A comparison of bond strengths measured using cantilever bending and micro-tensile methods

Objectives

The purpose of this study was to evaluate the cantilever-bending test as a bond-strength measurement method for enamel/composite adhesion.

Materials and methods

The buccal surface of bovine incisors were flattened and subsequently placed with composite Z250 (3M ESPE) incrementally after either self-etching adhesive (SE) or etch-and-rinse adhesive (SB) was applied. Then, they were cut with a low-speed cutter to obtain stick-shape samples. The samples were divided into four groups (n = 30 each) according to the adhesive and test method: SET, SE-B, SB-T and SB-B, where T denotes the microtensile test and B denotes the cantilever-bending test. The failure mode of each sample was examined under the microscope. Those samples with the fracture surface lying entirely or partially in the adhesive layer were considered to have provided successful measurements. The results from the two test methods were compared.

Results and discussion

The cantilever-bending method produced a comparable success rate of bond strength measurement to that of the microtensile method. The bond strengths of SE and SB from the cantilever-bending test were 58% and 40% higher, respectively, than those measured with the microtensile method. The adhesive SE exhibited almost the same bond strength as SB, irrespective of the test method.

Conclusions

Cantilever bending can be used as an alternative method for bond strength measurement. The ratio of bending to tensile strength is around 1.5.     

Occlusal alterations in unilateral coronal craniosynostosis

There are few studies on maxillomandibular skeletal alterations. Twenty-one patients with unilateral coronal craniosynostosis were analysed and compared with controls. Landmarks analysed were: sella-nasion-point A and B angles, point A-nasion-point B angle, interincisal angle, angle of superior incisor axis on the sella-nasion plane, lower incisor to mandibular plane angle, Frankfort mandibular plane angle, zygomatic-frontal suture (Z), point on the most concave part of pyramidal apophysis of the upper maxilla (Mx), antegonial incisure (AG), upper (UMT) and lower (LMT) molar teeth. Differences were significant for class II dentoskeletal occlusion (p < 0.0001), mandibular hyperdivergence (p < 0.0001), lingualization of superior incisor (p < 0.005), deviation of inferior interincisal contralateral line to the synostosis (p < 0.0001) in the plagiocephalic population. Compared with contralateral counterpoints, Z (p < 0.05), Mx (p < 0.005) and UMT (p < 0.0005) on the affected side were closer to the midline; AG (p < 0.0005) and LMT (p < 0.05) were further from it. On the frontal plane, Z, Mx, UMT, LMT and AG on the affected side were higher. Vertical and transversal contraction of the jaw of the synostotic side and laterodeviation of the mandibular interincisal line of the contralateral synostotic were clear. The altered position of the glenoid cavity, anteriorized in unilateral coronal craniosynostosis, could be the cause of mandibular dentoskeletal asymmetry.     

Global oral health inequalities in incidence and outcomes for oral cancer: causes and solutions

The mouth and oropharynx are among the ten most common sites affected by cancer worldwide, but global incidence varies widely. Five-year survival rates exceed 50% in only the best treatment centers. Causes are predominantly lifestyle-related: Tobacco, areca nut, alcohol, poor diet, viral infections, and pollution are all important etiological factors. Oral cancer is a disease of the poor and dispossessed, and reducing social inequalities requires national policies co-ordinated with wider health and social initiatives - the common risk factor approach: control of the environment; safe water; adequate food; public and professional education about early signs and symptoms; early diagnosis and intervention; evidence-based treatments appropriate to available resources; and thoughtful rehabilitation and palliative care. Reductions in inequalities, both within and between countries, are more likely to accrue from the application of existing knowledge in a whole-of-society approach. Basic research aimed at determining individual predisposition and acquired genetic determinants of carcinogenesis and tumor progression, thus allowing for targeted therapies, should be pursued opportunistically.     

Iatrogenic injury to oral branches of the trigeminal nerve: records of 449 cases

The aims of this study were threefold: (1) to describe iatrogenic lesions to oral branches of the trigeminal nerve, signs and symptoms, and functional status, (2) to report on a simple neurosensory examination method, and (3) to discuss means of prevention of iatrogenic injury. The etiology and functional status of 449 injuries to oral branches collected over 18 years were retrospectively reviewed. A simple scheme of a clinical neurosensory examination was applied to enable a quantified rating of the perception. Injury to the lingual nerve (n = 261) is not only the most prevalent type of lesion, it also seems to be the most devastating type of lesion. Third molar surgery (n = 319) counts for the majority of injuries to the lingual, inferior alveolar, and buccal nerves. Lesions related to the injection of local analgesics was the second most frequent etiology (n = 78), and the lingual nerve was affected more frequently and severely than other oral branches of the trigeminal nerve. The female gender was overrepresented in incidence of injured nerves but no difference was found in the severity of affection between females and males. All grades of loss of neurosensory functions were found, and a range of neurogenic malfunctions was reported. Methodological obstacles in clinical neurosensory examination of trigeminal nerve injury and the magnitude of neurosensory impairment are discussed. Many nerve injuries are avoidable by critical reevaluation of indications, increased awareness of potential hazards, and modified surgical procedures.     

Clinical effects after subgingival polishing with a non-aggressive ultrasonic device in initial therapy

OBJECTIVES: The Vector ultrasonic system provides root debridement supported by different abrasive irrigation fluids. The aim of this study was to investigate the clinical outcome of initial therapy with subgingival low-abrasive debridement. MATERIAL AND METHODS: Twenty patients, who had at least two teeth with pocket depths >5 mm in each quadrant, took part in this prospective randomized clinical study. Patients were treated in a split-mouth design as one test quadrant (1) subgingivally with Vector fluid polish (VU-H) and as three control quadrants, (2) with only supragingival polishing (PO-H), (3) with hand instruments (HI-H) performed by a hygienist and (4) with hand instruments (HI-D) performed by a dentist. At baseline, 3 and 6 months after treatment, pocket depths and attachment levels (ALs) were measured and bleeding on probing (BOP) was recorded. RESULTS: At 6-month evaluation, all groups showed an improvement in clinical parameters. No statistically significant differences in any of the investigated parameters could be observed between the Vector group and the hand scaling groups, or when comparing the results of the two different operators. CONCLUSION: This study demonstrates that Vector treatment with polishing fluid was able to reduce pocket depths and the prevalence of BOP and improve clinical AL in a similar way as scaling with curettes.     

Effects of low power red laser on induced-dental caries in rats

OBJECTIVE: The purpose of this study was to investigate the effects of low power red laser associated with acidulated phosphate fluoride on the development of induced-dental caries in rats. DESIGN: Dental caries were induced in molars of 40 rats divided into five groups: control group (CG), the teeth were not submitted to any treatment; laser group (LG), teeth were irradiated with a low power red laser (LPRL), power of 30 mW and dose of 5 J/cm(2); fluoride group (FG), teeth were treated with topical acidulated phosphate fluoride (APF) 1.23% applied for 4 min; laser+fluoride group (LFG), teeth were irradiated with LPRL followed by APF; fluoride+laser group (FLG), teeth were treated with APF followed by LPRL. The animals were killed after 48 days, and the first and second molars were extracted to analyze the caries lesion area, microhardness, and calcium and phosphorus ratio. RESULTS: There were no statistical differences among FG, LFG, and FLG regarding to caries area and microhardness, although the caries area were smaller in LFG. Ca/P ratio did not show significant differences among all groups. CONCLUSIONS: Although LPRL before APF application appeared to diminish the caries progression, LPRL did not present any additional benefit compared with acidulated phosphate fluoride on the prevention of induced-dental caries in rats.