**3. Role of laser microgrooved zirconia surface in dental implant treatment**

Although titanium can still be considered the reference standard material for dental implants with a few limitations such as rare allergy to metals or gingival retraction or translucidity in thin gingival biotypes and subsequent unsatisfactory esthetic [62, 63]. The development of high mechanical strength ceramics has made them a viable alternative [64]. Yttrium-partially stabilized tetragonal zirconia (Y-TZP) offers several advantages due to its flexural strength and high resistance to fracture, favorable esthetics as well as excellent osseointegration observed in animal studies [65, 66].

However, roughening the surface of the zirconia implant is a challenge mainly due to its resistance to chemical or physical modifications. Several approaches have been proposed as follows: chemical and pharmacological surface modification, sand-blasting and acid etching, the use of nanotechnology, or biomimetic coatings, and addition of micro-and macro-reten‐ tions [67–69]. These modifications result in various degrees of surface roughness and content of contaminants.

The zirconia dental implants available on the market are sandblasted. Recently, technique for microstructuring cylindrical zirconia implants by femtosecond laser ablation has been introduced. In addition to sandblasting, surface is modified using femtosecond laser ablation, which creates an isotropic pattern of microgrooves on the implant surface [5]. This technique is fast, provides precise control of texture allowing production of textures with complex shape, and as a non-contact procedure, it does not cause contamination [5].

Cells modify their morphology, adhesion, and cytoskeletal organization according to the substrate topography [70]. On flat zirconia dental implant surface, osteoblasts are disorganized and loosely attached with few lamellipodia mainly directed toward the cracks or other topographical accidents (**Figure 10a–c**). Creation of microgrooves of 30 μm width and 70 μm separation on zirconia dental implant surface induces favorable cell morphology, increases cell density, and enhances cell activity [71]. Osteoblasts align along the axis of microgrooves with lamellipodia directed toward the inner surface and connected to the base and walls of the microgrooves (**Figure 10d–f**). Filopodia extensions retained in the nanometric structures of the microgroove walls cell further improve adhesion of osteoblasts to modified zirconia surface and increase cell density (**Figure 11a–d**). Osteoblasts adhesion occurs first in micro‐ grooves and later on the flat area of zirconia surface (**Figure 12a–f**). Further, activity of the osteoblasts is tripled by adding the microgrooves to zirconia surface [71]. Microgrooves on zirconia implants host bioactive molecules and enhance the initial stages of bone formation [72].

Favorable cellular events directed by microgrooved zirconia implant surface are provided by increased roughness and enhanced chemical composition of the sandblasted zirconia sur‐ face following its laser modification. This surface treatment increases proportions of zirconi‐ um and oxygen, whereas decreases content of carbon and aluminum allowing high osteoblastic activity on sandblasted, laser micro-grooved zirconia [71]. This modified zirco‐ nia surface exhibit higher values of roughness parameters and reduced the presence of con‐ taminants not only in comparison with its predecessor, nongrooved sandblasted zirconia, but also to sandblasted, hightemperature-etched titanium implants (**Tables 2** and **3**) [73].


Surface roughness parameters (Ra, Rq, Rz, Rt ) expressed as (*x*¯ ± SD) (\*p < 0.05).

**Table 2.** Topographic characteristics of implant surfaces.

Microangiopathies and hyperglycemia associated with diabetes mellitus impaires bone regeneration and might affect early implant failure rates in such patients. Diabetic patients with glycated hemoglobin above 8.0% have delayed implant osseointegration and require a longer healing time [58, 59]. Despite the promising result of animal research that SLActive surface provides accelerated osseointegration of dental implants and better prognosis for implant treatment in diabetic patients, clinical assessment revealed similar outcomes for

**3. Role of laser microgrooved zirconia surface in dental implant treatment**

Although titanium can still be considered the reference standard material for dental implants with a few limitations such as rare allergy to metals or gingival retraction or translucidity in thin gingival biotypes and subsequent unsatisfactory esthetic [62, 63]. The development of high mechanical strength ceramics has made them a viable alternative [64]. Yttrium-partially stabilized tetragonal zirconia (Y-TZP) offers several advantages due to its flexural strength and high resistance to fracture, favorable esthetics as well as excellent osseointegration

