Marco Beolchini Niklaus P. Lang Emanuele Ricci Franco Bengazi Barbara Garcia Triana Daniele Botticelli
Authors’ affiliations: Marco Beolchini, Franco Bengazi, Barbara Garcia Triana, Daniele Botticelli, Faculty of Dentistry, University of Medical Science, La Habana, Cuba Niklaus P. Lang, Daniele Botticelli, The University of Hong Kong, Prince Philip Dental Hospital, Hong Kong, China Niklaus P. Lang, University of Zurich, Zurich, Switzerland Emanuele Ricci, Dipartimento di Scienze Odontostomatologiche, Reparto di chirurgia orale, Universita di Bologna, Bologna, Italy Daniele Botticelli, Faculdade de Odontologia de Aracßatuba, UNESP - Universidade Estadual Paulista, Paulista, Brasil Daniele Botticelli, ARDEC, Ariminum Odontologica, Rimini, Italy Corresponding author: Dott. Daniele Botticelli Avenida Salvador Allende y G Vedado 10400 La Habana Cuba Tel: 537 879 3360 Fax: 537 870 3312 e-mail: [email protected]
Influence on alveolar resorption of the buccal bony plate width in the edentulous ridge expansion (E.R.E.) – an experimental study in the dog
Key words: animal study, bone augmentation, bone healing, bone width, buccal bony plate,
dental implants, edentulous ridge expansion, histology, implant dentistry, ridge expansion, split crest Abstract Objective: To compare the hard tissue changes at implants installed applying edentulous ridge expansion (E.R.E.) at sites with a buccal bony wall thickness of 1 or 2 mm. Material and methods: In six Labrador dogs, the first and second maxillary incisors were extracted, and the buccal alveolar bony plates and septa were removed. After 3 months of healing, partialthickness flaps were dissected, and the E.R.E. was applied bilaterally. Hence, an expansion of the buccal bony crest was obtained in both sides of the maxilla with a displacement of either a 1- or a 2-mm-wide buccal bony plate at the test and control sites, respectively. After 3 months of healing, biopsies were obtained for histological analyses. Results: A buccal vertical resorption of the alveolar crest of 2.3 0.8 and 2.1 1.1 mm, and a coronal level of osseointegration at the buccal aspect of 2.7 0.5 and 2.9 0.9 mm were found at the test (1 mm) and control (2 mm) sites, respectively. The differences did not reach statistical significance. The mean values of the mineralized bone-to-implant contact (MBIC%) ranged from 62% to 73% at the buccal and lingual sites. No statistically significant differences were found. Horizontal volume gains of 1.8 and 1.1 mm were observed at the test and control sites, respectively, and the difference being statistically significant. Conclusions: Implants installed using the E.R.E. technique yielded a high degree of osseointegration. It is suggested that the displacement of buccal bony plates of 1 mm thickness is preferable compared with that of wider dimensions.
Date: Accepted 28 October 2013 To cite this article: Beolchini M, Lang NP, Ricci E, Bengazi F, Triana BG, Botticelli D. Influence on alveolar resorption of the buccal bony plate width in the edentulous ridge expansion (E.R.E.) – an experimental study in the dog. Clin. Oral Impl. Res. 26, 2015, 109–114 doi: 10.1111/clr.12308
Two decades ago, a novel technique was proposed to augment the width of the alveolar ridge concomitantly with implant installation in case of deficient bone volume. This technique, identified as edentulous ridge expansion (E.R.E.; Scipioni et al. 1994), was studied in an experiment in dogs (Scipioni et al. 1997) and compared with control sites. Similar results were observed both at the test and control sites, documenting that the E.R.E. surgical approach produced predictable outcomes. However, data on the width of the alveolar buccal bony walls at the test sites were not available. The influence of the buccal bony wall width at conventional sites has been discussed in several clinical (Spray et al. 2000; Grunder et al. 2005; Buser et al. 2004; Belser et al. 2008) and experimental studies (Baffone
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
et al. 2013a,b; Bengazi et al. 2013). While an increased width of the buccal bony wall has been suggested in clinical studies to positively influence esthetic outcomes (Spray et al. 2000; Grunder et al. 2005; Buser et al. 2004), experimental studies failed to demonstrate a substantial effect of the buccal bony plate dimension on soft and hard tissue changes during healing (Baffone et al. 2013a, b; Bengazi et al. 2013). On the contrary, a higher horizontal bony ridge resorption was observed at the wider compared with the thinner buccal bony walls (Baffone et al. 2013a,b; Bengazi et al. 2013). Applying E.R.E. was compared with standard implant installation in a recent study in dogs (Beolchini et al. 2013). It was shown that implants installed using E.R.E. osseointegrated to a similar degree compared with
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control sites. In that study, the width of the buccal bony wall was measured at 1- and 3-mm levels apically to the buccal bony crest after the preparation of the recipient sites. It was observed that the width of the wall in E.R.E. sites was similar at the 1- and 3-mm levels (1.6 and 1.7 mm, respectively). Conversely, at control sites, the thickness was 1.2 and 2.6 mm at 1- and 3-mm levels, respectively. The influence of the thickness of the buccal wall in the E.R.E. technique has not yet been studied. Hence, the objective of the present experiment was to compare the hard tissue changes and bony crest resorption at implants installed preparing recipient sites with a buccal bony wall thickness of 1 or 2 mm applying the E.R.E. technique.
