Interaction of Systemic Morbidity and Oral Health in Ambulatory Patients in Need of Home Care (InSEMaP): an observational study at the sector boundary between dental and general practice care in Germany.

INTRODUCTION: Older people in need of home care are at risk of declining oral health as their visits to dentists are becoming less frequent due to restricted mobility. There is increasing evidence that poor oral health and systemic diseases are closely associated, for example, in cardiological, metabolic or neurodegenerative conditions. Thus, Interaction of Systemic Morbidity and Oral Health in Ambulatory Patients in Need of Home Care (InSEMaP) is investigating the need, provision and utilisation of oral healthcare, systemic morbidity and clinical status of the oral cavity in older people. METHODS AND ANALYSIS: InSEMaP consists of four subprojects (SP), all involving the target population of older people in need of home care. In SP1 part a, a sample is surveyed using a self-report questionnaire. In SP1 part b, stakeholders (general practitioners, dentists, medical assistants, family and professional caregivers) are interviewed regarding barriers and facilitators using focus groups and personal interviews. In SP2, a retrospective cohort study, health insurance claims data are examined to investigate the utilisation of oral healthcare, its association with systemic morbidity and healthcare costs. In SP3, a clinical observational study will assess the oral health of participants by a dentist's visit at home. SP4 synthesises the results of SP1, SP2 and SP3 to develop integrated clinical pathways, identifying strategies to uphold oral healthcare in older people. In assessing and evaluating the process of oral healthcare, and its associated systemic morbidity, InSEMaP aims to improve general healthcare across the sector boundary of dental and general practitioner care. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Institutional Review Board of the Hamburg Medical Chamber (approval number: 2021-100715-BO-ff). The results of this study will be disseminated through conference presentations and publications in peer-reviewed journals. An expert advisory board to support the InSEMaP study group will be established. TRIAL REGISTRATION NUMBER: German Clinical Trials Register: DRKS00027020.

Air polishing with erythritol powder - In vitro effects on dentin loss.

CONTEXT: Low-abrasive polishing powders such as glycine (GLY) or erythritol (ERY) are used for subgingival air polishing. GLY was reported to possibly affect the dentin surface, while this is unclear for ERY. AIMS: This in vitro study aimed to evaluate the substance loss from the dentin surface by air polishing with ERY at different settings for pressure (PR), distance (DI), and angulation of the spray jet to the surface (AJ). MATERIALS AND METHODS: The in vitro testing was performed on smooth human root dentin surfaces. In 18 groups with 10 specimens each, ERY was applied with constant water supply for 5 s without moving the handpiece at the following settings: PR minimum (min), medium (med), and maximum (max); DI at 1, 3, and 5 mm; and 45° or 90° AJ. The substance loss was measured as defect depth (DD) using three-dimensional (3D)-laser profilometry. ANOVA with Bonferroni correction and α = 0.05 were used for statistical analysis. RESULTS: The DD was statistically significantly higher at a DI of 1 mm compared to a DI of 5 mm for the respective groups of the same PR and AJ (P < 0.05). For DI 1 mm, max PR, and AJ 90°, the maximum loss of substance amounted DD of 117 ± 43 µm. The minimal loss of substance occurred at minimal PR, 45° AJ, and a DI of 5 mm (15 µm × 20 µm). DD related directly with the parameters PR and AJ and inversely with DI. The highest influence on DD was proven for DI. CONCLUSIONS: Slight loss of dentin might occur during air polishing with ERY depending on DI, PR and AJ. The setting influences the amount of dentin loss.

Differences of the tumour cell glycocalyx affect binding of capsaicin-loaded chitosan nanocapsules.

The glycocalyx regulates the interaction of mammalian cells with extracellular molecules, such as cytokines. However, it is unknown to which extend the glycocalyx of distinct cancer cells control the binding and uptake of nanoparticles. In the present study, exome sequencing data of cancer patients and analysis of distinct melanoma and bladder cancer cell lines suggested differences in cancer cell-exposed glycocalyx components such as heparan sulphate. Our data indicate that glycocalyx differences affected the binding of cationic chitosan nanocapsules (Chi-NCs). The pronounced glycocalyx of bladder cancer cells enhanced the internalisation of nanoencapsulated capsaicin. Consequently, capsaicin induced apoptosis in the cancer cells, but not in the less glycosylated benign urothelial cells. Moreover, we measured counterion condensation on highly negatively charged heparan sulphate chains. Counterion condensation triggered a cooperative binding of Chi-NCs, characterised by a weak binding rate at low Chi-NC doses and a strongly increased binding rate at high Chi-NC concentrations. Our results indicate that the glycocalyx of tumour cells controls the binding and biological activity of nanoparticles. This has to be considered for the design of tumour cell directed nanocarriers to improve the delivery of cytotoxic drugs. Differential nanoparticle binding may also be useful to discriminate tumour cells from healthy cells.

