Horizontal and Vertical Ridge Augmentation in Localized Alveolar ...

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IMPLANT DENTISTRY / VOLUME 21, NUMBER 3 2012

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Horizontal and Vertical Ridge Augmentation in Localized Alveolar Deficient Sites: A Retrospective Case Series Susanna Annibali, MD, DDS,* Isabella Bignozzi, DDS, PhD,† Gilberto Sammartino, MD, DDS,‡ Gerardo La Monaca, DDS, PhD,§ and Maria Paola Cristalli, DDS, PhDk

he rehabilitation of partial and total edentulism using dental implants is a modality of treatment that has predictable long-term clinical outcomes.1–4 Nevertheless, a poor bone volume following clinical situations such as long-time edentulism, dental trauma, periodontal breakdown, and untreated chronic infections can prevent appropriate implant placement in a prosthetically guided position. Several techniques have been proposed to recreate adequate bone volume and morphology at alveolar edentulous deficient ridges. It has been demonstrated that onlay bone graft harvesting from intraoral or extraoral sites is a predictable procedure,5–8 although few data are available regarding the long-term dimensional stability of grafted bone.9 Furthermore, this technique is associated with

T

*Associate Professor of Oral Surgery, Department of Oral and Maxillofacial Sciences, “Sapienza” University of Rome, Rome, Italy. †Lecturer, Department of Oral and Maxillofacial Sciences, “Sapienza” University of Rome, Rome, Italy. ‡Associate Professor of Oral Surgery, Department of Oral and Maxillofacial Sciences, University of Naples Federico II, Naples, Italy. §Lecturer, Department of Oral and Maxillofacial Sciences, “Sapienza” University of Rome, Rome, Italy. kAssistant Professor of Oral Surgery, Department of Oral and Maxillofacial Sciences, “Sapienza” University of Rome, Rome, Italy.

Reprint requests and correspondence to: Susanna Annibali MD, DDS, Department of Oral and Maxillofacial Sciences, “Sapienza” University of Rome, 6, Caserta St., 00161 Rome, Italy, Phone: +39 06 49976651, Fax: +39 06 44230811, E-mail: susanna. [email protected] ISSN 1056-6163/12/02103-175 Implant Dentistry Volume 21  Number 3 Copyright © 2012 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0b013e31824ee3e9

Purpose: This study reviews the clinical outcomes of ridge augmentations performed via horizontal- or vertical-guided bone regeneration (h-GBR, v-GBR) or edentulous ridge expansion. Materials and Methods: The degree of defect correction, the marginal bone level, and the horizontal stability of the augmented bone (five patients) were examined with a new proposed rigid resin survey template. Results: Thirty ridge defects ranging from 1 to 8 mm were corrected, and 56 implants were positioned. The percentages of alveolar defect correction were 91.85% 6 22.30%, 97.13% 6

4.48%, and 90.42% 6 11.93% for h-GBR, edentulous ridge expansion, and v-GBR, respectively; a limited amount of marginal bone level was reported for all three groups, while a large amount of horizontal bone resorption was detected. Conclusions: All surgical techniques considered in this study are predictable procedures, and the proposed survey template measurement system showed to be a reliable method of evaluating horizontal bone stability of the augmented ridges. (Implant Dent 2012;21:175–185) Key Words: dental implants, ridge augmentation, guided bone regeneration, ridge expansion, split crest, bone stability

significant morbidity and requires a second surgical site. Distraction osteogenesis allows for a natural formation of bone and soft tissues between the basal and the distracted segments with restricted morbidity and operating time.10 Nevertheless, a poor control of the trajectory of distraction in the planes of space11,12 as well as considerable long-term bone resorption have been reported.13 The Le Fort I osteotomy with interpositional or revascularized bone grafts is recommended in the presence of severe atrophy and unfavorable

intermaxillary relationships14 or for the reconstruction of maxillary and mandibular wide defects after oncologic surgery.15 These techniques have extremely limited clinical applications, are highly sensitive to the skill of the operator, require general anesthesia, and imply a relevant postoperative morbidity.16,17 Guided bone regeneration (GBR) is a well-documented surgical procedure that was designed to provide atrophic alveolar ridge augmentation and correct development of deficient implant sites.18–20 The rationale underlying the

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Fig. 1. Cortical bone drilled to expose marrow spaces: (A) vertical defect, (B) horizontal defect.

Fig. 2. Bone particles positioned to cover the exposed implant surfaces: (A) vertical defect, (B) horizontal defect.

Fig. 3. Expanded polytetrafluoroethylene (e-PTFE) titanium-reinforced membrane secured to the bone surface with titanium fixation screws: (A) vertical defect (Gore-Tex membrane), (B) horizontal defect (Citoplast membrane).

