INTRODUCTION
Before the dawn of recorded history, caregivers, parents, and health care providers have had to treat the pain and discomfort that accompanies the arrival of an infant's first tooth. Once viewed as a disease state, teething is now considered a normal part of the human growth cycle. Obviously, caregivers will want to minimize the discomfort that is associated with the process. The purpose of this review is to discuss normal tooth development in the growing child, the signs and symptoms that accompany teething, and what treatment options are available to provide relief.
NORMAL TOOTH DEVELOPMENT
To most caregivers, teething is the period of time preceding the eruption of an infant tooth. In actuality, teething begins prior to birth. Primary tooth formation is an ongoing process that begins in utero and proceeds through early childhood, when the root formation of the particular tooth is completed, which may be 2 to 3 years after its initial eruption from the gum.1 The pulp and dentin develop from the mesoderm while the enamel arises from the ectoderm approximately 28 days after conception. Primary (i.e., baby teeth) develop below the gumline during the first trimester, approximately during the sixth week of pregnancy; permanent teeth (i.e., adult teeth) develop at 3 or 4 months of age, which is when the primary teeth become calcified (i.e., covered with a hard enamel). A substantial amount of calcification occurs between 3 and 12 months of age. This process starts with the anterior teeth and should end, between 18 months and 3 years of age, with the posterior teeth. It is a symmetrical process that occurs on both sides of the mouth simultaneously. Calcification can be influenced by a variety of conditions, such as jaundice, infection, medications used during infancy, and maternal drug use during the prenatal period.2
The first tooth may erupt from the gum as early as 4 months of age, but in most cases, infants will not acquire their first tooth until approximately 6 months of age. It has been estimated that 1% of infants have their first tooth erupt before 4 months of age and another 1% may not acquire their first tooth until after 12 months of age. In children less than 2 years of age, the following formula will help estimate the average number of teeth that should be visible at any given time: begin with the child's age, in months, and subtract 6 (e.g., an infant aged 9 months would be expected to have 3 teeth).3 Another method dictates that, beginning at 7 months of age, infants and children will gain 4 teeth every 4 months. 2
Typically, teeth erupt in pairs; the 2 anterior bottom teeth appear first, followed by the top central incisors. Additional front teeth (i.e., specifically the lateral incisors) will then appear, followed by the molars and then the canines. The back molars are the last to appear. It is a rare occurrence when teeth do not emerge by 1 year of age in an otherwise healthy child. By 3 years of age, most children will have a full set of 20 primary teeth (i.e., 4 incisors, 2 canines, and 4 molars in each jaw). Permanent teeth will not begin replacing the primary teeth until a year after that.
Interestingly, the teeth of premature infants emerge later than those of full-term infants. In one study, premature infants did not have their first tooth appear until approximately 7 months of age while full-term infants were typically 6 months of age when the first tooth emerged.4
Even obesity has been proven to have an effect on the timing of tooth eruption. A recent study examined the association between obesity and the timing of tooth eruption.5 Data collected from 3 consecutive cycles of the National Health and Nutrition Examination Survey (NHANES) (from 2001 to 2006) were analyzed to correlate the number of teeth erupted with obesity status (body mass index [BMI] z-score > 95th percentile BMI) among children from 5 to 14 years of age. Investigators determined that the teeth of obese children erupted earlier than those of nonobese children, with obese children having approximately 1.44 more teeth than nonobese children (P < 0.0001). These findings may have a clinical impact on the risk for dental caries because the primary teeth are exposed in the oral cavity for a longer period of time; in addition, different timing of tooth emergence may increase the likelihood of malocclusions.
