The multidisciplinary management of hypodontia: a team approach
IN BRIEF
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D. S. Gill*1 and C. S. Barker2
PRACTICE
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Provides an understanding of the importance of close communication and joint planning for the management of hypodontia. Highlights the treatment for hypodontia that can be provided at different ages. Discusses the role of orthodontic treatment in managing hypodontia.
Hypodontia is a frequently encountered condition within general dental practice. Its successful management involves the interplay of a number of clinicians. The general dental practitioner plays a key role in the management of patients. The aim of this short article is to outline some of the principles of the multidisciplinary management of hypodontia with an emphasis on orthodontic treatment.
INTRODUCTION Hypodontia can be defined as the developmental absence of one or more teeth excluding the third molars. This condition has also been described as dental agenesis. Oligodontia has been used to describe the absence of a large number of teeth, and anodontia to describe the total absence of teeth. Hypodontia, the preferred term within this article, can be classified into three severity groups according to the number of missing teeth: • Mild: 1–2 missing teeth • Moderate: 3–5 missing teeth • Severe: 6 or more missing teeth.
Prevalence The prevalence of hypodontia has been reported to be between 4.6–6.3% within the permanent dentition of white European populations; 3.2–4.6% in white North Americans; and 6.1–7.7% in Chinese.1 Females are affected more frequently than males and the site of agenesis varies within the arch; it is most frequently observed at the end of each dental series (for example, maxillary lateral incisors, second premolars, third molars). The mandibular second premolar is the most commonly affected tooth (2.91–3.22%), followed by the maxillary lateral incisor (1.55–1.78%) and then the maxillary second premolar (1.39–1.61%).1 It is estimated that 2.6% of Consultant Orthodontist, Great Ormond Street NHS Foundation Trust, UCLH Eastman Dental Hospital, London; 2Consultant in Orthodontics, Mid Yorkshire Hospitals NHS Trust, Pinderfields General Hospital, Wakefield *Correspondence to: Daljit S Gill Email: [email protected] 1
Refereed Paper Accepted 28 January 2015 DOI: 10.1038/sj.bdj.2015.52 © British Dental Journal 2015; 218: 143-149
Table 1 Dental features co-associated with hypodontia Feature
Comments
Microdontia
May be localised or generalised; may affect the crowns and roots of teeth; is a contributor to spacing9
Conical teeth
May be localised (for example, peg lateral incisors) or generalised
Ectopic eruption
Ectopic eruption into the lateral incisor space; impaction and transposition may affect the maxillary canine
Retained primary teeth
Teeth maybe infra-occluded10
Reduced alveolar development
Can complicate prosthodontic management and orthodontic tooth movement
Delayed eruption of permanent teeth
Average delay in eruption is 1.5 years.11 Can delay onset of orthodontic treatment
Altered craniofacial morphology
Tendency towards Class III malocclusion and reduced lower anterior facial height12
subjects with hypodontia have severe hypodontia which is the absence of six or more teeth (overall prevalence 0.14%). The prevalence of hypodontia within the primary dentition is estimated to be 0.08–1.55%, with equal distribution between males and females.2 The successional teeth of the permanent dentition (incisors, canines and premolars) develop from localised proliferations within the dental lamina of each primary tooth germ. The absence of the primary tooth germ therefore results in the absence of its permanent successor.
Aetiology It has been suggested that both genetic and environmental factors can play a part in the aetiology of hypodontia. The condition may be isolated and non-syndromic, or part of a syndrome involving ectodermal tissues (for example, the ectodermal dysplasias). Nonsyndromic hypodontia can be autosomal dominant, autosomal recessive or sex-linked and may have varying degrees of expression.3
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The higher prevalence of hypodontia within families would suggest a genetic link that is not yet fully understood. Genes of interest include MSX1 (muscle segment homeobox 1) and PAX9 (paired box 9), which are homeobox transcription factors, and AXIN2. MSX1 and PAX9 encode transcription factors that are strongly expressed in the ectomesenchymal compartment of the developing tooth and are essential for odontogenesis to progress beyond the bud stage in mice.4,5 In humans, mutations in these genes are predominantly loss-of-function when associated with hypodontia.6 Examples of environmental causes of hypodontia include the use of chemotherapy in early infancy for childhood malignancy and the presence of a cleft palate.7,8
Associated features There are a number of dental features coassociated with hypodontia and the important ones are summarised in Table 1. 143
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PRACTICE Fig. 1 The management of hypodontia requires close communication between a number of clinicians
Fig. 2 A DPT of a ten year old patient showing late forming lower second premolars
Poor aesthetics due to spacing is the most common complaint of patients with hypodontia. 13 There may be an association between the aesthetic impact of hypodontia and the number of missing teeth, the retention of primary teeth, microdontia or the presence of spacing.14 Hypodontia can be a feature of a number of medical conditions and the possibility of it being a presenting feature of a systemic condition should not be overruled, particularly within a patient presenting with several missing teeth. As there are genetic associations with hypodontia, the presence of hypodontia in a parent or sibling should raise the possibility of its occurrence in other family members. Hypodontia is a frequently encountered condition within general dental practice, and its care is complex, involving interaction between many speciality areas of dentistry (Fig. 1). It is important for the general dental practitioner to understand how care should be planned for patients. It is essential that there is close communication between all those involved in the care of patients, especially the orthodontist and restorative dentist. Ideally, the care of patients should be planned within a multidisciplinary clinic even though actual treatment can be undertaken more locally once a coordinated treatment plan has been agreed. The aim of this article is to outline the management of hypodontia during the primary/early mixed dentition, late mixed dentition and permanent dentition stages with a special emphasis on orthodontics.
PRIMARY/EARLY MIXED DENTITION When patients first present they may or may not be aware of a diagnosis of hypodontia.
Features that may be indicative of this diagnosis include a family history of the condition, the presence of features associated with the condition as outlined in Table 1 and the occurrence of an associated medical condition (for example, the ectodermal dysplasia or Downs syndrome). A definitive diagnosis can often be established by undertaking a radiographic examination but care is required to ensure that radiographs are not taken too early, as permanent tooth formation can begin as late as 9–10 years for second premolars (Fig. 2).15 It may also not be possible to undertake any treatment at a young age, making radiographic exposure more of an academic interest rather than a clinical need. The authors approach is to generally wait until above the age of 9 years before undertaking a dental panoramic examination for the diagnosis of hypodontia. As well as counselling about the possible future implications which come with a diagnosis of hypodontia,16 an important aim of the initial assessment is to understand the main family and patient concerns (for example, aesthetic concerns due to spacing/misshapen teeth or functional concerns) and the general attitude towards dental care, as this may impact upon the complexity of any future treatment plan. It is important that the initial contact with the dental team is always positive as this will help to develop good rapport which is particularly important as dental input may be required for many years to come. Typical treatment approaches for the management of hypodontia are summarised in Table 2. The first aim of treatment should be to introduce a preventive regime to facilitate
the retention of the teeth present. Preventive techniques which should be considered by the dental team include: • Diet analysis and advice • Oral hygiene advice, including techniques for keeping microdont, spaced teeth clean • Fluoride supplementation • Fissure sealing of permanent molars, deep pits and primary molars to be retained • Mouth guards to protect protrusive maxillary incisors during contact sports • Artificial saliva in patients with xerostomia (for example, ectodermal dysplasia). In those with severe hypodontia or anodontia early treatment may involve the placement of removable dentures to help improve appearance and function. These can be placed at a young age but are especially important, psychologically, just before the start of school. Surprisingly, children can often cope well with dentures especially if the denture for the arch with the best prognosis is fitted first as this will help with adaptation.16 Parents should be warned about the problems related to denture wear including speaking difficulties, dietary limitations, loss of the appliance and the need for frequent adjustments. In children with less severe hypodontia, the psychological impact may not become apparent until eruption of the permanent incisors when the child may notice spacing and possibly be bullied at school. If the psychological impact is significant it may be appropriate to build up microdont teeth with composite resin to help reduce spacing or supply dentures to replace missing anterior teeth. Simple orthodontic treatment can also be considered at this stage (for example, diastema closure) but does then commit the patient to wearing fixed or removable retainers for a number of years until definitive orthodontic treatment is commenced. Natural physiological spacing (for example, the ugly duckling phase) should not BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Table 2 Treatment approaches for the management of hypodontia Stage
Treatment
Comments
Primary/early mixed dentition
Prevention
Diet advise, fluoride, fissure sealants, mouth guards, saliva
Removable dentures for psychological and functional reasons.
