Investigating the impact of diameters and thread designs on the Biomechanics of short implants placed in D4 bone: a 3D finite element analysis.

BACKGROUND: Dental implants emerge as a dependable and efficacious alternative for patients experiencing partial or complete tooth loss. The stability of these implants is influenced by surface topography and macro-level design. In cases where the height of the maxillary posterior region is diminished, employing short implants can prove advantageous. With the aim of examining the distribution of von Mises stress, strain, and micromovement in D4 bone quality surrounding platform-switched short implants, measuring 6 mm in length and featuring diameters ranging from 4 to 6 mm, as well as different thread designs, an in-depth finite element analysis was conducted under immediate loading conditions. METHODOLOGY: A 3D finite element model was constructed to simulate maxillary molar crowns, incorporating an implant with a length of 6 mm and varying diameters and thread designs. The diameters utilized were 4/3.6 mm, 5/4 mm, and 6/4.8 mm, while the thread designs included buttress, square, and triangle patterns. Each model underwent analysis with a 100 N force applied in two directions: vertical and oblique, relative to the long axis of the implant. Stress, strain, and micromovement in the peri-implant region were recorded, employing the Ansys Workbench R v.18.1 software for modelling and analysis. RESULTS: When comparing all three diameters, the wide diameter (6 mm threads) exhibited the lowest values of peri-implant von Mises stresses (3.3 MPa and 35.1 MPa), strains (194 Ɛ and 484 Ɛ), and micromovements (0.7 µm and 1.3 Ɛ) subjected to axial and non-axial loading of a 100 N force. Notably, square microthreads yielded the most favorable stress parameters among the different thread shapes, manifesting the minimum values of stress, strains, and micromovements in their vicinity. CONCLUSION: For the treatment of atrophic ridges or in scenarios necessitating extensive surgical preparation of the implant site, a combination of short implants, wide diameters, and platform switching can be employed. In situations with reduced bone height and the requirement for an implant-supported prosthesis to replace a missing permanent maxillary molar, the utilization of wide-diameter platform-switched short implants measuring 6 mm in length, featuring a square thread design, should be taken into consideration.

Three-Dimensional FEA Analysis of the Stress Distribution on Titanium and Graphene Frameworks Supported by 3 or 6-Implant Models.

Titanium is the main component of dental implants. It is also routinely used as a framework material for implant-supported full-arch prostheses due to its low density, biocompatibility, and other mechanical properties. Remarkable mechanical properties such as lesser mass density and higher young's modulus of graphene have gained popularity among scientists, improving the properties of biomedical implants. Thus, our study aimed to compare the outcome through the von Mises stresses generated on All-on-6 and All-on-3 implant models, as well as on the framework, and evaluate the effect of stress patterns on the crestal bone around implants in the mandible. FEA (Finite Element Analysis) study was carried out using edentulous mandible models. Four 3D FEA models with 3 and 6 implants were used (Model 1: Titanium bar-supported 6 straight implants; Model 2: Graphene bar-supported 6 straight implants; Model 3: Titanium bar-supported 3 implants with 30 degrees-tilted; Model 4: Graphene bar-supported 3 implants with 30 degrees-tilted) in order to simulate endosseous implant designs. The implant measuring 4.2 mm in diameter and 11.5 mm in length were used. The most distal implants in the 3-implant models were placed with angulation of 30 degrees; in 6 implants, they were vertically placed. All the models were analyzed for vertical and oblique axis with a single force magnitude of 100 N. In all four implant models and under loading conditions, the peak stress points were always on the neck of the most distal implant. von Mises stresses were within the normal stress range. In a conventional six-straight implant model supported by a titanium framework, the cortical stress in the region of implants was 25.27 MPa, whereas, in the graphene framework, it was 12.18 MPa. Under vertical load, there was a significant difference in the cortical stress around the tilted implants (30 degrees) in the 3-implant system of titanium and graphene frameworks, respectively, 70.31 MPa and 21.27 MPa. The graphene framework demonstrated better results than the titanium framework for the conventional six-implant system under vertical load, achieving stress of 30.09 MPa and 76.60 MPa, respectively. In the case of the 3-implant system, a significant difference in the bar stress was observed between graphene and titanium, respectively, 256.32 MPa and 180.1 MPa of bar stress. Within the limitation of this study, the peri-implant stresses were decreased using graphene framework models. Hence, it was possible to conclude that the best load-bearing capacity results were found in the graphene framework group compared to the titanium framework for All-on-6 and All-on-3 implant models, even though both materials are reliable options used as framework materials in implant-supported full-arch prostheses.

