Gisele Rodrigues da Silva

Effect of post type and restorative techniques on the strain and fracture resistance of flared incisor roots

Restoring flared endodontically treated teeth continues to be a challenge for clinicians. This study evaluated the effect of post types and restorative techniques on the strain, fracture resistance, and fracture mode of incisors with weakened roots. One hundred five endodontically treated bovine incisors roots (15 mm) were divided into 7 groups (n=15). The two control groups were (C) intact roots restored with Cpc (cast posts and core) or Gfp (glass fiber posts). The five experimental groups were (F) flared roots restored with GfpAp (Gfp associated with accessory glass fiber posts), GfpRc (anatomic Gfp, relined with composite resin), and GfpRcAp (anatomized Gfp with resin and accessory glass fiber posts). All teeth were restored with metal crowns. Mechanical fatigue was performed with 3x10(5)/50 N. Specimens were loaded at 45º, and the strain values (μS) were obtained on root buccal and proximal surfaces. Following that, the fracture resistance (N) was measured. One-way ANOVA and Tukeys HSD tests (α=0.05) were applied, and failure mode was checked. No significant difference in strain values among the groups was found. Cpc presented lower fracture resistance and more catastrophic failures in flared roots. Gfp associated with composite resin or accessory glass fiber posts seems to be an effective method to improve the biomechanical behavior of flared roots.

Fracture strength of composite fixed partial denture using bovine teeth as a substitute for human teeth with or without fiber-reinforcement

This study evaluate the use of bovine teeth as a substitute for human teeth on fracture strength tests of composite fixed partial dentures (Cpd), with and without fiberglass reinforcement (Fg). Eighty teeth were selected, being 40 bovine incisors, 20 human premolars and 20 molars. Bovine incisors were ground to get a platform, simulating an occlusal surface of human molar. Teeth in pairs were embedded in polystyrene resin, simulating the periodontal ligament and divided in 4 groups: B-Cpd-Fg: bovine teeth restored with Cpd with Fg; B-Cpd-NFg: bovine teeth restored with Cpd without Fg; H-Cpd-Fg: human teeth restored Cpd with Fg; and H-Cpd-NFg: human teeth restored with Cpd without Fg. The Cpd were adhesively fixed and submitted to an axial compression load at the pontic center with a crosshead speed of 0.5 mm/min until fracture. Failure modes were assessed and classified. Data were subjected to two-way ANOVA and Tukeys HSD test (α=0.05). The tooth type had no influence on fracture strength and fracture mode. The inclusion of fiberglass increased significantly the fracture strength. The failure modes were more reparable in groups with fiber-reinforcement. Bovine teeth can be used as a substitute for human teeth in these types of fracture strength tests.

Ceramic restoration repair: report of two cases

The esthetic and functional rehabilitation of patients with multiple missing teeth can be performed with several techniques and materials. Ceramic restorations provide reliable masticatory function and good esthetics. However, fracture can occur in some cases due to their brittle behavior. In some cases, the replacement of an extensive prosthesis is a problem due to the high treatment cost. In this paper, two cases are presented, in which fractures occurred in extensive metal-ceramic fixed partial dentures, and their replacement was not possible. Ceramic repair was chosen and the sequences of treatment with and without presence of the ceramic fragment are also discussed. The cases illustrate that, in some situations, fractured metal-ceramic partial dentures can be successfully repaired when prosthetic replacement is not a choice. Prosthodontists must use alternatives that allow a reliable repair to extensive metal-ceramic fixed partial dentures. Surface preparation of the ceramic with hydrofluoric acid in conjunction with a silane coupling agent is essential for a predictable bonding of composite resin. The repair performed with composite resin is an esthetic and functional alternative when extensive fixed partial dentures cannot be replaced.

Microtensile Bond Strength of Methacrylate and Silorane Resins to Enamel and Dentin

The aim of this study was to evaluate the microtensile bond strength (µTBS) of two substrates (enamel and dentin) considering two study factors: type of composite resin [methacrylate-based (Filtek Supreme) or silorane-based (Filtek LS)] and aging time (24 h or 3 months). Twenty human molars were selected and divided into 2 groups (n=10) considering two dental substrates, enamel or dentin. The enamel and dentin of each tooth was divided into two halves separated by a glass plate. Each tooth was restored using both tested composite resins following the manufacturers instructions. The samples were sectioned, producing 4 sticks for each composite resin. Half of them were tested after 24 h and half after 3 months. µTBS testing was carried out at 0.05 mm/s. Data were analyzed by three-way ANOVA and Tukeys HSD tests at α=0.05. Significant differences between composite resins and substrates were found (p<0.05), but no statistically significant difference was found for aging time and interactions among study factors. The methacrylate-based resin showed higher µTBS than the silorane-based resin. The µTBS for enamel was significantly higher than for dentin, irrespective of the composite resin and storage time. Three months of storage was not sufficient time to cause degradation of the bonding interaction of either of the composite resins to enamel and dentin.

