Effect of 3 cements on white spot lesion formation after full-coverage rapid maxillary expander: A comparative in-vivo study.

INTRODUCTION: The aim of this study was to assess the effects of 3 luting agents (glass ionomer cement, compomer, and polycarboxylate cement) on white spot lesion formation in patients with full-coverage bonded acrylic splint expanders. White spot lesion formation was assessed with quantitative light-induced fluorescence. METHODS: Full-coverage rapid maxillary expanders were cemented with glass ionomer cement, compomer, and polycarboxylate cement in groups 1, 2, and 3, respectively. A control group comprised patients who never had orthodontic treatment. Quantitative light-induced fluorescence images taken before and after rapid maxillary expansion treatment were analyzed for these parameters: the percentages of fluorescence loss with respect to the fluorescence of sound tooth tissue (ΔF) and maximum loss of fluorescence intensity in the whole lesion; lesion area with ΔF equal to less than a -5% threshold; and the percentage of fluorescence loss with respect to the fluorescence of sound tissue times the area that indicated lesion volume. RESULTS: All 3 groups showed statistically significantly greater demineralization than the control group. The 3 experimental groups differed from each other in half of the parameters calculated. Teeth in the polycarboxylate group developed the most white spot lesions. CONCLUSIONS: With the highest rate of white spot lesion formation, polycarboxylate cements should not be used for full-coverage bonded acrylic splint expanders. Compomers may be preferred over glass ionomer cements, based on the findings of this study.

Amphiphilic Polycarbonates from Carborane-Installed Cyclic Carbonates as Potential Agents for Boron Neutron Capture Therapy.

Carboranes with rich boron content have showed significant applications in the field of boron neutron capture therapy. Biodegradable derivatives of carborane-conjugated polymers with well-defined structure and tunable loading of boron atoms are far less explored. Herein, a new family of amphiphilic carborane-conjugated polycarbonates was synthesized by ring-opening polymerization of a carborane-installed cyclic carbonate monomer. Catalyzed by TBD from a poly(ethylene glycol) macroinitiator, the polymerization proceeded to relatively high conversions (>65%), with low polydispersity in a certain range of molecular weight. The boron content was readily tuned by the feed ratio of the monomer and initiator. The resultant amphiphilic polycarbonates self-assembled in water into spherical nanoparticles of different sizes depending on the hydrophilic-to-hydrophobic ratio. It was demonstrated that larger nanoparticles (PN150) were more easily subjected to protein adsorption and captured by the liver, and smaller nanoparticles (PN50) were more likely to enter cancer cells and accumulate at the tumor site. PN50 with thermal neutron irradiation exhibited the highest therapeutic efficacy in vivo. The new synthetic method utilizing amphiphilic biodegradable boron-enriched polymers is useful for developing more-selective and -effective boron delivery systems for BNCT.

Assessment of alkoxylphenacyl-based polycarbonates as a potential platform for controlled delivery of a model anti-glaucoma drug.

Treatment strategies for glaucoma will benefit from injectable and/or implantable delivery systems that can achieve sustained delivery of neuroprotective agents (to the posterior segment) and/or intraocular pressure lowering drugs (to the anterior segment). In this regard, we have evaluated the suitability of a new polymer (alkoxylphenacyl-based polycarbonates copolymer with polycaprolactone; AP-PCL 20% w/w) as a platform for ocular drug delivery. Brimonidine tartrate (BRT) was applied as a model anti-glaucoma drug. The polymer was applied to develop injectable (nanoparticles) and implantable (microfilms) delivery systems. Nanoparticles fabricated from AP-PCL were stable and have an average size less than 200nm. The AP-PCL microfilms prepared by compression molding showed a gradual hydrolytic in-vitro degradation monitored by water uptake, weight loss, microscopy, DSC and FT-IR measurements. AP-PCL microfilms achieve sustained delivery of BRT for up to 90days. Biocompatibility of AP-PCL-based delivery systems was demonstrated from studies in human trabecular meshwork cell line as well as after intravitreal injections in rats. The overall trend demonstrated that AP-PCL delivery systems may be considered as suitable candidates for prolonged drug delivery in chronic ocular disorders such as glaucoma.

