Basic Science

Editor's Note: Starred reviews (*) were prepared by Kuo-Yang Liao, DDS, Aladdin Al-Ardah, DDS, Olivier Henry-Savajol, DDS, and Israel Puterman, DMD, who are graduate students enrolled in the Implant Program at Loma Linda University, Jaime Lozada, DDS, director.

“A Removal Torque of the Laser-Treated Titanium Implants in Rabbit Tibia,” by S. A. Cho, S. K. Jung. Biomaterials, 24:4895–4863, 2003.

This in vivo study compared the torque required to remove implants with a laser-treated surface. Ten rabbits had a total of 14 implants (5 mm long × 3.75 mm diameter) placed into their tibia. Seven of the implants (control) were commercially machined pure titanium, and the other 7 implants were identical with the exception that their surface was laser etched. After 8 weeks of healing, the animals were killed and the implants were exposed and tested for the torque required for their removal. The results indicated that the laser-treated implants required significantly greater torque for removal compared with the nontreated controls. Before implantation, scanning electron microscopy demonstrated that the laser etching created a deep and regular honeycomb pattern on the surface compared with a grooved and relatively smooth surface on the control implants. These results indicate that laser etching titanium implants significantly increases implant removal torque compared with nontreated machined surfaces in a rabbit model. A shortcoming of this study was the low numbers used. The authors suggest that this method of surface treatment should be compared with other methods currently used to increase implant surface roughness.

“Ion Implantation Surface Treatment for Improving the Bone Integration of Titanium and Ti6Al4V Dental Implants,” by M. de Maeztu, J. I. Alava, C. Gay-Escoda. Clin Oral Implant Res, 14:57062, 2003.

This in vivo study examined the effect of ion implantation surface treatment of root-form implants on the bone-to-implant interface. A total of 88 implants were used in the study. Forty-four implants were commercially pure (CP) titanium (Impla-Medical-Sterngold, Sunrise, Fla) and 44 were titanium alloy (TI alloy) Ti6Al4V (Sulzer Calcitek, Carlsbad, Calif). Five groups of 8 of each implant type were used. One group of each implant type consisted of untreated controls. The remaining 4 groups of each implant type were subjected to ion implantation. The ions implanted were carbon oxide ion (CO+), nitrogen ion (N+), carbon ion (C+), and neon ion (Ne+). The Ne+ implants were also immersed in a collagen solution after ion implantation. Two implants of each type were implanted into the tibial plateaus of 22 rabbits. One of the implants was placed in the metaphyseal zone and the other in the epiphyseal zone. After 3-months healing, the rabbits were killed and subjected to analysis, which included visual, radiographic, histologic, histomorphometric, scanning electron microscopic, electron microsonide, and X-ray photoelectron spectroscopic studies. Two of the rabbits died after surgery, resulting in a loss of 8 implants. The bone-to-implant contact (BIC) for both materials was 74.44 % in the tibial epiphysis and 55.73% in the metaphyseal region. There was no difference between the groups placed into the epiphyseal zone. In the metaphyseal zone, the BIC was 43.31% for the control CP implants and increased to 55.08% for the ion-treated implants as a group. The results for the TI alloy implants were 52.04% for controls and 60.72% for the ion-treated groups. There was no significant difference when comparing the CP or TI alloy implants. With the ion treatment, there was a general trend to increased BIC vs controls. In the CP group, the C+ ion treatment resulted in significantly greater BIC. In the TI alloy group, the CO+ treatment resulted in significantly greater BIC. The implants treated with CO+ demonstrated covalent bonds between the implant and the bone, a stronger bond than the ion bonds that are usually found between implants and bone. These results suggest that ion implantation of endosseous implants can improve BIC.

Case Report

“Mandibular Fracture as a Complication of Inferior Alveolar Nerve Transposition and Placement of Endosseous Implants: A Case Report,” by V. Karlis, R. Bae, R. Glickman. Implant Dent, 12:211–216, 2003.