Material and methods The research protocol was submitted to and approved by the Ethical Committee of the University of Medical Sciences, School of Dentistry, La Habana, Cuba. Six Labrador dogs (each approximately 19.5 kg in weight and with a mean age of 1 year) were used. The animals were provided by Centro Nacional para la Producci on de Animales de Laboratorio (CENPALAB) of Havana, Cuba. Clinical procedures
At each surgical session, the animals were pre-anesthetized with atropine 0.02 mg/kg i.v. (Mayne Pharma, Napoli, Italia) and anesthetized with 0.04 mg/kg metedomidine (Medetorâ, Virbac, Glattbrugg, Switzerland) + 5 mg/kg of ketamine-50 (Liorad, Havana, Cuba) mixed in a syringe and administered i.m. 10 min after pre-medication. The animals were maintained with 2–3% IsofluraneVetâ (Merial, Merial Tolosa, France) + O2 at 95% and kept with an intravenous fluid of 0.9% saline solution 10 ml/kg/h. Local anesthesia was provided as well. The blood pressure and the O2 perfusion were monitored. Surgical procedures
An intrasulcular incision was performed from the third right to the third left maxillary incisors, and full-thickness flaps were elevated. The first and second incisors were luxated and carefully extracted using forceps, in both sides of the maxilla. The vestibular bony plate of the extraction sockets as well as the bony septa between alveoli were removed in both sides of the maxilla aiming at the establishment of a reduced-width narrow bony
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ridge after healing. The flaps were subsequently sutured. After 3 months of healing, an incision was performed with a blade (BD Beaver 376400; BD Ophthalmic System, Waltham, MA, USA) in the center of the alveolar crest encompassing the anterior segment of the six incisors. Buccal and lingual partial-thickness (split) flaps were dissected with the scalpel from the underlining periosteum that was left attached to the alveolar bone (Fig. 1a). Two longitudinal bone incisions were performed in the bony mid-crest region, one on the right and one on the left side of the maxilla. Buccal alveolar bony walls of approximately 1 mm (Test sites) and 2 mm (Control sites) of thickness were produced in the right and left sides of the maxilla, respectively. The incision in the bone was performed with the same scalpel used for the mucosa, and a mallet was used to deepen the incision to a depth of about 10 mm. Two beveled vertical releasing incisions were performed at the buccal aspect, distally and mesially to the primary incisions, both at the right and left sides (Fig. 1b). The mobilization of each of the buccal bony walls was performed using an elevator, and, once mobilized, the bottom of the recipient sites were prepared with round drills of increasing diameters (1.0– 1.8 mm). Bone expanders (Sweden & Martina SPA, Due Carrare, Italy) were subsequently applied to further expand the ridge and to prepare the implant recipient sites. Lastly, a dedicate final drill was used to prepare the bottom of the recipient site as well as the palatal aspect. The thickness of the buccal flap containing the residual alveolar bone and covering connective tissue was assessed at (i) 1 mm and (ii) at 3 mm from the alveolar crest by using Iwannsson calipers (KLS Martin Group, Umkirch, Germany). Two implants, 8.5 mm long and 3.3 mm in diameter (Pilotâ, Sweden & Martina SPA), with a polished collar of 0.8 mm and a ZirTiâ surface, were placed with the shoulder flush to the buccal bony crest (Fig. 1c). The following clinical measurements were taken using an UNC 15 probe (Hu-Friedy, Chicago, IL, USA); (iii) the horizontal gap between the buccal and lingual walls mesially and (iv) distally to the implant; (v) the first contact of the bone to the implant surface at the mesial and (vi) distal aspect of the implant. Healing abutments were placed onto the implants, and the flaps were secured around the abutments to allow a non-submerged healing. A tape made of fiberglass was attached to the remaining incisors and reinforced with
composite aiming to protect the area from mechanical injuries, such as tongue, biting. Further details on the surgical technique had been illustrated previously (Beolchini et al. 2013). Postoperative period
The animals were kept under anti-inflammatory/analgesic drugs: 2 mg/kg tramadol (Altadolâ, Formevet, Milan, Italy) for 5 days after surgery, and antibiotics were administered (0.1 mg/kg Fortiusâ L.A., Virbac, Jalisco, Mexico) for 15 days postoperatively. The dogs were kept on concrete runs at the university’s field laboratory with free access to water and fed with moistened balanced dogs’ chow. Postoperatively, the wounds were inspected daily for clinical signs of complications, and the healing screws were cleaned. Three months after surgery, the animals were euthanized. The dogs were first anesthetized with a dose of 1 mg/kg of Xylazine (Rompunâ, Kiel, Germany) + 10 mg/kg of Ketamine (Liorad) mixed in a syringe and administered i.m. They were maintained with 2–3% Isoflurane-Vetâ (Merial) + O2 95%. Eparin 12 i.u./kg i.v. (Athena Pharma, Pomezia, Italy) was injected before the heart was arrested with 25 meq of potassium chloride i.v. (Aica, La Habana, Cuba). The carotid arteries were perfused with a fixative (4% of formaldehyde solution). Histological preparation
Individual bone blocks containing the implants and the surrounding soft and hard tissues were fixed in 4% formaldehyde solution, followed by dehydration in a series of graded ethanols, and finally embedded in resin (Technovitâ 7200 VLC, Kulzer, Friedrichsdorf, Germany). The blocks were cut using a diamond band saw fitted in a precision slicing machine (Exaktâ, Apparatebau, Norderstedt, Germany). One central section was selected and reduced to a thickness of about 50 lm using a cutting–grinding device (Exaktâ, Apparatebau). The histological slides were stained with toluidine blue and examined under a standard light microscope for histometric analysis. Histological examination
In an Eclipse 50i (Nikon Corporation, Tokyo, Japan) equipped with a digital video camera (Digital Sight DS-2Mv, Nikon Corporation) connected with a computer, the following landmarks were identified: IS, implant shoulder; C, coronal location of the adjacent bony crest; B, the most coronal point of boneto-implant contact; S, the surface of the
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Beolchini et al Alveolar ridge expansion
(a)
(b)
(c)
Fig. 1. Clinical occlusal views of the surgical procedures. (a) With the use of a scalpel, buccal, and lingual partial-thickness (split) flaps were dissected from the underlining periosteum that remained attached to the alveolar bone. (b) Bone incisions were performed using scalpel and mallet to prepare the buccal bony walls that were subsequently mobilized using elevators. The width of the buccal walls was thicker at the control compared with the test sites. (c) The recipient sites were prepared with drills, and bone expanders and implants were installed.
implant at the neck region; OC, the outer contour of the bony crest. Using the software NIS-Elements V.4.1 (Nikon Corporation), the following vertical measurements were taken parallel to the long axis of the implant, at a magnification of 9100 (Fig. 2): (i) the distance between IS and C (IS-C); (ii) the distance between IS and B (IS-B); (iii) the amount of mineralized boneto-implant contact (MBIC%) around the implant evaluated from B to the apical termination of the implant, both buccally and lingually. The width of the alveolar bony crest was measured from S to OC at 1 and 3 mm apically to IS (Fig. 2). The total horizontal resorption at 1 and 3 mm apically to IS (D1 and D3, respectively) was calculated by subtracting the histological from the clinical
measurements taken at the time of implant installation. The total horizontal gain was calculated at the 3-mm level (Net gain at 3 mm) subtracting the horizontal resorptions at the 3-mm level (D3) from the mean values between the horizontal displacement at the mesial and distal aspects of the implants. Data analysis
Mean values and standard deviations as well as 25th, 50th (median), and 75th percentiles were calculated for each outcome variable. The main interest was focused on vertical and horizontal bone resorption. Hence, the primary variables were IS-C, D1, D3, and Net gain at 3 mm. Differences between test and control sites were analyzed using the Wilcoxon test for paired observations using IBM SPSS Statistics V.19 (SPSS Inc., Chicago, IL, USA). The level of significance was set at a = 0.05.
