Baoxin Huang Huanxin Meng Weidong Zhu Lukasz Witek Nick Tovar Paulo G. Coelho

Authors’ affiliations: Baoxin Huang, Huanxin Meng, Weidong Zhu, Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing, China Baoxin Huang, Department of Oral Implantology, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China Baoxin Huang, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China Lukasz Witek, Nick Tovar, Paulo G. Coelho, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA Lukasz Witek, School of Chemical Engineering, Oklahoma State University, Stillwater, OK, USA Paulo G. Coelho, Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, NY, USA

Influence of placement depth on bone remodeling around tapered internal connection implants: a histologic study in dogs

Key words: animal study, biologic width, crestal bone resorption, implant-abutment interface,

subcrestal placement Abstract Objectives: To evaluate the influence of implant-abutment interface (IAI) placement depth on bone remodeling around implants with two different types of tapered internal IAI: screwed-in (SI) and tapped-in (TI) connections in dogs. Materials and methods: Eight weeks post mandibular tooth extraction in six beagle dogs, two SI implants (OsseoSpeedTM, Astra Tech, DENTSPLY) and two TI implants (Integra-CPTM, Bicon LLC) were placed in one side of the mandible. The four experimental groups were as follows: (i) SI-placed equicrestally (SIC); (ii) TI-placed equicrestally (TIC); (iii) SI-placed 1.5 mm subcrestally (SIS); and (iv) TI-placed 1.5 mm subcrestally (TIS). Healing abutments were connected 12 weeks after implant placement. Sixteen weeks later, the dogs were sacrificed and histomorphometric analysis was performed. Histometrical outcomes were evaluated using a nonparametric Brunner–Langer model. Results: Mean distance from the IAI to first bone-implant contact (IAI-fBIC) was 0.88 mm (median:

Corresponding author: Dr. Huanxin Meng Department of Periodontology Peking University School and Hospital of Stomatology Zhongguancun Nandajie No. 22, Haidian District, Beijing 100081, China Tel.: 86 10 82195372 Fax: 86 10 62173402 e-mail: [email protected]

0.77; SD: 0.54) for SIC group, 1.23 mm (median: 1.22; SD: 0.66) for TIC group, 0.41 mm (median: 0.31; SD: 0.36) for SIS group, and 0.41 mm (median: 0.26; SD: 0.45) for TIS group. Subcrestal groups showed lower IAI-fBIC compared with equicrestal groups (P < 0.001). Connective tissue presented similar measurements regardless of the IAI placement depth and IAI type (P > 0.05), but the epithelium length and peri-implant soft tissue length in subcrestal groups were significant larger than that in the equicrestal groups (P < 0.001 and P = 0.004, respectively). Conclusion: Subcrestal implant placement with tapered internal IAI is beneficial for bone contact with the implant neck, and concurrently, it may not increase the soft tissue inflammation around IAI.

Date: Accepted 5 March 2014 To cite this article: Huang B, Meng H, Zhu W, Witek L, Tovar N, Coelho PG. Influence of placement depth on bone remodeling around tapered internal connection implants: a histologic study in dogs. Clin. Oral Impl. Res. 26, 2015, 942–949 doi: 10.1111/clr.12384

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The replacement of missing teeth by implant-supported prosthesis has become an evidence based treatment modality in dentistry. Clinically, two-stage implants are often placed subcrestally in esthetic areas for an ideal emergence profile (Buser & von Arx 2000; Barros et al. 2010). Additionally, subcrestal implant placement may reduce strain levels in peri-implant bone from biomechanical perspective (Chou et al. 2010). However, the interface or microgap between the implant and abutment has been suggested to have a detrimental effect on the marginal bone level (Hermann et al. 1997; Broggini et al. 2006). Several previous in vitro studies have been carried out to evaluate the potential microbial leakage at the implant-abutment interface (IAI) (Jansen et al. 1997; Dibart et al.

