Australian Dental Journal

The official journal of the Australian Dental Association

Australian Dental Journal 2016; 61: 208–218 doi: 10.1111/adj.12337

Outcomes of placing short implants in the posterior mandible: a preliminary randomized controlled trial AA Al-Hashedi,*† TB Taiyeb-Ali,‡ N Yunus§ *Department of Prosthodontic Dentistry, Sana’a University, Sana’a, Yemen. †Department of Oral Biology and Biomedical Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia. ‡Professor, Department of Oral Biology and Biomedical Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia. §Professor, Department of Restorative Dentistry, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia.

ABSTRACT Background: Short dental implants can be an alternative to bone augmentation procedures at sites of reduced alveolar bone. Most studies on short implants are retrospective or multicentre reports that lack controlled and consistent comparison between different systems. This study aimed to compare clinical and radiographic outcomes of short implants in two different systems in the posterior mandible. Methods: Twenty patients with two adjacent missing posterior teeth were recruited. Patients were assigned equally and randomly into two groups; Biconâ (6 or 8 mm) and Ankylosâ (8 mm) implants. A two-stage surgical approach and single crowns were used for implant placement and loading. Outcomes included peri-implant clinical parameters, implant stability (Periotest values; PTVs) and peri-implant bone changes, which were assessed at baseline, 2, 6 and 12 months post-loading. Results: No implant loss was encountered up to 12 months post-loading. No significant difference in the clinical or radiographic parameters was observed except for PTVs (p < 0.05) that was lower in Ankylosâ implants. Conclusions: The use of short dental implants was associated with excellent 12 months clinical and radiographic outcomes. Ankylosâ and Biconâ implants demonstrated similar peri-implant soft tissue and alveolar bone changes. However, Ankylosâ implants demonstrated better implant stability at all evaluation intervals. Keywords: Ankylosâ, Biconâ, implant stability, partial edentulism, short implants. Abbreviations and acronyms: CAL = clinical attachment loss; CBCT = cone beam computed tomography; GI = Gingival Index; mBI = modified Bleeding Index; PD = Probing Depth; PI = Plaque Index; PTVs = Periotest values; RH = Recession Height; WKM = width of keratinized mucosa. (Accepted for publication 2 May 2015.)

INTRODUCTION Over the last decades, implant prostheses have been routinely used to rehabilitate partial and complete edentulous patients due to their biocompatibility and high survival rates.1,2 However, in the posterior mandible with reduced alveolar bone height, implant length is further limited by the position of the inferior alveolar nerve.3,4 From the biomechanical aspect, occlusal bite forces are significantly higher in the posterior region (≥500 N) compared to the anterior region (7 mm. (e) May have exudates history.

Good to guarded, depending on the ability to reduce and control stress.

IV. Failure (clinical or absolute failure)

Any of following: (a) Pain on function. (b) Mobility. (c) Radiographic bone loss >1/2 implant length. (d) Uncontrolled exudates. (e) No longer in the mouth.

Failure in all statistical data.

lapse of 30 seconds between probing and scoring, were determined on mesial, distal, buccal and lingual surfaces of each implant. Averages of the four obtained values of each implant were calculated and considered as the index value.34 (3) Recession height was measured as the distance from the abutment finish line (abutment/crown junction) to the gingival margin. The width of the keratinized mucosa was measured as the distance from the gingival margin to the mucogingival junction.34 All readings were assessed in millimetres at the mid-facial and mid-lingual aspects of each implant. (4) Clinical attachment level was calculated by summing the values of the recession height and probing depth at the facial and lingual surfaces of each implant. (5) Implant stability was assessed by means of Periotest (Periotestâ M Instrument, Medizintechnik Gulden e.K. Modautal, Germany). It has the advantages of rapid, safe and non-invasive measurement35 that are useful for long-term implant follow-up. The measurements were performed by positioning the device perpendicular to the long axis of the implant within a distance of 0.6 to 2 mm from the crown facial surface. The assessment was repeated until the Periotest recorded © 2016 Australian Dental Association