Internal diseases encountered by dental students while treating dental patients during undergraduate training.

BACKGROUND: The number of internal diseases, disorders and syndromes (IMDDSs) encountered in dental practice is increasing. Dentists report to feel ill prepared by their undergraduate dental training for the management of IMDDSs. To increase the effectiveness of internal medicine training at dental school it might be necessary to focus on IMDDs encountered by dental students. The aim of our study was to identify IMDDSs dental students come across while treating dental patients during the clinical years of their undergraduate training. METHODS: All dental patients treated between April and July 2015 by 116 dental students enrolled at the Medical Faculty of Hamburg University in the semesters 7 to 10 were anonymously analysed retrospectively with respect to age, gender, smoking habits, drinking habits, current or previous diseases, allergies, current medication, dental diagnoses, and dental treatment in the current semester. Identified IMDDSs were clustered and evaluated. RESULTS: The 116 dental students treated 511 patients with 559 IMDDSs with a median of one IMDDS per patient. The IMDDSs encountered most frequently could be assigned to the subspecialties cardiology, endocrinology/diabetology, and rheumatology. Arterial hypertension occurred most frequently in dental patients, followed by diabetes mellitus type 2, and chronic bronchitis. CONCLUSIONS: We identified the spectrum of IMDDSs encountered by dental students in the clinical years of their undergraduate dental education. Further studies are needed to test the effects of learning internal medicine with an internal medicine course based on the IMDDSs encountered by dental students and including additional IMDDSs specific relevance for dentists.

Recommendations on the clinical application of air polishing for the management of peri-implant mucositis and peri-implantitis.

Air polishing was introduced as an alternative approach for the supra- and submucosal biofilm management at dental implants. An international expert meeting involving competent clinicians and researchers took place during the EUROPERIO 8 conference in London, UK, on 4 June 2015. Prior to this meeting a comprehensive systematic review dealing with the efficacy of air polishing in the treatment of peri-implant mucositis and peri-implantitis was prepared and served as a basis for the group discussions. This paper summarizes the consensus statements and practical recommendations on the clinical application of air polishing for the management of peri-implant mucositis and peri-implantitis.

Cleaning effectiveness of implant prophylaxis instruments.

PURPOSE: The aim of this study was to evaluate the cleaning effectiveness of implant prophylaxis instruments on polished and acid-etched implant surfaces. MATERIALS AND METHODS: Biofilm layers of Streptococcus mutans were grown on a total of 80 titanium disks; 40 disks were polished and 40 were acid-etched. Five disks of each surface were cleaned using each of seven implant prophylaxis instruments: (1) manual plastic curette, (2) manual carbon fiber-reinforced plastic (CFRP) curette, (3) sonic-driven prophylaxis brush, (4) rotating rubber cup with prophylaxis paste, (5) sonic-driven polyether ether ketone (PEEK) plastic tip, (6) ultrasonic-driven PEEK plastic tip, and (7) air polishing with amino acid (glycine) powder. Ten disks (five of each surface type) served as controls. After cleaning, the surfaces with remaining bacteria were assessed by light microscopy. Statistical analyses of the results were performed with one-way and two-way analyses of variance with Bonferroni-Dunn multiple comparisons post hoc analysis (α = .05). RESULTS: The cleaning effectiveness of the plastic curette was significantly lower than those of all machine-driven instruments on the polished surface. Significantly lower cleaning effectiveness occurred with the CFRP curette compared to the prophylaxis brush and to both oscillating PEEK plastic tips on the polished surface. The rubber cup provided less cleaning effectiveness compared to the ultrasonic PEEK plastic tip and air polishing on the acid-etched surface. Superior results, with less than 4% of the biofilm remaining, were obtained for both oscillating PEEK plastic tips and air polishing on both implant surfaces. The cleaning ability of the prophylaxis brush, rubber cup, and ultrasonic PEEK plastic tip differed significantly between both surface structures. CONCLUSIONS: Cleaning effectiveness, ie, less than 4% of the biofilm remaining, was not observed with all tested implant prophylaxis instruments. The cleaning ability of the devices depended on the implant surface structure.

