Short Communication: Collagenated Cortico‐Cancellous Porcine Bone Grafts. A Study in Rabbit Maxillary Defects

Background: Bone substitutes of collagenated porcine bone (CPB) have previously been shown to have osteoconductive properties and to be resorbed with time. The influence of different ratios between bone particles and collagen on bone response is not yet known. Purpose: The objective of the study was to evaluate the effect of different collagen ratios on the bone tissue responses to CPB grafts. Materials and Methods: Eight rabbits were used in the study. Bilateral bone defects, 5 × 8 × 3 mm, were created in the maxilla and were filled with 60% CPB/40% collagen gel or with 80% CPB/20% collagen gel. Animals were killed after 8 weeks for histological and morphometrical evaluations. Results: There were no differences between the two biomaterials tested. Both materials showed a high degree of bone formation, 42% and 46%, respectively. Both materials were showing signs of resorption at time of sacrifice. Conclusions: Different collagen/CPB ratios do not influence the bone tissue responses to CPB. Both materials exhibited osteoconductive properties and were starting to be resorbed at 8 weeks.     

A clinico‐pathological comparison between mandibular and maxillary ameloblastomas in Sri Lanka

J Oral Pathol Med (2010) 39 : 236–241 Background: The aim of this retrospective study was to analyse the relative prevalence and the clinico‐pathological characteristics of mandibular and maxillary ameloblastomas in Sri Lanka. Methods: Clinico‐pathological features of a total of 286 cases of ameloblastomas were analysed. Results: Out of the 286 cases, 87.8% (251/286) of ameloblastomas occurred in the mandible, while 10.8% (31/286) occurred in the maxilla indicating a ratio of 8:1. In the mandible, 54% (136/251), 40% (100/251) and 6% (15/251) of tumours and in the maxilla, 23% (7/31), 48% (15/31) and 29% (9/31) of tumours were solid/multicystic ameloblastomas (SMA), unicystic ameloblastomas (UA) and desmoplastic ameloblastomas (DA) respectively. No gender predilection was observed in mandibular or maxillary ameloblastomas. Most of the lesions were observed in 2nd to 5th decade of life (mean age 33.2 years). No differences between mandibular and maxillary ameloblastomas were observed with reference to overall cellularity and mitotic activity. Solid/multicystic and UAs showed a predilection to posterior region, while DAs were frequently found in the anterior region of both jaws. Twenty‐one percentage (60/286) of ameloblastomas presented with recurrences, and 94% (34/36) of these recurrences were observed in cases treated conservatively. Conclusion: In conclusion, mandibular ameloblastomas were more prevalent than maxillary ameloblastomas, while no differences were observed in age or gender distribution between the mandibular and maxillary ameloblastomas. However, higher proportion of DAs and UAs was observed in the maxilla compared with some of the other studies. SMA should be treated with resection to prevent recurrences.     

Maxillary implant‐supported overdentures opposed by (partial) natural dentitions: a 5‐year prospective case series study

The aim of this study was to assess the 5‐year treatment outcome of maxillary implant‐retained overdentures opposed by natural antagonistic teeth. Fifty consecutive patients received maxillary overdentures supported by six dental implants. Implants were placed in the anterior region, if enough bone was present (n = 25 patients) Implant were placed in the posterior region if implant placement in the anterior region was not possible (n = 25 patients). Variables assessed included survival of implants, condition of hard and soft peri‐implant tissues and patients' satisfaction. The five‐year implant survival rate was 97·0% and 99·3%, and mean radiographic bone loss was 0·23 and 0·69 mm in the anterior and posterior group, respectively. Median scores for plaque, calculus, gingiva, bleeding and mean scores for pocket probing depth were low and stayed low. Patients' satisfaction after treatment was high in both groups. Within the limits of this 5‐year study, it is concluded that six dental implants (placed in the anterior or posterior region) connected with a bar and opposed to natural antagonistic teeth result in acceptable results for clinical parameters and good outcomes for marginal bone level changes and patient satisfaction.     

