The histopathology of pulpitis
Acute pulpitis
Early changes within the pulp from the advancing carious lesion involve the production of tertiary dentine by the odontoblasts. Tertiary dentine, formerly known
as irregular secondary dentine, contains fewer tubules than primary or secondary dentine. Tertiary dentinemay be reactionary, laid down by primary odontoblasts
in response to a mild stimulus, or reparative dentine,laid down by secondary odontoblasts derived from otherpulp cells. This attempt at a barrier to the advancing
lesion can be effective if the lesion progresses slowly and particularly so if it arrests. However, with the advancinglesion, bacteria invade the odontoblasts and destroy the
surrounding tissues. Clinically it is characterised by the patient feeling pain in response to temperature changewhich lasts for the duration of the stimulus. There is normally
no pain on biting or when the tooth is percussed. The inflammation of the pulp is reversible if the causeis successfully treated, e.g. by the removal of the caries.
As the pulpal inflammation becomes more extensive, the pain experienced as a result of temperature changebecomes more severe and persists after the removal ofthe stimulus usually for several minutes or even longer.As the lesion approaches the pulp, inflammatoryresponses are detected in front of the advancing lesion.Once penetration of the pulp by bacteria has taken place,the inflammatory process becomes more profound.
The response of the tissues to this invasion is seen clinicallyas acute pulpitis. The inflammation produces anincrease in pressure on the walls surrounding the pulpbecause of the presence of additional inflammatory cells,increased vascularity (hyperaemia) and the inability ofthe pulp chamber to expand to relieve the pressure causingthe typical symptoms of acute pulpitis. These are:
�¡ A constant, throbbing pain in the affected tooth that is
often made worse by reclining or lying down.
■ A lack of pain on biting unless the inflammation has
spread beyond the confines of the pulp.
■ The inability to obtain relief from the pain.
Other processes which can lead to bacteria penetrating the pulp are trauma, e.g. a fractured tooth or traumaticexposure during cavity preparation (iatrogenic), toothwear, via the periodontal membrane or, rarely, via a bacteraemia,e.g. induced by a tooth xtraction from anothersite (anachoresis).
Chronic pulpitis
Chronic pulpitis may be the result of persistent mild to moderate irritation of the pulp or it may follow a periodof acute pulpitis. The symptoms are:
�¡ A mild intermittent pain over an extended period
of time.
■ Pain of varying intensity.
�¡ Pain which is often difficult to localise.
�¡ Pain usually induced by thermal change or sweet
liquids or solids.
Symptoms may be relieved by taking analgesics which act on the central nervous system (
Patients have been known to try to alleviate the symptoms by placing an analgesic tablet, e.g. aspirin, adjacentto the suspected tooth. Aspirin has no analgesic affect
locally and is likely to compound the discomfort by inducing a mucosal burn because of the high local concentrationof acetylsalicylic acid.
The result of bacterial invasion is an influx of antiinflammatory cells (macrophages) into the pulp and anincrease in lymphocytes and plasma cells. This producesdead bacteria, other necrotic debris and sometimesdiscrete areas of calcification including pulp stones.
The ratio of dead to living cells increases and can lead eventually to death of the pulp.
Abscess formation
Acute abscess
Once the pulp dies the pulpal space is invaded by bacteria which progress to the apical tissues. Early changes involve localised tissue response to the bacteria and their
by-products. Unless the carious lesion is large and associated with extensive tissue breakdown, the only exit pathway for necrotic tissue in the pulp is through the apical
foramen and into the supporting bone. The potential exists for this to increase to produce an area which contains  predominantly dead cells from the bacteria, bone and inflammatory cells. Accumulation of these cells in an enclosed space produces greater tissue destruction and the formation of pus, a liquid containing large numbers
of polymorphonuclear cells, necrotic tissue and bacterial toxins. The pus increases in amount until tissue expansion  results in a breakout, usually along the line of least
resistance into the soft tissues, either via the periodontal ligament or directly into the mouth. It may also spread into the soft tissues to create a cellulitis. Such spread can
be dictated by the related anatomical structures. Infection via fascial planes can be rapid and extend some distance from the original abscess site, occasionally resulting in
occlusion of the airway by oedema, e.g. Ludwig’s angina. Rarely it may also spread into the deeper medullary space of the alveolar bone producing a spreading osteomyelitis.
There can also be an indirect spread of infection, either via the lymphatics to the regional lymph nodes in thehead and neck (the submental, submandibular, deep cervical,
parotid or occipital), which can become enlarged and tender, or more rarely, via the blood vessels to other organs, e.g. the heart or brain. The onset of an abscess is usually characterised by a severe throbbing pain, often easily localised by the patient. The tooth is normally very sensitive to biting and percussion because of the inflammation of the supporting structures. Due to the increase in pressure in the periapical region with a periapical abscess, the tooth is usually elevated in the socket which results in increased
mobility and causes the patient to experience additional pain due to a premature contact on occlusion. A periapical abscess will give a negative response to electrical or
hermal pulp testing (unlike a periodontal abscess where  the tooth can also be sensitive to biting or percussion).
Chronic abscess
When the abscess bursts through the bone into the adjacent soft tissues, there is usually an immediate reduction in the symptoms and, providing the abscess can continue
to maintain drainage, it will tend to go into a chronic phase which is frequently asymptomatic. In the chronic phase, a sinus links the main abscess cavity with the skin
or mucosal surface and allows further drainage to take place. This process can be associated with both primary and permanent teeth. In both cases the progression from
a carious lesion to a chronic abscess may be completely asymptomatic and visual examination will reveal a discharging sinus usually adjacent to the carious tooth. The
sinus drainage pathway may become blocked, resulting in an elevated lesion or gum boil at the gingival margin. As the pressure increases this will intermittently burst
and discharge into the oral cavity. A dentoalveolar abscess is usually polymicrobial
consisting of predominantly anaerobic organisms which include Streptococcus sanguis, milleri-group streptococci, Actinomyces spp.

