CLINICAL EVALUATION of THE ASSOCIATION BETWEEN NONCARIOUS CERVICAL LESIONS and OCCLUSAL FORCES

Statement of problem. Noncarious cervical lesions (NCCLs) are a frequent challenge in clinical dental practice, given the variety of opinions regarding their etiology, diagnosis, and treatment.Purpose. The purpose of this study was to assess the potential relationship between occlusal forces and the occurrence of NCCLs.Material and methods. The participant population consisted of 111 volunteers (30 male and 81 female, mean age 23.6 years). General personal information was recorded, after which participants were examined for the presence and location of NCCLs, gingival recession, fracture lines, dental and restoration fractures, presence and location of tooth wear, type of occlusal guidance scheme for lateral mandibular movements, and existence of occlusal interference or premature contacts. The participants were divided according to the presence or absence of NCCLs, and data were statistically analyzed with the Independent t test, the Chi-square test, and the Fisher exact test (alpha=.05).Results. A significant association was found between the presence of NCCLs and age (P=.008), gingival recession (P<.001), occlusal trauma (P<.001), presence (P<.001) and location of tooth wear, and group function as occlusal guidance scheme in lateral excursive movements (P<.001).Conclusions. A strong relationship between the presence of NCCLs and occlusal overload was found. (J Prosthet Dent 2012;108:298-303)

Estudo morfológico da polpa de molares de ratos Wistar frente a uma oclusão traumática experimental

As alterações morfológicas pulpares, decorrentes de um estímulo externo experimental (interferência oclusal), foram estudadas, em nível de microscopia de luz. Utilizaram-se restaurações de amálgama, em sobreoclusão nos primeiros molares superiores direitos de dez ratos Wistar, divididos em 3 grupos e sacrificados por perfusão transcardíaca com formol a 10%, aos 10, 20 e 30 dias. A avaliação foi feita nos molares inferiores direitos (lado experimental) e esquerdos (lado controle). As peças ósseas após descalcificação em solução de EDTA associada às microondas, seguiram técnica histológica de rotina e coloração por hematoxilina-eosina e tricrômico de Mallory. Verificou-se no lado controle uma reação intensa caracterizada por um posicionamento atípico dos odontoblastos, seguida pelo aparecimento de cálculos pulpares e posteriormente por uma aparente e uniforme acomodação tecidual em toda a polpa, com moderada incidência de fibras colágenas. No lado experimental, as alterações foram similares parecendo, porém, aumentar com o tempo, principalmente aos 30 dias, onde a imagem histológica era semelhante à do lado controle aos 10 dias. Os resultados obtidos permitiram concluir que a interferência oclusal provocou alterações no tecido conjuntivo pulpar tanto no lado experimental como no controle e que as mesmas foram proporcionais à direção dos movimentos mandibulares.

Aspectos oclusais na etiologia das desordenstemporomandibulares

Since the occlusion area is presented in almost all specialties of Dentistry, its relationship with the health of the patient has been shown. The etiology of temporomandibular disorders is multifactorial and the occlusion is considered an etiologic factor. This study aimed to discuss the functional occlusion aspects and the presence of temporomandibular disorders. Literature Review: The loss of orthopedic balance can induce temporomandibular disorder. Therefore, both the physiological and functional occlusions have been analyzed as a dental relation. Several functional occlusal factors have been linked to the temporomandibular disorders such as deviations of centric relation to maximum intercuspation, occlusal interferences, absence of posterior teeth, changes on the occlusion vertical dimension, malocclusion, orthodontic treatment and parafunction. Conclusion: The most common occlusal factors related to temporomandibular disorders are quite frequent; however, the diagnosis and treatment of such disorders should be considered individually

Multidisciplinary treatment ofadult patients with Class III malocclusion

This article describes the multidisciplinary treatment of an adult patient presenting with Angle Class III malocclusion, alteration of the mandibular position, vertical alveolar bone loss and absence of teeth in the lower posterior region. With advancing age the existence of occlusal interference due to loss of teeth or tooth structure is very common, resulting in periodontal problems due to occlusal trauma. The options for treatment of Class III malocclusion in adolescent and adult patients include compensatory orthodontic treatment in mild to moderate cases and orthognathic surgery for moderate to severe cases. The combination of various dental specialties enabled improvement in the social circumstances of the patient. This can be observed objectively by the final dental relationship and by the skeletal and tegumentary cephalometric comparison between the situation at the beginning and at the end of the treatment. The compensatory treatment performed permitted the successful correction of a Class III malocclusion in the clinical case presented.

Statistical analysis and reduction of multiple access interference in MC-CDMA systems

Multicarrier code division multiple access (MC-CDMA) is a very promising candidate for the multiple access scheme in fourth generation wireless communi- cation systems. During asynchronous transmission, multiple access interference (MAI) is a major challenge for MC-CDMA systems and significantly affects their performance. The main objectives of this thesis are to analyze the MAI in asyn- chronous MC-CDMA, and to develop robust techniques to reduce the MAI effect. Focus is first on the statistical analysis of MAI in asynchronous MC-CDMA. A new statistical model of MAI is developed. In the new model, the derivation of MAI can be applied to different distributions of timing offset, and the MAI power is modelled as a Gamma distributed random variable. By applying the new statistical model of MAI, a new computer simulation model is proposed. This model is based on the modelling of a multiuser system as a single user system followed by an additive noise component representing the MAI, which enables the new simulation model to significantly reduce the computation load during computer simulations. MAI reduction using slow frequency hopping (SFH) technique is the topic of the second part of the thesis. Two subsystems are considered. The first sub- system involves subcarrier frequency hopping as a group, which is referred to as GSFH/MC-CDMA. In the second subsystem, the condition of group hopping is dropped, resulting in a more general system, namely individual subcarrier frequency hopping MC-CDMA (ISFH/MC-CDMA). This research found that with the introduction of SFH, both of GSFH/MC-CDMA and ISFH/MC-CDMA sys- tems generate less MAI power than the basic MC-CDMA system during asyn- chronous transmission. Because of this, both SFH systems are shown to outper- form MC-CDMA in terms of BER. This improvement, however, is at the expense of spectral widening. In the third part of this thesis, base station polarization diversity, as another MAI reduction technique, is introduced to asynchronous MC-CDMA. The com- bined system is referred to as Pol/MC-CDMA. In this part a new optimum com- bining technique namely maximal signal-to-MAI ratio combining (MSMAIRC) is proposed to combine the signals in two base station antennas. With the applica- tion of MSMAIRC and in the absents of additive white Gaussian noise (AWGN), the resulting signal-to-MAI ratio (SMAIR) is not only maximized but also in- dependent of cross polarization discrimination (XPD) and antenna angle. In the case when AWGN is present, the performance of MSMAIRC is still affected by the XPD and antenna angle, but to a much lesser degree than the traditional maximal ratio combining (MRC). Furthermore, this research found that the BER performance for Pol/MC-CDMA can be further improved by changing the angle between the two receiving antennas. Hence the optimum antenna angles for both MSMAIRC and MRC are derived and their effects on the BER performance are compared. With the derived optimum antenna angle, the Pol/MC-CDMA system is able to obtain the lowest BER for a given XPD.