to increase the efficiency of the scavenging (active scavenging).

Key Points
To reduce nitrous oxide pollution
use a scavenging system;
use a scavenging nasal hood (block air entrainment valves in older nasal hoods);
discourage mouth breathing (do not let the child talk);
use rubber dam.

Intravenous sedation

Introduction

The circumstances when intravenous sedation can be used in paediatric dentistry are limited, although there is a slow but steady trend to extending its use especially in adolescents.

Intravenous agents

There are many intravenous agents available in the BNF, but for dental purposes the practical choice is between midazolam, a benzodiazepine that is water soluble and well tolerated by tissues (important if some midazolam inadvertently becomes deposited outside rather than inside a vein) and propofol, which leads to rapid sedation and rapid recovery. Unfortunately, the risk of unintended loss of consciousness is high with propofol because of the narrow therapeutic range of the drug that leads quickly to anaesthesia. Therefore, propofol is used only when there is an anaesthetist present.

Equipment for intravenous sedation

The general surgery set up is the same as for inhalation sedation. A disposable tray should be prepared with the following:

(1) a 5 ml syringe;
(2) a venflon;
(3) adhesive tape;
(4) a green needle gauge 21;
(5) isopropyl alcohol swab;
(6) a single ampoule of the intravenous sedation drug;
(7) an ampoule of flumazenil (for urgent reversal of benzodiazepine sedation);
(8) a tourniquet.

The technique can be carried out as shown in the following sections.

Intravenous technique

The standard regimen is to use 0.07 mg/kg of midazolam infused slowly until the signs of satisfactory sedation are reached. This usually entails a loading dose of 2 mg followed by further increments as appropriate.

The technique requires the insertion of a venflon that is allowed to remain in situ until the treatment for that visit is complete. This applies to manual infusion by the dental surgeon, diffusion pump infusion supervised by the dental surgeon, and patient controlled anaesthesia (PCA). For anxious children this is an almost insuperable problem as 'the needle' is the cause of their fear. Nevertheless, there appears to be a group of older children, usually adolescents requiring dento-alveolar surgery, who are willing to allow the placement of a needle in the dorsum of the hand or the antecubital fossa for infusion of benzodiazepine drugs.

Intravenous access

The two most common sites of access are the antecubital fossa and the dorsum of the hand. In children especially, the antecubital fossa carries with it the danger of the needle causing damage to the vein and surrounding structures if the arm is bent during sedation. For this reason the dorsum of the hand is the preferred site.

Procedure

1. The patient's medical history is checked.
2. The arm is extended and a tourniquet applied.
3. The pulse oximeter is applied to the contralateral arm. Note: a very anxious patient might be distressed by these procedures so they can be left until the patient is sedated.
4. The venflon is inserted into the vein and taped into place.
5. The patient is asked to touch the tip of the nose to demonstrate good neuromotor control.
6. The first dose of drug is administered over 30 s.
7. The patient's response is assessed after 2 min to determine whether further (smaller) increments of the sedative agent are required.
8. Dental treatment is carried out. If sedation becomes inadequate further increments of the sedative agent may be given.
9. Once dental treatment is complete, the patient is allowed to recover sufficiently to be helped to the recovery area.
10. Recovery must be under the supervisory eye of a specially trained personnel.
11. Once the patient is 'street fit', they are discharged into the care of an accompanying adult.
12. Postoperative instructions are reiterated.

Monitoring during intravenous sedation

This involves alert clinical monitoring and at least the use of a pulse oximeter.

Unexpected loss of consciousness

On the rare occasions when the patient becomes unconscious the dentist and their staff should follow the following routine.

1. Cease the operative procedure immediately.
2. Ensure that the mouth is cleared of all fluids by using high-volume suction.
3. Turn the patient on to his or her side in the 'recovery' position.
4. Consider the administration of 100% oxygen.
5. If intravenous sedation is being used, leave the venflon in place so that emergency drugs can be administered through it if required.
6. Consider monitoring pulse, blood pressure, and respiration. Be ready to start resuscitation.
7. Dentist to stay with the patient until full signs of being awake are present (eyes open, independent maintenance of the airways, and verbal contact).
8. Follow-up of the patient by review within 3 days.
9. Full documentation of the incident.
10. Inform the patient's general medical practitioner of the incident.