This paper reports on the occurrence of a mandibular fracture when a nerve-transposition technique was used in conjunction with root-form implants. A 67-year-old man reported to the Department of Oral and Maxillofacial Surgery with a complaint of pain and swelling of his right face and parasthesia of the right lower lip and chin. He had undergone a simultaneous nerve transposition and implant placement 4 weeks previously. A panoramic radiograph revealed 2 root-form implants that engaged but did not penetrate the inferior border of the right posterior mandible. The most posterior implant displayed an area of radiolucency around the implant with a nondisplaced fracture through the inferior border of the mandible. The fracture was initially treated with a closed-reduction technique. At 1-week follow-up, increasing bony destruction was evident around the implant. The patient then underwent an open-reduction procedure with a titanium bone plate. In addition, both implants were noted to be mobile at the time of the reduction. After their removal, the resultant defect present was grafted with iliac crest bone. The patient healed uneventfully; however, as of the 6-month follow-up, he did not report any improvement to his parasthesia. In their discussion, the authors hypothesized that the nerve-transposition procedure together with the placement of implants weakened the atrophic posterior mandible, especially during the early healing phase, thus exposing a risk for fracture. Nevertheless, only 1 other case of mandibular fracture with nerve-transposition procedures has been reported.

Bone Grafting

“Bone Biological Box (BBB): An Evolution of the Sinus Graft,” by M. Politi, M. Robiony, F. Polini, F. Costa. J Oral Maxillofac Surg, 61:1108–1112, 2003.

This paper reports on a variation of the sinus-grafting procedure, which the authors dub the bone biological box (BBB). A traditional bony window is made in the lateral wall of the maxillary sinus. The membrane is elevated and the bony trap door is swung upwards with the membrane, creating a ceiling. A corticocancellous bone graft is obtained from the iliac crest to augment the sinus. Three separate cortical portions are used in the graft. One is placed just below the trap-door fragment to complete the ceiling of the graft. Another piece is placed posteriorly in the sinus to form a posterior wall for the graft. After these 2 cortical plates are in position, the sinus is filled with a mixture of platelet-rich plasma and cancellous bone. Once filled, the window into the sinus is closed with the last cortical plate that is attached to the lateral wall of the sinus with bone screws. The authors report that they have used the BBB in 45 patients. Twenty cases were selected for this study. They reported no instances of graft or implant failure. Bone biopsies were obtained at 4-months posthealing (at screw removal and implant placement). These biopsies demonstrated mature bone that was not completely mineralized. Radiographic analysis de-monstrated adequate graft dimensions without graft resorption. Excellent clinical photographs and diagrams were in-cluded that completely illustrated this procedure. A shortcoming of the paper was the apparent nonrandom nature of the cases included for analysis and the lack of objective statistical analysis. In addition, histomorphometric data were not performed on the biopsy graft samples.

“Imaging of Peri-implant Bone Levels of Implants with Buccal Bone Defects: A Radiographic and Histometric Accuracy Study,” by H. Schliephake, M. Wichmann, F. Donnerstag, S. Vogt. Clin Oral Implant Res, 14:193–200, 2003.

The purpose of this study was to compare the amount of bone identified by various methods in implants with known buccal defects. Twenty-four implants were placed in the mandibles of 6 dogs. The first 4 threads of the implants on the buccal side were exposed at the time of placement. These defects were grafted with autogenous bone with and without membranes. After 5-months healing, the dogs were killed and the mandibular segments were retrieved for study. The segments were radiographed by 3 methods: periapical radiographs, direct image magnification (DIMA), and computed tomography (CT) (coronal and sagittal reformation). Two bone levels were obtained by the histometric measurements: the lingual bone level and the average bone level around the implant (true bone level). These were compared with the estimated bone level obtained by the radiographic methods. The periapical, DIMA, and sagittal CT views gave an accurate estimation of lingual bone levels but significantly overestimated the true (buccal) bone level around the implants. The coronal CT images significantly overestimated lingual bone levels and underestimated the buccal levels. These results demonstrate that radiographs (including sagittal CT) overestimate the level of bone-to-implant anchorage when buccal bone defects are present around root-form implants.

*“Nonceramic Hydroxyapatite Bone Derivative in Sinus Augmentation Procedures: Clinical and Histomorphometric Observations in 10 Consecutive Cases,” by Z. Artzi, C. E. Nemcovsky, D. Dayan. Int J Periodontics Restor Dent, 23:381–389, 2003.