Biocompatibility and antioxidant activity of a novel carrageenan based injectable hydrogel scaffold incorporated with Cissus quadrangularis: an in vitro study.

BACKGROUND: Over the past years, polysaccharide-based scaffolds have emerged as the most promising material for tissue engineering. In the present study, carrageenan, an injectable scaffold has been used owing to its advantage and superior property. Cissus quadrangularis, a natural agent was incorporated into the carrageenan scaffold. Therefore, the present study aimed to assess the antioxidant activity and biocompatibility of this novel material. METHODS: The present in vitro study comprised of four study groups each constituting a sample of 15 with a total sample size of sixty (n = 60). The carrageenan hydrogel devoid of Cissus quadrangularis acted as the control group (Group-I). Based on the concentration of aqueous extract of Cissus quadrangularis (10% w/v, 20% w/v and 30% w/v) in carrageenan hydrogel, respective study groups namely II, III and IV were considered. Antioxidant activity was assessed using a 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay, whereas the biocompatibility test was performed using a brine shrimp lethality assay. The microstructure and surface morphology of the hydrogel samples containing different concentrations of Cissus quadrangularis aqueous extract was investigated using SEM. One-way ANOVA with the post hoc tukey test was performed using SPSS software v22. RESULTS: A significant difference (P < 0.05) in the antioxidant activity was observed among the study groups. Group III reported the highest activity, whereas the control group showed the least antioxidant activity. Additionally, a significant (P < 0.01) drop in the antioxidant activity was observed in group IV when compared with group III. While assessing the biocompatibility, a significant (P < 0.001) dose-dependent increase in biocompatibility was observed with the increasing concentration of aqueous extract of Cissus quadrangularis. SEM analysis in group III showed even distribution throughout the hydrogel although the particles are close and densely arranged. Reduced antioxidant activity in group IV was probably due to clumping of the particles, thus reducing the active surface area. CONCLUSION: Keeping the limitations of in vitro study, it can be assumed that a carrageenan based injectable hydrogel scaffold incorporated with 20% w/v Cissus quadrangularis can provide a favourable micro-environment as it is biocompatible and possess better antioxidant property.

Evaluation of Shear Bond Strength between Resin Composites and Conventional Glass Ionomer Cement in Class II Restorative Technique-An In Vitro Study.

The success of dental restorations depends mainly on the ability to bond to other filling materials and tooth substances, in order to resist the multitude of forces acting on the bond within the oral cavity. Although the shortcomings of composite resins have been significantly reduced over the past three decades, microleakage due to shrinkage under masticatory loads is unavoidable. In order to overcome such problems, two materials laminated with matched properties can be used to achieve optimum results. The sandwich technique is an approach in which dentine is replaced by glass ionomer cement (GIC), and enamel is replaced by composite resin. In the past, numerous materials have been proposed with adequate properties to be used in this manner, but the results are conflicting in terms of bonding to the various forms of GIC, and the appearance of microcracks or gap formation during functional loading. This study aimed to evaluate the shear bond strength (SBS) and mode of failure between the following core materials: composite resins (CR) (Methacrylate Z350™, Ceram X™, and Spectrum™) with a base material of glass ionomer cement (GIC, Ketac Molar™). Eight samples were made with the help of polytetrafluoroethylene sheets (TEFLON, Wilmington, DE, USA). Each sheet consisted of holes which were 4 mm in diameter and 2 mm in thickness. The combination of materials was sandwiched. The samples were stored in distilled water and then placed in an incubator for 24 h in order to ensure complete polymerization. The samples were thermocycled for 500 cycles between 5-55 °C/ 30 s. Following thermocycling, SBS testing was performed using a universal testing machine. Additionally, scanning electron microscopy (SEM) was performed on representative samples for the bond failure analysis between GIC and the composite resins. The Ceram-X™ nanocomposite showed significantly higher bond strength than Methacrylate Z350™ or Spectrum™ (p = 0.002). The Methacrylate Z350™ and the Spectrum™ composite specimens demonstrated a similar SBS (p = 0.281). The SBS of the Ceram X™ to GIC was the highest compared to Methacrylate Z350™ and Spectrum™. Therefore Ceram X™ may produce a better bond with GIC, and may protect teeth against recurrent caries and failure of the restoration. Methacrylate Z350™ is comparable to Spectrum™ CR and can be used as an alternative. A combination of adhesive and mixed failure was observed in Methacrylate Z350™ CR and GIC, while adhesive failure was predominantly found in both Ceram X™ and Spectrum™ with GIC restorations.

