Comparison of two different techniques for deepithelialization: a split-mouth case series.

AIM: The aim of the present preliminary study was to observe and make a histologic comparison of connective tissue grafts (CTGs) harvested from the lateral palatal mucosa through the use of two different harvesting techniques. MATERIALS AND METHODS: Three patients were enrolled in the study, providing six standardized CTGs. One well-experienced periodontist collected the replacement grafts using two different methods. After outlining the grafts to a fixed dimension, the graft on one side was deepithelialized by a round coarse bur intraorally before harvesting. The graft on the contralateral side was obtained by harvesting from the palate first; subsequently, deepithelialization was performed extraorally with the aid of a no. 15c blade. After finalization, histologic evaluation was performed. RESULTS: No apparent differences were found between the two observed techniques in terms of graft thickness, proportion, and composition. After deepithelialization, epithelial remnants were clearly evident in five out of six cases. Despite being more technique sensitive, the removal of epithelium by bur scored better. Proper graft handling and graft regularity are described as advantages of the more conventional epithelial excision by blade. CONCLUSIONS: Despite the wide use and broad variety of commonly applied techniques of graft deepithelialization, the present authors assume that full excisions with the use of a blade are hardly ever achieved. Despite the unpredictable retrieval of epithelium by blade, graft handling and graft regularity can be proposed as the biggest advantages. On the other hand, the presented novel in situ deepithelialization with a round bur seems to be more predictable.

Screening of Hydroxyapatite Biomaterials for Alveolar Augmentation Using a Rat Calvaria Critical-Size Defect Model: Bone Formation/Maturation and Biomaterials Resolution.

BACKGROUND: Natural (bovine-/equine-/porcine-derived) or synthetic hydroxyapatite (HA) biomaterials appear to be the preferred technologies among clinicians for bone augmentation procedures in preparation for implant dentistry. The aim of this study was to screen candidate HA biomaterials intended for alveolar ridge augmentation relative to their potential to support local bone formation/maturation and to assess biomaterial resorption using a routine critical-size rat calvaria defect model. METHODS: Eighty adult male Sprague Dawley outbred rats obtained from a approved-breeder, randomized into groups of ten, were used. The calvaria defects (ø8 mm) either received sham surgery (empty control), Bio-Oss (bovine HA/reference control), or candidate biomaterials including bovine HA (Cerabone, DirectOss, 403Z013), and bovine (403Z014) or synthetic HA/ß-TCP (Reprobone, Ceraball) constructs. An 8 wk healing interval was used to capture the biomaterials' resolution. RESULTS: All biomaterials displayed biocompatibility. Strict HA biomaterials showed limited, if any, signs of biodegradation/resorption, with the biomaterial area fraction ranging from 22% to 42%. Synthetic HA/ß-TCP constructs showed limited evidence of biodegradation/erosion (biomaterial area fraction ≈30%). Mean linear defect closure in the sham-surgery control approximated 40%. Mean linear defect closure for the Bio-Oss reference control approximated 18% compared with 15-35% for the candidate biomaterials without significant differences between the controls and candidate biomaterials. CONCLUSIONS: None of the candidate HA biomaterials supported local bone formation/maturation beyond the native regenerative potential of this rodent model, pointing to their limitations for regenerative procedures. Biocompatibility and biomaterial dimensional stability could suggest their potential utility as long-term defect fillers.

Early bone formation around immediately placed two-piece tissue-level zirconia implants with a modified surface: an experimental study in the miniature pig mandible.