Influence of residual alveolar bone height on osseointegration of implants in the maxilla: a pilot study

Aims/Background: For sinus floor augmentation and simultaneous implant placement, a minimum of 5 mm of residual bone height has been recommended empirically. This study was designed to test this assumption in an experimental animal trial. Material and methods: In eight mini pigs, three premolars and two molars were removed on one side of the maxilla. Three months later, the animals were assigned to four groups of two animals each. A cavity was created at the base of the alveolar process so that the residual bone height was reduced to 2, 4, 6 and 8 mm, respectively. Six implants were installed and an inlay augmentation procedure was carried out using a particulated iliac bone graft. Implants were loaded with fixed provisional restorations after a healing period of 6 months. The animals were sacrificed after 6 months of functional loading. Histologic specimens were prepared and histomorphometric analysis was performed [bone‐to‐implant contact (BIC) ratio, interthread bone area, peri‐implant bone area, crestal bone resorption (CBR)]. Results: Two implants were lost during follow‐up and fibrous encapsulation was detected in one additional implant. All failures occurred in one animal with a residual alveolar height of 2 mm. On the buccal aspect, BIC turned out to be significantly higher for 6 mm when compared with 2/4 mm (75.8 ± 26.1 vs. 58 ± 23.2/53.9 ± 22.8; P<0.05), while on the palatal aspect, BIC was significantly higher for 6/8 mm when compared with 2/4 mm (80 ± 17.8/78.9 ± 10.3 vs. 55.8 ± 26.5/55.6 ± 21.3; P<0.05). For an alveolar height of 8 mm, CBR tended to be significantly lower than for bone heights of 2/4 mm (3.8 ± 2.3 vs. 5.3 ± 2.6/5.8 ± 3.9; P<0.05). Correlation analysis revealed a significant association of BIC and interthread bone area as well as a negative association to CBR on the palatal aspect. Conclusion: The results of the present study show that the combination of maxillary inlay grafting and simultaneous implant placement does not hinder osseous integration even though the alveolar crest has been reduced to a residual height of 4 mm and below. However, according to histomorphometry, the highest predictability is gained in sites with residual bone heights of 6 and 8 mm.     

颅骨骨巨细胞瘤的影像诊断

目的 探讨颅骨骨巨细胞瘤(GCT)的CT、MRI征象, 提高对本病的认识.方法 回顾性分析经手术病理证实的5例颅骨GCT的CT、MRI表现, 5例患者均行普通CT平扫,2例行CT增强扫描;3例以颞骨破坏为主的病例,均行颞骨MRI平扫、增强扫描及HRCT扫描及听骨链、面神经计算机重建.结果 5例均单侧发病, 右侧4例、 左侧1例.CT平扫显示广泛的膨胀性骨质破坏、残存骨嵴及骨包壳.肿瘤信号多变,在T1WI呈低-等信号;在T2WI肿瘤呈不均匀的高信号,病灶周边T2WI呈现特征性的低信号,增强扫描:实性部分表现为不均匀强化.结论 颅骨GCT的CT平扫显示广泛的膨胀性骨质破坏不伴硬化边、残存骨嵴及骨包壳,T2WI病灶周边低信号是本病的特征性影像学表现;颞骨HRCT扫描及听骨链、面神经CPR重建为术前评估听小骨、面神经受累情况,为临床制定治疗策略提供更准确的影像信息.     

Influence of residual alveolar bone height on implant stability in the maxilla: an experimental animal study