Retrieval analysis of a failed TriboFit polycarbonate urethane acetabular buffer.

The purpose of this research was to determine the failure mechanisms and damage features of a TriboFit acetabular buffer implanted directly against a native, prepared acetabulum which was revised after 11months. Retrieval analyses were carried out via light microscopy, gravimetric wear assessment, and observer scoring of visible damage features on the buffer. The volume of material abraded from the backside of the buffer was estimated via three-dimensional reconstruction using a laser scanner. Scanning electron microscopy was used to confirm damage features and mechanisms. Severe abrasion to the backside of the buffer was the primary damage feature, while stippling damage was seen on the articular surface of the buffer. Material loss due to backside abrasion was approximated to be between 0.13360.085 g (gravimetric analyses) and 0.19360.053 g (three-dimensional reconstruction). Implantation of the TriboFit buffer against the patient's native acetabulum without a metal backing allowed for significant movement of the buffer against the bone, resulting in the abrasion seen on this implant. The stippling damage on the articular surface indicates an adhesive wear mechanism which exacerbates movement of the buffer against the acetabulum, thereby increasing backside abrasion.

A trans-well-based cellular model for the rapid pre-evaluation of tympanic membrane repair materials.

It is important to have a standardized tympanic membrane (TM) perforation platform to evaluate the various myringoplasty materials that have been studied and developed extensively during recent years. However, currently there are no cellular models specifically designed for this purpose, and animal models remain unsatisfactory. The purpose of this study is to propose an inexpensive, readily available, well-controlled, and easy-to-create cellular model as a substitute for use in the evaluation of TM repairing materials. A trans-well model was created using a cell culture insert with a round hole created at the center of the polycarbonate membrane. HaCaT cells were cultured on the fenestrated culture insert, and the desired myringoplasty graft was placed at the center of the window for one week and observed by fluorescent microscopy under vital staining. Under this cellular model, there was notable migration of HaCaT cells onto the positive control graft (rabbit fascia), while only a few cell clusters were observed on the negative control graft (paper). Model validation showed that the cell migration ratio for the PLLA + 1% hyaluronic acid (HA) graft is significantly higher than using myringoplasty paper, poly L-lactide (PLLA), or PLLA + 0.5% HA (p < 0.05). This trans-well-based cellular model might be a useful pre-evaluation platform for the evaluation of TM repairing materials. The model is inexpensive, readily available, easy to create, and standardized for use.

Retentive strength of implant-supported base metal copings over short metal abutments using different luting agents and surface treatments.

PURPOSE: To evaluate the effect of surface treatments on retention of implant-supported restorations over short abutments. MATERIALS AND METHODS: One hundred twenty metal copings were made on Straumann solid abutments (3 mm length). The copings were divided into 2 groups: control and air abraded (50 µm Al2O3). The copings were luted using Fleck's, Poly F, Panavia F, and Fuji Plus. In resin cements groups, 2 subgroups were studied base on the application of Alloy Primer (n = 10). After conditioning in saliva and 5000 thermal cycles, retentive strengths of specimens were measured. Data were analyzed by 1-way ANOVA and Tukey honestly significant difference tests (α = 0.05). RESULTS: Panavia F 2.0 combined with Alloy Primer showed the most retentive values. In control and air abraded groups, there was no significant difference between the studied luting agents. Alloy Primer significantly increased the retention of copings luted with Panavia F 2.0. CONCLUSION: Within the limitations of this study, the retentive strength of metal copings over short implant abutments was not improved by airborne-particle abrasion. However, Alloy primer enhanced the retention of metal copings that were luted using Panavia F 2.0.

Sealing properties of three luting agents used for complete cast crowns: a bacterial leakage study.

