Planning for Immediate Loading of Implant-Supported Prostheses: Literature Review

The evolution of dentistry increased the use of osseointegrated implants as a treatment alternative for rehabilitation of multiple or single edentulous areas.^1–3 

According to the conventional protocol, a healing period of 3 to 6 months without loading is necessary after implant placement to allow osseointegration without formation of fibrous tissue.^4–6  After this period, a new surgical procedure is carried out to insert healing caps previously to the prosthesis fabrication.⁵ 

However, considering the need to reduce the time for treatment,⁴  the original protocol was replaced by the 1-step surgical technique^1,7  and immediate loading with provisional or final restorations.^8,9  According to Schiroli³  and Bilhan et al,¹⁰  the immediate loading of implants is a safe procedure with success rates higher than 90%.

Some studies^11,12  demonstrated that several factors are important to enhance treatment success, such as primary stability of the implant, splinting for multiple rehabilitations, reduction of mechanical loading, and fabrication of stable restorations to avoid displacement or removal of the implant. In addition, it is important to obtain adequate positioning of the implant, healing of the soft and bone tissues, and adequate function and esthetics with 1 surgical step.¹³ 

So the success of the immediate loading of implants depends on accurate planning to evaluate bone quality and quantity as well as the biomechanics to reveal alterations that may counterindicate the procedure.¹⁰  Furthermore, the planning should be prosthetically driven to restore comfort, function, and esthetics.

According to this, although radiographic examinations associated with diagnostic waxing have been widely used for planning of treatment with implants,¹⁴  recent technologies are available to increase the accuracy and safety for planning and insertion of implants, such as computerized tomography (CT), virtual planning, prototyping, and computer-guided surgery systems.^15–17 

The aim of this study was to present the factors important for planning of immediate loading of implants through a literature review to provide enough information for treatment success.

The literature review was conducted in the PubMed database including clinical trials, case reports, classical studies, and comparative studies published from 2000 to 2011 with the keywords immediate implant loading, implant-supported prostheses, and implant planning.

The research in the database presented 140 studies. After analysis of the titles and abstracts, 48 studies were selected based on the aim of the present study.

Patients' requirements for faster and esthetic treatment can be provided by the protocol of immediate loading of implants.^18,19 

De Rouck et al²⁰  observed greater papilla maintenance and less gingival recession for restorations inserted immediately after the implant placement than for restorations inserted later. According to the authors, these results demonstrated that the immediate insertion of prostheses attached to the implants provides support to the peri-implant tissues, which is important for treatment esthetics.

Romanos et al²¹  stated that the peri-implant soft tissues are the present focus of implant research because soft-tissue health is critical to the patient's perception of a successful restoration and long-term biofunctionality, and esthetic appearance is mainly based on the stability of the biologic width.

According to this, Tselios et al²²  also demonstrated that immediate prosthesis insertion preserves the bone tissue that supports the gingival tissue, which allows long-term maintenance of soft tissue necessary for treatment esthetics. In addition, the insertion of a fixed prosthesis provides greater comfort to the patient since it presents lower risk to fracture than a removable denture does.¹⁰ 

Raes et al²³  evaluated the soft-tissue dynamics following single immediate and conventional implant treatment in the anterior maxilla. After a 1-year follow-up, the immediate implants demonstrated fairly stable soft-tissue levels with minor cases showing recession, which is important for esthetic success.

Considering the effect of soft-tissue healing on treatment success, Shibly et al²⁴  evaluated 60 patients who were randomly assigned to receive implants with either immediate or conventional loading during 1 year. The results demonstrated that both methods presented a similar outcome regarding treatment success rates and stability of radiographic bone level. However, immediate loading showed better attached gingiva and mucogingival junction harmony with fewer soft-tissue adverse effects.

Considering that the primary stability is also primordial for this treatment modality,^25,26  sufficient bone quality and quantity are required for its indication. Thus, regions presenting severe bone resorption may counterindicate the immediate loading of implants or should be reconstructed by grafts previously to the implants insertion.¹⁹ 

In addition, considering the importance of occlusal equilibrium during the healing phase to allow adequate osseointegration, patients presenting parafunctional habits as bruxism may counterindicate the immediate loading alternative due to risk of implant loss.²⁷  According to Schiroli,³  the osseointegration occurs gradually and may be jeopardized if excessive loading compromises the bone formation at the implant-bone interface.

Bashutski and Wang²⁸  reported that the presence of pathologies and infection in the region of implant placement also counterindicates the immediate loading mainly when the implant will be inserted immediately after exodontia. Similarly, patients with systemic alteration, severe periodontitis, deficient oral hygiene, or smokers should be carefully evaluated for indication of immediate loading protocol.¹⁰ 

Several authors stated that any alteration on implant positioning in relation to the prosthesis during planning may compromise the final result with alteration on occlusal equilibrium, esthetics, and biomechanics.^6,29,30  This should also be considered for the immediate loading treatment to avoid implant instability.⁶ 

According to Askary,³¹  the evaluation of the dental-gingival complex previously to the surgical phase is primordial for an adequate planning. The literature suggests that a correct diagnosis is more important than the implant design and abutment type to restore function and esthetics.^32,33  Thus, Levine³⁴  reported that the clinical evaluation of the edentulous area should consider the patient's smile line, gingival morphology, interarch relation, condition of the adjacent teeth, condition of the supporting tissues, and radiographic examinations.

