Effect of various polymerization protocols on the cytotoxicity of conventional and self-adhesive resin-based luting cements.

OBJECTIVES: This study evaluated the cytotoxicity of resin-based luting cements on fibroblast cells using different polymerization protocols. MATERIALS AND METHODS: Two conventional dual-polymerized (RelyX ARC, VariolinkN) and two self-adhesive resin cements (RelyX Unicem, Multilink Speed) specimens were polymerized using four different polymerization protocols: (a) photo-polymerization with direct light application, (b) photo-polymerization over ceramic and (c) resin nano-ceramic discs and (d) auto-polymerization. The specimens were then assigned to four groups to test cytotoxicity at 0, 1, 2 and 7 preincubation days (n = 5). MTT test was performed using NIH/3T3 fibroblast cells. Data were analysed using three- and one-way ANOVA. Multiple comparisons were made using Bonferroni post hoc test (p < 0.05). RESULTS: The highest cytotoxic values were recorded at day 2 for conventional resin cements and at day 0 for self-adhesive resin cements. Self-adhesive resin cements showed the most cytotoxic effect at the second day, while conventional resin cements presented immediate cytotoxicity. Auto-polymerized resin specimens and especially Multilink Speed demonstrated the most cytotoxic effect regardless of the preincubation time. Cytotoxicity of cements tested reached the lowest level at day 7. Interposition of ceramic or nano-ceramic restorative material did not significantly affect the cytotoxicity of tested luting cements (p > 0.05). CONCLUSIONS: Cytotoxicity of dual-polymerized resin cements was material-dependent and decreased gradually up to 7 days. Photo-polymerization plays an important role in reducing the cytotoxic effects. CLINICAL RELEVANCE: When luting ceramic or resin nano-ceramic restorations of which thickness does not exceed 2 mm, the level of cytotoxicity with the tested materials is not significant. Luting of restorative materials that do not allow for light transmission such as metal-fused porcelain, clinicians should be cautious in the use of dual-polymerized conventional resin cements as only auto-polymerization of resin cements takes place under such materials.

Bonding effectiveness of a self-adhesive resin-based luting cement to dentin after provisional cement contamination.

PURPOSE: To evaluate the influence of provisional luting cements on the bonding performance of a resin-based self-adhesive luting cement to dentin vs that of currently used resin-based luting agents with different adhesion strategies. MATERIALS AND METHODS: Forty-five prepared human molars were randomly and equally divided into three main groups according to the type of provisional luting cement applied: eugenol-containing provisional cement (Temp Bond, Kerr), eugenol-free provisional cement (Temp Bond NE, Kerr), and control where the provisionalization step was omitted. Each group was further subdivided into 3 groups based on the category of adhesive systems/ luting materials used: a two-step etch-and-rinse system (Single Bond/RelyX ARC; 3M ESPE) (RX), a two-step self-etching system (Clearfil Liner Bond 2V/ Panavia F; Kuraray) (PF), and a self-adhesive luting cement (Rely X Unicem; 3M ESPE) (RU). Finally, 9 groups of 5 teeth each were prepared for the microtensile test. RESULTS: Two-way analysis of variance (ANOVA) and post-hoc Bonferroni tests revealed that definitive luting cement, provisional luting cement, and the interactions of these two factors had significant influences on dentin bond strength. The highest bond strength was obtained for PF (32.05 MPa), followed by RX (26.57 MPa) and RU (16.56 MPa) for the controls. Contamination with either eugenol-containing or eugenol-free provisional cement significantly decreased the bonding effectiveness of RX (19.08 and 19.69 MPa, respectively) and PF (14.21 and 16.67 MPa respectively) to dentin (p < 0.05). RU showed comparable bond strength values before and after provisional cement (13.93 and 14.49 MPa, respectively) application (p > 0.05). Eugenol in provisional luting cement did not produce material-related alterations in the bonding performance of the resin luting cements tested (p > 0.05). CONCLUSION: Based on these results, the self-adhesive cement which was not influenced by the provisional cement application may be promising. However, long-term laboratory and clinical performance of this cement needs to be assessed before recommending it as an alternative to the technically more demanding approaches. Moreover, an effective surface cleansing procedure is critical to achieve a successful bond between the contaminated dentin and luting cement.

Masticatory performance, maximum occlusal force, and occlusal contact area in patients with bilaterally missing molars and distal extension removable partial dentures.

