Constantino Vignato, DMD

Crown preps (and the unexpected challenges they can present) are among my favorite procedures. I love the test of turning my focus to a single tooth for an hour or 2. In our office, we commonly talk about striving to make each one the “best crown ever”—prep design, hemostasis, impressions, temporaries, crown fit, occlusion, and cement all play a role in trying to achieve this.

Implant selection may influence overall clinical success, especially when immediate loading is required. As implants under function have the predominance of load in the crestal portion of the ridge, the bone thickness plays a significant factor in maintenance of that aspect of the bone-to-implant contact (BIC).

 The majority of loading under function occurs at the crestal portion of the implant.

 The thicker the crestal bone around the implant, the better the load handling and preservation of this critical bone over time. Frequently, the thin buccal crestal aspect of bone adjacent to the implant resorbs, which may contribute to soft tissue recession and resultant esthetic compromise. Given time, this may progress to peri-implantitis and compromise the health of the implant. The thicker the crestal bone at the buccal/lingual dimension and between implants or the implant and adjacent natural teeth, the easier it is to preserve that critical crestal bone long term.

 Typically, when the tooth has been or will be lost to periodontal disease or the site has healed, the ridge width at the superior aspect of the ridge is narrower.

 This often results in thin bone thickness adjacent to the implant’s coronal aspect, which has the potential to resorb over time, or is related to homecare issues leading to peri-implantitis and other complications. Soft tissue thickness crestally also plays a factor in bone maintenance with a higher incidence of crestal bone loss reported in
thin biotypes.

Implant design plays a factor with how thick the crestal bone and soft tissue are following implant placement. Platform switching between the implant and abutment has been used to increase soft tissue thickness and aid in preservation of both the hard and soft tissues long term. Traditional implants may result in thinner tissue whereas an implant design that has a platform switch within the crestal portion of the implant will be apical to the implant’s platform. Maintenance of crestal bone is important to long-term success of the implant.

Clinical Benefits of the PRAMA Implant

The PRAMA implant (Sweden & Martina, Due Carrare, PD, Italy) addresses these issues by design, positioning the implant’s platform more coronal than traditional bone level implants (

). This decreases the potential for peri-implantitis by placing the platform more coronal to the biofilm and, therefore, associated bacteria are further from the crestal bone. The PRAMA implant is available in 3 body types designed for use in different bone densities (

). The PRAMA style has a flat self-tapping apex allowing better penetration ability with excellent primary stability. The PRAMA RF (root form) has a rounded apex with a tapered morphology designed specifically for the maxilla and lower density bone clinical situations to create maximum stability due to osseocompression upon insertion into the osteotomy. It is suitable when a crestal sinus elevation will be performed as part of implant placement. The PRAMA SL has deeper, more aggressive threads and is designed for use in less-dense bone (type 3) or in immediate placement into extraction sites to achieve higher BIC and implant stability. The design of the PRAMA neck being parallel in profile allows thicker bone crestally than standard designs with a flared neck (

Bone density plays a factor and correlates to the implant’s thread design. This is especially true in the less-dense bone of the maxilla. Immediate implant placement at the time of extraction has the potential for less BIC, so that thread design plays an important factor in initial implant stability.

 The implant’s thread design correlates to bone density at the time of placement and the deeper the threads, the greater the contact with the socket walls in immediate placement situations. This also plays a factor in implant placement in healed sites, especially in the less-dense bone of the maxilla. Sharper threads provide a self-tapping feature in bone of any density, increasing initial stability with higher insertion torque, permitting immediate loading.

The PRAMA implant is available in 3.8-mm, 4.25-mm, and 5.0-mm diameters with a platform switch to 3.40 mm at the top of the platform in each of the
3 diameters. The hyperbolic curve of the neck has different dimensions, according to the implant diameter (

). This standardizes the restorative components used. With maximizing crestal bone around the implant’s platform in mind, the PRAMA implant is designed with a slight platform switch at bone level or slightly subcrestal upon placement. The neck design provides the surgeon with the option as to placement depth depending on the clinical situation that presents with available neck heights of 1.80, 2.80, and 3.80 mm (

). The concave neck design provides what has been termed bone platform switching, to preserve additional marginal bone beyond the platform switch.

The neck design preserves a ring of marginal bone, reducing stress on the crestal cortical bone. This prevents vascular compression while preserving the peri-implant soft tissue. The implant-abutment connection additionally provides a platform switch with a smaller diameter coronal to the crestal bone. This provides increased space for biologic width, limiting potential bone resorption while stabilizing the soft tissue, ensuring papilla esthetics and its maintenance.

The PRAMA neck has microthreads, which are ideal for soft tissue attachment following healing and also permits osseointegration when in contact with hard tissues, thus making tissue management easier in post-extraction sockets and irregular crests (

). Moreover, it offers the option of a deeper insertion of the implant when needed. Those microgrooves provide mechanical stimulus to help preserve marginal bone, increase the surface area of the implant, and offer the ability of an implant to resist axial loads. The addition of microgrooves on the concave neck provides a bone-preservation strategy, serving a biomechanical purpose to increase implant surface area, reducing stress while promoting crestal bone maintenance under functional loading.

 The enhanced bone volume cervically provides greater resistance to bone resorption, reducing overall stress on the crestal cortex. The strategy of a platform switch and thicker crestal bone around the neck optimizes bone resorption resistance, stabilizing both hard and soft tissue. Additionally, when placing adjacent implants and the mesial-distal space is limited, the concave neck allows for thicker soft tissue, aiding in preservation of the interdental papilla and esthetic maintenance. A frequent occurrence when implants are placed at bone level may present with crestal bone loss over time following restoration of the implants (

). When compared with standard implants, the platform switch afforded by the PRAMA’s design provides thicker hard and soft tissue crestally, which will improve the stability of those delicate tissues (

 Implants with a convergent abutment profile favor axial development of peri-implant connective tissue. Moreover, the microthreaded surface of that convergent neck has been associated with denser and greater connective tissue organization, which may improve the peri-implant soft tissue seal.