Results Clinical evaluation
Hard tissue dimensions at the time of implant installation are reported in Table 1 for both thin (test) and thick (control) bony plates. The thickness of the buccal bony wall was about 1 mm at the test and 2 mm at the control sites. The horizontal bucco-lingual gaps, measured mesially and distally of the implants, ranged between 2.2 and 2.6 mm, while the vertical defects ranged between 5.3 and 5.5 mm. Only the difference between the width of the buccal walls reached statistical significance. After 3 months of healing, the reinforced composite protections were still partially present. No signs of inflammation were visible in the soft tissues surrounding the implants. Fig. 2. IS, implant shoulder; C, coronal top of the bony crest; B, most coronal contact of the bone to the implant; S, surface of the implant at the neck region; OC, the outer contour of the bony crest.
Histological evaluation
No artifacts occurred during the histological preparation, and all implants were fully
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
osseointegrated, and hence, test and control sites yielded an n = 6. Table 2 reports the data regarding marginal bone dimensional changes and the degree of osseointegration after 3 months of healing. Figure 3a,b depict ground sections illustrating the healing at the test and control sites, respectively. A similar buccal vertical resorption (IS-C) of the bony crest was found at the test (2.3 0.8 mm) and at the control sites (2.1 1.1 mm). Also, the most coronal contact of the bone to the implant (B) was found to be located at a similar level at test (IS-B = 2.7 0.5 mm) and control sites (ISB = 2.9 0.9 mm). No statistically significant differences were yielded. Although not statistically significant, a lower mineralized bone-to-implant contact (MBIC%) was found at the buccal aspect of the thinner buccal bone (63.1%) compared with the thicker sites (73.3%). S-OC evaluated after 3 months of healing was, at the 1-mm level apically to IS, close to 0 mm both at the test and control sites. The values obtained at the 3-mm level apically to IS were 0.6 mm for both groups. When these values were subtracted from the clinical measurements taken at the time of implant installation, horizontal resorptions (D) were disclosed that at 1-mm level (D1): 1.0 0.1 and 1.9 0.1 mm, while, at 3-mm level (D3), the resorption was 0.5 0.5 and 1.4 0.6 mm at the test and control sites, respectively. The differences were statistically significant. When the horizontal resorption (D3) was subtracted from the value of the displacement of the buccal bony plate, a net gain (Net gain at 3 mm) in the outline of the alveolar bony ridge of 1.8 and 1.1 mm resulted in the thin and thick sites, respectively (Table 3). This difference was statistically significant.
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Table 1. Clinical dimensions of bone and marginal defects in millimeters at implant installation Buccal width
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
Horizontal displacement
Coronal bone contact
1 mm
3 mm
Mesial
Distal
Mesial
Distal
1.0 (0.1) 0.9; 1.1*; 1.1
1.1 (0.1) 1.1; 1.2*; 1.2
2.5 (0.5) 2.0; 2.5; 3.0
2.2 (0.4) 2.0; 2.0; 2.0
5.3 (0.6) 5.0; 5.0; 5.8
5.5 (0.3) 5.5; 5.5; 5.5
2.0 (0.2) 1.9; 2.0*; 2.0
2.1 (0.1) 2.0; 2.1*; 2.1
2.4 (0.5) 2.0; 2.3; 2.9
2.6 (0.4) 2.5; 2.5; 2.9
5.3 (0.5) 5.0; 5.0; 5.8
5.3 (0.5) 5.1; 5.5; 5.5
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. *P < 0.05 between test and control.
Table 2. Histological measurements of hard tissues dimensions in millimeters after 3 months of healing IS-C
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
IS-B
MBIC%
b
l
b
l
b
l
2.3 (0.8) 2.0; 2.6; 2.9
1.2 (0.5) 0.9; 1.1; 1.3
2.7 (0.5) 2.4; 2.9; 2.9
2.9 (0.9) 2.3; 3.1; 3.4
63.1 (15.3) 52.0; 57.2; 75.7
61.8 (23.1) 48.5; 57.4; 82.1
2.1 (1.1) 1.5; 2.5; 2.9
1.7 (0.3) 1.4; 1.7; 1.9
2.9 (0.9) 2.4; 3.2; 3.6
3.0 (0.8) 2.5; 3.4; 3.5
73.3 (18.1) 62.9; 82.7; 91.7
65.6 (17.5) 55.6; 64.8; 80.1
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. IS, implant shoulder; C, top of the bony crest; B, most coronal point of bone-to-implant contact; MBIC, mineralized bone-to-implant contact. P < 0.05 between test and control.
(a)
Discussion The objective of the present experiment was to compare the hard tissue dimensional changes and bony crestal resorption at implants installed applying the E.R.E. technique with a buccal bony wall thickness of 1 or 2 mm. A similar vertical buccal bony crest resorption was observed at both sites. However, a greater horizontal buccal bony resorption was seen at the thicker compared with the thinner bony walls. The fact that buccal bony crestal resorption occurs at implants installed using the E.R.E. technique has already been described in a previous study in dogs of a similar nature to the present study (Beolchini et al. 2013). Even though the difference did not reach statistical significance, a higher vertical resorption at the E.R.E. test sites (2.2 mm) was found compared with the pristine control sites (1.6 mm). The vertical resorption that occurred at implants installed in conventional sites has been described in several clinical (e.g., Wennstr€ om et al. 2005; Cardaropoli et al. 2006) as well as experimental studies (e.g., Botticelli et al. 2004; Baffone et al. 2013b; Rossi et al. 2013). In a dog model (Rossi et al. 2013), the healing after 5, 10, 20, and 30 days at implants installed in healed alveolar ridges revealed that a marginal buccal resorption
(b)
Fig. 3. Ground sections illustrating the healing after 3 months from implant installation. Toluidine blue stain. All implants healed with a high degree of bone-to-implant contact. The vertical resorption was similar at both sides, while the horizontal resorption was larger at the control compared with the test sites. (a) Test site, thin buccal bone wall. (b) Control site, thick buccal bone wall.
