Purpose Primary stability has been regarded as a key factor to ensure uneventful osseointegration of dental implants. Such stability is often achieved by placing implants in undersized drilled bone. ...The present study evaluated the effect of drilling dimensions in insertion torque and early implant osseointegration stages in a beagle dog model. Materials and Methods Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before death. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in diameter. The insertion torque was recorded for all samples. After death, the implants in bone were nondecalcified processed and morphologically and morphometrically (bone-to-implant contact and bone area fraction occupancy) evaluated. Statistical analyses were performed using the Kruskal-Wallis test followed by Dunn's post hoc test for multiple comparisons at the 95% level of significance. Results The insertion torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2-mm and 3.8-mm groups ( P = .003). Despite a significant increase in the bone-to-implant contact over time in vivo for all groups ( P = .007), no effect for the drilling dimension was observed. Additionally, no effect of the drilling dimension and time was observed for the bone area fraction occupancy parameter ( P = .31). The initial healing pathways differed between implants placed in bone drilled to different dimensions. Conclusions Although different degrees of torque were observed with different drilling dimensions and these resulted in different healing patterns, no differences in the histometrically evaluated parameters were observed.
The authors analyzed the in vitro and in vivo performance of lithium disilicate glass-ceramic (LDGC) restorations and yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) (that is, zirconium ...oxide) restorations with regard to reliability, clinical performance and abrasion resistance.
In the in vitro study, four authors subjected samples of LDGC, Y-TZP and metal-ceramic crowns to step-stress fatigue testing. Four investigators assessed the in vivo clinical performance of LDGC and zirconium oxide-based restorations at four and seven years, respectively. In addition, one author conducted a randomized, controlled clinical trial to analyze the volumetric loss of enamel and ceramic antagonist surfaces.
The LDGC crowns exhibited the highest fatigue load-to-failure values in the in vitro analysis. The results of the in vivo assessment showed that the clinical performance of the LDGC restorations at four years was comparable to that of the zirconium oxide-based crowns at seven years. The results of the in vivo, randomized, controlled clinical trial showed that LDGC crowns were not only resistant to wear, but also were wear friendly to enamel antagonist surfaces.
The LDGC crowns in the in vitro and in vivo studies exhibited high durability, and they were wear friendly to opposing natural dentition.
LDGC and zirconium oxide-based crowns are a clinically acceptable means of treating teeth that require full-coverage restorations. In addition, LDGC materials exhibit excellent clinical performance, as well as demonstrate acceptable abrasion compatibility with the opposing natural dentition.
All-Ceramic Systems: Laboratory and Clinical Performance Guess, Petra C., DDS, Dr Med Dent; Schultheis, Stefan, DDS, Dr Med Dent; Bonfante, Estevam A., DDS, MSc, PhD ...
The Dental clinics of North America
55, Številka:
2
Journal Article
Recenzirano
Several all-ceramic systems have been developed in dentistry to meet the increased expectations of patients and dentists for highly aesthetic, biocompatible, and long-lasting restorations. However, ...early bulk fractures or chippings have led the research community to investigate the mechanical performance of the all-ceramic systems. This overview explores the current knowledge of monolithic and bilayer dental all-ceramic systems, addressing composition and processing mechanisms, laboratory and clinical performance, and possible future trends for all-ceramic materials.
Purpose To investigate the influence of different materials and fixation methods on maximum principal stress (MPS) and displacement in reconstruction plates using in silico 3-dimensional finite ...element analysis (3D-FEA). Materials and Methods Computer-assisted designed (CAD) models of the mandible and teeth were constructed. Champy and AO/ASIF plates and fixation screws were designed with CAD software. 3D-FEA was performed by image-based CAE software. Maximum and minimum values of biomechanical stability, MPS, and displacement distribution were compared in Champy and AO/ASIF plates made from commercially pure titanium grade 2 (cp-Ti) and a titanium-and-molybdenum (14.47% wt) alloy (Ti-15Mo). Results For plates fixed on a model of a fractured left angle of the mandible, the maximum and minimum values of MPS in the cp-Ti–constructed Champy plate, upper AO/ASIF plate, and lower AO/ASIF plate were 19.5 and 20.3%, 15.2 and 25.3%, and 21.4 and 4.6% lower, respectively, than those for plates made from Ti-15Mo. In the same model, the maximum and minimum values of displacement in the cp-Ti–constructed Champy plate, upper AO/ASIF plate, and lower AO/ASIF plate were 1.6 and 3.8%, 3.1 and 2.7%, and 5.4 and 10.4% higher, respectively, than those for plates made from Ti-15Mo. Conclusions This in silico 3D-FEA shows that Ti-15Mo plates have greater load-bearing capability.
