Which antibiotics is contraindicated in children less than 9 years of age and due to the risk of permanent staining of teeth and enamel dysplasia in children?

Figs. 2.17 and 2.18

Intrinsic tooth discolorations may arise from developmental tooth abnormalities or an endogenous material that is incorporated into tooth structure during development. Because these do not represent surface stains, removal is not possible. Developmental discolorations include variants of amelogenesis imperfecta, dentinogenesis imperfecta, and dental fluorosis.

The development of deciduous tooth crowns extends from the 4th month of gestation to approximately the 12th month of life, whereas the crowns of the permanent teeth begin formation around birth with completion at approximately 8 years of age. During this time, stains can be permanently incorporated into the developing teeth from a variety of conditions (such as erythropoietic porphyria, alkaptonuria, hyperbilirubinemia) and medications (especially tetracycline and minocycline). In the majority of these situations, the discoloration affects only the portion of the tooth developing at the time the condition or medication was present. One exception is minocycline. This agent has the ability to stain dental pulp, which can result in a diffuse discoloration of teeth long after formation has been completed.

Intrinsic discoloration

Intrinsic tooth discoloration is a result of a structural change in either the thickness or composition of the dental hard tissues. Examples of causes are provided in Box 7.5. The most common examples are the brown discoloration, known as mottling, caused by excessive intake of fluoride (Fig. 7.23), and the yellow/grey discoloration resulting from administration of tetracyclines (Fig. 7.24).

Fortunately, staining due to tetracycline is not as prevalent as in the past, due to medical awareness in the prescription of this drug to susceptible age groups, and while excessive intake of fluoride rarely causes mottling in the developed world, there is still a risk of overingestion of fluoride to the extent that enamel opacities are becoming more prevalent. As a result, children under the age of 6 years who are at low risk of developing dental caries should use a toothpaste containing no more than 600 ppm of fluoride; children at higher risk of caries should use a standard (1000 ppm) or higher (1450 ppm) fluoride toothpaste, and accept that there may be a small risk of developing enamel opacities. In the UK fluorosis is likely to be mild, presenting as white striations, or ‘ice caps' on the incisal edge. Fluorosis should be distinguished from demarcated enamel opacities which are usually the result of trauma to the developing permanent dentition. Such lesions are deeper than the somewhat superficial fluorotic hypomineralisation and, if treatment is required, this is usually more aggressive than that for fluorosis.

Intrinsic tooth discoloration cannot be polished away without the use of special abrasive techniques. In cases where the discoloration is severe and of concern to the patient, restorative intervention may be warranted. The least invasive techniques are hydrochloric acid microabrasion, macroabrasion and veneering with resin composite or ceramic. There has been reported success using tooth bleaching techniques (using hydrogen peroxide in custom trays) to reduce the aesthetic impact of fluorosis. In these cases the whiteness of the tooth is increased, creating a more homogeneous appearance. Some success with this technique has also been described for cases of mild tetracycline staining.

Appearance.

​Tetracycline discoloration may be yellow, yellow-brown, brown, gray, or blue. The intensity of the staining varies widely. Distribution of discoloration usually is diffuse, and severe cases may exhibit banding. The staining usually is bilateral and affects multiple teeth in both arches.

The hue and severity of tooth discoloration depend on four factors associated with tetracycline administration:

Age at the time of administration: Anterior primary teeth are susceptible to discoloration by systemic tetracycline from 4 months in utero through 9 months postpartum. Anterior permanent teeth are susceptible from 3 months postpartum through age 7 years.91

Duration of administration: The severity of the staining is directly proportional to the length of time the medication was administered.92,93

Dosage: The severity of the staining is directly proportional to the administered dosage.91,94,95

Type of tetracycline: Coloration has been correlated with the specific type of tetracycline administered.96

Chlortetracycline (Aureomycin): Gray-brown stain

Demethylchlortetracycline (Ledermycin): Yellow stain

Doxycycline (Vibramycin): Does not cause staining

Oxytetracycline (Terramycin): Yellow stain

Tetracycline (Achromycin): Yellow stain

Yellow tetracycline staining slowly darkens to brown or gray-brown when exposed to sunlight. Therefore, the anterior teeth of children often darken first, whereas the posterior teeth, because of reduced exposure to sunlight, darken more slowly.10 In adults, however, natural photobleaching of the anterior teeth (see the preceding section on Mechanism section under Tetracycline Staining) has been observed, particularly in individuals whose teeth are excessively exposed to sunlight because of maxillary lip insufficiency.87 Hypocalcified white areas of varying opacity, size, and distribution also may be present.