PURPOSE: To histologically examine early bone formation around transmucosal implants and to evaluate the influence of surface characteristics on early peri-implant bone healing using a miniature pig model. For this, commercially available dental implants with a rough zirconia (YTZP) surface were compared to surface-modified Ti control implants at 4 and 8 weeks after placement. METHODS: Immediately following the extraction of six mandibular premolars, 20 two-piece, tissue-level, screw-shaped YTZP implants (Patent™ Standard Zirconia Implant ø4.1 × 11 mm) with a modified rough blasted before sintering surface were inserted in four adult miniature pigs. In addition, four titanium (Ti) tissue-level implants (Straumann® Standard RN ø4.1 × 10 mm Roxolid®) with a moderate surface (SLActive®), one per animal, were placed as control implants. A histological analysis was performed on the hard tissues after 4 and 8 weeks of transmucosal healing. RESULTS: The results show a high rate of osseointegration of the test YTZP dental implants at 4 and 8 weeks following insertion. At 4 weeks, a bone-to-implant contact ratio (BIC) of 73.7% (SD ± 16.8) for the test implants (n = 10) and 58.5% for the first control implant was achieved. The second control implant had to be excluded from analysis. At 8 weeks, a BIC of 82.4% (SD ± 16.9) for the test implants (n = 9) and 93.6% (SD ± 9.1) (n = 2) for the control implant was achieved. No statistical difference was observed comparing 4 and 8 weeks YTZP data (p = 0.126). CONCLUSIONS: The results indicate a predictable osseointegration of immediate zirconia implants with a modified YTZP implant surface and a high degree of BIC present at 4 weeks following insertion. After 8 weeks of healing both the zirconia implants and the Ti implants show a BIC indicating full osseointegration. Further studies involving a larger sample size with more time points are needed to confirm these results.

Buccal Bone Remodeling Around Immediate Implants in STZ-Induced Diabetic Dogs: A Histologic and Microcomputed Tomographic Analysis.

Buccal bone remodeling around immediate implants placed in animals with streptozotocin (STZ)-induced diabetes has not been investigated. The present histologic and microcomputed tomography (µCT) in vivo experiment assessed the buccal bone remodeling around immediate implants, extraction socket healing, and bone-to-implant contact (BIC) in dogs with and without STZ-induced diabetes. Three male beagle dogs with STZ-induced diabetes and three healthy dogs (controls) were included. Fasting blood glucose levels were measured using a glucometer. Under general anesthesia, all animals underwent atraumatic tooth extraction of bilateral maxillary and mandibular second premolar teeth using Piezosurgery and immediate implant placement in the distal root socket. Primary closure was achieved for all implants and adjacent socket sites. After 11 months, all animals were sacrificed, and buccal bone thickness (BBT), marginal bone loss (MBL), BIC, and mesial extraction socket bone volume were assessed in control and diabetic animals using histologic and µCT examination. High-resolution µCT analyses were performed to identify the percentage of osteocytes and blood vessels in bone specimens harvested from a mesial extraction socket in each group. BBT and BIC were significantly higher in control dogs (P < .05), and diabetic dogs demonstrated significantly more MBL than control dogs (P < .05). Compared to healthy subjects, the sockets of induced diabetic dogs lost over 50% of bone horizontally and vertically. Control group had more significant osteocytes (38.85%) and blood vessels (37.87%), whereas the same values for STZ-induced diabetic dogs were 27.92% and 27.76%, respectively. Buccal bone loss and MBL were significantly higher around immediate implants placed in dogs with STZ-induced diabetes and were associated with multiple implant buccal thread exposure. A large percentage of socket space in diabetic dogs healed with nonosseous structure following tooth extraction.

Comparison of extraction sites versus artificial defects with xenogenic bone substitute in minipigs.

