Chu, Stephen J.

Achieving primary stability is a critical challenge presented by immediate implant therapy. Surgeons often utilize wider, tapered implants for this purpose, or they use longer implants to achieve primary stability. Both strategies are associated with negative ramifications. Prosthetically guided implant placement must respect biologic principles, such as tooth-implant and implant-implant distance, gap space between the implant and the facial cortex, and, when possible, screw-retention of the prosthesis. A novel implant design geared toward achieving a predictable level of primary stability while adhering to the aforementioned physiologic principles was recently introduced. Both primary and secondary implant stability, along with hard and soft tissue stability, are demonstrated in this study of 107 consecutively placed implants. Rotational and axial stability can be produced with this newly designed implant, along with predictable osseointegration and tissue preservation.

Immediate tooth replacement therapy (ITRT), ie, immediate implant placement and provisional restoration in postextraction sockets, has been shown to achieve favorable outcomes in reference to soft tissue stability and esthetics. However, avoiding socket perforation with uniaxial implants in the anterior maxilla can be challenging due to the inherent anatomy. Dual or co-axis subcrestal angle correction (SAC) implants have been developed to change the restorative angle of the clinical crown restoration subcrestally at the implant-abutment interface to enhance the incidence of screw-retained definitive restorations. An additional benefit of this macrodesign implant feature is variable platform switching (VPS) that increases soft tissue gap distance above the implant platform. The purpose of this prospective study on ITRT in maxillary anterior postextraction sockets was to investigate the effect of SAC with VPS (SAC/VPS) compared to conventional platform-switch–design implants (PS) relative to ridge dimension stability and peri-implant soft tissue thickness. A total of 29 patients had undergone ITRT and received either a PS or SAC/VPS implant; previously described measurements were made compared to the contralateral natural tooth sites. When the comparison of buccal soft tissue thickness was made, SAC/VPS showed a greater increase compared to PS (3.12 mm vs 2.39 mm, respectively) with statistical significance (P = .05). The increase was independent from periodontal phenotype. Therefore, SAC/VPS may increase peri-implant soft tissue thickness and help minimize recession following ITRT.

Immediate tooth replacement therapy (ITRT) in the maxillary anterior sextant is an increasingly frequent treatment option sought by patients and performed by clinicians worldwide. Achieving long-term results that are predictable, stable, esthetic, and healthy is the ultimate goal. This trend also lends itself to minimally invasive surgery as well as defining the procedure to a singular surgical intervention. Preserving and augmenting hard and soft tissues at the time of immediate implant placement provides the best opportunity to achieve these goals. Incorporating an implant with a subcrestal angle correction [SAC] or biaxial feature facilitates screw retention of both provisional and definitive restorations through the cingulum portion of the crown. Compared to uniaxial implants, these implants also feature an extended or variable platform switch [VPS] facially. Measurements of the peri-implant soft tissue thickness 2.0 mm apical to the facial free gingival margin were compared between two groups of 15 consecutively treated patients with different implant designs to evaluate the effect of SAC/VPS for ITRT. The null hypothesis was that there is no difference between uniaxial and biaxial implants with bone grafting and dermis allograft. These authors contend that using a combined hard and soft tissue grafting approach along with SAC/VPS biaxial implants has a synergistic effect on increasing peri-implant soft tissue thickness compared to uniaxial implants.

Extraction and immediate implant placement/restoration in the esthetic zone is clinically challenging; benefits include fewer surgical appointments and maintenance of peri-implant soft tissues throughout the treatment period, and limitations include gingival recession and bone dehiscence during surgery. Macrohybrid implants (large-diameter apical/narrow-diameter occlusal) were placed in 19 patients immediately following the extraction of hopeless maxillary anterior teeth. Immediate restorations were fabricated without occlusal contacts. Pre- and postplacement cone beam computed tomography (CBCT) scans were taken. Nineteen implants were available for recall 13 to 25 months postoperatively. The overall implant cumulative survival rate was 100% (range: 13 to 25 months, mean: 19 months), and mean insertion torque value was 65 Ncm. Mean Pink Esthetic Score was 12.63 at 6 months, and was 13 at the 18- to 24-month follow-up. Mean mesial and distal tooth-to-implant distances immediately after implant placement were 2.55 ± 1.29 mm and 2.29 ± 0.82 mm, respectively. Interproximal bone crest width, distance, and height were maintained at implant platforms, mesially and distally, 18 to 24 months postoperative. The results of this study indicated that the macro-hybrid implant geometry for this immediate surgical/restorative protocol provided excellent and stable 2-year results relative to implant survival (100%), labial plate thickness via CBCT evaluations, tooth-to-implant distances immediately post-implant placement, PES, and interproximal bone crest width, distance, and heights, which were maintained at the implant platforms.

The peri-implant soft tissue seal consists of a connective tissue cuff and a junctional epithelium that is different from the arrangement of periodontium around a natural tooth. However, the peri-implant soft tissue complex lacks Sharpey's fibers, thus offering less resistance to clinical probing and biofilm penetration compared to the natural dentition. Therefore, the proper restorative emergence profile design is essential to facilitate favorable esthetic outcomes and maintain periimplant health. The aim of this article is to review the currently available evidence related to the design of subgingival (critical and subcritical) and supragingival contours of the implant restorative emergence profile (IREP) as well as provide a flowchart for decision-making in clinical practice. Theoretically, the subgingival contours of the crown/abutment complex should mimic the morphology of the root and the cervical third of the anatomic crown as much and as often as possible. However, this is highly dependent upon the three-dimensional spatial position of the implant relative to the hard and soft tissue complex, in addition to the location of the definitive restoration. Frequently, a convex critical contour is required on the facial aspect of a palatally or incisally positioned implant to support an adequate gingival-margin architecture. Conversely, if the implant is placed too far facially, then a flat or concave contour is recommended. In instances where soft tissue support is not needed, the subcritical area may be undercontoured to increase the thickness, height, and stability of the soft tissue cuff.

