Clinical and microbiologic investigation of an expedited peri-implantitis dog model: an animal study.

BACKGROUND: Animal studies are pivotal in allowing experimentation to identify efficacious treatment protocols for resolution of peri-implantitis. The purpose of this investigation was to characterize an expedited dog peri-implantitis model clinically, radiographically, and microbiologically. METHODS: Eight hound dogs underwent extractions (week 0) and implant (3.3 × 8.5 mm) placement with simultaneous surgical defect creation and ligature placement for induction of peri-implantitis (week 10). Ligatures were replaced at 6 weeks (week 16) and removed after 9 weeks (week 19) when supporting bone loss involved approximately 50% of the peri-implant bone. Microbial samples from the defects and healthy control implant sites collected at week 19 were analyzed utilizing a microarray. Clinical measures of inflammation were obtained and radiographic bone loss was measured from periapical radiographs. Radiographic depth and width measurements of bony defect were repeated at weeks 10 (baseline), 16, and 19. Canonical analysis of principal coordinates was used to visualize overall differences in microbial abundance between peri-implantitis and healthy implants. RESULTS: This accelerated disease protocol led to intrabony defect creation with a mean depth and width of 4.3 mm and 3.5 mm, respectively after 9 weeks of ligature placement. Microbial identification revealed 59 total bacteria in peri-implant sites, 21 of which were only present in peri-implant sites as compared to healthy controls. Overall microbial beta diversity (microbial between-sample compositional diversity) differed between peri-implantitis and healthy implants (p = 0.009). CONCLUSIONS: Within the limitations of this study, this protocol led to expedited generation of peri-implant defects with a microbial profile indicative of a shift to disease and defect patterns conducive to regenerative treatment. However, the possibility of potential spontaneous resolution of lesions due to the lack of a chronicity interval as compared to chronic disease models need to be further clarified and considered during preclinical peri-implantitis model selection.

Postmortem evaluation of mandibular implant-supported fixed complete denture after 30 years of service.

A postmortem evaluation of a 5-implant-supported mandibular fixed complete denture that had successfully opposed a maxillary conventional complete denture for 30 years was undertaken. Before embalming, radiographs, implant stability measurements, push-in failure load tests, and histomorphometric analyses were performed on the implants and the mandible. Evaluation of this cadaver suggests that an edentulous mandible restored with an implant-supported fixed prosthesis can function successfully for over 30 years with few complications.

Digital versus conventional impressions for full-coverage restorations: A systematic review and meta-analysis.

BACKGROUND: The primary objective of this systematic review was to investigate the survival of full-coverage restorations fabricated by using digital impressions (DIs) versus that of those fabricated by using conventional impressions. The authors also compared secondary outcomes of marginal and internal fit and occlusal and interproximal contacts. TYPES OF STUDIES REVIEWED: The authors conducted a systematic literature search in multiple databases to identify clinical trials with no restrictions by publication type, date, or language. The authors assessed study-level risk of bias and outcome-level strength of evidence. The authors performed a meta-analysis by using a random-effects model. RESULTS: Ten studies met the inclusion criteria. The authors identified no studies in which the investigators compared the impression techniques with respect to survival of full-coverage restorations. Mean differences for marginal gap and internal gap were -9.0 micrometers (95% confidence interval, -18.9 to 0.9) and -15.6 µm (95% confidence interval, -42.6 to 11.4), respectively. Studies assessing internal gap were substantially heterogeneous (I2 = 72%; P = .003). CONCLUSIONS AND PRACTICAL IMPLICATIONS: Research is lacking to draw robust conclusions about the relative benefits of DIs in terms of restoration survival. Low-quality evidence for marginal fit and internal fit suggested similar performance for both techniques. Evidence quality for interproximal contact and occlusal contact was very low and insufficient to draw any conclusions regarding how the impression techniques compared. Given the uncertainty of the evidence, results should be interpreted with caution. With increasing popularity and adoption of digital scanners by dentists, pragmatic practice-based trials involving standardized, patient-centered outcomes may improve confidence in the comparative effectiveness of DIs.

