Influence of different surface treatments on surface zirconia frameworks

Objectives

To evaluate the effect of different chemo-mechanical surface treatments of zirconia ceramic in the attempt to improve its bonding potential.

Methods

Sintered zirconium oxide ceramic discs (Lava™ Ø10 mm × 1 mm height) were treated with (n = 4): (1) airborne particle abrasion with 125 μm Al₂O₃ particles; (2) 9.5% HF acid etching; (3) selective infiltration etching (SIE); (4) experimental hot etching solution applied for 10, 30 and 60 min; (5) no treatment.Ceramic discs surfaces were analyzed by atomic force microscopy (AFM) recording average surface roughness measurements of the substrate. Data were statistically analyzed by Kruskall–Wallis analysis of variance and Mann–Whitney tests (α = 0.05). The same discs were used for bi-dimensional zirconia ceramic surface characterization with scanning electron microscope (SEM).

Results

Ceramic surface treatments significantly influenced surface topography and roughness (p < 0.001). Bi-dimensional changes in ceramic surface morphology were assessed on a nanometric scale. The experimental hot etching solution improved surface roughness, independently from the application time.

Conclusion

Zirconia conditioning with the experimental hot etching solution may enhance ceramic roughness and improve the surface area available for adhesion allowing the formation of micromechanical retention. The influence of this surface treatment with regard to bond strength of zirconia needs to be addressed.     

Surface EMG of jaw elevator muscles: effect of electrode location and inter-electrode distance

This study addresses methodological issues on surface electromyographic (EMG) signal recording from jaw elevator muscles. The aims were (i) to investigate the sensitivity to electrode displacements of amplitude and spectral surface EMG variables, (ii) to analyse if this sensitivity is affected by the inter-electrode distance of the bipolar recording, and (iii) to investigate the effect of inter-electrode distance on the estimated amplitude and spectral EMG variables. The superficial masseter and anterior temporalis muscles of 13 subjects were investigated by means of a linear electrode array. The percentage difference in EMG variable estimates from signals detected at different locations over the muscle was larger than 100% of the estimated value. Increasing the inter-electrode distance resulted in a significant reduction of the estimation variability because of electrode displacement. A criterion for electrode placement selection is suggested, with which the sensitivity of EMG variables to small electrode displacements was of the order of 2% for spectral and 6% for amplitude variables. Finally, spectral and, in particular, amplitude EMG variables were very sensitive to inter-electrode distance, which thus should be fixed when subjects or muscles are compared in the same or different experimental conditions.     

表面水分和不同种类的手套对于硅橡胶印模材聚合时间的影响

目的:本文研究了表面水分和不同种类的手套对于硅橡胶印膜材料聚合时间的影响.方法:使用3种手套:一次性聚乙烯塑料薄膜手套,灭菌橡胶医用手套(无粉),以及橡胶检查手套(预撒粉),分别在潮湿和干燥环境下手动混合DENT SILICONE-PLUS重体型硅橡咬印模材,并记录其硬化时间.结果:干燥情况下使用塑料薄膜手套时,橡胶印模材聚合时间最短,平均2分10秒;乳胶材料和表面水分均可延长聚合时间,达到3～分钟时间;而预撒粉则可显著延长聚合时间,超过1小时.结论:临床运用硅橡胶制取印模时,建议使用一次性聚乙烯塑料薄膜手套在干燥环境下进行操作,预撒粉的橡胶检查手套必须更换,以避免操作失败.     

Histological and immunohistochemical analysis of initial and early osseous integration at chemically modified and conventional SLA titanium implants: preliminary results of a pilot study in dogs

