Journal of Oral Implantology Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs --Manuscript Draft-Manuscript Number:
aaid-joi-D-14-00114R1
Full Title:
Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs
Short Title:
Dental implants with and without flap elevation
Article Type:
Dental Implant Science Research
Keywords:
dental implants; flap, no flap; bone loss
Corresponding Author:
Richard Dennis Trushkowsky, DDS NYU College of Dentistry New York, New York UNITED STATES
Corresponding Author Secondary Information: Corresponding Author's Institution:
NYU College of Dentistry
Corresponding Author's Secondary Institution: First Author:
Nicolas; Elian,, DDS
First Author Secondary Information: Order of Authors:
Nicolas; Elian,, DDS Wayne Kye, DDS Hanae Saito, DDS, MS, CCRC Michel M Dard, DDS, MD.PhD Richard Dennis Trushkowsky, DDS Dennis Tarnow, DDS
Order of Authors Secondary Information: Abstract:
Abstract -The technique of immediate implant placement after extraction has been conceived for preserving the residual bone support and soft tissue morphology. Nowadays this procedure is still not predictable and presents inconveniences both for the patient and the dentist. Therefore, the healing process around a dental implant placed into an extraction socket needs to be deeply investigated in order to increase the predictability of this surgical approach. The aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. This study evaluated by histologic and histomorphometric analyses tissue healing around dental implants with marginal bone defects with and without flap elevation 1 week, 4 weeks and 12 weeks following implantation in the dogs. The main qualitative findings showed that after 1 week of implantation, almost no bone repair was observed and there was no significant difference between the two groups in terms of bone healing performance, inflammatory infiltrates (slight to moderate grade) and bone resorption (moderate to marked grade) limited to the coronal portion of the implanted sites. The two groups with or without flap elevation behaved similarly at this time period of implantation. Under the experimental conditions of this study, it appeared that no biological differences were observed between the two groups with and without flap elevation in terms of crestal bone repair, inflammation, marginal bone loss and soft tissue downgrowth. The qualitative differences observed might be imputable to fortuitous events. The histomorphometric measurements confirmed the qualitative trends observed. The limitations of this study, as of all animal studies, have to be found Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
in their translational aspects. The investigation on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method would be beneficial.
Response to Reviewers:
ewers' comments: April 21, 2014: Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs (aaid-joi-D-14-00114). A numerical rubric was used to measure and assess this manuscript. Points were assigned as: 0 points = too little information was provided; 5 basic information was provided; 10 points = ample information was provided. Points were reported as assigned points/possible points (Total Maximum Points Possible = 100). I.Title (9/10): II.Abstract (7/10): The abstract may be improved by briefly addressing the following to help people with annotated bibliographic searches: A.Limitations of the study. B.Implications of the study. C.Recommendations for future research. -The sentence “
“ was added to the abstract.
III.Introduction (9/10): IV.Methods (5/30): The following information may improve this manuscript: A.Animals: 1.Specifically indicting that the AICUC addressed the AWA [The Animal Welfare Act (AWA) (7 U.S.C. § 2131)] would help to support the importance of the protection of animals during research. -The relevant sentence was changed to “After ethical committee approval of study by theIACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.” 2.How were the dogs selected? -Still needs to be addressed (?) Marshall BioResources, USA 3.What were the inclusion and exclusion criteria for the dogs? Still needs to be addressed (?) Adult male (12 month old), mongrel dogs weighting 2530 kg What long-term follow-up monitoring and care did the dogs receive? -This was addressed in point 1 and reference was done to the relevant part of the methods when this is addressed (under surgery) B.Instrumentation: 1.(line 108): Who made the observations of the dependent variables? If it was only the author(s), how was experimenter bias controlled? -Still needs to be addressed (?) Two independent experienced investigators (board certified periodontologist or implantologist) did the clinical observations/measurements. In case of more than 10% discrepancies between their clinical observations/measurements a third investigator was involved. -The histological observations/measurements where conducted by a professional independent histologist relying on more than10 years experience in the field of bonemedical devices. This histologist is the Head of the Histology dept at NAMSA (USA) Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
2.(line 109 - 110): "These parameters allowed accurate evaluation?." Because the dependent variables were measured observationally, what calibration was used to help insure that the observed data were both reliable (inter rater and intra-rater) and valid? Still needs to be addressed (?). If no validation was done specifically for this study, Straumann must have validation studies for the different used measurements, one could give a reference. See above B 1. and all the study was conducted according to Dard M Methods and interpretation of performance studies for dental implants.In: BOUTRAND J.: Biocompatibility and performance of medical devices. Woodhead Publishing Ltd, Cambridge, UK, 2012, pp. 308-344 3.(line 109): "?graded from 0 (absent) to 4 (very marked or server) according to the ISO 10993-6." (line 130): "Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values." This is a problem and it is addressed in V-A (below). V. Results (5/30): A.The 0 - 4 scale (lines 109, 130) used in this study was an ordinal level measurement scale; therefore, means and standard deviations would not be an appropriate descriptive index of ordinal level measurements. -Table 1 was re-edited and results are now presented as counts of the different grading levels, and are consequently treated as ordinal in comparisons. B.((line 179): "The results of the descriptive statistical analysis are presented in table?.." (line 181): "The application of the Signed rank test revealed that it does not appear to be statistically significant?" There is a problem with this statement (see V-C below). -The description of the statistical analysis under ‘Methods’ has been re-edited. We describe in addition how the semi-quantitative results were summarized and compared. Results have been thoroughly re-edited. C.The "Sign rank" test, assuming that the author(s) means the Wilcoxon signed-rank test, is a formal inferential statistical test. The Wilcoxon is not used for informal "..descriptive statistical analysis?" -The name of the test was amended. The Wilcoxon signed-rank test was used when examining unadjusted comparisons and it was not meant to be related directly to the descriptive statistics in table 2. The presented unadjusted results presented under the first part of ‘Quantitative histological analysis’ have been changed. Now we present the mean difference between the values for flap minus values for no flap. We apologize for the confusion. D.(line 181): "The application of the Signed rank test revealed that it does not appear to be any statistically significant differences between groups?" Inferential statistical conclusions are made as either significant or not significant; therefore, "?does not appear?" is confusing. -The ‘Results’ have been re-edited as described in the point above and in te point under. E.A summary table for the "Signed rank test" would be helpful. -We would prefer to keep the results for the ‘unadjusted’ comparisons short and therefore present the ‘adjusted’ comparisons in more detail, as it is presented now in the results. Of course if the reviewer agrees. F.Table 1, 2, etc.: Tables need to be more clearly labeled. Some tables are extracted for citation in other publications (with journal approval). Table 1, for example, does not even indicate the source of the information (i.e., dogs, people, etc.).
