Coronectomy of impacted mandibular third molars: a clinical and radiological retrospective case series study with 2-9 years of follow-up.

BACKGROUND: Impacted mandibular third molars occasionally are in intimate relation to the inferior alveolar nerve (IAN). Coronectomy has been proposed as a good alternative to prevent injury of the IAN. The present study evaluates the clinical and radiological outcomes of impacted mandibular third molars presenting radiographic signs associated with a high risk of IAN injury, and which were treated with the coronectomy technique. MATERIAL AND METHODS: A retrospective case series evaluated the outcomes of coronectomies of impacted mandibular third molars. The inclusion criteria were: available preoperative, immediate postoperative and two-year panoramic radiographs, preoperative cone-beam computed tomography (CBCT), and a complete case history. The clinical evaluation comprised intraoperative complications (mobilized fragments of root and damage to adjacent structures), short-term complications (sensory alterations and postoperative infection), and long-term complications (infection or oral exposure). The IAN position with respect to the roots, root shape, eruption status, third molar position, radicular-complex migration and bone above roots were radiographically evaluated as well. RESULTS: Approximately a total of 2000 mandibular third molars were removed from 2011 to 2022. Of these, 39 molars in 34 patients were partially extracted using the coronectomy technique. The mean age was 36 years (range 22-77), and the mean follow-up was 28 months (range 24-84). There were two short-term postoperative infections. One of them was resolved through reintervention to remove the roots after antibiotic treatment, while the other required hospital admission and removal of the roots. One case of short-term transient lingual paresthesia was also recorded. Two long-term oral exposures were detected, and the root fragments had to be extracted. There were no permanent sensory alterations. CONCLUSIONS: In our case series of 39 impacted mandibular molars in intimate contact with the IAN and treated with the coronectomy technique, the number of complications was low (two infections and a single case of transient lingual paresthesia), and no permanent sensory alterations were observed. Prospective studies, especially randomized clinical trials, are needed to compare this technique with conventional extraction.

Systematic review of surgical regenerative treatment for apicomarginal lesions in periapical surgery.

BACKGROUND: Apicomarginal lesions affect the root apex and root surface concurrently and reduce the success rate in periapical surgery. The purpose of this systematic review was to analyze the published literature on the surgical treatment of apicomarginal lesions in periapical surgery. MATERIAL AND METHODS: A systematic review was conducted on PRISMA statement. Three data bases (PubMed-Medline, Scopus, and Embase) were searched up to March 2023. The inclusion criteria for this systematic review encompass studies pertaining to apicomarginal lesions and their surgical treatment, both preclinical and clinical in nature (including randomized trials, prospective, and retrospective observational trials), without any language or time limitations. Exclusion criteria encompass studies with duplicated population data, no description of the surgical treatment or regenerative material. Different tools for the assessment of bias were applied for each study design Results: A total of 155 articles were searched and 10 were included. Studies on teeth with apicomarginal lesions undergoing periapical surgery showed a high success rate when regenerative techniques were used, resulting in reduced probing depth, increased bone formation on the root surface, increased root cementum formation, and reduced healing by junctional epithelium. Guided tissue regeneration, platelet-rich plasma or fibrin, and enamel matrix derivatives have emerged as alternative treatments offering favorable outcomes. CONCLUSIONS: The use of regenerative materials in periapical surgery could improve the prognosis of apicomarginal lesions. Future research in this field should aim to standardize classification and healing criteria to enhance comparability across studies and provide more conclusive evidence for optimal treatment approaches.

Variation in nerve autograft length increases fibre misdirection and decreases pruning effectiveness: an experimental study in the rat median nerve.

OBJECTIVES: In the clinical set, autologus nerve grafts are the current option for reconstruction of nerve tissue losses. The length of the nerve graft has been suggested to affect outcomes. Experiments were performed in the rat in order to test this assumption and to detect a possible mechanism to explain differences in recovery. METHODS: The rat median nerve was repaired by ulnar nerve grafts of different lengths. Rats were evaluated for 12 months by behavioural assessment and histological studies, including ATPase myofibrillary histochemistry and retrograde neuronal labelling. RESULTS: It was demonstrated that graft length interferes in behavioural functional recovery that here correlates to muscle weight recovery. Short nerve grafts recovered faster and better. Reinnervation was not specific either at the trunk level or in the muscle itself. The normal mosaic pattern of Type I muscle fibres was never restored and their number remained largely augmented. An increment in the number of motor fibres was observed after the nerve grafting in a predominantly sensory branch in all groups. This increment was more pronounced in the long graft group. In the postoperative period, about a 20% reduction in the number of misdirected motor fibres occurred in the short nerve graft group only. CONCLUSION: Variation in the length of nerve grafts interferes in behavioural recovery and increases motor fibres misdirection. Early recovery onset was related to a better outcome, which occurs in the short graft group.