In rare instances, some infants will be born with a tooth already fully emerged. These are often referred to as natal teeth. The terms congenital teeth, dentitia praecox, and fetal teeth have also been used to describe this phenomenon and Leung et al reported an incidence rate of approximately 1 in 3000.6 Some possible causes include the premature eruption of an actual primary tooth or the presence of an additional tooth that grew above the primary teeth. In the case of the latter, it will fall out when the primary teeth start to erupt. Natal teeth may appear normal, but they will often have poor root formation and excessive mobility. Oftentimes, to minimize the risk of aspiration when the tooth begins to loosen, these extra teeth will be removed as the primary teeth emerge. Natal teeth may also cause ulceration of the infant's oral mucosa or tongue, and may even bruise the nipple during nursing.6
Both the loss of primary teeth (i.e., exfoliation) and the appearance of permanent teeth occur between 6 and 13 years of age and these events are more variable among children than the pattern that developed as the primary teeth emerged. Usually the central lower incisors are the first to erupt. Unlike infants, children rarely complain of pain with the eruption of the permanent teeth.2 The third molars (i.e., wisdom teeth) may erupt during the second or third decade of life.
TEETHING DEFINED
Osteoclasts must resorb alveolar bone so a tooth can erupt. Proteins such as interleukin-1 α (IL-1 α) and macrophage colony-stimulating factor are stimulated during the eruption process7; in fact, some may consider the eruption of a tooth an inflammatory process. Although the exact mechanism of tooth eruption has yet to be elucidated, gingival biopsies obtained from impacted deciduous teeth showed significant inflammation.2 It is not known if this is typical for non-impacted teeth. Teething pain appears to be worse with the first 2 to 4 teeth and lessens over time as the infant becomes more familiar with the experience.1
Modification of the immune system may also occur during teething. According to one case report, a girl 5 months of age, who was diagnosed with severe combined immunodeficiency (SCID) and who underwent a bone marrow transplant, experienced 2 episodes of severe acute graft-versus-host disease (GVHD) while teething; the condition improved dramatically after tooth eruption.8 Health care professionals, after investigation, determined that the teething process triggered the release of IL-1, which led to GVHD. In a similar study, researchers hypothesized that the condition primary herpetic gingivostomatitis may be responsible for those signs and symptoms commonly attributed to teething in infants.9 Twenty infants diagnosed as experiencing teething difficulty by their caregivers were included in this study (Group A); 20 infants in no distress were involved as controls (Group B). Oral swab samples were obtained from each infant, as well as assays for herpes simplex virus (HSV); the temperature and oral status of each infant were also recorded. Nine infants in the symptomatic group (45%) tested positive for HSV; of these 9 infants, 7 had elevated temperatures (< 37.8ºC) and all had signs of oral infection that varied in severity. The remaining 11 infants in Group A tested negative for HSV, but 5 of those infants had elevated temperatures and none had evidence of oral infection. The infants in Group B were all negative for HSV, fever, and signs of oral infection. Investigators postulated that herpes infections were more likely to occur during the second 6 months of life, after the infant loses maternal antibodies, which are present at birth. Based on these findings, the authors concluded that oral HSV infection should be included in the differential diagnosis of infants presenting with the traditional teething symptoms.
TEETHING MYTHS AND LEGENDS
A discussion about teething myths would not be complete without including a brief discussion about the tooth fairy. This childhood tradition dates back to 17th century France where children offered their baby teeth to the tooth mouse.2 According to the French fairy tale La Bonne Petite Souris (The Good Little Mouse), an imprisoned good queen and her daughter befriend a grey mouse who is really a good fairy in disguise. The mouse/fairy knocks out the teeth of the queen's captor when they are freed and then bestows baskets of jewels and money on the newly liberated queen and princess. In German folklore, children typically would hide their baby teeth in a mouse hole to prevent toothaches.2 In other cultures, teeth were thrown on rooftops or placed under pillows for good luck and to prevent tooth decay.2 By the 20th century, the tooth mouse was replaced by the tooth fairy. In France, the tooth fairy ironically leaves candy, while in the United States, money is traditionally left under the pillow. Most parents teach their children that the tooth fairy is female.
Other myths, however, are more troublesome and could potentially lead to patient harm if believed. For example, until the mid-20th century, infants were often diagnosed with teething convulsion, which allowed parents and physicians alike to ignore potentially serious symptoms, such as fever, diarrhea, and infection.10 With the passage of time, as a result of numerous studies, perceptions are changing, but there are still obstacles in convincing both caregivers and health care providers teething is not responsible for more serious symptoms.