A paradigm shift in mechanical biofilm management? Subgingival air polishing: a new way to improve mechanical biofilm management in the dental practice.

In the past few years indications for the use of the air polishing technology have been expanded from supragingival use (airflow) to subgingival air polishing (perioflow) by the development of new low-abrasive glycine-based powders and devices with a subgingival nozzle. Several studies on the subgingival use of air polishing have been completed. On 7 June 2012, during the Europerio 7 Congress in Vienna, a consensus conference on mechanical biofilm management took place aiming to review the current evidence from the literature on the clinical relevance of the subgingival use of air polishing and to make practical recommendations for the clinician. Bernita Bush (Bern), Prof Johannes Einwag (Stuttgart), Prof Thomas Flemmig (Seattle), Carmen Lanoway (Munich), Prof Ursula Platzer (Hamburg), Prof Petra Schmage (Hamburg), Brigitte Schoeneich (Zurich), Prof Anton Sculean (Bern), Dr Clemens Walter (Basel), and Prof Jan Wennström (Gothenburg) discussed under the moderation of Klaus-Dieter Bastendorf and Christian Becker (both ADIC Association for Dental Infection Control) the available clinical studies to reach a consensus on available clinical evidence. This paper summarizes the main conclusions of the consensus conference and points to the clinical relevance of the findings for the dental practitioner.

Preparation time and surface roughness of core foundation resins and dentin.

STATEMENT OF PROBLEM: It is unclear if the preparation of core foundation resins is similar to that of dentin. PURPOSE: The purpose of this in vitro study was to compare the preparation time and resulting roughness of 5 core foundation resins and dentin. MATERIAL AND METHODS: Standardized preparations (10 mm length, 5 mm height) were made of 5 specimens of 5 core materials with a device-mounted dental handpiece (150 000 rpm, water-cooling) with weight-controlled contact pressure (50 g). To assess the cutting time of 100 µm grit cylindrical diamond rotary cutting instruments, 2 mm and 4 mm depths were cut 3 times (n=15). Afterwards surface roughness Ra and Rz were measured. Blocks of dentin were used as a control. Both preparation time and surface roughness data were statistically analyzed (1-way ANOVA, Scheffé correction, α=.05). RESULTS: The average preparation times for dentin were 7 seconds for a 2 mm preparation depth and 22 seconds for a 4 mm depth with an average Ra of 5.4 µm or Rz of 30 µm. For a 4 mm depth, preparation times for Build-It, Rebilda LC, and Ti-Core ranged from 24 to 27 seconds. The preparation times of these 3 core foundation materials did not differ significantly from dentin for a 4 mm depth. The results of Core Paste and Luxacore were significantly lower (10 and 11 seconds, P<.001). For a 2 mm cutting depth, Core Paste and Luxacore showed similar preparation times compared to dentin (7 seconds, P>.05). Build-It (12 seconds) and Rebilda LC (10 seconds) showed greater preparation times compared to dentin, whereas Ti-Core preparation (5 seconds) was less. ANOVA revealed significantly lower Ra (5.0 µm) and Rz values (23-26 µm) after preparation of Core Paste, Luxacore, and Ti-Core than those of dentin (P<.05). CONCLUSIONS: The preparation times of only some core foundation materials were comparable to dentin. Regarding the cutting depths, different materials provided a dentin-like preparation ability. The surface roughness values of core resins were comparable with or significantly lower than those of dentin.

Effects of 10 cleaning instruments on four different implant surfaces.