2005; Coelho et al. 2008; Aloise et al. 2010; do Nascimento et al. 2012). The capability of bacteria, fluid and small molecules passing through the IAI was proven by several studies. Furthermore, clinical investigations have also confirmed that the presence of microbes associated with pathology on the interior of the two-stage implant (Callan et al. 2005; Cosyn et al. 2011). Results from animal experiments indicated that crestal bone was located ~1.5 to 2 mm below the IAI of custom-made two-part implants (Hermann et al. 1997, 2000). Peri-implant inflammatory cell accumulation was significantly increased in implants with subcrestal IAI compared to implants with crestal IAI (Broggini et al. 2006). Likewise, lower peri-implant crevicular fluid and lower levels of inflammatory factor such as interleukin-1 beta and tumor

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Huang et al  Bone level of crestal vs. subcrestal implant

necrosis factor-alpha around implants with supra-crestal placement of IAI compared to implants with crestal placement of IAI were reported recently (Boynuegri et al. 2012). Thus, while supra-crestal implant placement of IAI was recommended, pure interferencefit connections or one-piece implants may be the suitable alternatives (Broggini et al. 2006). In recent years, the concept of platformswitching design using abutments with a reduced diameter has been proposed to reduce the detrimental effects related to the microgap of IAI (Lazzara & Porter 2006; Barros et al. 2010; Farronato et al. 2012). Clinical studies reported that the platformswitching concept was beneficial for maintaining the peri-implant crestal bone (Donovan et al. 2010; Annibali et al. 2012). However, some studies did not indicate significant differences in crestal bone resorption between mismatched and matched abutments (Becker et al. 2007, 2009). Another clinical study showed that implants with platform-switched abutments exhibited significantly less bone loss only in subcrestal locations compared to those with matched abutments (Veis et al. 2010). It should be noted that different IAI designs might cause different peri-implant bone defects, and a more recent animal study reported that implants with an internal conical abutment connection had greater bone preservation than implant with parallel internal abutment connection (Heitz-Mayfield et al. 2013). Implants with tapped-in (TI) internal conical abutment connection (locking-taper) possess a unique microbial sealing ability, as reported in vitro (Dibart et al. 2005). And a clinical study exhibited that freestanding single-tooth implant restoration using an implant with locking-taper connection seemed a reliable solution to treat posterior edentulism (Muftu & Chapman 1998). However, there is limited information available regarding the influence of vertical insertion depth on soft and hard tissue around this type of IAI configuration. Furthermore, it was unclear whether there was different periimplant soft and hard tissue response between implants with tapped-in internal conical or screwed-in internal conical abutment connections. Therefore, the present study aimed to evaluate the soft and hard tissue histologic dimensions around implants with tapped-in (TI) internal conical abutment connection (Bicon LLC, Boston, MA, USA)-placed crestally and subcrestally, compared with implants with screwed-in (SI) internal conical abutment

connection (Astra, canine model.

M€ olndal,

Sweden)

in

Material and methods Animals

The experimental protocol (No. LA2010–032) was evaluated and approved by the Medical Ethical Committee for Animal Investigations of Peking University Health Science Center in Beijing, China. Six beagle dogs, 1–2 years old, weighting ~10–12.5 kg, were included in the experiment. The dogs were housed individually and fed once per day with soft food and water during the experiment. All surgical procedures were performed under general anesthesia, using intravenous sodium pentobarbital (30 mg/kg). Implants

Schematic implants used in this study are presented in Fig. 1. Implants with screwed-in tapered internal IAI (SI) (3.5 9 8 mm; Astra

Fig. 1. Schematic implants with tapered internal implant-abutment interface used in this study. SI, screwed-in connection; TI, tapped-in connection.

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Tech Dental, M€ olndal, Sweden) have screw root form and micro-thread (MicrothreadTM; Astra Tech AB) at their coronal collar with a fluoride-modified TiO-blast surface (OsseospeedTM; Astra Tech AB). Implants with tapped-in tapered internal IAI (TI) (3.5 9 8 mm; Bicon Dental Implant, Boston, MA, USA) have plateau root form and sloping shoulder with plasma-sprayed calcium phosphate surface (Integra-CPTM; Bicon Dental Implant). Surgical procedure