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-Tables 1 and 2 have been re-edited, actually table 1 has been newly done. Clear titles were assigned and relevant foot notes added. -In the precedent version of the manuscript, table 1 was added as a picture but that table was not published before, permission would have not been necessary. We apologize for the confusion again. G.It would help if figures 1 - 5 were all discussed in text to assist readers to better understand their importance and use as they relate to the research question. -Figures 2 to 5 are presented in the ‘Results’ section, relevant values for the parameters were added to the figures under the graphs. We believe that this will make it easier for the reader (or for interested researchers in the specific values). Figure 1 was described under the ‘Methods’ section. Relevant figure legends have been added after the ‘Tables’ section, at the end of the manuscript. VI.Conclusion/Discussion (5/10): (line 259): A. "The qualitative differences observed might be imputable to fortuitous events." We have to delete this sentence This statement does not make empirical sense. Conclusions need to address the research question(s). Qualitative histology was conducted in full respect of the ISO Norm 10993-6 -Now your turn….still needs to be addressed (?) B. What were the limitations of the study? -Still needs to be addressed (?) -The limitations of this study, as of all animal studies, have to be found in their translational aspects. In the present case the choice of the animal and of the experimental models correspond both to state of the art recommendations (Dard, 2012) -Dard M. -Animal models for experimental surgical research in implant dentistry. -In: BALLO A.: Implant dentistry research guide: basic, translational and experimental clinical research. Nova Science Publishers, Inc., Hauppauge NY, USA, 2012, pp. 167190 C.What are the recommendation for future research? -Still needs to be addressed (?) To investigate on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method.. VII. Comments: The study is very interesting; however, there are major concerns that would need to be addressed before it would be considered for publication. The authors are encouraged to address the concerns listed by the reviewer and resubmit their work. -We thank the reviewer for his/hers constructive comments ??) Not necessary
VIII. Points: 40/100 April 21, 2014: Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs (aaid-joi-D-14-00114). A numerical rubric was used to measure and assess this manuscript. Points were assigned as: 0 points = too little information was provided; 5 basic information was provided; 10 points = ample information was provided. Points were reported as assigned points/possible points (Total Maximum Points Possible = 100). I.Title (9/10): II.Abstract (7/10): The abstract may be improved by briefly addressing the following to help people with annotated bibliographic searches: Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
A.Limitations of the study. B.Implications of the study. C.Recommendations for future research. -The sentence “
“ was added to the abstract.
III.Introduction (9/10): IV.Methods (5/30): The following information may improve this manuscript: A.Animals: 1.Specifically indicting that the AICUC addressed the AWA [The Animal Welfare Act (AWA) (7 U.S.C. § 2131)] would help to support the importance of the protection of animals during research. -The relevant sentence was changed to “After ethical committee approval of study by theIACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.” 2.How were the dogs selected? -Still needs to be addressed (?) 3.What were the inclusion and exclusion criteria for the dogs? -Still needs to be addressed (?) 4.What long-term follow-up monitoring and care did the dogs receive? -This was addressed in point 1 and reference was done to the relevant part of the methods when this is addressed (under surgery) B.Instrumentation: 1.(line 108): Who made the observations of the dependent variables? If it was only the author(s), how was experimenter bias controlled? -Still needs to be addressed (?) 2.(line 109 - 110): "These parameters allowed accurate evaluation?." Because the dependent variables were measured observationally, what calibration was used to help insure that the observed data were both reliable (inter rater and intra-rater) and valid? -Still needs to be addressed (?). If no validation was done specifically for this study, Straumann must have validation studies for the different used measurements, one could give a reference. 3.(line 109): "?graded from 0 (absent) to 4 (very marked or server) according to the ISO 10993-6." (line 130): "Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values." This is a problem and it is addressed in V-A (below). V. Results (5/30): A.The 0 - 4 scale (lines 109, 130) used in this study was an ordinal level measurement scale; therefore, means and standard deviations would not be an appropriate descriptive index of ordinal level measurements. -Table 1 was re-edited and results are now presented as counts of the different grading levels, and are consequently treated as ordinal in comparisons. B.((line 179): "The results of the descriptive statistical analysis are presented in table?.." (line 181): "The application of the Signed rank test revealed that it does not appear to be statistically significant?" There is a problem with this statement (see V-C below). Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
-The description of the statistical analysis under ‘Methods’ has been re-edited. We describe in addition how the semi-quantitative results were summarized and compared. Results have been thoroughly re-edited. C.The "Sign rank" test, assuming that the author(s) means the Wilcoxon signed-rank test, is a formal inferential statistical test. The Wilcoxon is not used for informal "..descriptive statistical analysis?" -The name of the test was amended. The Wilcoxon signed-rank test was used when examining unadjusted comparisons and it was not meant to be related directly to the descriptive statistics in table 2. The presented unadjusted results presented under the first part of ‘Quantitative histological analysis’ have been changed. Now we present the mean difference between the values for flap minus values for no flap. We apologize for the confusion. D.(line 181): "The application of the Signed rank test revealed that it does not appear to be any statistically significant differences between groups?" Inferential statistical conclusions are made as either significant or not significant; therefore, "?does not appear?" is confusing. -The ‘Results’ have been re-edited as described in the point above and in te point under. E.A summary table for the "Signed rank test" would be helpful. -We would prefer to keep the results for the ‘unadjusted’ comparisons short and therefore present the ‘adjusted’ comparisons in more detail, as it is presented now in the results. Of course if the reviewer agrees. F.Table 1, 2, etc.: Tables need to be more clearly labeled. Some tables are extracted for citation in other publications (with journal approval). Table 1, for example, does not even indicate the source of the information (i.e., dogs, people, etc.). -Tables 1 and 2 have been re-edited, actually table 1 has been newly done. Clear titles were assigned and relevant foot notes added. -In the precedent version of the manuscript, table 1 was added as a picture but that table was not published before, permission would have not been necessary. We apologize for the confusion again. G.It would help if figures 1 - 5 were all discussed in text to assist readers to better understand their importance and use as they relate to the research question. -Figures 2 to 5 are presented in the ‘Results’ section, relevant values for the parameters were added to the figures under the graphs. We believe that this will make it easier for the reader (or for interested researchers in the specific values). Figure 1 was described under the ‘Methods’ section. Relevant figure legends have been added after the ‘Tables’ section, at the end of the manuscript. VI.Conclusion/Discussion (5/10): (line 259): A. "The qualitative differences observed might be imputable to fortuitous events." This statement does not make empirical sense. Conclusions need to address the research question(s). -Now your turn….still needs to be addressed (?) B. What were the limitations of the study? -Still needs to be addressed (?) C.What are the recommendation for future research? -Still needs to be addressed (?)
