In the 1960s and 1970s, several studies were conducted sponsored by the U.S. Atomic Energy Commission, with the aim of finding a link between genetics and hypodontia.

MIH examination should be carried out on clean, wet teeth. The ideal age for examination is when the child is 8 years old - the age where all permanent first molars and most of the incisors are erupted. The permanent first molar will also still be in a comparatively sound condition without excessive post-eruption breakdown. Judgements of each individual teeth should be recorded, aiding the correct diagnosis of the condition.

There is currently a lack of standardisation in the scoring system and severity indices used to record the diagnosis of MIH. Various systems commonly employed in studies include:

- Modified Defect of Dental Enamel (DDE) Index: This set of criteria allows for enamel defects to be detected, enabling a distinction between demarcated and diffused opacities.

- European Academy of Paediatric Dentistry (EAPD) judgement criteria: This set of criteria was developed in 2003 to standardise classifications for use in epidemiological studies. However, while it allows the categorisation of the enamel condition, it does not address the severity of the enamel condition.

- Molar Hypomineralisation Severity Index (MHSI): This set of criteria has been developed to address deficiencies in indices concerning the severity of hypomineralisation. It is based on both the clinical characteristics of hypomineralised defects and the EAPD judgement criteria.

The oral rehabilitation of hypodontia, especially where a significant number of teeth have not developed, is often a multidisciplinary process, involving a specialist orthodontist, a consultant in restorative dentistry, and a paediatric dentist in the earlier years. The process of treating and managing hypodontia begins in the early years of the patient's dentition where absent teeth are identified and the process of maintaining the remaining teeth begins. This is largely conducted by the paediatric dentist with orthodontic input. Once all the adult teeth have erupted the orthodontist is likely to liaise with the restorative dentist regarding optimal positioning of teeth for subsequent replacement with prosthodontic methods. This may include the utilisation of a resin-retained bridge and implants for spaces or composite resin, veneers or crowns where teeth are diminutive or misshaped.

AI can be classified according to their clinical appearances:

- Type 1 - Hypoplastic

Enamel of abnormal thickness due to malfunction in enamel matrix formation. Enamel is very thin but hard & translucent, and may have random pits & grooves. Condition is of autosomal dominant, autosomal recessive, or x-linked pattern. Enamel differs in appearance from dentine radiographically as normal functional enamel.

- Type 2 - Hypomaturation

Enamel has sound thickness, with a pitted appearance. It is less hard compared to normal enamel, and are prone to rapid wear, although not as intense as Type 3 AI. Condition is of autosomal dominant, autosomal recessive, or x-linked pattern. Enamel appears to be comparable to dentine in its radiodensity on radiograpshs.

- Type 3 - Hypocalcified

Enamel defect due to malfunction of enamel calcification, therefore enamel is of normal thickness but is extremely brittle, with an opaque/chalky presentation. Teeth are prone to staining and rapid wear, exposing dentine. Condition is of autosomal dominant and autosomal recessive pattern. Enamel appears less radioopaque compared to dentine on radiographs.

- Type 4: Hypomature hypoplastic enamel with taurodontism

Enamel has a variation in appearance, with mixed features from Type 1 and Type 2 AI. All Type 4 AI has taurodontism in common. Condition is of autosomal dominant pattern.

Other common features may include an anterior open bite, taurodontism, sensitivity of teeth.

Differential diagnosis would include dental fluorosis, molar-incisor hypomineralization, chronological disorders of tooth development.

Although these teeth are usually asymptomatic and pose no threat to the individual, they are often extracted for aesthetic reasons. This is done particularly if the mesiodens is positioned in the maxillary central incisor region. The traditional method of removal is done by using bone chisels, although a more advanced technique has been found to be more beneficial, especially if surgery is required . Through the use of Piezoelectricity, Piezoelectric ultrasonic bone surgery may be more time consuming than the traditional method but it seems to reduce the post-operative bleeding and associated complications quite significantly.

Preventive and restorative care are important as well as esthetics as a consideration. This ensures preservation of the patient's vertical face height between their upper and lower teeth when they bite together. The basis of treatment is standard throughout the different types of DI where prevention, preservation of occlusal face height, maintenance of function, and aesthetic needs are priority. Preventive efforts can limit pathology occurring within the pulp, which may render future endodontic procedures less challenging, with better outcomes.

- Challenges are associated with root canal treatment of teeth affected by DI due to pulp chamber and root canal obliteration, or narrowing of such spaces.

- If root canal treatment is indicated, it should be done in a similar way like with any other tooth. Further consideration is given for restoring the root-treated tooth as it has weaker dentine which may not withstand the restoration.

