Effect of Different Silane Coupling Agents on the Bond Strength between Hydrogen Peroxide-Etched Epoxy-Based- Fiber-Reinforced Post and Composite Resin Core.

The aim of the study was to evaluate the effect of various silane coupling agents on the micro-push-out bond strength between a hydrogen peroxide-etched epoxy-based fiber-reinforced post and composite resin core. Seventy-five cross-linked epoxy-based fiber-reinforced posts were etched with 24% hydrogen peroxide for 10 min. Then they were divided into five groups according to various silane coupling agents and bonded to a composite core. A Universal Testing Machine was utilized to evaluate the push-out bond strength. In addition, all groups' modes of failure were assessed. The push-out bond strength data in MPa were analyzed using ANOVA and a Tukey HSD post hoc test to reveal any difference between the groups. Results revealed that the application of a two-bottle silane coupling agent exhibited the highest bond strength, while the application of a one-bottle silane coupling agent demonstrated the lowest bond strength for a hydrogen peroxide-etched fiber post bonded to a composite core material, which was statistically significant (p < 0.05). The strongest association with the highest bond strength was found with the two-bottle silane coupling agent when compared to the one-bottle. The study highlighted that the application of a silane-coupling agent may affect the bond strength between composite and epoxy-based fiber-reinforced posts.

Cephalometrics of Libyan adults.

BACKGROUND: Cephalometric radiography enables a physician to identify specific areas of craniofacial disproportionality and decide on a treatment plan. Cephalometric analysis is a method for localizeing malocclusion with the facial skeleton and soft tissue structures. This study reports the results from the cephalometric analysis of Libyan adults, as a surrogate for the population of North Africa. METHODS: Lateral cephalometric radiographs were taken of 100 non-growing Libyan adults: 74 males and 26 females, aged 17-45 years. All subjects had no previous orthodontic treatment. The mean values and standard deviations of 92 parameters were determined. RESULTS: The hard tissue cephalometric analysis revealed lower variability in the length of vertical distances compared to those extending more horizontally. In adult Libyans, linear and angular midface measurements (hard tissue and soft tissue) exhibit less variability compared to other measurements taken. Libyans exhibit some of the structural deviations from Bolton's means that were previously found in Americans of African descent. Namely, they are characterized by the greater development of the maxillomandibular complex and by the presence of dentoalveolar protrusion, which must be taken into account when treating patients of this ethnic group. CONCLUSION: The current study once again confirmed the need to develop cephalometric norms for different ethnic groups, the Arab population in North Africa in particular.

Substantial in-vitro and emerging clinical evidence supporting immediate dentin sealing.

The application of resin adhesive to freshly cut dentin after teeth preparation, the so-called immediate dentin sealing (IDS) has been suggested as an alternative to the delayed dentin sealing (DDS), a technique in which resin adhesive is applied just before final bonding of indirect restorations. The aim of this review is to demonstrate the evidence of the claimed advantages made by the proponents of IDS technique. The results of this review revealed substantial in-vitro evidence supporting the IDS benefits including improved bond strength, reduced dentin permeability, improved restorations' adaptation, and increased fracture strength of the restorations. Clinical studies have shown that IDS improves survival of ceramic laminate veneers bonded to prepared teeth with increased exposure of dentin. Moreover, it has been shown that IDS reduces post-cementation hypersensitivity in full coverage restorations, which is characterized by exposure of a large number of dentinal tubules. The selection of filled resin adhesive that is capable of producing thick adhesive layer appears to contribute to the success of the technique. Furthermore, careful management of the oxygen inhibition layer before conventional impression making and proper cleaning of the residual temporary cement used with provisional restorations appears to affect the outcome of the restorations.

Pediatric dental emergency management and parental treatment preferences during COVID-19 pandemic as compared to 2019.

Pediatric dental emergency management were temporarily suspended during the COVID-19 pandemic, which worsened urgent dental needs. This retrospective study investigated the management of pediatric emergencies during COVID-19 lockdown and the trends in parental preferences from March to July in 2019 and 2020. Pediatric dental emergencies managed during pandemic was collated, procedures were categorized (emergency, restorative, preventive, elective) and trends in parental treatment preference was compared from March-July 2019/2020. Bivariate analysis was performed using fisher-exact test and statistical significance was set at 5%. Total 1081 children were treated during COVID-19 lockdown, and 1509 procedures were performed, of which 20.8% were emergency, 42% restorative, 24.4% preventive, 12.6% elective. In 2019, 7462 children were treated; and except for emergency (10.6%), other procedures were comparable to 2020. Extractions (267) predominated in 2020 followed by sealants (195); but in 2019, pulectomy (1268), scaling (1251) were predominant. None of the residents who performed aerosol procedures got infected with COVID-19 during the lockdown. Emergency dental needs among pediatric patients were very high during the COVID-19 pandemic in South India, and there was not much change in the trend in parental treatment preference in 2019 and 2020. Further, aerosol procedures did not increase the risk of COVID-19 during the pandemic provided proper universal precautions were followed.

