Slow drilling speeds for single-drill implant bed preparation. Experimental in vitro study.

AIMS: To evaluate the real-time bone temperature changes during the preparation of the implant bed with a single-drill protocol with different drill designs and different slow drilling speeds in artificial type IV bone. MATERIALS AND METHODS: For this experimental in vitro study, 600 implant bed preparations were performed in 10 bovine bone disks using three test slow drilling speeds (50/150/300 rpm) and a control drilling speed (1200 rpm). The temperature at crestal and apical areas and time variations produced during drilling with three different drill designs with similar diameter and length but different geometry were recorded with real-life thermographic analysis. Statistical analysis was performed by two-way analysis of variance. Multiple comparisons of temperatures and time with the different drill designs and speeds were performed with the Tukey's test. RESULTS: T Max values for the control drilling speed with all the drill designs (D1 + 1200; D2 + 1200; D3 + 1200) were higher compared to those for the controls for 11 ± 1.32 °C (p < 0.05). The comparison of T Max within the test groups showed that drilling at 50 rpm resulted in the lowest temperature increment (22.11 ± 0.8 °C) compared to the other slow drilling speeds of 150 (24.752 ± 1.1 °C) and 300 rpm (25.977 ± 1.2 °C) (p < 0.042). Temperature behavior at crestal and apical areas was similar being lower for slow drilling speeds compared to that for the control drilling speed. Slow drilling speeds required significantly more time to finish the preparation of the implant bed shown as follows: 50 rpm > 150 rpm > 300 rpm > control (p < 0.05). CONCLUSIONS: A single-drill protocol with slow drilling speeds (50, 150, and 300 rpm) without irrigation in type IV bone increases the temperature at the coronal and apical levels but is below the critical threshold of 47 °C. The drill design in single-drill protocols using slow speeds (50, 150, and 300 rpm) does not have an influence on the thermal variations. The time to accomplish the implant bed preparation with a single-drill protocol in type IV bone is influenced by the drilling speed and not by the drill design. As the speed decreases, then more time is required.

Osteogenic potential of platelet-rich plasma in dental stem-cell cultures.

The purpose of this study was to analyse the potential of platelet-rich plasma (PRP) culture media to induce osteogenic differentiation of periodontal ligament stem cells and dental pulp stem cells compared with four other methods of culture. Both types of cell were collected from 35 healthy patients and cultured in five different media (Dulbecco's modified eagle's medium (DMEM); DMEM and melatonin; DMEM and PRP; DMEM and ascorbic acid 200µmol; DMEM and l-ascorbate 2-phosphate 50µmol). Cells were characterised by flow cytometry. Alizarin Red stain, alkaline phosphatase stain, and the expression of collagen type 1 (Col-1), runt-related transcription factor (RUNX2), osteoprotegerin, and osteopontin (quantified by qRT-PCR) were used to detect the osteogenic profile in each culture. Flow cytometry showed that both types of stem cell were a homogeneous mixture of CD90(+), CD105(+), STRO-1(+), CD34 (-), and CD45 (-) cells. Dental pulp stem cells that were cultured with PRP showed the best osteogenic profile (RUNX2 p=0.0002; osteoprotegerin p=0.001). The group of these stem cells that showed the best osteogenic profile was also cultured with PRP (osteoprotegerin p=0.001). Medium five (with l-ascorbate 2-phosphate 50µmol added) showed an increase in all osteogenic markers for periodontal ligament stem cells after PRP, while the best culture conditions for osteogenic expression of dental pulp stem cells after PRP was in medium four (ascorbic acid 200µmol added). These results suggested that culture in PRP induces osteogenic differentiation of both types of stem cell, modulating molecular pathways to promote bony formation.

Temperature and time variations during osteotomies performed with different piezosurgical devices: an in vitro study.