PURPOSE: The aim of this study was to evaluate the effects of a variety of implant cleaning instruments on different implant surfaces, specifically surface roughness and cleaning efficacy. MATERIALS AND METHODS: Biofilm layers of Streptococcus mutans were cultivated on titanium disks with four different surface structures (polished, grit-blasted, acid-etched, and acid-etched/grit-blasted). Five disks each were cleaned using nine mechanical implant cleaning instruments or an erbium:yttrium-aluminum-garnet laser. Surface roughness (average, Ra; maximum, Rz) and waviness (Lr) were evaluated by two-dimensional laser profilometry. Surface structure damage and cleaning scores were assessed by scanning electron microscopy. Statistical analyses of the results were performed with one- and two-way analyses of variance and Bonferroni-Dunn multiple-comparison post hoc analysis (α = .05). RESULTS: Ra and Rz values for the acid-etched surfaces and Ra, Rz, and Lr values for the polished and the grit-blasted surfaces showed no significant differences between the different cleaning methods or cleaning instruments compared to the control (not cultured, not cleaned) groups. Significantly lower Ra and Rz values on grit-blasted/acid-etched implant surfaces were found following use of the Sonic-Flex clean with prophylaxis brush and the plastic curette compared to Satelec ProphyMax with Periosoft curette. Ra and Rz values of the different implant structure surfaces before cleaning were significantly different between all implant surfaces except for the polished compared to the acid-etched surfaces. CONCLUSIONS: Cleaning effect and alterations of the implant surfaces were strongly dependent on the implant cleaning method used.

The effect of changes in head position on enlargement of structures during panoramic radiography.

PURPOSE: Accuracy of panoramic radiographs is essential for distance measurements during implant planning, but it might be compromised by various factors. The aim of the present study was to evaluate the effect of vertical and horizontal head positioning on area-dependent enlargement ratios of digital panoramic radiography. MATERIALS AND METHODS: The mandible of a dry skull was marked with small steel globes. The skull was moved 1 to 4 degrees in 1-degree increments to the left and right and up and down. A series of 17 panoramic radiographs was obtained with the same digital radiographic device. For the rotated skull, horizontal and vertical distances, indicated by the steel globes, were compared to the distances with the ideal positioning of the skull. The results were analyzed statistically. RESULTS: Head positioning and angulation, anatomical site, and distance orientation influenced horizontal measurements. Enlargement ratios of horizontal distances of the right canine and first molar regions (skull rotation to the right 2 to 4 degrees) were significantly lower than those for the corresponding anatomical sites on the left side. Horizontal distance measurements of the different anatomical sites of the left and the right jaw did not differ significantly from each other when the skull was moved downward. When the skull was rotated upward, no significant differences were obtained for corresponding anatomical sites of the right and left arches. Enlargement ratios of vertical distances of different anatomical sites, as well as within the same anatomical site, were not significantly different from each other for the given skull rotations. CONCLUSIONS: Ideal head positioning for digital panoramic radiographs is mandatory to avoid improper enlargement ratios of horizontal distances, which can be important in implant dentistry.

Resistance against pull-out force of prefabricated coated FRC posts.

PURPOSE: To investigate the effect of a prefabricated tribochemical coating of FRC (fiber-reinforced composite) posts with and without aging on the pull-out forces compared to posts without conditioning. MATERIALS AND METHODS: Post space preparations were performed on 108 extracted anterior teeth. Thirty-six uncoated FRC posts (DentinPost) and 72 prefabricated tribochemically coated FRC posts (DentinPost Coated) were used at a length of 12 mm. Thirty-six of the coated posts were thermally aged. FRC posts (n = 9) were placed using DentinBuild or MultiCore Flow foundation composite resins or Panavia F2.0 or RelyX Unicem resin cements. Following water storage (37°, 24 h) and thermocycling (5000 cycles, 5° to 55°C, 30 s), pull-out force testing was performed. Fracture modes were assessed using a light microscope. Data were analyzed statistically (1-way and 3-way ANOVA, Bonferroni-Dunn correction, α = 0.05). RESULTS: Significantly higher pull-out forces of posts luted with Panavia F2.0 were observed for the coated and coated/aged FRC posts compared to the unconditioned posts (control group, p < 0.001). The pull-out forces of tribochemically coated FRC posts luted with MultiCore Flow were significantly lower than of coated posts luted with Panavia F2.0 (p < 0.001). Coated/aged FRC posts exhibited similar pull-out forces for the tested luting composite resins (p > 0.05). Except for DentinBuild (coated posts), more mixed or cohesive fractures were assessed for coated and coated/aged FRC posts than for unconditioned FRC posts. CONCLUSION: Prefabricated tribochemical coating of FRC posts provided a stable interface between coating and post and remained stable over time.