A synthetic, nonceramic resorbable hydroxyapatite (R-HA) as a sinus augmentation material in 10 consecutive patients was evaluated at 12 months in all sites at the lateral and deep augmented areas. Ten healthy patients (5 women, 5 men) ranging in age from 36 to 66 years who were to receive posterior implant-supported fixed prostheses had maxillary sinus augmented with R-HA material. Eight patients had sinus augmentation and implant placement at the same time. Two patients had implants placed 6 months after the sinus augmentation because the residual ridge height was 1 to 3 mm. R-HA particles, 300 to 400 μm, were soaked with venous blood and filled the augmented sites, and a resorbable membrane (BioGide) was applied over the entire area. At the implant uncovery time, the buccal flap was further elevated to the previous window area, and a 2.5-mm internal diameter trephine bur was drilled upward through the previous lateral window frame toward the new location of the Schneiderian membrane. The specimens were stained with hematoxylin-eosin and picrosirius red for polarized light microscopy. All implants (n = 36) were clinically stable during the healing abutment placement at 12 months. Morphometrically, mean bone-area fraction at the lateral/external side of the 10 specimens was 28.1% (range 22.3%–38.9%) and medial/deep side was 37.8% (range 30.2%–53.3%). Mean lamellar-woven bone ratio at the lateral/external was 0.15 (1:7.2) and at the medial/deep side was 0.27 (1:4.2). Differences in both mean bone-area fraction and woven-lamellar bone ratio were statistically significant for lateral/external and medial/deep side. No correlation was observed between bone area percentage and lamellar-woven bone ratio. R-HA is a biocompatible and osteoconductive material in sinus-augmentation procedure. Bone-area fraction and remodeling increased in a lateral to medial direction toward the vicinity of the Schneiderian membrane.

Implant Prosthodontics

“Residual Ridge Resorption in the Edentulous Maxilla in Patients With Implant-Supported Mandibular Overdentures: An 8-Year Retrospective Study,” by M. Kreisler, N. Behneke, A. Behneke, B. d'Hoedt. Int J Prosthodont, 16:295–300, 2003.

This retrospective study examined the effects that mandibular implant overdentures (IODs) have on the resorption pattern of the edentulous maxillary ridge. Thirty-five completely edentulous patients had 2 root-form implants placed in the interforaminal region of the mandible. The mandibular IODs were fabricated with bar retention. At the same time, new maxillary complete dentures were made. Residual bone loss was tracked with standardized panoramic radiographs up to an 8-year period. Statistical analysis revealed a steady decline in alveolar bone. When comparing the anterior and the posterior segments of the maxilla, there was a significantly greater loss of bone in the anterior region. These results suggest that the use of 2 IODs may result in a combination syndrome-like bone loss of the maxilla.

“A Randomized Clinical Trial Comparing 2 Mandibular Implant Overdenture Designs: 3-Year Prosthetic Outcomes Using a 6-Field Protocol,” by J. Walton. Int J Prosthodont, 16:255–260, 2003.

This study compared the maintenance requirements of 2 different retention mechanisms for 2 implant mandibular overdentures (IODs). Two groups of 50 patients were enrolled at the start of the study. One group had the overdenture secured with ball abutments and titanium alloy cap attachments. The other group had the denture secured with a bar-clip mechanism. Both mechanisms were Branemark designs (Nobel Biocare, Toronto, Canada). For both groups, the components attached to the implants were defined as the patrix, and the retentive components were termed the matrix. The patients were followed for a mean of 3 years. At the time of this study, 87 patients were available. Repair frequency and types of repairs were tabulated. The bar-clip design was found to be significantly more successful than the ball design. Sixty-three percent of bar-clip IODs were deemed successful at the time of this study compared with 23% of the ball designs. Sixty percent of the ball patients required repairs that were deemed excessive compared with 17% of the bar-clip patients. The ball patients required 324 repairs over 3 years compared with 72 repairs for the bar-clip patients. The conclusion of the study was that for these particular IOD designs, the bar clip was significantly more successful (requiring less maintenance) than the ball design.

“Evaluation of the Precision of Fit Between the Procera Custom Abutment and Various Implant Systems,” by L. Lang, M. Sierraalta, M. Hoffensperger, R. F. Wang. Int J Oral Maxillofac Implants, 18:652–658, 2003.

