Purpose: The purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.
Methods: A flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].
Results: Three-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].
Conclusions: Chlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.

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Purpose: The purpose of this study was to determine the effect of number of chewing strokes on change in blood flow in denture-supporting maxillary mucosa.
Methods: Subjects consisted of 11 healthy dentate men. Mastication was simulated by intermittent loading (10 N, 1/0.75 Hz) on a lateral area of the hard palate using a 2-cm² test plate. Loading duration was set at 1, 4, 8 or 12 min (80, 320, 640 or 960 chewing strokes). A non-contact laser Doppler blood flow meter was used to determine change in blood flow and time taken for recovery to 110% of the pre-loading value. Mean blood flow at pre-loading and at each duration of intermittent loading were compared using a repeated measures ANOVA (α = 0.05) and the Dunnett test. Recovery times for each loading duration were compared using a one-way ANOVA (α = 0.05) and the Bonferroni-test.
Results: Three subjects showed no increase in mean blood flow with loading. Eight subjects consistently showed an increase in mean blood flow during intermittent loading relative to at pre-loading. Duration of loading yielded no significant difference in mean blood flow. Significant differences were observed in recovery time between at after 8 min loading and at after the other 3 loading (1, 4, and 12 min loading) durations.
Conclusion: Number of simulated chewing strokes showed no influence on mean blood flow during intermittent loading in denture-supporting mucosa. It did, however, affect recovery time taken for blood flow to return to its pre-loading level.

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Purpose: The purpose of this study was to compare the tensile strength of commercially pure titanium dowels and cores cemented with zinc phosphate or resin cements.
Methods: Twenty-one extracted human canines were endodontically treated. The root preparations were accomplished using Largo reamers (10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the dowel and cores were made, and specimens were cast in commercially pure titanium (n = 7) and divided in three groups: TZ–CP Ti dowels luted with zinc phosphate luting agent, TP–CP Ti dowels luted with Panavia F and TR–CP Ti dowels luted with RelyX U100. Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The results (N) were statistically analyzed by ANOVA and Tukey tests (α = 0.01).
Results: The ANOVA indicated that there were significant differences among the groups tested. A Tukey multiple comparison procedure was performed and revealed statistically significant higher retention values for the dowel luted with RelyX U100 when compared with zinc phosphate or Panavia F.
Conclusion: Cast commercially pure titanium dowels and cores fixed with RelyX U100 cement presented superior bond strength retention when compared to zinc phosphate and Panavia F.

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Purpose: Aerosol deposition is a technology for coating ceramics with impact consolidation at room temperature. The aim of the present study was to investigate the thickness and the microstructure of the aluminium oxide layer on different three dental resin composite materials created by means of aerosol deposition.
Methods: Disk-shaped specimens were fabricated with three resin composites (Estenia C&B, Targis, and Gradia). The specimens were ground flat, and then subjected to aerosol deposition using aluminium oxide submicron particles without inducing a localized temperature rise. The average thickness (AVH) and maximum thickness (Hmax) of the aluminium oxide layer deposited on the resin composite material were measured using a profilometer. Data were analyzed by ANOVA and post hoc Tukey compromise test at α = 0.05. The specimen surfaces were also observed using a scanning electron microscope.
Results: The aluminium oxide layer formed on Estenia C&B (AVH 8.1 μm, Hmax 9.1 μm) and Targis (AVH 7.7 μm, Hmax 8.9 μm) were significantly thicker than that on Gradia (AVH 4.2 μm, Hmax 5.4 μm). The micrograph showed that the aluminium oxide layer on Estenia C&B was similar to that on Targis. However, the aerosol deposition area of Gradia was seen relatively rough and partly caved.
Conclusions: The type of resin composite affected the microstructure of the deposited aluminium oxide layer. The highly filled light- and heat-cured resin composites are advantageous as a target material rather than the lower filled light-cured resin composite.