OBJECTIVES: The preclinical evaluation of bone substitutes is frequently performed in artificially created defects. However, such defects do not reflect the predominant clinical application of bone substitutes for socket preservation. Hence, the goal of this animal study was to compare the performance of a xenogenic bone substitute in extraction sites versus artificial defects. MATERIAL AND METHODS: Four study sites each were created in the mandibles of four minipigs in the region of the third premolars and first molars, respectively. On one side, fresh extraction sockets were established while contralaterally trephine defects were created in healed alveolar bone. All sites were augmented using a particulate xenogenic bone substitute, covered by resorbable membranes and allowed to heal for 12 weeks. The amounts of new bone, non-bone tissue and remaining bone substitute granules were quantified through histological and micro-CT analysis. Comparative statistics were based on t-tests for two samples and ANOVA with the level of significance set at α = 0.05. RESULTS: Histomorphometric data from only two animals could be quantitatively analyzed due to difficulty with identifying the surgical sites. The percentage of newly formed bone ranged between 53.2% ± 5.6% for artificial defects and 54.9% ± 12.4% for extraction sites. With the exception of ANOVA indicating a greater amount of non-bone tissue in extraction sites as compared to artificial sites (p = 0.047), no statistically significant differences were observed. Micro-CT scans showed patterns similar to the ones observed in histomorphometry. As extraction sites could be identified only in two micro-CT reconstructions, quantitative assessment was not undertaken. CONCLUSIONS: Despite the comparable performance of bone substitute material in artificial defects and extraction sites found here, the data gathered with this experiment was insufficient for showing equivalence of both approaches.

Human Clinical and Histologic Evaluations of Laser-Assisted Periodontal Therapy with a 9.3-µm CO² Laser System.

This investigation was designed to evaluate the healing response of 9.3-µm CO2 laser-assisted periodontal therapy. Five patients presenting with moderate to severe periodontitis, with an initial pocket depth (PD) ≥ 5 mm and with teeth predetermined to be surgically extracted, were enrolled and consented to treatment with full-mouth CO2 laser-assisted therapy. The laser treatment was carried out in the Ultraguide Mode at a setting of 0.25-mm spot size, with an average power of 0.65 to 1.15 watts and 20% mist. The laser tip was passed from the gingival margin and down apically to the base of the pocket with a sweeping L motion. The teeth were intensely scaled with piezoultrasonic instrumentation afterwards. A second pass of the laser tip was performed for the study teeth. At 9 months, all patients were clinically reevaluated. For sites with an initial pocket depth of ≥ 7 mm, a mean PD reduction of 3.97 ± 1.36 mm and a mean clinical attachment level gain of 3.54 ± 1.54 mm were achieved, resulting in a mean PD of 3.91 ± 0.77 mm. En bloc biopsy samples of four teeth were obtained and analyzed; two demonstrated histologic evidence of new bone formation while the other two healed with a long junctional epithelium with minimal inflammatory infiltrate. Further long-term clinical studies are needed to investigate the treatment stability obtained with a 9.3-µm CO2 laser compared to conventional surgical therapy. Nevertheless, the encouraging clinical results indicated that adjunctive use of the 9.3-µm CO2 laser-assisted periodontal therapy can be beneficial for treatment of periodontally compromised patients.

Effect of Sintering on In Vivo Biological Performance of Chemically Deproteinized Bovine Hydroxyapatite.

The influence of the manufacturing process on physicochemical properties and biological performance of xenogenic biomaterials has been extensively studied, but its quantification on bone-to-material contact remains poorly investigated. The aim of this study was to investigate the effect of different heat treatments of an experimental chemically-deproteinized bovine hydroxyapatite in vivo in terms of new bone formation and osteoconductivity. Protein-free hydroxyapatite from bovine origin was produced under sub-critical conditions and then either sintered at 820 °C or 1200 °C. Structural and morphological properties were assessed by scanning electron microscopy (SEM), measurement of surface area and X-ray diffractometry (XRD). The materials were then implanted in standardized alveolar bone defects in minipigs and histomorphometric evaluations were performed using non-decalcified sections. Marked topographical differences were observed by SEM analysis. As the sintering temperature of the experimental material increased, the surface area significantly decreased while crystallite size increased. In vivo samples showed that the highly sintered BHA presented a significantly lower percentage of newly formed bone than the unheated one (p = 0.009). In addition, the percentage of bone-to-material contact (BMC) was significantly lowered in the highly sintered group when compared to the unsintered (p = 0.01) and 820 °C sintered (p = 0.02) groups. Non-sintered or sintered at 820 °C BHA seems to maintain a certain surface roughness allowing better bone regeneration and BMC. On the contrary, sintering of BHA at 1200 °C has an effect on its morphological and structural characteristics and significantly modify its biological performance (osteoconductivity) and crystallinity.