OBJECTIVE: To assess the sealing properties of three different luting materials used for cementation of full cast crowns on extracted human premolars. METHODS: Thirty noncarious human premolars were prepared in a standardized fashion for full cast crown restorations. All margins were placed in dentin. After impressions of the preparations, stone dies were fabricated on which copings were waxed, which were cast in type III alloy using standardized laboratory methods. Teeth were randomly assigned to three groups of 10 samples each (n=10), for which the following cements were used: 1) a resin-modified glass ionomer cement, Rely X Luting Plus (3M ESPE, St Paul, MN, USA); 2) a self-adhesive resin cement, Maxcem Elite (Kerr Corporation, Orange, CA, USA); and 3) a glass ionomer cement, Ketac Cem (3M ESPE), the latter used as control. After cementation the samples were allowed to bench-set for 10 minutes, stored in water at 37°C, subjected to thermal cycling (2000×, between 5°C and 55°C, dwell time 35 seconds), and then stored in sterile phosphate buffer for seven days at 37°C. Subsequently, the occlusal surface was carefully reduced until the dentin was exposed. Finishing on wet sand paper removed the gold flash caused by grinding. After sterilization, the specimens were subjected to bacterial microleakage in a dual chamber apparatus for 60 days. Bacterial leakage was checked daily. Data were analyzed using the Kaplan-Meier survival test. Significant pairwise differences were analyzed using the log-rank test followed by Fisher exact test at a p<0.05 level of significance. RESULTS: Rely X Luting Plus showed the lowest microleakage scores, which statistically differed significantly from Maxcem Elite and Ketac Cem (p<0.05). CONCLUSIONS: Rely X Luting Plus cement displayed significantly lower microleakage scores than a self-adhesive resin-based and conventional glass ionomer cement.

Effect of buttonhole cannulation with a polycarbonate PEG on in-center hemodialysis fistula outcomes: a randomized controlled trial.

BACKGROUND: Quality improvement strategies to increase and maintain the numbers of arteriovenous fistulas (AVFs) are a critical drive in enhancing the quality of care of patients receiving treatment with hemodialysis. How the AVF is needled is an important consideration in AVF survival; the ideal cannulation technique has not been established to date. STUDY DESIGN: Prospective randomized single-center trial. SETTING & PARTICIPANTS: Patients on maintenance hemodialysis therapy (N = 140). INTERVENTION: A 1-year intervention of buttonhole (constant site) or usual-practice (different site) cannulation. OUTCOMES: Primary study outcome was AVF survival over 1 year, in which AVF failure was defined as an AVF no longer used for hemodialysis (also referred to as assisted patency). Secondary outcomes included primary patency, number of access interventions, bleeding time, infection rate, cannulation time and pain, and aneurysm formation. RESULTS: Demographic data were similar for both groups. The primary outcome measure of AVF survival at 1 year was statistically significantly increased in the buttonhole group (100% vs 86% with usual practice; P = 0.005, log-rank test). In the buttonhole group, there were fewer interventions (19% vs 39% in usual practice) and less existing aneurysm enlargement (23% vs 67% in usual practice). There were no bacteremia events in the buttonhole group and 2 in the usual-practice group (0.09/1,000 AVF days). There were no significant differences in bleeding times and lignocaine use between the 2 groups. LIMITATIONS: A single-center study, lack of blinding. CONCLUSIONS: In this study, AVF survival was significantly greater when using buttonhole cannulation. The buttonhole technique significantly decreased the need for access interventions and reduced existing aneurysm enlargement. Concerns of increased infection rates or prolonged bleeding times with the buttonhole technique were not seen in this study. The buttonhole technique should be considered the cannulation technique of choice for AVFs.

A prospective clinical study of polycarboxylate cement in periapical surgery

Objective: To evaluate the clinical efficacy of polycarboxylate cement as retrograde filling material. Design: A prospective clinical study was made of 25 patients subjected to periapical surgery with ultrasound and magnifying loupes, in which polycarboxylate cement was used as retrograde filling material. Measurements were made of the area and diameter of the lesions pre- and postoperatively, and 6 and 12 months after the operation. The apical resection and retrograde filling areas were also measured, and the prognosis following surgery was recorded. Results: A total of 23 patients with 31 apicoectomized teeth were studied (2 patients being lost to follow-up). The mean area of the periapical lesions before surgery was 52.25 mm2, with a mean major diameter of 6.1 mm and a mean lesser diameter of 4.8 mm. The success rate after 12 months was 54.7%, according to the criteria of VonArx and Kurt. The prognosis was poorer in females, in larger lesions, and in cases with larger retrograde fillingareas. Conclusions: Polycarboxylate cement offers good results, with important bone regeneration after periapical surgery (AU)

Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and FRC posts.

