RESIN BOND TO DENTAL CERAMICS,PART I: REVIEW AND SILICA‐BASED CERAMICS

Silica‐based ceramics (eg, feldspathic, glass, and leucite‐reinforced feldspathic ceramics) are preferred materials for conservative, highly esthetic indirect restorations such as laminate veneers, ceramic inlays and onlays, and full‐coverage crowns because of their optical properties, biocompatibility, and longevity. Adhesive cementation of ceramics to the supporting tooth using resin cements has been identified as the main determinant for the excellent clinical success of bonded silica‐based ceramic restorations. The first article discussed in this Critical Appraisal reviews the current evidence for the need of adhesive technologies to support ceramics. Even though review articles typically are not addressed in this section, its thoroughness and clear conclusions make this article an important contribution to the field of esthetic and restorative dentistry. Controlled clinical trials are ideal to evaluate the success of certain materials or therapeutic interventions. However, laboratory studies are necessary to compare large varieties of materials and influencing parameters and to identify superior materials and bonding techniques prior to their clinical application. Numerous in vitro studies have evaluated the ceramic‐composite resin interface. The in vitro studies reviewed in this section indicate that acid‐etching and silane application are ideal methods to achieve strong and durable resin bonds to silica‐based ceramics. The selected articles indicate interesting trends in testing methods and interpretation of results. Earlier studies favor shear bond strength testing methods and emphasize the importance of surface microstructure and mechanical interlocking. However, some recent studies prefer modified tensile bond strength methods, and find silane application, and therefore chemical interaction, to be the main contributor to reliable resin‐ceramic bonds. Unfortunately, direct comparisons between different studies are difficult owing to the variations in methods and materials and the lack of standard protocols.     

Experimental aspects of the pathogenesis of Robin sequence.

OBJECTIVE: The Pierre Robin Sequence (PRS) is a good example of disturbed embryonic development of the secondary palate involving insufficient mandibular growth, failed forward tongue movement, and, in the case of a cleft, impeded fusion of the secondary palate. Discussion continues regarding which of the involved pathogenetic factors is the primary cause of the induced cascade of signs: insufficient mandibular growth or failed descent of the tongue. DESIGN: Forty-five randomly selected, 18-day-old formalin-fixed A/WySn mouse fetuses were investigated. The strain is known to have a basic genetic defect and as much as 44% clefts in the offspring. Twenty-four fetuses in the group had a cleft palate. Mandible position was measured relative to the head and to the presence or absence of a cleft. Cleft width and tongue position were also determined. Thirty-eight NMRI mouse fetuses of the same age served as controls. RESULTS: All A/WySn fetuses showed marked mandibular retrognathia, which was more severe in the cleft group (p < .05), but there was no correlation between the degree of retrognathia and cleft width. The median cleft width was 3.4 mm (1.6 through 6.3 mm). The tongue was in the cleft in all 12 fetuses with wide clefts (>3.4 mm wide), and free in the oral cavity in the other 12. Tongue position did not influence the degree of retrognathia (p < .05). Moreover, the tongue was free in all fetuses with severe retrognathia. CONCLUSION: The results support the primary role of retroposition of the mandible in the development of cardinal symptoms of Pierre Robin Sequence.     

Selected characteristics of a new polyvinyl siloxane impression material--a randomized clinical trial.

OBJECTIVES: This study evaluated the ability of a new polyvinyl siloxane impression material (Affinis, Coltène/Whaledent, material A) to obtain final impressions free of bubbles and voids for indirect fixed cuspal-coverage restorations. The results were compared to a control polyvinyl siloxane impression material (material B). Both materials were handled by inexperienced clinicians (undergraduate dental students) in student clinics. METHOD AND MATERIALS: One-hundred and thirty patients who were treated in the Louisiana State University School of Dentistry Junior Student Clinic for indirect fixed cuspal-coverage restorations and who met the inclusion criteria were randomly assigned to either one of two treatment groups, group A (n = 65) or group B (n = 65). Two calibrated examiners evaluated the first impression of prepared posterior teeth at a magnification of 10x for acceptability (no voids or bubbles). Position of tooth, type of preparation, preparation finish line (Class I-V), and gingival bleeding scores were recorded. All statistical tests were performed with the level of significance set at .05. RESULTS: The Fisher-Freeman-Halton test did not reveal significant associations between material and gingival bleeding score (P = .492). Significant differences in the location of the preparation finish line between materials were observed (P = .0096); material A was more frequently used in cases where the preparation finish line was located at least 2 mm subgingivally. Logistic regression was used to assess the effect of the material on the success of the impression (acceptable/ unacceptable). Material was highly significant in the logistic model (P < .001) with an odds in favor of an acceptable impression being eight times higher with material A than with material B (odds ratio = 8.00; 95% confidence index for odds ratio: 2.832, 22.601). The 60/65 (92.3%) impressions made with material A and 39/65 (60%) impressions made with material B were rated "acceptable." CONCLUSION: The new polyvinyl siloxane impression material provided a significantly higher proportion of impressions free of bubbles and voids than the control polyvinyl siloxane material.     