At the start of the experiment, three premolars (second, third, and fourth premolar) and the first molar were extracted on both sides of the mandible in each dog. After an 8-week healing period, implant surgery was performed. Two SI implants and two TI implants were placed on one side of mandible of each dog (n = 24). The four experimental groups were as follows: SI-placed equicrestally (SIC); TI-placed equicrestally (TIC); SI-placed 1.5 mm subcrestally (SIS); and TI-placed 1.5 mm subcrestally (TIS) (Fig. 2). Anterior and posterior positions between implant systems were alternated to minimize any bias. Additionally, the order of equicrestal and subcrestal groups within the same implant system was randomly determined. Supragingival calculus was removed by supragingival scaling one week prior to the surgical procedures. For implant placement, horizontal crestal incisions were made from the distal region of the first premolar to the mesial region of the second molar. Buccal and lingual mucoperiosteal flaps were elevated in the mandibles. The edentulous osseous ridge was flattened, and osteotomies for implants were drilled according to recommendation from manufacturers. Commercial surgical kits for corresponding implant systems were used. Subsequently, two SI and two TI implants were placed. For standardizing the depth of subcrestal implant, vertical distance between crestal bone and IAI was measured using a periodontal probe (UNC-15; Hu-Friedy, Chicago, IL, USA) during implant placement. The depth of implant placement was further confirmed by standardized periapical radiographs. A distance of approximately 10 mm between dental implant centers was maintained to avoid interaction among the bone defects. Subsequently, covering screws and/or plug inserters were adjusted in order to allow a submerged healing protocol. Flaps were sutured with 4-0 nylon sutures. Antibiotic (penicillin G procaine 40,000 IU/kg intramuscular) and analgesic were administered once every 24 h for

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Huang et al  Bone level of crestal vs. subcrestal implant

Fig. 2. Clinical images of the four groups at implant placement. From left to right: TIS, TIC, SIS and the SIC.

7 days. During the first week post surgery, the local wound area was carefully cleaned with 0.12% chlorhexidine solution. The sutures were removed after 10 days of healing. After 12 weeks of healing, the second-stage surgery was carried out by performing small crestal incisions without raising the buccal and lingual flaps to minimize bone loss caused by the exposure of bone. Cover screws and/or plug inserters were removed and replaced by healing abutments and/or temporary abutments. Special attention was taken to avoid occlusal contact. Implant sites were irrigated with 0.12% chlorhexidine every second day for the first 10 days following surgery. Subsequently, a plaque control program that included cleaning of implants and teeth using a toothbrush every other day was initiated. Clinical and radiographic parameters were recorded at 4, 10, and 16 weeks after second-stage surgery, which were reported previously (Huang et al. 2012). Histological preparation

Sixteen weeks after the second-stage surgery, sacrifice was performed by over-dose via intravenous injections of sodium pentobarbital and perfused through the carotid arteries with a fixative containing 4% formaldehyde. The mandibles were removed and placed in the fixative. Buccal peri-implant gingival tissues specimens were collected by a surgical incision longitudinally targeting the implant. Blocked sections of the implant sites from the mandible were created using an oscillating saw such that the mesial and distal soft tissues remained intact. The bone blocks were fixed in 4% formaldehyde, followed by a gradual dehydration using a series of alcohol solutions ranging from 70% to 100% ethanol. Following dehydration, the samples were embedded in a methacrylate-based resin (Technovit 9100; Heraeus Kulzer GmbH, Wehrheim, Germany) for non-decalcified sectioning. From each implant unit, one buccal– lingual section and one distal section (~300 lm thickness) were prepared aiming the center of the implant along its long axis with a precision diamond saw (Isomet 2000;

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Buehler Ltd, Lake Bluff, IL, USA), glued to acrylic plates with an acrylate-based cement, and a 24-h setting time was allowed before grinding and polishing. The sections were then reduced to a final thickness of ~30 lm by means of a series of SiC abrasive papers (400, 600, 800, 1200, and 2400) in a grinding/ polishing machine under water irrigation (Marin et al. 2010). The buccal–lingual sections were then toluidine blue-stained. The distal sections were stained with a Goldner trichromic staining for the visualization of soft tissue. Histologic analyses

All sections were referred to optical microscopy for histomorphologic evaluation. The following landmarks were identified (Fig. 3): IAI, implant-abutment interface; PM, periimplant free mucosal margin; aJE, apical position of the junctional epithelium; and fBIC, first bone-to-implant contact. The following linear measurements in distal sections were performed parallel to the long axis of the implant: IAI-fBIC, bone level; PM-aJE, epithelial length; aJE-fBIC, connective tissue length; and PM-fBIC, peri-implant soft tissue length (the sum of epithelial length and connective tissue length). Buccal, lingual, and distal bone levels were measured independently. Statistical analysis

