Dentin hypersensitivity is a relatively common condition. Due to differences in populations studied and methods of detection, the reported incidence ranges from 4-74%. Dentists may under-report dentin hypersensitivity due to difficulty in diagnosing and managing the condition. When questionnaires are used, the reported incidence is usually higher than when clinical examination is used. Overall, it is estimated to affect about 15% of the general population to some degree.

It can affect people of any age, although those aged 20–50 years are more likely to be affected. Females are slightly more likely to develop dentin hypersensitivity compared to males. The condition is most commonly associated with the maxillary and mandibular canine and bicuspid teeth on the facial (buccal) aspect, especially in areas of periodontal attachment loss.

Acidic drinks and foods lower the pH level of the mouth so consuming them causes the teeth to demineralise. Drinks low in pH levels that cause dental erosion include fruit juices, sports drinks, wine, beer and carbonated drinks. Orange and apple juices are common culprits among fruit juices. Carbonated drinks such as colas, lemonades are also very acidic, as are fruit-flavoured drinks and dilutables. Frequency rather than total intake of acidic juices is seen as the greater factor in dental erosion; infants using feeding bottles containing fruit juices (especially when used as a comforter) are therefore at greater risk of acid erosion.

Saliva acts as a buffer, regulating the pH when acidic drinks are ingested. Drinks vary in their resistance to the buffering effect of saliva. Studies show that fruit juices are the most resistant to saliva's buffering effect, followed by, in order: fruit-based carbonated drinks and flavoured mineral waters, non-fruit-based carbonated drinks, sparkling mineral waters; Mineral water being the least resistant. Because of this, fruit juices in particular, may prolong the drop in pH levels.

A number of medications such as vitamin C, aspirin and some iron preparations are acidic and may contribute towards acid erosion.

The aetiology of dental abrasion can be due to a single stimuli or, as in most cases, multi-factorial. The most common cause of dental abrasion, is the combination of mechanical and chemical wear.

Tooth brushing is the most common cause of dental abrasion, which is found to develop along the gingival margin, due to vigorous brushing in this area. The type of toothbrush, the technique used and the force applied when brushing can influence the occurrence and severity of resulting abrasion. Further, brushing for extended periods of time (exceeding 2-3 min) in some cases, when combined with medium/hard bristled toothbrushes can cause abrasive lesions.

Different toothbrush types are more inclined to cause abrasion, such as those with medium or hard bristles. The bristles combined with forceful brushing techniques applied can roughen the tooth surface and cause abrasion as well as aggravating the gums. Repetitive irritation to the gingival margin can eventually cause recession of the gums. When the gums recede, the root surface is exposed which is more susceptible to abrasion.

Comparatively, electric toothbrushes have less abrasive tendencies.

Types of toothpastes can also damage enamel and dentine due to the abrasive properties. Specific ingredients are used in toothpaste to target removal of the bio-film and extrinsic staining however in some cases can contribute to the pastes being abrasive.

Whitening toothpastes are found to be one of the most abrasive types of toothpastes, according to the RDA Scale, detailed below. In-home and clinical whitening have been proven to increase the likelihood of an individual experiencing dental abrasion. It is believed that dental abrasion due to the whitening process is caused by a combination of both mechanical and chemical irritants, for example, using whitening toothpaste and at home bleaching kits together. However, if an individual is regimented in their after-whitening care then they can avoid loss of dentine minerals and in turn abrasion can be avoided. (that contribute to developing abrasion).

Another factor that can contribute to abrasion is alteration of pH levels in the saliva. This can be sugary/ acidic foods and liquids. The reasoning behind this is that an increase in acidity of saliva can induce demineralization and therefore compromising the tooth structure to abrasive factors such as tooth brushing or normal wear from mastication. When the tooth structure is compromised, this is where the mineral content of the saliva can create shallow depressions in the enamel and thus, when brushed can cause irreparable damage on tooth surface. The dental abrasion process can be further stimulated and accelerated through the effects of dental Acid erosion.

Dentin hypersensitivity may affect individuals' quality of life. Over time, the dentin-pulp complex may adapt to the decreased insulation by laying down tertiary dentin, thereby increasing the thickness between the pulp and the exposed dentin surface and lessening the symptoms of hypersensitivity. Similar process such as formation of a smear layer (e.g. from toothbrushing) and dentin sclerosis. These physiologic repair mechanisms are likely to occur with or without any form of treatment, but they take time.