Influence of different load application devices on fracture resistance of restored premolars

This in vitro study analyzed the effect of different load application devices on fracture resistance and failure mode of maxillary premolars restored with composite resin. Sixty human maxillary premolars received standardized mesio-occluso-distal cavity preparations and were restored with composite resin. The specimens were randomly divided into 6 groups (n=10). Compressive loading was applied using 6 different metallic devices: S2: 2-mm sphere; S6: 6-mm sphere; C2: 2-mm cylinder; C6: 6-mm cylinder; WS: wedge shape device; and MAT: individualized metallic antagonist tooth. Data were analyzed statistically using one-way ANOVA and Tukeys test (α=0.05). The failure mode was recorded based on the 4 sequential levels. Statistical analysis revealed that WS presented significantly higher fracture resistance than S6 and C6. No significant difference was found among MAT, C2, S2 and S6. Sphere and cylinder with 6 mm were similar, with the lowest values of all groups. MAT presented the least number of catastrophic failures while C2, S2 and WS presented the highest. The type of load application device influences significantly the behavior of the teeth-restoration complex during mechanical fracture resistance test.

Impact of rehabilitation with metal-ceramic restorations on oral health-related quality of life

Dental ceramics present excellent ability to reproduce the natural teeth regarding esthetic and biomechanics. Recently, due to the advancement of ceramic technology, metal-free restorations were developed. However, the traditional metal-ceramic restorations still present the requirements of high strength, long survival in the oral environment and favorable aesthetics. In this context, it is essential to know the specificity of each ceramic system available in order to apply it properly to various clinical situations. This report describes an integrated rehabilitation using metal-ceramic restorations of a patient at 50 years of age, who presented edentulous spaces, and previous unsatisfactory composite and amalgam restorations, and indirect metallic restorations, leading to compromised quality of life in both functional and psychosocial aspects. The impact on quality of life was measured using a generic instrument, OHIP-14, validated for the World Health Organization, which covers both the biological and the psychosocial dimensions. This instrument was applied to the patient before and after treatment. The patient had an overall OHIP-14 score of 28 before the treatment and after treatment the score decreased to 0, showing that dental and oral health conditions are factors that do impact on the quality of life. Rehabilitation has provided functional and aesthetic restorations, harmony of the stomatognathic system and improvement of life quality.

An Evaluation of the Light Output from 22 Contemporary Light Curing Units

This study measured the radiant power (mW), irradiance (mW/cm2) and emission spectra (mW/cm2/nm) of 22 new, or almost new, light curing units (LCUs): - Alt Lux II, BioLux Standard, Bluephase G2, Curing Light XL 3000, Demetron LC, DX Turbo LED 1200, EC450, EC500, Emitter C, Emitter D, KON-LUX, LED 3M ESPE, Led Lux II, Optilight Color, Optilight Max, Optilux 501, Poly Wireless, Radii cal, Radii plus, TL-01, VALO Cordless. These LCUs were either monowave or multiple peak light emitting diode (LED) units or quartz-tungsten-halogen LCUs used in anterior and posterior teeth. The radiant power emitted by the LCUs was measured by a laboratory grade laser power meter. The tip area (cm²) of the LCUs was measured and used to calculate the irradiance from the measured radiant power source. The MARC-Patient Simulator (MARC-PS) with a laboratory grade spectrometer (USB4000, Ocean Optics) was used to measure the irradiance and emission spectrum from each LCU three times at the sensor located on the facial of the maxillary central incisors and then separately at the occlusal of a maxillary second molar. The minimum acceptable irradiance level was set as 500 mW/cm2. Irradiance data was analyzed using two-way ANOVA and the radiant power data was analyzed by one-way ANOVA followed by Tukey test (a=0.05). In general, the irradiance was reduced at the molar tooth for most LCUs. Only the Valo, Bluephase G2 and Radii Plus delivered an irradiance similar to the anterior and posterior sensors greater than 500 mW/cm2. KON-LUX, Altlux II, Biolux Standard, TL-01, Optilux 501, DX Turbo LED 1200 LCUs delivered lower irradiance values than the recommended one used in molar region, KON-LUX and Altlux II LCUs used at the maxillary incisors. Bluephase G2 and Optilight Max delivered the highest radiant power and KON-LUX, Altlux II and Biolux Standard delivered the lowest power. The emission spectrum from the various monowave LED LCUs varied greatly. The multi-peak LCUs delivered similar emission spectra to both sensors.