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VII. Comments: The study is very interesting; however, there are major concerns that would need to be addressed before it would be considered for publication. The authors are encouraged to address the concerns listed by the reviewer and resubmit their work. -We thank the reviewer for his/hers constructive comments ??)
VIII. Points: 40/100
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Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs Nicolas Elian DDS Vizstara, Englewood Cliffs, New Jersey, 201 816-4000, [email protected] Wayne Kye DDS, Clinical Associate Professor, Periodontology & Implant Dentistry David B Kriser Dental Center, 421 First Avenue, New York, NY US 10010 tel: +1 212 998 9839, [email protected] 4904 43rd Ave, Woodside, NY, 11377, 718-898-9049, Hanae Saito DDS, Clinical Assistant Professor, Department of Periodontics ,University of Maryland School of Dentistry 650 W. Baltimore Street Rm 4201,Baltimore, MD 21201 , T-410-706-7152 , F- F:410-706-7201, [email protected] Michel M Dard, DDS, MD, Ph.D David B Kriser Dental Center, Periodontology & Implant Dentistry,421 First Avenue, Floor 3W New York, NY US 10010, 212 998 9741, [email protected] , [email protected] Richard D. Trushkowsky. David B Kriser Dental Center, Department of Cariology and Comprehensive Care. 421 First Avenue, Floor 7W New York, NY US 10010, tel: +1 212 992 7111 tel: +1 212 998 9746 fax: +1 212 995 4568 483 Jefferson Blvd, Staten Island, NY 10312, T-718-948-5808, F-718-948-4453 [email protected], [email protected] Dennis Tarnow DDS, Clinical Professor, Division of Periodontics, Columbia University College of Dental Medicine
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630 West 168th Street, Box 20 New York, NY 10032 150 E 58th St Suite 3200, New York, NY 10155. 212-752-7937, [email protected]
Abstract -
The technique of immediate implant placement after extraction has been conceived for preserving the residual bone support and soft tissue morphology. Nowadays this procedure is still not predictable and presents inconveniences both for the patient and the dentist. Therefore, the healing process around a dental implant placed into an extraction socket needs to be deeply investigated in order to increase the predictability of this surgical approach. The aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. This study evaluated by histologic and histomorphometric analyses tissue healing around dental implants with marginal bone defects with and without flap elevation 1 week, 4 weeks and 12 weeks following implantation in the dogs. The main qualitative findings showed that after 1 week of implantation, almost no bone repair was observed and there was no significant difference between the two groups in terms of bone healing performance, inflammatory infiltrates (slight to moderate grade) and bone resorption (moderate to marked grade) limited to the coronal portion of the implanted sites. The two groups with or without flap elevation behaved similarly at this time period of implantation. Under the experimental conditions of this study, it appeared that no biological differences were observed between the two groups with and without flap elevation in terms of crestal bone
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repair, inflammation, marginal bone loss and soft tissue downgrowth. The qualitative differences observed might be imputable to fortuitous events. The histomorphometric measurements confirmed the qualitative trends observed. The limitations of this study, as of all animal studies, have to be found in their translational aspects. The investigation on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method would be beneficial.
Key Words: dental implants, flap, no flap, bone loss
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Introduction In the late 1970s, Brånemark utilized extensive surgical flaps to adequately survey the surgical field prior to implant placement.1 An incision in the mucosa or mucobuccal fold would be made to allow the creation of a flap to expose the underlying bone. Implants would subsequently be placed and the flaps repositioned and sutured. 2,3 When a tooth is extracted, some loss of bone is inevitable.4 The resulting bone loss that ensues is mainly in the horizontal aspect with some loss also occurring in the vertical dimension. 5 This is due to collapse of the buccal wall of the socket in the lingual direction due to remodeling of the bone. 4 The first published work on immediate implants in 1978 has resulted in amplified interest since that time. 6 The placement of implants into extraction sockets has been shown to be as predictable as implants placed in healed sites. 7, 8 The use of immediate placement in the maxillary anterior region where esthetics is of critical importance has demonstrated a potential problem. Recession of the peri-implant mucosa may occur to varying degrees depending upon: tissue biotype, connection of a provisional immediately following implant placement, thickness of buccal bone, location of the implant shoulder and grafting of the labial peri-implant marginal defect with bone or bone replacements. 9 In addition to these factors the facial socket wall consists mainly of bundle bone that is vulnerable to vertical and horizontal resorption. 10 Originally it was thought that immediate implant placement would maintain the anatomy and contour of the ridge. 11 However, additional studies failed to prove this premise but these studies were implemented with both vestibular and lingual flaps. 12, 13 Additional studies by others that compared immediate placement (flap vs. flapless) into extraction sockets did not show prevention of alveolar resorption or lack of dimensional changes of the alveolar process subsequent to extraction. 14, 15 An earlier study by some of the same authors demonstrated that
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immediate flapless surgery resulted in significant decrease in vestibular biologic width and minor reduction in buccal plate resorption. 16 Another study concluded flapless surgical placement may result in increased initial implant stability compared to implants placed with a mucoperiostal flap. 17 In view of the diverse results, the aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. A qualitative, semiquantitative and a histomorphometric evaluation were done. The dimensions, geometry and positions of the gap between the implant and the bone, the thickness of the surrounding bone, particularly buccal, the flap or flapless implant placement technique were examined since they will determine and influence the healing process.
Materials and Methods. Animals This study was performed on 9 male Mongrel dogs, age 12/months old, weight 25-30kg selected from Marshall BioResources, USA. After ethical committee approval of study by the IACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.