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© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Beolchini et al Alveolar ridge expansion
Table 3. Horizontal dimension of buccal bone in millimeters after 3 months of healing D
S-OC
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
1 mm
3 mm
D1
D3
Net gain at 3 mm
0.0 (0.0) 0.0; 0.0; 0.0
0.6 (0.5) 0.2; 0.9; 0.9
1.0 (0.1) 0.9; 1.1*; 1.1
0.5 (0.5) 0.2; 0.3*; 0.9
1.8 (0.8) 1.2; 2.0*; 2.2
0.1 (0.2) 0.0; 0.0; 0.0
0.6 (0.6) 0.3; 0.5; 0.8
1.9 (0.1) 1.8; 1.9*; 2.0
1.4 (0.6) 1.2; 1.5*; 1.9
1.1 (0.8) 0.5; 0.8*; 1.7
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. S, the surface of the implant at the neck region; OC, the outer contour of the bony crest; D, total horizontal resorption at 1 mm (D1) and 3 mm (D3) apically to IS. Net gain at 3 mm, horizontal gain calculated at the 3-mm level. *P < 0.05 between test and control.
of 1.1 mm was already present after 5 days, increased up to 10 days, and then decreased to 0.8 mm after 1 month of healing. The changes in height of the bony crest, that were consistent with those of the most coronal level of osseointegration, were attributed to the remodeling processes that occurred at the cortical region of the hard tissue surrounding the implants (Rossi et al. 2013). In the present study, a horizontal resorption of the buccal bony wall was observed at both thin and thick buccal bony plate sites. This is in agreement with the aforementioned similar experiment (Beolchini et al. 2013). In that study, the horizontal resorption was evaluated at 1 and 3 mm apically to the implant shoulder. At the E.R.E. sites, the resorption was 1.4 and 0.7 mm at 1- and 3-mm levels, respectively, while the corresponding figures at the pristine control sites were 0.9 and 0.7 mm, respectively. In the present study, the residual width of the buccal bone facing the implant surface, measured at 1- and 3-mm levels, was similar in both test and control sites. This, in turn, means that at the sites where the buccal bony wall was thicker, a higher resorption occurred compared with the test sites with a thinner bony wall. This is in agreement with other experiments in dogs in which implants were installed into conventional alveolar ridges (Baffone et al. 2013b; Bengazi et al. 2013). In one of the previous experiments (Baffone et al. 2013b), osteotomies were prepared in such a way that the thickness of the buccal wall was 1 or 2 mm. A higher buccal bony crestal resorption was observed at the thicker compared with the thinner buccal bony walls. Moreover, in another study
(Bengazi et al. 2013), the healing at implant sites surrounded solely by alveolar mucosa was compared with sites that were bordered by masticatory mucosa. Osteotomies with buccal wall thickness of 1 or 2 mm were prepared. More vertical and horizontal resorption occurred at the alveolar mucosa sites than at sites with keratinized mucosa, and, again, a greater horizontal resorption was found at the sites with a thicker buccal bony wall. The fact that buccal bony walls of different size presented, after 3 months of healing, similar horizontal dimensions may be related to physiological factors that may have produced more resorption at the thicker compared with the thinner bony walls. It may be speculated that such factors may be related to the establishment of the biological width, or to the forces produced by muscles or to the pressure produced by lips or tongue. In the present study, a mineralized boneto-implant contact percentage (MBIC%) between 62% and 73% was obtained. No differences between test and control sites or between buccal and lingual aspects were found. This, in turn, means that E.R.E. is a predictable procedure to achieve a proper osseointegration. These results corroborate others from a previously described study (Beolchini et al. 2013). In that study, the osseointegration ranged between 43% and 48%. In the present study, a higher MBIC% was found at the buccal aspects of the sites with a thicker (73%) compared with those with thinner buccal bony walls (63%). Even though the difference did reach statistical significance, it may be speculated that the thickness of the buccal bony wall may influence the degree of osseointegration.
In the present study, the buccal bony walls were buccally displaced leading to a buccal restoration of the surgically reduced alveolar ridge of approximately 2.2–2.6 mm (Table 1). At the 1-mm level apically to the IS, this gain in restoration was lost due to the vertical resorption that occurred at both test and control sites. However, at the 3-mm level apically to the IS, 0.6 mm residual width of buccal bone was observed at both test and control sites. This, in turn, means that a net horizontal gain of 1.8 and 1.1 mm of the buccal aspect of the alveolar ridge was obtained at the thin and thick buccal bony aspects, respectively (Table 3). This difference between test and control sites was statistically significant. In conclusion, implants installed using E.R.E. yielded a high degree of osseointegration. Vertical and horizontal resorption of the displaced buccal bony plates occurred, however. Nevertheless, a net gain of horizontal width was obtained at both test and control sites. This net gain was statistically significantly greater at the sites with thinner compared with sites with thicker displaced buccal bony plates. Owing to these outcomes, it is suggested that, when exercising E.R.E., buccal bony plates of 1 mm of thickness are to be preferred for buccal displacement to thicker bony plate dimensions. Moreover, due the vertical resorption occurring after E.R.E., a deeper placement of the implant is suggested with this technique.
Acknowledgments: This study has been supported by a grant from Sweden & Martina SRL, Due Carrare, Padova, Italia, by ARDEC, Ariminum Odontologica SRL, Rimini, Italia, and by the Clinical Research Foundation (CRF) for the Promotion of Oral Health, Brienz, Switzerland. The support of o, TePeâ Munhygienprodukter AB, Malm€ Sweden for the oral hygiene products is appreciated.
Conflict of interests The authors declare no conflict of interests.
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Implants Research. doi: 10.1111/clr.12097. [Epub ahead of print] Scipioni, A., Bruschi, G.B. & Calesini, G. (1994) The edentulous ridge expansion technique: a five-year study. The International Journal of Periodontics and Restorative Dentistry 14: 451– 459. Scipioni, A., Bruschi, G.B., Giargia, M., Berglundh, T. & Lindhe, J. (1997) Healing at implants with and without primary bone contact. An experimental study in dogs. Clinical Oral Implants Research 8: 39–47. Spray, J.R., Black, C.G., Morris, H.F. & Ochi, S. (2000) The influence of bone thickness on facial marginal bone response: stage 1 placement through stage 2 uncovering. Annals of Periodontology 5: 119–128. Wennstr€ om, J.L., Ekestubbe, A., Gr€ ondahl, K., Karlsson, S. & Lindhe, J. (2005) Implant-supported single-tooth restorations: a 5-year prospective study. Journal of Clinical Periodontology 32: 567–574.