The same myosin isoforms are found in the female and male sexually dimorphic levator ani muscle of the rat, but their postnatal transitions are not synchronous.

The levator ani of the female adult rat is greatly atrophied in comparison to the same muscle in males. In the present study, the female levator ani was, nevertheless, found to contain type IIb myosin isoforms similar to those contained in the male muscle. These adult type isoforms were, however, synthesized later in the female than in the male levator ani: the half-transition times of the myosin transition curve were 20 days postnatal in the male and 35 days postnatal in the female. The transition curves for castrated and uncastrated male rats were the same. Thus, the presence of male gonadal hormones apparently did not affect the myosin transition.

Opposite regulations by androgenic and thyroid hormones of V1 myosin expression in the two types of rabbit striated muscle: skeletal and cardiac.

The finding that V1 cardiac myosin is expressed in masticatory skeletal muscles of the rabbit provided a unique opportunity for comparing the hormonal regulation of V1 in skeletal and cardiac muscles. Thyroid hormones had no significant effect on the postnatal expression of V1 in masticatory muscles, but increased this expression in cardiac ventricles. In contrast, androgenic hormones reduced V1 expression in masticatory muscles, but did not affect it significantly in cardiac ventricles. Modulation of V1 gene transcription in striated muscle is thus shown here to depend both on the target muscle and on the hormone.

Relationship between muscle myosin isoforms and contractile features in rabbit fast-twitch denervated muscle.

The effects of 8-day-old rabbit fast-twitch gastrocnemius denervation on the type of myosin isoforms and on contractile features (maximum velocity Vmax and contraction time (CT) of the muscle were followed between 15 and 60 days postnatal. The myosin isoforms and the Vmax and CT values of the denervated gastrocnemius displayed large changes during this period. These changes, which led at 2 months postnatal to a muscle displaying the properties of a slow-twitch muscle did not occur in synchrony: complete conversion to slow-type myosin isoforms occurred only at 60 days postnatal, whereas complete conversion to slow-twitch Vmax and CT values occurred as soon as 35 days postnatal. The results address a new question concerning the relationship between muscle myosin and contractile features.

Expression and neural control of myogenic regulatory factor genes during regeneration of mouse soleus.

Given the importance of the myogenic regulatory factors (MRFs) for myoblast differentiation during development, the aims of this work were to clarify the spatial and temporal expression pattern of the four MRF mRNAs during soleus regeneration in mouse after cardiotoxin injury, using in situ hybridization, and to investigate the influence of innervation on the expression of each MRF during a complete degeneration/regeneration process. For this, we performed cardiotoxin injury-induced regeneration experiments on denervated soleus muscle. Myf-5, MyoD, and MRF4 mRNAs were detected in satellite cell-derived myoblasts in the first stages of muscle regeneration analyzed (2--3 days P-I). The Myf-5 transcript level dramatically decreased in young multinucleated myotubes, whereas MyoD and MRF4 transcripts were expressed persistently throughout the regeneration process. Myogenin mRNA was transiently expressed in forming myotubes. These results are discussed with regard to the potential relationships between MyoD and MRF4 in the satellite cell differentiation pathway. Muscle denervation precociously (at 8 days P-I) upregulated both the Myf-5 and the MRF4 mRNA levels, whereas the increase of both MyoD and myogenin mRNA levels was observed later, in the late stages of regeneration (30 days P-I). This significant accumulation of each differentially upregulated MRF during soleus regeneration after denervation suggests that each myogenic factor might have a distinct role in the regulatory control of muscle gene expression. This role is discussed in relation to the expression of the nerve-regulated genes, such as the nAChR subunit gene family. (J Histochem Cytochem 49:887-899, 2001)

Muscle fiber type reorganization and behavioral functional recovery of rat median nerve repair with vascularized or conventional nerve grafts.

