19: Basic surgery for implant placement

Chapter 19

Basic surgery for implant placement

This chapter discusses the surgical techniques for implant placement. Three different cases demonstrate individual techniques that can be considered when replacing teeth in different areas of the mouth.

Surgical placement of an implant to replace an upper first molar

Summary

A 55-year-old female presents with pain from UR6, which had been endodontically treated and crowned more than 10 years ago.

History

image Complaint

The patient is complaining of pain from UR6, particularly when biting.

image History of complaint

The tooth was endodontically treated and a porcelain-fused-to-metal crown provided, which had remained functional for approximately 10 years. The patient first started to experience pain when biting on this tooth approximately 1 week ago; since then, the pain has become progressively worse.

image Dental history

The patient has been a regular dental attendee and has had several restorations and extractions throughout the years. The patient is now concerned about the long-term prognosis for her dentition. She is keen to avoid a removable prosthesis.

Examination

image Intraoral examination

The dentition is heavily restored. Most of the posterior teeth are crowned or have intracoronal restorations (< ?xml:namespace prefix = "mbp" />Figure 19.1). The upper central incisors are crowned, and the lateral incisors are restored with labial porcelain veneers. The restorations are functional, albeit with minor defects.

image

Fig 19.1 Occlusal view of maxillary dentition.

UR6 has a porcelain-fused-to-metal crown. The tooth is tender to percussion.

image Radiographic examination

UR6: Single-cone root fillings are noted in the two buccal canals, and obturation voids are noted in the palatal canal. A slight widening of the lamina dura is noted in the mesiobuccal canal (Figure 19.2).

UR7: Single-cone root fillings are present in the buccal canals. The tooth has been restored with cast post and core crown.

UR5: Has a distal–occlusal restoration, with no periapical pathology.

image

Fig 19.2 Radiograph of UR6 showing undercondensed root fillings with radiolucency in the furcation area.

What is the diagnosis and what factors will determine the prognosis of this tooth?

Diagnosis: Chronic periapical periodontitis in UR6.

The prognosis depends on two main factors:

1. Endodontic retreatment

2. Restorability of the tooth

Endodontic retreatment is possible and has a predictable outcome. The removal of existing obturation seems straightforward. However, one should be suspicious of a possible fourth canal (second mesiobuccal). A conscious effort to identify it and, if present, instrument appropriately is imperative in achieving success.

Moreover, the restorability of the tooth has to be determined. Although the tooth may be successfully treated after endodontic retreatment, the long-term prognosis will also depend on the underlying restorability of the tooth. It is advisable to dismantle the extracoronal restoration to investigate the amount of remaining tooth structure.

Once the crown was removed, underneath was primarily a core of composite resin. The mesial margin was subgingival (Figure 19.3), and it would not have been possible to achieve a crown margin on sound tooth structure without carrying out a surgical crown-lengthening procedure.

image

Fig 19.3 Removal of the existing restoration and underlying core, demonstrating lack of adequate coronal dentine.

After discussing the risks and benefits, it was decided to extract the tooth.

What replacement restorations would you consider and why?

1. Conventional three-unit bridge (UR5 to UR7)

Overall, a conventional bridge has a 10-year survival rate of 89.2% and would be cost-effective. However, UR7 is already restored with a post–core crown and would therefore be prone to a higher failure rate. In addition, UR5 has a small intracoronal restoration, and preparing it for a bridge would result in significant loss of healthy tooth tissue.

2. Single-tooth implant crown

A single-tooth implant restoration is independent and does not require support from adjacent teeth. It would provide a long-term successful restoration, with a reported survival rate of 89.4% after 10 years. However, an implant requires a surgical procedure with its related postoperative complications, protracted treatment time, and it is expensive in comparison to conventional options.

After a detailed discussion about the options, the patient chose to have the tooth replaced by an implant-retained crown.

Preimplant assessment

image What factors would you consider when planning an implant to replace a maxillary and a mandibular molar?

See Table 19.1.

Table 19.1 Factors to assess when considering implant replacement of molar teeth

Factor Comments
Anatomical structures Maxillary molar: maxillary sinus (Figure 19.4)
Mandibular molar: inferior dental canal and mandibular foramen (Figure 19.5)
Bone height Adequate bone height for the selected implant length using plain radiograph paralleling technique or a cone beam CT scan.
In the mandible, watch for lingual concavity
Bone width Clinical assessment and cone beam CT scan
Functional and aesthetic outcome Although it is a molar, the final restoration should blend with the adjacent teeth
Implant selection Implant with a wider body diameter is selected. It is desirable to choose an implant with a wider restorative head (platform), which will facilitate a good crown emergence for a molar tooth (Figure 19.6)
image

Fig 19.4 Radiograph showing limited alveolar ridge height due to position of the maxillary sinus floor.

image

Fig 19.5 A cross-sectional view of mental foramen and mandibular canal.

image

Fig 19.6 An appropriate-diameter implant to replace a molar tooth. The shape of the implant allows an ideal emergence for a molar tooth to be developed.

image Describe the surgical technique pertinent to molar region

As outlined in Table 19.1, the maxillary sinus and the mandibular canal are two important limiting anatomical landmarks when surgically placing implants in maxilla and mandible, respectively. It is necessary to drill short of these structures, and in order to prevent damage to the inferior dental nerve, drilling is carried out at least 2 mm short of the canal.

The patient should sign an informed consent prior to surgery. The surgery can usually be performed under local anaesthesia. A crestal incision is extended to include a tooth on either side. A vertical releasing incision can also be made to gain better access. A surgical template is advisable and fabricated using an appropriate technique. A series of drills of widening diameters (Figure 19.7), as supplied by each implant manufacturer, are used to prepare the implant site (Figure 19.8) to the desired length and diameter under copious irrigation, at a low rpm of approximately 700–900. Finally, the implant is inserted using a gentle insertion torque.

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Jan 5, 2015 | Posted by in Implantology | Comments Off on 19: Basic surgery for implant placement
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