Comparison of Initial Implant Stability of Implants Placed Using Bicortical Fixation, Indirect Sinus Elevation, and Unicortical Fixation.

PURPOSE: The aim of this study was to determine if self-threading dental implants placed using stopper drills to bicortically engage both the alveolar crest and sinus floor (bicortical fixation) achieved primary and/or secondary stability comparable to that of short implants only engaging alveolar crest cortical bone (unicortical fixation) or implants engaging both the crest and sinus floor but via greenstick fracture and grafting (indirect sinus elevation). MATERIALS AND METHODS: Thirty-eight patients exhibiting 7 to 11 mm of bone coronal to the sinus floor as confirmed by preoperative CBCT were recruited. Forty-five implants were randomly assigned to one of the placement techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla while using different surgical techniques. An Osstell ISQ was employed immediately after implant placement to measure stability six times in a buccolingual dimension. Secondary stability was measured at stage-two surgery after a 3- to 6-month healing period. RESULTS: The greatest primary implant stability was achieved via indirect sinus elevation. However, no statistically significant difference was found among the three surgical techniques (P = .13; bicortical fixation: 71.4 [standard error = 2.1]), unicortical fixation: 69.6 [2.1], indirect sinus elevation: 75.9 [2.3]). The three techniques had similar secondary stability (P > .999; 79.9 [1.2], 80.0 [1.2], and 80.0 [1.3], respectively). Baseline residual ridge height measured on CBCT was similar (P = .1; 8.8, 9.9, and 9.4 mm, respectively), but implant diameter and length placed in the maxilla differed (P = .03/P < .001; 4.7/11.4 mm, 4.3/8.1 mm, and 4.7/11.8 mm, respectively). Primary implant stability was significantly correlated to CBCT bone density (r = 0.37). CONCLUSION: Primary and secondary implant stabilities of bicortical fixation did not differ significantly from those of unicortical fixation and indirect sinus elevation. However, use of the bicortical fixation technique is warranted since it is simpler and more economical than indirect sinus elevation; plus, it allows for longer implants than the unicortical fixation while yielding similar secondary implant stability.

The effects of image acquisition control of digital X-ray system on radiodensity quantification.

OBJECTIVES: Aluminum step wedge (ASW) equivalent radiodensity (eRD) has been used to quantify restorative material's radiodensity. The aim of this study was to evaluate the effects of image acquisition control (IAC) of a digital X-ray system on the radiodensity quantification under different exposure time settings. MATERIALS AND METHODS: Three 1-mm thick restorative material samples with various opacities were prepared. Samples were radiographed alongside an ASW using one of three digital radiographic modes (linear mapping (L), nonlinear mapping (N), and nonlinear mapping and automatic exposure control activated (E)) under 3 exposure time settings (underexposure, normal-exposure, and overexposure). The ASW eRD of restorative materials, attenuation coefficients and contrasts of ASW, and the correlation coefficient of linear relationship between logarithms of gray-scale value and thicknesses of ASW were compared under 9 conditions. RESULTS: The ASW eRD measurements of restorative materials by three digital radiographic modes were statistically different (p = 0.049) but clinically similar. The relationship between logarithms of background corrected grey scale value and thickness of ASW was highly linear but attenuation coefficients and contrasts varied significantly among 3 radiographic modes. Varying exposure times did not affect ASW eRD significantly. CONCLUSIONS: Even though different digital radiographic modes induced large variation on attenuation of coefficient and contrast of ASW, E mode improved diagnostic quality of the image significantly under the under-exposure condition by improving contrasts, while maintaining ASW eRDs of restorative materials similar. Under the condition of this study, underexposure time may be acceptable clinically with digital X-ray system using automatic gain control that reduces radiation exposure for patient.