Will require regular adjustments during growth. Retention and stability maybe problematic in those with poorly developed alveolar ridges.
Late mixed dentition/early permanent dentition
>12 years (Permanent dentition)
Composite build ups to improve aesthetics of microdont permanent teeth or worn primary teeth and to reduce spacing.
Consider only if high patient concerns
Simple orthodontic treatment to help close spacing.
Consider only if high patient concerns. Long-term retention maybe necessary. Consider frenectomy for low attached midline maxillary frenum to aid retention of diastema closure.
Interceptive treatment
Extraction of primary canines if permanent canines palatally positioned; extraction of severely infraoccluded molars
Prevention
See above
Removable dentures
See above
Composite build ups to improve aesthetics of microdont permanent teeth or worn primary teeth.
See above
Consider interceptive extractions to guide eruption
Problems may include palatal maxillary canines and infraocclusion.
Simple orthodontic treatment for space redistribution
For example, a diastema that cannot be closed restoratively. Will require long-term retention
Orthodontic treatment
Pontics can be placed on the fixed appliance and the retainer following orthodontics as a temporary measure.
Resin bonded bridges following orthodontics for tooth replacement.
Other methods of tooth replacement include maintaining the primary predecessor, dentures, fixed bridges and transplantation.
Composite build ups of microdont or hypoplastic teeth.
16–20 years
Overdentures (severe hypodontia)
Abutments help maintain alveolar bone, improve retention and stability and provide proprioception.
Single tooth implants or implant retained fixed or removable prosthesis
Placed when the majority of growth is complete. Tends to be earlier in females (17-18 years) than males (18-19 years). Bone augmentation procedures maybe required before implant placement.
Orthodontics in combination with orthognathic surgery.
For patients with severe skeletal discrepancies.
be closed, as this may impact on the future development of the permanent dentition. The burden of treatment needs to be fully considered by the family as repeated episodes of orthodontic treatment may lead to reduced future compliance and impact upon dental health if appliances are worn for long periods and not maintained adequately. In the case of missing, or peg shaped maxillary lateral incisors, it is important for the
general dental practitioner and orthodontist to maintain a high index of suspicion for palatal maxillary canine impaction as there is an association between the two anomalies (Fig. 3).17 It is widely recommended that the maxillary canine buccal bulge is palpated at the age of 9 years and if it cannot be felt then a radiographic investigation is undertaken to check for the position of the maxillary canine.18 Vertical or horizontal parallax
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Fig. 3 (a) A DPT showing an ectopic upper right canine. (b) A cone beam computed tomogram of the same patient showing that the canine has caused extensive damage to the central incisor roots
Table 3 Some clinical features of ectodermal dysplasia Clinical manifestations of ectodermal dysplasias Dental • Hypodontia or anodontia • Malformed teeth (cone or peg shaped) Sweat glands • Dry scaling skin • Reduced or absent sweating leading to heat intolerance Hair follicles • Sparse fair hair or alopecia • Eyebrows or eyelashes absent/sparse Nails • Leukonychia, dystrophic and malformed Salivary glands • Aplasia leading to xerostomia
can be employed, using two radiographs, to establish the position of the crown of the permanent canine relative to the adjacent teeth. If impaction is confirmed, cone beam computed tomography may be indicated to determine whether the maxillary canine has damaged the roots of the surrounding teeth, as this may influence extraction patterns. Interceptive extraction of the primary canine may be recommended by an orthodontist in an attempt to normalise the eruption path of the successor.19 Root resorption caused by ectopic teeth can lead to significant damage and eventual tooth loss in rare cases (Fig. 3b). Generally, in patients with moderate/ severe hypodontia it is important to have 145
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PRACTICE a high index of suspicion for an underlying medical condition, such as the ectodermal dysplasias that maybe undiagnosed up to that point. There are over 150 types of ectodermal dysplasia and Table 3 outlines some of the clinical features of this condition. If such a condition is suspected, it is recommended that a letter is written to the general medical practitioner recommending referral to a geneticist for further investigation.
