File Breakage in Conventional Versus Contracted Endodontic Cavities.

OBJECTIVE: To compare rotations to failure and tip separation length of a nickel-titanium (Ni-Ti) rotary in- strument within a simulated mesio-buccal canal of a mandibular molar with a conventional or contracted endodontic cavity. METHODS: Two identical lithium disilicate #30 crowns were milled. A conventional or contracted endodontic cavity was prepared. A custom glass tube was fabricated with taper and length replicating a mesio-buccal canal, including buccal and lingual curvature, and placed at the mesio-buccal orifice of each crown, held in a silicone mold. Instrumentation was simulated using 30/.04 Ni-Ti rotary files following manufacturer recommended 1.8 Nm torque and 500 RPM (n=20 per access type). Instrumentation was video recorded to determine time (sec- onds) and rotations to failure. The length of broken tips was measured. The experimental data were compared using a t-test (significance level 0.05). Stresses in the instruments were examined using finite element analysis. RESULTS: Number of rotations to failure (mean±standard deviation) was 599±126 for conventional and 465±65 and for contracted access; tip separation lengths (mean±standard deviation) were 3.99±0.29 for conventional and 4.90±1.02 mm for contracted access. Number of rotations to failure and tip separation lengths were signifi- cantly different between the two access openings (p<0.001). Finite element analysis confirmed higher file curva- ture and accompanying higher stress levels with contracted access and the maximum stress further from the tip. CONCLUSION: Within the limitations of this study, the contracted access caused earlier failure of the Ni-Ti in- strument with longer tip separation lengths than the conventional access due to higher stresses towards the middle section of the instrument. (EEJ-2022-11-143).

A quantitative and visual examination of sealed restorative specimens following exposure to artificial aging.

Low-viscosity polymer resins, or surface sealants (SSs), have been utilized as a means of finalizing the polishing step following the placement of composite resin restorations. The aim of this study was to measure the surface roughness (Ra) of composite resins treated with different SSs before and after exposure to an accelerated artificial aging protocol. The study included 5 experimental groups of composite resin discs (TPH Spectra ST) treated with different SSs (PermaSeal, Embrace WetBond Seal-n-Shine, OptiGuard, BisCover LV, and DuraFinish) and a control group consisting of untreated discs (n = 6 per group). The discs were prepared by inserting composite resin in 10 × 1-mm rings, covering the ring and material with a transparent strip, compressing the assembly between glass slides, and polymerizing through the slides on each side for 40 seconds with an LED curing light. Each disc except for the control specimens received a coating of the selected SS followed by application of a transparent matrix strip and then light polymerization for 20 seconds using an LED light source. Surface roughness measurements were obtained with a digital contact profilometer at baseline (immediately after polymerization) and following exposure to a thermocycling regimen to simulate aging. The data were analyzed using 2-way analysis of variance and post hoc Student-Newman-Keuls test with significance set at P < 0.05. There were no statistically significant differences among the groups at baseline. There were no statistically significant differences between the baseline and post-thermocycling Ra measurements except among the DuraFinish specimens, which were significantly rougher than all other groups after accelerated artificial aging. The use of SSs for the initial insertion and possibly for the long-term maintenance of composite resins could be minimally beneficial for restoration maintenance if a transparent covering medium is utilized during polymerization. However, due to the effects caused by formation of an oxygen-inhibited layer of unpolymerized monomers if a covering medium is not used, the results suggest the benefits do not offset the costs considering both gloss and Ra surface-testing parameters.

The effect of artificial ultraviolet light on the gloss of composite resin surface sealants.

