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Hypodontia: Etiology, Clinical Features, and Management

Hypodontia: Etiology, Clinical Features, and Management

Surgery

Hypodontia: Etiology, clinical features, and management

Parmanand J. Dhanrajani, FRACDS, FDSRCS, FFDRCSP

Patients who are congenitaliy missing one or more are Irequently encountered in routine practice. The etiology, classilication, and clinical leatures o! are reviewed, and treatment modalities are disoussed. One case ot m i Id-to-mode rate hypodontia and one case of severe hypcdontia are described. Osseointegrated implants have provided encouraging results, especially in patients who are missing ante- rior teeth or who have severe hypodontia. (Quintessence Int 2002:33:294-302)

Keywords: hypodontia, osseointegrated implant,

ypodontia is defined as the developmental ah- The developmental disruption arising from the H sence of one tooth or more. The absence of ali presence of cleft lip and palate involving the alveolus teeth () is rare, Hypodontia may present may aiso rcsuit in an ahsence of teeth in that region, with varying degrees of severity, and severe hypodon- notably the maxillary lateral ."** tia has been defined as the absence of six teeth or more, excluding third molars.' The term oligodontia is used to define deveiop- CLASSIFICATION mental absence of multiple teeth, usually associated with systemic manifestations.- Partial anodontia, a There is no consensus on classification of hypodontia contradictory term, was once widely used but is now in the literature. It is commonly classified according to obsolete. the severity of the condition'-*:

1. Mild-to-moderate hypodontia: Absence of usu- ETIOLOGY ally two teeth or more but fewer than six teeth, excluding third molars {Fig f). Hypodontia may arise as a familial condition; a high 2. Severe hypodontia: Ahsence of six teeth or more, proportion of affected individuals are members of fam- excluding third molars. It may be associated with ilies with a previous history of the condition.' The na- (Fig 2). ture of the inheritance is complex and not well under- 3. Oligodontia; Absence of multiple teeth, usually stood."*' Hypodontia may also arise in individuals with associated with systemic manifestations. no hereditary history.^ Hypodontia is aiso a common presenting feature in a numher of systemic conditions, such as hypohidrotic PREVALENCE eetodermal dysplasia, Down syndrome, and chon- droectodermal dysplasia.'^ Hypodontia in the permanent dentition occurs in 'S.i^k to 6-5% of the normal popuiation; females are af- fected more frequently than males by a ratio of 3:2.' Severe hypodontia of the permanent dentition occurs •'Consultant, Oral Surgery and Oral (uledicirie, Riyadh Dehtal Center, Riyadh, Saudi Arabia. in 0.3% of the popuiation. In the primary dentition, Reprint requests: Dr R J. Dhanrajani, Riyadh Dental Center, PO Box 704, the prevaience is O.f/n to 0,9%, and there is no signifi- Riyadh 11373, Saudi Arabia E-mail: [email protected] cant sex distribution.

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Fig 1 Miid-to-moderate tiypodontia. Both maxiilary iaterai inoisors and the mandibular ieft central inoiscr (arrows) are missing.

Rg 2 Severe hypodontia. Severai teeth are missing, ottiers are afieoted by mt- crodontia. and some primary teeth are re- tained.

The teeth most commonly affected arc the maxillary lateral incisors, the mandibular and maxillary second 1. The teeth are often microdontic, conical, or ta- premolars, and the mandibular incisors. Hypodontia pered, presenting esthetic and functional problems. involving the maxillary central incisors, the maxillary Preparation of such teeth for fixed restorations and mandibular canines, or the first moiars is rare and may be difficult, and lack of undercut presents re- mostly occurs in patients with severe hypodontia,' tention problems for removable restorations. 2. Eruption of may be delayed or abnormal.'" CLINICAL PRESENTATION 3. Ii the maxillary lateral incisors are microdontic or absent, the maxiliary canines may follow an A number of features have been shown to be associ- ectopic path." ated with hypodontia. These complicate treatment 4. The retained primary teeth may become infraoc- planning and patient management: cluded, resulting in loss of space because of tilting