However, roughening the surface of the zirconia implant is a challenge mainly due to its resistance to chemical or physical modifications. Several approaches have been proposed as follows: chemical and pharmacological surface modification, sand-blasting and acid etching, the use of nanotechnology, or biomimetic coatings, and addition of micro-and macro-reten‐ tions [67–69]. These modifications result in various degrees of surface roughness and content

The zirconia dental implants available on the market are sandblasted. Recently, technique for microstructuring cylindrical zirconia implants by femtosecond laser ablation has been introduced. In addition to sandblasting, surface is modified using femtosecond laser ablation, which creates an isotropic pattern of microgrooves on the implant surface [5]. This technique is fast, provides precise control of texture allowing production of textures with complex shape,

Cells modify their morphology, adhesion, and cytoskeletal organization according to the substrate topography [70]. On flat zirconia dental implant surface, osteoblasts are disorganized and loosely attached with few lamellipodia mainly directed toward the cracks or other topographical accidents (**Figure 10a–c**). Creation of microgrooves of 30 μm width and 70 μm separation on zirconia dental implant surface induces favorable cell morphology, increases cell density, and enhances cell activity [71]. Osteoblasts align along the axis of microgrooves with lamellipodia directed toward the inner surface and connected to the base and walls of the microgrooves (**Figure 10d–f**). Filopodia extensions retained in the nanometric structures of the microgroove walls cell further improve adhesion of osteoblasts to modified zirconia surface and increase cell density (**Figure 11a–d**). Osteoblasts adhesion occurs first in micro‐ grooves and later on the flat area of zirconia surface (**Figure 12a–f**). Further, activity of the osteoblasts is tripled by adding the microgrooves to zirconia surface [71]. Microgrooves on

and as a non-contact procedure, it does not cause contamination [5].

SLActive and SLA surfaces [60, 61].

140 Dental Implantology and Biomaterial

observed in animal studies [65, 66].

of contaminants.


Expressed in percentages as *x*¯ ± SD (\*p < 0.05).

**Table 3.** Elements present in surface chemical composition.

The addition of microgrooves in the 2-mm wide neck area of the implant increases surface roughness by 6.5 times and almost 12 times in the zirconia implants processed over the en‐ tire intraosseous surface. Microgrooves provide more retentive areas and greater bone-toimplant contact resulting in higher stability of this implants proven by the increase in insertion and removal torque and decrease of PTV values (**Tables 4**–**6**) [73].


**Table 4.** Insertion Torque values (IT) recorded at implant placement.


**Table 5.** Removal torque test (RT) performed at three evaluation time points.


**Table 6.** Changes in Periotests values (PTV) over time.

Microgrooved implants reduces crestal bone level in comparison with microthreaded titani‐ um implants and particularly with rough neck implants without microthreading (sandblast‐ ed zirconia) (**Table 7**). Although microthreads at implant neck transform the shear force between the implants and crestal bone into the compressive force to which bone is the most resistant allowing preservation of bone tissue, the addition of microgrooves that interlock the adjacent bone seems to be more efficient [73, 74].


**Table 7.** Radiographic crestal bone loss (RCBL).

The addition of microgrooves in the 2-mm wide neck area of the implant increases surface roughness by 6.5 times and almost 12 times in the zirconia implants processed over the en‐ tire intraosseous surface. Microgrooves provide more retentive areas and greater bone-toimplant contact resulting in higher stability of this implants proven by the increase in

*x***¯ SD SE Median**

**Month 1 Month 2 Month 3**

**Month 1 Month 2 Month 3**

insertion and removal torque and decrease of PTV values (**Tables 4**–**6**) [73].

**Table 4.** Insertion Torque values (IT) recorded at implant placement.

**Table 5.** Removal torque test (RT) performed at three evaluation time points.

**Surface RT (Ncm)**

**Surface PTV**

**Table 6.** Changes in Periotests values (PTV) over time.

Values expressed as ±SD (median).

