Quintessence International, 04/2006

There is an increased demand for restoration of anterior teeth based on esthetic requirements. Oftentimes, the teeth restored are compromised and have minimal remaining dentin after undergoing root canal treatment. Reduction of nonaxial forces by controlling incisal guidance is essential in improving the long-term prognosis of such situations. Another common complication when crowning anterior teeth is the lack of palatal space for restorative material. This is often evident in patients with anterior tooth wear and deep overbite. This article describes the Dahl principle, a conservative method for controlling incisal guidance and gaining palatal space for restorative material. A case presentation is used to illustrate the concepts discussed. Keywords: anterior teeth, biomechanical forces, Dahl principle, incisal guidance

Objective: The aim of this prospective clinical study was to evaluate the survival rates of IPS Empress 2 (Ivoclar Vivadent) all-ceramic crowns and fixed partial dentures (FPDs) after an observation period of up to 5 years. Method and Materials: Forty-three patients (19 women and 24 men) were included in this study. The patients were treated with a total of 58 adhesive bonded IPS Empress 2 restorations. A total of 27 single crowns were placed on molars and premolars, and 31 three-unit FPDs were placed in the anterior and premolar regions. Clinical follow-up examinations took place at 6, 12, 24, 36, 48, and 60 months after insertion. Statistical analysis of the data was calculated using the Kaplan-Meier method. Results: Results of the 50-month analysis (interquartile range, 33 to 61 months) showed that the survival rate was 100% for crowns and 70% for FPDs. Six failures that occurred exclusively in the three-unit FPDs were observed. Framework fractures were recorded in three FPD units where the connector dimensions did not meet the manufacturer specifications. Only one FPD exhibited an irreparable partial veneer fracture, and 2 FPDs showed evidence of biologic failures. The accuracy of fit and esthetic parameters were clinically satisfactory for crowns and FPDs. Conclusion: The results of this 5-year clinical evaluation suggest that IPS Empress 2 ceramic is an appropriate material for the fabrication of single crowns. Because of the reduced survival rates, strict conditions should be considered before the use of IPS Empress 2 material for the fabrication of three-unit FPDs. Keywords: all-ceramic, crowns, fixed partial dentures, IPS Empress 2, survival rate

Objective: Patients in the stomatology service of the Department of Oral Surgery and Stomatology who were clinically and histopathologically diagnosed with oral lichen planus (OLP) in the years 1995 to 2001 were examined for a possible malignant transformation of a previously biopsied OLP site. Method and Materials: For the 145 patients included, the recordings were searched for initial localization and type of OLP lesion, potential noxious agents, distribution between symptomatic and asymptomatic OLP types, and for a malignant transformation of a known OLP site during the follow-up period up to December 2003. Results: The group comprised 47 men and 98 women with a mean age of 56.3 years. Of the 497 lesions, almost half were classified as reticular or papular, predominantly located on the buccal mucosa, gingiva, and borders of the tongue. Four patients did not adhere to their scheduled control visits and were dropped from the study. During the follow-up period 4 patients developed malignant transformation of OLP. In 3 of these cases, dysplasia was present at the initial diagnosis of OLP. This results in a malignant transformation rate of 2.84% among the remaining 141 patients; if the 3 patients with initial dysplasia are excluded, the rate drops to 0.71%. Conclusions: Until further knowledge is derived from large prospective studies, the data supporting or negating a potential malignant character of OLP lesions remains inconclusive. Special emphasis has to be directed toward unified inclusion and exclusion criteria regarding clinical and histologic findings and identifiable risk factors to allow the comparison of different studies. Keywords: asymptomatic type, dysplasia, malignant transformation, oral lichen planus, symptomatic type