Comparison of push-in versus pull-out tests on bone-implant interfaces of rabbit tibia dental implant healing model.

PURPOSE: This study aimed to investigate whether push-in and pull-out tests measure mechanical properties of the bone-implant interface differently, and which test is more sensitive to changes over the healing period. MATERIALS AND METHODS: Two identical self-threading dental implants (3.3×8.5mm) were placed in medial surface of the proximal condyles of left and right tibias of 20 rabbits (40 implants total). Five rabbits each were sacrificed after 1, 4, 8, and 12 weeks of healing. Push-in test was performed on one side's tibia implant and pull-out on the other side's implant, at a rate of 6mm/min. Primary and secondary implant stabilities and tibia weight were measured on all implants. RESULTS: The push-in test generated significantly higher failure load (p=.0001; 530N vs 279N), lower displacement at failure (p=.0003; 0.436mm vs 0.680mm), and higher interface stiffness (p<.0001; 1,641N/mm vs 619N/mm) than pull-out test. Failure load, stiffness, and secondary implant stability were significantly higher for longer compared with shorter healing periods, while displacement, tibia weight, and primary stability were not. Failure load and stiffness differed significantly for four healing times for the push-in but not for the pull-out test. Failure load was significantly correlated with secondary implant stability for both push-in (r=0.66) and pull-out (r=0.48) tests, but stiffness was significantly correlated with secondary stability only for the push-in test (r=0.72; pull-out test r=0.40). CONCLUSION: The push-in test appeared more sensitive than pull-out to changes in mechanical properties at bone-implant interfaces during healing in rabbit tibia model.

Prevalence of sinus augmentation associated with maxillary posterior implants.

Pneumatization of the maxillary sinus limits the quantity of alveolar bone available for implant placement and may result in a lack of primary stability and difficulty in achieving osseointegration. The purpose of this study was to retrospectively analyze a group of patients who had implants placed in the posterior maxilla, calculate the prevalence of sinus augmentation, and identify factors related to sinus augmentation. With institutional review board approval, dental records from a population of patients who had implants placed in the maxillary posterior region between January 2000 and December 2004 were used to create a database. Independent variables were classified as continuous (age of the patient at stage 1 implant surgery [S1], time between extraction and S1, time between extraction and sinus augmentation, and time between sinus augmentation and S1) and categorical (gender, implant failure, American Society of Anesthesiologists system classification, smoking, osteoporosis, residual crestal bone height, implant position, implant proximity, prostheses type, and implant diameter and length). The dependent variable was the incidence of a sinus augmentation procedure. Simple logistic regression was used to assess the influence of each factor on the presence of sinus augmentation (P < .05). The final database included 502 maxillary posterior implants with an overall survival rate of 93.2% over a mean follow-up period of 35.7 months. Of 502 implants, 272 (54.2%) were associated with a sinus augmentation procedure. Among variables, residual crestal bone height (P < .001), implant position (P < .001), implant proximity (P < .001), prosthesis type (P < .001), implant failure (P < .01), and implant diameter (P < .01), were statistically associated with sinus augmentation. Within the limitations of this retrospective study, the results suggest that more than half (54.2%) of the maxillary posterior implants were involved with a sinus augmentation procedure. The prevalence of sinus augmentation increased with decreased residual crestal bone height, more posterior implant locations, and complete or partial edentulism. Sinus augmentation was significantly associated with implant failure and wide implants.

Effect of surgical guide design and surgeon's experience on the accuracy of implant placement.

