The Effects of Combining Drill Diameters Bypass , and Implant Bed under Preparation Protocols on Primary Stability of Dental Implant in Low-Density Bones ( Experimental Study )

Aims: The aim of the current study is to compare the impact of using different drilling protocols on the dental implants primary stability inserted in the low-density bones. Materials and Methods: Out of twenty-two, ten oxen ribs were used in this in-vitro study. Using computed tomography (CT) scan, the most proximal three centimeters (cm) of the rib was confirmed to be a low-density bone comparable to human edentulous jaw bones. Forty dental implants were inserted, each rib received four dental implants using four different techniques that are arranged into four study groups:Group (I): includes a number of ten dental implants where the drilling burs and implants have the same size. Fit-size technique (F.G).Group (II): includes a number of ten dental implants where the diameter of the drilling burs is less than the implant diameter. Under-sized technique (U.G) Group (III): includes a number of ten dental implants where the simplified drilling protocol (Drill bypass) (D.G) was used for insertion.Group (IV): includes a number of ten dental implants where combined drilling protocols (C.G) (Undersized U.G+ Drill bypass D.G) were used for insertion. Results: Results revealed a statistically significant difference in the mean of insertion torque values (IT) between combined group (C.G) (65.000 N.cm) and fit-sized group (F.G) (45.0000 N.cm).Concerning Periotest M, a statistically significant difference was found in the mean of (PTV) between combined group (C.G) (-6.4500) and fit-sized group. A statistically highly significant correlation was found between insertion torque values (ITs) and Periotest M values (PTVs). Conclusions: Dental implant insertion in low-density bones using simplified drilling protocol (Drill bypass) (D.G) is better to be combined with undersized implant bed preparation (U.G) to enhance The Effects of Combining Drill Diameters Bypass, and Implant Bed under Preparation Protocols on Primary Stability of Dental Implant in LowDensity Bones (Experimental Study) ISSN: 1812–1217 EISSN: 1998-0345 Al – Rafidain Dent J Vol. 20, No1, 2020 135 implant primary stability and with less time.


INTRODUCTION
Human teeth loss is still a major problem in ageing populations worldwide, although advanced methods of oral-health preservation are delaying teeth loss later in life (1) , teeth loss has an impact on chewing, function, dental esthetics and quality of life (2,3) .Endosseous dental implants are an increasingly widespread treatment option for achieving good functional and aesthetic outcomes (4) . Misch classified cancellous (spongy) bone density into 5 grades: D1: > 1250 HU; D2: 850 to 1250 HU; D3: 350 to 850 HU; D4: 150 to 350 HU; and D5: < 150 HU (5) . Implant stability plays a vital role for successful osseointegration, it may be defined as the capacity of the implant to withstand loading in the axial, lateral and rotational direction (6) . Implant stability serves as an indirect indication for osseointegration, and the clinical perception of implant stability is often related to the rotational resistance during placement of the dental implant (7) . Dental implant stability can be divided into "Primary" and "Secondary" components; primary stability refers to mechanical implant bracing in the bone and lack of any minimal movement, while secondary stability refers to successful "Osseointegration" of dental implant with the adjacent bone (8) . Accomplishing primary stability of dental implant is of essential importance at the time of implant insertion (9, 10) .
Primary stability of dental implant is influenced by a number of factors which include quality and quantity of local bone, implant-related factors like diameter, form, length, surface characterization and the drilling protocol followed meaning that size of the drill comparison to size of dental implant, pretapped or self-tapping implants (8,11,12) .
Many adjustments of the surgical procedures and drilling protocols have been established in order to increase the implant's primary stability in the low-density bone.
Under-sized implant preparations have been proposed through the use of smaller final drill diameter than the implant's diameter (13,14) . Some researchers suggest that the implant drilling protocols may be simplified (15) , these attempts to simplify drilling protocols are expected to contribute the improvement of

MATERIALS AND METHODS
The Dentium surgical kit was used invitro using oxen ribs. Bones were numbered from one to twenty-two before scanning by CT scan.
Out of twenty-two ribs, ten oxen ribs were selected according to previous research (18) on bone which showed that the proximal three centimeters of ribs were classified as a lowdensity bone after CT scan's confirmation. Oxen ribs frozen until used, each oxen rib was maintained at room temperature (21 ± 1°C) for three hours and wrapped in sterile isotonic saline solution gauze for hydration (19,20,21) . A parallel vise was used for fixation of rib bones.     A highly statistically significant correlation was found between insertion torque values (ITs) and

Effect of Combined Protocols (U.G+D.G) on Primary Stability of Implant:
The main results of the present study when

Comparison among the Four Surgical
Techniques: