Lichen Planus and its Association with Hypothyroidism

What is oral lichen planus?

Lichen planus is a common dermatologic disease that affects the oral mucosa caused by an overreaction of T lymphocytes in the immune system. Most patients that present with lichen planus are middle aged, and are more commonly female. The underlying main factor that causes lichen planus remains unknown.

The lesions of lichen planus are multifocal, meaning they show up in multiple areas of the oral mucosa. Typically, they present bilaterally on each side of the cheek (buccal mucosa).

There are two presentations that are characteristic of lichen planus – reticular and erosive.

Reticular lichen planus has a white, lacey look with underlying erythema that is described as Wickham’s stria. It is the most common form of lichen planus.

Erosive lichen planus has a central area of ulceration that is painful, but can still present Wickham’s stria like that seen in reticular lichen planus. Pain is a defining characteristic of erosive lichen planus.

(n.d.) A. Pourian. White Lesions. A.T. Still Missouri School of Dentistry and Oral Health.

What is the connection between oral lichen planus and hypothyroidism?

The thyroid organ is responsible for secreting hormones that monitor growth and development. There are various diseases of the thyroid, including Hashimoto’s thyroiditis which is the most common cause of hypothyroidism.

A meta-analysis was conducted of the associated between lichen planus and hypothyroidism and found a significantly high prevalence of thyroid disease among oral lichen planus patients compared with controls. The meta-analysis included eight studies in the review, but only four were used in the final review.

The mechanism between oral lichen planus and thyroid disease is not entirely clear. However, it can be assumed that thyroid disease may be involved in the pathogenesis of oral lichen planus, or that oral lichen planus is a clinical manifestation of thyroid disease.

Li, D., Li, J., Li, C., Chen, Q., & Hua, H. (2017). The Association of Thyroid Disease and Oral Lichen Planus: A Literature Review and Meta-analysis. Frontiers in Endocrinology, 8. doi: 10.3389/fendo.2017.00310

Eruption Sequence of the Permanent Dentition

Teeth generally erupt in pairs at the start of age six – however, there are many factors that dictate which teeth erupt first. For instance,

  • Girls’ teeth generally erupt before boys’ teeth
  • Mandibular teeth generally erupt before maxillary teeth (*except premolars)
  • Slim children have teeth that erupt before overweight children

What is a succedaneous tooth?

A succedaneous tooth is a permanent tooth that succeeds a primary tooth in the dentition. Children have five teeth in each quadrant – a central incisor, a lateral incisor, a canine, and two primary molars. Adults, however, have eight teeth in each quadrant – a central incisor, a lateral incisor, a canine, two premolars, and three molars. The permanent premolars take the place of the primary molars. Therefore, permanent molars are NOT succedaneous teeth (they do not succeed a tooth of primary dentition).

The first succedaneous tooth to erupt is the permanent mandibular central.

The first permanent tooth to erupt in the mouth (regardless of succedaneous classification), however, is the permanent mandibular first molar (nicknamed ‘The Six Year Molar’).

What is the correct eruption sequence of the permanent dentition?

At age 6/7, the mandibular first molar erupts first. This is followed by the maxillary first molar. Remember, teeth usually erupt in pairs (and mandibular before maxillary). At this age, it’s common to see the mandibular central incisors erupt, as well.

At age 7/8, the maxillary central incisors erupt, followed by the mandibular lateral incisor.

At age 8/9, the maxillary lateral incisors erupt.

At age 9/10, the mandibular canines erupt.

After age 10, things get a little more complicated. The maxillary premolars erupt BEFORE the mandibular premolars, and the maxillary canine generally erupts AFTER the maxillary first premolar erupts. To recap, at age 10/11, the maxillary first premolar erupts, followed by the maxillary canine. The mandibular first premolar then erupts. Finally, the maxillary second premolar erupts around age 10/12, followed by the mandibular second premolar at age 11/12.

At age 12/13, the mandibular second molar erupts, followed by the maxillary second molar.

At age 17/21, the mandibular third molar erupts, followed by the maxillary second molar.

Canida, B., Moore, B., Cheatham, K., & Cheatham, M. (2016). B&B Dental: Modernized Ndbe Part 1 Board Prep (2.8 ed.). B&B Dental.

The Inferior Alveolar Nerve and How to Properly Anesthetize It

What is the Inferior Alveolar Nerve and what does it innervate?

The inferior alveolar nerve (IAN) is part of the cranial nerve number V – the trigeminal nerve (Cranial Nerve V, CNV). The trigeminal nerve is divided into three branches, the V1, V2, and V3. The IAN is one of the final branches in the posterior division of the V3 (mandibular) nerve.

The IAN innervates sensory information to various portions of the mandible.

(n.d.) Dr. Brzezinski. Cranial Nerves V, VII, IX, and X. Missouri School of Dentistry and Oral Health.

(n.d). Dr. Caputo. Local Anesthesia Review. Missouri School of Dentistry and Oral Health.

What does the IAN block anesthetize?

  • Mandibular teeth to the midline
  • Buccal soft tissues anterior to the mandibular first molar
  • The body of the mandible, inferior portion
  • Anterior 2/3rds of the tongue
  • Lingual soft tissues/ periostium (must anesthetize lingual nerve)

What is the correct technique for anesthetizing the IAN?

The injection should be along the pterygomandibular raphe. The syringe cartridge should be aligned with the contra-lateral premolars. If the syringe is hitting bone before full insertion, the needle is placed too far anteriorly.

The Effectiveness of Salt Water Rinse and Hypertension

Is salt water rinse effective in reducing the microbial load in the oral cavity?

According to a recent study, ‘salt water rinse can be used as adjunct to routine mechanical plaque control for prevention of oral disease.’ In this study, the Minimum Inhibitory Concentration of salt water against various microbes was first established. Then, participants were allocated into groups based on using a salt water rinse and control group (chlorhexidine) rinse. There was found to be a statistically significant reduction in plaque and A. actinomycetecomitans using salt water rinse, though chlorhexidine was superior against microbes such as S. mutans, L. acidophilus, and P. gingivalis. Unfortunately, only a small sample size of 30 was used during this study so more research is necessary in order to sufficiently understand the benefits of a salt water rinse.

Aravinth, V., Aswath Narayanan, M. B., Ramesh Kumar, S. G., Selvamary, A. L., & Sujatha, A. (2017, October/November). Comparative evaluation of salt water rinse with chlorhexidine against oral microbes: A school-based randomized controlled trial. Retrieved August 23, 2019, from

What is the definition of hypertension?

Cardiac pressure overload. Hypertension as described by our clinical parameters of care has a significant effect on our clinical effectiveness due to injection of epinephrine during routine local anesthesia. Definitions of stage 1 and stage 2 hypertension may have since changed (lowered by as much as 10 points).

Parameters of Care, Charles D. Fuszner DMD, A.T. Still University Missouri School of Dentistry and Oral Health

Does salt water rinse pose a problem to those with hypertension?

Unfortunately, research was not available at the time to confidently answer this question. Though many websites such as claim there is no real concern, the website does mention why a salt water rinse may be concerning for those who do have hypertension, stating –

“Salt water rinses contain as much as 1 tablespoon of table salt in every 6 to 8 ounces of water. Technically, this solution contains almost 7,000 milligrams of sodium, or about five times more sodium than someone with hypertension should have for the entire day.”

(n.d.). Can Swishing Salt Water in the Mouth Raise Blood Pressure? Retrieved from