Implant position is a key determinant of esthetic and functional success. Achieving the goal of ideal implant position may be affected by case selection, prosthodontically driven treatment planning, site preparation, surgeon's experience and use of a surgical guide. The combined effect of surgical guide design, surgeon's experience, and size of the edentulous area on the accuracy of implant placement was evaluated in a simulated clinical setting. Twenty-one volunteers were recruited to participate in the study. They were divided evenly into 3 groups (novice, intermediate, and experienced). Each surgeon placed implants in single and double sites using 4 different surgical guide designs (no guide, tube, channel, and guided) and written instructions describing the ideal implant positions. A definitive typodont was constructed that had 3 implants in prosthetically determined ideal positions of single and double sites. The position and angulation of implants placed by the surgeons in the duplicate typodonts was measured using a computerized coordinate measuring machine and compared to the definitive typodont. The mean absolute positional error for all guides was 0.273, 0.340, 0.197 mm in mesial-distal, buccal-lingual, vertical positions, respectively, with an overall range of 0.00 to 1.81 mm. The mean absolute angle error for all guides was 1.61° and 2.39° in the mesial-distal and buccal-lingual angulations, respectively, with an overall range of 0.01° to 9.7°. Surgical guide design had a statistically significant effect on the accuracy of implant placement regardless of the surgeon's experience level. Experienced surgeons had significantly less error in buccal-lingual angulation. The size of the edentulous sites was found to affect both implant angle and position significantly. The magnitude of error in position and angulation caused by surgical guide design, surgeon's experience, and site size reported in this study are possibly not large enough to be clinically significant; however, it is likely that errors would be magnified in clinical practice. Future research is recommended to evaluate the effect of surgical guide design in vivo on implant angulation and position error.

Ex vivo mechanical properties of dental implant bone cement used to rescue initially unstable dental implants: a rabbit study.

PURPOSE: Dental implant bone cement (DIBC) was developed to rescue unstable implants at the time of placement. The purpose of this study was to compare the mechanical properties of bone-cement-implant interfaces of cemented implants that were unstable initially and bone-implant interfaces of self-threaded implants placed in rabbit femurs after various healing periods. Interfaces and failure modes were also characterized using histology and scanning electron microscopy (SEM). MATERIALS AND METHODS: Eighty dental implants were placed in 20 rabbits. In each rabbit, two experimental and two control implants were placed in the right or left femur; one was in the distal epiphysis and the other in the cortical shaft. The experimental implants were cemented in loosely prepared bony sockets, while the control implants were self-threaded. The rabbits were sacrificed after varying healing periods. Magnetic pulse stability and push-in yield tests on ex vivo specimens measured secondary implant stability, 0.2% yield load, displacement, interface stiffness, and load at 100 µm. After loading tests, interfaces were evaluated with histology and SEM. Most analyses used mixed linear models. RESULTS: The 0.2% yield load, interface stiffness, load at 100 µm, and secondary stability were significantly higher for bone-cement-implant interfaces than for bone-implant interfaces. Mechanical properties of bone-cement-implant interfaces plateaued at 1 week, with minimal change over the following 12 weeks, whereas bone-implant interfaces improved gradually. SEM and histology showed intimate bone-cement-implant interfaces without soft tissue intervention and mainly cohesive failures within DIBC. Secondary stability was significantly correlated with interface stiffness and load at 100 µm. CONCLUSION: The results suggest that DIBC can provide early implant stability and mechanical properties superior to those of self-threaded implants while maintaining intimate interfaces without signs of osteonecrosis or soft tissue intervention.

Retrospective cohort study of the predictors of implant failure in the posterior maxilla.

