Clinical Evaluation of CAD/CAM Indirect Zirconia Restorations of Severely Destroyed Vital Teeth in the Posterior Area - Early Clinical Results.

BACKGROUND: Dental applications of CAD/CAM concept have been available for almost 30 years. They have allowed dentists to work with novel materials with better properties. One of these materials is zirconia ceramic. AIM: To evaluate prospectively the longevity of CAD/CAM indirect zirconia restorations of severely destroyed vital molars and to study the risk factors associated with restoration failures. MATERIALS AND METHODS: Thirty-two indirect zirconia restorations were made in 19 patients. The treated teeth were extremely destroyed vital molars. Thermal and electrical tests for pulp vitality were performed for all teeth. Radiographs were made pre-operatively, post-operatively, and at the 6-month recall. Cvar and Ryge criteria were used for direct clinical evaluation of each restoration at the 6-month recall. RESULTS: All 32 zirconia restorations were evaluated at 6 months. As per Cvar and Ryge criteria, discrepancies were found in two of the cases: postoperative sensitivity in only one of the teeth immediately after cementing the restoration; a partial fracture of one of the restorations after six months. Good marginal and gingival adaptation of the indirect restorations, good periodontal condition and no peri-apical lesions were observed clinically and radiographically. The thermal and electrical pulp tests were within the normal range for vital posterior teeth. CONCLUSIONS: The present study suggests that the new restorative zirconia materials are promising clinical alternative. They can give the clinicians a broader scope of opportunities in the treatment of their patients, aiming at more sustained and improved results.

Morphological changes in hard dental tissues prepared by Er:YAG laser (LiteTouch, Syneron), Carisolv and rotary instruments. A scanning electron microscopy evaluation.

AIM: This in vitro investigation aimed to study by means of scanning electron microscope the morphological changes in hard dental tissues after using several different methods for caries removal and cavity preparation. MATERIALS AND METHODS: Twenty freshly extracted human teeth with carious lesions were used in the study. They were assigned to four groups depending on the method used for preparation: Group 1--Cavity preparation using Er: YAG laser (LiteTouch, Syneron, Israel). Group 2--Chemomechanical preparation using colourless Carisolv gel (MediTeam AB, Savedalen, Sweden). Group 3--Mechanical rotary preparation using diamond burs and air turbine. Group 4--Mechanical rotary preparation using by steel burs and micromotor. The preparations were performed strictly according to the manufacturer's instructions for proper use of instruments. The teeth samples were prepared for histological study and investigated by a scanning electron microscope at different magnification; the morphological changes in the tissues were registered and compared. RESULTS: There were considerable differences in the surface characteristics of the dental tissues when we analysed the photomicrographs of the specimens obtained using scanning electron microscopy (SEM). The surface after laser treatment remained highly retentive with no residual smear layer; the second best results in this respect were registered when teeth were chemomechanically excavated with Carisolv gel. The mechanical methods of cavity preparation resulted in surfaces with a smear layer of dentin without any microretentions. CONCLUSION: The scanning electron microscopy of hard dental tissues prepared using steel and diamond burs showed surfaces covered with a thick smear layer that may be relevant to the subsequent bonding of adhesive restorative materials to the prepared cavity. In preparing the surface using a turbine with diamond burs the smear layer was thinner and part of the dentinal tubules orifices were open in the area of water turbulence. SEM analysis of hard dental tissues prepared with the help of colourless Carisolv gel showed a rough, retentive surface, some of the dentinal tubule lumens obstructed by denaturated collagen and surface contaminants. The teeth surfaces prepared with Er:YAG laser Lite Touch (Syneron) remained without smear layer and clearly exposed dentinal tubules orifices. The surfaces were highly retentive.