Three-Dimensional Finite Element Analysis on En-Masse Retraction of the Maxillary Anterior Teeth With Quantitative Combined Loading Control.

This study aims to elucidate the biomechanical effects of combined loading of maxillary anterior and posterior implants using the sliding method on en-masse retraction of the anterior teeth and to quantify the loading ratio (LR) of anterior and posterior implants to achieve controlled retraction of the maxillary anterior teeth. A three-dimensional finite element model of the maxilla-upper dentition appliance was constructed. Implants were placed on the distal (A) and mesial (B) sides of the lateral incisors as well as on the mesial (C) side of the first molar and different amounts of force were loaded between the implants using 2- or 5-mm traction hooks. The labiolingual movement of the anterior teeth was recorded and the relationship between the LR of the implants and the movement of the central incisors was evaluated. With 2-mm traction hooks, the central incisors exhibited a translation tendency during retraction at lower A/C and B/C LR and labial or lingual crown inclination at higher values. With 5-mm traction hooks, the central incisors, lateral incisors, and canine teeth exhibited a labial crown inclination. The results of this study suggest that 2-mm traction hooks can cause labial crown inclination, translation tendency during retraction, or lingual crown inclination of the central incisors due to alterations in the LR of the anterior and posterior implants. The central incisors only exhibited labial crown inclination during combined loading of the anterior and posterior implants when 5-mm traction hooks were used.

Three-dimensional finite element analysis of the stability of mini-implants close to the roots of adjacent teeth upon application of bite force.

To investigate the cause of mandibular implant loss, we evaluated the stress distribution in the bone under bite force when the miniimplant was near the root using three-dimensional finite element analysis. Our analysis involved four finite element models with different distances between the implant and adjacent tooth root and three loading conditions. With loading of the tooth only or both the tooth and implant, the peak stress within the bone around the implant neck, displacement, and stress surrounding the bone near the root increased as the distance between the implant and root decreased. However, with separate loading of the implant, the stress did not correlate with the distance between the implant and root. Application of bite force increases stress within bones surrounding mini-implants near the roots of adjacent teeth and may threaten implant stability, but simple orthodontic loading has little effect on the stress distribution at the mini-implant-bone interface.

Finite Element Analysis of Bone Stress for Miniscrew Implant Proximal to Root Under Occlusal Force and Implant Loading.

Because of the narrow interradicular spaces and varying oral anatomies of individual patients, there is a very high risk of root proximity during the mini implants inserting. The authors hypothesized that normal occlusal loading and implant loading affected the stability of miniscrew implants placed in proximity or contact with the adjacent root. The authors implemented finite element analysis (FEA) to examine the effectiveness of root proximity and root contact. Stress distribution in the bone was assessed at different degrees of root proximity by generating 4 finite element models: the implant touches the root surface, the implant was embedded in the periodontal membrane, the implant touches the periodontal surface, and the implant touches nothing. Finite element analysis was then carried out with simulations of 2 loading conditions for each model: condition A, involving only tooth loading and condition B, involving both tooth and implant loading. Under loading condition A, the maximum stress on the bone for the implant touching the root was the distinctly higher than that for the other models. For loading condition B, peak stress areas for the implant touching the root were the area around the neck of the mini implant and the point of the mini implant touches the root. The results of this study suggest that normal occlusal loading and implant loading contribute to the instability of the mini implant when the mini implant touches the root.

[Mini-implant stability analysis at different healing times before loading].

OBJECTIVE: This study aims to biomechanically analyze a mini-implant at different healing times before loading. METHODS: Sixty-four mini-implants with (12 +/- 1) N x cm insertion torque were placed in the low jaw of eight beagle dogs. The test mini-implants remained in the low jaw for 0, 1, 3, and 8 weeks of bone healing and for an additional 10 weeks under a force of 0.98 N. The unloaded control implants were further divided into four groups (1, 3, 8, and 10 weeks). Maximum removal torque (MRT) testing was performed to evaluate the interfacial share strength of each group. Surface analysis of the removed implants was performed by scanning electric microscope (SEM). RESULTS: The MRT for the loading implants at 0, 1, 3, and 8 weeks of healing were 4.10, 4.25, 2.42, and 4.42 N x cm, respectively. During the healing process, the removal torque values of the 3-week implants were significantly lower than those of the other healing groups (P < 0.05). The unloaded 3-week implants also had lower removal torques (P < 0.05). The implant surface of the 3-week test group showed more fibrous bone. However, the other loading implants had more lamellar-like tissue. CONCLUSION: A stable dangerous period occurred approximately 3 weeks after mini-implant insertion. A 3-week healing is disadvantageous to the stability of the implant. Orthodontics loading occurred immediately or after 1 week as a function of the healing time. The 8-week implant appeared to have a positive effect on peri-implant bone remodeling and implant stability.