Numerical analysis of the biomechanical behaviour of a weakened root after adhesive reconstruction and post-core rehabilitation

Objectives

The purpose of this study was to perform a finite element analysis to determine whether adhesive reconstruction is able to restore the original biomechanical behaviour of weakened roots, in terms of fracture resistance, when compared with post/crown-restored teeth with intact roots.

Methods

A three-dimensional model of a maxillary central incisor was created. The model simulated an endodontically treated tooth restored with a glass-fibre post, a composite-resin core and a metal crown (Model 1). Based on Model 1, a new volume was created in the root cervical third that represented the area where the dentine structure was lost, resulting in a structurally damaged root (Model 2). A 100 N load was applied to the palatal surface at 130° from the long axis of the tooth. After processing (Ansys^® 10.0 – Canonsburg, PA, USA), the principal normal stress data were analyzed (S1, tensile; S3, compressive).

Results

The models demonstrated a similar S1 distribution concentrated in the lingual cervical region but different S1 levels (Model 1: 28.7 MPa; Model 2: 35.3 MPa). The S3 distribution indicated differences in behaviour between the models (Model 1: −18 to −27 MPa along the buccal root surface; Model 2: −25 to −32 MPa on the post buccal surface and along the buccal root wall).

Conclusions

Although the stress distribution within the root walls remained below the ultimate stress limit of the root dentine, the adhesive reconstruction of the weakened roots did not recover the load resistance of structurally intact roots.

Clinical significance

The decision of when to prosthetically rehabilitate weakened roots with cervical dentine structural tissue loss is a challenge for clinicians. A ‘monoblock’ adhesive reconstruction has been proposed for root reinforcement. During treatment planning, the possibility of restoring the mechanical resistance of the root must be evaluated if successful long-term results are to be achieved.     

The influence of tongue strength on children's performance in computer games reliant on lingual force generation

Oral motor exercises, for recovering tongue strength, can be integrated with computer games to increase motivation, especially for treatments in children. The aim of this study was to investigate the influence of tongue strength on motor performance in computer games reliant on lingual force generation. An observational study was carried out at a speech-language pathology outpatient university clinic. Twenty participants (10 with normal tongue strength and 10 with reduced tongue strength) aged 8-13 years used an intra-oral joystick controlled by the tongue to play six computer games during which they had to reach targets that appeared on the screen. Motor performance was measured by the number of attempts to score and the time during which the target force was maintained. Tongue motor performance was compared between groups and across directions of tongue movement, resistance force levels, order of target appearance, continuous force application time on the target, age and sex. Children with normal tongue strength had a lower number of attempts to score (P = .014) and maintained the target force for longer periods (P = .002) than those with reduced tongue strength. The performance was better for both groups (a) in the downward direction compared with the performance in other directions, (b) in games with the lowest resistive force level (0.5 N) compared to those with other levels of resistive force and (c) in the second and third rounds compared with the first round. There were no gender-related differences in performance. Older participants performed better than younger participants. Tongue strength, direction of movement, force to reach the target, time of continuous force application, order of target appearance and age influenced tongue motor performance.     

Regulatory T cell phenotype and function 4 years after GAD–alum treatment in children with type 1 diabetes

Glutamic acid decarboxylase (GAD)₆₅ formulated with aluminium hydroxide (GAD‐alum) was effective in preserving insulin secretion in a Phase II clinical trial in children and adolescents with recent‐onset type 1 diabetes. In addition, GAD‐alum treated patients increased CD4⁺CD25^hi forkhead box protein 3⁺ (FoxP3⁺) cell numbers in response to in‐vitro GAD₆₅ stimulation. We have carried out a 4‐year follow‐up study of 59 of the original 70 patients to investigate long‐term effects on the frequency and function of regulatory T cells after GAD‐alum treatment. Peripheral blood mononuclear cells were stimulated in vitro with GAD₆₅ for 7 days and expression of regulatory T cell markers was measured by flow cytometry. Regulatory T cells (CD4⁺CD25^hiCD127^lo) and effector T cells (CD4⁺CD25^–CD127⁺) were further sorted, expanded and used in suppression assays to assess regulatory T cell function after GAD‐alum treatment. GAD‐alum‐treated patients displayed higher frequencies of in‐vitro GAD₆₅‐induced CD4⁺CD25⁺CD127⁺ as well as CD4⁺CD25^hiCD127^lo and CD4⁺FoxP3⁺ cells compared to placebo. Moreover, GAD₆₅ stimulation induced a population of CD4^hi cells consisting mainly of CD25⁺CD127⁺, which was specific of GAD‐alum‐treated patients (16 of 25 versus one of 25 in placebo). Assessment of suppressive function in expanded regulatory T cells revealed no difference between GAD‐alum‐ and placebo‐treated individuals. Regulatory T cell frequency did not correlate with C‐peptide secretion throughout the study. In conclusion, GAD‐alum treatment induced both GAD₆₅‐reactive CD25⁺CD127⁺ and CD25^hiCD127^lo cells, but no difference in regulatory T cell function 4 years after GAD‐alum treatment.     

Effects of sub-chronic combined treatment with pergolide and caffeine on contralateral rotational behavior in unilateral 6-hydroxydopamine-denervated rats

We studied the synergistic effects of pergolide and bromocriptine with caffeine on turning behavior in 6-OHDA denervated rats. Both pergolide and bromocriptine were synergistic with caffeine, and prevented tolerance to caffeine-induced turning. When caffeine was removed, tolerance to bromocriptine effects was observed for 1 day only, while no tolerance was observed to pergolide. These results suggest that caffeine could be useful in the treatment of Parkinson's disease, preferentially as an adjuvant of mixed dopaminergic agonists like pergolide.     

Cytomegalovirus maculopapular eruption in a kidney transplant patient

Abstract: Cytomegalovirus (CMV) is the most important viral agent in kidney transplantation. Clinical manifestations of CMV disease in transplantation include hepatitis, pneumonitis, pancreatitis, kidney allograft dysfunction, colitis, and meningoencephalitis. However, skin involvement is rare. We describe a severely compromised cadaveric‐kidney transplant recipient who developed renal failure, colonic ulcers, and a maculopapular rash accompanied by fever and malaise 4 months after transplantation. Only the skin biopsy was diagnostic and consistent with CMV disease. Intravenous ganciclovir administration resulted in clinical improvement of CMV‐induced skin lesions; kidney function normalized and the patient became asymptomatic after 14 days of ganciclovir therapy. Nephrologists should consider the diagnosis of CMV disease in the febrile immunosuppressed patient with skin involvement. Skin biopsy must be considered as a useful and safe procedure in patients with a rash to obtain a prompt diagnosis and efficiently treat this immunocompromised population.