In 1921, Ney introduced the concept of nerve grafts with preservation of the vascular blood supply. Today, over 70 years later, the use of vascularized nerve grafts in clinical practice is still controversial. Although the results of experiments with vascularized and conventional nerve grafts have been compared on the basis of electrophysiological and histological observations, the literature includes no vaJid comparison of the clinical and behavioral significance of these results. Therefore, in the experiments reported here, the rat median nerve was repaired using either a vascularized or a conventional ulnar nerve graft. The rates behavior between 0 and 360 days after surgery was assessed by the grasping test. Nienty-five, 120, 150, 210 and 360 days after surgery rats were submitted to retrograde labeling studies and muscle samples were removed and studied using routine hematoxilin-eosin and ATPase histochemistry. The present study provides evidence that autografting is a reliable procedure for nerve repair. Motor axons were able to reinnervate and largely respecify muscle properties. Reinnervation was not selective either at the nerve trunk level or at the muscle fiber. A mechanism of collateral pruning might have been present in the early phases of reinnervation. This mechanism was, however, self limiting and unable to correct all wrong projections. A mechanism of terminal sprouting was in part responsible for time-related improvement in muscle force recovery. While the present study does provide evidence that recovery was 20% faster in rats with vascularized grafts than in those with conventional grafts (P < 0.0001), it does not, however, provide evidence for better functional recovery in long-term assessment.

Persistence of functional neuromuscular junctions formed in a denervated skeletal muscle of the adult rat by axons that have regrown from the injured spinal cord through a peripheral nerve autograft.

In previous 'short-term' (2 to 7 months) experiments, we had demonstrated, in the adult rat, that motoneurons of the injured cervical spinal cord could extend lengthy axons into an autologous peripheral nerve segment which was connected to a nearby denervated skeletal muscle. In addition, we had shown that new functional motor endplates were formed by these axons both at the original sites of innervation and at ectopic locations of the denervated muscle. This substitution motor system, although quite functional, was anatomically very different from the original model of innervation in the intact animal, relating to its motoneuronal pool, the course of its motor axons and the sites of terminal innervation. The present 'long-term' (11 to 21 months) experiments demonstrate the anatomical and functional permanency of the new motor circuitry, despite a lack of strict specificity in the new neuromuscular connections. However, some minor modifications or adjustments were observed with time: (i) the maintenance of functional ectopic endplates could be consistently demonstrated, while functional reinnervated endplates at the initial sites of innervation were rare or even lacking; (ii) there was a definitive withdrawal of all non target-specific regenerated axons from the vicinity of the muscle. It is now necessary to address the question to what extent this substitution motor system is actually controlled by central and/or peripheral inputs.

Behavioral evaluating methods in the objective clinical assessment of motor function after experimental brachial plexus reconstruction in the rat.

Unfortunately, the results of brachial plexus surgery have not fulfilled expectations. Although the components of the rat brachial plexus are similar to those of the human plexus, experimental work in this field is limited. No functional test to assess experimental brachial plexus reconstruction has so far been published. We worked out a method of evaluating brachial plexus impairment in rats in the laboratory. It consists of a simple test in which a bowl of water is projected over the animal's head, eliciting grooming movements of the forepaws towards the head. This test is therefore called the 'grooming test'. A system of scoring the animals' performance is suggested. Rats were also submitted to walking tracks analysis, but this was of limited value in assessing brachial plexus impairment.

The grasping test: a simple behavioral method for objective quantitative assessment of peripheral nerve regeneration in the rat.

Behavioral recovery is the major goal of neuroscience research on the peripheral nervous system. However, behavioral methods of assessing peripheral nerve regeneration are still lacking. In the present work we used the median nerve and finger flexors as the experimental model. After resection or crush injury of the median nerve, rats were submitted daily to the grasping test. For this, they were gently lifted by the tail and allowed to grasp a grid connected to an ordinary electronic balance. While grasping the animal continued to be lifted by the tail with increasing firmness until it lost its grip. At this precise moment the value shown by the balance was recorded. In the crushed median nerve, recovery of function was clearly demonstrated by the grasping test. The test also indicated the exact day on which recovery began and its improvement with time. This very simple objective behavioral method provides a sensitive quantitative technique for assessing recovery. The experimental model using the median nerve seems to be better than the sciatic nerve model, as no articular contractures or autotomies were noted in the present experimental animals.