Effect of noble metal alloy post and core material on the fracture resistance of endodontically treated teeth.

The aim of this study was to investigate the effect of one particular brand of post and core system (ER Post) consisted of different post and core materials on the fracture resistance of endodontically treated teeth. Fifty caries-free maxillary central incisors were randomly assigned to five groups (n=10). All teeth were sectioned at the cemento-enamel junction except for the teeth in the control group. Four experimental groups consisted of cast gold post-and-core group (GG), Heraplat post/cast gold core group (HG), titanium post/composite core (TC), and titanium post/cast gold core (TG). The control group (ETT) consisted of endodontically treated teeth without posts. All posts were cemented in the roots with zinc phosphate cement. Following thermal cycling (5000 cycles between 5 degrees C and 55 degrees C with a dwell time of 30 seconds) a static load was applied to 2 mm below the incisal edge on the palatal surface of each specimen until they were fractured. Fracture data obtained and statistically analyzed with one-way ANOVA and a Tukey's test (p<0.05). Means of the fracture resistance during static loading were: 423.76 N (GG), 529.46 N (HG), 389.08 N (TC), 408.7 N (TG), 404.4 N (ETT, control). Heraplat post with cast gold core exhibited the highest fracture load than the other groups (p<0.05). Specimens in groups HG and ETT (control) showed the most repairable failure. Heraplat post with cast gold core had the highest fracture resistance of endodontically treated teeth.

Fracture resistance of endodontically treated teeth: effect of tooth coloured post material and surface conditioning.

This in vitro study evaluated the effects of the different endodontic posts and surface conditioning on the fracture resistance and fracture modes of endodontically treated teeth. The experimental groups consisted of zirconia ceramic post with a glasss-ceramic core [A], zirconia ceramic post with a composite core [B], glass fiber composite post (FRC) with a composite core [C], and titanium post with a composite core [D]. All posts in these groups were cemented with self-adhesive resin cement (Rely X Unicem Aplicap) combination with tribochemical silica coating (TSC). Groups E, F, G and H comprised the same post-and-core materials as the first 4 groups but cemented with the same resin cement without TSC. Specimens were subjected to thermal cycling between 5 degrees C and 55 degrees C for a total of 5000 cycles with 30s per cycle. Static load was applied to the palatal surface of each specimen until they were fractured. Statistical analysis was conducted using analysis of variance (ANOVA) followed by post-hoc comparisons (Tukey). The fracture resistance was significantly affected by the post material (P < 0.001) and surface conditioning (P < 0.001; two-way ANOVA). The application of TSC to post surface decreased the fracture resistance of zirconia ceramic post with composite core (p=0.002; Tukey) and glass FRC post with composite core (p=0.029; Tukey). No catastrophic failure was observed for groups B, C, D, E, F and G. Under the testing conditions used, the titanium post/composite core that had been silicoated exhibited the highest fracture resistance.

Effect of surface conditioning on the retentive bond strengths of fiberreinforced composite posts.

STATEMENT OF PROBLEM: Debonding is a common cause of failure encountered with fiber-reinforced composite (FRC) posts, and usually occurs along the post space-dentin adhesive interface. Surface conditioning of posts is expected to increase the chemical and mechanical bond between the luting composite resin and the post, but the best method has not been definitively determined. PURPOSE: The purpose of this in vitro study was to compare the effects of 3 surface-conditioning methods on the retentive bond strengths of FRC posts using 5 composite resin materials, and compare results to those of unconditioned FRC posts as well. MATERIAL AND METHODS: Post space preparations (DentinPost ER root post system, length of 12 mm) were performed on 200 human anterior teeth. Groups of 50 FRC posts (ISO size 90) each were treated using 1 of the following conditioning methods: silanization, etching with 5% hydrofluoric acid, tribochemical coating (CoJet system), or were left untreated (control group). FRC posts (n=10) in each group were placed using 1 of 5 composite resin materials (Calibra or RelyX Unicem resin cements or Build-It, MultiCore Flow, or Rebilda DC foundation composite resins). Following water storage (37 degrees C, 24 hours) and thermal cycling (5000 cycles, 5 degrees -55 degrees C, 30-second dwell time), tensile strength testing was performed. Fracture modes were assessed using a light microscope. Data were analyzed statistically (1-way and 2-way ANOVA, Bonferroni-Dunn correction, alpha=.05). RESULTS: Retentive bond strengths of FRC posts luted with MultiCore Flow in combination with the CoJet system, and of posts inserted with Rebilda DC in combination with hydrofluoric acid (HF) etching as well as with the CoJet system, were significantly higher than those of the corresponding unconditioned FRC posts (P<.001). No significant differences were noted between the bond strength values of RelyX Unicem with CoJet, MultiCore Flow with CoJet, and Rebilda DC with either CoJet or HF etching (P>.05). Retentive bond strengths were significantly lower for HF etching (Calibra, RelyX Unicem, Build-It), and for the treatment with the CoJet system in combination with Build-It compared to the corresponding control groups (P<.001). Fracture modes were primarily adhesive at the post surface or cohesive within the composite resin layer or within the FRC post. CONCLUSIONS: The retentive bond strengths differed significantly with respect to the tested combinations of conditioning method and luting composite resin.