Edentulous ridge expansion (ERE) aims to correct horizontal ridge deficiencies using a high-precision sagittal osteotomy and a controlled greenstick fracture that moves the buccal bone plate laterally. The result is the creation of a wider bony bed for simultaneous ideal implant placement,26–29 increasing the amount of well-keratinized gingiva and restoring both the mucogingival line and the fornix depth at the expanded site.30 Ridge expansion is a suitable technique for correcting areas of great bone deficiency with limited morbidity.26–29 Nevertheless, most studies that have focused on implants placed in regenerated bone have only considered the implant survival rate and, if available, the clinical success rate, with no evaluations of the amount of augmented bone and its stability.9 Augmented bone stability has been evaluated in only a few studies by the vertical measurement of marginal bone level (MBL) using periapical radiographs. Measurements of regenerated ridge stability are difficult to obtain unless reentry surgery28,31 or follow-up CT scans are made, procedures that are both associated with great biologic and economic impact for patients. This study assessed retrospectively the clinical results of GBR and ERE techniques considering the following parameters for each procedure: success rate of the augmentation technique, survival and success rates of the implants, and stability of the augmented bone.

MATERIALS

AND

METHODS

Patient Selection

Fig. 4. Surgical reentry: the implants completely surrounded by new-formed bone: (A) regenerated bone in the vertical defect site, (B) regenerated bone in the horizontal defect site.

GBR protocol lies in the prevention of undesirable, nonosteogenic cells from growing into the bony defect by providing a mechanical barrier. There is strong

evidence for the effectiveness and predictability of GBR in promoting vertical and lateral bone augmentation of ridge deficiencies.21–25

All patients who were consecutively treated with bone augmentation procedures according to GBR or ERE surgical protocols between May 2006 and January 2009 at the Oral Surgery Operative Unit of Sapienza–University of Rome meeting the following inclusion criteria were selected:  Patient treated with horizontal GBR (h-GBR), ERE, or vertical GBR (v-GBR) for localized edentulous ridge bone defects.  Availability of complete clinical records, including clinical

IMPLANT DENTISTRY / VOLUME 21, NUMBER 3 2012

Fig. 5. Buccal bone displaced facially.

Fig. 6. Implant placement in a prosthetically guided position.

Fig. 7. Survey template evaluation of the long-term horizontal bone stability.

photographs, diagnostic casts, wax-up, radiographic/surgical templates, panoramic radiographs and (CT) DentaScan, as needed, and periapical radiographs and clinical parameters taken at each follow-up recall. Exclusion criteria to treatment at the time of recruitment were impaired systemic conditions, smoking habit of more than 10 cigarettes per day,32 full

mouth plaque score, and full mouth bleeding score of .25%. All subjects provided written informed consent to undergo the augmentation surgical procedure and, if possible, simultaneous implant insertion. Clinical Procedures

For all patients, the prosthetically ideal positions of the fixtures was identified by means of a radiographic

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surgical template, according to a previously described procedure.33 Surgical technique selection was made in accordance with the therapeutically oriented defect classification presented by Tinti and Parma-Benfenati.34 During GBR technique,21 the bony defects around implants were evaluated clinically by using a 15-mm periodontal probe (XP23/UNC15, Hu-Friedy, Chicago, IL) for vertical defects and two perpendicularly crossed periodontal probes for horizontal defects. Cortical bone was drilled with a 0.5- to 0.8mm round surgical bur to expose the marrow spaces and to increase bleeding (Fig. 1, A and B). Either titanium-reinforced expanded polytetrafluoroethylene (GoreTex TR6Y or TR9W, W.L. Gore, Flagstaff, AZ; Citoplast Ti25OXL, Osteogenics Biomedical, Inc. Lubbock, TX) or resorbable membranes (BioGide, Geistlich Pharmaceutical, Wolhusen, Switzerland) were used depending on the defect morphology. The exposed implant threads were covered with autogenous bone chips which had been harvested using a grafter (Safescraper TWIST, Meta, C.G.M. S.p.a., Reggio Emilia, Italy) peripherally within the same surgical site. The autograft was enhanced with a second layer of demineralized freezedried bone allograft (DFDBA; Tutogen Medical, Neunkirchen am. Brand, Germany) or Bio-Oss (Geistlich Pharmaceutical) to achieve the desired amount and shape of bone graft and to overcontour the desired final anatomy18,35 (Fig. 2, A and B). The membrane was secured to the bone surface with titanium fixation screws (Fig. 3, A and B). A tension-free primary closure was achieved and stabilized with a double suture line (W.L. Gore). A checkup radiograph was then taken (T0). Reentry surgery was performed after 6 to 9 months of submerged membrane healing (Fig. 4, A and B). A clinical evaluation of ridge size was performed, in the same manner as in the first-stage surgery, to recalculate the bone dimension. At provisional restoration screwing (T1), a checkup periapical radiograph was taken using the long-cone parallel technique. After 3 months, a cementfused porcelain-to-metal final restoration

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Table 1. Characteristics of Patients and Clinical Results in Group A (Horizontal-GBR)

Patient No.