Experimental model Every of the nine animals received six implants with three implants immediately placed in extraction sites with no flap and another three implants placed on the contralateral side with a
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flap creating a split-mouth design with a total of 54 implant sites. The dental implants were randomly assigned to the left and right sites in each dog mandible. The implant duration was of 3 months. The dental implants used in this study were bone-level screw implants made of commercially pure titanium and prepared with a rough (sandblasted acid-etched) hydrophilic surface treatment. The dimensions of the implants used were 3.3 mm diameter with 10mm length.
Surgery Dogs were fasted at least 12 hours before administration of anesthesia to minimize risk of inhalation. One surgery was performed on each dog in the both sides of the mandible. The procedure was performed under aseptic conditions. The animals were sedated and then placed under general anesthesia. Pretreatment sedation was given 15-20 minutes prior to induction. (Acepromazine .05- 0.1 mg/kg IM). An IV line was placed in the front leg. Preinduction sedation included Atropine (0.05mg/kg SQ or IM), Ketamine (5mg/kg IV), and Valium (0.5mg/kg IV). The dogs were ventilated via an endotracheal tube with 100% oxygen and maintained under anesthesia with 1.5-2.0% Isoflurane in 2L/min. flow of oxygen. The respiratory rate was regulated at 12 breaths / min. Local anesthesia was injected in the area foreseen for surgery (Bupivacaine (max 4 mg/kg) The teeth P1-3 M1 were extracted and 6 dental implants were immediately inserted in the mandibles of each dog (3 each side). In one side of the mandible, crestal incisions were made extending from the distal aspect of the canine, buccally and lingually, to the distal aspect of the first molar, buccally and lingually, and a full-thickness flap was reflected. On the other side the flap was not opened. The mandibular premolars and first molar of both sides of the arch were
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extracted with care by hemisectioning with a long bur and gentle use of forceps to avoid any compromising of the bony ridges. Three Straumann® Bone Level Implants were placed. On one side, implant installation into the socket was performed without opening the flap. The recipient sites were prepared for implant surgery according to the guideline provided by the manufacturer (Straumann, Basel, Switzerland). The implants were placed so that the marginal level of the rough surface will be flush with the buccal bone crest. After completion of implant insertion, a gold alloy healing abutment was secured onto each. The flaps were sutured with absorbable materials (Vicryl, Ethicon). Animals were monitored and kept warmed immediately after surgery until fully recovered. Pain of the animals was controlled by help of a Fentanyl patch (75 µg/h for 72 hours). Antibiotics were administered: penicillin G q 48 h for 7 days. Animals were observed daily for bleeding, pain or discomfort and appetite. The responsible veterinary service was notified of any abnormalities and consulted for treatment options. The veterinary services observed the animals daily in the post-surgery and performed the oral hygiene procedure three times week. Plaque control was accomplished using a chlorhexidine solution that was sprayed on all mandibular experimental sites. The dogs were maintained in soft diet during the course of the study. Sets of three animals were sacrificed 1 week, 4 weeks and 12 weeks after implantation. This was conducted with an overdose of sodium-pentothal (Abbott Laboratories, Chicago, IL) (120 mg/kg body weight).
Histological preparation The mandibles were removed and block biopsies of each implant site was dissected using a diamond saw ‡‡‡ (Exact, Apparatebau, Norderstedt, Germany). The specimens were dehydrated
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in alcohol solutions of increasing concentration, cleared in xylene and embedded in PMMA (polymethylmetacrylate) resin. For each hemi-mandible, three bucco-lingual histological sections were prepared. . The sections were obtained by a micro-cutting and grinding technique adapted from Donath 18 The sections were then stained for qualitative and quantitative histology with the modified polychromatic Paragon staining. The sections obtained were about 20µ thick.
Qualitative Histopathological interpretation -
A qualitative and semi-quantitative histological evaluation was performed. Two independent experienced investigators (board certified periodontologist or implantologist) did the clinical observations/measurements. In case of more than 10% discrepancies between their clinical observations/measurements a third investigator was involved.
-
The histological observations/measurements where conducted by a professional independent histologist relying on more than10 years’ experience in the field of bonemedical devices. This histologist is the Head of the Histology dept at NAMSA (USA)
Each parameter was graded from 0 (absent) to 4 (very marked or severe) according to the ISO 10993-6. These parameters allowed an accurate evaluation of any inflammation, foreign body reaction, immunologic, bone ingrowth, fibrosis, bone maturation, or resorption and degradation of the implant material. The study was conducted according to Dard M
19
The histological
sections were observed using a Nikon microscope (Eclipse E600) fitted with x2, x4, x10, x20 and x40 objectives. Histological micrographs were taken.
Histomorphometric analysis
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The stained resin sections were observed using a Zeiss Axioscope microscope fitted with x5, x10, x20 and x40 objectives and equipped with color images analyzing system. The different parameters measured are presented in (Figure1).
Statistical analysis Parameters from the semi-quantitative histological evaluation were summarized as counts of the different grades. To compare the grading of implants with flap to without flap the implants were paired within animals by position in the mandible. The Sign test was used to evaluate the comparison of the ordinal grading. Outcome variables from the histomorphometric analysis, height of peri-implant mucosa, height of the connective tissue in contact with the implant surface, barrier epithelium, extension of epithelium downgrowth, distance from shoulder of the implant to the first bone to implant contact, distance from shoulder of the implant to the bone level, bone area to total area ratio and bone to implant contact, were measured in the buccal and in the lingual planes of each implant. Since the same treatment (flap or no-flap) was applied to the three implants in one side of the mandible, the measurements for the buccal plane of these three implants were averaged and the then compared to the similarly averaged measurements for the lingual plane using mixed regression models adjusted by mandible side and animal effects. Buccal and lingual measurements were significantly different for most of the outcomes, yielding two measurements per implant. Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values.