Stability of loaded and unloaded implants with different surfaces.

PURPOSE: To compare the torsional strengths and the effects of functional loading on five different implant surface structures. MATERIALS AND METHODS: This in vivo longitudinal study of 9 months' duration examined osseointegration in 180 stepped cylindric implants placed into the mandibles of 18 healthy sheepdogs. Implants with five different surface structures were placed (n = 36 in each group): (1) smooth surface; (2) deep profile structure (DPS); (3) titanium plasma sprayed (TPS); (4) hydroxyapatite coated; and (5) sol-gel hydroxyapatite coated (SGHA). All implants were investigated under standardized conditions. At uncovering (3 months), half the implants were loaded with prefabricated crowns for 6 months, and the other half remained unloaded. Removal torque values were evaluated at 3, 6, and 9 months after implant placement. The data were analyzed using analysis of variance and Scheffé correction (alpha < .05). RESULTS: All smooth-surface and SGHA implants failed in succession during the fourth and ninth months of the study. After 3 months the removal torque resistance of DPS, TPS, and hydroxyapatite-coated implants was significantly higher (P < .001) than that seen in the other two groups. Initially, the removal torque resistance of unloaded hydroxyapatite-coated implants was superior, and the decrease during the observation period was not significant. The increase in removal torque resistance under functional loading was not significant for the DPS implants. A significant increase was found in removal torque resistance for the loaded TPS implants (P < .05). The unloaded DPS and TPS implants showed no change in removal torque levels after the closed healing period of 3 months. CONCLUSIONS: Successful osseointegration was achieved with DPS, TPS, and hydroxyapatite-coated implants, and smooth-surface and SGHA implants failed. Removal torque resistance was enhanced with controlled functional loading.

Yield strength of fiber-reinforced composite posts with coronal retention.

STATEMENT OF PROBLEM: Currently, glass fiber-reinforced composite (FRC) posts with shank heads are only recommended for moderate coronal defects. Restoring endodontically treated teeth with large coronal defects remains a challenge, requiring posts with coronal retention and high bending resistance. PURPOSE: The purpose of this in vitro study was to investigate the yield strengths of FRC posts and titanium posts (TI) with coronal retention for core foundations compared to FRC and TI posts without coronal retention. MATERIAL AND METHODS: Tapered posts (ER root post system) of 4 diameters (ISO 50, 70, 90, 110), 2 lengths (tapered part: 9 and 12 mm) of identical shape, 2 materials (FRC, titanium), and 2 head designs (shank without retention (SH) and post head with horizontal retention (RET)) were evaluated (n=9). Titanium posts (TI-SH, TI-RET) served as the control. The 0.2% yield strengths (R(0.2)) of all specimens were tested in a universal testing machine. Three-way and 1-way ANOVAs with Bonferroni-Dunn's multiple comparison tests were performed (alpha=.05). RESULTS: The yield strengths of the control groups TI-RET were significantly higher for ISO 110 with a 9-mm length and for ISO 70 and 110 with a 12-mm length, compared to the respective FRC-RET posts (P<.001), whereas in all other groups, TI-RET and FRC-RET showed no significant differences. FRC-SH groups did not differ from FRC-RET groups. TI-SH showed significantly lower yield strength for ISO 70 compared to TI-RET, but significantly higher values for ISO 90 and 110 (P<.001). CONCLUSIONS: Head design of the tested FRC posts does not improve the yield strength, compared to FRC posts with a shank design. The diameter of the posts had a significant effect on the yield strengths of RET as well as SH groups.