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Fig. 5 (a) Both maxillary lateral incisors were missing. (b) All space has been orthodontically closed accepting the canine as a lateral incisor
LATE MIXED AND PERMANENT DENTITION Orthodontic treatment is most commonly undertaken during the late mixed and early permanent dentition stage. One particular problem encountered in hypodontia is that there may be a general delay in dental development,11 meaning that patients may not reach the permanent dentition stage and be ready to start treatment with fixed appliances until after their school peers. The delayed onset of treatment can be a concern to some parents, particularly if there is poor self-esteem. It is helpful to mention the possibility of delayed dental development, and possible delays in commencing orthodontic treatment, during the primary dentition stage so that the family are aware and can become accustomed to this particular problem. It should be noted, however, that not all patients with hypodontia will have delayed dental development.11 Orthodontic treatment will involve the correction of the general features of the malocclusion as well as treatment specifically directed towards management of the missing and microdont teeth. The orthodontic options for missing teeth are to open (Fig. 4), close (Fig. 5) or redistribute the space available. If microdont teeth are present (for example, peg lateral incisors) it may also be necessary to reposition these to facilitate future restorative care. It is essential that treatment planning is undertaken with close communication between the orthodontist and restorative/paediatric dentist. The family must also fully understand the responsibilities of each of the clinicians involved, the timing of procedures, the long-term nature of care, and the cost implications of current and future care. The hospital-based multidisciplinary clinic is one example of an ideal setting for this type of treatment planning to occur. Often it is not possible to create a definitive orthodontic treatment plan until the permanent dentition is established. For example, when the maxillary lateral incisor is developmentally absent, it is often important for the restorative dentist to assess the size, shape, colour and gingival margin position of the maxillary canine before a decision can be made if the canine
B
C
Fig. 4 (a) A missing upper left lateral incisor where the canine has drifted medially. The upper right lateral incisor is microdont. (b) space was opened with fixed appliance to restore the upper left lateral incisor and build up the upper right lateral incisors. (c) At completion of treatment a resin bonded bridge replaced the upper left lateral incisor and composite has been used to restore the upper right lateral incisor
will make a suitable substitute for the lateral incisor. Occasionally, the maxillary canine is impacted and the final decision of whether to open or close the lateral incisor space can only be made once the canine has been guided into the line of the arch with fixed orthodontic appliances. It has been suggested that the maxillary canines should be encouraged to erupt mesially, by extracting the primary lateral incisors and canines, when the maxillary lateral incisors are absent. Mesial migration of the canine will help to develop alveolar bone in the lateral incisor site. If it is later decided to distalise the canine to re-open the lateral incisor space, a good ridge of bone should remain for possible future implant placement.20 This process of bone augmentation has been termed ‘orthodontic implant site development’ (Fig. 6). As well as taking the patient’s/parental wishes into consideration, a number of clinical factors need to be considered by the orthodontist when deciding whether to open or close spaces such as: 1. The incisor relationship – In a Class II case, space is required in the upper arch
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Fig. 6 (a) The upper left canine was allowed to erupt into the position of the missing lateral incisor. As the canine erupts a thick alveolar ridge is developed
for incisor retraction so there may be a greater tendency to try to close at least one unit of space within each quadrant of the upper arch. 2. The molar relationship – A Class I molar relationship requires equal numbers of teeth anterior to the first molars in both arches, which will influence decisions regarding space opening or closing. Options for molar relationship correction can include functional BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE
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Fig. 7 A digital Kesling set-up can be used to show the possible treatment outcome. (a) Before and (b) after treatment
Fig. 8 Miniscrews can be used to provide absolute anchorage as in this case where a miniscrew is being used to retract the maxillary incisors
appliances, extractions, headgear or use of mini-screws 3. Degree of crowding or spacing – Space closure can be considered to help resolve crowding. It may not be possible to close very large spaces, particularly if the alveolus is atrophic, and leaving some space maybe necessary 4. The size, shape, colour and gingival margin position of the maxillary canine must be taken into consideration when the lateral incisor is missing. A restorative dentist should assess the maxillary canine carefully to determine if it can be made into a suitable substitute for the lateral incisor if space closure is an option. If it is felt that the canine cannot be successfully camouflaged as a lateral incisor then the decision may be made to open the space, which may require premolar extractions, or else the patient must accept the aesthetic compromise. This also needs careful consideration due to the financial consequences of
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Fig. 9 A pontic can be attached onto an archwire or composite can be used to build up teeth when there are aesthetic concerns when opening space for a missing tooth. (a) Acrylic pontics with brackets used to mask the upper lateral incisor spaces. (b) Composite resin addition used to mask the upper left lateral incisor space
additional restorative treatment (for example, implants) when a compromise is available 5. The orthodontist may consider other factors such as the fullness of the facial profile and gum exposure during smiling when considering whether to open or close space. When the decision is made to open space for a missing unit, it is essential that clear aims of treatment are outlined by both the orthodontist and the restorative dentist during treatment planning. It is important for the orthodontist to know the exact mesiodistal space required to place the crown of a tooth and the space required between the roots of teeth for implants to remain a viable option. The final planned restorative space requirements can then be incorporated into the treatment plan and teeth moved into the most appropriate position to facilitate optimal space for the final restoration(s). A Kesling diagnostic set-up can aid in planning the amount of space that should be created as well as being an excellent tool to explain the likely outcome to the patient. A three-dimensional set-up can also be created digitally using virtual study models to demonstrate to patients the possible outcome of a treatment (Fig. 7). With any form of diagnostic set-up it is essential not to raise the patient expectations excessively. For consenting purposes it is important to explain that the final outcome may not be exactly according to the diagnostic set-up.
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One particular orthodontic problem that can be encountered in patients with hypodontia is insufficient anchorage for distalisation of the maxillary canines and incisors in Class II corrections. This problem occurs because there maybe developmentally absent posterior units or the roots of the anchorage teeth are diminutive, offering less anchorage value. In addition to using more traditional techniques for anchorage reinforcement (for example, functional appliances, headgear), orthodontic mini-screws are increasingly being used for anchorage reinforcement (Fig. 8). Mini-screws, also known as miniimplants or temporary anchorage devices, are titanium bone screws that are placed through attached mucosa into alveolar bone. Mini-screws can be used directly or indirectly as anchorage units. This technique, when successful, can provide absolute anterior-posterior anchorage and also vertical anchorage reinforcement, particularly in deep bite cases with missing posterior units in the lower arch. If orthodontic treatment is carried out to open anterior space, patients can often become conscious of the gap that is created. It is possible to place an acrylic tooth with a bonded bracket into such a space for aesthetic enhancement during fixed appliance treatment or composite can be added to adjacent teeth to replicate the missing tooth with sequential addition during treatment (Fig. 9). Although spaces are more commonly opened or closed, space redistribution can be undertaken to facilitate future restorative treatment. This may involve moving a first premolar into a missing second premolar site because, in some instances, it can be easier to replace the first premolar rather than the second premolar. Another example is when a lower lateral incisor is moved into the site of a missing central incisor to open up the lateral incisor space. A lateral incisor space may be easier to restore than a central incisor space because a retainer for a resinbonded bridge can be cantilevered from the canine which offers a larger surface area for bonding. In the case of microdont teeth, it is important that the orthodontist receives a pretreatment prescription for tooth positioning in all three dimensions if future restorative treatment is planned. For example, in the case of a diminutive maxillary lateral incisor, consideration has to be given to the mesiodistal, vertical and anterior-posterior positioning. Mesio-distally the diminutive tooth may be placed in the middle of the space or asymmetrically depending on the preference of the restorative dentist. Vertically, teeth can be intruded to improve the positioning of the gingival margin in relation to the 147
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PRACTICE contralateral tooth. Anterior-posteriorly, if a full coverage restoration is planned then leaving a small overjet will help to reduce any palatal reduction. If only a labial veneer is planned then minimal overjet is preferable to allow a maximum thickness of restorative material on the labial aspect. In some cases, where it is not possible to close the space, it may be preferable to maintain a primary tooth in situ to help maintain aesthetics, function and alveolar bone. It can be common to maintain second primary molars if space is not required for correction of the malocclusion. Teeth that have good root morphology and are minimally affected by dental caries may continue to function successfully for many years. The width of the second primary molar can be reduced, by inter proximal enamel reduction, to provide some space for the relief of crowding or to facilitate molar correction if orthodontic treatment is to be undertaken. This may not be possible in some cases due to the divergence of the primary molar roots. Factors that can affect the long-term survival of retained primary teeth include:21 1. Root resorption 2. Infra-occlusion 3. Caries, tooth wear and periodontal disease. Before orthodontic appliances are removed, it is essential that the clinician who will undertake the final restorative treatment examines the patient to ensure that the correct amount of space has been created for tooth replacement and the restoration of microdont teeth. It is essential to take periapical radiographs, perpendicular to any prospective implant site(s), to ensure that the roots are parallel and adequately separated. The minimum interradicular space for a maxillary lateral is 6 mm. Ideally, the vertical space would be at least 7 mm from the alveolar bone crest to the opposing tooth. Following removal of appliances, patients should be provided with robust retainers to maintain the spacing that has been produced and to replace any missing units. It is preferable for patients to wear such appliances full time as they help to improve dental appearance by tooth replacement. Following restoration of the missing teeth, patients can wear retainers on a part-time nightly basis. It is important for the restorative dentist to liaise closely with the orthodontist so that retainers can be adjusted around new restorations to minimise the risk of relapse due to inadequate retainer wear. In patients with severe hypodontia, removable dentures may be the only
Multidisciplinary Planning Informed consent
Diagnostic Kesling set-up
Orthodontics
Pre-debond check
Radiographic assessment to check root seperation
Removal of appliances Restorative phase and retention Fig. 10 The care pathway for the management of hypodontia
treatment option for tooth replacement until an implant-retained prosthesis can be offered at the completion of growth. Overdentures can provide a useful treatment option in those patients with a few available teeth as they can help improve the stability and retention of appliances. Retained roots are also invaluable in helping to maintain alveolar bone volume. In less severe cases, a resin-retained bridge maybe provided as a permanent or semipermanent solution until the patient has matured for implant placement.
