Two critical factors that influence the accuracy of an impression include the proper manipulation of the impression materials and the technique used to make the impression. The purpose of this study was to clinically evaluate the effect of different mixing techniques on the accuracy of vinyl polysiloxane (VPS) impressions by assessing metal framework fit of fixed partial restorations. The study included 92 consecutive patients diagnosed with partial edentulism and treated with fixed partial denture restorations. The mixing technique was one of the two following mixing methods: hand mixing technique (45 patients), with the putty material mixed according to the manufacturer’s instructions; or mechanical mixing technique (47 patients), with the putty material mixed by a Pentamix device. Under both mixing methods, vinyl polysiloxane was used as the impression material. Two impression techniques were randomly used by the operators (One/Two-stage putty –wash impression techniques). The accuracy of the metal framework restorations was tested clinically and radiologically, resulting in significant statistical difference (p = 0.04) between different mixing techniques. The mechanical mixing produced more accurate restorations (metal framework misfit only in 14.9% of patients vs. hand mixing 31.1%). Regarding the impression techniques, the two-stage impression technique was found to be significantly more accurate (p = 0.04), resulting in 14.6% ill-fitted metal frameworks vs. 31.8%, in the one-stage technique. It can be concluded that mechanical mixing yields more accurate impressions leading to more accurate restorations, especially when combined with two-stage impression technique.

Little is reported about the prosthetic aftercare of implant-supported mandibular overdentures regarding the number of implants placed. The purpose of this study was to evaluate the prosthetic aftercare among edentulous patients restored with two vs. four mandibular implant-retained overdentures (MISOD). Forty-six consecutive edentulous patients treated by a new MISOD were retrospectively studied. Twenty-five patients had two-ball attachment MISOD (Group A), and 21 had four-ball attachment MISOD (Group B). The total amount of aftercare visits was recorded, as well as the type of treatments required (pressure sore spots relief, attachment liner replacement due to loss of retention, and metal ball attachment replacement due to wear). The mean follow-up duration was 93 ± 57 months (range 9–246 months). None of the implants was lost. There were significantly more visits for pressure sore spots relief in Group A vs. Group B (6.2 ± 2 in group A and 4.09 ± 1.54 in group B, p < 0.0001). Differences in the other two tested parameters (number of visits for liner replacement (2.3 ± 1.84 in group A and 2.4 ± 1.63 in group B) and attachment replacement (2.36 ± 1.85 in group A vs. 2.48 ± 1.63 in group B) yielded a non-significant outcome (p = 0.814 for liner replacement and p = 1.000 for attachment replacement). The use of four-ball attachments in MISOD was more beneficial than two-ball attachments with regards to the aftercare of pressure sore spots. The number of implants did not influence the mechanical wear.

Temporary dental crowns and bridges are commonly made of poly-methylmethacrylate (PMMA), a porous material attracting the microbial biofilm associated with malodor production. The purpose of the present study was to test pre-disinfection of PMMA on malodor-related parameters in an experimental oral biofilm. PMMA discs were pre-soaked in anti-malodor disinfecting solutions and controls: (i) Saline, (ii) essential oils (EO), (iii) herbal extracts (HE), and (iv) chlorhexidine (CHX). Following, discs were subjected to a salivary incubation assay and monitored for malodor-producing bacteria within the biofilm using confocal microscopy (CLSM), malodor production (organoleptic scale 0–5), volatile sulfide levels (Halimeter), and salivary protein degradation (SDS-PAGE). Results showed that disinfection solutions were significantly effective in reducing malodor-related parameters (CHX > HE > EO > Saline). Taken together, these results suggest that pre-disinfection may help to reduce malodor production in PMMA temporary dental restorations.

Previous study suggested that fixed dental prostheses (crowns) increase oral malodor production. There might be a role to temporary acrylic crowns contributing to oral malodor. In the current study, we analyzed the microbiome associated with malodorous temporary dental crowns. The study population comprised nineteen patients (mean age 45.8 ± 10.9, 8 females) who visited the Tel Aviv University dental clinic. Temporary crowns were scored by an odor judge using a 6-point malodor organoleptic scale (0–5) and temporary crowns that were scored 2 and above were assigned as malodor positive. Microbial DNA was extracted from the temporary dental crowns and analyzed using next generation 16S rDNA sequencing. Taxa identified could be classified into 11 phyla, 50 genera and 119 core species. Malodor positive samples demonstrated higher abundance of the phyla Proteobacteria and Actinobacteria and the genera Tannerella, Alloprevotella, Treponema, Olsenella and Bifidobacterium. Malodorous samples showed higher bacterial diversity and significant differences in microbial population. Taken together these results suggest a difference between the microbial populations of malodorous and non-malodorous temporary dental crowns both in composition and diversity.