Journey for a smile: multidisciplinary management of oligodontia. Case report

Case report

A 29-year-old male patient from Kandy, Sri Lanka presented to our clinic requesting treatment for what he felt was an unpleasant smile, and replacement of missing teeth. He was an undergraduate student who had not sought dental treatment during his childhood owing to a lack of awareness. He recalled the presence of retained lower anterior primary teeth at the age of 17 years, which exfoliated spontaneously. He reported no significant past medical history, neither was any abnormality detected on general examination suggestive of any genetic syndromes or non-syndromic isolated traits, such as Down's, Van der Woude, ectodermal dysplasia and cleft lip and palate. The patient was born to non-consanguineous parents. His family revealed no relevant history associated with similar dental or craniofacial abnormalities.

The patient had a Class III skeletal relationship and a concave facial profile. His lips were competent and everted, and he revealed a low smile line. He attempted to camouflage his aesthetic dental issues with a full beard (Figure 1).

The patient's gingiva was a healthy, thick-flat biotype and racially pigmented. His oral hygiene status was satisfactory. The teeth present were bilateral permanent central incisors, second premolars, and first molars in the upper arch, and bilateral permanent first premolars and first molars in the lower arch with retained primary canines, lower second molars, and several retained roots. An obvious dental asymmetry was observed as a result of the distribution of retained primary teeth (Figure 2).

Tooth wear was evident at the retained primary teeth and an abfraction lesion was present on the upper left deciduous canine. All the retained primary teeth exhibited gingival recession. The lower right canine had a clinical pulp exposure without accompanying symptoms. Except for the central incisors and upper first molars, all the other existing permanent teeth were normal in size and shape. A prominent median diastema was present and the edentulous ridges were poorly developed both vertically and horizontally.

Radiographic examination (OPG) confirmed the developmental absence of permanent teeth. The OPG further revealed that all the retained primary teeth had good bone support and unremarkable peri-apical tissues, except for the remaining primary incisal root, which was retained with less bone support and tooth substance (Figure 3).

The patient was informed about possible treatment options including:

Considering the patient's dentition and the remaining hard and soft tissue structure, conventional removable prostheses were considered the most realistic option for the restoration of the missing teeth and which would restore the multiple missing teeth, and soft tissues. The patient favoured this option for its less invasive treatment procedures and lower cost.

The informed verbal and written consent was obtained, and a multidisciplinary treatment was formulated that was split into four treatment phases.

Phase I: pre-orthodontic phase

The patient was introduced to the modified Bass brushing technique, using less abrasive fluoride toothpaste and a soft toothbrush. After full mouth scaling and polishing, tooth flossing was demonstrated. Root canal treatment was performed at the lower right deciduous canine and all the tooth wear and abfraction lesions were restored using composite resin. The left deciduous incisal roots were extracted owing to their poor prognosis.

Provisional upper and lower all-acrylic resin removable partial dentures (RPDs) were constructed to increase the occlusal vertical dimension (OVD) and to fulfill the patient's immediate aesthetic and functional needs. The dentures helped to re-establish his occlusion by replacing missing teeth and allowed the patient to become familiar with RPDs. A preliminary denture design was carried out and discussed with the orthodontist to aid in formulating and communicating an ortho-restorative dentistry combined treatment plan.

Phase II: orthodontic treatment

The orthodontic treatment goals were to correct the median diastema, align and derotate the upper premolars, extrude upper premolars to the proposed occlusal plane, and improve the incisal relationship by proclining and intruding the upper central incisors. These aims were achieved orthodontically with an upper pre-adjusted edgewise appliance (0.022″ ×0.028″) with MBT prescription.

The patient was reviewed at 4–6-month intervals regarding his prosthodontic–restorative needs during orthodontic treatment. Frequent modifications to the dentures were carried out to improve retention and aesthetics. The patient was monitored for oral hygiene maintenance and assisted with professional plaque control methods where needed (Figure 4).

After completing orthodontic treatment over 20 months, a fixed bonded orthodontic retainer was fitted on the central incisors palatally to avoid relapse. Advanced restorative treatments were commenced after 6 months of the orthodontic retentive period.

Phase III: prosthetic phase

A contemporary set of diagnostic casts was mounted in a semi-adjustable articulator using a facebow (ear bow type arbitrary facebow) centric and lateral relation records. Diagnostic tooth set-ups were constructed for demonstration of the final planned aesthetic outcome to the patient and the restorative team (Figure 5).

