Ozgur Inan

Evaluation of the effects of restorative materials used for occlusal surfaces of implant-supported prostheses on force distribution.

In this study, the functional stresses in alveolar bone created by restorative materials used in implant-supported prostheses were determined by the photoelastic stress analysis method. A photoelastic resin mandibular model, hollow-cylinder implants (3.5 mm diameter, 10 mm length), and fixtures and superstructures made of five different prosthetic materials were used. Vertical and 45-degree inclined loads were applied to the model. Subsequently, color photographs of the force line distribution observed on a polariscope were taken. Differences between vertical and inclined loads were statistically significant for all prosthetic materials (P < 0.01). The greatest stress distribution around the apex of the implant was observed with Ceramco II porcelain, followed by Biodent acrylic. The ArtGlass and Elcebond CCV composite materials had equal values, whereas Verebond Ni-Cr alloy showed minimum stress distribution.

Occlusal Contact Changes with Removable and Bonded Retainers in a 1-Year Retention Period

OBJECTIVE To test the hypothesis that there is no difference in the number of occlusal contacts in centric occlusion in patients treated with bonded and removable retention procedures and a control group during a 1-year retention period. MATERIALS AND METHODS Twenty-five patients received a removable Hawley retainer, and 25 patients received maxillary and mandibular bonded retainers. The retainer patients were compared with 20 control subjects with normal occlusions. Silicone-based impression bites were used to record occlusal contacts. Paired-sample t-test, analysis of variance (ANOVA), and Tukey tests were used to evaluate intragroup and intergroup differences. RESULTS An increased number of occlusal contacts were recorded in total-arch and posterior combined (actual/near) teeth during the retention period as compared with the control group. In the Hawley group, actual and total contacts on the first and second molar and actual contacts on the premolar and canine showed statistically significant increases. In the bonded retainer group, near and total contacts on the first and second molars and premolars showed statistically significant increases. Slight occlusal changes were seen in the control sample during the observation period, presumably from growth and development. ANOVA comparisons of total contacts of anterior and posterior teeth indicated statistically significant differences in the three groups on posterior segments. CONCLUSIONS The hypothesis is rejected. Both retention procedures allowed relative vertical movement of the posterior teeth, but the number of contacts on the posterior segment was increased more in the bonded retainer group than in the Hawley and control groups at the end of retention.

Effect of pontic framework design on the fracture resistance of implant-supported all-ceramic fixed partial dentures

Objective: The purpose of this study was to compare the fracture resistance of implant-supported all-ceramic fixed partial dentures, which have three different pontic designs. Material and Methods: Two implants were placed in a metal model simulating mandibular left second premolar and mandibular left second molar. Thirty standardized 3-unit all-ceramic fixed partial dentures with biconvex, convex or concave pontic designs were fabricated using IPS e.max system (n=10). Afterwards, specimens were centrally loaded on the pontics until failure with a universal testing machine. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests at 5% significance level. Results: The fracture resistance values of all-ceramic fixed partial dentures designed with biconvex, convex or concave pontics were 349.71, 438.20 and 300.78 N, respectively. There were no statistically significant differences between the fracture resistances of the groups (p>0.05), except for convex and concave groups (p<0.05 and p=0.009, respectively). Conclusions: Convex design showed the best mechanical properties as demonstrated by the high values of fracture resistance.

Implant-supported overdenture therapy: a 3- to 8-year prospective study.

Inflammatory changes in periimplant soft tissues and loss of alveolar bone can develop as in periodontal diseases. This clinical phenomena has been described as periimplantitis. Microorganisms such as Gram-negative anaerobic rods, spirochetes, and bacteroides that are seen in subgingival flora in periodontitis have also been found in sulcular microflora in periimplantitis. The purpose of this study was to evaluate periimplant tissue changes in totally edentulous patients who had implant-supported overdentures for 3 to 8 years (5-5.5 years) clinically from both a subjective and an objective point of view. The clinical parameters used in this study can be helpful in the evaluation of periimplant tissue health.