This study evaluated the effect of drilling speed on early bone healing in dog tibiae.
Thirty-six implants (4.0-mm diameter × 10-mm length) were placed in the proximal tibiae of 6 beagles with ...drilling speeds of 100, 500, and 1000 rpm, and insertion torque was recorded. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated.
Significant increase from 1 to 3 weeks was observed for all groups for BIC, whereas no significant differences between 1 and 3 weeks were detected for the 100- and 500-rpm groups for BAFO (P > .34 and P > .46, respectively). A significant difference from 1 to 3 weeks was observed for the 1000-rpm group (P < .03). The 100- and 500-rpm groups presented significantly higher BAFO than the 1000-rpm group at 1 week (P = .002).
Drilling speed is one of the decisive factors for early osseointegration, and overall, drilling at 1000 rpm seemed to yield the strongest biologic responses.
Purpose The present study evaluated the effect of different drilling dimensions (undersized, regular, and oversized) in the insertion and removal torques of dental implants in a beagle dog model. ...Methods Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before euthanasia. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in final diameter. The insertion and removal torque was recorded for all samples. Statistical analysis was performed by paired t tests for repeated measures and by t tests assuming unequal variances (all at the 95% level of significance). Results Overall, the insertion torque and removal torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2 mm and 3.5 mm relative to the 3.8 mm groups ( P < 0.03). Although insertion torque–removal torque paired observations was statistically maintained for the 3.5 mm and 3.8 mm groups, a significant decrease in removal torque values relative to insertion torque levels was observed for the 3.2 mm group. A different pattern of healing and interfacial remodeling was observed for the different groups. Conclusions Different drilling dimensions resulted in variations in insertion torque values (primary stability) and stability maintenance over the first weeks of bone healing.
Abstract Statement of problem Few studies have investigated the voids and gaps produced during the cementation of fiber posts using different techniques. Purpose The purpose of this study was to ...evaluate and quantify void and gap area formations of different fiber post cementation techniques using microcomputed tomography (μCT). Material and methods Standardized endodontically treated acrylic resin roots (N=24) were divided into 4 groups (n=6) according to different fiber posts cemented with the resin cement (FB); fiber posts relined with composite resin followed by cementation (FBR); fiber posts cemented using an ultrasonic device (FBU); and fiber posts relined with composite resin and cemented using an ultrasonic device (FBRU). Each specimen was scanned twice using micro-computed tomography (μCT; empty root, followed by after fiber post cementation). Digital imaging and communications in medicine (DICOM) files were transferred into 3-dimensional (3D) reconstruction software for analysis. Void volume in the cementation system and gap area formation were evaluated; quantitative and qualitative analyses were performed. The data were analyzed using 2-way ANOVA and the Tukey honest significant difference post hoc test (α=.05). Results FBR showed a lower percentage of voids than obtained for FB ( P <.05). Groups FB, FBU, and FBRU did not show significant difference in void formation ( P >.05). No significant differences were found in gap area formations among the experimental groups ( P >.05). Conclusions The use of a composite resin to reline the fiber post significantly decreased the void formation in the cementation procedure when no ultrasonic device was used. The use of an ultrasonic device did not decrease the percentage of void or gap formation for any technique evaluated.
Purpose The objective of the present study was to evaluate the biomechanical fixation and bone-to-implant contact (BIC) of plateau root form implants of varied surfaces. Materials and Methods Plateau ...root form implants, 3.5 mm in diameter, 8 mm in length, with 4 surfaces (n = 16 each)—machined, alumina-blasted/acid-etched, alumina-blasted/acid-etched plus nanothickness bioceramic coating, and plasma-sprayed calcium-phosphate—were used. They were bilaterally placed at the distal femur of 16 New Zealand rabbits and remained in place for 2 and 4 weeks in vivo. After euthanizing the rabbits, the implants were subjected to torque to interface fracture and were subsequently processed as nondecalcified ∼30-μm-thickness slides for histomorphologic analysis and BIC determination. Statistical analysis was performed using analysis of variance at the 95% level of significance, considering implantation time and implant surface as independent variables and the torque-to-interface fracture and BIC as dependent variables. Results The torque-to-interface fracture was significantly affected by the implant surface ( P < .001) but was not affected by the implantation time ( P > .20). The implantation time and implant surface had significant effects on the BIC ( P < .04 and P < .001, respectively). The greatest torque-to-interface fracture and BIC was observed for the plasma-sprayed calcium-phosphate. Conclusion The implant surface significantly influenced early bone healing around plateau root form implants.
