Dental bleaching during orthodontic treatment with aligners.

OBJECTIVE: The present study was undertaken to determine the tooth whitening effectiveness of trays with no reservoirs (Invisalign aligners or Vivera retainers used as bleaching trays), initially with a finite element analysis (FEA) and subsequently with a clinical study using spectrophotometry. MATERIALS AND METHODS: The FEA technique was used to determine the ideal distribution of bleaching gel between teeth and aligners in vitro. Three sample areas of gel application on the maxillary central incisors (the incisal edge, the middle part, and the gingival edge) were analyzed. Spectrophotometry was used to ascertain the clinical effectiveness of the bleaching gel as it related to the results of the FEA. More specifically, the chromatic variation obtained by the bleaching gel on teeth 41 and 32 (control teeth, with reservoirs) was compared with that on teeth 31 and 42 (study teeth, without reservoirs). RESULTS: The FEA results showed that the optimal gel distribution is reached when 2 mm3 of gel is applied to the center of the vestibular face of the tooth in the tray. As regards the clinical study, there were no relevant differences of whitening effectiveness between the teeth with reservoirs and those without. In both cases, the whitening was effective and the patients were completely satisfied with the results. CONCLUSIONS: The advantages for patients to receive dental bleaching during orthodontic treatment with aligners are evident. The procedure is not time consuming and requires less financial expense. Further clinical studies are required to assess the effectiveness of the procedure.

The Capacity of Periodontal Gel to Occupy the Spaces Inside the Periodontal Pockets Using Computational Fluid Dynamic.

The aim of the current work is to demonstrate the capacity of a new periodontal gel to occupy the spaces inside the periodontal pockets through Computational Fluid Dynamic (CFD). The test gel consists of two resorbable medical grade polymers (PEO, Poly Ethylen Oxide and HPMC, Hydroxy Propyl Metyl Cellulose), Type I Collagen, SAP (Vitamin C), and PBS (Saline Solution), while the control gel is 14% doxyclin controlled release gel, which is used for treating periodontal pockets with probing ≥5 mm after scaling and root plaining. The study examined the fluid dynamic analysis (Computational Fluid Dynamic-CFD) of two different gels, used in dentistry to treat periodontitis, in relation to both the geometry of the periodontal pocket and the function of two different types of needles that are used to distribute the preparation. The periodontal pocket was determined by reading DICOM images taken from the patient's CAT scan. The results show that the H42® gel comes out uniformly compared to the other gel. Moreover, it is possible to observe how the rheological properties of the gel allow the fluid to spread evenly within the periodontal pocket in relation to the geometry of the needle. In particular, H42® gel exits in a constant way both from the first and the second exit. In fact, it was observed that by changing the geometry of the needle or the type of periodontal gel, the distribution of the gel inside the pocket was no longer homogeneous. Thus, having the correct rheological properties and correct needle geometries both speeds up the gel and optimizes the pressure distribution. Currently, the literature is still lacking, therefore further studies will be needed to confirm these results.

3D finite element analysis to detect stress distribution: spiral family implants.

AIM: Spiral family implants are a root-form fixtures with increasing thickness of tread. This characteristic gives a self-tapping and self-condensing bone properties to implants. To study spiral family implant inserted in different bone quality and connected with abutments of different angulations a Finite Element Analysis (FEA) was performed. Once drawn the systems that were object of the study by CAD (Computer Aided Design), the FEA discretized solids composing the system in many infinitesimal little elementary solids defined finite elements. This lead to a mesh formation where the single finite elements were connected among them by nodes. For the 3 units bone-implant-abutments several thousand of tetrahedral elements having 10 parabolic nodes were employed. MATERIALS AND METHODS: The biomechanical behaviour of 4.2 mm × 13 mm dental implants, connecting screw, straight and 15° and 25° angulated abutment subjected to static loads, in contact with high and poor bone quality was evaluated by FEA. A double system was analyzed: a) FY strength acting along Y axis and having 200 N intensity; b) FY and FZ couple of strengths applied along Y and Z directions and having respectively 200N and 140N intensity. The materials were considered as homogeneous, linear and isotropic. Then the FEA simulation was performed hypothesizing a linearity between loads and deformations. RESULTS: The lowest stress value was found in the system composed by implants and straight abutments loaded with a vertical strength, while the highest stress value were found in implants and 15° angulated abutment loaded with a angulated strength. In addition, the lower is the bone quality (i.e. D4) the higher is the distribution of the stress within the bone. CONCLUSION: Spiral family implants can be used successfully in low bone quality but a straight force is recommended.