Evaluation of osteoblastic activity around dental implants using bone scintigraphy

OBJECTIVES The aim of this study was to evaluate the osteoblastic activity around delay-loaded intraosseous dental implants using nuclear medicine imaging techniques. MATERIAL AND METHODS Seven totally edentulous patients (two females and five males, between 48 and 57 years of age) were included in the study. Two implants were inserted into mandibular canine regions and removable prostheses were produced after 3 months. Whole-body bone scintigraphies with 20 mCi technetium 99m labelled methylene diphosphonate were taken from the patients before implant insertion, 3 months after implant placement just before the prostheses were made and 1 year after implant placement. Standardized count/pixel (SC/P) rates were calculated for each patient. Preimplantation SC/P values were compared with the 3- and 12-month values. Three-month values were compared with the 12-month values as well. RESULTS SC/P rates in the third month were significantly higher (P<0.05) than preoperative values and the SC/P rates of the 12th month were significantly lower (P<0.05) than 3-month values. The SC/P rates of the 12th month were relatively higher than first scintigraphies but the difference was insignificant (P>0.05). CONCLUSIONS Within the limitations of this study, in which delayed loading was applied, we showed that osteoblastic activity persisted more in delay loaded implants than immediate and early loading. After 1 year, there was no cellular activity around two implants and this implied that two implants were sufficient for a total prosthesis.

Bond strength of adhesively luted ceramic discs to different core materials.

The purpose of this in vitro study was to compare the shear bond strengths of resin, glass-ionomer, and ceramic-based core materials to all ceramic discs. Five core materials (Core max, Sankin; Clearfil AP-X, Kuraray; Empress Cosmo, Ivoclar-Vivadent; Photocore, Kuraray; Dyract Extra, Dentsply) were prepared as discs 10 mm in diameter and 2 mm in height according to the manufacturers instructions. Ten disc specimens per group were prepared, and dentin served as the control. All resin specimens were embedded in autopolymerizing acrylic resin, with one surface facing up. All ceramic discs (IPS Empress I, Ivoclar-Vivadent) 3 mm in diameter and 2 mm in height were prepared and bonded to core specimens with a dual-curing luting resin cement (Variolink II, Vivadent). Specimens were stored in distilled water at 37 degrees C. Shear bond strength of each sample was measured after 24 h using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed with one-way analysis of variance and Tukey HSD tests (alpha = 0.05). Shear bond strength varied significantly depending on the core material used (p < 0.05). Clearfil AP-X and Photocore showed the highest shear bond strength value while Empress Cosmo provided the lowest (p < 0.05). There were no statistically significant differences among Clearfil AP-X, Photocore, and Core-Max (p > 0.05). And also there were no statistically significant differences between Dyract Extra and the control group (p > 0.05). In vitro shear bond strengths of ceramic discs bonded to resin-based core materials showed higher bond strength values than ceramic-based core material.

The use of autogeneous mandibular bone block grafts for reconstruction of alveolar defects.

Objective: Purpose of this retrospective study was to evaluate outcomes autogenous bone block grafts obtained from mandible for different indications. The healing of the donor and recipient sites in the postoperative period, morbidity and the resorption of the graft were investigated. Patients and Methods: Twenty-nine patients grafted with mandibular bone block graft were participated in the present study. Grafting was applied in these patients for three indications; reconstruction of alveolar cleft, lateral crest augmentation before dental implantation and sinus floor augmentation. All operations were performed under local anesthesia and in some cases sedation was used as well. Results: Minimal exposure of the block graft occurred in three alveolar cleft patients. Secondary epithelization was achieved in all cleft patients with no symptoms of infection. In one patient infection was seen in donor site 1-week after the operation. The region was curetted and antibiotics administrated again. Two patients showed an infection of recipient site, after 4 weeks the grafts were removed. In all the patients, as the screw head became apparent until 1 thread, amount of the resorption were considered <1.5 mm. Conclusion: The usage of mandibular block grafts is a simple and effective treatment modality for reconstruction of different types of alveolar defects and it also reduces cost of treatment.

Efficiency of different light sources to polymerise composite material

Abstract The aim of this in vitro study is to examine the polymerisation efficacy of three different polymerisation units through simulated three different ceramic restorations (5 mm in diameter and 2 mm in height) by determining the degree of monomer conversion of a composite luting material. The curing efficiency was observed with Fourier transform infrared micromultiple internal reflectance spectroscopy after 24 h of polymerisation. The degree of conversion was calculated as a percentage of experimentally polymerised versus maximally polymerised composite. The degree of conversion values varied with the light source (light emitting diode, high intensity halogen and conventional halogen) (p<0·05) and the ceramic system (Cercon, IPS Empress 2 and Cerec) (p<0·05).