THE ESTABLISHED DENTITION The established dentition is considered to be the stage at which the majority of facial growth has occurred and definitive orthodontic treatment, in the case of patients requiring orthognathic surgery and restorative treatment (for example, implants), is undertaken. The age at which facial growth plateaus displays high individual variability, but it is considered to be approximately 18–19 years in males and 17–18 years in females. Growth can be monitored using height measurements. Craniofacial growth is one of the last to reach to adult levels, with some patients exhibiting continued craniofacial growth well into adulthood and old age.22 Serial cephalograms, taken 12 months apart, showing minimal growth provide good evidence for the cessation of the majority of growth. Orthodontics in combination with orthognathic surgery can be considered for those individuals where orthodontic treatment alone cannot be used to camouflage the
skeletal discrepancy. This form of treatment usually involves a preparatory phase of orthodontics (known as pre-surgical orthodontics) to decompensate the malocclusion, and this often makes the malocclusion appear worse. This is followed by jaw repositioning to correct the skeletal discrepancy, facial appearance and occlusion. Orthodontics continues post-surgically to detail the occlusion. This form of treatment should be jointly planned by the orthodontist, oral and maxillofacial surgeon and restorative dentist. As with orthognathic surgery, implant placement should occur at the completion of facial growth to prevent submergence of the implant restoration. This form of treatment should only be considered in those where there is adequate space between roots for implant placement and where there is sufficient alveolar bone volume. In cases with inadequate space between roots, one may need to consider orthodontic space recreation or accept bridgework instead of implants. Some patients can present for orthodontic treatment during their thirties and forties when retained primary teeth begin to fail. Adult patients can be more difficult to treat than children in a number of different respects. They may be less accepting of wearing fixed appliances compared to children and may demand less visible orthodontic appliances, which are usually more difficult for the orthodontist to use. The lack of growth in adults can make space closure and bite opening more difficult. On the other side, adults can be extremely motivated patients and very compliant with maintaining oral hygiene, minimising breakages and keeping regular appointments. The care pathway for the management of adults and children with hypodontia is similar (Fig. 10).
CONCLUSIONS Patients with hypodontia can require complex interdisciplinary care which may start at a young age leading to protracted treatment times and considerable burden to the family. This article has outlined the care pathway and the interaction of the dental specialties and the general dental practitioners in the care for this important group of patients. To summarise, the general dental practitioner has an important role in diagnosis, prevention, referral to the appropriate specialist, treatment planning and undertaking treatment. It is essential that there is good communication between all members of the team involved in patient care and that the treatment plan involves input from all the involved clinicians from the outset. BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Further information • Hobkirk J A, Gill D S, Jones S P et al. Hypodontia: A team approach to management. Wiley-Blackwell, 2011. • Bullying Online: www.bullying.co.uk • Ectodermal Dysplasia Society: www.ectodermaldysplasia.org/ • National Foundation for Ectodermal Dysplasias: www.nfed.org/ 1.
2. 3. 4. 5. 6. 7.
Polder B J, Van’t Hof M A, Van der Linden F P G M et al. A meta-analysis of the prevalence of dental a genesis of permanent teeth. Community Dent Oral Epidemiol 2004; 32: 217–226. Whittington B R, Durward C S. Survey of anomalies in primary teeth and their correlation with the permanent dentition. N Z Dent J 1996; 92: 4–8. Cobourne M T. Familial human hypodontia – is it all in the genes? Br Dent J 2007; 203: 203–208. Satokata I, Maas R. Msx1 deficient mice exhibit cleft palate and abnormalities of craniofacial and tooth development. Nat Genet 1994; 6: 348–356. Peters H, Neubuser A, Balling R. Pax genes and organogenesis: Pax9 meets tooth development. Eur J Oral Sci 1998; 106 (Suppl 1): 38–43. Nieminen P. Genetic basis of tooth agenesis. J Exp Zool B Mol Dev Evol 2009; 312B: 320–342. Paedersen L B, Clausen N, Schrøder H et al. Microdontia and hypodontia of premolars and
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permanent molars in childhood cancer survivors after chemotherapy. Int J Paediatr Dent 2012; 22: 239–243. Bartzela T N, Carels C E, Bronkhorst E M et al. Tooth agenesis patterns in unilateral cleft lip and palate in humans. Arch Oral Biol 2013; 58: 596–602. Brook A H, Griffin R C, Smith R N et al. Tooth size patterns in patients with hypodontia and supernumerary teeth. Arch Oral Biol 2009; 54(Suppl 1): S63–70. Shalish M, Peck S, Wasserstein A et al. Increased occurrence of dental anomalies associated with infraocclusion of primary molars. Angle Orthod 2010; 80: 440–445. Ruiz-Mealin E V, Parekh S, Jones S P et al. Radiographic study of delayed tooth development in patients with dental agenesis. Am J Orthod Dentofacial Orthop 2012; 141: 307–314. Acharya P N, Jones S P, Moles D et al. A cephalometric study to investigate the skeletal relationships in patients with increasing severity of hypodontia. Angle Orthod 2010; 80: 511–518. Hobkirk J A, Goodman J R, Jones S P. Presenting complaints and findings in a group of patients attending a hypodontia clinic. Br Dent J 1994; 177: 337–339. Laing E R, Cunningham S J, Jones S P et al. The psychosocial impact of hypodontia in children. Am J Orthod Dentofacial Orthop 2010; 137: 35–41. Wisth P J, Thunold K, Boe O E. The craniofacial morphology of individuals with hypodontia. Acta
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Odontol Scan 1974; 32: 281–290. 16. Gill D S, Jones S, Hobkirk J et al. Councelling patients with hypodontia. Dent Update 2008; 35: 344–352. 17. Sacerdoti R, Baccetti T. Dentoskeletal features associated with unilateral or bilateral palatal displacement of Maxillary canines. Angle Orthod 2004; 74: 725–732. 18. Husain J, Burden D, McSherry P. Management of the palatally ectopic maxillary canine. Guideline produced by the Royal College of Surgeons of England, March 2010. 19. Naoumova J, Kurol, Kjellberg H. Extraction of the primary canine as an interceptive treatment in children with palatal displaced canines – part I: shall we extract the primary canine or not? Eur J Orthod 2014; 10.1093/ejo/cju040. [Epub ahead of print]. 20. Kokich V G. Managing orthodontic-restorative treatment for the adolescent patient. In McNamara J A, Brudon W I, eds. Orthodontics and dentofacial orthopedics. . pp 423–452. Ann Arbor, Mich.: Needham Press, 2001. 21. Hvaring C L, Øgaard B, Stenvik A, Birkeland K. The prognosis of retained primary molars without successors: infraocclusion, root resorption and restorations in 111 patients. Eur J Orthod 2014; 36: 26–30. 22. Behrents R G. Growth in the aging craniofacial skeleton. In Monograph 17. Craniofacial Growth Series. Ann Arbor, Mich.: Centre for Human Growth and Development, University of Michigan; 1985.