Dental erosion can occur by non-extrinsic factors too. Intrinsic dental erosion is known as perimolysis, whereby gastric acid from the stomach comes into contact with the teeth. People with illnesses such as anorexia nervosa, bulimia, and gastroesophageal reflux disease (GERD) often suffer from this. GERD is quite common and an average of 7% of adults experience reflux daily. The main cause of GERD is increased acid production by the stomach. This is not exclusive to adults, as GERD and other gastrointestinal disorders may cause dental erosions in children. Rumination also may cause acid erosion.

Although the etiology is unclear and it is speculated to be multifactorial. Contributing factors may include the following:

1. children born preterm and those with poor general health or systemic conditions in their first 3 years may develop MIH.

2. environmental changes

3. exposure to dioxine by prolonged breast-feeding could lead to an increase in the risk of MIH

4. respiratory diseases and oxygen shortage of the ameloblasts

5. oxygen shortage combined with low birth weight

"Relative dentin abrasivity" ("RDA") is a standardised measurement of the abrasive effect that the components of the toothpaste have on a tooth.

The RDA scale was developed by the American Dental Association (ADA). The RDA scale compares toothpaste abrasivity to standard abrasive materials and measures the depth of cut at an average of 1 millimetre per 100,000 brush strokes onto dentine. This comparison generates abrasive values for the dentifrices that would be safe for daily use. In vitro dental studies showed a positive correlation between the highest RDAs and greater dentin wear.

Since 1998, the RDA value is set by the standards DIN EN ISO 11609. Currently, the claim on products such as toothpaste are not regulated by law, however a dentifrice is required to have a level lower than 250 to be considered safe and before being given the ADA seal of approval. The values obtained depend on the size, quantity and surface structure of abrasive used in toothpastes.

While the RDA score has been shown to have a statistically significant correlation to the presence of abrasion, it is not the only contributing factor to consider. Other factors such as the amount of pressure used whilst brushing, the type, thickness and dispersion of bristle in the toothbrush and the time spent brushing are other factors that contribute to dental abrasion.

Pulpitis may be caused by dental caries that penetrate through the enamel and dentin to reach the pulp, or it may be a result of trauma, such as physical abuse of the tooth or thermal insults, including overheating from insufficiently cooled dental drills and use of dental curing lights. More often it is from physical trauma rather than dental treatments.

Inflammation is commonly associated with a bacterial infection but can also be due to other insults such as repetitive trauma or in rare cases periodontitis. In the case of penetrating decay, the pulp chamber is no longer sealed off from the environment of the oral cavity.

When the pulp becomes inflamed, pressure begins to build up in the pulp cavity, exerting pressure on the nerve of the tooth and the surrounding tissues. Pressure from inflammation can cause mild to extreme pain, depending upon the severity of the inflammation and the body's response. Unlike other parts of the body where pressure can dissipate through the surrounding soft tissues, the pulp cavity is very different. It is surrounded by dentin, a hard tissue that does not allow for pressure dissipation, so increased blood flow, a hallmark of inflammation, will cause pain.

Pulpitis can often create so much pressure on the tooth nerve that the individual will have trouble locating the source of the pain, confusing it with neighboring teeth, called referred pain. The pulp cavity inherently provides the body with an immune system response challenge, which makes it very difficult for a bacterial infection to be eliminated.

If the teeth are denervated, this can lead to irreversible pulpitis, depending on the area, rate of infection, and length of injury. This is why people who have lost their dental innervation have a reduced healing ability and increased rate of tooth injury. Thus, as people age, their gradual loss of innervation leads to pulpitis.

It has been reported that MIH-affected teeth were more difficult to anaesthetise. Difficulty achieving anaesthesia in MIH-affected teeth may be caused by the chronic inflammation of the pulp due to the penetration of bacteria as the presence of inflammation can reduce the efficacy of local anaesthetics which may then result in more anaesthetic being given to achieve anaesthesia. Some dental treatment has been undertaken without local anaesthesia which could result in a child becoming more fearful and anxious when receiving dental treatment. This can be especially challenging in paediatric dentistry thus more specialised methods may be needed to increase the efficiency of anaesthetising teeth.

Increased sensitivity to stimuli, specifically hot and cold, is a common symptom of pulpitis. A prolonged throbbing pain may be associated with the disease. However, pulpitis can also occur without any pain.

Treatment may include smoothing, fluoride treatment, and crown restoration.

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.

Enamel infractions are microcracks seen within the dental enamel of a tooth. They are commonly the result of dental trauma to the brittle enamel, which remains adherent to the underlying dentine. They can be seen more clearly when transillumination is used.

Enamel infractions are found more often in older teeth, as the accumulated trauma is greatest.

Enamel infractions can also be found as a result of iatrogenic damage inadvertently caused by instrumentation during dental treatments.