Wear and hardness of different core build-up materials.

Before crown preparation, teeth with extensive coronal destructions are built up with core materials. Sometimes, these build ups are exposed to the oral environment without the protection of crowns. Therefore, this in vitro investigation was aimed at evaluating the wear, surface roughness, Vickers hardness, and surface structure of 10 core composites, two glass ionomer cements (GICs), and four posterior restoration composites. The three-body wear was tested after water storage and 2,00,000 cycles. We measured both surface roughness and Vickers hardness (DIN 50133) and evaluated the surface structures by scanning electron microscopy. Results were statistically analyzed by use of the Mann-Whitney U test (alpha = 0.05). Lowest wear was found for the restorative composites (20 microm Grandio; others about 40 microm). A comparison of the composites Build-It, Chroma Core, Rebilda LC, and Rebilda DC to Quixfil showed similar wear values for each material (43-50 microm). Wear values of GICs and all others core composites ranged between 58 and 75 microm. Only Ti-Core showed significantly higher wear than all other materials (p < 0.05). All core materials except Ti-Core (35 HV) showed Vickers hardness values between 42 and 61 HV. Most core composites, particularly Build-It, Multicore Flow, Rebilda LC, Ecusit, and Tetric Evo Ceram, showed more homogenous surface structures compared to GICs and restorative composites. Therefore, wear values of core build-up materials not only differed widely but were higher than those of conventional restorative materials; yet, core build-up materials showed advantageous surface structures.

Influence of oversized dowel space preparation on the bond strengths of FRC posts.

This study compared the bond strengths of fiber-reinforced composite (FRC) posts luted into oversized dowel spaces with FRC posts luted into precisely fitting dowel spaces using five different resin cements or build-up composites. The hypotheses examined were that bond strength does not present vast variations according to the width of the gap between the root canal and post and that bond strength increases for FRC posts luted with build-up composites compared with FRC posts luted with resin cements. Dowel space preparations (ER post-restoring system, 12 mm in length) were performed on 100 human anterior teeth up to ISO 90 and ISO 110 of 50 roots each. FRC posts, all ISO size 90, were inserted into the precisely fitting as well as into the oversized dowel spaces (n = 10) using five composite materials (Calibra, Multicore Flow, Rely X Unicem; resin cements and Build-It, Rebilda DC; build-up composites). The manufacturers' instructions of the composite materials were strictly followed except for Rebilda DC, which was used with Adhese for dentin bonding. Following water storage (37 degrees C, 24 hours) and thermocycling (5000 cycles, 5 degrees C-55 degrees C, 30 seconds) tensile strength testing was performed and fracture modes were assessed using SEM. Data were analyzed statistically (one-way and two-way ANOVA, Bonferroni/Dunn correction, alpha < 0.05). The retentive bond strengths of FRC posts in oversized dowel spaces decreased significantly for all luting composites except for Rebilda DC, compared with the respective groups with precise fitting (p < 0.011). Yet, the bond strengths of RelyX Unicem (454 N +/- 64 N), Build-It (422 N +/- 43 N) and Calibra (408 N +/- 50 N) showed significantly higher values for the precisely fitting posts than Rebilda DC (267 N +/- 54 N). RelyX Unicem revealed significantly higher values than Multicore Flow (296 N +/- 73 N). The bond strengths of FRC posts in oversized dowel spaces varied from 301 N +/- 78 N for Build-It to 152 N +/- 37 N for Calibra. The values of Build-It were significantly higher compared with Calibra, Multicore Flow (180 N +/- 47 N) and Rebilda DC (186 N +/- 52 N), as well as those of RelyX Unicem (256 N +/- 115 N) were significantly higher than Calibra. Fracture modes were shown to be mainly adhesive at the post surface or cohesive for precisely fitting posts and to occur between post and composite except for RelyX Unicem with cohesive fractures for the oversized dowel spaces. The build-up composite Build-It showed superior bond strengths in oversized canals, which were still not as high as those of posts in precisely fitting dowel spaces using common resin cements.

Repair strength of hypoallergenic denture base materials.