Purpose This study tested the null hypothesis that differences in surgical instrumentation, macrogeometry, and surface treatment imposed by different implant systems do not affect early biomechanical ...fixation in a canine mandible model. Materials and Methods The lower premolars of 6 beagle dogs were extracted and the ridges allowed to heal for 8 weeks. Thirty-six (n = 12 each group) implants were bilaterally placed, remaining for 1 and 3 weeks in vivo. The implant groups were as follows: group 1, Ti-6Al-4V with a dual acid-etched surface with nanometer scale discrete crystalline deposition (Nanotite; Certain Biomet-3i, West Palm Springs, FL); group 2, Ti-6Al-4V with a titanium oxide-blasted fluoride-modified surface chemistry (Osseospeed 4.0 S; Astra Tech, Mölndal, Sweden); group 3: Ti-6Al-4V with a bioceramic microblasted surface (Ossean; Intra-Lock International, Boca Raton, FL). Following euthanasia, implants were torqued to interface failure and histologically evaluated. General linear modeling (ANOVA) at 95% level of significance was performed. Results Histology showed that interfacial bone remodeling and initial woven bone formation were observed around all implant groups at 1 and 3 weeks. Torque values were significantly affected by time in vivo, implant group, and their interaction ( P = .016, P < .001, and P = .001, respectively). Regarding torque values, group 3, group 2, and group 1 ranked highest, intermediate, and lowest, respectively. Conclusion Early biomechanical fixation at 1 and 3 weeks was affected by surgical instrumentation, macrogeometry, and surface treatment present for one of the implant systems tested. The null hypothesis was rejected.
Abstract Statement of problem Few studies have investigated the volumetric polymerization shrinkage and film thickness of the different cementation techniques used to cement veneers. Purpose The ...purpose of this in vitro study was to evaluate the volumetric polymerization shrinkage (VS) and film thickness (FT) of various cementation techniques through 3-dimensional (3D) microcomputed tomography (μCT). Material and methods Forty-eight artificial plastic maxillary central incisors with standard preparations for veneers were provided by a mannequin manufacturer (P-Oclusal) and used as testing models with the manufacturer’s plastic veneers. They were divided into 8 groups (n=6): RelyX Veneer + Scotchbond Universal (RV+SBU); Variolink Esthetic LC+Adhese Universal (VE+ADU); Filtek Supreme Ultra Flowable + Scotchbond Universal (FF+SBU); IPS Empress Direct Flow + Adhese Universal (IEF+ADU); Filtek Supreme Ultra Universal + Scotchbond Universal (FS+SBU); IPS Empress Direct + Adhese Universal (IED+ADU); Preheated Filtek Supreme Ultra Universal + Scotchbond Universal (PHF+SBU); and Preheated IPS Empress Direct + Adhese Universal (PHI+ADU). Specimens were scanned before and after polymerization using a μCT apparatus (mCT 40; Scanco Medical AG), and the resulting files were imported and analyzed with 3D rendering software to calculate the VS and FT. Collected data from both the VS and FT were submitted to 1-way ANOVA (α=.05). Results VE+ADU had the lowest volumetric shrinkage (1.03%), which was not significantly different from RV+SBU, FF+SBU or IEF+ADU ( P >.05). The highest volumetric shrinkage was observed for FS+SBU (2.44%), which was not significantly different from RV+SBU, IED+ADU, PHF+SBU, or PHI+ADU ( P >.05). Group RV+SBU did not differ statistically from the remaining groups ( P >.05). Film thickness evaluation revealed the lowest values for RV+SBU, VE+ADU, FF+SBU, and IEF+ADU, with an average between groups of 0.17 mm; these groups were significantly different from FS+SBU, IED+ADU, PHF+SBU, and PHI+ADU ( P >.05), with an average of 0.31 mm. Conclusions Both the VS and the FT of direct restorative composite resins were higher than those of veneer cements and flowable composite resins, whether preheated or not preheated.
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