Pre-operative Planning and Implant Exposure

A hollow acrylic transitional restoration should be fabricated based on the original diagnostic preview with respect to the tooth form and position. Additional impressions may be required to incorporate any changes made during the course of treatment to this stage.

Implant exposure

Sound surgical principles to minimize the surgical exposure based on the access required should be employed. A series of surgical approaches to achieve this are described below.

1. Minimal exposure

When adequate tissue is present, the purpose of this phase is to remove tissue for the insertion of the abutment and a transitional restoration. However, the excision of this tissue with a circular punch, for example, may not achieve the ideal position for the gingival margin. It is for this reason that the minimal incision (H - shaped) was devised. This provides an opportunity to assess the contours and manipulate the tissues, if necessary, or to excise them, if more appropriate.

'H - Shaped' Incision

This type of incision is especially useful for:

•  The anterior maxilla or mandible.
•  Accurately identified implant position.
•  Exposure of a single implant.
•  Multiple implants with adequate inter - implant distance

The main incision over the palatal area of the implant and the parallel releasing portions next to the implant approximately 2 mm from the adjacent teeth.The size of the incision and its precise design will depend on the clinical circumstances. Undermining the soft tissue around the implant enables the access incision to be centred over the implant. The amount of tissue elevation is based on the design and size of the cover screw and abutment.

There has to be sufficient access for the removal of hard tissue and soft tissue from the top of the cover screw to enable the abutment to be seated properly. The amount of tissue that needs to be removed is also dependent on the type of connection between implant and abutment. Fitting the Morse taper design requires the least exposure of surgical site, as this is mainly to gain access to the internal area of the morse - taper. The abutment does not need to be seated on the implantbut fits within it. The butt joint connection with the external anti - rotation hexagon requires the greatest attention as it should not damage the implant shoulder or external hex and it needs the greatest amount of exposure

Continuous full - thickness incision

Continuous full - thickness incisions are indicated for a variety of situations outlined below. This type of incision may be used in the maxilla or the mandible; there are, however, certain distinctions that relate to the type of tissue present.
 

Fig.  Shows the cover screw being removed via a small incision. The cover screw fits within the diameter of the implant which facilitates its removal through a small incision.

Fig. shows the preselected abutment is attached at second stage surgery via a small incision, which is greatly enhanced by the nature of the connection between the abutment and the implant. Access to the entire top of the implant is not necessary, nor there is any need to remove bone that has over grown over edge of the implant,it is necessary however to ensure Morse taper has engaged.



Fig. (a): Shows the position of the incision and relationship to the implant to be exposed.



Fig. (b): shows the abutment attached to the implant, the soft tissue overlying the implants has been displaced labially to recreate the labial contours

Maxilla

The maxilla has ample keratinized tissue that covers the entire palate. This tissue is well-attached and more difficult to mobilize. Nevertheless, it is possible to re-position the attached tissue from the palatal to the labial aspect of the implant and to create papilla. This is fortunate, as it is the maxilla that is often more visible.

Mandible

In the mandible, attached keratinized tissue normally atrophies with the underlying bone. As a result there is generally a relatively narrow band of attached tissue available. Typically, in the mandible a crestal incisions is made which bisects the attached tissue, thus positioning the keratinized tissue on the lingual and labial aspects of the implant.

There is no attached tissue available for manipulation on the lingual aspect of the mandibular ridge. On occasion, however, when minimal ridge resorption has takenplace there may be thick band of keratinized tissue on the crest and the labial aspect of the ridge. It is therefore sometimes possible to use this tissue for papillary reconstruction, if required. Mandibular tissue is easily mobilized and therefore readily adapted around the implant.

The full thickness incision is indicated for:

•  Exposure of multiple implants adjacent to each other.
•  Implants where the position cannot be accurately identified
•  Single or multiple implants requiring papillary reconstruction
•  Repositioning of keratinized tissue.

A full - thickness incision is made on palatal aspect of implant. The flap is reflected to expose the implant, thus mobilizing the attached tissue towards the labial aspect of the implant. With the abutment inserted into the implant this would result in a deficiency of tissue on the mesial and distal aspects of the implant. The closure of this deficiency will depend on the need to create a papilla.A supplementary incision, either S - shaped or C - shaped, is normally undertaken after the abutment is attached in order to assess the precise design of the incision. The size, diameter and position of the abutment will clearly influence the soft tissue contours.Narrow abutments provide the maximum space for manoeuvre, as the amount of tissue that needs to be manipulated is minimized.

S-Shaped incision for a mini pedicle flap

The S - shaped incision is indicated where a papilla needs to be developed and was first described by Palacci. This type of incision is essentially designed to create a small pedicle flap, which is repositioned into the interdental area. For multiple implants placed unilaterally the pedicel flaps are designed to position the pedicle on the mesial aspect of the implant. The height of the ridge, the interdental space and thickness of the tissue influence the width of the pedicle. After attachment of the abutment the S-shaped incision started on its distal aspect. The clinician should be able to visualize the final position of the pedicle flap on the mesial aspect of the abutment. The first part of the incision is full thickness and the second part is a split - thickness incision of the periosteum, carried out sub-epithelially. This provides mobility for the pedicle flap without creating a cleft within the marginal epithelium. The first pedicle should be positioned within.The interdental space to accurately assess the starting point for the incision around the second abutment. On completion of the second incision and positioning of the pedicles the flap will lose spontaneously distal to the second implant. The S-shaped incision can also be carried out bilaterally around a single abutment, as long as there is sufficient soft tissue present.

Full - thickness flap with a c-shaped excisional incision

In case where there is adequate soft tissue, both in terms of papillary height and labial bulk, the excision of the epithelium around the attached abutment can be carried out accurately so that the flap fits back to provide full coverage. The amount of tissue excised will influence the gingival margin of the transitional restoration, which can later be altered to further influence the marginal contours of both the labial and interstitial aspects.

Fig. (a): The diagram shows the position of the full thickness incision extending from one tooth to another positioned on the palatal aspect of the implant to be exposed

Fig. : Shows the tissue displaced to the labial with the abutment attached to the implant. The exposed ridge can be seen at either side of the implant. X denotes the distance

Fig.: Shows the manner in which the pedicle flap is used to cover the exposed ridge on one side (A). This enables the elevated flap to be repositioned (B) to it's original position.

Fig. : Shows the labial view of the S - incision demonstrating both the full thickness and sub- epithelial components. The labial displacement of the flap simultaneously results in an apparent increase in the level of the mucosa.

Fig. : Illustrates the use of a double S - incision from the occlusal view. This is only possible when ample tissue is present and when augmentation of the papilla on both sides of the implant is required.

Fig. : Shows the labial view of the double S - incision, demonstrating both the full thickness and the sub-epithelial components as well as the direction in which the two separate pedicle flaps will be moved.

Fig. : Depicts the use of S - incision for the exposure of multiple implants. The exposure of the left maxillary lateral incisor and the canine is seen from the occlusal aspect.

Fig. : Shows the implants with the abutments attached. The incision (full thickness and sub-epithelial) is shown designed to move the pedicle flap towards the mesial of each abutment, effecting closure as illustrated by the arrows.

Fig.: Shows the pedicle flaps repositioned to cover the exposed ridge and the papillae reconstructed. Note that the pedicle flaps forming the papillae have been moved towards the mesial of each implant.

Fig. : Shows the use of the full thickness exposure with supplementary s- incisions for the exposure of four implants replacing the four incisors across the midline.