     The dental pulp

Dental pulp is the living, soft tissue structure which resides in the coronal pulp chamber and root canals of primary and permanent teeth.

Histologically, it is composed of loose connective tissue, surrounded on its periphery by a continuous layer of specialized secretory cells, the odontoblasts. Odontoblasts are unique to the dental pulp and are responsible for dentine deposition.

Blood vessels and nerves enter the pulp through the apical foramen and occasionally through lateral or accessory root canals. The pulps of primary and young permanent teeth, especially those with incomplete apices, have a very rich blood supply.

The most important function of the pulp is to lay down dentine which forms the basic structure of teeth, defines their general morphology, and provides them with mechanical strength and toughness.

Dentine deposition commences many months (primary teeth) or years (permanent teeth) before tooth eruption and while the crown of a newly erupted tooth has a mature external form, the pulp within still has considerable work to do in completing tooth development. Newly erupted teeth have short roots, their apices are wide and often diverging, and the dentine walls of the entire tooth are thin and relatively weak.

Provided the pulp remains healthy, dentine deposition will continue during the posteruptive year for primary teeth. One of the key goals of paediatric dentistry is therefore to protect and preserve the pulps of teeth in a healthy state at least until this critical phase of tooth development is complete.
 Diagnosis of pulp pathosis and rationale

Studies in the early 1970s had shown that in over 50% of the primary molars where the loss of the marginal ridge had occurred, pulp inflammation was irreversible. Research carried out recently in the Department of Paediatric Dentistry of the Leeds Dental Institute (Duggal et al., 2002), has corroborated these findings. In this study, it was shown that most teeth had pulp inflammation involving the pulp horn adjacent to the proximal carious lesion, even when caries had involved less than half the marginal ridge, studied by measuring the inter-cuspal distance (bucco-lingual) involved in the carious process. This suggests that inflammation of the pulp in primary molars develops at an early stage of proximal carious attack and by the time most proximal caries is manifest clinically, the pulp inflammation is quite advanced. These findings have important clinical implications, the most important being that restoration carried out without pulp therapy in most primary molars, where proximal caries has manifest clinically with the involvement of the marginal ridge, will fail. Once the breakdown of marginal ridge is evident pulp therapy is invariably required. It also reiterates the importance of early diagnosis of proximal caries with the use of BW radiographs. Because of this early onset of inflammation in primary molars direct pulp capping is also contraindicated.
Indirect pulp capping

In the majority of circumstances, carious lesions can and should be fully excavated before tooth restoration. A clinical dilemma is presented by a deep lesion in a vital, symptom-free tooth where complete removal of softened dentine on the pulpal floor is likely to result in frank exposure. The advancing front of a carious lesion contains very few cariogenic bacteria. Provided the bulk of infected overlying dentine is removed, a small amount of softened dentine may often be left in the deepest part of the preparation without endangering the pulp. This is the basis of indirect pulp capping.