Objective: The purpose of this study was to test the hypothesis that remineralized dentin lesions induced by glass ionomer are less vulnerable to subsequent acid challenge. Method and Materials: Baseline demineralized (BDe) lesions were created in 50 bovine dentin slices immersed for 3 weeks in acid solution. A resin-modified glass ionomer (RMGI) was applied to the specimens before immersion in salivalike solution to allow remineralization (Re) for 2 weeks (V2W) or 6 weeks (V6W). Resin-modifed glass ionomer was coated to block further ion release before a 3-week immersion in acid solution as a second demineralization (SDe). Control groups (C2W and C6W) were done simultaneously without RMGI. In another group, RMGI was left undisturbed (V2W+) to allow continuous ion release during SDe. Mineral content was converted from microradiographs, after BDe, Re, and SDe steps. Changes in mineral content were calculated and compared between groups. Results: The remineralized surface zone was maintained after SDe, but the lesion body became deeper. Percentage of mineral loss from SDe was not significantly different between V2W and C2W (t test, P > .05). When remineralization was extended to 6 weeks, V6W showed significantly less mineral loss than C6W. Mineral loss was lowest when RMGI was not blocked (V2W+). Conclusion: Dentin lesions remineralized in the presence of RMGI maintained the highly mineralized surface zone when subjected to second demineralization. However, the remineralized surface zone could not prevent advance of the lesion body. The subsequent demineralization was markedly reduced by extending the remineralization period or by leaving the RMGI undisturbed to resume ion release. Keywords: artificial caries, demineralization, dentin, glass ionomer, remineralization, subsequent acid challenge

All-ceramic crowns are used as alternatives to conventional metal-ceramic crowns for the restoration of single teeth. Traditionally all-ceramic restorations possessed physical properties that contraindicated their use in many treatment situations. The strength that zirconia ceramics exhibit seems to support the hypothesis that, in specific situations, an all-ceramic crown may be used to restore removable partial denture (RPD) abutments in areas previously reserved for metal or metal-ceramic restorations. Abutments for RPDs may now be fabricated with Procera AllZirkon with the classically prepared guide planes and rest seats. This article provides an overview of a technique for the fabrication of a zirconia-based crown to be used in conjunction with removable partial dentures using the Procera CAD/CAM technology. Keywords: abutment teeth, all-ceramic crown, Procera, removable partial denture, surveyed crown, zirconia

Objective: The purpose of this in vitro investigation was to evaluate the fracture strength of endodontically treated teeth restored with different all-ceramic posts and cores. Method and Materials: Seventy-two endodontically treated human maxillary central incisors were divided into 3 groups with 24 teeth each and restored with 1 of the following methods: prefabricated zirconia ceramic posts and resin composite buildups; zirconia ceramic posts and copy-milled alumina ceramic cores (2-piece technique), or copy-milled all-ceramic posts and cores made from a zirconia-reinforced glass-infiltrated alumina ceramic (1-piece technique). Each group was divided into 3 subgroups of 8 samples each, consisting of teeth that did not receive crown restorations and were stored for 60 days, teeth restored with all-ceramic crowns and stored for 60 days, and teeth restored with all-ceramic crowns and subjected to 1.2 million loading cycles with 30 N in a chewing simulator. Results: The mean fracture strengths ranged from 205 to 522 N. Prefabricated zirconia posts and resin composite buildups showed a statistically significantly lower fracture strength after chewing simulation than teeth restored with prefabricated zirconia posts and alumina ceramic cores. Conclusion: All-ceramic posts and cores made with the 2-piece technique showed promising fracture strengths under the tested conditions. Keywords: all-ceramic, artificial aging, chewing simulation, fracture strength, posts and cores

Objective: The aim of this study was to evaluate the remineralization of residual demineralized dentin underneath restorations by fluoride-releasing liners in vitro. Method and Materials: Two glass-ionomer cement liners, Lining Cement (GC) and RK-141A (GC), and two light-cured resin liners with and without 5 wt% NaF were used in this study. The resin liners were made by mixing TEGDMA and bis-GMA. Class 5 cavities were prepared on extracted human premolars. Demineralized dentin was promoted by using a bacterial caries induction system at the cavity floor. Cavities were restored with a resin composite following application of each liner. Specimens were then stored for 4 weeks at 37°C and 100% humidity. After storage, the specimens were cut through the restorations, and axial sections of about 80-µm thickness were prepared. Contact microradiographs were taken, and the radiopacity of the demineralized dentin layer underneath the liner was analyzed. Results: The ratios of radiopacity of demineralized dentin under the fluoride-releasing liners were significantly higher than those under the resin liner without fluoride release. Although the amounts of fluoride release from the glass-ionomer cement liners were lower than that from the resin liner with fluoride release, there were no significant differences in the ratios of radiopacity in demineralized dentin layers among the 3 liners with fluoride release. Conclusion: Although the fluoride released from liners can enhance remineralization of demineralized dentin, the amount of fluoride release does not affect the ratio of radiopacity in the remineralized dentin. Keywords: caries, demineralized dentin, fluoride, glass-ionomer cement, liner, remineralization, resin