Augmentation Site

Implant Site

1A 2A 3A

1A-1 2A-4 3A-4

4A§

4A-1

1.3 4.6 4.5 4.6 4.7 1.4k 1.6k 2.4k 2.6k 4.1 3.1 2.5 2.7 3.1 4.1 1.4 1.6 1.7 2.4k 2.6k 2.7k

4A-2 5A 6A 7A

5A-4 6A-3 7A-2

8A

8A-3/4

9A#

9A-1 9A-2

Total Mean 6 SD Range

Implant Manufacturer, Type, and Dimension S & M, Pilot, 3.8 3 13 S & M, Pilot, 6.7 3 10.5 TBR, 4 3 13 5 3 10 5 3 10 Nobel Speedy, 4310 538 Nobel Speedy, 4310 538 Nobel Straight, 3.5 3 13 Nobel Straight, 3.5 3 13 S & M, Pilot, 3.8 3 13 6.7 3 13 S & M, Pilot, 3.4 3 13 3.4 3 13 S & M, Pilot, 3.8 3 13 5.7 3 13 5.7 3 13 S & M, Pilot, 3.8 3 13 5.7 3 13 5.7 3 13

Regeneration Materials AP + Bio-Oss + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + Bio-Gide Res M AP + DFDBA + Gore-Tex NRM¶ AP + DFDBA + Gore-Tex NRM AP + Bio-Oss + Bio-Gide ResM AP + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + Bio-Oss + DFDBA + Gore-Tex NRM AP + Bio-Oss + DFDBA + Gore-Tex NRM**

11

h-Defect (mm)

Bone Gain (mm)

1.5 2 2 2 2 8 8.5 8 8.5 1 1 4 8 2 2 3 3 3.5 3 3 4

1 2 2 2 2 8 8 8 8 1 1 4 7 2 2 3 3 3 3 3 3

3.80 6 2.64 3.61 6 2.51 1–8.5 1–8

* Provisional crown delivery. † Final crown delivery. ‡ Last available follow-up. § Patient 4A corresponds to patient 2C in Table 3. k Implants placed via a staged approach. ¶ Membrane exposure 1 month after surgery. # Patient 9A corresponds to patient 5C in Table 3. ** Membrane exposure 2 months after surgery. AP indicates autogenous particulate; DFDBA, demineralized freeze-dried bone allograft; Res M, resorbable membrane; NRM, nonresorbable membrane; S & M, Sweden & Martina; h-defect, horizontal defect; MBL, marginal bone level; M, mesial; D, distal; BBR, buccal bone resorption; NR, not recorded.

was delivered and a standardized periapical radiograph, using a Rinn film holder (Dentsply Rinn, Elgen, IL) customized by polymerizing polyvinylsiloxane onto the occlusal surfaces of the final restoration, was taken (T2). During ERE technique,26 the buccal bone was displaced facially including at least 3 mm of cortical bone and 1.5 mm of spongy bone (Fig. 5), while a cortical bone plate at least 1-mm thick was left intact at the oral side. The top of the ridge was measured before and after expansion to quantify the reached bone gain with a 15-mm periodontal probe. The implants were placed according to the prosthetic need (Fig. 6). In case of crestal lack of soft tissues, a lyophilized equine collagen coat (Gingistat, Gaba Vebas, San Giuliano Milanese, Italy) was laid to support secondary intention healing. Interrupted 4-0 and 5-0 GoreTex sutures were placed to fit the flaps around healing abutment. A checkup radiograph was taken (T0).

A further checkup periapical radiograph was taken using the long-cone parallel technique at provisional restoration screwing (T1). After 3 months, a cement-fused porcelain-to-metal final restoration was delivered and a standardized periapical radiograph was taken at this stage (T2). All patients were included in a quarterly professional oral hygiene recall plan. Clinical and Radiographic Follow-Up

The degree of defect correction (expressed as a percentage) was evaluated at reentry surgery for GBR and after ridge expansion and implant placement for ERE, using a 15-mm periodontal probe. A complete defect fill (DF) was defined as full coverage of the implant surface until the top of the shoulder with a bone width of at least 1 mm all around the implants36 placed according to the restorative plan.