General anaesthesia

Introduction

The use of general anaesthesia in paediatric dentistry has a wide application, usually for the extraction of teeth. Fortunately, referrals have reduced, due to both the reduction in dental disease and to the use of sedation. Nevertheless, there will always be a need for general anaesthesia in dentistry, especially for pre-co-operative children.

Key Points
In the United Kingdom, general anaesthesia can now only take place in a hospital setting, and be administered by a consultant anaesthetist.
Risk of general anaesthesia:
    -mortality- 3 per million;
    -morbiditysymptoms associated with the procedure, distress at induction and during recovery, prolonged crying, nausea, sickness, and postoperative bleeding.
Referring dentists are obliged to:
    -explain the risks of general anaesthesia;
    -discuss the alternative treatment modalities;
    -explain why the option of general anaesthesia has been selected;
    -keep a copy of their referral letter;
    -the referring dentist must be assured of the appropriateness of the care provided by sedation or general anaesthetic service.
Indications for general anaesthesia
    -the child is pre cooperative (too young to cope)
    -uncontrolled fear
    -complexity of procedure.

Type of anaesthesia

In dentistry, anaesthesia falls into three main groups:

(1) out-patient short-case 'dental chair' anaesthesia traditionally with a nose mask but now more often with a laryngeal mask
(2) out-patient/day-stay 'intubation' anaesthesia;
(3) in-patient/hospital-stay 'intubation' anaesthesia.

Within these categories there are variations determined by anaesthetistic preference. Anaesthesia for dental treatment requires the help of a consultant anaesthetist. The organization of dental general anaesthesia lists, at least in the preliminary stages, is performed by a dental surgeon who therefore must understand the type of anaesthesia and the implications of any underlying medical condition.

Definition of anaesthesia

The state of anaesthesia is defined as: 'The absence of sensation artificially induced by the administration of gases or the injection of drugs or a combination of both'. The important feature of anaesthesia is that the patient is completely without the ability to independently maintain physiological function, such as breathing and protective reflexes, and is acutely vulnerable to the loss of any foreign bodies or fluids down the throat.

Out-patient 'short-case' general anaesthesia

This is used for ASA class I or class II patients requiring short, 2-10 min, procedures with rapid induction and early recovery, for example, dental extractions. Anaesthesia is induced either by inhalation of an anaesthetic vapour in an oxygen-nitrous oxide mixture using a face mask or by an intravenous injection for example, propofol. Occasionally, the child is premedicated with a benzodiazepine. The parent commonly accompanies the child to help them cope with the anaesthetic induction. Irrespective of the induction method, anaesthesia is maintained by the anaesthetic vapour, for example, sevofluorane, carried in a mixture of oxygen and nitrous oxide, and the face mask is exchanged for a nose mask or a laryngeal mask. Following this, the oropharynx is packed with gauze to protect the airway. This gauze is the reason why children sometimes later complain of a sore throat. Monitoring for this type of anaesthesia usually consists of an electrocardiograph, pulse oximeter, and a blood pressure cuff.

On completion of treatment, the gauze is removed and the patient turned into the recovery position and removed to a quiet recovery room so that he/she can be monitored during their final recovery. The child is discharged when he or she is able to drink a glass of water without being sick and able to stand without swaying or appearing dizzy. Although the child is deemed 'street fit', once he or she has arrived home the combined effects of anxiety, the general anaesthetic, and the dental surgery, make it necessary for the child to play 'quietly at home' for the rest of that day.

Out-patient 'day-stay' general anaesthesia

This is usually reserved for ASA class I or class II patients who require dental treatment that lasts more than 10 min, for example, removal of supernumeraries, complex and compound odontomes, exposing and bonding impacted teeth, or extensive conservative dentistry. Day surgery units commonly offer premedication and pre-anaesthetic visits to facilitate the child's ability to cope with the visit.

