Crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged and submerged implants in the canine mandible

BACKGROUND: Today, implants are placed using both non-submerged and submerged approaches, and in 1- and 2-piece configurations. Previous work has demonstrated that peri-implant crestal bone reactions differ radiographically under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of the interface (microgap) between the implant and abutment/restoration in 2-piece configurations. The purpose of this investigation was to examine histometrically crestal bone changes around unloaded non-submerged and submerged 1- and 2-piece titanium implants in a side-by-side comparison. METHODS: A total of 59 titanium implants were randomly placed in edentulous mandibular areas of 5 foxhounds, forming 6 different implant subgroups (types A-F). In general, all implants had a relatively smooth, machined coronal portion as well as a rough, sandblasted and acid-etched (SLA) apical portion. Implant types A-C were placed in a non-submerged approach, while types D-F were inserted in a submerged fashion. Type A and B implants were 1-piece implants with the rough/smooth border (r/s) at the alveolar crest (type A) or 1.0 mm below (type B). Type C implants had an abutment placed at the time of surgery with the interface located at the bone crest level. In the submerged group, types D-F, the interface was located either at the bone crest level (type D), 1 mm above (type E), or 1 mm below (type F). Three months after implant placement, abutment connection was performed in the submerged implant groups. At 6 months, all animals were sacrificed. Non-decalcified histology was analyzed by evaluating peri-implant crestal bone levels. RESULTS: For types A and B, mean crestal bone levels were located adjacent (within 0.20 mm) to the rough/smooth border (r/s). For type C implants, the mean distance (+/- standard deviation) between the interface and the crestal bone level was 1.68 mm (+/- 0.19 mm) with an r/s border to first bone-to-implant contact (fBIC) of 0.39 mm (+/- 0.23 mm); for type D, 1.57 mm (+/- 0.22 mm) with an r/s border to fBIC of 0.28 mm (+/- 0.21 mm); for type E, 2.64 mm (+/- 0.24 mm) with an r/s border to fBIC of 0.06 mm (+/- 0.27 mm); and for type F, 1.25 mm (+/- 0.40 mm) with an r/s border to fBIC of 0.89 mm (+/- 0.41 mm). CONCLUSIONS: The location of a rough/smooth border on the surface of non-submerged 1-piece implants placed at the bone crest level or 1 mm below, respectively, determines the level of the fBIC. In all 2-piece implants, however, the location of the interface (microgap), when located at or below the alveolar crest, determines the amount of crestal bone resorption. If the same interface is located 1 mm coronal to the alveolar crest, the fBIC is located at the r/s border. These findings, as evaluated by non-decalcified histology under unloaded conditions, demonstrate that crestal bone changes occur during the early phase of healing after implant placement. Furthermore, these changes are dependent on the surface characteristics of the implant and the presence/absence as well as the location of an interface (microgap). Crestal bone changes were not dependent on the surgical technique (submerged or non-submerged).     

Comparison of healed tissues adjacent to submerged and non‐submerged unloaded titanium dental implants. A histometric study in beagle dogs.

This study involved histometry of the healed tissues around submerged and nonsubmerged dental implants in beagle dogs. In a split‐mouth design, 19 submerged and 19 nonsubmerged commercially pure titanium implants, titanium plasma‐sprayed in the bone anchoring part and smooth in the transmucosal portion were placed in the mandibles of 6 dogs. Oral hygiene was performed 3 times weekly. After 3 months of healing, transmucosal abutments were inserted in the submerged implants. Six weeks after second stage surgery, the dogs were sacrificed and specimens obtained and processed for histology and histometry. Using a light microscope and a digitizing pad, the distance from implant top to mucosa border (DIM), the extent of epithelial downgrowth (ED), the attachment level (AL). the length of connective tissue contact (CTC) and the distance of the first coronal alveolar bone contact from the implant top (DIB) were measured at the mesial and distal aspects. Means+standard deviations for submerged and nonsubmerged implants were calculated, with the dog being the unit of measure. No statistically significant differences between submerged and nonsubmerged implants here found for DIM, CTC and DIB. However, significant differences were observed for ED and AL. This study in beagle dogs indicates that the apical extension of the peri‐implant epithelium is significantly greater and the attachment level significantly lower adjacent to submerged implants with second‐stage transmucosal abutments than in nonsubmerged, one‐stage implants.     

