and Treatment Planning: A Surgical Perspective

Fig. 2.1

Successful, aesthetic and functional rehabilitation of patient utilizing graft-less approach to maxilla and mandible. Four implants per jaw were used in an immediate load protocol

Diagnosis and treatment planning of the edentulous patient is a complex and challenging task. Treatment planning of this often older and medically compromised patient population should always begin with a complete medical evaluation. In brief, any uncontrolled disease process that would compromise complete bone and soft-tissue healing should exclude a patient from implant therapy. Diabetes, osteoporosis, and cardiac and vascular disease may be of concern but if controlled are not absolute contraindications for implant therapy [13]. Currently the most concerning and absolute contraindication for implant therapy is intravenous bisphosphonate or other antiresorptive therapies [14].

The surgical evaluation of the patient’s oral condition should be systematic and methodical. The diagnostic criteria are ultimately used by the surgeon to determine the correct course of action to satisfy the three absolute surgical requirements:

  1. 1.

    Space: Adequate inter-arch space required for the prosthesis

     
  2. 2.
    Spread: Adequate A-P spread to support the prosthesis (Fig. 2.2)

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    Fig. 2.2

    The A-P spread is determined by the distance between the lines intersecting the platform of the distal implants and the most anterior implants. The A-P spread should be as large as possible to compensate for the magnified occlusal forces of the cantilever

     
  3. 3.

    Stability: High primary stability of placed dental implants

     
The surgical diagnostic criteria discussed in this chapter will apply to a patient who is being treatment planned for a full-arch, fixed metal-ceramic, hybrid [15], profile [16] or fixed-removable (Marius type) [17] prosthetic appliance. The surgeon must evaluate the following anatomic factors for all restorative options listed:

  1. 1.

    Magnitude of three-dimensional anatomical defect

     
  2. 2.

    The visibility of the prosthetic transition line

     
  3. 3.

    The volume and quality of bone available in the maxillary zones

     
  4. 4.

    Position of the inferior alveolar nerve and mental foramen

     

The prosthetic diagnostic criteria and concerns will be discussed in another publication in this series.

Loss of teeth and subsequent resorption of supporting structures create an anatomical defect within the maxillofacial structures that will have profound influence on the type of the restoration best suited to the patient. Subsequently, the type of restoration selected to satisfy the patient’s condition and desires will determine the implant positions. Therefore, loss of tissue should be assessed first to determine the correct position of the osseous anchorage. Loss of teeth creates a “tooth-only” defect whereas subsequent loss of supporting bone and soft-tissue creates what is termed a “composite defect” [18]. In patients where a tooth-only defect with minimum resorption of the supporting structures has occurred, a metal-ceramic implant-supported appliance is most aesthetic and appropriate. However, in most cases edentulous patients present with varying degrees of horizontal as well as vertical composite defect. To assess the magnitude of the resorptive defect, a dental set-up with appropriate tooth position, inter-arch relationship and occlusion must be fabricated. The denture set-up is subsequently duplicated in a transparent clear acrylic and worn by the patient. With the clear denture in place two dimensions are measured:

  1. 1.
    The relative space between the cervical line of the denture teeth to the residual ridge: This measurement represents the available restorative space (Fig. 2.3).

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    Fig. 2.3

    Assessment of available restorative space by utilization of clear acrylic dental set-up. Note the distance from planned incisal edge to the existing alveolar ridge. Horizontal and vertical relationship between the incisal edge and the alveolar ridge can be measured

     
  2. 2.

    The facial surface of teeth to apex of the residual crest, representing the lip support requirements.

     
With the data available from these two measurements the restorative and surgical clinicians can determine the appropriate appliance for the patient. The decision to fabricate a metal-ceramic appliance with or without pink ceramic gingiva vs. a hybrid appliance is made by the restorative dentist based on the relative position of the proposed teeth to the existing ridge. The surgical specialist must have a clear understanding of the space required to satisfy the aesthetic and structural requirements of the planned appliance [19, 20]. In the case of a hybrid appliance roughly 15 mm of space is required per arch measured from the incisal edge to implant platform. The management of restorative space is an absolute prosthetic requirement but a surgical responsibility. If insufficient inter-arch space is detected, then space should be created. Most often the creation of space is accomplished by bone reduction or alveolectomy. The surgeon and restorative dentist should collaborate on determination of the magnitude of bone reduction required in each of the jaws to satisfy prosthetic requirements. The dimensions of alveolectomy are communicated to the surgeon by the “bone reduction guide ”. This surgical stent is a tissue- or tooth-supported acrylic stent fabricated on an altered plaster model with markings for reduction (Fig. 2.4).

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Fig. 2.4

Examples of both tooth- and tissue-borne bone reduction guides. This guide is used by the surgeon to determine the desired position of the alveolar platform for implant placement. The final incisal-edge position is simulated in the stent and surgeon removes appropriate height of alveolar bone to assure sufficient restorative space and proper prosthetic labial contours

A large horizontal deficiency will create a prosthetic ledge which will be both unaesthetic and unhygienic for the patient. The surgeon may alter the vertical position of the dental implants relative to the incisal edge to allow for an appropriate labial curvature of the appliance. The available vertical dimensions of the bone must be taken into consideration. If insufficient vertical bone dimension exists to allow appropriate vertical position of the implants then a fixed-removable appliance with flange such as Marius Bridge may be selected [17].

The next step in clinical evaluation of patient is assessment of the “transition line”. This line represents the junction of the dental prosthesis and residual alveolar gingiva. The failure to assess the visibility of the transition line may result in an unaesthetic outcome for the patient (Fig. 2.5). The transition line may become visible during normal animation of the lips particularly during smiling. The edentulous patients’ typical hesitation to smile during examination may be source of underestimation of the exposure. Therefore, the evaluation of the lip animation should begin during the initial conversations with patients. Next, lip length is measured from subnasale to stomion during maximal animation with the denture in place (Fig. 2.6). Subsequently the denture is removed and patient asked to smile and verified with measurement of lip length. Any visible alveolar ridge during the maximal smiling is noted and measured. Ideally in an edentulous patient the final transition line should be 3–5 mm above the highest animated smile line. For an edentulous patient with a visible ridge on smiling, the decision to conserve or resect alveolar bone is based on the patient’s aesthetic demands. If artificial ceramic or acrylic gingiva is unacceptable to the patient then the dental implants will have to be placed in precise teeth positions and a metal-ceramic prosthesis of appropriate teeth proportions constructed. If a patient has a composite defect and the ridge is visible then metal-ceramic prosthesis may not be feasible. In this class of patients teeth will appear long and unaesthetic without gingival coloured soft-tissue component. In a situation where alveolar ridge is visible and artificial gingiva are not of aesthetic concern to the patient then alveolar resection is indicated. Extra attention should be paid to patients with short or hyperactive lips. The dimension of alveolar reduction will be the sum of visible ridge measurement plus an additional 3–5 mm of reduction. The entire visible alveolar ridge from the premaxilla to the tuberosity must be considered when planning for alveolectomy. Once the vertical dimensions of alveolectomy in all zones of the maxilla or mandible are determined the patient radiographs will be evaluated to assess the anticipated remaining alveolar bone below the sinus and nasal cavity and above the inferior alveolar nerve.

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Dec 6, 2018 | Posted by in General Dentistry | Comments Off on and Treatment Planning: A Surgical Perspective
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