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Comparisons of flap to no flap treatment for each of the endpoints were first examined using the Wilcoxon signed-rank test for paired comparisons and then using mixed regression models which included mandible side, implant position in the mandible and measurement plane as fix effects and the factor animal as a random effect. Last, comparisons among endpoints were performed using similar models, but stratifying by treatment (flap or no flap). Mixed models provide an allowance for the effect of repeated measurements and possible correlations due to position of the implants in the mandible. The level of significance was set at p
aaid-joi-D-14-00114R1
Full Title:
Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs
Short Title:
Dental implants with and without flap elevation
Article Type:
Dental Implant Science Research
Keywords:
dental implants; flap, no flap; bone loss
Corresponding Author:
Richard Dennis Trushkowsky, DDS NYU College of Dentistry New York, New York UNITED STATES
Corresponding Author Secondary Information: Corresponding Author's Institution:
NYU College of Dentistry
Corresponding Author's Secondary Institution: First Author:
Nicolas; Elian,, DDS
First Author Secondary Information: Order of Authors:
Nicolas; Elian,, DDS Wayne Kye, DDS Hanae Saito, DDS, MS, CCRC Michel M Dard, DDS, MD.PhD Richard Dennis Trushkowsky, DDS Dennis Tarnow, DDS
Order of Authors Secondary Information: Abstract:
Abstract -The technique of immediate implant placement after extraction has been conceived for preserving the residual bone support and soft tissue morphology. Nowadays this procedure is still not predictable and presents inconveniences both for the patient and the dentist. Therefore, the healing process around a dental implant placed into an extraction socket needs to be deeply investigated in order to increase the predictability of this surgical approach. The aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. This study evaluated by histologic and histomorphometric analyses tissue healing around dental implants with marginal bone defects with and without flap elevation 1 week, 4 weeks and 12 weeks following implantation in the dogs. The main qualitative findings showed that after 1 week of implantation, almost no bone repair was observed and there was no significant difference between the two groups in terms of bone healing performance, inflammatory infiltrates (slight to moderate grade) and bone resorption (moderate to marked grade) limited to the coronal portion of the implanted sites. The two groups with or without flap elevation behaved similarly at this time period of implantation. Under the experimental conditions of this study, it appeared that no biological differences were observed between the two groups with and without flap elevation in terms of crestal bone repair, inflammation, marginal bone loss and soft tissue downgrowth. The qualitative differences observed might be imputable to fortuitous events. The histomorphometric measurements confirmed the qualitative trends observed. The limitations of this study, as of all animal studies, have to be found Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
in their translational aspects. The investigation on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method would be beneficial.
Response to Reviewers:
ewers' comments: April 21, 2014: Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs (aaid-joi-D-14-00114). A numerical rubric was used to measure and assess this manuscript. Points were assigned as: 0 points = too little information was provided; 5 basic information was provided; 10 points = ample information was provided. Points were reported as assigned points/possible points (Total Maximum Points Possible = 100). I.Title (9/10): II.Abstract (7/10): The abstract may be improved by briefly addressing the following to help people with annotated bibliographic searches: A.Limitations of the study. B.Implications of the study. C.Recommendations for future research. -The sentence “
“ was added to the abstract.
III.Introduction (9/10): IV.Methods (5/30): The following information may improve this manuscript: A.Animals: 1.Specifically indicting that the AICUC addressed the AWA [The Animal Welfare Act (AWA) (7 U.S.C. § 2131)] would help to support the importance of the protection of animals during research. -The relevant sentence was changed to “After ethical committee approval of study by theIACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.” 2.How were the dogs selected? -Still needs to be addressed (?) Marshall BioResources, USA 3.What were the inclusion and exclusion criteria for the dogs? Still needs to be addressed (?) Adult male (12 month old), mongrel dogs weighting 2530 kg What long-term follow-up monitoring and care did the dogs receive? -This was addressed in point 1 and reference was done to the relevant part of the methods when this is addressed (under surgery) B.Instrumentation: 1.(line 108): Who made the observations of the dependent variables? If it was only the author(s), how was experimenter bias controlled? -Still needs to be addressed (?) Two independent experienced investigators (board certified periodontologist or implantologist) did the clinical observations/measurements. In case of more than 10% discrepancies between their clinical observations/measurements a third investigator was involved. -The histological observations/measurements where conducted by a professional independent histologist relying on more than10 years experience in the field of bonemedical devices. This histologist is the Head of the Histology dept at NAMSA (USA) Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
2.(line 109 - 110): "These parameters allowed accurate evaluation?." Because the dependent variables were measured observationally, what calibration was used to help insure that the observed data were both reliable (inter rater and intra-rater) and valid? Still needs to be addressed (?). If no validation was done specifically for this study, Straumann must have validation studies for the different used measurements, one could give a reference. See above B 1. and all the study was conducted according to Dard M Methods and interpretation of performance studies for dental implants.In: BOUTRAND J.: Biocompatibility and performance of medical devices. Woodhead Publishing Ltd, Cambridge, UK, 2012, pp. 308-344 3.(line 109): "?graded from 0 (absent) to 4 (very marked or server) according to the ISO 10993-6." (line 130): "Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values." This is a problem and it is addressed in V-A (below). V. Results (5/30): A.The 0 - 4 scale (lines 109, 130) used in this study was an ordinal level measurement scale; therefore, means and standard deviations would not be an appropriate descriptive index of ordinal level measurements. -Table 1 was re-edited and results are now presented as counts of the different grading levels, and are consequently treated as ordinal in comparisons. B.((line 179): "The results of the descriptive statistical analysis are presented in table?.." (line 181): "The application of the Signed rank test revealed that it does not appear to be statistically significant?" There is a problem with this statement (see V-C below). -The description of the statistical analysis under ‘Methods’ has been re-edited. We describe in addition how the semi-quantitative results were summarized and compared. Results have been thoroughly re-edited. C.The "Sign rank" test, assuming that the author(s) means the Wilcoxon signed-rank test, is a formal inferential statistical test. The Wilcoxon is not used for informal "..descriptive statistical analysis?" -The name of the test was amended. The Wilcoxon signed-rank test was used when examining unadjusted comparisons and it was not meant to be related directly to the descriptive statistics in table 2. The presented unadjusted results presented under the first part of ‘Quantitative histological analysis’ have been changed. Now we present the mean difference between the values for flap minus values for no flap. We apologize for the confusion. D.(line 181): "The application of the Signed rank test revealed that it does not appear to be any statistically significant differences between groups?" Inferential statistical conclusions are made as either significant or not significant; therefore, "?does not appear?" is confusing. -The ‘Results’ have been re-edited as described in the point above and in te point under. E.A summary table for the "Signed rank test" would be helpful. -We would prefer to keep the results for the ‘unadjusted’ comparisons short and therefore present the ‘adjusted’ comparisons in more detail, as it is presented now in the results. Of course if the reviewer agrees. F.Table 1, 2, etc.: Tables need to be more clearly labeled. Some tables are extracted for citation in other publications (with journal approval). Table 1, for example, does not even indicate the source of the information (i.e., dogs, people, etc.).
