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Space Requirements

Mesiodistal Dimension

  • Space Requirements: A minimum of 7 mm mesiodistal space is necessary for placing a single implant with a 4 mm diameter. This allows for a 1.5 mm distance between the implant and adjacent teeth. When placing adjacent implants, a greater distance is required to maintain proper spacing; a minimum of 3 mm is recommended between two implants.
  • Danger Zones: The mesiodistal danger zones are located 1.0-1.5 mm from adjacent root surfaces. To avoid complications such as bone resorption and compromised restoration outcomes, implants should be positioned at least 1.5 mm from neighbouring roots (Esposito et al., 1993). Failure to do so may result in loss of interproximal bone and reduced papillary height, leading to poor embrasure forms and emergence profiles.

 

Orofacial Dimension

  • Comfort Zone: The implant shoulder should be positioned within the orofacial comfort zone, which is approximately 1.5-2.0 mm wide from the ideal emergence point.
  • Facial Danger Zone: Placing the implant too far facially can lead to soft-tissue recession and complications with the restoration due to reduced thickness of the facial bone wall.
  • Palatal Danger Zone: Positioning the implant more than 2 mm palatal to the emergence line can result in a ridge-lap restoration design, which may lead to aesthetic and functional issues. The facial bone wall should ideally measure at least 2 mm in thickness to ensure adequate soft-tissue support and avoid resorption.

 

Coronoapical Dimension

In the coronoapical dimension, the ideal positioning of implants is crucial for aesthetic and functional outcomes. For tissue-level implants, the shoulder should be approximately 1 mm apical to the cemento-enamel junction (CEJ) of the adjacent tooth (Buser & von Arx, 2000; Buser et al., 2004). In contrast, for bone-level implants, the ideal distance is 3-4 mm apical to the CEJ to accommodate the bone levels and soft tissue contours.

This placement ensures that the implant shoulder is about 2 mm apical to the mid-facial gingival margin of the restoration. This positioning can be precisely determined using a surgical template that highlights the planned gingival margin (Higginbottom & Wilson, 1996). For cases without vertical tissue deficiencies, a periodontal probe aligned with the CEJs of adjacent teeth can be used to guide placement (Buser & von Arx, 2000).

It's important to account for variations in the CEJ location depending on the tooth being replaced. For instance, the CEJ of lateral incisors is typically more coronal compared to central incisors or canines. Placing the implant too far apical (3 mm or more) can lead to facial bone resorption and gingival recession. Conversely, positioning the implant shoulder too coronal can result in a visible metal margin and poor emergence profile.

To ensure proper adaptation of the facial flap over the implant site, a short, beveled healing cap can be used. For patients without local bone defects and who do not require bone grafting, soft-tissue grafting may enhance the thickness and contour of the facial mucosa.

 

Digital planning

  • Baseline Scan: A digital scan of the patient’s teeth or a physical model of their teeth to establish a starting reference for treatment (STL file).
  • Wax-Up: A digital or physical model showing the planned restoration of missing teeth, created using wax or a similar material to visualise the final outcome (digital wax-up or scan of analogue wax-up).
  • Cone Beam Computed Tomography: A three-dimensional imaging scan used to capture detailed views of the dental and bone structures, provided in digital file format (CBCT, DICOM files).

 

Implant Numbers

When determining the minimum number of dental implants needed based on the number of teeth being replaced, the following guidelines apply:

  • Anterior Tooth Replacement:
    • One Missing Tooth: Generally, one implant is required to replace a single anterior tooth.
    • Two Missing Teeth: Two implants are typically needed to replace two adjacent anterior teeth.
    • Three Missing Teeth: Either two or three implants may be necessary. The exact number depends on factors such as the spacing and the condition of the surrounding bone and tissues.
    • Four Missing Teeth: Between two and four implants may be required. The number depends on the specific case, including bone quality and the alignment of the remaining teeth.
  • Posterior Tooth Replacement:
    • One Molar: Usually, one or two implants are needed to replace a single posterior molar, depending on factors like bone density and the overall load expected on the implant.
    • Two Molars: Generally, two to three implants are necessary to replace two adjacent posterior molars.
  • Overdentures: For a full arch overdenture, the typical implant requirements are:
    • Maxilla (Upper Jaw): Four implants are usually needed to support an overdenture.
    • Mandible (Lower Jaw): Two implants are generally sufficient for an overdenture, though more may be used depending on specific needs and conditions.