149 © 2015 Macmillan Publishers Limited. All rights reserved
IN BRIEF
•
•
D. S. Gill*1 and C. S. Barker2
PRACTICE
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Provides an understanding of the importance of close communication and joint planning for the management of hypodontia. Highlights the treatment for hypodontia that can be provided at different ages. Discusses the role of orthodontic treatment in managing hypodontia.
Hypodontia is a frequently encountered condition within general dental practice. Its successful management involves the interplay of a number of clinicians. The general dental practitioner plays a key role in the management of patients. The aim of this short article is to outline some of the principles of the multidisciplinary management of hypodontia with an emphasis on orthodontic treatment.
INTRODUCTION Hypodontia can be defined as the developmental absence of one or more teeth excluding the third molars. This condition has also been described as dental agenesis. Oligodontia has been used to describe the absence of a large number of teeth, and anodontia to describe the total absence of teeth. Hypodontia, the preferred term within this article, can be classified into three severity groups according to the number of missing teeth: • Mild: 1–2 missing teeth • Moderate: 3–5 missing teeth • Severe: 6 or more missing teeth.
Prevalence The prevalence of hypodontia has been reported to be between 4.6–6.3% within the permanent dentition of white European populations; 3.2–4.6% in white North Americans; and 6.1–7.7% in Chinese.1 Females are affected more frequently than males and the site of agenesis varies within the arch; it is most frequently observed at the end of each dental series (for example, maxillary lateral incisors, second premolars, third molars). The mandibular second premolar is the most commonly affected tooth (2.91–3.22%), followed by the maxillary lateral incisor (1.55–1.78%) and then the maxillary second premolar (1.39–1.61%).1 It is estimated that 2.6% of Consultant Orthodontist, Great Ormond Street NHS Foundation Trust, UCLH Eastman Dental Hospital, London; 2Consultant in Orthodontics, Mid Yorkshire Hospitals NHS Trust, Pinderfields General Hospital, Wakefield *Correspondence to: Daljit S Gill Email: [email protected] 1
Refereed Paper Accepted 28 January 2015 DOI: 10.1038/sj.bdj.2015.52 © British Dental Journal 2015; 218: 143-149
Table 1 Dental features co-associated with hypodontia Feature
Comments
Microdontia
May be localised or generalised; may affect the crowns and roots of teeth; is a contributor to spacing9
Conical teeth
May be localised (for example, peg lateral incisors) or generalised
Ectopic eruption
Ectopic eruption into the lateral incisor space; impaction and transposition may affect the maxillary canine
Retained primary teeth
Teeth maybe infra-occluded10
Reduced alveolar development
Can complicate prosthodontic management and orthodontic tooth movement
Delayed eruption of permanent teeth
Average delay in eruption is 1.5 years.11 Can delay onset of orthodontic treatment
Altered craniofacial morphology
Tendency towards Class III malocclusion and reduced lower anterior facial height12
subjects with hypodontia have severe hypodontia which is the absence of six or more teeth (overall prevalence 0.14%). The prevalence of hypodontia within the primary dentition is estimated to be 0.08–1.55%, with equal distribution between males and females.2 The successional teeth of the permanent dentition (incisors, canines and premolars) develop from localised proliferations within the dental lamina of each primary tooth germ. The absence of the primary tooth germ therefore results in the absence of its permanent successor.
Aetiology It has been suggested that both genetic and environmental factors can play a part in the aetiology of hypodontia. The condition may be isolated and non-syndromic, or part of a syndrome involving ectodermal tissues (for example, the ectodermal dysplasias). Nonsyndromic hypodontia can be autosomal dominant, autosomal recessive or sex-linked and may have varying degrees of expression.3
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The higher prevalence of hypodontia within families would suggest a genetic link that is not yet fully understood. Genes of interest include MSX1 (muscle segment homeobox 1) and PAX9 (paired box 9), which are homeobox transcription factors, and AXIN2. MSX1 and PAX9 encode transcription factors that are strongly expressed in the ectomesenchymal compartment of the developing tooth and are essential for odontogenesis to progress beyond the bud stage in mice.4,5 In humans, mutations in these genes are predominantly loss-of-function when associated with hypodontia.6 Examples of environmental causes of hypodontia include the use of chemotherapy in early infancy for childhood malignancy and the presence of a cleft palate.7,8
Associated features There are a number of dental features coassociated with hypodontia and the important ones are summarised in Table 1. 143
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PRACTICE Fig. 1 The management of hypodontia requires close communication between a number of clinicians
Fig. 2 A DPT of a ten year old patient showing late forming lower second premolars
Poor aesthetics due to spacing is the most common complaint of patients with hypodontia. 13 There may be an association between the aesthetic impact of hypodontia and the number of missing teeth, the retention of primary teeth, microdontia or the presence of spacing.14 Hypodontia can be a feature of a number of medical conditions and the possibility of it being a presenting feature of a systemic condition should not be overruled, particularly within a patient presenting with several missing teeth. As there are genetic associations with hypodontia, the presence of hypodontia in a parent or sibling should raise the possibility of its occurrence in other family members. Hypodontia is a frequently encountered condition within general dental practice, and its care is complex, involving interaction between many speciality areas of dentistry (Fig. 1). It is important for the general dental practitioner to understand how care should be planned for patients. It is essential that there is close communication between all those involved in the care of patients, especially the orthodontist and restorative dentist. Ideally, the care of patients should be planned within a multidisciplinary clinic even though actual treatment can be undertaken more locally once a coordinated treatment plan has been agreed. The aim of this article is to outline the management of hypodontia during the primary/early mixed dentition, late mixed dentition and permanent dentition stages with a special emphasis on orthodontics.
PRIMARY/EARLY MIXED DENTITION When patients first present they may or may not be aware of a diagnosis of hypodontia.