PURPOSE: The aim of this study was to compare the masticatory performance, maximum occlusal force, and occlusal contact area of subjects with bilaterally missing molars, treated either with the shortened dental arch (SDA) concept or with distal extension removable partial dentures (RPDs), during a 1-year follow-up. MATERIALS AND METHODS: This study included three groups of 10 subjects each, in which SDA and RPD groups displayed bilateral molar loss in the mandible. Subjects with complete natural dentition (CD) served as the control group. Masticatory performance was evaluated by the multiple sieve method. Standard cubes (edge length: 8 mm, 0.9 g) shaped from a high viscosity polysiloxane molding material (Zetaplus, Zhermack) were used as the test food. Maximum occlusal force (N) and occlusal contact area (mm2) were evaluated using dental prescale films. RESULTS: No statistically significant differences regarding masticatory performance between the groups or evaluation periods were demonstrated. In the RPD group, masticatory performance with and without prostheses showed no significant differences. SDA patients showed significantly lower contact area and occlusal force than both the CD and RPD groups (P < .05). CONCLUSION: SDA can be an alternative to distal extension RPDs with respect to masticatory performance in subjects with bilaterally missing molars in one dental arch, despite remarkable reductions in maximum occlusal force and occlusal contact area.

An immunohistochemical evaluation of cell adhesion molecules in human dental pulp after tooth preparation and application of temporary luting cements.

OBJECTIVE: The aim of this study was to determine if temporary luting cements used with provisional restorations alter the expression of cell adhesion molecules (CAMs) in human dental pulp. STUDY DESIGN: Twenty-five healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to 5 experimental groups. Group 1 included untreated teeth as negative control. In groups 2-5, provisional crowns were cemented to the prepared teeth with either eugenol-containing or eugenol-free temporary cement and extracted 24 or 48 h after the treatment. Expression ratio and staining intensity of CAMs, including E-selectin, P-selectin, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and platelet endothelial cell adhesion molecule 1 (PECAM-1), was investigated in the pulp samples. The assessment of immunohistochemical reactions was performed by 2 independent observers using a semiquantitative scale. RESULTS: Significant reductions were recorded in the expression ratio and/or the staining intensity of E-selectin, ICAM-1, and VCAM-1 in samples removed 48 h after treatment with eugenol-containing cement compared with intact teeth. This reduction was significant only for ICAM-1 for 48-h eugenol-free samples. Moreover, the eugenol-free cement group indicated considerably higher E-selectin, ICAM-1, and VCAM-1 expression compared with the eugenol-containing group (P < .005) 48 h after the application. The PECAM-1 reactivity was similar for all of the experimental groups. CONCLUSION: Application of temporary luting cements after tooth preparation for full crown causes alterations in the expression of endothelial CAMs in the dental pulp.

Rehabilitation of a congenital palatal defect with a modified technique: a case report.

INTRODUCTION: Constuction of the obturator prostheses and providing the patient's comfort with them are very difficult. Primary and the most important stage for these prostheses is to perform a proper impression. CASE PRESENTATION: A 55-year-old edentulous Turkish female patient with a congenitally maxillary defect was rehabilitated with an open hollow obturator prosthesis. After the preliminary impression was completed, a metal frame suitable with the maxillary defect was constructed manually and used for making the impression of the defect area. After the first part of the obturator was finished, second part which separates nasal cavity and oral cavity was constructed by the aid of the bulb. CONCLUSION: When constructing an obturator prosthesis, making a detailed impression from the defect area can be performed by the aid of a metal frame, and an intraorally shaped extension that separates oral cavity from nasal cavity might be more effective for adaptation of the prosthesis.

Immunohistochemical evaluation of endothelial cell adhesion molecules in human dental pulp: effects of tooth preparation and adhesive application.