IS TEETHING AN ILLNESS OR JUST PART OF THE GROWTH CYCLE?
Treatment for the discomfort associated with teething has been around since ancient times who described this discomfort as a "worm eating through the teeth."2 Since the time of Hippocrates, many physicians have considered the fever that accompanies teething to be inevitable. In addition, Hippocrates associated the teething process to such conditions as pruritus of the gums, fevers, diarrhea, and convulsions. Others also considered teething a potentially fatal condition. In 19th century England, the British Registrar General's office reported teething to be the cause of death in 4.8% of infants less than 1 year of age and 7.3% of children between 1 and 3 years of age.2 Similarly, between 1847 and 1881, pioneers in Utah attributed the deaths of 521 children to teething. In 1910, the British Registrar General noted that 1600 children died from the teething process. More recently, teething convulsions were reported as the cause of death for a small group of children, in Sheffield, England, between 1947 and 1979.2
Jaber et al interviewed the mothers of 46 healthy infants at a wellness baby clinic.11 They were told to record rectal temperatures, examine the gums for evidence of tooth eruption, and report any symptoms, such as diarrhea or bronchial disease, or anything else that may have occurred prior to the eruption of the first tooth. The investigators noted that a fever (i.e., body temperature > 37.5°C) was reported on the day of tooth eruption for 20 infant participants; however, they stress that other causes must first be ruled out before teething is confirmed as the cause of the fever.
Child caregivers, and even some health care professionals, may attribute certain symptoms to the teething process; there is the long-standing belief that teething may predispose the child to other medical conditions, such as otitis media and upper respiratory tract infections. The results of related study data are mixed, with some supporting and others refuting the association of teething with specific symptoms. As noted by Nield et al, there may be temporal associations between teething and some symptoms, but it does not necessarily prove a cause and effect relationship.1 Similarly, in one study conducted by Tasanen et al, 150 children in a Finnish child care center were assessed when the first incisor became palpable.12 The author reported that restlessness, drooling, gum rubbing, and the sucking of fingers were noted in teething infants but diarrhea and sleep disturbances were unaffected; furthermore, it was noted that when the pressure was applied to the gums of teething children, no increase in pain was observed. It was also noted, however, that teething infants with an intercurrent infection did have higher temperatures.
Child caregivers, in general, continue to exhibit a knowledge deficit when it comes to teething. In one 2010 study by Owais et al, more than1400 parents were surveyed about teething signs and symptoms and common treatment options.13 Almost 75% thought fever, diarrhea, and sleep disturbances were common symptoms experienced by the teething infant. Changing these long-held beliefs continues to be a challenge. Thus, patient education is essential to effectively minimize inappropriate medication use and to ensure that infants get prompt medical attention for comorbid conditions.
TEETHING SIGNS AND SYMPTOMS
In the 1960s Illingworth stated, "teething produces nothing but teeth." Almost 50 years later, practitioners still agree that very few of the symptoms observed in a teething infant can be attributed to the process.2,14 Caregivers will often consult their pharmacist before their pediatrician for medical advice when an infant is experiencing a fever, nasal congestion, or diarrhea; and they will balk if the pharmacist recommends a visit to the physician because caregivers still associate these symptoms with teething. It is imperative that the pharmacist impresses on the caregiver that none of these symptoms is related to teething and that additional medical attention is warranted.