Therapy during Pregnancy

During pregnancy, doxycycline has been associated with the teratogenic effects of bone deformity and dental discoloration. In addition, hepatotoxicity and pancreatitis may occur in the mother. Although also associated with significant teratogenic risk, chloramphenicol is considered the treatment of choice for pregnant women with RMSF and should be considered the treatment of choice for pregnant dogs with this disease as well. Short-term doxycycline therapy has been used to successfully treat A. phagocytophilum and E. chaffeensis in pregnant women without complication to the fetus. Given the variable in vitro efficacy of chloramphenicol against these agents, the use of doxycycline could be considered instead of chloramphenicol in severely life-threatening or nonresponsive infections during pregnancy, but that choice must be heavily weighed against the risk of severe bone deformity and other serious complications in the fetus and bitch associated with the use of doxycycline. Interestingly, rifampin has in vitro activity against A. phagocytophilum and E. chaffeensis and has been used to successfully treat pregnant women with HGA. The efficacy of rifampin for treating ehrlichioses and anaplasmoses in canine patients is unknown.

Case 24.4: Oral Reconstruction for Broken, Discolored, and Missing Teeth With a Poor Smile and Facial Collapse (Fig. 24.4)

Good preventive care can prolong the clinical health of dental tooth structures. However, many older patients present with worn teeth, discoloration, drifted spacing, and bite collapse. These patients require a comprehensive full-mouth reconstruction. A detailed treatment plan includes diagnostic analysis, interim treatment, and final restorations.

Implant-supported fixed restorations have replaced the use of a removable partial denture in many clinical situations. For this patient, a full mouth reconstruction was completed, including three implants to restore the upper left quadrant; veneers and crowns were cemented over the teeth and implant abutments.

Traumatized Primary and Permanent Anterior Teeth

Children often sustain accidental injury to the maxillary or mandibular anterior primary teeth. Such injury may result in pulpal death and tooth discoloration.66,67 These complications usually will develop within 2 to 6 weeks after trauma to the area. Infants and toddlers 7 months to 5 years of age have benefited from treatment with a 660-nm or 830-nm low-level laser placed over the root areas of the injured teeth for 1 minute. Patients with slightly mobile, partially avulsed, or displaced front teeth who received LLLT within 24 h of injury demonstrated clinically and radiographically normal teeth in color and vitality and remained asymptomatic for as long as 36 months after trauma (Figures 11-28 and 11-29).

For treatment of traumatic injury to primary and permanent teeth, a radiograph is taken to ensure that the tooth has not sustained a root fracture. The low-level laser is placed over the lingual and facial areas of the root for approximately 1 minute (4 J/area). A soft diet is then instituted. Depending on the degree of injury, additional LLLT, at the same energy setting, may be performed at 3 and 5 days postoperatively (Case Study 11-1).

Scenario 4

Consider that the same scenario presents many years later but this time without having caused the patient any symptoms, the sole concern being tooth discoloration. The intact tooth will in all probability give negative pulp test responses and may or may not be associated with a periapical radiolucency. In the case of a periapical radiolucency, the decision is easier, as it would be reasonable to recommend root-canal treatment, bleaching (Fig. 5.12) and, if necessary, a porcelain veneer to mask residual discoloration caused by increased thickness of sclerosed dentine. The morbidity of treatment, that is, the potential of an acute flare-up, should also be considered since about 10–15% of teeth associated with asymptomatic periapical radiolucencies, without sinus tracts, become acute on commencement of root-canal treatment. The decision is even more difficult in the absence of a periapical radiolucency because of the potential to infect a necrotic pulp and precipitate further problems. If the pulp chamber and canal space is obliterated, locating and accessing the canal for root-canal treatment may be problematic. External bleaching may be considered as the sole treatment.

57.2.4 Coffee and Tooth Staining

Currently, there has been increased demand for cosmetic dentistry20 and, in this context, patients seek bleaching treatments for resolution of tooth discoloration.32 Drinks such as coffee, when consumed frequently, are related to extrinsic staining that is present on the outer surface of teeth.20,33,34 Coffee has been reported to be one of the main staining agents.24,33,35 Probably, this effect may be related to its pH value (around 5.0)36 and its components (flavonoids and phenols)29 that play a role in the degree of discoloration. In addition, the inherent roughness, fissures, and porosities in tooth surfaces may contribute to the increased staining caused by certain solutions.33 These structural defects facilitate the diffusion of the staining agent, and this might be a reason for the common failure of toothbrushing to remove stains caused by coffee,33,37 making bleaching treatment necessary.