Preservation of occlusal face height may be tackled by use of stainless steel crowns which are advocated for primary teeth where occlusal face height may be hugely compromised due to loss of tooth tissue as a result of attrition, erosion of enamel.

In most cases, full-coverage crowns or veneers (composite/porcelain) are needed for aesthetic appearance, as well as to prevent further attrition. Another treatment option is bonding, putting lighter enamel on the weakened enamel of the teeth and with lots of treatments of this bonding, the teeth appear whiter to the eye, but the teeth on the inside and under that cover are still the same. Due to the weakened condition of the teeth, many common cosmetic procedures such as braces and bridges are inappropriate for patients with Dentinogenesis imperfecta and are likely to cause even more damage than the situation they were intended to correct.

Dental whitening (bleaching) is contraindicated although it has been reported to lighten the color of DI teeth with some success; however, because the discoloration is caused primarily by the underlying yellow-brown dentin, this alone is unlikely to produce normal appearance in cases of significant discoloration.

If there is considerable attrition, overdentures may be prescribed to prevent further attrition of remaining teeth and for preserving the occlusal face height.

Preventive and restorative dental care is very important as well as considerations for esthetic issues since the crown are yellow from exposure of dentin due to enamel loss. The main objectives of treatment is pain relief, preserving patient's remaining dentition, and to treat and preserve the patient's occlusal vertical height.

Many factors are to be considered to decide on treatment options such as the classification and severity of AI, the patient's social history, clinical findings etc. There are many classifications of AI but the general management of this condition is similar.

Full-coverage crowns are sometimes being used to compensate for the abraded enamel in adults, tackling the sensitivity the patient experiences. Usually stainless steel crowns are used in children which may be replaced by porcelain once they reach adulthood. These aid with maintaining occlusal vertical dimension.

Aesthetics may be addressed via placement of composite or porcelain veneers, depending on patient factors eg age. If the patient has primary or mixed dentition, lab-made composite veneers may be provided temporarily, to be replaced by permanent porcelain veneers once the patient has stabilized permanent dentition. The patient's oral hygiene and diet should be controlled as well as they play a factor in the success of retaining future restorations.

In the worst-case scenario, the teeth may have to be extracted and implants or dentures are required. Loss of nerves in the affected teeth may occur.

It is recommended to parents and caregivers to take their children to a dental professional for examination as soon as the first few teeth start to erupt into the oral cavity

. The dental professional will assess all the present dentition for early carious demineralization and may provide recommendations to the parents or caregivers the best way to prevent ECC and what actions to take.

Studies suggest that children who have attended visits within the first few years of life (an early preventive dental visit) potentially experience less dental related issues and incur lower dental related costs throughout their lives.

Bisphosphonates have recently been introduced to treat several bone disorders, which include osteogenesis imperfecta.

A recognized risk of this drug relevant to dental treatments is bisphosphonate-associated osteonecrosis of the jaw (BRONJ). Occurrences of this risk is associated with dental surgical procedures such as extractions.

Dental professionals should therefore proceed with caution when carrying out any dental procedures in patients who have Type 2 DI who may be on bisphosphonate drug therapy.

Before root canal treatment or extraction are carried out, the clinician should have thorough knowledge about the root canal morphology to avoid complications.

Cast restorations may include full coverage crowns for MIH-affected permanent teeth. Generally cast restorations requiring tooth preparation are not recommended in young children due to large pulp size, short crown height and potential difficulties in obtaining a good impression for subgingival crown margins.

Teeth affected by macrodontia are either contoured, aligned or extracted. Contouring involves shaving the tooth down to change shape and size. However, the result is minimal change as this could be dangerous for the dentin and dental pulp. Aligning involves the use of braces to straighten, align, and make space for larger teeth to grow. When extracted, they are replaced with an implant or bridge. This is done in cases in which the patient suffers from pain that cannot be treated by other methods.

The presence of a supernumerary tooth, particularly when seen in young children, is associated with a disturbance of the maxillary incisor region. This commonly results in the impaction of the incisors during the mixed dentition stage. The study debating this also considered many other factors such as: the patient’s age, number, morphology, growth orientation and position of the supernumerary tooth. Therefore, the presence of a supernumerary tooth when found must be appropriately approached with the correct treatment plan incorporating the likelihood of incisal crowding.

On eruption of the first primary tooth in a child, tooth brushing and cleaning should be performed by an adult. This is important as the plaque that attaches to the surface of the tooth has bacteria that have the ability to cause caries (decay) on the tooth surface.