OBJECTIVES: The aim of the present pilot study was to investigate initial and early tissue reactions to modified (mod) and conventional sand-blasted, large grit and acid-etched (SLA) titanium implants. MATERIAL AND METHODS: Implantation of modSLA and SLA implants was performed bilaterally in both the mandible and maxilla of dogs. The animals were sacrificed after a healing period of 1, 4, 7 and 14 days, respectively. Peri-implant tissue reactions were assessed in non-decalcified tissue sections using conventional histology (Toluidine blue-TB and Masson Goldner Trichrome stain-MG) and immunohistochemistry using monoclonal antibodies to transglutaminase II (TG) (angiogenesis) and osteocalcin (OC). Bone density (BD) and bone to implant contact (BIC) were assessed histomorphometrically. RESULTS: Day 1 revealed an early TG antigen reactivity in the provisional fibrin matrix adjacent to both implant surfaces. Day 4 was characterized by the formation of a collagen-rich connective tissue (MG), which revealed the first signs of OC synthesis adjacent to modSLA surfaces. Immunohistochemical staining for TG revealed a direct correlation between angiogenesis and new bone formation, which was clearly identifiable after 7 days by means of increasing BD, BIC and OC values. After 14 days, modSLA surfaces seemed to be surrounded by a firmly attached mature, parallel-fibered woven bone. CONCLUSIONS: Within the limits of the present study, it might be concluded that the combination of immunohistochemical and conventional histological stainings in non-decalcified tissue sections is a valuable technique to evaluate the initial and early stages of wound healing around endosseous titanium implants.     

Healing and osseointegration of submerged microtextured oral implants

The success of dental implants is primarily dependent upon the degree of osseointegration or bone-to-implant contact (BIC), possibly facilitated by a roughened implant surface. This study was performed to histologically evaluate the nature of osseointegration and bone healing of submerged microtextured implants in eight dogs. Three months following tooth extraction in the posterior mandibulae, three microtextured submerged implants were placed in each quadrant. Block biopsies were harvested at 4 and 16 weeks (four dogs each) following surgery, and histologic preparation was performed. Histomorphometric analysis demonstrated that % BIC value increased marginally from 40% at 4 weeks to 48% at 16 weeks, without a statistically significant difference. The first bone-to-implant contact (f-BIC) at 16 weeks was significantly lower than the 4-week f-BIC (0.81 mm vs. 0.56 mm). In conclusion, this study found minimal change in BIC over time (from 4 to 16 weeks) in unloaded microtextured implants, while the mean f-BIC value significantly increased during this same observation period.     

Epithelial-connective tissue interaction on the tooth surface: An in vitro model

In the present study, and in vitro system was developed and designed to examine the interaction between gingival fibroblasts (GF) and epithelial cells (EC) on the tooth surface. Porcine roots were cut transversely into 300 microns-thick root slices (RS). Gingival explants were placed on the upper RS surface and cultured in a defined medium permissive for the growth of EC. After 4 or 6 days, RS yielding EC were transferred onto confluent cultures of GF and further co-cultured for either 4 or 8 d. Cultures were then fixed and examined by SEM. The upper RS surfaces and the upper half of their peripheral aspect were covered by EC. The lower half of the peripheral RS surfaces were populated by GF originating from the confluent culture of GF. EC and GF made contact at approximately the middle of the side of the root slice. In cultures of epithelial components grown in defined medium for either 4 or 6 d and harvested 4 d after assembling the system, the EC-GF junction was located 117 +/- 45 and 271 +/- 82 microns, respectively from the upper RS aspect. Extending the co-culture period did not affect the EC-GF junction location. These results indicate that GF-EC contact stops the migration of these cells on root surfaces in vitro. The described system should be valuable for studying cellular events that may affect the formation of a new dentogingival junction following surgical periodontal therapy.     

Early endosseous integration enhanced by dual acid etching of titanium: a torque removal study in the rabbit