A radiographic evaluation of bone healing around submerged and non-submerged dental implants in beagle dogs

BACKGROUND: The rehabilitation of the oral cavity with dental implants has become a predictable treatment modality. However, there have been only a few direct comparisons evaluating the submerged and nonsubmerged placement techniques. The purpose of this study was to characterize radiographic peri-implant bone changes following the insertion of submerged and nonsubmerged implants in the beagle dog. METHODS: At the end of the extraction healing phase, 19 submerged and 19 nonsubmerged implants were randomly placed in a split-mouth study design and observed over an 18-week period. For submerged implants, a second stage surgery and transmucosal abutment attachment was performed at week 12. Standardized dental radiographs taken at baseline, week 12, and week 18 were used to measure peri-implant bone changes. The radiographs were analyzed with a simple computer assisted method. RESULTS: A total of 43 standardized radiographs were exposed to evaluate the 38 implants. During the study period, all submerged and nonsubmerged implants demonstrated peri-implant bone loss. At baseline, both submerged and nonsubmerged implants had similar bone levels (P > or = 0.05). When the mean peri-implant bone levels for submerged and nonsubmerged implants were compared from baseline to week 12, nonsubmerged implants had a significantly greater amount and rate of bone resorption than submerged implants (P < or = 0.05). Following week 12, the initially submerged implant had a significantly higher rate and amount of peri-implant bone loss than the nonsubmerged implants (P < or = 0.05). However, by the end of the study period, week 18, both submerged and nonsubmerged implants had comparable bone levels (P > or = 0.05). CONCLUSIONS: The study indicates that, although the temporal patterns of peri-implant bone resorption differed, there were no differences between submerged and nonsubmerged implants in the overall amount and rate of peri-implant bone loss.     

Soft tissue healing at titanium implants coated with type I collagen. An experimental study in dogs

Objective: To analyse the soft tissue healing at titanium implants coated with type 1 collagen. Material and methods: Six dogs were used. The mandibular pre‐molars and the three anterior maxillary pre‐molars were extracted. Three months later mucoperiosteal flaps were raised and two test and two control implants were installed (3i^® TG Osseotite^®3.75 × 10 and 2.8 mm transmucosal collar). The test implants were coated with a purified porcine type I collagen. Cover screws were placed and flaps were sutured. The sutures were removed 2 weeks later and a plaque‐control programme was initiated. Another 2 weeks later, the procedure was repeated in the contra‐lateral mandibular region. Four weeks after the second implant surgery, biopsies were obtained and prepared for histological examination. Results/Conclusion: The vertical dimensions of the epithelial and connective tissue components as well as the composition of the connective tissue portion facing the implant were similar at collagen‐coated and uncoated implants after 4 and 8 weeks of healing. It is suggested that soft tissue healing to implants coated with type I collagen was similar to that at non‐coated titanium implants and that no adverse reactions to the collagen‐coated implants occurred.     

Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible.

