Long-term oral bisphosphonates delay healing after tooth extraction: a single institutional prospective study

Tooth extraction in patients receiving bisphosphonates is thought to be a risk factor for osteonecrosis of the jaw (ONJ); however, ONJ did not develop, even when tooth extraction was performed with continued oral bisphosphonate therapy. A drug holiday from bisphosphonates before tooth extraction may not be necessary.

INTRODUCTION

It is controversial whether bisphosphonate withdrawal is necessary prior to invasive procedures such as tooth extraction in order to prevent bisphosphonate-related osteonecrosis of the jaw (BRONJ). This study aimed to evaluate the clinical safety of continuing oral bisphosphonate therapy in patients undergoing tooth extraction.

METHODS

We prospectively enrolled 132 patients (20 men, 112 women) who were receiving oral bisphosphonates for the prevention or treatment of osteoporosis and required tooth extraction. All patients were managed using an identical protocol, which included preoperative antibiotic prophylaxis and did not necessarily require complete wound closure. The patients were classified into groups according to the duration of bisphosphonate administration: < 2 years (n = 51), 2-5 years (n = 41), 5-10 years (n = 28), and > 10 years (n = 12). The groups were compared regarding the time taken for the extraction socket to heal, and the occurrence of BRONJ. Follow-up duration was at least 3 months.

RESULTS

A total of 274 teeth were removed. Long-term oral bisphosphonate therapy for > 5 years significantly delayed the healing of the extraction socket in comparison with administration for < 5 years; however, BRONJ did not develop in any group. There was no prolongation of wound healing due to systemic risk factors such as glucocorticoid administration and diabetes mellitus. There were no adverse skeletal events such as bone fracture.

CONCLUSIONS

Patients who underwent tooth extraction with continued oral bisphosphonate therapy showed delayed healing of the extraction socket as the cumulative administration period prolonged, but BRONJ did not develop.

Accumulation of unstable periodic orbits and the stickiness in the two-dimensional piecewise linear map

We investigate the stickiness of the two-dimensional piecewise linear map with a family of marginal unstable periodic orbits (FMUPOs), and show that a series of unstable periodic orbits accumulating to FMUPOs plays a significant role to give rise to the power law correlation of trajectories. We can explicitly specify the sticky zone in which unstable periodic orbits whose stability increases algebraically exist, and find that there exists a hierarchy in accumulating periodic orbits. In particular, the periodic orbits with linearly increasing stability play the role of fundamental cycles as in the hyperbolic systems, which allows us to apply the method of cycle expansion. We also study the recurrence time distribution, especially discussing the position and size of the recurrence region. Following the definition adopted in one-dimensional maps, we show that the recurrence time distribution has an exponential part in the short time regime and an asymptotic power law part. The analysis on the crossover time T(c)(*) between these two regimes implies T(c)(*) approximately -log[micro(R)] where micro(R) denotes the area of the recurrence region.

Semiclassical study on tunneling processes via complex-domain chaos

We investigate the semiclassical mechanism of tunneling processes in nonintegrable systems. The significant role of complex-phase-space chaos in the description of the tunneling processes is elucidated by studying a kicked scattering model. Behaviors of tunneling orbits are encoded into symbolic sequences based on the structure of a complex homoclinic tangle. By means of the symbolic coding, the phase space itineraries of tunneling orbits are related with the amounts of imaginary parts of actions gained by the orbits, so that the systematic search of dominant tunneling orbits becomes possible.

Tunneling mechanism due to chaos in a complex phase space

We have revealed that the barrier-tunneling process in nonintegrable systems is strongly linked to chaos in complex phase space by investigating a simple scattering map model. The semiclassical wave function reproduces complicated features of tunneling perfectly and it enables us to solve all the reasons why those features appear in spite of absence of chaos on the real plane. Multigeneration structure of manifolds, which is the manifestation of complex-domain homoclinic entanglement created by complexified classical dynamics, allows a symbolic coding and it is used as a guiding principle to extract dominant complex trajectories from all the semiclassical candidates.