Comparative study of wide-diameter implants placed after dental extraction and implants positioned in mature bone for molar replacement

OBJECTIVE: The aim of this study was to compare wide-diameter implants placed in mature bone versus implants inserted in postextraction bone. MATERIAL AND METHODS: A retrospective case study was made; the sample was composed of subjects who had had wide implants placed in the molar area between 2003 and 2005. Two groups were formed: implants placed in mature bone and implants in postextraction bone. A protocol was prepared in which patient age, sex, oral hygiene, implant length, type of prosthesis, and antagonist dentition were collected. After 12 months, data relating to the clinical and radiologic conditions of the implants and the success rate (criteria of Buser et al) were recorded. A statistical analysis of the variables was made (t test, Pearson correlation coefficient, analysis of variance, chi-square). RESULTS: The study examined 162 implants placed in 100 patients. Of the 162 implants, 130 were placed in mature bone and 32 in postextraction bone. Four implants placed in mature bone failed in 4 patients (success rate of 96.9%). None of the implants placed in postextraction bone failed. CONCLUSIONS: The placement of wide-diameter implants in recent molar extraction sites has been shown to achieve similar results to implants placed in healed mature bone after 12 months of follow-up, within the limitations of this study.     

Treatment of skeletal open bite with a device for rapid molar intrusion: a preliminary report

An open bite is one of the most difficult malocclusions the clinician has to deal with. In recent years, interest has increased regarding mechanics that reduce dependency upon patient compliance for success. Some patient-independent mechanism for molar intrusion or vertical control is desirable. The rapid molar intruder (RMI) appliance consists of two elastic modules that are secured to orthodontic bands on the upper and lower first molars. Vertical forces from these modules typically produce intrusion of the permanent molars in four to six months. The RMI modules may be used in the mixed dentition or incorporated in full-fixed mechanics in the permanent dentition. To avoid buccal flaring of the molars, these modules should be attached to a transpalatal arch and a mandibular lingual arch. Case reports are provided to stimulate interest in further investigation of the properties of this appliance.     

Survival of dental implants placed in vascularised fibula free flaps after jaw reconstruction

Purpose

Ablative oncological surgery to treat head-and-neck cancer often triggers a requirement for jaw reconstruction. Modern surgical procedures using free microvascular flaps afford acceptable outcomes in terms of restoration of bony and soft tissue defects. A fibula free flap is often the preferred flap, as the bone length is considerable and a two-surgeon approach is possible. Dental implants play important roles in functional rehabilitation. Our aim was to evaluate the survival of dental implants placed in reconstructed areas after transfer of fibula tissue to the jaw.

A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

Objectives

Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw.

Material and methods

Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment.

Results

There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001.

Conclusion

This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.     

Changes in shape of posterior parts of upper jaws after extraction of teeth and prosthetic treatment

Changes in the sagittal and transverse profiles of the anterior and posterior parts of the alveolar process after extraction of all teeth and insertion of immediate dentures were studied during a five-year period using casts of 14 patients. The casts were oriented in a uniform way with the help of reference points in the hard palate. The desired profiles could then be reproduced with a special tracing apparatus. Four profiles made during the five-year period were compared for each patient. Changes in shape of the upper jaws in the median sagittal plane agreed well with the results obtained in earlier investigations and showed a reduction of the anterior part of the alveolar process for each patient. In the posterior part of the upper jaw, on the other hand, an increase in size was seen in the transverse section of the alveolar process in most patients examined.     

CBCT和曲面断层在下颌后牙区种植中的应用价值分析

目的:比较牙颌面专用锥形束CT(CBCT)与普通X线曲面断层片在下颌后牙区种植术前诊断、治疗设计中的应用价值。方法:对181例(205侧,347个位点)下颌后牙游离端缺失患者在种植术前进行CBCT和曲面断层影像学检查,利用两种检查方法分别进行术前诊断和设计,计算各自的可植入率,进行比较分析。结果:通过对347个缺牙位点的测量分析,曲面断层影像检查结果显示,后牙区牙槽骨量≥12mm,可接受种植的位点235个,可植入率为67.72%。CBCT图像检查显示,后牙区牙槽骨量≥12mm,可以接受种植的位点287个,可植入率为82.71%。结论:CBCT与曲面断层片相比,可以更准确评估术前下颌后牙区的牙槽骨骨量,做出更加合理的治疗计划。     