All caries is first cleared from the cavity margins with a steel round bur running at slow speed. Gentle excavation then follows on the pulpal floor, removing as much of the softened dentine as possible without exposing the pulp. Precisely how much dentine should be removed becomes a matter of experience and clinical judgement, although some have advocated the use of indicator dyes (e.g. 0.5% basic fuchsin) to show when all infected dentine has been eliminated. A thin layer of setting calcium hydroxide cement is then placed on the cavity floor to destroy any remaining micro-organisms and to promote the deposition of reparative secondary dentine.

In its classical application, the indirect pulp cap was covered with zinc oxide-eugenol cement, and following several weeks' observation, the cavity was re-entered to remove all remaining softened dentine. More commonly, the calcium hydroxide pulp cap is simply covered with a layer of hard setting cement and the tooth permanently restored at the same visit. Periodic clinical and radiographic review is then undertaken to monitor the pulp response.

If, as has been discussed in the previous sections, the pulp is deemed to be inflamed, pulp therapy should be considered even in the absence of a clinical exposure. Direct pulp capping should not be carried out if an exposure is found on removal of caries, as placing a medicament, such as calcium hydroxide on an inflamed pulp will lead to failure.

8.8.4 The vital pulpotomy

Pulp therapy usually refers to two terms; pulpotomy and pulpectomy. A pulpotomy involves the coronal removal of the pulp tissue that is diagnosed to be inflamed or infected as a result of deep caries. This usually leaves an intact radicular pulp tissue upon which a medicament is applied before placing a coronal restoration.

Indications for a pulpotomy

There are certain conditions such as congenital heart defects, history of heart surgery where pulpotomy is not usually performed due to the risk of precipitating bacterial endocarditis. Also, in immuno-compromised (e.g. leukaemia) or deficient conditions, pulpotomy is contraindicated and extraction with the relevant essential precautions is usually preferred.

The pulpotomy technique

Pulpotomy medicament

Formocresol has traditionally been used and widely recognized within the profession, as a medication that has delivered the best long-term results. A one-fifth dilution of original Buckleys formulation has been shown to be as effective as the full strength concentrate. Formocresol is not easily available in the United Kingdom and there have been some concerns about its toxicity, both locally and systemically. These concerns have grown recently with formaldehyde, one of the important components of formocresol linked to certain forms of cancer. Attempts have been ongoing for the last few years to find a suitable replacement and one material that has generated a lot of interest recently as a suitable alternative to formocresol is ferric sulfate. Ferric sulfate has been widely used to control gingival bleeding, prior to impression taking and also in endodontics. It is an excellent haemostatic agent, forming a ferric ion-protein complex on contact with blood, which then stops further bleeding by sealing the vessels. It has also now been shown to be as effective as formocresol in medium-and long-term studies when used in a concentration of 15.5%. This is available commercially as Astringident. The authors view is that ferric sulfate will emerge as the most suitable alternative to formocresol in the next few years. In light of recent evidence, ferric sulfate can be used as a suitable alternative for those concerned about the toxicity of formocresol or have difficulty obtaining it in the United Kingdom. However, it must be remembered that ferric sulfate has no "fixative" effect. For this reason, an accurate diagnosis of the state of the pulp tissue being left behind and on which ferric sulfate is being applied will need to be made.

Key Points
 Ferric Sulfate is a suitable medicament for pulpotomy in primary molars when the inflammation is diagnosed to be restricted only to the coronal pulp.
 Though it stops bleeding at the site of amputation of the coronal pulp, it should be applied, almost immediately, for about 1 min.

Follow-up

Teeth that have undergone pulpotomy should be reviewed clinically and if possible radiographically, though the authors accept that routine radiographic follow-up is not possible in general dental practice. Clinically, the following criteria indicate success:

 absence of symptoms;
 absence of any abscess or draining sinus;
 no excessive mobility or tenderness.

Radiographically there should be:

1. Either no further bone loss in the furcation region or regeneration of bone in this area. Figure 8.19  (e) demonstrates good bone condition in the bifurcation region 6 months after the pulpotomy was performed.

2. No evidence of internal resorption. Internal resorption usually indicates chronic inflammation and the activity of giant cells causing resorption of the dentine. It creates few symptoms, and is usually detected as an incidental finding on radiographic examination. It should be considered as a form of irreversible pulpitis (Fig. 8.22 ).