Histologic Evaluation of Human Intrabony Periodontal Defects Treated with Deproteinized Bovine Bone Mineral in Combination with Orthodontic Tooth Movement: A Case Series.

The aim of this case series was the histologic evaluation of guided tissue regeneration utilizing deproteinized bovine bone mineral (DBBM) when regenerative surgery was combined with (test) or without (control) early orthodontic tooth movement. Core biopsy samples were harvested from previously defected sites after 9 months. The histologic section showed integration of DBBM particles in newly formed bone in the apical and middle thirds of the defect, while in the coronal part, graft materials were mainly embedded in connective tissues in the control patient. DBBM particles showed partial resorption with more de novo bone formation in test samples.

Al2O3 Particles on Titanium Dental Implant Systems following Sandblasting and Acid-Etching Process.

Dental implants with moderately rough surfaces show enhanced osseointegration and faster bone healing compared with machined surfaces. The sandblasting and acid-etching (SA) process is one technique to create moderately rough dental implant surfaces. The purpose of this study was to analyse different commercially available implant systems with a SA-modified surface and to explore the widespread notion that they have similar surface properties regarding morphology and cleanliness. SA-modified surfaces of nine implant systems manufactured by Alpha-Bio Tec Ltd, Camlog Biotechnologies AG, Dentsply Sirona Dental GmbH, Neoss Ltd, Osstem Implant Co. Ltd, Institute Straumann AG, and Thommen Medical AG were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and examined for surface cleanliness. Six implants from three different lots were selected per each implant system. Mean particle counts for each implant and the mean size of the particles were calculated from three different regions of interest and compared using ANOVA and Tukey's test. SEM analysis showed presence of particles on the majority of analyzed implant surfaces, and EDX evaluations determined that the particles were made of Al2O3 and thus remnants of the blasting process. SPI®ELEMENT INICELL® and Bone Level (BL) Roxolid® SLActive® implant surfaces showed the highest mean particle counts, 46.6 and 50.3 per area, respectively. The surface of BL Roxolid® SLActive® implant also showed the highest variations in the particle counts, even in samples from the same lot. The mean size of particles was 1120±1011 µm2, measured for USIII CA Fixture implants, while the biggest particle was 5900 µm2 found on a BL Roxolid® SLActive® implant. These results suggest that not all manufacturers are able to produce implant surfaces without particle contamination and highlight that the surface modification process with the SA technique should be appropriately designed and controlled to achieve a clean and consistent final medical device.

Safety and efficacy of a novel anodized abutment on soft tissue healing in Yucatan mini-pigs.

BACKGROUND: It is well established that electrochemical anodization of implant surfaces contributes to osseointegration and long-term implant survival. Few studies have investigated its effect on soft tissue healing. PURPOSE: To evaluate the safety and efficacy of a novel abutment surface prepared by electrochemical oxidation compared to commercially available machined titanium abutments. MATERIALS AND METHODS: Twelve 16-19 months-old, Yucatan mini-pigs received three dental implants in each mandibular jaw quadrant. Each side was randomized to receive either an anodized or a machined titanium abutment. Titanium healing caps were placed on both abutments. Animals were euthanized at 6 and 13 weeks. Radiographic and histological analyses were performed. RESULTS: No significant differences were observed histologically between groups in regard to inflammation, epithelium length, mucosal height, bone-to-implant contact, or bone density for any time point. Radiographically, crestal bone level change from baseline to 6 weeks was significantly lower for anodized than machined abutments (P = 0.046); no significant differences were observed at 13 weeks (P = 0.12). CONCLUSIONS: The novel anodized abutment showed a comparable effect on soft and hard tissue healing/remodeling and inflammation reaction to standard titanium abutments. Clinical studies should confirm these findings and explore the positive radiographic results observed at the early time point.

New Bone Formation Using an Extracted Tooth as a Biomaterial: A Case Report with Histologic Evidence.