Deciduous canines were minimally prepared to receive metal-alloy copings and for use as overdenture abutments. Cast metal-alloy copings were cemented using luting glass ionomer cement (luting GIC) (GC gold, Fuji, Japan). Replacement upper and lower provisional overdentures were constructed to the predetermined OVD. All the upper and lower posterior teeth were restored with direct composite resin restorations using a vacuum-formed thermoplastic matrix constructed on the duplicated diagnostic tooth set-up models.

According to the preliminary denture design, the lower deciduous molars were planned for surveyed crowns. The preparation margin was finished at the most bulbous part of the tooth with a chamfer margin to reduce the removal of healthy tooth tissue. Occlusal surface preparation was not performed on the natural tooth structure as composite resin had already been placed. A definitive impression was made with a light body and putty silicone material (3M ESPE Express VPS, USA). Metal-alloy surveyed crowns were designed and with disto-occlusal rests and mesio-buccal undercuts. Finally, the crowns were cemented using luting GIC (Figure 6).

During the period of orthodontic treatment, the patient experienced localized inflammatory gingival enlargement at the upper central incisors for which he needed professional plaque control support frequently. This condition persisted even after the completion of the orthodontic treatments and he was found to have pseudo pockets and bleeding on probing. Therefore, non-surgical root surface debridement was arranged and the gingivae regained health in colour and texture. However, fibrous sub-gingival pockets persisted at the labial aspect. Gingivectomy combined with gingivoplasty on the labial aspect of the central incisors was performed under local anaesthesia to improve the size and shape of the central incisors (Figure 7).

After a healing period of 2 weeks, composite resin restorations were bonded to the distal surface of the upper central incisor teeth to increase the width, and thereby improve the height-to-width ratio of the teeth.

The preliminary denture design was used as the design for the definitive cobalt–chrome-based RPD (Figure 8a). Following necessary tooth preparations for the definitive RPD, impressions were made using regular body vinyl polysiloxane impression material (3M ESPE Express VPS). Metal frameworks were tried intra-orally (Figure 8b) and occlusal registration was performed to the predetermined OVD.

The prosthetic tooth shade was matched to the existing upper central incisors. The trial dentures were checked for occlusion and aesthetics. Once the patient was satisfied with the aesthetics and tooth arrangement, the finished cobalt–chrome dentures were processed and delivered to the patient.

Phase IV: review and maintenance

The patient was comfortable with the prostheses and was happy about his dental appearance (Figure 9). Orthodontic wire was in place and no unexpected tooth movement was visible throughout the follow-up period. He was recalled at 3-monthly intervals to identify any complications, and then followed up biannually for review visits.

Discussion

Tooth development is a complex process involving multiple genes. Hypodontia may occur as part of a recognized genetic syndrome, or as a non-syndromic isolated trait. Syndromic hypodontia can occur with syndromes such as Down's, Van der Woude, ectodermal dysplasia and cleft lip and palate.⁶ Recent genetic discoveries have identified variant genes that are responsible for non-syndromic hypodontia. These are mainly pathogenic variants of AXIN2, EDAR, FGFR1, GREM2, IRF6, LRP6, MSX1, PAX9 or WNT10B, WNT10A and EDA, which can be inherited in an autosomal dominant, autosomal recessive or sex-linked manner.⁷

The diagnosis of severe type of hypodontia can have several implications for the affected individual and their family. Therefore psychosocial, medical, educational, functional and financial implications should be addressed, as well as any dental problems.⁸

Depending upon a variety of factors, restoration of the missing teeth may be achieved through adhesive bridges, conventional prostheses, implant-supported fixed or removable prostheses, auto-transplantation, or a combination of some or all these modalities.⁹ Resin-bonded bridges or conventional bridges are not possible options for restoring long-span and multiple missing teeth. Implant-supported prostheses require adequate volume of alveolar bone and soft tissues. Patients who lack adequate tissue volume will need time-consuming surgical planning for bone and soft tissue augmentation, and the surgical journey may be complex and can be very long. Therefore, in oligodontia, RPDs are a predictable solution to replace soft and hard tissue deficiencies.¹⁰

