Quintessence International, 01/2006

Periodontitis is a common chronic disease worldwide. It is a major cause of tooth loss among adults and recently has been suggested to increase the risk for developing several systemic diseases, including cardiovascular disease. Populations are not equally affected by periodontal disease because there are several environmental and host factors modulating susceptibility. Cardiovascular disease shares many of the same susceptibility factors. The purpose of this report is to identify risk factors and indicators common to periodontitis and cardiovascular disease, and also to discuss their possible interrelationship in this association. Recent findings to support a causal association between the 2 conditions are also presented. Keywords: coronary artery disease, periodontitis, risk factors

Objective: The purpose of this study was to determine the fracture strength of zirconium implant abutments and the torque required to unfasten the retaining screw before and after applying cyclic loading to the implant-abutment assembly. The dynamic behavior and stress distribution pattern of zirconium abutments were also evaluated. Methods and materials: Static and cyclic loading of 7 XiVE implants with straight Cercon zirconium abutments were simulated under worst-case conditions. Cyclic loading tests were performed via a servohydraulic dynamic testing machine at loads between 100 and 450 N, for up to 5 million loading cycles, at 15 Hz. The dynamic behavior of the zirconium abutments was analyzed by finite element modeling and Pro/Mechanica software, comparing van-der-Mises and maximum stress levels. Results: Cercon zirconium-ceramic abutments exhibited a maximum fracture strength of 672 N during static loading and 269 N at 800,000 to 5 million cycles runout point, and 403 N at 10,000 cycles runout point during cyclic loading. The mean torque value required to unfasten the abutment retaining screws after (initial) tightening was 21 Ncm ± 1 and 20 Ncm ± 1 (measurement accuracy ± 2 Ncm) after loading with up to 5 million cycles respectively. Torque values decreased minimally and screw loosening did not occur. Within the limited number of test specimens (7), the difference was statistically significant (P = .015). FEM analysis displayed higher stress peaks up to 800 MPa at the cervical aspect of the zirconium abutment and at the apical third of its retaining screw at an external load of 250 N. Conclusion: Within the limitations of this study, zirconium implant abutments exceeded the established values for maximum incisal bite forces reported in the literature and tightly fit into the titanium implant after several millions of loading cycles. Keywords: cyclic loading, finite element analysis, fracture strength, screw loosening, zirconium implant abutments

In a previous clinical study, all-ceramic resin-bonded 3-unit inlay-retained fixed partial dentures (IRFPDs) had a significantly worse outcome in the posterior region than did crown-retained 3-unit FPDs made from the same material. Debonding or fractures were causes of failure. To improve the clinical outcome of IRFPDs, a new framework design was developed: (1) The inlay retainers were made out of CAD/CAM-manufactured zirconia ceramic to improve fracture resistance, and additional veneering of the inlays was omitted. (2) The inlay retainers were completed with a shallow occlusal inlay (1-mm minimum thickness) and an oral retainer wing (0.6-mm minimum thickness). The wings were designed to reduce stress on the inlay retainer caused by torsion forces when the FPD is loaded nonaxially and to increase the enamel adhesive surface area. The pontic was circumferentially veneered with feldspathic porcelain. The clinical and laboratory procedures of this new treatment modality are described, and 2 exemplary clinical cases are presented. This new preparation and framework design might improve the clinical outcome of all-ceramic resin-bonded IRFPDs. However, adequate evidence of long-term safety and efficacy is required before this new design can be recommended for general clinical practice. Keywords: adhesive, all-ceramic restoration, CAD/CAM, fixed partial dentures, inlay-retained, preparation, zirconia

Objective: The aim of this study was to calculate enamel bond strengths of 4 self-etch adhesives in function of conditioning time. Methods and materials: Sixty proximal surfaces of 30 extracted human molars were roughened and assigned to 4 self-etch adhesives: AdheSE (Ivoclar Vivadent), Adper Prompt L-Pop (3M Espe), Clearfil SE Bond (Kuraray America), and Tyrian SPE/One-Step Plus (Bisco). Prime&Bond NT (Dentsply) was used as the total-etch control. For 30 surfaces, the adhesives were applied per the manufacturers' directions. For the remaining 30, enamel was conditioned for twice the time recommended by the manufacturer. Buildups were constructed with Filtek Z250 (3M ESPE). Bonded specimens were sectioned in sticks and tested to tensile failure. Data were analyzed with 2-way ANOVA and Duncan's test at P .05. The pH of the self-etch solutions and the phosphoric acid gel was measured with a pH meter. A correlation coefficient was computed to measure the linear association between pH and bond strengths. Results: Tyrian SPE and Prime&Bond NT, the adhesives whose acidic conditioners yielded the lowest pH, ranked in the highest subset regardless of application time. AdheSE and Clearfil SE Bond, which had the highest pH, were the only adhesives for which double application time resulted in statistically higher bond strengths than the recommended time. When means were pooled for application time, Tyrian SPE and Prime&Bond NT resulted in bond strengths that were significantly higher than those of the remaining adhesives. AdheSE resulted in statistically lower bond strengths than any other adhesive. A significant correlation was found between pH and mean bond strengths. Conclusion: Doubling the enamel conditioning time might increase bond strengths for specific self-etch adhesives. Keywords: acid-etching, dental bonding, enamel bonding, microtensile strength, self-etching primers