Effect of Fiber Post-Resin Matrix Composition on Bond Strength of Post-Cement Interface.

OBJECTIVE: To evaluate the influence of 3 different post-resin matrix systems cemented with dual-cure resin cement in simulated root canals made of PMMA acrylic sheet. METHODS: 3 types of fiber posts (n = 60) with different resin matrixes divided into 3 groups: group 1 cross-linked FRC Postec Plus post (n = 20), group 2 cross-linked Rely X post (n = 20), and group 3 Interpenetrated IPN Everstick post (n = 20). All posts were cemented using Multilink Automix dual-cure cement. Posts were cemented into acrylic blocks in order to purely test the strength of cement-post interface. After one week storage at 37°C, two sections of 1 mm thickness from middle-third were subjected to micro-push-out test at crosshead speed 0.5 mm/min. RESULTS: The data were analyzed using one-way analysis of variance (ANOVA). The variable fiber post-matrix system was found to significantly affect the push-out bond strength (p < 0.001). Group 2 exhibited that the highest mean push-out bond strength was (5.36 + 2.3 MPa), and group 3 showed the lowest mean push-out (0.41 + 0.4 MPa). There was significant difference among the groups regarding the failure mode as chi-square test revealed (p < 0.001). CONCLUSION: Prefabricated cross-linked posts with epoxy-based matrix demonstrated higher bond strength than prefabricated cross-linked posts with Bis-GMA-based matrix and posts with semi-IPN matrix when luted with dimethacrylate-based dual-cured resin cement.

Effects of ovariectomy on turnover of alveolar bone in the healed extraction socket in rat edentulous mandible.

OBJECTIVE: The number of patients with postmenopausal osteoporosis receiving dental implants because of edentulism is increasing. Since osseointegration around implants requires formation and maintenance of new bone, knowledge of how ovariectomy (OVX) affects turnover of mandibular and maxillary bone is required. In the present study, we investigated the effects of OVX on turnover of alveolar bone in the healed extraction socket of the rat left mandibular incisor. METHODS: The molars and the incisor on left side in 6-month-old Sprague-Dawley female rats (n=38) were extracted and left to heal for 4 months. Animals were then ovariectomized and killed at the time of OVX (baseline) (n=4), 6 weeks (n=10), 6 months (n=12) and 9 months (n=12) post-OVX. Changes in bone mass and bone turnover were assessed using static and dynamic histomorphometric parameters. RESULTS: Bone turnover was increased by ovariectomy (OVX) as reflected by increased static parameters of bone formation and resorption. The changes in dynamic parameters were not statistically significant. Cancellous bone volume/total volume (%) in the post-OVX group decreased more than that in the control group. CONCLUSIONS: Our results suggest that OVX increases the turnover of alveolar bone in the healed extraction socket of rat mandibular incisor, resulting in a decrease of cancellous bone volume with time.

Comparison of the effect of ovariectomy on bone mass in dentate and edentulous mandibles of adult rats.

We investigated the effect of ovariectomy (OVX) on bone changes in the edentulous and dentate mandibles and compared these to changes in tibiae and femorae using dual energy x-ray absorptiometry (DEXA) and histomorphometric measurements. One hundred and fifteen female rats had their molars and the incisor on one side of the mandible extracted at six months of age and allowed to heal for 4 months. At 10 months of age, animals were divided into an experimental group, which underwent bilateral ovariectomy, and a control group of intact animals. Sixteen OVX and sixteen control animals were sacrificed at 6-weeks, and at 6- and 9-months post-OVX. In addition 12 animals were sacrificed at the time of OVX to act as an internal control group. Bone mineral density measurements (BMD) using DEXA and bone volume measurements on undecalcified sections evaluated under backscattered electron microscopy were investigated in the edentulous and dentate mandibles as well as in tibiae and femorae. At 6-weeks post-OVX, there were no significant differences between the edentulous mandibles, dentate mandibles, tibiae and femorae of OVX and control groups. At 6 months post-OVX, BMD and cancellous bone volume were significantly decreased in the edentulous mandibles (-15.9%; -21.8%), proximal tibiae (-15.6%; -38.5%) and proximalfemorae (-9.7%; -39.6%) of OVX group as compared to the control group. At 9 months post-OVX, BMD and cancellous bone volume were further decreased in the edentulous mandibles (-17.2%; -24%), proximal tibiae (-16.1%; -58.9%) and proximal femorae (-10.3%; -49.9%) of the OVX group as compared to the control group. On the other hand, OVX had no effect on the BMD and cancellous bone volume of the dentate mandibles at 6-weeks and at 6- and 9-months post-OVX. These results show that loss of bone mass in the edentulous mandible of OVX animals is similar to that occurring in the tibiae and femorae, while lack of a significant effect of OVX on bone mass in the dentate mandible suggests that functional loading related to biting force prevented bone loss in the dentate mandible.

Quantitative assessment of post-extraction healing and alveolar ridge remodelling of the mandible in female rats.

