Quintessence International, 09/2002

Objective: The degree of color change and the dental sensitivity associated with the use of different concentrations (10%, 15%, and 20%) of carbamide peroxide every night for 6 months was evaluated in tetracycline-stained teeth. Method and materials: Fifty-nine subjects were shown how to place two different concentrations of carbamide peroxide in the custom trays with reservoirs. For a period of 6 months, the patients were to insert the tray every evening before retiring. Patients returned in 1 and 2 weeks and at 1, 2, 3, 4, 5, 6, 7, 8, and 9 months for evaluation of the degree of color change by subjective shade matching and by photographic means. Sensitivity of hard or soft tissues was self-reported. Results: Fifty-two subjects attended more than 90% of the recalls. A colorimeter was used to convert shade guide tabs to Commission Internationale de l'Eclairage color spaces (CIELAB). The most rapid whitening occurred in the first month. At 3 and 9 months, 91% and 85% of the subjects, respectively, were at least "a little pleased" with the results of the bleaching. In the professional evaluation, 90% of the teeth were deemed to have an excellent or satisfactory esthetic result. The higher the concentration of carbamide peroxide, the more rapidly the lightness value and color difference changed. There was no difference among the three concentrations in resulting gingival sensitivity. Patients experienced less tooth sensitivity with 10% gel than they did with 15% and 20% gels. Conclusion: Bleaching with 10%, 15%, and 20% carbamide peroxide is effective for removing tooth staining caused by tetracycline. The 10% concentration has the most advantages and the fewest disadvantages.

Prosthetic treatment of patients with dentinogenesis imperfecta is a challenge for the dental practitioner because numerous factors have to be considered. The use of all-ceramic restorations to rehabilitate the dentition of a young patient with dentinogenesis imperfecta is reported. Clinical and laboratory procedures are described.

Concussion and subluxation injuries to permanent teeth lead to obliteration of the pulp canal space in 3% to 11% of cases, depending on the severity of the injury and the developmental stage of the tooth. Obliteration of the pulp canal space may make root canal treatment necessary because of the development of apical periodontitis or for cosmetic reasons. If carefully executed, root canal treatment in teeth with an obliterated pulp canal space is highly successful and may act as a basis for internal bleaching.

Overfilling of the root canal is one of the most common errors encountered in dental practice. A 40-year-old woman complained of paresthesia and swelling affecting the left side of the mandible. Panoramic radiographs revealed that the root canal was overfilled; endodontic restorative material extended as far as the mandibular angle. Several months after surgical removal of the tooth and excess filling material, the symptoms subsided.

The palatal lift prosthesis is used to alleviate rhinopharyngeal closure dysfunction. It is generally problematical to use in edentulous patients, because the palatal lift prosthesis requires secure retention of the denture base and is difficult for the patient to retain while eating. This article describes the fabrication of a complete denture with a removable palatal lift prosthesis and a clinical evaluation of the denture's stability. A sprue pin and tube were used as a connecting attachment between the removable palatal lift prosthesis and the denture base. The force required for lifting the soft palate and the denture's stability were measured in the clinical evaluation. The prosthesis required an average retentive force of 0.26 N for each 1 mm of soft palate lift. The force required to dislodge the denture was measured with and without the palatal lift prosthesis in place. The force required to dislodge the conventional complete dentures of five healthy individuals was also measured as a reference. The denture was 24.4% less stable when the palatal lift prosthesis was in place and was generally easier to dislodge than were conventional dentures. This denture with a removable palatal lift prosthesis is useful for patients with dysfunction of the soft palate involving hypernasal speech who have difficulty in retaining the prosthesis while eating.

Objective: The purpose of this study was to compare the effects of experimentally derived surfactant-containing acid gel with those of different surface-conditioning agents on microleakage of unfilled and filled sealants applied to permanent teeth following noninvasive and invasive procedures. Method and materials: Four main groups of surface-conditioning agents (NRC; NRC + Prime&Bond NT; Email Preparator Blue; and experimental acid gel) were subdivided into 16 subgroups (n = 8). Subgroups were designed according to the surface preparation procedures applied (noninvasive and invasive) and fissure sealants used (Helioseal and Helioseal F). After application of the test materials, the specimens were subjected to thermocycling and then immersed in 0.5% basic fuchsin dye. Following sectioning, specimens were examined under a stereomicroscope and microleakage scores were assigned. Results: Subgroups 9 (Email Preparator Blue + Helioseal), 11 (invasive + Email Preparator Blue + Helioseal), 13 (experimental acid gel + Helioseal), and 15 (invasive + experimental acid gel + Helioseal) showed no microleakage. The differences between those subgroups and subgroups 1 (NRC + Helioseal), 2 (NRC + Helioseal F), 3 (invasive + NRC + Helioseal), 4 (invasive + NRC + Helioseal F), 5 (NRC + Prime&Bond NT + Helioseal), and 6 (NRC + Prime&Bond NT + Helioseal F) were statistically significant. Conclusion: Email Preparator Blue and surfactant-containing experimental acid gel, combined with an invasive/noninvasive surface preparation procedure and Helioseal, significantly prevented microleakage.