The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically treated bovine incisors restored with fiber-reinforced-composite (FRC) posts and crowns. Forty-eight endodontically treated incisors were restored with FRC posts, composite build-ups, and cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermal cycling with 10,000 cycles at 5-55°C and mechanical aging, loading the specimens in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45°. The loading test showed that cementation mode and fatigue testing had an influence on the load bearing capability. Before fatigue testing no statistically significant differences between the different cementation modes could be detected. After fatigue testing, conventionally cemented FRC posts lead to statistically significant higher fracture loads compared to adhesively luted posts. Most specimens fractured in a favourable way, independent from the type of cementation.

Comparison of electrosurgical pulpotomy with zinc oxide eugenol or zinc polycarboxylate cements sub-base.

PURPOSE: The aim of this study was to compare the clinical and radiographic success rates of electrosurgical pulpotomy of human primary molars with zinc oxide eugenol (ZOE) and zinc polycarboxylate (ZPC) cements. METHODS: In this randomized clinical trial study, 120 primary second molar teeth were treated by electrosurgical pulpotomy. Teeth were randomly assigned to two groups according to whether ZOE or ZPC cement was used as a sub-base. Teeth were restored with stainless steel crowns and were evaluated clinically and radiographically after 3, 6, and 12 months by two independent examiners. Clinical treatment outcomes and radiographic findings were statistically analyzed using Fishers' exact test with statistically significant differences defined for P < 0.05. RESULTS: At 12 months, the clinical and radiographic success rates in the ZOE group were 98.2% and 84.2% and in the ZPC group were 96.2% and 75%, respectively (P > 0.05 for all). CONCLUSIONS: The outcomes of this study suggested that either ZPC or ZOE sub-base have similar clinical and radiographic success in electrosurgical pulpotomy.

Tyrosine-derived polycarbonate membrane in treating mandibular bone defects. An experimental study.

This study was designed to evaluate the suitability of a novel bioabsorbable material in treating bone defects. A poly(desaminotyrosyl-tyrosine-ethyl ester carbonate) (PDTE carbonate) membrane (thickness 0.2-0.3 mm) was implanted into the mandibular angle of 20 New Zealand White rabbits to cover a through-and-through defect (12 x 6 mm). In group 1, the defects were left unfilled but covered with membrane and in group 2 the defects were filled with bioactive glass mesh and covered with membrane, too. Controls were left uncovered and unfilled. The animals were followed for 6, 12, 24 and 52 weeks, respectively. The material was evaluated by qualitative analysis of histological reactions and newly formed bone. We found that PDTE carbonate elicited a modest foreign body reaction in the tissues, which was uniform throughout the study. New bone formation was seen in all samples after six weeks. Group 1 had more new bone formation until 24 weeks and after this the difference settled. Based on findings of this study it was concluded that PDTE carbonate membranes have good biocompatibility and are sufficient to enhance bone growth without additional supportive matrix.

[Clinical results of potassium nitrate use in polycarboxylate cement for biological treatment of reversible pulpitis].

To determine effectiveness of indirect pulp capping with 5% potassium nitrate in polycarboxylate cement for biological treatment of reversible pulpitis, a clinical study of 232 teeth with active caries lesions from 205 healthy patients aged from 16 to 40 years was performed. They were divided into 2 groups: the study group--140 teeth of 127 persons with 5% potassium nitrate in polycarboxylate cement (Carboxy Adhesor); control group--92 teeth of 78 persons with calcium-hydroxide cement (Dycal). Short-term clinical results showed better desensitizing effect and faster recovery to normal values of electric vitality in teeth treated by potassium nitrate in comparison with Dycal lining (p<0.001). Long-term follow-up (up to 2 years) showed good functional conditions, preserved vitality and x-ray status of the treated teeth.

The influence of orifice sealing with various filling materials on coronal leakage.