Study of Lateral Wall Thickness of the Maxillary Sinus in Left and Right Sides for Female and Male: A Cross Sectional Retrospective Study Using Cone Beam Computed Tomography.

BACKGROUND: Dental implants are considered the first option to replace missing teeth. Alveolar bone resorption gradually progresses following tooth extraction leading to loss of vertical bone dimension for implant placement. The lateral window approach is the most commonly used procedure to treat vertical bone loss. OBJECTIVE: The aim of the present study is to evaluate the Lateral Wall Thickness (LWT) of the maxillary sinus and determine the influence of gender and side on maxillary LWT. METHODS: This study involved a cross sectional retrospective study. Cone- beam computed tomography data were collected from 99 patients with a total of 198 maxillary sinuses that met the inclusion criteria. The patient age ranged between 18 to 35 years. On the selected sagittal section, the points of measurement are determined by a perpendicular line at 5 mm from the lowest point of the sinus floor. Measurements were taken at four different areas; first premolar (P1), second premolar (P2), first molar (M1), and second molar (M2). Descriptive statistics were used to calculate mean lateral wall thickness for each tooth, and student's t-test was used to test the effect of gender and side on maxillary LWT. RESULTS: The greatest mean LWT was observed around the left first maxillary molar (2.43±0.82), while the lowest mean LWT was observed around the right second maxillary premolar (1.62±0.61). There was no significant difference in the LWT around any tooth (M1 p=0.56, M2 p=0.92, P1 p=0.14, P2 p=0.19). CONCLUSION: There was no significant difference in both males and females of the lateral wall thickness in the left and right side of maxillary sinus.

Effectiveness of antimicrobial photodynamic therapy as an adjunct to mechanical instrumentation in reducing counts of Enterococcus faecalis and Candida albicans from C-shaped root canals.

BACKGROUND/PURPOSE: The aim was to assess the effectiveness of antimicrobial photodynamic therapy (aPDT) as an adjunct to mechanical instrumentation (MI) in reducing Enterococcus faecalis (E faecalis) and Candida albicans (C albicans) counts from C-shaped root-canals. METHODS: Teeth with C-shaped canals as identified on cone beam computed tomographic images were included. Following incubation with E faecalis and C albicans, samples were divided into 4 groups a four follows: Group-1: MI with adjunct aPDT; Group-2: aPDT alone; Group-3: MI alone; and Group-4: no treatment. The pulp chambers of these teeth were exposed and coronal pulp was mechanically derided using sterile endodontic excavators. Using flexible files, all canals were debrided up to size #30 K-files with intermittent irrigation with 2.5% sodium hypochlorite irrigation. In Groups 1 and 3, methylene-blue was injected in all canals and aPDT was performed using a 600 nm diode laser. Sample-size estimation was done on data from a pilot investigation and group-comparisons were done using one way analysis of variance and Bonferroni post-hoc adjustment tests. P < .05 was considered statistically significant. RESULTS: Sixty periodontally hopeless mandibular second molars with C-shaped canals were included. There was a statistically significant reduction CFU/mL of E faecalis (P < .001) and C albicans (P < .001). At post-operative microbial assessments in Group-1. There was no difference CFU/mL of E faecalis and C albicans at post-operative microbial assessments in Groups 2-4. CONCLUSION: MI with adjunct aPDT is more effective in reducing count of E faecalis and C albicans from C-shaped root canals.

A Clinical Case Report of a Potential Acute Allergic Reaction with Titanium Dental Implant.