This study evaluated how exposure to ultraviolet (UV) light affected the gloss of composite resins following application of resin-based surface sealants (SSs). Thirty composite resin discs were fabricated using cylindrical molds and randomly assigned to 1 of 5 SS groups (n = 6 each). Both sides of each disc received a polyester film clear matrix surface finish, and then rotary finishing and polishing procedures were performed on 1 side only. Six baseline measurements for each disc surface were performed using a 60-degree-angle gloss meter. The finished and polished side then received an SS application and was polymerized with an LED light through a polyester film matrix. Gloss measurements were then obtained. All specimens were then exposed to an artificial UV light source for a total of 382 hours, after which final gloss measurements were made. A 2-way repeated-measures analysis of variance and Student-Newman-Keuls pairwise multiple comparison tests revealed statistically significant differences between the SS materials and surface treatments (P < 0.05). No statistically significant (P > 0.05) differences were found between the surfaces that were mechanically finished and polished and those that only received a polyester film finish. However, all specimens exhibited significantly (P < 0.0001) higher gloss readings after SS application. Following UV exposure, all SS specimens exhibited significantly (P < 0.0001) lower gloss readings. The study results suggest that application of SSs to composite resin discs increases the gloss on a short-term basis; however, long-term exposure of SSs to an artificial UV light source might have a negative effect on the surface properties. Thus, dentists need to periodically evaluate composite resin restorations.

Microscopic evaluation of luting techniques for a fiber-reinforced post system.

This study assessed application techniques for cementation of fiber-reinforced posts (FRPs). The treatment groups were defined by FRP luting application techniques and included 5 groups of 10 simulated teeth each: 1, application of the cement on the post using a syringe; 2, application of the cement in the canal using a syringe; 3, application of the cement in the canal and on the post using a syringe; 4, application of the cement in the canal using a syringe/Lentulo spiral instrument; and 5, application of the cement in the canal using a syringe/Lentulo spiral and on the post using a syringe. A dual-curing, automixing cement was utilized as the luting agent. For each group, the canals were endodontically prepared using tapered hand and rotary files and obturated, and then the FRPs were cemented in place. All specimens were encased in acrylic and sectioned at 2 locations, creating 4 viewing surfaces: coronal (C), middle coronal (MC), middle apical (MA), and apical (A). The surfaces were examined using a stereomicroscope and digitized computer software. The efficacy of each FRP application technique was determined in terms of percentages of cement void area by group and by surface. Group 1 exhibited a significantly (P < 0.05) greater overall percentage of cement void area than all other groups. Group 2 exhibited the smallest overall percentage of void area, although the difference was not always statistically significant. There were no statistically significant differences among the surfaces in cement void area (P > 0.05) when the areas of the different groups were combined. The most efficacious cementation method was the injection of cement into the canal space with a syringe, while the use of a Lentulo spiral instrument was found to be an unnecessary step.

Evaluation of the marginal integrity of a bioactive restorative material.

This in vitro study evaluated the marginal microleakage of a bioactive restorative with other restorative materials in standard Class V preparations. Sixty previously extracted, noncarious human molars were randomly assigned to 3 experimental groups (n = 20): a bioactive composite resin, a universal hybrid composite resin, and a resin-modified glass ionomer restorative. Class V cavities were prepared on the facial or lingual surface of each tooth so that coronal margins were located in enamel and apical margins in cementum (dentin). After the cavity preparations were restored with the appropriate material, the specimens were artificially aged in water baths. The root apices were sealed with utility wax, the tooth surfaces were coated with nail varnish to within 1 mm of the restoration, and specimens were immersed in 1% methylene dye solution for 8 hours. The teeth were invested in clear polymer resin, sectioned longitudinally, and examined under a stereomicroscope to assess dye penetration. Nonparametric scores indicated that microleakage was significantly greater at the apical margins than the coronal margins for all groups (P > 0.0001). The specimens restored with the bioactive material exhibited greater microleakage at both the coronal and apical margins than did specimens restored with the composite resin or resin-modified glass ionomer material, although the differences were not statistically significant (P > 0.05). Based on the results of the present study, the type of restorative material did not appear to have a significant influence on microleakage. Rather, the marginal position (coronal versus apical) of the restoration was the determining factor in microleakage.