ENDODONTIC RETREATMENT USING MTA-BASED SEALANTS IN A TOOTH WITH PERFORATION AND PERIAPIAL LESION: A CLINICAL CASE REPORT

Introduction: To report an endodontic retreatment with a root perforation and use of reparative cement and filling sealant based on mineral trioxide aggregate (MTA). Summary: Retreatment in teeth with root perforations can reduce the longevity of the treatment, because it depends on the rapid location and proper sealing, with biocompatible materials that promote tissue repair. A female patient came to the dental office complaining of pain in tooth 36, with an indication of retreatment on it. Radiographically, it presented thickening of the periodontal ligament and periapical lesion in the mesial and distal roots, leading to the diagnosis of chronic apical periodontitis. With the help of an operative microscope, it was possible to find a perforation in the most cervical portion in the furcation region of the mesio-vestibular root canal. To treat this perforation, it was filled with MTA HP Repair, to enable preparation of root canals and subsequent filling with MTA Fillapex, through the Schilder Plus technique and execution of a 12mm relief on distal root for placement of the intra-radicular retainer. Rehabilitation of teeth with root perforations can be performed with MTA-based filling sealants, presenting satisfactory results for repairs in cases of perforations and periapical lesions. Key learning points: Root perforations are accidental unwanted complications that can occur in stages of the endodontic treatment; The prognosis for endodontic perforations depends on the size and location of the defect and how quickly the perforated area was sealed with biocompatible material.

Influence of Hemostatic Solution on Bond Strength and Physicochemical Properties of Resin Cement

The aim of this study was to evaluate the degree of conversion, color stability, chemical composition, and bond strength of a light-cured resin cement contaminated with three different hemostatic solutions. Specimens were prepared for the control (uncontaminated resin cement) and experimental groups (resin cement contaminated with one of the hemostatic solutions) according to the tests. For degree of conversion, DC (n = 5) and color analyses (n = 10), specimens (3 mm in diameter and 2 mm thick) were evaluated by Fourier transform infrared spectroscopy (FTIR) and CIELAB spectrophotometry (L*, a*, b*), respectively. For elemental chemical analysis (n = 1), specimens (2 mm thick and 6 mm in diameter) were evaluated by x-ray energy-dispersive spectroscopy (EDS). The bond strengths of the groups were assessed by the microshear test (n = 20) in a leucite-reinforced glass ceramic substrate, followed by failure mode analysis by scanning electron microscopy (SEM). The mean values, except for the elemental chemical evaluation and failure mode, were evaluated by ANOVA and Tukeys HSD test. The color stability was influenced by storage time (p<0.001) and interaction between contamination and storage time (p<0.001). Hemostop and Viscostat Clear contamination did not affect the DC, however Viscostat increased the DC. Bond strength of the resin cement to ceramic was negatively affected by the contaminants (p<0.001). Contamination by hemostatic agents affected the bond strength, degree of conversion, and color stability of the light-cured resin cement tested.

Influence Of Crosshead Speed On Failure Load And Failure Mode Of Restored Maxillary Premolars.

We analyzed the effect of the crosshead speed of an applied load on failure load and failure mode of restored human premolars. Fifty intact, noncarious human premolars were selected. Class II mesio-occlusodistal preparations were made with a water-cooled high-speed preparation machine, and the teeth were restored with composite resin. The specimens were divided into five groups (n = 10 each) and tested individually in a mechanical testing machine, in which a 6.0-mm-diameter steel cylinder was mounted to vary the crosshead speed: v0.5: 0.5 mm/min; v1: 1.0 mm/min; v2.5: 2.5 mm/min; v5: 5.0 mm/min; and v10: 10.0 mm/min. The cylinder contacted the facial and lingual ridges beyond the margins of the restorations. Peak load to fracture was measured for each specimen (N). The means were calculated and analyzed with one-way analysis of variance followed by Tukeys test (a = 0.05). The mean load at failure values were (N) as follows: v0.5, 769.4 ± 174.8; v1, 645.2 ± 115.7; v5, 614.3 ± 126.0; v2.5, 609.2 ± 208.1; and v10, 432.5 ± 136.9. The fracture modes were recorded on the basis of the degree of the tooth structural and restorative damage: (I) fracture of the restoration involving a small portion of the tooth; (II) fractures involving the coronal portion of the tooth with cohesive failure of the composite resin; (III) oblique tooth and restoration fracture with periodontal involvement; and (IV) vertical root and coronal fracture. Varying crosshead speeds of 0.5-5.0 mm/min did not influence the failure load of restored maxillary premolars; however, increasing the crosshead speed to 10 mm/min decreased the failure load values and the degree of tooth structural damage.