BMC Oral Health最新文献

Background: The retrieval of fractured high-speed handpiece burs during mandibular third molar surgery, particularly those adjacent to the mandibular canal or complicated by infection, presents a significant clinical challenge. Conventional techniques often fail in such scenarios owing to anatomical constraints and limited resources in primary care settings. This case report highlights the innovative application of a modified mild steel probe technique for managing this rare but serious complication, demonstrating its adaptability across diverse clinical environments.

Case presentation: We present two cases with deeply embedded bur fragments. Patient 1 involved a 28-year-old female with a 2.8-mm fragment near the mandibular canal. Using a novel, real-time shapable (≤ 120°) unquenched mild steel probe and a "three-point" localization method under panoramic radiography, the fragment was successfully retrieved in 35 min, with resolved neurosensory deficits at the 1-month follow-up. Patient 2 involved a 27-year-old female with a larger fragment (3.2 mm × 1.5 mm) complicated by infection and bone destruction. Under CBCT guidance, an upgraded probe was shaped into a 135° reverse hook and used with a "layered dissection" technique, achieving retrieval in 25 min. The patient experienced significant symptom relief by day 3 and near-complete bone regeneration at 3 months.

Conclusions: This case report demonstrates that a malleable, non-quenched mild steel probe technique may offer a material-independent, angle-adaptive, and cost-effective alternative for retrieving deeply embedded bur fragments. Its core innovation lies in overcoming the inflexibility of conventional rigid instruments and the material limitations of magnetic systems, providing a practical solution particularly in resource-conscious settings or for non-ferromagnetic fragments.

Background: To investigated the combined effect of adhesive type and film thickness on dentin bond strength by comparing one and two-step universal adhesives applied in single and double layers.

Methods: Forty caries-free human third molars were collected and standardized Class I cavities were prepared. Specimens were restored using one-step (Clearfil Tri-S Bond Universal, Japan) and two-step (G2-Bond Universal, Japan) universal adhesive systems. Each group was subdivided into single and double-layer applications, light-cured, and restored with a universal composite resin. Sticks with a cross-sectional 1 × 1 mm² were prepared for testing. Adhesive film thickness was measured under a stereomicroscope at ×80 magnification. Micro-tensile bond strength (µTBS) was evaluated either immediately or after 5000 thermocycles (TC). Failure modes were assessed under ×40 magnification. Wilcoxon Signed Ranks Test was used for paired comparisons of immediate and after TC tensile bond strengths. Mann-Whitney U test compared single vs. double layers of the adhesives. For adhesive film thickness, Independent Samples t-test was applied for group comparisons (p < 0.05).

Results: Double-layer application produced significantly thicker adhesive films for Clearfil Tri-S Bond and G2-Bond Universal compared with single-layer application (p < 0.05). However, no significant differences in µTBS were observed between single and double-layer groups of either adhesive, regardless of aging. Thermocycling significantly reduced bond strength for both systems (p < 0.05). Overall, the two-step adhesive demonstrated higher µTBS values than the one-step adhesive.

Conclusion: Although double-layer application increased adhesive film thickness, it did not improve dentin bond strength. The two-step universal adhesive system showed superior bonding performance compared with the one-step system, both immediately and after thermocycling.

Objective: The objective of this study is to evaluate the flexural strength and surface hardness of denture base resins that have been milled using computer-aided design and computer-aided manufacturing milling (CAD/CAM) and conventional heat-polymerized denture base resins (HP).

Methods: Eighty samples were made using CAD/CAM resin material (Polident CAD/CAM and Interdent CC discs) and conventional heat-polymerised acrylic resin (HP) (IvoBase CAD and PMMA). Based on the denture base material, the samples were categorised into eight groups: each group (n = 10), flexural strength (n = 40), surface hardness (n = 40). Both the surface hardness and flexural strength were evaluated using the Vickers hardness test and the three-point flexure test, respectively. A statistical analysis with a significance level of α = 0.05 was used to analyze the data.

Results: Compared with HP resins, milled CAD/CAM resins demonstrated significantly higher flexural strength and surface hardness (p < 0.001). The flexural strength of MHC 72.72 ± 5.95 is significantly lower than that of IHC 78.96 ± 3.36, PCC 108.59 ± 6.51, and VCC 99.88 ± 6.05 MPa. Surface hardness is significantly lower in MHC (18.40 ± 2.28 VHN) than in the other groups: IHC (21.30 ± 2.40 VHN), PCC (31.07 ± 2.07 VHN), and VCC (27.09 ± 1.55 VHN).

Conclusion: Compared with heat-polymerized acrylic resin, milled CAD/CAM resins performed exceptionally well in terms of flexural and surface mechanical properties.