The aim of this study was to evaluate the sealing ability of materials filled in the orifice after root canal treatment. A total of 100 root canal-treated teeth were divided into six experimental groups: 1, Protect Liner F (PL); 2, Panavia F (PF); 3, DC core-Light cured (DCL); 4, DC core-Chemically cured (DCC); 5, Super-EBA (SE); 6, Ketac (KC). The materials were filled--to a depth of 4 mm--in the coronal part of the root canals, and evaluated for microleakage. The number of teeth that failed to stop dye penetration in the filled materials differed statistically between PL and DCL or SE or KC, PF and SE or KC, DCC and KC, DCL and KC. The mean distance of dye penetration differed significantly between PL and SE or DCC, PF and SE or DCC. Hence, these results indicated the advantageous sealing ability of adhesive and flowable materials.

Early clinical results from the use of 5% potassium nitrate in polycarboxylate cement for biological treatment of reversible pulpitis.

UNLABELLED: The aim of the present study was to obtain immediate and early clinical results from the use of 5% potassium nitrate (KNO3) in polycarboxylate cement for biological treatment of reversible pulpitis. MATERIAL AND METHODS: The method was applied in 140 teeth, mostly premolars and molars, with a clinical diagnosis of reversible pulpitis and indications for biological treatment of the inflamed dental pulp by means of indirect pulp capping. All teeth had clinically healthy periodontium and no non-carious lesions of the hard dental tissues. The study sample consisted of 127 patients aged between 16 and 40 years. The control group included 92 teeth in 78 patients, which were treated by a calcium hydroxide liner. The follow-up examinations were conducted 24 hours after treatment and on day 3 for the immediate results, and on days 7, 14, 30, and 90 for the early clinical results assessing the functional condition of the teeth, presence of thermal stimulus-induced pain and the measurements from the electric pulp vitality tests. The results were analysed with the analysis of variance and graphic analysis. RESULTS: The immediate and early clinical results of the biological treatment of reversible pulpitis with 5% KNO3 in polycarboxylate cement show that pain as a symptom of the initial inflammatory process in the dental pulp is rapidly and effectively relieved, leaving the treated teeth in good functional condition. The comparison of the measurements from the electric pulp tests of all teeth reveals a statistically significant difference (u = 8.51; P < 0.001) in favour of the group treated with potassium nitrate and polycarboxylate cement. CONCLUSIONS: 1. The immediate and early clinical results of our study suggest that treating reversible pulpitis with 5% KNO3 in polycarboxylate cement has an a very good analgesic action 2. The normal electrical excitability of the treated teeth is restored faster than that in the teeth treated by calcium hydroxide-based materials (P < 0.001).

A new condensable composite for the restoration of posterior teeth.

Undoubtedly the greatest resistance of clinicians to use composite resins in posterior teeth relates to technique sensitivity, time consumption, and complexity. Placing conventional posterior composite resins does not take into account that composites differ considerably from amalgam. This is particularly true with respect to its physical characteristics, especially insertion and packing properties. The development of a posterior composite resin that can be placed by an amalgam carrier and subsequently packed or condensed as an amalgam, should assist clinicians greatly in their ability to successfully restore class II cavity preparations. Acknowledgment is expressed to Bruce Small, DMD, for the clinical dentistry and slides.

Bactericidal eradication from carious lesions of prepared abutments by an antibacterial temporary cement.

PURPOSE: The aim of this study was to observe the antibacterial potential of polycarboxylate temporary cement containing a mixture of metronidazole, ciprofloxacin, and cefaclor on carious lesions of prepared abutments that were designed to leave caries on the abutments. MATERIAL AND METHODS: Antibacterial efficacy was estimated in vitro and in vivo by measuring bacterial recovery from the lesions. Bacteria counts ranged from 10(4) to 10(7) both in vitro (nine samples) and in vivo (five samples) in time-zero samples, just before the application of the antibacterial cement. RESULTS: No bacteria were recovered from carious lesions in vitro (six samples) or in vivo (four samples) after the lesions were covered by the antibacterial temporary cement. For the remaining samples, some bacteria (5 to 80 counts per sample) were recovered, with one notable exception in which marginal leakage provided a bacteria count of 10(3). Bacteria counts ranging from 10(3) to 10(5) occurred in carious lesions covered by temporary cement without antibacterial agents, which indicated that temporary cement alone was not a potent disinfectant. CONCLUSIONS: The results of this study indicated that the antibacterial temporary cement can be useful for eradicating bacteria from carious lesions of prepared abutments.