Textured implant surfaces are thought to enhance endosseous integration. Torque removal forces have been used as a biomechanical measure of anchorage, or endosseous integration, in which the greater forces required to remove implants may be interpreted as an increase in the strength of bony integration. The purpose of this study was to compare the torque resistance to removal of screw-shaped titanium implants having a dual acid-etched surface (Osseotite) with implants having either a machined surface, or a titanium plasma spray surface that exhibited a significantly more complex surface topography. Three custom screw-shaped implant types - machined, dual acid-etched (DAE), and titanium plasma sprayed (TPS) - were used in this study. Each implant surface was characterized by scanning electron microscopy and optical profilometry. One DAE implant was placed into each distal femur of eighteen adult New Zealand White rabbits along with one of the other implant types. Thus, each rabbit received two DAE implants and one each of the machined, or TPS, implants. All implants measured 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Eighteen rabbits were used for reverse torque measurements. Groups of six rabbits were sacrificed following one, two and three month healing periods. Implants were removed by reverse torque rotation with a digital torque-measuring device. Three implants with the machined surface preparation failed to achieve endosseous integration. All other implants were anchored by bone. Mean torque values for machined, DAE and TPS implants at one, two and three months were 6.00+/-0.64 N-cm, 9.07+/-0.67 N-cm and 6.73+/-0.95 N-cm; 21.86+/-1.37 N-cm, 27.63+/-3.41 N-cm and 27.40+/-3.89 N-cm; and 27.48+/-1.61 N-cm, 44.28+/-4.53 N-cm and 59.23+/-3.88 N-cm, respectively. Clearly, at the earliest time point the stability of DAE implants was comparable to that of TPS implants, while that of the machined implants was an order of magnitude lower. The TPS implants increased resistance to reverse torque removal over the three-month period. The results of this study confirm our previous results that demonstrated enhanced bony anchorage to dual acid-etched implants as compared to machined implants. Furthermore, the present results indicate that dual acid etching of titanium enhances early endosseous integration to a level which is comparable to that achieved by the topographically more complex TPS surfaces.     

The microbiological profiles of saliva, supragingival and subgingival plaque and dental caries in adults with and without type 2 diabetes mellitus

INTRODUCTION: The relationships between suspected bacteria in saliva, yeasts in oral rinse, and supragingival and subgingival plaque versus root surface and coronal caries in adults with type 2 diabetes mellitus and a non-diabetic group were explored. METHODS: One-hundred and five patients with type 2 diabetes and 103 non-diabetic subjects were recruited; their periodontal status, plaque index and magnitude of root surface and coronal caries were assessed. Saliva and an oral rinse were cultured for mutans streptococci, lactobacilli and yeasts. Toothbrush samples of supragingival plaque and curette samples of subgingival plaque were assessed for 17 bacterial species using the checkerboard DNA-DNA hybridization method. RESULTS: Type 2 diabetes patients had significantly more severe periodontitis, a higher plaque index and a higher prevalence and magnitude of root surface caries than non-diabetic subjects. Significantly more diabetic subjects had higher levels of Treponema denticola, Prevotella nigrescens, Streptococcus sanguinis, Streptococcus oralis and Streptococcus intermedius in their supragingival plaque than non-diabetic subjects. No significant difference was found for the organisms in saliva, oral rinse and subgingival plaque between the two groups. After adjustment for diabetic status, root surface caries was associated with an increased count of mutans streptococci, lactobacilli and yeasts in saliva and of Streptococcus mutans in supragingival plaque samples. Coronal caries was only associated with lactobacilli and yeasts in saliva. CONCLUSION: The number of cariogenic organisms in saliva and oral rinse estimated by culture demonstrated a stronger association with both root surface and coronal caries compared to those 17 species assessed with the checkerboard method in supragingival and subgingival plaque.     

The Effect of Brushing on Surface Roughness of Denture Lining Materials

PURPOSE: The purpose of this study was to test the effect of brushing on surface roughness of two resilient liners (Luci Sof and Sofreliner) compared with an acrylic resin (QC 20). MATERIALS AND METHODS: Twenty specimens of each material were prepared (25 mm x 14 mm x 3 mm). Ten specimens served as controls and were stored in distilled water and not brushed. The remaining ten specimens were subjected to mechanical brushing, using an MSEt plus machine to simulate brushing at a rate of 5.0 strokes per second (30,000 cycles). Surface roughness measurements were recorded before and after brushing. Random samples were analyzed using scanning electron microscope. Data collected were analyzed by a two-way analysis of variance using material and treatment as variables, followed by Tukey's test (alpha= 0.05). RESULTS: Initial surface roughness of materials indicated that QC 20 was the smoothest (0.13 microm), and Luci Sof the roughest (0.68 mum). Sofreliner had an intermediate value (0.31 microm). All materials were significantly different. Mechanical brushing significantly increased surface roughness in all the materials. Although there was no statistical difference between QC 20 and Luci Sof after mechanical brushing (0.88 and 1.00 microm, respectively), both differed significantly from Sofreliner (7.74 microm). CONCLUSION: The two resilient liners and the acrylic resin became rougher, to a greater or lesser extent, when subjected to mechanical brushing.