STATEMENT OF PROBLEM: Hypoallergenic denture base materials are commonly used for patients with allergic reactions to polymethyl methacrylate (PMMA) denture base materials. The goal for repaired fractured dentures fabricated from hypoallergenic denture base materials is to restore the dentures to their original strength. PURPOSE: The purpose of this in vitro study was to investigate the flexural properties of 7 hypoallergenic denture base materials after repair compared with a conventional PMMA-based heat-polymerizing resin. MATERIAL AND METHODS: Specimens (n=5) of the following hypoallergenic denture base materials with differing polymerization modes: Eclipse base material, Luxene, Microbase, Polyan, Puran HC, Alldent Sinomer, and The.r.mo.Free, were repaired with Versyo.com as well as the respective repair systems for 4 of the tested materials. A heat-polymerized acrylic resin (Paladon 65) was repaired using autopolymerizing acrylic resin (Palapress), which served as the control. Flexural strengths (MPa) and flexural moduli (MPa) were assessed before and after repair of each material, according to ISO 1567. The data were analyzed with repeated measures 2-way and 3-way ANOVA, 1-way ANOVA, and Bonferroni-Dunn's multiple comparisons post hoc analysis, or with the paired t test (alpha=.05). RESULTS: Flexural strengths and flexural moduli of both repair methods (repair according to manufacturer's instructions or repair with Versyo.com) for all materials were significantly lower than those of the intact specimens (P<.001). Alldent Sinomer and The.r.mo.Free repaired with Versyo.com showed flexural strengths comparable to the intact material. The flexural modulus of Puran HC, Alldent Sinomer, and The.r.mo.Free repaired with Versyo.com did not differ significantly from the original, nonrepaired material. No significant differences were noted between the flexural strength (P=.616) and the flexural modulus (P=.138) values regarding the 2 repair methods of the respective materials. None of the repaired hypoallergenic denture base materials demonstrated significantly higher flexural strengths than repaired Paladon 65. Flexural strengths of repaired Puran HC and Alldent Sinomer were significantly lower than those of repaired Paladon 65 specimens (P<.001). Flexural moduli of repaired Puran HC, Alldent Sinomer, and The.r.mo.Free showed a significant decrease compared to the repaired Paladon 65 specimens (P<.001). Eclipse and Luxene passed the flexural property requirements of ISO 1567 before and after repair. CONCLUSIONS: No significant influence of the repair systems was found, but the flexural properties of the repaired materials differed significantly with respect to the tested acrylic resins.

Influence of luting agent on the microleakage of all-ceramic crowns.

PURPOSE: In this in-vitro study, microleakage of all-ceramic crowns was evaluated at enamel and dentin margins. MATERIALS AND METHODS: Forty maxillary central incisors were randomly divided into 4 groups (n = 10). While buccal and palatal margins were placed on enamel, mesial and distal margins were placed below the cementoenamel junction. In groups 1 to 3, IPS Empress 2 crowns were luted with Variolink 2/Syntac Classic (group 1), Bifix DC/Solobond Plus (group 2) and Calibra/Prime & Bond NT combinations (group 3), respectively. In the control group (group 4), porcelain-fused-to-metal crowns were luted with a zinc-phosphate cement. All specimens were subjected to 5000 thermocycles (at 5 degrees C to 55 degrees C; 30-s dwell time). After immersion in India ink for 48 h at 37 degrees C, the specimens were sectioned both buccolingually and mesiodistally. Each section was evaluated for microleakage under a stereomicroscope at 24X magnification. RESULTS: According to the Krukal-Wallis test, in all groups, there were significant differences in microleakage at the enamel margins (p = 0.001). Nevertheless, the margins finished in dentin showed no significant differences (p = 0.163). According to the Mann-Whitney U-test, statistically significant differences were observed in microleakage between groups 1 and 3 (p = 0.049), groups 1 and 4 (p = 0.001), groups 2 and 4 (p = 0.002), and between groups 3 and 4 (p = 0.045) at the enamel margin. In group 1, significantly greater microleakage was observed at the dentin margin compared to the enamel margin (p = 0.007). CONCLUSION: The adhesive luting technique demonstrated an excellent ability to minimize microleakage of all-ceramic crowns at the enamel margins. Water-based dentin bonding systems showed less microleakage than the water-free acetone-based dentin bonding system at the enamel margin.