The ovate pontic for fixed bridgework

Definition

The ovate pontic11 is an approach for aesthetically demanding anterior bridgework. An ovate pontic design can be defined as one which has an increased amount of mucosal contact and applies light pressure to the underlying mucosa in an attempt to improve aesthetics,^11,12 (Figure 3c). This pontic design has been proposed to address the issue of emergence profile aesthetics. Use of the ovate pontic must be combined with effective oral hygiene procedures so that the mucosal contact and minimal tissue pressure do not become a cause for concern.

History

In the early twentieth century, pontics were designed with extensive mucosal contact and bridges had porcelain root pontics extending into extraction sockets or surgically prepared sites.13 Authors advocated that the porcelain root pontics should extend a short distance into the socket so that the mucosa healed and epithelialized underneath the porcelain roots. However, this technique was associated with poor oral hygiene, inflammation, mucosal swelling and infections; it consequently fell out of favour.

In the mid-1960s, Stein's work confirmed early clinical experience, advocating that mucosal contact and pressure should be avoided.8 The modified ridge lap pontic subsequently became the design of choice. However, once the importance of plaque control in maintaining the adjacent mucosal health was appreciated, clinicians began to revisit and modify pontic designs. The modern, hygienic development of the porcelain root extension design is the ovate pontic.

Periodontal considerations

Research into the periodontal impact of restorative prostheses highlighted the importance of plaque control in maintaining periodontal and mucosal health. Silness et al14 investigated the effects of oral hygiene procedures (interdental brushes and dental floss) on the mucosal and gingival health associated with bridge pontics. This research showed that mucosal and gingival health could be maintained despite the contact and pressure of the pontic if regular, effective oral hygiene procedures were conducted. The key factors for the biological success of any pontic design are in the access for adequate plaque control and the efficacy with which this can be conducted. The histological effects of the mucosal contact have been investigated by Zitzmann et al15 who biopsied comparative sites of mucosa under ovate pontics after 12 months. It was reported that, although there were increased numbers of inflammatory cells and a thinning of the keratinized layer, clinical signs of inflammation were not common. They concluded that the ovate pontic design, if correctly cleansed with bridge floss, was compatible with oral health. The type of material in contact with the mucosa is not critical as long as it is highly polished and the entire pontic's mucosal surface is amenable to cleaning.16 If good oral hygiene is maintained, provisional restorative materials can be used to develop the pontic site and soft tissue form without adverse inflammatory changes in the mucosa.17

Clinical considerations

To optimize plaque control, the ovate pontic must have a highly polished, convex mucosal surface that will aid the passage of floss, allowing it to contact the entire under surface of the pontic. The pontic should be designed so that the convex surface extends into the mucosa by 1–2 mm, depending on the thickness and visco-elastic nature of the mucosa (Figure 6). This mucosal depth creates the appearance of the pontic emerging from the gingival tissues and allows a more realistic tooth replacement. The other reported advantage is that the papillae may be supported and maintained, when used as an immediate replacement, and may reduce the occurrence of ‘black triangles’ which result from the recession of the interdental papillae. A summary of the advantages of the ovate pontic are:

In order for the ovate pontic to be successful, there must be sufficient height and width of alveolar ridge. The early papers reporting this technique advocated surgical augmentation of the pontic site with roll flaps and connective tissue grafts to enhance the emergence profile.^11,12,18 This pontic design is ideal for the anterior maxilla, especially if there is a high smile line or when aesthetic demands are high.19

The development of the recipient sites can involve gingivoplasty or the use of a long-term provisional restoration. The gingivoplasty can be conducted by either the use of high-speed rotary instruments or electrosurgery (Figures 7, 8). Before the site is developed it should be anaesthetized so that the depth and visco-elastic nature of the mucosa can be assessed by bone sounding with a periodontal probe. At least 1 mm of mucosa should be maintained over the underlying alveolar bone. Another important consideration is the distance from the contact point to the underlying crestal bone. If this distance is 5 mm or less, the presence of a papilla is more predictable.20 This requires bone sounding and clear communication to the technician. In cases where there is insufficient mucosal depth, the edentulous space can be grafted prior to restoration to increase tissue depth.^11,18

Electrosurgery should be used with caution, as prolonged tissue contact will cause excessive tissue loss, especially if the mucosa is thin. The timing of the gingivoplasty can also vary. It can be prior to impression taking or immediately prior to the fitting of the definitive restoration. If the former is chosen, a suitable provisional must be constructed to maintain the shape created. The provisional restoration needs to be highly polished, convex and apply light pressure to the area but still allow the passage of floss. It is possible to reline an existing denture or provide a suitably constructed Essix retainer. Following gingivoplasty, the mucosa heals by secondary intention over a period of weeks. With regard to the use of a long-term provisional restoration, the authors of this article would advise that 3 months is a suitable period, but there is little evidence for this.^21,22 The advantages of preparing the recipient site prior to the impression stage are that the clinician can assess the mucosal depth and degree of viscoelastic compression of the tissue. It also gives the clinician more control over the emergence profile of the restoration. If the clinician develops the site at the time of fitting the bridge, the laboratory technician has to estimate the thickness and compression of the mucosa, which is not ideal.

In cases where the pontic site is to be developed at the time of fitting the prosthesis, the technician has to prepare the cast in order to provide sufficient space for the pontic. If a diagnostic wax-up has been used, the position of the pontic and the emergence profile will have been agreed prior to construction of the restoration. A silicone index of this agreed position will aid the technician in determining the correct emergence profile of the pontic. Prior to fitting the bridge, the clinician has to prepare the recipient site to receive the pontic. To guide the process, the clinician can use pressure indicating paste on the pontic which, when seated, will indicate where the mucosal tissue should be removed (Figure 9 a–e).

It is, however, preferable that the ovate pontic position and emergence profile remain a clinical decision. This is in respect of detailed guidance which should be given to the technician, with the site recorded in the impression material. Figure 10 provides a pictorial guide to providing a resin-bonded bridge with an ovate pontic to replace a lateral incisor.

Once the decision has been made to provide a bridge, the ideal situation for excellent aesthetics is where an unrestorable tooth is carefully extracted to preserve the buccal bone and an immediate removable partial denture or provisional bridge is constructed prior to provision of a definitive fixed bridge. The socket fit design of the denture or bridge has a convex acrylic surface that extends 1–2 mm below the gingival margin. During the healing process, this can maintain the gingival architecture and help to reduce the occurrence of ‘black triangles’.21 Once the healing is complete, the definitive fixed restoration can be constructed and the pontic fitted to the cast. It should have the optimal emergence profile to mimic a natural tooth.