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-Tables 1 and 2 have been re-edited, actually table 1 has been newly done. Clear titles were assigned and relevant foot notes added. -In the precedent version of the manuscript, table 1 was added as a picture but that table was not published before, permission would have not been necessary. We apologize for the confusion again. G.It would help if figures 1 - 5 were all discussed in text to assist readers to better understand their importance and use as they relate to the research question. -Figures 2 to 5 are presented in the ‘Results’ section, relevant values for the parameters were added to the figures under the graphs. We believe that this will make it easier for the reader (or for interested researchers in the specific values). Figure 1 was described under the ‘Methods’ section. Relevant figure legends have been added after the ‘Tables’ section, at the end of the manuscript. VI.Conclusion/Discussion (5/10): (line 259): A. "The qualitative differences observed might be imputable to fortuitous events." We have to delete this sentence This statement does not make empirical sense. Conclusions need to address the research question(s). Qualitative histology was conducted in full respect of the ISO Norm 10993-6 -Now your turn….still needs to be addressed (?) B. What were the limitations of the study? -Still needs to be addressed (?) -The limitations of this study, as of all animal studies, have to be found in their translational aspects. In the present case the choice of the animal and of the experimental models correspond both to state of the art recommendations (Dard, 2012) -Dard M. -Animal models for experimental surgical research in implant dentistry. -In: BALLO A.: Implant dentistry research guide: basic, translational and experimental clinical research. Nova Science Publishers, Inc., Hauppauge NY, USA, 2012, pp. 167190 C.What are the recommendation for future research? -Still needs to be addressed (?) To investigate on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method.. VII. Comments: The study is very interesting; however, there are major concerns that would need to be addressed before it would be considered for publication. The authors are encouraged to address the concerns listed by the reviewer and resubmit their work. -We thank the reviewer for his/hers constructive comments ??) Not necessary
VIII. Points: 40/100 April 21, 2014: Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs (aaid-joi-D-14-00114). A numerical rubric was used to measure and assess this manuscript. Points were assigned as: 0 points = too little information was provided; 5 basic information was provided; 10 points = ample information was provided. Points were reported as assigned points/possible points (Total Maximum Points Possible = 100). I.Title (9/10): II.Abstract (7/10): The abstract may be improved by briefly addressing the following to help people with annotated bibliographic searches: Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
A.Limitations of the study. B.Implications of the study. C.Recommendations for future research. -The sentence “
“ was added to the abstract.
III.Introduction (9/10): IV.Methods (5/30): The following information may improve this manuscript: A.Animals: 1.Specifically indicting that the AICUC addressed the AWA [The Animal Welfare Act (AWA) (7 U.S.C. § 2131)] would help to support the importance of the protection of animals during research. -The relevant sentence was changed to “After ethical committee approval of study by theIACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.” 2.How were the dogs selected? -Still needs to be addressed (?) 3.What were the inclusion and exclusion criteria for the dogs? -Still needs to be addressed (?) 4.What long-term follow-up monitoring and care did the dogs receive? -This was addressed in point 1 and reference was done to the relevant part of the methods when this is addressed (under surgery) B.Instrumentation: 1.(line 108): Who made the observations of the dependent variables? If it was only the author(s), how was experimenter bias controlled? -Still needs to be addressed (?) 2.(line 109 - 110): "These parameters allowed accurate evaluation?." Because the dependent variables were measured observationally, what calibration was used to help insure that the observed data were both reliable (inter rater and intra-rater) and valid? -Still needs to be addressed (?). If no validation was done specifically for this study, Straumann must have validation studies for the different used measurements, one could give a reference. 3.(line 109): "?graded from 0 (absent) to 4 (very marked or server) according to the ISO 10993-6." (line 130): "Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values." This is a problem and it is addressed in V-A (below). V. Results (5/30): A.The 0 - 4 scale (lines 109, 130) used in this study was an ordinal level measurement scale; therefore, means and standard deviations would not be an appropriate descriptive index of ordinal level measurements. -Table 1 was re-edited and results are now presented as counts of the different grading levels, and are consequently treated as ordinal in comparisons. B.((line 179): "The results of the descriptive statistical analysis are presented in table?.." (line 181): "The application of the Signed rank test revealed that it does not appear to be statistically significant?" There is a problem with this statement (see V-C below). Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation
-The description of the statistical analysis under ‘Methods’ has been re-edited. We describe in addition how the semi-quantitative results were summarized and compared. Results have been thoroughly re-edited. C.The "Sign rank" test, assuming that the author(s) means the Wilcoxon signed-rank test, is a formal inferential statistical test. The Wilcoxon is not used for informal "..descriptive statistical analysis?" -The name of the test was amended. The Wilcoxon signed-rank test was used when examining unadjusted comparisons and it was not meant to be related directly to the descriptive statistics in table 2. The presented unadjusted results presented under the first part of ‘Quantitative histological analysis’ have been changed. Now we present the mean difference between the values for flap minus values for no flap. We apologize for the confusion. D.(line 181): "The application of the Signed rank test revealed that it does not appear to be any statistically significant differences between groups?" Inferential statistical conclusions are made as either significant or not significant; therefore, "?does not appear?" is confusing. -The ‘Results’ have been re-edited as described in the point above and in te point under. E.A summary table for the "Signed rank test" would be helpful. -We would prefer to keep the results for the ‘unadjusted’ comparisons short and therefore present the ‘adjusted’ comparisons in more detail, as it is presented now in the results. Of course if the reviewer agrees. F.Table 1, 2, etc.: Tables need to be more clearly labeled. Some tables are extracted for citation in other publications (with journal approval). Table 1, for example, does not even indicate the source of the information (i.e., dogs, people, etc.). -Tables 1 and 2 have been re-edited, actually table 1 has been newly done. Clear titles were assigned and relevant foot notes added. -In the precedent version of the manuscript, table 1 was added as a picture but that table was not published before, permission would have not been necessary. We apologize for the confusion again. G.It would help if figures 1 - 5 were all discussed in text to assist readers to better understand their importance and use as they relate to the research question. -Figures 2 to 5 are presented in the ‘Results’ section, relevant values for the parameters were added to the figures under the graphs. We believe that this will make it easier for the reader (or for interested researchers in the specific values). Figure 1 was described under the ‘Methods’ section. Relevant figure legends have been added after the ‘Tables’ section, at the end of the manuscript. VI.Conclusion/Discussion (5/10): (line 259): A. "The qualitative differences observed might be imputable to fortuitous events." This statement does not make empirical sense. Conclusions need to address the research question(s). -Now your turn….still needs to be addressed (?) B. What were the limitations of the study? -Still needs to be addressed (?) C.What are the recommendation for future research? -Still needs to be addressed (?)
