Alveolar Bone Loss Around The Implant After Use Of The Ridge Expansion Technique : A Clinical Review And An Experimental Research

Background: In clinical work, we found that the alveolar bone loss in patients was very serious for periodontal disease, trauma and other factors, which made it difficult to implant. When the alveolar bone volume was low, we often needed to use surgical approaches to redevelop it. In recent years, there was emerging a number of bone augmentation techniques to expand the indications of dental implant, including bone grafts, guided bone regeneration, bone compression, bone splitting, distraction osteogenesis and maxillary sinus augmentation, etc. When the residual alveolar height was acceptable, while the width was insufficient, we often used the method of bone splitting to provide adequate space for the implant application. Because it could make the implants inserted simultaneously, which reduced the bone grafts significantly, it was widely used in clinical practice.With the development of domestic and international researches, the scientists found that the bone splitting technique was flawed, because the marginal bone was absorbed, which often lead to gingival recession and implant neck exposed. For the poor aesthetic results, bone splitting technique was used in posterior area which was so-called non-aesthetic area. Therefore, we modified the bone splitting procedures and put forward the concept of "alveolar ridge extension for implant application ". This technique was built on the basis of bone splitting technique, and combined with bone grafting and GBR techniques. Furthermore we improved a few surgical details, such as the use of auxiliary mesial and distal splitting incision, reserving the periosteal of bone plates in flap surgery, etc. In the last 7 years, the results of this technique were perfect.This subject included the clinical research and animal experiments. First, we evaluated the clinical effects of the technique, alveolar ridge extension for implant application. Second, in the animal model, we studied the marginal bone stability by using 2 different flap approaches for alveolar ridge expansion. We hoped this study would contribute to the clinical application of this approach.PartⅠAlveolar ridge extension for implant application: a 5-year retrospective clinical study and a radiographic evaluation.Objective: To evaluate the clinical application of alveolar ridge expansion for dental implant.Methods: From October 2004 to December 2008, 209 implants of 142 patients had been implanted in the department of Oral Implants, the Fourth Military Medical University Stomatology Hospital. The mean age was 36.12-years-old, and the mean bone healing period was 7.46 months. During the implant surgery, there were 6 cases which had to change the operation plan after the bone plate fractured.In the 136 patients, there were 77 patients who had been taken alveolar ridge extension for implant application, and 59 patients who had been taken alveolar ridge extension with GBR and bone graft for implant application. Meanwhile, there were 170 Straumann implants, 23 Nobel Replace implants and 8 Camlog implants. All patients had been completed the crown restoration. Followed-up 6 to 56 months, it could be evaluated by X-ray measurements and clinical observation. We can use the life table method to calculate cumulative survival rate of 5 years. And the data from X-ray measurements were compared by using paired t test and ANOVA with SPSS software.Results: 22.1% of 136 patients were lost. Bone integration of all return-visit implants were completed with no implant dropped out, and the cumulative survival rates were 100% in 5 years. The bone loss value was no significant correlation between the mesial and distal groups, P> 0.05. There were no significant differences between the bone resorption values and the factors, such as the patients'ages, implants'types, implants'lengthes and diameters, P> 0.05. Before the loading, the mean of bone loss values in aesthetic zone was 1.21mm and 1.46mm in non-aesthetic areas, it was significantly different, P <0.05. In the 1st year after restoration, the mean of bone loss values in aesthetic zone was 0.47mm and 0.56mm in non-aesthetic areas, it was significantly different, P <0.05. Before the loading, the mean of bone loss values in the group of alveolar ridge extension was 1.55mm and 1.01mm in the group of alveolar ridge extension with GBR and bone graft, it was significantly different, P <0.05. In the 1st year after restoration, the mean of bone loss values in the group of alveolar ridge extension was 0.72mm and 0.43mm in the group of alveolar ridge extension with GBR and bone graft, it was significantly different, P <0.05. Before the loading and in the 1st year, there were significantly different between patients who had been taken alveolar ridge extension and ones with GBR grafts, P <0.05.. In the 1st year and 2nd year, there were significantly different, too.Conclusions: It had a good long-term effect to use the alveolar ridge extension for implant application.PartⅡThe design and manufacture of an improved caliper by measuring the bone plate thickness with the dental implant as the center and its evaluation.Objective: To investigate a method of measuring the bone thickness with the dental implant as the center and to evaluate the accuracy of an improved vernier caliper by the method.Methods: An improved caliper were made by Solid Edge software, which had the Straumann implant as the center for measuring the bone thickness. First, the implant was placed into the transparent composite resin block. Second, the lateral wall thickness of the transparent compound resin surrounding the implant was measured by the improved caliper. Then the resin block with the implant was cut into halves through the long axis of implant. Third, the exact thickness was digitized and measured by Digimizer software. The data from the two groups were compared by using paired t test with SPSS software.Results: The results detected by the 10 improved caliper groups were 7.97-8.09 mm, while that were 7.98-8.12 mm of the 10 resin block longitudinal groups. The standard deviation of two sets was 0.03, the t value was 1.09, and the P value was 0.28. There was no statistical difference between the two methods.Conclusions: The improved caliper was fit for measuring the bone thickness with the dental implant as the center. With higher precision and better repeatability, it could be used to estimate the bone loss around the implant.PartⅢAlveolar bone loss impacted by 2 different flap approaches for alveolar ridge extension: an experimental research in dogs. Objective: We investigated 2 different flap approaches of alveolar ridge extension for implant application in dogs, as the bone loss of labial plate and BIC should be studied.Methods: 3 hybrid male dogs were used. 3 months after extraction of maxillary anterior teeth, this edentulous ridge was randomly assigned to left and right side, one side was the experimental control group(mucoperiosteum flap), the other side was the experimental group(mucosal flap) and the conventional control group, each group had been implanted 1 implant. Animals were killed after 3 months and drawn. During the operation and after it 3 months, we measured the bone thickness with the improved caliper, and measured IS-BC with the periodontal probe. The samples had been measured for the bone thickness and IS-BC by MicroCT. Then the samples had been produced into hard tissue grinding and observed in light microscopy with the bone thickness, IS-BC and BIC. The data were compared by using paired t test and ANOVA with SPSS software.Results: 3 dogs were healing well without inflammation around implant and without exposure. During the operation the mean of bone thickness values was (2.04±0.90)mm and (1.37±1.00)mm after 3 months by the improved caliper, it was significantly different, P <0.05. During the operation the mean of IS-BC values was (0.40±0.31)mm and (0.69±0.36)mm after 3 months by the periodontal probe, it was significantly different, P <0.05. In addition, the values of bone thickness changing were significantly different in the experimental control group (0.92±0.35)mm and experimental group (0.62±0.40)mm, P<0.05. And the values of bone thickness changing were not significantly different in the experimental group (0.62±0.40)mm and conventional control group (0.45±0.13)mm, P>0.05. The values of IS-BC changing were significantly different in the experimental control group (0.63±0.34)mm and experimental group (0.47±0.33)mm, P<0.05. And the values of IS-BC changing were not significantly different in the experimental group (0.47±0.33)mm and conventional control group (0.36±0.28)mm, P>0.05. Moreover, the values of bone thickness changing were significantly different in 2mm under the neck edge group (0.86±0.40)mm and 7mm group (0.46±0.17)mm, P <0.05. With measuring in the light microscope, BIC in the experimental control group was 84%, it was 91% in the experimental group and 95% in the conventional control group.Conclusions: Consequently, the use of mucosal flap during operation can effectively prevent the vertical bone resorption. It was worth promoting in the clinical application.