Abstract:

This study aimed to evaluate stress distribution around two and four implants supporting maxillary implant overdentures retained by locator attachments, comparing full and partial palatal coverage designs. Four identical acrylic models representing completely edentulous maxillary arches were fabricated and covered with polyvinyl siloxane impression material to simulate the oral mucosa overlying the residual ridge. The models were divided into two main groups according to the number of installed implants (two or four), and each group was further subdivided based on palatal design (full or partial palatal coverage). Locator abutments (female components) were secured to the implants using an abutment driver, after which the prosthetic frameworks were constructed. Four strain gauges were bonded to each implant fixture using strain gauge cement to record strain values. A LLOYD digital loading device was employed to apply controlled compressive loads, and the resulting stresses around the implants were measured for each configuration.

Statistical analysis revealed a significant difference in stress values between two-implant overdentures with full palatal coverage (30.64 ± 17.47 N/m × 10²) and those with partial palatal coverage (49.72 ± 23.17 N/m × 10²), with higher stresses observed in the partial coverage design. In contrast, although four-implant overdentures with partial palatal coverage (8.77 ± 4.54 N/m × 10²) demonstrated higher mean stress values than those with full palatal coverage (5.51 ± 3.83 N/m × 10²), this difference was not statistically significant.

Within the limitations of this in vitro study, full palatal coverage design resulted in lower stress values compared to partial palatal coverage in two-implant-supported maxillary overdentures. For four-implant-supported overdentures, full palatal coverage also showed lower stress values; however, the difference was not statistically significant.

Abstract 

Dental caries is a widespread infectious disease influenced by bacterial activity, dietary factors, and host 

susceptibility. Community water fluoridation has been a key public health measure for caries prevention, 

particularly in children. The optimal fluoride concentration in drinking water (0.7 mg/L) balances caries 

reduction with minimal fluorosis risk. This study assessed fluoride levels in drinking water and their 

correlation with dental caries in primary school children in Gharyan, Libya. A cross-sectional study was 

conducted on 350 children (aged 7–10 years) from urban and rural schools in Gharyan. Water samples from 

five stores and one groundwater source were analyzed for fluoride concentration using an ion-selective 

electrode. Dental caries was assessed using the dmft/DMFT index. Fluoride levels in water stores were 

negligible (0.0–0.1 mg/L), while unfiltered groundwater exhibited high concentrations (6.0–7.0 mg/L), 

exceeding WHO guidelines (1.5 mg/L). The low fluoride availability in most drinking sources suggests 

limited caries-preventive effects from water fluoridation in this region. The study highlights insufficient 

fluoride exposure in Gharyan’s public water supply, potentially contributing to higher caries prevalence. 

Further research is needed to evaluate alternative fluoride delivery methods and assess groundwater safety 

to optimize oral health outcomes.

Keywords. Fluoride Concentration, Drinking Water, Dental Caries, Primary School.

The most common antibiotics prescribed by dentists for dental infections in Gharyan city and neighbour regions