David M. Kim

A 10-year prospective clinical and radiographic study of one-stage dental implants.

OBJECTIVE The purpose of this prospective study was to evaluate one-stage dental implants clinically and radiographically after 10 years in function. MATERIAL AND METHODS Twenty-five patients with a total of 68 implants [46 hollow screws (HS) and 22 hollow cylinders (HC)] who previously participated in 5-year prospective clinical study returned for a 10-year follow-up. For each patient, informed consent was obtained, medical and dental history was reviewed and soft and hard tissue conditions were evaluated using the modified plaque index, modified sulcus bleeding index, probing depth, suppuration, attachment level, distance from the implant crown margin to the coronal border of the peri-implant mucosa keratinized mucosa and periapical radiographs to calculate crestal bone-level changes. RESULTS As expected, the mean crestal bone-level changes were the greatest in the first year following restoration placement, while only minimal changes were noticed in the subsequent years. HC implants showed a statistically significant higher mean crestal bone loss when compared with HS implants at year 10. Gender was also statistically significantly related to the mean crestal bone loss at years 1, 3, 5 and 10, with male subjects exhibiting more bone loss than female subjects. However, age and peri-implant soft tissue parameters showed low levels of correlation with the mean crestal bone-level changes, and proved to be weak predictors for the mean crestal bone loss at years 5 and 10. CONCLUSIONS This study confirms that the mean crestal bone loss rates of the HS and HC implants are well within the clinically acceptable parameters. In addition, some of the clinical parameters could be used to assess and predict future crestal bone loss.

A Prospective, Randomized Controlled Preclinical Trial to Evaluate Different Formulations of Biphasic Calcium Phosphate in Combination With a Hydroxyapatite Collagen Membrane to Reconstruct Deficient Alveolar Ridges

Many patients and clinicians would prefer a synthetic particulate bone replacement graft, but most available alloplastic biomaterials have limited osteogenic potential. An alloplast with increased regenerative capacity would be advantageous for the treatment of localized alveolar ridge defects. This prospective, randomized controlled preclinical trial utilized 6 female foxhounds to analyze the osteogenic impact of different formulations of biphasic calcium phosphate (BCP) in combination with an hydroxyapatite-collagen membrane and their ability to reconstruct deficient alveolar ridges for future implant placement. The grafted sites were allowed to heal 3 months, and then trephine biopsies were obtained to perform light microscopic and histomorphometric analyses. All treated sites healed well with no early membrane exposure or adverse soft tissue responses during the healing period. The grafted sites exhibited greater radiopacity than the surrounding native bone with BCP particles seen as radiopaque granules. The graft particles appeared to be well-integrated and no areas of loose particles were observed. Histologic evaluation demonstrated BCP particles embedded in woven bone with dense connective tissue/marrow space. New bone growth was observed around the graft particles as well as within the structure of the graft particulate. There was intimate contact between the graft particles and newly formed bone, and graft particles were bridged by the newly formed bone in all biopsies from the tested groups. The present study results support the potential of these BCP graft particulates to stimulate new bone formation. Clinical studies are recommended to confirm these preclinical findings.

The Combination of Purified Recombinant Human Platelet-Derived Growth Factor-BB and Equine Particulate Bone Graft for Periodontal Regeneration

BACKGROUND The objective of this study is to evaluate the potential for periodontal regeneration of a critical-sized defect with the application of recombinant human platelet-derived growth factor (rhPDGF-BB) combined with either a particulate equine or a β-tricalcium phosphate (β-TCP) matrix. METHODS Critical-sized intrabony 2-wall defects were created bilaterally on the distal surface of the second premolar and the mesial surface of the first molar in nine hounds. Twelve defects received rhPDGF-BB/equine treatment, 12 defects received rhPDGF-BB/β-TCP treatment, and the remaining 12 sites served as sham-surgery controls. The animals were sacrificed after a 10-week healing period. RESULTS Clinical healing was uneventful without obvious signs of overt gingival inflammation. Histologic and histomorphometric analyses revealed statistically that there were differences among the three groups in terms of new bone formation (P <0.001). The amount of test material for both rhPDGF-BB/equine and rhPDGF-BB/β-TCP groups was comparable, but the amount of newly formed bone was significantly higher (P <0.01) in favor of the rhPDGF-BB/equine group. The amount of new cementum formed for the rhPDGF-BB/equine group (4.8 ± 1.3 mm) was significantly higher (P =0.001) than the sham-surgery control group (1.7 ± 1.9 mm). CONCLUSION Both rhPDGF-BB/equine and rhPDGF-BB/β-TCP have the potential to support the regeneration of the periodontal attachment apparatus.