PURPOSE: The purpose of this study was to retrospectively analyze a cohort of patients who had implants placed in the posterior maxilla and assess and identify the predictors of implant failure. MATERIALS AND METHODS: With institutional review board approval, dental records from a population of patients who had maxillary posterior implants placed were used to create a database. Independent variables were divided into continuous (age of the patient at stage-one implant surgery [S1], time between extraction and S1, time between extraction and sinus augmentation, time between sinus augmentation and S1, time between S1 and stage-two implant surgery [S2], and the time between S2 and restoration of the implant) and categorical (gender, American Society of Anesthesiologists [ASA] status, current smoking status, implant position, implant proximity, residual crestal bone height, implant length and diameter, and sinus augmentation technique and materials). The dependent variable was implant failure, which was defined as complete removal of the implant. Simple logistic regression was used to assess the influence of each of the predictors on implant failure (P < .05). RESULTS: The final database included 504 maxillary posterior implants with an overall survival rate of 93.2% over a mean follow-up period of 35.7 months. For the continuous variables, the age of the patient at S1 was statistically associated with implant failure (P = .028), as was the time between extraction and S1 (P = .014). For the categorical variables, ASA status (P < .001), implant proximity (P = .043), residual crestal bone height (P < .001), implant diameter (P = .050), sinus augmentation technique (P = .002), and sinus graft materials (P < .001) were statistically associated with implant failure. CONCLUSION: Within the limitations of this retrospective study, the results suggest that there are risk factors associated with maxillary posterior implant failure. Implants placed in areas with inadequate residual crestal bone height that required sinus augmentation were statistically associated with implant failure.

Expression of TGF-beta1, osteonectin, and BMP-4 in mandibular distraction osteogenesis with compression stimulation: reverse transcriptase-polymerase chain reaction study and biomechanical test.

PURPOSE: This study compared the levels of transforming growth factor-beta1 (TGF-beta1), osteonectin, and bone morphogenetic protein-4 (BMP-4) expression in regenerated bone in a rabbit mandible that had undergone conventional distraction osteogenesis (DO) with those in regenerated bone from a modified DO technique with compression stimulation. MATERIALS AND METHODS: A total of 42 rabbits were used in this reverse transcriptase-polymerase chain reaction study. In the control group, distraction was performed at 1 mm/day for 8 days. In the experimental group, overdistraction was performed for 10 days, followed by a 3-day latency period and 2 days of compression to achieve the same amount of DO. Three rabbits per subgroup were killed at 0, 5, 13, 20, 27, 34, and 41 days after the initial osteotomy. The levels of TGF-beta1, osteonectin, and BMP-4 in the bone regenerates were measured by reverse transcriptase-polymerase chain reaction. A biomechanical microhardness test was also performed in 8 rabbits as a separate experiment. RESULTS: Reverse transcriptase-polymerase chain reaction revealed a greater level of TGF-beta1 in the experimental group immediately after applying the compression force that continued for 2 weeks. The level then decreased to that of the control group at 3 weeks. The greater level of osteonectin in the experimental group after compression than that in the control group continued for 3 weeks. In the experimental group, the level of BMP-4 increased immediately after compression. However, the level in the control group decreased. The microhardness ratio of distracted bone to normal bone on the cortex was statistically different at 0.47 in the control group and 0.80 in the experimental group (P = .049) at 55 days after osteotomy. CONCLUSION: The effectiveness of the new DO technique with compression stimulation was confirmed by the gene expression study and the biomechanical test findings.

Potential damage to bone-implant interface when measuring initial implant stability.

BACKGROUND: An electronically controlled mechanical tapping device (MTD) to measure implant stability has been studied extensively for its ability to measure initial stability at the time of surgical placement and predict an implant's survival prognosis, with few reported complications. METHODS: Initial stability data, measured repeatedly with a resonance frequency analysis device and the MTD, for seven of 28 implants placed in jawbones of four fresh human cadavers and the histologic images of bone-implant interfaces are presented as evidence for potential damage to the bone-implant interface using these techniques. RESULTS: A progressive increase in mobility from stable (-1) to less stable (4) and eventually to visibly mobile (999) was observed after three measurements with the MTD. Corresponding histologic images revealed that the buccal threads in the coronal half of the implants were displaced lingually and apically from the bony indentations that were created during insertion of the self-threading implants, subsequent to repeated MTD measurements in the buccal and axial directions. The histologic images and changes in MTD values indicated that repeated MTD measurements at the time of implant placement surgery may damage the bone-implant interface, and a stable or borderline implant may become mobile after repeated MTD measurements. CONCLUSIONS: Histologic images showed potential damage to the bone-implant interface during repeated initial implant-stability measurements using the MTD. Initial implant-stability measurements using the MTD should be performed with caution, and they may be contraindicated for implants placed in low-quality bone.