This case report aims to demonstrate the regenerative potential of particles obtained from a crushed extracted tooth. Following tooth removal, the clean root was ground and the dentin and cementum granules were grafted into a fresh extraction socket for a ridge preservation procedure. After 24 weeks, a successful implant placement was allowed. Tissue healing was evaluated by histologic and radiologic analysis. The volume of the ridge was preserved. Histologically, a dentin-bone complex was reported. New bone formation was evident, with an intimate contact between bone and both dentin/cementum. This novel procedure suggests the use of tooth particles as graft material.

Cartilage Health in Knees Treated with Metal Resurfacing Implants or Untreated Focal Cartilage Lesions: A Preclinical Study in Sheep.

BACKGROUND: Full-depth cartilage lesions do not heal and the long-term clinical outcome is uncertain. In the symptomatic middle-aged (35-60 years) patient, treatment with metal implants has been proposed. However, the cartilage health surrounding these implants has not been thoroughly studied. Our objective was to evaluate the health of cartilage opposing and adjacent to metal resurfacing implants. METHODS: The medial femoral condyle was operated in 9 sheep bilaterally. A metallic resurfacing metallic implant was immediately inserted into an artificially created 7.5 mm defect while on the contralateral knee the defect was left untreated. Euthanasia was performed at 6 months. Six animals, of similar age and study duration, from a previous study were used for comparison in the evaluation of cartilage health adjacent to the implant. Cartilage damage to joint surfaces within the knee, cartilage repair of the defect, and cartilage adjacent to the implant was evaluated macroscopically and microscopically. RESULTS: Six animals available for evaluation of cartilage health within the knee showed a varying degree of cartilage damage with no statistical difference between defects treated with implants or left untreated ( P = 0.51; 95% CI -3.7 to 6.5). The cartilage adjacent to the implant (score 0-14; where 14 indicates no damage) remained healthy in these 6 animals showing promising results (averaged 10.5; range 9-11.5, SD 0.95). Cartilage defects did not heal in any case. CONCLUSION: Treatment of a critical size focal lesion with a metal implant is a viable alternative treatment.

Screening of candidate biomaterials for alveolar augmentation using a critical-size rat calvaria defect model.

OBJECTIVE: To screen candidate biomaterials intended for alveolar augmentation relative to their potential to enhance local bone formation using a routine critical-size (ø8-mm) rat calvaria defect model. METHODS: One hundred and forty male Sprague Dawley outbred rats, age 11-12 weeks, weight 325-375 g, obtained from USDA approved breeder, randomised into 14 groups of 10 animals, each received one of the following treatments: sham-surgery (empty control), Bio-Oss (bovine HA/reference control), or candidate biomaterials including bovine HA, synthetic HA/ß-TCP and calcium phosphate constructs, mineralised/demineralised human bone preparations, a ß-TCP/calcium sulphate and an HA/calcium sulphate putty. A 4-week healing interval was chosen to discern local bone formation using incandescent and polarised light microscopy. Statistical analysis used one-way ANOVA followed by Bonferroni for pairwise comparisons. RESULTS: Candidate biomaterials all displayed biocompatibility. They exhibited limited, if any, appreciable bioerosion or biodegradation. No statistically significant differences in mean linear defect closure were observed among experimental groups, sham-surgery displaying the highest score (48.1 ± 24.3%). Sham-surgery also showed a significantly greater bone area fraction than all other groups (19.8 ± 13.9%, p < .001). The HA/calcium sulphate putty showed a significantly greater residual biomaterial area fraction than all other groups (61.1 ± 8.5%, p < .01). CONCLUSION: Within the limitations of this animal model, although biocompatible, none of the tested biomaterials enhanced local bone formation beyond the innate regenerative potential of this craniotomy defect.

Late Dental Implant Failures Associated with Retained Root Fragments: Case Reports with Histologic and SEM Analysis.