This study examined the precision of fit of the Procera abutment (Nobel Biocare, Goteborg, Sweden) and the external hex platform of the following different implant types: Branemark 3.75- × 10-mm implants (Nobel Biocare), Lifecore Restore 3.75- × 10-mm implants (Lifecore Biomedical, Chaska, Minn), 3i system 3.75- × 10-mm implants (Implant Innovations, West Palm Beach, Fla), ImplaMed 3.75- × 10-mm implants (Sterngold-ImplaMed, Attleboro, Mass), and Paragon Taper Lock 4.0- × 10-mm implants (Paragon, Encino, Calif). Thirty standardized Procera abutments were fabricated for 6 implants for each of the implant systems. The abutment-implant compatibility was established by 3 methods: (1) measuring the internal hex and bearing surface of the abutment and comparing it with the external hex and bearing surface of the implants, (2) tightening the abutments to the implants (32 Ncm) with the abutment screws from each of the implant systems and radiographically evaluating the abutment for fit, and (3) comparing the screws of the Procera abutment with the standard abutment screws for each implant manufacturer. The results indicated that in the direct measurement test there was compatibility with all systems platform. When the abutments were connected to the implants, the Procera abutment did not fit tightly to the Paragon implants after tightening the screws. The Lifecore and 3i screws did not fit properly within the Procera abutment when viewed radiographically. The abutment screw heads of the ImplaMed and 3i were larger than the Procera screw. The Lifecore and Paragon were smaller. The smallness of the Paragon's screw head was deemed to be responsible for the looseness of the abutment when it was tightened with the manufacturer's screws. The internal screw bores for all the implant systems were found to be the same. These findings suggest that the Procera abutment can be used with all the implant systems studied. Because of screw discrepancies, only the Procera abutment screw should be used.

*“Clinical and Radiographic Evaluation of Soft- and Hard-Tissue Changes Around Implants,” by J. C. Joly, A. F. Martorelli de Lima, et. al. J Periodontol, 74:1097–1103, 2003.

The aim of this pilot study was to evaluate the clinical and radiographic changes in the peri-implant tissues around 1-stage implants with varying smooth neck lengths, before and after functional prosthetic loading. Four patients with bilateral edentulous posterior ridges were selected. A total of 12 ITI (Straumann AG, Waldenburg, Switzerland) titanium-plasma spray (TPS) 1-stage implants 4.1 mm diameter and 10 mm length with machine-smooth suprabony portion of 2.8 or 1.8 mm were used. Implant location was randomly assigned into 2 groups of 6: group 1 implants were 2.8 mm, and group 2 implants were 1.8 mm. Manufacturer's protocol was followed for implant placement with the machine surfaces at the level of alveolar bone. Implants were restored and loaded 4 months after surgery with cement-retained metal ceramic crowns. The ensuing parameters plaque index (PI), gingival index (GI), probing depth (PD), gingival marginal level (GML), relative clinical attachment level (r-CAL), and optical density (OD) were measured at loading (4 months) and 12 months after implant placement. The radiographic parameter osseous level (OL) was measured at implant placement, loading (4 months), and at 12 months. The results showed significant differences (P < .05) for both groups for PD, r-CAL, and OL for intragroup comparisons over time. No significant differences were found for PI, GI, PD, GML, OD, and OL between groups. The results suggest that bone loss will always occur regardless of the transmucosal length, and it apparently does not inhibit bone resorption. From the results in this study, it is concluded that bone loss was initiated before loading and progressed until the end of the experimental period. The peri-implant soft tissues adapted and were maintained regardless of collar height.

*“Clinical Complications With Implants and Implant Prostheses,” by C. J. Goodacre, G. Bernal, K. Rungcharassaeng, J. Y. K. Kan. J Prosthet Dent, 90:121–132, 2003.

One of the purposes of this article is to provide data regarding the types of complications that have been reported in conjunction with endosseous root-form implants and associated crowns/prostheses. Another purpose is to identify the most common implant complication. A third purpose is to compare the complications incidences associated with implant prostheses with those encountered with fixed restorations/prostheses. A Medline and an extensive hand search were performed on English-language publications covering the years 1981 to 2001. The searches focused on publications that contained clinical data regarding success, failure, and complications. The complications were divided into the following 6 categories: surgical, implant loss, bone loss, peri-implant soft tissue, mechanical, and esthetic or phonetic. The most common implant complications were loosening of the overdenture retentive mechanism (33%), implant loss in irradiated maxillae (25%), hemorrhage-related complications (24%), resin veneer fracture with fixed partial denture (22%), implant loss with maxillary overdentures (21%), overdentures needing to be relined (19%), implant loss in type IV bone (16%), and overdenture clip or attachment fracture (16%). Even though it was not possible to calculate an overall complications incidence for implants and their associated prostheses, there appears to be a greater number of clinical complications associated with implant prostheses than with single crowns, fixed partial dentures, all-ceramic crowns, resin-bonded prostheses, and posts and cores.

*“Anterior Loop of the Mental Nerve: A Morphological and Radiographic Study,” by D. Kuzmanovic, A. Payne, J. Kieser, G. Dias. Clin Oral Implant Res, 14:464–471, 2003.