Bone loss may result crestally depending on the position of the implant in relation to the crestal bone. Factors that influence that are implant-abutment connection design, implant geometry, implant position, bone density, surface finish material of the implant, and micro gap. Subcrestal implant placement results in greater distance from the implant platform to the crestal bone coronally on the implant. A study reported that mean crestal cortical bone thickness values at the dental implant sites were 0.93 ± 0.75 mm in maxilla and 1.44 ± 1.15 mm
in mandible.

Gingival stability around the implant relates to several factors, including gingival health related to the absence of inflammation and gingival thickness. Thin soft tissue crestally has a tendency to recede (migrate apically) and this becomes more important in patients with thinner soft tissue biotypes. That thinner soft tissue is also more prone to gingival inflammation. The goal to soft tissue maintenance and its underlying hard tissue crestally is creating a thicker gingival cuff to provide tissue stability.

RAMPA (Italian for ramp) refers to the soft tissue’s coronal migration during healing related to the concave (convergent) neck of the PRAMA implant. The convergent neck permits development of thicker gingival soft tissue as healing occurs following implant placement (

). The PRAMA’s microthreads on its neck give the collagen fibers of the gingival tissue an anchorage point on the implant, providing tissue stability. The result is coronal migration of the gingiva, a “ramping” up the convergent neck of the implant (

). The design of the neck allows maintenance of biological width due to the thicker soft tissue and crestal bone long term (

). Thus, esthetics is maintained long term.

Marginal bone loss is also minimized due to the thicker crestal bone when the implant has a convergent neck.

 This decreases the potential for peri-
implant changes that may result when thinner crestal bone is present at the implant’s coronal aspect. A study reported that less peri-implant bone loss occurs around supracrestal implants with convergent transmucosal morphology than implants with parallel or divergent transmucosal morphology.

The use of PRAMA’s transmucosal implant creates a shift of the inflammatory cell infiltrate away from the crestal bone level, thereby decreasing peri-implantitis potential and resulting in better long-term stability of hard and soft tissues.

 Results of a cohort study of 66 PRAMA implants during the 3-year follow-up showed that the implants were stable and free from complications. They indicated a high pink esthetic score and low percentage of bleeding on probing.

 This was supported by another study of 120 implants placed in 53 patients where the PRAMA implant exhibited less peri-implant bone loss than bone level implants regardless of the type of prosthesis used.

A patient presented with a maxillary lateral incisor with failing endodontic treatment performed in the past and hypereruption of the tooth (

). The tooth was extracted, and an immediate PRAMA SL implant (4.25 mm x 10 mm) was placed. Sufficient insertion torque was achieved. A healing abutment was placed and radiograph taken to document placement in relation to the adjacent anatomy (

). An immediate provisional restoration was fabricated, and the soft tissue positioned in a more coronal direction to correct the recession that had been present on the natural tooth (

). The provisional restoration was adjusted to be out of occlusion in all positions to avoid any hampering of osseointegration.

Following a 4-month osseointegration period, the patient was deemed to be ready for fabrication of the final restoration. The patient presented with healthy soft tissue with elimination of the pretreatment recession (

). Removal of the provisional restoration noted healthy soft tissue around the implant’s neck and RAMPA effect had occurred (

). An impression was taken and the lab fabricated the final restoration. Upon insertion of the final restoration, a periapical radiograph was taken demonstrating stability of the crestal bone as compared to the radiograph taken at insertion (

A patient presented with a coronally fractured maxillary premolar following loss of the existing crown. A radiograph was taken to evaluate the tooth (

). The tooth had prior endodontic treatment and was deemed structurally inadequate to restore the tooth due to lack of any coronal tooth structure. The patient was recommended immediate implant placement following extraction. If adequate insertion torque was achieved, an immediate provisional restoration would be placed.

The tooth was extracted under local anesthetic and a PRAMA implant (3.8 x 10 mm with a 2.85-mm neck) was placed at the level of the crest post extraction following osteotomy preparation (

). Although 45 Ncm insertion torque was achieved, it was decided not to provisionalize the implant and a healing abutment would be placed and a radiograph taken (

). A healing abutment was placed, and a radiograph taken to confirm full seating of the healing abutment at the implant’s platform (

). Allograft that was 50% cortical/cancellous graft material was placed into the coronal aspect of the socket around the healing abutment and the site sutured to contain the graft material (

). An OsseoGuard RCM membrane (ZimVie) was placed over the extraction socket with poncho technique using healing abutment.

The patient presented at the 4-month recall appointment and the implant was deemed ready to restore. The healing abutment was removed, and a healing gingival cuff was noted with RAMPA effect present (

). An impression was taken and sent to the lab for fabrication of the restoration. The final restoration was returned to the practice and inserted into the patient. A radiograph was taken to verify restoration seating at the implant’s platform (

). When the radiographs taken at implant placement are compared with the post-restoration radiographs, the crestal bone is noted to have maintained the same position, demonstrating the stability the PRAMA neck provides to hard and soft tissues.

The concave design of the PRAMA implant with its microgrooves allows for thicker crestal bone and soft tissue that improves maintenance of those surrounding tissues.

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Articles

Critical to an implant’s long-term success is tissue stability. We take a deep dive into implant design and how to improve maintenance for implant success.  