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of the adjacent permanent teeth. Usually these re- Treatment options.^" tained teeth are ankylosed, and their surgical and 1, No treatment or simple improvement with resin orthodontic implications must he considered,'^ composite: Patients with minimal spacing may 5. The lack of teeth is often associated with a devel- feel that the appearance of their teeth is satisfac- opmental failure of alveolar bone, resulting in an tory. For others, resin composite may be used to apparent atrophy of the ridge and lack of poste- improve tooth appearance by closing a small di- rior support. astema,^" 2, Space closure: The space corresponding to miss- ing lateral incisors may be closed by protraction TREATMENT MODALITIES of the canines and the buccal segments; the final objective is a Class II buccal . Selective In general, the options for treatment depend on the grinding and resin composite can he used to alter severity of the hypodontia. Care requires a team ap- the canines and first premolars to simulate the proach, including pédiatrie, orthodontic, and restora- lateral incisors and canines, respectively,^' tive specialists, and the patient must be treated at an 3, Space opening: The alternative to space closure early age.'^ is to maintain or to create the necessary space The patient and parent must be fully informed for a prosthetic replacement of the missing tooth. about the condition and the aims and objectives of Replacement options include removable partial treatment,'^•' A number of factors must be taken into , conventional fixed partial dentures, account at the time of treatment planning: resin-honded fixed partial dentures, and single- tootb i 1, The age of the patient 2, The number and condition of retained teeth Case report. A 17-year-old Saudi girl was treated in 3, The number of missing teeth the orthodontic clinic of the Riyadh Dental Center, 4, The presence of carious teeth She was an intelligent, cooperative, college student 5, The condition of supporting tissues and conscientious about her oral health and esthetics. 6, The occlusion She was undergoing orthodontic treatment to close 7, The interocclusal rest space the diastemas in her maxillary anterior teeth. Examination revealed good facial symmetry. Class I The following procedures may he considered during occlusion on both sides, congenitally missing maxillary treatment planning: lateral incisors, and retained primary lateral incisors. The maxillary arch showed spacing between the ante- 1, Timely extraction of primary teeth in cases of po- rior teeth; in addition, there was minor crowding of the tential crowding can result in spontaneous space mandihular arch. Radiographie examination revealed closure and may lessen the need for intervention an unerupted supernumerary tooth in the region of the later. missing maxillary left lateral (Fig 3a), 2, Ectopic teeth may require surgical exposure to Objectives of the orthodontic treatment were to facilitate eruption and orthodontic traction, provide adequate space for restoration of missing lat- 3, The removal of enlarged frena and crown-length- eral incisors, to close residual spaces in the maxilla, ening procedures may help in provision of fixed and to correct the crowding of the mandibular ante- prostheses, rior teeth. 4, The removal of infraoccluded primary teeth may She was referred to a specialist to determine the be necessary to facilitate orthodontic or restora- possihility of using Implant-retained teeth to replace tive treatment, the lateral incisors, Worldng in a multidisciphnary ap- 5, may contribute to the overall man- proach, the patient, orthodontist, oral surgeon, agement of hypodontia by closing or redistributing restorative dentist, and dental technician agreed on spaces, Tbis may involve a full range of functional, the following treatment goals: removable, and fixed orthodontic appliances, 1, To remove the supernumerary tooth carefully /W/W or moderate hypodontia without damaging the retained primary left lat- eral incisor The most common situation is absence of maxillary 2, To wait for 1 year to allow complete bone heal- lateral incisors. Patients with congenitally missing ing prior to placement of an implant maxillary lateral incisors may seek orthodontic ther- 3, To restore the maxillary lateral incisors with im- apy as a part of a restorative plan,'^-'^ plant-supported crowns

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Fig 3a Management of •r\ .:\--\.- :.:.--.- - p.>j,j iiia Both pei- manent maKillaty lateial I.'"ICIOC:Í ,=1= i.,iio.iiy. botlT pr,i-nary maxil- lary lateral incisors are retained tieft arrow), and a supernumeraty tooth (right arrows) is present in the area of the Iett lateral incisor.