Key Points
 Direct pulp capping has a poor prognosis in carious primary molars.
 Pulpotomy has a better prognosis than pulp capping.
 A pulpotomy should only be performed when the pulp inflammation is thought to be limited to the coronal pulp.
 Ferric sulfate (15.5%), available as Astringident is emerging as a good alternative to formocresol for use as a pulp medicament.

  Management of non-vital and abscessed primary molarsthe pulpectomy technique

Primary molars with abscesses are usually indicated for extractions. Persistent and chronic infection in primary molars can cause damage to the developing permanent tooth germs and such foci of infection should be removed.

In some cases the non-vital primary molars  or ones with a chronic discharging sinus might need to be retained. Some of the reasons for this could be:

 orthodontic,
 medical, where extraction is not appropriate, such as in severe haemophiliacs,
 parents refusal to accept extraction.

In such cases these teeth can be retained by carrying out the Pulpectomyprocedure. In the United Kingdom, there is reluctance among many dentists to carry out a pulpectomy as it is perceived to be difficult in a young child, with extraction being preferred. The authors feel that this is a misconception. This technique should be learnt by all paediatric dentists, as it can often save the child from the trauma of a GA for extraction of primary teeth. Pulpectomy involves accessing the root canal system of primary molars, cleaning them as best as is possible, and then using an appropriate material, usually pure zinc oxide eugenol, to obturate the root canals. Pure zinc oxide eugenol is preferred as it is entirely resorbable and is easily removed as the roots of the primary teeth undergo resorption. Also, if it is extruded through the apices, it gets completely resorbed by the apical tissues. Other materials such as Iodoform paste, and even calcium hydroxide are also sometimes used.

The root canal morphology of primary molars is quite similar to that of permanent molars with either three of the four root canals present. In the lower primary molars there are always two mesial root canals-buccal and mesio-lingual, with one or sometimes two distal root canals. In upper primary molars there are three root canals-buccal, disto-buccal, and palatal .

Indications for pulpectomy

 Irreversible pulpitis involving both the coronal and radicular pulp.
 Non-vital primary molars or incisors that need to be maintained in the arch.
 Abscessed primary molars.
 Primary molars with radiographic evidence of furcation pathology.

The steps for performing a pulpectomy are shown in the flow diagram.

It's a diagrammatic representation of the technique. In some cases where there is acute infection or persistent discharge from the root canals, it may be necessary to defer the root canal obturation to a second visit. In such cases a medicated cotton pledget, barely moistened with formocresol is sealed in the pulp chamber with either glass ionomer cement or IRM. (For those who are concerned about the safety of formocresol, Ledermix would be a suitable alternative.) In the second visit the pledget is removed and the pulpectomy procedure completed.

Follow-up and review

Though the pulpectomy technique carries a good prognosis, the outcome is not as good as a vital pulpotomy. Clinical follow-up augmented by one periapical radiograph on a yearly basis is required.The following clinical and radiographic parameters can be taken as indications of success:

Clinical

 alleviation of acute symptoms;
 tooth free from pain and mobility.

Radiographic

 improvement or no further deterioration of bone condition in the furcation area.

Root canal treatment of primary incisors

The technique described above can also be used to treat non-vital or abscessed primary incisors. Increasingly, parents are reluctant to have their child's upper anterior teeth extracted. In a modern society, where a child's self-esteem is important, it is the duty of the dentists to maintain aesthetics wherever possible. Many primary incisors with abscesses that are extracted can be retained with the help of a pulpectomy technique, and the root canal morphology is such that this can easily be performed , the only limiting factor being the child's co-operation. Indications for a pulpectomy in primary incisors include carious or traumatized primary incisors with pulp exposures or acute or chronic abscesses.It'sshows an example of primary central incisors treated with pulpectomy.

Key Points
 A pulpectomy should be considered wherever it is essential to preserve a primary tooth that cannot be treated with other means, such as a pulpotomy.
 Both primary molars and incisors can be treated with a pulpectomy technique.

TREATMENT OF A CHILD WITH HIGH CARIES RATE

It is absolutely true that restoration of children's teeth without adequate prevention is like replacing windows in a burning house. When presented with a child with a high caries rate, establishing a good preventive regime should be the first and foremost item in the treatment plan. However, it would be a folly to think that prevention alone will maintain the child in a pain free state. Restorative treatment or extraction of decayed teeth that are not suitable for restoration should be planned alongside securing good prevention. Therefore, when dealing with a high caries risk child, a comprehensive visit by visit treatment plan that deals with the preventive and restorative care of the child should be established.

