Mandibular block success rate in relation to needle insertion and position: a self-report survey

To evaluate possible associations between successful mandibular block injection and location of penetrating the oral mucosa, location of injection on the ramus and the needle insertion length.

The study consisted of 101 dentists, of whom, 33 were oral surgeons, 33 certified paediatric dentists and 35 general dental practitioners. The dentists were asked to estimate their rate of success in mandibular block injections, defined as the proportion of their patients for whom only a single carpule was necessary, and to indicate the needle insertion length and the location of the injection on a photograph of a ramus and on a photograph of the oral mucosa.

Injecting a single carpule for achieving full anaesthesia in 90% or more of their patients was reported by 79.3 and 57.8% of the dentists treating children and adults, respectively. Of practitioners treating children, experienced dentists (>5 years in occupation) reported higher success rates than did inexperienced ones (p = 0.05). A positive correlation was found between failure rate reported in children, shorter length of the inserted needle (R = 0.356, p = 0.001) and injecting at the central (superior inferior dimension) most anterior quarters of the ramus (p = 0.006; odd ratio = 3.9375). Routine waiting period of more than 5 min after the injection and before operative treatment was associated with higher rates of failure (p = 0.042, χ(2) = 6.335). No correlation was found between the success rates of mandibular block injection and the location of penetrating the oral mucosa in children (p = 0.94), adults (p = 0.57), or between success rates and the target location on the ramus in adults (p = 0.42).

χ(2) test was used to determine the significance of differences among proportions and t test for continuous variables. Pearson's correlation analysis was used to analyse the correlation between the length of the needle inserted in children and adults by the same dentist.

Shorter needle insertion lengths and targeting the injecting to the most anterior quarters of the ramus were positively correlated with failure of anaesthesia in children, according to dentists' reports. A routine waiting period of over 5 min did not increase the success rates of mandibular block injection.