BACKGROUND: Endosseous implants can be placed according to a non-submerged or submerged approach and in 1- or 2-piece configurations. Recently, it was shown that peri-implant crestal bone changes differ significantly under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of an interface (microgap) between the implant and abutment/restoration in 2-piece configurations. Several factors may influence the resultant level of the crestal bone under these conditions, including movements between implant components and the size of the microgap (interface) between the implant and abutment. However, no data are available on the impact of possible movements between these components or the impact of the size of the microgap (interface). The purpose of this study was to histometrically evaluate crestal bone changes around unloaded, 2-piece non-submerged titanium implants with 3 different microgap (interface) dimensions and between implants with components welded together or held together by a transocclusal screw. METHODS: A total of 60 titanium implants were randomly placed in edentulous mandibular areas of 5 hounds forming 6 different implant subgroups (A through F). In general, all implants had a relatively smooth, machined suprabony portion 1 mm long, as well as a rough, sandblasted, and acid-etched (SLA) endosseous portion, all placed with their interface (microgap) 1 mm above the bone crest level and having abutments connected at the time of first-stage surgery. Implant types A, B, and C had a microgap of < 10 microns, approximately 50 microns, or approximately 100 microns between implant components as did types D, E, and F, respectively. As a major difference, however, abutments and implants of types A, B, and C were laser-welded together, not allowing for any movements between components, as opposed to types D, E, and F, where abutments and implants were held together by abutment screws. Three months after implant placement, all animals were sacrificed. Non-decalcified histology was analyzed histometrically by evaluating peri-implant crestal bone changes. RESULTS: For implants in the laser-welded group (A, B, and C), mean crestal bone levels were located at a distance from the interface (IF; microgap) to the first bone-to-implant contact (fBIC) of 1.06 +/- 0.46 mm (standard deviation) for type A, 1.28 +/- 0.47 mm for type B, and 1.17 +/- 0.51 mm for type C. All implants of the non-welded group (D, E, and F) had significantly increased amounts of crestal bone loss, with 1.72 +/- 0.49 mm for type D (P < 0.01 compared to type A), 1.71 +/- 0.43 mm for type E (P < 0.02 compared to type B), and 1.65 +/- 0.37 mm for type F (P < 0.01 compared to type C). CONCLUSIONS: These findings demonstrate, as evaluated by non-decalcified histology under unloaded conditions in the canine mandible, that crestal bone changes around 2-piece, non-submerged titanium implants are significantly influenced by possible movements between implants and abutments, but not by the size of the microgap (interface). Thus, significant crestal bone loss occurs in 2-piece implant configurations even with the smallest-sized microgaps (< 10 microns) in combination with possible movements between implant components.     

Peri-implant tissues at submerged and non-submerged titanium implants

The present experiment was performed to study the peri-implant tissue response to non-submerged (1-stage) and initially submerged (2-stage) implant installation procedures. 6 beagle dogs were used. All mandibular premolars and the 1st, 2nd and 3rd maxillary premolars were extracted. After 3 months of healing, 3 fixtures of the Astra Tech System were installed and submerged in the right (or the left) edentulous, premolar region in each of the 6 dogs. Radiographs were obtained immediately after fixture installation. In the radiographs, the distance between the abutment-fixture junction and the most "coronal" bone in contact with the implant surface was determined. 3 months later, abutments were connected to the initially submerged fixtures and another 3 fixtures of the same system were installed in the contralateral, edentulous premolar region. Abutments were, however, immediately connected to the newly-installed fixtures (non-submerged side; test side). The mucosal flaps were replaced, adjusted and sutured in such a way that the coronal portion of the abutments remained exposed in the oral cavity. A new set of radiographs were obtained from all 6 implant sites in each animal. A period of plaque control was initiated. Clinical examinations were performed and radiographs obtained from all implant sites after another 3 months and at the termination of the experiment. 9 months after the 1st fixture installation procedure, the animals were sacrificed, the mandibles were removed, and each implant region dissected. The most mesially-located implant sites were processed for ground sectioning. The remaining biopsies were processed and embedded in EPON. The histometric analysis included assessment of the vertical dimension of the marginal soft and mineralized peri-implant tissues. The ground sections were used for measurements describing (i) "bone to implant contact" and (ii) "bone density". It was observed that the mucosa and bone tissue that formed at implants placed in a non-submerged or a submerged procedure had many features in common. Thus, figures describing (i) the height of the mucosa, (ii) the length of the junctional epithelium and the height and quality of the zone of "connective tissue integration", (iii) the % of bone to implant contact as well as (iv) the density of the peri-implant bone, were similar in the submerged and the non-submerged groups. It is therefore suggested that a non-submerged (1-stage) installation technique may provide conditions for tissue integration that are similar to those obtained using a submerged (2-stage) approach.     