OBJECTIVE: To quantitatively evaluate the healing and bone changes in the mandible of adult female rats following unilateral extraction of the mandibular molars and the incisor. METHODS: Six-month old female rats had their mandibular molars and the incisor on one side of the mandible extracted. Nine rats were sacrificed at 0, 14, 28, 56 and 112 days post-extraction. Bone mineral density (BMD) as observed by dual energy X-ray absorptiometry (DEXA) and histomorphometric measurements of total bone volume (TBV/TV%) as well as changes in size; height and width on backscattered electron microscopy images of cross-sections of the mandible were evaluated. RESULTS: There was a total increase of 28% in BMD of the body of the mandible and 35.1% increase in TBV/TV% at 112 days post-extraction. A maximal increase of 25% in BMD was observed at 14 days post-extraction. TBV/TV% increased by 9.5% at 14 days post-extraction and further increased by 15.9% (P < 0.001) from 14 to 28 days and by 9.2% (P < 0.001) from 28 to 56 days. A further slight but non-significant increase of 6% (P = 0.108) occurred from 56 to 112 days post-extraction. Regression equations demonstrated that the maximal increase in TBV/TV% and BMD occurred between 0 and 28 days, which subsequently slowed down between 28 and 56 days and further declined between 56 and 112 days post-extraction. Healing was associated with a reduction in cross-sectional area (32.89%), height (21%) and width of the mandible (12.84%). CONCLUSIONS: BMD of the edentulous mandible following extraction of mandibular molars and the incisor on one side of the mandible increases up to 56 days, but that total bone volume increases up to 112 days post-extraction. This indicates that bone volume measurement is more sensitive than BMD measurements in detecting small increase in bone formation at later stages of healing, possibly because of changes in geometry of the edentulous mandible following teeth extraction. The edentulous mandible undergoes a significant reduction in size as a result of reduction in both height and width up to 112 days post-extraction.

Effect of ovariectomy on dexamethasone- and progesterone-dependent osteoprogenitors in vertebral and femoral rat bone cell populations.

We have found previously that the skeleton of adult female rats contains dexamethasone (Dex)- and progesterone (Prog)-dependent osteoprogenitors, and that estrogen treatment in vitro upregulates proliferation and differentiation of the Prog-dependent but not of the Dex-dependent osteoprogenitors (Bone 1997;20:17-25). The purpose of the present study was to determine whether ovariectomy (OVX) would have different effects on these two classes of osteoprogenitors. Six-month-old Sprague-Dawley rats underwent OVX and the lumbar vertebrae and proximal femurs were collected 1.5, 3, and 6 months after OVX. Cells were obtained from outgrowths of explant cultures and grown in alpha-MEM with 10% FBS, 50 microg/ml ascorbic acid, and 5 mM beta-glycerophosphate. Osteoprogenitors were identified by their ability to generate a colony of osteoblastic cells forming bone (bone nodule). We also evaluated the number of colony-forming units-fibroblast (CFU-F) and of alkaline phosphatase (AP)-positive CFU-F. In cell populations obtained from vertebrae of rats ovariectomized for 1.5, 3, and 6 months and their corresponding control rats, both Dex (1-100 nM) and Prog (1-10 microM) dose-dependently stimulated nodule formation. Both Dex- and Prog-induced nodule formation were higher in cell populations from control rats than in those from ovariectomized rats (P < 0.001). Numbers of CFU-F and AP-positive CFU-F were also higher in cell populations from control rats compared with those from ovariectomized rats. Estrogen (10 nM) enhanced Prog-dependent bone nodule formation but decreased Dex-dependent bone nodule formation in populations from both control and ovariectomized rats. In femoral populations, the responses to Dex (10 nM), Prog (3 microM), and estrogen (10 nM) were similar to those of the vertebral populations in both control and ovariectomized rats. Our results demonstrate that ovariectomy in rats results in a dramatic decrease in the number of both Dex- and Prog-dependent osteoprogenitors in cell populations from vertebrae and proximal femurs. In addition, we confirmed our previous observation that estrogen upregulated proliferation and differentiation of Prog-dependent progenitors, but found here that estrogen clearly downregulated proliferation and differentiation of the Dex-dependent progenitors.

Implant prosthodontics in medically challenged patients: the University of Toronto experience.

A series of prospective studies started in the mid-1980s at the University of Toronto have provided evidence of the efficacy and effectiveness of implants in the treatment of the fully and partially edentulous patients. These studies have focused primarily on treatment outcomes at the surgical and prosthodontic levels, with an overall failure rate of 7.7% over a 20-year period. Because a considerable proportion of these failures (4.2%) occurred before insertion of the prosthesis, and because osseointegration is essentially a wound-healing process, factors that interfere with healing, including systemic conditions, may contribute to implant failure. This paper reviews studies on the impact of selected systemic conditions, including osteoporosis, cardiovascular diseases, diabetes mellitus, and hypothyroidism, as well as smoking behaviour, on the success or survival of oral implants in patients treated in the Implant Prosthodontic Unit at the University of Toronto.