Influence of bone density, screw size and surgical procedure on orthodontic mini-implant placement - part B: implant stability.

This in vitro study aimed to investigate the influence of bone density, implant size, and surgical procedure on the primary stability (PS) of orthodontic mini-implants (OMIs). In total, 640 OMIs of various sizes (2.0 × 7, 2.3 × 7, 2.0 × 11 and 2.3 × 11 mm) were inserted in the artificial bone of different densities (D1-D4). Placement was performed with an insertion angle of 90° or 60° to the bone surface and in 320 cases without predrilling, which resulted in 64 groups. PS was measured on the basis of implant stability quotient (ISQ) and insertion torque (IT). With regard to all possible influencing parameters, the mean PS differed between 39.20 and 60.00 (ISQ), and 10.00 and 39.00 Ncm (IT). The effect of OMI size and surgical procedure was dependent on bone quality. For example, implant size had less effect in high-density bone and was stronger with decreasing density. Overall, implant length had a greater influence than the diameter, and a high correlation was found among both PS measurement techniques. Therefore, a suitable choice of implant size and surgical protocol with regard to bone density can positively influence PS. In principle, ISQ and IT are suitable for measuring OMI stability.

Influence of bone density, screw size and surgical procedure on orthodontic mini-implant placement - part A: temperature development.

The aim of this in vitro study was to determine the influence of bone density, orthodontic mini-implant (OMI) size, and the surgical procedure on temperature increase during implant site osteotomy and placement. OMIs of different sizes (2.0×7, 2.3×7, 2.0×11, and 2.3×11mm) were placed in artificial bone blocks of different densities (D1-D4). Optionally, the drilling and insertion angle was 90° or 60° to the bone surface. A total of 640 OMIs were inserted, and predrilling was performed in 320 cases. All insertions were done without irrigation with an axial load of 20N, which resulted in 64 groups. Temperature measurements were performed during implant site preparation and placement using Type-K-thermocouples. Mean temperature increase differed for OMI osteotomy between 1.38°C and 8.75°C and placement between 3.8°C and 18.74°C, respectively. Critical thermal increase was especially reached during placement using long implants. Increasing bone density and implant size (diameter

Treatment efficiency of mini-implant-borne distalization depending on age and second-molar eruption.

OBJECTIVE: The aim of this study was to evaluate the efficiency of molar distalization depending on age and second-molar eruption using the Beneslider. MATERIALS AND METHODS: Treatment of 51 patients (mean age 17.8 ± 9.6 years) was investigated retrospectively by means of pre- and posttreatment cephalograms. Patients were divided into three groups: 14 children with unerupted upper second molars (group 1), 23 adolescents with second molar in place (group 2), and 14 adults (group 3). The distalization forces applied were 2.4 N in group 1 and 5.0 N in groups 2 and 3. Treatment changes were evaluated and examined statistically for significant differences. RESULTS: In all patients a Class I molar relationship was achieved. All mini-implants remained stable during treatment. Mean distalization distance as measured by the displacement of the center of resistance was 3.6 ± 1.9 mm (range 1.2-8.5 mm depending on treatment needs). Since no significant tipping was detected, the type of movement can be described as bodily movement. Mean overall distalization speed was 0.6 ± 0.4 mm per month. There were no statistical differences between the groups. CONCLUSION: We found the Beneslider to be an effective appliance that enables bodily distalization in adequate treatment time. The higher resistance due to erupted second molars can be compensated by the use of higher forces without significantly reducing distalization speed.

Multipurpose use of orthodontic mini-implants to achieve different treatment goals.

OBJECTIVES: The goal of the study was to determine whether mini-implants inserted in the palate can be used to achieve more than one treatment goal consecutively or simultaneously in the same patient. MATERIALS AND METHODS: The treatment results of 43 patients were retrospectively assessed. Two implant-supported mechanical systems per patient were applied either consecutively in 19 patients (group A) or simultaneously in 24 patients (group B). Both groups were analyzed and compared by calculating success rates for achievement of the treatment goals, survival of the mini-implants, and quality of anchorage. Durations of treatment were also analyzed for intergroup differences. RESULTS: Except for a single case in group A, the treatment goals were achieved in all patients (success rates 94.7% in group A versus 100% in group B). Anchorage loss was confined to one patient per group (success rates 94.7% in group A and 95.3% in group B). Mini-implant mobility, and hence implant failure, was observed in three implants in group A (survival rate 91.8%) and two implants in group B (survival rate 95.6%). While none of these intergroup differences were statistically significant, the treatment durations in both groups differed widely: those in group B were significantly shorter (10.0 ± 4.2 months) than those in group A (14.4 ± 3.5 months; p = 0.001). CONCLUSION: Mini-implants inserted in the palate for skeletal anchorage can be used to achieve more than one treatment goal in the same patient. Such multipurpose application can succeed consecutively and simultaneously. The latter option can significantly expedite treatments and should, therefore, be preferred when feasible, depending on the nature of coexisting therapeutic indications in a given patient.

Impact of bone quality, implant type, and implantation site preparation on insertion torques of mini-implants used for orthodontic anchorage.

Mini-implants are widely used as skeletal anchorage in orthodontics. To reduce implant loss rate, sufficient primary stability is required. This study quantitatively analysed the impact of bone quality and pre-drilling diameter on the insertion torque of five different mini-implants. Twenty pig bone segments were dissected and embedded in resin. The insertion torques of two different mini-implant types (Tomas Pin, Dentaurum, Germany, 8 and 10 mm; and Dual Top, Jeil, Korea, 1.6 mm × 8 and 10 mm plus 2 mm×10 mm) were measured. After preparation of the implant sites using pilot drill diameters 1.0, 1.1, 1.2 and 1.3mm, 30 implants were inserted into each bone segment. Five reference implants were inserted into each segment for comparison. Micro CT evaluated bone compacta thickness. Insertion moments of orthodontic mini-implants, and hence primary stability, varied strongly depending on compacta thickness, implant design, and pre-drilling at the implant site. The Dual Top consistently showed higher primary stability than the Tomas Pin. Insertion moments higher than 230 Nmm resulted in fractures in some cases. Compacta thickness, implant design and preparation of implant site affect the insertion torque of mini-implants for orthodontic anchorage. To avoid fractures and high bone stresses, optimum pre-drilling diameters should be chosen.