Long-term stability of soft tissue changes in anterior open bite adults treated with zygomatic miniplate-anchored maxillary posterior intrusion

Objectives:To evaluate soft tissue changes and their long-term stability in skeletal anterior open bite adults treated by maxillary posterior teeth intrusion using zygomatic miniplates and premolar extractions.Materials and Methods:Lateral cephalograms of 26 patients were taken at pretreatment (T1), posttreatment (T2), 1 year posttreatment (T3), and 4 years posttreatment (T4).Results:At the end of treatment, the soft tissue facial height and profile convexity were reduced. The lips increased in length and thickness, with backward movement of the upper lip and forward movement of the lower lip. The total relapse rate ranged from 20.2% to 31.1%. At 4 years posttreatment, 68.9% to 79.8% of the soft tissue treatment effects were stable. The changes in the first year posttreatment accounted for approximately 70% of the total relapse.Conclusions:Soft tissue changes following maxillary posterior teeth intrusion with zygomatic miniplates and premolar extractions appear to be stable 4 years after treatment.     

Comparative assessment of adaptation processes in abutment tissues after prosthetic treatment with the use of dental implants according to microcirculatory indices

Gingival tissue blood circulation restoration after single implant implantation set in 4 and in 6 months after 2-3 implants introduction. In cases of abutment implant functional loading when treating partial dentition defect by single crowns and constructions with 2-3 abutment implants hyperemia was developed in gingival tissue microcirculatory bed that was later cut short in 1 and 6 months correspondingly.     

Biomechanical effects of double or wide implants for single molar replacement in the posterior mandibular region

Double implants have been thought to have biomechanical advantages for single molar replacement. To evaluate the effectiveness of double implants versus a wide implant, the vertical forces and torque on each implant were calculated by three-dimensional geometric analysis. Buccal load (100N) perpendicular to cuspal inclination (20 degrees) was applied at the occlusal surface of the superstructure. The three kinds of load points (A, B, C) were 1.5, 3.5, and 5.5 mm from the mesial contact point, respectively. Three implants were compared: mesial and distal double implants (phi 3.3 mm), and a wide implant (phi 5 mm). The wide implant showed torque around the long axis (1.8-15.0 N x cm) whereas double implants had no torque. On the other hand, the vertical forces on the mesial double implant were both smaller (60%: loaded at point C) and larger (140%: loaded at point A) than the wide implant. Given the smaller surface area of the mesial double implant, this large force may generate much higher stress in the peri-implant bone. These results suggest that the biomechanical advantage of double implants for single molar replacement is questionable when the occlusal force is loaded at the occlusal surface near the contact point.     

Short dental implants in patients with oral lichen planus: a long-term follow-up

Oral lichen planus is associated with the Koebner phenomenon, and trauma may exacerbate oral lesions. Short dental implants, as alternatives to bony augmentation, would reduce the number of interventions and their morbidity. However, we know of no studies that have analysed the long-term outcomes of short implants in patients with oral lichen planus. We have therefore designed a retrospective study of such patients treated with short implants (≤ 8.5 mm long), with survival of implants as the main outcome. The secondary outcomes were marginal bone loss and the development of complications. We calculated the implants’ survival and compared the outcomes statistically between erosive and reticular oral lichen planus. Sixty-six short implants were placed in 23 patients with a mean (SD) age of 58 (7)?years. The mean (SD) peri-implant bone loss was 0.96 (0.89)?mm mesially and 0.99 (1.1)?mm distally. Sixty-five of the 66 implants survived with a mean (SD) follow-up of 68 (32) months, and there were no significant differences between erosive and reticular disease. Stable long-term outcomes can be expected for short implants placed in patients with oral lichen planus, and graftless rehabilitation of missing teeth could be possible in these patients if short implants were used.