Fig 3b Bone healing (arrow) after removal of the supernumerary tooth.

Fig 3c Removatüie acrylic resin denture used as a space main- Fig 3d Removable acrylic resin denture m place dJnng the neal- tainer during the healing phase alter stage 1 implant surgery. ing phase.

Fig 3f Periapical radiographs at:er cementat'cn ot the crowhs. Fig 3e Periapical radiographs after stage 2 implant surgery

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Fig 3g Appearance after cementation ot ttie crowns. Fig 3fi Periapical radiographs oí implants atter 7 years of follow- up.

Fig 3i Smile 7 years after treatmenl

Two weeks after the soft tissue healing, an impres- The supernumerary tooth was surgically removed sion was made, and porcelain-fused-to-metal crowns from a palatal approach after administration of local were fabricated. The provisional crowns were replaced anesthesia (Fig 3b), One year following extraction, the with the permanent ones (Fig 3f), The emergence pro- area showed good hone healing. file achieved was excellent, and the patient was very Standard 13- and 15-mm Brânemark implants happy (Fig 3g), (Nobel Biocarc) were placed in the regions of the At the 7-year follow-up, the patient had no com- missing right and left lateral incisors, respectively, plaints (Figs 3h and 3i). under local anesthesia. The patient was given a remov- able acrylic resin pretrial denture as a space main- Severe hypodontia tainer during the healing phase (Figs 3c and 3d), After 4 months of healing, the orthodontic appli- The aforementioned classification of severe hypodon- ances were removed. Stage 2 surgery was carried out tia as a situation in which six permanent teeth or more under local anesthesia. Soft tissue surgery was per- are missing is essentially an epidemiologic definition," formed to achieve good interdental papillae, CeraOne The term is a poor indicator of potential difficulties of (3-mm) abutments (Nobe! Biocare) were secured in treatment (eg, tooth size, shape, position, interocclusal place and tightened with 32 nm of torque (Fig 3e), On rest space, and occlusion). Nevertheless, when larger the same day, provisional acrylic resin crowns were numbers of teeth are missing, the need and demand cemented. for treatment is likely to be greater,^^