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VII. Comments: The study is very interesting; however, there are major concerns that would need to be addressed before it would be considered for publication. The authors are encouraged to address the concerns listed by the reviewer and resubmit their work. -We thank the reviewer for his/hers constructive comments ??)
VIII. Points: 40/100
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Tissue healing around dental implants with marginal bone defects with and without flap elevation. An experimental study in dogs Nicolas Elian DDS Vizstara, Englewood Cliffs, New Jersey, 201 816-4000, [email protected] Wayne Kye DDS, Clinical Associate Professor, Periodontology & Implant Dentistry David B Kriser Dental Center, 421 First Avenue, New York, NY US 10010 tel: +1 212 998 9839, [email protected] 4904 43rd Ave, Woodside, NY, 11377, 718-898-9049, Hanae Saito DDS, Clinical Assistant Professor, Department of Periodontics ,University of Maryland School of Dentistry 650 W. Baltimore Street Rm 4201,Baltimore, MD 21201 , T-410-706-7152 , F- F:410-706-7201, [email protected] Michel M Dard, DDS, MD, Ph.D David B Kriser Dental Center, Periodontology & Implant Dentistry,421 First Avenue, Floor 3W New York, NY US 10010, 212 998 9741, [email protected] , [email protected] Richard D. Trushkowsky. David B Kriser Dental Center, Department of Cariology and Comprehensive Care. 421 First Avenue, Floor 7W New York, NY US 10010, tel: +1 212 992 7111 tel: +1 212 998 9746 fax: +1 212 995 4568 483 Jefferson Blvd, Staten Island, NY 10312, T-718-948-5808, F-718-948-4453 [email protected], [email protected] Dennis Tarnow DDS, Clinical Professor, Division of Periodontics, Columbia University College of Dental Medicine
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630 West 168th Street, Box 20 New York, NY 10032 150 E 58th St Suite 3200, New York, NY 10155. 212-752-7937, [email protected]
Abstract -
The technique of immediate implant placement after extraction has been conceived for preserving the residual bone support and soft tissue morphology. Nowadays this procedure is still not predictable and presents inconveniences both for the patient and the dentist. Therefore, the healing process around a dental implant placed into an extraction socket needs to be deeply investigated in order to increase the predictability of this surgical approach. The aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. This study evaluated by histologic and histomorphometric analyses tissue healing around dental implants with marginal bone defects with and without flap elevation 1 week, 4 weeks and 12 weeks following implantation in the dogs. The main qualitative findings showed that after 1 week of implantation, almost no bone repair was observed and there was no significant difference between the two groups in terms of bone healing performance, inflammatory infiltrates (slight to moderate grade) and bone resorption (moderate to marked grade) limited to the coronal portion of the implanted sites. The two groups with or without flap elevation behaved similarly at this time period of implantation. Under the experimental conditions of this study, it appeared that no biological differences were observed between the two groups with and without flap elevation in terms of crestal bone
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repair, inflammation, marginal bone loss and soft tissue downgrowth. The qualitative differences observed might be imputable to fortuitous events. The histomorphometric measurements confirmed the qualitative trends observed. The limitations of this study, as of all animal studies, have to be found in their translational aspects. The investigation on the same topic in a human population by setting up a controlled, randomized, prospective trial including a sufficient amount of patients who can be investigated on according to the split-mouth method would be beneficial.
Key Words: dental implants, flap, no flap, bone loss
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Introduction In the late 1970s, Brånemark utilized extensive surgical flaps to adequately survey the surgical field prior to implant placement.1 An incision in the mucosa or mucobuccal fold would be made to allow the creation of a flap to expose the underlying bone. Implants would subsequently be placed and the flaps repositioned and sutured. 2,3 When a tooth is extracted, some loss of bone is inevitable.4 The resulting bone loss that ensues is mainly in the horizontal aspect with some loss also occurring in the vertical dimension. 5 This is due to collapse of the buccal wall of the socket in the lingual direction due to remodeling of the bone. 4 The first published work on immediate implants in 1978 has resulted in amplified interest since that time. 6 The placement of implants into extraction sockets has been shown to be as predictable as implants placed in healed sites. 7, 8 The use of immediate placement in the maxillary anterior region where esthetics is of critical importance has demonstrated a potential problem. Recession of the peri-implant mucosa may occur to varying degrees depending upon: tissue biotype, connection of a provisional immediately following implant placement, thickness of buccal bone, location of the implant shoulder and grafting of the labial peri-implant marginal defect with bone or bone replacements. 9 In addition to these factors the facial socket wall consists mainly of bundle bone that is vulnerable to vertical and horizontal resorption. 10 Originally it was thought that immediate implant placement would maintain the anatomy and contour of the ridge. 11 However, additional studies failed to prove this premise but these studies were implemented with both vestibular and lingual flaps. 12, 13 Additional studies by others that compared immediate placement (flap vs. flapless) into extraction sockets did not show prevention of alveolar resorption or lack of dimensional changes of the alveolar process subsequent to extraction. 14, 15 An earlier study by some of the same authors demonstrated that
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immediate flapless surgery resulted in significant decrease in vestibular biologic width and minor reduction in buccal plate resorption. 16 Another study concluded flapless surgical placement may result in increased initial implant stability compared to implants placed with a mucoperiostal flap. 17 In view of the diverse results, the aim of the present investigation was to evaluate the healing of bone defects (fresh extraction sockets) following implant installation with flap elevation and primary closure compared to implant installation without flap elevation. A qualitative, semiquantitative and a histomorphometric evaluation were done. The dimensions, geometry and positions of the gap between the implant and the bone, the thickness of the surrounding bone, particularly buccal, the flap or flapless implant placement technique were examined since they will determine and influence the healing process.
Materials and Methods. Animals This study was performed on 9 male Mongrel dogs, age 12/months old, weight 25-30kg selected from Marshall BioResources, USA. After ethical committee approval of study by the IACUC of New York University College of Dentistry, the study was initiated and conducted according to the Animal Welfare Act (7 U.S.C § 2131) guidelines. The animals were kept in specially designated areas and under supervision of veterinarian staff during the whole study period as described below.