Previous findings show that coffee staining caused staining similar to cigarette smoke33 (Figure 57.2). To reverse tooth discoloration, bleaching has become the primary procedure to whiten teeth because of its safety, effectiveness, and minimally invasive characteristics.32 Several methods and approaches have been described in the literature for bleaching vital teeth, such as the use of different bleaching agents, concentrations, application times, and product formats.32,38 Bleaching procedures involve either hydrogen peroxide or carbamide peroxide, and the mechanism consists of an oxidation reaction with the release of free radicals.38,39 Although the mechanism of action of hydrogen peroxide is not well understood, it is considered to be an oxidation reaction in which the pigment molecules are broken down and the small compounds diffuse out of the tooth.32,39,40 The procedure basically uses hydrogen peroxide products, and, although it is proven effective, high concentrations of this compound can promote an increase in enamel surface roughness and a significant increase in fissures and pitting on the bleached surface.32,34 Because of this, studies have reported that the staining from dietary habits of the patient during or immediately after the whitening procedure may compromise the stability of the results obtained in the bleaching process.32,39,41

According to several studies,6,29,33 the average time to drink one cup of coffee is 15 min and the average amount of coffee consumed per day by coffee drinkers is about 3.5 cups, for an average period of 35 years. Therefore, in vitro studies use 72 h of simulated coffee consumption across 3 months,29 or daily exposure of 15 min, to simulate the habits of the patients.32,40,41 During the staining phase, the samples of teeth are maintained at a temperature of 37 °C to simulate oral conditions. The staining process commonly applied in laboratorial studies is presented in Figure 57.3.

Pregnancy

A number of antimicrobial agents have the potential to cause fetal harm if administered to a pregnant woman. For example, tetracyclines can cause tooth discoloration and hypoplasia of dental enamel and are thus avoided in pregnant women and young children. Streptomycin given during pregnancy can cross the placenta, and evidence of eighth nerve toxicity has been reported. A few other antimicrobials are labeled by the Food and Drug Administration (FDA) as pregnancy category D (evidence of human risk) or are contraindicated because of fetal harm (category X). Many more antimicrobials, however, are assigned to category C; for these drugs, the potential risk to the fetus is based on animal studies. When designing antimicrobial regimens, the possibility of pregnancy should be considered in any woman of childbearing age so that the risks of candidate agents can be individually reviewed and the safest possible therapy selected.

It should also be noted that many antibiotics used to treat lactating women can be found in breast milk. Thus, it may be necessary to suspend breast-feeding during treatment if exposure of the infant to the drug must be avoided.

Pregnant women may be particularly susceptible to certain antimicrobial-associated toxicities. Death resulting from hepatic failure has been described in pregnant women receiving large doses of tetracycline. Potentially life-threatening hepatic steatosis has been observed in patients treated with a combination of the antiretroviral agents didanosine plus stavudine; pregnant women may be especially vulnerable to this toxic effect.

Adverse Effects of Drugs on Teeth

The effects of drugs on teeth include extrinsic and intrinsic staining, physical alteration of tooth structure, and changes in tooth sensation.25 Tooth discoloration can range from white spots to yellow, to dark brown, to gray generalized discoloration. The most common form of alteration of tooth structure related to drug use is to the result of carious destruction of enamel and dentin associated with reduced salivary flow or the use of oral medications or nutritional supplements with high sucrose content. Acidic drugs (e.g., powdered antiasthmatic drugs) can cause enamel erosion, although the incidence and significance of this type of tooth damage are not known.25 Similarly, certain oral vitamin supplements are acidic and can cause similar damage.

Extrinsic tooth staining has been associated with the use of the antimicrobial mouth rinse chlorhexidine gluconate, liquid preparations of iron salts, some antibiotics in liquid form, and some essential oils.25 Fluoride is a known source of intrinsic tooth staining, particularly in regional areas where the fluoride content of the drinking water greatly exceeds the recommended limits of 1.0 ppm. By avoiding the offending drug and by initiating routine dental prophylaxis, some extrinsic stains can be removed. Medical agents such as antibiotics and cancer chemotherapeutic agents known to cause discoloration and distorted development of teeth should be avoided in pregnant females or in infants and children, unless the medical benefits of these agents are deemed to outweigh the risk of permanent damage to the dentition. Lightening (“bleaching”) agents may be of benefit in reducing the severity of dark, drug-related intrinsic staining, such as that produced by tetracycline antibiotics. Additionally, stained tooth structures can be masked by the placement of esthetic restorative materials on the labial surfaces of stained teeth. Caution should be exercised in choosing to place esthetic restorative materials in patients with less-than-optimal oral hygiene practices.