Stability of crestal bone level at platform-switched non-submerged titanium implants: a histomorphometrical study in dogs

Objectives: To investigate the influence of platform switching on crestal bone level changes at non-submerged titanium implants over a period of 6 months.
Material and Methods: Titanium implants ( n =72) were placed at 0.4 mm above the alveolar crest in the lower jaws of 12 dogs and randomly assigned to either matching or non-matching (circumferential horizontal mismatch of 0.3 mm) healing abutments. At 4, 8, 12, and 24 weeks, dissected blocks were processed for histomorphometrical analysis. Measurements were made between the implant shoulder (IS) and the apical extension of the long junctional epithelium (aJE), the most coronal level of bone in contact with the implant (CLB), and the level of the alveolar bone crest (BC).
Results: At 24 weeks, differences in the mean IS–aJE, IS–CLB, and IS–BC values were 0.2 ± 1.2, 0.3 ± 0.7, and 0.3 ± 0.8 mm at the buccal aspect, and 0.2 ± 0.9, 0.3 ± 0.5, and 0.3 ± 0.8 mm at the lingual aspect, respectively. Comparisons between groups revealed no significant differences at either the buccal or the lingual aspects.
Conclusions: It was concluded that (i) bone remodelling was minimal in both groups and (ii) platform switching may not be of crucial importance for maintenance of the crestal bone level.     

Comparative evaluation of the peri-implant bone tissue mineral density around unloaded titanium dental implants

OBJECTIVE: The mechanical properties of bone are greatly influenced by the percentages of organic and mineral constituents. Nevertheless, the information about the mineral content on a microscopic scale in peri-implant bone is scarce. The aim of this work was to analyze the bone mineral density of peri-implant bone under different techniques. DESIGN: Five unloaded titanium dental implants with a micro-structured surface (three XiVE plus and two Frialit 2, DENTSPLY-Friadent, Mannheim, Germany) were retrieved from the mandible of five patients after a 6-month period. scanning electron microscopy with backscattered electron signal (BSE), light microscopy (LM) with a double staining technique, fluorescence microscopy and confocal laser microscopy were used for measuring microscopic mineral content variations in peri-implant bone. Histomorphometry and image intensity (grey level) were evaluated using a software package for image analysis. RESULTS: The low mineral density index (LMDI) for LM was of 29.2+/-3.1 (mean+/-S.D.), while the high mineral density index (HMDI) was of 88.2+/-3.6 (mean+/-S.D.). The one-way ANOVA analysis showed a significant difference (P<0.001) among the groups. The pairwise Holm-Sidak test identified the differences among HMDI indexes for both LM and SEM values and also for cross-evaluation of the LMDI and HMDI values. The comparison between LMDI indexes for both SEM and LM did not show any significance. The fluorescence microscopy analysis showed clearly the difference between old (high mineralized) and new (low mineralized) bone tissue near the implant surface. Under confocal laser microscopy the same sections showed the area of bone modelling closest to implant surface. CONCLUSION: In this study it was found that bone around unloaded implants showed a low mineral density index under all the investigation methods used. It was also found that the conventional LM technique with the double staining method was able to intensely stain the bone area with a low mineral content.     

Influence of platform switching on crestal bone changes at non-submerged titanium implants: a histomorphometrical study in dogs

OBJECTIVES: The aim of the present study was to investigate histomorphometrically the influence of platform switching on crestal bone changes at non-submerged wide-body titanium implants in a dog model. MATERIAL AND METHODS: One-stage insertion of sand-blasted and acid-etched screw-type implants with either matching (CAM) or smaller-diameter healing abutments (CPS) were randomly assigned to the lower jaws of nine beagle dogs. The animals were killed after 7, 14, and 28 days of non-submerged healing. Dissected blocks were processed for histomorphometrical analysis. Measurements were made between the implant shoulder (IS) and:--the apical extension of the long junctional epithelium (aJE), --the most coronal level of bone in contact with the implant (CLB), and --the level of the alveolar bone crest (BC). RESULTS: At 7, 14, and 28 days, the mean IS-aJE values were significantly the lowest at CPS implants. However, after 28 days of healing, both groups revealed significantly increased mean IS-BC values at the buccal aspect of the alveolar bone. The difference in IS-CLB and IS-BC between groups was not significant. CONCLUSIONS: Within the limits of the present study, it was concluded that both CAM and CPS implants revealed crestal bone-level changes after 28 days of healing.     

