Removal of osseointegrated dental implants: a systematic review of explantation techniques

Objectives

This systematic review aims to evaluate current literature regarding available techniques for removal of osseointegrated implants in terms of explantation’s success, complications, and bone loss.

Material and methods

Two reviewers conducted a systematic literature search through electronic databases (PubMed and EMBASE), complimented by manual and grey literature searches. Successful explantation was defined as the primary outcome. Complications and availability of residual bone for immediate implantation were defined as secondary outcomes.

Results

Eighteen articles, comprising 372 implants and 241 patients, were included. Five techniques were identified: reverse torque, trephines, burs, piezosurgery, and laser-assisted explantation. Peri-implantitis was the most common reason for explantation, followed by crestal bone loss, fracture, and malpositioning. The reverse torque was the most frequently reported technique (284 implants) with 87.7% success rate. Burs were used for explantation of 49 implants with a 100% success rate, while trephines were utilized for removal of 35 implants with 94% success. Piezosurgery (11 implants) and Er.Cr:YSGG laser (1 implant) showed 100% success. One study reported perforation of the sinus floor following trephine explantation, while another reported fracture of 3 implants following reverse torque application. Further analysis was hindered by the quality of the available studies and their lack of data.

Conclusions

Reverse torque seems the most conservative, and in the authors’ opinion, should be the first choice for explantation despite its inferior success rate. Additional studies with randomized controlled designs and larger sample sizes are required.

Clinical relevance

Dental implants have become the leading choice to replace missing teeth with gradually increasing numbers of complications and failures. An effective, conservative, and economic explantation technique is necessary to allow a successive implant placement.

     

Development of bimetallic nickel-based catalysts supported on activated carbon for green fuel production

In this work, the catalytic deoxygenation of waste cooking oil (WCO) over acid–base bifunctional catalysts (NiLa, NiCe, NiFe, NiMn, NiZn, and NiW) supported on activated carbon (AC) was investigated. A high hydrocarbon yield above 60% with lower oxygenated species was found in the liquid product, with the product being selective toward n-(C₁₅ + C₁₇)-diesel fractions. The predominance of n-(C₁₅ + C₁₇) hydrocarbons with the concurrent production of CO and CO₂, indicated that the deoxygenation pathway proceeded via decarbonylation and decarboxylation mechanisms. High deoxygenation activity with better n-(C₁₅ + C₁₇) selectivity over NiLa/AC exposed the great synergistic interaction between La and Ni, and the compatibility of the acid–base sites increased the removal of oxygenated species. The effect of La on the deoxygenation reaction performance was investigated and it was found that a high percentage of La species would be beneficial for the removal of C–O bonded species. The optimum deoxygenation activity of 88% hydrocarbon yield with 75% n-(C₁₅ + C₁₇) selectivity was obtained over 20% of La, which strongly evinced that La leads to a greater enhancement of the deoxygenation activity. The NiLa/AC reusability study showed consistent deoxygenation reactions with 80% hydrocarbon yield and 60% n-(C₁₅ + C₁₇) hydrocarbon selectivity within 6 runs.

In this work, the catalytic deoxygenation of waste cooking oil (WCO) over acid–base bifunctional catalysts (NiLa, NiCe, NiFe, NiMn, NiZn, and NiW) supported on activated carbon (AC) was investigated.     

Occurrence of a mosquito vector in bird houses: Developmental consequences and potential epidemiological implications

Even with continuous vector control, dengue is still a growing threat to public health in Southeast Asia. Main causes comprise difficulties in identifying productive breeding sites and inappropriate targeted chemical interventions. In this region, rural families keep live birds in backyards and dengue mosquitoes have been reported in containers in the cages. To focus on this particular breeding site, we examined the capacity of bird fecal matter (BFM) from the spotted dove, to support Aedes albopictus larval growth. The impact of BFM larval uptake on some adult fitness traits influencing vectorial capacity was also investigated. In serial bioassays involving a high and low larval density (HD and LD), BFM and larval standard food (LSF) affected differently larval development. At HD, development was longer in the BFM environment. There were no appreciable mortality differences between the two treatments, which resulted in similar pupation and adult emergence successes. BFM treatment produced a better gender balance. There were comparable levels of blood uptake and egg production in BFM and LSF females at LD; that was not the case for the HD one, which resulted in bigger adults. BFM and LSF females displayed equivalent lifespans; in males, this parameter was shorter in those derived from the BFM/LD treatment. Taken together these results suggest that bird defecations successfully support the development of Ae. albopictus. Due to their cryptic aspects, containers used to supply water to encaged birds may not have been targeted by chemical interventions.     