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Authors’ affiliations: Marco Beolchini, Franco Bengazi, Barbara Garcia Triana, Daniele Botticelli, Faculty of Dentistry, University of Medical Science, La Habana, Cuba Niklaus P. Lang, Daniele Botticelli, The University of Hong Kong, Prince Philip Dental Hospital, Hong Kong, China Niklaus P. Lang, University of Zurich, Zurich, Switzerland Emanuele Ricci, Dipartimento di Scienze Odontostomatologiche, Reparto di chirurgia orale, Universita di Bologna, Bologna, Italy Daniele Botticelli, Faculdade de Odontologia de Aracßatuba, UNESP - Universidade Estadual Paulista, Paulista, Brasil Daniele Botticelli, ARDEC, Ariminum Odontologica, Rimini, Italy Corresponding author: Dott. Daniele Botticelli Avenida Salvador Allende y G Vedado 10400 La Habana Cuba Tel: 537 879 3360 Fax: 537 870 3312 e-mail: [email protected]
Influence on alveolar resorption of the buccal bony plate width in the edentulous ridge expansion (E.R.E.) – an experimental study in the dog
Key words: animal study, bone augmentation, bone healing, bone width, buccal bony plate,
dental implants, edentulous ridge expansion, histology, implant dentistry, ridge expansion, split crest Abstract Objective: To compare the hard tissue changes at implants installed applying edentulous ridge expansion (E.R.E.) at sites with a buccal bony wall thickness of 1 or 2 mm. Material and methods: In six Labrador dogs, the first and second maxillary incisors were extracted, and the buccal alveolar bony plates and septa were removed. After 3 months of healing, partialthickness flaps were dissected, and the E.R.E. was applied bilaterally. Hence, an expansion of the buccal bony crest was obtained in both sides of the maxilla with a displacement of either a 1- or a 2-mm-wide buccal bony plate at the test and control sites, respectively. After 3 months of healing, biopsies were obtained for histological analyses. Results: A buccal vertical resorption of the alveolar crest of 2.3 0.8 and 2.1 1.1 mm, and a coronal level of osseointegration at the buccal aspect of 2.7 0.5 and 2.9 0.9 mm were found at the test (1 mm) and control (2 mm) sites, respectively. The differences did not reach statistical significance. The mean values of the mineralized bone-to-implant contact (MBIC%) ranged from 62% to 73% at the buccal and lingual sites. No statistically significant differences were found. Horizontal volume gains of 1.8 and 1.1 mm were observed at the test and control sites, respectively, and the difference being statistically significant. Conclusions: Implants installed using the E.R.E. technique yielded a high degree of osseointegration. It is suggested that the displacement of buccal bony plates of 1 mm thickness is preferable compared with that of wider dimensions.
Date: Accepted 28 October 2013 To cite this article: Beolchini M, Lang NP, Ricci E, Bengazi F, Triana BG, Botticelli D. Influence on alveolar resorption of the buccal bony plate width in the edentulous ridge expansion (E.R.E.) – an experimental study in the dog. Clin. Oral Impl. Res. 26, 2015, 109–114 doi: 10.1111/clr.12308
Two decades ago, a novel technique was proposed to augment the width of the alveolar ridge concomitantly with implant installation in case of deficient bone volume. This technique, identified as edentulous ridge expansion (E.R.E.; Scipioni et al. 1994), was studied in an experiment in dogs (Scipioni et al. 1997) and compared with control sites. Similar results were observed both at the test and control sites, documenting that the E.R.E. surgical approach produced predictable outcomes. However, data on the width of the alveolar buccal bony walls at the test sites were not available. The influence of the buccal bony wall width at conventional sites has been discussed in several clinical (Spray et al. 2000; Grunder et al. 2005; Buser et al. 2004; Belser et al. 2008) and experimental studies (Baffone
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
et al. 2013a,b; Bengazi et al. 2013). While an increased width of the buccal bony wall has been suggested in clinical studies to positively influence esthetic outcomes (Spray et al. 2000; Grunder et al. 2005; Buser et al. 2004), experimental studies failed to demonstrate a substantial effect of the buccal bony plate dimension on soft and hard tissue changes during healing (Baffone et al. 2013a, b; Bengazi et al. 2013). On the contrary, a higher horizontal bony ridge resorption was observed at the wider compared with the thinner buccal bony walls (Baffone et al. 2013a,b; Bengazi et al. 2013). Applying E.R.E. was compared with standard implant installation in a recent study in dogs (Beolchini et al. 2013). It was shown that implants installed using E.R.E. osseointegrated to a similar degree compared with
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control sites. In that study, the width of the buccal bony wall was measured at 1- and 3-mm levels apically to the buccal bony crest after the preparation of the recipient sites. It was observed that the width of the wall in E.R.E. sites was similar at the 1- and 3-mm levels (1.6 and 1.7 mm, respectively). Conversely, at control sites, the thickness was 1.2 and 2.6 mm at 1- and 3-mm levels, respectively. The influence of the thickness of the buccal wall in the E.R.E. technique has not yet been studied. Hence, the objective of the present experiment was to compare the hard tissue changes and bony crest resorption at implants installed preparing recipient sites with a buccal bony wall thickness of 1 or 2 mm applying the E.R.E. technique.