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Treatment options. The age of the patient is a most noncontrihutory He was the only child affected in the important consideration during treatment planning. family All the family members tested positive for he- patitis B surface antigen and antibody to hepatitis C 1. Prerestorative orthodontics: Some patients may virus. There was no history of previous blood transfu- require orthodontic intervention to move teeth to sion. The cause of their hepatitis infection could not a favorable position or to extrude submerged teeth he substantiated. Results of tests of his liver function, before restorative procedures are initiated."-'* prothrombin time, and partial thromhoplastin time 2. Restoration with a removable partial denture: were within normal limits. The potentially harmfui effects of removable par- The patient was eager to replace the missing anterior tial dentures are well documented,'-^'" and they teeth with implants. Conventionai fixed partial den- should be used only as a diagnostic appliance or tures were contrai ndicated because of the need for a when they ciearly represent the hest method of long span as weil as the microdontia and retained pri- treatment mary teeth. The following treatment goals were estab- 3. Restoration with a conventional fixed partial lished atter discussion with the patient and his parents: denture: As a general principle, fixed restorations are preferable to removable ones, particularly if 1. To evaluate the width of the anterior alveolar adhesive techniques can he employed. In gen- ridges under local anesthesia for the possibility eral, a conventional porceiain-fused-to-metal of placing implants (The patient refused any fixed prosthesis should be avoided in younger hone augmentation procedures.) patients. A large-span fixed prosthesis always 2. To use selective grinding to modify the tooth in carries the risk of dehonding. area 22 so that it would resemble a lateral incisor 4. Restoration with an implant-retained prosthesis: 3- To use a resin composite buildup on tooth 64 to Implants are one of the best aiternative treatment simulate tooth 23 options for patients with severe hypodontia. Their advantages over removable and conven- After administration of locai anesthesia and under tional fixed prostheses are well documented.""^' strict infection control, three implants (3.3 mm, Nobel Biocare) were installed in both the maxillary and Case report. An 18-year-old Saudi man, a regular mandibular anterior regions. A fixed partial denture patient of the Riyadh Denfal Center, was referred to design was selected rather than individual crowns. The the implantology clinic for evaluation and possibly for direction of the implant in area 21 was not ideal be- replacement of missing teeth with implant-retained cause of a buccal bone deficit. The patient was pre- prostheses. The patient was a cooperative, intelligent, scribed antibiotics (amoxicillin, 500 mg, every 8 college student and hygiene conscious. He had maxil- hours) for 5 days. lary and mandihular acrylic resin removable partial The postoperative phase was uneventful. The pa- dentures, which he did not like to wear. tient refused to wear dentures during the healing Examination revealed the following dental problems: phase. Following 6 months of healing, stage 2 surgery was carried out under local anesthesia. Cover screws 1. Missing teeth: 11(8), 12(7), 13(6}, 22(fO), 23(11), were replaced with the healing abutments, which were 24(12), 31(24), 32(23), 38(17), 41(25), 42(26), then changed to Mirus cone ahutments (Nobel and 48(32) (Fig 4a) Biocare) (Figs 4c and 4d) 2 weeks later. 2. Retained teeth: 54(B), 63(H), and 64(1) Impressions were taken with silicone rubber, and 3. Amalgam-filled teeth: 16(3), 17(2), 26(14), provisionai fixed partial dentures were fabricated. In 27(15), 36(19), and 46(30) the mandibular arch, four anterior teeth were missing, 4. Microdontia of the teeth that were present (Fig 4b) and space was available for more than four teeth. It was decided to increase one tooth rather than to in- Serial radiographs in his chart documented that crease the size of the mandibular incisor, which was tooth 11 had heen removed because of previous esthetically not acceptable to the patient. trauma and tooth 21 was transposed in the area of The esthetics achieved with the acrylic resin provi- tooth 22 (Fig4h). sional prosthesis was not satisfactory, because of tooth Clinical and radiographie examination of the alveo- 22 (Fig 4e)- The insertion holes of the prosthesis were lar ridges in the maxillary and mandibular anterior re- unfavorable in the areas of teeth 13 and 11, It was de- gions revealed that the width of available bone was cided to fabricate a final metal framework in which nof promising. porcelain crowns for teeth 12 and 11 would be one screw-retained unit and teefh 13 and 21 would be sep- A diagnosis of a case of severe hypodontia with mi- arate cement-retained crowns (Figs 4f and 4g), crodontia was established. The family history was

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Fig 4a Management of severe hypodontia. Maxiliary and Fig 4b Panoramic radiograph showing missing teeth, retained mandibular anterior ¡eeth are missing, the teeth that are present , and microdontia (arrows). are affected by micradontia, and three primary teeth are retained.

Fig 4c Stage 2 implan Fig 4d Panoramic radiograph a^er the stage 2 procedure.

Fig 4e Placement of maxillary and mandibular prostheses

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Fig 4f Maxillary right oentral and lateral incisor crowns tabri- Fig 4g Maxiliary ngtit canina and lelt central incisor crowns ce- cateO as a single unit and seoured to tne metal framework with a monted to their melal frameworks. sorew.

Rg 4ti Panoramic radiograph after iinai treaiment Fig 4i Smile atter treatment.

Fig 4i Periapioal radiograph of the maxiiiary prosthesis after 3 years ot toliow-up.

Fig 4k Periapicai radiograph of the mandibular prosthesis atter 3 years of foliow-up.

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