142 Dental Implantology and Biomaterial

**Surface IT(Ncm)**

**Sandblasted, high temperature etched titanium** 57.10 1.80 0.51 55.76 **Sandblasted zirconia** 46.08 0.70 0.20 44.87 **Sandblasted zirconia with microgrooved neck** 53.20 1.30 0.37 50.98 **Sandblasted zirconia all microgrooved** 69.60 1.20 0.34 67.82

**Sandblasted zirconia** 64.08 ± 0.42 (64.07) 78.24 ± 0.35 (78.38) 199.19 ± 0.99 (199.47) **Sandblasted zirconia with microgrooved neck** 69.19 ± 0.37 (69.17) 88.82 ± 0.41 (88.86) 215.13 ± 0.99 (215.06) **Sandblasted zirconia all microgrooved** 84.95 ± 0.25 (85.03) 126.96 ± 0.81 (126.65) 240.15 ± 1.04 (239.90) **Sandblasted, high temperature etched titanium** 71.25 ± 0.43 (71.28) 99.85 ± 0.44 (99.98) 226.98 ± 1.06 (226.72)

**Sandblasted zirconia** −1.52 ± 0.01 (−1.52) −2.17 ± 0.01 (−2.17) −2.41 ± 0.02 (−2.41) **Sandblasted zirconia with microgrooved neck** −1.85 ± 0.02 (−1.85) −2.42 ± 0.01 (−2.42) −3.11 ± 0.01 (−3.11) **Sandblasted zirconia all microgrooved** −2.49 ± 0.02 (−2.5) −4.16 ± 0.01 (−4.16) −5.69 ± 0.03 (−5.7) **Sandblasted, high temperature etched titanium** 2.11 ± 0.35 (−2.00) −2.70 ± 0.01 (−2.70) −3.59 ± 0.05 (−3.60)

Microgrooved implants reduces crestal bone level in comparison with microthreaded titani‐ um implants and particularly with rough neck implants without microthreading (sandblast‐ ed zirconia) (**Table 7**). Although microthreads at implant neck transform the shear force between the implants and crestal bone into the compressive force to which bone is the most The addition of microgrooves to the entire intraosseous surface of zirconia dental implants enhances primary and secondary implant stability, which promotes bone tissue ingrowth and preserves crestal bone levels [73]. Data from animal models indicate that zirconia femtosecond laser all-treated surface achieves good osseointegration and could be predictable treatment option in the implantological daily practice [75]. Histological, radiological, and histomorpho‐

**Figure 10.** SEM evaluation of cell morphology on sandblasted (a-c) and sandblasted, laser micro grooved zirconia (d-F) at 7 days. (a) a cell in the base of an implant thread; (b) close-up view of a couple of cell bodies close to the base of the thread; (c) a cell body with very short cell lamellipodia located in a crack surface (shown at high magnification); (d) cell at the border of a microgroove; (e) lamellipodia extend inside microgrooves, bridging microgroove borders; (f) cell body aligned in the direction of the microgroove.

metric evaluation of zirconia implants treated with femtosecond laser revealed that they can be successfully subjected to immediate loading protocol [72].

**Figure 11.** Cells on sandblasted, microgrooved zirconia surface at 7 days (high magnification). (a) lateral view of multi‐ ple cells firmly adhered to the inner surface of the microgrooves; (b) cell body alignment at the base of the micro‐ grooves; (c) lamellipodia network at walls and base of the microgrooves; (d) inner wall of a microgroove showing filopodia connected to the nanorough texture of the microgroove walls.

**Figure 12.** SEM evaluation of cell morphology on sandblasted (a–c) and sandblasted, laser micro grooved zirconia (d–f) at 15 days. The cells established intercellular contacts and formed layers; contact between the cell and the surface occur mainly in topographic accidents (high magnification) (a–c). Cells fill the microgroove completely; cells also form in the pitch areas (d–f).