The best method of maintaining the health of teeth is to practice exemplary oral hygiene. More tooth loss is likely to occur if intervention takes place. However, factors such as present complaint, patient age, severity of the problem, can affect the treatment plan or options.

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.

Stainless steel crowns which also known as "hall crowns" can prevent tooth wear and maintain occlusal dimension in affected primary teeth. However, if demanded, composite facings or composite strip crowns can be added for aesthetic reasons.

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.

Dens invaginatus, also known as dens in dente ("tooth within a tooth") is a condition found in teeth where the outer surface folds inward. There are coronal and radicular forms, with the coronal form being more common.

Dens invaginatus is a malformation of teeth most likely resulting from an infolding of the dental papilla during tooth development or invagination of all layers of the enamel organ in dental papillae. Affected teeth show a deep infolding of enamel and dentine starting from the foramen coecum or even the tip of the cusps and which may extend deep into the root. Teeth most affected are maxillary lateral incisors and bilateral occurrence is not uncommon. The malformation shows a broad spectrum of morphologic variations and frequently results in early pulp necrosis. Root canal therapy may present severe problems because of the complex anatomy of the teeth. Cause, prevalence, classification, and therapeutic considerations including root canal therapy, apical surgery and prevention of pulpal involvement are reviewed.

1-coronal

2-radicular

Types

- Type 1-That is confined to the crown

- Type 2-Extend below CEJ and ends in a blind sac that may or may not communicate with adjacent dental pulp

- Type 3-Extend to the root and perforate in the apex or lateral radicular area without communicating the pulp

The exact incidence of amelogenesis imperfecta is uncertain. Estimates vary widely, from 1 in 700 people in northern Sweden to 1 in 14,000 people in the United States.

This condition is neither caused by nor the equivalent of dental fluorosis. A manifestation of amelogenesis imperfecta known as "snow capping" is confined to the outer prismless enamel layer. It may superficially resemble dental fluorosis, and indeed "snow capping" may be used as a descriptive term in some incidents of dental fluorosis.

Most blinded conscious provocation studies have failed to show a correlation between exposure and symptoms, leading to the suggestion that psychological mechanisms play a role in causing or exacerbating EHS symptoms. In 2010, Rubin et al. published a follow-up to their 2005 review, bringing the totals to 46 double-blind experiments and 1175 individuals with self-diagnosed hypersensitivity. Both reviews found no robust evidence to support the hypothesis that electromagnetic exposure causes EHS, as have other studies. They also concluded that the studies supported the role of the nocebo effect in triggering acute symptoms in those with EHS.

Some other types of studies suggest evidence for symptoms at non-thermal levels of electromagnetic exposure. A review in 2010 of ten studies on neurobehavioral and cancer outcomes near cell phone base stations found eight with increased prevalence, including sleep disturbance and headaches. Since 1962, the microwave auditory effect or tinnitus has been shown from radio frequency exposure at levels below significant heating. Studies during the 1960s in Europe and Russia claimed to show effects on humans, especially the nervous system, from low energy RF radiation; the studies were disputed at the time.

Other studies on sensitivity have looked at therapeutic procedures using non-thermal electromagnetic exposure, genetic factors, an alteration in mast cells, oxidative stress, protein expression and voltage-gated calcium channels. Mercury release from dental amalgam and heavy metal toxicity have also been implicated in exposure effects and symptoms. Another line of study has been the nature of hyper-sensitivity or intolerance and the range of environmental exposures which may be related to it. Some 80% of people with self-diagnosed electromagnetic intolerance also claim intolerance to low levels of chemical exposure.

Vertical root fracture can be a difficult diagnosis to make where the fracture line is not evident.

Use of cone-beam computerized tomography has been described.

Healthcare providers may use podiatry drills on onychauxic (thickened) nails of patients to alleviate or eliminate pain, prevent or treat subungual ulcerations, allow better penetration of topical antifungal agents, or improve cosmesis, all in effort to improve the patient’s “quality of life.” In a study conducted by Miller, 65% of respondents reported routinely drilling thickened toenails. However, the improved effectiveness of antifungal drugs such as itraconazole and terbinafine reduces the need to drill these infected nails.

Podiatry drills have a mechanical rotating burr that can be set at a range of speeds usually up to 12,000 rpm and may or may not have an integrated local ventilation extraction system. Even with the most effective dust extractors, the electric nail debridement process is not totally risk free because the extractors range from 25% - 92% effective in reducing airborne particles. While the large particles settle out to the floor, varying amounts of smaller particles remain suspended and are inhaled by or adhere to the practitioner and clinical environment. The particle sizes range from 0.1 to 100 um and 86% of these particles are less than 5 um in diameter and therefore capable of entry into the alveoli.