Median nerve neurotization by peripheral nerve grafts directly implanted into the spinal cord: anatomical, behavioural and electrophysiological evidences of sensorimotor recovery.

Over the years, peripheral nerve grafts, a favorable environment to support axonal elongation, have given rise to increasing interest as a possible solution for promoting spinal cord repair. In the experiments described here, following an avulsion injury of the rat brachial plexus, the median nerve was repaired by a peripheral nerve graft (PN) inserted directly into the dorsal side of the spinal cord. Eight months later the animals were submitted to behavioral tests, electrophysiological and histological studies. Regrowth of axons from both motoneurons and ganglionic neurons was demonstrated following a single superficial dorsal implantation of a PN. Sensorimotor peripheral reinnervation allowed most of the studied animals to recover enough flexor activity for grasping. Reinnervation was achieved even without prior root avulsion suggesting that the presence of a PN is sufficient to induce sprouting in the spinal cord from axotomized and non-axotomized neurons.

Reinnervation of denervated extensor digitorum longus of the rat by the nerve of the soleus does not induce the type I myosin synthesis directly but through a sequential transition of type II myosin isoforms.

The fast-contracting extensor digitorum longus (EDL) muscle of 1-month-old rats was denervated and reinnervated by the nerve innervating the slow-contracting soleus muscle. After variable periods of time, the myosin isoform content of the EDL was analyzed by sensitive electrophoretic techniques, which allowed to discriminate between the slow-type I and the three, IIA, (IID or IIX) and IIB, fast-type II myosin isoforms. Compared to the control EDL, which contains predominantly the IIB isoform, the operated muscles contained variable proportions of all the isoforms. Analysis of the results leads us to conclude that reinnervation of EDL induces a sequential transition of myosin isoforms: IIB----(IID or IIX)----IIA----I.

Long-term denervation modulates differentially the accumulation of myogenin and MRF4 mRNA in adult Xenopus muscle.

In adult Xenopus laevis, we analyzed, using reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization, the influence of long-term muscle denervation on the accumulation of MRF4 and myogenin transcripts. The brachial muscle was denervated by cutting the brachial nerve and was examined after 4 months. MRF4 mRNA levels decreased about two-fold in denervated muscle as compared with contralateral muscle. Myogenin mRNA levels, by contrast, were induced about five-fold by denervation. This report shows that muscle denervation persistently reduces the levels of MRF4 transcripts suggesting that MRF4 expression may be induced by innervation and hence may be involved in mediating transcriptional responses to innervation. The up-regulation of myogenin by denervation suggests that myogenin expression may compensate for the down-regulation of MRF4 gene.

Formation of functional endplates by spinal axons regenerating through a peripheral nerve graft. A study in the adult rat.

Peripheral nerve (PN) autografts were used in the adult rat to join the midcervical spinal cord to a nearby denervated skeletal muscle. Retrograde tracing, morphological and electrophysiological studies indicated the following: 1) a great number of neurons, located bilaterally, between C3 and C7 in most laminae of the grey matter, extended axons into the PN grafts, 2) a lesser number of neurons regenerated up to the reconnected muscle, but most of them were typical motoneurons, 3) neuromuscular junctions were formed in ectopic locations, around the tip of the grafted nerve, and at the sites of original endplates, 4) these junctions were functional and formed by axons that had regenerated into the PN bridges, as muscle contraction was obtained by electrical stimulation of the grafted nerves, 5) they were proved to be cholinergic since endplate potentials, evoked by stimulating the PN graft, were suppressed by curare. These results strongly suggest that spinal neurons, and especially motoneurons, are involved in the formation, through PN bridges, of new functional cholinergic connections with denervated skeletal muscles.

Selective restoration of sensation by peripheral nerve grafts directly implanted into the contralateral C7 dorsal root ganglion: an experimental study in rat brachial plexus.

OBJECTIVE: In brachial plexus injuries, when the dorsal root ganglion (DRG) is avulsed from the spinal cord there is no possibility of direct repair. Therefore, in the present report the median nerve was connected directly to the contralateral C7 DRG, to restore forepaw sensation. METHODS: The ulnar nerve was sectioned, and a 15-mm segment of nerve was removed. The median nerve was sectioned, transposed dorsally, and repaired using a sural nerve graft directly implanted into the C7 contralateral DRG. Rats were then assessed 6 and 12 months later by behavioral, histological, and plasma extravasion techniques. RESULTS: All animals recovered sensation in the forepaw. Retrogradely labeled sensory neurons were demonstrated in the C7 DRG, and the whole forepaw was labeled after plasma extravasion induction by median nerve antidromic stimulation. Several myelinated and positively neurofilament-stained fibers were demonstrated in the grafted median nerve. CONCLUSION: The surgical strategy proposed might be a useful alternative to selective sensory repair in the emerging field of brachial plexus reconstruction by direct spinal cord surgery.