The type of treatment instituted for patients with rampant caries depends on the patients' and parents' motivation towards dental treatment, the extent of decay, and the age and co-operation of the child. Initial treatment, including temporary restorations, diet assessment, oral hygiene instruction, and home and professional fluoride treatments, should be performed before any comprehensive restorative programme commences. However, in patients presenting with acute and severe signs and symptoms of gross caries, pain, abscess, sinus, or facial swelling, immediate treatment is indicated. This may involve extractions and even a general anaesthetic in a young child. It is wiser to extract all the teeth with a dubious prognosis under one general anaesthetic rather than have an acclimatization programme interrupted by a painful episode in the future.

Summarizes the preventive regimens that should be employed for rampant caries in different age groups.

Once rampant caries is under control, then comprehensive restorative treatment can be undertaken. This should aim to retain the primary dentition with the methods described in this chapter and in Chapter 7 , and deliver the child pain free into adolescence and adulthood.

8.10 SUMMARY

1. A full preventive programme must be instituted before any definitive restorations in a child with a high caries rate.

2. Repetitive treatment should be avoided and with careful treatment planning and choice of restorative materials long-lasting restorations can be carried out in children.

3. The stainless-steel metal crown is the most durable restoration in the primary dentition for large cavities and endodontically treated teeth.

4. Resin-modified glass ionomers and polyacid-modified composite resins may have an increased role in the future in the restoration of primary teeth.

5. Rubber dam should be placed, if at all possible, prior to the restoration of all teeth.

6. Careful evaluation of the state of pulp inflammation should be carried out before the placement of proximal restorations in primary teeth. Wherever the pulp is deemed to be involved, pulp therapy should be carried out prior to the coronal restoration.

7. Formocresol is likely to be replaced with newer, safer medicaments such as Ferric Sulphate.

 ACKNOWLEDGEMENTS

Some parts of this text have been reproduced from Dental Update, with the kind permission of George Warman Publications.
Conservative treatment options

Various techniques have a part to play in conservation of teeth with deep caries.

 Indirect pulp capping.
 Direct pulp capping
 Pulpotomy
 Pulpectomy

When the tooth erupts its roots are incompletely formed and approximately 20-40% shorter than the mature root. It may take up to 5 years after eruption for the root to complete its formation and develop an apical constriction.

Key Point
Whenever it is thought that caries removal might result in a pulpal exposure, efforts should be made to preserve pulp vitality in order to enable normal root maturation to occur.

Indirect pulp capping

If it is thought that exposure is likely to occur with full caries removal then sometimes it is expedient to leave caries in the deepest part of the lesion. Place a radio-opaque, biocompatible base over the remaining carious dentine to stimulate healing and repair. It is important to completely remove caries from all the lateral walls of the cavity before placement of a restoration since failure to do so will result in spread of secondary caries and the need for future intervention.

Traditionally operators have used calcium hydroxide for indirect pulp capping because it has a good success rate. Alternatives suggested include adhesive resins, and glass ionomer cements, but as yet there are no published studies looking at these techniques in permanent teeth. Whichever material is utilized, the crucial factor is to isolate the pulp well from the oral environment. Re-investigation of these teeth after about 6 months when the pulp has had an opportunity to lay down reparative dentine used to be recommended. However studies have found that the residual carious dentine mostly re-mineralizes and hardens and caries progression does not occur in the absence of micro-leakage. Returning to the operative site, to complete caries removal increases the risk of pulp exposure, therefore the authors consider it wiser to perform the indirect pulp capping and definitive restoration in one appointment.

The direct pulp cap

When a small exposure is encountered during cavity preparation the operator can place a direct pulp cap. The concept once again is to preserve the vitality of the pulp. Calcium hydroxide has traditionally been used as the direct capping agent. Total etching and sealing with a dentine-bonding agent has been tried but this resulted in increased non-vitality, so it is now contraindicated. As in traumatic exposures, pulp capping has given disappointing results compared with the technique of partial pulpotomy, so should only be used if a pulpotomy cannot be performed.

For all techniques in which the pulp is preserved it is important to assess the situation correctly before embarking on the treatment:

 There should be no history of spontaneous pain.
 There should be no swelling, mobility, discomfort to percussion.
 A normal periodontal appearance should be present radiographically.
 Pulp tissue should appear normal and vital.
 Cessation of bleeding from the pulp exposure site should occur with isotonic irrigation within 2 min.