A preclinical pilot study was performed to evaluate the safety, efficacy, primary stability, and wound healing of a hybrid dental implant with a unique macrogeometry design in which the coronal section is narrower and cylinder-shaped followed by a wider, tapered apical portion, each comprising approximately one half the length of the implant. Eighteen hybrid macrogeometry-designed dental implants were placed bilaterally into three foxhounds in the mandibular third and fourth premolar and first molar (P3, P4, and M1, respectively) extraction sockets of different dimensions immediately following full periosteal flap elevation and removal of teeth without socket grafting. Bone plate thickness, implant position and depth, gap distance, and insertion torque values were measured following implant installation. Surgical sites were healed uneventfully for 3 months, and then samples of soft and hard tissues surrounding the implants were retrieved to perform light microscopic and histomorphometric analyses. All 18 implants were stable and osseointegrated both clinically and radiographically. The analyses revealed that the amount of hard tissue alteration and bone fill that occurred during the healing period was significantly influenced by the thickness of the bone plate, the size of the horizontal buccal gap, and the implant diameter, position, and depth within the extraction socket. The P3 and P4 hybrid implants placed approximately 1.0 mm subcrestal from the interproximal height of bone with less gap distance (≤ 1.0 mm) exhibited minor to modest (1.5 to 2.0 mm) crestal bone remodeling relative to the implant platform. Conversely, M1 implants positioned with greater depth (≥ 2.0 mm) and gap distance (≥ 2.0 mm) that were evaluated in a buccal-lingual dimension exhibited minimal crestal change with first bone-to-implant contact within 1.0 mm (range: 0.00 to 0.89 mm) of the machined-collar surface. The thicker lingual bone plate on all M1 implants was relatively maintained and unaffected. The apical half of the implant provided high initial stability (range: 65 to 100 Ncm). The mean percentage of bone-to-implant contact was 56.34% (range: 40.15% to 72.04%). This preclinical study provided clinical and histologic evidence to support the safety and efficacy of a new hybrid macrogeometry implant design that achieved excellent primary and secondary stability in immediate extraction sockets without grafting.

This paper presents the results of a prospective study on the clinical effect of grafting the buccal gap with platform switching, following flapless tooth extraction and immediate implant placement and provisional restoration, on (1) alterations in buccolingual ridge dimension and (2) midfacial peri-implant soft tissue thickness. Fifty-six patients were placed in one of four treatment groups: (1) a non-platform-switching implant (Non-PS, n = 14); (2) a non-platform-switching implant and bone graft (BG/Non-PS, n = 14); (3) a platform-switching implant (PS, n = 15); and (4) a platform-switching implant and bone graft (BG/PS, n = 13). Buccolingual ridge dimensional change and peri-implant soft tissue thickness at 2 mm below the free gingival margin were measured. Both PS and BG/PS groups showed an increase in buccolingual dimension compared to the contralateral natural tooth site as well as peri-implant soft tissue thickness of > 2.5 mm, clinically. Platform switching was associated with significantly greater midfacial soft tissue thickness than bone grafting (mean ± standard deviation: 2.17 ± 0.04 for Non-PS and 3.55 ± 0.14 for PS). Using platform-switched implants, in conjunction with immediate implant placement and immediate provisional restoration, was associated with a significantly greater stability of ridge dimension and peri-implant soft tissue thickness than using non-platform-switched implants when measured 12 months after placement of the final restoration. Platform switching may help achieve preservation of ridge dimension and enhance the stability of peri-implant soft tissue following immediate implant placement and provisional restoration without bone grafting. Further research is required to assess the long-term outcome.

A prospective cohort clinical study was performed to evaluate the concept and design of a novel macro hybrid implant placed into maxillary anterior postextraction sockets. Thirty-three patients with an equal number of hybrid implants were used to replace nonrestorable single anterior teeth with immediate tooth replacement therapy (immediate implant placement and immediate provisional restoration). The macro features of this hybrid implant are unique in geometry, as it combines two different shapes-a cylindrical coronal and tapered apical portion-into a singular body design, each comprising roughly half of the implant length. The hybrid design of this platform-switched implant also has a subcrestal angle correction, or Co-Axis feature, that facilitates screw-retained restorations. Mean implant survival at 1 year relative to primary stability, labial bone plate thickness with socket grafting at two reference points (L1 and L2), tooth-to-implant interproximal bone crest thickness, and pink esthetic score (PES) were evaluated. A mean insertion torque value of 65 Ncm (range 45 to 100 Ncm) was reached with the use of the tapered apical half of the implant body. No implants failed during an average healing period of 1 year. A labial plate dimension between 1.8 and 2.1 mm was attained immediately posttreatment and remained stable over time. A toothto- implant interdental bone crest distance and dimension of 2.3 to 2.6 mm was reached; it was also sustained at the 1-year follow-up. The average PES was 12.5 (range 9.0 to 14.0), with nearly 90% of treated sites with an "almost perfect" score. This macro hybrid implant in concept and design may be useful in immediate tooth replacement therapy of maxillary anterior postextraction sockets to achieve successful implant survival and esthetic outcomes, specifically labial plate and papilla preservation without midfacial or interdental tissue loss and discoloration.