Methacrylate Resin Adhesion in Root Canals Conditioned with Phosphoric Acid and Ethylenediaminetetraacetic Acid.

OBJECTIVE: The purpose of this study was to determine the ability of a methacrylate resin dentin bonding agent to adhere to the dentin surfaces of prepared and conditioned root canals with either 32% phosphoric acid (PA) or 17% ethylenediaminetetraacetic acid (EDTA). METHODS: Prior to the application of the methacrylate resin, the root canals of 54 intact, caries-free, single- rooted, de-crowned, extracted human maxillary incisor and canine teeth were endodontically prepared and conditioned with either 32% PA or 17% EDTA or with distilled water as the unconditioned control. The resin-treated roots were cross-sectioned at three levels and scanning electron microscope (SEM) imaged for circumferential views of the root canals at 60-90× magnification and site-specific views at 250× magnification, and then randomly coded for independent and blind evaluation by four calibrated examiners. The circumferential surface of the root canals that showed no resin adhesion were digitally measured and subtracted from the digitally measured total root canal circumference, and resin adhesion was expressed as a percentage of the circumference. RESULTS: The mean percentages of resin adhesion were 97% for the PA group, 94% for the EDTA group, and 76% for the control group. There were statistically significant differences among the PA, EDTA, and control groups. CONCLUSION: Root canals conditioned with 32% PA or 17% EDTA had more resin adhesion than unconditioned root canals. Root canals conditioned with 32% PA had more resin adhesion than those conditioned with 17% EDTA.

An evidence-based review of dental matrix systems.

The restoration of proximal surface cavities, originating from Class II carious lesions, to "normal" anatomical specifications is a fundamental objective for the dental practitioner. Cognitive interpretation of tooth morphology attained from evidence-based resources, together with the necessary psychomotor skills for correct design and completion, are considered essential strategies for restoration success. Also, the visualization of the original tooth structure, if present, should substantially benefit the dentist in the creation of a clinically satisfactory restoration. The purpose of this evidence-based review is to define the cause and effect of decisions based on optimum treatment standards of care for the patient. The concepts of form and function, as related to the oral environment, and the consequences of unsatisfactory dental restorative care will be scrutinized. This article will identify and explain the different challenges and solutions for restoration of dental proximal lesions and provide an overview of past, present, and future procedures.

Effect of occlusal calculus utilized as a potential "biological sealant" in special needs patients with gastric feeding tubes: a qualitative in vitro contrast to pit and fissure sealant restorations.

The aim of this case report and in vitro investigation was to evaluate the marginal microleakage of intact occlusal calculus of primary molars extracted from a special needs patient who received nutrition via a gastric feeding tube. An adolescent with a history of developmental disturbance presented for routine dental care in a hospital facility. Prophylaxis was performed, and 2 mandibular permanent molars were restored. Five primary molars were extracted due to mobility and delayed retention. Heavy deposits of intact calculus were present on the occlusal surfaces of the primary teeth. The extracted teeth were immersed in methylene blue dye solution, invested in acrylic resin, sectioned into blocks, and photographed at 20× and 40× magnification. Previously photographed calculus-free molars with pit and fissure sealants were reviewed and served as contrasting "restorations." The occlusal calculus on the primary teeth extracted from the patient absorbed the dye, while the comparison teeth containing pit and fissure sealants exhibited varying degrees of marginal dye penetration (microleakage). No marginal microleakage was noted in the calculus specimens, indicating that this substrate may serve as a "natural" occlusal surface sealant and that its removal from occlusal surfaces during routine oral prophylaxis may be unnecessary.

Provisional Replacement of Anterior Teeth: A Review of Clinical Techniques and Case Report in a Dental School Training Experience.