Despite the various treatment options available, the presence of retained deciduous teeth, with the absence of permanent successors is often a challenge in treatment planning. The clinician must decide whether to retain the deciduous tooth, or commit to its removal and replacement as part of a comprehensive restorative treatment plan. Survival of retained deciduous teeth with associated tooth aplasia has been found to be high (83–93%).¹¹ Prognostic factors for deciduous tooth survival have been reviewed in the literature and include deciduous tooth type, degree of root resorption, the presence of infra-occlusion/submergence, presence of caries, periodontal health, and the restorative status of the tooth.¹¹ It has also been shown that retaining maxillary and mandibular primary canines and primary second molars can have a better prognosis when compared to primary incisors and first molars.¹² The retention of lower primary second molars affected by infra-occlusion (0.5–4.5 mm) has been reported in 55% of study cases.¹³ However, these teeth can be retained to improve function and aesthetics if the root and crown structures are stable.¹² Furthermore, root resorption has been described as slow if primary lower second molars were retained until the age of 20 years of age, and following this age their prognosis is very good over the long term.¹³

Extraction of successfully surviving lower second primary molars aimed at space closure or implant placement is not advisable in hypodontia patients because there is difficulty in closing space without adversely affecting the facial profile.^5,12 However, retained primary teeth in an unsuitable position are challenging as they often cannot be moved orthodontically without root resorption. In such instances, rather than extracting the tooth, it may be desirable to retain them provisionally to maintain appearance, alveolar bone and masticatory function.⁵ The benefit of this approach is that minimal maintenance will be required and the primary tooth is likely to preserve the bone and soft tissue architecture.¹⁴ In addition, early removal of primary teeth may compromise future restorative management, particularly the placement of dental implants. It has been calculated that the alveolar ridge narrows by 25% in the succeeding 4 years following the extraction of primary second molars.¹⁵

Therefore, infra-occluded primary molars can be provided with indirect restorations to improve function. When the treatment involves an increase in the vertical dimension, primary molars that are being retained are often restored in this manner.⁵ In such circumstances, no or minimal tooth preparation with a cervical chamfer margin is required if the tooth has a moderate taper. Occlusal reduction may also not be necessary.¹⁰ Effects of building up the deciduous teeth remain uncertain, where some authors mention that the occlusal loading may become less favourable and the long contact points of the built-up tooth with adjacent teeth may result in oral hygiene problems.¹⁴ Such restorations can be designed to assist in the support and retention of the definitive partial denture too, as in this presented case.^2,10

Achieving the main biomechanical principles of a metal-alloy RPD becomes challenging in hypodontia patients. Metal-alloy denture support is gained by occlusal rests.¹⁶ With microdontic teeth, retained deciduous teeth and tilted or malpositioned teeth, the main problem is adequately achieving retentive undercuts for clasp units. This can be overcome with orthodontics and/or restorative modification of teeth.^3,5 In addition to orthodontic treatment, surveyed crowns and indirect overdenture abutments have been used to gain adequate retention and support. Usually, the minimum length of a cobalt–chrome clasp should be 15 mm, but a premolar or a canine will require less than this, which makes the clasp stiffer as a result of its shorter length. If an occlusally approaching clasp is indicated for a premolar, it should be made of wrought wire. Therefore, wrought wire may provide a more flexible and aesthetic clasp on premolars.¹⁶ Additionally, there are instances where clasps can be used for stability more than for retention. Therefore, a short cobalt–chrome occlusally approaching clasp can be placed on a non-undercut area of a premolar to gain bracing and some amount of retention through the frictional contact with the tooth.¹⁶

Prepared overdenture abutments are susceptible to caries. Topical fluoride application and the use of dentine bonding agents and metal copings can prevent caries progression.¹⁷ However, secondary caries and periodontal conditions can be associated with metal copings and composite resin copings. Therefore, fluoride-releasing materials, such as GIC or compomers, can be used to cement the copings and to prevent caries.¹⁸

The patient should be thoroughly instructed to maintain oral and prosthetic hygiene as a routine. If patients have good manual dexterity and motivation for maintaining oral hygiene, they are good candidates for prosthetic rehabilitation. At each recall visit, the patient should be examined and oral hygiene be reinforced, as well as checking for any defects in the restorations that need to be repaired.

In the maintenance phase, several problems and challenges were expected. Even though the literature-based studies express a satisfactory longevity of the posterior composites, restoration fractures or chips were expected.¹⁹ The patient was informed about this matter and was educated regarding other possible treatment options to be considered. These included indirect restorations (porcelain and metal crowns) on the posterior permanent teeth that bore the metal denture supportive and retentive elements, the implant-retained prosthetic rehabilitation option that would need soft tissue and bone augmentation procedures prior to implant therapy.

Conclusion

A successful outcome can be anticipated for a hypodontia patient through good communication between the multidisciplinary professional team and the patient. Correct diagnosis and treatment planning will aid in good clinical outcomes. These patients will most likely require combined orthodontic and restorative dentistry advanced treatments that will need life-long maintenance.