ABSTRACT
Surface treatments play an important role in enhancing the osseointegration of Titanium (Ti) and its alloys. This study introduces a method employing biomimetic hydroxyapatite (Hap) deposition guided by molecularly organized phospholipids, affixed to the metal implant surface. Using the Langmuir-Blodgett technique, phospholipids were deposited onto Ti-screws by using CaCl2 or CaCl2/SrCl2 aqueous solution in the subphase of a Langmuir trough in the target proportion (i.e. 10 and 90 mol% of Sr2+ in relation of Ca2+) followed by immersion in phosphate buffer and in supersaturated simulated body fluid. Coating composition and morphology were evaluated using infrared spectroscopy and scanning electron microscopy, respectively, while contact angle measurements assessed coating wettability and surface energy. Randomized screws were then implanted into the tibias of healthy and osteoporotic female rats (G1: Control-Machined, G2: Hap, G3: HapSr10, G4: HapSr90). Osseointegration, assessed 60 days post-implantation, included reverse torque, fluorochrome area, bone tissue-screw contact area, and linear extent of bone-screw contact. Results, grouped by surface treatment (Machined, Hap, HapSr10, HapSr90), revealed that the deposition of Hap, HapSr10, and HapSr90 resulted in thin and rough coatings composed of hydroxyapatite (Hap) on the screw surface with nanoscale pores. The coatings resulted in increased wettability and surface energy of Ti surfaces. The minerals are chemically similar to natural bone apatite as revealed by FTIR analysis. In vivo analyses indicated higher torque values for strontium-containing surfaces in the osteoporotic group (p = 0.02) and, in the control group superior torque for screw removal on the Hap surface (p = 0.023). Hydroxyapatite-treated surfaces enhance morphology, composition, and reactivity, promoting screw osseointegration in healthy and osteoporotic female rats. The incorporation of strontium into the mineral phase has been proposed to not only stimulate osteoblast activity but also reduce osteoclastic resorption, which may explain the improved outcomes observed here in experimental osteoporotic conditions.
ABSTRACT
PURPOSE: To evaluate the tendency of movement, stress distribution, and microstrain of single-unit crowns in simulated cortical and trabecular bone, implants, and prosthetic components of narrow-diameter implants with different lengths placed at the crestal and subcrestal levels in the maxillary anterior region using 3D finite element analysis (FEA). MATERIALS AND METHODS: Six 3D models were simulated using Invesalius 3.0, Rhinoceros 4.0, and SolidWorks software. Each model simulated the right anterior maxillary region including a Morse taper implant of Ø2.9 mm with different lengths (7, 10, and 13 mm) placed at the crestal and subcrestal level and supporting a cement-retained monolithic single crown in the area of tooth 12. The FEA was performed using ANSYS 19.2. The simulated applied force was 178 N at 0°, 30°, and 60°. The results were analyzed using maps of displacement, von Mises (vM) stress, maximum principal stress, and microstrain. RESULTS: Models with implants at the subcrestal level showed greater displacement. vM stress increased in the implant and prosthetic components when implants were placed at the subcrestal level compared with the crestal level; the length of the implants had a low influence on the stress distribution. Higher stress and strain concentrations were observed in the cortical bone of the subcrestal placement, independent of implant length. Non-axial loading influenced the increased stress and strain in all the evaluated structures. CONCLUSIONS: Narrow-diameter implants positioned at the crestal level showed a more favorable biomechanical behavior for simulated cortical bone, implants, and prosthetic components. Implant length had a smaller influence on stress or strain distribution than the other variables.
Subject(s)
Dental Implants , Finite Element Analysis , Dental Stress Analysis/methods , Dental Prosthesis Design , Software , Stress, Mechanical , Biomechanical PhenomenaABSTRACT
STATEMENT OF PROBLEM: How the performance of dental implants is related to their occlusogingival placement, crestal or subcrestal, is unclear. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate marginal bone loss, implant survival rate, and peri-implant soft tissue parameters between implants placed at the crestal and subcrestal bone level. MATERIAL AND METHODS: Two independent reviewers searched the PubMed/MEDLINE, Embase, and Cochrane Library databases for randomized clinical trials published up to September 2020. The meta-analysis was based on the Mantel-Haenszel and the inverse variance methods (α=.05). RESULTS: The search identified 928 references, and 10 studies met the eligibility criteria. A total of 393 participants received 709 implants, 351 at crestal bone levels and 358 at subcrestal bone levels. Meta-analysis indicated that crestal bone level implants showed similar marginal bone loss to that seen with subcrestal bone level implants (mm) (P=.79), independent of the subcrestal level (P=.05) and healing protocol (P=.24). The bone level implant placement did not affect the implant survival rate (P=.76), keratinized tissue (mm) (P=.91), probing depth (mm) (P=.70), or plaque index (%) (P=.92). CONCLUSIONS: The evidence suggests that both approaches of implant placement are clinically acceptable in terms of peri-implant tissue parameters and implant-supported restoration survival.