Quintessence International, 07/2001

When nonabsorbable membranes are used for guided bone regeneration (GBR), second surgeries are required for membrane retrieval. In addition, these types of membranes show a high incidence of flap sloughing and membrane exposure that often lead to infection and unfavorable results. Absorbable barriers such as collagen membranes were developed to overcome these drawbacks. This article presents the principles and the clinical procedure of using barrier membranes composed of absorbable collagen in GBR aimed at the repair and regeneration of ridge dehiscence defects around implants. The unique properties of collagen membranes that make them ideally suited to GBR procedures are reviewed. In addition, the indications and contraindications for using collagen membranes for GBR procedures are examined. Finally, cases are presented to demonstrate details of surgical principles and techniques.

The purpose of this article is to report on the use of a neodymium-iron-boron magnet enclosed in a laser-welded stainless steel casing as a viable method of retention for removable partial dentures. This mode of retention dispenses with unsightly clasps, at the same time providing direct tooth support via the overdenture abutment. Magnetic attachments are simpler to incorporate into the prosthesis than mechanical attachments, which require springs, coplanar surfaces, or screws. Overdentures of this nature have the added advantage of being more stable and retentive than conventional partial dentures, and they are easily removed and seated without the patient having to grapple with clasps and complex paths of insertion. This particular magnetic attachment exhibited no deterioration after 3 years in function, and the results so far have been promising.

Although cleft palate patients are not regularly seen in general dental practice, their number is not negligible. Prosthodontic treatment of such patients requires good planning that takes into account all remaining teeth and roots, deformation of maxillary segments, residual palatal defects, and the disproportion between the maxillary and mandibular alveolar ridge. With the aim to provide satisfactory function and esthetics and alleviation of the deformities, the authors describe prosthetic therapy of a cleft palate patient using root copings, attachments, telescope and cone crowns, and a metal-base partial prosthesis. The patient's mastication, phonation, and esthetics were improved. Successful results can be best achieved through the judicious use of appropriate treatment modalities tempered by clinical experience and creativity.

Dental amalgam has come under attack for its allegedly poor physical properties and clinical performance in addition to its poor appearance. It has been claimed that the American Dental Association has a hidden agenda to protect amalgam and that other countries have banned its use. A literature search revealed that the vast majority of amalgam restorations do not cause fractured cusps or have recurrent caries. Most amalgam restorations have been shown to last longer than resin composite restorations. In addition, the materials and techniques involved in amalgam restorations have vastly improved in recent years. Like resin composite restorations, amalgam restorations can often be repaired. The American Dental Association has no vested interest in protecting amalgam. The use of amalgam has not been banned in any country in the European Union. According to the latest scientific information available, dental amalgam is a remarkably durable and long-lasting restorative material. Although its appearance is unesthetic, its clinical performance and effectiveness are unsurpassed by those of resin composite.

Pulpal complications involving inflammation, degradation, and necrosis are the result of a series of traumatic injuries. The restorative dentist must minimize the trauma to dentin and pulp inflicted during clinical procedures, including that inflicted during tooth preparation. Part II of this series discusses the structural and physiologic changes in the pulp-dentin complex that result from crown and cavity preparation and the clinical implication of these changes.

Objective: An analysis is made of the influence of continuous compression loading on different types of cast posts and cores and its effects on the crowns and teeth. Method and materials: Thirty extracted maxillary canines were prepared and divided into three groups (n = 10) according to the type of cast posts and cores used for restoration: chrome-nickel alloy, acetalic resin, and IPS-Empress porcelain. Metallic cast crowns were luted onto the cores. The specimens were evaluated with an Instron testing machine at an angulation of 45 degrees and a forward speed of 0.5 mm/min. After testing, the specimens were sectioned along the axis and examined under 340 magnification. Results: Mean load resistance of the restorations until fracture was 2,120 N, 1,491 N, and 2,139 N in the chrome-nickel, IPS-Empress ceramic, and acetalic resin groups, respectively. Conclusion: Significant differences in resistance were observed between metal and porcelain and between resin and porcelain. Microscopically, the apical portion was found to be most affected by fracture and compromised the teeth subjected to chrome-nickel restorations. The metal cast posts and cores exhibited different angulations, while the ceramic restorations showed cracks. The acetalic resin cast posts and cores presented no fractures.

Objective: The purpose of this study was to evaluate the in vivo remineralization of the possible non-resin infiltrated hybridoid layer between the hybrid layer and the subjacent dentin substrate using nanoindentation, energy dispersive x-ray spectroscopy microanalyses (EDS), and scanning electron microscopy (SEM) technologies. Method and materials: Twenty Class V cavities were placed in healthy adult monkey teeth. Each cavity was total etched with 37% phosphoric acid for 60 seconds, rinsed, and air dispersed, and SA-Primer was applied to the collagen layer. Cavities were divided into two groups: In group 1, Protect Liner (low-viscosity resin) and Clearfil AP-X (resin composite) were placed per manufacturer's directions, and no bonding agent was placed on the acid-etched interface. In group 2, Clearfil Photobond (bonding agent) was applied, and Protect Liner and Clearfil AP-X were placed as in group 1. Teeth were observed at 7 days (control) and 6 months by nanoindentation, EDS, and SEM. Results: Six-month data showed an increased nanohardness in areas 5 µm adjacent to the demineralized or partially demineralized dentin interface. Following treatment with a conventional adhesive system on the acid-etched interface (group 2), there were increased nanohardness and calcium EDS measurements in the substrate just below the resin-dentin impregnated layer. Conclusion: Our 6-month in vivo nanoindentation and EDS data demonstrate that the non-resin infiltrated zone becomes remineralized following adhesive resin treatment.

Objective: The purpose of this study was to evaluate the surface micromorphology of resin-modified glass-ionomer cements and polyacid-modified resin composites subjected to a neutral sodium fluoride (NNaF) and an acidulated phosphate fluoride (APF) gel application. Method and materials: Thirty standardized cylindric specimens were randomly obtained from each of two resin-modified glass-ionomer cements-Fuji II LC Improved and Photac-Fil Aplicap-and two polyacid-modified resin composites-Dyract and F2000-amounting to 120 samples. After 1 week, the specimens were finished and polished with aluminum oxide disks. Surface treatments with fluoride gels, or distilled water as a control, were performed four times, interspersed with eight pH cycles, simulating high cariogenic challenges. Five calibrated evaluators assessed the surface micromorphology through photomicrographs. Results: The Kruskal-Wallis test showed no significant difference between the control and experimental groups for Fuji II LC Improved and Dyract. Photac-Fil Aplicap showed less micromorphologic change as a result of distilled water application, unlike the NNaF and APF treatments, which revealed no significant difference from each other. For F2000, there was no significant difference between the surfaces treated by NNaF and distilled water; the highest degradation occurred with the APF. Conclusion: Both the resin-modified glass-ionomer cements and the polyacid-modified resin composites showed erratic behaviors concerning their micromorphology when subjected to fluoride gel application.