Effects of surface hydrophilicity and microtopography on early stages of soft and hard tissue integration at non-submerged titanium implants: an immunohistochemical study in dogs

BACKGROUND: The aim of the present study was to investigate the effects of surface hydrophilicity and microtopography on soft and hard tissue integration at non-submerged titanium implants. METHODS: Implantation of conventional sand-blasted large grit and acid-etched (SLA) and chemically modified SLA (modSLA) titanium implants with differently structured transmucosal surfaces (SLA implants: machined [M-SLA] or SLA [SLA-SLA]; modSLA implants: mod acid-etched [modA] [modA-modSLA] or modSLA [modSLA-modSLA]) was performed bilaterally in the upper and lower jaws of 15 beagle dogs. The animals were sacrificed after 1, 4, 7, 14, or 28 days. Tissue reactions were assessed histomorphometrically and immunohistochemically using monoclonal antibodies to transglutaminase II (angiogenesis) and osteocalcin. RESULTS: Although the junctional epithelium commonly was separated from M-SLA and SLA-SLA implants by a gap, the epithelial cells appeared to be in close contact with modA-modSLA surfaces after 14 days of healing. Moreover, modA-modSLA and modSLA-modSLA groups showed a well-vascularized subepithelial connective tissue exhibiting collagen fibers that started to extend and attach partially perpendicular to the implant surface. The highest and statistically significant mean bone-to-implant contact areas were observed in the modA-modSLA and modSLA-modSLA groups at days 7, 14, and 28. CONCLUSION: Within the limits of this study, it may be concluded that soft and hard tissue integration was influenced mainly by surface hydrophilicity rather than by microtopography.     

Bone reactions to titanium screw implants in ovariectomized animals

OBJECTIVE: The purpose of this study was to investigate the reactions of bone tissue after the placement of implants into the tibiae of osteopenic model rats. STUDY DESIGN: Commercially pure titanium screw implants were placed in the bilateral proximal tibial metaphyses 168 days after ovariectomy had been performed on 12-week-old female Wistar rats. For control purposes, implants were similarly placed in sham-ovariectomy rats. The healing process was examined histologically by means of undecalcified sections at various intervals from 7 to 168 days after implantation. Through use of an automated imaging analytic system, changes in relative bone mass and implant-bone contact were histomorphometrically evaluated. RESULTS: In the cortical bone area, only a slight difference in bone contact was noted with the implant until 28 days after implantation. However, ovariectomy significantly affected bone contact at 56 days after implantation. The rate of bone contact in the cancellous bone area and the relative bone mass around the implant were significantly lower in the test group than in the control group. CONCLUSIONS: It is considered that a decrease in bone mass causes a reduction in the contact area between implant and bone and may also cause a reduction in the supporting ability of the implant because of thinning of the surrounding bone tissue.     