Correlations between physical properties of jawbone and dental implant initial stability.

STATEMENT OF PROBLEM: There is confusion in the literature about how physical properties of bone vary between maxillary and mandibular regions and which physical properties affect initial implant stability. PURPOSE: The purpose of this study was to determine correlations between physical properties of bone and initial implant stability, and to determine how physical properties and initial stability vary among regions of jawbone. MATERIAL AND METHODS: Four pairs of edentulous maxillae and mandibles were retrieved from fresh human cadavers. Six implants per pair were placed in different anatomical regions (maxillary anterior, right and left maxillary posterior, mandibular anterior, right and left mandibular posterior). Immediately after surgery, initial implant stability was measured with a resonance frequency device and a tapping device. Implant surgeries and initial stability measurements were performed within 72 hours of death. Elastic modulus (EM) and hardness were measured using nano-indentation. Composite apparent density (cAD) was measured using Archimedes' principle. Bone-implant contact percentage and cortical bone thickness were recorded histomorphometrically. Mixed linear models and univariate-correlation analyses were used (alpha=.05). RESULTS: Generally, mandibular bone had higher initial implant stability and physical properties than maxillary bone. Initial implant stability was higher in the anterior region than in the posterior. EM was higher in the posterior region than in the anterior; the reverse was true for cAD. CONCLUSIONS: Of the properties evaluated, cAD had the highest correlation with initial implant stability (r=0.82). Both physical properties of bone and initial implant stability differed between regions of jawbone.

Accuracy of friction-style and spring-style mechanical torque limiting devices for dental implants.

STATEMENT OF PROBLEM: Accurate delivery of torque to implant prosthetic screws is critical to generate ideal preload in the screw joint and offer protection against screw loosening. Mechanical torque limiting devices (MTLDs) are available in 2 different styles that have not been compared for accuracy. PURPOSE: The purpose of this study was to determine the accuracy of friction-style and spring-style MTLDs in delivering target torque values. MATERIAL AND METHODS: Five MTLDs from each of 6 different implant manufacturers (n=30) were selected to determine their accuracy relative to their target torque values. All MTLDs were new; 3 types were of the friction style while 3 were of the spring style. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck to hold the driver was used. Force was applied to the MTLD until either the friction style released at a precalibrated torque value or the spring style flexed to a precalibrated limit. The peak torque value registered by the digital torque gauge was recorded and the procedure was repeated 50 times for each MTLD. Statistical analysis used repeated-measures ANOVA (alpha=.05) to assess the accuracy of the MTLDs in delivering target torque values. RESULTS: Both the mean absolute difference (ABSDIFF) and the mean percentage deviation (PERDEV) between measured torque values and target torque values differed significantly (P<.001) for the friction-style MTLDs (3.83 Ncm, 13.74%) and for the spring-style MTLDs (0.82 Ncm, 2.36%). CONCLUSIONS: Within the limitations of this study, MTLDs that use spring-style components are significantly more accurate than those that use friction-style components in achieving their target torque values.

Initial stability measurement of dental implants placed in different anatomical regions of fresh human cadaver jawbone.