The SPSS software (SPSS 18.0, Chicago, IL, USA) and the R software (version 3.0.1; R foundation for Statistical Computing, Vienna, Austria) were used for data analysis, including values for mean, median, standard deviation (SD), the range from the lower quartile (25th percentile) to the upper quartile (75th percentile). The R-library “nparLD 2.1” (Noguchi et al. 2012) was used to perform the Brunner–Langer nonparametric analysis of longitudinal data in factorial experiments (Brunner et al. 2002). Effects of IAI placement depth, IAI type, and their interaction on peri-implant bone level and soft tissue dimensions were assessed. P < 0.05 was considered as being statistically significant.

Fig. 3. Landmarks used for the soft tissue dimensions and bone level calculation: PM, Peri-implant free gingival margin; aJE, apical position of the junctional epithelium; IAI, implant-abutment interface; fBIC, first bone-to-implant contact.

Results Clinical findings

During the experiment, healing was uneventful in all implants. Clinical healthy periimplant mucosa was observed around implant at the follow-up examinations. The experimental procedures had no influence on the health status of each animal. Histologic observations

Regardless of the implant system and the insertion depth of the implants, direct contact was observed between bone and all implants. Images of each group are presented in Figs 4–7. IAIs in the equicrestal groups were located at the coronal position of the ridge (Figs 4 and 6), and at the apical position in the subcrestal groups (Figs 5 and 7). In sections of subcrestal groups, bone had established histological contact in proximity of IAI (Fig. 8). Histomorphometric results

The buccal orientation had significantly larger IAI-fBIC in comparison with the lingual

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Huang et al  Bone level of crestal vs. subcrestal implant

and distal measurements of each implant were averaged and used in the analyses of comparing implant subgroups. Results of the histometric measurements are summarized and presented in Table 1. The mean IAI-fBIC was 0.88 mm (median: 0.77; SD: 0.54) for SIC group, 1.23 mm (median: 1.22; SD: 0.66) for TIC group, 0.41 mm (median: 0.31; SD: 0.36) for SIS group, and 0.41 mm (median: 0.26; SD: 0.45) for TIS group. A statistically significant effect of IAI placement depth on bone level (IAI-fBIC) has been revealed, where subcrestal groups showed lower IAI-fBIC compared with equicrestal groups (P < 0.001) (Tables 1 and 2). Independent of the two IAI types, the epithelial length (PM-aJE), and peri-implant soft tissue length (PM-fBIC) in the subcrestal groups were significantly larger than that in the equicrestal groups (P < 0.001 and P = 0.004, respectively) (Tables 1 and 2). IAI placement depth and IAI type had insignificant effect on peri-implant connective tissue length (P > 0.05) (Tables 1 and 2).

Fig. 4. Histological image of SI implant-placed equicrestally (SIC). L, lingual (toluidine blue stain); D, distal (Goldner trichromic stain).

Fig. 5. Histological image of SI implant-placed 1.5 mm subcrestally (SIS). L, lingual (toluidine blue stain); D, distal (Goldner trichromic stain).

and distal orientation (P < 0.001), and the lingual and distal orientation did not indicate a significant difference (P = 0.394). The

differences in IAI-fBIC between the buccal aspects and lingual and distal aspects ranged from 1.19 to 1.26 mm. As a result, lingual

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Discussion In this study, Brunner–Langer nonparametric analysis of longitudinal data in factorial experiments was applied to determine the main effect of the differences observed. In the variables of IAI-fBIC, PM-aJE, and PMfBIC, only IAI placement depth had a significant effect without interaction with the IAI type. The results of this experimental study revealed that significantly lower IAI-fBIC around implant with internal conical abutment connection-placed subcrestally when compared with those placed equicrestally. Bone directly contacted to the implant neck around IAI of subcrestal implants. In addition, the epithelial dimension and periimplant soft tissue lengths were larger in the subcrestal implant compared with those of the equicrestal implant. There were no significant differences in bone level and soft tissue dimension between the two different implant designs. The IAI of two-piece implants might play an important role in the crestal bone remodeling, which has been emphasized in several studies (Hermann et al. 2000; Broggini et al. 2006). Hermann et al. investigated the crestal bone changes around one-piece implants and two-piece implants with microgap of IAI about 50 lm in a dog model. They concluded that greater amounts of bone loss were observed if the microgap was moved apical to the alveolar crest. Further study results

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Fig. 6. Histological image of TI implant-placed equicrestally (TIC). L, lingual (toluidine blue stain); D, distal (Goldner trichromic stain).