Features that may be indicative of this diagnosis include a family history of the condition, the presence of features associated with the condition as outlined in Table 1 and the occurrence of an associated medical condition (for example, the ectodermal dysplasia or Downs syndrome). A definitive diagnosis can often be established by undertaking a radiographic examination but care is required to ensure that radiographs are not taken too early, as permanent tooth formation can begin as late as 9–10 years for second premolars (Fig. 2).15 It may also not be possible to undertake any treatment at a young age, making radiographic exposure more of an academic interest rather than a clinical need. The authors approach is to generally wait until above the age of 9 years before undertaking a dental panoramic examination for the diagnosis of hypodontia. As well as counselling about the possible future implications which come with a diagnosis of hypodontia,16 an important aim of the initial assessment is to understand the main family and patient concerns (for example, aesthetic concerns due to spacing/misshapen teeth or functional concerns) and the general attitude towards dental care, as this may impact upon the complexity of any future treatment plan. It is important that the initial contact with the dental team is always positive as this will help to develop good rapport which is particularly important as dental input may be required for many years to come. Typical treatment approaches for the management of hypodontia are summarised in Table 2. The first aim of treatment should be to introduce a preventive regime to facilitate
the retention of the teeth present. Preventive techniques which should be considered by the dental team include: • Diet analysis and advice • Oral hygiene advice, including techniques for keeping microdont, spaced teeth clean • Fluoride supplementation • Fissure sealing of permanent molars, deep pits and primary molars to be retained • Mouth guards to protect protrusive maxillary incisors during contact sports • Artificial saliva in patients with xerostomia (for example, ectodermal dysplasia). In those with severe hypodontia or anodontia early treatment may involve the placement of removable dentures to help improve appearance and function. These can be placed at a young age but are especially important, psychologically, just before the start of school. Surprisingly, children can often cope well with dentures especially if the denture for the arch with the best prognosis is fitted first as this will help with adaptation.16 Parents should be warned about the problems related to denture wear including speaking difficulties, dietary limitations, loss of the appliance and the need for frequent adjustments. In children with less severe hypodontia, the psychological impact may not become apparent until eruption of the permanent incisors when the child may notice spacing and possibly be bullied at school. If the psychological impact is significant it may be appropriate to build up microdont teeth with composite resin to help reduce spacing or supply dentures to replace missing anterior teeth. Simple orthodontic treatment can also be considered at this stage (for example, diastema closure) but does then commit the patient to wearing fixed or removable retainers for a number of years until definitive orthodontic treatment is commenced. Natural physiological spacing (for example, the ugly duckling phase) should not BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Table 2 Treatment approaches for the management of hypodontia Stage
Treatment
Comments
Primary/early mixed dentition
Prevention
Diet advise, fluoride, fissure sealants, mouth guards, saliva
Removable dentures for psychological and functional reasons.
Will require regular adjustments during growth. Retention and stability maybe problematic in those with poorly developed alveolar ridges.
Late mixed dentition/early permanent dentition
>12 years (Permanent dentition)
Composite build ups to improve aesthetics of microdont permanent teeth or worn primary teeth and to reduce spacing.
Consider only if high patient concerns
Simple orthodontic treatment to help close spacing.
Consider only if high patient concerns. Long-term retention maybe necessary. Consider frenectomy for low attached midline maxillary frenum to aid retention of diastema closure.
Interceptive treatment
Extraction of primary canines if permanent canines palatally positioned; extraction of severely infraoccluded molars
Prevention
See above
Removable dentures
See above
Composite build ups to improve aesthetics of microdont permanent teeth or worn primary teeth.
See above
Consider interceptive extractions to guide eruption
Problems may include palatal maxillary canines and infraocclusion.
Simple orthodontic treatment for space redistribution
For example, a diastema that cannot be closed restoratively. Will require long-term retention
Orthodontic treatment
Pontics can be placed on the fixed appliance and the retainer following orthodontics as a temporary measure.
Resin bonded bridges following orthodontics for tooth replacement.
Other methods of tooth replacement include maintaining the primary predecessor, dentures, fixed bridges and transplantation.
Composite build ups of microdont or hypoplastic teeth.
16–20 years
Overdentures (severe hypodontia)
Abutments help maintain alveolar bone, improve retention and stability and provide proprioception.
Single tooth implants or implant retained fixed or removable prosthesis
Placed when the majority of growth is complete. Tends to be earlier in females (17-18 years) than males (18-19 years). Bone augmentation procedures maybe required before implant placement.
Orthodontics in combination with orthognathic surgery.
For patients with severe skeletal discrepancies.
be closed, as this may impact on the future development of the permanent dentition. The burden of treatment needs to be fully considered by the family as repeated episodes of orthodontic treatment may lead to reduced future compliance and impact upon dental health if appliances are worn for long periods and not maintained adequately. In the case of missing, or peg shaped maxillary lateral incisors, it is important for the
general dental practitioner and orthodontist to maintain a high index of suspicion for palatal maxillary canine impaction as there is an association between the two anomalies (Fig. 3).17 It is widely recommended that the maxillary canine buccal bulge is palpated at the age of 9 years and if it cannot be felt then a radiographic investigation is undertaken to check for the position of the maxillary canine.18 Vertical or horizontal parallax
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A
B
Fig. 3 (a) A DPT showing an ectopic upper right canine. (b) A cone beam computed tomogram of the same patient showing that the canine has caused extensive damage to the central incisor roots
Table 3 Some clinical features of ectodermal dysplasia Clinical manifestations of ectodermal dysplasias Dental • Hypodontia or anodontia • Malformed teeth (cone or peg shaped) Sweat glands • Dry scaling skin • Reduced or absent sweating leading to heat intolerance Hair follicles • Sparse fair hair or alopecia • Eyebrows or eyelashes absent/sparse Nails • Leukonychia, dystrophic and malformed Salivary glands • Aplasia leading to xerostomia
can be employed, using two radiographs, to establish the position of the crown of the permanent canine relative to the adjacent teeth. If impaction is confirmed, cone beam computed tomography may be indicated to determine whether the maxillary canine has damaged the roots of the surrounding teeth, as this may influence extraction patterns. Interceptive extraction of the primary canine may be recommended by an orthodontist in an attempt to normalise the eruption path of the successor.19 Root resorption caused by ectopic teeth can lead to significant damage and eventual tooth loss in rare cases (Fig. 3b). Generally, in patients with moderate/ severe hypodontia it is important to have 145
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PRACTICE a high index of suspicion for an underlying medical condition, such as the ectodermal dysplasias that maybe undiagnosed up to that point. There are over 150 types of ectodermal dysplasia and Table 3 outlines some of the clinical features of this condition. If such a condition is suspected, it is recommended that a letter is written to the general medical practitioner recommending referral to a geneticist for further investigation.