Implant success was evaluated according to Albrektsson et al37 criteria, updated and integrated by Misch et al.38 The long-term vertical dimensional stability of the augmented bone was evaluated using radiographic examinations. The radiographs made at provisional restoration delivery (T1 ¼ preloading MBL), at final restoration delivery (T2), and at the last available radiographic follow-up (T3) were analyzed to evaluate the MBL around implants. Radiographs were digitalized by taking a photograph (Fine Pix S 5500, Fuji Photo Film, Tokyo, Japan) of the film superimposed on a millimeter grid from a standard position and at magnification of 1:1. The distance from the reference point, established at the outer edge of the implant shoulder, to the most coronal bone to implant contact on the mesial and distal aspects of each implant was assessed using Image Analysis Software (Graphisoft ArchiCAD 11).

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Table 1. (Continued) Mean BBR Mean BBR on Site Basis on Site Basis at 6 Months at 12 Months (mm) (mm)

T1* MBL (mm)

T2† MBL (mm)

T3‡ MBL (mm)

M

D

M

D

M

D

T3 (Month)

1.2 2.9 3.1 2.5 2.5 2 2.9 2.6 1.9 2.3 1.8 1.7 2.6 3.1 4 2.3 2 1.9 1.5 2.1 2.1

1.5 3 2.8 2.5 1.9 2 2.2 2.3 1.8 2.5 2 1.5 2.5 3.4 3.9 2.8 1.5 1.8 1.9 2.5 2.9

1.7 3.8 3.3 2.7 2.5 2.4 3.5 2.6 2.3 2.3 2 1.7 2.8 3.9 4.6 2.6 2 1.9 1.8 2.2 2.1

1.9 3.2 3 2.6 2.1 2.6 2.3 2.4 2.3 2.7 2 1.6 2.9 4.2 4.1 3.1 1.6 2 2.2 2.7 3.5

1.9 4 3.9 2.7 2.5 3.5 3.7 2.6 2.4 2.2 3.5 1.7 3.1 4.7 5 2.6 2 1.9 1.8 2.2 2.1

2.8 3.2 3 2.9 2.4 3.2 2.6 2.6 2.4 2.6 2.9 2.2 2.9 5 4.4 3.1 1.6 2 2.2 2.7 3.5

22 25 38

NR NR NR

NR NR NR

13

NR

NR

13

NR

NR

12 32 25

0 NR NR

0.23 NR NR

27

NR

NR

12

1.7 3.03 0.6 1.36 1.33 1.23

1.96 3.46 1.66 1.9 2.26 3.23

1.32 6 0.94 0–3.03

2.10 6 1.07 0.23–3.46

2.28 6 0.7 1.2–4

2.34 6 0.63 1.5–3.9

2.60 6 0.79 1.7–4.6

A pilot feasibility study for surveying long-term horizontal stability of the augmented ridge was carried out on five of the patients who received their final restoration at the starting point of the current study (patients 5A, 9A, 2B, 3C, and 5C), using a rigid resin customized template and an endodontic instrument. The survey template was manufactured on the basis of the final restoration and provided with several holes at points chosen for dimensional evaluation. After application of topical anesthetic (EMLA cream; AstraZeneca Spa, Basiglio, Milan, Italy), the endodontic instrument (40 K-file, Dentsply Maillefer, Ballaigues, Switzerland) was thrust through the template holes into the mucosa, perpendicular to bone plate, so that it came into contact with it (Fig. 7). The part of the K-file that entered the template hole was measured at final crown delivery (T2), at 6-month follow-up (T2a), and at final follow-up (T3) using a CCD laser micrometer

2.61 6 0.71 1.6–4.2

2.67 6 1.10 1.7–5

2.86 6 0.75 1.6–4.4

12

20.61 6 9.82 12–38

(Keyence, Osaka, Japan) to evaluate horizontal bone remodeling of the regenerated bone. All measurements were collected on the same clinical session independently by two trained examiners who were different from the surgeons and who were blinded to the treatment allocation of the subjects (ie, h-GBR, ERE, or v-GBR). Statistical Analysis

The variables of interest were the success of augmentation procedures, with the complication rate being used as a statistical unit of analysis of the augmentation procedure in itself, and the percentage of defect correction, with survival and success rates of implants and marginal stability over time of the augmented bone with the single implant as references. In particular, the percentage of clinically evaluated DF at each implant site was plotted on a box plot, and mean and SD values were calculated for groups A (h-GBR),

B (ERE), and C (v-GBR). One-way analysis of variance (ANOVA) (P , 0.01) was used to identify significant differences among the three treatment groups for the variable DF. Changes in the radiographic vertical MBL over the time interval T2 (final crown delivery) to T3 (last available radiographic follow-up after final crown delivery; T2–T3) were obtained as differences of paired mesial (M) and distal (D) values for each implant between the two follow-up time points. These values are presented as mean 6 SD values. One-way ANOVA (P , 0.01) was used to identify significant differences among groups A, B, and C for this variable. When statistical significance was identified among serial means by ANOVA, Bonferroni post hoc testing (P , 0.05) was carried out to determine which of the paired means showed a statistically significant difference. Finally, to test the reproducibility of the method used to assess horizontal