Material and methods The research protocol was submitted to and approved by the Ethical Committee of the University of Medical Sciences, School of Dentistry, La Habana, Cuba. Six Labrador dogs (each approximately 19.5 kg in weight and with a mean age of 1 year) were used. The animals were provided by Centro Nacional para la Producci on de Animales de Laboratorio (CENPALAB) of Havana, Cuba. Clinical procedures
At each surgical session, the animals were pre-anesthetized with atropine 0.02 mg/kg i.v. (Mayne Pharma, Napoli, Italia) and anesthetized with 0.04 mg/kg metedomidine (Medetorâ, Virbac, Glattbrugg, Switzerland) + 5 mg/kg of ketamine-50 (Liorad, Havana, Cuba) mixed in a syringe and administered i.m. 10 min after pre-medication. The animals were maintained with 2–3% IsofluraneVetâ (Merial, Merial Tolosa, France) + O2 at 95% and kept with an intravenous fluid of 0.9% saline solution 10 ml/kg/h. Local anesthesia was provided as well. The blood pressure and the O2 perfusion were monitored. Surgical procedures
An intrasulcular incision was performed from the third right to the third left maxillary incisors, and full-thickness flaps were elevated. The first and second incisors were luxated and carefully extracted using forceps, in both sides of the maxilla. The vestibular bony plate of the extraction sockets as well as the bony septa between alveoli were removed in both sides of the maxilla aiming at the establishment of a reduced-width narrow bony
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ridge after healing. The flaps were subsequently sutured. After 3 months of healing, an incision was performed with a blade (BD Beaver 376400; BD Ophthalmic System, Waltham, MA, USA) in the center of the alveolar crest encompassing the anterior segment of the six incisors. Buccal and lingual partial-thickness (split) flaps were dissected with the scalpel from the underlining periosteum that was left attached to the alveolar bone (Fig. 1a). Two longitudinal bone incisions were performed in the bony mid-crest region, one on the right and one on the left side of the maxilla. Buccal alveolar bony walls of approximately 1 mm (Test sites) and 2 mm (Control sites) of thickness were produced in the right and left sides of the maxilla, respectively. The incision in the bone was performed with the same scalpel used for the mucosa, and a mallet was used to deepen the incision to a depth of about 10 mm. Two beveled vertical releasing incisions were performed at the buccal aspect, distally and mesially to the primary incisions, both at the right and left sides (Fig. 1b). The mobilization of each of the buccal bony walls was performed using an elevator, and, once mobilized, the bottom of the recipient sites were prepared with round drills of increasing diameters (1.0– 1.8 mm). Bone expanders (Sweden & Martina SPA, Due Carrare, Italy) were subsequently applied to further expand the ridge and to prepare the implant recipient sites. Lastly, a dedicate final drill was used to prepare the bottom of the recipient site as well as the palatal aspect. The thickness of the buccal flap containing the residual alveolar bone and covering connective tissue was assessed at (i) 1 mm and (ii) at 3 mm from the alveolar crest by using Iwannsson calipers (KLS Martin Group, Umkirch, Germany). Two implants, 8.5 mm long and 3.3 mm in diameter (Pilotâ, Sweden & Martina SPA), with a polished collar of 0.8 mm and a ZirTiâ surface, were placed with the shoulder flush to the buccal bony crest (Fig. 1c). The following clinical measurements were taken using an UNC 15 probe (Hu-Friedy, Chicago, IL, USA); (iii) the horizontal gap between the buccal and lingual walls mesially and (iv) distally to the implant; (v) the first contact of the bone to the implant surface at the mesial and (vi) distal aspect of the implant. Healing abutments were placed onto the implants, and the flaps were secured around the abutments to allow a non-submerged healing. A tape made of fiberglass was attached to the remaining incisors and reinforced with
composite aiming to protect the area from mechanical injuries, such as tongue, biting. Further details on the surgical technique had been illustrated previously (Beolchini et al. 2013). Postoperative period
The animals were kept under anti-inflammatory/analgesic drugs: 2 mg/kg tramadol (Altadolâ, Formevet, Milan, Italy) for 5 days after surgery, and antibiotics were administered (0.1 mg/kg Fortiusâ L.A., Virbac, Jalisco, Mexico) for 15 days postoperatively. The dogs were kept on concrete runs at the university’s field laboratory with free access to water and fed with moistened balanced dogs’ chow. Postoperatively, the wounds were inspected daily for clinical signs of complications, and the healing screws were cleaned. Three months after surgery, the animals were euthanized. The dogs were first anesthetized with a dose of 1 mg/kg of Xylazine (Rompunâ, Kiel, Germany) + 10 mg/kg of Ketamine (Liorad) mixed in a syringe and administered i.m. They were maintained with 2–3% Isoflurane-Vetâ (Merial) + O2 95%. Eparin 12 i.u./kg i.v. (Athena Pharma, Pomezia, Italy) was injected before the heart was arrested with 25 meq of potassium chloride i.v. (Aica, La Habana, Cuba). The carotid arteries were perfused with a fixative (4% of formaldehyde solution). Histological preparation
Individual bone blocks containing the implants and the surrounding soft and hard tissues were fixed in 4% formaldehyde solution, followed by dehydration in a series of graded ethanols, and finally embedded in resin (Technovitâ 7200 VLC, Kulzer, Friedrichsdorf, Germany). The blocks were cut using a diamond band saw fitted in a precision slicing machine (Exaktâ, Apparatebau, Norderstedt, Germany). One central section was selected and reduced to a thickness of about 50 lm using a cutting–grinding device (Exaktâ, Apparatebau). The histological slides were stained with toluidine blue and examined under a standard light microscope for histometric analysis. Histological examination
In an Eclipse 50i (Nikon Corporation, Tokyo, Japan) equipped with a digital video camera (Digital Sight DS-2Mv, Nikon Corporation) connected with a computer, the following landmarks were identified: IS, implant shoulder; C, coronal location of the adjacent bony crest; B, the most coronal point of boneto-implant contact; S, the surface of the
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Beolchini et al Alveolar ridge expansion
(a)
(b)
(c)
Fig. 1. Clinical occlusal views of the surgical procedures. (a) With the use of a scalpel, buccal, and lingual partial-thickness (split) flaps were dissected from the underlining periosteum that remained attached to the alveolar bone. (b) Bone incisions were performed using scalpel and mallet to prepare the buccal bony walls that were subsequently mobilized using elevators. The width of the buccal walls was thicker at the control compared with the test sites. (c) The recipient sites were prepared with drills, and bone expanders and implants were installed.
implant at the neck region; OC, the outer contour of the bony crest. Using the software NIS-Elements V.4.1 (Nikon Corporation), the following vertical measurements were taken parallel to the long axis of the implant, at a magnification of 9100 (Fig. 2): (i) the distance between IS and C (IS-C); (ii) the distance between IS and B (IS-B); (iii) the amount of mineralized boneto-implant contact (MBIC%) around the implant evaluated from B to the apical termination of the implant, both buccally and lingually. The width of the alveolar bony crest was measured from S to OC at 1 and 3 mm apically to IS (Fig. 2). The total horizontal resorption at 1 and 3 mm apically to IS (D1 and D3, respectively) was calculated by subtracting the histological from the clinical
measurements taken at the time of implant installation. The total horizontal gain was calculated at the 3-mm level (Net gain at 3 mm) subtracting the horizontal resorptions at the 3-mm level (D3) from the mean values between the horizontal displacement at the mesial and distal aspects of the implants. Data analysis
Mean values and standard deviations as well as 25th, 50th (median), and 75th percentiles were calculated for each outcome variable. The main interest was focused on vertical and horizontal bone resorption. Hence, the primary variables were IS-C, D1, D3, and Net gain at 3 mm. Differences between test and control sites were analyzed using the Wilcoxon test for paired observations using IBM SPSS Statistics V.19 (SPSS Inc., Chicago, IL, USA). The level of significance was set at a = 0.05.