Guided tissue regeneration. An experimental procedure in beagle dogs

This preliminary study examined the healing following an experimental procedure designed to facilitate coronal migration of progenitor cells from the periodontal ligament circumferentially on roots of premolar teeth in beagle dogs. Mucoperiosteal flaps were reflected on the buccal and lingual aspects of premolars in six beagle dogs with periodontal disease. Following root preparation, pieces of orthodontic wire were placed interproximally on the crowns to bridge the spaces between teeth. Biobrane, a synthetic membrane bonded to a knitted nylon fabric and coated with collagen, was placed as a physical barrier between the roots and the flaps to be replaced. The membrane extended as a single piece from the cementoenamel junction (CEJ) to overlap the crest of alveolar bone by 3 to 4 mm on both the buccal and lingual surfaces of the three premolars in each quadrant. The membrane was attached to the crowns at the CEJ with resin. The flaps were replaced and sutured. Postoperative care included plaque control and the membranes were removed after 5 weeks. The dogs were sacrificed to provide observation periods of 8 and 16 weeks after placement of membranes. Histologic examination revealed new connective tissue attachment in the apical part of the 8- and 16-week experimental specimens. Some experimental specimens showed new attachment up to 2.94 mm while others showed a long junctional epithelium (JE). Root resorption was also seen in some specimens. These preliminary findings suggest that placement of physical barriers between root surface and flaps may be beneficial in facilitating coronal migration of progenitor cells from the periodontal ligament.     

Osteoclast activity around loaded and unloaded implants: a histological study in the beagle dog

The mechanisms of bone loss around dental implants are poorly understood. The osteoclast is the most important bone-resorbing cell. Humoral factors seem able to stimulate the differentiation of osteoclasts from mononuclear phagocytes. Bacterial lipopolysaccharides seem to be directly involved in inflammatory bone loss by stimulation of the survival and fusion of preosteoclasts. Excessive load seems to be able to cause bone loss. The aim of this paper was to evaluate the presence and number of osteoclasts in peri-implant bone in control (unloaded) and test (loaded) implants in order to determine if loading per se could be a contributing factor in peri-implant bone resorption. Forty-eight implants were inserted in the mandibles of 4 beagle dogs. After 3 months, a prosthetic superstructure was inserted on 24 implants, whereas in 24 implants only the healing screws were positioned. Twenty-four implants (12 test and 12 control) were retrieved at 6 months, and 24 implants (12 test and 12 control) were retrieved at 12 months. All implants were osseointegrated. The number of osteoclasts found in the crestal bone in the first 3 mm from the implant surface was evaluated. The mean number of osteoclasts were the following: control implants (6 months), 5.66 +/- 0.81; control implants (12 months), 2.55 +/- 1.05; test implants (6 months), 5.25 +/- 1.55; and test implants (12 months), 2.5 +/- 1.0. No statistically significant differences were observed between the control and test implants. According to our data, loading does not seem to have a relevant importance on the osteoclast activation in peri-implant bone.     

A removal torque and histomorphometric study of bone tissue reactions to commercially pure titanium and Vitallium implants.

Screw-shaped commercially pure (CP) titanium and Vitallium implants were inserted in the rabbit tibial metaphysis. After a healing period of 3 months, it was demonstrated that a higher torque was needed to remove the CP titanium implants (average 24.9 Ncm) compared to Vitallium implants (average 11.7 Ncm). The histomorphometric part of the study revealed more bone-to-metal contact for the CP titanium implants (average 34.7%) compared to the Vitallium implants (average 21.7%). The results obtained in this study could be explained by differences in the topography or in biocompatibility of the metals, or a combination of these two factors.     

Putative periodontal and teeth in pathogens on titanium implants and teeth in experimental gingivitis and periodontitis in beagle dogs

The microflora around titanium implants and teeth in 4 beagle dogs was analyzed in order to follow the longitudinal development from healthy conditions to experimental gingivitis and periodontitis. A 2-month plaque control program was performed to establish healthy conditions on titanium implants and control teeth (baseline, day 0). Subgingival bacterial samples and radiographs were obtained. The plaque control was ceased and all measurements were repeated on day 21 (gingivitis). A new period of plaque control was initiated to re-establish healthy conditions (day 49). A cotton ligature was placed subgingivally around the implants and the control teeth to induce tissue breakdown. The ligatures were removed on day 91. The study was completed with registrations on day 121 (periodontitis). No significant microbiological difference was found between titanium implants and teeth in healthy conditions and in gingivitis and periodontitis. The mean total viable count increased 10 times on implants as well as on teeth. Streptococci were dominating at baseline: 40.2% on implants and 60.6% on teeth and decreased in gingivitis to 11.7% and 5.4%. When periodontitis had developed, the proportion of streptococci was < 1%. At baseline few Porphyromonas gingivalis and Prevotella intermedia were detected. They increased at gingivitis to 37.4% and 21.0%; when periodontitis developed, they comprised about 25.0%. Microbial colonization and establishment on titanium implants with healthy gingiva, experimental gingivitis and periodontitis follow the same pattern as on teeth.     