Anaesthetic induction is similar to that for 'short case' anaesthesia but an endotracheal tube is used, instead of a nose mask, either inserted through the nose (nasotracheal tube) or through the mouth (orotracheal tube). To insert it, a short-acting neuromuscular paralysing agent needs to be used, when this wears off the patient then breaths spontaneously. Occasionally, a longer-acting neuromuscular paralysing agent is selected to enable the anaesthetist to ventilate the patient artificially. These forms of anaesthesia have a greater intrusion upon the patient's physiological state. However, the use of a laryngeal mask instead of an endotracheal tube is gaining in popularity because it avoids the use of the paralysing agent reducing postoperative muscle pain. Nevertheless, the same principles of protecting the airways apply. In addition to the tube, the throat will be packed with gauze. If conservation is required it is prudent to use a rubber dam, as good isolation is essential for a high standard of operative dentistry. For surgical procedures, local anaesthesia infiltration (2% lignocaine with 1 : 80,000 adrenaline) reduces bleeding and aids visibility during surgery while reducing the risk of cardiac dysrhythmias.

Once the treatment is complete the patient is placed in the recovery position and wheeled to a recovery suite. The recovery from such extensive anaesthesia is such that the patient may not be able to return home for several hours. Usually it is necessary to have access to a car as the children are never quite as 'street fit' as those who have had a short anaesthetic, so public transport is best avoided.

In-patient/hospital-stay 'intubation' anaesthesia

Patients who are unfit for short or medium length general anaesthetics are usually in ASA class III. These patients have a medical problem that constitutes a significant increased risk, so anaesthetists advise that they are treated in a hospital operating theatre, which is always close to the facilities of an intensive care unit. The dental surgery is no more complex than that carried out for 'short-' and 'day-stay' anaesthesia, but the underlying medical condition requires the increased level of care that may be needed in the operating theatre environment and during post-operative recovery, and even later on the ward.

Key Points
There are different types of dental anaesthesia, dependent on the complexity and length of time for the planned dental procedure.
Children with a medical condition may require hospital admission.

Summery

1. Most patients can be treated using local anaesthesia and good behaviour management.
2. A significant minority of patients will require some form of sedation to enable them to undergo dental treatment.
3. A small minority of patients require general anaesthesia.
4. All techniques require careful and systematic assessment of the patient before being used.
5. Dentists and their staff require careful training and regular updates in the techniques of anaesthesia and sedation for children.

Watch-Preparation for Full metal Crown Video

Conventional Over-Denture-Introduction

A conventional over-denture rests over some healthy natural tooth roots.

An overview of the Jaw

Maintaining a denture on the jaw bone ridge (called alveolar ridge) is essential to preventing it from becoming loose during eating, speaking and other activities.

Preserving the alveolar ridge facilitates denture stability

The body tends to conserve energy and nutrients by maintaining only structures with apparent immediate value. A typical example is the bulk reduction of a broken leg held immobile by a full leg cast for a month or more.

The body "recognizes" the only one purpose for alveolar bone is to hold tooth roots.

Alveolar bone no longer supporting a tooth root is removed, or literally dissolved away by the body. This is called resorption or simply shrinkage.

Resorption progresses at varying rates in the same person at different times and at different rates between different people. Resorption progresses rapidly within the first year of loosing a tooth after which time the rate progresses at a slower pace.

Preserving the Jaw bone

IF the maximum amount of bone is to be maintained then preserving the maximum number of healthy tooth roots should achieve that end.

Preserving the sensation of having teeth

Studies demonstrate that even though only roots are preserved, and they are covered by a denture, a patient still has sensory input sensations similar to that experienced with teeth, as opposed to individuals with conventional dentures and no preserved roots. Over-denture patients also appear to have a more natural perceived directional sense in their chewing activities. In other words, many patients relate that they still feel like they have teeth - - a positive comment.

Why an over-denture?

If a patient is treatment planned to have a denture, and the roots of some remaining teeth are supported in healthy alveolar bone - - then a conventional over-denture is a viable consideration.

However, only a licensed dental professional can determine if a conventional over-denture is a suitable consideration for a certain person, after a comprehensive examination.