Brachial plexus repair by peripheral nerve grafts directly into the spinal cord in rats. Behavioral and anatomical evidence of functional recovery.

Over the years, peripheral nerve grafts, a favorable environment for the support of axonal elongation, have attracted interest as a possible means of promoting spinal cord repair. In the experiments described here, rats underwent an avulsion injury of the brachial plexus, and the musculocutaneous nerve was repaired by direct insertion of peripheral nerve grafts into the spinal cord. After varying postoperative periods, the rats were submitted to a series of behavioral tests to evaluate forelimb and hindlimb function. They also underwent retrograde double-labeling studies. Nerve grafts were harvested and processed for electronic microscopy. The biceps muscle was removed and weighed and its histology studied. After surgery, central axons effectively regenerated about 65 mm along the peripheral nerve grafts, restoring normal active elbow flexion. Forelimb movements were well coordinated in both voluntary and automatic activities. Clinical investigations showed that there were no side effects in the ipsilateral forepaw, contralateral forelimb, or either hindlimb. Regenerating axons stemmed from original motoneurons, foreign motoneurons, and even antagonist motoneurons, but this did not impair function. Ganglionic neurons from adjacent roots also sent processes to the peripheral nerve grafts.

Selective motor hyperreinnervation using motor rootlet transfer: an experimental study in rat brachial plexus.

Misdirection of sensory fibers into motor pathways is, in part, responsible for the poor results obtained after peripheral nerve repair. After avulsion of the C-5 root in rats, the authors connected a C-4 ventral rootlet to the musculocutaneous nerve by means of a sural nerve graft. In this way, they were able to increase the number of regenerating motor fibers and avoid growth of sensory fibers into the nerve grafts. Functional recovery was evaluated electrophysiologically and histologically. The origin of the axons that reinnervated the nerve graft was analyzed by means of morphological studies including retrograde labeling procedures. Motor neurons survived and regenerated after the rootlet transfer and there was no functional impairment. Many neurons were retrograde labeled in the ventral horn and widespread biceps muscle reinnervation was demonstrated with recovery of nearly normal electrophysiological properties. Motor hyperreinnervation of the musculocutaneous nerve was observed. This high degree of reinnervation in a long (40-mm) graft was attributed to the good chance that a muscle fiber can be reinnervated by a motor fiber when the number of regenerating motor neurons is increased and when competitive sensory fibers are excluded from reinnervation.

Vascular freezing--a new method for immediate and permanent vasospasm relief: an experimental study in the rat.

Although much work has been done on the etiology and prevention of vasospasm, a spasmolytic agent capable of firmly protecting against or reversing vasospasm has not yet been found. In this paper, we describe a new physical method of treating vasospasm. It consists of directly freezing the arterial walls. Experiments were performed on the epigastric artery of 40 female Sprague-Dawley rats. A vasospasm was created by mechanical vessel manipulation. The vasospasm was treated by freezing the vessel walls with a dermatologic hand-held liquid nitrogen spray. Vascular spasm and patency controls were made immediately after thawing and 30 minutes and 3, 10, and 120 days after freezing. Epigastric island flaps were harvested based on the frozen artery at 3, 10, and 120 days after the freezing procedure. Histologic studies also were effectuated 3, 10, and 120 days after the freezing procedure. Relief from vasospasm was instantaneous and permanent. After freezing, almost all the cells in the media and endothelium died and the adrenergic fibers degenerated. This was followed by a phagocytic debridement, complete regeneration of the endothelium, and a limited regeneration of the muscle fibers in the media. The adrenergic innervation was recovered, and no alterations in the adrenergic fibers distal to the lesion were noted at any time. None of the arteries examined underwent thrombosis, and all the flaps harvested survived very well, indicating that the vascular bed distal to the site of the freezing was normal. This vascular freezing technique may well have clinical applications for microsurgical transfers and for the prophylactic treatment of vasospasm disease. However, its indications still require clarification.