It is recommended to brush children’s teeth using a soft bristled, age and size appropriate toothbrush and age appropriate toothpaste twice daily, however children below the age of two usually don’t require toothpaste. These researches also suggest that it is suitable to brush children’s teeth until they reach the approximate age of 6; where they will begin to learn adequate dexterity and cognition needed for adequate brushing by themselves. It is encouraged to watch children brushing their teeth until they are competently able to brush appropriately alone.

The diagnosis of cracked tooth syndrome is notoriously difficult even for experienced clinicians. The features are highly variable and may mimic sinusitis, temporomandibular disorders, headaches, ear pain, or atypical facial pain/atypical odontalgia (persistent idiopathic facial pain).

When diagnosing cracked tooth syndrome, a dentist takes many factors into consideration. A bite-test is commonly performed to confirm the diagnosis, in which the patient bites down on either a Q-tip, cotton roll, or an instrument called a Tooth Slooth.

Treatment is only required if the occlusion or bite of the person is compromised and causing other dental problems. Multiple long-term clinical problems can arise such as occlusal interferences, aesthetic disturbances, loss of pulp vitality, irritation of tongue during mastication and speech, caries and displacement of the affected tooth. Most people with talon cusp will live their normal lives unless the case is severe and causes a cascade of other dental issues that lead to additional health problems. This dental anomaly would not be considered fatal. Generally talon cusps on lower teeth require no treatment, but talon cusps on upper teeth may interfere with the bite mechanics and may need to be removed or reduced.

Small talon cusps that produce no symptoms or complication for a person can remain untreated. However large talon cusps should not.

Some common treatments include:

- Fissure sealing

- Composite resin restoration

- Reduction of cusp

- Pulpotomy

- Root canal (endodontic treatment)

- Extraction

The condition is usually benign, but it can cause mild irritation to soft tissues around the teeth and the tongue, and if large enough, may pose an aesthetic problem. Talon cusps that are too large are filed down with a motorized file, and then endodontic therapy is administered.

In order to prevent any future dental complications, when talon cusp is present due to an early diagnosis it would be best to see a dentist regularly every six months for routine dental checkups, remain under observation, brush and floss properly and undergo regular topical applications of fluoride gel to prevent caries and to promote enamel strength.

This anomaly is large enough to be seen with the naked eye. One can see the projection on the incisal edge of a tooth looking into the mouth of the affected person. The structure is described to be "T'shaped" or "X-shaped" however will differ depending on its shape, size, structure, location and site of origin. X-rays and radiographs can also show evidence of the abnormality. The digital images would show a tooth with talon cusp as if it were "double teeth".

When looking at a radiograph some features to look for would be location, edge, shape and number. The location would be on an anterior tooth, the edge would be clear and well defined and can be seen even by the naked eye, and the shape would appear "talon-like" over the top portion or crown of the affected tooth. There could potentially be one, two or multiple protrusions depending on the type of cusp.

Talon cusp can fall under three categories: Type I, Type II and Type III. They are created based on the cusp formation shape and length of extension.

- Type I - Talon: The additional cusp or talon projects from the palatal surface of a primary or permanent anterior (front) tooth that extends at least half of the distance from the cemento enamel junction to the incisal edge.

- Type II - Semi Talon: The semi talon cusp measures about 1mm or more in length but extends less than half of the distance seen in Type I Talon.

- Type III - Trace Talon: The projection originates from the cingulum (also known as the "cervical third") of the root and is enlarged or prominent in any form (conical, or tubercle-like)

Since many cases of Talon cusp go unreported, it is hard to draw linkage maps but it is safe to assume that dental formation is influenced by genetic factors. Talon cusp is also seen in association with conditions such as Rubinstein-Taybi syndrome, Mohr syndrome, Ellis–van Creveld syndrome, Incontinentia pigmenti achromians, Berardinelli-Seip syndrome, and Sturge–Weber syndrome.

A child with posterior crossbite should be treated immediately if the child shifts his mandible on closing which is often seen in a unilateral crossbite as mentioned above. The best age to treat a child with crossbite is in their mixed dentition when their palatal sutures have not fused to each other. Palatal expansion allows more space in an arch to relieve crowding and correct posterior crossbite. The correction can include any type of palatal expanders that will expand the palate which resolves the narrow constriction of the maxilla. There are several therapies that can be used to correct a posterior crossbite: braces, 'Z' spring or cantilever spring, quad helix, removable plates, clear aligner therapy, or a Delaire mask. The correct therapy should be decided by the orthodontist depending on the type and severity of the crossbite.

One of the keys in diagnosing the anterior crossbite due to skeletal vs dental causes is diagnosing a CR-CO shift in a patient. An adolescent presenting with anterior crossbite may be positioning their mandible forward into centric occlusion (CO) due to the dental interferences. Thus finding their occlusion in centric relation (CR) is key in diagnosis. For anterior crossbite, if their CO matches their CR then the patient truly has a skeletal component to their crossbite. If the CR shows a less severe class 3 malocclusion or teeth not in anterior crossbite, this may mean that their anterior crossbite results due to dental interferences.