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Table 2. Characteristics of Patients and Clinical Results in Group B (Edentulous Ridge Expansion)

Augmentation Site

Patient No. 1B

1B-4

2B

2B-4

3B 4B

3B-4 4B-1

4.6 4.7 4.6 4.7 4.6 1.5 1.7 2.5 2.7 3.5 3.7 4.5 4.7 1.5 2.5 3.4 3.5 4.4 4.5

4B-2 4B-3 4B-4 5B

5B-1 5B-2 5B-3 5B-4

Total Mean 6 SD Range

Implant Site

Implant Manufacturer, Type, and Dimension S & M, Pilot, 5.7 3 10.5 5.7 3 10.5 Nobel Speedy, 6310 6 3 10 S & M, Pilot, 3.8 3 13 S & M, Pilot, 4.7 3 10.5 6.7 3 10.5 S & M, Pilot, 4.7 3 10.5 6.7 3 10.5 S & M, Pilot, 4.7 3 10.5 5.7 3 10.5 S & M, Pilot, 4.7 3 10.5 5.7 3 10.5 S & M, Pilot, 5.7 3 10.5 S & M, Pilot, 5.7 3 10.5 S & M, Pilot, 3.8 3 13 3.8 3 10.5 S & M, Pilot, 3.8 3 13 5.7 3 10.5

h-Defect (mm)

Bone Gain (mm)

5 5 5 5.5 4.5 5 7 5 7 3 3 2 3 5.5 5.5 4 5 4 4

5 5 5 5 3.8 4.7 6.7 4.7 6.7 3 3 2 3 5 5.5 4 5 4 4

4.63 6 1.30 2–7

4.45 61.19 2–6.7

11

S & M indicates Sweden & Martina; h-defect, horizontal defect; MBL, marginal bone level; M, mesial; D, distal; h-RR, horizontal ridge resorption; NR, not recorded.

Table 3. Characteristics of Patients and Clinical Results in Group C (Vertical GBR)

Patient No.

Augmentation Implant Site Site

1C

1C-3

2C*

2C-3 2C-4

3C 4C

3C-3 3.7 4C-3 4C-4

5C†

Total Mean 6 SD Range

5C-3 3.7 5C-4

3.6 3.7 3.6 3.7 4.6 4.7 3.5 3.6 3.7 4.5 4.6 3.5 4.5 4.7

Implant Manufacturer, Type, and Dimension S & M, Pilot 5.7 3 10.5 5.7 3 10.5 Nobel Straight, 5 3 10 5 3 10 Nobel Straight, 5310 5 3 10 S & M, Pilot, 3.8 3 10.5 5.7 3 10.5 S & M, Pilot, 3.8 3 10.5 4.7 3 13 S & M, Pilot 3.8 3 10.5 3.8 3 13 S & M, Pilot, 3.8 3 13 5.7 3 10.5 S & M, Pilot, 3.8 3 10.5 5.7 3 8.5

Regeneration Materials AP + Bio-Oss + Gore-Tex NRM AP + DFDBA + Gore-Tex NRM AP + DFDBA + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + Bio-Oss + Gore-Tex NRM AP + DFDBA + Gore-Tex NRM AP + DFDBA + Gore-Tex NRM

v-Defect (mm)

Bone Gain (mm)

4 5 4.5 5 3.5 3 6 6.5 3 2 5.5 5.5 4 4 4 3

3 5 4 5 3 3 6 5 3 1.5 4 4 4 4 4 3

8 4.28 6 1.23 3.84 6 1.09 2–6.5 1.5–6

* Patient 2C corresponds to patient 4A in Table 1. † Patient 5C corresponds to patient 9A in Table 1. AP indicates autogenous particulate; DFDBA, demineralized freeze-dried bone allograft; NRM, nonresorbable membrane; S & M, Sweden & Martina; v-defect, vertical defect; MBL, marginal bone level; M, mesial; D, distal; h-RR, horizontal ridge resorption; NR, not recorded.