Interest has recently developed in the purposeful retention of root fragments with their periodontal apparatus to support bone and soft tissue at immediate implant sites in the esthetic zone. This methodology is designed to avoid bone grafting, connective tissue grafts, and the use of membranes and may have short-term benefits in terms of tissue preservation. However, it is not completely without long-term risks. At times, implants may be unintentionally placed into edentulous sites where root fragments remain. This report presents two cases of long-term failure postloading associated with unintentionally retained root fragments. Histologic evaluation evidenced retained root fragments in close association with dental implants and the surrounding bone. Scanning electron microscopic evaluation revealed that the failed implant surfaces were infiltrated by bacterial deposits and calculus. Clinicians should exercise caution when placing dental implants in sites with retained root fragments, as long-term risks may be associated with this therapy.

Impact of biomaterial microtopography on bone regeneration: comparison of three hydroxyapatites.

AIMS: The primary objective of this study was to compare the in vivo performance, namely in terms of quantity of newly formed bone and bone-to-material contact (osteoconductivity), of three hydroxyapatite-based biomaterials (HA) of different origins (natural or synthetic) or manufacturing process in a sinus lift model in rabbits. The secondary objective was to correlate the findings with the physical and topographical characteristics of the biomaterials. MATERIALS AND METHODS: Two bovine HA manufactured with different processes (bovine hydroxyapatites [BHA] and cuttlebone hydroxyapatite [CBHA]) and a synthetic hydroxyapatite (SHA) sintered at high temperature were characterised with scanning electronic microscopy (SEM) and the measurement of specific surface area (BET). The materials were implanted in a sinus lift model in rabbits; histological and histomorphometric evaluation using non-decalcified sections was performed at 1, 5 and 12 weeks after implantation. RESULTS: The studied biomaterials displayed a different surface topography. The two natural HA displayed significantly higher bone quantities (P = 0.0017; BHA vs. SHA, P = 0.0018 and CBHA vs. SHA, P = 0.033) at 5 and 12 weeks compared to the synthetic one (SHA). Moreover, the osteoconductivity (bone-to-material contact) was significantly higher in the BHA group compared to the two other groups (P = 0.014; BHA vs. SHA, P = 0.023 and BHA vs. CBHA, P = 0.033). CONCLUSION: HA-based biomaterials from diverse origins and manufacturing processes displayed different topographical characteristics. This may have influenced different regenerated bone architecture observed; more bone was found with natural HA compared to the synthetic one, and significantly higher bone-to-material contacts were found with BHA.

A Prospective, Case-Controlled Study Evaluating the Use of Enamel Matrix Derivative on Human Buccal Recession Defects: A Human Histologic Examination.

BACKGROUND: Connective tissue grafts (CTGs) and coronally advanced flaps (CAFs) do not regenerate periodontal attachment apparatus when used to treat gingival recessions (GRs). Instead of generating new bone, cementum, and inserting periodontal ligament fibers, CTG+CAF repairs through a long epithelial junction and connective tissue attachment. Enamel matrix derivatives (EMDs) have demonstrated proof-of-principle that periodontal regeneration can be achieved, although data are limited. METHODS: Three patients, each requiring extraction of four premolars before orthodontic treatment, were enrolled in a randomized, open-label study. Two months after induction of Miller Class I and II GR, each patient received EMD+CAF for three teeth and CTG+CAF for one tooth for root coverage. Nine months after root coverage, all four premolars from each of the three patients were surgically extracted en bloc for histologic and microcomputed tomography (micro-CT) analysis, looking for evidence of periodontal regeneration. Standard clinical measurements, radiographs, and intraoral photographs were taken over prescribed time points. RESULTS: Seven of the nine teeth treated with EMD+CAF demonstrated varying degrees of periodontal regeneration, detailed through histology with new bone, cementum, and inserting fibers. Micro-CT corroborated these findings. None of the three teeth treated with CTG+CAF showed periodontal regeneration. Clinical measurements were comparable for both treatments. One instance of root resorption and ankylosis was noted with EMD+CAF. CONCLUSIONS: EMD+CAF continues to show histologic evidence of periodontal regeneration via human histology, this being the largest study (nine teeth) examining its effect when treating GR. The mechanism of action, ideal patient profile, and criteria leading to predictable regeneration are in need of further exploration.