Goal to treat unilateral crossbites should definitely include removal of occlusal interferences and elimination of the functional shift. Treating posterior crossbites early may help prevent the occurrence of Temporomandibular joint pathology.

Unilateral crossbites can also be diagnosed and treated properly by using a Deprogramming splint. This splint has flat occlusal surface which causes the muscles to deprogram themselves and establish new sensory engrams. When the splint is removed, a proper centric relation bite can be diagnosed from the bite.

Aetiology of CTS is multifactorial, the causative factors include:

- previous restorative procedures.

- occlusal factors

- developmental conditions/anatomical considerations.

- trauma

- others, e.g, aging dentition or presence of lingual tongue studs.

Most commonly involved teeth are mandibular molars followed by maxillary premolars, maxillary molars and maxillary premolars. in a recent audit, mandibular first molar thought to be most affected by CTS possibly due to the wedging effect of opposing pointy, protruding maxillary mesio-palatal cusp onto the mandibular molar central fissure.

Literature states that very few crossbites tend to self-correct which often justify the treatment approach of correcting these bites as early as possible. Only 0–9% of crossbites self-correct. Lindner et al. reported that in a 50% of crossbites were corrected in 76 four year old children.

Taurodontism is a condition found in the molar teeth of humans whereby the body of the tooth and pulp chamber is enlarged vertically at the expense of the roots. As a result, the floor of the pulp and the furcation of the tooth is moved apically down the root. The underlying mechanism

of taurodontism is the failure or late invagination of Hertwig's epithelial root sheath, which is responsible for root formation and shaping causing an apical shift of the root furcation.

The constriction at the amelocemental junction is usually reduced or absent. Taurodontism is most commonly found in permanent dentition although the term is traditionally applied to molar teeth.

In some cases taurodontism seems to follow an autosomal dominant type of inheritance.

Taurodontism is found in association with amelogenesis imperfecta, ectodermal dysplasia and tricho-dento-osseous syndrome.

The term means "bull like" teeth derived from similarity of these teeth to those of ungulate or cud-chewing animals.

According to Shaw these can be classified as hypotaurodont, hypertaurodont and mesotaurodont.

According to Mangion taurodontism may be:

- A (mentally retarded) character

- A primitive pattern

- Mendelian recessive character

- Atavistic feature

- A mutation

It has also been reported in Klinefelter's syndrome, XXYY and Down's syndrome .

The teeth involved are invariably molars, sometimes single and at the other times multiple teeth may be involved. The teeth themselves may look normal and do not have any particular anatomical character on clinical examination.

On a dental radiograph, the involved tooth looks rectangular in shape without apical taper. The pulp chamber is extremely large and the furcations may be only a few millimeters long at times.

Macrodontia of a single tooth is attributed to a disturbance of morphodifferentiation. Generalized macrodontia is usually attributed to some hormonal imbalance (e.g., pituirary gigantism). It can also be associated with facial hemihyperplasia. Macrodontia stems from systematic disturbances. These include KBG syndrome, otodental syndrome, and insulin-resistant diabetes. Ethnicity and gender also factors that influence macrodontia. Asians and males are more likely to be effected.

Geoffrey Greenlee and others published a meta-analysis in 2011 which concluded that patients with orthognathic surgical correction of open bite had 82% stability in comparison to non-surgical correction of open bite which had 75% of stability after 1or more year of treatment. Both the groups started with 2-3mm of open bite initially.

Prosthetic replacement of missing teeth is possible using dental implant technology or dentures. This treatment can be successful in giving patients with anodontia a more aesthetically pleasing appearance. The use of an implant prosthesis in the lower jaw could be recommended for younger patients as it is shown to significantly improve the craniofacial growth, social development and self-image. The study associated with this evidence worked with individuals who had ectodermal dysplasia of varying age groups of up to 11, 11 to 18 and more than 18 years. It was noted that the risk of implant failure was significantly higher in patients younger than 18 years, but there is significant reason to use this methodology of treatment in those older. Overall the use of an implant-prosthesis has a considerable functional, aesthetic and psychological advantage when compared to a conventional denture, in the patients.

The cause of germination is still unknown. However, there are a few possible factors contributing to germination:

- Vitamin deficiency

- Hormonal irregularities

- Infection or inflammation of areas near to the developing tooth bud

- Drug induced

- Genetic predisposition

- Radiotherapy that caused damage to the developing tooth germ