[Effect of full crown preparation with ultrasound instrument on marginal adaption: a randomized controlled trial].

PURPOSE: To study the effect of full crown ultrasound preparation on crown margin. METHODS: Thirty-two patients with 35 units of full crown were randomly divided into 2 groups. Teeth in the experimental group were prepared with ultrasound diamond instrument while teeth in the control group were prepared with a high-speed hand piece with regular diamond burs. Teeth in both groups were restored using Zirconia full ceramic crowns. Then all patients were evaluated for morphology of finishing line, marginal adaptation and marginal gingival coloration in the proximal side after 6-month of follow-up, respectively. SPSS17.0 software package was used for statistical analysis. RESULTS: Marginal adaptation did not show significant difference between the experimental and control group (P>0.05). Morphology of finishing line and marginal gingival coloration in the proximal side showed significant difference (P<0.05). CONCLUSIONS: It is recommended to perform tooth preparations with ultrasound diamond instruments, which may produce significantly less marginal gingival coloration in the proximal margin after 6-month of follow-up.

[A prospective study of changes in oral health-related quality of life during "all-on-four" immediate restoration for edentulous individuals].

PURPOSE: This clinical study was to evaluate oral health-related quality of life (OHRQoL) changes in patients who underwent all-on-4 treatment in one or both jaws. METHODS: Eleven patients underwent placement of 4 to 6 dental implants on the basis of all-on-4 treatment concept in the maxilla, mandible or both jaws and immediate loading with acrylic interim prostheses. The prostheses were replaced after 3-6 months, and definitive prostheses with metal framework and reinforced resin facing were fixed after another 3 months or more. The subjects completed the shortened Chinese version of the Oral Health Impact Profile (OHIP-14) before surgery (T0), 1 week after interim prostheses were placed (T1) and 3 months after definitive prosthesis placement (T2). The data of 11 subjects were analyzed with Wilcoxon signed-rank test using SPSS 13.0 software package. RESULTS: The total OHIP-14 score significantly reduced only at T2 (P<0.05). "Functional limitation," "physical pain," "physical disability," and "psychological disability" scores significantly decreased at T2, and "psychological discomfort" scores also significantly dropped at T1. "Social disability" and "handicap" scores remained unchanged throughout the treatment course. CONCLUSIONS: Fixed definitive prostheses with metal framework are more effective in improving OHRQoL than fixed acrylic prostheses during all-on-4 treatments.

[Analysis of retention of 3 different aesthetic Co-Cr-Mo alloy clasps on premolars].

PURPOSE: To evaluate the 3-D surface topography of ultrasonically prepared tooth. METHODS: Ten extracted human maxillary premolars were prepared for crowns. A split-tooth model was used to refine the margins: half of the margin was finished with traditional rotary instruments, the other with ultrasonic instruments. The 3-D profiles of the prepared surface were observed under scanning electron microscopy and Talysurf CCI 3000 non-contact 3D profiler, and a quantitative comparison of 3-D surface roughness average(SA) and the surface of skewness(SSK) was conducted with Talymap Gold software. The data were analyzed by independent sample t test using SPSS13.0 software package. RESULTS: The surface finished with ultrasonic instruments exhibited a smoother surface. 3-D surface roughness analysis showed that the SA and SSK of surfaces made by ultrasonic instruments were significantly lower, compared with surfaces produced using conventional rotary instruments. CONCLUSIONS: The ultrasonic instruments produce surface in better condition than the conventional rotary instruments.

[The acceleration of titanium implant osseointegration by low intensity pulsed ultrasound: an experimental study in rats].

OBJECTIVE: To establish an animal model of titanium implant and to investigate the effects of low intensity pulsed ultrasound (LIPUS) on the implant osseointegration. METHODS: Twenty-four female Sprague Dawley (SD) rats were used. Titanium implants were inserted into tibia metaphysis bilaterally in each SD rat. Since the second day following implant surgery, LIPUS stimulation were carried out around the implant on the right side for 20 minutes per day, and implants on the left side remain untouched as self-control. Eight rats were sacrificed and tibiae specimens were harvested on the end of the 4th, 8th, and 12th week respectively. X-ray picture, micro-CT analysis and histological sections were performed to evaluate the effects of LIPUS on the implant osseointegration. RESULTS: Osseointegration at the interface between the implant and bone tissue was observed bilaterally. In the micro-CT histomorphometry analysis, the percentage of osseointegration (%OI) of experiment side were (45.708 ± 3.316)%, (46.231 ± 1.954)%, and (46.807 ± 1.451)% on the end of the 4th, 8th, and 12th week. Meanwhile, the %OI of control side were (43.021 ± 3.558)%, (44.272 ± 3.023)%, and (44.894 ± 4.215)% respectively. The %OI on the 4th weekend, bone volume ratio (BV/TV) on the 4th and 8th weekend, trabecular thickness (Tb. Th) and degree of anisotropy (DA) on the 8th and 12th weekend of the experiment side tibia were significantly greater than those on the control side (P < 0.05). The histological examination showed that the thickness of new bone around the implant and the bone-implant contact area was obviously greater in the LIPUS treated side compared to the control side. CONCLUSIONS: The LIPUS therapy may accelerate the bone healing and osseointegration at the interface between titanium implant and bone, and promote remodeling of bone trabecula on the early stage.

[Fracture resistance and failure modes of endodontically treated human teeth restored with four different post-core systems].

OBJECTIVE: To compare the fracture resistance and failure modes of endodontically treated human upper premolars restored with different post-core systems. METHODS: 32 extracted human upper premolars were endodontically treated and crowns were sectioned at 2 mm above the labial cement enamel junction (CEJ). The teeth were randomly and equally divided into 4 groups: Group A, teeth restored with cast metal post and metal crown; group B, Tenax Fiber White fiber post and metal crown; group C, EverStick fiber post 1.5 mm in diameter and metal crown; group D, EverStick fiber post 1.5 mm in diameter and add another 1.2 mm diameter EverStick fiber post and metal crown. All the teeth were embedded in acrylic resin blocks, and were subjected to a compressive load at 1 mm/min crosshead speed which delivered at a 45 degrees to the long axis until the first sign of failure was noted. The fracture load and the mode of fracture were recorded. RESULTS: Fracture resistances of the four groups of restored teeth were not significantly different (P>0.05). However, fracture modes in fiber post groups were nearer to CEJ than cast metal post group. CONCLUSION: Fracture resistance of endodontically treated teeth restored with EverStick fiber post is enhanced that it can meet the clinical need, although the flexural resistance of EverStick fiber post itself is the weakest. Fracture modes of all fiber post groups are more favorable than cast metal post group.