Based on reliable reports from parents and caregivers, babies who are teething do experience an increase in salivation and transient negative changes. It is understood that when a tooth emerges, the oral mucosa becomes irritated as pressure is exerted on the tissue; so, transient discomfort is to be expected. Although there is no one specific treatment for managing teething discomfort, supportive care, such as chewing on hard or cold food, may offer temporary relief.15
To confirm a teething diagnosis, the gingival tissue should be visually examined and palpated for evidence of tooth emergence. Gum swelling often occurs with the eruption of the primary teeth. In some instances, there may be a bluish area around the swollen gum where a tooth is expected, which may indicate an eruption cyst secondary to a hematoma. Slight bleeding may occur when the tooth finally breaks through the surface. No special treatment is necessary and caregivers should simply be reassured. If the hematoma persists for more than a week without the tooth erupting, the patient should be brought to their pediatrician for further evaluation.2 Oral ulcers, however, are not associated with teething and infants should be checked for viral infections, such as coxsackie and herpes, when ulcers are present. Neither oral abrasions nor erythema with excessive drooling are associated with teething and other conditions, such as caustic ingestion, should be considered. Similarly, infants with cervical lymphadenopathy should be evaluated for dental or pharyngeal infections because this condition is not linked to teething. Although fussiness and irritability are often associated with teething, teething infants who are fussy should be consolable. Those who continue to remain irritable and inconsolable (i.e., insists on being carried and screams when put down) should be evaluated for more serious conditions, such as a urinary tract infection (UTI) or sepsis. Other noninfectious causes, such as corneal abrasion or hair tourniquet syndrome, should also be considered.
Sleep disturbances during the teething period should be minimal.2,16 Other changes in sleep patterns, such as frequent nighttime awakening, are common in infants between 6 and 12 months of age. Night awakening is a normal developmental event, unrelated to teething, that occurs in this age group when the infant develops a sense of object permanence and calls out to their parents at night.
Diarrhea has often been linked to teething, although many pediatricians will dispute this. Hippocrates, in fact, stated infants who developed diarrhea were less likely to develop convulsions; this was probably related to the concept that bad humors left the body via the stools.2 If diarrhea is present during teething, the symptom should pass within 24 hours. If the diarrhea persists longer than 24 hours, the child should be referred to a pediatrician because an infection may be present. In some instances, especially in underdeveloped countries, parents may ignore diarrhea symptoms and fail to give their children adequate fluids. Caregivers may fail to seek medical attention when symptoms continue or worsen, which can lead to serious illness.
IS IT TEETHING OR IS IT SOMETHING ELSE?
It is appropriate to investigate all signs and symptoms, such as irritability, fevers higher than 38.8°C, diarrhea, and changes in appetite, before attributing them to teething. Any hesitation to identify the cause of the symptoms may cause a delay in the diagnosis of a more serious illness. It is concerning that many health care providers may believe the same myths as their patients. For example, although current medical opinion considers teething-related diarrhea to be a myth, in one study by Coreil et al, in which 215 pediatricians in Florida were surveyed regarding their beliefs about teething-related diarrhea, more than 35% thought there was a real association between tooth eruption and diarrhea.17 More recently an 8-month longitudinal study, involving 47 noninstitutionalized Brazilian infants between 5 and 15 months of age, was conducted to determine if there was any association between primary tooth eruption and the common perceived signs and symptoms of teething.18 Daily tympanic and axillary temperature readings and oral examinations were performed. Mothers were interviewed daily and the occurrence of one or more of 13 signs and symptoms of teething was recorded for each 24-hour period. Although irritability, increased salivation, runny nose, loss of appetite, diarrhea, rash, and sleep disturbance were associated with primary tooth eruption, the investigators concluded that the occurrence of severe signs and symptoms, such as fever, could not be attributed to teething. Likewise, Wake et al, in a prospective cohort study involving 21 children with 90 emerged teeth, found no statistically significant relationship between fever and tooth eruption.16 Similarly, other symptoms, such as drooling, rashes, and mood balances, were also found to be uncommon and unrelated to the teething process. As a result, the investigators concluded that teething was often blamed for any discomfort experienced by children 6 to 24 months of age.
The challenge remains to determine what symptoms are absolutely associated with teething. Macknin et al, also, attempted to determine which symptoms may be attributed to teething and confirmed that many of the mild symptoms traditionally associated with teething (i.e., drooling, gum rubbing, loose stools, mild elevation in temperature [0] Take Exam[->1] Print Course[->2]
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