Objective: The aim of this study was to evaluate the anxiety levels of patients attending a university oral diagnosis clinic. Avoidance, felt physiologic responses, and the most fear-producing stimuli of dental treatment were also evaluated. Method and Materials: A total of 1,437 patients were asked to complete a questionnaire consisting of the Dental Anxiety Scale (DAS), Dental Fear Scale (DFS), and questions about age, gender, education level, and frequency of dental visits. The patients were grouped according to gender and divided into 5 age categories. Statistical analysis was made by descriptive statistics, two-proportion z test, analysis of variance, Tukey's Honestly Significant Difference test, and Scheffé test. Results: The mean DAS score was 9.52 (SD 4.08) for females, 7.96 (SD 3.30) for males, and 8.76 (SD 3.80) for the total sample. There was no statistically significant difference between the mean DAS scores of age groups. Patients with a primary school education and those who had never visited the dentist had the highest anxiety scores. According to the DFS, the most felt autonomic response was increased heart rate, and the most fear-producing stimuli were the sight of the needle (25.1%) and sensation of the injection (24.1%). Of the patients 10.5% avoided calling for an appointment, and 4.9% canceled or did not appear for appointment. Conclusion: Some patients are afraid of some of the stimuli involved with dental treatment. This could affect the patient-dentist relationship and the dental treatment plan; therefore, before dental treatment, patients' anxiety and fear levels should be assessed. Keywords: anxiety, attendance, dental anxiety scale, dental fear scale, dentistry, fear

Objective: It is common practice for clinicians to adjust the porcelain surfaces of dental prostheses. The change in surface roughness after different surface finishing techniques has attracted the attention of prosthodontists. The present study was undertaken to investigate the average surface roughness of 2 dental ceramics: IPS Empress 2 (layering glass-ceramic, Ivoclar Vivadent) and In-Ceram/Vitadur Alpha (Vita), either glazed, unglazed, or refinished using different techniques. Method and Materials: Disks of 6-mm diameter and 2-mm thickness were prepared from IPS Empress 2 and In-Ceram Alumina/Vitadur Alpha ceramics. Specimens were finished for 1 minute to the various stages provided in the sequence of instruments in the Shofu porcelain veneer kit. The average roughness measurements were taken from each specimen with a surface roughness tester. Results: Significant differences in surface roughness were observed between the ceramics and among the finishing techniques used for both IPS Empress 2 and In-Ceram/Vitadur Alpha. It was found that unglazed IPS Empress 2 is rougher than unglazed In-Ceram/Vitadur Alpha. Conclusion: Regardless of the type of ceramic or pretreatment, any adjusted ceramic restoration should be reglazed or subjected to a finishing sequence that is followed through to a final stage of polishing with diamond paste. Keywords: finishing, glazing, IPS Empress 2, In-Ceram/Vitadur Alpha, surface roughness

Removal of foreign objects from the root canal can be very frustrating. The use of a variety of instruments and techniques has been suggested for the retrieval of obstacles from root canals during endodontic treatment. This article describes a method for retrieving a large mass of amalgam restoration that was wedged into the root canal. The amalgam, which had served as the provisional restorative material during apexification of an immature anterior tooth, was inadvertently pushed into the root canal. After the mass was bypassed, the amalgam was loosened with the aid of copious irrigation, chelation, and flotation. Hedstrom files twisted around the object allowed sufficient grip for its retrieval, enabling completion of the root canal treatment. Keywords: amalgam, bypass, chelation, foreign object, retrieval, root canal