Results Clinical evaluation
Hard tissue dimensions at the time of implant installation are reported in Table 1 for both thin (test) and thick (control) bony plates. The thickness of the buccal bony wall was about 1 mm at the test and 2 mm at the control sites. The horizontal bucco-lingual gaps, measured mesially and distally of the implants, ranged between 2.2 and 2.6 mm, while the vertical defects ranged between 5.3 and 5.5 mm. Only the difference between the width of the buccal walls reached statistical significance. After 3 months of healing, the reinforced composite protections were still partially present. No signs of inflammation were visible in the soft tissues surrounding the implants. Fig. 2. IS, implant shoulder; C, coronal top of the bony crest; B, most coronal contact of the bone to the implant; S, surface of the implant at the neck region; OC, the outer contour of the bony crest.
Histological evaluation
No artifacts occurred during the histological preparation, and all implants were fully
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
osseointegrated, and hence, test and control sites yielded an n = 6. Table 2 reports the data regarding marginal bone dimensional changes and the degree of osseointegration after 3 months of healing. Figure 3a,b depict ground sections illustrating the healing at the test and control sites, respectively. A similar buccal vertical resorption (IS-C) of the bony crest was found at the test (2.3 0.8 mm) and at the control sites (2.1 1.1 mm). Also, the most coronal contact of the bone to the implant (B) was found to be located at a similar level at test (IS-B = 2.7 0.5 mm) and control sites (ISB = 2.9 0.9 mm). No statistically significant differences were yielded. Although not statistically significant, a lower mineralized bone-to-implant contact (MBIC%) was found at the buccal aspect of the thinner buccal bone (63.1%) compared with the thicker sites (73.3%). S-OC evaluated after 3 months of healing was, at the 1-mm level apically to IS, close to 0 mm both at the test and control sites. The values obtained at the 3-mm level apically to IS were 0.6 mm for both groups. When these values were subtracted from the clinical measurements taken at the time of implant installation, horizontal resorptions (D) were disclosed that at 1-mm level (D1): 1.0 0.1 and 1.9 0.1 mm, while, at 3-mm level (D3), the resorption was 0.5 0.5 and 1.4 0.6 mm at the test and control sites, respectively. The differences were statistically significant. When the horizontal resorption (D3) was subtracted from the value of the displacement of the buccal bony plate, a net gain (Net gain at 3 mm) in the outline of the alveolar bony ridge of 1.8 and 1.1 mm resulted in the thin and thick sites, respectively (Table 3). This difference was statistically significant.
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Table 1. Clinical dimensions of bone and marginal defects in millimeters at implant installation Buccal width
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
Horizontal displacement
Coronal bone contact
1 mm
3 mm
Mesial
Distal
Mesial
Distal
1.0 (0.1) 0.9; 1.1*; 1.1
1.1 (0.1) 1.1; 1.2*; 1.2
2.5 (0.5) 2.0; 2.5; 3.0
2.2 (0.4) 2.0; 2.0; 2.0
5.3 (0.6) 5.0; 5.0; 5.8
5.5 (0.3) 5.5; 5.5; 5.5
2.0 (0.2) 1.9; 2.0*; 2.0
2.1 (0.1) 2.0; 2.1*; 2.1
2.4 (0.5) 2.0; 2.3; 2.9
2.6 (0.4) 2.5; 2.5; 2.9
5.3 (0.5) 5.0; 5.0; 5.8
5.3 (0.5) 5.1; 5.5; 5.5
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. *P < 0.05 between test and control.
Table 2. Histological measurements of hard tissues dimensions in millimeters after 3 months of healing IS-C
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
IS-B
MBIC%
b
l
b
l
b
l
2.3 (0.8) 2.0; 2.6; 2.9
1.2 (0.5) 0.9; 1.1; 1.3
2.7 (0.5) 2.4; 2.9; 2.9
2.9 (0.9) 2.3; 3.1; 3.4
63.1 (15.3) 52.0; 57.2; 75.7
61.8 (23.1) 48.5; 57.4; 82.1
2.1 (1.1) 1.5; 2.5; 2.9
1.7 (0.3) 1.4; 1.7; 1.9
2.9 (0.9) 2.4; 3.2; 3.6
3.0 (0.8) 2.5; 3.4; 3.5
73.3 (18.1) 62.9; 82.7; 91.7
65.6 (17.5) 55.6; 64.8; 80.1
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. IS, implant shoulder; C, top of the bony crest; B, most coronal point of bone-to-implant contact; MBIC, mineralized bone-to-implant contact. P < 0.05 between test and control.
(a)
Discussion The objective of the present experiment was to compare the hard tissue dimensional changes and bony crestal resorption at implants installed applying the E.R.E. technique with a buccal bony wall thickness of 1 or 2 mm. A similar vertical buccal bony crest resorption was observed at both sites. However, a greater horizontal buccal bony resorption was seen at the thicker compared with the thinner bony walls. The fact that buccal bony crestal resorption occurs at implants installed using the E.R.E. technique has already been described in a previous study in dogs of a similar nature to the present study (Beolchini et al. 2013). Even though the difference did not reach statistical significance, a higher vertical resorption at the E.R.E. test sites (2.2 mm) was found compared with the pristine control sites (1.6 mm). The vertical resorption that occurred at implants installed in conventional sites has been described in several clinical (e.g., Wennstr€ om et al. 2005; Cardaropoli et al. 2006) as well as experimental studies (e.g., Botticelli et al. 2004; Baffone et al. 2013b; Rossi et al. 2013). In a dog model (Rossi et al. 2013), the healing after 5, 10, 20, and 30 days at implants installed in healed alveolar ridges revealed that a marginal buccal resorption
(b)
Fig. 3. Ground sections illustrating the healing after 3 months from implant installation. Toluidine blue stain. All implants healed with a high degree of bone-to-implant contact. The vertical resorption was similar at both sides, while the horizontal resorption was larger at the control compared with the test sites. (a) Test site, thin buccal bone wall. (b) Control site, thick buccal bone wall.