Fungi are ubiquitous organisms that play a vital role in decomposing organic matter. Many species of fungi live on the human body and some will infect nails causing a condition called onychomycosis. There are oral and topical antifungal therapies for this condition, however, in some instances cutting, filing, or abrading the nail may be necessary to improve cure rates. Thickened nails caused by injury, infection, diabetes, psoriasis, or vascular disease may require the use of a mechanical therapy, which can expose the healthcare worker to microbial dust.

Exposure to nail dust was first discussed and described in the literature as an occupational hazard in the early 70’s. In 1975, two female chiropodists were diagnosed with allergic hypersensitivity to nail dust Since that time, there have been a number of occupational-related complaints pertaining to airborne nail dust exposure and efforts have been made to study the podiatric professionals to determine related symptoms. Biological dust from the hand and foot care procedures may deposit in the conjunctiva, nose, and throughout the respiratory tract. The local irritation of these areas can lead to conjunctivitis, itching, tearing, rhinitis, sneezing, asthmatic attacks, bronchitis, and coughing.

The literature suggests that nail dust can be a respiratory sensitizer, which is defined as a substance that when breathed in can trigger an irreversible allergic reaction in the respiratory system. Sensitization does not usually take place immediately, but rather after months or years of exposure to the agent. Once sensitized, even the smallest amount of the substance can trigger asthma, rhinitis, or conjunctivitis that may exhibit the following symptoms: coughing, wheezing, chest tightness, runny or stuffy nose, and watery or prickly eyes. Millar found that within the podiatry profession there is four times the national prevalence of asthma. Hypersensitivity reactions are the most probable disposition for healthcare workers inhaling nail dust, although more serious lung pathology can not be ruled out

It is widely known and accepted that fungi will induce asthma, but it is estimated that only 10% of the population has allergic antibodies to fungal antigens, and half of them, that is 5% of the population, would be asymptomatic, further complicating the link between the fungal dust and troubling symptoms. "Trichophyton rubrum" is the most common fungal cause of nail dystrophy. Studies conducted in England found that the prevalence of "trichophyton rubrum" antibodies in podiatrists ranged from 14%-31%. This is evidence that the podiatrist is heavily exposed to "trichophyton rubrum" as observed in increased precipitating antibodies compared to the general population. It has been suggested that absorption of "trichophyton" fungal antigens can give rise to immunoglobulin E (IgE) antibody production, sensitization of the airways, and symptomatic asthma and rhinitis.

Nail work requiring clipping and drilling is also a potential cause for ocular injury and infection to the podiatrists, podiatric staff, and patients that are exposed to nail fragments and high-speed drills used for grinding. Possible ocular hazards result from exposure to foreign bodies, allergens, bacteria, viruses, fungi and protozoa that can be introduced at the time of eye trauma, or enter as a consequence of damage to the ocular structures; permitting the entry of opportunistic infection. The high-speed rotation of podiatry drill burrs potentially expose the healthcare worker to aerosols containing bloodborne pathogens such as Hepatitis B, Hepatitis C, or HIV. Davies et al. surveyed podiatrists and found that 41% of them complained of eye problems, particularly soreness, burning, itching and excess lacrimation.

A 1990 case illustrates the potential for ocular trauma to the healthcare provider: A podiatrist suffered a lacerated cornea when hit by a metallic shard from the grinding bit or by a fragment from the patient’s toenail. The podiatrist reported fleeting periods of blurriness for several months following the incident. The healthcare worker’s exposure to foreign bodies is not well documented in the literature like they are with dental staff using similar equipment; however, many of these incidents are certain to go unreported. The healthcare provider’s risk of injury during nail care, however slight, warrants the use of simple and inexpensive preventative measures.

Vertical root fractures are a type of fracture of a tooth. They can be characterized by an incomplete or complete fracture line that extends through the long axis of the root toward the apex. Vertical root fractures represent between 2 and 5 percent of crown/root fractures. The greatest incidence occurs in endodontically treated teeth, and in patients older than 40 years of age.

The occurrence of a complete vertical root fracture is often catastrophic for the individual tooth as tooth extraction is usually the only reasonable treatment.

Vertical root fracture is more likely where teeth have undergone extensive prior treatment. It is thought that excessive removal of dentine during procedures such as root canal treatment weakens the tooth. For this reason excessive canal shaping should be avoided. Fracturing may be caused by excessive forces placed on the tooth, such as during compaction of gutta-percha during the obturation phase of endodontics. Trauma can also cause crack formation.