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Table 2. (Continued)

T1 MBL (mm)

T2MBL (mm)

T3MBL (mm)

Mean h-RR Mean h-RR on Site on Site Basis at 12 Basis at 6 Months (mm) Months (mm)

M

D

M

D

M

D

T3 (Month)

1.9 1.7 2.4 1.9 2 1.9 3 3.2 3.9 1.8 1.8 1.9 1.5 3.2 2.1 1.6 2.8 2.3 3.8

2.8 2 2.5 1.6 2 1.6 2.9 3.3 4.8 1.8 1 1.9 1.7 2.3 2.3 2.2 2.3 2.9 3

2.8 2.4 2.5 1.9 2.2 2.3 3.2 3.8 4.3 2.4 2 2.4 1.5 3.4 2.5 2 3 2.6 4.1

3.2 2.3 2.8 1.6 2 2.3 3.4 3.5 4.9 2.3 1 2.2 1.7 2.6 2.5 2.7 2.7 3.1 3.2

4.3 3.0 3.6 2 3.1 3.1 3.7 3.8 4.8 2.4 2 2.4 1.9 3.7 2.9 2.9 3.4 3.6 4.1

3.7 3.5 2.9 1.7 3.2 2.7 3.8 3.5 4.9 2.3 1 2.8 1.7 3.3 3.3 2.7 2.7 3.3 3.5

6

NR

NR

6 12 14

0.43 0.2 NR NR

0.48 0.22 NR NR

14

NR

NR

14

NR

NR

14

NR

NR

14 14 14

NR NR NR

NR NR NR

14

NR

NR

2.35 6 0.74 2.36 6 0.82 2.70 6 0.76 2.63 6 0.84 3.19 6 0.81 2.97 6 0.88 1.5–3.9 1–4.8 1.5–4.1 1–4.9 1.9–4.8 1–4.9

12.21 6 3.32 0.31 6 0.16 6–14 0.2–0.43

0.35 60.18 0.22–0.48

Table 3. (Continued)

T1 MBL (mm)

T2 MBL (mm)

T3 MBL (mm)

Mean h-RR Mean h-RR on Site on Site Basis at 12 Basis at 6 Month (mm) Month (mm)

M

D

M

D

M

D

T3 (Month)

2.5 1.2 2.5 1.5 2.6 2.8 1.9 3.2 2.3 1.8 1.8 1.6 1.2 2.2 2.3 2.5

1.5 1.2 2.9 1.3 2.9 1.4 1.9 2.2 1.8 2.9 1.8 1.2 1.9 1.6 2.9 2.5

2.6 1.4 2.7 1.7 2.8 2.8 2.5 3.6 2.9 1.8 1.8 1.7 1.7 2.4 2.9 3

1.8 1.2 3.5 1.6 3.2 1.6 2.2 2.2 2.6 2.9 1.8 1.2 2.8 1.8 3.3 3.1

3.1 1.4 2.7 2.4 3.7 2.8 2.7 5.4 3 2.8 5.8 5.7 1.7 2.4 3.1 3.4

2 1.5 3.5 2.1 3.4 1.8 3.1 4.9 2.7 3.1 5.8 5.2 2.8 1.8 3.3 3.1

14

NR

NR

13

NR

NR

13

NR

NR

12 12

0.13 0.8 NR

0.5 3.32 NR

12

NR

NR

12

0.5 0.83 0.7 0.73

1.83 3.23 2.36 2.73

2.11 6 0.57 1.99 6 0.64 2.39 6 0.62 2.30 6 0.76 3.25 6 1.30 3.13 6 1.25 1.2–3.2 1.2–2.9 1.4–3.6 1.2–3.5 1.4–5.8 1.5–5.8

12

12.5 6 0.73 0.61 6 0.26 12–14 0.13–0.83

2.32 0.5–3.32

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bone remodeling of the augmented ridge using the survey template, the consistency between the two examiner evaluations was calculated as the percentage of values that were identical or affected by a negligible difference (defined as ,0.1 mm). Pearson correlation analysis was used to determine the interobserver agreement.

RESULTS Seventeen patients treated between May 2006 and January 2009 with h-GBR (group A), ERE (group B), and v-GBR (group C) fulfilled the study inclusion criteria: 30 ridge defects ranging 1 to 8 mm (4.22 6 1.90 mm) were corrected and 56 implants were positioned in the augmented bone. Of the 22 horizontal defects, 11 were treated with h-GBR (group A) and 11 were treated with ERE (group B: 5 in the maxilla and 6 in the mandible); all vertical deficiencies (n ¼ 8) were in the mandible and were treated with v-GBR (group C). The alveolar ridge defect was 3.80 6 2.64 mm (range, 1–8 mm) in group A, 4.63 6 1.30 mm (range, 2–7 mm) in group B, and 4.28 6 1.23 (range, 2–6.5 mm) in group C. Twenty-one implants (13 in the maxilla and 8 in the mandible) were placed in bone augmented with h-GBR, 19 implants (7 in the maxilla and 12 in the mandible) were placed in the ridge split with ERE, and 16 implants in mandibles augmented with v-GBR. Surgeons were able to place one to three implants with a simultaneous approach (ie, at the same time as bone regeneration), according to the original treatment plan, in all augmentation sites except three (patient 4A, augmentation sites 4A-1 and 4A-2, implants 4A-14, 4A-16, 4A-24, and 4A-26; patient 9A, augmentation site 9A-2, implants 9A24, 9A-26, and 9A-27). In these three exceptions, the severity of the defects and the lack of primary stability necessitated both h-GBR and a sinus lift procedure followed by delayed implant placement. The subjects’ characteristics and clinical results are summarized in Tables 1 (group A), 2 (group B), and 3 (group C). All the augmentation