Two adjacent short implants in posterior mandible almost two similar successive measurements. The measurements were identified as implants Periotest values (PTVs) and classified according to the manufacturer’s guide as follows: –0.8 to 0: good osseointegration, the implant is well integrated and pressure can be applied to it; +1 to +9: a clinical examination is required, the application of pressure on the implant is generally not possible; +10 to +50: osseointegration is insufficient and no pressure should be applied on the implant. (6) Radiographic peri-implant bone changes were measured on standardized digital intraoral periapical radiographs (RVG, Trophy Radiology, Inc., Marietta, GA, USA) at the mesial and distal surfaces of each implant. Intraoral radiographs were taken with a long cone paralleling technique (70 kV, 6 mA and 0.160 seconds). The radiographs were scanned (VistaScan scanner, D€ urr Dental AG, Germany) with an effective resolution of 22 lp/mm (1100 dpi) and images were digitized by using imaging software (D€ urr Dental AG, Bietigheim-Bissingen, Germany). The marginal bone level was determined by measuring the linear distance from the implant–abutment interface to the point of the first visible bone-toimplant contact.36 Both the mesial and distal implant sites were measured separately and an average value was calculated. Marginal bone changes were calculated as the difference between the last measurement (6 or 12 months) and the first (baseline) measurement for each implant. Negative values indicated bone loss and positive values indicated bone gain. (7) Crown-to-implant ratio (C/I) was determined by dividing the crown length to the implant length for all implants and then averaged. The crown length was measured from the highest point of the crown to the implant shoulder and the implant length from the implant shoulder to its apex, then ratios were calculated. For descriptive analysis, the C/I ratios were further categorized into two groups: C/I ratio ≤1 and C/I ratio >1. In order to correct the dimensional distortion of radiographic data, the accuracy of the radiograph measurements was achieved by measuring the implant width or height on the image and by using the known dimensions as a standard to calibrate the software measuring tools before each measurement. (8) Occlusal parameters included the relative maximum biting force and occlusion time were measured at 2, 6 and 12 months to evaluate changes in occlusal force balance over the observation time using T-Scan III system28 following the manufacturer’s protocol. © 2016 Australian Dental Association

Statistical analysis Data were analysed with the SPSS programme (IBM SPSS Statistics 20, Statistical Packages for Social Science, New York, USA). Shapiro–Wilk test and measures of skewness were used to determine the normality of distribution of all clinical and radiographic data. A p-value of 1

Age group (Years) Bone quality (Hounsfield units)

Implant location Arch side Abutment diameter (mm) Abutment angulation (˚)

Crown/Implant ratio

Biconâ Patients/implants n (%) 1 9 5 5 0 8 12 0 2 18 6 14 6 14 17 0 3 0 4 16

Ankylosâ Patients/implants n (%)

(10%) (90%) (50%) (50%) (0%) (40%) (60%) (0%) (10%) (90%) (31.6%) (68.4%) (30%) (70%) (85%) (0%) (15%) (0%) (20%) (80%)

5 5 6 4 2 3 11 4 0 20 10 10 7 13 15 1 0 4 1 19

(50%) (50%) (60%) (40%) (10%) (15%) (55%) (20%) (0%) (100%) (50%) (50%) (35%) (65%) (75%) (5%) (0%) (20%) (5%) (95%)

Total

P value*

6 14 11 9 2 11 23 4 2 38 16 24 13 27 32 1 3 4 5 35

0.01 0.7 0.04 Min Exp count = 1 0.07 0.3 0.9 0.043 Min Exp count = 0.50 0.1

*

Indicates between implant groups significant difference (p ≤ 0.05) based on chi-square test.