A prospective 9-month human clinical evaluation of Laser-Assisted New Attachment Procedure (LANAP) therapy.

This investigation was designed and implemented as a single-center, prospective study to evaluate the clinical response to the Laser-Assisted New Attachment Procedure (LANAP). Eight patients with advanced periodontitis were enrolled and treated with full-mouth LANAP therapy and monitored for 9 months. Fullmouth clinical measurements, including clinical attachment level (CAL), probing depth (PD), and recession, were provided at baseline and after 9 months of healing by a single calibrated examiner, including a total of 930 sites and 444 sites with initial PD equal to or greater than 5 mm. Clinical results for the 930 sites measured pre- and postoperatively revealed that mean PD was reduced from 4.62 ± 2.29 mm to 3.14 ± 1.48 mm after 9 months (P < .05). CAL decreased from 5.58 ± 2.76 mm to 4.66 ± 2.10 mm (P < .05) and recession increased from 0.86 ± 1.31 mm to 1.52 ± 1.62 after 9 months (P < .05). For the subset of 444 sites with initial PD greater than or equal to 5 mm, the PD decreased from 6.50 ± 2.07 mm to 3.92 ± 1.54 mm (P < .05) and CAL decreased from 7.42 ± 2.70 mm to 5.78 ± 2.06 mm (P < .05). As demonstrated by the clinical evaluation, the majority of treated sites demonstrated clinical improvement. LANAP therapy should be further investigated with long-term clinical trials to compare the stability of clinical results with conventional therapy.

Maintaining interimplant crestal bone height via a combined platform-switched, Laser-Lok implant/abutment system: a proof-of-principle canine study.

Interimplant papillae are critical for achieving esthetic implant-supported restorations in the maxillary esthetic zone. Stable papillary anatomy, however, depends upon a stable volume of underlying crestal bone for support. Multiple studies have documented a critical interimplant distance of 3 mm under which crestal bone resorption occurs. This preclinical proof-of-principle canine study examines a novel implant-abutment system design, combining platform switching with precisely configured laser-ablated abutment and implant microgrooves to maintain interimplant crestal bone at interimplant distances of 2 and 4 mm. Results of this initial preclinical study suggest that it is possible through precise implant/abutment design modifications to place adjacent implants at distances of 2 to 4 mm without inducing subpapillary crestal bone loss.

Early bone formation adjacent to oxidized and machined implant surfaces: a histologic study.

Various designs of dental implants representing different geometries and surface technologies are commercially available for patient treatment. However, data with regard to the biologic events that occur immediately after implant placement, regardless of the surface characteristic, are scarce. It has become a common procedure to perform immediate/early prosthetic loading rather than delayed loading. The goal of this study was to observe the early biologic events of peri-implant healing to understand the role of surface modifications in relation to the early phases of bone integration. The secondary goal was to observe the possible differences in the healing pattern at two oral implant surfaces differing in morphology and roughness (Ra, with Ra values ranging from 0.5 μm (machined surface; MS) to 1.5 μm (oxidized surface; OS). A total of 36 implants were placed in six foxhound dogs, equally divided between machined and oxidized surfaces. Three implants were positioned per hemimandible following a randomization scheme. Each animal was euthanized at a specific time point for histologic observation and histomorphometry: immediately after implant insertion and after 24 hours, 7 days, 15 days, 30 days, and 90 days. The study demonstrated an extremely low bone-implant contact (BIC) for both OS and MS implant surfaces during the first 15 days after implant placement (ranging from 12.9% to 26.9% independent of the implant surface). Increased BIC values were observed only in the 30- and 90-day specimens. The presence and the degradation of residual bone particles acted as centers for new bone formation, with osteoblasts lining osteoid tissue and subsequently woven bone independent of the implant surface characteristics. The bone-forming activity appeared strongly reduced after 30 days of healing and seemed to be complete only in the 90-day specimens, where abundant lamellar bone was evident. There is a continuing effort to develop improved titanium surfaces to achieve more rapid osseointegration and improve BIC, with the ultimate goal of applying occlusal load as early as possible. Since immediate or early implant loading is applied during and not after the first 15 days, the findings in the present study of an extremely low BIC and limited mineralized bone formation for both implant surfaces during the first 15 days after implant placement suggest that the surface roughness may not be a key factor for successful osseointegration of immediately or early loaded implants. Within the limits of this study, it can be stated that osseointegration follows a similar healing pattern with machined and oxidized implant surfaces.