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procedures were successful,24 and the bone gain achieved at each implant site was 3.61 6 2.51 mm (range, 1–8 mm) with h-GBR, 4.45 6 1.19 mm (range, 2–6.7 mm) with ERE, and 3.84 6 1.09 (range, 1.5–6 mm) with v-GBR. No statistically significant differences were identified by ANOVA (P , 0.01) for this parameter. A complete DF was obtained in 71.42%, 63.15%, and 56.25% of implant sites for groups A, B, and C, respectively. Two h-GBR sites (4A-1 and 9A-2) met with early membrane exposure between 1 and 2 months after surgery. These patients received systemic antibiotic therapy (1 g amoxicillin clavulanate twice a day for 6 days) and reentry surgery. The membrane was removed and after irrigation with sterile saline and tetracycline solution (Minocin, Teofarma, Pavia, Italy), the flap was closed and the graft was allowed to heal for an additional period ranging from 3 (4A-1) to 8 months (9A-2). One v-GBR site (1C-3) had late membrane exposure at 4 months after the augmentation procedure. The membrane was removed and a covering tissue that was not completely organized was found. Nevertheless, because the required amount of defect filling was achieved, healing abutment connection was carried out. In this case, follow-up radiographs showed stable MBL after loading, despite the reported complication (Table 3). Finally, another v-GBR site (4C-4) developed an abscess without membrane exposure 6 months after surgery. The same protocol of reentry surgery as other sites with complications (systemic antibiotic therapy, membrane removal, sterile saline, and tetracycline irrigation) was applied, and the healing abutments were screwed to the implants. The complication rate for augmentation procedures was 18% in group A and 25% in group C. No complications were reported in group B. The followup period after implant final prosthetic loading was 20.61 6 9.82 months in group A, 12.21 6 3.32 months in group B, and 12.5 6 0.73 months in group C. The overall implant survival rate was 100% in all three groups, while the success rate was 100% only for group A. In group B, the success rate was 94.7%,

due to one implant (1B-46) that exhibited a critical MBL of 1.5 mm at 6 months of follow-up37,38 (Table 2). In group C, a success rate of 81.25% was found: the two implants (4C-45 and 4C-46) present at augmentation site 4C-4 that developed an abscess 12 months after loading, although still in place, exhibited an MBL of 1.8 mm (M) and 2.7 mm (D), with an apparent lack of integration between the implant and the newly regenerated bone (Table 3). Preloading MBLs of 2.28 6 0.7 mm (M) and 2.34 6 0.63 mm (D), 2.35 6 0.74 mm (M) and 2.36 6 0.82 mm (D), and 2.11 6 0.57 mm (M) and 1.99 6 0.64 mm (D) were found for groups A, B, and C, respectively, at provisional crown delivery, probably due in part to incomplete DF and in part to reestablishment of the biologic width after healing abutment connection39,40; this variable did not differ significantly among the groups (ANOVA, P , 0.01). The change in MBL (M and D) over the T2–T3 time period (T2–T3 MBL; ie, the marginal bone resorption after definitive prosthetic loading) was 0.25 6 0.41 mm (M) and 0.24 6 0.32 mm (D) for group A, 0.49 6 0.44 mm (M) and 0.34 6 0.39 mm (D) for group B, and 0.86 6 1.32 mm (M) and 0.83 6 1.40 mm (D) for group C. The T2–T3 MBL data differed significantly (ANOVA, P , 0.01) among the three groups. Serial means were subjected to multiple comparisons with Bonferroni correction (P , 0.05), which revealed that they only differed significantly between groups A and C. The survey template evaluation revealed a poor predictability affecting the long-term horizontal bone stability of the regenerated bone (Tables 1–3) specially for h-GBR technique. The interexaminer variability in the evaluation of horizontal bone remodeling using the survey template appeared negligible, with 168 (96.55%) reevaluated values being identical or differing by ,0.05 mm and 174 (100%) differing by #0.1 mm. Pearson correlation analysis was used to check the interexaminer reproducibility, revealing a covariance of 1.5022 with a correlation index of 0.9998, indicating a good

IMPLANT DENTISTRY / VOLUME 21, NUMBER 3 2012 reliability of the survey template measuring system.