Some characteristics of a conventional over-denture

• Most of a tooth crown (that part of the tooth above the gums) is removed. This often necessitates root canal therapy if not already done.
• Remaining tooth, projecting above the gum, is rounded and usually covered with a similarly shaped artificial crown-like covering.
• Various configurations and extensions may be built onto some retained roots. In those cases, that portion of the denture overlying these configurations is modified to contain attachments that clip onto a framework or receive the individual extensions. In addition to preserving alveolar bone and sensory input, the denture is securely held in place, but may be comfortably and easily removed for cleaning.

Advantages of a conventional over-denture

1. Feels more like having teeth
2. More retentive in many cases
3. Helps reduce shrinkage of surrounding bone
4. Reduces pressure to portions of the alveolar ridge
5. Positive psychological advantage of still having teeth

Disadvantages of a conventional over-denture

1. Scrupulous oral hygiene is essential in order prevent decay and gum disease.
2. The over-denture may feel bulkier than a conventional denture.
3. Frequent maintenance examinations are necessary.
4. Generally this is a more expensive approach than a conventional denture.

Implant Over-Denture

An implant over-denture connects to cylinder-like configurations (called implants) that have been surgically implanted into jaw bone.

The denture appears like a traditional prosthesis. However, that part of the denture overlying implants is modified to retain various semi-rigid attachments that receive implant extensions projecting above the gum. This arrangement helps keep a denture securely in place while eating, speaking and during other oral activities, but still allows easy self-removal of the denture for cleaning purposes.

There are two phases to this process. The first is a surgical phase consisting of two stages, and the second is a prosthetic phase (making the implant denture). 

The surgical phase

Surgical insertion stage

Implants are completely inserted into precise preparations in jaw bone. While there are various implant configurations, they are essentially cylindrical in shape and made of pure titanium metal. After implants are inserted into jaw bone, gum tissue over the implant is closed with sutures in most cases.

While a minimum of two implants may be inserted for an acceptable outcome, a person may be treatment planned to receive three or more - - depending upon individual needs and anatomical limitations. More implants will give additional support and retention to the implant denture.

Healing and surgical exposure stage

During healing, an existing or temporary denture may continue to be worn after adjustments have been made to adapt to the surgerized site. If the existing denture cannot be altered sufficiently, a provisional prosthesis should be fabricated.

Implants are left undisturbed beneath gum tissue for at least several months as determined by the dental professional. During this time bone reorganizes and grows around the implant surface, anchoring it securely into the jaw (this is called osseointegration).

At the end of the healing stage, the top of the implant is exposed by removing gum tissue directly over it.

An extension that is then screwed into the exposed implant projects slightly above the gum tissue. After adjustments, an existing denture can be worn over an implant extension while the gum heals.

However, the denture must be reshaped to conform to surgical site contours in order to avoid unnecessary pressure areas on the newly surgerized site.

The prosthetic phase (making the implant denture)

A precision superstructure is fabricated that is screwed into the implant extensions. This superstructure may have various interface configurations ranging from interconnecting metal bars to specially shaped singular extensions.

A denture is fabricated with special provisions on the inside surface to receive various types of attachments (interlocks). Depending on the attachment, they interact in various ways with the superstructure. For example, a metal or plastic attachment may clip onto metal superstructure bars, a nylon receptacle may receive a specially configured implant extension, and so forth.

The attachment/superstructure configuration helps to securely maintain a denture while eating and speaking, and still allows a person to comfortably and easily remove the prosthesis for cleaning purposes.

Essential maintenance needs

As might be expected, exemplary oral hygiene is essential to helping prevent the development of disease around implants that could cause their failure.

Implants, superstructure, attachments and the over-denture must be checked and professionally maintained by a licensed dental professional on a regular basis. Attachments often need periodic adjustment or replacement due to wear.

While the implant over-denture approach is complex and expensive, the value received by an individual usually far exceeds monetary considerations.

How long will implant over-dentures last?

An implant may last for a lifetime (current reports show many implants lasting twenty years) or deteriorate in a few years  - many factors are involved that reduce the life expectancy of implants, such as oral hygiene, general health, habits such as smoking, grinding, and so forth. The superstructure or implant extensions may need to be replaced after five years. Depending on the implant system used, some parts may need to be replaced annually, or sooner, because of wear or deterioration. These time frames are generalities. The dental profession continues to strive for long-term durability.