Objectives: The purpose of this study was to evaluate the dimensional accuracy of stone dies produced from standardized impressions with 1 new and 1 conventional polyether impression material and a polyvinyl siloxane reference material. Methods and materials: Impressions with the polyether materials P2 and Impregum and with the polyvinyl siloxane Flexitime were produced at 23°C or 37°C from a truncated steel cone in cylindrical steel trays giving 4-mm impression layer thickness at the prominence line. Stone dies were poured after 1 or 24 hours of storage at ambient atmosphere. Additional impressions were stored at different relative humidity levels (0%, 33%, 50%, 75%, or 100%) for 24 hours prior to die pouring. The accuracy of the stone dies was determined as axial discrepancy between a steel ring, which fit perfectly on the steel die and the occlusal die surface. The base-diameter deviation (∆d) was calculated. Results: After 1 hour, a similar increase in ∆d was noticed for impression materials when dies were poured at impression temperature. Impressions made at 37°C exhibited significantly higher ∆d than at 23°C. Light-bodied P2 showed the highest ∆d increase when dies were poured after 24 hours. Flexitime showed moderate ∆d differences at the 2 pouring times. The ∆d of dies made from polyether materials decreased significantly with increasing humidity, whereas polyvinyl siloxane was not adversely affected. Conclusion: The dimensional accuracy of P2 is comparable to that of the conventional polyether impression material after short-term storage. Polyethers may absorb water, significantly compromising die accuracy upon storage at high humidity. Keywords: dimensional accuracy, elastomeric impression materials, polyether, polyvinyl siloxane, storage humidity, storage time

Objective: Exposure of the gingival sulcus and control of hemorrhage are prerequisites to the treatment of cervical lesions and improving the quality of impressions prior to fabricating indirect restorations. Gingival retraction cords saturated with different medicaments are widely used for this purpose. However, the long-term effects of the chemicals in gingival tissues are not clear. The purpose of this study was to compare the histopathologic effects of 2 different retraction solutions in gingival tissue. Methods and materials: In this in vivo study, a solution of 10% aluminum chloride and a solution of 15.5% ferric sulfate were used as retraction medicament in dogs. The saturated cords were allowed to remain in the gingival sulcus of the dogs for 3 minutes. After the removal of the cords, gingival biopsies were taken at 30 minutes, 24 hours, 7 days, and 12 days. For all specimens, histologic evaluation was performed by light microscopy to determine the degree of epithelial loss, alteration of the connective tissue, and inflammation. Results: Histopathologic examination of gingival tissue revealed that the ferric sulfate solution caused significant changes in gingival tissues at the beginning. However, the tissue returned to its normal histologic appearance at the end of day 12. Conclusion: The results of this study revealed that the biologic effects of ferric sulfate solution are more satisfactory than aluminum chloride solution. However, both medicaments are reliable and can be used in gingival retraction. Keywords: aluminum chloride, ferric sulfate, gingival retraction cord, gingival retraction medicament

Objective: There is a need for an ideal polishing system for resin composite restorations. The purpose of this study was to investigate the influence of polishing instruments on the surface texture of light-cured resin composites. Methods and materials: Four polishing systems-Compomaster (Shofu), Silicone Points C Type (Shofu), Super-Snap (Shofu), and Enhance Finishing and Polishing System (Dentsply/DeTrey)-were used to polish the flat surface of cylindrical blocks made of 3 different resin composites: Beautifil (Shofu), Clearfil AP-X (Kuraray Medical), and Lite-Fil II A (Shofu). The average surface roughness (Ra) and surface gloss (Gs60°) were determined. Scanning electron microscopic observations of the polished specimens were made. The polished samples were immersed in a 0.3% acid rhodamine B solution for 1 week, and change in color was determined. Results: The multiple-step systems, Enhance and Super-Snap, resulted in the best surface finishes. A new single-step point, Compomaster, ranked third in surface finish but was significantly better than the older point system, Silicone Points C. The color-staining experiments showed that there were no significant differences between the Compomaster system and the multiple-step systems, which were all significantly better than the older polishing point. Conclusion: The newly introduced 1-step polishing point has the ability to polish resin composites as effectively as multistep polishing systems. Keywords: polishing, resin composite, staining, surface gloss, surface roughness

Objective: The aim of the study was to review all the cases of ameloblastoma seen at the Oral and Maxillofacial Surgery Clinic of the Lagos University Teaching Hospital, Nigeria, between 1980 and 2003. Methods and materials: In this retrospective study, case files and biopsy reports of new cases of ameloblastoma covering a 24-year period were retrieved and analyzed for sex, age on presentation, histologic type, and site distribution. Results: A total of 207 cases of ameloblastoma were seen in the given period. One hundred and ninety-eight (95.7%) were benign, and 9 (4.3%) were malignant. A male-to-female ratio of 1.1:1 was found. The average ages on presentation for ameloblastoma and ameloblastic carcinoma were 31.67 and 46.44 years, respectively. The lesion was found to be more common in the premolar-molar region of the mandible. The most common histologic type was follicular ameloblastoma (25.1%). Nine (4.3%) cases of ameloblastic carcinoma were also reported. Conclusions: Ameloblastoma with a predilection for the posterior mandibular region is relatively common in our environment. Sex and site distributions are similar to previous reports in the literature. Keywords: ameloblastoma, analysis, Nigerians