Objective: The purpose of this study was to evaluate the marginal microleakage and the extent of polymerization in Class II resin composite restorations prepared with two restorative techniques and two polymerization systems. Method and materials: One hundred twenty Class II cavities were prepared in bovine teeth and randomly divided into four groups: Bulk placement and conventional polymerization (Conv 1); buccolingual increments and conventional polymerization (Conv 3); bulk placement and soft-start polymerization (Soft 1); buccolingual increments and soft-start polymerization (Soft 3). All cavities were restored with the Z100/Single Bond system. After thermocycling, the specimens were immersed in 2% methylene blue solution and then evaluated for microleakage. Half of the samples were embedded in polyester resin and polished. The Knoop microhardness of the restorations was measured. Results: There was no dye penetration in 54.44% of Conv 1, 70.11% of Conv 3, 42.53% of Soft 1, and 63.22% of Soft 3 specimens. There were statistically significant differences in microleakage among groups. There were no statistically significant differences in microhardness among any groups at any depth. Conclusion: The incremental placement technique resulted in less microleakage. The soft-start system provided adequate polymerization but could not improve marginal sealing.

Objective: This study evaluated the cleaning and polishing effect of a prophylaxis paste (Cleanic), two differently shaped abrasive-bristle brushes (Occlubrush normal cup and Occlubrush minipoint), and a nylon-bristle brush (Prophy brush) on a fine (Tetric Ceram) and a coarse hybrid resin composite (Tetric Condense) under standardized conditions. Method and materials: A total of 48 round specimens with a diameter of 17.2 mm (232.32 mm²) of a fine and a coarse hybrid resin composite were readied and fixed on scanning electron microscopic mounts. After a standardized polishing procedure, the mean surface roughness values were evaluated using five horizontal and five vertical measurements over an area of 1 X 3 mm. The gloss of each specimen was assessed with a spectrophotometer. Both hybrid resin composite groups were treated with one of the following instruments: a nylon-bristle brush (n = 8), a normal-cup abrasive-bristle brush, or a minipoint abrasive-bristle brush. The medium used was either water (control) or a prophylaxis paste. Surface roughness and gloss were measured after instrumentation times of 15, 30, 60, 90, and 120 seconds. For the evaluation of cleaning ability, another 48 total round specimens of fine and coarse hybrid resin composite were covered with a thin layer of black dispersion color and air dried for 24 hours. Specimens were treated with a nylon-bristle brush or an abrasive-bristle brush in combination with water or prophylaxis paste for 15, 30, 60, 90, and 120 seconds. At the beginning and after every treatment interval, the specimens were scanned, the images were digitized, and the percentage of cleaned surface was measured planimetrically. Results: The abrasive-bristle brush, used in combination with water, produced the best outcomes for cleaning ability, surface roughness, and gloss on resin composite restorations. Conclusion: There is no positive cumulative effect when an abrasive-bristle brush, with its cleaning and polishing effect, is used in conjunction with a prophylaxis paste. Abrasive-bristle brushes used with plain water are highly suitable for cleaning and polishing resin composite surfaces.

Objective: The purpose of this investigation was to assess the effects of aging on the dimensional stability of vacuum-formed, pressure-formed, and pressure-laminated custom-made mouthguards. Method and materials: A master model representing the dental arch was fabricated in acrylic resin. Two ethylene vinyl acetate thermoplastic materials were tested: Essix (regular) and Proform (prelaminated). The model was benchmarked in five places along the curvature of the arch. The model was used to fabricate 10 specimens for each of the following groups: 1 = vacuum-formed (3-mm) Essix; 2 = vacuum-formed (4-mm) Proform; 3 = pressure-formed (3-mm) Essix; 4 = pressure-formed (4-mm) Proform; 5 = pressure-laminated (3-mm + 2-mm) Essix; 6 = pressure-laminated (3-mm + 3-mm) Essix. Die stone was poured into the newly made specimens and measured. Aging of the specimens was simulated by reproducing cleaning cycles (48 hours' soaking in water at 60°F and brushing 100 times with a soft denture brush in soapy water at 140°F for 20 minutes). Die stone was poured into the aged specimens and measured. Initial and post-aging measurements were compared. Results: All specimens showed dimensional changes post-aging, mainly decreases. Pressure-laminated specimens showed the best dimensional stability. Conclusion: Aging induced various dimensional changes in mouthguards, depending on the materials and processing techniques used. Most of the dimensional change for all mouthguards occurred at the central incisor region, the most important area for the protection of the anterior teeth and the premaxilla. Pressure-laminated mouthguard specimens showed the smallest range of changes at the central incisor region, suggesting potentially improved fit, comfort, and protection.