羟基磷灰石涂层钛正畸支抗种植体颈部组织改变的动物实验评价

将羟基磷灰石涂层钛种植体处期植入狗颌骨，以施以１５０ｇ的正畸力，动态分析支抗种植体受力后３个月内的牙龈出血指数，菌斑，牙石指数，松动度，种植体颈周深度及颈中骨量变化。结果显示：种植体均稳固，种植体周围软组织有轻微炎症，但颈部骨组织无明显吸收，颈部骨量在压力侧与张力侧的变化无差异。     

Palatal implants in adolescents: a histological evaluation in beagle dogs

Objectives: Small osseointegrated implants inserted in the palate provide a reliable anchorage control during orthodontic treatment. When these implants are inserted in the median palatal suture in adolescents, there might be interference with normal transverse development of the maxilla. The aim of this study was to determine histometrically the influence of implants inserted in the median palatal suture in adolescent beagle dogs on transverse maxillary development and to determine the amount of osseointegration of unloaded palatal implants in the median palatal suture in adolescent beagle dogs.
Material and methods: Two palatal implants were inserted in the median palatal suture in four of five adolescent beagle dogs. The experimental period took 25 weeks, and the dogs were subjected to a scheme of sequential point labelling with vital stains every 6 weeks. Insertion sites were examined microscopically and histometric analysis was performed.
Results and discussion: Both anterior width and posterior width were wider in the control dog as compared with the average in the test dogs, 3.7% and 9.5%, respectively. After loss of a palatal implant, immediate repair of the bone in the suture area could be observed. In the posterior region, the repaired suture looked more like a suture in the infantile stage in humans, instead of having a sinusoidal course, as was observed in the control dog and in adolescent humans. The amount of osseointegration varied from 43% to 64.3%.
Conclusion: The results of this study support the idea that in adolescents, palatal implants should not be inserted in the median palatal suture because of possible growth impairment (transverse maxillary development). The amount of osseointegration of unloaded palatal implants in the median palatal suture in adolescent dogs is less as compared with dental implants in dogs and loaded palatal implants in adult humans.     

Secondary stability assessment of titanium implants with an alkali-etched surface: a resonance frequency analysis study in beagle dogs

PURPOSE: This study was carried out to quantify the effect of an alkali-modified surface on implant stability during healing using an animal model. MATERIALS AND METHODS: A total of 24 screw-shaped, self-tapping, commercially pure titanium dental implants, divided into a test group (implants with an alkali-modified surface or "biosurface") and a control group (implants with a turned, machined surface) were inserted without pretapping in the tibiae of 3 beagle dogs. The resonance frequency analysis method was used to measure the implant stability quotient (ISQ) 0, 1, 3, 9, and 12 weeks after implantation. The animals were sacrificed after 2, 5, and 12 weeks, and the bone-implant contact (BIC%) was evaluated histomorphometrically. RESULTS: The difference in the osseointegration rates (deltaISQ/deltahealing time) between the implants with alkali-modified surface (biosurface) and those with a turned, machined surface was evaluated as a mean of 0.843 ISQ/week within the first 9 weeks of healing. The mean increase in the secondary implant stability was found to be proportional to the mean increase in the BIC at healing period earlier than 5 weeks. DISCUSSION: The characteristics that differed between the implant surfaces, ie, specific surface area, contact angle, and hydroxylation/hydration, may represent factors that influence the rate of osseointegration and the secondary implant stability. CONCLUSION: The alkali-treated surface enhances the secondary stability in the early stages of healing compared to the turned, machined surface, as a consequence of faster BIC formation.