Pymeshfix/Pyvista unexpected cleaning result

Question

I try to repair the following mesh (a dental bridge):

Within the mesh are some holes and also intersecting triangles. I use the function tin.small_boundaries() and if i detect intersecting triangles also tin.clean(max_iters=10, inner_loops=3). Unfortunately, the dental bridge is split, leaving only one tooth in the end:

Do you maybe have some ideas how i can fix this issue? You can find the used source code and the *.stl file below: ScriptAndModel.zip

# -*- coding: utf-8 -*-
import pymeshfix



def plotMesh(tin):
    
    # return vertices and faces
    vertices, faces = tin.return_arrays()
    
    # Create object from vertex and face arrays
    meshfix = pymeshfix.MeshFix(vertices, faces)

    # Plot input
    meshfix.plot()





# Create TMesh object
tin = pymeshfix.PyTMesh()

# load stl file
tin.load_file("bridge08.stl")

# visualize input Mesh
plotMesh(tin)



###############################################################################
# CLEANING ROUTINE

# Attempt to join nearby components
# tin.join_closest_components()

# Fill holes
tin.fill_small_boundaries()
print('There are {:d} boundaries'.format(tin.boundaries()))

# check for intersecting triangles
faces = [tin.select_intersecting_triangles()]

# if intersecting triangles are detected within the mesh
if faces:
    # Clean (removes self intersections)
    tin.clean(max_iters=10, inner_loops=3)
###############################################################################



# visualize output Mesh
plotMesh(tin)