Pulpotomy

Pulpotomies are successful in young teeth due to their increased pulpal circulation and ability to repair. The procedure consists of applying rubber dam after local analgesia and then clearing all lateral margins around the exposure and the pulpal floor of any caries. The superficial layer of the exposed pulp and the surrounding dentine are excised to a depth of 2 mm using a high speed diamond bur. The technique is the same as the Cvek pulpotomy described in Chapter 12  for pulp exposure in traumatized teeth. Only tissue judged to be inflamed should be removed. Whether sufficient tissue has been removed is ascertained by gently irrigating the remaining pulp surface with isotonic saline until bleeding stops. If bleeding does not cease easily, it is probable that the tissue is still inflamed and a further millimetre of pulp tissue is removed. Similarly if there is no bleeding at all then further pulp tissue should be removed until bleeding is found. After haemostasis has been obtained a soluble paste of calcium hydroxide is applied to the wound surface. It is important that there is no blood clot between the wound surface and the dressing as this will prevent repair and reduce the chances of success. Recently, MTA (mineral trioxide aggregate) has been proposed for pulp capping and pulpotomy dressings, but most of the published studies so far on this topic have been performed on animals. Hence at present calcium hydroxide, the tried and tested remedy should still be used. In order to aid repair, the clinician should apply dry sterile pellets of cotton wool carefully with modest pressure to adapt the calcium hydroxide medicament to the prepared cavity and remove excess water from the paste.

As in pulp capping it is essential that the operator fills the cavity with a material that provides a good hermetic seal. The latter can be the final restoration as there is no need to re-enter the wound site. Although the presence of a dentinal bridge radiographically represents a success, its absence does not indicate failure. After a year, success is represented by a tooth where there are no signs of clinical or radiographic pathology and where the root has developed apically and thickened laterally. The pulpotomy technique has much to recommend it, viz. a good success rate and continued root development. It is therefore considered the treatment of choice when there has been a pulp exposure in an immature permanent tooth.

Pulpectomy

Root canal therapy following pulpectomy has a poor success rate in young permanent molars. In a recent study only 36% of young root filled molar teeth were considered a success. Hence, pulpectomy should be reserved only for cases exhibiting symptoms where the pulp is irreversibly damaged.

  HYPOMINERALIZED, HYPOMATURE, OR HYPOPLASTIC FIRST PERMANENT MOLARS

Introduction

As caries has declined generally, it has become more apparent that there is another problem that commonly affects first permanent molars and incisors. Very recently this condition has been called 'molar-incisor hypomineralization' (MIH). This term covers a range of developmental anomalies from small white, yellow, or brown patches to extensive loss of tissue from almost the whole enamel surface. It is characterized by a very rapid breakdown of the enamel, which can be extremely sensitive. The breakdown may even occur in a few months while the tooth is still erupting. The difficulties of cleaning a partially erupted tooth are then compounded by the sensitivity. This produces an area where plaque builds up and which leads to rapid carious attack. As is always the case with first permanent molars, exfoliation of primary molars does not precede their eruption, so children and parents are often unaware of their presence and thus they do not seek treatment until the teeth start to cause problems.

Molar-incisor hypomineralization has been defined as 'hypomineralization of systemic origin of one to four permanent molars frequently associated with affected incisors'. The expression of the phenomenon can vary in severity between patients but also within a mouth, so in one quadrant there may only be a small hypomineralized area, while in others almost total destruction of the occlusal surface.

Usually the incisors do not suffer the same breakdown of the surface and sensitivity as the molars. However, they do frequently cause a cosmetic defect. This can be treated as the child becomes conscious of it, either by coverage with composite (veneer) or partial removal of the defect and coverage with composite (localized composite restoration).

The first problem to remedy in molars is the sensitivity. Various desensitizing agents theoretically and anecdotally do help, but no clinical trials specifically related to MIH have been reported. They include:

 Repeated application of 5% sodium fluoride varnish (Duraphat).
 Commercially available 'sensitive tooth toothpastes'.
 Daily use of 0.4% stannous fluoride gels.