This study determined if a correlation existed between the anatomically dissected path of the mental neurovascular bundle in 22 sectioned human-head specimens and their radiographically estimated path by using the (Soridex, Orinon Corp, Helsinki, Finland) radiographic unit jaw panorama (Programme 001, magnification 1.3) and dental panorama (Programme 003, magnification 1.7). The specimens were accurately positioned with the guidance of light lines for the midsagittal, frontal, and horizontal planes and were correctly placed relative to the anatomical land. Two calibrated observers interpreted the radiographic exams. Bilateral anatomical dissection was then performed on all specimens. The anterior loop of the inferior alveolar canal was identified in only 6 panoramic radiographs (27%) (range 0.5–3 mm). There was a significant positive correlation between both observers of the radiographs and between the 2 radiographic programs used. Anatomical measurements of the anterior loop of the mental neurovascular bundle revealed its presence in 8 dissected specimens (37%) (range 0.11–3.31 mm). Fifty percent of the radiographically observed anterior loops were misinterpreted by observers with both radiographic programs, and 62% of the anatomically identified loops were not observed radiographically. Anatomical dissection also revealed that the mean diameter of the incisive nerve was 1.80 + 0.46 mm (range 0.9–2.53 mm). Clinicians should not rely on panoramic radiographs for identifying the anterior loop of the mental nerve during implant-treatment planning. However, on the basis of our anatomical findings, a safe guideline of 4 mm from the most anterior point of the mental foramen is recommended.

*“Morphology and Dimensions of the Mandibular Jaw Bone in the Interforaminal Region in Patients Requiring Implants in the Distal Areas,” by M. Quirynen, N. Mraiwa, D. van Steenberghe, R. Jacobs. Clin Oral Implant Res, 14:280–285, 2003.

This study evaluated anatomical variations of the mandibular interforaminal region in 210 patients by computed tomography (CT) analysis. The consecutively selected subjects consisted of patients presenting for implant-supported prostheses in the mandible. The patient ages ranged from 18 to 80 years with a mean of 55. The vast majority of patients (186 of 210) had partially edentulous interforaminal regions, with an additional 4 patients fully edentulous in this area. Three distinct morphologies of the interforaminal area were noted: type I (with lingual concavity), type II (with near-constant width but clear lingual tilt), and type III (with narrowed crestal bone). These morphologies were found in frequencies of 2.4% for type I, 28.1% for type II, and 69.5% for type III. In type I morphology, the lingual concavity had a depth of 6 ± 2 mm, the lingual cortex had a very slight lingual slope (85°), and the maximal bone height superior to the concavity was 10.5 ± 2.7 mm. The lingual slope observed in type II morphology was 67.6° ± 6.5°. In type III morphology, the apical third was found to consistently be 1 mm wider than the middle third of the mandible. These results demonstrate that even in partially edentulous mandibular interforaminal areas morphologic variations can frequently be present, in particular a lingual slope (28.1%) and a narrowing crestal ridge (69.5%). The authors postulated that in fully edentulous mandibles the resorption patterns would display a further frequency of type I and II morphology. The authors note that the use of 3-dimensional imaging, such as CT, would lessen the risk of complications during the placement of dental implants in the interforaminal region.

Endosseous Implants

*“Early Tissue Reaction at the Interface of Immediately Loaded Dental Implants,” by U. Meyer, H. P. Wiesmann, T. Fillies, U. Joos. Int J Oral Maxillofac Implants, 18:489–499, 2003.

The purpose of this study was to investigate the early response of osteoblasts and the extent of mineral formation at the titanium surface of implants that are designed to elicit homogenous physiologic strains at the implant surface. After the extraction of the mandibular second premolars and allowing a healing period of 3 months, 32 implants were placed in the mandibles of 8 minipigs. Sixteen of the implants were immediately loaded under occlusal contact and served as the test group, whereas the remaining 16 implants were not loaded and served as a control. All the implants healed uneventfully except for 1 that showed signs of tissue inflammation. The ultrastructural analysis of the specimens showed intimate attachment between the osteoblast and the implant surface at the early stages (day 1). There was no difference in the morphology of the osteoblasts between the test group and the study group, and the electron microscopy and diffraction analysis showed a direct contact of bone minerals over the whole implant surface with no alterations at the crestal bone level. These results indicate that this design of implants can be immediately loaded without causing any alterations to the osteoblastic morphology and attachment characteristics at the early phase of loading and conclude that immediate loading can be performed without disturbing the normal bone biology and healing.