Effect of Platform Shift/Switch on Crestal Bone Levels and Mucosal Profile Following Flapless Surgery and Crestal/Subcrestal Implant Placement.

BACKGROUND: Crestal remodeling/bone loss appears a common sequel to dental implant placement. Several hypotheses and clinical strategies have been advanced to explain and avert crestal remodeling; however, causative mechanisms remain unclear and the efficacy of clinical protocol uncertain. OBJECTIVE: The objective of the present study was to provide a histologic record of crestal versus subcrestal implant placement on crestal remodeling and mucosal profile comparing platform shift/switch and standard abutments following flapless implant surgery using a dog model. METHODS: Four dental implants each were placed into the left and right edentulated posterior mandibles in five adult male hound-Labrador mongrel dogs using a flapless approach including crestal versus subcrestal placement and using platform shift versus standard abutments. Block biopsies were collected for histological/histometric analysis following an 8-week healing interval. RESULTS: Both crestal and subcrestal implant installation resulted in significant crestal remodeling and bone loss, in particular at buccal sites, without significant differences between platform shift/switch and standard abutments. Implants installed subcrestally exhibited a significantly taller mucosal profile over crestal-level implants without significant differences between platform shift/switch and standard abutments; the epithelial attachment at all times arrested on the abutment surface. CONCLUSIONS: Comparing platform shift/switch versus standard abutments using a minimally invasive flapless approach including crestal or subcrestal implant placement, the platform shift/switch abutments offer no selective advantage over standard abutments.

Effect of Platform Shift on Crestal Bone Levels and Mucosal Profile Following Flap Surgery and Subcrestal Implant Placement in Presence/Absence of Gap Defects.

BACKGROUND: Physiologic remodeling resulting in crestal bone loss appears a common corollary to dental implant surgery. Several hypotheses and clinical strategies have been advanced to explain and avert crestal remodeling; however, causative mechanisms remain unclear and the efficacy of clinical protocols uncertain. PURPOSE: The objective of the present study was to provide a histologic account of crestal bone levels and mucosal profile at implant sites receiving platform shift/switch and standard abutments following conventional flap surgery and subcrestal implant placement in presence or absence of crestal gap defects using a dog model. MATERIALS AND METHODS: Four dental implants were placed into the left/right edentulated posterior mandible in five adult male Hound Labrador mongrel dogs using flap surgery including subcrestal placement with/without a 1 × 5 mm (width × depth) gap defect, and using platform shift/switch and standard abutments. Block biopsies were collected for histological/histometric analysis following an 8-week healing interval. RESULTS: No significant differences in crestal resorption were observed among experimental groups; crestal resorption being significantly more advanced at buccal than at lingual sites (p < .001). Similarly, crestal bone-implant contact was not significantly different among groups; crestal bone-implant contact being consistently below the implant platform at buccal sites (p < .01). Moreover, the peri-implant mucosal profile was not statistically different among groups, the mucosal height being significantly greater at buccal than at lingual sites (p < .001). Also, no significant differences among groups were observed for the apical extension of the epithelial attachment, the epithelial attachment being arrested more than 2 mm above the implant platform at both platform shift/switch and standard abutments. CONCLUSIONS: Using a clinical strategy including flap surgery and subcrestal implant placement, implant technology comparing platform shift/switch with standard abutments, surgical approach, and abutment selection seems to have a limited impact on crestal remodeling, associated bone loss, and mucosal profile.

Enhancement of the Regenerative Potential of Anorganic Bovine Bone Graft Utilizing a Polyglutamate-Modified BMP2 Peptide with Improved Binding to Calcium-Containing Materials.