A
A
B
Fig. 5 (a) Both maxillary lateral incisors were missing. (b) All space has been orthodontically closed accepting the canine as a lateral incisor
LATE MIXED AND PERMANENT DENTITION Orthodontic treatment is most commonly undertaken during the late mixed and early permanent dentition stage. One particular problem encountered in hypodontia is that there may be a general delay in dental development,11 meaning that patients may not reach the permanent dentition stage and be ready to start treatment with fixed appliances until after their school peers. The delayed onset of treatment can be a concern to some parents, particularly if there is poor self-esteem. It is helpful to mention the possibility of delayed dental development, and possible delays in commencing orthodontic treatment, during the primary dentition stage so that the family are aware and can become accustomed to this particular problem. It should be noted, however, that not all patients with hypodontia will have delayed dental development.11 Orthodontic treatment will involve the correction of the general features of the malocclusion as well as treatment specifically directed towards management of the missing and microdont teeth. The orthodontic options for missing teeth are to open (Fig. 4), close (Fig. 5) or redistribute the space available. If microdont teeth are present (for example, peg lateral incisors) it may also be necessary to reposition these to facilitate future restorative care. It is essential that treatment planning is undertaken with close communication between the orthodontist and restorative/paediatric dentist. The family must also fully understand the responsibilities of each of the clinicians involved, the timing of procedures, the long-term nature of care, and the cost implications of current and future care. The hospital-based multidisciplinary clinic is one example of an ideal setting for this type of treatment planning to occur. Often it is not possible to create a definitive orthodontic treatment plan until the permanent dentition is established. For example, when the maxillary lateral incisor is developmentally absent, it is often important for the restorative dentist to assess the size, shape, colour and gingival margin position of the maxillary canine before a decision can be made if the canine
B
C
Fig. 4 (a) A missing upper left lateral incisor where the canine has drifted medially. The upper right lateral incisor is microdont. (b) space was opened with fixed appliance to restore the upper left lateral incisor and build up the upper right lateral incisors. (c) At completion of treatment a resin bonded bridge replaced the upper left lateral incisor and composite has been used to restore the upper right lateral incisor
will make a suitable substitute for the lateral incisor. Occasionally, the maxillary canine is impacted and the final decision of whether to open or close the lateral incisor space can only be made once the canine has been guided into the line of the arch with fixed orthodontic appliances. It has been suggested that the maxillary canines should be encouraged to erupt mesially, by extracting the primary lateral incisors and canines, when the maxillary lateral incisors are absent. Mesial migration of the canine will help to develop alveolar bone in the lateral incisor site. If it is later decided to distalise the canine to re-open the lateral incisor space, a good ridge of bone should remain for possible future implant placement.20 This process of bone augmentation has been termed ‘orthodontic implant site development’ (Fig. 6). As well as taking the patient’s/parental wishes into consideration, a number of clinical factors need to be considered by the orthodontist when deciding whether to open or close spaces such as: 1. The incisor relationship – In a Class II case, space is required in the upper arch
A
B
Fig. 6 (a) The upper left canine was allowed to erupt into the position of the missing lateral incisor. As the canine erupts a thick alveolar ridge is developed
for incisor retraction so there may be a greater tendency to try to close at least one unit of space within each quadrant of the upper arch. 2. The molar relationship – A Class I molar relationship requires equal numbers of teeth anterior to the first molars in both arches, which will influence decisions regarding space opening or closing. Options for molar relationship correction can include functional BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE
A
B
Fig. 7 A digital Kesling set-up can be used to show the possible treatment outcome. (a) Before and (b) after treatment
Fig. 8 Miniscrews can be used to provide absolute anchorage as in this case where a miniscrew is being used to retract the maxillary incisors
appliances, extractions, headgear or use of mini-screws 3. Degree of crowding or spacing – Space closure can be considered to help resolve crowding. It may not be possible to close very large spaces, particularly if the alveolus is atrophic, and leaving some space maybe necessary 4. The size, shape, colour and gingival margin position of the maxillary canine must be taken into consideration when the lateral incisor is missing. A restorative dentist should assess the maxillary canine carefully to determine if it can be made into a suitable substitute for the lateral incisor if space closure is an option. If it is felt that the canine cannot be successfully camouflaged as a lateral incisor then the decision may be made to open the space, which may require premolar extractions, or else the patient must accept the aesthetic compromise. This also needs careful consideration due to the financial consequences of
A
B
Fig. 9 A pontic can be attached onto an archwire or composite can be used to build up teeth when there are aesthetic concerns when opening space for a missing tooth. (a) Acrylic pontics with brackets used to mask the upper lateral incisor spaces. (b) Composite resin addition used to mask the upper left lateral incisor space
additional restorative treatment (for example, implants) when a compromise is available 5. The orthodontist may consider other factors such as the fullness of the facial profile and gum exposure during smiling when considering whether to open or close space. When the decision is made to open space for a missing unit, it is essential that clear aims of treatment are outlined by both the orthodontist and the restorative dentist during treatment planning. It is important for the orthodontist to know the exact mesiodistal space required to place the crown of a tooth and the space required between the roots of teeth for implants to remain a viable option. The final planned restorative space requirements can then be incorporated into the treatment plan and teeth moved into the most appropriate position to facilitate optimal space for the final restoration(s). A Kesling diagnostic set-up can aid in planning the amount of space that should be created as well as being an excellent tool to explain the likely outcome to the patient. A three-dimensional set-up can also be created digitally using virtual study models to demonstrate to patients the possible outcome of a treatment (Fig. 7). With any form of diagnostic set-up it is essential not to raise the patient expectations excessively. For consenting purposes it is important to explain that the final outcome may not be exactly according to the diagnostic set-up.
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One particular orthodontic problem that can be encountered in patients with hypodontia is insufficient anchorage for distalisation of the maxillary canines and incisors in Class II corrections. This problem occurs because there maybe developmentally absent posterior units or the roots of the anchorage teeth are diminutive, offering less anchorage value. In addition to using more traditional techniques for anchorage reinforcement (for example, functional appliances, headgear), orthodontic mini-screws are increasingly being used for anchorage reinforcement (Fig. 8). Mini-screws, also known as miniimplants or temporary anchorage devices, are titanium bone screws that are placed through attached mucosa into alveolar bone. Mini-screws can be used directly or indirectly as anchorage units. This technique, when successful, can provide absolute anterior-posterior anchorage and also vertical anchorage reinforcement, particularly in deep bite cases with missing posterior units in the lower arch. If orthodontic treatment is carried out to open anterior space, patients can often become conscious of the gap that is created. It is possible to place an acrylic tooth with a bonded bracket into such a space for aesthetic enhancement during fixed appliance treatment or composite can be added to adjacent teeth to replicate the missing tooth with sequential addition during treatment (Fig. 9). Although spaces are more commonly opened or closed, space redistribution can be undertaken to facilitate future restorative treatment. This may involve moving a first premolar into a missing second premolar site because, in some instances, it can be easier to replace the first premolar rather than the second premolar. Another example is when a lower lateral incisor is moved into the site of a missing central incisor to open up the lateral incisor space. A lateral incisor space may be easier to restore than a central incisor space because a retainer for a resinbonded bridge can be cantilevered from the canine which offers a larger surface area for bonding. In the case of microdont teeth, it is important that the orthodontist receives a pretreatment prescription for tooth positioning in all three dimensions if future restorative treatment is planned. For example, in the case of a diminutive maxillary lateral incisor, consideration has to be given to the mesiodistal, vertical and anterior-posterior positioning. Mesio-distally the diminutive tooth may be placed in the middle of the space or asymmetrically depending on the preference of the restorative dentist. Vertically, teeth can be intruded to improve the positioning of the gingival margin in relation to the 147
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PRACTICE contralateral tooth. Anterior-posteriorly, if a full coverage restoration is planned then leaving a small overjet will help to reduce any palatal reduction. If only a labial veneer is planned then minimal overjet is preferable to allow a maximum thickness of restorative material on the labial aspect. In some cases, where it is not possible to close the space, it may be preferable to maintain a primary tooth in situ to help maintain aesthetics, function and alveolar bone. It can be common to maintain second primary molars if space is not required for correction of the malocclusion. Teeth that have good root morphology and are minimally affected by dental caries may continue to function successfully for many years. The width of the second primary molar can be reduced, by inter proximal enamel reduction, to provide some space for the relief of crowding or to facilitate molar correction if orthodontic treatment is to be undertaken. This may not be possible in some cases due to the divergence of the primary molar roots. Factors that can affect the long-term survival of retained primary teeth include:21 1. Root resorption 2. Infra-occlusion 3. Caries, tooth wear and periodontal disease. Before orthodontic appliances are removed, it is essential that the clinician who will undertake the final restorative treatment examines the patient to ensure that the correct amount of space has been created for tooth replacement and the restoration of microdont teeth. It is essential to take periapical radiographs, perpendicular to any prospective implant site(s), to ensure that the roots are parallel and adequately separated. The minimum interradicular space for a maxillary lateral is 6 mm. Ideally, the vertical space would be at least 7 mm from the alveolar bone crest to the opposing tooth. Following removal of appliances, patients should be provided with robust retainers to maintain the spacing that has been produced and to replace any missing units. It is preferable for patients to wear such appliances full time as they help to improve dental appearance by tooth replacement. Following restoration of the missing teeth, patients can wear retainers on a part-time nightly basis. It is important for the restorative dentist to liaise closely with the orthodontist so that retainers can be adjusted around new restorations to minimise the risk of relapse due to inadequate retainer wear. In patients with severe hypodontia, removable dentures may be the only
Multidisciplinary Planning Informed consent
Diagnostic Kesling set-up
Orthodontics
Pre-debond check
Radiographic assessment to check root seperation
Removal of appliances Restorative phase and retention Fig. 10 The care pathway for the management of hypodontia
treatment option for tooth replacement until an implant-retained prosthesis can be offered at the completion of growth. Overdentures can provide a useful treatment option in those patients with a few available teeth as they can help improve the stability and retention of appliances. Retained roots are also invaluable in helping to maintain alveolar bone volume. In less severe cases, a resin-retained bridge maybe provided as a permanent or semipermanent solution until the patient has matured for implant placement.