Fissure sealants can be useful where the affected areas are small and the enamel is intact. The use of bonding agents as described above under the resin sealant should help with bonding if the margin of the sealant is left on an area of hypomineralized enamel. The application of the bonding agents alone, once polymerized may reduce the sensitivity in the affected teeth per se. It is important to remember to monitor fissure sealants in these teeth very carefully as there is a high chance of marginal breakdown. If there is surface breakdown the tooth will require some form of restoration. The first decision to make is whether the clinician needs to maintain the tooth throughout life or if it is more pragmatic to consider extraction . If the decision is that the first molars will be extracted as part of a long-term orthodontic plan, it is probable that they will still need temporisation because of the high level of sensitivity. These teeth are very difficult to anaesthetize, often staying sensitive when the operator has given normal levels of analgesic agent. If a child complains during treatment of a hypomineralized molar tooth, credibility should be given to their grievance. If a child experiences pain or discomfort during treatment, they will become increasingly anxious in successive treatments. This has been shown to be true for 9-year-old children, where dental fear, anxiety, and behaviour management were far more common in those children with severely hypomineralized first permanent molars when compared with unaffected controls.

Inevitably, a balance has to be made between using simpler methods, such as dressing with a glass ionomer cement that may well need replenishment often on several occasions before the optimum time for extraction, and deciding early within the treatment to provide a full coverage restoration, for example. a stainless-steel crown which should last without requiring replacement prior to extraction time. All adjuncts to help the analgesia, such as inhalation sedation should be used, if indicated. It is also useful to use rubber dam for all the usual reasons plus the protection afforded by exclusion of spray from the other three un-anaesthetized molars, which probably will also be very sensitive.

If the intention is to maintain the molar in the long term, then the choice of restorative techniques expands. If the area of breakdown of the hypomineralized enamel is relatively confined then the operator should use conventional restorative techniques. It is however difficult to determine where the margins of a preparation should be left as sometimes seemingly normal enamel (to visual examination) undergoes breakdown.

Amalgam is of limited use, because, further breakdown often occurs at the margins, and it is non-adhesive so does not restore the strength of the tooth. Composite resins, on the other hand, when used with an appropriate bonding agent in well, demarcated lesions, should have a good success rate. Deciding where to leave the margin in these teeth presents difficulty. Fayle (2003) described his approach of investigating abnormal looking enamel at the margins of the defect with a slow rotating steel bur extending into these areas until good resistance is detected. This approach is at present not backed up by clinical studies but is a technique adopted by many dentists and could help avoid unnecessary sacrifice of sound tissue. 

Most hypomineralized molars with surface breakdown involving one cusp or more will need a restoration with greater coverage. Either stainless-steel crowns or cast adhesive copings provide the most satisfactory options.

  Preformed metal crowns (stainless-steel crowns)

The advantages of these are:

1. Single visit for placement.

2. Relatively quick and simple procedure.

3. Usually reduce sensitivity totally, because they cover the whole tooth.

4. Inexpensive compared with cast restorations.

5. Good retention rate.

The disadvantages are:

1. Require more tooth preparation than cast preparations.

2. Once a tooth has been prepared for a stainless-steel crown, it will need a full coverage restoration eventually. It has been suggested that placing orthodontic separators 1 or 2 weeks prior to preparation reduces the amount of tissue requiring removal. However, some reduction is usually necessary.

3. Gingival margins are sub-gingival.

Operative technique

1. Obtain adequate anaesthesia.

2. Isolate the tooth to be crowned.

3. Select the crown size.

4. Remove any carious dentine and enamel.

5. Replace tooth bulk with glass ionomer.

6. Reduce the occlusion minimally.

7. Reduce the mesial and distal surfaces, slicing with a fine tapered bur. Depending on the natural anatomy of the tooth it may be necessary to create a peripheral chamfer on the buccal and lingual surfaces.

8. Try the selected crown; adjust the shape cervically, such that the margins extend ~1 mm below the gingival crest evenly around the whole of the perimeter of the crown. Sharp Bee Bee scissors usually achieve this most easily, followed by crimping pliers to contour the edge to give spring and grip. Permanent molar preformed metal crowns need this because they are not shaped accurately cervically. This is because there is such a variation in crown length of the first permanent molars.

9. After the contouring, smooth and polish the crown to ensure that it does not attract excessive amounts of plaque.

10. After test fitting of the crown remove the rubber dam to check the occlusion then re-apply for cementation.

11. Cement the crown usually with a glass ionomer based cement.

12. Remove excess cement carefully with an explorer and knotted floss. Finally recheck the occlusion.