Titanium hypersensitivity is rare, but it may exist among patients who need dental implant treatment. It could contribute to mild or severe peri-implant tissue hypersensitivity reactions and affect patients' oral and general health according to some clinical reports. In extreme cases, it may lead to implant failure or extraction. In this case report, a 64-year-old Caucasian female patient received a titanium implant placement on #5. Right after the implant placement, she reported the symptoms of pain, eczema, and slight extraoral swelling, along with significant burning sensation occurring intra- and extraorally. The symptoms were not released after the systemic intervention of antibiotics for six days. On retrieving her medical history, the patient reported a previous allergic reaction to jewelry-like earrings in her childhood. The diagnosis of titanium hypersensitivity was made based on the rapid onset of symptoms and her metal allergy history. Therefore, the dental implant was removed after diagnosis, and a bone allograft was used to preserve the alveolar bone volume. Immediately after implant extraction, the swelling and burning sensation were receded. A complete recovery was achieved three weeks later. The dimension of the alveolar ridge bone was found well maintained in 10 weeks follow-up visit. Conclusion. Rapid onset of peri-implant gingival swelling may indicate a hypersensitivity to titanium implant in the clinic. For patients with a history of allergy to jewelry, the hypersensitivity tests to titanium alloy such as patch test or lymphocyte transformation test should be recommended as part of the dental implant treatment plan.

Evaluation of 2% Chlorhexidine and 2% Sodium Fluoride as Endodontic Irrigating Solutions on Root Dentine Microhardness: An In Vitro Study.

OBJECTIVES: The aim of this study was to evaluate the effects of 2% chlorhexidine gluconate (CHG) and 2% sodium fluoride (NaF) as endodontic irrigants on microhardness of root dentin. MATERIALS AND METHODS: In this in vitro study, access cavity and root canal preparations were done on 24 freshly extracted anterior teeth. After sectioning into 24 dentin discs using hard tissue microtome in 2 mm thickness, all samples were immersed in solutions of 17% ethylenediamine tetra-acetic acid (EDTA) (2 minutes) followed by 2.5% of sodium hypochlorite (NaOCl) (10 minutes). Then samples were randomly divided into three groups based on the irrigant used: Group I: saline (control group); Group II: 2% NaF; Group III: 2% CHG for two minutes each. Dentin microhardness was measured before (pretreatment), during (after treatment with 17% EDTA and 2.5% NaOCl), and after the experimental period (after treatment with saline, 2% NaF, and 2% CHG) using a Vickers indenter. Statistical evaluation of the data was done using one-way analysis of variance (ANOVA) and the Student's t-test, and the values are tabulated. RESULTS: Specimens rinsed in 2% CHG showed a significant increase in Vickers hardness number (VHN) values (p < 0.05), as compared with EDTA and NaOCl groups, whereas saline and 2% NaF groups showed no significant difference. CONCLUSIONS: NaF did not show any significant effect on microhardness of the root dentin. CHG as an irrigant was seen to have a strengthening effect on dentin microhardness in comparison to NaOCl and EDTA, which has decreased the strength of root dentin.

Efficacy of calcium hydroxide and resin-modified calcium silicate as pulp-capping materials: a retrospective study.

The aim of this study was to compare the clinical success rates of light-cured, resin-modified calcium silicate (TheraCal LC) and calcium hydroxide (Dycal) as pulp-capping materials in permanent teeth. In this retrospective electronic record review of patients treated in the years 2012 through 2015, the postoperative data of 120 patients (n = 60 per material) were collected. In these 2 groups, 69 teeth were treated with calcium hydroxide (29 in men, 40 in women) and 79 with calcium silicate (37 in men, 42 in women). The following data were recorded: treated tooth; patient age and sex; reason for treatment; direct or indirect pulp cap; date of treatment; date of most recent dental appointment; and treatment outcome. The selected patients met the following inclusion criteria: They had received either a direct or an indirect pulp cap in an anterior or posterior tooth after excavation of deep caries as part of a routine restorative procedure using either amalgam or composite resin; and they had returned to the clinic for other dental care at least 3 months after the pulp-capping treatment. Patients were excluded from the study if they reported symptoms of irreversible pulpitis or chronic tooth pain before the restorative treatment was started. The treatment outcome was considered clinically successful if the tooth was still present and asymptomatic at the appointments following the procedure. The outcome was considered unsuccessful if the tooth was extracted due to symptoms or if endodontic treatment had been performed postoperatively. There was no statistically significant difference between the clinical success rates of calcium silicate (85.5%) and calcium hydroxide (84.8%), according to the Fisher exact test (P < 0.05). Neither the patient's sex nor the tooth location affected the outcome. Within the limitations of this retrospective clinical study, it may be concluded that TheraCal LC calcium silicate can be considered equivalent inefficacy to calcium hydroxide for both direct and indirect pulp capping. A prospective clinical study with a larger sample size is needed to confirm these findings.