Misfit and fracture load of implant-supported monolithic crowns in zirconia-reinforced lithium silicate

Abstract Zirconia-reinforced lithium silicate (ZLS) is a ceramic that promises to have better mechanical properties than other materials with the same indications as well as improved adaptation and fracture strength. Objective In this study, marginal and internal misfit and fracture load with and without thermal-mechanical aging (TMA) of monolithic ZLS and lithium disilicate (LDS) crowns were evaluated. Material and methods Crowns were milled using a computer-aided design/computer-aided manufacturing system. Marginal gaps (MGs), absolute marginal discrepancy (AMD), axial gaps, and occlusal gaps were measured by X-ray microtomography (n=8). For fracture load testing, crowns were cemented in a universal abutment, and divided into four groups: ZLS without TMA, ZLS with TMA, LDS without TMA, and LDS with TMA (n=10). TMA groups were subjected to 10,000 thermal cycles (5-55°C) and 1,000,000 mechanical cycles (200 N, 3.8 Hz). All groups were subjected to compressive strength testing in a universal testing machine at a crosshead speed of 1 mm/min until failure. Student's t-test was used to examine misfit, two-way analysis of variance was used to analyze fracture load, and Pearson's correlation coefficients for misfit and fracture load were calculated (α=0.05). The materials were analyzed according to Weibull distribution, with 95% confidence intervals. Results Average MG (p<0.001) and AMD (p=0.003) values were greater in ZLS than in LDS crowns. TMA did not affect the fracture load of either material. However, fracture loads of ZLS crowns were lower than those of LDS crowns (p<0.001). Fracture load was moderately correlated with MG (r=-0.553) and AMD (r=-0.497). ZLS with TMA was least reliable, according to Weibull probability. Conclusion Within the limitations of this study, ZLS crowns had lower fracture load values and greater marginal misfit than did LDS crowns, although these values were within acceptable limits.

Early treatment of nonsyndromic oligodontia: a clinical case report / Tratamento precoce da oligodontia não-sindrômica: relato de caso clínico

This report aims to describe the clinical case of a 10-year-old male patient (R.C.B.C.), presenting nonsyndromic oligodontia with maternal family trait and absence of 22 permanent teeth. Clinically, the patient had prolonged retention of some primary teeth and presence of permanent maxillary left central incisor, permanent mandibular right central incisor and four first permanent molars. Radiographically, only permanent maxillary second molars and mandibular third molars were developing, whereas all other germs of permanent teeth were missing. Treatment consisted of maxillary expansion followed by moving permanent maxillary left central incisor bucco-mesially, and rehabilitation of spaces with removable denture, where the main goal was to restore function and esthetic harmony. The case has been monitored for the past six years. Nonsyndromic oligodontia is a rare condition that poses significant functional and psychosocial difficulties. Treatment usually requires a multidisciplinary approach among which pediatric dentistry and orthodontics play a major role. In view of its complexity, treatment should be initiated as early as possible to minimize future functional and aesthetic issues. Dental implants are considered as definitive treatment of cases of oligodontia, however, until the patient reached the ideal age, other treatments to ensure aesthetics and function must be performed.

O objetivo deste trabalho é descrever o caso clínico do paciente R.C.B.C., dez anos de idade, gênero masculino, portador de oligodontia não associada à síndrome, com traço familiar materno e ausência de 22 dentes permanentes. Clinicamente, o paciente apresentava retenção prolongada de alguns incisivos, todos os caninos e molares decíduos e presença do incisivo central superior esquerdo, incisivo central inferior direito e os quatro primeiros molares, todos da dentição permanentes. Radiograficamente, apenas os segundos molares superiores e os terceiros molares inferiores estavam em desenvolvimento, com ausência dos demais germes dos dentes permanentes. Terapeuticamente, foi instituída a expansão maxilar seguida de mesialização e vestibularização do incisivo central superior esquerdo e de reabilitação com prótese removível, sendo o objetivo principal restaurar a harmonia estética e a função. O caso foi acompanhado há seis anos. A oligodontia não-sindrômica é considerada rara e impõe importantes dificuldades funcionais e psicossociais aos seus portadores. Geralmente, o tratamento requer uma abordagem interdisciplinar, onde a odontopediatria e a ortodontia desempenham papel primordial. Devido à complexidade envolvida, o tratamento deve ser iniciado o mais cedo possível, para minimizar futuras questões funcionais e estéticas. Os implantes dentários são considerados como tratamento definitivo para os casos de oligodontia, entretanto, até os pacientes alcançarem a idade ideal, outros tratamentos para garantir estética e função devem ser realizados.