Towards quantitative analysis of enamel erosion by focused ion beam tomography.

OBJECTIVES: The purpose of this work is a proof of concept to introduce a new quantitative 3D-analysis of dental erosion obtained by focused ion beam (FIB) tomography associated with silver nitrate penetration into porosities in etched enamel. METHODS: One sample selected was sound enamel after removal of the aprismatic surface. The other was studied after applying an additional attack with orthophosphoric acid. Both surfaces were infiltrated with silver nitrate via immersion. After dehydration, samples were observed in a dual column FIB/SEM station. Serial FIB sectioning was conducted with a current of 3nA at 30keV and an increment step of 20nm for the healthy enamel and of 40nm for the etched one. 3D analysis was performed with Fiji software and BoneJ plugin and several parameters were obtained to characterize the tissue: non-mineralized phase content (NMP), connected porosity fraction (CPF) and degree of anisotropy (DA) of the NMP. RESULTS: Healthy enamel showed an NMP content of 0.5vol.%, with a bimodal distribution of non-mineralized regions, inside the prisms and between the prisms. No silver penetration was noticed in the healthy enamel, demonstrating the absence of open porosity. In contrast, silver nitrate penetration after acidic exposure was observed, up to a depth of 12µm, which allowed the calculation of an interconnected porosity volume fraction (CPF) of 3.1vol.%, mostly between the prisms. Values for DA of 0.56 for sound enamel and 0.81 for acid-etched surface were determined, highlighting a higher degree of anisotropy in the latter. SIGNIFICANCE: Quantitative analysis of FIB tomography using NMP, CPF and DA should contribute to a better understanding and follow up of dental erosion, correlation between erosion and attrition or abrasion process, and the ability to develop enamel remineralization procedures.

Continuation of subcutaneous or intramuscular injectable contraception when administered by facility-based and community health workers: findings from a prospective cohort study in Burkina Faso and Uganda.

OBJECTIVE: The aim of this study was to examine continuation of subcutaneous and intramuscular depot medroxyprogesterone acetate (DMPA-SC and DMPA-IM) when administered by facility-based health workers in Burkina Faso and Village Health Teams (VHTs) in Uganda. STUDY DESIGN: Participants were family planning clients of health centers (Burkina Faso) or VHTs (Uganda) who had decided to initiate injectable use. Women selected DMPA-SC or DMPA-IM and study staff followed them for up to four injections (providing 12 months of pregnancy protection) to determine contraceptive continuation. Study staff interviewed women at their first injection (baseline), second injection, fourth injection and if they discontinued either product. RESULTS: Twelve-month continuation in Burkina Faso was 50% for DMPA-SC and 47.4% for DMPA-IM (p=.41, N=990, 492 DMPA-SC and 498 DMPA-IM). Twelve-month continuation in Uganda was 77.8% for DMPA-SC and 77.4% for DMPA-IM (p=.85, N=1224, 609 DMPA-SC and 615 DMPA-IM). Reasons for discontinuation of DMPA across groups in Burkina Faso included side effects (90/492, 18.3%), being late for injection (68/492, 13.8%) and refusal of spouse (51/492, 10.4%). Reasons for discontinuation in Uganda included being late for injection (65/229, 28.4%), received from non-VHT (50/229, 21.8%) and side effects (34/229, 14.8%). Increased age (adjusted hazard ratio=0.98, p=.01) and partner acceptance of family planning (adjusted hazard ratio=0.48, p<.001) had protective effects against discontinuation in Burkina Faso; we did not find statistically significant variables in Uganda. CONCLUSIONS: There is no difference in 12-month continuation (through four injections) between DMPA-SC and DMPA-IM whether from facility-based health workers in Burkina Faso or VHTs in Uganda. Continuation was higher through community-based distribution in Uganda than health facilities in Burkina Faso. IMPLICATIONS: The subcutaneous formulation of depot medroxyprogesterone acetate (DMPA-SC) is increasingly available in Family Planning 2020 countries. Use of DMPA-SC does not appear to change continuation relative to traditional intramuscular DMPA. Growing evidence of DMPA-SC's suitability for community-based distribution and self-injection may yield indirect benefits for contraceptive continuation and help reach new users.

A new testing protocol for zirconia dental implants.