Modulation of G-protein expression and adenylyl cyclase signaling by high glucose in vascular smooth muscle

OBJECTIVE: We have recently shown a decreased expression of Gialpha proteins and associated functions in aorta from short term (5 days) streptozotocin-induced diabetic rats. Since hyperglycemia is one of the underlying causes of diabetes-induced cardiovascular complications, it was of interest to examine if hyperglycemia may play a direct role in down regulating the expression of Gialpha in vascular smooth muscle cells of diabetic subjects. For this, the effect of high glucose treatment on Gialpha protein expression and adenylyl cyclase signaling in intact aorta and vascular smooth muscle cells (A10 cells) was investigated. METHODS: The cells were grown in normal glucose (5.5 mM) medium and were subsequently exposed to high glucose (26 mM) or normal medium for various time periods (24-96 h). Aorta from control rats were exposed to normal and high glucose medium for 72 h. The levels of G-proteins were determined by immunoblotting using specific antibodies. Adenylyl cyclase activity stimulated or inhibited by agonists was determined to examine the functions of G-proteins. RESULTS: The levels of Gialpha-2 and Gialpha-3 proteins in membranes from A10 cells and aorta exposed to high glucose for 3 or 4 days were significantly decreased as compared to control cells and control aorta, respectively, whereas the levels of Gsalpha protein were not altered. In addition, receptor-dependent and -independent functions of Gialpha proteins were attenuated in hyperglycemic cells, as demonstrated by inhibition of forskolin (FSK)-stimulated adenylyl cyclase activity by low concentration of GTPgammaS or by angiotensin II (Ang II), oxotremorine or C-ANP(4-23) (a ring deleted analog of atrial natriuretic peptide). On the other hand, the stimulatory effects of GTPgammaS, glucagon, isoproterenol, FSK and sodium fluoride on adenylyl cyclase were significantly augmented in hyperglycemic cells as compared to control cells, whereas basal adenylyl cyclase activity was significantly lower in hyperglycemic cells as compared to control cells. CONCLUSION: These results indicate that high glucose decreased the levels and functions of Gi proteins in A10 VSMC and aorta. It may thus be suggested that decreased levels and activity of Gi proteins and adenylyl cyclase signaling induced by hyperglycemia may be one of the important mechanisms contributing to the cardiovascular complications associated with diabetes.     

Whole exome sequencing unravels disease‐causing genes in consanguineous families in Qatar

Whole exome sequencing (WES) has greatly facilitated the identification of causal mutations for diverse human genetic disorders. We applied WES as a molecular diagnostic tool to identify disease‐causing genes in consanguineous families in Qatar. Seventeen consanguineous families with diverse disorders were recruited. Initial mutation screening of known genes related to the clinical diagnoses did not reveal the causative mutations. Using WES approach, we identified the definitive disease‐causing mutations in four families: (i) a novel nonsense homozygous (c.1034C>G) in PHKG2 causing glycogen storage disease type 9C (GSD9C) in a male with initial diagnosis of GSD3; (ii) a novel homozygous 1‐bp deletion (c.915del) in NSUN2 in a male proband with Noonan‐like syndrome; (iii) a homozygous SNV (c.1598C>G) in exon 11 of IDUA causing Hurler syndrome in a female proband with unknown clinical diagnosis; (iv) a de novo known splicing mutation (c.1645+1G>A) in PHEX in a female proband with initial diagnosis of autosomal recessive hypophosphatemic rickets. Applying WES as a diagnostic tool led to the unambiguous identification of disease‐causing mutations in phenotypically complex disorders or correction of the initial clinical diagnosis in ?25% of our cases.     

The Effects of Annealing Temperatures on Composition and Strain in SixGe1?x Obtained by Melting Growth of Electrodeposited Ge on Si (100)

The effects of annealing temperatures on composition and strain in Si_xGe_1−x, obtained by rapid melting growth of electrodeposited Ge on Si (100) substrate were investigated. Here, a rapid melting process was performed at temperatures of 1000, 1050 and 1100°C for 1 s. All annealed samples show single crystalline structure in (100) orientation. A significant appearance of Si-Ge vibration mode peak at ~00 cm⁻¹ confirms the existence of Si-Ge intermixing due to out-diffusion of Si into Ge region. On a rapid melting process, Ge melts and reaches the thermal equilibrium in short time. Si at Ge/Si interface begins to dissolve once in contact with the molten Ge to produce Si-Ge intermixing. The Si fraction in Si-Ge intermixing was calculated by taking into account the intensity ratio of Ge-Ge and Si-Ge vibration mode peaks and was found to increase with the annealing temperatures. It is found that the strain turns from tensile to compressive as the annealing temperature increases. The Si fraction dependent thermal expansion coefficient of Si_xGe_1−x is a possible cause to generate such strain behavior. The understanding of compositional and strain characteristics is important in Ge/Si heterostructure as these properties seem to give significant effects in device performance.