Fig. 7. Histological image of TI implant-placed 1.5 mm subcrestally (TIS). L, lingual (toluidine blue stain); D, distal (Goldner trichromic stain).

from the same research group showed that subcrestal placement of IAI promoted a significantly greater maximum density of

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inflammatory reaction, which correlated with bone loss (Broggini et al. 2003, 2006). In this context, it should be noted that a microgap

of IAI of about 50 lm was not really comparable with microgaps of commercially available implants used in the clinic, which usually never exceed 10 lm (Jansen et al. 1997). In the present study, the interesting finding that subcrestal groups had low IAI-fBIC (mean IAI-fBIC: 0.41 mm for SIS, 0.41 mm for TIS) and had established fBIC in proximity of IAI was in contrast with previously reported observations. One obvious difference between the current study and the previous studies was the implant-abutment configuration. Both implants used in present study were the internal conical abutment connection, which has better tightness and rigidity than those with matched (butt-joint)-abutment connection (Jansen et al. 1997; Tesmer et al. 2009). Previous in vitro studies have shown tapped-in and screwed-in internal conical abutment connection could prevent or minimize the bacterial leakage along the IAI, even when different experimental conditions were used (Dibart et al. 2005; Aloise et al. 2010). This performance may be attributed to the slight gap size at the implant-abutment connection of conical abutments. A marginal gap size of less than 0.5 lm was found for the TI implant and of ~1–2 lm for the SI implant (Jansen et al. 1997; Dibart et al. 2005). Therefore, the present results could be partly explained by the absence or reduced presence of bacteria in the microgap of these implants. Several in vivo studies supported our explanation. Weng et al. (2008) reported that the “dish shaped” defect configuration was more pronounced in implant with external hex butt-joint connection compared with implant with conical abutment connection. Recently, Heitz-Mayfield et al. (2013) in an experiment in minipigs, also found that implants with parallel internal connection had greater bone loss compared with two commercially available implants with internal conical abutment connection. Furthermore, Welander et al. (2009) found that healing of implants placed in a subcrestal position could result in osseointegration to the abutment region of the implant. These results and the findings of the present study might illustrate that the microgap or microbial leakage between the implant and conical abutment, if exist, might not contribute to bone loss. In this study, mean IAI-fBIC in implants of the equicrestal groups was 0.88 mm and 1.23 mm for the SI group and the TI group, respectively. Ridge loss of approximately 0.38–0.62 mm was primarily caused by surgical trauma and was established at the time of

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Huang et al  Bone level of crestal vs. subcrestal implant

Fig. 8. Histologic microphotograph showing the bone established histological contact in proximity of implant-abutment interface (IAI) (red arrow showed the fBIC); toluidine blue stain. fBIC, first bone-implant contact.

second-stage surgery by the X-ray evaluation (Huang et al. 2012). Thus, subcrestal placement of such implant should be favored to avoid metal exposure in cases within the esthetic zone. Additionally, two different types of tapered internal IAI were compared. Except IAI, other implant features, such as implant neck shape, implant surface characteristics, formation of biological width, surgical trauma, and thread design, may also affect the loss of crestal bone level (Berglundh & Lindhe 1996; Oh et al. 2002; Abrahamsson & Berglundh 2009). Result of present study showed that SI and TI implants have comparable bone level

and soft tissue dimension. Two design similarities that may have contributed to the present result are the internal conical IAI and rough collar design. Studies showed that bone tissue favors rough implant surfaces compared with relatively smooth titanium surfaces (H€ammerle et al. 1996; Schwarz et al. 2008). Another interesting observation in the present study was the fact that PM-fBIC in subcrestal groups was larger than that in equicrestal groups. The variability in PMfBIC was mainly contributed by the variability in epithelium. Connective tissue dimension was similar among the four groups,