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Purpose: The purpose of this study was to evaluate survival rate and the reasons of failure of fixed dental prostheses (FDPs) without having regular maintenance in a long-term after insertion.
Materials and methods: The subjects were 55 patients (69 FDPs, 142 abutment teeth) who had received no regular maintenance after insertion of FDPs at the Prosthodontic Clinic, Tohoku University Dental Hospital in Japan from 1983 to 1989. Extraction of abutment teeth or removal of FDPs was considered as failure. Abutment teeth and FDPs requiring additional treatments were considered as the complications. The survival curves were analyzed using the Kaplan–Meier method. The reasons for failures and their frequency as well as complications were also examined.
Results: The average follow-up period was 16.5 years. 14 out of 142 abutment teeth were extracted, resulting in 10% failure rate. 22 out of total 66 FDPs were removed; the failure rate of FDPs was 33%. The most common reason for the failure and complication was periodontal disease. The mean value of plaque index was 43.2%. The analysis of the survival curves with the Kaplan–Meier method showed that the survival rates of FDPs at 15 years after insertion were 74%. As the status before treatment was not clearly stated, we cannot make an easy comparison; however, our data presented very similar results with reports from previous long-term clinical studies.
Conclusion: This study suggested that the abutment teeth and FDPs in patients without regular maintenance had many periodontal problems due to dental plaque.

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Purpose: The All-on-4 is used in the therapy of edentulous mandibles. However, few studies have investigated the effect of such implants on supporting bone. To clarify differences in stress in peri-implant cortical bone between 2-patterns of 6 implants and 8-patterns of 4 implants with change in inclination angle based on the All-on-4.
Methods: Three-dimensional finite element analysis models based on the mean value of the Japanese edentulous mandible were constructed. Implants 13 or 15 mm in length were inserted between the mental foramina. In the 6-implant model, implants were inserted in parallel. In the 4-implant model, the 2 anterior implants were inserted in parallel and the 2 posterior implants in parallel or on a slant. Implants were splinted with a superstructure. A 50 N load was applied to the occlusal surface under condition A, at 2 mm distal from the distal implant, or condition B, at the distal end of the superstructure. Maximum von Mises stress on cortical bone was measured.
Results: Stress was concentrated around the posterior-most implant on the right side. Under condition A, stress increased with 4 implants and increase in angulation. At 45°, stress increased by 23% of that in the 6-implant model. Under condition B, stress increased with 4 implants, although stress decreased with increase in angulation. At 45°, stress decreased by 45% of that in the 6 implants.
Conclusions: The use of 4 implants or inclined implants increased stress on peri-implant cortical bone. However, when used in conjunction with a short cantilever, inclined implants decreased stress on peri-implant cortical bone.

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Purpose: This study was to develop a titanium dioxide (TiO₂)-coated implant abutment, surface with ultraviolet (UV) light-induced hydrophilicity and investigate the initial response of human, fibroblasts to the surface modification.
Materials and methods: Commercially pure titanium (JIS 2 grade) disks were coated with TiO₂ to various, thicknesses (1, 2 or 3 μm) using peroxotitanium acid solution. The surface characteristics of each disk, were examined with X-ray diffraction (XRD), surface roughness equipment and scanning electron, microscopy (SEM). The hydrophilic change of each disk was determined by the contact angles at 0–24 h, after 24-h UV irradiation. The biological response at the surface of each disk was examined by using, human periodontal ligament fibroblasts (HPLFs). The data were statistically analyzed with analysis of variance (ANOVA) and multiple-comparison tests.
Results: The TiO₂-coated disk surface had an anatase structure. Surface roughness did not differ, significantly among the disks; the surface morphology was smooth and had a hydrophilic or superhydrophilic, status. HPLF proliferation significantly increased on the TiO₂-coated disks compared with the uncoated disks and depended upon the coated film thickness.
Conclusion: An anatase TiO₂-coated surface under UV irradiation markedly improves the initial response of human fibroblasts.

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Patient: A patient who had undergone left segmental mandibulectomy reconstructed with an autogenous bone graft presented with the chief complaint of difficulty in eating and speaking. Intraoral examination revealed thick, freely movable soft tissues with scar formation, loss of alveolar ridge, and obliteration of buccal and lingual sulcus in the entire left half of mandibular region. When given the options of pre-prosthetic surgery and dental implants, patient refused to undergo an additional surgery and requested a non-surgical treatment option. Consequently, conventional complete denture therapy modified by neutral zone technique was undertaken.
Discussion: Prosthetic rehabilitation of this patient was challenging due to inadequate amount of supporting tissues on the defect side resulting from cancer surgery. The fabrication procedure of the denture was carefully modified to achieve retention and stability. Tissue surface of the denture was relined with resilient liner, polished surface contours and tooth positioning were recorded with neutral zone technique and occlusal surfaces were modified to achieve balanced occlusion.
Conclusion: Conventional complete denture therapy with carefully recorded intaglio surface, cameo surface, and balanced occlusal surface can provide favorable retention and stability even though the denture bearing tissues are unfavorable especially in segmental mandibulectomy patients.

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