Tải bản đầy đủ - 0 (trang)
1 Rational and Indications for the Use of Immediate Provisional Restorations

1 Rational and Indications for the Use of Immediate Provisional Restorations

Tải bản đầy đủ - 0trang

176



T. R. Schoenbaum and P. R. Klokkevold



Fig. 8.1  The implant-supported screw-retained provisional prosthesis (ISP) is a critical component for predictable treatment of implants in the aesthetic zone. It is used to preserve and shape the

peri-implant soft tissues



zone. It not only maximizes the potential of the peri-implant tissues but allows

all involved the opportunity to evaluate the treatment – in situ prior to the fabrication of the definitive prosthesis.

The ISP provides an environment around the implant which encourages maximum tissue volume through the use of appropriate emergence contours and biocompatible materials [6–10]. It will preserve the initial soft tissue architecture and be

subsequently modified to appropriately position gingival margins and papilla [2, 7,

8, 11–14]. In areas of significant hard and soft tissue defects, the ISP is used to

determine whether or not additional surgical augmentation or pink prosthetic materials are needed to satisfactorily complete the treatment [15–17].

The ISP should be fabricated and delivered at the time of implant placement or

stage 2 uncovering [18, 19].

A removable provisional prosthesis is not capable of preserving and shaping the

soft tissue with the accuracy and delicacy of one supported by the implant. The

movement inherent in a removable provisional restoration may also have a deleterious effect on the potential augmentation and healing of the surgical site. As the

peri-implant wound heals, the development of the circumferential connective tissue

“ring” will occur against the highly polished surface of the ISP [20]. During the

time required for osseointegration, this ring of fibrous tissue will mature and tighten

to enhance the seal at implant-abutment junction (IAJ) as described in Chap. 16.

This area should be left undisturbed for at least 3 months to ensure minimal remodeling of the peri-implant bone and soft tissue [21, 22]. One study demonstrated

histologically that simply removing and replacing healing abutments once a month



8  The Implant-Supported Screw-Retained Provisional Prosthesis



177



resulted in nearly 1 mm of bone loss and 1.5 mm of soft tissue loss compared to

abutments left in place without removal [21]. The integrity of the peri-implant area

is critical to the long-term biological and aesthetic success of the implant and prosthesis. Every effort must be made to avoid disturbing the healing and maturation of

the tissues during the first 3 months after implant placement.

The ISP can theoretically be fabricated with screw retention or cement retention.

This chapter will focus on the use of screw retention [5]. The rationale against the

use of a cemented provisional restoration is that most manufacturers make abutments for cemented provisional restorations out of polyether ether ketone (PEEK)

which is not as strong or durable as titanium. Breakage of the abutment during the

critical integration and maturation phase can greatly compromise the chances for

success. The cemented provisional also introduces a margin (where PEEK, cement,

and the restorative materials meet) in a subgingival wound space. Even assuming

that the clinician was capable of removing all cement, the irregularities at the margin will negatively affect the maturation of the peri-implant tissues [23, 24].

Conversely, the screw-retained provisional can be easily formed and polished to

produce surfaces well suited to the healing tissues. In situations where the implants

are angled facially, these too can have reasonably aesthetic screw-retained provisional restorations fabricated (Fig. 8.2a–d). This applies even to situations wherein

the definitive restoration will be cemented due to angulation concerns. The provisional restoration will be in place during the healing and maturation phase and

should be designed with the health of the tissues as the primary concern. Should the

a



b



c



d



Fig. 8.2  In situations where the implants have been placed such that their straight-line access exits

through the facial, the ISP should still be done as a screw-retained restoration. This can be reasonably

accomplished and avoids the placement of margins and cement into the healing implant site (a–d)



178



T. R. Schoenbaum and P. R. Klokkevold



definitive prosthesis be cement retained, the abutments will be designed with clearly

visible margins, no deeper than 1 mm subgingival [23, 24] as described in Chaps. 12

and 14.

It is challenging to provide definitive criteria for when an implant can be immediately loaded; however available evidence does provide some guidance [18]. For

partially edentulous patients, the immediate implant placement and provisional restoration are best utilized for maxillary incisors or premolars or aesthetic zone FDPs.

As a single tooth, the canines are a poor candidate for immediate loading due to the

large width and length of the root, thus making primary stability of the implant difficult. Additionally, the canine is placed under oblique loads during excursive contact, which are the most problematic for osseointegration. To consider immediate

loading, there must be sufficient bone to engage a reasonable portion of the implant.

For maxillary incisors, this is found in the palatal bone and at the mesial and distal

of the root apex. The amount of the bone that can be engaged depends on the implant

length, width, taper, thread design, and anatomy of the remaining bone. The primary

stability of the implant in the bone is critical to the success of immediate loading.