OBJECTIVES: Based on the current lack of standards concerning zirconia dental implants, we aim at developing a protocol to validate their functionality and safety prior their clinical use. The protocol is designed to account for the specific brittle nature of ceramics and the specific behavior of zirconia in terms of phase transformation. METHODS: Several types of zirconia dental implants with different surface textures (porous, alveolar, rough) were assessed. The implants were first characterized in their as-received state by Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB), X-Ray Diffraction (XRD). Fracture tests following a method adapted from ISO 14801 were conducted to evaluate their initial mechanical properties. Accelerated aging was performed on the implants, and XRD monoclinic content measured directly at their surface instead of using polished samples as in ISO 13356. The implants were then characterized again after aging. RESULTS: Implants with an alveolar surface presented large defects. The protocol shows that such defects compromise the long-term mechanical properties. Implants with a porous surface exhibited sufficient strength but a significant sensitivity to aging. Even if associated to micro cracking clearly observed by FIB, aging did not decrease mechanical strength of the implants. SIGNIFICANCE: As each dental implant company has its own process, all zirconia implants may behave differently, even if the starting powder is the same. Especially, surface modifications have a large influence on strength and aging resistance, which is not taken into account by the current standards. Protocols adapted from this work could be useful.

Low temperature degradation and reliability of one-piece ceramic oral implants with a porous surface.

UNLABELLED: Low temperature degradation of zirconia (3Y-TZP) oral implants and its effect on fatigue reliability is poorly documented. OBJECTIVE: The aim of this investigation was to follow the aging process occurring at the surface of implants exhibiting a porous coating and to assess its influence on their mechanical (fatigue) properties. METHODS: Tetragonal to monoclinic transformation (t-m) was evaluated during accelerated aging tests up to 100h in autoclave (134°C, 2 bars) by X-ray diffraction (XRD) and focused ion beam (FIB). A series of implants were steam-aged for 20h before fatigue testing. Such temperature-time conditions would correspond roughly to 40 years in vivo. The aged specimens and a non-aged control group were step-stress fatigued until failure or survival. RESULTS: The evolution of XRD surface monoclinic content was slow, i.e. 16% and 35% for 20 and 100h respectively. However, FIB revealed a significant transformation, initiated at the interface between the porous layer and the bulk, preferentially growing towards the bulk. FIB is therefore better indicated than XRD to follow aging in such implants. Higher average fatigue strength (aged 1235N versus non-aged 826N) and reliability levels were observed for the 20h aged group. SIGNIFICANCE: After aging for durations compatible with clinical use, 3Y-TZP with porous surface presented higher fatigue performance. This is in contrast to previous studies where loss of strength due to aging was often reported. Generalizations must therefore be avoided when considering aging of zirconia dental products and every new material/process combination should be tested before drawing conclusions.

Changes in sexual behaviour among HIV-infected women in west and east Africa in the first 24 months after delivery.

OBJECTIVE: Describe changes in sexual behaviour and determinants of unsafe sex among HIV-infected women in the 24 months after delivery. DESIGN: Cohort analysis nested within a prevention of mother-to-child transmission trial in Burkina Faso (n = 339) and Kenya (n = 432). METHODS: Women were followed during pregnancy and until 12-24 months after delivery. At each visit, structured questionnaires were administered about sexual activity and condom use, and risk-reduction counselling and condoms were provided. RESULTS: At study entry, a median 2 months after HIV testing (interquartile range =1-4), 411/770 (53.4%) of women reported partner disclosure, increasing to 284/392 (71.9%) at the final visit. Although most partners were supportive following disclosure, between 5 and 10% of disclosed women experienced hostile or unsupportive partner responses during follow-up visits. At each visit, about a third of sexually active women reported unsafe sex (unprotected sex with HIV-uninfected or unknown status partner). In multivariable logistic regression, unsafe sex was 1.70-fold more likely in Kenyan than in Burkinabe women [95% confidence interval (95% CI) = 1.14-2.54], and in those with less advanced HIV disease or aged 16-24 years. Compared with women who disclosed their status to partners and others, unsafe sex was over six-fold higher in nondisclosers (95% CI = 3.31-12.11), the effect size reducing with increasing disclosure. CONCLUSION: HIV-infected women who recently delivered have a high potential for further HIV transmission, especially as HIV discordance is common in Africa. Longitudinal care for women, including positive-prevention interventions, is needed within new services providing antiretroviral prophylaxis during breastfeeding - this repeated interface with services could focus on reducing unsafe sex. Much remains unknown about how to facilitate beneficial disclosure.