Upon the premature loss of permanent anterior teeth from unanticipated trauma or by ongoing patient neglect requiring surgery, patient requisites of functional and esthetic considerations must be addressed. Interim management can be achieved through the use of several diverse fixed and/or removable treatment modalities. The purposes of this report are to provide a review of traditional and unconventional techniques for interim replacement of missing anterior teeth and to present a clinical report demonstrating the fabrication of a removable, thermoplastic (vacuum-formed) EssixTM prosthesis, utilizing composite resin as the surrogate material of choice for the absent teeth. This measure proved to be an immediate, esthetic, and transitional treatment solution prior to a permanent resolution for the patient's long-term dental requirements.

Determination and Correlation of Depth of Cure of a New Composite Resin Delivery System.

OBJECTIVES: To quantify the depth of cure (DOC) of a composite resin system using two different testing criteria. METHOD AND MATERIALS: The DOC testing employed two different experimental protocol: 1) Forty-eight previously extracted human molars were randomly assigned to four groups of twelve each (n = 12): Group 1 SonicFill composite resin system, shade A1; Group 2 SonicFill, shade A3; Group 3 Herculite Ultra composite resin, shade A1; Group 4 Herculite Ultra, shade A3. Cylindrical cavities (4.0 mm diameter and 10 mm depth) were prepared at the tooth CEJ, in a mesiodistal direction. The preparations were filled with each composite resin material in one bulk increment and polymerized with a LED light for 20 seconds. After 5 minutes, the occlusal surfaces of the teeth (specimens) were ground flat until the composite was exposed in a transverse plane. The uncured (soft) composite was scraped away, using a "modified" ISO 4049 DOC specification, and the remaining cured (hard) material was measured. Three measurements, at different positions of the specimen, were performed, for a total of thirty-six measurements per specimen group. The measurements were averaged and divided by fifty percent, arriving at the final DOC for each specimen. 2) A DOC testing protocol was performed using a two-piece (4.0 mm x 10.0 mm) custom-made Teflon device (mold). The groupings duplicated the previous experimental protocol. The mold was filled with each composite resin material in one bulk increment to a 10 mm length (depth). Excess composite material was removed, followed by placement of a Mylar strip over the external orifice. The composite resin specimen was light-polymerized for 20 seconds. Again, the uncured (soft) composite was scraped away, with the same measurement protocol followed as in method 1. Statistical analyses were conducted using ANOVA tests at a p < .05 level of significance. RESULTS: Statistical differences were exhibited between the two different DOC methodologies, extracted teeth versus the Teflon device. Considering each method, the SonicFilTM composite revealed significantly greater DOC compared to the Herculite Ultra composite resin. Also, significant differences were displayed between the Al compared to the A3 shades, with the A1 (lighter) shades exhibiting greater DOC. CONCLUSION: The prepped teeth seemed a more realistic DOC testing approach due to the variables of light interaction of the composite resin to either tooth substance (enamel/dentin) versus using the Tefion mold, although greater DOCs were recorded using the manufactured device. The SonicFill composite system did reveal greater DOC compared to the Herculite Ultra composite regardless of experimental method or material shade.

Fracture resistance of permanent anterior incisors using fiber-reinforced composite posts.

This in vitro study investigated whether permanent anterior incisors that are endodontically treated with cemented fiber-reinforced composite (FRC) posts without additional canal preparation can potentially increase the resistance to fracture and thus reduce the rate of clinical failure in root canals. Extracted human permanent maxillary central incisors (n = 120) were randomly assigned to 2 experimental groups (n = 60): thermocycled (Group 1) and non-thermocycled (Group 2). These 2 groups were then further divided into 3 subgroups (n = 20). Subgroup 1.1 specimens had root canals prepared and obturated with FRC posts placed. Subgroup 1.2 specimens were prepared and obturated, but did not receive posts. Subgroup 1.3 specimens did not receive root canal preparation, and served as a control. The same processes were repeated for Subgroups 2.1, 2.2, and 2.3, respectively. Significant differences were found between the thermocycled and the non-thermocycled subgroups. Subgroup comparison within the thermocycled group (Group 1) showed significantly higher fracture resistance values for the teeth with post cementation (P < .0001).