which was independent to the IAI placement depth. This result differed from Todescan et al. (2002) who reported that subcrestal implant had larger epithelium and connective tissue dimension compared with those of equicrestal implant. The higher amount of epithelium and connective tissue noted in Todescan’s study might be from more pronounced bone loss in subcrestal implants with a matched (butt-joint)-abutment connection. This study, the connective tissue dimension was relatively constant, and bone had established histological contact in proximity of IAI, meaning that such IAI designs might greatly reduce marginal inflammation. These findings were in accordance with a recent animal study by Cochran et al. (2013), in which similar results were obtained using another commercial implant with screwed-in internal conical abutment connection. The epithelium in subcrestal groups was larger than that in crestal groups, which corroborates the clinical observation of greater periimplant probing depth in subcrestal groups than in equicrestal groups (Huang et al. 2012). This observation suggests that in clinical indications where implant with tapered internal IAI was placed subcrestally, apical extension of the junctional epithelium seemed to be predictable. In this context, it must be emphasized that since clinical probing is an essential procedure for the diagnosis and monitoring of peri-implant diseases (Lindhe et al. 2008) and probe penetration tented to stop at the histological level of connective tissue adhesion in health condition (Lang et al. 1994), the establishment of baseline probing depth value for subcrestal implant was important for monitoring the peri-implant soft tissue status. However, results should be interpreted with caution regarding to the small sample sizes. The validity of these results and its clinical relevance need to be addressed in further studies.

Table 1. Descriptive statistics for the measured outcomes* Equicrestal Outcome

Parameter

SI (SIC)

IAI-fBIC (mm)

Mean  SD Median (Q1, Mean  SD Median (Q1, Mean  SD Median (Q1, Mean  SD Median (Q1,

0.88 0.77 1.32 1.23 0.71 0.77 2.03 2.11

PM-aJE (mm) aJE-fBIC (mm) PM-fBIC (mm)

Q3) Q3) Q3) Q3)

 0.54 (0.53, 1.48)  0.68 (0.76, 2.03)  0.41 (0.26, 1.02)  0.91 (1.21, 2.88)

Subcrestal TI (TIC) 1.23 1.22 1.51 1.50 1.19 1.00 2.70 2.46

 0.66 (0.61, 1.83)  0.13 (1.40, 1.64)  0.73 (0.73, 1.55)  0.82 (2.17, 3.10)

SI (SIS) 0.41 0.31 2.12 2.02 1.11 1.10 3.23 3.39

 0.36 (0.15, 0.61)  0.77 (1.60, 2.97)  0.30 (0.89, 1.25)  0.85 (2.62, 3.93)

TI (TIS) 0.41 0.26 1.92 1.87 1.18 1.11 3.10 3.23

 0.45 (0.08, 0.78)  0.45 (1.62, 2.30)  0.57 (0.64, 1.72)  0.73 (2.60, 3.68)

IAI-fBIC, bone level; PM-aJE, epithelial length; aJE-fBIC, connective tissue length; PM-fBIC, peri-implant soft tissue length; SD, standard deviation; Q1, first quartile; Q3, third quartile; SI, screwed-in IAI; TI, tapped-in IAI; SIS, SI-placed 1.5 mm subcrestally; TIC, TI-placed equicrestally; SIC, SI-placed equicrestally; IAI, implant-abutment interface. * n = 6. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

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Table 2. Effects of IAI placement depth, IAI type, and their interaction on peri-implant bone level and soft tissue dimensions IAI placement depth (Equicrestal vs. Subcrestal)

IAI-fBIC PM-aJE aJE-fBIC PM-fBIC

IAI placement depth 9 IAI type

IAI type (SI vs. TI)

Statistic*

P-value

Statistic*

P-value

Statistic*

P-value

15.868 26.022 1.151 8.073

Influence of placement depth on bone remodeling around tapered internal connection implants: a histologic study in dogs.

To evaluate the influence of implant-abutment interface (IAI) placement depth on bone remodeling around implants with two different types of tapered i...
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