STATEMENT OF PROBLEM: Initial implant stability has been used as an indicator for future osseointegration and whether an immediate/early loading protocol should be applied. However, differences in initial stability in relation to anatomical regions of jawbone have not been studied extensively because of the risks involved with stability measurements. PURPOSE: The purpose of this study was to determine whether initial implant stability varies with anatomical regions of the jawbone. MATERIAL AND METHODS: Four pairs of edentulous maxillae and mandibles were retrieved from fresh human cadavers. Six implants (Biomet 3i) per pair were placed in different anatomical regions (maxillary anterior, right and left maxillary posterior, mandibular anterior, right and left mandibular posterior). Immediately after implant placement, initial implant stability was measured with a custom-made resonance frequency analyzer, a commercial resonance frequency analysis device (Osstell), and a mechanical tapping device (Periotest). All implant surgeries and initial stability measurements were performed within 72 hours of death to simulate a clinical setting. Repeated measures ANOVA (alpha=.05) and univariate correlation analyses were used to analyze the data. RESULTS: Mandibular implants had significantly higher initial stability than maxillary implants. Posterior maxillary implants were least stable. Stability was less buccolingually than mesiodistally. The measurements from 3 stability measuring devices were strongly associated with each other. CONCLUSIONS: Initial implant stability varied among anatomical regions of jawbone. Rank of Periotest value and implant stability quotient (Osstell) had the highest correlation (r=-0.852).

Current ceramic materials and systems with clinical recommendations: a systematic review.

STATEMENT OF PROBLEM: Developments in ceramic core materials such as lithium disilicate, aluminum oxide, and zirconium oxide have allowed more widespread application of all-ceramic restorations over the past 10 years. With a plethora of ceramic materials and systems currently available for use, an overview of the scientific literature on the efficacy of this treatment therapy is indicated. PURPOSE: This article reviews the current literature covering all-ceramic materials and systems, with respect to survival, material properties, marginal and internal fit, cementation and bonding, and color and esthetics, and provides clinical recommendations for their use. MATERIAL AND METHODS: A comprehensive review of the literature was completed seeking evidence for the treatment of teeth with all-ceramic restorations. A search of English language peer-reviewed literature was undertaken using MEDLINE and PubMed with a focus on evidence-based research articles published between 1996 and 2006. A hand search of relevant dental journals was also completed. Randomized controlled trials, nonrandomized controlled studies, longitudinal experimental clinical studies, longitudinal prospective studies, and longitudinal retrospective studies were reviewed. The last search was conducted on June 12, 2007. Data supporting the clinical application of all-ceramic materials and systems was sought. RESULTS: The literature demonstrates that multiple all-ceramic materials and systems are currently available for clinical use, and there is not a single universal material or system for all clinical situations. The successful application is dependent upon the clinician to match the materials, manufacturing techniques, and cementation or bonding procedures, with the individual clinical situation. CONCLUSIONS: Within the scope of this systematic review, there is no evidence to support the universal application of a single ceramic material and system for all clinical situations. Additional longitudinal clinical studies are required to advance the development of ceramic materials and systems.

Bone regeneration in mandibular distraction osteogenesis combined with compression stimulation.

PURPOSE: This study compared modified distraction osteogenesis (DO) protocol with conventional DO protocol on healing bone formation. Computer simulation was performed to understand the mechanical environment of modified DO protocol, which applies compression during the consolidation period. MATERIALS AND METHODS: Fifty rats were used in this study. Twenty-five rats in the conventional DO (control) group were sacrificed at postoperative days 11, 21, 28, 35, and 49 after osteotomy. In the modified DO (experimental) group, compression was applied on day 7 after distraction (day 18 postoperatively) for 4 days during the early consolidation period and 25 rats were sacrificed on postoperative day 19, 28, 39, 46, and 53. The histologic and radiographic findings were used to compare the 2 groups. Further, computer simulation was used to predict the mechanical environment of healing bone under conventional and modified DO protocol. RESULTS: Radiographic findings showed that the experimental group resulted in denser and wider healing bone. Histologically, the experimental group yielded more mature lamellar bone than the control group. Computer simulation showed that absolute values of tissue strains were nearly double in the control group because of the softer healing tissues. Both the experimental and control groups showed high strains at the ridge crest. Concentrated tensile strain along the distraction direction at the ridge crest might hinder bone formation at the interface, while compressive strain could facilitate the process. CONCLUSION: This study proposed a modified DO protocol of adding compression during the early consolidation period of conventional DO protocol. This new technique appears to provide faster and denser bone regeneration.