THE ESTABLISHED DENTITION The established dentition is considered to be the stage at which the majority of facial growth has occurred and definitive orthodontic treatment, in the case of patients requiring orthognathic surgery and restorative treatment (for example, implants), is undertaken. The age at which facial growth plateaus displays high individual variability, but it is considered to be approximately 18–19 years in males and 17–18 years in females. Growth can be monitored using height measurements. Craniofacial growth is one of the last to reach to adult levels, with some patients exhibiting continued craniofacial growth well into adulthood and old age.22 Serial cephalograms, taken 12 months apart, showing minimal growth provide good evidence for the cessation of the majority of growth. Orthodontics in combination with orthognathic surgery can be considered for those individuals where orthodontic treatment alone cannot be used to camouflage the
skeletal discrepancy. This form of treatment usually involves a preparatory phase of orthodontics (known as pre-surgical orthodontics) to decompensate the malocclusion, and this often makes the malocclusion appear worse. This is followed by jaw repositioning to correct the skeletal discrepancy, facial appearance and occlusion. Orthodontics continues post-surgically to detail the occlusion. This form of treatment should be jointly planned by the orthodontist, oral and maxillofacial surgeon and restorative dentist. As with orthognathic surgery, implant placement should occur at the completion of facial growth to prevent submergence of the implant restoration. This form of treatment should only be considered in those where there is adequate space between roots for implant placement and where there is sufficient alveolar bone volume. In cases with inadequate space between roots, one may need to consider orthodontic space recreation or accept bridgework instead of implants. Some patients can present for orthodontic treatment during their thirties and forties when retained primary teeth begin to fail. Adult patients can be more difficult to treat than children in a number of different respects. They may be less accepting of wearing fixed appliances compared to children and may demand less visible orthodontic appliances, which are usually more difficult for the orthodontist to use. The lack of growth in adults can make space closure and bite opening more difficult. On the other side, adults can be extremely motivated patients and very compliant with maintaining oral hygiene, minimising breakages and keeping regular appointments. The care pathway for the management of adults and children with hypodontia is similar (Fig. 10).
CONCLUSIONS Patients with hypodontia can require complex interdisciplinary care which may start at a young age leading to protracted treatment times and considerable burden to the family. This article has outlined the care pathway and the interaction of the dental specialties and the general dental practitioners in the care for this important group of patients. To summarise, the general dental practitioner has an important role in diagnosis, prevention, referral to the appropriate specialist, treatment planning and undertaking treatment. It is essential that there is good communication between all members of the team involved in patient care and that the treatment plan involves input from all the involved clinicians from the outset. BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Further information • Hobkirk J A, Gill D S, Jones S P et al. Hypodontia: A team approach to management. Wiley-Blackwell, 2011. • Bullying Online: www.bullying.co.uk • Ectodermal Dysplasia Society: www.ectodermaldysplasia.org/ • National Foundation for Ectodermal Dysplasias: www.nfed.org/ 1.
2. 3. 4. 5. 6. 7.
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permanent molars in childhood cancer survivors after chemotherapy. Int J Paediatr Dent 2012; 22: 239–243. Bartzela T N, Carels C E, Bronkhorst E M et al. Tooth agenesis patterns in unilateral cleft lip and palate in humans. Arch Oral Biol 2013; 58: 596–602. Brook A H, Griffin R C, Smith R N et al. Tooth size patterns in patients with hypodontia and supernumerary teeth. Arch Oral Biol 2009; 54(Suppl 1): S63–70. Shalish M, Peck S, Wasserstein A et al. Increased occurrence of dental anomalies associated with infraocclusion of primary molars. Angle Orthod 2010; 80: 440–445. Ruiz-Mealin E V, Parekh S, Jones S P et al. Radiographic study of delayed tooth development in patients with dental agenesis. Am J Orthod Dentofacial Orthop 2012; 141: 307–314. Acharya P N, Jones S P, Moles D et al. A cephalometric study to investigate the skeletal relationships in patients with increasing severity of hypodontia. Angle Orthod 2010; 80: 511–518. Hobkirk J A, Goodman J R, Jones S P. Presenting complaints and findings in a group of patients attending a hypodontia clinic. Br Dent J 1994; 177: 337–339. Laing E R, Cunningham S J, Jones S P et al. The psychosocial impact of hypodontia in children. Am J Orthod Dentofacial Orthop 2010; 137: 35–41. Wisth P J, Thunold K, Boe O E. The craniofacial morphology of individuals with hypodontia. Acta
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Odontol Scan 1974; 32: 281–290. 16. Gill D S, Jones S, Hobkirk J et al. Councelling patients with hypodontia. Dent Update 2008; 35: 344–352. 17. Sacerdoti R, Baccetti T. Dentoskeletal features associated with unilateral or bilateral palatal displacement of Maxillary canines. Angle Orthod 2004; 74: 725–732. 18. Husain J, Burden D, McSherry P. Management of the palatally ectopic maxillary canine. Guideline produced by the Royal College of Surgeons of England, March 2010. 19. Naoumova J, Kurol, Kjellberg H. Extraction of the primary canine as an interceptive treatment in children with palatal displaced canines – part I: shall we extract the primary canine or not? Eur J Orthod 2014; 10.1093/ejo/cju040. [Epub ahead of print]. 20. Kokich V G. Managing orthodontic-restorative treatment for the adolescent patient. In McNamara J A, Brudon W I, eds. Orthodontics and dentofacial orthopedics. . pp 423–452. Ann Arbor, Mich.: Needham Press, 2001. 21. Hvaring C L, Øgaard B, Stenvik A, Birkeland K. The prognosis of retained primary molars without successors: infraocclusion, root resorption and restorations in 111 patients. Eur J Orthod 2014; 36: 26–30. 22. Behrents R G. Growth in the aging craniofacial skeleton. In Monograph 17. Craniofacial Growth Series. Ann Arbor, Mich.: Centre for Human Growth and Development, University of Michigan; 1985.
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