Aims/Background: Empirically, for implant placement associated with sinus floor augmentation, a minimum of five mm of residual crestal bone height has been recommended in order to achieve sufficient initial implant stability. It has been the aim of the study to test this assumption in an experimental animal trial. Material and methods: In eight mini pigs, three premolars and two molars were removed on one side of the maxilla. Three months later the animals were assigned to four groups of two animals each. A cavity was created at the base of the alveolar process so that the residual bone height was reduced to 2, 4, 6 and 8 mm, respectively. The coronal part of the alveolar crest remained unchanged. An inlay augmentation procedure was carried out using a particulated autogenous bone graft from the iliac crest, and six implants (Xive, diameter 3.8 mm, length 13 mm) were placed. Implant stability was assessed by resonance frequency analysis at the time of implant placement (T0), after 6 months of unloaded healing (T1) and after 6 months of functional loading (T2). Results: During follow‐up, two implants were lost in sites with a residual alveolar bone height of 2 mm. At the time of implant placement, resonance frequencies were 6754.4±268, 6500.3±281.5, 6890.3±255.4 and 7877.9±233.7 Hz for residual bone heights of 2, 4, 6 and 8 mm, respectively. At stage‐two surgery and after 6 months of functional loading, resonance frequencies were 6431.7±290.8, 6351.8±437.6, 6213.4±376.2 and 6826.8±458.9 Hz vs. 6171±437.4, 6047±572.4, 6156.7±272.6 and 6412.8±283.5 Hz. Statistical analysis revealed an association of residual alveolar height and implant stability at T0 and T1 only (P<0.01), while bone height was not found to influence implant survival. Conclusion: The results of the present trial demonstrate an association of alveolar bone height and implant stability at the time of implant placement and stage‐two surgery. Yet the assumption that 5 mm of residual crestal bone height is a relevant threshold for simultaneous implant placement and sinus floor augmentation is not supported from an experimental point of view.     

Placement of Brånemark implants in the maxillary tuber region: anatomical considerations, surgical technique and long-term results

Background: Fixture placement in the tuber area is one way to overcome the problem of insufficient bone volume for routine implant surgery in the posterior maxilla due to severe resorption of jawbone and an extensive enlargement of the maxillary sinus. However, little is known about the long‐term results. Purpose: The aim of this study was to retrospectively evaluate the survival rate and marginal bone conditions at fixtures placed in the tuber region of the maxilla. Material and methods: Twenty‐one patients previously treated with at least one implant in the tuber region of the maxilla were included in this retrospective analysis. A total of 23 standard Brånemark System fixtures with a turned surface had been surgically placed in the tuber regions and 71 additional implants in adjacent areas to support fixed dental bridges. All implants were allowed to heal for 6–8 months before abutment connection and following prosthetic treatment. The patients were radiographed after 1–12 years for evaluation of marginal bone levels. In addition, the relation between the apex of the fixture in the tuberosity area and the posterior border of the maxilla was measured. Results: Twenty of the 21 patients representing 22 tuber and 64 additional implants were radiographically evaluated. No implants in the tuber areas were lost during the follow‐up whereas two fixtures in the anterior region had to be removed, one before loading and the other after 4 years of loading not interfering with the prosthesis stability. The mean marginal bone level at tuber implants was situated on average 1.6 mm (SD 1.1, n=22) from the abutment‐fixture junction, whilst the other implants showed an average bone level of 1.9 mm (SD 0.8, n=64). The results were similar when comparing partially and totally edentulous patients. Conclusion: The present retrospective study shows good clinical outcome with standard Brånemark fixtures placed in the tuber region of the posterior maxilla using a two‐stage procedure. In appropriate cases where bone of adequate volume and density is available, our data indicate that the technique can be used as an alternative to more extensive surgery and especially to the sinus lift procedure. However, prospective comparative studies are needed in order to evaluate the efficacy of the described technique for this purpose.     

种植支抗后牵引猴上颌骨颌面形态变化的实验研究

目的 研究种植支抗后牵引猴上颌骨颌面形态的变化。方法 选用生长发育期雄性恒河猴3只,随机分为2组,对照组1只,实验组2只。于双侧颧骨植入钛板,通过镍钛拉簧牵拉上颌骨种植体,向后牵引上颌骨。牵引力值每侧2.94 N, 时间3个月。对比研究治疗前后面像、牙牙合模型和X线头影测量数值。结果 实验期间,种植体稳定;实验组前牙覆盖及上牙弓长度均显著减小,上牙弓宽度增加;实验组SNA、ANB减小,A点均后移2 mm;实验组和对照组的上颌平面角都增加,上颌骨轻度顺时针旋转。结论 口内种植支抗后牵引上颌骨能抑制上颌向前生长,为治疗生长发育期上颌前突错牙合畸形新方法提供实验依据。