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© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
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Table 3. Horizontal dimension of buccal bone in millimeters after 3 months of healing D
S-OC
Thin (test) 1 mm Mean (SD) 25th; 50th; 75th Thick (control) 2 mm Mean (SD) 25th; 50th; 75th
1 mm
3 mm
D1
D3
Net gain at 3 mm
0.0 (0.0) 0.0; 0.0; 0.0
0.6 (0.5) 0.2; 0.9; 0.9
1.0 (0.1) 0.9; 1.1*; 1.1
0.5 (0.5) 0.2; 0.3*; 0.9
1.8 (0.8) 1.2; 2.0*; 2.2
0.1 (0.2) 0.0; 0.0; 0.0
0.6 (0.6) 0.3; 0.5; 0.8
1.9 (0.1) 1.8; 1.9*; 2.0
1.4 (0.6) 1.2; 1.5*; 1.9
1.1 (0.8) 0.5; 0.8*; 1.7
Mean values, standard deviations (SD), and percentiles 25th, 50th (median), and 75th in millimeters. S, the surface of the implant at the neck region; OC, the outer contour of the bony crest; D, total horizontal resorption at 1 mm (D1) and 3 mm (D3) apically to IS. Net gain at 3 mm, horizontal gain calculated at the 3-mm level. *P < 0.05 between test and control.
of 1.1 mm was already present after 5 days, increased up to 10 days, and then decreased to 0.8 mm after 1 month of healing. The changes in height of the bony crest, that were consistent with those of the most coronal level of osseointegration, were attributed to the remodeling processes that occurred at the cortical region of the hard tissue surrounding the implants (Rossi et al. 2013). In the present study, a horizontal resorption of the buccal bony wall was observed at both thin and thick buccal bony plate sites. This is in agreement with the aforementioned similar experiment (Beolchini et al. 2013). In that study, the horizontal resorption was evaluated at 1 and 3 mm apically to the implant shoulder. At the E.R.E. sites, the resorption was 1.4 and 0.7 mm at 1- and 3-mm levels, respectively, while the corresponding figures at the pristine control sites were 0.9 and 0.7 mm, respectively. In the present study, the residual width of the buccal bone facing the implant surface, measured at 1- and 3-mm levels, was similar in both test and control sites. This, in turn, means that at the sites where the buccal bony wall was thicker, a higher resorption occurred compared with the test sites with a thinner bony wall. This is in agreement with other experiments in dogs in which implants were installed into conventional alveolar ridges (Baffone et al. 2013b; Bengazi et al. 2013). In one of the previous experiments (Baffone et al. 2013b), osteotomies were prepared in such a way that the thickness of the buccal wall was 1 or 2 mm. A higher buccal bony crestal resorption was observed at the thicker compared with the thinner buccal bony walls. Moreover, in another study
(Bengazi et al. 2013), the healing at implant sites surrounded solely by alveolar mucosa was compared with sites that were bordered by masticatory mucosa. Osteotomies with buccal wall thickness of 1 or 2 mm were prepared. More vertical and horizontal resorption occurred at the alveolar mucosa sites than at sites with keratinized mucosa, and, again, a greater horizontal resorption was found at the sites with a thicker buccal bony wall. The fact that buccal bony walls of different size presented, after 3 months of healing, similar horizontal dimensions may be related to physiological factors that may have produced more resorption at the thicker compared with the thinner bony walls. It may be speculated that such factors may be related to the establishment of the biological width, or to the forces produced by muscles or to the pressure produced by lips or tongue. In the present study, a mineralized boneto-implant contact percentage (MBIC%) between 62% and 73% was obtained. No differences between test and control sites or between buccal and lingual aspects were found. This, in turn, means that E.R.E. is a predictable procedure to achieve a proper osseointegration. These results corroborate others from a previously described study (Beolchini et al. 2013). In that study, the osseointegration ranged between 43% and 48%. In the present study, a higher MBIC% was found at the buccal aspects of the sites with a thicker (73%) compared with those with thinner buccal bony walls (63%). Even though the difference did reach statistical significance, it may be speculated that the thickness of the buccal bony wall may influence the degree of osseointegration.
In the present study, the buccal bony walls were buccally displaced leading to a buccal restoration of the surgically reduced alveolar ridge of approximately 2.2–2.6 mm (Table 1). At the 1-mm level apically to the IS, this gain in restoration was lost due to the vertical resorption that occurred at both test and control sites. However, at the 3-mm level apically to the IS, 0.6 mm residual width of buccal bone was observed at both test and control sites. This, in turn, means that a net horizontal gain of 1.8 and 1.1 mm of the buccal aspect of the alveolar ridge was obtained at the thin and thick buccal bony aspects, respectively (Table 3). This difference between test and control sites was statistically significant. In conclusion, implants installed using E.R.E. yielded a high degree of osseointegration. Vertical and horizontal resorption of the displaced buccal bony plates occurred, however. Nevertheless, a net gain of horizontal width was obtained at both test and control sites. This net gain was statistically significantly greater at the sites with thinner compared with sites with thicker displaced buccal bony plates. Owing to these outcomes, it is suggested that, when exercising E.R.E., buccal bony plates of 1 mm of thickness are to be preferred for buccal displacement to thicker bony plate dimensions. Moreover, due the vertical resorption occurring after E.R.E., a deeper placement of the implant is suggested with this technique.
Acknowledgments: This study has been supported by a grant from Sweden & Martina SRL, Due Carrare, Padova, Italia, by ARDEC, Ariminum Odontologica SRL, Rimini, Italia, and by the Clinical Research Foundation (CRF) for the Promotion of Oral Health, Brienz, Switzerland. The support of o, TePeâ Munhygienprodukter AB, Malm€ Sweden for the oral hygiene products is appreciated.
Conflict of interests The authors declare no conflict of interests.
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