Oral health impact in patients wearing removable prostheses: relations to somatization, pain sensitivity, and body consciousness

PURPOSE: Previous studies investigating associations between patient personality traits and complaints related to wearing dental prostheses have been inconclusive. From the perspective of cognitive behavioral theory, the current study investigated whether pain sensitivity, body consciousness, and somatization affected the oral health of patients wearing removable dentures. MATERIALS AND METHODS: Eighty-eight patients were supplied with removable partial and complete dentures. The Oral Health Impact Profile (OHIP), with six subscales measuring oral health impairment and disability during daily living, the Pain Sensitivity Index, the Private Body Consciousness scale, and the Somatization Scale of the SCL-90-R, were used. RESULTS: The variables pain sensitivity, body consciousness, and somatization correlated significantly with all six OHIP subscales in removable denture wearers. In multiple hierarchic regression analyses, patient personality accounted for 38.0% of functional limitation and 41.5% of physical pain. CONCLUSION: Pain sensitivity and bodily preoccupation might be important factors in explaining the subjective oral health effects of removable denture wearing.     

Adhesion of endodontic sealers: scanning electron microscopy and energy dispersive spectroscopy

The microscopic details of the debonded interfaces between endodontic sealers and dentin or gutta-percha were assessed in this study. Dentin, conditioned with 37% H3PO4 for 30 s, 25% citric acid for 30 s, 17% EDTA for 5 min, or a rinse with 10 ml of distilled H2O (control), and gutta-percha surfaces were coated with freshly mixed sealer: Grossman's sealer, Apexit, Ketac-Endo, AH Plus, RoekoSeal Automix, or RoekoSeal Automix with an experimental primer. The surfaces were pressed together and the sealers were allowed to set. After tensile bond strength testing, the morphological aspects of the fractured surfaces were assessed by scanning electron microscopy and energy dispersive spectroscopy. The energy dispersive spectroscopy successfully traced sealer components to the debonded surfaces. Some of the sealers penetrated into the dentinal tubules when the dentin surface had been pretreated with acids. However, these sealer tags remained occluding the tubules after bond failure in some instances only (Grossman's sealer, RoekoSeal Automix with an experimental primer, AH Plus/EDTA). Penetration of the endodontic sealers into the dentinal tubules when the smear layer was removed was not associated with higher bond strength.     

Reaction of sound and demineralised dentine to Carisolv in vivo and in vitro.

OBJECTIVES: The aim of the present study was to assess the structural reaction of intact dentine to Carisolv in vivo and in vitro. METHODS: For the in vivo study occlusal cavities were prepared in 48 caries-free molars in Wistar rats (age: three months) and Carisolv-solution was placed into the cavities of 24 M for 1, 10 and 20 min. Twenty four contralateral molars served as controls and were treated with an inert liquid containing purified water, carmellose and erythrosin for corresponding periods. For the in vitro study 24 rat molars were resected en bloc and fractured to expose an area of crown dentine area. Molars were demineralised with EDTA for eight weeks to expose the collagenous dentinal matrix. One half of the specimens was then coated with Carisolv-solution for 20 min. The other half served as a control and was coated with an inert solution for 20 min. RESULTS: In the in vivo specimens no signs of pulp cell damage were observed in the experimental group. The odontoblastic processes were destroyed in proximity to the floor of the cavity but were intact in the inner portion of dentinal tubules in experimental molars and a mechanical damage was noted in the control molars. In the in vitro specimens no structural discrepancy was detected between the experimental molars and the control molars in collagen fibrils of demineralised dentine. CONCLUSIONS: Carisolv causes destruction of cellular components of odontoblastic processes but does not attack healthy collagen fibrils.     

Remineralization of artificial interproximal carious lesions using a fluoride mouthrinse

PURPOSE: To evaluate remineralization and fluoride uptake of demineralized enamel specimens in artificial interproximal spaces using a 250 ppm fluoride mouthrinse (100 ppm amine fluoride and 150 ppm sodium fluoride) compared to a placebo-mouthrinse. METHODS: This was a two-way, double-blind, in situ study. 24 volunteers wore intraoral appliances in the lower jaw with mounted demineralized enamel specimens forming an artificial interproximal space. The volunteers rinsed their mouths for 28 days, twice a day with the respective mouthrinse and brushed their teeth at least twice a day with a fluoride-free dentifrice. The specimens were cleaned once a day to simulate the use of dental floss. For analysis methods transversal microradiography, fluoride content measurement and quantitative light-induced fluorescence were used. RESULTS: Mineral gain was significantly higher after the use of the fluoride mouthrinse: 571.88 Vol.% x microm (+/- 79.33 Vol.% x microm SEM) compared to the placebo treatment 51.14 Vol.% x microm (+/- 72.14 Vol.% x microm SEM). Significantly more fluoride uptake was observed after using the fluoride mouthrinse: 3666.39 microg/cm3 (+/- 513.50 microg/cm3 SEM) than after the placebo mouthrinse: 516.95 microg/cm3 (+/- 75.83 microg/cm3 SEM). The quantitative light-induced fluorescence showed a significant remineralizing effect after the fluoride treatment: -388.47 % x mm2 (+/- 18.76% x mm2 SEM) compared to the placebo treatment -27.88% x mm2 (+/- 20.19% x mm2 SEM).