Effect of Different Primers on Shear Bond Strength of Base Metal Alloys and Zirconia Frameworks.

Ensuring a secure bond between a framework structure and layering composite resin veneer is essential for a long-lasting dental restoration. A variety of primer systems are available to facilitate the adhesive bonding. Nevertheless, the growing preference for efficiency and simplicity in dentistry has made the one-bottle universal primers a desirable option. This study aims to compare the effectiveness of universal primers on the shear bond strength (SBS) of base metal alloy (BMA) and zirconia to layering composite resin. Each 160 BMA and zirconia 20 × 10 × 5 mm test specimen was fabricated. Eight different primers (SunCera Metal Primer, Metal Primer Z, Reliance Metal Primer, Alloy Primer, MKZ Primer, Monobond Plus, ArtPrime Plus, and Clearfil Ceramic Primer Plus) were applied to 20 specimens in each group. Subsequently, a 5 × 2 mm composite resin build-up was applied. SBS tests were performed after 24 h of water storage and after thermocycling (25,000 cycles, 5-55 °C). On BMA, after water storage for 24 h, the bond strength values ranged from 26.53 ± 3.28 MPa (Metal Primer Z) to 29.72 ± 2.00 MPa (MKZ Primer), while after thermocycling, bond strength values ranged from 25.19 ± 1.73 MPa (MKZ Primer) to 27.69 ± 2.37 MPa (Clearfil Ceramic Primer Plus). On a zirconia base, after 24 h, the bond strengths values ranged from 22.63 ± 2.28 MPa (Reliance Primer) to 29.96 ± 2.37 MPa (MKZ Primer) and from 23.77 ± 3.86 MPa (Metal Primer Z) to 28.88 ± 3.09 MPa (Monobond Plus) after thermocycling. While no significant difference in bond strength was found between the primers on the BMA base, five primer combinations differed significantly from each other on zirconia (p = 0.002-0.043). All primers achieved a bond strength greater than 23 MPa on both framework materials after thermocycling. Thus, all primers tested can be applied to both framework materials with comparable results.

Functional Load Capacity of Teeth with Reduced Periodontal Support: A Finite Element Analysis.

The purpose of this study was to investigate the functional load capacity of the periodontal ligament (PDL) in a full arch maxilla and mandible model using a numerical simulation. The goal was to determine the functional load pattern in multi- and single-rooted teeth with full and reduced periodontal support. CBCT data were used to create 3D models of a maxilla and mandible. The DICOM dataset was used to create a CAD model. For a precise description of the surfaces of each structure (enamel, dentin, cementum, pulp, PDL, gingiva, bone), each tooth was segmented separately, and the biomechanical characteristics were considered. Finite Element Analysis (FEA) software computed the biomechanical behavior of the stepwise increased force of 700 N in the cranial and 350 N in the ventral direction of the muscle approach of the masseter muscle. The periodontal attachment (cementum-PDL-bone contact) was subsequently reduced in 1 mm increments, and the simulation was repeated. Quantitative (pressure, tension, and deformation) and qualitative (color-coded images) data were recorded and descriptively analyzed. The teeth with the highest load capacities were the upper and lower molars (0.4-0.6 MPa), followed by the premolars (0.4-0.5 MPa) and canines (0.3-0.4 MPa) when vertically loaded. Qualitative data showed that the areas with the highest stress in the PDL were single-rooted teeth in the cervical and apical area and molars in the cervical and apical area in addition to the furcation roof. In both single- and multi-rooted teeth, the gradual reduction in bone levels caused an increase in the load on the remaining PDL. Cervical and apical areas, as well as the furcation roof, are the zones with the highest functional stress. The greater the bone loss, the higher the mechanical load on the residual periodontal supporting structures.

Effectiveness of Individual Oral Health Care Training in Hospitalized Inpatients in Geriatric Wards.

OBJECTIVE: To investigate the effectiveness of individual oral health care training (IndOHCT) on dental plaque removal and denture cleaning in hospitalized geriatric inpatients. BACKGROUND: The literature reveals neglect of hygiene and oral care in people aged over 65 years, especially in persons in need of care. Hospitalized geriatric inpatients have poorer dental health than those non-hospitalized. Furthermore, the existing literature reporting on oral healthcare training interventions for hospitalized geriatric inpatients is scarce. MATERIALS AND METHODS: This pre-post-controlled intervention study dichotomized 90 hospitalized geriatric inpatients into an intervention group (IG) and a control group (CG). Inpatients in the IG received IndOHCT. Oral hygiene was assessed using the Turesky modified Quigley-Hein index (TmQHI) and the denture hygiene index (DHI), at baseline (T0), at a second examination (T1a), and after supervised autonomous tooth brushing and denture cleaning (T1b). The influence of the Mini Mental State Examination (MMSE), Geriatric Depression Scale (GDS), and Barthel Index (BI) scores on oral hygiene was examined. RESULTS: There was no significant plaque reduction on teeth or dentures between T0 and T1a in either group. Between T1a and T1b, plaque reduction on the teeth was more effective in the IG than in the CG (p < 0.001). Inpatients with 1-9 remaining teeth removed significantly more dental plaque than inpatients with 10 or more remaining teeth. Inpatients with lower MMSE scores (p = 0.021) and higher age (p = 0.044) reached higher plaque reduction on dentures. CONCLUSIONS: IndOHCT improved oral and denture hygiene in geriatric inpatients by enabling them to clean their teeth and dentures more effectively.