Experimental model Every of the nine animals received six implants with three implants immediately placed in extraction sites with no flap and another three implants placed on the contralateral side with a
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flap creating a split-mouth design with a total of 54 implant sites. The dental implants were randomly assigned to the left and right sites in each dog mandible. The implant duration was of 3 months. The dental implants used in this study were bone-level screw implants made of commercially pure titanium and prepared with a rough (sandblasted acid-etched) hydrophilic surface treatment. The dimensions of the implants used were 3.3 mm diameter with 10mm length.
Surgery Dogs were fasted at least 12 hours before administration of anesthesia to minimize risk of inhalation. One surgery was performed on each dog in the both sides of the mandible. The procedure was performed under aseptic conditions. The animals were sedated and then placed under general anesthesia. Pretreatment sedation was given 15-20 minutes prior to induction. (Acepromazine .05- 0.1 mg/kg IM). An IV line was placed in the front leg. Preinduction sedation included Atropine (0.05mg/kg SQ or IM), Ketamine (5mg/kg IV), and Valium (0.5mg/kg IV). The dogs were ventilated via an endotracheal tube with 100% oxygen and maintained under anesthesia with 1.5-2.0% Isoflurane in 2L/min. flow of oxygen. The respiratory rate was regulated at 12 breaths / min. Local anesthesia was injected in the area foreseen for surgery (Bupivacaine (max 4 mg/kg) The teeth P1-3 M1 were extracted and 6 dental implants were immediately inserted in the mandibles of each dog (3 each side). In one side of the mandible, crestal incisions were made extending from the distal aspect of the canine, buccally and lingually, to the distal aspect of the first molar, buccally and lingually, and a full-thickness flap was reflected. On the other side the flap was not opened. The mandibular premolars and first molar of both sides of the arch were
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extracted with care by hemisectioning with a long bur and gentle use of forceps to avoid any compromising of the bony ridges. Three Straumann® Bone Level Implants were placed. On one side, implant installation into the socket was performed without opening the flap. The recipient sites were prepared for implant surgery according to the guideline provided by the manufacturer (Straumann, Basel, Switzerland). The implants were placed so that the marginal level of the rough surface will be flush with the buccal bone crest. After completion of implant insertion, a gold alloy healing abutment was secured onto each. The flaps were sutured with absorbable materials (Vicryl, Ethicon). Animals were monitored and kept warmed immediately after surgery until fully recovered. Pain of the animals was controlled by help of a Fentanyl patch (75 µg/h for 72 hours). Antibiotics were administered: penicillin G q 48 h for 7 days. Animals were observed daily for bleeding, pain or discomfort and appetite. The responsible veterinary service was notified of any abnormalities and consulted for treatment options. The veterinary services observed the animals daily in the post-surgery and performed the oral hygiene procedure three times week. Plaque control was accomplished using a chlorhexidine solution that was sprayed on all mandibular experimental sites. The dogs were maintained in soft diet during the course of the study. Sets of three animals were sacrificed 1 week, 4 weeks and 12 weeks after implantation. This was conducted with an overdose of sodium-pentothal (Abbott Laboratories, Chicago, IL) (120 mg/kg body weight).
Histological preparation The mandibles were removed and block biopsies of each implant site was dissected using a diamond saw ‡‡‡ (Exact, Apparatebau, Norderstedt, Germany). The specimens were dehydrated
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in alcohol solutions of increasing concentration, cleared in xylene and embedded in PMMA (polymethylmetacrylate) resin. For each hemi-mandible, three bucco-lingual histological sections were prepared. . The sections were obtained by a micro-cutting and grinding technique adapted from Donath 18 The sections were then stained for qualitative and quantitative histology with the modified polychromatic Paragon staining. The sections obtained were about 20µ thick.
Qualitative Histopathological interpretation -
A qualitative and semi-quantitative histological evaluation was performed. Two independent experienced investigators (board certified periodontologist or implantologist) did the clinical observations/measurements. In case of more than 10% discrepancies between their clinical observations/measurements a third investigator was involved.
-
The histological observations/measurements where conducted by a professional independent histologist relying on more than10 years’ experience in the field of bonemedical devices. This histologist is the Head of the Histology dept at NAMSA (USA)
Each parameter was graded from 0 (absent) to 4 (very marked or severe) according to the ISO 10993-6. These parameters allowed an accurate evaluation of any inflammation, foreign body reaction, immunologic, bone ingrowth, fibrosis, bone maturation, or resorption and degradation of the implant material. The study was conducted according to Dard M
19
The histological
sections were observed using a Nikon microscope (Eclipse E600) fitted with x2, x4, x10, x20 and x40 objectives. Histological micrographs were taken.
Histomorphometric analysis
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The stained resin sections were observed using a Zeiss Axioscope microscope fitted with x5, x10, x20 and x40 objectives and equipped with color images analyzing system. The different parameters measured are presented in (Figure1).
Statistical analysis Parameters from the semi-quantitative histological evaluation were summarized as counts of the different grades. To compare the grading of implants with flap to without flap the implants were paired within animals by position in the mandible. The Sign test was used to evaluate the comparison of the ordinal grading. Outcome variables from the histomorphometric analysis, height of peri-implant mucosa, height of the connective tissue in contact with the implant surface, barrier epithelium, extension of epithelium downgrowth, distance from shoulder of the implant to the first bone to implant contact, distance from shoulder of the implant to the bone level, bone area to total area ratio and bone to implant contact, were measured in the buccal and in the lingual planes of each implant. Since the same treatment (flap or no-flap) was applied to the three implants in one side of the mandible, the measurements for the buccal plane of these three implants were averaged and the then compared to the similarly averaged measurements for the lingual plane using mixed regression models adjusted by mandible side and animal effects. Buccal and lingual measurements were significantly different for most of the outcomes, yielding two measurements per implant. Measurements of the outcome variables were then summarized by calculating their means, standard deviations and quartile values.
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Comparisons of flap to no flap treatment for each of the endpoints were first examined using the Wilcoxon signed-rank test for paired comparisons and then using mixed regression models which included mandible side, implant position in the mandible and measurement plane as fix effects and the factor animal as a random effect. Last, comparisons among endpoints were performed using similar models, but stratifying by treatment (flap or no flap). Mixed models provide an allowance for the effect of repeated measurements and possible correlations due to position of the implants in the mandible. The level of significance was set at p