Hess et al³⁵  demonstrated that if the initial conditions are unfavorable, corrections should be made using reconstructive techniques of soft and/or bone tissue as well as orthodontics to achieve the success. After evaluation of these factors, the immediate loading of the implants and the type of provisional and final restorations can be planned.²⁸ 

The amount of bone tissue is critical for the success of implants' immediate loading since its deficiency may jeopardize the stability and cause gingival recession, loss of papilla, and inadequate positioning.²⁸  So when deficient bone tissue and keratinized mucosa are observed,²⁸  regenerative techniques should be planned during the initial phase of the treatment,³¹  such as guided bone regeneration, grafts of bone, and/or soft tissue³³  or even orthodontic extrusion.^36,37 

Considering the bone density of the region, most studies about immediate loading are limited to the anterior maxillary region.¹⁹  As this region presents adequate bone quality and quantity, most of these reports demonstrated bicortical anchorage and primary stability of the implants. On the other hand, the low bone density of maxilla challenges the immediate loading, mainly for edentulous ridges with severe bone resorption in the posterior region. For these cases, the planning should consider reconstructions before the immediate loading to achieve treatment success.

Besides the planning of the surgical phase, the provisional and final restorations should be also planned for success of immediate loading treatment. According to Jayme et al,¹⁹  rotational forces should be avoided to maintain the stability. Thus, these authors suggested the use of the same abutment for implant insertion as a base for the provisional restoration to avoid the torque necessary for changing the abutments, which could jeopardize the osseointegration.

Similarly, the final restoration should be also planned before the surgical phase³⁸  and inserted after implant placement.^6,39  Thus, recent technologies allow accurate planning for proper prosthesis insertion and adaptation to avoid alterations that may compromise implant stability.

Although conventional methods for implant positioning with immediate loading allow diagnostic waxing, evaluation of occlusion, and fabrication of surgical guides based on the prosthesis, such guides are not used during surgery, which may compromise the implant placements in the adequate position.⁶ 

Several technologies, such as CT, software for virtual planning of implants, and computer-guided surgery systems have been developed.^15–17  The introduction of these methods increased the accuracy and safety for planning and insertion of implants with immediate loading. In addition, it is possible to fabricate the prosthesis before the surgical procedure according to bone quality and density available.⁶ 

According to Angelopoulos and Aghaloo,⁴⁰  the success of implant surgery and restoration relies mostly on diagnostic imaging. In this sense, dental CT is superior to conventional x-ray techniques since it eliminates superimposition and distortion, which provides accurate information about the positions of important structures to determine the implant required. In addition, dental CT enables analysis of the state, quality, and quantity of bone on 2-dimensional and 3-dimensional reformatted images with high spatial resolution. Thus, all the information provided by CT facilitates achievement of a successful implantation.⁴¹ 

The association of the CT to evaluate the bone dimension and the residual ridge contour³³  with the virtual planning allows positioning of the implants according to the bone anatomy and final restoration.²  Thus, the implants can be planned and inserted with greater accuracy and predictability, preserving the anatomical structures.² 

Recently, the softwares for virtual planning provide information to evaluate the bone structure based on the data obtained with tomography and the image of the prosthesis that will be fabricated. The 3-dimensional images can be rotated to visualize the implants, abutments, and prosthesis in relation to the supporting and anatomical structures.¹⁴  Thus, any alteration can be concluded virtually previously to the surgical step, which increases the safety and accuracy of the procedure.

Furthermore, some softwares determine the primary stability that will be achieved through the measurement of bone density, which provides predictability to the protocol of immediate loading of implants.²⁷ 

Considering the need to transfer the virtual planning to the patient's mouth, prototyping has been used to fabricate a physical model of the anatomical region selected in real scale.¹⁹  This model allows planning of the distribution and length of the implants as well as fabrication of an accurate surgical guide.

The technical report of Balshi et al⁴²  described a successful method using CT and virtual planning to conduct 2 surgical procedures (alveoplasty and implant placement) into a single 1-hour procedure with immediate insertion of prosthesis. Similarly, Casap et al⁴³  demonstrated that the association of CT and image-guided planning enables accurate planning of implant number and location to be achieved together with planning for a prefabricated metal frame for immediate loading.

Considering the advancement in implantology planning and restorative methods to replace the conventional techniques, Meloni et al⁴⁴  also evaluated 15 patients treated by software planning and guided flapless surgery with immediate provisional prosthesis delivery in the fully edentulous maxilla. After an 18-month-follow-up, the patients were satisfied with the treatment, and high success rates were achieved. This conclusion is in agreement with the study of Vasak et al,⁴⁵  which observed that the use of CT for template-guided implantation ensures reliable transfer of preoperative computer-assisted planning into surgical practice since all maximum deviations measured in this clinical study were within the safety margins recommended by the planning software.

Thus, this technology not only increases the accuracy and predictability of the implant placement but also provides information for the flapless surgery technique.⁴⁶  This surgical technique is important for the success of immediate loading since it is a less invasive procedure with adequate and faster healing^6,18,39  that favors long-term success.^47,48  However, a case report⁶  associating the virtual planning technology and the flapless surgery for implants' immediate loading demonstrated that this surgical technique should be preceded by evaluation of angulation and contour of the residual ridge to avoid perforations in the cortical layer.

Casap et al³⁹  presented a case report of immediate loading with flapless and computer-guided surgery. According to the authors, this technology transfers the detailed digital planning to the surgery, guiding the perforations for implants insertion. Thus, the implants can be positioned according to the ideal position of the prosthesis instead of adapting the prosthesis to the implant distribution.

However, virtual planning presents some limitations, such as high costs to obtain the software, train the professional, and fabricate the guide. On the other hand, this cost can be overcome by faster treatment, predictability of planning, and reduction of risks.⁴⁶ 

CT

computerized tomography