Effects of reducing excess dental adhesive on bacterial adhesion in the bracket periphery.

OBJECTIVES: White spot lesions are one of the most common side effects of orthodontic therapy with a multibracket appliance and may indicate a preliminary stage of caries, also known as initial caries. Several approaches may be utilized to prevent these lesions, such as reducing bacterial adhesion in the area surrounding the bracket. This bacterial colonization can be adversely affected by a number of local characteristics. In this context, the effects of excess dental adhesive in the bracket periphery were investigated by comparing a conventional bracket system with the APC flash-free bracket system. MATERIALS AND METHODS: Both bracket systems were applied to 24 extracted human premolars, and bacterial adhesion with Streptoccocus sobrinus (S. sobrinus) was performed for 24 h, 48 h, 7 d, and 14 d. After incubation, bacterial colonization was examined in specific areas by electron microscopy. RESULTS: Overall, significantly fewer bacterial colonies were found in the adhesive area around the APC flash-free brackets (n = 507 ± 13 bacteria) than the conventionally bonded bracket systems (n = 850 ± 56 bacteria). This is a significant difference (**p = 0.004). However, APC flash-free brackets tend to create marginal gaps with more bacterial adhesion in this area than conventional bracket systems (n = 265 ± 31 bacteria). This bacterial accumulation in the marginal-gap area is also significant (*p = 0.029). CONCLUSION: A smooth adhesive surface with minimal adhesive excess is beneficial for reducing bacterial adhesion but also poses a risk of marginal gap formation with subsequent bacterial colonization, which can potentially trigger carious lesions. CLINICAL RELEVANCE: To reduce bacterial adhesion, the APC flash-free bracket adhesive system with low adhesive excess might be beneficial. APC flash-free brackets reduce the bacterial colonization in the bracket environment. A lower number of bacteria can minimize white spot lesions in the bracket environment. APC flash-free brackets tend to form marginal gaps between the bracket adhesive and the tooth.

Wear pattern-associated color stability of prefabricated composite veneers versus ceramic veneers.

PURPOSE: To evaluate the effect of different surface wear patterns on the discoloration tendency of two different prefabricated composite veneers and lithium disilicate ceramic veneers. MATERIALS AND METHODS: Discoloration tendency of two prefabricated composite resin veneers (Visalys Veneer Chairside (VIS) and Componeer (COM)) were compared to lithium disilicate veneers (IPS) in vitro. For each material, n = 60 samples were allocated to different test groups, and therefore each n = 10 specimens per group went through different wear tests. Mechanical abrasion tests were conducted using a toothbrush simulator, while erosive effects were carried out by citric acid (pH 1.57). A combination of abrasion and erosion tests was conducted as well. Four groups of wear tests were implemented: (1) abrasion, (2) abrasion followed by erosion, (3) erosion, and (4) erosion followed by abrasion. Another group was stored in distilled water as the control and one group was stained without a prior wear test. The staining solution was made from a coffee-tobacco brew. Specimens were stored in the coffee-tobacco solution for 21 days. Color measurements were performed with VITA Easyshade. To evaluate intramaterial discoloration, one half of every specimen was protected with foil. After storage in the staining solution, the first measurement was carried out on the 'protected' (untreated) surface, followed by a second measurement on the 'processed' (treated) discolored surface. Euclidean distance (ΔE) of discoloration was calculated according to the CIE-L*C*h* system. Data were analyzed with ANOVA followed by Games-Howell post hoc test and paired t-test (α = 0.05). RESULTS: Highest changes in ΔE were found in COM after 'abrasion' (ΔE -2.55) and 'erosion followed by abrasion' (ΔE -1.41). The discoloration tendency of VIS was affected by all wear tests, but changes were below the perceptive threshold (ΔE -0.19-0.32). Only abrasion followed by erosion affected the discoloration of IPS significantly, but findings were below the perceptive threshold, as well (ΔE -0.09). CONCLUSIONS: Prefabricated composite resin veneers revealed a low level of discoloration tendency after different wear tests. Nevertheless, in most cases the lowest discoloration tendency was found in specimens made from lithium disilicate.