Autogenous bone is the gold standard material for bone grafting in craniofacial and orthopedic regenerative medicine. However, due to complications associated with harvesting donor bone, clinicians often use commercial graft materials that may lose their osteoinductivity due to processing. This study was aimed to functionalize one of these materials, anorganic bovine bone (ABB), with osteoinductive peptides to enhance regenerative capacity. Two peptides known to induce osteoblastic differentiation of mesenchymal stem cells were evaluated: (1) DGEA, an amino acid motif within collagen I and (2) a biomimetic peptide derived from bone morphogenic protein 2 (BMP2pep). To achieve directed coupling of the peptides to the graft surface, the peptides were engineered with a heptaglutamate domain (E7), which confers specific binding to calcium moieties within bone mineral. Peptides with the E7 domain exhibited greater anchoring to ABB than unmodified peptides, and E7 peptides were retained on ABB for at least 8 weeks in vivo. To assess the osteoinductive potential of the peptide-conjugated ABB, ectopic bone formation was evaluated utilizing a rat subcutaneous pouch model. ABB conjugated with full-length recombinant BMP2 (rBMP2) was also implanted as a model for current clinical treatments utilizing rBMP2 passively adsorbed to carriers. These studies showed that E7BMP2pep/ABB samples induced more new bone formation than all other peptides, and an equivalent amount of new bone as compared with rBMP2/ABB. A mandibular defect model was also used to examine intrabony healing of peptide-conjugated ABB. Bone healing was monitored at varying time points by positron emission tomography imaging with (18)F-NaF, and it was found that the E7BMP2pep/ABB group had greater bone metabolic activity than all other groups, including rBMP2/ABB. Importantly, animals implanted with rBMP2/ABB exhibited complications, including inflammation and formation of cataract-like lesions in the eye, whereas no side effects were observed with E7BMP2pep/ABB. Furthermore, histological analysis of the tissues revealed that grafts with rBMP2, but not E7BMP2pep, induced formation of adipose tissue in the defect area. Collectively, these results suggest that E7-modified BMP2-mimetic peptides may enhance the regenerative potential of commercial graft materials without the deleterious effects or high costs associated with rBMP2 treatments.

Effect of Platform Shift/Switch and Concave Abutments on Crestal Bone Levels and Mucosal Profile following Flap and Flapless Implant Surgery.

BACKGROUND: Crestal remodeling/bone loss appears to be a common sequel to dental implant placement. Several hypotheses/clinical strategies have been proposed to explain/avert crestal remodeling; however, causative mechanisms remain unclear and the efficacy of these clinical approaches uncertain. OBJECTIVE: The objective of the present study was to provide a histological account of crestal bone levels and mucosal profile at platform shift/switch and concave abutments following flapless and conventional flap surgery and subcrestal implant placement using a dog model. METHODS: Four dental implants each were placed in the left/right mandibular posterior jaw quadrants in five adult male Hound/Labrador mongrel dogs using flap surgery with a 1 × 5 mm gap defect or using a flapless approach, both involving placement 2 mm subcrestally and platform shift/switch versus concave abutments. Block biopsies for histological/histometric analysis were collected at 8 weeks. RESULTS: No significant differences were observed regarding crestal bone levels, with all groups showing mean bone levels above the implant platform. Similarly, crestal bone-implant contact was not significantly different among groups. Moreover, peri-implant mucosal profiles were not statistically different among groups for buccal sites; average mucosal height reached 4.1 to 4.9 mm above the implant platform. Comparison between buccal and lingual sites showed a nonsignificant tendency toward greater crestal resorption at buccal sites, adjusting for other factors. Mean crestal bone-implant contact level approximated the implant platform for lingual sites while consistently remaining below the platform at the buccal sites. Peri-implant mucosal height was significantly higher at buccal than at lingual sites, with the epithelial attachment located a significant distance away from the implant platform at buccal sites. CONCLUSIONS: The surgical approaches (subcrestal implant placement by flap surgery or a flapless approach) and abutment designs (platform shift/switch or concave) used in this study seem to have a limited impact on crestal remodeling, associated bone loss, and mucosal profile. Bioclinical strategies should be developed to circumvent the limitations of current clinical protocol.