6-month intervals. However, at 12 months postloading a significant bone gain of 0.04 mm  0.33 was reported (p = 0.03). Biconâ implants demonstrated a bone gain of 0.07 mm  0.37 at 6 months and 0.12 mm  0.40 at 12 months postloading but this bone change was not significant (p = 0.3). The crown-to-implant ratio was comparable in both implant groups (1.4:1  0.21). The univariate model analysis based on bone changes at 6 and 12 months showed no detectable effect on bone with different implant systems (p = 0.44 and 0.17), implant length (p = 0.63 and 0.59) or C/I ratio (p = 0.76 and 0.66), respectively. Digital occlusal analysis showed no significant changes in relative maximum biting force and occlusion time between initial baseline and 12 months records for both implant groups (Fig. 3). Surgical and prosthetic complications Satisfactory clinical and radiographic outcomes were recorded over time with no noticeable signs or symptoms of biologic complications or unusual radiographic findings. In relation to technical complications, one case of abutment loosening in each implant group (two in total), and two cases of crown loosening were recorded in the Ankylosâ group. These complications were easily managed in the same visit without recurrence, indicating minimal postoperative complications in both implant groups. DISCUSSION The present preliminary randomized controlled trial evaluated and compared the success outcomes of 214

placing two adjacent short implants (8 mm length) of two different systems, loaded with single crowns in the posterior mandible. The clinical and radiographic implant outcomes of the two study groups were comparable and consistent with those reported in previous clinical studies on short implants,11 with no recorded implant failure up to 12 months post-loading. First-year outcomes have been reported to be crucial for the success of short implants.16,37 Indeed, the reported 100% one-year success rate in the present study provided evidence on the short-term high predictability of using short implants for partial rehabilitation of the posterior mandible. This finding is consistent with the results of previous short implant studies that reported survival/success rates ranging from 99% to 100%,11,16,38 and is higher than that reported in other studies.12,21 This high success rate may be attributed to implementing strict surgical and restorative protocols, appropriate patient selection, careful evaluation of the subject’s clinical history and accompanied radiologic evaluation. Careful treatment planning including periodontal and restorative treatments before implant placement to ensure periodontal health, careful adjustment and monitoring of the occlusion using the T-Scan system may also be contributing factors. The results showed healthy tissue and good oral hygiene that could be attributed to proper patient compliance with oral hygiene instructions and the reinforcement of oral hygiene in each follow-up visit. Our results are in agreement with that reported in single-tooth implants studies.39,40 Periotest values indicated satisfactory osseointegration and the overall decrease in PTVs over time indicated positive development of implant stability in © 2016 Australian Dental Association

Two adjacent short implants in posterior mandible Table 4. Mean ( standard deviation) and median (Quartiles) values of the clinical and radiographic parameters of Ankylosâ (n = 20) and Biconâ (n = 20) short implants at different observation intervals Parameter

PI

Implant system

Baseline n = 40 Mean (SD) Median (IQR)

2 months n = 40 Mean (SD) Median (IQR)

6 months n = 40 Mean (SD) Median (IQR)

12 months n = 40 Mean (SD) Median (IQR)

p** value

Ankylos

0.60 (0.29) 0.50 (0.0,0.50) 0.29 (0.27) 0.25 (0.0,0.5) 0.00 0.28 (0.44) 0.0 (0.0,0.0) 0.25 (0.08) 0.0 (0.0,0.0) 0.08 1.98 (0.45) 2.0 (1.75,2.25) 1.98 (0.56) 1.88 (1.66,2.19) 0.65 1.89 (0.37) 2.0 (1.56,2.00) 1.98 (0.51) 2.0 (1.66,2.19) 0.82 0.30 (0.37) 0.25 (0.0,0.50) 0.41 (0.48) 0.25 (0.0,0.94) 0.63 0.18 (0.37) 0.0 (0.0,0.0) 0.03 (0.11) 0.0 (0.0,0.0) 0.14 3.15 (1.06) 3.0 (2.5,3.88) 2.48 (0.95) 2.5 (2.0,3.0) 0.07 -1.61 (2.02) -1.95 (-3.,-1) 2.15 (2.52) 2.1 (0.23,3.5)

Outcomes of placing short implants in the posterior mandible: a preliminary randomized controlled trial.

Short dental implants can be an alternative to bone augmentation procedures at sites of reduced alveolar bone. Most studies on short implants are retr...
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