Comparison of Wear Resistance of Prefabricated Composite Veneers Versus Ceramic and Enamel.

PURPOSE: To measure surface roughness before and after wear-tests of two different prefabricated composite veneers and compare them to ceramic veneers and human dental enamel. MATERIALS AND METHODS: Roughness (Ra-values) of two prefabricated composite veneers (Visalys Veneer Chairside (VIS) and Componeer (COM)) were compared to lithium disilicate Veneers (e.max CAD) and dental enamel (DENT) in vitro. In total n = 45 specimens per material and enamel samples were used for wear-tests. Wear-out tests were conducted by abrasion tests with a toothbrush simulator (22,000 strokes/ 100 g load; approximately equal to two years of cleansing) and erosion tests were carried out using citric acid (pH 1.57). Ra- and Sa-values were detected by white light interferometer before and after wear-tests. Data were analyzed with ANOVA followed by Games-Howell post hoc test and t-test (α = 0.05). RESULTS: At baseline the lowest Ra- and Sa-values were found in VIS (Ra: 0.01 µm; Sa: 0.04 µm) while DENT revealed significantly higher surface roughness (Ra: 0.11 µm, p < 0.05; Sa: 0.30, p = 0.186). COM had significantly higher Ra-values (Ra: 0.10 µm; Sa: 0.22 µm) after abrasion, while e.max CAD was most resistant to the treatments (Ra: 0.01 µm, p < 0.05; Sa: 0.05 µm, p < 0.05). Compared to DENT all veneers were significantly less affected by citric acid (p < 0.001). CONCLUSIONS: Prefabricated composite veneers have demonstrated less wear after abrasion and erosion tests compared to DENT, nevertheless, they revealed more wear compared to e.max CAD.

Comparison of Gingival Retraction Materials Using a New Gingival Sulcus Model.

PURPOSE: To investigate the pressure generated by different retraction materials using a novel gingival sulcus model. MATERIALS AND METHODS: A gingival sulcus model was made using a polymer frame filled with silicon. A pressure sensor and a sulcus-fluid simulation were embedded into the silicon chamber to evaluate the pressure generated by different retraction materials. Six sizes of Ultrapak retraction cords (Ultradent, sizes #000 - 3), 4 retraction pastes (Expazen, Expasyl, Acteon, Access Edge, Traxodent) and 2 retraction gels (Sulcus Blue, Racegel) were analyzed. The mean and median pressure, interquartile range, and standard deviation (SD) of n = 10 repeated measurements were calculated. Statistical analysis was conducted by Kruskal-Wallis test for differences between the main groups of retraction materials, and Mann-Whitney U-test was performed to analyze differences between the single retraction materials. RESULTS: Pressure (mean ± SD) generated by retraction cords increased with increasing size (48.26 ± 11.29 kPa, size #000 to 149.27 ± 28.75 kPa for #3). There was a significant difference between sizes (p < 0.01), except in #0 versus #1, and #2 versus #3. Retraction pastes generated pressures that ranged from 82.74 ± 29.29 kPa (Traxodent) to 524.35 ± 113.88 kPa (Expasyl). Retraction gels generated pressures from 38.96 ± 14.68 kPa (Racegel) to 95.15 ± 24.18 kPa (Sulcus Blue). Pressure generated by Expasyl was significantly higher than pressure generated by all other tested materials (p < 0.001). CONCLUSION: Pressure generated by retraction pastes and gels depends on the consistency of the retraction material, while pressure generated by retraction cords increased with increasing size of cords. Expasyl was found to generate the highest pressure compared to all other retraction materials.

Tailor-made material characteristics of bacterial cellulose for drug delivery applications in dentistry.

Bacterial cellulose (BC) has shown high potential as innovative wound dressing and drug delivery system. Bringing both together, drug-loaded BC was investigated for applications in dental therapies such as dental extraction or mucosal transplantation. Both applications would benefit from a material which degrades under physiological conditions, and from an antibiotic environment. Consequently, periodate-oxidation of BC was investigated to facilitate modified degradation behaviour. A periodate concentration of 0.14 mol/L at ϑ = 25 °C and t = 8 h resulted in a material loss of <10%, but at the same time a sufficient degree of degradation. Additionally, native and oxidised BC loaded with doxycycline was tested for prophylaxis against infection. An in vitro-toxicity test (MTT assay) provided a first confirmation of biocompatibility, whereas agar diffusion tests proved antibiotic efficiency against pathogenic oral bacteria. Release studies of the drug from native and oxidised BC confirmed a comparative biphasic release behaviour.