Quintessence International, 06/2003

Many morphologic, physical, and iatrogenic factors, such as deep grooves, pronounced intraoral temperature fluctuation, poor cavity preparation design, and wrong selection of restorative materials, may predispose posterior teeth to an incomplete fracture. The resulting cracked tooth syndrome is frequently associated with bizarre symptoms that may complicate diagnosis and can persist for many years. Epidemiologic data reveal that splits or fractures are the third most common cause of tooth loss in industrialized countries, primarily affecting maxillary molars and premolars and mandibular molars. This finding indicates that the cracked tooth syndrome is of high clinical importance. Thus, at-risk teeth should be reinforced early, for instance by castings with cusp coverage or by internal splinting with adhesive ceramic restorations.

Objectives: The aim of this study was to investigate the clinical performance of 120 posterior composite restorations placed in 38 patients after a period of 7 years. Method and materials: Eighty-eight Class I and 32 Class II restorations were made (93 molars and 27 premolars) using three different resin composite materials: Z100, Clearfil Ray-Posterior, and Prisma TPH. The restorations were evaluated using Ryge's criteria for color match, marginal discoloration, marginal adaptation, secondary caries, surface texture, and anatomic form at baseline, 1, 2, 5, and 7 years. Photographs and radiographs were taken at each recall period. Results: At 7-year recalls, 70 restorations were available for examination. Four restorations had failed due to secondary caries. Saliva sampling was performed to determine the level of mutans streptococci and lactobacilli for the four failed restorations at the last recall. No statistically significant differences were found among the materials in regard to color match, anatomic form, and secondary caries. Clearfil Ray-Posterior had statistically significantly rougher surface texture than the surrounding enamel compared to the other resin composites. Z100 showed more cavosurface margin discoloration after 5 years than the other two resin composites. All materials had slight marginal adaptation problems at the 7-year recall. There was no apparent relationship between the levels of mutans streptococci and lactobacilli in saliva and the failed restorations. Conclusion: The three posterior composites tested had acceptable clinical performance after 7 years.

Objective: This retrospective study was designed to investigate changes of cervical dentin hypersensitivity (CDH) in response to occlusal equilibration. Method and materials: Written records for 250 active-care patients were randomly selected and analyzed for associations between CDH, and its resolution following occlusal equilibration. Patients in group A (treatment) and B (delayed treatment) received occlusal equilibration following the detection of verified CDH using the air indexing method. Group C patients were not detected with verified CDH during the study period of 17 years. The resolution of CDH was measured by the loss of a positive patient threshold response to air stimulation. Results: Significant associations existed between CDH, hyperfunction, parafunction, and abfractive lesions. Furthermore, it was found that occlusal equilibration resulted in the long-term resolution of CDH. Conclusions: The resolution of CDH by occlusal equilibration, thus negating the null hypothesis, suggests that further studies are indicated to evaluate the impact of these findings upon restoring and maintaining health of the masticatory system.

Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification acts through a distinct process that is associated with unique clinical characteristics. Accurate prevalence data for each classification are not available since indices do not necessarily measure one specific etiology, or the study populations may be too diverse in age and characteristics. The treatment of teeth in each classification will depend on identifying the factors associated with each etiology. Some cases may require specific restorative procedures, while others will not require treatment. A review of the literature points to the interaction of the three entities in the initiation and progression of lesions that may act synchronously or sequentially, synergistically or additively, or in conjunction with other entities to mask the true nature of tooth wear, which appears to be multifactorial.

Objective: To compare, using transmission electron microscopy (TEM), the ultrastructure of the hybrid layers formed beneath a one-bottle adhesive system using the total-etch technique with that of a self-etching system. Method and materials: Occlusal cavity preparations were made in vivo in 18 human premolars and randomly appointed to three groups (n = 6), according to the following bonding procedures: (1) OptiBond Solo, a single-bottle adhesive system, was applied following 15 seconds etching with 37% phosphoric acid and rinsing; (2) Clearfil Liner Bond 2V, a self-etching adhesive system was applied; and (3) no bonding material was used, with the untreated smear layer acting as a control. The cavities were then filled with resin composite restorations. Results: In group 1, dense resin tags obturated the tubules. A layer of inorganic silicon microgranules formed at the top of the interdiffusion zone, and below this was a zone of loosely arranged collagen fibers. Toward the base, there was a more dense accumulation of hydroxyapatite crystals. In group 2, dense resin tags obturated the tubular orifices. Collagen fibers were densely compacted within monomer material. Toward the base, hydroxyapatite crystals were observed between collagen bundles. In group 3, a rough fragmented smear layer covered the dentinal floor and occluded the tubules. Conclusion: Irregularities occurred in the coronal zone of the hybrid layer in both systems. In the one-bottle system, this was attributed to the etching technique, while in the case of the self-etching system, this was attributed to the resin materials. These irregularities are potential sites for debonding in the clinical situation.

Oral infection caused by the herpes simplex virus represents one of the more common conditions the dental practitioner will be called upon to manage. Unique in its ability to establish latency and undergo subsequent recurrence, it is an ubiquitous infectious agent for which a cure does not exist. For the immunocompetent patient, herpes virus simplex infection typically represents nothing more than a nuisance. However, for the immunocompromised patient, this infection is associated with increased morbidity and mortality. Recently introduced antiviral drug regimens may reduce the morbidity and potential mortality of the herpes simplex virus, especially in immunocompromised patients. The value of antiviral therapy in the management of recurrent herpes simplex virus infection in the immunocompetent patient remains an area of contentious debate.

Objectives: To compare the surface microhardness of a resin composite following exposure to a pulse-delayed activation routine and a standard continuous routine using a quartz-halogen lamp. Additionally, to assess the effect of increasing the distance between the activator light and the specimen using a continuous exposure routine. Method and materials: Disk specimens of a commercial resin composite restorative material were exposed to a quartz-halogen lamp in a three-step pulse-delayed routine. A continuous exposure was used as a control. Surface microhardness was recorded at the end of each step and at 1 hour after initial exposure. The data yielded four groups and the control (n = 15). Further specimens were exposed to the activator light held at a predetermined distance from the specimen. Results: The pulse-delayed routine yielded a progressive and significant increase in mean microhardness at the end of each step, and the maximum mean value was significantly lower than the control. The effect of increasing the exposure distance yielded a significant decrease in mean hardness number with increasing distance for the distances selected. Regression analysis indicated a positive linear relationship between microhardness and the natural logarithm of time and a negative correlation between microhardness and distance, respectively. Conclusion: The modified activation routines investigated resulted in significantly reduced surface microhardness numbers compared with the controls.

Objective: The aim of this study was to research the antimicrobial activity of fluoride-releasing dental materials on strains of mutans streptococci using a new in vitro method. Method and materials: Using microplaques for the cell cultures, specimens were made with a conventional glass ionomer (Ketac-Cem), a photo-cured ionomer (Vitremer), and a compomer (Dyract). Three groups were made, each focusing on a distinct situation: In the first group, the antimicrobial activity was tested after curing; in the second, the materials were exhausted from their disposable fluoride for 14 days; and in the third group, fluoride was reincorporated into the specimens after a topical application of 2% sodium fluoride gel for 4 minutes. Results: The results demonstrated that the photo-cured ionomer had the best antimicrobial activity of all groups, followed by the conventional glass ionomer and compomer groups, respectively. All materials studied presented antimicrobial activity in all stages of the experiment, which was statistically proven using the Student's t test. Conclusions: The fluoride-releasing materials studied in the current report demonstrated antimicrobial activity on strains of mutans streptococci in every group studied. This new method demonstrated more accuracy and practicability than others commonly used.