This stability can be judged by the surgeon using “feel,” the torque required to seat

the implant, or with a device which reads the implant stability quotient (ISQ). There

is no unified agreement on which method is most reliable or what torque or ISQ is

required for immediate loading, though recommendations exist [25]. The

Immediately loaded provisional must be designed well out of occlusal contact in

MIP and throughout the excursive range. This will likely require a tooth that is

thinned out palatally and short at the incisal edge. The patient is instructed to not use

the provisional tooth for any eating purposes. Patient selection and occlusion are

key in this regard, because even with sufficient primary stability, if the immediate

implant is loaded excessively (especially with oblique forces), it is at a significantly

higher risk of failure. Best available data suggest that there is no increased risk by

creating interproximal contacts with the provisional. A more detailed analysis of

occlusion on implant restorations can be found in Chap. 15.

In Sect. 8.2 below, the technical steps to fabricate the provisional restoration will

be described, but should the implant fail to reach sufficient stability at placement,

the implant should not be loaded, and an alternative provisional must be fabricated.

Both a bonded pontic (Fig. 8.3a, b) and an “Essix provisional” can be rapidly produced at the time of surgery. Neither will preserve and shape the soft tissues as well

as the ISP, but nor will they overload a poorly stabilized implant.

The ISP will be fabricated and delivered at the time of implant placement

(Fig. 8.4) or at the stage 2 surgery. As such, it will generally require chairside fabrication. The materials selected for the ISP are based on producing the most biocompatible environment possible [6], eliminating the risk of abutment fracture, and

producing as reasonably aesthetic result. If the implant was placed in a two-stage

approach, an index of the implant position can be made at the stage 1 surgery and

used by a laboratory technician to fabricate a provisional restoration in its entirety

that will be delivered at the stage 2 uncovering. The technical steps for fabrication

of the immediate ISP are described below.



8  The Implant-Supported Screw-Retained Provisional Prosthesis



a



179



b



Fig. 8.3  Should the implant fail to reach sufficient stability at placement, it should not be immediately loaded with the ISP. In such scenarios, alternatives for provisionalization include the use of

a bonded composite pontic (a) or a removable Essix-type retainer. Wings on the pontic as seen here

(b) facilitate accurate placement and are removed after bonding as needed to establish proper

occlusion

Fig. 8.4  The ISP

delivered at the time of

surgery should preserve

and protect the peri-­

implant tissues, while

leaving space for coronal

migration of the papilla

and gingival margin



8.2



 abrication of the Immediate Provisional Prosthesis

F

(ISP)



The implant-supported screw-retained provisional prosthesis (ISP) can be fabricated chairside at the time of implant placement. When done in conjunction with the

extraction of the tooth, this procedure is commonly known as “immediate loading.”

However, it will be designed completely out of occlusion to minimize loading on

the implant. Prior to initiating the procedure, impressions must be made of the areas

and a shade selected for the crown. Parts for the implant to be used will also need to

be ordered in advance. The materials needed are found in Table 8.1.

The preoperative impressions are used by the technician to fabricate the composite provisional shell (Fig.  8.5a–d). This is essentially a crown or a bridge made

by  the laboratory technician out of composite of the appropriate shade. Acrylic



180

Table 8.1  Materials needed

for fabrication of the ISP



a



T. R. Schoenbaum and P. R. Klokkevold

 – Provisional shell (made from composite resin)

 – Titanium provisional abutment with screw

 – Implant analog

 – Composite bonding resin

 – Light-curing unit

 – Flowable composite

 – Opaquing resin

 – Metal cutting disc

 – 30 fluted (red stripe), egg shape carbide (i.e. 7408)

 – Composite polishing instruments



b



c



d



Fig. 8.5  The technician will fabricate composite shells (a) prior to the procedure. These are essentially hollow crown forms (c, d). They should not have the access holes drilled unless a guided

surgical approach is utilized. PMMA and other acrylics are a poor alternative due to their inability

to bond to composite and difficulty in using acrylic in a surgical site. The shells should be designed

out of occlusion (b) to minimize forces to the implant when immediately loading



(i.e., PMMA) is a poor alternative for the provisional shell as using acrylic in and

around a fresh surgical site is challenging at best. Additionally, connecting an

acrylic shell to the abutment with composite resin will typically result in debonding.

The internal aspect of the composite shell should be sandblasted and steam cleaned

prior to use. Alternatives to the composite shell are the patient’s natural tooth or pre-­

existing crown (Fig. 8.6a–e).

The provisional abutment is a critical component in the fabrication of the ISP

(Fig. 8.7a–c). It is responsible for ensuring the integrity of the provisional during the

integration and maturation phases. It also makes up the apical area of the restoration

which will be in contact with the healing tissues. As such, these requirements are

best met only through the use of titanium provisional abutments (as opposed to

PEEK). Titanium has a well-proven record for both strength and biocompatibility.



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

1 Rational and Indications for the Use of Immediate Provisional Restorations

Tải bản đầy đủ ngay(0 tr)

×