OBJECTIVE: Studies have demonstrated that restorative procedures can initiate pulpal inflammation. Adhesion molecules on endothelial cells mediate the leukocyte-endothelium interaction, which is the fundamental event of inflammation. The aim of this study was to evaluate possible changes in the endothelial cell adhesion molecules (CAMs) of human dental pulp with tooth preparation, and after the application of one-step self-etch adhesive. MATERIALS AND METHODS: Twenty healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to four experimental groups. Group 1 involved sound intact teeth representing the controls. In group 2, teeth were prepared for full crown and extracted within 2h. Groups 3 and 4 comprised the teeth coated with one-step self-etch adhesive, iBond Gluma inside following the preparation and extracted after 24 and 48h, respectively. Tissue distribution and staining intensity of CAMs including E-selectin, P-selectin, ICAM-1, VCAM-1 and PECAM-1 was investigated in the pulp samples using monoclonal antibodies and the streptavidin-biotin-horse-radish immunoperoxidase procedure. The assessment of immunohistochemical reactions was performed by two independent observers using a semi-quantitative scale. RESULTS: All the CAMs evaluated were expressed by the healthy pulp tissues. Significant alterations in the distribution and staining intensity of CAMs were detected following tooth preparation. One-step self-etch adhesive tested in the present study induced inflammatory reactions in the pulp (P<0.05, Mann-Whitney U-test). CONCLUSION: It seems evident that tooth preparation for full crown and application of one-step self-etch adhesive on prepared teeth had a potential to interfere with the inflammatory response.

An analysis of maxillary anterior teeth: facial and dental proportions.

STATEMENT OF PROBLEM: The size and form of the maxillary anterior teeth are important in achieving pleasing dental and facial esthetics. However, little scientific data have been defined as criteria for evaluating these morphological features. PURPOSE: This study analyzed the clinical crown dimensions of maxillary anterior teeth to determine whether consistent relationships exist between tooth width and several facial measurements in a subset of the Turkish population. MATERIAL AND METHODS: Full-face and anterior tooth images of 100 Turkish dental students viewed from the front and engaged in maximum smiling were recorded with digital photography under standardized conditions. Gypsum casts of the maxillary arches of the subjects were also made. The dimensions of the anterior teeth, the occurrence of the golden ratio, the difference between the actual and perceived sizes, and the relationship between the anterior teeth and several facial measurements by gender were analyzed using the information obtained from both the computer images and the casts. One-sample, 2-sample, and paired t tests, and repeated-measures analysis of variance and Duncan multiple-range tests were performed to analyze the data (alpha=.05). RESULTS: The dimensions of the central incisors (P<.05) and canines (P<.01) varied by gender. The existence of the so-called "golden proportion" for the maxillary anterior teeth as a whole was not found. Significant differences emerged when the mean ratios between various perceived widths were compared with their ideal golden ratios (P<.01). Proportional relationships between the bizygomatic width and the width of the central incisor, and the intercanine distance and the interalar width in women were observed. CONCLUSION: The maxillary central incisor and canine dimensions of men were greater than those of women in the Turkish population studied, with the canines showing the greatest gender variation. Neither a golden proportion nor any other recurrent proportion for all anterior teeth was determined. Bizygomatic width and interalar width may serve as references for establishing the ideal width of the maxillary anterior teeth, particularly in women.

Computer-based evaluation of gender identification and morphologic classification of tooth face and arch forms.

STATEMENT OF PROBLEM: In prosthodontics, sex-related differences in tooth forms are assumed, and optimal esthetics is further assumed to be achieved only if the face, arch, and tooth forms are in harmony. However, there is no universally accepted rule or mathematical method to define these morphologic features. PURPOSE: The purpose of this study was to evaluate whether anterior tooth from reflected gender and to question the hypothesis that there was a correlation among face, arch, and tooth forms on the basis of dentists' perceptions. MATERIALS AND METHODS: Photographic records including full face, dental arch, and anterior tooth images of 60 dental students were made by use of digital photography. A database was arranged as a questionnaire for evaluation by prosthodontists who were asked to define the sex and morphologic features of the subjects by examining stored images of the subjects. Thirteen prosthodontists, all with at least 10 years of experience, served as experts and performed these evaluations twice at 2-week intervals. Kappa statistic was used to measure intraobserver and interobserver agreement. RESULTS: The average correctly identified values in females and males were 53% and 58%, respectively. However, the proportions of females and males who were identified correctly and completely the same in both the first and second evaluations were 36% for females and 41% for males. According to the observations of the experts, face-to-arch form (54%) and face-to-tooth form (51%) correlations were higher than the tooth-to-arch form correlation. The overall correlation among face, arch, and tooth forms was 31%. The experts were in fair agreement in defining tooth forms. CONCLUSIONS: The results of gender identification of the subjects showed that the experts were unsuccessful in distinguishing the actual sex by the visual assessment of anterior tooth segment alone, with a fair agreement between 2 evaluation sessions. There were also significant interobserver and intraobserver differences in classifying face, arch, and especially tooth forms. Furthermore, the correlation among these forms was not highly defined.