AIM: The aim of this experimental in vitro study was to evaluate the effects of the piezoelectric device in temperature and time variations in standardized osteotomies performed with similar tip inserts in bovine bone blocks. METHODS: Two different piezosurgical devices were used the OE-F15(®) (Osada Inc., Los Angeles, California, USA) and the Surgybone(®) (Silfradent Inc., Sofia, Forli Cesena, Italy). Serrated inserts with similar geometry were coupled with each device (ST94 insert/test A and P0700 insert/test B). Osteotomies 10 mm long and 3 mm deep were performed in bone blocks resembling type II (dense) and type IV (soft) bone densities with and without irrigation. Thermal changes and time variations were recorded. The effects of bone density, irrigation, and device on temperature changes and time necessary to accomplish the osteotomies were analyzed. RESULTS: Thermal analysis showed significant higher temperatures during piezosurgery osteotomies in hard bone without irrigation (P < 0.05). The type of piezosurgical device did not influence thermal variations (P > 0.05). Time analysis showed that the mean time values necessary to perform osteotomies were shorter in soft bone than in dense bone (P < 0.05). CONCLUSIONS: Within the limitations of this in vitro study, it may be concluded that the temperature increases more in piezosurgery osteotomies in dense bone without irrigation; the time to perform the osteotomy with piezosurgery is shorter in soft bone compared to hard bone; and the piezosurgical device have a minimal influence in the temperature and time variations when a similar tip design is used during piezosurgery osteotomies.

Histomorphometric and mineral degradation study of Ossceram: a novel biphasic B-tricalcium phosphate, in critical size defects in rabbits.

OBJECTIVE: To carry out a histomorphometric analysis of a new highly porous (95%) biphasic calcium phosphate (hydroxyapatite 60%/B-tricalcium phosphate 40%), used to fill critical size defects in rabbit tibiae, supplementing histomorphometric findings with radiographic thermal imaging, EDX analysis and Ca/P ratio mapping at different time stages. MATERIALS AND METHODS: Two critical size defects of 6 mm diameter were created in both tibiae of 21 New Zealand rabbits, test group (Ossceram) and control group. Histomorphometric, radiographic thermal imaging, EDX and element mapping analysis were performed at 15, 30 and 60 days after graft insertion. RESULTS: Histomorphometric analysis at 30 days showed more new bone formation in defects filled with Ossceram 4.41 ± 0.23 mm than the test group 1.94 ± 0. 28 mm (P<0.05). Element analysis revealed higher percentages of Ca (42.33 ± 2.8%) and P (1.3 ± 0.8%) in the test group than in the control group (P<0.05). Element mapping showed that Ca and P were concentrated in medullar and cortical zones in the test group but were concentrated only in cortical zones in the control group. Test group histomorphometry at 60 days showed complete closure of the cortical defect 5.37 ± 0.32 mm more than the control group 2.3 ± 0.54 mm. There was no cortical defect closure or medullar bone formation in the control group (P<0.05). Element analysis revealed higher percentages of Ca (32.26 ± 21.7%) and P (1.5 ± 0.3%) in the test group than in the control group (P<0.05). CONCLUSION: Defects of a critical size in a rabbit tibia model can be sealed using a highly porous biphasic calcium phosphate; this supports new bone formation, creates a bridge between borders and facilitates bone ingrowth. Furthermore, this study observed partial dissolution of the mineral phase of the graft material and its incorporation into the surrounding bone. Radiographic thermal imaging may be used to supplement histological and chemical analyses.

Femtosecond laser microstructuring of zirconia dental implants.

This study evaluated the suitability of femtosecond laser for microtexturizing cylindrical zirconia dental implants surface. Sixty-six cylindrical zirconia implants were used and divided into three groups: Control group (with no laser modification), Group A (microgropored texture), and Group B (microgrooved texture). Scanning electron microscopy observation of microgeometries revealed minimal collateral damage of the original surface surrounding the treated areas. Optical interferometric profilometry showed that ultrafast laser ablation increased surface roughness (R(a), R(q), R(z), and R(t)) significantly for both textured patterns from 1.2 x to 6 x-fold when compared with the control group (p < 0.005). With regard to chemical composition, microanalysis revealed a significant decrease of the relative content of contaminants like carbon (Control 19.7% ± 0.8% > Group B 8.4% ± 0.42% > Group A 1.6% ± 0.35%) and aluminum (Control 4.3% ± 0.9% > Group B 2.3% ± 0.3% > Group A 1.16% ± 0.2%) in the laser-treated surfaces (p < 0.005). X-ray diffraction and Raman spectra analysis were carried out to investigate any change in the crystalline structure induced by laser processing. The original predominant tetragonal phase of zirconia was preserved, whereas the traces of monoclinic phase present in the treated surfaces were reduced (Control 4.32% > Group A 1.94% > Group B 1.72%) as the surfaces were processed with ultrashort laser pulses. We concluded that femtosecond laser microstructuring offers an interesting alternative to conventional surface treatments of zirconia implants as a result of its precision and minimal damage of the surrounding areas.