DISCUSSION The overall implant survival and success rates in this study were 100% and 91.98%, respectively, and are consistent with published results of implants placed in horizontally or vertically augmented ridges by GBR or ERE techniques, respectively.9,19,20,24 Studies on h-GBR and v-GBR have found implant survival rates from 96.9% to 100%,41 with rates ranging from 86.2% to 100% reported for ERE procedures9,24; both sets of findings are consistent with those of implants placed in pristine sites. Comparison of clinical outcomes appears to be difficult because of the high degree of heterogeneity that exists among the published data regarding study design, procedures, timing, materials, evaluated outcomes and chosen units of statistical analysis, and range of follow-up periods.24 In many articles, different surgical techniques or regenerative materials were used without separating the survival rate of implants on the basis of procedure,22,42 and the success rate of implants analyzed according to well-established criteria is often lacking. For lateral augmentations, most studies present a staged approach,31,43,44 while only dehiscences, fenestrations, or postextraction defects seem to be treated by simultaneous h-GBR.45,46 In this study, a simultaneous approach, with implant placement conducted at the regeneration time point, was used in all the three procedures, even in the presence of no-space-giving defects,34 the only exceptions being cases (augmentation sites 4A-1, 4A-2, and 9A-2) where h-GBR in combination with lateral window sinus lift were performed to correct sites that exhibited both horizontal and vertical deficiencies, in the presence of a good implant–crown ratio but without reliability for adequate primary stability. The reported complication rates for GBR (18.2% for h-GBR and 25% for v-GBR) appear to be acceptable in comparison with data presented in the literature, which in fact are highly dissimilar and disagree among

themselves, ranging from 2.5%47 to 13%31 and up to 64%48 for h-GBR and from 8%49 to 19%22 and up to 45%23 for v-GBR. The most common complication that other authors have encountered with ERE, buccal bone plate fracture, was not found within the current retrospective case series. It is noteworthy that universally accepted ridge augmentation success criteria are lacking, and this is an obstacle for comparing different trials and surgical techniques. Moreover, in most studies, there is a lack of data regarding the initial defect size and shape, the postoperative degree of defect reduction, and the stability over time of the augmented bone.41 The success rate for augmentation procedures was 100% in this study, based on the possibility of implant placement in a ideal position, driven by the restorative plan, the osseointegration of implants in regenerated and pristine bone, and the maintenance of function for at least 6 months after loading.24 Of course, this is a somewhat permissive criterion that could also judge as successful a regenerative procedure with incomplete DF or showing a large amount of bone resorption over time. Of course, the degree of DF and the long-term stability of augmented bone could be important variables that will reflect the success of the augmentation procedure and confirm the importance of correction even in localized, moderate deficiencies to provide long-term implant success. In the current study, the initial mean defect size and the degree of defect correction did not differ significantly among the groups (ANOVA, P , 0.01), indicating that the three surgical techniques have a comparable clinical effectiveness. Moreover, the mean pre- and postloading MBL values collected at T1, T2, and T3 appeared to be in agreement with previously reported clinical data.20,22,42,45,50 Marginally statistically significant differences were noticed only regarding postloading (T2–T3) MBL among the three treatment groups (ANOVA, P , 0.01), in particular between groups A and C (Bonferroni post hoc test, P , 0.01).

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Nevertheless, radiographic evaluation of MBL presents a relevant limitation, being able to monitor only boneto-implant contact variations along the vertical dimension of the mesial and distal sides of implants and being unable to show any dimensional variation of the buccal bone surface. Chiapasco et al evaluated the amount of horizontal bone remodeling that occurred after hGBR31 and ERE28 using a surgical caliper during reentry surgery and after prosthetic loading through the mucosa, trying to repeat measurements in the same position using a resin stent. Those authors reported measurements as absolute width variations of the ridge at different time points, because the caliper does not permit the distinction between buccal bone remodeling and lingual or palatal bone remodeling and introduces a small but unavoidable methodological limitation because measurements made during surgery were compared with those made without reopening of the sites. Conversely, neither open flap measurements nor CT can be considered feasible routine methods of monitoring bone stability over time because of their unreasonable economical and biological costs. In this study, a pilot feasibility investigation was conducted to evaluate an experimental device aimed to measure horizontal bone remodeling at augmented sites after definitive prosthetic loading. Although these data, obtained only for five patients, cannot be considered as significant clinical findings, a good reproducibility of the applied measurement system was reported, indicating the customized survey template as a reliable method for evaluating the postloading horizontal stability of augmented ridges.

CONCLUSIONS Survival and success rates of implants placed in bone augmented using the GBR and ERE techniques appeared to be similar to those of implants placed in pristine sites. Membrane exposure could adversely affect the degree of defect correction obtained with GBR, while an excellent degree of defect correction and lower complication rate were

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reported for ERE. The tested survey template, showing good reproducibility of the measurements, may be considered a reliable method to evaluate long-term horizontal stability of regenerated bone.

DISCLOSURE The authors claim to have no financial interest in any company or any of the products mentioned in this article.

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