Vertical ridge augmentation using an equine bone and collagen block infused with recombinant human platelet-derived growth factor-BB: a randomized single-masked histologic study in non-human primates.

BACKGROUND This study tests the effectiveness of hydroxyapatite and collagen bone blocks of equine origin (eHAC), infused with recombinant human platelet-derived growth factor-BB (rhPDGF-BB), to augment localized posterior mandibular defects in non-human primates (Papio hamadryas). METHODS Bilateral critical-sized defects simulating severe atrophy were created at the time of the posterior teeth extraction. Test and control blocks (without growth factor) were randomly grafted into the respective sites in each non-human primate. RESULTS All sites exhibited vertical ridge augmentation, with physiologic hard- and soft-tissue integration of the blocks when clinical and histologic examinations were done at 4 months after the vertical ridge augmentation procedure. There was a clear, although non-significant, tendency to increased regeneration in the test sites. As in the first two preclinical studies in this series using canines, experimental eHAC blocks infused with rhPDGF-BB proved to be a predictable and technically viable method to predictably regenerate bone and soft tissue in critical-sized defects. CONCLUSION This investigation supplies additional evidence that eHAC blocks infused with rhPDGF-BB growth factor is a predictable and technically feasible option for vertical augmentation of severely resorbed ridges.

Recombinant human platelet-derived growth factor BB for reconstruction of human large extraction site defects.

This study investigated the ability of growth factor-enhanced matrices combined with a tenting screw scaffolding system and resorbable membrane to regenerate large alveolar extraction site defects. Eight patients were randomized to treatment either with a bovine or equine matrix mixed in a ratio of 1.0 mL (0.3 mg/mL) recombinant human platelet-derived growth factor BB (rh-PDGF-BB) per gram of xenograft and allowed to absorb for 10 minutes. Tenting screws were used to provide additional support, and the growth factor-enhanced particulate matrix was incrementally placed and condensed into the defect and covered by a resorbable membrane. Reentry surgery after 5 months allowed for trephine core biopsies and implant placement. All sites healed well with evidence of bonelike hard tissue that was confirmed histologically as vital bone around the remaining graft particulate in both treatment groups. The results of this study demonstrate the capability of growth factor-enhanced matrices combined with tenting screws and a resorbable membrane to support the reconstruction of large extraction site defects.

Use of Er: YAG laser to decontaminate infected dental implant surface in preparation for reestablishment of bone-to-implant contact

The prevalence of peri-implantitis is of concern to all clinicians participating in implant dentistry. Peri-implant inflammation results in the loss of supporting bone for the implant that may or may not be accompanied by bleeding on probing and suppuration. Early diagnosis and intervention are mandated, but there is a paucity of evidence leading to the most effective therapy. There is agreement that one of the challenges in surgically treating peri-implant defects is the process of cleaning and decontaminating the implant surface, which may be contaminated by bacterial aggregates. This preclinical canine study investigates the erbium:yttrium-aluminum-garnet laser to decontaminate the complex rough surface of the implant by stripping the contaminated oxide layer for induction of hard and soft tissue adaptation to a compromised or failing implant. The results provide evidence of new bone-to-implant contact established at a level representative of the size of the defects. The soft tissues contain little or no evidence of inflammation, which can be interpreted as an arrest of the disease progression process. The results can be translated to a treatment goal of stabilizing the prognosis of an implant that has been compromised.

Equine-derived bone mineral matrix for maxillary sinus floor augmentation: a clinical, radiographic, histologic, and histomorphometric case series.

The objective of this proof-of-principle multicenter case series was to examine the bone regenerative potential of a newly introduced equine-derived bone mineral matrix (Equimatrix) to provide human sinus augmentation for the purpose of implant placement in the posterior maxilla. There were 10 patients requiring 12 maxillary sinus augmentations enrolled in this study. Histologic results at 6 months demonstrated abundant amounts of vital new bone in intimate contact with residual graft particles. Active bridging between residual graft particles with newly regenerated bone was routinely observed in intact core specimens. A mean value of 23.4% vital bone formation was observed at 6 months. This compared favorably with previous results using xenografts to produce bone in the maxillary sinus for the purpose of dental implant placement. Both the qualitative and quantitative results of this case series suggest comparable bone regenerative results at 6 months to bovine-derived xenografts.